Comparison of three different sedative-anaesthetic protocols (ketamine, ketamine-medetomidine and alphaxalone) in common marmosets (Callithrix jacchus)

Hematological and Serum Biochemical Reference Intervals for Alphaxalone Sedated Common Marmosets (Callithrix jacchus)

Marmosets are routinely used in biomedical research, therefore there is an increasing need for updated reference intervals calculated using a large sample size, correct statistics, and considering different variables. Hematological and biochemical values from 472 healthy common marmosets sedated with alphaxalone were collected over a ten-year period (2013-2023). The variables assumed to have influenced the blood-based parameters were compared, i.e., sex, age, housing condition, pregnancy, and contraceptive use. Reference intervals were calculated based on observed percentiles without parametric assumptions, and with parametric assumptions following Box-Cox transformation. Juvenile marmosets showed increased ALP, phosphate, WBC, lymphocyte count, and basophil count and decreased levels of GGT and Fe compared to adults. Marmosets housed strictly indoors showed increased ALT and GGT levels and decreased levels of total bilirubin and neutrophil count compared to marmosets housed with outdoor access. Pregnant marmosets showed increased ALP, total bilirubin, neutrophil count, monocyte count, and basophil count, and decreased levels of AST, ALT, cholesterol, Fe, and lymphocyte count compared to non-pregnant marmosets. Etonogestrel contracepted marmosets showed decreased P-LCR compared to females who were not contracepted. Updated reference intervals will aid researchers and veterinarians in identifying physiological and pathological changes, as well as improve the reproducibility of research in this species.

Evaluation of Anesthetic and Cardiorespiratory Effects after Intramuscular Administration of Three Different Doses of Telazol® in Common Marmosets (Callithrix jacchus)

Marmosets' small body size makes anesthesia challenging. Ideally, small volumes of drugs should be administered intramuscularly (i.m.). In addition, dose-dependent sedation and anesthesia are desirable properties for sedatives and anesthetics in marmosets. Telazol® (tiletamine and zolazepam) is highly concentrated, allowing the use of small injection volumes and dose-dependent sedation and anesthesia. A randomized, blinded study with crossover design in ten healthy adult common marmosets (Callithrix jacchus) was performed to evaluate the anesthetic and cardiorespiratory effects of three doses of i.m. Telazol® (respectively, 5, 10, and 15 mg/kg). Depth of anesthesia, cardiorespiratory effects, and induction, immobilization, and recovery times were determined. A significant difference was observed in immobilization time between 5 and 15 mg/kg of Telazol®. In addition, 15 mg/kg of Telazol® resulted in increased recovery times compared to 5 mg/kg. The cardiorespiratory effects during the first 45 min of immobilization were within clinically acceptable limits. The pedal withdrawal reflex was the best indicator of the anesthetic depth.

Effects of Anesthesia on Cerebral Blood Flow and Functional Connectivity of Nonhuman Primates

Nonhuman primates (NHPs) are the closest living relatives of humans and play a critical and unique role in neuroscience research and pharmaceutical development. General anesthesia is usually required in neuroimaging studies of NHPs to keep the animal from stress and motion. However, the adverse effects of anesthesia on cerebral physiology and neural activity are pronounced and can compromise the data collection and interpretation. Functional connectivity is frequently examined using resting-state functional MRI (rsfMRI) to assess the functional abnormality in the animal brain under anesthesia. The fMRI signal can be dramatically suppressed by most anesthetics in a dose-dependent manner. In addition, rsfMRI studies may be further compromised by inter-subject variations when the sample size is small (as seen in most neuroscience studies of NHPs). Therefore, proper use of anesthesia is strongly demanded to ensure steady and consistent physiology maintained during rsfMRI data collection of each subject. The aim of this review is to summarize typical anesthesia used in rsfMRI scans of NHPs and the effects of anesthetics on cerebral physiology and functional connectivity. Moreover, the protocols with optimal rsfMRI data acquisition and anesthesia procedures for functional connectivity study of macaque monkeys are introduced.

Performance of Marmoset Monkeys as Embryo Donors Is Reflected by Different Stress-Related Parameters

Non-human primates (NHPs) serve as embryo donors for embryo collection in order to mimic genetic diseases in humans by genetic modification. Reproductive health of the embryo donors is crucial, and chronic distress needs to be avoided. Embryo retrieval rates (ERR), anti-Müllerian hormone (AMH) concentrations, cortisol levels, and body weight fluctuations were assessed as markers for fertility and distress. With regard to successful embryo retrievals (total n = 667), the animals were either used for extended periods (long-term group; LTG) or only for short periods (short-term group; STG). Retrospective evaluation expectedly showed that animals in the LTG had a higher ERR than animals in the STG (p < 0.0001). Importantly, ERR in the LTG remained stable throughout the experimental period, and high embryo rates were already encountered during the first year of experimental use (p = 0.0002). High ERR were associated with high AMH and low cortisol levels, and minimal body weight fluctuations following anesthesia, indicating a superior ability of the LTG animals to handle distress. We conclude that the long-term experimental use of marmosets does not impair their fertility or health status per se, supporting the view that animal reuse can be in accordance with the 3R-principle, implying reduction, replacement, and refinement in animal experimentation.

The use of alfaxalone for short-term anesthesia can confound serum progesterone measurements in the common marmoset: a case report

Alfaxan^® (alfaxalone) is a steroid general anesthetic widely used in veterinary medicine for induction and maintenance of anesthesia in several species. While the use of alfaxalone in veterinary practice has several benefits compared to the use of other anesthetic agents, the fact that it is derived from progesterone may confound the measurement of the latter in the blood of animals under alfaxalone treatment. In the present case study, we report the measurement of serum progesterone in an individual common marmoset (Callithrix jacchus) during five ovarian cycles in which luteolysis was induced by PGF2α. Blood samples were usually taken from the awake animal with the exception of the fifth cycle in which the sample was collected under alfaxalone anesthesia in connection with a tooth extraction. In contrast to the previous four cycles in which luteolysis resulted in the expected marked decrease in progesterone concentrations, the – apparent – progesterone level in the cycle under alfaxalone treatment remained unexpectedly high. Cross-reactivity of the non-specific antibody used in the progesterone assay with alfaxalone most likely explains this finding.

Synthetic neuroactive steroids as new sedatives and anaesthetics: Back to the future

Since the 1990s, there has been waning interest in researching general anaesthetics (anaesthetics). Although currently used anaesthetics are mostly safe and effective, they are not without fault. In paediatric populations and neonatal animal models, they are associated with learning impairments and neurotoxicity. In an effort to research safer anaesthetics, we have gone back to re-examine neuroactive steroids as anaesthetics. Neuroactive steroids are steroids that have direct, local effects in the central nervous system. Since the discovery of their anaesthetic effects, neuroactive steroids have been consistently used in human or veterinary clinics as preferred anaesthetic agents. Although briefly abandoned for clinical use due to unwanted vehicle side effects, there has since been renewed interest in their therapeutic value. Neuroactive steroids are safe sedative/hypnotic and anaesthetic agents across various animal species. Importantly, unlike traditional anaesthetics, they do not cause extensive neurotoxicity in the developing rodent brain. Similar to traditional anaesthetics, neuroactive steroids are modulators of synaptic and extrasynaptic γ-aminobutyric acid type A (GABA_A ) receptors and their interactions at the GABA_A receptor are stereo- and enantioselective. Recent work has also shown that these agents act on other ion channels, such as high- and low-voltage-activated calcium channels. Through these mechanisms of action, neuroactive steroids modulate neuronal excitability, which results in characteristic burst suppression of the electroencephalogram, and a surgical plane of anaesthesia. However, in addition to their interactions with voltage and ligand gated ions channels, neuroactive steroids interact with membrane bound metabotropic receptors and xenobiotic receptors to facilitate signaling of prosurvival, antiapoptotic pathways. These pathways play a role in their neuroprotective effects in neuronal injury and may also prevent extensive apoptosis in the developing brain during anaesthesia. The current review explores the history of neuroactive steroids as anaesthetics in humans and animal models, their diverse mechanisms of action, and their neuroprotective properties.

Ketamine treatment upon memory retrieval reduces fear memory in marmoset monkeys

Emotionally arousing experiences are retained very well as seen in posttraumatic stress disorder (PTSD). Various lines of evidence indicate that reactivation of these memories renders them labile which offers a potential time-window for intervention. We tested in non-human primates whether ketamine, administered during fear memory reactivation, affected passive (inhibitory) avoidance learning. For the consolidation of contextual emotional memory, the unescapable foot-shock paradigm in a passive avoidance task with two compartments (dark vs illuminated) was used. After entering the dark compartment, marmoset monkeys received four random foot-shocks (1 mA, 4 s) within 15-min. This stressful exposure increased the saliva cortisol and heart rate and impaired REM-sleep (p<0.05). One week later the monkeys were re-exposed to the stressful situation for the reconsolidation of the fearful experience. During the re-exposure the monkeys were treated with ketamine (0.5 mg/kg) or saline. In week 3, the monkeys were placed in the experimental setting to test their memory for the fearful experience. In contrast to the vehicle-treated monkeys, who avoided the dark compartment, the ketamine-treated monkeys entered the dark compartment that was previously associated with the fearful experience (p<0.05). Post-mortem analysis of the hippocampus showed that ketamine-treated animals exhibited less doublecortin positive neurons and BrdU-labeled cells in the dentate gyrus. This study reveals that a single low dose of ketamine, administered upon fear retrieval in monkeys, reduce contextual fear memory and attenuate neurogenesis in the hippocampus. These are important findings for considering ketamine as a potential candidate to target traumatic memories in PTSD.

Comparison between three dosages of intramuscular alfaxalone and a ketamine-dexmedetomidine-midazolam-tramadol combination in golden-headed lion tamarins (Leontopithecus chrysomelas)

OBJECTIVES

To characterize the cardiopulmonary and anesthetic effects of alfaxalone at three dose rates in comparison with a ketamine-dexmedetomidine-midazolam-tramadol combination (KDMT) for immobilization of golden-headed lion tamarins (GHLTs) (Leontopithecus chrysomelas) undergoing vasectomy.

STUDY DESIGN

Prospective clinical trial.

ANIMALS

A total of 19 healthy, male, wild-caught GHLTs.

METHODS

Tamarins were administered alfaxalone intramuscularly (IM) at 6, 12 or 15 mg kg^-1, or KDMT, ketamine (15 mg kg^-1), dexmedetomidine (0.015 mg kg^-1), midazolam (0.5 mg kg^-1) and tramadol (4 mg kg^-1) IM. Immediately after immobilization, lidocaine (8 mg kg^-1) was infiltrated subcutaneously (SC) at the incision site in all animals. Physiologic variables, anesthetic depth and quality of immobilization were assessed. At the end of the procedure, atipamezole (0.15 mg kg^-1) was administered IM to group KDMT and tramadol (4 mg kg^-1) SC to the other groups; all animals were injected with ketoprofen (2 mg kg^-1) SC.

RESULTS

A dose-dependent increase in sedation, muscle relaxation and immobilization time was noted in the alfaxalone groups. Despite the administration of atipamezole, the recovery time was longer for KDMT than all other groups. Muscle tremors were noted in some animals during induction and recovery with alfaxalone. No significant differences were observed for cardiovascular variables among the alfaxalone groups, whereas an initial decrease in heart rate and systolic arterial blood pressure was recorded in KDMT, which increased after atipamezole administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Alfaxalone dose rates of 12 or 15 mg kg^-1 IM with local anesthesia provided good sedation and subjectively adequate pain control for vasectomies in GHLTs. KDMT induced a deeper plane of anesthesia and should be considered for more invasive or painful procedures. All study groups experienced mild to moderate hypothermia and hypoxemia; therefore, the use of more efficient heating devices and oxygen supplementation is strongly recommended when using these protocols.

Current Topics in Marmoset Anesthesia and Analgesia

Anesthetic and analgesics are essential components of both clinical and research procedures completed in marmosets. A review of current anesthetic and analgesic regimens for marmosets has been complied to provide a concise reference for veterinarians and investigator teams. Published dose regimens for injectable and inhalant anesthetic drugs and analgesic drugs are included. Appropriate physiological monitoring is key to the success of the procedure and perianesthetic options are provided. Although recent publications have refined anesthesia and analgesia practices, our review demonstrates the continued need for evidence-based resources specific to marmosets.

Effects of alfaxalone on cerebral blood flow and intrinsic neural activity of rhesus monkeys: A comparison study with ketamine

OBJECTIVE

Alfaxalone has been used increasingly in biomedical research and veterinary medicine of large animals in recent years. However, its effects on the cerebral blood flow (CBF) physiology and intrinsic neuronal activity of anesthetized brains remain poorly understood.

METHODS

Four healthy adult rhesus monkeys were anesthetized initially with alfaxalone (0.125 mg/kg/min) or ketamine (1.6 mg/kg/min) for 50 min, then administrated with 0.8% isoflurane for 60 min. Heart rates, breathing beats, and blood pressures were continuously monitored. CBF data were collected using pseudo-continuous arterial spin-labeling (pCASL) MRI technique and rsfMRI data were collected using single-shot EPI sequence for each anesthetic.

RESULTS

Both the heart rates and mean arterial pressure (MAP) remained more stable during alfaxalone infusion than those during ketamine administration. Alfaxalone reduced CBF substantially compared to ketamine anesthesia (grey matter, 65 ± 22 vs. 179 ± 38 ml/100g/min, p<0.001; white matter, 14 ± 7 vs. 26 ± 6 ml/100g/min, p < 0.05); In addition, CBF increase was seen in all selected cortical and subcortical regions of alfaxalone-pretreated monkey brains during isoflurane exposure, very different from the findings in isoflurane-exposed monkeys pretreated with ketamine. Also, alfaxalone showed suppression effects on functional connectivity of the monkey brain similar to ketamine.

CONCLUSION

Alfaxalone showed strong suppression effects on CBF of the monkey brain.The residual effect of alfaxalone on CBF of isoflurane-exposed brains was evident and monotonous in all the examined brain regions when used as induction agent for inhalational anesthesia. In particular, alfaxalone showed similar suppression effect on intrinsic neuronal activity of the brain in comparison with ketamine. These findings suggest alfaxalone can be a good alternative to veterinary anesthesia in neuroimaging examination of large animal models. However, its effects on CBF and functional connectivity should be considered.

Pharmacokinetics and effects on clinical and physiological parameters following a single bolus dose of propofol in common marmosets (Callithrix jacchus)

The objectives of this study were (a) to establish a population pharmacokinetic model and (b) to investigate the clinical and physiological effects of a single bolus dose of propofol in common marmosets. In Study 1, pharmacokinetic analysis was performed in six marmosets under sevoflurane anaesthesia. 8 mg/kg of propofol was administrated at a rate of 4 mg kg^-1  min^-1 . Blood samples were collected 2, 5, 15, 30, 60, 90, 120 or 180 min after starting propofol administration. Plasma concentration was measured, and population pharmacokinetic modelling was performed. A two-compartment model was selected as the final model. The population pharmacokinetic parameters were as follows: V₁  = 1.14 L, V₂  = 77.6 L, CL₁  = 0.00182 L/min, CL₂  = 0.0461 L/min. In Study 2, clinical and physiological parameters were assessed and recorded every 2 min after 12 mg/kg of propofol was administrated at a rate of 4 mg kg^-1  min^-1 . Immobilization was sustained for 5 min following propofol administration without apparent bradycardia. While combination of propofol and sevoflurane caused apnoea in Study 1, apnoea was not observed following single administration of propofol in Study 2. These data provide bases for further investigation on intravenous anaesthesia using propofol in common marmosets.

A Comparison of the Efficacy and Cardiopulmonary Effects of 3 Different Sedation Protocols in Otolemur garnettii

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 recommended over Alf or Ket alone for brief sedation of healthy galagos.

Evaluation of anaesthetic and cardiorespiratory effects after intramuscular administration of alfaxalone alone, alfaxalone-ketamine and alfaxalone-butorphanol-medetomidine in common marmosets (Callithrix jacchus)

BACKGROUND

Anaesthesia is often required in common marmosets undergoing various procedures. The aim of this study was to evaluate anaesthetic and cardiopulmonary effects of alfaxalone, alfaxalone-ketamine and alfaxalone-butorphanol-medetomidine in common marmosets.

METHODS

The following treatments were repeatedly administered to seven female common marmosets: Treatment A, alfaxalone (12 mg kg^-1 ) alone; treatment AK, alfaxalone (1 mg animal^-1 ) plus ketamine (2.5 mg animal^-1 ); treatment AMB, alfaxalone (4 mg kg^-1 ), medetomidine (50 µg kg^-1 ) plus butorphanol (0.3 mg kg^-1 ); and treatment AMB-Ati, AMB with atipamezole at 45 minutes.

RESULTS AND CONCLUSIONS

Marmosets became laterally recumbent and unresponsive for approximately 30 minutes in A and AK and for approximately 60 minutes in AMB. The animals showed rapid recovery following atipamezole injection in AMB-Ati. The decrease in heart rate and SpO₂ was significantly greater in AMB compared to A and AK. Oxygen supplementation, anaesthetic monitors and atipamezole should be available especially when AMB is administered.

Combination of intramuscular alfaxalone, butorphanol, and midazolam as a novel immobilization protocol in 3 ring-tailed lemurs (Lemur catta)

Background

There is very little data on the optimal anaesthetic management of ring-tailed lemurs, and the available information is mostly based on extrapolation from other species. In addition, a thorough pre-anaesthetic assessment of lemurs might not be possible without prior chemical immobilization, making a safe immobilization protocol essential.

Case presentation

Three ring-tailed lemurs (Lemur catta) were immobilized using a combination of intramuscular alfaxalone (5 mg/kg), butorphanol (0.2 mg/kg), and midazolam (0.2 mg/kg), at the University College Dublin Veterinary Hospital. One lemur was anaesthetised once, two lemurs twice, amounting to five anaesthetic events. Conversion to general anaesthesia was warranted in all five occasions, and anaesthesia was maintained with either sevoflurane in oxygen or alfaxalone infusion. The immobilization protocol provided an adequate duration of deep sedation for diagnostic procedures and in some occasions allowed the intubation of the trachea. Analgesia was also provided for minor procedures. No major complications were noted with the protocol used.

Conclusions

The combination of intramuscular alfaxalone, butorphanol and midazolam provided a clinically useful sedation/immobilization in ring-tailed lemurs with only minor complications such as mild hypothermia, hypotension, hypoventilation and bradycardia. This protocol could be considered in ring-tailed lemurs that need to be immobilized for minor procedures, or as a pre-anaesthetic premedication, especially if a full pre-anaesthetic clinical exam is not possible.

Sedative and physiological effects of alfaxalone intramuscular administration in cynomolgus monkeys (Macaca fascicularis)

To evaluate the sedative and physiological effects of alfaxalone intramuscular (IM) administration, 12 healthy cynomolgus monkeys were administered single IM doses of alfaxalone at 0.625 mg/kg (ALFX0.625), 1.25 mg/kg (ALFX1.25), 2.5 mg/kg (ALFX2.5), 5 mg/kg (ALFX5), 7.5 mg/kg (ALFX7.5), or 10 mg/kg (ALFX10); saline was used as the control (CONT). The sedative effects were subjectively evaluated using a composite measure scoring system in six animals. Changes in respiratory rate, pulse rate, non-invasive blood pressure, percutaneous oxygen-hemoglobin saturation (SpO₂), and rectal temperature were observed after IM treatments in the other six animals. All animals were allowed to lay down following the ALFX5, ALFX7.5, and ALFX10 treatments, whereas lateral recumbency was achieved in only two animals after ALFX2.5 treatment and none after the CONT, ALFX 0.625, and ALFX1.25 treatments. The median time (interquartile range) to lateral recumbency was 6.5 min (5.3–7.8), 4.0 min (4.0–4.0), and 3.0 min (3.0–3.8), and the duration of immobilization was 27.5 min (19.0–33.8), 56.0 min (42.3–60.8), and 74.5 min (62.8–78.0) after the ALFX5, ALFX7.5, and ALFX10 treatments, respectively. Endotracheal intubation was achieved in all six animals after the ALFX7.5 and ALFX10 treatments. Dose-dependent decreases in respiratory rate, non-invasive blood pressure, SpO₂, and rectal temperature were observed, and the quality of recovery was smooth in all animals after the ALFX5, ALFX7.5, and ALFX10 treatments. Thus, alfaxalone IM induced a dose-dependent sedative effect in cynomolgus monkeys, but at higher doses, hypotension, hypoxemia, and hypothermia could be induced.

Comparison of three reversible injectable chemical restraint protocols in Spix´s Owl monkeys (Aotus vociferans) using ketamine, xylazine and midazolam

BACKGROUND

There is scarce information detailing clinical and physiological effects of reversible injectable protocols of chemical restraint on Neotropical primates.

METHODS

Nineteen captive Spix´s Owl monkeys (Aotus vociferans) were assessed in a double-blind randomized crossover study using the following: ketamine/xylazine [KX], ketamine/midazolam [KM] and ketamine/xylazine/midazolam [KXM]. During immobilization, respiratory and pulse rates, rectal temperature, haemoglobin oxygen saturation and arterial blood pressure were recorded at 5-minute intervals during a 20-minute period; afterwards, antagonist drugs (yohimbine for xylazine and flumazenil for midazolam) were, respectively, administered. Quality and duration of induction, immobilization and recovery periods were recorded.

RESULTS

Ketamine/xylazine increased manipulation sensitivity and produced poor muscle relaxation. KM maintained all assessed parameters within physiological ranges. KXM produced depressant cardiorespiratory effects and hypotension. All protocols produced hypothermia.

CONCLUSIONS

Based on its adequate anaesthetic depth and minimum effects on physiological parameters, KM is suitable for immobilizing A vociferans and performing short-term procedures lasting around 20 minutes.

Comparison of physiological responses of Arabian striped hyaena (Hyaena hyaena sultana) to effective immobilisations with ketamine-medetomidine and ketamine-xylazine in (semi-) captive conditions

Chemical immobilisation is an integral component for the conservation of wild animals and can be stressful if proper protocols are not administered. References on the immobilisation of Arabian striped hyaena (Hyaena hyaena sultana) are scarce. The current study was designed to evaluate the physiological and clinical responses of Arabian striped hyaena, immobilised with ketamine-medetomidine (KM) and ketamine-xylazine (KX); and to compare immobilisation effectiveness of the two combinations in a cross-sectional clinical study. A total of 15 (six males, nine females) (semi-) captive and adult Arabian striped hyaena with an average weight of 31.39 ± 0.36 kg were immobilised 50 times for annual vaccination and translocation purposes from January 2014 till March 2018 on Sir Bani Yas Island, United Arab Emirates. A total of 34 immobilisations were executed with (Mean ± SE) 2.27 ± 0.044 mg/kg ketamine and 0.04 ± 0.001 mg/kg medetomidine; while 16 with 4.95 ± 0.115 mg/kg ketamine and 0.99 ± 0.023 mg/kg xylazine. The drugs were remotely delivered intramuscular. The evaluation of physiological and clinical parameters included monitoring of vital signs through pulse oximetry, blood gas analysis of arterial blood through Istat blood gas analyser, and blood biochemistry and haematology. The quality of induction, anaesthesia and recovery was also assessed. Atipamezole (0.21 ± 0.003 mg/kg) was used to antagonise the effects of KM and 0.09 ± 0.003 mg/kg atipamezole or by 0.23 ± 0.006 mg/kg yohimbine for KX. Data were analysed using the general linear model and inferential statistics. KM was more effective in induction (scores; KM = 1.41 ± 0.10; KX = 1.31 ± 0.12), anaesthesia (KM = 1.00 ± 0.00; KX = 2.0 ± 0.0) and recovery (KM = 1.76 ± 0.15; KX = 2.69 ± 0.12) phases as compared to KX. There was a significant difference (P < 0.05) amongst the two combinations for anaesthesia time (KM = 59.5 ± 2.41; KX = 49.25 ± 1.31 min.), time to stand after reversal (KM = 4.91 ± 0.60; KX = 10.38 ± 1.48 min.) and full loss of the signs of anaesthetics (KM = 12.32 ± 1.37; KX = 21.25 ± 2.16 min.) along with rectal temperature (KM = 37.58 ± 0.29; KX = 36.00 ± 0.68 °C), pulse rate (KM = 50.46 ± 1.90; KX = 61.14 ± 2.79 beats/min), respiration rate (KM = 29.44 ± 0.99; KX = 23.80 ± 1.57 breaths/min.) and partial pressure of oxygen (KM = 89.59 ± 1.34; KX = 82.06 ± 3.92%). The blood oxygen saturation by oximeter indicated hypoxaemia in KX (82.06 ± 3.92), supported by the data from blood gas analyser. KM combination was more suitable for the immobilisation of Arabian striped hyaena, providing a better quality of induction, anaesthesia and recovery compared to KX. However, we strongly suggest further investigation to see the effects of oxygen supplementation for the compensation of hypoxaemia.

Effects of buprenorphine, butorphanol or tramadol premedication on anaesthetic induction with alfaxalone in common marmosets (Callithrix jacchus)

OBJECTIVE

To investigate the clinical and physiological effects of intravenous (IV) alfaxalone alone or in combination with buprenorphine, butorphanol or tramadol premedication in marmosets.

STUDY DESIGN

Prospective, randomized, blinded, crossover design.

ANIMALS

Nine healthy marmosets (391 ± 48 g, 3.7 ± 2.2 years old).

METHODS

Meloxicam 0.20 mg kg^-1 subcutaneously, atropine 0.05 mg kg^-1 intramuscularly (IM) and either buprenorphine 20 μg kg^-1 IM (BUP-A), butorphanol 0.2 mg kg^-1 IM (BUT-A), tramadol 1.5 mg kg^-1 IM (TRA-A) or no additional drug (control) were administered to all marmosets as premedication. After 1 hour, anaesthesia was induced with 16 mg kg^-1 alfaxalone IV. All animals received all protocols. The order of protocol allocation was randomized with a minimum 28 day wash-out period. During anaesthesia, respiratory and pulse rates, rectal temperature, haemoglobin oxygen saturation, arterial blood pressure, palpebral and pedal withdrawal reflexes and degree of muscle relaxation were assessed and recorded every 5 minutes. Quality of induction and recovery were assessed. Duration of induction, immobilization and recovery were recorded. Blood samples were analysed for aspartate aminotransferase, creatine kinase and lactate dehydrogenase concentrations. The protocols were compared using paired t tests, Wilcoxon's signed-rank test with Bonferroni's corrections and linear mixed effect models where appropriate.

RESULTS

Out of nine animals, apnoea was noted in eight animals administered protocol BUP-A and two animals administered protocol BUT-A. With TRA-A and control protocols, apnoea was not observed. No other significant differences in any of the parameters were found; however, low arterial blood pressures and hypoxia occurred in TRA-A.

CONCLUSIONS AND CLINICAL RELEVANCE

Our study employing different premedications suggests that the previously published dose of 16 mg kg^-1 alfaxalone is too high when used with premedication because we found a high incidence of complications including apnoea (BUP-A), hypotension and hypoxaemia (TRA-A). Appropriate monitoring and countermeasures are recommended.

Alfaxalone anaesthesia in Lemur catta following dexmedetomidine-butorphanol-midazolam sedation

OBJECTIVE

To evaluate the clinical effects and quality of sedation, induction, maintenance and recovery in Lemur catta after dexmedetomidine-butorphanol-midazolam sedation and alfaxalone anaesthesia.

STUDY DESIGN

Prospective, observational study.

ANIMALS

Six male L. catta weighing 3.0 ± 0.6 kg undergoing surgical castration.

METHODS

Lemurs were sedated with intramuscular dexmedetomidine (0.015 mg kg^-1), butorphanol (0.2 mg kg^-1) and midazolam (0.2 mg kg^-1). Anaesthesia was induced with intravenous alfaxalone 0.5 mg kg^-1 over 60 seconds; further boluses were administered until tracheal intubation was feasible and final dose recorded. Alfaxalone continuous infusion was used to maintain anaesthesia. Atipamezole (0.15 mg kg^-1) was administered during recovery. The quality of sedation, induction, intubation, maintenance and recovery was assessed using a scoring system. Physiological parameters were recorded during sedation, maintenance and recovery.

RESULTS

Sedation was achieved in 13.6 ± 5.6 minutes and no reactions were observed during handling or venepuncture. The mean dose of alfaxalone required for induction and maintenance was 2.09 ± 0.65 and 0.08 ± 0.02 mg kg^-1 minute^-1, respectively. Quality of induction, intubation and maintenance was good in almost all animals. Mild self-limiting muscle twitching was observed after alfaxalone administration in three animals. Cardiorespiratory function was stable in all animals but one. One lemur showed respiratory depression and required oxygen administration and manual ventilation. The mean maintenance time was 29.2 ± 7.4 minutes. The mean times from the end of alfaxalone administration to extubation, atipamezole administration and full recovery were: 15.3 ± 8.0, 22.2 ± 4.6 and 60.0 ± 8.4 minutes, respectively. Recovery was considered good in all animals.

CONCLUSIONS AND CLINICAL RELEVANCE

Dexmedetomidine-butorphanol-midazolam combination provided reliable sedation and adequate muscle relaxation in L. catta. Alfaxalone proved to be a useful drug for induction and maintenance of anaesthesia and might be considered an option for injectable anaesthesia in lemurs.

MRI-guided stereotaxic brain surgery in the infant and adult common marmoset

In the past decade, the New World common marmoset (Callithrix jacchus) has taken a seminal position in neurobiological research, fueled in part by its smooth cortical sheet, which allows cortical areas to be easily accessed by current technologies on the dorsal surface of the brain. In this protocol, we describe a method for the precision placement of agents (e.g., tracers or neurotoxins) into small brain regions of the infant and adult marmoset, using an MRI-guided approach. This strategy uses a protocol for prolonged anesthesia without the need for intubation that we have recently developed, alongside appropriate analgesia and monitoring. The protocol can be readily adapted to be used together with advanced research techniques, such as two-photon microscopy and optical imaging. Including a 5-d postoperative care plan, this protocol takes 7 d to complete. The protocol requires a team of personnel experienced in marmoset care and handling, and small-animal neurosurgery; an assistant for monitoring the animal and assisting with anesthesia; and an MRI technician.

The Effect of Anesthesia on Blood Pressure Measured Noninvasively by Using the Tail-Cuff Method in Marmosets (Callithrix jacchus)

In this study, we evaluated the validity of measuring blood pressure (BP) noninvasively in marmosets by using the tail-cuff method. The number of measurements needed for a valid reading was calculated by plotting the average SD of 5 consecutive readings in 10 naïve marmosets; the SD for both systolic and diastolic BP readings plateaued after 4 readings. To evaluate how anesthesia (alphaxalone, 15 mg/kg IM) affected BP in marmosets, we measured 4 animals every minute for 60 min after injection. The average length of anesthesia was 47.3 ± 13.2 min. The variability in the systolic and diastolic BP was the smallest at 10 to 30 min after injection (systolic SD, 6.29 mm Hg; diastolic SD, 5.27 mm Hg) and almost doubled at 30 to 60 min after injection (systolic SD, 13.5 mm Hg; diastolic SD, 12.3 mm Hg). The within- and between-session repeatability and reproducibility were calculated by measuring 12 marmosets twice at the same time of day (±1 h) 1 wk apart. The coefficients of repeatability and reproducibility were 1.98% and 14.5% for systolic BP and 3.37% and 16.2% for diastolic BP, respectively. Our results indicate that using the volumetric tail-cuff method to measure BP noninvasively in anesthetized marmosets is safe and feasible. The measures are least variable within 10 to 30 min after the injection of anesthetic, and variability increases slightly between sessions.