Postanesthetic hind limb adductor myopathy in five horses.

Five horses that underwent prolonged anesthesia (greater than 3 hours) in dorsal recumbency for a surgical procedure were unable to stand after recovery and were euthanatized. A provisional diagnosis of postanesthetic myopathy was confirmed at necropsy in all 5 horses. However, distribution of affected muscles in these horses was atypical, because there was bilateral hind limb adductor muscle involvement.