Emergency Medicine

Tox i c o l o g y 17 7

SPECIFIC POISONS

(i) Naloxone is a short-acting opioid antagonist that may be

administered by the i.m., i.v., s.c. or endotracheal routes.

(ii) It is safe and rarely associated with complications, but may cause

acute withdrawal and severe agitation in the opioid-dependent

individual.

(iii) Use it to reverse severe respiratory depression, apnoea and

oversedation, or for cases of undifferentiated coma with

respiratory depression and pinpoint pupils.

3 Continue to monitor for respiratory depression and hypoxia. Further doses
of na loxone or an inf usion may be required due to its short ha lf-life.

4 Observe all patients for a period, because re-sedation with respiratory
depression may occur as the naloxone wears off.

Iron

DIAGNOSIS

1 Acute iron overdose is a potentially life-threatening condition, particularly
in children who mistake iron tablets for sweets.

2 The clinical course following iron overdose includes:
(i) Gastrointestinal toxicity: haemorrhagic gastroenteritis with
vomiting, abdominal pain and bloody diarrhoea. Failure to
develop significant gastrointestinal symptoms within 6 h of
ingestion effectively rules out significant iron poisoning.
(ii) Systemic toxicity: hypotension, shock, lethargy, metabolic
acidosis, seizures, coma, and acute liver and renal failure.

3 Toxicit y is determined by t he quantit y of elementa l iron ingested:
(i) <20 mg/kg: usually asymptomatic.
(ii) 20–60 mg/kg: gastrointestinal symptoms predominate.
(iii) 60–120 mg/kg: systemic toxicity and high lethality.

4 Send blood for FBC, U&Es, LFTs, a serum iron level and venous blood gas
(VBG).
(i) Serum iron levels peak at 4–6 h after ingestion.
(ii) Levels >90 mol/L are associated with systemic toxicity.

5 Request a plain AXR to show residual whole tablets or a concretion, as most
iron preparations are radio-opaque.
(i) A negative AXR does not rule out ingestion.

MANAGEMENT

1 This depends on the initial assessment and clinical manifestations, and the
potential amount of elemental iron ingested.

2 Start aggressive f luid resuscitation in patients with signs of gastrointestinal
or systemic toxicity, and institute decontamination and chelation measures.