Arterial Blood Sampling in Male CD-1 and C57BL/6J Mice with 1% Isoflurane is Similar to Awake Mice.

Isoflurane (ISO) is a commonly used anesthetic that offers rapid recovery for laboratory animal research. Initial studies indicated no difference in PaCO2 or pH between conscious (NO ISO) and 1% ISO exposed CD-1 mice. Our laboratory investigated if arterial blood sampling with 1% ISO is a suitable alternative to NO ISO sampling for monitoring ventilation in a commonly studied mouse strain. We hypothesized similar blood chemistry, breathing patterns and cardiovascular responses with NO ISO and 1% ISO. C57BL/6J mice underwent unrestrained barometric plethysmography to quantify the pattern of breathing. Mice exposed to hypoxic and hypercapnic gas under 1% ISO displayed blunted responses; with air there were no breathing differences. Blood pressure and heart rate were not different between NO ISO and 1% ISO exposed mice breathing air. Oxygen saturation was not different between groups receiving 2% ISO, 1% ISO, or air. Breathing frequency stabilized at ~11 minutes of 1% ISO following 2% ISO exposure, suggesting that 11 minutes is the optimal time for a sample in C57BL/6J mice. Blood samples at 1% ISO and NO ISO revealed no differences in blood pH and PaCO2 in C57BL/6J mice. Overall, this method reveals similar arterial blood sampling values in awake and 1% ISO CD-1 and C57BL/6J mice exposed to air. While this protocol may be appropriate in other mouse strains when a conscious sample is not feasible, caution is warranted to first identify breathing frequency responses at 1% ISO to tailor the protocol.