increased deep tendon reflexes Although the pupils may be dilated, they usually respond to light Severe tricyclic antidepressant overdoses warrant gastric decontamination Tricyclic antidepressants decrease GI motility, so unabsorbed drug may remain in the stomach for prolonged periods Because acidosis worsens the effects of TCAs, seizures should be treated aggressively with benzodiazepines and/or barbiturates, or even with neuromuscular paralysis, if needed, to prevent acidosis Barbiturates may cause hypotension and reduce cardiac output Continuous EEG monitoring is recommended if the patient is paralyzed Significant conduction delays or arrhythmias resulting from tricyclic antidepressants may benefit from alkalinization of the blood A sodium bicarbonate bolus of to mEq/kg can be given during continuous EKG monitoring Bicarbonate infusion can then be used to keep the serum pH at 7.45 to 7.55 These therapeutic maneuvers likely serve to decrease drug binding to the myocardium Additional bolus doses of sodium bicarbonate may be required if the QRS interval widens An additional benefit of the sodium cation is to overcome the sodium channel blockade that is believed to cause the membrane depressant effect If arrhythmias persist, institute appropriate antiarrhythmic therapy, perhaps using lidocaine (see Chapters A General Approach to the Ill or Injured Child and 86 Cardiac Emergencies ) Avoid quinidine and procainamide because these may increase heart block Physostigmine can worsen ventricular conduction defects and lower the seizure threshold and thus is contraindicated in cyclic antidepressant overdoses, particularly in the setting of an abnormal EKG In the presence of hypotension, many clinicians have advocated the use of norepinephrine infusions (0.1 to 0.3 μg/kg/min) This approach is based on the observation that the hypotension is the result of norepinephrine depletion secondary to the block of catecholamine uptake caused by tricyclic antidepressants Other clinicians have reported that dopamine is as effective; however, the occurrence of ventricular arrhythmias has been reported with dopamine Other Antidepressants CLINICAL PEARLS