Anesthesia as a science has massively evolved from ether machines to sophisticated dedicated subspecialty branches, the progress of which equally parallels the booming advancement in corollary fields of surgery. This article encompasses discussion on thoracic anesthesia, endobronchial tube positioning, complications and other issues, cardiac anesthesia and neuroanesthesia.

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bronchoscopy

Image: “Bronchoscopy.” by Unknown photographer – This image was released by the National Cancer Institute, an agency part of the National Institutes of Health, with the ID 1951. License: Public Domain


Thoracic Anesthesia

Thoracic anesthesia is one of the most complex anesthetic subspecialty evolved till date.

Progress in lung isolation techniques, ventilation management and pain control strategies have collectively culminated in improved patient outcome. Airway management is continually improving as more sophisticated technological advances and devices forming a part of our armamentarium make lung isolation, easy surgical access, better intra-operative visibility and optimal access to the operative field feasible.

One-lung anesthesia

Patients requiring thoracic surgery often require isolation of the operative lung during the surgery. Only one lung is ventilated and it is vital that this lung is able to provide oxygenation and ventilation adequate to support life.

Management of one lung anesthesia is one of the most difficult skills required by anesthesiologists.

Positioning of the endobronchial tube

The right main stem bronchus is shorter than the left and the distal cuff of a right endobronchial tube must be placed so ventilation occurs to the RUL (right upper lobe). It is essential that both these tubes pass too deeply into the bronchus; in both cases, the upper bronchus is either obstructed or bypassed.

While the tube to the left lung ventilates the left lower lobe, the tube to the right lung ventilates only the RUL and the middle lobe. Presence of leak that prevents positive pressure ventilation may be lethal.

The anesthesiologist must be an expert at using a fiber-optic bronchoscope to position the tube.

Bronchial blocker

Endobronchial blocker use to achieve one-lung ventilation is another alternative. A standard endotracheal tube is placed in the trachea and a blocker is passed by it into the left main stem bronchus. The right lung can be ventilated but the left lung can be ventilated only when the blocker is removed.

Again, the use of a fiber-optic bronchoscope is essential for positioning of the blocker.

Complications and other issues

Any subspecialty is inevitably accompanied by its fair share of complications and controversies. Thoracic anesthesia is no exception. The potential problems can be tabulated as follows:

Complications

Explanation

Dislodgement of the endobronchial tube or blocker

Common complication, aggressive use of bronchoscope to reposition is the key

Hypoxemia (low oxygen in the blood)

It can be minimized by correct tube placement and the addition of PEEP to the non-operated lung and CPAP to the operated lung.

Massive hemorrhage

Blood can contaminate the ventilated lung impairing gas exchange.

Post-operative ALI

Potentially lethal complication

Post-operative pain management

Post-operative pain is the worst of its genre in thoracic surgery patients. Consequently, they tend to splint their chests during respiration leading to decreased air entry in the lungs and higher chances of collapse, atelectasis and infection. The placement of a thoracic epidural for pain relief allows patients to be comfortable, ambulate early and deep breath and cough when necessary.

Cardiac Anesthesia

Cardiac anesthesia with the cardiopulmonary bypass at its heart sets a unique challenge to the anesthetist to perform his basic duty; ensure analgesia, amnesia and adequate muscle relaxation.

heart-lung bypass

Image: “The image shows how a heart-lung bypass machine works during surgery.” by National Heart Lung and Blood Institute (NIH). License: Public Domain

Cardio-pulmonary bypass (CPB)

The cardio-pulmonary bypass machine is a testimony to progress of medical science. However a boon it might be, its use is burdened with complications. CPB results in pharmacodynamic and pathophysiologic changes that perturb the usual homeostasis of the body. These changes equally affect the serum concentrations, metabolism and subsequent action of IV fluids, anesthetic drugs and volatile agents, making CPB a tantalizing challenge.

The cardio-pulmonary bypass machine allows the patient’s blood to bypass the heart and lungs during surgery but be pumped back into the patient to assure perfusion to other organs. The heart is at a standstill during bypass allowing the surgeon to work on a stable target. Some surgeons prefer to operate on a beating heart for certain procedures.

The anesthesiologist is usually responsible for maintaining the patient during CPB. Coming off bypass (a critical period in the surgery) is managed by the anesthesiologist.

Left ventricular assist device (LVAD)

The concept of “destination therapy”, permanent use of a LVAD as treatment modality for advanced heart failure and “ bridge” therapy as a transit to heart transplant has ushered specific expectations from the anesthesiologists. The significant issues are summarized as follows:

Issue

Explanation

Induction of LVAD flow

May unveil right ventricular dysfunction demanding aggressive management, sometimes to the extent that a RVAD might be indicated

Recirculation forced by aortic insufficiency

Acutely remonstrate the flow capacity of the LVAD and also reduce its potential functional life

Systemic ‘‘vasoparesis”

May necessitate the administration of a-adrenergic agonists, vasopressin, or methylene blue to endorse optimum systemic arterial pressures

Compound coagulation disturbances with subsequent re-exploration for bleeding

Not infrequent in the early postoperative period

Valves

Valve replacement procedures have stood the test of time and are generally safe, less morbid, and standardized. Any superiority of a particular genre of valve is equivocal. Post-operative management depends on the valve type used. The important differences can be summarized as follows:

Valve type

Benefits

Risks

Metal valves

Longevity: last around 20 years

Lifelong anticoagulation is needed, to prevent strokes and embolic phenomena

Tissue valves

Short lifespan: last about 10 years

Anticoagulation is not needed.

Technological advances in the field of valve surgery have yielded genesis of an indigenous percutaneous device – the MitraClip, which potentially ameliorates mitral regurgitation by transatrial septal placement of a ‘‘double alligator’’ clip. Intra-operative, three-dimensional trans-esophageal echocardiography (TEE) has great advantage in apt placement of the MitraClip.

Anesthesia responsibilities

The need for near-continuous TEE combined with the anticipated duration of the procedure favors general endotracheal anesthesia.

Cardiac anesthesia exists to ensure absence of bradycardia, vasoconstriction, optimum fluid management and observant monitoring.

Short acting, potent, inhalational anesthetics are preferred; neuromuscular blockers are not called for. Need for inotropic agents frequently arises prior to bypass and coming off bypass.

When reversed from bypass, unstable vital parameters often demand intensive care unit transfer. These patients are usually ventilated electively and transferred to floor only once stable.

Complications

Cardiac surgeries and CPB used to be a very morbid affair in the not too distant past. Advances in technological know-how and better optimization of heart while on CPB have dramatically changed the picture. The significant complications are as tabulated below:

Complication

Explanation

Failure to come off bypass

This is now relatively rare but used to cause many deaths.

Heart failure coming off bypass

May require LVAD or RVAD

Massive hemorrhage both from use of anticoagulants and the actions of the CPB device

Nearly lethal

Cardiac arrhythmias, particularly atrial fibrillation

Early detection followed by aggressive rapid reversal is critical.

Cardiac tamponade

Potentially life threatening, immediate correction of utmost essence; usually requires the transport of an unstable patient back to the OR.

Pain from sternal movement post-operatively

Occasionally severe; requires treatment

Recall during anesthesia

Much less frequent during modern anesthesia though; the use of high doses of opioids for this surgery must be accompanied by amnestic drugs.

Cardiac arrest in the OR or the CSICU

The chest should be opened and open cardiac massage employed; external cardiac massage on an unstable chest wall is ineffective.

Heart block

Requires the insertion of a pacemaker.

Neuro-Anesthesia

Most neurosurgical procedures require general anesthesia but few can be done with deep sedation.

The most critical aspect of neuro-anesthesia is control of intra-cranial pressure (ICP).

If ICP is lowered too aggressively, cerebral blood flow can be reduced and ischemic brain damage can occur.

Drug

Effect on cerebral blood flow

ICP

Vapors

Increase

Increase

Propofol

Decrease

Decrease

Ketamine

Increase

Increase

Etomidate

Little effect

Decrease

Narcotics

Little effect

Little effect

There are alternative measures available to reduce ICP such as having the patient hyperventilate before induction and then provide mild hyperventilation once intubated.

Osmotic diuretics (mannitol) and loop diuretics (furosemide) reduce water load of the brain and can be utilized as cerebral decongestants.

Role of local anesthesia and sedation in neuro-anesthesia

deep brain stimulation parkinson's disease

Image: “Deep brain stimulation in a Parkinson’s patient.” by Hellerhoff – Own work. License: CC BY-SA 3.0

Burr holes to relieve bleeding have been done for centuries without anesthesia and are now often done with local anesthesia.

More modern procedures (e.g. deep brain stimulation for patients with Parkinson’s disease) can be done with virtually nothing except local anesthesia and a little sedation. The surgeon inserts probes deep into the brain and stimulates ganglia associated with Parkinson’s disease.

Complications of neuroanesthesia

Neuroanesthesia is an unforgiving branch. One needs to maintain the critical equation between intracranial pressure and cerebral perfusion. Complications are as follows:

Complication

Explanation

Massive hemorrhage

Very difficult to treat

Cerebrovascular accidents (strokes)

Often lead to permanent morbidity

Failure to awaken from anesthesia

A thorough search for surgical cause and/or a disease cause and/or anesthetic cause must be sought.

Increased ICP

Permanent damage to the brain

Neuroanesthesia has specific problems to deal with, which calls in for customized management. The important, relevant clinical scenarios are discussed as below:

Issue

Explanation

Airway management in acromegalic patients

Acromegaly is characterized by macroglossia, prognathism, and hypertrophy of pharyngeal and laryngeal tissues, which lead to mask fit, mask ventilation, laryngoscopy, and correct tracheal tube placement difficult. Mallampati classification is used for objective assessment and further management.

Neuroendoscopic procedures

Cardiac arrhythmia, hemodynamic changes, cranial nerve dysfunction and intracranial hemorrhage are the anesthetic concerns.

Sitting position

Strongly fallen out of favor in many places; cerebral hypoperfusion, pneumocephalus, venous air embolism with hypotension are potential issues.

Intracranial lesions located around the eloquent areas

Fascinating and equally challenging; “awake craniotomy” is often used in these patients.

Pain management

Brain lacks pain receptors, but the rich innervation of the skin, periosteum of the skull, and the meninges demolishes the old belief that minimal pain management is required in intracranial surgeries.

Summary

Anesthesia has outgrown its conventional form to encompass various specialties which demonstrate parallel development and progress as their surgical counterparts.

One of the most complex branches, thoracic anesthesia, involves one-lung ventilation, use of endobronchial tubes and blockers and pain management.

Cardiac anesthesia revolves around preservation of heart during use of CPB machine. Recall during cardiac surgeries is the modern cardiac anesthesiologist’s nightmare.

Neuroanesthesia is as unforgiving and subtle as neurosurgery. The issues are specific and demand customized management.

All these specialized sects of anesthesia abound with complications but one needs to exercise constant vigilance and aggressive management to ultimately bring about effective patient care.

Review Questions on Anesthesia for Special Operations

The correct answers can be found below the references.

  1. Which of the following is true regarding management of dislodged endobronchial tube?
    1. Remove the tube immediately to avoid atelectasis.
    2. Remove the tube immediately to avoid hyperinflation.
    3. Use of bronchoscope solves the problem.
    4. Do not do anything as it is not sigificant.
  2. Recall after cardiac surgery can be prevented by use of what?
    1. Potent amnestic agents
    2. Opioids
    3. Adequate liquids preoperatively
    4. Neuromuscular blockers
  3. Which classification is used in acromegalic patients to assess the airway?
    1. Wilson classification
    2. Murthy classification
    3. Acromegaly assessment protocol
    4. Mallampati classification
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