Peer-reviewed veterinary case report
Clinical observations surrounding an increased incidence of postanesthetic myopathy in halothane-anesthetized horses.
- Journal:
- Veterinary anaesthesia and analgesia
- Year:
- 2006
- Authors:
- Duke, Tanya et al.
- Affiliation:
- Department of Small Animal Clinical Studies · Canada
- Species:
- horse
Plain-English summary
Over an eight-year period, veterinarians noticed more cases of postanesthetic myopathy (muscle damage after anesthesia) in horses. To understand why this was happening, an independent anesthesiologist looked into the anesthesia methods being used. They compared two groups of horses: one group had lower blood pressure managed with smaller amounts of fluids and certain medications, while the other group had higher blood pressure managed with larger amounts of fluids and a different medication. They found that muscle enzyme levels increased in five horses from the first group and in one horse from the second group, suggesting that the changes in treatment might help reduce the risk of muscle damage. Overall, using higher blood pressure management techniques may lessen the severity of this condition.
Abstract
BACKGROUND: During an 8-year period of clinic improvements, an increased incidence of postanesthetic myopathy (PAM) was observed in horses undergoing anesthesia. A request was made for an independent anesthesiologist to examine possible reasons for this increase. Routine methods used for anesthesia were then compared with new methods introduced by the anesthesiologist. OBSERVATIONS: Investigative observations were conducted from October 1999 to April 2000. Following premedication with xylazine or detomidine, anesthesia was induced with diazepam or guiaifenesin followed by ketamine. Maintenance of anesthesia was with halothane/O(2) with mechanical ventilation. Information was gathered from observing routine anesthetics. Seventeen horses were designated group A (October-December 1999) for which hypotension was defined as mean arterial pressure (MAP) <60 mmHg and managed using low-volume crystalloid fluid therapy, etilefrine, or dopamine. In the next 18 horses (group B), hypotension was redefined as MAP <70 mmHg, and was managed using high-volume fluid therapy and dobutamine (January-April 2000). No other changes were made. In both groups, creatine kinase (CK) and aspartate transaminase (AST) concentrations were measured before induction, 1 and 25 hours after standing. Occurrence of PAM was defined as CK and/or AST concentrations above 1000 IU L(-1) and analyzed with Fisher's exact test between groups. Muscle enzymes increased in five horses in group A (two with clinical signs) and in one horse in group B (difference between groups: p = 0.088). CONCLUSIONS: Maintaining MAP >70 mmHg with high-volume fluid therapy and dobutamine may help to reduce the severity of myopathy.
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Search related cases →Original publication: https://pubmed.ncbi.nlm.nih.gov/16476002/