00851-A: The Effect of Physiologic Dexamethasone on Blood Glucose Level in Dogs Following Congenital Portosystemic Shunt Ligation

Grant Amount: $12,177.83

Beth M. Johnson, DVM; University of Tennessee

October 1, 2006 - September 30, 2009

Sponsor(s): Tibetan Terrier Club of America/Tibetan Terrier Health & Welfare Foundation

Breed(s): -All Dogs

Research Program Area: Hepatic Disease

Project Summary

Several small dog breeds, including Yorkshire Terriers, Miniature Schnauzers, Maltese, and others, suffer from the development of an abnormal blood vessel, or shunt, which bypasses the liver. Treatment for this defect includes surgical closure of the shunt. Following shunt surgery, for an unknown reason, over half of the dogs at our hospital develop low blood sugar that does not respond to standard medical management. Previous data from our lab suggest that one cause of this low blood sugar is an inadequate production of cortisol, the hormone responsible for increasing blood sugar in times of stress, disease or surgery. In this study, the researchers administered dexamethasone (a cortisol-like drug) immediately after surgery to evaluate its effectiveness at preventing low blood sugar. They hypothesize that dogs receiving dexamethasone will have less incidence of low blood sugar following surgery. Due to the very small number of hypoglycemic dogs and the lack of statistically significant findings, we have not published a manuscript at this time. The conclusions to date are as follows: Using < 60 mg/dl as the definition for hypoglycemia, approximately 6.8% of dogs in our study became hypoglycemic following congenital portosystemic shunt ligation. This was much lower than the almost 50% occurrence of post-operative hypoglycemia observed in a previous study by our group. Using < 70 mg/dl as the definition for hypoglycemia, 23% of our control dogs became hypoglycemic following surgery compared to 10% of our test dogs that received dexamethasone at the time of extubation. This suggests a possible trend toward supporting our hypothesis; however, statistics did not support its significance. Therefore, statistically, these findings contradict the hypothesis that relative adrenal insufficiency alone is the cause of post operative hypoglycemia in this population of dogs. We concurrently evaluated insulin/glucagon ratios at the time of hypoglycemia, or at 6 hours post-op in patients that remained euglycemic, to investigate hormonal causes of hypoglycemia other than decreased cortisol. Unfortunately, we could not make any conclusions with our small number of hypoglycemic dogs. We did find that post-operative glucagon levels were significantly increased compared to pre-operative glucagon levels in this population of dogs as a whole; no significant change when evaluating hypoglycemic versus euglycemic dogs. The significance of this finding is unknown. We will bank this data for possible future evaluation of a larger number of dogs and/or further investigation of the significance of pre and post-operative insulin and glucagon levels; however, this report is the conclusion of this project at this time.

Publication(s)

None at this time.