What is the immediate treatment for anaphylactic shock in a pediatric patient after administration of Cefaclor (Cephalosporin)?

Hypothetical Case Study: Anaphylactic Shock from Cefaclor in a 7-Year-Old Female

Patient Presentation

A 7-year-old female, weighing 25 kg, develops acute anaphylactic shock within 5 minutes of receiving oral Cefaclor 250 mg for suspected otitis media in the pediatric clinic.

• Initial symptoms: Facial flushing, perioral tingling, and complaints of throat tightness 1
• Rapid progression (2-3 minutes): Generalized urticaria, audible wheezing, severe respiratory distress with stridor, and altered mental status 1
• Vital signs at 5 minutes: Blood pressure 65/40 mmHg (shock), heart rate 145 bpm, respiratory rate 40/min with accessory muscle use, oxygen saturation 88% on room air 1
• Physical examination: Diffuse urticaria, angioedema of lips and tongue, bilateral wheezing, weak peripheral pulses, delayed capillary refill >3 seconds 1

Immediate Management (First 5 Minutes)

Intramuscular epinephrine is the immediate, life-saving intervention and must be administered without delay. 1

Primary Interventions

• Epinephrine 0.15 mg (0.15 mL of 1:1000) IM into the anterolateral thigh (vastus lateralis) - this is the correct pediatric dose for a child under 6-12 years 1
• Call for emergency medical services immediately - activate 911 and request advanced life support 1
• Position patient supine with legs elevated to improve venous return and cardiac preload 1
• Administer 100% oxygen at 6-8 L/min via non-rebreather mask 1
• Discontinue Cefaclor immediately - remove all potential causative agents 1

Airway Assessment (Critical Priority)

• Assess for rapidly progressive laryngeal edema - stridor, voice changes, and difficulty swallowing indicate impending airway obstruction 1
• Prepare for emergency airway management - given the potential for rapid oropharyngeal/laryngeal edema, immediate referral to personnel with advanced airway expertise is essential 1
• Consider early intubation if stridor worsens - waiting too long may make intubation impossible, potentially requiring emergency cricothyroidotomy 1

Secondary Management (5-15 Minutes)

Repeat Epinephrine Dosing

• Administer second dose of epinephrine 0.15 mg IM at 5 minutes if inadequate response - persistent hypotension, ongoing respiratory distress, or worsening symptoms 1
• Epinephrine can be repeated every 5 minutes as necessary - there is no absolute contraindication to epinephrine in anaphylaxis 1
• Between 7-18% of pediatric anaphylaxis cases require multiple epinephrine doses 1

Intravenous Access and Fluid Resuscitation

• Establish large-bore IV access (18-20 gauge in pediatric patient) 1
• Administer normal saline 0.9% rapid bolus 500 mL (20 mL/kg = 500 mL for 25 kg child) - repeat boluses as needed for persistent hypotension 1
• Large volume crystalloid resuscitation may be required - up to 20-30 mL/kg due to massive vasodilation and capillary leak 1

Consideration of IV Epinephrine (If Available)

• If IV access is established and patient remains in shock despite IM epinephrine, consider IV epinephrine 5-10 mcg bolus (0.05-0.1 mg) - this is 5-10% of the cardiac arrest dose 1
• IV epinephrine is appropriate when shock persists and IV access is available 1
• Alternatively, start epinephrine infusion at 0.05-0.1 mcg/kg/min if multiple boluses required 1

Refractory Management (After 10 Minutes of Inadequate Response)

Persistent Hypotension

• Escalate epinephrine dosing by doubling the bolus dose 1
• Consider epinephrine infusion 0.05-0.1 mcg/kg/min peripherally if more than three boluses administered 1
• Add vasopressin 1-2 IU bolus for refractory hypotension unresponsive to epinephrine 1

Persistent Bronchospasm

• Administer inhaled albuterol via nebulizer or metered-dose inhaler (if breathing system connector available) 1
• Consider IV salbutamol infusion for severe, persistent bronchospasm 1
• Consider IV magnesium sulfate or aminophylline as adjunctive bronchodilators 1

Adjunctive Medications (After Epinephrine and Fluids)

These are second-line agents and should never delay epinephrine administration. 1

• Diphenhydramine 1 mg/kg IV (maximum 50 mg) or chlorphenamine 0.2 mg/kg IV - H1-antihistamine after adequate epinephrine/fluid resuscitation 1
• Ranitidine 1 mg/kg IV or famotidine 0.25 mg/kg IV - H2-antihistamine (H1 and H2 work better together) 1
• Methylprednisolone 1-2 mg/kg IV or hydrocortisone 5 mg/kg IV - may prevent biphasic reactions, though evidence is limited 1

Diagnostic Testing

Mast Cell Tryptase

Obtain serial mast cell tryptase levels to confirm anaphylaxis diagnosis. 1

• First sample: As soon as feasible after resuscitation starts (do not delay treatment) 1
• Second sample: 1-2 hours after symptom onset 1
• Third sample: 24 hours later or at follow-up (baseline comparison) 1
• Label all samples with exact time and date 1

Observation and Disposition

• Observe in monitored setting for minimum 6 hours or until stable and symptoms regressing 1
• Admit to pediatric intensive care unit given severity of initial presentation with shock and respiratory compromise 1
• Risk of biphasic reactions is likely low (estimated 7-18%) but can occur outside typical observation periods 1, 2

Follow-Up Allergy Evaluation

Outpatient Allergy Referral (4-6 Weeks Post-Event)

• Skin testing to cephalosporins and penicillin reagents - IgE-mediated hypersensitivity is confirmed in approximately 79% of immediate cephalosporin reactions in children 3
• Specific IgE testing for cefaclor - though sensitivity is limited (30-60% for some cephalosporins), positive results confirm IgE-mediated mechanism 1, 3
• Cross-reactivity assessment - cephalosporins with disparate R1 side chains are generally tolerated, but those with similar R1 side chains (like aminopenicillins) may cross-react 4, 5

Patient Education and Prevention

• Prescribe epinephrine auto-injector (EpiPen Jr 0.15 mg) for immediate availability 1
• Provide anaphylaxis action plan with instructions to self-administer at first sign of reaction 1
• Medical alert bracelet documenting cephalosporin allergy 1
• Avoid all cephalosporins, particularly first and second generation given confirmed anaphylaxis 1
• Exercise caution with penicillins - cross-reactivity occurs, particularly with aminopenicillins sharing R1 side chains 4, 5

Critical Pitfalls to Avoid

• Never delay epinephrine administration - fatalities result from delayed epinephrine, not from epinephrine itself 1
• Never administer IV epinephrine injudiciously - several anaphylaxis fatalities attributed to inappropriate IV epinephrine use; use controlled boluses or infusions 1
• Never rely on antihistamines or corticosteroids as primary treatment - these are adjuncts only 1
• Never assume subcutaneous epinephrine is equivalent to IM - IM administration in the thigh produces higher, more rapid peak levels 1
• Never give test doses of antibiotics - this is ineffective for predicting anaphylaxis and wastes critical time 1

Outcome of This Case

Following the immediate administration of IM epinephrine, IV fluid resuscitation with 1000 mL normal saline, and a second dose of epinephrine at 7 minutes, the patient's blood pressure improved to 95/60 mmHg, wheezing decreased, and oxygen saturation increased to 96% on supplemental oxygen. She was intubated prophylactically due to persistent stridor and transferred to the PICU, where she was extubated 18 hours later. Mast cell tryptase levels were elevated at 45 mcg/L (normal <11.4), confirming anaphylaxis. She was discharged on hospital day 3 with an EpiPen Jr and allergy referral, with complete recovery and no long-term sequelae.