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

Objective To report anesthetic-related complications and determine risks associated with anesthesia in draft horses. Study design Retrospective study. Animals A total of 401 anesthetic records for draft horse breeds that underwent general anesthesia from January 2010 through December 2020 were reviewed; horses euthanized during general anesthesia were excluded. Methods Demographics, perioperative drugs used, proced-ure type and duration, time to extubation, number of at-tempts to stand, use of sling in recovery and perioperative morbidity and mortality were investigated. Morbidity and mortality statistical evaluation included univariable logistic regression analysis and ordinal regression analysis. Results American Society of Anesthesiologists (ASA) status I -II, ASA III -V and total mortality rate for all cases was 0.69% (2/288), 6.19% (7/113) and 2.24% (9/401), respectively, with Belgian horses being overrepresented (6/ 9). Cardiac arrest occurred in six out of nine horses that died without euthanasia, and five out of six of these horses underwent colic surgery. Factors associated with increased mortality risk included ASA status of III -V, increased body weight, emergency status and horses presenting for colic. Hypotension, hypercarbia and hypoxemia occurred in 56% (224/401), 46% (186/401) and 14% (58/401) of horses, respectively. During recovery from anesthesia, lighter horses and horses undergoing shorter anesthetic procedures were more likely to be successful on the first or second attempt to stand and were less likely to require a sling in recovery. Conclusions and clinical relevance Draft horses undergo-ing general anesthesia had a higher mortality rate than previously reported for all types and breeds of horses.