Effects of injectable anesthetic combinations on left ventricular function and cardiac morphology in Sprague-Dawley rats.

Novel anesthetic agents or combinations may provide superior general anesthesia for echocardiography in rodents with the potential for reduced adverse effects. This study sought to characterize the effects of 3 injectable anesthetics on left ventricular (LV) systolic function and cardiac morphology in healthy male and female rats. Rats underwent echocardiographic assessment after general anesthesia via pentobarbital or combinations of ketamine and medetomidine (KME) and ketamine and midazolam (KMI) according to a crossover Latin-square design. Blood samples for serum estradiol measurements were obtained from all females after echocardiography with each anesthetic. Rats given KMI showed superior LV systolic function with the highest values for fractional shortening (FS), ejection fraction (EF) and stroke volume, whereas heart rate was greatest with pentobarbital, followed by KMI and then KME. KME produced the greatest effects on cardiac morphology, most notably during systole, including reduced septal and posterior wall thickness and increased LV chamber dimensions and volumes. In addition, KME had the greatest cardiac-depressing effects on LV systolic function, including reduced FS, EF, and heart rate values. Compared with male rats, female rats had superior LV function with greater EF and FS values, whereas male rats showed higher heart rate. Significant negative correlations were noted between serum estradiol levels and FS and EF values in female rats receiving KME. We conclude that the combination of KMI may be a superior anesthetic for use in male and female rats undergoing echocardiography.