Poisons and Poisoning

Dr Ian Wilkinson

Clinical Pharmacology Unit

Accidental?

                                                                               

Deliberate?

Suicides in the UK

• ~6,300 suicides pa– 20% of deaths in young people

• ~140,000 attempted suicides (parasuicides)– Most common 15-19 year old females– Most common method is poisoning

• 50% paracetamol

General Comments

• Try and get as much history as possible including witnesses

• People truly wanting to commit suicide often lie

• Remember the ABCs:

– Airway Clear mouth & throat, gag reflex

– Breathing O2 saturation, ABGs

– Circulation Venous access, IV fluids if shocked

• Assess GCS

• Examination

History

• When, what, how much ?

• Why?

• Circumstances

• PMHx, Drug history

• Psychiatric history

• Assess mental status and capacity

Care with names!

• Distalgesic

• Anadin

Investigations

• Always check blood glucose.

• Send blood & urine for toxicology screening.• ALWAYS measure paracetamol & salicylate levels

– Failure to diagnose & treat is negligent.

• U&Es, LFTs, glucose, ABG, clotting, bicarbonate• ECG, CXR• Specific blood levels

Management

• Supportive– Correct hypoxia, hypotension, dehydration, hypo-

hyperthermia, and acidosis

– Control seizures

• Monitor– TPR, BP, ECG, Oxygenation, GCS

• General Absorption Elimination

– Specific antidotes

Absorption

• NEVER Ipecacuanha

• Gastric lavage– Only if within 1 hour & life-threatening amount– Never for corrosives– If LOC intubate

• Activated charcoal– 50 g single or repeated dose ( elimination)– Doesn’t bind heavy metals, ethanol, acids

Elimination

• Multiple dose activated charcoal– Quinine, phenobarbitone

• Charcoal haemoperfusion– Barbiturates, theophylline

• Diuresis

• Urinary alkalinization

• Dialysis

Paracetamol Overdose

• Most common drug taken in overdose• Few symptoms or early signs• As little as 12g can be fatal• Hepatic and renal toxin

– Centrolobular necrosis

• More toxic if liver enzymes induced or reduced ability to conjugate toxin

Paracetamol Metabolism

Management

• General measures including– U&Es, LFTs, glucose, clotting ABG, bicarbonate,

paracetamol and salicylate levels– Activated charcoal

• <8 hours– Take level after four hours– Start N-aceylcysteine if above treatment line– Patients are usually declared fit for discharge from

medical care on completion of its administration. However, check INR, creatinine and ALT before discharge. Patients should be advised to return to hospital if vomiting or abdominal pain develop or recur

Management 2

• >8 hours– Urgent action required because the efficacy of NAC

declines progressively from 8 hours after the overdose

– Therefore, if > 150mg/kg or > 12g (whichever is the smaller) has been ingested, start NAC immediately, without waiting for the result of the plasma paracetamol concentration

• >24 hours– Still benefit from starting NAC

Treatment Graph

N-acetylcysteine

• Supplies glutathione• Dosage for NAC infusion - ADULT

– (1) 150mg/kg IV infusion in 200ml 5% dextrose over 15 minutes, then

– (2) 50mg/kg IV infusion in 500ml 5% dextrose over 4 hours, then

– (3) 100mg/kg IV infusion in 1000ml 5% dextrose over 16 hours

• Side-effects– Flushing, hypotension, wheezing, anaphylactoid reaction

• Alternative is methionine PO (<12 hours)

Aspirin Overdose

• Early features– hyperventilation, sweating, tremor, tinnitus, nausea /

vomiting, or hyperpyrexia

• Metabolic features– Hypo- or hyper-glycaemia, hypokalaemia, respiratory

alkalosis, metabolic acidosis

• Others– renal failure, pulmonary oedema, seizures, coma, death

Management

• General measures• Bloods

– Salicylate (paracetamol) level >2 hours, and after 2hrs– >700 potentially lethal– >500 moderate-severe poisoning– U&Es, glucose, ABG, bicarbonate

• Activated charcoal• Rehydrate, monitor glucose, correct acidosis and K+• If levels >500mg/L alkalanize urine (HCO3

-)• Levels > 700 mg/L before rehydration, renal failure

or pulmonary oedema consider haemodialysis

TCAs -Introduction

• Potentially fatal (2.5 to 3.5g of amitriptyline)• Neurological and cardiac problems common

– Toxicity due to anticholinergic actions, and direct quinidine-like effect on the myocardium

• Serious toxicity results from:-– Ventricular dysrhythmias– Seizures– Hypotension– Respiratory depression

• Initial symptoms at presentation may be trivial, and most major problems occur within 6hrs

TCAs-Features of poisoning

• Peripheral– Sinus tachycardia, hot dry skin, dry mouth, urinary

retention, hypotension and hypothermia may occur

• CNS– Dilated pupils, ataxia, nystagmus, squint, LOC, coma,

seizures, respiratory depression, tone, reflexes, plantars

• ECG– prolonged PR and QRS interval, QT

– ventricular dysrhythmias

TCAs -Management

• GCS and QRS, best indicators of toxicity• Supportive

– do not use flumazenil if benzo taken

• Check airway, maintain ventilation, correct hypoxia– Check ABG, if CO2 requires ventilation

• Correct hypotension (crystalloids)• Gastric lavage if within 1 hr, and activated charcoal• Rx fits and agitation with diazepam• Rewarm slowly if hypothermic• Close monitoring for 24hrs

TCAs- Dysrhythmias

• Carful ECG monitoring is required– QRS interval is a guide to cardiac toxicity (>100ms)

• Avoid antidysrhythmic drugs. They may make matters worse

• Correct hypoxia and acidosis. Aim for a pH of 7.45-7.50 (no higher)– use iv boluses of sodium bicarbonate

• Sodium loading may also help• Prolonged CPR may be of use

Tricyclic OD – Initial ECG

Tricyclic OD – Recovery ECG

Benzodiazepine Overdose

• Deaths from poisoning with benzodiazepines alone are rare, but may be lethal in combination with other CNS depressants

• Treatment is supportive and aimed at maintaining adequate ventilation whilst supporting cardiovascular depression

• Flumazenil (specific benzodiazepine antidote) is not licensed (in the UK) for routine use in benzodiazepine overdoses

• Flumazenil may induce seizures; particularly dangerous where tricyclic antidepressants have been taken

• Flumazenil, may however, be used in the differential diagnosis of unclear cases of multiple overdoses but expert advice is ESSENTIAL.

Other agents

• Opiates Naloxone

• IronDesferrioxamine

• Lead Sodium EDTA

• Digoxin FAB

• Calcium blockers Calcium

• Ethylene glycol Ethanol

• Lithium Dialysis