The anesthetic mortality rate in horses is between 1% and 19.5%, depending on several factors that include the reason for anesthesia and time of day anesthesia is performed.1,2 Serious injury (most frequently long-bone fracture) during recovery that results in death is responsible for 12.5% to 38% of anesthetic-related deaths in horses.1 Consequently, identification of factors that increase morbidity and fatalities and methods and techniques that improve the quality of anesthetic recovery for horses is warranted. Numerous studies3–9 have been conducted to investigate various methods of improving the quality of the recovery period for horses. Examples of variables that have been evaluated include inhalation and injectable anesthetics, sedatives, analgesics, acetylcholinesterase inhibitors, recovery stall illumination, recovery surface, sling use during recovery, and use of a pool.
Evaluation of the quality of recovery from anesthesia for horses is most often performed by use of subjective visual grading scales. These include a VAS or numeric rating scale, which assigns 1 number to the overall recovery event; an SDS, which assigns a single word to the overall recovery event; or a CGS, which assigns a score to individual aspects of recovery that are summed to yield an overall score.10,11 Because these scales are subjective, they have more sources of systemic errors than do objective measurements.12 Additionally, subjective scoring systems for recovery of horses can have low sensitivity, low repeatability, and high variability; tend to be overly complex; and have institutional and sex bias in certain populations.13–16
Diplomates of the ACVAA are recognized as experts in veterinary anesthesia. They complete rigorous training programs and must pass certification examinations to be awarded diplomate status. Extensive training and demonstrated knowledge in equine anesthesia is a requirement of the training programs. Thus, ACVAA diplomates may have similar opinions and biases regarding quality of recovery of horses from anesthesia. However, it is unknown whether subjective recovery scores assigned by ACVAA diplomates would be similar.
Accelerometry is the quantitative determination of acceleration and deceleration of an object during movement. It is the measure of how rapidly velocity changes and is measured in g or m/s2. It can be used to measure acceleration during physical activity of animals. Three-axis accelerometry is measured with a device that has 3 separate accelerometers mounted orthogonally, which allows for measurement of acceleration in any direction. In human medicine, accelerometry has been widely used, including within the discipline of anesthesia to assess movement disorders of patients after anesthesia and surgery.17 In veterinary medicine, accelerometry has been used to detect estrus in cattle,18 investigate physical activity in dogs,19 assess analgesic treatments in dogs,20 perform gait analysis in dogs,21 and evaluate severity of osteoarthritis in cats.22 For horses, accelerometry has been used to assess lameness,23 racing surfaces,24 load weight,25 and response to flexion testing.26 A system that involves the use of objective accelerometry measurements of horses during recovery from anesthesia would minimize or eliminate subjective biases. However, a standardized system for this purpose has not yet been developed.
Objectives of the study reported here were to evaluate agreement among diplomates of the ACVAA for scores determined by use of an SDS for horses during recovery from anesthesia and evaluate agreement among other diplomates of the ACVAA for scores determined by use of a CGS for horses during recovery from anesthesia. If ACVAA diplomates were not in agreement for scores determined by use of a subjective measurement scale, it was our intent to develop a system that involved the use of 3-axis accelerometry for evaluation of horses during recovery from anesthesia. On the basis that there was common training and testing to achieve diplomate status, hypotheses for the first 2 objectives were that diplomates of the ACVAA would be in agreement when using an SDS or subjective CGS to evaluate horses during recovery from anesthesia.
Presented in abstract form at the 12th World Congress of Veterinary Anaesthesiology, Kyoto, Japan, September 2015.
American College of Veterinary Anesthesia and Analgesia
Composite grading scale
Simple descriptive scale
Visual analogue scale
Exselle surcingle, National Bridle Shop Inc, Lewisburg, Tenn.
GP1-L programmable accelerometer, Sensr, Elkader, Iowa.
AnaSed, Akorn, Decatur, Ill.
Hospira Inc, Lake Forest, Ill.
Ketaset, Fort Dodge, Fort Dodge, Iowa.
Replay video capture, Applian Technologies Inc, San Anselmo, Calif.
OneDrive, Microsoft Corp, Redmond, Wash.
Sensware, version 18.104.22.168, Sensr, Elkader, Iowa.
CurveExpert Pro, DG Hyams, Madison, Ala.
SAS, version 9.3, SAS Institute Inc, Cary, NC.
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