Objective—To characterize the effect of general
anesthesia and minor surgery on renal function in
Animals—9 mares with a mean (± SE) age and body
weight of 9 ± 2 years and 492 ± 17 kg, respectively.
Procedure—The day before anesthesia, urine was
collected (catheterization) for 3 hours to quantitate
baseline values, and serum biochemical analysis was
performed. The following day, xylazine (1.1 mg/kg, IV)
was administered, and general anesthesia was
induced 5 minutes later with diazepam (0.04 mg/kg,
IV) and ketamine (2.2 mg/kg, IV). During 2 hours of
anesthesia with isoflurane, PaCO2 was maintained
between 48 and 52 mm Hg, and mean arterial blood
pressure was between 70 and 80 mm Hg. Blood and
urine were collected at 30, 60, and 120 minutes during
and at 1 hour after anesthesia.
Results—Baseline urine flow was 0.92 ± 0.17 ml/kg/h
and significantly increased at 30 and 60 minutes after
xylazine administration (2.14 ± 0.59 and 2.86 ± 0.97
ml/kg/h respectively) but returned to baseline values
by the end of anesthesia. Serum glucose concentration
increased from 12 ± 4 to 167 ± 8 mg/dl at 30 minutes.
Glucosuria was not observed.
Conclusions and Clinical Relevance—Transient
hyperglycemia and an increase in rine production
accompanies a commonly used anesthetic technique
for horses. The increase in urine flow is not trivial and
should be considered in anesthetic management
decisions. With the exception of serum glucose concentration
and urine production, the effect of general
anesthesia on indices of renal function in clinically
normal horses is likely of little consequence in most
horses admitted for elective surgical procedures.
(Am J Vet Res 2002;63:1061–1065)