An 18-year-old schizophrenic female was recently treated after overdosing on
trihexyphenidyl,
thioridazine and an unknown
antidepressant. On presentation to a local hospital, she was cyanotic with dilatated pupils and in acute
respiratory failure. She was intubated prior to transfer. While in our Emergency Department, she exhibited occasional
premature ventricular contractions which later became intermittent
torsade de pointes. As this was an
anticholinergic overdose we infused
sodium bicarbonate in an attempt to increase protein binding, hoping to decrease the concentration of toxic metabolites. We also tried to suppress the dysrhythmia by infusing
magnesium. The
potassium level was borderline low so a supplemental infusion was initiated. Defibrillation was attempted. To try to shorten the action potential duration by activating the K+ channel, an
isuprel infusion was also attempted. All methods failed. The patient fluctuated between an irregular sinus rhythm with prolonged QT interval and pulseless
torsade de pointes for almost 24 hours. At all times, she responded appropriately to
pain. Finally we attempted blockade of the
calcium channel using
verapamil with dramatic results. Each single bolus (0.1 mg/kg) successfully converted the patient back to sinus rhythm for some 15-20 minutes before the torsade recurred. After the initiation of a continuous
verapamil infusion (0.005 mg/kg/hr), the patient remained in stable sinus rhythm.
Verapamil proved highly effective in this patient with an
anticholinergic overdose induced dysrhythmia.