BackgroundMedetomidine-ketamine (MK) and dexmedetomidine-ketamine (DK) are widely used to provide general anaesthesia in laboratory animals, but have not been compared directly in many of these species, including rodents. This study aimed to compare the onset and depth of anaesthesia, and changes in vital signs, after intraperitoneal (IP) or subcutaneous (SC) administration of ketamine (75 mg kg-1) combined with medetomidine (1 mg kg-1) or dexmedetomidine (0.5 mg kg-1) using a randomised semi-crossover design with ≥ 48 hours between treatments in 10 male and 10 female mice. Each mouse was anaesthetised twice using the same administration route (IP or SC): once with each drug-ketamine combination. Anaesthetised mice were monitored on a heating pad without supplemental oxygen for 89 minutes; atipamezole was administered for reversal. The times that the righting reflex was lost post-injection and returned post-reversal were analysed using general linear models. Tail-pinch and pedal reflexes were examined using binomial generalized linear models. Pulse rate (PR), respiratory rate (fr), and arterial haemoglobin saturation (SpO2) were compared using generalized additive mixed models.ResultsThere were no significant differences among treatments for the times taken for loss and return of the righting reflex, or response of the tail-pinch reflex. The pedal withdrawal reflex was abolished more frequently with MK than DK over time (P = 0.021). The response of PR and SpO2 were similar among treatments, but fr was significantly higher with MK than DK (P ≤ 0.0005). Markedly low SpO2 concentrations occurred within 5 minutes post-injection (83.8 ± 6.7%) in all treatment groups and were most severe after 89 minutes lapsed (66.7 ± 7.5%). No statistical differences were detected in regards to administration route (P ≤ 0.94).ConclusionsThis study failed to demonstrate clinical advantages of the enantiomer dexmedetomidine over medetomidine when combined with ketamine to produce general anaesthesia in mice. At the doses administered, deep surgical anaesthesia was not consistently produced with either combination; therefore, anaesthetic depth must be assessed before performing surgical procedures. Supplemental oxygen should always be provided during anaesthesia to prevent hypoxaemia.

Volatile agents for anaesthesia are widely used for anaesthetizing laboratory primates, and isoflurane is one of the most frequently used agents. Sevoflurane has been shown to offer a more rapid recovery than isoflurane in a number of species, but no comparisons have been made in non-human primates. This study compared the recovery characteristics of isoflurane and sevoflurane in rhesus macaques undergoing experimental neurosurgery. Twelve primates (7 males and 5 females) were randomly allocated to the treatment groups. They were sedated with ketamine (10 mg/kg) and anaesthesia was induced with propofol (usually 8 mg/kg intravenously [IV]). Anaesthesia was maintained with either sevoflurane (SEVO) (2.2 ± 0.4%) or isoflurane (ISO) (1.2 ± 0.2%) and alfentanil (0.2-0.5 µg/kg/min IV) for 332-592 min. Animals were mechanically ventilated. Meloxicam (0.3 mg/kg) and methylprednisolone infusion (5.4 mg/kg/h) were also administered. Time to extubation after cessation of anaesthesia was significantly shorter with sevoflurane (ISO: 7.0 ± 1.8 min; SEVO: 3.6 ± 1.5; *P = 0.005) as was the time to the animal sitting unaided (ISO: 15.7 ± 8.2 min; SEVO: 7.1 ± 1.7 min; *P = 0.004) . No significant difference in the quality of recovery following isoflurane or sevoflurane anaesthesia was found. In conclusion, isoflurane and sevoflurane are both suitable volatile agents for the maintenance of general anaesthesia in rhesus macaques undergoing experimental neurosurgical procedures. The two volatile agents presented a similar emergence quality profile, however sevoflurane anaesthesia was associated with a faster recovery, offering the possibility of conducting earlier post-operative neurological assessment.

Maximizing animal wellbeing by minimizing drug-related side effects is a key consideration when choosing pharmaceutical agents for chemical restraint in nonhuman primates. One drug combination that may promote this ideology is butorphanol (27.3 mg/mL), azaperone (9.1 mg/mL), and medetomidine (10.9 mg/mL; BAM). Based on results from a pilot study, 2 doses of BAM (16 and 24 µL/kg IM) were compared in healthy, 3-y-old rhesus macaques. Physiologic parameters and anesthetic quality were assessed and recorded every 5 min. Experimental endpoints were established for hypoxemia (85% or less peripheral oxygen saturation with oxygen supplementation), pulse rate (80 bpm or less for 2 consecutive readings), mean arterial pressure (MAP; 50 mm Hg or less), and hypothermia (97 °F or less); if any endpoint was achieved, medetomidine was reversed by using atipamezole (0.22 mg/kg IM). Both BAM doses resulted in immobilization of all animals with no clinically significant differences between groups. All animals initially exhibited hypoxemia that resolved with oxygen supplementation. Regardless of dose, most macaques (71%) reached established experimental endpoints for bradycardia (62 to 80 bpm) or hypotension (44 to 50 mm Hg MAP). Given the results of this study, our recommendation regarding the use of 16-or 24-µL/kg BAM for immobilizing rhesus macaques is dependent on caution regarding cardiopulmonary parameters and the provision of supplemental oxygen.

West Nile virus (WNV) was first detected in Florida in July 2001, with 404 human cases reported to the Centers for Disease Control and Prevention as of February 2020. The subtropical climate of Florida is ideal for the mosquitoes that transmit WNV. We investigated the WNV seroprevalence in 3 NHP species housed outdoors at The Mannheimer Foundation in South Florida. From January to December 2016, 520 3 to 30 y old NHP were sampled at our 2 closed sites in Homestead and LaBelle:200 rhesus macaques (Macaca mulatta), 212 cynomolgus macaques (Macaca fascicularis), and 108 hamadryas baboons (Papiohamadryas hamadryas). The presence of WNV IgG antibodies in these animals was determined by serum neutralizationassays, which found a total seroprevalence of 14%. Seroprevalence was significantly higher in the baboons (29%) than the rhesus (11%) and cynomolgus (9%) macaques. The probability of seropositivity significantly increased with age, but sex and site did not significantly affect seroprevalence. The frequency of WNV seropositivity detected in these outdoor-housed NHP suggests that screening for WNV and other vector-borne diseases may be necessary prior to experimental use, particularlyfor infectious disease studies in which viremia or viral antibodies could confound results, and especially for populations housed outdoors in warm, wet climates. As no seropositive subjects demonstrated clinical signs of WNV and WNV exposure did not appear to significantly impact colony health, routine testing is likely unnecessary for most NHP colonies. However,WNV infection should still be considered as a differential diagnosis for any NHP presenting with nonspecific neurologic signs. Mosquito abatement plans and vigilant sanitation practices to further decrease mosquito and avian interaction withresearch NHP should also be considered.