Procedure—Llamas were allocated to 1 of 3 groups
(3 llamas/group). Fentanyl patches (each providing
transdermal delivery of 75 µg of fentanyl/h) were
placed on shaved areas of the antebrachium of all llamas.
In group 1, llamas were treated with 1 patch
(anticipated fentanyl dosage, 75 µg/h). In group 2, llamas
were treated with 2 patches (anticipated fentanyl
dosage, 150 µg/h). In group 3, llamas were treated
with 4 patches (anticipated fentanyl dosage,
300 µg/h). For each llama, the degree of sedation was
assessed by use of a subjective scoring system and a
blood sample was collected for determination of
serum fentanyl concentration at 12, 24, 36, 48, 60,
and 72 hours after patch placement.
Results—Following the placement of 4 patches,
mean ± SD serum fentanyl concentration in group 3
llamas reached 0.3 ± 0.08 ng/mL within 12 hours. This
concentration was sustained for 72 hours. In group 2,
application of 2 patches provided inconsistent results;
in group 1, application of 1 patch rarely provided measurable
serum fentanyl concentrations. No llamas
became sedated at any time.
Conclusions and Clinical Relevance—Results suggest
that application of four 75 µg/h fentanyl patches
provides consistent, sustained serum fentanyl concentrations
without sedation in llamas. However, the
serum concentration of fentanyl that provides analgesia
in llamas is not known. (Am J Vet Res
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.