Poison & Venom

Everything is poison,in appropriate dose.

Paracelsus, father of toxicology

Poisoning Poison- a chemical that injures/kills Poisoning- a predictable dose-related

response to a toxic substance Exposure- Ingestion- methanol, Celphos, hair dye Inhalation- cyanide, carbon-monoxide Skin- nerve gas, organophosphates IV- potassium chloride Corrosive- chemicals that destroy locally,

without absorption

Assessment Exposure- what, when, how? Vital signs- Consciousness PR, BP Respiration Temperature Pupils- size, reaction Investigation- CBC Cr, SGPT, blood sugar ABG, CxR Urine & blood for poison analysis

Characteristic presentation Coma, hypotonia/reflexia, hypotension-

barbiturates, benzodiazepines Coma, miosis, decreased RR- opioids Agitation/hallucination, convulsion, mydriasis, tremor,

sweating, tachycardia- sympathomimetics- Ecstasy, theophylline, cocaine

Salivation, lacrimation, urination, defecation, GI cramps, emesis, miosis, bronchorrhea, bradycardia- cholinergics- organophosphates

Coma, hypertonia/reflexia, warm dry skin, urinary retention, mydriasis, tachycardia- anticholinergics- TCA

Nausea/vomiting, tinnitus, hyperventilation, tachycardia- salicylate

Management Simultaneous with assessment Airway.Breathing.Circulation- support as required Decontamination- for ingested poison Gastric lavage- within 1 hour of ingestion, preferably NG aspiration- for liquid poison Activated charcoal Whole bowel irrigation- for sustained release poison Emetics & cathartics- not recommended Enhanced excretion- diuresis or dialysis for ethylene

glycol, methanol, theophylline, salicylates

Antidotes- specific Paracetamol Opioids Benzodiazepines Warfarin Ethylene glycol/

methanol Organophosphates

N-acetylcysteine Naloxone Flumazenil Vitamin K Ethanol or

Fomepizole Atropine &

Pralidoxime

Aluminium phosphide Tablets used for preservation of grains Common poison in India Fatal dose- ~0.5 gm (fresh tablet) Liberates phosphine gas in stomach,

inhibits mitochondrial respiration, leading to cell death

Clinical Patient is conscious, till late Vomiting & SOB are common Hypotension leads to decreased organ

perfusion & dysfunction Dx- smell of phosphine, arrythmia Rx- supportive- gastric lavage (with

coconut oil), IVF, vasopressors, MgSO4 Px- bad after ingestion of fresh tablet

Hair dye Poison- paraphenylene-diamine Ingestion causes- Severe angioneurotic edema, laryngeal edema with stridor Rhabdomyolysis, metabolic acidosis Intravascular hemolysis with hemoglobinuria leading to ARF Rx- Gastric lavage Endotracheal intubation/tracheostomy IV fluids, soda-bicarbonate, dialysis

Caustic ingestion Strong acid/alkali- are corrosive Found in toilet/floor/utensil/laundry cleaners,

batteries Acids cause coagulation necrosis, alkali

cause liquefaction necrosis Cause stomatitis, esophagitis, gastritis,

esophageal perforation (stricture later) Dx- UGI endoscopy No gastric lavage Rx- supportive

Organophosphate poisoning Common insecticides Inhibit cholinesterase (organophosphates irreversibly &

carbamates reversibly) activity Cause cholinergic symptoms- SLUDGE & muscle fasciculations

with weakness May cause delayed muscle weakness Dx- symptoms, RBC cholinesterase activity Reversal with Atropine- Dx & Rx Rx- Supportive- monitoring Benzodiazepines- for seizures Decontamination- remove clothing, wash with soap & water, activated charcoal Atropine- till reversal of bronchospasm & bronchorrhea Pralidoxime- to relieve neuromuscular symptoms

Sedatives Barbiturates & Benzodiazepines Usually prescription drugs Good GI absorption Metabolized in liver, with active metabolites Cause CNS depression, upto coma & respiratory

depression Dx- clinical, Flumazenil for benzodiazepines Rx- Supportive- monitoring of vital signs GI decontamination- with multiple-dose activated charcoal Alkalinization of urine ± dialysis- for barbiturates

Opioid poisoning Intentional or misjudged potency Causes respiratory depression,

drowsiness/coma, miosis, bradycardia Rx- Supportive- prophylactic endotracheal intubation Gastric lavage Naloxone

Venom

A biologic toxin Injected by a bite or sting

Snake bite Few snakes are poisonous, most are not Cobra, krait, mamba, coral snake- common in India Pit viper, rattlesnake, copperhead- common in USA Snakes use poison for defense or to hunt Venom, modified saliva, contains proteases &

nucleases, injected through fangs Cobra venom- local pain & necrosis,

neurotoxic causing respiratory paralysis Pit viper venom- local tissue necrosis, hemorrhage, hemolysis,

DIC & finally circulatory collapse

Management Severity- depends upon Size of victim & snake Location & depth of bite Treatment- Rest, immobilization of affected part Wide constriction band to impede lymph flow Supportive- mechanical ventilation, TT Antivenom- lyophilized powder of refined horse serum,

reconstituted & given IV, 50200 ml i.e. 5-20 vials, watch for allergic reaction to horse serum

Insect stings Stinging insects belong to order Hymenoptera Apids- honeybee, bumblebee- sting for protection & leave

stinger, bee dies Vespids- wasp- sting to paralize prey, can cause multiple stings Formicids- fire-ants s/s- immediate burning pain, erythema,

edema; anaphylaxis may occur Rx- Epinephrine for anaphylaxis Remove stinger Symptomatic treatment for pain, swelling, itching

Prevention

Better than cure