Diagnosis and management of poisoning

Agents involved in poisoning: National Poisons Information Service (NPIS) enquiries

Patient age

Age and poisonings Children (< 5years) Accidental/household products/usually low toxicity Adults Usually para-suicide with readily available drugs Most need little/no medical intervention Elderly Often significant psychiatric problems Access to more prescription drugs of higher toxicity Tolerate poisonings less well

Common agents in adult overdoses OTC drugs: (paracetamol/NSAID/vitamins) Alcohol Pyschotropic drugs: (TCAs, SSRIs, major tranquillisers, benzodiazepines, lithium) ‘Street’ drugs: (heroin)

Common features in adult overdoses Para-suicide Readily available agents Frequently in combination Frequently combined with alcohol

Poisoning: clinical approach History What has the patient taken and when? Where and under what circumstances has the self-harm occurred? Why has the patient self-harmed? Is this a repeat episode? Previous psychiatric or sociopathic history?

Poisoning: clinical approach History The type and quantity of drug(s) taken is (are) almost always known. (Volunteered by patient, known to relatives/friends or empty bottles).

Poisoning: clinical approach History Was the patient likely to be found quickly after the episode of self-harm? Considered or impetuous episode of self- harm? Drunk? Suicide note?

Poisoning: clinical approach History Why? Family or interpersonal disagreement? Psychiatric symptoms or history? Sociopath? Serial self-harm?

Poisoning: clinical approach Examination Usually perfectly well or drunk Conscious level Integrity of airway Cardio- respiratory Urine output

Poisoning: clinical approach investigations Routinely, SaO 2, U/E/LFT, FBC, ECG Specific toxicological tests Unknown drug screens

Diagnosis of poisoning: specific toxicological tests Prognostic information Need for elimination therapy Need for antidote

Specific toxicological investigations Paracetamol Aspirin Iron Theophylline Lithium Digoxin (Ethanol/alcohols/glycols)

Repeated drug levels Aspirin Theophylline Lithium

Diagnosis of poisoning: unknown drug screens Usually not available in appropriate time scale Usually of little or no clinical value, so discuss with laboratory/NPIS Coma is not an indication for drug screening Consider in those who are thought to have overdosed with unknown drugs and are clinically unstable Save urine and blood for critically ill cases (HM Coroner)

Poisoning: clinical approach ‘so what do I do next’ Is this serious? What additional tests do I need? What’s the clinical management?

Poisoning: clinical approach ‘so what do I do next’ TOXBASE

National Poisons Information Service (NPIS) Managed network of centres: Belfast, Birmingham, Cardiff, Edinburgh, London, Newcastle TOXBASE as first tier database Single phone number

Clinical management of the poisoned patient Observation/supportive Techniques to prevent drug absorption Techniques to eliminate the drug(s) Antidotes

Gut decontamination Syrup of ipecac Gastric lavage Activated charcoal

Elimination techniques Repeat dose activated charcoal Urinary alkalinisation/acidification Dialysis

Antidotes N-acetyl cysteine (Paracetamol) Naloxone (Opiates) Flumazenil (Benzodiazepines) Desferrioxamine (Iron) Digibind (Digoxin) Pralidoxime (Organophosphates)

Some common clinical presentations

Paracetamol

Paracetamol: standard management ‘Toxic’ paracetamol concentration N acetyl cysteine (NAC, Parvolex 300mg/Kg over 20 hours Check INR/creatinine before discharge

Paracetamol ‘High-risk’ patients: Alcoholics Co-prescription enzyme-inducing drugs Starvation/anorexia

Paracetamol: late presentation Prolonged NAC infusion Standard: 300 mg/kg over 20 hours Prolonged: standard course + (150 mg/kg over 16 hours) n Monitor urine output Monitor INR Monitor blood glucose

Paracetamol: prognosis Usual biochemical LFTs are not related to outcome Poor prognosis ( % mortality) if: p pH < 7.3 or p creatinine > 300  mol/L + PT > 100 secs + grade 3/4 encephalopathy

Ethanol Very common Clinical effects of any given blood ethanol concentration vary with prior experience of ethanol use/abuse

Alcohol dehydrogenase metabolism EthanolAcetaldehydeAcetate Alcohol dehydrogenase Aldehyde dehydrogenase

Ethanol intoxication Central nervous system Excitation Obtunded Metabolic Hypoglycaemia Metabolic acidosis Fluid/electrolyte disturbances

Ethanol intoxication: clinical management Maintain airway patency Avoid inhalation of vomitus Intravenous fluids Monitor blood glucose and pH

Tricyclic anti-depressants Coma/convulsions/cardiac dysrrhythmias Serious overdoses: coma, ECG abnormalities (QRS prolongation), serum total tricyclic anti-depressant levels > 1000  g/L

Opiates Respiratory depression Hypoxia/anoxic brain damage SaO 2, PaO 2 Naloxone (infusion) Rhabdomyolysis Compartment syndrome/myoglobinuria CPK

Benzodiazepines Coma Often prolonged (especially elderly) Respiratory depression unusual unless mixed overdose with other CNS depressants

Amphetamines/Ecstasy(MDMA) Agitation/delirium/coma Hypertension/tachycardia/mydriasis Hyperpyrexia AST/CPK elevated Rarely: DIC, hyponatraemia, multi-organ failure