Toxicology Flashcards
Lead poisoning
Lead can be accumulated via ingestion, inhalation, or direct skin contact
Aetiology:
- Occupational exposure e.g. miners, welders, storage battery workers, pottery glaze workers
- Environmental exposure
Features:
- Abdominal pain
- acts on intestinal smooth muscle
- RBC abnormalities
- acts on red cell enzymes involved in haem
synthesis
- Peripheral motor neuropathy
- Interstitial nephritis
- Blue-grey/blue-black gingival line
- Anterior uveitis/iritis
- Can progress to encephalopathy
Investigations:
- Blood lead levels
- Blood film - RBCs:
- Punctate basophilic stippling
- clover-leaf morphology
- Renal biopsy
- Interstitial nephritis
Management:
- Lead-chelating agents
- Severe - IV calcium EDTA, IV dimercaprol
Benzodiazepine withdrawal
Features:
- Anxiety
- Insomnia
- Irritability
- Depersolanisation
- Parasethesias
- Flushing
- Diplopia
- Hyperventilation
Onset varies between benzodiazepines
Carbon monoxide poisoning
Pathophysiology:
- CO binds Hb with 240x the affinity of oxygen, leading to tissue hypoxia
- Forms carboxyhaemoglobin
Features:
- Initial non-specific flu-like sx
- Headache
- Nausea, vomiting
- Weakness
- Tachypnea
- Then neurological symptoms
- Confusion/reduced GCS
- Dizziness
- Ataxia
- Seizures
- Neuropsychiatric symptoms can present up to 40 days later
- Memory loss
- Personality change
- Parkinsonism
- Respiratory failure
- Myocardial ischaemia
- Hypotension
- Cerebral oedema
- Cherry red skin
Investigations:
- Blood gas
- Severe symptoms if carboxyhaemoglobin >
20%
- NB heavy smokers can have levels up to 10%
- Routine blood panel
Management:
- High-flow oxygen
- Supportive care
- Specialist CO pulse oximeter
Common toxidromes
Sympathomimetics
- Causes:
- Amphetamines + cocaine
- Pseudoephrines
- Methylphenidate
- Caffeine
- Features:
- Agitation, tremors, delirium, seizures
- Pupil dilatation
- High HR, RR, BP, temp
- Diaphoresis
- Increased bowel motility
Anticholinergic
- Causes:
- Antihistamines
- TCAs
- Phenothiazines
- Antispasmodics
- Features:
- Agitation, seizures
- Dilated pupils
- High HR, RR, BP, temp
- Flushed red skin
- Dry mucus membranes
- Constipation and urinary retention
Cholinergic
- Causes:
- Organophosphates
- Nicotine
- Alzheimer’s and MG medications
- Nerve gas
- Features:
- Seizures, muscle weakness
- Constricted pupils
- Low HR
- Diaphoresis
- Diarrhoea, drooling, incontinence
- Bronchospasm with risk of arrest
Opioid
- Causes:
- Heroin, morphine etc.
- Features:
- Pupil constriction
- Cardiac + respiratory depression
Sedative-hypnotic
- Causes:
- Z-drugs
- Antiepileptics
- Barbiturates
- Benzodiazepines
- Antipsychotics
- ETOH
- Features:
- Confusion, stupor, coma
- Slurred speech
- Diplopia, nystagmus, ataxia
- Respiratory depression
Alcohol Withdrawal Syndrome
Features:
- 6-12hr - autonomic arousal - tremor, anxiety, nausea/vomiting, sweating, palpitations
- 12-24hr - hallucinations
- 24-48hr - tonic-clonic seizures
- 48-72hr - delirium tremens, cardiovascular compromise
Management:
- Treat hypoglycaemia
- IV Pabrinex TT TDS
- PRN oral chlordiazepoxide or IV lorazepam
Paracetamol overdose
Management is subdivided by intentionality, whether staggered or single, presence of adverse features
Features:
- Nausea/vomiting (first 24hr)
- Hepatocellular necrosis (48-96hr)
- Renal tubular acidosis (rare)
Poor prognostic factors:
- INR > 3.0
- Creatinine > 200 mmol/L
- pH < 7.3
- Signs of encephalopathy
Activated charcoal:
If ingestion of > 12g or > 150mg/kg occurring < 1hr ago
NAC
- Indications:
- Staggered OD > 150mg/kg
- OD > 150mg/kg over 8hr ago, adverse
features, or unable to obtain timely
paracetamol levels
- Adverse features = jaundice, raised ALT, INR
> 1.3
- 3 consecutive IV infusions totalling 300mg/kg over 21hr
Nitric oxide misuse
Acute:
- Short-lived and reversible CNS disturbances
e.g. elation, sedation
Chronic:
- Dose-dependent inactivation of vitamin B12
- Therefore causes peripheral neuropathy, subacute combined degeneration of the cord, anaemia
- Management:
- Admit if unable to walk or has severe
neurological/haem symptoms
- IM vit B12 1mg daily for 2 weeks, then
weekly for 4 weeks, then monthly until
recovered
Methaemoglobinaemia
Pathophysiology:
- Functionally useless form of Hb (unable to carry oxygen) due to iron binding in the Fe3+ form
Aetiology:
- Congenital
- Haemoglobinopathies which keep iron in
Fe3+ form
- Enzyme defects in iron reduction pathway
- Acquired
- Exposure to toxins
e.g. NO, aniline dyes, sulphonamides,
primaquine
Features:
- Methamoglobinaemia on ABG/VBG
- Brown blood
- Cyanosis
Management:
- Remove any cause
- Oral ascorbic acid or IV methene blue
