Risk factors for colic in horses after general anaesthesia for MRI or nonabdominal surgery: absence of evidence of effect from perianaesthetic morphine.

The research paper discusses a study that aimed to identify the risk factors that contribute to the development of post-anaesthetic colic in horses, and whether the use of perianaesthetic morphine increases the said risk. The study used data from 553 anaesthetic and clinical records of 500 horses which underwent either magnetic resonance imaging (MRI) or nonabdominal surgery. The study concluded that morphine administration did not increase the risk, but further research is recommended because of the low prevalence of post-anaesthetic colic.

Methodology

• The researchers analyzed the anaesthetic and clinical records of 500 horses at the Animal Health Trust. The records were drawn from 342 MRI procedures and 211 nonabdominal surgeries, majority of which were orthopedic surgery.
• The main focus of the study was to identify any association between the use of perianaesthetic morphine and the development of post-anaesthetic colic.
• A multivariable logistic regression analysis was employed to study the association between post-anaesthetic colic and several variables, including the use of perianaesthetic morphine.

Results

• Post-anaesthetic colic occurred in 20 horses, amounting to 3.6% of all cases, within 7 days after receiving general anaesthesia.
• Significantly more horses who underwent surgery (7.1%) were observed to develop post-anaesthetic colic compared to the horses who underwent MRI (1.5%).
• The study revealed that the use of isoflurane during anaesthesia and the administration of benzyl penicillin and/or ceftiofur were associated with an increased risk of colic.
• On the other hand, the premedication of horses with romifidine and the longer duration of anaesthesia, as well as sedation within 2 days of general anesthesia, were factors associated with a reduced risk of colic.
• The use of perianaesthetic morphine was found not to contribute to an increased risk of post-anaesthetic colic.

Conclusions and further recommendations

• The researchers concluded that the risk of post-anaesthetic colic in horses is not increased by the use of perianaesthetic morphine.
• They also identified other novel risk factors such as the use of isoflurane, benzyl penicillin, and/or ceftiofur that are associated with an increased risk of colic, whereas the use of romifidine, as well as extended duration of anaesthesia and sedation within two days following general anesthesia, are linked to a reduced risk of colic.
• Due to the low prevalence of post-anaesthetic colic as observed in the study and the resulting low study power, the researchers recommend that larger, multicentre studies be carried out to corroborate the findings obtained from this study.