Poisoning – Comprehensive Lecture Notes

Objectives of the Lecture

• Describe GI decontamination, recognize common toxidromes (cholinergic, sympathomimetic, anticholinergic, narcotic), identify specific antidotes, and initiate ED management for overdose cases.

Key Foundational Quote (Paracelsus)

• "Everything is a poison, nothing is a poison. It is the dose that makes the poison." (Dose–response principle).

Warm-Up Clinical Scenario (Initial Thought Exercise)

• For a patient with unknown overdose: stabilize ABCs, obtain focused history (time, agent, intent), and query antidote availability.

Epidemiology of Poisoning in Ghana

Typical Patterns

• Accidental: pesticide mishandling, children ingesting kerosene/pesticides, herbal potions, food-borne toxins.

• Intentional/Ilicit: pharmaceutical overdoses (e.g., clandestine abortion), suicidal ingestions.

KBTH (Korle-Bu Teaching Hospital) Data Jan 2013 – Jul 2016 (n = $5346$)

• Age $21{-}30$ y ($36\%$), $66\%$ female.

• Agents: household detergent ($25\%$), organophosphates ($23\%$), industrial chemicals ($18\%$).

• Intent: Suicidal ($95\%$).

• Outcomes: Mortality $6\%$; $88\%$ discharged within $72$ h.

General ED Approach to the Poisoned Patient

• Safety (PPE), Resuscitation (ABC), Parallel focused history, Decontamination, Antidote administration, Disposition.

Essential Elements of Overdose History

• Exact time, witness accounts, original container, assume co-ingestants (alcohol, acetaminophen, aspirin).

Decontamination Strategies

Routes & Rationale

• GI exposure ($\sim$75\%$ of toxin entries): prevent absorption.

• Topical: remove clothes, wash skin.

• Enhance elimination: MDAC, urinary alkalinization, WBI, extracorporeal methods.

Specific Techniques & Indications

• Induce vomiting: Not recommended (aspiration risk).

• Gastric lavage: Only early (<2 h), for life-threatening agents (e.g., tricyclics, iron) with protected airway.

• WBI: Sustained-release preparations, "body packers."

Activated Charcoal

• Adult dose $50$ g PO; paediatric $1$ g / kg PO.

• Give within $1$ h of ingestible toxin. Ineffective for metals, corrosives, alcohols.

• Contra-indications: impaired airway (unless intubated), bowel obstruction, caustic ingestion.

Clinical Clues to Poisoning (Bedside Examination)

• Table of signs (pupils, vitals, skin, lungs, neuro) aids toxidrome recognition.

Major Toxidromes Covered

• Cholinergic, Sympathomimetic, Anticholinergic, Narcotic (opioid), Paraquat & Organophosphates.

Agrochemical Focus: Paraquat Poisoning

Chemical & Exposure Facts

• Bipyridyl herbicide (blue, emetic, odorant).

• Lethal oral dose: adults $10{-}20$ ml of $20\%$ w/v solution (≈ $4{-}5$ ml for children).

• Mechanism: Concentrates in kidneys/lungs $\rightarrow$ superoxide radicals $\rightarrow$ cell damage $\rightarrow$ multiorgan failure, pulmonary fibrosis.

Clinical Features

• Local: mucosal burns ("paraquat tongue"), GI upset.

• Respiratory: progressive alveolitis $\rightarrow$ hypoxia.

• Systemic: AKI, hepatic failure, cardiotoxicity.

Investigations

• Labs for dehydration/organ failure (RFT, LFT, ABG, lactate, coag profile).

• Imaging: CXR diffuse infiltrates.

• Bedside urinary dithionite test.

Management Principles

• Medical emergency ($50{-}80\%$ mortality).

• Strict staff safety, decontamination, ocular irrigation.

• If <2 h post-ingestion: single dose charcoal (avoid gastric lavage).

• Airway: maintain; avoid supplemental $\mathrm{O_2}$ unless \text{SpO}*2<88\% (amplifies injury).

• Fluid/electrolyte replacement, analgesia.

• Consider immunosuppression, antioxidants (uncertain benefit), early hemofiltration/plasmapheresis.

• GI consult, palliative care for fulminant cases.

Poor Prognostic Indicators

• Age >50, generalized skin burning sensation, pre-existing renal disease, hypoxemia, metabolic acidosis, high serum lactate, extensive pulmonary infiltrates.

Classic Toxidromes – Detailed Review

1. Cholinergic (Excess Acetylcholine)

• Etiology: organophosphates, nerve agents.

• Pathophysiology: acetylcholinesterase inhibition $\rightarrow$ ACh accumulation.

• Signs: Nicotinic (tachycardia, fasciculations, weakness), Muscarinic ("SLUDGE" or "DUMBELS" - Salivation, Lacrimation, Urination, Defecation/Diarrhoea, GI cramps, Emesis; Killer “B”s: Bradycardia, Bronchorrhoea, Bronchospasm), CNS (anxiety $\rightarrow$ coma).

• Management: ABCs, decontamination, Atropine ($2$ mg IV q $5{-}10$ min, titrate), Pralidoxime (organophosphates), Benzodiazepines for seizures.

2. Sympathomimetic (Adrenergic Excess)

• Agents: cocaine, amphetamines, caffeine.

• Presentation: agitation, HTN, tachycardia, hyperthermia, mydriasis, diaphoresis (wet skin, present bowel sounds).

• Management: ABCs, sedation (benzodiazepines), active cooling. Avoid $\beta$-blockers in cocaine overdose.

3. Anticholinergic (ACh Receptor Blockade)

• Sources: atropine, antihistamines, TCAs, Jimsonweed.

• Hallmark: "Blind as a bat" (mydriasis), "Hot as a hare" (hyperthermia, flushed), "Mad as a hatter" (delirium), "Dry as a bone" (anhidrosis, dry mucosa). "Can’t see, can’t pee, can’t spit, can’t s—t."

• Physical: tachycardia, HTN, urinary retention, absent bowel sounds, dry axillae.

• Management: ABCs, GI decontamination, urinary catheterization. Benzodiazepines for agitation.

4. Narcotic / Opioid

• Agents: heroin, morphine, fentanyl.

• Classic triad: miosis, CNS depression, respiratory depression.

• Management: Support ventilation, Naloxone (up to $2$ mg IV q 2 min, repeat/infuse).

Key Investigations in Poisoning Work-up

• Toxicology screen (urine, serum, breath alcohol).

• Routine labs (U&E, LFT, CK, coagulation).

• ECG (QRS/QT prolongation).

Antidotes to Selected Toxins (Quick Reference)

• Organophosphates $\rightarrow$ Atropine $\pm$ Pralidoxime.

• Opioids $\rightarrow$ Naloxone.

• Carbon monoxide $\rightarrow$ High-flow $\mathrm{O_2}$.

• Paracetamol $\rightarrow$ N-acetylcysteine.

• Salicylate $\rightarrow$ IV $\mathrm{NaHCO_3}$ (alkalinize urine); hemodialysis.

• TCAs $\rightarrow$ IV $\mathrm{NaHCO_3}$.

• Calcium channel blockers $\rightarrow$ IV calcium gluconate, glucagon, HDI.

• $\beta$-Blockers $\rightarrow$ Atropine, glucagon, HDI.

• Benzodiazepines $\rightarrow$ Flumazenil (cautiously).

• Iron $\rightarrow$ Deferoxamine.

• Cyanide $\rightarrow$ Dicobalt edetate or $\text{NaNO}*2$ + $\text{Na}*2\text{S}*2\text{O}*3$ or hydroxocobalamin.

Disposition & Multi-Disciplinary Care

• Admit all poisoned patients; ICU/HDU for severe cases.

• Early involvement: toxicologist, emergency physician, intensivist.

• Psychiatric assessment for intentional ingestions.

Closing Case Revisited

Case Part 1 (Unknown 20-Tablet OD, 2 h post-ingestion)

• Management: Safety, ABCs, monitor vitals, IV access, consider activated charcoal, focused history, pill count, baseline labs, prepare antidote.

Case Part 2 (Findings: lethargy, pinpoint pupils, RR 6)

• Likely narcotic toxidrome. Immediate actions: Airway positioning, assist ventilation (BVM + high-flow $\mathrm{O_2}$), Naloxone ($0.4{-}2$ mg IV, repeat until RR >12), continuous monitoring, full history, toxicology screen, admit, psychiatric consult.

Ethical & Practical Considerations

• Rapid, protocol-driven care is crucial. Maintain patient dignity and confidentiality. Prevention: education on safe storage, limiting access to lethal means, mental health support.

Numerical / Formulaic Highlights

• Lethal paraquat dose: $10{-}20\,\text{mL}$ of $20\%$ w/v (adult).

• Activated charcoal adult dose: $50\,\text{g}$; paediatric: $1\,\text{g kg}^{-1}$.

• Atropine initial dosing: $2\,\text{mg IV q }5{-}10\,\text{min}$.

• Naloxone dosing: up to $2\,\text{mg IV q }2\,\text{min}$.