Overdose Flashcards
What are important questions to ask in any overdose setting?
-Patient and collateral Hx
-Substance taken - volume, timings, alcohol, combination
-Symptoms?
-Intentional or accidental?
-Prescribed or recreational?
-Psych assessment
What dose of paracetamol is likely to cause liver damage?
- > 250mg/kg = likely
- > 12g total = potentially fatal
What is the pathophysiology of paracetamol overdose?
-Sulfation = metabolism of paracetamol (liver, 95%)
-Metabolites from sulfation are harmless and excreted through urine
-In OD, paracetamol is conjugated via an alternative pathway (P450) due to inundation of liver pathways
-NAPQI is formed as a result, which is toxic
-NAPQI is inactivated by glutathione, but only if glutathione levels are >30%, otherwise NAPQI causes hepatic cell necrosis
-Alcohol, rifampicin, phenobarbital, phenytoin and carbamazepine all increase toxicity as they are P450 inducers
What are the symptoms of paracetamol OD?
- <24h - N+V, can be asymptomatic
- 24-72h - RUQ pain, can progress to acute liver failure
- > 72h - jaundice, encephalopathy, oliguria, hypoglycaemia, renal failure, lactic acidosis
How should you assess someone with paracetamol OD?
-Thorough history including quantity of tablets over what time frame
-Bloods - paracetamol level, clotting/INR, U+Es, LFTs (high ALT indicates toxicity), BG (hypoglycaemia common), ABG (acidosis)
How should you manage someone with paracetamol OD in 0-1hr?
-Consider giving activated charcoal
How should you manage someone with paracetamol OD in 0-4hrs?
-Wait til 4hrs to measure paracetamol level
-BUT if symptomatic or >150mg/kg taken then give NAC ASAP
NB NAC = parvolax
How should you manage someone with paracetamol OD in 4-8hrs?
-Measure PCM level and plot on graph
-If above threshold, treat with NAC (discharge if below)
How should you manage someone with paracetamol OD in 8-15hrs?
-Treat with NAC immediately
-Then measure PCM level to decide whether to continue
How does NAC work?
-Acts as a precursor for glutathione, promotion normal conjugation of paracetamol
-Provides thiols which act as antioxidants
-Efficacy decreases sharply after 8hrs post ingestion
How is NAC delivered?
-Given as IV infusions with 5% glucose, rash is common
NEW (12h)
- 1st bag 100mg/kg over 2h
- 2nd bag 200mg/kg over 10h
OLD (21h)
-1st bag = 150mg/kg over 1hr
-2nd bag = 50mg/kg over 4hrs
-3rd bag = 100mg/kg over 16hrs
How are simple alcohol withdrawal and delirium tremens differentiated?
SIMPLE WITHDRAWAL = 12h after last drink
-Anxious, restless, tremor, insomnia, sweating
-Palpitations, headache, N+V
-Tachycardia, ataxia, nystagmus
DELIRIUM TREMENS = 24-72h, medical emergency
-As above + autonomic hyperactivity ie hyperreflexia, hypertension, fever, hallucinations, fits
-Sinister delusions
-Confusion
-Arrhythmias
IF SEVERE CAN LEAD TO WERNICKE-KORSAKOFF SYNDROME
What is included in Wernicke’s encephalopathy’s clinical triad?
- Ophthalmoplegia (paralysis of eye muscles)
- Gait ataxia
- Confusion
What investigations should be carried out for someone in alcohol withdrawal?
-Monitor blood alcohol level
-BG (to exclude hypoglycaemia)
-FBC (macrocytic anaemia)
-WCC
-Clotting + LFTs (liver function)
-Amylase
-ABG (metabolic acidosis)
How should you treat alcohol withdrawal?
-Supportive treatment
-Chlordiazepoxide stops withdrawal symptoms and seizures
-IV/IM thiamine vit B1 (pabrinex)
What are some examples of commonly used opiates in overdose?
-Codeine, morphine, methadone, heroin, buprenorphine, diamorphine
What clinical findings would you expect after an opiate overdose?
-Pinpoint pupils
-Decreased RR
-Decreased GCS
-Hypothermia, pulmonary oedema, rhabdomyolysis
What investigations would you order for someone with opiate overdose?
-ABG (resp acidosis)
-Urine toxicology
-Exclude hypoglycaemia or head trauma / serious injury
How would you manage opiate overdose?
-A-E
-Naloxone (shorter half-life than morphine)
-Respiratory support (O2 if necessary)
-Monitor closely
-Risk assessment
What examples of TCAs are used in overdose?
-Amitriptyline
-Dosulepin
-Trimipramine
What clinical findings are present in TCA overdose?
-Dry mouth
-Agitation
-Dilated pupils
-Tachycardia
-Blurred vision
-Seizures
-Decreased GCS
-Dysrhythmia
-Metabolic acidosis
What investigations would you order for TCA overdose?
-ABG (met acidosis)
-ECG - sinus tachycardia, wide PR/QRS complex, QTc prolongation
How would you manage a patient with TCA overdose?
No reliable antidote
-A-E
-IV bicarbonate (reduce risk of seizures/arrhythmias)
-IV lipid emulsion (binds free drug and reduced toxicity)
-Treat symptoms, risk assess
What clinical findings would you expect in amphetamine overdose?
-Tachycardia
-Hyperthermia
-Dilated pupils
-Volume depletion
-Agitation
-Seizures
-Rhabdomyolysis
What investigations would you order for amphetamine overdose?
-BG
-U+Es
-ABG (met acidosis)
-Urine amphetamine screen
-?CT head if other cause suspected
How should you manage an amphetamine overdose?
-Directed at controlling CNS and CV signs
-Benzos for seizures
-Beta blockers for tachyarrhythmias
-IV fluids for hyperthermia / volume depletion / elimination of amphetamines / renal function
