Lab Case 18 – Interpretation

A 35 year old man with significant COHb level of 28.5%, altered level of consciousness (?other co ingestions), elevated lactate indicating severe carbon monoxide poisoning in the context of an attempted suicide.

Normal pH, CO2

HCO3 mildly elevated – is the patient vomiting

Anion Gap 6

A-a gradient (if assume O2 delivered at about 80 %) is high, however note previously on NP O2. Consider VQ mismatch (hypoxic lung injury/ aspiration)

Glucose 9.4 – elevated – stress response

Electrolytes normal

Tachycardia and mild hypertension – Carbon Monoxide poisoning and myocardial ischaemia


1. Resuscitation – no acute resusc issues. High flow Oxygen via non rebreather with reservoir

2. Risk assessment –

agent – carbon monoxide

dose – short exposure, high concentration

time -30 minutes exposure

Clinical features – altered GCS, high lactate, ??VQ mismatch

Patient factors – co morbidities (none given), young patient with good functional reserve.

3. Supportive Care – O2 as mentioned, ivi access and fluid

4. Investigations


Bloods – FBC, UEC, LFT, lipase, Coags, Troponin, CK, 4 hour paracetamol level

Other – Ct head, MMSE, Neuropsychiatric testing (in patient tests)

5. Enhanced Elimination/ Disposition

High flow Oxygen and discussion with Hyperbaric unit if available

6. Decontamination/ Antidote – not in this case

Carbon Monoxide Poisoning

Car exhaust exposures are high concentrations for a short period, deaths usually occur out of hospital and they have a lower risk of long term neurologic sequelae

High risk Features – LOC/ coma, persistant neuro dysfunction ( confusion), abnormal cerebellar examination, myocardial ishaemia and age over 55

Loose correlation between levels and symptoms

<10% background in a smoker

10% usually asymptomatic, slight headache

20% dizziness, N, dyspnoea, throbbing headache

30% vertigo, ataxia, visual disturbance

40% confusion, coma, seizures, syncope

50% CVS and Resp failure, arrhythmia, seizures and death