Effects of anesthetics

The aim of this study was to compare the systemic hemodynamic effects of four commonly used anesthetic regimens in mice chronically instrumented for direct and continuous measurements of cardiac output (CO). Mice (CD-1, Swiss and C57Bl6) were instrumented with a transit-time flow probe placed around the ascending aorta for measurement of CO. An arterial catheter was inserted four to five days later into the aorta for blood pressure measurements. After full recovery hemodynamic parameters including, stroke volume (SV), heart rate (HR), CO, mean arterial pressure (MAP) and total peripheral resistance (TPR) were measured in the conscious state. General anesthesia was then induced in these mice using isoflurane (ISO), urethane (UR), pentobarbital (PB), or ketamine/xylazine (K/X). The dose and route of administration of these agents was given as is required for general surgical procedures in these animals. Compared to the values obtained in the conscious resting state, MAP and CO fell during all anesthetic interventions with hemodynamic effects being smallest for ISO (MAP =-24±3%, CO =-5±7%, n=15) and greatest for K/X (MAP =-51±6%, CO =-37±9%, n=8), respectively. The hemodynamic effects of K/X were fully antagonized by administration of the α 2-antagonist atipamezole (n=8). These results indicate that the anesthetic isoflurane has fewer systemic hemodynamic effects in the mouse than the non-volatile anesthetics.