Risk of anesthesia-related complications in draft horses: a retrospective, single-center analysis

A Retrospective Study on Pre- and Intraoperative Predictors on the Recovery Quality of Horses After General Anesthesia

Equine anesthesia is related to high morbidity and mortality rates and recent studies suggested that the period of recovery remains the phase associated with the greatest risk of mortality in horses. Intraoperative hypotension, hypoxemia, and hypercapnia are recognized as potential determinants of recovery quality. This study, conducted at the Equine University Hospital of Liege, aimed to explore how these factors influence recovery outcomes and compare complications between non-emergency and emergency procedures. We analyzed data from 1057 horses, with a mean weight of 498 kg (ranging from 150 to 850 kg) and a mean age of 10.7 (ranging from 0.5 to 37 years), undergoing standardized general anesthesia for non-emergency and emergency procedures to assess which factors influence recovery quality. Recoveries were graded as 'good' or 'bad' and age, sex, breed, American Society of Anesthesiologists (ASA) physical status classification, weight, anesthesia duration, presence of hypotension, hypoxemia, and hypercapnia were compared with a logistic regression analysis. Our findings highlight the multifactorial nature of anesthetic recovery in horses, with breed, age, anesthesia and recovery duration, and emergency status emerging as significant influencing factors. Additionally, monitoring and managing hypoxemia and hypotension remain critical due to their recognized impact on recovery quality. However, despite their clinical relevance, the specific effects of these variables on anesthetic recovery in horses remain insufficiently studied, emphasizing the need for further research to refine perioperative management strategies and improve outcomes.

Comparison of Ketamine/Diazepam and Tiletamine/Zolazepam Combinations for Anaesthesia Induction in Horses Undergoing Partial Intravenous Anaesthesia (PIVA): A Retrospective Clinical Study

The aim of this retrospective clinical study was to compare the combinations of ketamine/diazepam (KD group) and tiletamine/zolazepam (TZ group) for the induction of general anaesthesia in horses undergoing elective surgery. The data from the clinical and the anaesthetic records of 138 horses from 2021 to 2023 were evaluated, and the horses were divided in two groups: KD (n = 60) and TZ (n = 72). The horses were premedicated with romifidine and methadone IV; anaesthesia was induced with ketamine/diazepam for the KD group and tiletamine/zolazepam for the TZ group and was maintained with isoflurane and a constant rate infusion of romifidine. The data encompassed sex and neuter status, age, breed, weight, American Society of Anaesthesiologists physical status, type of surgical procedure performed under anaesthesia, induction time, induction score, surgery time, recovery time, and the recovery score using a descriptive scale. Baseline heart rate (HR), intraoperative HR, baseline respiratory rate (fR), intraoperative fR, mean arterial pressure (MAP), oxygen saturation (SpO2), and fraction of expired isoflurane (FE'Iso) were also recorded. The induction time was significantly longer (p = 0.004) in the TZ group (60 (40-120)) as compared to the KD group (50 (30-120)). Recovery time was also significantly longer (p ≤ 0.001) in the TZ group (46.5 (15-125)) as compared to the KD group (30 (5-105)). These findings suggested that, in adult horses undergoing elective surgery, TZ could be considered a valid alternative to KD for the induction of general anaesthesia. Additional experimental studies comparing the two induction regimens and their pharmacokinetic and pharmacodynamic characteristics are needed.

A review of equine anesthetic induction: Are all equine anesthetic inductions "crash" inductions?

Horses are the most challenging of the common companion animals to anesthetize. Induction of anesthesia in the horse is complicated by the fact that it is accompanied by a transition from a conscious standing position to uncconconscious recumbency. The purpose of this article is to review the literature on induction of anesthesia with a focus on the behavioral and physiologic/pharmacodynamic responses and the actions and interactions of the drugs administered to induce anesthesia in the healthy adult horse with the goal of increasing consistency and predictability.

Risk assessment in equine anesthesia: a first evaluation of the usability, utility and predictivity of the two-part CHARIOT

Introduction

An accurate risk score that can predict peri-anesthetic morbidity and mortality in equine patients could improve peri-operative management, outcome and client communication.

Materials and methods

Three hunded horses underwent pre-anesthetic risk assessment using the American Society of Anesthesiologists-Physical Status augmented with equine-specific diseases (ASA-PS-Equine), a multifactorial 10-part rubric risk scale (10-RS), and a combination of both, the Combined horse anesthetic risk identification and optimization tool (CHARIOT). Intra-and post-anesthetic complications, the recovery phase and mortality were recorded over a period of 7 days following general anesthesia. To compare the utility and predictive power of the 3 scores, data were analyzed using binominal logistic regression (p ≤ 0.05) and receiver operating characteristic curve analysis. In addition, inter-observer reliability, speed, safety, ease of use and face validity of the ASA-PS-Equine and the 10-RS were analyzed based on five hypothetical patients.

Results

All scores showed statistically significant associations with various intra-anesthetic complications and parameters of the recovery phase. The discriminant ability of the scores related to the occurrence of intra-anesthetic (AUC = 0.6093-0.6701) and post-anesthetic (AUC = 0.5373-0.6194) complications was only low. The highest diagnostic accuracy for all scores was observed for overall mortality (AUC = 0.7526-0.7970), with the ASA-PS-Equine differentiating most precisely (AUC = 0.7970; 95% CI 0.7199-0.8741). Inter-observer reliability was fair for the 10-RS (κ = 0.39) and moderate for the ASA-PS-Equine (κ = 0.52). Patient assignment to the CHARIOT was predominantly rated as rather easy and quick or very quick.

Limitations and conclusion

The main limitations of the study are the monocentric study design and failure to obtain the full range of points. In conclusion, all 3 scores provide useful information for predicting the mortality risk of equine patients undergoing general anesthesia, whereas intra-and postoperative complications cannot be predicted with these scores.

Investigation of integrated time nanosecond pulse irreversible electroporation against spontaneous equine melanoma

Introduction

Integrated time nanosecond pulse irreversible electroporation (INSPIRE) is a novel tumor ablation modality that employs high voltage, alternating polarity waveforms to induce cell death in a well-defined volume while sparing the underlying tissue. This study aimed to demonstrate the in vivo efficacy of INSPIRE against spontaneous melanoma in standing, awake horses.

Methods

A custom applicator and a pulse generation system were utilized in a pilot study to treat horses presenting with spontaneous melanoma. INSPIRE treatments were administered to 32 tumors across 6 horses and an additional 13 tumors were followed to act as untreated controls. Tumors were tracked over a 43-85 day period following a single INSPIRE treatment. Pulse widths of 500ns and 2000ns with voltages between 1000 V and 2000 V were investigated to determine the effect of these variables on treatment outcomes.

Results

Treatments administered at the lowest voltage (1000 V) reduced tumor volumes by 11 to 15%. Higher voltage (2000 V) treatments reduced tumor volumes by 84 to 88% and eliminated 33% and 80% of tumors when 500 ns and 2000 ns pulses were administered, respectively.

Discussion

Promising results were achieved without the use of chemotherapeutics, the use of general anesthesia, or the need for surgical resection in regions which are challenging to keep sterile. This novel therapeutic approach has the potential to expand the role of pulsed electric fields in veterinary patients, especially when general anesthesia is contraindicated, and warrants future studies to demonstrate the efficacy of INSPIRE as a solid tumor treatment.

The Effects of Antimicrobial Protocols and Other Perioperative Factors on Postoperative Complications in Horses Undergoing Celiotomy: A Retrospective Analysis, 2008-2021

Recognition of antimicrobial resistance in equine practice has increased over the past decade. The objective of this study was to provide an updated retrospective review of antimicrobial regimens in one tertiary referral hospital and to evaluate the association with postoperative complications. A secondary objective was to evaluate other perioperative factors including surgical procedure, anesthetic and recovery parameters, and the effect of perioperative medications on complications and outcomes. A computerized search of medical records was performed to identify horses undergoing exploratory celiotomy from 1 January 2008 to 31 December 2021. A total of 742 celiotomies were performed (608 completed, 134 terminated intraoperatively). Factors recorded were evaluated using logistic regression for the presence of either incisional infection, postoperative ileus, or other complications postoperatively. Antimicrobial type or timing (pre-, intra-, or postoperative) were not associated with decreased risk of incisional infection or postoperative ileus; however, the duration of NSAID use was positively associated with incisional infection (OR 1.14 per day). Lidocaine and alpha-2-agonist administration postoperatively were also associated with increased incidence of postoperative ileus (OR 21.5 and 1.56, respectively). Poor recovery quality (OR 4.69), the addition of other antimicrobials besides penicillin/gentamicin postoperatively (OR 3.63), and an increased number of different NSAID classes used (OR 1.46 per additional) were associated with other complications. Implementation of enterotomy was associated with decreased risk of other complications (OR 0.64). These findings provide an updated summary of factors associated with postoperative complications in horses undergoing celiotomy.