Journal of the American Association for Laboratory Animal Science Vol 59, No 5 Copyright 2020 September 2020 by the American Association for Laboratory Animal Science Pages 557–566 A Comparison of the Efficacy and Cardiopulmonary Effects of 3 Different Sedation Protocols in Otolemur garnettii Kelsey R Finnie,1,* Carissa P Jones,1 William D Dupont,2 Kenneth J Salleng,1 and Katherine A Shuster1 The Northern greater galago (Otolemur garnettii) is a prosimian primate most commonly used to study the evolutionary development of vision and somatosensation. This study aimed to investigate the efficacy and cardiopulmonary effects of 3 sedation protocols commonly used in other primate species: 1) alfaxalone (Alf; 8 mg/kg IM) 2) ketamine alone (Ket; 20 mg/ kg IM) and 3) ketamine + dexmedetomidine (Ket+Dex; 4 mg/kg + 25 μg/kg IM) with reversal (atipamezole; 250 µg/kg IM). A total of 34 animals were evaluated, including 11 juveniles and 23 adults. Cardiopulmonary parameters such as indirect blood pressure, heart rate, respiratory rate, and SpO2 were measured, and blood was collected for blood gas analysis and a chemistry panel. To examine the efficacy of each sedation protocol, induction time, immobilization time, and recovery time were recorded. Subjective measures of quality and efficacy included quality of induction, pedal withdrawal reflex, palpebral reflex, muscle tension, rectal temperature, and quality of recovery. All 3 protocols successfully immobilized the animals and all animals recovered from sedation. Heart rates were highest among the Ket group and the lowest for the Ket+Dex group. On average, the Alf group was immobilized for twice as long as either the Ket or Ket+Dex groups. The Ket+Dex group had the fastest average recovery time and subjectively had the best quality of recovery. Based on these results, Ket+Dex is recom- mended over Alf or Ket alone for brief sedation of healthy galagos. Abbreviations: BE, base excess; BP, blood pressure; CK, creatine kinase; DAP, diastolic arterial blood pressure; HCO3, bicarbonate; HR, heart rate; MAP, mean arterial blood pressure; RR, respiratory rate; SAP, systolic arterial blood pressure; SpO2, oxygen- hemoglobin saturation; SO2, oxygen saturation; TCO2, total blood carbon dioxide DOI: 10.30802/AALAS-JAALAS-19-000158 The Northern greater galago (Otolemur garnettii; also com- breathing.21,42,47,50 Recovery from ketamine sedation can be slow monly known as the small-eared galago, Garnett’s greater and animals frequently exhibit excessive salivation during the galago, or bush baby) is a nocturnal, arboreal, prosimian recovery period.25,47 In addition, the pH (3.5 to 5.5) of ketamine primate.6,51 Since the 1940’s Otolemur garnettii has been used is known to cause muscle damage in primates.4,15,32,37 When to study the evolutionary development of vision and soma- dexmedetomidine, an α-2 agonist, is used in combination with tosensation.20,38,52 ketamine, muscle relaxation is achieved and excessive saliva- Chemical restraint is often required to perform veterinary tion is usually limited.25,50,56 Because the combination requires and research procedures on laboratory primates. However, a smaller dose of ketamine to reach the same effect, and dexme- the literature devoted to the safety and/or efficacy of different detomidine is reversible with atipamezole, recovery is usually sedative and anesthetic drugs in prosimians is limited. Even faster.4,50,56 Dexmedetomidine administered alone causes a more scarce are publications pertaining specifically to galagos. decrease in heart rate, cardiac output, and blood pressure, in One study evaluated the cardiopulmonary and anesthetic ef- addition to respiratory depression.21,42,47,50 The combination of fects of sevoflurane anesthesia in Otolemur garnettii, finding it ketamine and dexmedetomidine usually results in increased a safe and effective drug for the induction and maintenance of heart rate and blood pressure, a net decrease in cardiac output, anesthesia.33 However, while inhalants can be useful in many and respiratory depression.21,36,42,47,51 situations, injectable drugs are often necessary to sedate animals In addition to ketamine and dexmedetomidine, alfaxalone within their primary enclosure. (alphaxalone) has also historically been recommended as an Ketamine is a commonly used sedative for many nonhuman injectable sedative in nonhuman primates.21,42,50 Alfaxalone primates, including prosimians.21,42,50,62 As a NMDA (N-methyl- is a neurosteroid which acts as a GABA (γ-aminobutyric acid) D-aspartate) antagonist, ketamine provides variable sedation agonist.21,31,42,47,50 The original veterinary formulation of with poor muscle relaxation.25,47 Ketamine is known to cause alfaxalone, branded Saffan, was a combination of alfaxalone an increase in heart rate, cardiac output, and blood pressure, and alphadolone, solubilized in Cremophor EL.31 Although in addition to a form of respiratory depression called apneustic historically used successfully to immobilize nonhuman pri- mates, Saffan was removed from the market due to reports in dogs of severe adverse events that included histamine release Received: 12 Nov 2019. Revision requested: 09 Jan 2020. Accepted: 09 Mar 2020. 1 2 and anaphylactic reactions linked to the Cremophor EL vehi- Division of Comparative Medicine, and Department of Biostatistics,Vanderbilt Uni- 9,31,49 versity Medical Center, Nashville, Tennessee cle. A new veterinary formulation of alfaxalone, Alfaxan, *Corresponding author. Email: [email protected] was approved by the Food and Drug Administration in 2014. 557 Vol 59, No 5 Journal of the American Association for Laboratory Animal Science September 2020 Formulated without alphadolone or Cremophor EL, Alfaxan of treatments = 3, and the block size = 12. Age was considered has since been used extensively and successfully in a wide the factor most likely to influence outcomes and therefore, 12 range of species including fish, amphibians, reptiles, birds, and juveniles (defined as animals age 1.5 to 3 y old) were assigned mammals, including nonhuman primates.4,7,31,63 Alfaxalone is within one of the 3 blocks and evenly distributed among the reported to have minimal effects on the cardiovascular system. treatment groups. During the study, 2 subjects were identified The most common effects include a transient reflex tachycardia with health concerns and one animal was noted to be pregnant. and a mild reduction in cardiac output reflected as a mild reduc- As these animals did not meet study criteria, their data were tion of blood pressure, with apnea sometimes reported after IV excluded, and alternate subjects were randomly selected to induction.31,40,41,47 replace them. Suitable alternate subjects were unavailable for 2 While the use of ketamine alone, ketamine and dexmedeto- original subjects and therefore the final population demographic midine combined, and alfaxalone alone have been investigated included 11 juveniles and 23 adults. Final treatment group sizes in other nonhuman primate species, including some prosim- were (1) ketamine alone (ket): n = 12, (2) alfaxalone (alf): n = 11, ians, no specific publications address their safety or efficacy and (3) ketamine and dexmedetomidine combined (ket+dex): n in Otolemur garnettii.24,63,64 The objective of this study was = 11. Age distribution by treatment group was (1) ket: 1.7 to 7.4 to evaluate and compare the efficacy and cardiopulmonary y, (2) alf: 1.5 to 6.3 y, and (3) ket+dex: 2.1 to 10.6 y. Sex ratio by effects of sedation with ketamine alone, ketamine combined treatment group was (1) ket: n = 7 males (M), 5 females (F), (2) with dexmedetomidine, and alfaxalone alone. We posed the alf: n = 2 M, 9 F, and (3) ket+dex: n = 8 M, 3 F. Weight distribu- following 3 hypotheses with regard to comparing the 3 drug tion by treatment group was (1) ket: 0.84 to 1.68 Kg, (2) alf: 0.84 regimens: 1) there would be no significant differences in ef- to 1.21 Kg, and (3) ket+dex: 0.88 to 1.53 Kg. ficacy, as measured by induction time, quality of induction, Sedation procedures. The study was performed over a pe- immobilization time, muscle tension, pedal withdraw reflex, or riod of 3 mo (December-February). All animals were sedated palpebral reflex; 2) there would be no significant differences in between 0839 and 1050 during their wake cycle. Food was the cardiopulmonary effects associated with sedation, as meas- withheld from each subject 16 to 18 h prior to sedation. The ured by heart rate (HR), respiratory rate (RR), blood pressure morning of the study, each animal was hand caught from the (BP), rectal temperature, or blood parameters (pH, pCO2, BE home cage, placed in an empty pet carrier (Petmate, Arlington, (base excess), HCO3 (bicarbonate), glucose, and lactate); and 3) TX), and weighed on a tared scale (Seca baby scale, Model alfaxalone would have a shorter recovery time, better recovery 354, Chino, CA). To administer the anesthetic injection, each quality, and less evidence of muscle damage as measured by animal was hand caught from the carrier and manually re- CK (creatine kinase), AST (aspartate aminotransferase), and strained while a second person administered the sedative into ALT (alanine aminotransferase). the cranial quadriceps muscle of the left leg using a 25-gauge needle. Total sedative dose volumes across all groups ranged Materials and Methods from 0.09 mL to 1.24 mL dependent on the animal’s weight. Animals. Animals were housed in an AAALAC-accredited Maximum intramuscular administration volumes per injection facility in accordance with the Guide for the Care and Use of Labo- site of 1.0 mL alfaxalone and 0.5 mL ketamine were approved ratory Animals,30 the Public Health Service Policy on Humane by the IACUC. The dose volume for the heaviest animal in the Care and Use of Laboratory Animals,44 and the Animal Welfare alfaxalone group exceeded this maximum allowable volume Act and Regulations.61 All research procedures involving ani- and therefore was divided into 2 equivalent doses (0.62 mL) mals were approved by the Institutional Animal Care and Use and administered in 2 sites in the cranial quadriceps muscle Committee at Vanderbilt University Medical Center (VUMC).