CARDIOVASCULAR EFFECTS OF INTERMITTENT POSITIVE PRESSURE VENTILATION IN THE ANESTHETIZED HORSE

Intermittent positive pressure ventilation (IPPV) is useful method for compensate of respiratory function in anesthetized horses. However, I PPV may decrease cardiac output. Alterations in cardiac output of thre e groups (N = 5) healthy, halothane-anesthetized mares were determined and compared during a 120 min period of anesthesia. The groups were a s follows: spontaneous ventilation (SV), controlled ventilation using an end-inspiratory pressure of 20 cmH2O (CV20) and a third group using 25 cmH2O (CV25) inspiratory pressure. In the CV groups, respiratory f unction was adequately maintained. Although, cardiac output tended to decrease over time in each group. After 105 min of anesthesia in the C V groups, the cardiac outputs decreased below 50 percent of pre-anesth etic values. In the CV25 group, cardiac outputs were significant diffe rence (p<0.05) from the SV group after 45, 90 and 120 min of anesthesi a. There was no significant difference in cardiac output between SV an d CV20 group over time. These values suggest that when long durations of anesthesia was used with the IPPV, decrease of cardiac output shoul d be improved. In clinical use of halothane anesthesia, an end-respira tory pressure of 20 CMH2O seems to be appropriate because the mild dec rease in cardiac output was observed even though a little high PaCO2.