Substance Abuse Flashcards
How does amphetamine ingestion present?
Euphoria Agitation Sweating Dilated pupils Palpitations Tachycardia Hypertension
How does an amphetamine overdose present?
Sympathetic overdrive
Hyperpyrexia Dehydration Muscle rigidity Convulsions (due to hyponatraemia from polydipsia) Rhabdomyolysis Arrhythmias Coma DIC
How do you manage an amphetamine overdose?
Refer to TOXBASE
Activated charcoal if <1hr after ingestion
Supportive treatment:
- Cooling measures, if rectal temp > 39 consider dantrolene
- Correct electrolyte imbalance
- Sodium bicarbonate
- Diazepam for convulsions
- Metoprolol for narrow complex tachycardias
- Nifedipine for hypertension
How does an opiate overdose present?
Parasympathetic overdrive
Pinpoint pupils
Respiratory depression
Decreased GCS - potential coma
Hypotension
What would an ABG show in amphetamine overdose?
Metabolic acidosis
What would an ABG show in opiate overdose?
Respiratory acidosis
What is the treatment for opiate overdose?
IV naloxone 0.4-2mg - repeat every 2 min until breathing adequate
Naloxone’s half life is shorter than morphine so may need to be given often
How is paracetamol normally metabolised?
Metabolism occurs in the liver
By glucuronidation, 95% paracetamol is metabolised to harmless metabolites (glucoronide and sulphate)
5% of paracetamol is metabolised by the CYP450 system to NAPQ1 (harmful metabolite)
NAPQ1 is then metabolised by glutathione to harmless metabolites
How does paracetamol overdose affect its metabolism?
In overdose, the pathways are saturated and there is insufficient glutathione to metabolise all the NAPQ1 so there is a build up of NAPQ1
What dose of paracetamol is potentially fatal?
150mg/kg
12g = 24 tablets
If malnourished, 75mg/kg can be fatal
How does paracetamol overdose present depending on the time since ingestion?
<24 hours: nausea and vomiting (or asymptomatic)
24-72 hours
- Nausea + vomiting
- RUQ pain
> 72 hours = symptoms of liver failure
- Jaundice
- Confusion
- Coagulopathy - bleeding, bruising
- Hypoglycaemia
- AKI
How do you decide whether to treat a paracetamol overdose?
Do blood paracetamol level at 4 hours post dose
Plot graph of plasma concentration of paracetamol vs time since dose
Treat if the point is above the line
If symptoms of overdose prior to 4 hours, start treatment ASAP
If time of ingestion is unknown or staggered, treat anyway
What defines a staggered dose of paracetamol?
Doses taken over more than one hour
What is important to find out in the psychiatric assessment of somebody who has taken a paracetamol overdose?
Intentions at time
- Was it a suicide attempt and was it planned?
- Any precautions against being found?
- Did they seek help after?
- Was there a final act e.g. suicide note?
Present intentions
- Do you feel suicidal?
- Do you wish it had worked?
What problems led to the act
Is there a psychiatric disorder?
What are your resources?
- Friends, family, work, personality
What factors increase the likelihood of suicide risk?
SAD PERSONS scale for suicide risk
Sex - Male Age - <19 or >45 years old Depression or hopelessness Previous suicide attempts or psychiatric disorder Excessive alcohol or drug use Rational thinking loss Unemployed Separated/divorced/widowed Organised or serious attempt No social supports Stated future intent
What is the criteria for liver transplant?
King’s College Hospital criteria for paracetamol-induced liver failure
Either: - pH < 7.3 24 hours after ingestion Or all of: - PT > 100 secs - Creatinine > 300 - Grade 3 or 4 encephalopathy
What LFTs would be deranged in paracetamol overdose?
ALT > 1000 indicates hepatotoxicity
AST increased
INR increased
How is paracetamol overdose managed if it’s before 4 hours since the overdose?
0-1hr: activated charcoal
0-4hr: wait for 4hr to measure paracetamol levels BUT if symptoms start N-acetylcysteine ASAP
How is N-acetylcysteine administered in paracetamol overdose?
IV infusion in 5% glucose, 3 consecutive doses over 21 hours
- 150mg/kg in 200ml glucose over 1 hour
- 50mg/kg in 500ml over 4 hour
- 100mg/kg in 1 L over 16 hour
What are the side effects of n-acetylcysteine?
Rash - treat with chlorphenamine
Nausea and vomiting
Sweating and flushing
Congested face - runny nose, puffy eyes
When should you continue treating with N-acetylcysteine until?
Until clotting is normal - INR <1.3 and ALT less than 2 times the upper limit of normal
How does tricyclic antidepressant overdose present?
Can’t see, pee, shit, spit
- Dry skin and mouth
- Dilated unreactive pupils
- Urinary retention
- Jerky limb movements, ataxia
- Drowsiness, coma
- Tachycardia
- Hypertonia and hyperreflexia
What might tricyclic depressant overdose be mistaken for?
Ventricular tachycardia - Broad QRS complexes seen on ECG
What is seen on ABG of TCA overdose?
Metabolic acidosis
What is the treatment for TCA overdose?
IV sodium bicarbonate to treat acidosis and arrhythmias
How is paracetamol overdose managed if it’s 4-8 hours since the overdose?
Take bloods - plot paracetamol levels on the graph and if above the treatment line, give NAC
How is paracetamol overdose treated if it’s > 8 hours since the overdose?
Start NAC straight away and take bloods for reference
In which patients should you start NAC immediately if they present with paracetamol overdose?
Administer NAC immediately if there is increased risk of toxicity
- Patient on long-term enzyme inducers
- Regular alcohol excess
- Pre-existing liver disease
- Glutathione-deplete states: eating disorders, malnutrition and HIV
