General Measures

Supportive care consists of airway protection, adequate ventilation, and hemodynamic monitoring. Patients who are drowsy after an unquantified CCB overdose should receive naloxone and fingerstick glucose determination. If the patient still does not follow verbal commands, endotracheal intubation is advised, regardless of hemodynamic status. Endotracheal intubation may help prevent pulmonary aspiration during gastric instillation of charcoal, should vomiting occur. Mechanical ventilation eliminates work of breathing, which can translate into improved cardiac output. The minute ventilation can be adjusted to produce a slight respiratory alkalosis (PaCo2 25-30 mmHg), which may reduce negative inotropy. Additionally, the patient can be positioned safely (and administered skeletal muscle paralytic agents, if necessary) for central venous cannulation. A #8.5 French central venous catheter is quite useful for managing CCB overdose because it can provide a portal for pulmonary artery catheterization and can be used to administer calcium salts, which are irritating to peripheral veins. All patients require Foley catheterization to monitor urine production as a key index of organ perfusion.

Reducing drug absorption and enhancing elimination are the next objectives in treating CCB overdose. All CCBs bind to activated charcoal, which should be administered after the patient's airway is secured. With massive overdose, sustained-release preparations can form gastrointestinal concretions (with ileus) that can persist for days, rendering charcoal less useful. Accordingly, whole-bowel irrigation with polyethylene glycol has been advocated to accelerate removal of sustained-release CCB pill fragments.8 Drug elimination can be enhanced by extracorporeal removal. For example, charcoal hemoperfusion may lower verapamil and diltiazem concentrations but may have less use for nifedipine or other dihydropyridine poisoning. 1,12

No firm rules can dictate the selection and sequencing of cardiotonic agents to treat CCB toxicity. A guideline algorithm is offered in Fig 170-1. Several basic resuscitation efforts should be addressed prior to or simultaneously with the use of an inotropic agent. These include administration of a volume bolus (10-20 mL/kg), correction of acidemia (keep arterial pH above 7.20 by hyperventilation or with sodium bicarbonate infusion), and rapid correction of hyperkalemia with a bolus infusion of calcium chloride (1 g 10% w/v, diluted to 100 cc in normal saline, IV) simultaneously with a bolus of insulin (0.2 unit/kg, IV). Although the treatment objective is to establish normal sinus rhythm with normal blood pressure, with severe poisoning, treatment goals should focus on stabilization rather than on normalization of heart rate, arterial blood pressure, urine output, arterial base deficit, and cardiac output (if available) or left ventricular ejection fraction. There are no reports of perminant cardiomyopathy or central nervous system (CNS) dysfunction from direct CCB effect.

FIG. 170-1. Treatment guidelines for severe CCB ingestion.
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