Comparison of two insulin protocols for diabetic dogs undergoing cataract surgery

Objective To evaluate the effectiveness of two insulin doses to maintain an acceptable range of blood glucose concentrations (70-200 mg dL^-1) in the peri-operative period in diabetic dogs. Animals Twenty-four diabetic dogs with a median weight of 20.6 kg and a median age of 8 years old. Methods The dogs were randomly assigned to receive either 25 or 100% of their normal insulin dose subcutaneously on the morning of surgery. The anesthetic and feeding protocols were standardized. On the day before surgery, venous blood was collected for measurement of β-hydroxybutyrate, cholesterol, glucose, glycosylated hemoglobin, hematocrit, total plasma protein and urea nitrogen. On the day of surgery, blood glucose concentrations were measured prior to anesthesia, prior to the start of surgery, 1 and 2 hours after beginning of surgery, 1 hour after extubation, at 16 : 00 hours and at 20 : 00 hours. β-hydroxybutyrate concentrations were measured at 20 : 00 hours that day. At 08 : 00 hours the following day, β-hydroxybutyrate and glucose concentrations were measured. The significance of differences between groups was tested with Wilcoxon's two-tailed rank-sum test, Chi-square test and Fisher's exact test. Results There were no differences in insulin treatments, clinical signs, concurrent diseases and most clinicopathological parameters between the two groups of dogs at entry to the study. The 25% dose group had blood glucose values of 296 (102-601) mg dL^-1 at 16 : 00 hours and 429 (97-595) mg dL^-1 at 20 : 00 hours on the day of surgery. The 100% insulin dose group had lower corresponding values of 130 (55-375) mg dL^-1 (p = 0.04) and 185 (51-440) mg dL^-1 (p = 0.004). No other differences (p < 0.05) were detected between the two groups. Conclusions The administration of a full dose of insulin is only marginally advantageous for reducing glucose to normal (70-120 mg dL^-1) after anesthesia but neither dose consistently induced glycemic values in an acceptable range (70-200 mg dL^-1) or normoketonemia. Clinical relevance Blood glucose should be measured immediately before anesthesia and periodically throughout the peri-operative period in all diabetic dogs because presurgical subcutaneous administration of 25 or 100% of the normal insulin dose resulted in unpredictable blood glucose concentrations.