Hemodynamic response to anesthesia in pregnant and nonpregnant ICR mice

Mean arterial blood pressure (BP) and heart rate (HR) during and after recovery from anesthesia in pregnant and nonpregnant ICR mice were evaluated. Mice were evaluated during mechanical ventilation, from 15 to 60 min after induction of anesthesia. The anesthetic protocols were pentobarbital (80 mg/kg, given intraperitoneally [i.p.]); two low doses of ketamine and xylazine (90 mg/kg, 7.5 mg/kg, respectively, i.p., with a second dose given 20 min after the initial dose); and a single high dose of ketamine and xylazine (150 mg/kg, 12.5 mg/kg, respectively, i.p.). The BP was measured in the right carotid artery, using a fluid-filled catheter connected to a chamber containing a solid-state pressure transducer. Mechanical ventilation was performed via tracheotomy, using a normalized minute ventilation of 3.5 ml*min-1*g-1 for nonpregnant mice and 3.0 ml*min-1*g-1 for pregnant mice. Mean BP was lower and HR was higher in pregnant than in nonpregnant mice for each anesthetic protocol. Pentobarbital induced significantly greater tachycardia and hypotension than did the other protocols. The average BP and HR were similar between two low doses and a single high dose of ketamine and xylazine. During spontaneous breathing from 30 to 180 min after recovery from anesthesia by use of a single low dose, ketamine and xylazine induced similar HR profiles, but mean BP in pregnant mice recovered earlier than did that in nonpregnant mice. These results suggest that ketamine and xylazine induced adequate anesthesia for superficial surgical procedures in pregnant and nonpregnant mice while inducing small changes in HR and BP, and pregnancy resulted in a different hemodynamic reaction in response to ketamine and xylazine. These data will be useful for the design and interpretation of physiologic protocols using pregnant and nonpregnant genetically targeted mice.