AKT · Acute care/Toxicology & overdoselow yield

Salicylate (aspirin) overdose

Salicylate → mixed respiratory alkalosis + metabolic acidosis

Overview

Aspirin toxicity stimulates the respiratory centre (early respiratory alkalosis) and uncouples oxidative phosphorylation (metabolic acidosis) — the classic mixed acid–base picture, with tinnitus, hyperventilation and sweating. Treated with urinary alkalinisation; haemodialysis if severe.

Recognise

Tinnitus/deafness, nausea/vomiting, hyperventilation, sweating, fever
Mixed acid–base: early respiratory alkalosis then metabolic acidosis
Severe: agitation, seizures, coma, pulmonary/cerebral oedema

Red flags

Severe acidosis, very high levels, altered consciousness, seizures, renal failure → haemodialysis

Differentials & how to tell them apart

DKA / other metabolic acidosisketones/glucose; no tinnitus/salicylate level

Sepsisfever + tachypnoea; check salicylate level/history

Other overdosescreen co-ingestants

Investigations

Serial salicylate levels (continued absorption), venous/arterial gas (mixed picture), glucose, U&E, lactate; paracetamol co-ingestion.

Management

IV sodium bicarbonate (urinary alkalinisation) + fluids; haemodialysis if severe

1Resuscitate, correct dehydration/hypokalaemia, activated charcoal if early. IV sodium bicarbonate to alkalinise the urine and enhance excretion.Gate: Severe features (very high level, acidosis, seizures/coma, renal failure, pulmonary oedema) → HAEMODIALYSIS
2Serial levels (ongoing absorption), maintain potassium (needed for effective alkalinisation), monitor acid–base and glucose.

IV sodium bicarbonate (urinary alkalinisation) — enhances salicylate excretion; maintain potassium

Activated charcoal — if early; repeated doses sometimes

Haemodialysis — severe toxicity (very high levels, acidosis, renal failure, CNS features)

Key points

The mixed respiratory-alkalosis-plus-metabolic-acidosis picture is the giveaway. Potassium must be replete for urinary alkalinisation to work.

Monitor & prognosis

Serial salicylate levels, acid–base, K+, glucose, urine pH, GCS.

Good if treated; severe toxicity is life-threatening.

Source: TOXBASE; BNF