Principles of Toxicology Flashcards
Which screening tests are essential in all deliberate poisonings?
12 lead ECG
BSL
Paracetamol level
—> at presentation. If neg, no need to repeat at 4 hours.
—> if suspected initially, don’t ‘screen’ at arrival: do 4 hr level.
BHCG
What are the fever thresholds for intervention in poisoning?
Over 38.5
-> continuous rectal temp
Over 39.5
-> emergency. Paralyse and intubate.
Single dose activated charcoal:
1g/kg (50g for adults)
Alert and cooperative: self administer
Intubated: NGT
Other patients NOT SUITABLE
Up to 4 hours (1st hour best)
Cons:
- Mess
- Vomit
- Aspiration
- If direct to lung (misplaced NGT): death
- Impaired absorption of subsequent antidotes/ therapies
- Detracts from resus
CI:
- Obtunded (unless intubated)
- Seizure or decreased LOC expected
- Uncooperative
- Ongoing resus (higher priority)
- Ingestion low risk or easily treated in other ways
- 4 hours +
- Agent doesn’t bind to AC
- Corrosive ingestions (acid, alkali)
Can reduce absorbed dose by 50%
Adsorbs for faecal elimination
Which agents bind poorly to activated charcoal? (Ie. Doesn’t work)
Corrosives
(acids, alkali)
Periodic table
(lithium, Fe, K, arsenic etc.)
Alcohols and hydrocarbons
(ethanol, isopropyl, ethylene glycol, methanol)t
APPROACH TO POISONING:
Whole bowel irrigation:
Used for:
- Sustained release
- Enteric coated
—> ie. still present down GI
- Don’t bind to AC
Life threatening dose and first couple of hours
Takes up to 6 hours
1 on 1 nursing
NGT
2L/hr (25ml/kg/hr) of PEG-ELS (bowel prep)
Continue until diarrhoea runs clear
Give antiemetics
Give AC first (if useful for agent)
Cons:
- N&V
- NAGMA
- Aspiration
- Time/ personnel/ logistics
- Detracts from resus
- No good if obtunded (or expected to be), vomiting, or intubated (asp risk)
Verapamil XR
Iron
Gastric lavage:
Rarely used because complications + and very few situations suitable
First 1 hour
Large lavage tube (36-40G) down
Head down, lie left side
200ml water/saline in
Passively drain into bucket
Repeat until clear
+- AC dose post
Cons:
- Aspiration
- Laryngospasm
- GI injury
- Water intoxication (kids)
- Hypothermia
- Distraction from resus
Multi dose activated charcoal:
Enhanced elimination (unlike SDAC which is decontamination)
- Prevents enterohepatic cycling
- GI dialysis (concentration gradient)
Standard initial dose 50g (1g/kg)
Repeat half dose 2 hourly
Rarely beyond 6 hours
CARBAMAZEPINE
Phenobarbitone
Theophylline
Urinary alkalisation:
Only 2 drugs (acids)
- Salicylate
- Phenobarbitone coma
- (Crush injury)
Ionises and prevents renal reabsorption
Correct HypoK
Bolus 1-2 mmol/kg sodi bic IV
Infuse 150mmol sodi bic (made with 5% dextrose to 1L), over 4 hours.
URINE DIP pH
—> aim >7.5
Continue until toxidrome resolved
*Watch K (likely to drop)
*4 hourly gas
Drugs amenable to haemodialysis:
PK:
- Small molecule
- Small VD
- Slow endogenous elimination
INTERMITTENT dialysis more effective than continuous, or filtration.
*mostly anticonvulsants
Lithium (chronic)
Phenobarbitone
Valproate
Carbamazepine
Toxic alcohols
Salicylate
Theophylline
Metformin
Dabigatran
DO NOT FORGET point when ventilating tox patient:
Set the RR to match any preintubation compensatory hyperventilation.
If don’t —> death
Most common causes of tox seizure:
Venlafaxine
Tramadol
Amphetamines
(Bupropion- smoking cess)
WITHDRAWAL
- Alcohol
- BZD
Treatment options for tox seizure:
NOT PHENYTOIN- exacerbates Na channel blockade (and less effective)
1- BENZOS
(Eg. 5-10mg IV diaz, 0.1-0.3mg/kg in children. Repeat PRN.)
2- BARBITURATES
Eg.
Phenobarbitone: 20mg/kg IV
Thiopentone: 3-5mg/kg IV
**require intubation
3- Tube and heavily sedate (propofol, clonaz, inhalation all etc.)
*Pyridoxine in isoniazid
Tox causes of SEIZURE:
TCA, Propanolol, local anaesthetic
Venlafaxine
Sympathomimetics (cocaine, ecstasy, amphetamine)
Tramadol
Hypoglycaemics
Salicylates
CO
Toxic alcohols
WITHDRAWAL
Tox causes of HYPONATRAEMIA:
Cocaine
Ecstasy
SSRI/ SNRI
