Pocket Emergency Medicine (Pocket Notebook Series) 3rd Ed.

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