Objective: To determine the effect of a hypertonic saline and dextran (HSD) solution on blood pressure and QS duration during severe cyclic antidepressant (CA) toxicity in swine.
Methods: Ten domestic swine weighing 20-24 kg were anesthetized and placed on mechanical ventilation. Nortriptyline solution was infused intravenously to achieve hypotension (systolic blood pressure equal to 50% of baseline) and a QRS duration of 120 msec. After reaching toxicity, the animals received in a randomized fashion either 10 mL/kg of a 7.5% saline/6% dextran solution or an equal volume of 0.9% saline as a rapid intravenous bolus. The animals were observed for one hour or until they died. Blood pressure and ECG were recorded continuously. Arterial pH was maintained in the physiologic range by controlled ventilation.
Results: Mean systolic blood pressure 10 minutes after treatment was 45 +/- 8 torr in the normal- saline group compared with 115 +/- 12 torr in the HSD group (p < 0.05). Mean QRS duration 10 minutes after treatment was 180 +/- 8 msec in the normal-saline group; it was 88 +/- 13 msec in the HSD group (p < 0.05). All normal-saline--group animals died within 20 minutes, and four of the five animals in the HSD group survived to 60 minutes (p < 0.05). The mean peak sodium concentration was 157 mmol/dL (mEq/dL) in the HSD group, and this was transient.
Conclusion: In this swine model of severe CA toxicity, a solution of 7.5% saline/6% dextran significantly reversed hypotension and QRS prolongation. HSD also improved survival to 60 minutes.