Emergency Medicine

182 Tox icolog y

SPECIFIC POISONS

3 Give high-dose metoclopramide 10–40 mg i.v. for intractable vomiting, or

give ondansetron 4–8 mg i.v. if t his fails.

4 Give midazolam 0.05–0.1 mg/kg, diazepam 0.1–0.2 mg/kg i.v., or lorazepam

0.07 mg/kg i.v. up to 4 mg for seizures, although endotracheal intubation

may be required.

5 Administer a -blocker such as propranolol 1 mg i.v. over 1 min, repeated up

to a maximum of 10 mg only in a non-asthmatic patient with supraventricu-

lar tachycardia, hypokalaemia and hyperglycaemia.

6 Admit all patients with signs of toxicity for cardiac monitoring.

(i) Refer patients with severe toxicity, obtundation and seizures to

ICU for haemodialysis or charcoal haemoperfusion.

-BLOCKERS

DIAGNOSIS

1 Significant -blocker toxicity is associated particularly with propranolol

ingestion, coexistent cardiac disease, and in polypharmacy overdose with

calcium-channel blockers and TCAs.

2 Clinical evidence of toxicity usually presents within the first 6 h of overdose.

Toxicity is associated with:

(i) Bradycardia, arrhythmias, hypotension and cardiogenic shock.

(ii) Sedation, altered mental status, convulsions and coma.

3 Gain i.v. access and send blood for U&Es and a blood sugar level, as hypo-

glycaemia may occur, especially with atenolol. Attach a cardiac monitor and

pulse oximeter to the patient.

4 Perform an ECG. Look for toxic conduction defects such as atrioventricular

block, right bundle branch block, prolongation of the QRS (propranolol) and

ventricular arrhythmias (particularly with sotalol).

MANAGEMENT

1 Ensure the airway is secure and administer high-f low oxygen. Commence

i.v. f luid administration for hypotension.

2 Administer ora l activated charcoa l as soon as possible.

3 Give atropine 0.6 –1.2 mg i.v. for bradycardia, up to a ma ximum of 0.04 mg/kg.

4 Give glucagon 50–150 g/kg i.v. bolus followed by an infusion at 1–5 mg/h.

5 Titrate an adrenaline (epinephrine) or isoprenaline infusion to maintain

organ perfusion in resistant cases. Cardiac pacing may be necessary.

6 Admit all symptomatic patients to coronary care or ICU.

7 Propranolol is potentially the most toxic agent. It acts as a sodium-channel

blocker agent similar to TCAs, and should be treated in the same way (see p.

174).