Effects of tail fat on recovery times of anesthesia with isoflurane in fat-tailed Iranian Lori-Bakhtiyari lambs

In the present study, the effect of tail fat on recovery times in intact sheep and sheep with a ligated median sacral artery following similar anesthetic exposure with isoflurane was investigated. This study was performed using seven healthy fat-tailed Iranian Lori-Bakhtiyari ewe lambs. The lambs were anesthetized twice at two week intervals (the experiment was performed in two stages). After mask induction with isoflurane in 100% oxygen, sheep were intubated and anesthesia was maintained for 4 hr using a rebreathing system. Induction and extubation times and time to sternal recumbency and attempts to stand were recorded during anesthetic induction and recovery (Stage 1). Two weeks later, prior to the second anesthesia, the median sacral artery (MSA) was ligated under epidural anesthesia in sheep. All sheep were anesthetized as mentioned above (Stage 2). No significant differences were observed for the induction time between two stages (p > 0.05) but extubation, sternal recumbency and attempts to stand times were significantly longer in intact sheep (Stage 1) after 4 hr anesthesia with isoflurane (p < 0.05). Recovery time was decreased following MSA ligation in fat-tailed sheep, which suggested that body fat had a major role in the recovery time of isoflurane in sheep. We developed an animal model to investigate fat drug solubility of isoflurane gas. Therefore, using less-soluble in fat anesthetics is better than high-soluble anesthetics for prolonged anesthesia to decrease postoperative complication in obese patient.