Differential Effects of Selective and Nonselective Potassium Channel Inhibitors in Ovine Endotoxemic Shock (Macrocirculation) and in a Rat Model of Septic Shock (Microcirculation).

BACKGROUND

Potassium-(K)-channel inhibitors may increase systemic vascular resistance in vasodilatory shock states.

OBJECTIVE

The purpose of the present study was to compare the macro- and microvascular effects of the adenosine triphosphate-sensitive K-channel-(KATP)-inhibitor glipizide and the nonselective K-channel inhibitor tetraethylammonium (TEA) in ovine endotoxemic shock and septic shock in rats.

DESIGN

Two randomized, controlled laboratory studies.

ANIMALS

Thirty female sheep and 40 male Sprague Dawley rats.

SETTING

Animal research facility INTERVENTION:: Systemic hemodynamics were analyzed in ovine endotoxemic shock with guideline-oriented supportive therapy. Sheep were allocated to three treatment groups for 12 h: glipizide 10 mg kg·h, TEA 8 mg kg·h, or 0.9% saline. The microvascular effects of each drug were evaluated in septic rats (cecal ligation and puncture model) receiving a 2-h infusion of each study drug: glipizide 20 mg kg·h; TEA 50 mg kg·h, or 0.9% saline, respectively, followed by intravital microscopy of villi microcirculation.

RESULTS

Compared with the control group, glipizide infusion increased systemic vascular resistance index and decreased cardiac index and heart rate (HR) in sheep (P < 0.05), whereas TEA infusion decreased HR and resulted in a decreased survival time (P = 0.001). In rats, glipizide infusion resulted in an increase in mean arterial pressure and a decrease in HR compared with baseline measurement (P < 0.05) without relevant effects on the villi microcirculation. TEA decreased HR and decreased capillary perfusion of the villi microcirculation compared with the sham group (P = 0.002).

CONCLUSIONS

Selective inhibition of KATP-channels in ovine endotoxemic shock with glipizide partially restored vasomotor tone without exerting harmful effects on intestinal microcirculation in septic shock in rats. On the contrary, nonselective K-channel inhibition with TEA showed deleterious effects in both models, including impaired microcirculation and decreased survival time. Future research on glipizide in vasodilatory shock may be warranted.