Toxicological causes of cardiac arrest

Overview

The differential diagnosis of toxicological causes of cardiac arrest are many and varied. It is useful to consider the causes in terms of mechanism.

Causes and mechanisms

Airway compromise

• Acids, alkalis, pesticides, paraquat

Respiratory compromise

• Sedative / hypnotics, alcohols, opioids, baclofen
• Cholinergic agents, e.g. organophosphates, nerve agents
• Acute lung injury from hydrocarbon aspiration, paraquat

Circulatory compromise

• Sodium channel blockers, e.g. tricyclics, propanolol, cocaine, chloroquine, antiarrhythmics, local anesthetics
• Potassium efflux blockade, e.g.
• Catecholamine hypersensitivity, e.g. chloral hydrate, organochlorines
• Adenosine antagonism, e.g. theophylline
• Peripheral vasodilation, e.g. calcium channel blockers
• Myocardial depression, e.g. alcohol
• Sympathomimetic effects, e.g. cocaine, amphetamines
• Na+/K+ ATPase inhibition, e.g. digoxin, oleander
• Acute coronary syndromes, e.g. cocaine, amphetamines

Neurological effects

• CNS depressants, e.g. antipsychotics, antidepressants, benzodiazepines, barbiturates, baclofen, opioids, clonidine, alcohols, hydrocarbons
• Seizures, e.g. tramadol, venlafaxine, amphetamines, bupropion, isoniazid, theophylline
• Neuromuscular effects, e.g. serotonin toxicity, neuroleptic malignant syndrome, envenoming
• Cerebral edema, e.g. salicylates, valproate

Systemic and metabolic effects

• Hypocalcemia, e.g. hydrofluoric acid, ethylene glycol
• Hypoglycemia, e.g oral hypoglycemics, quinine, ethanol, beta-blockers
• Temperature disturbance, e.g. sedative/ hypnotics, serotonin toxicity, neuroleptic malignant syndrome, sympathomimetics
• Hyperkalemia, e.g. potassium, cardiac glycosides
• Hypoglycemia, e.g. oral hypoglycemics, quinine, ethanol, beta-blockers
• Hypocalcemia, e.g. fluorosis
• Acidemia, e.g. carbon monoxide, cyanide, toxic alcohols, toluidine, salicylates, metformin, iron, isoniazid, propylene glycol
• Abnormal hemoglobin, e.g. dapsone, nitrites
• Temperature dysregulation, e.g. sympathomimetics, sedatives/ hypnotics, serotonin toxicity, neuroleptic malignant syndrome
• Organ toxicity, e.g. paracetamol hepatoxicity, sodium valproate, heavy metals, pesticides
• Coagulopathy, e.g. envenoming, superwarfarins

CCC Differential Diagnosis Series
NEURO	Anosmia, Ataxia, Blepharospasm, Bulbar and Pseudobulbar palsy, Central Pontine Myelinosis, Cerebellar Disease, Chorea, Cranial nerve lesions, Dementia, Dystonia, Exophthalmos, Eye trauma, Facial twitches, Fixed dilated pupil, Horner syndrome, Loss of vision, Meningism, Movement disorders, Optic disc abnormality, Parkinsonism, Peripheral neuropathy, Radiculopathy, Red eye, Retinal Haemorrhage, Seizures, Sudden severe headache, Tremor, Tunnel vision
RESP	Bronchial breath sounds, Bronchiectasis, High airway pressures, Massive haemoptysis, Sore throat, Tracheal displacement
CVS	Atrial Fibrillation, Bradycardia, Cardiac Failure, Chest Pain, Murmurs, Post-resuscitation syndrome, Pulseless Electrical Activity (PEA), Pulsus Paradoxus, Shock, Supraventricular tachycardia (SVT), Tachycardia, VT and VF, SVC Obstruction
GIT	Abdominal distension, Abdominal mass, Abdominal pain, Asterixis, Dysphagia, Hepatomegaly, Hepatosplenomegaly, Large bowel obstruction, Liver palpation abnormalities, Lower GI haemorrhage, Malabsorption, Medical causes of abdominal pain, Rectal mass, Small bowel obstruction, Upper GI Haemorrhage
GUT	Genital ulcers, Groin lump, Scrotal mass, Urine colour, Urine Odour, Urine transparency,
MSK	Arthritis, Shoulder pain, Wasting of the small muscles of the hand
DERM	Palmar erythema, Serious skin signs in sick patients, Thickened Tethered Skin, Leg ulcers, Skin Tumour, Acanthosis Nigricans
ENDO	Diabetes Insipidus, Diffuse Goitre, Gynaecomastia, Hirsutism, Hypoglycaemia, SIADH, Weight Loss
HAEM	Splenomegaly
PAEDS	Floppy infant
MISC	Anaphylaxis, Autoimmune associated diseases, Clubbing, Parotid Swelling, Splinter haemorrhages, Toxic agents and abnormal vitals, Toxicological causes of cardiac arrest
IMAGING	CHEST: Atelectasis, Hilar adenopathy, Hilar enlargement on CXR, Honeycomb lung, Increased interstitial markings, Mediastinal widening on mobile CXR, Pulmonary fibrosis, Pseudoinfiltrates on CXR, Pulmonary opacities on CXR, ABDO: Gas on abdominal X-ray, Kidney mass, BRAIN: Intracranial calcification, Intracranial structures with contrast, Ventriculomegaly, OTHER: Pseudofracture on X-Ray,
LABS	LOW: Anaemia, Hypocalcaemia, hypochloraemia, Hypomagnesaemia,  HIGH: Bilirubin and Jaundice, Hyperammonaemia, Hypercalcaemia, Hyperchloraemia, Hyperkalaemia, Hypermagnesaemia,  ACID BASE: Acid base disorders, Resp. acidosis, Resp. alkalosis, Creatinine, CRP, Dipstick Urinalysis, Laboratory Urinalysis, Liver function tests (LFTs), Pleural fluid analysis, Urea, Urea Creatinine Ratio, Uric acid, Urinalysis, Urine Electrolytes

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