Adverse Anesthetic Events
This document provides a structured overview of various adverse events that can occur during anesthesia,
including their risk factors, identification, and management strategies. It covers a range of topics from
common issues like laryngospasm to critical conditions like malignant hyperthermia.

Laryngospasm
What are the risk factors for laryngospasm?
Laryngospasm can be triggered by several factors, which are categorized as anesthetic-related,
patient-related, and surgical-related.

Anesthetic-related factors include:
  • Insufficient depth of anesthesia.
  • Irritation during tracheal extubation.
  • Use of irritant anesthetic agents (desflurane is most irritant; halogen and sevoflurane are least).
  • Presence of mucus or blood in the airway.
  • Manipulation with a suction catheter or during laryngoscopy.
  • Use of thiopentone (propofol is less likely to cause laryngospasm).
Patient-related factors include:
  • Recent upper respiratory tract infection (surgery should be delayed for at least four weeks).
  • Airway hyper-reactivity (e.g., in patients with active asthma).
  • Tobacco smoke (abstinence for two days reduces risk).
  • Conditions like obstructive sleep apnea, gastroesophageal reflux, and airway abnormalities (e.g., tracheal stenosis, Pierre Robin syndrome, Parkinson's disease).
Surgical-related factors include:
  • Shared airway procedures like tonsillectomy and adenoidectomy.
  • Thyroid surgery (due to risk of superior laryngeal nerve injury or hypocalcemia).
  • Esophageal surgery (stimulation of distal afferent nerves).
  • Procedures like appendectomy, cervical dilation, hypospadias repair, skin grafting, and dilation of the anus or cervix.
How does laryngospasm present and what is the immediate management?
The presentation can include simple airway obstruction, inspiratory stridor, increased respiratory effort,
paradoxical respiratory movements, and regurgitation or vomiting.

Immediate management steps:
  1. Discontinue nitrous oxide and administer 100% oxygen.
  2. Remove the precipitating stimulus and any irritants from the airway.
  3. Deepen the anesthetic.
  4. Consider performing Larson's maneuver while maintaining 100% oxygen and CPAP.
  5. If occurring at induction, deepen anesthesia with further propofol (0.5 mg/kg) or increase volatile agent. Note that partial obstruction can slow volatile anesthetic uptake.
  6. If laryngospasm fails to improve, administer succinylcholine (0.25 to 0.5 mg/kg) IV, sublingually, or intramuscularly if IV access is not available.

Hazards of Blood Transfusion
What are the specific hazards of blood transfusion and how can their incidence be reduced?
Specific hazards include TACO (transfusion-associated circulatory overload), TRALI (transfusion-related acute lung injury),
hemolytic reactions (immediate and delayed), non-hemolytic reactions (febrile and allergic), post-transfusion purpura,
graft-versus-host disease, and iron overload.

Preventive strategies for each hazard:
  • TACO: Careful pre-transfusion assessment for heart failure, calculation of appropriate dose (especially in children), and monitoring of heart rate, respiratory rate, blood pressure, and saturation during and after transfusion.
  • TRALI: Use universal leukodepletion and exclusive use of male donors for FFP and plasma for platelets.
  • Hemolytic reactions: Implement robust transfusion education, training, policies, and standard operating procedures to prevent mismatched transfusions.
  • Acute non-hemolytic reactions (febrile/allergic): Universal leukodepletion reduces febrile reactions. Use of solvent-detergent treated FFP may reduce allergic reactions.
  • Post-transfusion purpura and Graft-versus-host disease: Universal leukodepletion and gamma irradiation of blood products.
  • Bacterial and viral infection: Thorough disinfection of the donor arm and discarding the initial flow of blood. Universal leukodepletion also reduces risk of viral transmission (e.g., CMV).
What is the general treatment approach for a hemolytic transfusion reaction?
Treatment involves immediate steps to support the patient and investigate the reaction.
  1. Stop the transfusion and maintain IV access with crystalloid infusion.
  2. Provide cardiorespiratory support, including inotropes if necessary.
  3. Return the blood unit to the blood bank for investigation.
  4. Seek hematological support.
  5. Take blood samples from the recipient for full blood count, clotting screen, Coombs test, and repeat cross-match.
  6. Maintain urine output >100 mL/hour.
  7. Send urine samples for hemoglobin and urea analysis.
  8. Treat disseminated intravascular coagulation (DIC) with appropriate clotting products.

Anaphylaxis
What are the common triggers and key steps in managing anaphylaxis during anesthesia?
Common triggers include neuromuscular blocking agents (suxamethonium), NSAIDs, beta-lactam antibiotics,
latex, radio-contrast dyes, and chlorhexidine.

Management follows the ABC approach:
  1. Airway: Maintain airway and administer 100% oxygen.
  2. Breathing: Consider bronchodilators for bronchospasm. Intubate to protect the airway if necessary.
  3. Circulation: Administer adrenaline (epinephrine) as the first-line treatment. Consider antihistamines and corticosteroids. Start a catecholamine infusion if required.
  4. Check arterial blood gases for acidosis and give bicarbonate when necessary.
Follow-up is crucial and includes referral to an anesthetic allergy clinic for skin testing,
mast cell tryptase evaluation, and testing for antigen-specific IgE antibodies. The patient should be
given a detailed record of the drugs and advised to wear a medical alert bracelet.

Latex Allergy
Which patient populations are at high risk for latex allergy?
High-risk populations include:
  • Patients with neural tube defects (e.g., spina bifida) due to recurrent bladder catheterization (sensitivity up to 20-25%).
  • Individuals with atopy, such as asthma, rhinitis, or severe dermatitis.
  • People with occupational exposure, including those in the rubber industry and healthcare workers.
  • Patients with fruit allergens due to cross-reactivity with bananas, chestnuts, avocado, and kiwi fruit.
What perioperative precautions are necessary for a patient with a known latex allergy?
Precautions should be taken before, during, and after the procedure:
  • Pre-operative: Alert all team members. Schedule the patient first on the list. Prepare the operating theater the night before and place latex allergy notices on the anesthetic and theater doors.
  • Intra-operative: Use only latex-free equipment (breathing circuits, airways, CVP lines, ECG leads, blood pressure cuffs). Remove non-essential equipment and limit staff traffic. Ensure resuscitation equipment is latex-free. Some hospitals wash down theater walls and surfaces to minimize airborne latex particles.
  • Medication: Be aware of drugs that are available in latex-free stoppers.

Malignant Hyperthermia
What are the triggering agents and immediate steps to manage a malignant hyperthermia crisis?
The primary trigger agents are succinylcholine and volatile anesthetics (e.g., halothane, sevoflurane, desflurane).

Immediate management steps:
  1. Stop all volatile anesthetics and remove the vaporizer.
  2. Increase oxygen delivery to 100% at high flow rates (e.g., 50 L/min) to eliminate triggering agents and CO2. Use activated charcoal filters if available, otherwise hyperventilate.
  3. Change the breathing circuit and soda lime as it may get exhausted quickly.
  4. Maintain anesthesia with intravenous agents.
  5. Administer dantrolene, the mainstay of treatment.
  6. Institute active cooling measures for hyperthermia.
  7. Establish invasive monitoring (arterial and central venous lines).
  8. Treat complications: hyperkalemia (insulin/dextrose, calcium chloride), acidosis (sodium bicarbonate), arrhythmias (amiodarone, beta-blockers), and acute kidney injury (crystalloids, furosemide, urine alkalinization).
  9. Treat DIC supportively.
  10. Refer the patient to a malignant hyperthermia clinic for muscle biopsy and caffeine testing.
What are the clinical signs of malignant hyperthermia?
Signs appear in a sequence:
  • Early signs: Tachycardia and tachypnea.
  • Intermediate sign: Rising core body temperature.
  • Late sign: Myoglobinuria (from rhabdomyolysis).

Extravasation and Intra-arterial Injection
What types of drugs can cause damage with extravasation or intra-arterial injection?
Drugs cause damage through different mechanisms:
  • Vasoconstriction and ischemic necrosis: Epinephrine, dobutamine.
  • Direct toxicity or osmotic damage: Hyperosmolar drugs.
  • Acid or alkali effects: Aminophylline, amiodarone.
  • Extrinsic mechanical compression: Large volumes of fluid.
What are the general principles for managing accidental extravasation or intra-arterial injection?
The basic principles are to stop injection, dilute the irritant, reverse vasospasm, and prevent thrombosis.

Specific steps:
  1. Stop the injection and disconnect the infusion.
  2. Aspirate as much drug as possible from the cannula, but leave the cannula in place for further treatment.
  3. Flush the vessel with isotonic saline.
  4. Administer a local anesthetic (e.g., 1% lidocaine) to reduce vasospasm and pain.
  5. Administer a vasodilator (e.g., phentolamine).
  6. Consider sympathetic blockade (e.g., stellate ganglion block) or heparinization to minimize the risk of late thrombosis.

Aspiration
What are the risk factors for pulmonary aspiration during anesthesia?
Risk factors can be patient-related, surgical, or anesthetic.

Patient-related factors:
  • Full stomach (emergency surgery, GI obstruction).
  • Delayed gastric emptying (diabetes, chronic kidney disease, recent trauma, opioids, raised ICP, pregnancy).
  • Incompetent lower esophageal sphincter (hiatus hernia, regurgitation, pregnancy).
  • Morbid obesity.
Surgical factors:
  • Upper abdominal surgery.
  • Lithotomy or head-down position.
Anesthetic factors:
  • Light anesthesia.
  • Use of first-generation supraglottic airway devices.
  • Positive pressure ventilation.
  • Surgery length >2 hours.
  • Difficult airway management.
What strategies are available to reduce the risk of aspiration?
Strategies target different aspects of the risk:
  • Reduce gastric volume: Pre-operative fasting, nasogastric aspiration, pro-kinetic drugs.
  • Avoid general anesthesia: Use a regional technique.
  • Increase gastric pH: Administer antacids, H2 antagonists, proton pump inhibitors.
  • Protect the airway: Tracheal intubation, use of second-generation supraglottic devices.
  • Prevent regurgitation: Apply cricoid pressure during rapid sequence induction.
  • Safe extubation: Extubate the patient awake with airway reflexes reversed, in an upright or lateral position.

General Principles of Management and Follow-up
What are the common themes in managing adverse anesthetic events?
Across all scenarios, remedial measures generally include three key components:
  1. Prevention: Identifying risk factors and taking steps to minimize the chance of the event occurring.
  2. Treatment: Immediate and appropriate management of the event when it does occur.
  3. Subsequent care and referral: Providing follow-up care and referring the patient to a specialized center (e.g., allergy clinic, malignant hyperthermia diagnostic center) for further investigation and long-term management.
What is the recommended approach for investigating a suspected perioperative allergic reaction?
The approach depends on the urgency of the surgery.

For a non-urgent, elective procedure:
  • Gather all relevant charts.
  • If an allergy is suspected or no information is available, postpone the surgery.
  • Refer the patient for allergy investigation and follow the advice from the allergy clinic.
For an emergency procedure:
  • Gather relevant charts and determine if an allergy is suspected. Identify all exposures before the reaction.
  • Avoid all identified allergens and use alternative drugs.
  • Consider using inhalational or regional techniques and use as few drugs as possible.
  • Avoid neuromuscular blocking agents, latex, disinfectants, penicillins, and cephalosporins.
  • Maintain a high degree of suspicion for early signs and symptoms of a reaction.