Toxicology Flashcards
Indications and contraindications to activated charcoal
Ingestion within 1 hour of potentially toxic substance
Contraindications:
- low binding affinity for charcoal (iron, lithium)
- Decreased LOC
- Risk of GI bleed
Drugs causing anticholinergic toxidrome
Anticholinergics - benztropine, atropine
TCAs
Antipsychotics - chlorpromazine, quetiapine
Antihistamines - chlorpheniramine, promethazine
Antispasmodics - oxybutynin
Anticholinergic toxidrome presentation
Mad as a hatter - Confusion, delirium
Blind as a bat - Mydriasis
Dry as a bone - Dry skin, urinary retention
Red as a beet - Flushed skin
Hot as a hare - fever
Palpitations
Seizures
Drugs causing cholinergic toxidrome
Organophosphates
Carbamates - insecticide
Pilocarpine - treatment dry eyes and mouth
Neostigmine - reverses neuromuscular blockade
Donepezil
Mushrooms
Sarin nerve gas
Types of opioid overdose
Intentional
Unintentional recreational or prescribed
Unintentional iatrogenic
Presentation for opioid overdose
Miosis
Hypopnoea <12 breaths/min
Stupor
With suggestive history
Management of opioid overdose
Airway management
Naloxone
Beware rebound sedation as naloxone wears off
Check for transdermal patches
Check signs of IVDU
Check for compartment syndrome
Causes of sympathomimetic overdoses
Amphetamines
Ritalin
Cocaine
Pseudoephedrine
Caffeine
Symptoms of sympathomimetic overdose
Symptom onset within 2 hours, life-threatening complications 2-6 hours
Agitation, hyperalert, paranoia, mania, psychosis
Mydriasis
Tachycardia, tachypnoea, hypertension, arrhythmia
Tremor, hyperreflexia, seizure, diaphoresis
Management of sympathomimetic overdose
Asymptomatic - observe at home for 4 hours
Symptomatic - medical observation, cardiac monitoring, bloods, and cooling
Benzos for agitation, psychosis, seizure
Triad of symptoms in serotonin syndrome
- CNS - agitation, confusion, altered mental state, seizures
- Neuromuscular - clonus, myoclonus, hyperreflexia, rigidity, tremor
- Autonomic disturbance - hyper/hypotension, tachy/bradycardia, hyperthermia, dysrhythmia, flushing, sweating, mydriasis
Hunter Serotonin toxicity criteria
Use of serotonergic agent in last 5 weeks AND
- Spontaneous clonus
- Inducible clonus + agitation or diaphoresis
- Ocular clonus + agitation or diaphoresis
- Tremor + hyperreflexia
- Ocular clonus OR inducible clonus + rigidity OR hypotonia + hyperthermia
Drugs causing serotonin syndrome
SSRIs, SNRIs
Opiates + fentanyl, tramadol, pethidine
TCAs
MAOis
Mood stabilisers: Lithium, sodium valproate
Linezolid (abx)
Ondansetron, metoclopramide
Rec drugs - amphetamines, LSD, ecstasy
Herbal - St John’s wort, ginseng
Cardinal features of neuroleptic malignant syndrome
Other symptoms
Use of neuroleptic or withdrawal of anti-Parkinsonian medications within last 4 weeks
Temp >38
Muscle rigidity
Tachycardia, labile BP, dehydration, SOB, altered mental state, pseudo-Parkinsonism, incontinence, dysphagia, diaphoresis, salivation
Rate of ETOH metabolism
One standard drink, 10g ETOH, per 1 hour
Driving limit for ETOH
Under 20 - zero
Over 20
- 50mg/100mL blood
250mcg/1000mL breath
Lethal dose of ETOH
5-8g/kg adult
3g/kg child
Intoxicated patient with altered mental state, other conditions to rule out
Head trauma
Hypothermia
Hypoglycaemia
Hypoxia
Hepatic encephalopathy
Metabolic derangement
Other substances
Definition of ETOH abuse
- Maladaptive pattern of ETOH use causing clinical distress, impairment of social/occupational function.
- High daily consumption, weekend heavy drinking, binge
- In last 12 months at least one of:
Failed to fulfil obligation
Physical hazards
Legal problems
Social/interpersonal problems
Audit-C questionnaire
How often drink of ETOH?
Never, </=monthly, 2-3/month, 2-3/week, 4+/week
How many drinks on a typical session?
1-2, 3-4, 5-6, 7-9, 10+
How often 6 or more drinks?
Never, <monthly, monthly, weekly, daily
Score >5 - Full Audit questionnaire
ETOH guidelines
Men:
3/day, 15/week
5 in one session
Women:
2/day, 10/week
4 in one session
At least 2 ETOH free days/week
Most common overdose
Paracetamol
Suspect in all deliberate self-poisonings
Symptoms of paracetamol overdose
nausea, vomiting
Pallor, diaphoresis
RUQ pain
Hepatotoxicity within 48-72 hours
Management of paracetamol OD with known time of ingestion
<2 hours - consider activated charcoal
2-8 hours
Paracetamol levels at 4 hours
Treat according to nomogram
> 8 hours
Paracetamol level and LFTs
Start NAC
Below nomogram and ALT <50 - stop NAC
Otherwise finish NAC and repeat LFTs
Threshold for dangerous level of paracetamol ingestion
Single ingestion (within 8 hours):
>200mg/kg child <6
>10g adult
Repeated supra therapeutic:
>10g or 200mg/kg over 24 hours
>6g or 150mg/kg daily over 48 hours
>4g or 100mg/kg daily >48 hours PLUS symptoms of liver damage
Etiology of carbon monoxide poisoning
CO binds Hb with 200x affinity of O2
Carboxyhaemoglobin
Reduces O2 binding
Hypoxia
Carbon monoxide poisoning pertinent history
COMA
Cohabitants and companions - similar symptoms?
Outside and away - feel better?
Maintenance - appliances well serviced?
Alarm - CO alarm in the house?
Symptoms of carbon monoxide poisoning
Acute:
Headache, lethargy
Nausea, vomiting
Abdo pain
Chest pain, SOB
Neuro symptoms
Chronic:
Memory impairment
Fatigue
Mood changes
Hearing loss
Ataxia, tremor, incoordination, slow movement
Cherry red lips
Normal sats reading
Management of CO poisoning
High flow O2/hyperbaric chamber
Treatment for 6 hours
Notifiable to MOH
Psych review if intentional poisoning
Symptoms of organophosphate exposure
Nicotinic then muscarinic
Nicotinic:
Monday - Mydriasis
Tuesday - Tachycardia
Wednesday - Weakness
Thursday - Hypertension
Friday - Fasiculations
Muscarinic:
Diarrhoea
Urination
Miosis
Bradycardia
Bronchorrhoea, bronchospasm
Emesis
Lacrimation
Salivation
Neuro:
Anxiety, confusion, drowsiness, seizures, hallucinations, insomnia, memory loss
Intermediate: Neck flexion, proximal muscle weakness, resp insufficiency, decreased deep tendon reflexes, cranial nerve abnormality
Late: glove and stocking neuropathy, flaccid paralysis LL=>UL
Management of organophosphate exposure
Refer to gen med
PPE
Decontaminate - burn clothing, irrigate
Do not induce vomiting
IV fluids
Atropine 0.05mg/kg or 2-5mg IV
benzos for seizure/agitation
Symptoms of salicylate toxicity
May come on 6-12 hours post ingestion
Mild <150mg/kg
Nausea, abdo pain, headache, dizziness, tinnitus, tachypnoea
Mild-moderate 150-300mg/kg
Confusion, slurred speech, hallucination
Tachycardia, worse tachypnoea
Orthostatic hypotension
Severe >300mg/kg
Reduced GCS, seizures
Hypoventilation
Dysrhythmia - usually sinus tachy
Cardiac arrest
Hyperthermia/fever
Blood gas progression in salicylate poisoning
- Respiratory alkalosis, alkaluria
- Respiratory alkalosis, paradoxical acuduria <6
- Repiratory alkalosis, metabolic acidosis, hypokalaemia
Management of salicylate poisoning
Decontamination:
- Activated charcoal
- Urine alkalisation +- haemodialysis
- Flushing, wash with soap + water
ABCs
Correct hypoglycaemia
Toxic level of oil of wintergreen
98% salicylate - 1 tsp = 7000mg
<6 - more than lick/taste
>6 - more than 4mL
Symptoms of TCA poisoning
Anticholinergic
Fever, flushing, dry skin, mydriasis, palpitations, urinary retention
Cardiovascular - tachycardia, hypertension > hypotension
Sodium channel blockade: ECG - long QRS, terminal R wave >3mm in aVR
CNS - drowsy, confusion, delirium, seizure, coma, resp depression
Symptoms of lithium toxicity
Altered mental state
Nausea, vomiting, diarrhoea
Tremor, weakness, ataxia
Renal toxicity
Hypotension, dysrhythmia, seizure, coma
Background condition resulting in volume or sodium loss
Level of lithium toxicity
> 40mg/kg
No clear correlation between serum levels and symptoms
ECG changes in lithium toxicity
Sinus node dysfunction
Long QT
Intraventricular conduction defects
T wave flattening
U wave
