Malignant hyperthermia-like reactions in three anesthetized horses.

Problems encountered during halothane anesthesia in 3 horses included increasing rectal temperature, muscle rigidity or movement during anesthesia, irregular breathing patterns, and difficulty in stabilizing blood pressure. One horse had prolonged muscle fasciculations and failure to relax after administration of succinylcholine in addition to halothane. That horse developed severe, bilateral myositis of the triceps, lumbar, and gluteal muscles. Problems encountered were similar to those caused by the disease known as malignant hyperthermia.

Monitoring the anesthetized horse.

The objectives of monitoring are to gain much information as possible about the anesthetized horse and to follow changes in that information, with the ultimate aim of making anesthesia and surgery as safe as possible for the horse. Information necessary to achieve that aim will vary depending on patient category. For example, a young, healthy horse undergoing a short elective procedure can be clinically well monitored by patient signs, electrocardiogram, and indirect blood pressure response. More invasive monitoring is justified and warranted if the health status of the horse is in question. The degree of invasion will be determined by the information needed to provide optimal support. The constantly changing picture should be recorded. The anesthetist who defines anesthesia as long stretches of boredom interspersed with moments of sheer panic is surely guilty of failure to heed warning signs that were present, had he looked for them.