Effects of Remimazolam With or Without Remifentanil on Oral Tissue Blood Flow and Oxygen Tension in Rabbits

To clarify the effects of remifentanil and remimazolam on the cardiovascular system, oral tissue blood flow, and oral tissue oxygen tension during general anesthesia in rabbits.

Male Japanese white rabbits (body weight, 2.5 kg; N = 11) were treated with remimazolam at a dose of 1 mg/kg/h continuously. Measurements included blood pressure, heart rate, tissue blood flow (common carotid artery, tongue mucosal, mandibular bone marrow and masseter muscle), and tissue oxygen tension (mandibular bone marrow and masseter muscle). Remifentanil was then administered at 0.2 μg/kg/min and each measurement was collected again. The dose of remifentanil was increased to 0.4 μg/kg/min and each measurement was collected again. The same measurements were collected when remimazolam was administered at doses of 2 mg/kg/h and 4 mg/kg/h.

Remimazolam administration did not significantly alter the parameters of each observation. Blood pressure, heart rate, and tissue blood flow (common carotid artery, tongue mucosal, mandibular bone marrow, and masseter muscle) decreased significantly in a dose-rate dependent manner under remifentanil administration, whereas tissue oxygen tensions (mandibular bone marrow and masseter muscle) were maintained.

Remimazolam anesthesia in rabbits had minimal effects, but in combination with remifentanil, it produced remifentanil dose-dependent decreases in oral tissue blood flow as well as blood pressure and heart rate.