General principles of management of poisoning

In managing a patient who has been exposed to toxins, a holistic approach should be considered.

Resuscitation and stabilization

Airway, breathing, and circulation should be reassessed and treated accordingly as a priority. Refer to approach to patient with emergency conditions chapter.

Note

• A low respiratory rate with decreased oxygen saturations may indicate hypoventilation. A normal saturation does not exclude hypercarbia or hypoxia in carbon monoxide poisoning. If in any doubt, arterial blood gases should be measured. Tachypnoea can be seen with metabolic acidosis (e.g. tricyclics, methanol), anxiety, stimulant drug overdose, and as an early feature of salicylate poisoning (respiratory alkalosis).

• Supplementary oxygen via facemask should be given to all patients initially, taking account of pulse oximetry (noting limitations described above).

• Many drugs exhibit cardiovascular toxicity such as hypotension and/or cardiac arrhythmias in overdose (e.g. tricyclics, β-blockers, digoxin, lithium). ECG should be recorded, intravenous access established, and initial fluid resuscitation given as appropriate.

• General examination may give corroborating evidence of significant ingestions or clues in unknown overdoses. SSRIs, tricyclics, and phenothiazines may have serotonergic or anticholinergic effects with pupil dilatation and extrapyramidal movements, whilst opioid-type drugs will cause sedation and pinpoint pupils.

• Temperature and blood glucose should be checked (low in β-blocker and ethanol poisoning).

• Weight is important in identifying a toxic dose and may guide treatment (e.g. paracetamol overdose).

• Examination for injury (intentional or unintentional self-harm) should be performed, and possible co-ingestions such as alcohol considered.

• If clinical condition allows, an assessment of the patient’s mental state should be made.

Use of toxidromes

Use the tabulated toxidromes to identify toxins and apply appropriate antidotes.

Common toxidromes

Sympathomimetic toxidrome

• Mental status: Hyperalert, agitation, hallucination, paranoia, anxiety, delirium

• Pupils: Mydriasis

• Vitals: Hyperthermia, tachycardia, hypertension, widened pulse pressure

• Other manifestations: Diaphoresis, tremors, hyperreflexia, seizures, hyperpyrexia

• Examples of toxic agents: Cocaine, amphetamines, ephedrine, theophylline, caffeine, phencyclidine (PCP), lysergic acid (LSD), withdrawal from narcotics, benzodiazepines, alcohol, long-term β-blocker therapy

Cholinergic toxidrome

• Mental status: Confusion, drowsiness, coma

• Pupils: Miosis

• Vitals: Bradycardia, hypotension, tachypnea, bradypnea, hypothermia

• Other manifestations: Salivation, urinary incontinence, defecation, gastric cramping, hypermotility, emesis, diaphoresis, lacrimation, bronchoconstriction, muscle fasciculations and weakness, seizures

• Examples of toxic agents: Organophosphate and carbamate insecticides, nerve agents, nicotine, physostigmine, edrophonium

Anticholinergic toxidrome

• Mental status: Agitation, hallucinations, delirium, coma

• Pupils: Mydriasis

• Vitals: Hyperthermia, tachycardia, hypertension, tachypnea

• Other manifestations: Dry flushed skin, dry mucous membranes, decreased bowel sounds, urinary retention, myoclonus

• Examples of toxic agents: Antihistamines, tricyclic antidepressants, antiparkinsonism agents, atropine, antispasmodics

Hallucinogenic toxidrome

• Mental status: Hallucinations, perceptual distortions, depersonalization, agitation

• Pupils: Mydriasis (usually)

• Vitals: Hyperthermia, tachycardia, hypertension, tachypnea

• Other manifestations: Nystagmus

• Examples of toxic agents: Phencyclidine (PCP), MDMA, MDEA

Opioid toxidrome

• Mental status: CNS depression, coma

• Pupils: Miosis

• Vitals: Bradypnea, apnea

• Other manifestations: Hyporeflexia, pulmonary edema, needle marks

• Examples of toxic agents: Heroin, morphine, methadone, diphenoxylate

Sedative-hypnotic toxidrome

• Mental status: CNS depression, confusion, stupor, coma

• Pupils: Variable

• Vitals: Often normal; may include hypothermia, bradycardia, hypotension, bradypnea, apnea

• Other manifestations: Hyporeflexia

• Examples of toxic agents: Benzodiazepines, barbiturates, alcohols, zolpidem

Serotonin syndrome

• Mental status: Confusion, agitation, coma

• Pupils: Mydriasis

• Vitals: Hyperthermia, tachycardia, hypertension, tachypnea

• Other manifestations: Tremors, myoclonus, hyperreflexia, clonus, diaphoresis, flushing, trismus, rigidity, diarrhea

• Examples of toxic agents: MAOIs, SSRIs, meperidine, dextromethorphan, tricyclic antidepressants

Toxins causing dysrhythmias

Tachycardia

• Narrow QRS:

  • Amphetamines

  • Anticholinergic agents

  • Theophylline

• Wide QRS:

  • Antihistamines

  • Cocaine

  • Propoxyphene

  • Sodium channel blockers and tricyclic antidepressants

Bradycardia

• α-adrenergic lytic agents

• β-adrenergic blocking agents

• Calcium channel antagonists

• Cardiac glycosides

• Class Ia antiarrhythmics

• Sodium channel blockers

• Calcium channel antagonists

Note

• For patients presenting with cardiac problems, consider ECG interpretation and use the table above to guide possible causes.