Sheep (Ovis aries) training protocol for voluntary awake and unrestrained structural brain MRI acquisitions

Magnetic resonance imaging (MRI) is a non-invasive technique that requires the participant to be completely motionless. To date, MRI in awake and unrestrained animals has only been achieved with humans and dogs. For other species, alternative techniques such as anesthesia, restraint and/or sedation have been necessary. Anatomical and functional MRI studies with sheep have only been conducted under general anesthesia. This ensures the absence of movement and allows relatively long MRI experiments but it removes the non-invasive nature of the MRI technique (i.e., IV injections, intubation). Anesthesia can also be detrimental to health, disrupt neurovascular coupling, and does not permit the study of higher-level cognition. Here, we present a proof-of-concept that sheep can be trained to perform a series of tasks, enabling them to voluntarily participate in MRI sessions without anesthesia or restraint. We describe a step-by-step training protocol based on positive reinforcement (food and praise) that could be used as a basis for future neuroimaging research in sheep. This protocol details the two successive phases required for sheep to successfully achieve MRI acquisitions of their brain. By providing structural brain MRI images from six out of ten sheep, we demonstrate the feasibility of our training protocol. This innovative training protocol paves the way for the possibility of conducting animal welfare-friendly functional MRI studies with sheep to investigate ovine cognition.

Use of ketamine and xylazine anesthesia in dogs: A retrospective cohort study of 3,413 cases

The information regarding the risk of anesthesia-related death in veterinary medicine is scarce, and little is known about the mortality risk of specific anesthetics. The study conducted during 2019 at University of Sarajevo, Veterinary faculty, aimed to estimate the mortality risk of intermittent injectable ketamine-xylazine anesthesia in dogs and to investigate the potential relationship between mortality rate and anesthesiologists’ experience. Anesthetic records, where ketamine and xylazine combination was used for anesthesia induction and maintenance, were reviewed and divided into two groups: inexperienced (AN1) and experienced anesthesiologists (AN2). Inexperienced anesthesiologists were constantly supervised by experienced ones, whose corrective interventions were recorded. Overall detected mortality rate was 0.15%, with 0.18% and 0.11% in the AN1 and AN2 groups, respectively. A statistically significant difference was not found. Records of the AN1 group revealed interventions of experienced anesthesiologist in 92% of cases. Detected mortality rate was within the values previously established for inhalant anesthesia indicating high safety in usage of investigated protocol, if performed by experienced anesthesiologists. The high percentage of interventions of a senior anesthesiologist suggests that supervised upskilling of inexperienced anesthesiologists before their independent work could result in a better outcome.

Safety and Efficacy of Nalbuphine, Medetomidine, and Azaperone for Immobilizing Aoudad (Ammotragus lervia)

We evaluated the safety and efficacy of nalbuphine (40 mg/mL), plus medetomidine (10 mg/mL), plus azaperone (10 mg/mL) under the premixed label NalMed-A. From January to March 2020, 10 aoudad (Ammotragus lervia) were immobilized via dart-gun for seven separate sampling periods for a total of 45 recorded individual immobilization events. Induction and reversal times with NalMed-A were 5.53±2.61 min and (following atipamezole administration) 5.08±2.43 min while previous studies with alpha-2 agonist-ketamine combinations gave median and average induction times of 4.6 min and 11.2 min using medetomidine-ketamine and xylazine-ketamine, respectively. Overall, NalMed-A adequately immobilized aoudad, with 13% incidence of hyperthermia and 2.22% mortality when delivered via dart.

Avian anaesthesia related mortality and the associated risk factors in a UK zoological collection

OBJECTIVE

To analyse avian anaesthesia-related mortality in a UK zoological collection over a 5-year period and identify risk factors for mortality.

STUDY DESIGN

Retrospective cohort study.

ANIMALS

A total of 135 individual birds across 37 species, anaesthetized during 206 events in a UK zoological collection between 1 January 2014 and 30 June 2019 (inclusive).

METHODS

Anaesthesia records were reviewed and variables such as age, body condition, weight, sex, duration of anaesthesia and health status were collated. Anaesthesia-related mortality was defined as those deaths occurring during anaesthesia and up to 7 days postanaesthesia. Outcome was analysed using multivariable conditional logistic regression. Overall mortality was defined and included birds euthanised during anaesthesia for non-anaesthesia related reasons. Data were summarised as median (range). A value of p < 0.05 was considered significant. Relative risks and 95% confidence intervals (95% CI) were calculated for the association between risk factors and anaesthetic death where a statistically significant difference was found.

RESULTS

The overall mortality rate was 10.19% (95% CI = 6.06-14.3%), while anaesthesia-related mortality was 3.88% (95% CI = 1.69-7.51%). Birds with an abnormal health status had a 15.53-fold (95% CI = 1.95-123.63) increased risk of death compared with those with a normal health status. The duration of anaesthesia was also a statistically significant risk factor (p = 0.021) in the univariable analysis, but not when combined with health status. No other variables were associated with anaesthesia-related mortality.

CONCLUSIONS AND CLINICAL RELEVANCE

Abnormal health status and longer anaesthetic procedures were associated with a significantly increased risk of anaesthesia-related death in this population of birds. It is recommended that anaesthetic duration is minimized, and pre-existing diseases are diagnosed where possible prior to general anaesthesia of birds. Anaesthetizing healthy birds was associated with a low risk of mortality.

Retrospective study of gross and histopathologic lesions associated with closed chest cardiopulmonary resuscitation in dogs

OBJECTIVES

To investigate and characterise the incidence of iatrogenic complications secondary to closed chest cardiopulmonary resuscitation in dogs.

MATERIALS AND METHODS

Necropsy reports and histologic sections of tissues were retrospectively examined from 180 dogs that had received closed chest cardiopulmonary resuscitation to determine lesions associated with resuscitation.

RESULTS

The most common complication was pulmonary haemorrhage (81/163, 49.7%, 95% confidence interval: 42.1 to 57.3), although only nine dogs had pulmonary haemorrhage of at least moderate severity. Liver fractures occurred in 16 of 180 cases (8.9%, 95% confidence interval: 5.5 to 14.0). Blood loss of >15% of blood volume into the abdomen and/or thorax occurred in 13 of 180 cases (7.2%, 95% confidence interval: 4.2 to 12.1).

CLINICAL SIGNIFICANCE

Significant haemorrhage secondary to cardiopulmonary resuscitation may decrease the chances of achieving the return of spontaneous circulation or may cause or compound ischemic damage to critical organs if the return of spontaneous circulation is achieved. Following successful cardiopulmonary resuscitation, animals should be screened for cavitary or pulmonary haemorrhage, as significant haemorrhage could be a factor in recurrence of cardiac arrest.

Quantification of reservoir bags as airway pressure-limiting devices in a nonrebreathing system

OBJECTIVE

To evaluate the influence of reservoir bag types, volumes and previous use on the peak pressures (Pmax) and the times to develop 30 cmH₂O pressure (P30) within a nonrebreathing system with a closed adjustable pressure-limiting (APL) valve.

STUDY DESIGN

In vitro study using three-way factorial design with repeated measure on one factor.

SUBJECTS

A total of 75 new anesthesia reservoir bags (five types, three volumes, five bags from each type × volume). The bag types were reusable latex (RL), disposable latex (DL) and three disposable neoprene (DN-1, DN-2 and DN-3).

METHODS

Each bag was tested three times (treatments): new, after prestretching and 1 week later. The bags were attached to a Bain system and anesthesia machine with closed APL valve and patient port with O₂ flow 2 L minute^-1 until Pmax was reached. The Pmax and time to reach P30 values were determined from recorded pressure traces. General linear mixed model analysis was used to examine the effects of bag type, volume and treatment. One-sided 95% upper prediction limits of Pmax were calculated to test the null hypothesis that predicted Pmax of new bags would be ≥ 50 cmH₂O for each factor combination.

RESULTS

RL bags were the least and DN-3 bags were the most compliant. Prestretching increased compliance in all bag types. Smaller bags of RL, DL and DN-1 were less compliant than larger ones. The predicted Pmax values were < 50 cmH₂O only for DN-3 bags after prestretching. The time to reach P30 was critically low when using 0.5 L bags (median 17 seconds).

CONCLUSIONS AND CLINICAL RELEVANCE

To minimize the risk of barotrauma, highly compliant reservoir bags (e.g. DN-3) are recommended and reusable bags should be avoided. Bags should be prestretched before first use, 0.5 L bags should be avoided and fresh gas flow minimized.

Development of a severity scoring system for acute haemorrhage in anaesthetized domestic cats: the CABSS score

OBJECTIVE

To determine whether physiological, haematological, biochemical or electrolyte variables can predict severe haemorrhage in cats.

STUDY DESIGN

Randomized crossover study whereby each cat underwent mild and severe haemorrhage, with a 2 month period between events.

ANIMALS

A group of six domestic cats aged 21 ± 1 months and weighing 4.9 ± 1.2 kg, mean ± standard deviation.

METHODS

Cats were anaesthetized (buprenorphine, alfaxalone, isoflurane in oxygen at a fixed end-tidal concentration of 1.7%) before the haemorrhage event. In total, 34 variables were measured twice (prehaemorrhage and posthaemorrhage). The difference and percent change for each variable were compared between haemorrhage events (paired t test). Significant variables were placed into 13 different ratios (posthaemorrhage value of one variable divided by a posthaemorrhage value of a second variable) and compared (paired t test), and Cohen's d (d) was calculated. Receiver operating characteristic curves were plotted and cut-off values for weak, moderate and strong indicators of severe haemorrhage were obtained.

RESULTS

The blood loss was 4.5 ± 1.1 mL kg^-1 and 26.8 ± 5.5 mL kg^-1 for mild and severe haemorrhage events, respectively. The most significant variables with large effect sizes were heart rate (HR), systolic arterial blood pressure (SAP), end-tidal carbon dioxide (Pe'CO₂), serum albumin, haematocrit and actual bicarbonate ion concentration [HCO₃^-(act)]. The most robust ratios were: 1) shock index (d = -2.8; HR:SAP); 2) HR:Pe'CO₂ (d = -2.9); 3) serum albumin: haematocrit (d = 1.5); and 4) HR:HCO₃^-(act) (d = -1.6). These ratios were included in the final proposed Cat Acute Bleeding Scoring System (CABSS).

CONCLUSIONS

and clinical relevance Cats subjected to mild and severe haemorrhage demonstrated statistically and clinically relevant changes whereby four ratios could be created to make up the CABSS. The ratios detected and quantified the presence of severe haemorrhage in anaesthetized cats.

Behavioural risks in female dogs with minimal lifetime exposure to gonadal hormones

Spaying of female dogs is a widespread practice, performed primarily for population control. While the consequences of early spaying for health are still being debated, the consequences for behaviour are believed to be negligible. The current study focused on the reported behaviour of 8981 female dogs spayed before 520 weeks (ten years) of life for reasons other than behavioural management, and calculated their percentage lifetime exposure to gonadal hormones (PLGH) as a proportion of their age at the time of being reported to the online Canine Behavioral Assessment and Research Questionnaire (C-BARQ). We found that 23 behaviours differed between entire and spayed dogs, of which 12 were associated with PLGH and 5 with age-at-spay (AAS). Two behaviours, chewing and howling, were significantly more likely in dogs with longer PLGH. In contrast, longer PLGH was associated with significantly reduced reporting of 10 (mostly unwelcome) behaviours. Of these, one related to fearfulness and three to aggression. The current data suggest that dogs' tendency to show numerous behaviours can be influenced by the timing of spaying. They indicate how female dog behaviour matures when gonadal hormones are allowed to have their effect. The differences reported here between undesirable behaviours of spayed and entire dogs were in the range of 5.33% and 7.22%, suggesting that, for some dogs, partial or complete denial of maturation may reduce howling and chewing and improve retrieval and recall, but have other undesirable consequences. Veterinarians may take these data into account to discuss the risks and benefits of spaying with clients, and the timing of the procedure.

Alfaxalone-Xylazine Anesthesia in Laboratory Mice (Mus musculus)

Since its recent reformulation, alfaxalone has gained popularity as an injectable veterinary anesthetic, including promising studies demonstrating the use of alfaxalone-xylazine for anesthesia in mice. Here we sought to expand these studies by testing additional dose ranges, elaborating on physiologic monitoring, testing sex- and strain-associated differences, and evaluating efficacy during actual surgical conditions. C57BL/6J mice showed significant sex-associated differences in anesthetic sensitivity, with males requiring higher doses of alfaxalone (80-120 mg/kg IP alfaxalone with 10 mg/kg IP xylazine) than females (40-80 mg/kg IP alfaxalone with 10 mg/kg IP xylazine) to achieve a surgical plane of anesthesia. In addition, female outbred CD1 mice were less sensitive to alfaxalone than female inbred C57BL/6J mice. When used during actual surgery, alfaxalone-xylazine administered intraperitoneally provided adequate anesthesia for a model of orthopedic surgery, whereas the same anesthetic regimen during laparotomy resulted in unacceptably high mortality; survival during laparotomy increased when drugs were administered subcutaneously. These results indicate that alfaxalone-xylazine may be a viable option for injectable surgical anesthesia in mice, although strain- and sex-associated differences and alternative routes of administration should be considered when optimizing the anesthetic regimen for specific experimental conditions.

Critical incident technique analysis applied to perianesthetic cardiac arrests at a university teaching hospital

OBJECTIVE

To apply the critical incident technique (CIT) methodology to a series of perianesthetic cardiac arrest events at a university teaching hospital to describe the factors that contributed to cardiac arrest.

STUDY DESIGN

CIT qualitative analysis of a case series.

ANIMALS

A group of 16 dogs and cats that suffered a perioperative cardiac arrest between November 2013 and November 2016.

METHODS

If an arrest occurred, the event was discussed among the anesthesiologists. The discussion included a description of the case, a description of the sequence of events leading up to the arrest and a discussion of what could have been done to affect the outcome. A written description of the case and the event including animal signalment and a timeline of events was provided by the supervising anesthesiologist following discussion among the anesthesiologists. Only dogs or cats were included. After the data collection period, information from the medical record was collected. A qualitative document analysis was performed on the summaries provided about each case by the supervising anesthesiologist, the medical record and any supporting documents. Each case was then classified into one or more of the following: animal, human, equipment, drug and procedural factors for cardiac arrest.

RESULTS

The most common factor was animal (n=14), followed by human (n=12), procedural (n=4), drugs (n=1) and equipment (n=1). The majority (n=11) of animals had multiple factors identified.

CONCLUSIONS AND CLINICAL RELEVANCE

Cardiac arrests during anesthesia at a referral teaching hospital were primarily a result of animal and human factors. Arrests because of procedural, drug and equipment factors were uncommon. Most animals experienced more than one factor and two animals arrested after a change in recumbency. Future work should focus on root cause analysis and interventions designed to minimize all factors, particularly human ones.

Veterinary Forensic Pathology: The Search for Truth

Veterinary forensic pathology is emerging as a distinct discipline, and this special issue is a major step forward in establishing the scientific basis of the discipline. A forensic necropsy uses the same skill set needed for investigations of natural disease, but the analytical framework and purpose of forensic pathology differ significantly. The requirement of legal credibility and all that it entails distinguishes the forensic from routine diagnostic cases. Despite the extraordinary depth and breadth of knowledge afforded by their training, almost 75% of veterinary pathologists report that their training has not adequately prepared them to handle forensic cases. Many veterinary pathologists, however, are interested and willing to develop expertise in the discipline. Lessons learned from tragic examples of wrongful convictions in medical forensic pathology indicate that a solid foundation for the evolving discipline of veterinary forensic pathology requires a commitment to education, training, and certification. The overarching theme of this issue is that the forensic necropsy is just one aspect in the investigation of a case of suspected animal abuse or neglect. As veterinary pathologists, we must be aware of the roles filled by other veterinary forensic experts involved in these cases and how our findings are an integral part of an investigation. We hope that the outcome of this special issue of the journal is that veterinary pathologists begin to familiarize themselves with not only forensic pathology but also all aspects of veterinary forensic science.

The effects of multiple anaesthetic episodes on equine recovery quality

BACKGROUND

Although rare, 70% of equine fatalities during recovery from general anaesthesia (GA) are due to catastrophic fractures from poor recovery quality.

OBJECTIVE

To determine the effect of repeated GA recovery on GA recovery quality.

STUDY DESIGN

Experimental blinded trial.

METHODS

Eight adult horses underwent six GA events on sevoflurane for distal limb MRI examination over a 14-week period. Prior to GA recovery, xylazine was administered. Randomly ordered video-recorded GA recoveries were scored by three blinded board certified veterinary anaesthesiologists, unaware of patient identity or GA event number, for nine parameters using a 100 mm visual analogue scale (VAS) where 0 = worst and 100 = best. The number of attempts to stand, duration of lateral and sternal recumbency, total recovery duration and physiologic parameters during each GA event were recorded. Repeated measures ANOVA were used to detect differences. Agreement between observer VAS scores was determined via inter-rater reliability using an intraclass correlation.

RESULTS

With GA recovery experience, VAS scores for balance and coordination, knuckling, and overall quality of recovery were improved and the duration of lateral recumbency was increased. There were no differences in total recovery duration, number of attempts to stand, physiologic parameters other than heart rate during GA, or VAS scores for activity in lateral recumbency, move to sternal, move to stand, or strength.

MAIN LIMITATIONS

Each GA event was relatively short and there was no surgical stimulation. The same results may not occur if there was surgical stimulation and pain during each GA event.

CONCLUSION

Recovery from GA improves with multiple anaesthetic episodes in horses. Clinicians can advise clients that horses are likely to have better GA recovery on repeated GA recovery due to improved balance and coordination and reduced knuckling. Additionally, there is no change in anaesthetic morbidity with six repeated GA events over a 14-week period.