Toxicities and drug overdoses Flashcards
Paracetamol overdose presentation
patients taking liver enzyme-inducing drugs (rifampicin, phenytoin, carbamazepine, chronic alcohol excess, St John’s Wort)
malnourished patients (e.g. anorexia nervosa) or patients who have not eaten for a few days
Nausea and vomiting are very common feature
ACIDOSIS
Loin pain, haematuria, and proteinuria after the first 24 hou
ABDO pain
jaundice, hepatomegaly, asterixis, hepatic encelopathy
ALT high, AST high
INR, bleeding time High
Paracetamol overdose management
The minority of patients who present within 1 hour may benefit from activated charcoal to reduce absorption of the drug.
give NAC if
above a single treatment line joining pointsregardless of risk factors of hepatotoxicity
there is a staggered overdose* or there is doubt over the time of paracetamol
ingestion, regardless of the plasma paracetamol concentration;
patients who present 8-24 hours after ingestion of an acute overdose of more than 150 mg/kg
patients who present > 24 hours if they are clearly jaundiced or have hepatic tenderness, their ALT is above the upper limit of normal
acetylcysteine should be continued if the paracetamol concentration or ALT remains elevated whilst seeking specialist advice
Acetylcysteine is now infused over 1 hour (rather than the previous 15 minutes) to reduce the number of adverse effects –care gives anaphyloid reaction (non IgE anaphylaxis)-stop and lower the rate
liver transplant if—
Arterial pH < 7.3, 24 hours after ingestion
or all of the following:
prothrombin time > 100 seconds
creatinine > 300 µmol/l
grade III or IV encephalopathy
Salicylate poisoning presentation
due to intake of aspirin/
A key concept for the exam is to understand that salicylate overdose leads to a mixed respiratory alkalosis and metabolic acidosis. Early stimulation of the respiratory centre leads to a respiratory alkalosis whilst later the direct acid effects of salicylates (combined with acute renal failure) may lead to an acidosis
hyperventilation (centrally stimulates respiration)
tinnitus
lethargy
sweating, pyrexia*
nausea/vomiting
hyperglycaemia and hypoglycaemia
seizures
coma
Salicylate poisoning management
Treatment
general (ABC, charcoal)
urinary alkalinization with intravenous sodium bicarbonate - enhances elimination of aspirin in the urine
haemodialysis
Indications for haemodialysis in salicylate overdose
serum concentration > 700mg/L
metabolic acidosis resistant to treatment
acute renal failure
pulmonary oedema
seizures
coma
Opioid toxicity presentation and management
drowsy/confused with pin point pupils and low Resp Rate
Features of opioid misuse
rhinorrhoea
needle track marks
pinpoint pupils
drowsiness
watering eyes
yawning
Mx-
IV or IM naloxone in acute -short acting
NICE recommend methadone or buprenorphine as the first-line treatment in opioid detoxification
Benzodiazepine overdose presentation and management
Flumazenil
The majority of overdoses are managed with supportive care only due to the risk of seizures with flumazenil. It is generally only used with severe or iatrogenic overdoses.
Slurred speech
Incoordination
Unsteady gait
Impaired attention or memory
Dilated pupils are a sign of an overdose
RR depression, coma, other
Tricyclic overdose presentation and management
Amitriptyline and dosulepin (dothiepin) are particularly dangerous in overdose.
Features of severe poisoning include:
arrhythmias
seizures
metabolic acidosis
coma
ECG changes include:
sinus tachycardia
widening of QRS
prolongation of QT interval
Widening of QRS > 100ms is associated with an increased risk of seizures whilst QRS > 160ms is associated with ventricular arrhythmias
Mx
IV bicarbonate
first-line therapy for hypotension or arrhythmias
indications include widening of the QRS interval >100 msec or a ventricular arrhythmia
intravenous lipid emulsion is increasingly used to bind free drug and reduce toxicity
dialysis is ineffective in removing tricyclics
AVOID CLASSIC ANTIARRYTHMICS (amiodarone, fleicanide, etc)
Lithium overdose presentation and management
Toxicity may be precipitated by:
dehydration
renal failure
drugs: diuretics (especially thiazides), ACE inhibitors/angiotensin II receptor blockers, NSAIDs and metronidazole.
Features of toxicity
coarse tremor (a fine tremor is seen in therapeutic levels)
hyperreflexia
acute confusion
polyuria
seizure
mild-moderate toxicity may respond to volume resuscitation with normal saline
haemodialysis may be needed in severe toxicity
sodium bicarbonate is sometimes used but there is limited evidence to support this.
Warfarin toxicity management
Major bleeding Stop warfarin
Give intravenous vitamin K 5mg
Prothrombin complex concentrate - if not available then FFP*
INR > 8.0 (small/minor bleed)
Stop warfarin
Give intravenous vitamin K 1-3mg
Restart warfarin when INR < 5.0
INR >5 with bleed-give IV Vit K
INR >5 without bleed- Omit 1 Warfarin dose
Heparin toxicity management
Prothamine sulphate is the counteracting agent (partially effective)
B-Block toxicity mangement
Atropine for bradycardia
in resistant cases glucagon may be used
Ethylene glycrol toxicity presentation and management
its anti-freeze
Features of toxicity are divided into 3 stages:
Stage 1: symptoms similar to alcohol intoxication: confusion, slurred speech, dizziness
Stage 2: metabolic acidosis with high anion gap and high osmolar gap. Also tachycardia, hypertension
Stage 3: acute kidney injury
fomepizole, an inhibitor of alcohol dehydrogenase, is now used first-line in preference to ethanol
haemodialysis also has a role in refractory cases
Raised anion gap
Methanol poisoning present and management
Methanol poisoning
Management
fomepizole or ethanol
haemodialysis
Raised anion gap
Organophosphate poisoning present and management
Features can be predicted by the accumulation of acetylcholine (mnemonic = SLUD)
Salivation
Lacrimation
Urination
Defecation/diarrhoea
cardiovascular: hypotension, bradycardia
also: small pupils, muscle fasciculation
mx- ATROPINE
Digoxin toxicity present and management
Features
generally unwell, lethargy, nausea & vomiting, anorexia, confusion, yellow-green vision
arrhythmias (e.g. AV block, bradycardia)
gynaecomastia
classically: hypokalaemia
renal failure
myocardial ischaemia
drugs: amiodarone, quinidine, verapamil, diltiazem, spironolactone, thiazides. loop
(ANYTHING THAT LOWERS K)
Management
Digibind (antibody)
correct arrhythmias
monitor potassium
