A comparison of four systems for scoring recovery quality after general anaesthesia in horses

The Use of an Air-Inflated Pillow for Assisted Recovery After General Anaesthesia in Horses: A Preliminary Study

Different assisted recovery techniques have been developed to enhance the safety and quality of equine recoveries. This case series evaluates the recovery of horses using an air-inflated pillow (Equi-lift®). With owner consent, the following data were collected from 19 horses undergoing open castration and 21 horses where a difficult recovery was anticipated: age, bodyweight, procedure, anaesthetic protocol, time required for proper positioning in the Equi-lift®, time to extubation, time to standing, number of attempts to stand, number of stimuli, behaviour during recumbency/first attempts, and overall impression. Horses were 1-24 years old, with a bodyweight of 483.5 ± 106.8 kg. The median time to properly position a horse into the system was 6 min (range: 1-15 min). The recovery duration was 42 min (range: 21-181 min), with a median of 4 attempts (range: 1-12 attempts) and 1 stimulus (range: 0-10) before fully standing. Recovery was calm in most horses (32/40) and moderate (with signs of anxiety and/or excitation) in 3/40 horses. In five horses, the use of this technique was discontinued. All horses recovered without any injuries or other immediate postoperative complications. In conclusion, this recovery technique shows promising results, but further studies are needed to confirm the findings.

Evaluation of Recovery Time and Quality After Two Different Post-Operative Doses of Medetomidine in Spanish Purebred Horses Anaesthetized with Medetomidine-Isoflurane Partial Intravenous Anaesthesia

Recovery from general anaesthesia is risky in horses. Alpha2-agonist administration after anaesthesia enhances the quality of recovery but may prolong this phase. Recovery time and quality were investigated after medetomidine administration at the end of general anaesthesia in a prospective, randomised, masked and clinical study. Horses underwent medetomidine-isoflurane partial intravenous anaesthesia. Medetomidine (0.5 or 1 µg/kg) IV was administered just after isoflurane was discontinued. The duration of different recovery phases and the number of attempts were recorded. A composite scale (from 1-excellent to 6-accident) was used for quality assessment. Mann-Whitney U-test was performed (p < 0.05). Twenty-seven horses per group were included. Results for 0.5 and 1 µg/kg groups were as follows: lateral recumbency time: 35 (24-45) and 43 (35-55) minutes; sternal recumbency time: 6 (3-15) and 5 (2-15) minutes; total recovery time: 47 (40-59) and 49 (42-62) minutes; number of attempts to sternal: 1 (1-1) and 1 (1-2) and to standing: 1 (1-3) and 1 (1-2); and, quality: 2 (1-2) and 2 (1-2), respectively. No significant differences between the groups were found. Medetomidine 0.5 µg/kg dose did not decrease the recovery time but maintained the recovery quality.

Incidence of and risk factors for poor recovery quality in dogs recovering from general anaesthesia-a prospective case control study

OBJECTIVE

To investigate the incidence of and identify risk factors associated with poor quality of recovery in dogs recovering from general anaesthesia.

STUDY DESIGN

Case controlled study.

METHODS

All dogs undergoing general anaesthesia at the University of Liverpool Small Animal Teaching Hospital between January 2020 and January 2021 were eligible for recruitment. Signalment, anaesthetic case management and a recovery score were recorded. Univariable and multivariable logistic and ordinal logistic regression analysis were used to identify factors which impact incidence of poor quality of recovery.

RESULTS

A total of 247 dogs undergoing general anaesthesia were included. Overall, 72 [29.1%; 95% confidence interval (CI) 23.8%-35.1%] dogs experienced a poor quality recovery. Of these, 40 (55.5%) required sedation to manage behaviours associated with poor recovery. Multivariable logistic regression revealed American Society of Anesthesiologists (ASA) physical status classification of III or higher was associated with a decreased incidence of poor quality recovery [odds ratio (OR) = 0.34, 95% CI 0.12-0.93, p = 0.037] and the use of multiple inhalational anaesthetics during one procedure was associated with an increased incidence of poor quality of recovery (OR = 42.5, 95% CI 3.0-598.3, p = 0.005).

CONCLUSIONS AND CLINICAL RELEVANCE

Poor quality recovery is common in dogs recovering from general anaesthesia and sedation is often required for resolution. It is more likely to occur in healthy veterinary patients (ASA I and II). The use of multiple inhalational anaesthetic agents during one procedure should be discouraged as this may increase the likelihood of poor quality of recovery.

The influence of hypoxaemia, hypotension and hypercapnia (among other factors) on quality of recovery from general anaesthesia in horses

OBJECTIVE

To investigate the effect of hypoxaemia, hypotension and hypercapnia, among others, on quality of recovery from general anaesthesia in horses.

STUDY DESIGN

Retrospective, single-centre study.

ANIMALS

A sample of 1226 horses that underwent general anaesthesia between June 2017 and June 2021.

METHODS

Horses and ponies weighing > 200 kg, aged > 6 months, anaesthetized using a xylazine- or medetomidine-isoflurane balanced anaesthesia protocol and presenting a complete anaesthetic record were included. Data were extracted from the clinic record system and from the original anaesthesia records. Recoveries were divided into 'good' and 'bad' based on the available recovery scores. Influence of hypoxaemia [PaO2 < 60 mmHg (7.99 kPa)], hypotension (mean arterial pressure < 70 mmHg for at least 15 minutes) and hypercapnia [PaCO2 > 60 mmHg (7.99 kPa)], anaesthesia protocol, body weight, age, breed, sex, American Society of Anesthesiologists status, type of procedure, emergency or nonemergency, duration of anaesthesia, positioning, times spent in lateral and sternal recumbency during recovery, time until standing and nonassisted or assisted recovery on the assigned recovery score (good/bad) were investigated using generalized linear regression analysis (p < 0.05).

RESULTS

Hypoxaemia and prolonged duration of anaesthesia were significantly associated with a bad recovery score. No other factors had a significant influence on recovery quality.

CONCLUSION AND CLINICAL RELEVANCE

Hypoxaemia and prolonged anaesthesia duration have a negative effect on quality of anaesthetic recovery in horses. Clinically, this highlights the importance of keeping anaesthetic time as short as possible and to monitor oxygenation and treat hypoxaemia as soon as possible.

Retrospective study of the prevalence of factors contributing to successful standing at first attempt in horses recovering from general anesthesia

OBJECTIVE

Several factors affect the quality of recovery from general anesthesia in horses. These can increase the likelihood of injury. Body and limb position during recovery may correlate with successful standing. The objective of this study was to identify the prevalence of and the factors associated with successful standing at the first attempt in horses undergoing general anesthesia.

STUDY DESIGN

Retrospective study.

METHODS

Video of recovery and anesthetic records from 221 equine patients were reviewed by six veterinary students. Cases with poor video quality or incomplete anesthetic records were excluded. Demographic variables, type of procedure, perioperative drugs administered, assistance during recovery and body and limb positions during the first attempt to stand were recorded. Association between putative variables (including specific descriptors for body and limb position) and success for standing were analyzed using backward logistic regression; significance was set at 0.05. A decision tree for a successful attempt was created to predict the outcome of a recovery attempt based on these variables.

RESULTS

Extension of the carpal joints, head and neck alignment with the thoracic limbs, greater time in lateral recumbency, coordination during sternal recumbency, longer time to first attempt to stand and pelvic limb position were associated with successful standing at the first attempt. The association between extension of the carpal joints with wide base positioning of the pelvic limbs provided the best success rate for standing, whereas the association of flexed carpal joints and head and neck orientation different from the thoracic limbs resulted in a worse success rate.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that certain limb and body positions displayed by horses during recovery may be associated with the likelihood of successful standing at the first attempt. These variables may be useful for assessing recovery quality in future research.

Recovery of horses from general anaesthesia: A systematic review (2000-2020) of risk factors and influence of interventions during the recovery period

BACKGROUND

In equine anaesthesia, the recovery period is a time of considerable risk and has been the focus of prolific research. Risk factors, including age, type and duration of procedure or temperament may influence recovery quality. Unfortunately, the anaesthetist is unable to control for these factors, therefore various pharmacological interventions and recovery methods have been developed with the objective of improving recovery quality. However, no consensus among anaesthetists has been reached for many of these interventions and their implications for recovery-related mortality and morbidity.

OBJECTIVES

To conduct a systematic review of the published evidence relating to risk factors and interventions in the recovery period which may influence recovery quality from equine general anaesthesia (GA).

STUDY DESIGN

A systematic evaluation of the equine veterinary literature using the GRADE framework.

METHODS

A literature search was performed and studies were assessed for eligibility by both authors utilising PRISMA guidelines. Studies meeting inclusion criteria were evaluated by both authors, categorically summarised and the quality of evidence for each sub-topic was assessed using the GRADE framework.

RESULTS

Thirty-nine studies were identified which directly assessed the impact of risk factors and recovery interventions on recovery quality after equine GA. There was evidence to support that peri-anaesthetic risk factors such as anaesthesia duration, American Society of Anesthesiologists (ASA) physical status and surgical procedure influenced recovery quality. We also identified sufficient evidence that administration of α-2 adrenoreceptor agonists immediately prior to recovery, improves recovery quality.

MAIN LIMITATIONS

The validity of the results of some studies may have been compromised by missing data and small sample sizes.

CONCLUSIONS

Recovery quality is influenced by factors including: anaesthesia duration, ASA physical status and surgical procedure. Recovery quality can be improved by the administration of an α-2 adrenoreceptor agonist immediately prior to recovery.

Comparison of Recovery Quality Following Medetomidine versus Xylazine Balanced Isoflurane Anaesthesia in Horses: A Retrospective Analysis

Simple Summary

Recovery from general anaesthesia poses the most critical phase of equine anaesthesia and is the main cause for the relatively high anaesthetic mortality rate compared to other species. It is, therefore, essential to identify anaesthetic protocols that promote safe recoveries. This retrospective study compared the quality of 470 recoveries following general anaesthesia with the anaesthetic gas isoflurane combined with a constant rate infusion of two different alpha-2 adrenergic agonists (xylazine or medetomidine). On the basis of video recordings, recovery quality was scored by two observers unaware of animal details, procedure, or drugs used. Additionally, factors that may affect recovery (e.g., breed, age, procedure, duration of anaesthesia, and intraoperative complications) were taken into consideration. Horses needing higher doses of xylazine to sedate prior to anaesthesia, the intraoperative use of tetrastarch for cardiovascular support, and the use of salbutamol to improve inadequate blood oxygenation during general anaesthesia were related to poorer recovery scores. Whilst recoveries of horses treated with medetomidine took significantly longer compared to xylazine, the attempts to stand and the overall quality of recovery were similar for both groups, indicating that both anaesthetic protocols promote similarly safe recoveries.

Abstract

Medetomidine partial intravenous anaesthesia (PIVA) has not been compared to xylazine PIVA regarding quality of recovery. This clinical retrospective study compared recoveries following isoflurane anaesthesia balanced with medetomidine or xylazine. The following standard protocol was used: sedation with 7 µg·kg⁻¹ medetomidine or 1.1 mg·kg⁻¹ xylazine, anaesthesia induction with ketamine/diazepam, maintenance with isoflurane and 3.5 µg·kg⁻¹·h⁻¹ medetomidine or 0.7 mg·kg⁻¹·h⁻¹ xylazine, and sedation after anaesthesia with 2 µg·kg⁻¹ medetomidine or 0.3 mg·kg⁻¹ xylazine. Recovery was timed and, using video recordings, numerically scored by two blinded observers. Influence of demographics, procedure, peri-anaesthetic drugs, and intraoperative complications (hypotension, hypoxemia, and tachycardia) on recovery were analysed using regression analysis (p < 0.05). A total of 470 recoveries (medetomidine 279, xylazine 191) were finally included. Following medetomidine, recoveries were significantly longer (median (interquartile range): 57 (43–71) min) than xylazine (43 (32–59) min) (p < 0.001). However, the number of attempts to stand was similar (medetomidine and xylazine: 2 (1–3)). Poorer scores were seen with increased pre-anaesthetic dose of xylazine, intraoperative tetrastarch, or salbutamol. However, use of medetomidine or xylazine did not influence recovery score, concluding that, following medetomidine–isoflurane PIVA, recovery is longer, but of similar quality compared to xylazine.

Total Intravenous Anaesthesia with Ketamine, Medetomidine and Midazolam as Part of a Balanced Anaesthesia Technique in Horses Undergoing Castration

To evaluate the use of ketamine-medetomidine-midazolam total intravenous infusion as part of a balanced anaesthetic technique for surgical castration in horses. Five healthy Standardbred cross colts were premedicated with IV acepromazine (0.01–0.02 mg/kg), medetomidine (7 µg/kg) and methadone (0.1 mg/kg) and anaesthesia induced with IV ketamine (2.2 mg/kg) and midazolam (0.06 mg/kg). Horses were anaesthetised for 40 min with an IV infusion of ketamine (3 mg/kg/h), medetomidine (5 µg/kg/h) and midazolam (0.1 mg/kg/h) while routine surgical castration was performed. Cardiorespiratory variables, arterial blood gases, and anaesthetic depth were assessed at 5 to 10 min intervals. Post-anaesthesia recovery times were recorded, and the quality of the recovery period was assessed. The anaesthetic period and surgical conditions were acceptable with good muscle relaxation and no additional anaesthetic required. The median (range) time from cessation of the infusion to endotracheal tube extubation, head lift and sternal recumbency were 17.2 (7–35) min, 25 (18.9–53) min and 28.1 (23–54) min, respectively. The quality of anaesthetic recovery was good, with horses standing 31.9 (28–61) min after the infusion was ceased. During anaesthesia, physiological variables, presented as a range of median values for each time point were: heart rate 37–44 beats/min, mean arterial pressure 107–119 mmHg, respiratory rate 6–13 breaths/min, arterial partial pressure of oxygen 88–126 mmHg, arterial partial pressure of carbon dioxide 52–57 mmHg and pH 7.36–7.39. In conclusion, the co-administration of midazolam, ketamine and medetomidine as in IV infusion, when used as part of a balanced anaesthetic technique, was suitable for short term anaesthesia in horses undergoing castration.

Recovery after General Anaesthesia in Adult Horses: A Structured Summary of the Literature

Simple Summary

Recovery is the most dangerous phase of general anaesthesia in horses. Numerous publications have reported about this phase, but structured reviews that try to reduce the risk of bias of narrative reviews/expert opinions, focussing on the topic are missing. Therefore, the aim of the present article was to publish the first structured review as a summary of the literature focussing on the recovery phase after general anaesthesia in horses. The objective was to summarise the available literature, taking into account the scientific evidence of the individual studies. A structured approach was followed with two experts in the field independently deciding on article inclusion and its level of scientific evidence. A total number of 444 articles, sorted by topics and classified based on their levels of evidence, were finally included into the present summary. The most important findings were summarised and discussed. The present structured review can be used as a compilation of the publications that, to date, focus on the recovery phase after general anaesthesia in adult horses. This type of review tries to minimise the risk of bias inherent to narrative reviews/expert opinions.

Abstract

Recovery remains the most dangerous phase of general anaesthesia in horses. The objective of this publication was to perform a structured literature review including levels of evidence (LoE) of each study with the keywords “recovery anaesthesia horse”, entered at once, in the search browsers PubMed and Web of Science. The two authors independently evaluated each candidate article. A final list with 444 articles was obtained on 5 April 2021, classified as: 41 “narrative reviews/expert opinions”, 16 “retrospective outcome studies”, 5 “surveys”, 59 “premedication/sedation and induction drugs”, 27 “maintenance with inhalant agents”, 55 “maintenance with total intravenous anaesthesia (TIVA)”, 3 “TIVA versus inhalants”, 56 “maintenance with partial intravenous anaesthesia (PIVA)”, 27 “other drugs used during maintenance”, 18 “drugs before/during recovery”, 18 “recovery systems”, 21 “respiratory system in recovery”, 41 “other factors”, 51 “case series/reports” and 6 “systems to score recoveries”. Of them, 167 were LoE 1, 36 LoE 2, 33 LoE 3, 110 LoE 4, 90 LoE 5 and 8 could not be classified based on the available abstract. This review can be used as an up-to-date compilation of the literature about recovery after general anaesthesia in adult horses that tried to minimise the bias inherent to narrative reviews.

The effects of flumazenil on ventilatory and recovery characteristics in horses following midazolam-ketamine induction and isoflurane anaesthesia

BACKGROUND

Flumazenil antagonises the actions of benzodiazepines. There has been no prior research specifically investigating this anaesthetic reversal agent for horses.

OBJECTIVES

To determine the effects of flumazenil administration in horses on (a) ventilatory parameters after midazolam-ketamine induction and maintenance with isoflurane in oxygen and on (b) the characteristics of recovery from general anaesthesia.

STUDY DESIGN

Blinded, randomised, crossover experiment.

METHODS

Six horses were randomly assigned to receive high-dose flumazenil (F_high , 20 µg/kg), low-dose flumazenil (F_low , 10 µg/kg) and saline (control). Cardioventilatory parameters were monitored. After 90 minutes of isoflurane anaesthesia, a bolus of F_high , F_low or saline was administered i.v. The horses were recovered using head and tail rope assistance. The times to first movement, to achievement of sternal recumbency, to the first attempt to stand and the total recovery time were determined. The recovery quality was evaluated using a 115-point recovery scoring system. The cardioventilatory parameters and recovery times were analysed using mixed-effects regression analyses. Intraclass correlation (ICC) analysis was used to evaluate the recovery scores. A Mann-Whitney U test assessed the relationship between recovery score and flumazenil administration.

RESULTS

A significant difference with flumazenil administration was found for SpO₂ , mean arterial pressure, I:E ratio, minute volume of ventilation (MV) and peak inspiratory pressure. There was a significant difference with flumazenil administration for the time to sternal recumbency, the time to the first attempt to rise and the total recovery time. There was no significant difference in total recovery score with flumazenil administration.

MAIN LIMITATIONS

Plasma levels of midazolam and flumazenil were not obtained.

CONCLUSIONS

Flumazenil has a dose-dependent effect on MV and recovery time, which may make it useful in cases for which a prolonged anaesthetic recovery is undesirable.

The effect of intra-articular mepivacaine administration prior to carpal arthroscopy on anesthesia management and recovery characteristics in horses

OBJECTIVE

To evaluate the effects of intra-articular (IA) mepivacaine administration prior to carpal arthroscopy on anesthetic drug requirements, blood pressure support, hemodynamic variables, and quality of recovery in horses.

STUDY DESIGN

Experimental, analytical, cohort study.

SAMPLE POPULATION

Twenty-two horses (n = 11 horses/group).

METHODS

Horses were anesthetized by using the same protocol, but an IA injection of mepivacaine or saline was performed before carpal arthroscopy. End-tidal isoflurane concentration, heart rate, and mean arterial pressure were recorded at specific time points. Quality of recovery was scored by the anesthetist, who was unaware of group assignment. Data were analyzed by using two-way repeated-measures analysis of variance.

RESULTS

Mean arterial pressure was higher during joint distension in the control group compared with baseline (7% higher, P = .02) and with the treatment group (10% higher, P = .04). Heart rate was higher in the control group compared with the treatment group during joint distension (8% higher, P = .04) and chip removal (11% higher, P = .03). Heart rate was higher in the control group compared with baseline during chip removal (5.5% higher, P = .04). Two horses in the control group required additional ketamine vs none in the treatment group. Quality of recovery was not different between groups.

CONCLUSION

Intra-articular mepivacaine resulted in fewer detectable reactions to surgical stimulation, with similar recovery scores and blood pressure support requirements.

CLINICAL SIGNIFICANCE

Intra-articular anesthesia prior to arthroscopy can be used safely in the horse and should be considered as a part of balanced anesthetic protocols.

Recovery of horses from general anesthesia after induction with propofol and ketamine versus midazolam and ketamine

OBJECTIVE To evaluate quality of recovery from general anesthesia in horses after induction with propofol and ketamine versus midazolam and ketamine. DESIGN Prospective randomized crossover study. ANIMALS 6 healthy adult horses. PROCEDURES Horses were premedicated with xylazine (1.0 mg/kg [0.45 mg/lb], IV), and general anesthesia was induced with midazolam (0.1 mg/kg [0.045 mg/lb], IV) or propofol (0.5 mg/kg [0.23 mg/lb], IV), followed by ketamine (3.0 mg/kg [1.36 mg/lb], IV). Horses were endotracheally intubated, and anesthesia was maintained with isoflurane. After 60 minutes, horses were given romifidine (0.02 mg/kg [0.009 mg/lb], IV) and allowed to recover unassisted. Times to first movement, sternal recumbency, and standing and the number of attempts to stand were recorded. Plasma concentrations of propofol or midazolam were measured following induction and immediately before recovery. Recovery quality was scored by 3 graders with a recovery rubric and a visual analog scale. RESULTS Number of attempts to stand was significantly lower when horses received propofol (median, 2; range, 1 to 3) than when they received midazolam (median, 7.5; range, 3 to 16). For both the recovery rubric and visual analog scale, recovery quality was significantly better when horses received propofol than when they received midazolam. Plasma drug concentration at recovery, as a percentage of the concentration at induction, was significantly lower when horses received propofol than when they received midazolam. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that for horses undergoing short (ie, 60 minutes) periods of general anesthesia, recovery quality may be better following induction with propofol and ketamine, compared with midazolam and ketamine.

Total intravenous anaesthesia with ketamine, medetomidine and guaifenesin compared with ketamine, medetomidine and midazolam in young horses anaesthetised for computerised tomography

BACKGROUND

There is no information directly comparing midazolam with guaifenesin when used in combination with an alpha-2 agonist and ketamine to maintain anaesthesia via i.v. infusion in horses.

OBJECTIVES

To compare ketamine-medetomidine-guaifenesin with ketamine-medetomidine-midazolam for total intravenous anaesthesia (TIVA) in young horses anaesthetised for computerised tomography.

STUDY DESIGN

Prospective, randomised, blinded, crossover trial.

METHODS

Fourteen weanlings received medetomidine 7 μg/kg bwt i.v. and anaesthesia was induced with ketamine 2.2 mg/kg bwt i.v. On two separate occasions horses each received infusions of ketamine 3 mg/kg bwt/h, medetomidine 5 μg/kg bwt/h, guaifenesin 100 mg/kg bwt/h (KMG) or ketamine 3 mg/kg bwt/h, medetomidine 5 μg/kg bwt/h, midazolam 0.1 mg/kg bwt/h (KMM) for 50 min. Cardiorespiratory variables and anaesthetic depth were assessed every 5-10 min. Recovery times after the infusions ceased were recorded and recovery quality was assessed using a composite score system (CSS), simple descriptive scale (SDS) and visual analogue scale (VAS). Multivariable models were used to generate mean recovery scores for each treatment and each recovery score system and provide P-values comparing treatment groups.

RESULTS

Anaesthesia was uneventful with no difference in additional anaesthetic requirements and little clinically relevant differences in cardiopulmonary variables between groups. All horses recovered without incident with no significant difference in recovery times. Quality of the anaesthetic recovery was significantly better for the KMM group compared with the KMG group using the CSS (P<0.001), SDS (P<0.001) and VAS (P<0.001).

MAIN LIMITATIONS

No surgical stimulus was applied and study animals may not represent general horse population.

CONCLUSION

Midazolam is a suitable alternative to guaifenesin when co-infused with ketamine and medetomidine for anaesthesia in young horses undergoing noninvasive procedures. Both infusions produce a clinically comparable quality of anaesthesia; however, recovery from anaesthesia is of a better quality following an infusion of ketamine-medetomidine-midazolam.

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.

Clinical comparison of dexmedetomidine and medetomidine for isoflurane balanced anaesthesia in horses

OBJECTIVE

To compare the effects of two balanced anaesthetic protocols (isoflurane-dexmedetomidine versus medetomidine) on sedation, cardiopulmonary function and recovery in horses.

STUDY DESIGN

Prospective, blinded, randomized clinical study.

ANIMALS

Sixty healthy adult warm blood horses undergoing elective surgery.

METHODS

Thirty horses each were sedated with dexmedetomidine 3.5 μg kg^-1 (group DEX) or medetomidine 7 μg kg^-1 (group MED) intravenously. After assessing and supplementing sedation if necessary, anaesthesia was induced with ketamine/diazepam and maintained with isoflurane in oxygen/air and dexmedetomidine 1.75 μg kg^-1 hour^-1 or medetomidine 3.5 μg kg^-1 hour^-1. Ringer's lactate (7-10 mL kg^-1 hour^-1) and dobutamine were administered to maintain normotension. Controlled mechanical ventilation maintained end-tidal expired carbon dioxide pressures at 40-50 mmHg (5.3-6.7 kPa). Heart rate, invasive arterial blood pressure, inspired and expired gas composition and arterial blood gases were measured. Dexmedetomidine 1 μg kg^-1 or medetomidine 2 μg kg^-1 was administered for timed and scored recovery phase. Data were analysed using two-way repeated-measures analysis of variance and chi-square test. Significance was considered when p≤0.05.

RESULTS

In group DEX, significantly more horses (n=18) did not fulfil the sedation criteria prior to induction and received one or more supplemental doses, whereas in group MED only two horses needed one additional bolus. Median (range) total sedation doses were dexmedetomidine 4 (4-9) μg kg^-1 or medetomidine 7 (7-9) μg kg^-1. During general anaesthesia, cardiopulmonary parameters did not differ significantly between groups. Recovery scores in group DEX were significantly better than in group MED.

CONCLUSIONS AND CLINICAL RELEVANCE

Horses administered dexmedetomidine required more than 50% of the medetomidine dose to reach equivalent sedation. During isoflurane anaesthesia, cardiopulmonary function was comparable between the two groups. Recovery scores following dexmedetomidine were better compared to medetomidine.

Reliability of video recordings to evaluate quality of anesthesia recovery in dogs

OBJECTIVE

To assess the reliability of using video recordings to evaluate anesthesia recovery in dogs.

STUDY DESIGN

Prospective study.

ANIMALS

A total of 30 dogs undergoing surgery.

METHODS

Recovery monitoring and video recording lasted from extubation until 1 hour later. Scoring was done in real time at the end of the hour by a graduate student using three systems: a simple descriptive scale, visual analog scale and numeric rating scale. Videos were distributed to three American College of Veterinary Anesthesia and Analgesia board-certified anesthesiologist raters as well as the original rater to score. These videos were revisited 4 months later, and the recoveries were scored again. To assess reliability, Cohen's and Fleiss' kappa values evaluated the agreement between sessions. Wilcoxon signed-rank tests were run comparing each observer's two sessions. Recoveries were classified as 'good' or 'bad' according to the cut-off values for each system.

RESULTS

Correlation values among raters ranged from 0.50 to 0.82 and from 0.26 to 0.60 in the first and second session, respectively. Bland-Altman plots revealed biases between 0.133 and 1.633 points for each of the three scoring systems. Cohen's kappa had agreement ranging from 0.29 to 0.79 during the first viewing and from 0.17 to 0.44 during the second. Fleiss' kappa values were 0.06, 0.16, 0.22 and 0.26 for various data combinations. Considering overall recovery, Fleiss' kappa showed agreement ranging from 0.54 to 0.71 and from 0.13 to 0.49 for the first and second session, respectively. Of the 12 Wilcoxon tests run, seven found significantly different scores between the two scoring sessions. The recoveries given an overall good or bad were the same on both occasions that they were reviewed.

CONCLUSIONS AND CLINICAL RELEVANCE

The use of a video to evaluate recovery in dogs should be used with caution. Individual raters' agreement for specific scores was poor, but evaluating recovery overall had perfect agreement.

Comparison between the effects of postanesthetic xylazine and dexmedetomidine on characteristics of recovery from sevoflurane anesthesia in horses

OBJECTIVE

To compare postanesthetic xylazine and dexmedetomidine on recovery characteristics from sevoflurane anesthesia in horses.

STUDY DESIGN

Randomized, crossover study.

ANIMALS

Six geldings, mean±standard deviation (SD) (range), 17±4 (11-24) years and 527±80 (420-660) kg.

METHODS

Horses were anesthetized with sevoflurane for 60 minutes under standardized conditions for a regional limb perfusion study. In recovery, horses were administered either xylazine (200 μg kg^-1) or dexmedetomidine (0.875 μg kg^-1) intravenously. Recoveries were unassisted and were video-recorded for later evaluation of recovery events and quality by two individuals unaware of treatment allocation. Recovery quality was assessed using a 100 mm visual analog scale (VAS) (0=poor recovery, 100=excellent recovery), the Edinburgh Scoring System (ESS) (0-100; 100=excellent recovery) and the mean attempt interval (MAI) (longer=better). Data are mean±SD.

RESULTS

All recovery quality assessments (xylazine and dexmedetomidine, respectively: VAS: 71±21 mm, 84±13 mm; ESS: 65±22, 67±30; MAI: 52±24 minutes, 60±32 minutes) and events (first limb movement: 37±8 minutes, 42±10 minutes; first attempt to lift head: 44±12 minutes, 48±9 minutes; first attempt to sternal posture: 57±28 minutes, 50±7 minutes; number of head bangs: 2.0±3.0, 0.5±0.5; time to first attempt to stand: 72±6 minutes, 78±13 minutes; time to standing: 79±14 minutes, 84±13 minutes) did not differ significantly between treatments (p>0.05).

CONCLUSIONS AND CLINICAL RELEVANCE

Recovery characteristics did not differ significantly between postanesthetic xylazine and dexmedetomidine following 1 hour of sevoflurane anesthesia in horses in this study. Further evaluations in more horses and in younger horses are required to confirm these results.

Cardiopulmonary effects and anaesthesia recovery quality in horses anaesthetized with isoflurane and low-dose S-ketamine or medetomidine infusions

OBJECTIVES

To evaluate cardiopulmonary effects and anaesthesia recovery quality in horses anaesthetized with isoflurane receiving medetomidine or S-ketamine infusions.

STUDY DESIGN

Randomized, blinded, prospective clinical trial.

ANIMALS

Fifty horses undergoing elective surgery.

METHODS

After acepromazine and flunixin meglumine premedication, horses received medetomidine (7 μg kg^-1 ) intravenously (IV). Anaesthesia was induced with midazolam and racemic ketamine (Med treatment group; 2.2 mg kg^-1 ; n = 25) or S-ketamine (S-ket treatment group; 1.1 mg kg^-1 ; n = 25) IV and maintained with isoflurane in oxygen/air and medetomidine (Med; 3.5 μg kg^-1 hour^-1 ) or S-ketamine (S-ket; 0.5 mg kg^-1 hour^-1 ). All horses were mechanically ventilated. Cardiopulmonary variables were evaluated. Isoflurane end-tidal concentrations (Fe'Iso), dobutamine requirements and thiopental boli were recorded. Plasma samples were collected in six horses to evaluate S-ketamine and S-norketamine concentrations. After surgery, medetomidine 2 μg kg^-1 was administered IV. Four independent observers scored recovery using a visual analogue scale and a numerical rating scale.

RESULTS

Both groups required similar mean Fe'Iso (1%). However, S-ket horses needed more thiopental boli. Median intraoperative cardiac index values were higher with S-ket (4.5 L minute^-1  m^-2 ) than Med (3.9 L minute^-1  m^-2 ). Overall, there were no differences in heart rate, blood pressure or dobutamine requirements; however, horses in S-ket showed higher heart rate values at 30 minutes after anaesthesia induction. Compared with Med horses, S-ket horses showed decreased PaO₂ and increased pulmonary venous admixture values estimated with the Fshunt calculation. Recoveries were shorter and of poorer quality with S-ket. During infusion, S-ketamine and S-norketamine plasma concentrations lay in the ranges of 0.209-0.917 μg mL^-1 and 0.250-0.723 μg mL^-1 , respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Despite the higher intraoperative cardiac index with S-ket, both protocols were considered to provide acceptable cardiovascular function. However, recovery quality was significantly better in the Med group.

Twenty years later: a single-centre, repeat retrospective analysis of equine perioperative mortality and investigation of recovery quality

OBJECTIVES

To determine the mortality rates associated with equine anaesthesia for elective and emergency (colic and non-colic) cases in one equine, university teaching hospital and to investigate the effect of several horse- and anaesthetic-related variables on anaesthetic recovery quality.

STUDY DESIGN

Retrospective data analysis.

ANIMALS OR ANIMAL POPULATION

In total, 1416 horses undergoing anaesthesia between May 2010 and December 2013.

METHODS

Patient information and details of the anaesthetic, recovery period and immediate complications were extracted from an archiving database. Statistical evaluation of factors affecting mortality included chi-squared tests and binary logistic regression. Factors affecting recovery quality were investigated using univariable and multivariable ordinal logistic regression. Statistical significance was set at p < 0.05.

RESULTS

Anaesthesia/recovery-related mortality was 1.1% for all cases, 0.9% for elective cases, 1.6% for colics and 0% for non-colic emergencies. Fractures and dislocations accounted for the majority (71.4%) of deaths. No intra-operative deaths occurred during the study period. Risk factors for mortality included increasing age and American Society of Anesthesiologist's (ASA) status but these and other factors were confounded by 'colic'. Non-fatal complications in the immediate recovery period included postanaesthetic myopathy/neuropathy and postanaesthetic respiratory obstruction. Recovery quality was associated with body mass (p = 0.016), ASA status 3 and 4 (p = 0.020 and 0.002, respectively), duration of anaesthesia (p < 0.001) and out-of-hours anaesthesia (p = 0.013). Although recovery quality was also influenced by age and breed-type, these factors were removed from the final model as age was highly associated with both ASA status (p < 0.001) and colic surgery (p < 0.001), and breed-type was a determinant of body mass.

CONCLUSION AND CLINICAL RELEVANCE

Anaesthetic/recovery-associated mortality was comparable to previously reported figures except intra-operative deaths were not reported. Fractures remained responsible for the largest proportion of recovery-associated deaths. Improvements to the recovery process that can reduce fracture occurrence are still required.

Electrocardiographic indicators of excitability in horses for predicting recovery quality after general anaesthesia

OBJECTIVE

To determine whether preoperative electrocardiographic measurements linked to sympathetic nervous activity could be used to predict recovery quality after general anaesthesia in horses.

STUDY DESIGN

Prospective, clinical study.

ANIMALS

Eighteen adult client-owned horses.

METHODS

The electrocardiogram (ECG) was recorded presurgery in horses under three standard conditions: stabled unattended; with a groom whilst being led along a standard course; alone in the induction box. After surgery, each animal's recovery quality was scored by eight experienced anaesthetists or technicians using Donaldson's scoring system (2000). The digitized ECG recordings were analyzed for T-wave morphology, mean heart rate (HR), HR variability (HRV) and HRV derivatives including mean R-R interval, standard deviation of normal intervals (SDNN) and the root mean square of successive intervals (RMSSD), low (LF) and high frequency (HF) activity and the LF/HF ratio in both fast Fourier transformed and autoregressive spectra. Correlations between ECG variables and recovery score were examined using Spearman's rank correlation.

RESULTS

There was no significant correlation between preanaesthetic ECG measurements and recovery quality.

CONCLUSIONS

Predictions of recovery quality after general anaesthesia in horses cannot be based on preanaesthetic ECG variables.

CLINICAL RELEVANCE

Measures other than those based on the ECG should be investigated as predictors of recovery quality.

Factors affecting the perception of recovery quality in horses after anaesthesia

REASONS FOR PERFORMING STUDY

A significant effect of gender, experience and background, i.e. an evaluator's relationship with horses as equine anaesthetists, orthopaedic surgeons, practitioners or owners, on perceptions of recovery quality after anaesthesia would reduce the validity of recovery quality scoring systems.

OBJECTIVES

To determine the effects of evaluator background, experience and gender on their perceptions of recovery quality; and questionnaire response rate as a function of background.

STUDY DESIGN

Cross-sectional survey.

METHODS

A total of 440 potential evaluators were invited to evaluate the video-recorded recoveries of 24 horses using a visual analogue scale (VAS) in which 0 = worst, 100 = best possible recovery. A mean score was generated for each of the 1-24 recoveries within each background group. These were compared using Spearman's rank correlation. The effect of gender and experience on VAS scores were analysed using an ordinal logistic regression after scores were categorised into 'intermediate, 'worst' and 'best' recovery categories based on median, 25th and 75th percentile VAS scores, respectively.

RESULTS

The overall response rate was 35%. The greatest was from the anaesthetists (78%) followed by surgeons (43%). The response rate among owners and practitioners was 26%. Correlation among VAS scores across all background groups was high (Spearman rank > 0.90; P < 0.001). Among the combined veterinarians, there was no significant gender (P = 0.551) or experience (P = 0.103) effect. Among horse owners, the effect of experience was not significant (P = 0.116) although gender was (P = 0.027). Male horse owners awarded significantly greater scores than females.

CONCLUSIONS

When VAS are used to grade recovery quality, neither the background nor the gender of veterinary evaluators affects quality perception. Male owners awarded greater scores than female owners, implying that they are less critical of recovery quality and a gender effect among horse owners must be considered when VAS are used to score recovery quality.

Assessment of unassisted recovery from repeated general isoflurane anesthesia in horses following post-anesthetic administration of xylazine or acepromazine or a combination of xylazine and ketamine

OBJECTIVES

To compare the effects of sedative doses of acepromazine, xylazine or xylazine/ketamine administered to horses after isoflurane anesthesia on the quality of recovery and anesthesia recovery times. To determine if recovery scores improve after repeated consecutive anesthetic episodes.

STUDY DESIGN

Prospective, randomized, crossover study.

ANIMALS

Fifteen adult research horses, 6.5±3.4 years old and weighing 499±40 kg.

METHODS

Horses undergoing three anesthetic episodes with isoflurane for magnetic resonance of the forelimbs were administered acepromazine (0.02 mg kg(-1) i.v.) or xylazine (0.3 mg kg(-1) i.v.) or xylazine (0.15 mg kg(-1) i.v.) combined with ketamine (0.3 mg kg(-1) i.v.) in random order upon arrival in recovery. The quality of recovery was compared between the three treatments using a composite numerical rating and a general descriptive scoring system.

RESULTS

Horses administered xylazine had better recovery scores than horses administered xylazine/ketamine, associated with better scores during their move to sternal, strength and number of attempts to standing. Horses administered acepromazine had similar recovery scores to horses administered xylazine and to horses administered xylazine/ketamine. Time to sternal recumbency and time to extubation were statistically longer for the xylazine treatment. Time to standing was similar between treatments. Horses had better recovery scores during the third anesthetic episode, regardless of the sedative drug administered, associated with better scores for strength and number of attempts to standing.

CONCLUSIONS

Xylazine administration was superior to xylazine/ketamine but similar to acepromazine. This study also indicates that horses improve the quality of recovery during consecutive anesthetics associated with longer time to sternal and to standing, regardless of the sedative used.

CLINICAL RELEVANCE

All treatments provided good quality recoveries. The experience of the individual horse gained during recent previous anesthetic episodes may have a positive effect in facilitating a better recovery.

Quantitative and qualitative comparison of three scoring systems for assessing recovery quality after general anaesthesia in horses

OBJECTIVE

To assess the reproducibility and repeatability of two commonly used recovery quality scoring systems and compare them with those of a novel system based on a greater number of objective criteria.

ANIMALS

The video-recorded recoveries of ten client-owned horses selected from all recovery recordings taken between September 2005 and March 2006 at the Royal (Dick) School of Veterinary Studies.

MATERIALS AND METHODS

A digital versatile disc (DVD) was produced using edited video recordings of ten horses recovering from general anaesthesia. Twelve experienced equine anaesthetists (raters) studied the DVD on three occasions, and scored the recovery quality of each horse using one of three scoring systems (P, D or E) on each occasion. The process was repeated 6 months later (t = 6) to measure intra-observer reliability (repeatability). At first use (t = 0) raters were asked to comment on the advantages and disadvantages of each system.

RESULTS

Inter-rater variability was limited for each system: at each observation period raters accounted for 0.3-4.4% variation. System P was insensitive to differences between recoveries. In system D, score variability increased as recovery quality deteriorated. Intra-rater variability varied with system: using system P, raters provided consistent scores between the observation periods for some, but not all horses ('horse' and 'rater' accounted for 9.7% and 1.9% of variation respectively). Raters were less consistent between t = 0 and t = 6 using system D, but each horse was scored with similar consistency. System E produced little variation at the level of horse (1.0%) and rater (1.9%). Raters broadly agreed on the principle advantages and disadvantages of the three systems.

CONCLUSIONS AND CLINICAL RELEVANCE

The systems examined showed reliability and reproducibility but practicality and simplicity of use appeared to be inextricably linked with imprecision. Further work is required to produce a suitable recovery quality scoring system.