Relation of cyclic guanosine monophosphate and cyclic adenosine monophosphate in reducing the toxic effects of protamine administration

Cardiovascular effects of enoximone and epinephrine on heparin reversal with protamine in conscious dogs

OBJECTIVE

To compare enoximone with epinephrine as treatments for the cardiotoxic effects of protamine sulfate.

STUDY DESIGN

Prospective randomized study.

ANIMAL POPULATION

12 healthy cross-bred dogs weighing 23 +/- 4 kg.

METHODS

The dogs were anesthetized with xylazine and ketamine to allow instrumentation. Femoral arterial and venous catheters were inserted for pressure monitoring and to allow drug infusion. A thermodilution catheter mounted with a fast response thermistor was inserted into the pulmonary artery via the jugular vein to measure cardiac output and right ventricular volumes. Heparin 300 units/kg followed by protamine 4.5 mg/kg were administered 45 minutes after the xylazine/ketamine. Four animals were not treated (controls), four received enoximone, and four were given epinephrine. Cardiopulmonary parameters were monitored for a period of 30 minutes.

RESULTS

Cardiac index was 104 +/- 15 mL/kg/min in the enoximone group, 72 +/- 13 mL/kg/min in the epinephrine group, and 63 +/- 10 mL/kg/min in the control group (P < .05 enoximone versus control and epinephrine). Right ventricular end systolic volume was 18 +/- 3, 27 +/- 4, and 29 +/- 6 mL in the enoximone, epinephrine, and control groups (P < .05 enoximone versus control and epinephrine). There were no differences in mean arterial pressure or pulmonary and systemic vascular resistance between the groups.

CONCLUSION AND CLINICAL RELEVANCE

In this study, enoximone was more effective than epinephrine at reversing the hemodynamic changes associated with protamine sulfate administration.