What is the management of delayed post-anesthetic reactions?

Management of Delayed Post-Anesthetic Reactions

The management of delayed post-anesthetic reactions requires prompt recognition and treatment following the ABCDE approach, with adrenaline administration as the cornerstone of therapy for anaphylactic reactions that can occur up to an hour after exposure to certain anesthetic agents. 1

Recognition of Delayed Reactions

Delayed post-anesthetic reactions typically present within minutes to an hour after exposure to certain substances, including:

• Latex
• Antibiotics
• Intravenous colloids
• Cidex OPA (used to disinfect surgical instruments) 1

Clinical Features to Monitor For:

• Cardiovascular signs: Hypotension, cardiovascular collapse, bradycardia, cardiac arrest (occurs in 74.7% of allergic anaphylaxis cases)
• Respiratory signs: Bronchospasm (39.8% of allergic anaphylaxis cases)
• Cutaneous signs: Widespread flushing, urticaria, angioedema (71.9% of allergic anaphylaxis cases) 1

Important: The absence of cutaneous signs does not exclude anaphylaxis.

Management Algorithm

Immediate Management

1. Airway, Breathing, Circulation (ABC) approach

   • Team-working enables several tasks to be accomplished simultaneously

2. Remove all potential causative agents

   • Discontinue IV colloids, latex, chlorhexidine
   • Maintain anesthesia with inhalational agent if necessary

3. Call for help and note the time

4. Secure airway and administer oxygen

   • Provide 100% oxygen
   • Intubate if necessary and ventilate with oxygen

5. Position the patient

   • Elevate legs if hypotension is present

6. Begin CPR if appropriate

   • Follow Advanced Life Support Guidelines

7. Administer adrenaline intravenously

   • Adult dose: 50 μg IV (0.5 ml of 1:10,000 solution)
   • May require several doses for severe hypotension or bronchospasm
   • Consider adrenaline infusion if multiple doses needed 1, 2

8. Administer IV fluids

   • Saline 0.9% or lactated Ringer's solution at a high rate
   • Use appropriate gauge IV cannula (large volumes may be required) 1

Secondary Management

1. Administer antihistamine

   • Chlorphenamine 10 mg IV (adult dose) 1

2. Administer corticosteroid

   • Hydrocortisone 200 mg IV (adult dose) 1

3. Consider alternative vasopressors

   • If blood pressure doesn't recover despite adrenaline infusion
   • Options include metaraminol based on clinician experience 1

4. Treat persistent bronchospasm

   • IV salbutamol infusion
   • Consider metered-dose inhaler if appropriate connector available
   • Consider IV aminophylline or magnesium sulfate 1

5. Arrange transfer to Critical Care

6. Take blood samples for Mast Cell Tryptase

   • Initial sample as soon as feasible after resuscitation starts
   • Second sample at 1-2 hours after symptom onset
   • Third sample at 24 hours or during follow-up 1

Adrenaline Infusion Protocol

If multiple doses of adrenaline are required, consider starting an infusion:

• Standard concentration: 1:100,000 (1 mg in 100 mL saline)
• Initial rate: 5-15 μg/min
• Alternative preparation: 1:250,000 (1 mg in 250 mL D5W) at 1-4 μg/min
• Dosing range: 0.05-2 μg/kg/min
• Titration: Adjust every 10-15 minutes in increments of 0.05-0.2 μg/kg/min 2

Monitoring During Infusion

• Frequent blood pressure measurements (every 1-5 minutes during initiation)
• Continuous pulse oximetry
• Clinical assessment for signs of adequate perfusion
• Watch for signs of adrenaline toxicity (tachyarrhythmias, hypertension, myocardial ischemia, tremor) 2

Pediatric Dosing

Adrenaline (IM)

• 12 years: 500 μg (0.5 ml of 1:1000 solution)

• 6-12 years: 300 μg (0.3 ml of 1:1000 solution)
• <6 years: 150 μg (0.15 ml of 1:1000 solution) 1

Hydrocortisone (IV/IM)

• 12 years: 200 mg

• 6-12 years: 100 mg
• 6 months-6 years: 50 mg
• <6 months: 25 mg 1

Chlorphenamine (IV/IM)

• 12 years: 10 mg

• 6-12 years: 5 mg
• 6 months-6 years: 2.5 mg
• <6 months: 250 μg/kg 1

Common Pitfalls and Caveats

1. Delayed recognition: Reactions can occur up to an hour after exposure, particularly with latex, antibiotics, and IV colloids 1

2. Underestimating severity: Absence of cutaneous signs doesn't exclude anaphylaxis

3. Inadequate monitoring: Post-anesthetic patients require systematic ABCDE assessment and monitoring of vital signs 3

4. Insufficient fluid resuscitation: Ensure adequate volume status with crystalloids at 5-10 mL/kg before considering vasopressors 2

5. Failure to collect tryptase samples: These are crucial for confirming the diagnosis

6. Overlooking alternative diagnoses: Consider other causes of post-anesthetic complications such as residual anesthetic effects, respiratory depression, or metabolic disturbances 4

7. Inadequate follow-up: All patients with suspected anaphylactic reactions should be referred for further investigation to identify the causative agent