The study of anesthesiology has greatly expanded to encompass in its spectrum the care of the most critical patients in the hospital. This article addresses the basic tenets of intensive care unit (ICU); its organization, composition, components, modern technical armamentarium and concludes with a prologue to brain death and its determination.

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clinicians in intensive care unit

Image: “Clinicians in intensive care unit.” by Calleamanecer – Own work. License: CC BY-SA 3.0

Intensive Care Unit (ICU)

ICU epitomizes the critical sections of the hospital where the sickest patients are cared for. The physicians and staff in the ICU have specialized training to allow them to care for the sickest patients. There are drugs used only in the ICU and highly sophisticated pieces of equipment which assist in providing care. The majority of patients in an ICU will have more than one critical illness in more than one organ system.

The concept of holistic intensive care dates back to the 1952 Copenhagen polio epidemic. Mortality rates close to 90% drastically plummeted to 40 as medical students provided manual positive pressure ventilation. We have come a long way since then. Today’s intensive care units are specialized medical battle grounds with medical personnel on field armed with modern technological armamentarium.

Types of intensive care units

The operating room is often seen as an ICU. The anesthesiologists frequently are the primary physicians in the ICU. There exist different ICUs for different ailments. Some are as tabulated below:

General ICU

Created to manage all critical patients

Surgical ICU

Manages patients who are very sick post-operatively or optimizes them pre-operatively


Managed by neurosurgeons and intensivists

Mobile intensive care unit (MICU)

Specialized on field intensive care is mediated through these mobile units. Provisions for advanced life care support (ACLS) and resuscitation exist.

Neonatal ICU

Neonates are managed in these establishments with utmost attention to asepsis.

Trauma ICU

For patients with life-threatening injuries; under supervision of trauma surgeons and intensivists

Cardiac surgical ICU

Specifically designed and armed for management of patients with cardiac morbidities; manned by cardiac anesthesiologists

Medical ICU

Designated to manage patients with medical morbidities; not secondary to surgical interventions

Post-anesthesia care units (PACU)

Also goes by the name “recovery room”, renders immediate post-operative stabilization to patients following surgical procedures

Coronary care units

For patients with ischemic heart disease; usually managed by cardiologists

Pediatric ICU

Children are not small adults. Their needs, diseases and responses need specialized attention and hence separate intensive care units.

High dependency units (HDU)

These are transitory step down units housing patients not serious enough to merit ICU care; but grave enough to demand continuous observation.

Employees in intensive care units

ICU physician

He is the captain of the ship, the intensivist; a physician with advanced intensive care medicine training after specialization in medicine, anesthesiology or general surgery usually leads the team in accordance with the primary treating personnel.

Qualification: Different countries have different qualifying norms for “intensivists”. In many countries, the training is divided into medical intensivist and surgical intensivist training. In rural communities, it is usually an anesthesiologist or internist. In Canada, before being qualified, an intensivist must complete specialty training in anesthesiology, internal medicine, general surgery, or emergency medicine prior to entering a 2 year residency which is accredited by the Royal College of Physicians and Surgeons of Canada. They are obliged to pass a Royal College exam before qualifying as an intensivist.

Duty: every patient must undergo a very complete physical exam inclusive of:

  • Head-to-toe assessment
  • Special focus on gross neurological exam and level of consciousness
  • Pulmonary exam with focus on observing the respiratory pattern and ruling out pneumothorax
  • Cardiovascular assessment with emphasis on volume status – often includes cardiac ultrasound and assessment of central venous pressure
  • Daily abdominal exam and assessment of bowel sounds
  • Assessment for skin lesions, edema
  • Focused exam of the areas of greatest concern.

Admitting examination takes about 15-30 minutes, while daily examination is a matter of 5-7 minutes.

ICU nurse

The ICU nursing staff is highly proficient in critical care and is adept with intensive care procedures.

Qualification: The ICU nurse is experienced medical personnel with specialized training in intensive care after working for several years as a general duty nurse. This experience is instrumental in assessing patients, reacting quickly to changing conditions, making decisions quickly, and being cognizant of management of highly potent drugs and operation of complex equipment. It is often up to the nurse to manage the patient’s changing condition for some time before a physician becomes available.

Duty: anticipated to reflect a high degree of responsibility for the patient, following chores are expected of an ICU nurse:

  • Complete evaluation at the change of shift
  • Ability to infuse very potent drugs safely
  • Constant assessment of hemodynamics and adjustment of drugs as necessary
  • Constant assessment of ventilation
  • Knowledge of how to manage transducers
  • Constant assessment of level of consciousness
  • Management of sedation, pain, muscle relaxation
  • Management of continuous renal dialysis
  • Management of end of life care
  • Communication with the patient and family (in collaboration with the physician)


Nutrition has a pivotal role in the recovery of critical patients. The dietician optimizes insidiously escalating customized regimen of assortment of nutrition for every patient and follows the same diligently.


Immobilization is a vice of intensive care medicine. With it come along morbidities like atelectasis, pneumonia, deep venous thrombosis and pressure sores. In these circumstances, the role of physiotherapists for mobilization of patients should not be under-estimated.

Social worker

Intensive care extracts heavily on mental and financial assets of patients and their relatives. Presence of social workers eases these difficult times.


Intensive care units have a pharmacist on round to highlight possible drug interactions and render the most conducive drug regime to patients with different co-morbidities.

Speech therapist

They are seen more in ICUs with neurological patients.

Occupational therapist

In conjunction with physiotherapists, they help in providing suitable prosthesis and orthoses for patients to enhance early mobilization and rehabilitation.


Often seen as the critic, it is the responsibility of the microbiologist to ensure adherence to asepsis, evade breach of sterility and regulate infection control guidelines.

Medical physics technician

They are responsible for maintenance of the medical equipments.

Common ICU Conditions

Failing organ systems

Heart failure – earlier use of left ventricular assist devices (LVAD) as a bridge to heart transplant has mortality benefit.

Renal failure – now treated with continuous renal replacement (CRRT); a slow technique with less hemodynamic changes as compared to hemodialysis

Respiratory failure – previously called Adult Respiratory Distress Syndrome (ARDS); care for acute lung injury (ALI) has been revolutionized by using much smaller ventilator volumes than previously. This has culminated in decreased ventilator associated lung trauma dramatically and subsequent improved outcomes.

SIRS (systemic inflammatory response syndrome)

sepsis steps

Image: “Teaching slide for help in identifying possible sepsis syndrome, severe sepsis, and septic shock.” by Hadroncastle – Own work. License: CC BY-SA 4.0

Systemic inflammatory response syndrome is a part of spectrum which dictates clinical outcome of the patient as a part of non-specific response to ischemia, trauma, inflammation and/ or infection.

Characterized by generalized tissue inflammation with general breakdown of the body’s immune system, it is a part of a continuum and is often seen as the presenting condition in the continuum.

A patient is said to have SIRS if 2 or more of the following criteria are met:

  • Temperature more than 38 degree Celsius (100.4 ° F) or less than 36 degrees Celsius (96.8 ° F)
  • Heart rate more than 90 beats per minute
  • Respiratory rate more than 20 or Pa CO2 less than 32 mm Hg
  • WBC (White blood cell) count more than 12000/ or less than 4000/ or more than 10% band forms.

One needs to be aware of the following closely related but distinct terms in a continuum:

  • Sepsis: SIRS with suspected or present source of infection
  • Severe sepsis: Sepsis with organ dysfunction, hypotension or hypoperfusion; characterized by presence of lactic acidosis, systolic blood pressure less than 90 mm Hg or systolic blood pressure drop of more than 40 mm Hg of normal.
  • Septic shock: sepsis with shock: hypotension despite adequate fluid resuscitation.
  • Multiple organ dysfunction syndrome: Evidence of 2 or more organs failing.

High in the progression hierarchy of SIRS, multiple organ dysfunction syndrome (MODS) represents the irrevocable grave undesired ill consequence of SIRS. Most patients of MODS are damaged beyond repair.

Close evaluation for other causes of shock should be made in case a particular patient does not satisfy the SIRS criteria.

Treatment: Early antibiotic therapy is essential. Every hour delay in administering antibiotics increases mortality by 8%.

Effective volume management is crucial. The question as to which of the fluids is the best for replacement therapy has dazzled many brilliant minds. The choice is to be made among artificial colloid, albumin, normal saline, balanced salt, high concentration saline ( 3% or 5% saline) and hypotonic solutions. The answer still eludes us. However, what is known is that maintenance of the central venous pressure on the higher side of the normal spectrum is the best approach irrespective of the fluid used.

Effective hemodynamic support is essential but at the same time difficult. The current drug of choice is norepinephrine (noradrenaline).

Special Devices in Intensive Care Units

Skilled emergent clinical acumen goes hand in hand with a robust infrastructure support in the ICU. Technological artificial equivalents for the major organ systems exist. If they really help give good quality of life or merely delay death is a matter of debate. The gadgetry includes myriad equipments, monitors and analyzers. Some of the salient ones are as follows:

Ventricular assist device

The impetus to the exponential development of mechanical circulatory support (MCS) devices came from the REMATCH trial. The ventricular assist device is of following types:

  • Left ventricular assist device (LVAD): most commonly used.
  • Right ventricle assist device (RVAD)
  • Simultaneous left and right ventricular assist device: biventricular assist device (BIVAD)
  • Replacement of both the ventricles: Total artificial heart.

Placed by cardiac surgeons, the basic biomechanics revolve around a balloon placed in the ascending aorta. The cuff of the LVAD is placed below the carotid and subclavian exits from the aorta. The balloon inflates during cardiac diastole thus increasing the afterload and improving coronary perfusion.

It deflates during cardiac systole with subsequent decrease in afterload and improved cardiac output. The ECG tracing is modified and the pressure tracing looks quite different from a normal BP tracing.

Common indications:

  • Stabilize patients prior to cardiac surgery
  • Maintain patient until heart transplant is possible
  • Small devices can be implanted and used as temporary “artificial heart”


respirator icu

Image: “Respirator “Evita4” in an ICU.” by Blogotron – Own work. License: CC0

The first demonstration of artificial ventilation came from George Poe who allegedly revived asphyxiated dogs with his gadgets. We have come a long way since then. Today’s ventilators find origin in World War II military warfare technological developments to facilitate respiration of pilots at high altitudes.

The different configurations available are:

  • Positive pressure ventilators
  • Transport ventilators
  • Neonatal ventilators
  • Intensive care ventilators

The modern ventilator is a highly sophisticated piece of equipment which can deliver different modes of ventilation according to the patient’s needs. They are:

  • Volume controlled ventilation: the commonest mode; the volume and ventilatory rate are set in accordance to the patient’s arterial oxygen and carbon dioxide levels.
  • Pressure controlled ventilation: This mode is utilized in patients with high airway pressures who are at risk of barotraumas with volume controlled ventilation. A maximum inspiratory volume is set and the ventilatory rate is modulated as per blood gases.
  • Pressure assisted ventilation: facilitates the patient’s ventilatory exertions by providing a boost in pressure with each breath to ensure adequate ventilation.
  • Positive end-expiratory pressure (PEEP): improves gas exchange by assuring that lung volume is partially maintained at the end of expiration.
  • Non-invasive ventilation (BIPAP) is being increasingly used nowadays.

Role of tracheostomy: In patients with anticipated need for prolonged mechanical ventilation or failure to wean off the ventilator, endotracheal tube usage has its own caveats. These patients stand to benefit from tracheostomy eliminating the dead space, allowing oral hygiene and lowering chances of aspiration pneumonia.


Being poor quasi-substitutes for lungs; ventilators are fraught with complications like:

  • Ventilator associated pneumonia
  • Ventilator associated lung injury, barotraumas and volutrauma
  • Atrophy of the diaphragm
  • Impaired muco-ciliary transport.

Continuous Renal Replacement Therapy (CRRT)

Usually ordered by intensivist and managed by ICU nurse, the following are advantages of CRRT over conventional hemodialysis:

  • Less hemodynamic disruption
  • Slow and continuous
  • Better outcome in acute renal failure with often complete recovery
  • Better stabilization of patients with chronic renal failure optimizing them to return to hemodialysis after recovery from ICU condition.

Sedation in ICU

Notwithstanding the fact that sedation, pain control and muscle relaxation are integral elements of intensive care to enhance patient comfort and compliance, caution needs to be exercised in liberal use of the same.

Muscle relaxants should be used with great care in the ICU. It is easy to produce immobility in presence of awareness and pain. If they are used, a peripheral nerve stimulator should be utilized to assess the degree of paralysis.

For pain management, continuous opiod infusion comprises the standard of care, but one needs to be wary of patients with renal dysfunction and renal failure.

Sedation drugs range from benzodiazepines (midazolam, lorazepam), anesthetics (propofol, ketamine) and central alpha2 agonists (dexmetedomidine, clonidine). Intermittent sedation pauses come of high recommendation. No sedation mode has been shown to be superior to others, but some (dexmetedomidine) are aggressively marketed irrespective.

One is expected to titrate sedation throughout as per the Richmond Agitation Sedation Scale (RASS). The scale is as tabulated below:






Overtly combative or violent; immediate danger to staff


Very agitated

Pulls on or removes tube(s) or catheter(s); is aggressive



Frequent nonpurposeful movement, fights ventilator



Anxious but movements not aggressive or vigorous


Alert and calm

Heeds to the caregiver



Not fully alert, but has sustained awakening (eye-opening/eye contact) to voice(more than 10 seconds)


Light sedation

Briefly awakens with eye contact to voice (less than 10 seconds)


Moderate sedation

Movement or eye opening to voice (but no eye contact)


Deep sedation

No response to voice, but any movement or eye opening to physical stimulation



No response to voice or physical stimulation

Nutrition in ICU

Intensive care nutrition is an exhausting, huge, complex and controversial topic.

When possible, nutrition is given enterally (through the gut). It can be delivered through a gastric tube or an enteral tube passed into the duodenum or upper jejunum. Evidence supports improved outcomes in critically ill patients with early enteral nutrition.

Parenteral mode of nutrition administration is an alternative. Nutrients can be administered by central line directly into the circulatory system. It is complex, expensive and often complicated by infection and inadequate calorie delivery.

Brain Death

Each country has its own legal criteria for neurological determination of death (NDD).

Minimum criteria for NDD in Canada are as follows:

  • Establishment of etiology capable of causing neurological death in the absence of reversible conditions capable of mimicking neurological death is essential.
  • Presence of deep unresponsive coma with bilateral absence of motor responses, excluding spinal reflexes needs to be ascertained.
  • Absent brainstem reflexes as defined by absent gag and cough reflexes and the bilateral absence of corneal responses
    • Papillary responses to light, with pupils mid-size or greater
    • Vestibule-ocular responses
    • Absent respiratory effort based on the apnea test
  • Absent confounding factors: excluding the following confounding factors is critical as they preclude the clinical diagnosis:
    • Deep sedation
    • Unresuscitated shock
    • Hypothermia (core temperature less than 34 degrees Celsius; a patient has to be essentially normothermic before being declared brain dead)
    • Severe metabolic disorders capable of causing a potentially reversible coma
    • Peripheral nerve or muscle dysfunction or neuromuscular blockade potentially accounting for unresponsiveness.
    • Clinically significant drug intoxications (e.g. alcohol, barbiturates, sedatives and hypnotics); however, therapeutic levels or therapeutic dosing of anticonvulsants, sedatives and analgesics do not preclude the diagnosis.


ICU is the unnerving region of the hospital where the sickest patients of the hospital are cared for. There are different types of ICU each designed to serve a particular subset of patients in a customized manner.

The prominent ICU employees are the physician-intensivist, nurse, physiotherapist, dietician and social worker.

Each personnel are assigned specific duties and responsibilities, simultaneous fulfillment of which optimizes ICU care.

Some of the special devices found only in the ICU are continuous renal replacement therapy, left ventricular assist device, ventilator and myriad other monitors and analyzers.

SIRS represents generalized non-specific response of the body to infection, inflammation, ischemia or trauma. Timely intervention is critical to evade progression to MODS.

Sedation use in ICU has equivocal evidence. Intermittent sedation as per RASS is recommended.

Brain death determination has a pivotal role in transplant medicine. Every country has its own protocol. It is necessary to objectively conduct few tests to ascertain brain death while ruling out circumstances which closely mimic brain death.

Review Questions

The correct answers can be found below the references.

  1. Which of the following is not a feature of modern ICU?
    1. In-house CT scan in the ICU
    2. Continuous renal replacement therapy in ICU
    3. Left ventricular assist device in ICU
    4. Mechanical ventilation in ICU
  2. Which of the following is not a defining criterion of SIRS?
    1. WBC count > 12,000
    2. WBC count < 4,000
    3. Altered sensorium with hypotension
    4. Temperature > 38 degree Celsius
  3. Which of the following condition closely mimics brain death?
    1. Traumatic extradural hemorrhage
    2. Severe hypothermia
    3. Diabetic ketoacidosis
    4. Hepatic encephalopathy

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