Management of Overdose/Toxicity Flashcards by Zoe Doak

Management of paracetamol overdose

if <1hr ago - activated charcoal
N-acetylcysteine
Liver transplantation

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Naloxone is the antidote for an overdose of which substance?

Opioids/opiates

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A severe overdose of benzodiazepines is treated with which antidote?

Flumanezil
- only used with severe or iatrogenic overdoses
- due to seizure risk

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Management of tricyclics overdose

IV bicarbonate
- correct acidosis
=> may reduce risk of seizures and arrhythmias in severe toxicity

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Dialysis is ineffective in removing tricyclics from the circulation. TRUE/FALSE?

TRUE

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What antiarrhythmics should NOT be used in Tricyclic overdose?

Class 1a (e.g. Quinidine)
Class Ic antiarrhythmics (e.g. Flecainide)

Class III (Amiodarone)

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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

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Reversal agent for warfarin

Vitamin K
Prothrombin Complex

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Heparin reversal agent

Protamine sulphate

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Management of beta-blocker toxicity/overdose

Atropine if bradycardic
in resistant cases, glucagon may be used

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Management of organophosphate insecticides toxicity/overdose

Atropine

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Treatment of digoxin toxicity?

Digoxin-specific antibody fragments

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Iron overload

Desferrioxamine, a chelating agent

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Mechanism of action of cocaine

blocks uptake of:
dopamine, noradrenaline and serotonin

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Cardiac adverse effects of cocaine

coronary artery spasm
MI
tachycardia/bradycardia
hypertension
QT prolongation
aortic dissection

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Neurological adverse effects of cocaine

seizures
mydriasis (dilated pupils)
hypertonia
hyperreflexia

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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