Overdose

Question 1

What are important questions to ask in any overdose setting?

Answer 1

-Patient and collateral Hx
-Substance taken - volume, timings, alcohol, combination
-Symptoms?
-Intentional or accidental?
-Prescribed or recreational?
-Psych assessment

Question 2

What dose of paracetamol is likely to cause liver damage?

Answer 2

• > 250mg/kg = likely
• > 12g total = potentially fatal

Question 3

What is the pathophysiology of paracetamol overdose?

Answer 3

-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

Question 4

What are the symptoms of paracetamol OD?

Answer 4

• <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

Question 5

How should you assess someone with paracetamol OD?

Answer 5

-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)

Question 6

How should you manage someone with paracetamol OD in 0-1hr?

Answer 6

-Consider giving activated charcoal

Question 7

How should you manage someone with paracetamol OD in 0-4hrs?

Answer 7

-Wait til 4hrs to measure paracetamol level
-BUT if symptomatic or >150mg/kg taken then give NAC ASAP
NB NAC = parvolax

Question 8

How should you manage someone with paracetamol OD in 4-8hrs?

Answer 8

-Measure PCM level and plot on graph
-If above threshold, treat with NAC (discharge if below)

Question 9

How should you manage someone with paracetamol OD in 8-15hrs?

Answer 9

-Treat with NAC immediately
-Then measure PCM level to decide whether to continue

Question 10

How does NAC work?

Answer 10

-Acts as a precursor for glutathione, promotion normal conjugation of paracetamol
-Provides thiols which act as antioxidants
-Efficacy decreases sharply after 8hrs post ingestion

Question 11

How is NAC delivered?

Answer 11

-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

Question 12

How are simple alcohol withdrawal and delirium tremens differentiated?

Answer 12

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

Question 13

What is included in Wernicke’s encephalopathy’s clinical triad?

Answer 13

1. Ophthalmoplegia (paralysis of eye muscles)
2. Gait ataxia
3. Confusion

Question 14

What investigations should be carried out for someone in alcohol withdrawal?

Answer 14

-Monitor blood alcohol level
-BG (to exclude hypoglycaemia)
-FBC (macrocytic anaemia)
-WCC
-Clotting + LFTs (liver function)
-Amylase
-ABG (metabolic acidosis)

Question 15

How should you treat alcohol withdrawal?

Answer 15

-Supportive treatment
-Chlordiazepoxide stops withdrawal symptoms and seizures
-IV/IM thiamine vit B1 (pabrinex)

Question 16

What are some examples of commonly used opiates in overdose?

Answer 16

-Codeine, morphine, methadone, heroin, buprenorphine, diamorphine

Question 17

What clinical findings would you expect after an opiate overdose?

Answer 17

-Pinpoint pupils
-Decreased RR
-Decreased GCS
-Hypothermia, pulmonary oedema, rhabdomyolysis

Question 18

What investigations would you order for someone with opiate overdose?

Answer 18

-ABG (resp acidosis)
-Urine toxicology
-Exclude hypoglycaemia or head trauma / serious injury

Question 19

How would you manage opiate overdose?

Answer 19

-A-E
-Naloxone (shorter half-life than morphine)
-Respiratory support (O2 if necessary)
-Monitor closely
-Risk assessment

Question 20

What examples of TCAs are used in overdose?

Answer 20

-Amitriptyline
-Dosulepin
-Trimipramine

Question 21

What clinical findings are present in TCA overdose?

Answer 21

-Dry mouth
-Agitation
-Dilated pupils
-Tachycardia
-Blurred vision
-Seizures
-Decreased GCS
-Dysrhythmia
-Metabolic acidosis

Question 22

What investigations would you order for TCA overdose?

Answer 22

-ABG (met acidosis)
-ECG - sinus tachycardia, wide PR/QRS complex, QTc prolongation

Question 23

How would you manage a patient with TCA overdose?

Answer 23

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

Question 24

What clinical findings would you expect in amphetamine overdose?

Answer 24

-Tachycardia
-Hyperthermia
-Dilated pupils
-Volume depletion
-Agitation
-Seizures
-Rhabdomyolysis

Question 25

What investigations would you order for amphetamine overdose?

Answer 25

-BG
-U+Es
-ABG (met acidosis)
-Urine amphetamine screen
-?CT head if other cause suspected

Question 26

How should you manage an amphetamine overdose?

Answer 26

-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