Anaphylaxis after intramuscular ceftriaxone in a rural clinic with one nurse
Rural outpatient clinic, 45 minutes from the district hospital. A 34-year-old man attends for his first dose of ceftriaxone 1 g IM for community-acquired pneumonia. Ten minutes after the gluteal injection he complains of itching of the scalp and a lump in his throat, and becomes hoarse. He is flushed, has urticaria on the neck and chest, blood pressure 82/48, pulse 132, SpO2 89% on room air. He takes metoprolol for hypertension. The clinic's emergency kit contains six ampoules of adrenaline 1 mg/mL, one ampoule of chloropyramine 20 mg/mL, prednisolone 30 mg/mL, 500 mL sodium chloride, a salbutamol inhaler and an oxygen concentrator with a nasal cannula. There is no autoinjector. The nurse on duty is alone with one nursing assistant; the doctor is on a home visit 20 minutes away.
1. Set out your immediate management, with drugs, doses and routes, in the order you would do it.
Read the worked answer
This is anaphylaxis with airway involvement (hoarseness, throat tightness) and hypotension. Adrenaline comes first; an antihistamine does not treat airway obstruction or shock.
- Stop the trigger and note the time of the injection.
- Adrenaline 0.5 mg IM - that is 0.5 mL of a 1 mg/mL ampoule, injected into the anterolateral thigh (vastus lateralis). No dilution is needed for the IM route. Repeat every 5 minutes if there is no improvement; several doses are commonly required, so one ampoule is not a course.
- Call the ambulance at the same time, not after the adrenaline has worked; tell them 'anaphylaxis, airway involvement'.
- Position supine with the legs raised. If breathing dominates, allow a position of comfort, but never let him stand or walk - sudden deterioration on standing is well described.
- Oxygen at 10–15 L/min by reservoir mask. A nasal cannula at 2 L will not correct an SpO2 of 89%, and the concentrator's flow limit must be checked.
- IV access and a rapid 500 mL sodium chloride bolus, repeated according to blood pressure.
- Monitor pulse, blood pressure, SpO2 and conscious level every 5 minutes; record the times of every dose.
- Chloropyramine and prednisolone are second-line: give them after adrenaline if at all. Steroids act over hours and prevent biphasic reactions, not the current one.
Reassess at 5 minutes: no better means a second 0.5 mg IM dose.
2. Why IM rather than IV adrenaline here, and how does his metoprolol change your thinking?
Read the worked answer
IM into the thigh is the route of choice: absorption is fast and reliable, and the arrhythmia risk is far lower than with IV. IV adrenaline is reserved for cardiac arrest or refractory shock, given as 1:10,000 (1 mg diluted to 10 mL) in 1 mL boluses by staff trained and equipped to monitor for it. Pushing an undiluted 1 mg/mL ampoule IV can be fatal. With one nurse, one assistant, no monitor and no doctor present, IV adrenaline is the more dangerous option, not the more aggressive and therefore better one.
The metoprolol matters. Beta-blockade can make anaphylaxis refractory to adrenaline, because adrenaline's beta effects are blocked while its alpha effects are unopposed - hypertension, bradycardia and bronchospasm can worsen. If the response to repeated IM adrenaline is poor, the doctor should consider glucagon 1–5 mg IV, which stimulates adenylate cyclase independently of beta receptors.
Also consider: chloropyramine may sedate and lower blood pressure further; the salbutamol inhaler helps persistent wheeze but not laryngeal oedema; and he must not be discharged simply because he says he feels better, since biphasic reactions occur in a few percent of cases.
3. What do you hand over, document and arrange after he stabilises?
Read the worked answer
Handover to the ambulance, written before departure rather than recalled at the hospital: the drug, dose, route and time of each adrenaline dose; the response after each one; blood pressure and SpO2 trend; fluids given; whether stridor or hoarseness persists.
Observation. At least 6–12 hours in a facility with monitoring, because biphasic reactions can occur hours after apparent recovery - especially in a patient who needed more than one dose or who was hypotensive.
Documentation and system duties:
- Complete the emergency record with times, doses and observations.
- Flag the allergy prominently in the outpatient card and the electronic record: ceftriaxone must never be given again, and related cephalosporins and penicillins need assessment before any future use.
- Submit the adverse drug reaction notification to the pharmacovigilance system - a reporting duty, not optional paperwork.
- Debrief the team: why the oxygen was set up with a nasal cannula, why there is no autoinjector, and what the resupply plan is for the six ampoules.
Teach the patient: he must carry the allergy information, say the word 'ceftriaxone' at every encounter, and know that a throat lump or hoarseness after any medicine means an emergency call, not a wait-and-see.