Hypertonic sodium bicarbonate is effective in the acute management of verapamil toxicity in a swine model

Study objective: This study was conducted to determine whether hypertonic s odium bicarbonate would improve the hypotension associated with severe vera pamil toxicity compared with volume expansion. Methods: The study design used a nonblinded acute animal preparation. Twent y-four anesthetized and instrumented swine were poisoned with verapamil del ivered at a rate of 1 mg/kg per hour for 10 minutes followed by incremental increases of 1 mg/kg per hour every 10 minutes until the endpoint of a mea n arterial blood pressure of 45% of baseline was achieved. Animals alternat ely received either 4 mEq/kg of hypertonic sodium bicarbonate intravenously over 4 minutes or similar volumes of 0.6% sodium chloride in 10% mannitol (control). The main outcome parameter followed was mean arterial pressure. In addition, physiologic parameters including cardiac output, heart rate, p H, PCO2, PO2, plasma ionized calcium, sodium, and potassium were monitored. Results: Verapamil toxicity, as defined by a mean arterial pressure of 45% of baseline, was produced in all animals following an average verapamil inf usion dose of 0.6+/-0.12 mg/kg. This dose produced an average plasma verapa mil concentration of 728.1+/-155.4 mug/L, with no significant difference be tween groups. Swine treated with hypertonic sodium bicarbonate experienced a significant increase in mean arterial pressure (>50%) and cardiac output (>30%) over the first 20 minutes that slowly equilibrated with the control group over the remainder of the experiment. As expected, plasma sodium conc entrations were elevated significantly in the sodium bicarbonate group whil e plasma potassium concentrations were decreased significantly. Finally, th ere was a significant decrease in plasma ionized calcium concentration in t he sodium bicarbonate-treated group compared with controls. Conclusion: Hypertonic sodium bicarbonate reversed the hypotension and card iac output depression of severe verapamil toxicity in a swine model.