Head injury or intoxication? Unidentified eye drop ingestion resulting in naphazoline toxicity in a toddler.

Abstract

Objective: Over the counter (OTC) eye-drops and nasal sprays containing imidazoline vasoconstrictors can cause clonidine-like toxicity when ingested. These are often sold without child-resistant caps. We describe a toddler with, initially unrecognised, naphazoline intoxication after ingestion of OTC eye-drops. Case report: A healthy 2-year-old, 14 kg, female presented to a regional emergency department (ED) with drowsiness. Prior to presentation, she had an unwitnessed fall without head-strike or loss of consciousness. Twenty minutes later, she fell asleep. On rousing, she was pale, lethargic and drowsy with an unsteady gait. In the ED, her Glasgow Coma Scale (GCS) fell to 3 and she was urgently transferred to our tertiary paediatric ED with suspected head injury. En route, her conscious state fluctuated between drowsiness and agitation. On arrival to our ED, GCS was 6 and she was intubated. Vital signs showed a fluctuating heart rate (45-140/ min) and BP (75/- to 200/- mmHg) and hypothermia (34.8degreeC). Intracranial injury was suspected but cerebral magnetic resonance imaging (MRI) was normal. Empiric treatment with IV antibiotics was commenced for suspected meningoencephalitis. Three hours later she self-extubated in the PICU but remained drowsy for several more hours. During this period, pulse ranged from 75-120/ min with BP 90/40. Further questioning of her parents revealed that 4 hours before presentation, she was playing with a full 15 ml bottle of eye-drops containing naphazoline hydrochloride 0.25 mg/mL and pheniramine maleate 3 mg/mL (Naphcon). Suspected naphazoline intoxication was identified at this point. She made a full recovery over the next 24 hours. Conclusion(s): Naphazoline and other imidazoline agents, applied topically, produce peripheral alpha1-sympathomimetic vasoconstriction. The typical volume of nasal/ophthalmic products is 15-30 mL. Ingestion of as little as 3 mL can cause toxicity mimicking clonidine intoxication in toddlers. Initial peripheral alpha1-sympathomimetic stimulation leads to transient hypertension. Subsequent central nervous alpha2-sympathomimetic stimulation causes miosis, drowsiness/coma, hypothermia, bradycardia, hypotension and respiratory depression. Intoxication with naphazoline can occur with ingestion of less than 0.05 mg/kg (0.7 mg or 3 mL in this child). Management is supportive. In this case, lack of history of ingestion resulted in investigation of suspected closed-head injury and treatment for CNS infection. In cases of sudden unexplained coma in toddlers, associated with bradycardia and alternating hypo/hypertension, exposure to imidazoline decongestants and clonidine should be considered in the differential diagnosis.