Effects of ketamine, diazepam, and their combination on intraocular pressures in clinically normal dogs

OBJECTIVE: To evaluate the effects of ketamine, diazepam, and the combination of ketamine and diazepam on intraocular pressures (IOPs) in clinically normal dogs in which premedication was not administered. ANIMALS: 50 dogs. PROCEDURES: Dogs were randomly allocated to 1 of 5 groups. Dogs received ketamine alone (5 mg/kg [KET5] or 10 mg/kg [KET10], IV), ketamine (10 mg/kg) with diazepam (0.5 mg/kg, IV; KETVAL), diazepam alone (0.5 mg/kg, IV; VAL), or saline (0.9% NaCl) solution (0.1 mL/kg, IV; SAL). Intraocular pressures were measured immediately before and after injection and at 5, 10, 15, and 20 minutes after injection. RESULTS: IOP was increased over baseline values immediately after injection and at 5 and 10 minutes in the KET5 group and immediately after injection in the KETVAL group. Compared with the SAL group, the mean change in IOP was greater immediately after injection and at 5 and 10 minutes in the KET5 group. The mean IOP increased to 5.7, 3.2, 3.1, 0.8, and 0.8 mm Hg over mean baseline values in the KET5, KET10, KETVAL, SAL, and VAL groups, respectively. All dogs in the KET5 and most dogs in the KETVAL and KET10 groups had an overall increase in IOP over baseline values. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with baseline values and values obtained from dogs in the SAL group, ketamine administered at a dose of 5 mg/kg, IV, caused a significant and clinically important increase in IOP in dogs in which premedication was not administered. Ketamine should not be used in dogs with corneal trauma or glaucoma or in those undergoing intraocular surgery.     

Clinical observations surrounding an increased incidence of postanesthetic myopathy in halothane-anesthetized horses

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.