Comparison Study of Anesthetic Indices and Cardiopulmonary Functions between Sevoflurane and Isoflurane in Unpremedicated Cats
Sevoflurane is a new halogenated inhalation anesthetic which is used in small animals.
To compare the minimum alveolar concentration (MAC), apneic concentration and cardiopulmonary effects of sevoflurane and isoflurane anesthesia applied in unpremedicated cats.
Sixteen healthy adult cats were anesthetized repeatedly at 1-week intervals with two anesthetics. Anesthesia was induced by administering sevoflurane or isoflurane through a face mask. After induction of anesthesia, MAC was determined with a tail clamp method while cats were mechanically ventilated. Apneic concentration was determined while cats were breathing spontaneously by increasing the anesthetic concentration until cats became apneic. Anesthetic index was calculated as apneic concentration divided by MAC.
MAC was significantly different between sevoflurane (3.64 ± 0.08%) and isoflurane (1.91 ± 0.06%) (P<0.05). The apneic concentration and anesthetic index of sevoflurane was 10.26 ± 0.27 % and 2.81 ± 0.11. However, the agent of isoflurane could not cause apnea in these cats. Both anesthetics showed similar cardiopulmonary effects (P>0.05). With both agents, as anesthetic agent concentration increased, heart rates, systolic arterial pressures (SAP), diastolic arterial pressures (DAP), mean arterial pressures (MAP) and respiratory rate (RR) decreased while partial pressure of end tidal carbon dioxide (PETCO2) increased.
Sevoflurane was a safe alternative to be used in maintenance of anesthesia as well as isoflurane. In this study, sevoflurane could cause apnea condition but isoflurane did not, the reasons about the phenomenon need further investigation.