OBJECTIVE To compare characteristics of recovery from isoflurane anesthesia in healthy nonpremedicated dogs after anesthetic induction by IV administration of tiletamine-zolazepam with those observed after induction by IV administration of alfaxalone, ketamine-diazepam, or propofol.
DESIGN Prospective, randomized crossover study.
ANIMALS 6 healthy adult hounds.
PROCEDURES Each dog underwent the 4 treatments in random order with a ≥ 7-day washout period between anesthetic episodes. Anesthesia was induced by IV administration of the assigned induction drug or combination (each to effect in 25% increments of calculated dose) and maintained with isoflurane in oxygen for 60 minutes. Cardiorespiratory variables and end-tidal isoflurane concentration (ETISO) were measured just before isoflurane administration was discontinued. Dogs were observed and video recorded during recovery. Recovery characteristics were retrospectively scored from recordings by 3 raters. Interrater and intrarater reliability of scoring was assessed by intraclass correlation coefficient calculation. Linear and mixed ANOVAs were used to compare extubation times, recovery scores, and body temperature among treatments.
RESULTS Most cardiorespiratory variables, body temperature, ETISO, and time to extubation did not differ between tiletamine-zolazepam and other induction treatments. Recovery scores were lower (indicating better recovery characteristics) with propofol or alfaxalone than with tiletamine-zolazepam but did not differ between tiletamine-zolazepam and ketamine-diazepam treatments. Anesthetic episode number and ETISO had no effect on extubation time or recovery score. Intrarater and interrater correlations for recovery scores were excellent.
CONCLUSIONS AND CLINICAL RELEVANCE Recovery of healthy dogs from anesthesia with isoflurane after induction with tiletamine-zolazepam was uncomplicated and had characteristics comparable to those observed following induction with ketamine-diazepam. However, recovery characteristics were improved when anesthesia was induced with propofol or alfaxalone.
OBJECTIVE To compare effects of tiletamine-zolazepam, alfaxalone, ketamine-diazepam, and propofol for anesthetic induction on cardiorespiratory and acid-base variables before and during isoflurane-maintained anesthesia in healthy dogs.
ANIMALS 6 dogs.
PROCEDURES Dogs were anesthetized with sevoflurane and instrumented. After dogs recovered from anesthesia, baseline values for cardiorespiratory variables and cardiac output were determined, and arterial and mixed-venous blood samples were obtained. Tiletamine-zolazepam (5 mg/kg), alfaxalone (4 mg/kg), propofol (6 mg/kg), or ketamine-diazepam (7 and 0.3 mg/kg) was administered IV in 25% increments to enable intubation. After induction (M0) and at 10, 20, 40, and 60 minutes of a light anesthetic plane maintained with isoflurane, measurements and sample collections were repeated. Cardiorespiratory and acid-base variables were compared with a repeated-measures ANOVA and post hoc t test and between time points with a pairwise Tukey test.
RESULTS Mean ± SD intubation doses were 3.8 ± 0.8 mg/kg for tiletamine-zolazepam, 2.8 ± 0.3 mg/kg for alfaxalone, 6.1 ± 0.9 mg/kg and 0.26 ± 0.04 mg/kg for ketamine-diazepam, and 5.4 ± 1.1 mg/kg for propofol. Anesthetic depth was similar among regimens. At M0, heart rate increased by 94.9%, 74.7%, and 54.3% for tiletamine-zolazepam, ketamine-diazepam, and alfaxalone, respectively. Tiletamine-zolazepam caused higher oxygen delivery than propofol. Postinduction apnea occurred in 3 dogs when receiving alfaxalone. Acid-base variables remained within reference limits.
CONCLUSIONS AND CLINICAL RELEVANCE In healthy dogs in which a light plane of anesthesia was maintained with isoflurane, cardiovascular and metabolic effects after induction with tiletamine-zolazepam were comparable to those after induction with alfaxalone and ketamine-diazepam.
To determine the dose of alfaxalone for IM administration combined with dexmedetomidine and hydromorphone that would allow endoscopic-guided orotracheal intubation in rabbits without causing a decrease in respiratory rate or apnea.
15 sexually intact (9 females and 6 males) healthy Miniature Lop rabbits weighing a mean ± SD of 2.3 ± 0.3 kg and ranging in age from 4 to 9 months.
In a randomized, controlled clinical trial, rabbits received 0.1 mg of hydro-morphone/kg and 0.005 mg of dexmedetomidine/kg, plus alfaxalone at either 2 mg/kg (5 rabbits), 5 mg/kg (5 rabbits), or 7 mg/kg (5 rabbits). Drugs were mixed in a single syringe and administered IM. Semiquantitative rating scales were used to evaluate quality of anesthesia and intubation. Orotracheal intubation was attempted with endoscopy and confirmed by capnography.
The number of successful intubations was 0, 3, and 4 in rabbits receiving 2, 5, and 7 mg of alfaxalone/kg, respectively. Median (range) anesthesia quality scores (scale, 0 to 12; 12 = deepest anesthesia) were 3 (2 to 5), 6 (5 to 6), and 6 (4 to 9) for rabbits receiving 2, 5, and 7 mg of alfaxalone/kg, respectively. The median (range) intubation quality scores (scale, 0 to 3 [ie, intubation not possible to easiest intubation]) were 0 (0 to 0), 2 (0 to 3), and 2 (0 to 3) for rabbits receiving 2, 5, and 7 mg of alfaxalone/kg, respectively. None of the rabbits experienced a decrease in respiratory rate or apnea.
CONCLUSIONS AND CLINICAL RELEVANCE
Increasing doses of alfaxalone combined with hydromorphone and dexmedetomidine increased the success rate of endoscopic-guided orotracheal intubation. Increasing the dose of alfaxalone had no effect on respiratory rate.