5. TCA overdose: (example elavil, amitriptyline, amoxapine, flexeril, doxepin, tofranil, desipramine)
Effects: antihistamine, antimuscarinic/anticholinergic (dry mouth, sinus tachycardia, sedation, agitation, confusion, ataxia, coma, dilated pupils, hyperthermia, dry skin, ileus, urinary retention, increased muscle tone, tremor), K+ channel blockade (QT prolongation-------->> Torsades de pointes)
****Na-channel blockade (class 1 antiarrhythmic) ------------>>>>cardiotoxicity (decreased conduction, contractility, prolong PR, QRS, RAD, various heart blocks)
serious toxicity within 6 hrs or ingestion ; expect life threatening in dose of 10mg/kg, may deteriorate rapidly
hypertension early, hypotension late, anticholinergic toxicity (may need foley or NGT)
SVT, vtach, seizures, cardiovascular collapse, complete heart block, respiratory depression, asp PNA, rhabdo, *pulm edema
EKG changes due to Na blockade
prolonged QRS (>.10) and PR interval (>.20), bradycardia, RAD in terminal 40msec of the QRS (deep R wave in aVR >3mm)
QRS > 120msec threshold for treatment serial ECGs check for co-ingestants (tylenol level)
Tx: serum alkalinization with NaHCO3 sodium bicarbonate for QRS > 100msec, hypotension, vent. dysrhythmias
start with boluses of 1-2mEq/kg every 3-5 minutes until QRS narrows then
NaHCO3 drip 3 amps in 1L of D5W at 2ml/kg/hr
(titrate drip to blood pH 7.5-55) enhances TCA serum protein binding, decreases inhibition of sodium ion influx (hypertonic saline?)
alkalinization beyond this can be deleterious
Gastric lavage early, AC 1 g/kg will help bind TCAs and decrease absorption
monitor serum potassium levels, IV K+ usually required
treat seizures with benzos/phenobarbital Phenytoin is INEFFECTIVE
Class Ia, Ic and III, BB and CCB are contraindicated
Flumazenil can precipitate seizures
Hypotension treat with IVF, NaHCO3, most effective vasopressor is norepinephrine
lidocaine is second agent for dysrhythmias (after NaHCO3) 1 mg/kg
Torsades de Pointes treat with Magnesium Sulfate 2g IV
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