Anesthesiology: History and Basic Concepts

Anesthesiology is the field of medicine that focuses on interventions that bring a state of anesthesia upon an individual. General anesthesia is characterized by a reversible loss of consciousness along with analgesia, amnesia, and muscle relaxation. General anesthesia is induced via the administration of gaseous or injectable agents before surgical procedures or other medical interventions. On the other end of the spectrum is local anesthesia, which is achieved via the use of topical agents or the local administration of injectable anesthetics to the area of concern. The use of anesthetics has been well documented in history, but the practice of modern anesthesiology only began by the end of the 18th century.

Last updated: 29 Nov, 2021

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Introduction

Definition

Anesthesiology is the field of medicine focusing on interventions that bring about a state of anesthesia, which is characterized by a reversible loss of consciousness, as well as analgesia, amnesia, and muscle relaxation.

State of anesthesia

  • Induced via the administration of gaseous or injectable agents before surgical procedures or other medical interventions
  • Effects:
    • Analgesia: relief from pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways or the prevention of pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
    • Amnesia: loss of awareness and/or memory Memory Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory. Psychiatric Assessment of pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways/experience
    • Hypnosis: temporary unconsciousness or the absence of anxiety Anxiety Feelings or emotions of dread, apprehension, and impending disaster but not disabling as with anxiety disorders. Generalized Anxiety Disorder
    • Paralysis: adequate muscle relaxation

Certified personnel who perform and manage anesthesia

  • Anesthesiologists
  • Certified registered nurse anesthetists
  • Anesthesia assistants

Settings where anesthesia is performed

  • ORs
  • EDs EDS Ehlers-danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders that are characterized by hyperextensible skin, hypermobile joints, and fragility of the skin and connective tissue. Ehlers-Danlos Syndrome
  • Endoscopy Endoscopy Procedures of applying endoscopes for disease diagnosis and treatment. Endoscopy involves passing an optical instrument through a small incision in the skin i.e., percutaneous; or through a natural orifice and along natural body pathways such as the digestive tract; and/or through an incision in the wall of a tubular structure or organ, i.e. Transluminal, to examine or perform surgery on the interior parts of the body. Gastroesophageal Reflux Disease (GERD) suites
  • Interventional radiology Interventional radiology Subspecialty of radiology that combines organ system radiography, catheter techniques and sectional imaging. Penetrating Abdominal Injury suites
  • Interventional cardiology laboratories
  • Ambulatory surgical centers (centers for “day surgery”)
  • Post-anesthesia care units (PACUs)
  • ICUs

History

  • The practice of medicine was transformed in the middle of the 19th century with the discovery of general anesthesia.
  • In previous centuries, surgery was performed as a last resort and desperate measure due to the unbearable pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways it caused.
  • The use of chemical compounds to induce a state of anesthesia in modern medicine dates back to the 18th century with the introduction of inhaled anesthetics Inhaled anesthetics Inhaled anesthetics are chemical compounds that can induce and maintain general anesthesia when delivered by inhalation. Inhaled anesthetics can be divided into 2 groups: volatile anesthetics and gases. Volatile anesthetics include halothane, isoflurane, desflurane, and sevoflurane. Inhaled Anesthetics.
Historical landmarks in the development of anesthesia
Years Events
4000 BCE–0 CE The use of opium poppy; herbal remedies using Hyoscyamus niger, Mandragora, and aconitum; and acupuncture performed with bones, cannabis vapors, and carotid compression Compression Blunt Chest Trauma is documented in records from ancient China, Greece, and Egypt.
1799–1850 CE
  • 1799: Humphry Davy observes that nitrous oxide Nitrous oxide Nitrogen oxide (N2O). A colorless, odorless gas that is used as an anesthetic and analgesic. High concentrations cause a narcotic effect and may replace oxygen, causing death by asphyxia. Inhaled Anesthetics (N2O) relieves physical pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways.
  • 1805: Friedrich Sertürner isolates morphine Morphine The principal alkaloid in opium and the prototype opiate analgesic and narcotic. Morphine has widespread effects in the central nervous system and on smooth muscle. Opioid Analgesics from opium.
  • 1845: Horace Wells inhales N2O as anesthesia for his own dental extraction at Massachusetts General Hospital.
  • 1845: William Morton is the 1st to publicly and successfully demonstrate the use of ether anesthesia for surgery.
  • 1847: James Simpson administers chloroform to relieve pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways during childbirth.
1850–1900 CE
  • 1853: Charles Pravaz and Alexander Wood invent the hollow hypodermic needle and create the syringe.
  • 1853 & 1857: John Snow popularizes obstetric anesthesia by using chloroform during Queen Victoria’s births.
  • 1863: Quincy Colton reintroduces N2O as an inhalation anesthetic.
  • 1884: Karl Koller introduces cocaine Cocaine An alkaloid ester extracted from the leaves of plants including coca. It is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. It also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. Cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake. Local Anesthetics as an ophthalmic anesthetic.
  • 1898: August Bier conducts the 1st spinal block using cocaine Cocaine An alkaloid ester extracted from the leaves of plants including coca. It is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. It also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. Cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake. Local Anesthetics.
1900–1925 CE
  • 1901: Caudal epidural analgesia is described.
  • 1902: The words “anesthesiology” and “anesthesiologist” are coined.
  • 1923: Isabella Herb administers the ethylene-oxygen surgical anesthetic.
1925–1950 CE
  • 1929: John S. Lundy popularizes the use of the IV anesthetic thiopental Thiopental A barbiturate that is administered intravenously for the induction of general anesthesia or for the production of complete anesthesia of short duration. Intravenous Anesthetics (Pentothal).
  • 1942: The 1st successful use of a muscle relaxant as an anesthetic is recorded.
  • 1944: Lidocaine Lidocaine A local anesthetic and cardiac depressant used as an antiarrhythmic agent. Its actions are more intense and its effects more prolonged than those of procaine but its duration of action is shorter than that of bupivacaine or prilocaine. Local Anesthetics is introduced as a local anesthetic.
1950–1975 CE
  • 1954: Perioperative mortality Mortality All deaths reported in a given population. Measures of Health Status related to anesthesia begins to be recorded.
  • 1956: Michael Johnstone clinically introduces halothane Halothane A nonflammable, halogenated, hydrocarbon anesthetic that provides relatively rapid induction with little or no excitement. Analgesia may not be adequate. Nitrous oxide is often given concomitantly. Because halothane may not produce sufficient muscle relaxation, supplemental neuromuscular blocking agents may be required. Inhaled Anesthetics, the 1st modern-day brominated general anesthetic.
  • 1960: Joseph Artusio begins human trials of the inhalational anesthetic methoxyflurane.
  • 1964: Günter Corssen begins human trials of the dissociative IV anesthetic ketamine Ketamine A cyclohexanone derivative used for induction of anesthesia. Its mechanism of action is not well understood, but ketamine can block NMDA receptors (n-methyl-d-aspartate receptors) and may interact with sigma receptors. Intravenous Anesthetics.
  • 1966: Robert Virtue begins human trials of the inhalational anesthetic enflurane.
  • 1972: The inhalational anesthetic isoflurane Isoflurane A stable, non-explosive inhalation anesthetic, relatively free from significant side effects. Inhaled Anesthetics is introduced into clinical practice.
1975–2000 CE
  • 1992: The inhalational anesthetic desflurane Desflurane A fluorinated ether that is used as a volatile anesthetic for maintenance of general anesthesia. Inhaled Anesthetics is introduced into clinical practice.
  • 1993: A safe and systematic approach to ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing during general anesthesia is established.
  • 1994: The inhalational anesthetic sevoflurane Sevoflurane A non-explosive inhalation anesthetic used in the induction and maintenance of general anesthesia. It does not cause respiratory irritation and may also prevent platelet aggregation. Inhaled Anesthetics is introduced into clinical practice.
2000 CE–present The American Society of Anesthesiologists establishes a Simulation Education Network (SEN) to continue educating and certifying anesthesiologists.

Preoperative Evaluation

Focused evaluation and planning for anesthesia should be completed in advance for all surgeries, interventions, and procedures.

  • Risk stratification is an important part of preoperative planning.
  • Low-risk individuals can be evaluated immediately before anesthesia on the day of the procedure. 
    • Low-risk individuals are those who are:
      • < 65 years of age
      • Having stable and adequately controlled medical conditions
      • Undergoing low-risk procedures
    • Risk increase with:
      • Age
      • Complexity of comorbid medical conditions
      • Complexity of planned anesthesia and/or medical/surgical procedures
      • Duration of planned anesthesia and/or medical/surgical procedures
  • Intermediate-to-high risk may need stabilization and/or optimization of comorbid medical conditions prior to anesthesia and/or planned procedures.
  • Emergency anesthesia and/or planned procedure necessitate the initiation of measures with minimal preparation time and are, by their very nature, high risk.

Goals

  • Assessing medical status and readiness for the planned procedure
  • Reducing the risks of anesthesia and surgery
  • Creating an anesthetic plan and preparing the individual

Components of preoperative evaluation

  • Clinical evaluation:
    • Medical history
    • Current medications
    • History of prior anesthesia and surgeries
    • Physical examination
  • Risk assessment Risk assessment The qualitative or quantitative estimation of the likelihood of adverse effects that may result from exposure to specified health hazards or from the absence of beneficial influences. Preoperative Care:
    • Evaluation of factors that increase the likelihood of perioperative morbidity Morbidity The proportion of patients with a particular disease during a given year per given unit of population. Measures of Health Status and mortality Mortality All deaths reported in a given population. Measures of Health Status
    • An objective observation commonly used by the anesthesiology team to create ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing and intubation Intubation Peritonsillar Abscess plans
    • Assessment of the anatomy of the head and neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess to determine the difficulty of intubation Intubation Peritonsillar Abscess:
    • Inclusion of the individual’s underlying health problems
    • Identification Identification Defense Mechanisms of medication allergies Allergies A medical specialty concerned with the hypersensitivity of the individual to foreign substances and protection from the resultant infection or disorder. Selective IgA Deficiency
    • Response to prior anesthesia methods
    • Other aids AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS in risk assessment Risk assessment The qualitative or quantitative estimation of the likelihood of adverse effects that may result from exposure to specified health hazards or from the absence of beneficial influences. Preoperative Care include:
      • Prognostic biomarkers (e.g., B-type natriuretic peptide)
      • CBC (to rule out anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types, infection, thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia)
      • Electrolyte panel (to evaluate electrolyte imbalance and metabolic disturbance)
      • Coagulation studies Coagulation studies Coagulation studies are a group of hematologic laboratory studies that reflect the function of blood vessels, platelets, and coagulation factors, which all interact with one another to achieve hemostasis. Coagulation studies are usually ordered to evaluate patients with bleeding or hypercoagulation disorders. Coagulation Studies (to evaluate for coagulopathy)
      • Creatinine, GFR GFR The volume of water filtered out of plasma through glomerular capillary walls into Bowman’s capsules per unit of time. It is considered to be equivalent to inulin clearance. Kidney Function Tests
      • CRP
      • Functional status/ability to engage in daily activities as reported subjectively by the individual
  • Optimization of diseases and comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus:
    • Optimally managing and treating comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus before surgery and anesthesia to decrease morbidity Morbidity The proportion of patients with a particular disease during a given year per given unit of population. Measures of Health Status and mortality Mortality All deaths reported in a given population. Measures of Health Status
    • Common examples include:
      • Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
      • Ischemic heart disease Ischemic heart disease Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease
      • Heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR)
      • Obstructive sleep Sleep A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility. Physiology of Sleep apnea
      • Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus mellitus
      • Thyroid Thyroid The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck. Thyroid Gland: Anatomy disease
      • Anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types
    • Smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases cessation at least 2 weeks before surgery
  • Preoperative testing:
    • Diagnostic testing for preexisting conditions and comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus should be obtained preoperatively to monitor conditions postoperatively.
    • Patient-specific testing, for example:
      • If blood transfusion is anticipated, blood typing and crossmatching Crossmatching Testing erythrocytes to determine presence or absence of blood-group antigens, testing of serum to determine the presence or absence of antibodies to these antigens, and selecting biocompatible blood by crossmatching samples from the donor against samples from the recipient. Crossmatching is performed prior to transfusion. Transfusion Reactions are imperative before surgery and anesthesia.
      • If a woman of childbearing age is to undergo surgery and anesthesia, a pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care test is indicated to avoid fetal loss.
Summary of high-risk conditions that warrant preoperative assessment and perioperative planning
Preexisting disease/condition Diagnostic testing
Age > 65 years Albumin Albumin Serum albumin from humans. It is an essential carrier of both endogenous substances, such as fatty acids and bilirubin, and of xenobiotics in the blood. Liver Function Tests, creatinine, hemoglobin
Alcohol abuse ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG), electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes, hemoglobin, liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy function test, platelet count, PT/INR
Anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types CBC, creatinine, ferritin Ferritin Iron-containing proteins that are widely distributed in animals, plants, and microorganisms. Their major function is to store iron in a nontoxic bioavailable form. Each ferritin molecule consists of ferric iron in a hollow protein shell (apoferritins) made of 24 subunits of various sequences depending on the species and tissue types. Hereditary Hemochromatosis, iron Iron A metallic element with atomic symbol fe, atomic number 26, and atomic weight 55. 85. It is an essential constituent of hemoglobins; cytochromes; and iron-binding proteins. It plays a role in cellular redox reactions and in the transport of oxygen. Trace Elements, transferrin Transferrin An iron-binding beta1-globulin that is synthesized in the liver and secreted into the blood. It plays a central role in the transport of iron throughout the circulation. Heme Metabolism saturation, TSH, T3 T3 A T3 thyroid hormone normally synthesized and secreted by the thyroid gland in much smaller quantities than thyroxine (T4). Most T3 is derived from peripheral monodeiodination of T4 at the 5′ position of the outer ring of the iodothyronine nucleus. The hormone finally delivered and used by the tissues is mainly t3. Thyroid Hormones, T4 T4 The major hormone derived from the thyroid gland. Thyroxine is synthesized via the iodination of tyrosines (monoiodotyrosine) and the coupling of iodotyrosines (diiodotyrosine) in the thyroglobulin. Thyroxine is released from thyroglobulin by proteolysis and secreted into the blood. Thyroxine is peripherally deiodinated to form triiodothyronine which exerts a broad spectrum of stimulatory effects on cell metabolism. Thyroid Hormones, vitamin B12 Vitamin B12 A cobalt-containing coordination compound produced by intestinal microorganisms and found also in soil and water. Higher plants do not concentrate vitamin B 12 from the soil and so are a poor source of the substance as compared with animal tissues. Intrinsic factor is important for the assimilation of vitamin B 12. Folate and Vitamin B12, blood typing, screening Screening Preoperative Care
Cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) disease BNP BNP A peptide that is secreted by the brain and the heart atria, stored mainly in cardiac ventricular myocardium. It can cause natriuresis; diuresis; vasodilation; and inhibits secretion of renin and aldosterone. It improves heart function. It contains 32 amino acids. Renal Sodium and Water Regulation, ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG), +/- stress testing
Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus Creatinine, HbA1c HbA1c Products of non-enzymatic reactions between glucose and hemoglobin a, occurring as a minor fraction of the hemoglobin components of human erythrocytes. Hemoglobin a1c is hemoglobin a with glucose covalently bound to the terminal valine of the beta chain. Glycated hemoglobin a is used as an index of the average blood sugar level over a lifetime of erythrocytes. Diabetes Mellitus, glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance
Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy disease Albumin Albumin Serum albumin from humans. It is an essential carrier of both endogenous substances, such as fatty acids and bilirubin, and of xenobiotics in the blood. Liver Function Tests, BUN, creatinine, electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes, hemoglobin, liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy function test, platelet count, PT/INR
Pulmonary disease Pulmonary disease Diseases involving the respiratory system. Blastomyces/Blastomycosis Chest X-ray Chest X-ray X-ray visualization of the chest and organs of the thoracic cavity. It is not restricted to visualization of the lungs. Pulmonary Function Tests
Thyroid Thyroid The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck. Thyroid Gland: Anatomy disease T3 T3 A T3 thyroid hormone normally synthesized and secreted by the thyroid gland in much smaller quantities than thyroxine (T4). Most T3 is derived from peripheral monodeiodination of T4 at the 5′ position of the outer ring of the iodothyronine nucleus. The hormone finally delivered and used by the tissues is mainly t3. Thyroid Hormones, T4 T4 The major hormone derived from the thyroid gland. Thyroxine is synthesized via the iodination of tyrosines (monoiodotyrosine) and the coupling of iodotyrosines (diiodotyrosine) in the thyroglobulin. Thyroxine is released from thyroglobulin by proteolysis and secreted into the blood. Thyroxine is peripherally deiodinated to form triiodothyronine which exerts a broad spectrum of stimulatory effects on cell metabolism. Thyroid Hormones, TSH
T3 T3 A T3 thyroid hormone normally synthesized and secreted by the thyroid gland in much smaller quantities than thyroxine (T4). Most T3 is derived from peripheral monodeiodination of T4 at the 5′ position of the outer ring of the iodothyronine nucleus. The hormone finally delivered and used by the tissues is mainly t3. Thyroid Hormones: triiodothyronine Triiodothyronine A T3 thyroid hormone normally synthesized and secreted by the thyroid gland in much smaller quantities than thyroxine (T4). Most T3 is derived from peripheral monodeiodination of T4 at the 5′ position of the outer ring of the iodothyronine nucleus. The hormone finally delivered and used by the tissues is mainly t3. Thyroid Hormones
T4 T4 The major hormone derived from the thyroid gland. Thyroxine is synthesized via the iodination of tyrosines (monoiodotyrosine) and the coupling of iodotyrosines (diiodotyrosine) in the thyroglobulin. Thyroxine is released from thyroglobulin by proteolysis and secreted into the blood. Thyroxine is peripherally deiodinated to form triiodothyronine which exerts a broad spectrum of stimulatory effects on cell metabolism. Thyroid Hormones: thyroxine Thyroxine The major hormone derived from the thyroid gland. Thyroxine is synthesized via the iodination of tyrosines (monoiodotyrosine) and the coupling of iodotyrosines (diiodotyrosine) in the thyroglobulin. Thyroxine is released from thyroglobulin by proteolysis and secreted into the blood. Thyroid Hormones
TSH: thyroid-stimulating hormone Thyroid-stimulating hormone A glycoprotein hormone secreted by the adenohypophysis. Thyrotropin stimulates thyroid gland by increasing the iodide transport, synthesis and release of thyroid hormones (thyroxine and triiodothyronine). Thyroid Hormones
Table: Risk-stratification categories used to classify perioperative risk based on subject characteristics (preoperative risk classification by the American Society of Anesthesiologists)
American Society of Anesthesiologists physical status classification Definition Examples
I A normal, healthy individual without known diseases Healthy, nonsmoker, minimal alcohol use
II An individual with mild systemic disease Current smoker, mild hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension, mild lung disease
III An individual with severe systemic disease Poorly controlled hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension or diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus mellitus, chronic obstructive pulmonary disease Pulmonary disease Diseases involving the respiratory system. Blastomyces/Blastomycosis
IV An individual with severe systemic disease that is a constant threat to life Recent MI MI MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction, severely reduced ejection fraction Ejection fraction Cardiac Cycle, sepsis Sepsis Systemic inflammatory response syndrome with a proven or suspected infectious etiology. When sepsis is associated with organ dysfunction distant from the site of infection, it is called severe sepsis. When sepsis is accompanied by hypotension despite adequate fluid infusion, it is called septic shock. Sepsis and Septic Shock, ARDS ARDS Acute respiratory distress syndrome is characterized by the sudden onset of hypoxemia and bilateral pulmonary edema without cardiac failure. Sepsis is the most common cause of ARDS. The underlying mechanism and histologic correlate is diffuse alveolar damage (DAD). Acute Respiratory Distress Syndrome (ARDS)
V An individual who is not expected to survive without the intended operation Brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification bleed, ruptured aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms, massive trauma
VI An individual declared brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification dead or whose organs are being harvested
Modified mallampati classification

Mallampati classification Mallampati Classification Preoperative Care to assess ease of airway Airway ABCDE Assessment access for intubation Intubation Peritonsillar Abscess:
I: The soft palate Palate The palate is the structure that forms the roof of the mouth and floor of the nasal cavity. This structure is divided into soft and hard palates. Palate: Anatomy, fauces, uvular, and pillars are visible.
II: The soft palate Palate The palate is the structure that forms the roof of the mouth and floor of the nasal cavity. This structure is divided into soft and hard palates. Palate: Anatomy, fauces, and part of the uvula Uvula A fleshy extension at the back of the soft palate that hangs above the opening of the throat. Peritonsillar Abscess are visible.
III: The soft palate Palate The palate is the structure that forms the roof of the mouth and floor of the nasal cavity. This structure is divided into soft and hard palates. Palate: Anatomy and base of the uvula Uvula A fleshy extension at the back of the soft palate that hangs above the opening of the throat. Peritonsillar Abscess are visible.
IV: Only the hard palate Palate The palate is the structure that forms the roof of the mouth and floor of the nasal cavity. This structure is divided into soft and hard palates. Palate: Anatomy is visible.

Image: “Modified Mallampati classification Mallampati Classification Preoperative Care” by Department of Anaesthesiology, Copenhagen University Hospital, Nordsjælland Hospital, 3400, Hillerød, Denmark. License: CC BY 2.0

Patient education

  • Essential for the affected individual’s satisfaction and safety
  • Provides information on how to reduce the risks of surgery and anesthesia:
    • Stop smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases before and after surgery.
    • Medications that are to be taken or avoided before surgery
    • Cessation of eating and drinking by midnight prior to the procedure to prevent aspiration of gastric contents
    • Sanitary measures prior to the procedure (e.g., antibacterial Antibacterial Penicillins soap prep)
  • Involve the individual in the decision-making and planning steps.
  • Answer all questions.
  • Address all concerns.

Informed consent Informed consent Informed consent is a medicolegal term describing the documented conversation between a patient and their physician wherein the physician discloses all relevant and necessary information to a patient who is competent to make an informed and voluntary decision regarding their care. Competency, disclosure, and voluntariness are the key elements upon which IC is based. Informed Consent

  • Based on the premise that individuals have the right to receive information and ask questions about recommended treatments so that they can make well-informed decisions about their care
  • Treating physicians Physicians Individuals licensed to practice medicine. Clinician–Patient Relationship should discuss all risks and complications associated with the procedure and associated anesthesia before asking for informed consent Informed consent Informed consent is a medicolegal term describing the documented conversation between a patient and their physician wherein the physician discloses all relevant and necessary information to a patient who is competent to make an informed and voluntary decision regarding their care. Competency, disclosure, and voluntariness are the key elements upon which IC is based. Informed Consent.
  • Results in the individual’s agreement or refusal to undergo a specific medical intervention
  • Usually obtained in a written format

Anesthesia plan

The creation of a plan for anesthesia involves the consideration of:

  • Surgery requirements
  • Duration of surgery
  • Comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus
  • Postoperative considerations
  • The individual’s preference
  • Preferences of the surgeon and the anesthesiologist

Postoperative care Postoperative care After any procedure performed in the operating room, all patients must undergo close observation at least in the recovery room. After larger procedures and for patients who require hospitalization, observation must continue on the surgical ward. The primary intent of this practice is the early detection of postoperative complications. Postoperative Care

Considerations include:

  • Pain management Pain Management Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage. Pain is a subjective experience. Acute pain lasts < 3 months and typically has a specific, identifiable cause. Pain Management
  • Hemodynamics Hemodynamics The movement and the forces involved in the movement of the blood through the cardiovascular system. Vascular Resistance, Flow, and Mean Arterial Pressure
  • Pulmonary hygiene
  • Early interventions
  • Requirement of ICU ICU Hospital units providing continuous surveillance and care to acutely ill patients. West Nile Virus vs appropriate hospital wing vs outpatient care for recovery

Types of Anesthesia

Several types of anesthesia are used for surgery or other medical procedures. Choosing the appropriate type depends on:

  • Procedure to be performed
  • Procedure requirements
  • Area that needs to be anesthetized
  • Duration of surgery
  • Patient-specific comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus
  • Postoperative anesthesia plans and considerations
  • Individual’s preference
  • Preferences of the provider and the anesthesiologist

Types of anesthesia:

  • General
  • Neuraxial
  • Peripheral nerve block
  • IV regional anesthesia
  • Monitored anesthesia care (MAC)

General anesthesia

  • Drug-induced loss of consciousness
  • Affects the whole body
  • Appropriate for most major surgical procedures
  • The goal of general anesthesia is to attain:
    • Unconsciousness
    • Analgesia
    • Muscle relaxation with immobility
    • Blockage of noxious stimuli during surgery

The 3 stages of general anesthesia are:

  1. Induction:
  2. Maintenance:
    • Typically achieved via a primary inhalation technique using IV drugs
    • Goal is to reduce the total dosage Dosage Dosage Calculation of any 1 agent; thus, anesthetic combinations are commonly used.
  3. Emergence:
    • Involves removing anesthetic agents and reversing their residual effects for the return of consciousness and movement
    • Extubation Extubation Removal of an endotracheal tube from the patient. Invasive Mechanical Ventilation can be performed when the individual can protect their airway Airway ABCDE Assessment, follow simple commands, and ventilate without assistance.
Table: Induction agents
Class Commonly used drugs
IV sedative-hypnotics Propofol Propofol An intravenous anesthetic agent which has the advantage of a very rapid onset after infusion or bolus injection plus a very short recovery period of a couple of minutes. Propofol has been used as anticonvulsants and antiemetics. Intravenous Anesthetics, etomidate Etomidate Imidazole derivative anesthetic and hypnotic with little effect on blood gases, ventilation, or the cardiovascular system. It has been proposed as an induction anesthetic. Intravenous Anesthetics, ketamine Ketamine A cyclohexanone derivative used for induction of anesthesia. Its mechanism of action is not well understood, but ketamine can block NMDA receptors (n-methyl-d-aspartate receptors) and may interact with sigma receptors. Intravenous Anesthetics
IV adjuvants Opioids Opioids Opiates are drugs that are derived from the sap of the opium poppy. Opiates have been used since antiquity for the relief of acute severe pain. Opioids are synthetic opiates with properties that are substantially similar to those of opiates. Opioid Analgesics, lidocaine Lidocaine A local anesthetic and cardiac depressant used as an antiarrhythmic agent. Its actions are more intense and its effects more prolonged than those of procaine but its duration of action is shorter than that of bupivacaine or prilocaine. Local Anesthetics, midazolam Midazolam A short-acting hypnotic-sedative drug with anxiolytic and amnestic properties. It is used in dentistry, cardiac surgery, endoscopic procedures, as preanesthetic medication, and as an adjunct to local anesthesia. The short duration and cardiorespiratory stability makes it useful in poor-risk, elderly, and cardiac patients. It is water-soluble at ph less than 4 and lipid-soluble at physiological pH. Benzodiazepines
Inhalation agents Nitrous oxide Nitrous oxide Nitrogen oxide (N2O). A colorless, odorless gas that is used as an anesthetic and analgesic. High concentrations cause a narcotic effect and may replace oxygen, causing death by asphyxia. Inhaled Anesthetics, halothane Halothane A nonflammable, halogenated, hydrocarbon anesthetic that provides relatively rapid induction with little or no excitement. Analgesia may not be adequate. Nitrous oxide is often given concomitantly. Because halothane may not produce sufficient muscle relaxation, supplemental neuromuscular blocking agents may be required. Inhaled Anesthetics, isoflurane Isoflurane A stable, non-explosive inhalation anesthetic, relatively free from significant side effects. Inhaled Anesthetics
Neuromuscular blockers Neuromuscular blockers Neuromuscular blockers are skeletal muscle relaxant medications that block muscle contraction through a couple of mechanisms. Depolarizing neuromuscular blockers bind to nicotinic cholinergic receptors (nAChRs), locking the ion channel open. This results in muscle relaxation and paralysis. Neuromuscular Blockers Vecuronium Vecuronium Monoquaternary homolog of pancuronium. A non-depolarizing neuromuscular blocking agent with shorter duration of action than pancuronium. Its lack of significant cardiovascular effects and lack of dependence on good kidney function for elimination as well as its short duration of action and easy reversibility provide advantages over, or alternatives to, other established neuromuscular blocking agents. Neuromuscular Blockers, rocuronium Rocuronium An androstanol non-depolarizing neuromuscular blocking agent. It has a mono-quaternary structure and is a weaker nicotinic antagonist than pancuronium. Neuromuscular Blockers, succinylcholine Succinylcholine A quaternary skeletal muscle relaxant usually used in the form of its bromide, chloride, or iodide. It is a depolarizing relaxant, acting in about 30 seconds and with a duration of effect averaging three to five minutes. Succinylcholine is used in surgical, anesthetic, and other procedures in which a brief period of muscle relaxation is called for. Cholinomimetic Drugs

Neuraxial anesthesia

  • A type of anesthesia that involves anesthetizing the nerves of the CNS
  • Neuraxial anesthesia is commonly used for lower abdominal and lower extremity surgeries or for pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways relief.
  • 2 main types:
    • Spinal anesthesia: A needle is inserted between the vertebrae and the anesthetic is injected directly into the subarachnoid space Subarachnoid space The space between the arachnoid membrane and pia mater, filled with cerebrospinal fluid. It contains large blood vessels that supply the brain and spinal cord. Subarachnoid Hemorrhage.
    • Epidural anesthesia: A catheter is inserted between the vertebrae and the anesthetic is injected directly into the epidural space Epidural space Space between the dura mater and the walls of the vertebral canal. Epidural Hemorrhage.
Localization of epidural

Epidural anesthesia is commonly used during childbirth:
Anesthesiologists place a catheter between the L3 and L4 vertebrae into the epidural space Epidural space Space between the dura mater and the walls of the vertebral canal. Epidural Hemorrhage for the continuous delivery of local anesthetics Local anesthetics Local anesthetics are a group of pharmacological agents that reversibly block the conduction of impulses in electrically excitable tissues. Local anesthetics are used in clinical practice to induce a state of local or regional anesthesia by blocking sodium channels and inhibiting the conduction of painful stimuli via afferent nerves. Local Anesthetics. Common epidural agents include lidocaine Lidocaine A local anesthetic and cardiac depressant used as an antiarrhythmic agent. Its actions are more intense and its effects more prolonged than those of procaine but its duration of action is shorter than that of bupivacaine or prilocaine. Local Anesthetics, bupivacaine Bupivacaine A widely used local anesthetic agent. Local Anesthetics, and ropivacaine Ropivacaine An anilide used as a long-acting local anesthetic. It has a differential blocking effect on sensory and motor neurons. Local Anesthetics.

Image: “Localization of epidural” by Gurch. License: Public Domain

Peripheral nerve blocks

  • A type of regional anesthesia
  • The anesthetic is injected near a specific nerve or a bundle of nerves to block sensations of pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways from a specific area of the body.
  • Commonly used for procedures involving the upper and lower extremities
  • Fluoroscopy Fluoroscopy Production of an image when x-rays strike a fluorescent screen. X-rays or ultrasound guidance is often used for needle or catheter insertion and placement.
  • Long-acting local anesthetics Local anesthetics Local anesthetics are a group of pharmacological agents that reversibly block the conduction of impulses in electrically excitable tissues. Local anesthetics are used in clinical practice to induce a state of local or regional anesthesia by blocking sodium channels and inhibiting the conduction of painful stimuli via afferent nerves. Local Anesthetics provide prolonged postoperative analgesia.
Ultrasound-guided nerve block

Ultrasound-guided nerve block:
Ultrasound demonstrating a needle (row of white arrowheads) and an anesthetic solution (dark area surrounding the ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy) injected around the ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy for successful peripheral nerve block. Anesthetic blockade of a nerve bundle blocks all nerves downstream, providing adequate analgesia for a procedure. Notice how the anesthesiologist identified the ulnar artery Ulnar Artery The larger of the two terminal branches of the brachial artery, beginning about one centimeter distal to the bend of the elbow. Like the radial artery, its branches may be divided into three groups corresponding to their locations in the forearm, wrist, and hand. Forearm: Anatomy to avoid puncturing it.

Image: “Ultrasound-guided nerve block” by Richard Amini et al AL Amyloidosis. License: CC BY 4.0

Intravenous regional anesthesia Intravenous Regional Anesthesia Inhaled Anesthetics ( IVRA IVRA Inhaled Anesthetics)

  • Also known as a “ Bier block Bier Block Complex Regional Pain Syndrome (CRPS)
  • Less invasive alternative to peripheral nerve blocks
  • Suitable for shorter procedures of the hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy, forearm Forearm The forearm is the region of the upper limb between the elbow and the wrist. The term “forearm” is used in anatomy to distinguish this area from the arm, a term that is commonly used to describe the entire upper limb. The forearm consists of 2 long bones (the radius and the ulna), the interosseous membrane, and multiple arteries, nerves, and muscles. Forearm: Anatomy, and foot Foot The foot is the terminal portion of the lower limb, whose primary function is to bear weight and facilitate locomotion. The foot comprises 26 bones, including the tarsal bones, metatarsal bones, and phalanges. The bones of the foot form longitudinal and transverse arches and are supported by various muscles, ligaments, and tendons. Foot: Anatomy
  • Estimated blockage time: approximately 1.5 hours
  • Appropriate for surgeries lasting 1 hour or less
  • Procedure:
    1. Compression Compression Blunt Chest Trauma and exsanguination of the extremity using an Esmarch bandage
    2. A tourniquet is used to keep the blood out of the extremity and retain anesthesia.
    3. An infusion of 0.5% lidocaine Lidocaine A local anesthetic and cardiac depressant used as an antiarrhythmic agent. Its actions are more intense and its effects more prolonged than those of procaine but its duration of action is shorter than that of bupivacaine or prilocaine. Local Anesthetics via a peripheral vein establishes anesthesia.
    4. The surgeon can work in a completely anesthetized and bloodless surgical field for a limited time.
Bier block

Basic setup for a Bier block Bier Block Complex Regional Pain Syndrome (CRPS)

Image by Lecturio.

Monitored anesthesia care

  • Involves monitoring an individual’s vitals and administering sedatives, anxiolytics, or analgesics accordingly
  • Commonly used during outpatient procedures
  • If needed, anesthesiologists are ready to convert to general anesthesia at any time.
  • A common example is administering propofol Propofol An intravenous anesthetic agent which has the advantage of a very rapid onset after infusion or bolus injection plus a very short recovery period of a couple of minutes. Propofol has been used as anticonvulsants and antiemetics. Intravenous Anesthetics whenever an anesthesiologist deems it necessary during an endoscopy Endoscopy Procedures of applying endoscopes for disease diagnosis and treatment. Endoscopy involves passing an optical instrument through a small incision in the skin i.e., percutaneous; or through a natural orifice and along natural body pathways such as the digestive tract; and/or through an incision in the wall of a tubular structure or organ, i.e. Transluminal, to examine or perform surgery on the interior parts of the body. Gastroesophageal Reflux Disease (GERD) based on the individual’s vitals and mobility Mobility Examination of the Breast.

Perioperative Monitoring

Standard monitors

  • Used by the anesthesiology team during a procedure
  • Includes:
    • Pulse oximetry
    • ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG)
    • Noninvasive blood pressure monitoring device
    • Thermometers
    • Integrated monitors with alarms

Monitoring of ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing

  • Serialized visual inspection Inspection Dermatologic Examination, auscultation, palpation Palpation Application of fingers with light pressure to the surface of the body to determine consistency of parts beneath in physical diagnosis; includes palpation for determining the outlines of organs. Dermatologic Examination, and O2 saturation
  • Ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing monitoring is essential during anesthesia due to the risk of respiratory depression and hypoxia Hypoxia Sub-optimal oxygen levels in the ambient air of living organisms. Ischemic Cell Damage.
  • Ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing is monitored in several ways:
    • Clinical monitoring:
      • Visualization of chest excursion
      • Auscultation of breath sounds
      • Movement of the reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli bag
      • O2 saturation monitor
    • Capnography: a graph showing the respiratory rate Respiratory rate The number of times an organism breathes with the lungs (respiration) per unit time, usually per minute. Pulmonary Examination and CO2 concentration over time
    • Other measures:
      • End-tidal CO2 concentration
      • Inspired O2 concentration
      • Quantitative volume of expired gas
Normal capnogram

Normal capnogram reflecting appropriate CO2 levels in an individual receiving general anesthesia:
Capnography reflects adequate ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing during surgery.

Image by Lecturio.

Monitoring of hemodynamics Hemodynamics The movement and the forces involved in the movement of the blood through the cardiovascular system. Vascular Resistance, Flow, and Mean Arterial Pressure

  • Serialized recording of automated blood pressure, ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG), and HR
  • More accurate hemodynamic monitoring can be achieved via invasive approaches such as:
    • Intra-arterial pressure monitor
    • Central venous pressure Central venous pressure The blood pressure in the central large veins of the body. It is distinguished from peripheral venous pressure which occurs in an extremity. Central Venous Catheter monitor
    • Pulmonary artery Pulmonary artery The short wide vessel arising from the conus arteriosus of the right ventricle and conveying unaerated blood to the lungs. Lungs: Anatomy catheter
    • Transesophageal echocardiography Echocardiography Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic. Tricuspid Valve Atresia (TVA) ( TEE TEE Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues using a transducer placed in the esophagus. Imaging of the Heart and Great Vessels) probes
  • Hemodynamics Hemodynamics The movement and the forces involved in the movement of the blood through the cardiovascular system. Vascular Resistance, Flow, and Mean Arterial Pressure are monitored based on:
  • Vasoactive drugs can be administered to maintain optimal intravascular volume status Volume Status ACES and RUSH: Resuscitation Ultrasound Protocols throughout anesthesia.

Monitoring of neurologic status

  • Neurologic status may be difficult to assess in individuals who are sedated and/or paralyzed.
  • EEG EEG Seizures may be used for the neuromonitoring of cortical function.
  • IM paraspinal and/or limb electrodes Electrodes Electric conductors through which electric currents enter or leave a medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum. Electrocardiogram (ECG) may be used to monitor nerve stimulation during neurosurgical, orthopedic, or interventional spinal procedures.
  • Intracranial pressure Intracranial Pressure Idiopathic Intracranial Hypertension may be monitored during neurosurgical procedures.

Depth of anesthesia

Table: Stages of anesthesia depth
Stage I Conscious and rational with decreased pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways perception Perception The process by which the nature and meaning of sensory stimuli are recognized and interpreted. Psychiatric Assessment
Stage II Unconscious Unconscious Those forces and content of the mind which are not ordinarily available to conscious awareness or to immediate recall. Psychotherapy and reflexive with an irregular breathing pattern
Stage III Inability to protect the airway Airway ABCDE Assessment due to increased muscle relaxation
Stage IV Cardiovascular and respiratory depression (medullary)

Postoperative Care

All individuals are monitored postoperatively in a PACU, where standard procedures are followed:

  • Antiemetics Antiemetics Antiemetics are medications used to treat and/or prevent nausea and vomiting. These drugs act on different target receptors. The main classes include benzodiazepines, corticosteroids, atypical antipsychotics, cannabinoids, and antagonists of the following receptors: serotonin, dopamine, and muscarinic and neurokinin receptors. Antiemetics for postoperative nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics and/or vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia
  • Fluid administration and monitoring for the inability to void via strict inputs and outputs
  • Respiratory, cardiovascular, and neurological monitoring
  • Monitoring and control of hypothermia Hypothermia Hypothermia can be defined as a drop in the core body temperature below 35°C (95°F) and is classified into mild, moderate, severe, and profound forms based on the degree of temperature decrease. Hypothermia and hyperthermia
  • Pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways control
  • Reassurance Reassurance Clinician–Patient Relationship, reorientation, and potential drug reversal for delayed emergence (failure to return to a conscious state within 60 minutes of anesthesia cessation)
  • Recovery assessment
  • Reduction of postoperative adverse events
  • Streamline discharge
  • Transferring to an ICU ICU Hospital units providing continuous surveillance and care to acutely ill patients. West Nile Virus vs appropriate hospital wing vs outpatient care for recovery

References

  1. Falk, S. (2020) Overview of anesthesia. Retrieved October 15, 2021, from https://www.uptodate.com/contents/overview-of-anesthesia
  2. Robinson, D., Toledo, A.H. (2012). Historical development of modern anesthesia. Journal of Investigative Surgery: The Official Journal of the Academy of Surgical Research, 25, 141–149. https://doi.org/10.3109/08941939.2012.69032
  3. Harrah, S. (2015). Medical Milestones: Discovery of Anesthesia & Timeline. University of Medicine and Health Sciences. https://www.umhs-sk.org/blog/medical-milestones-discovery-anesthesia-timeline 
  4. Nizamuddin, J. (2019). Anesthesia for surgical patients. Schwartz’s Principles of Surgery, 11e. McGraw-Hill. https://accessmedicine-mhmedical-com.ezproxy.unbosque.edu.co/content.aspx?bookid=2576&sectionid=216218112 
  5. Romero-Ávila, P. (2021). Historical development of the anesthetic machine: From Morton to the integration of the mechanical ventilator. Brazilian Journal of Anesthesiology (English Edition), 71, 148–161. https://www.sciencedirect.com/science/article/pii/S0104001421000361?via%3Dihub
  6. Wood Library-Museum of Anesthesiology. History of Anesthesia. Retrieved June 21, 2021, from https://www.woodlibrarymuseum.org/history-of-anesthesia/

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