Sun28November0628PM 9

A 45-year-old man with a past medical history of multiple sclerosis was admitted to hospital following an overdose of baclofen. He was diagnosed with relapsing and remitting multiple sclerosis 20 years ago and is usually mobile with two sticks. He performs intermittent self-catheterisation and his only medication is baclofen 20 mg three times a day.

He was found surrounded by empty packets previously containing baclofen by his son after returning from a night out with his friends. Earlier that evening, the patient and his partner had an argument and this was thought to have precipitated his actions. According to his partner, there were approximately 20 tablets left in the packet, each containing 10 mg of baclofen. (150 mg of baclofen is associated with severe toxicity.)

He is a non-smoker and is teetotal. The only other past medical history of note is a previous admission 18 months ago with severe community acquired pneumonia, for which he needed mechanical ventilation.

On examination, he was drowsy with a respiratory rate of 5/min. He had a Glasgow coma scale (GCS) of 8/15 (eye = 2, verbal = 2, motor = 4) and neurological examination revealed generalised hyporeflexia. Pulse rate was 60/min and blood pressure was 95 systolic and 60 diastolic. Examination of respiratory, cardiovascular and abdominal system was unremarkable.

His arterial gases on 50% inspired O2 were as follows:

pH 7.34 (7.36-7.44)

PO2 24.0 kPa (11.3-12.6)

PCO2 7.2 kPa (4.7-6.0)

HCO3 27 mmol/L (20-28)

Base excess 0.3 mmol/L (+/-2)

What would be your next step in the management of this patient?

(Please select 1 option)

Non-invasive positive pressure ventilation (NIPPV)

Reduce concentration of inspired oxygen Incorrect answer selected

Intravenous doxapram infusion

Intubation and mechanical ventilation This is the correct answer

Increase concentration of inspired oxygen

Explanation

His CO2 retention is likely to be due to central nervous system depression and reduction in diaphragmatic contraction secondary to baclofen toxicity. Onset of toxicity is rapid and its effect can last up to 35-40 hours post ingestion.

Features include:

Drowsiness

Coma

Respiratory depression

Hyporeflexia

Hypotonia

Hypothermia, and

Hypotension.

Bradycardia with first degree heart block and prolongation of Q-T interval can occur.

Treatment is usually supportive and often requires intensive care.

The presence of hypoxic drive is unlikely as the patient is a non-smoker thus a reduction in inspired oxygen would not increase his respiratory drive.

NIPPV would be an option but not in a patient with a GCS 8/15.

Patients with a high risk of aspiration pneumonia are a contraindication to non-invasive ventilation.

Doxapram has no place in the treatment of baclofen toxicity.

Answer Statistics

1

4%

2

20%

3

6%

4

72%

5

1%

Times answered: 311