What is the management of anaphylaxis in pregnancy?

Management of Anaphylaxis in Pregnancy

Anaphylaxis in pregnancy should be managed with the same aggressive treatment principles as in non-pregnant patients, with immediate intramuscular epinephrine as first-line therapy, aggressive fluid resuscitation, and left uterine displacement to prevent aortocaval compression. 1

Immediate Management

Epinephrine Administration

• Administer epinephrine 1:1000 (1 mg/mL) at 0.5 mg (0.01 mg/kg) intramuscularly into the mid-outer thigh (vastus lateralis) immediately 1, 2
• Repeat every 5 minutes as necessary to control symptoms and blood pressure 1
• There is no absolute contraindication to epinephrine in pregnancy—the benefits to both mother and fetus far outweigh theoretical risks 3, 2
• The FDA classifies epinephrine as Pregnancy Category C, but it remains the drug of choice for anaphylaxis during pregnancy 3

Critical Positioning

• Position the parturient with left uterine displacement to avoid aortocaval compression—this is essential and unique to pregnant patients 1
• Place patient in recumbent position with lower extremities elevated 1, 4

Fluid Resuscitation

• Administer crystalloid fluids (normal saline) at 20 mL/kg as rapid bolus, repeated as needed 1
• Large volumes may be necessary—up to 30 mL/kg in the first hour 1
• For persistent hypotension, consider colloid-containing solutions 1

Airway and Oxygen

• Assess and maintain airway patency (endotracheal intubation or cricothyrotomy may be required) 1, 4
• Administer oxygen at 6-8 L/min 1, 4
• Establish venous access immediately 1, 4

Graded Response Based on Severity

Grade II Reactions (Moderate)

• Epinephrine 20 mcg IV bolus initially 1
• If inadequate response at 2 minutes, escalate to 50 mcg 1
• 500 mL crystalloid rapid bolus, repeat as needed 1

Grade III Reactions (Severe)

• Epinephrine 50 mcg IV bolus, or 100 mcg if inadequate response to other vasopressors 1
• 1 L crystalloid rapid bolus 1
• If inadequate response at 2 minutes, escalate to 200 mcg 1
• Repeat fluid boluses up to 30 mL/kg 1

Grade IV Reactions (Cardiac Arrest)

• Epinephrine 1 mg IV, repeat per advanced life support guidelines 1
• Consider extracorporeal membrane oxygenation (ECMO) if systolic BP <50 mmHg or end-tidal CO2 <3 kPa 1

Obstetric Considerations

Emergency Delivery Decisions

• Consider emergent cesarean section early if there is persistent hypotension despite aggressive resuscitation 1
• Perimortem cesarean delivery should be initiated if persistent hypotension after 4 minutes of cardiac arrest 1
• Delivery of the fetus should be performed 1 minute later (at 5 minutes) if usual resuscitation measures have not achieved return of spontaneous circulation 1
• This improves outcomes for both mother (relieves aortocaval compression, improving resuscitation effectiveness) and neonate 1, 5

Second-Line Adjunctive Therapies

Antihistamines (Second-Line Only)

• Diphenhydramine 25-50 mg IV or 1-2 mg/kg parenterally 4
• Consider ranitidine 50 mg IV (1 mg/kg) diluted and administered over 5 minutes 4
• Never use antihistamines as first-line therapy or alone—they are adjuncts only 4

Bronchodilators

• Nebulized albuterol 2.5-5 mg in 3 mL saline if bronchospasm persists despite epinephrine 4

Corticosteroids

• Consider systemic glucocorticosteroids for patients with asthma or severe/prolonged anaphylaxis 1, 4
• Methylprednisolone 1.0-2.0 mg/kg/day IV every 6 hours, or oral prednisone 0.5 mg/kg for less critical episodes 4
• Corticosteroids are not helpful acutely but may prevent biphasic or protracted reactions 4

Refractory Hypotension

• If hypotension persists despite epinephrine and fluids, consider vasopressors such as dopamine 2-20 mcg/kg/min 4
• Glucagon 1-5 mg IV (20-30 mcg/kg in children, max 1 mg) over 5 minutes followed by infusion (5-15 mcg/min) if patient is on beta-blockers 1, 4

Common Triggers in Pregnancy

• Beta-lactam antibiotics (58% of cases), latex (25%), and anesthetic agents (17%) are the most common causes during cesarean section 6
• 49-74% of anaphylaxis cases in pregnancy occur during cesarean section 6
• Neuromuscular blocking agents are also commonly implicated 1

Critical Pitfalls to Avoid

• Delaying epinephrine administration is the most common and dangerous error—epinephrine must be given immediately 4, 2
• Failing to position patient with left uterine displacement worsens both maternal hypotension and fetal compromise 1
• Using antihistamines or corticosteroids as first-line treatment instead of epinephrine 4
• Inadequate fluid resuscitation—pregnant patients may require very large volumes 1
• Failing to consider early cesarean delivery in severe cases with persistent hypotension 1, 5
• Withholding epinephrine due to pregnancy concerns—prompt maternal resuscitation is essential for good outcomes for both mother and fetus 1, 3

Post-Acute Management

• Observe in monitored area for minimum 6 hours from onset of reaction 1
• Most patients with Grade III-IV reactions require ICU admission 1
• Prescribe epinephrine auto-injector and provide education on self-administration 1, 4
• Refer to allergist-immunologist for comprehensive evaluation and allergy testing to identify specific trigger 1, 4, 6
• Advise patient to wear medical identification (Medic Alert jewelry) 1, 4

Special Considerations

• Anaphylaxis-induced hyperfibrinolysis can occur and may exacerbate postpartum hemorrhage—monitor coagulation parameters 7
• Concomitant beta-blocker therapy increases risk of severe reactions and may require glucagon 1, 4
• The frequency of anaphylaxis during pregnancy is estimated at 1.5-3.8 per 100,000 pregnancies 6
• With appropriate and timely management, even severe anaphylaxis can result in excellent maternal and fetal outcomes 2, 5