Dexmed/Buspirone Synergism on Shivering

The purpose of this research is to determine if the combination of buspirone and dexmedetomidine are effective as a treatment to induce therapeutic hypothermia. The design of the study includes four study days done in random order. The days are as follows: 1) Control (no drug); 2) Buspirone 60 mg orally; 3) Dexmedetomidine (delivered by a computer-controlled IV infusion to a target plasma concentration of 0.6 ng/ml); and, 3) the combination of buspirone 60 mg and dexmedetomidine (target plasma concentration of 0.6 ng/ml). a 20 cm-long catheter will be inserted into a cubital vein using standard aseptic technique In addition to the PIC line catheter, a simple peripheral catheter will be inserted into the other arm for drug administration. Throughout the study period, mean-skin temperature will be maintained at 31°C by adjusting the temperature of circulating water (Cincinnati Sub-Zero, Cincinnati, OH) and forced-air warmers (Augustine Medical, Inc., Eden Prairie, MN). Furthermore, the back, upper-body, and lower-body will individually be maintained at the designated skin temperature. Lactated Ringer\'s solution cooled to ≈3°C will be infused via the PIC-line at rates sufficient to decrease tympanic membrane temperature ≈1.5°C/h. Fluid will be administered as long as oxygen consumption or electromyographic intensity (see below) continues to increase or a total of 5 liters of fluid is given. Heart rate will be measured continuously using an electrocardiogram; blood pressure will be determined oscillometrically at 5 min intervals at the ankle. In case heart rate and/or blood pressure changes unexpectedly (by more than 30% of the baseline), the study will stop and the volunteer will be re-warmed immediately.