Toxicology
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Toxicology

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    Toxicology Toxicology Presentation Transcript

    • Toxicology Paleerat Jariyakanjana, MD Faculty of Medicine Naresuan University 27 Jan 2014
    • Scope General Management of Poisoned Patients Acetaminophen Organophosphorus and Carbamate Insecticides Antihistamines
    • Diagnosis of Poisoning History Physical examination Lab Toxicology screening Abdominal x-rays
    • Tintinalli's Emergency Medicine, 7e
    • Tintinalli's Emergency Medicine, 7e
    • Essential clinical laboratory tests 1. 2. 3. 4. 5. 6. 7. 8. 9. Serum osmolality and calculation of the osmolar gap e’: Na, K & AG Serum glucose BUN/Cr LFT CBC UA: crystalluria, hemoglobinuria, or myoglobinuria ECG Stat serum acetaminophen level and serum ethanol level 10.UPT
    • Tintinalli's Emergency Medicine, 7e
    • Tintinalli's Emergency Medicine, 7e
    • Decontamination Surface decontamination  Skin  Eyes  Inhalation GI decontamination       Emesis Gastric lavage Activated charcoal Cathartics Whole-bowel irrigation Other oral binding agents  Surgical removal
    • Gastric lavage not necessary for small-moderate ingestions of most substances if activated charcoal can be given promptly
    • Gastric lavage Indications  massive overdose or particularly toxic substance + within 30–60 minutes  several hours after ingestion of agents that slow gastric emptying (eg, salicylates or anticholinergic drugs)
    • Contraindications A. Obtunded, comatose, or convulsing patients B. Ingestion of sustained-release or enteric-coated tablets C. Use of gastric lavage after ingestion of a corrosive substance
    • Activated charcoal Indications  ≤4 hr Drugs and Toxins Poorly Adsorbed by Activated Charcoal Alkali Inorganic salts Cyanide Iron Ethanol and other Lithium alcohols Mineral acids Ethylene glycol Potassium Fluoride Heavy metals
    • Activated charcoal Contraindications  drowsy patient Technique 60–100 g (1 g/kg), orally or by gastric tube
    • Whole-bowel irrigation Indications A. iron, lithium, or other drugs poorly adsorbed to activated charcoal B. sustained-release or enteric-coated tablets C. foreign bodies or drug-filled packets or condoms
    • Whole-bowel irrigation Contraindications A. Ileus or intestinal obstruction. B. Obtunded, comatose, or convulsing patient unless the airway is protected.
    • Whole-bowel irrigation Technique Administer bowel preparation solution (polyethylene glycol), 2 L/h by gastric tube (children: 500 mL/h or 35 mL/kg/h), until rectal effluent is clear.
    • Enhanced Elimination Urinary manipulation Hemodialysis Hemoperfusion Peritoneal dialysis Continuous renal replacement therapy Repeat-dose activated charcoal
    • Urinary manipulation Forced diuresis Alkalinization  sodium bicarbonate: 1-2 mEq/kg IV bolus or 3-4 mEq/kg IV infusion over 1 hour  Keep urine pH 7.5-8.5
    • Tintinalli's Emergency Medicine, 7e
    • Repeat-dose activated charcoal 20–30 g or 0.5–1 g/kg every 2–3 hours interrupting enterohepatic or enteroenteric recirculation of the drug or toxin
    • Disposition of the Patient Emergency department discharge or intensive care unit admission? Psychosocial evaluation
    • Acetaminophen
    • Toxic dose Acute ingestion >200 mg/kg in children or 6-7 g in adults Chronic toxicity >200 mg/kg within 24-hr period >150 mg/kg/d (or 6 g/d) x ≥2 d >100 mg/kg/d (or 6 g/d) x ≥3 d
    • Clinical presentation Tintinalli's Emergency Medicine, 7e
    • Diagnosis many clinicians routinely order acetaminophen levels in all overdose patients regardless of the history of substances ingested
    • Diagnosis Specific levels 1. acute overdose: 4-hour postingestion acetaminophen level  Obtain a second level at 8 hours if the 4-hour value is borderline or if delayed absorption is anticipated. 2. The nomogram should not be used to assess chronic or repeated ingestions.
    • Diagnosis Other useful laboratory studies electrolytes, glucose, BUN, creatinine, liver transaminases, bilirubin and PT/INR
    • Treatment Emergency and supportive measures Specific drugs and antidotes
    • Emergency and supportive measures ABC 4- to 6-hour period
    • Specific drugs and antidotes Acute single ingestion Above the “possible toxicity” line  NAC  Maximum benefit if start within 8-10 hr Extended-release tablets  Repeat the serum acetaminophen level at 8 & 12 hr
    • Specific drugs and antidotes Tintinalli's Emergency Medicine, 7e
    • Specific drugs and antidotes Specific drugs and antidotes  Duration of NAC treatment  If evidence of liver injury develops, NAC is continued until liver function tests are improving.
    • Decontamination activated charcoal Gastric lavage
    • Enhanced elimination Hemodialysis  effectively removes acetaminophen from the blood  not generally indicated because antidotal therapy is so effective  considered for massive ingestions with very high levels (eg, >1000 mg/L) complicated by coma and/or hypotension
    • Organophosphorus and Carbamate Insecticides
    • Clinical presentation Tintinalli's Emergency Medicine, 7e
    • Clinical presentation Nicotinic effects muscle weakness and tremors/fasciculations Central nervous system manifestations agitation, seizures, and coma
    • Diagnosis Specific levels RBC AChE (red blood cell acetylcholinesterase) PChE (plasma pseudocholinesterase) blood, urine, gastric lavage fluid, and excretion for specific agents and their metabolites
    • Diagnosis Other useful laboratory studies to consider ABG, pulse oximetry, ECG, electrolytes, glucose, BUN, creatinine, lactic acid, CK, lipase and LFT, and CXR
    • Treatment Emergency and supportive measures Specific drugs and antidotes
    • Emergency and supportive measures ABC Observe asymptomatic patients for at least 8–12 hours
    • Specific drugs and antidotes atropine 2-5 mg IV initially, and double the dose administered every 5 minutes until respiratory secretions have cleared
    • Specific drugs and antidotes Pralidoxime  Loading dose (30-50 mg/kg, total of 1–2 g in adults) over 30 minutes, followed by a continuous infusion of 8-20 mg/kg/h  continue 2-PAM for 24 h after the patient becomes asymptomatic, or at least as long as atropine infusion is required  not recommended for carbamate intoxication  if the exact agent is not identified and the patient has significant toxicity, pralidoxime should be given empirically
    • Decontamination Skin and mucous membranes Ingestion  activated charcoal  Gastric lavage
    • Enhanced elimination not indicated
    • Antihistamines
    • Toxic dose >3–5 times the usual daily dose
    • Clinical presentation ~anticholinergic poisoning  drowsiness, dilated pupils, flushed dry skin, fever, tachycardia, delirium, hallucinations, and myoclonic or choreoathetoid movements ~TCA overdoses  QRS widening and myocardial depression QT interval prolongation and torsadetype atypical ventricular tachycardia
    • Diagnosis based on the history of ingestion and can usually be readily confirmed by the presence of typical anticholinergic syndrome
    • Diagnosis Specific levels not generally available or useful Other useful laboratory studies electrolytes, glucose, CK, arterial blood gases or pulse oximetry, and ECG monitoring
    • Treatment Emergency and supportive measures Specific drugs and antidotes
    • Emergency and supportive measures 1. ABC 2. Treat coma, seizures, hyperthermia, and atypical ventricular tachycardia if they occur. 3. Monitor the patient for at least 6–8 hours after ingestion.
    • Specific drugs and antidotes no specific antidote
    • Decontamination activated charcoal Gastric lavage Because of slowed gastrointestinal motility, gut decontamination procedures may be helpful even in late-presenting patients.
    • Enhanced elimination not effective
    • Take home message A: airway B: breathing C: circulation D: decontamination E: enhance elimination
    • Reference
    • ANY QUESTIONS?