Postural influence on systemic blood pressure, gas exchange, and acid/base status in the term-pregnant bitch during general anesthesia.

Effects of positioning on certain physiologic parameters were done in 7 term-pregnant bitches during general anesthesia. Five positions (right and left lateral recumbency, right and left 10 degrees to 15 degrees tilt toward lateral recumbency, and dorsal recumbency) were examined. Anesthesia was induced with thiamylal sodium and was maintained with halothane and nitrous oxide in oxygen. Direct arterial blood pressure, arterial blood gases, pH, base excess, heart rate, respiratory rate, and a lead II ECG were recorded from the bitches during each position. Effects of positioning for each bitch during general anesthesia were reexamined after the bitch weaned its pups; therefore, each bitch served as its own control. Maternal posture had no significant (P less than 0.05) effect on any measured parameters in bitches before or after parturition. Pregnancy had a significant (P less than 0.05) effect on every parameter, except heart rate. Pregnant bitches had a lower systolic blood pressure, lower Pao2, lower PCV, higher PaCO2, higher respiratory rate, and a more severe acidosis than did the bitches after parturition. Seemingly, supine hypotension did not occur in anesthetized term pregnant bitches (9 to 16 kg). Tilting the bitch 10 degrees to 15 degrees toward right or left lateral recumbency or true lateral recumbency was not preferable to dorsal recumbency for doing cesarean sections using general anesthesia.