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.Objective
Methods
Results
Conclusion
Experimental Protocol
Timeline of the study protocol illustrating the remimazolam and remifentanil infusions along with the periods of data collection. Isoflurane inhalation was stopped after completion of the study preparations.
(a and b) Cardiovascular System Changes
No interaction was found between remimazolam (RZ) and remifentanil (RF). Increasing the RZ rate did not significantly alter blood pressure (BP) and heart rate (HR), but RF caused dose-dependent decreases. The RF 0, 0.2, and 0.4 μg/kg/min in the table summarize each component of RZ. *Indicates P < .05.
(a–d) Oral Tissue Blood Flow Changes
No interaction was found between RZ and RF. Increasing the RZ rate did not significantly alter common carotid artery blood flow (CCBF; a), tongue mucosal tissue blood flow (TBF; b), mandibular bone marrow tissue blood flow (BBF; c), or masseter muscle tissue blood flow (MBF; d), but RF caused dose-dependent decreases. The RF 0, 0.2, and 0.4 μg/kg/min in the table summarize each component of RZ. *Indicates P < .05.
(a and b) Tissue Oxygen Tension Changes
No interaction was found between RZ and RF, and neither significantly altered mandibular bone marrow tissue oxygen tension (PbO2; a) or masseter muscle tissue oxygen tension (PmO2; b) in dose-dependent manners. The RF 0, 0.2, and 0.4 μg/kg/min in the table summarize each component of RZ. *Indicates P < .05.
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