XVI: TOXICOLOGY



History


•  Timing, quantity of ingestion/exposure, access to household chemicals/other meds, coingestions, enteric-coated/extended-release substances


Physical Exam


•  VS, pupils, skin, neuro findings (AMS, nystagmus, myoclonus, tremor), peristalsis, smell


Evaluation


•  ECG, FSG, CBC, chemistries, LFT’s, UA, ABG, hCG, osmolar/anion gap


•  Drug levels


•  Exposures for which drug level is useful: APAP, salicylates, theophylline, lithium, digoxin, EtOH, carboxyhemoglobin, methemoglobin, iron, methanol, ethylene glycol, lead, mercury, arsenic, organophosphate, anticonvulsants


Treatment




Dermal Decontamination


•  Irrigation w/ copious volumes of H2O (unless metallic Na, K, or phosphorus)


Ocular Decontamination


•  Irrigation w/ copious volumes of H2O


Enhanced Elimination


•  Urinary alkalinization w/ NaHCO3 (eg, salicylates, phenobarbital, formic acid)


•  HD (eg, ethylene glycol, methanol, lithium, salicylates)





Disposition


•  Admit for any significant ingestion/exposure; consider transfer for complex presentations & inadequate hospital resources


Pearl


•  Hospital tox screens vary → learn your hospital’s screen to guide your practice


ANTICHOLINERGIC INGESTION


Definition


•  Antagonists @ muscarinic cholinergic receptor → inhibit parasymp system




History


•  Blurred vision, dry mouth, fever, AMS, flushing; “blind as a bat, dry as a bone, hot as a hare, mad as a hatter, red as a beet”


Differential


•  Sympathomimetic OD, EtOH/benzo withdrawal, thyroid storm, sepsis/meningitis


Findings


•  ↑ HR, ↑ temp, dilated pupils, dry MM/skin, ↓ bowel sounds, urinary retention, myotonic activity, choreoathetosis, confusion/delirium, szs


Evaluation


•  ECG (≠ QTc Æ TCAs, neuroleptics); electrolytes; total CK (rhabdomyolysis); tox screen → r/o other ingestions; pulse ox; Tele


Treatment


•  Supportive: IV hydration, external cooling


•  Decontamination/elimination: Activated charcoal (1 dose, w/in 1–2 h), HD


•  BZD (IV): For agitation, szs


•  Physostigmine (IV): Reverses anticholinergic effects via acetylcholinesterase inhibition


•  NOT for routine use due to risk of intractable szs, AV block, asystole


Disposition


•  Admit; ICU for pts w/ cardiac instability or szs


Pearl


•  Rarely fatal unless significant hyperthermia is present


PSYCHOPHARMACOLOGIC INGESTION


Selective Serotonin Reuptake Inhibitors and Serotonin Syndrome


Approach


•  Spectrum for serotonin intoxication ranges from mild lethargy to serotonin syndrome


•  Consider serotonin syndrome for anyone on meds w/ serotonin activity, esp ≥2 agents


•  Greatest risk w/i min, h after starting new med or increasing dose of old med


Definition


•  SSRI: Selective serotonin reuptake inhibitors; SRIs: Serotonin reuptake inhibitors (also activity on epinephrine, norepinephrine, dopamine)








History


•  Akathisia, AMS, szs


Findings


•  ↑ HR, ↑ temp, ↑ reflexes, diaphoresis, mydriasis, ↑ ↓ BP, tremor, clonus, neuromuscular rigidity, ataxia


Evaluation


•  VS, CBC, chem 7, CK (rhabdo), ECG (↑ QRS, ↑ QTc, torsades), pulse ox, Tele


Treatment


Acute overdose


•  Activated charcoal, admit for monitoring


Serotonin Syndrome


•  Supportive: IV fluids, electrolyte correction, external cooling (may require sedation/paralysis for severe hypothermia)


•  Benzos (IV): For agitation, rigidity, szs


•  (Anecdotal evidence) Cyproheptadine (12 mg initially, 4 mg PO q1h), chlorpromazine 25–50 mg IV for severe sxs


Pearl




NEUROLEPTICS, NEUROLEPTIC MALIGNANT SYNDROME


Definition


•  Characterized by D2 antagonism ± serotonin receptor antagonism




History


•  Slurred speech, sedation, anticholinergic toxidrome, extrapyramidal sxs (dystonia, akathisia, parkinsonism, tardive dyskinesia)


•  NMS: ↑ HR, rigidity, AMS, szs, autonomic instability, metabolic acidosis, rhabdomyolysis


Evaluation


•  CBC, chem 20, CK (rhabdo), ECG (↑QTc, torsades), UA (myoglobin)


Treatment


•  Dystonia/akathisia: Diphenhydramine, benztropine, BZD


•  NMS: Cooling, IV fluids, benzos, nondepolarizing neuromuscular blockade, dantrolene, bromocriptine, amantadine


LITHIUM




History


•  Acute tox: GI sxs initially; neurologic findings may develop later


•  Chronic tox: Neurologic sxs




Evaluation


•  VS, ECG, CBC, chem7, Ca, Mg, PO4, TSH, free T4, UA


•  Lithium level: Not useful in acute ingestion (development of neurologic sx is better reflection of tox); in chronic tox, level >1.5 mEq is significant


•  Assess for causes of decreased lithium clearance: Eg, dehydration, renal failure


Treatment


•  IV fluids: Decreases tox & promotes Li excretion, NS bolus then ½ NS


•  GI decontamination: Activated charcoal ineffective, whole bowel irrigation may be useful


•  Sodium polystyrene sulfonate (Kayexalate), consider thiazides, indomethacin, or amiloride for nephrogenic DI


•  BZD for szs (avoid phenytoin, which ↓ Li renal excretion)


•  HD: For pts w/ severe neurologic sxs &/or clinical deterioration


Disposition


•  Admit all pts w/ sustained release ingestions, lithium level >1.5 mEq, or new neurologic signs; lesser ingestions can be treated & observed 4–6 h → re√ level ± psychiatry eval


Pearl


•  Li has narrow therapeutic window; consider Li tox in pts w/ ARF/↓ UOP


TRICYCLIC ANTIDEPRESSANTS


Approach


•  Sxs of overdose almost always occur w/in 6 h of ingestion






Evaluation


•  ECG, CBC, chem 7, Ca/Mg/PO4, CK, UA tox screen, pulse ox, Tele


Treatment


•  Supportive: IV fluids


•  GI decontamination/elimination: Activated charcoal ± gastric lavage, intralipid for clomipramine


•  Sodium bicarbonate: 1–2 mEq/kg boluses titrated to pH 7.45–7.55


•  Indications: QRS >100, new RAD, ↓ BP, &/or ventricular dysrhythmia


•  BZD: For szs


•  Lidocaine: For ventricular dysrhythmias refractory to NaHCO3, avoid procainamide or other type Ia or Ic antiarrhythmics


Disposition


•  Admit all pts w/ e/o cardiotoxicity or sz; d/c pts w/o sxs at 6 h after ingestion


Pearl


•  Antimuscarinic effects are absent in many cases of TCA overdose


ALCOHOLS


Definition


•  Ingestions of toxic alcohols


Approach


•  History


•  Type of alcohol ingested, time of ingestion, coingestants


•  PE: Monitor for airway protection, occult trauma (head injury)


•  Labs: Bedside glucose test (may be all that’s needed), BAL (declines 20 mg/dL/h), anion gap, serum/urine tox screen (if coingestants suspected), osmolar gap for alcohols other than EtOH


•  Osmol calc = 2 × Na + BUN/2.8 + glucose/18 + EtOH/4.6


•  Osmol gap = Osmol measured − osmol calc


•  Tx: Charcoal doesn’t bind alcohol, ± thiamine/folate




ETHANOL


History


•  EtOH ingestion, found down, lethargy, nausea, vomiting, ± associated trauma, ± aspiration, gastritis


Physical Findings


•  CNS, respiratory depression, slurred speech, ataxia, nystagmus


Evaluation


•  Bedside glucose (hypoglycemia common in alcoholics), ± BAL (if ingestion uncertain), ± CBC/BMP/LFTs/lipase, ± ECG (if pulse if irregular), ± magnesium level


Treatment


•  Maintain airway, serial exams, ± IVF/thiamine/folate (given but may not be necessary)


Disposition


•  Ambulating w/o ataxia + speaking clearly → d/c


Pearls


•  R/o head trauma, CNS infection, Wernicke encephalopathy, alcoholic ketoacidosis, hypoglycemia, alcohol withdrawal/DT, coingestions, SI/HI


•  Known EtOH ingestion/intoxication in pt w/ h/o same does not require lab & can be observed until clinically sober


METHANOL


Definition


•  Ingestion of methanol (peak levels 30–60 min, 24–30 h ½ life, hepatic metabolism)


History


•  Drinking: Paint solvents/antifreeze/windshield-washing fluid/canned fuels/gasoline additives, shellac/copy machine fluid/home heating fuels


Physical Findings


•  CNS depression, vomiting, papilledema/hyperemia, visual changes/loss, gastritis


Evaluation


•  ↑ Methanol level, ↑ Osmol gap, ↑ anion gap (profound), chemistries, ABG


Treatment


•  Based presumptive Dx if levels delayed, maintain airway


•  Fomepizole: Loading dose (15 mg/kg in 100 mL D5W over 30 min) → maintenance (10 mg/kg q12h × 4 doses → 15 mg/kg q12 to methanol concentration <20/dL)


•  Folate 50 mg IV q4h until resolution of acidemia (cofactor to convert formic acid → CO2 + H2O)


•  Dialysis: Absolute indications → visual impairment + detectible methanol level or >50 mL/dL, osmol gap >10, ingestion >1 mg/kg, severe acidosis, renal failure


Disposition


•  Admit


ETHYLENE GLYCOL


Definition


•  Ingestion of ethylene glycol (peak levels 30–180 min, 3–7 h ½ life, 70% hepatic metabolism)


History


•  Drinking: Antifreeze, coolants, paint, polishes, detergents, fire extinguishers


Physical Findings


•  3 phases: <12 h → ↓ CNS (like EtOH), gastritis; 12–24 h → ↑ HR/RR/BP/SOB; >12 h → ATN (oxylate crystal deposition)


Evaluation


•  Ethylene glycol level, ↑ osmol gap, ↑ AG, calcium oxylate crystals in urine, beta-hydroxybutyrate (used to distinguish from alcoholic ketoacidosis)


Treatment


•  Based presumptive Dx if levels delayed, maintain airway


•  Fomepizole: Loading dose (15 mg/kg in 100 mL D5W over 30 min) → maintenance (10 mg/kg q12h × 4 doses → 15 mg/kg q12h to methanol concentration <20/dL)


•  Folate/thiamine 100 mg IV q6h/pyridoxine 50 mg IV q6h until resolution of acidemia (cofactors in oxalic acid metabolism)


•  HD: Severe acidosis (pH <7.25) + osmol gap >10, renal failure (Cr >1.2 mg/dL), ethylene glycol level >50 mg/dL, deterioration despite supportive care


Disposition


•  Admit


Clinical Pearl


•  Urine/gastric contents fluorescence w/ Woods lamp due to antifreeze additives (early)


ISOPROPYL ALCOHOL


Definition


•  Ingestion of isopropyl alcohol (peak levels 30–180 min, 3–7 h ½ life, 80% hepatic metabolism, lethal dose 2–4 mL/kg)


History


•  Drinking: Rubbing alcohol, paint thinner, solvents, skin/hair products, nail polish remover


Physical Findings


•  Profound ↓ CNS (2–4 × EtOH), fruity odor on breath, respiratory depression, ↓ BP, gastritis


Evaluation


•  Chemistries, UA, FSG, isopropyl level, nl AG, ↑ osmol gap, falsely ↑ Cr (from acetone)


Treatment


•  Based presumptive Dx if levels delayed


•  Supportive (rarely lethal)


•  Dialysis: Refractory hypotension, levels >500 mg/dL


Disposition


•  Admit


ALCOHOL WITHDRAWAL


Definition


•  Abrupt cessation or significant reduction in alcohol intake (begins 6–24 h/peaks 48–72 h after last drink)


History


•  Heavy alcohol use w/ cessation, insomnia, anorexia, nausea, vomiting, restlessness, diaphoresis, sz


Physical Findings


•  Tremulousness, szs (25% of pts at 6–48 h), delirium, hallucinations (visual > auditory), autonomic hyperactivity (tachycardia, HTN, irritability, hyperreflexia), delirium tremens (rare/serious, 24 h–5 d after last drink): Tremor/autonomic hyperactivity/confusion/hallucinations/low-grade fever


Evaluation


•  Bedside glucose testing, CBC, BMP, LFTs/coags (if liver Dysfxn suspected), BAL


Treatment


•  Glucose (if hypoglycemic), thiamine, lorazepam 2 mg IV for sz, IV/IM/PO long-acting BZD (ie, lorazepam 1–4 mg IV q10–30min to sedation, diazepam 5 mg IV q5–10min to sedation, chlordiazepoxide), phenobarbital as 2nd-line


Disposition


•  Admit for if requiring IV medication/DTs ± ICU


Clinical Pearls


•  Rarely fatal (increased w/ aspiration due to sz) when treated appropriately


•  May require very large doses of IV BZD to control/treat


DRUGS OF ABUSE



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Sep 6, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on XVI: TOXICOLOGY

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