Evaluation of the Effects of Doxapram in Combination with Xylazine on Recovery of Horses Isoflurane-Anesthetized.

This randomized double-blinded study evaluated the recovery from isoflurane anesthesia in horses receiving doxapram and xylazine. 6 horses were anesthetized 4 times (minimum of 2-week washout period). Anesthesia was performed with xylazine (0.6 mg/kg), ketamine (2.2 mg/kg), midazolam (0.1 mg/kg), and maintained with isoflurane for 90 minutes. At recovery, horses received one of the following randomized treatments: RX: xylazine (0.2 mg/kg), RXD1: xylazine (0.2 mg/kg) and doxapram (0.1 mg/kg), RXD2: xylazine (0.2 mg/kg) and doxapram (0.2 mg/kg), or RS: saline. Recoveries were rope-assisted and evaluated with a descriptive qualitative scale. Heart rate, respiratory frequency (f), and blood gas analysis were evaluated at 5 minutes intervals while the horse allowed. Data were analyzed with ANOVA or Friedman test (P < .05). Times to sternal (minutes) were RX: 40.5 ± 12.3, RXD1: 25.8 ± 11.5, RXD2: 31.4 ± 7.0, and RS: 33.4 ± 5.3, and were not different. Times to standing (minutes) were RX: 41.0 ± 9.9, RXD1: 33.5 ± 6.2, RXD2: 40.0 ± 11.3, and RS: 36.3 ± 9.9, and were not different. Heart rate decrease over time within RXD1 and RXD2 (T0 = 47 ± 15 and 47 ± 15, T5 = 38 ± 8 and 38 ± 8, T10 = 39 ± 4 and 36 ± 6, respectively), but was not different among groups. There was no difference in f among groups or over time. There was no difference in recovery scores among groups. In conclusion, administration of doxapram to isoflurane-anesthetized horses did not change recovery time or quality.