Overdose and Poisoning

5 Principles of Managing Poisoned Patients

History

Examination

Investigations

Diagnosis

Management

History Points

Pinpoint information

Is it their own or someone else

Was anything else taken alongside

What time was it taken

Examination Points

Small pupils - opiates

Large pupils - sympathomimetics and anticholinergics

Jaundice - late paracetamol OD/ALD

Self harm

Track marks

Injuries

Extensive bruise

What is the risk of presenting with extensive bruising

Rhabdomyolysis

What bloods do you check for rhabdomyolysis

Creatine Kinase

Investigations Summary

Pulse rate

BP

RR

O2 stats

Temperature

12 lead ECG/Cardiac monitor

Blood tests

Specific toxin blood conc

Urine toxicological analysis

Imaging

What drugs need temperature monitoring

Drugs that cause hyperthermia

Cocaine, amphetamines, ecstasy, serotonergic (SSRIs)

What blood tests can be used

Urea, electrolytes, creatine

Glucose

Liver function tests

Clotting

Creatine kinase

Specific drug assays - blood and urine

Drugs monitored for specific toxin blood concentrations

Paracetamol

Salicylate

Iron

Lithium

Methanol/ ethylene glycol

Ethanol

Theophylline

Digoxin

Valproic acid

Carbamazepine

What is urine toxicological analysis used for

Drugs of abuse screening

Unknown overdose in comatose or delirious patients

Types of drug screens

Point of care urine dip

UPLC/MS - the classic drug screen

Time of flight - unknown drug screen

Point of care urine dip

Immunoassay based

Limited value

What class of drugs can a urine dip not recognise

Synthetic cannabinoids

UPLC/MS

Highly sensitive urine/blood testing

As comprehensive as test library

Time of flight - unknown drug screen

Less sensitive but highly specific

Software predicts compounds present from fragments identified

What is imaging useful for

Secondary complications - aspiration pneumonia

Ingested objects

Radio-opaque substances - elementary mercury

Toxidromes of opiates/opioids

Coma, miosis, reduced respiratory rate, hypoxia

Toxidromes of stimulants - ecstasy, amphetamines, cocaine

Agitation, delirium, mydriasis, hypertension, hyperthermia, tachycardia, arrhythmias

Toxidromes of anticholinergic syndrome, diphenhydramine hyoscine, promethazine, mirtazapine, TCA

Drowsiness, confusion, mydriasis, tachycardia, urinary retention

Toxidromes of salicylates

Nausea, vomiting, tinnitus, deafness, hyperpyrexia, hyperventilation, metabolic acidosis

Management summary

Symptomatic and supportive measures

Reducing absorption

Enhancing elimination

Specific antidotes

ABC of resuscitation

Airway - clear obstruction

Breathing - Oxygen - assisted ventilation

Circulation - Skin colours and temp

How to reduce absorption

Gastric lavage

Single-dose activated charcoal - does not bind alcohol, glycols, acids/alkalis, iron or lithium

White bowel irrigation

How to enhance elimination

MDAC - multiple-dose activated charcoal

Urine alkalinization

Extracorporeal elimination

Chelating Agents

How does MDAC work

Activated charcoal binds to drug to maintain low concentration of free drug

Urine alkalinization

Administration of intravenous sodium bicarbonate

Achieve urine pH of 7.5-8.5

Enhance salicylate clearance by favouring ionization

Require adequate fluid resuscitation, close monitoring of systemic pH and serum potassium

Extracorporeal elimination

Haemodialysis/hemodiafiltration

Poisoning complicated by renal failure

Specifically enhances elimination of ethanol, ethylene glycol, methanol, salicylates, lithium, metformin, valproic acid

Chelating agents

Heavy metal poisoning

Specific antidotes

Acetylcysteine

Naloxone

Flumazenil

Fomepizole

Methylthionine Chloride

Acetylcysteine

Glutathione precursor for paracetamol poisoning

Naloxone

Opiate antagonist

Flumazenil

GABA receptor antagonist

Benzodiazepine poisoning

Fomepizole

Alcohol dehydrogenase inhibitor

Toxic alcohol poisoning

Methylation chloride

Treatment of methemoglobinemia

What factors influence paracetamol hepatotoxicity

Dose of paracetamol ingested

Plasma paracetamol concentration

Time to antidote administration

Nature of overdose - single or staggered

What is the 8 hour rule

Treatment within 8 hours - unlikely to develop significant liver damage

What is the antidote for paracetamol poisoning

Glutathione precursors

How do glutathione precurosrs’ work

Supplement dietary glutathione

Augment the potential to detoxify NAPQ1

Acetylcysteine

Modified 12 hour regimen

Total dose is same as standard 24h 300mg/kg

Rate and duration is different

Lower peak plasma - lower risk of anaphylactoid reactions

Single acute event

Less than 60 mins

Staggered event

Spread over more than one hour

Therapeutic excess - toothache