Management of Overdose/Toxicity Flashcards
Management of paracetamol overdose
if <1hr ago - activated charcoal
N-acetylcysteine
Liver transplantation
Naloxone is the antidote for an overdose of which substance?
Opioids/opiates
A severe overdose of benzodiazepines is treated with which antidote?
Flumanezil
- only used with severe or iatrogenic overdoses
- due to seizure risk
Management of tricyclics overdose
IV bicarbonate
- correct acidosis
=> may reduce risk of seizures and arrhythmias in severe toxicity
Dialysis is ineffective in removing tricyclics from the circulation. TRUE/FALSE?
TRUE
What antiarrhythmics should NOT be used in Tricyclic overdose?
Class 1a (e.g. Quinidine)
Class Ic antiarrhythmics (e.g. Flecainide)
Class III (Amiodarone)
Methods of managing lithium toxicity/overdose
- mild-moderate = IVF with normal saline
- haemodialysis if severe toxicity
- sodium bicarbonate increases the alkalinity of the urine => promotes lithium excretion
Reversal agent for warfarin
Vitamin K
Prothrombin Complex
Heparin reversal agent
Protamine sulphate
Management of beta-blocker toxicity/overdose
Atropine if bradycardic
in resistant cases, glucagon may be used
Management of organophosphate insecticides toxicity/overdose
Atropine
Treatment of digoxin toxicity?
Digoxin-specific antibody fragments
Iron overload
Desferrioxamine, a chelating agent
Mechanism of action of cocaine
blocks uptake of:
dopamine, noradrenaline and serotonin
Cardiac adverse effects of cocaine
- coronary artery spasm
- MI
- tachycardia/bradycardia
- hypertension
- QT prolongation
- aortic dissection
Neurological adverse effects of cocaine
seizures
mydriasis (dilated pupils)
hypertonia
hyperreflexia
Management of cocaine toxicity
Chest pain:
benzodiazepines + GTN
HTN:
benzodiazepines + sodium nitroprusside
Features of ecstasy overdose
Neuro:
- agitation
- anxiety
- confusion
- ataxia
cardio:
- tachycardia
- hypertension
Other:
hyponatraemia
hyperthermia
rhabdomyolysis
Management of ecstasy overdose
Supportive
Dantrolene may be used for hyperthermia
Drugs which can be cleared with Haemodialysis
BLAST
Barbiturate
Lithium
Alcohol (inc methanol, ethylene glycol)
Salicylates
Theophyllines
Drugs which can’t be cleared with haemodialysis
tricyclics
benzodiazepines
dextropropoxyphene
digoxin
beta-blockers
What treatment can be given for paracetamol overdose if the patient presents within 1 hour of ingestion?
Activated charcoal
When should NAC be used?
- plasma conc above treatment line
- staggered overdose
- patients presenting 8-24 hours after ingestion of >150 mg/kg of paracetamol
- patients who present > 24 hours if jaundiced or have hepatic tenderness, or their ALT is above the upper limit of normal
What adverse reaction can NAC cause and how is this managed?
- anaphylactoid reaction (non-IgE mediated mast cell release)
- Stop infusion, then restart at a slower rate.
Criteria for liver transplantation in paracetamol overdose
Arterial pH < 7.3, 24 hours after ingestion
OR all of the following:
- PT > 100 seconds
- Creatinine > 300 µmol/l
- Grade III or IV encephalopathy
How does paracetamol cause liver damage?
- liver normally conjugates paracetamol with glucuronic acid/sulphate
- conjugation system becomes saturated => oxidation by P450 system to form toxic metabolite (N-acetyl-B-benzoquinone imine)
- Glutathione conjugates with toxin to form mercapturic acid
- glutathione stores run-out
- toxin forms covalent bonds with cell proteins, denaturing them and leading to cell death.
How does NAC help in the management of paracetamol overdose?
NAC = precursor of glutathione
=> increases hepatic glutathione production
=> can conjugate with toxin
What patient groups are at increased risk of hepatotoxicity in paracetamol overdose?
- Those taking liver enzyme-inducing drugs
(rifampicin, phenytoin, carbamazepine, chronic alcohol excess, St John’s Wort) - Malnourished patients (e.g. anorexia nervosa)
Features of Quinine Toxicity
Classical hallmarks:
- tinnitus
- visual blurring
- flushed and dry skin
- abdominal pain
- Prolonged QT (blocks Na and K channels)
=> risk of ventricular tachyarrhythmias - Hypoglycaemia (stimulates pancreatic insulin secretion)
- Pulmonary oedema
Management of quinine toxicity
Supportive:
- IVF
- inotropes
- Bicarb
- Positive pressure ventilation if pulmonary oedema
Describe the appearance on a blood gas when a patient has taken a salicylate overdose
Mixed respiratory alkalosis and metabolic acidosis.
- Early stimulation of respiratory centre = respiratory alkalosis
- later the direct acid effects of salicylates + acute renal failure) lead to an acidosis
- In children metabolic acidosis tends to predominate.
Features of salicylate overdose
- Hyperventilation
- tinnitus
- lethargy
- sweating, pyrexia
- nausea/vomiting
- hyper/hypoglycaemia
- seizures
Management of salicylate overdose
- ABCDE
- IV bicarb
- Haemodialysis
Indications for haemodialysis in salicylate overdose
- serum conc. > 700mg/L
- metabolic acidosis resistant to treatment
- acute renal failure
- pulmonary oedema
- seizures
Features of tricyclic overdose
ANTICHOLINERGIC:
- dry mouth
- dilated pupils
- agitation
- sinus tachycardia
- blurred vision.
severe poisoning:
- arrhythmias
- seizures
- metabolic acidosis
Common ECG changes in Tricyclic overdose
- sinus tachycardia
- widening of QRS
- prolongation of QT interval
QRS > 100ms= risk of seizures QRS > 160ms = ventricular arrhythmias
Management of tricyclic overdose
- IV bicarbonate
first-line therapy for hypotension or arrhythmias
indications - IV lipid emulsion is increasingly used to bind free drug and reduce toxicity
What can precipitate lithium toxicity?
- dehydration
- renal failure
- diuretics (especially thiazides)
- ACEi/ARB
- NSAIDs
- Metronidazole
Features of lithium toxicity
- coarse tremor
- hyperreflexia
- acute confusion
- polyuria
- seizure
Management of lithium toxicity
Mild-mod toxicity - normal saline
Severe - Haemodialysis
