Overdose & illicit drug use Flashcards
How is an opiate overdose treated?
Ventilation
IV/IM/SC Naloxone every 2-3mins
How does Naloxone work?
Competitively binds to opioid receptors causing a blockade
What needs to be taken into account when giving Naloxone?
Half life is shorter than the half life of opioids
Can resuscitate a patient but will quickly relapse if not maintained
What are the signs &symptoms of an opioid overdose?
CNS and respiratory depression Miosis Apnoea Fresh needle/track marks RARE: Frothy pink sputum, seizures, pulmonary rales
How is an opioid overdose investigated?
ECG- may see prolonged QRS
Tox screen
CXR - ARDS
Why are tricyclics damaging in overdose?
Narrow therapeutic range
Become potent cardiovascular and central nervous system toxins in moderate doses.
What receptors do tricyclics act on?
- Anticholinergic effects at muscarinic receptors
- Alpha-1 adrenergic receptor antagonism (vasoD)
- Fast Na channel blockade in cardiac cells (impaired CO & hypoT)
- Inhibition of pre-synaptic reuptake at terminals of norE/norA, serotonin, and dopamine
- Competitive antagonism of H1 and H2 receptors.
- Absorbed by the GI tract & peak at 2-8hrs
- Metabolised by the liver
What are the signs & symptoms of a tricyclic overdose?
CNS: delirium, lethargy, seizure, and coma, HypoT, arrhythmia, metabolic acidosis
Anticholinergic: Dry mouth, VasoD pupils, blurred vision, Tachy, agitation
Features of serotonin syndrome
Cerebellar signs: Ataxia, myoclonic movements, Inc muscle tone, hyperreflexia, extensor plantar responses
How is tricyclic overdose treated?
GI decontamination QRS >100/arrhythmia= sodium bicarb, ICU IV Lipid emulsion hypoT= vasopressors (NorA)/glucagon hyperV for cardiotoxicity Seizures: Benzos
How can risk of overdose be assessed?
- Suicide & depression risk
- Alcohol use
- Intent
- Did they want to die?
- Did they leave a note?
- Done in a place where they wouldn’t be found
- Was it planned? (giving away possessions)
- Stockpiling tablets
- Regret decision or want to try again?
How is a tricyclic overdose investigated?
ECG: Sinus Tachy, Prolonged QRS, R wave, prolonged QT
Blood tests
How is paracetamol metabolised? What is different in overdose?
Metabolised in the liver via 2 pathways
1) Glucuronidation: 60% of metabolism
2) Sulfation: 30% of metabolism
Breakdown
Partical breakdown by cytochrome P450 to a potentially toxic intermediate metabolite NAPQI
Normal conditions NAPQI combines w/intracellular glutathione = non-toxic mercapturate derivative
Metabolites excreted in the urine
In overdose minor cytochrome P450 pathway becomes dominant = inc NAPQI too much to detoxify
Excess binds to cellular components causing mitochondrial injury & hepatocyte death= acute liver failure
What are the signs & symptoms of a paracetamol overdose?
Asymptomatic until 24-72hours when acute liver failure occurs
N&V
Hepatic necrosis: Jaundice, RUQ pain, encephalopathy, hypoG
Renal failure
Metabolic acidosis
Oligouria
How is a paracetamol overdose investigated?
Paracetamol & salicylate levels: Only accurate >4hours after ingestion
LFTs
Glucose
U&Es
Prothrombin & INR: Indicator of acute liver failure
ABG: Acidosis
Commence Paracetamol treatment graph
How is a paracetamol overdose managed?
<8hours: Activated Charcoal if 150mg/kg ingested within the hour, IV Acetylcysteine & anti-emetic (Ondansetron)
>8hours: IV Acetylcysteine w/5% Dextrose
>24hours: Evaluate for liver transplant
Acetylcysteine given in 3 divided IV doses over 21hours
What are the types of paracetamol overdose?
Single acute: Ingestion of >4g in <1hour
Staggered: Doses taken over >1hour
Delayed presentation: Presentation to A&E >24hours after overdose
What are the side effects of Atropine?
Tachycardia
Hallucinations
Vasodilated pupils
What are the types of cholinergics that can be given?
Atropine
Atrovent
What levels of paracetamol are toxic?
< 75mg/kg: Rarely toxic
75-150mg/kg: Unlikely toxic
>150mg/kg: Serious toxicity- Parvolex started
Calc: How much they have had in total divided by their weight
What is the toxidrome for anticholinergic drugs?
E.g: Oxybutinin, Ipratropium ↑ HR & BP Normal RR ↑ Temp Dilated pupils ↓ Bowel sounds ↓ Diaphoresis (Sweating)
What is the toxidrome for cholinergic drugs?
E.g: Donepezil Normal HR & BP & RR & Temp Constricted pupils ↑ Bowel sounds ↑ Diaphoresis
What are the antidotes to:
- Salicylates
- Benzos
- Lithium
- Warfarin
- Heparin
- Beta blockers
- Methanol
- S: Haemodialysis, urinary arlkalinization (rare)
- B: Flumazenil
- Li: Mild-mod= Vol resus normal saline, Severe= haemodialysis
- W: Vit K, Prothrombin complex
- H: Protamine Sulphate
- BB: Brady= Atropine, Resistant= Glucagon
- M: Fomepizole/Ethanol, haemodialysis
What are the antidotes to:
- Ethylene Glycol
- CO
- Iron
- Digoxin
- Insecticide
- Lead
- Cyanide
- EG: Same as methanol (Fomepizole, Ethanol, Haemodialysis)
- CO: 100% O2, Hyperbaric O2
- I: Desferrioxamine (chelating agent)
- D: Digoxin specific antibody fragments
- In: Atropine
- L: Dimercaprol, Ca Edetate
- C: Hydroxocobalamin
