Does rebound hyperglycemia (the Symogyi effect) occur in diabetic cats? While long thought to occur in cats, studies in human diabetic patients have rejected that this is a common occurrence in people. What is rebound hyperglycemia? It is defined as hyperglycemia caused by the release of counter-regulatory hormones in response to insulin-induced hyperglycemia. The authors determined their goal was to evaluate the occurrence and prevalence of rebound hyperglycemia in diabetic cats, especially since the original work describing rebound hyperglycemia was performed in a cohort of just six cats.
In this retrospective study, the authors performed 10,767 blood glucose curves of 55 cats that were treated with glargine insulin using an intensive blood glucose regulation protocol. There was a median of five blood glucose measurements per day which evaluated for evidence of rebound hyperglycemic events. All the owners followed the same intensive blood glucose regulation using glargine and for the cats to be fed a low-carbohydrate wet-food diet exclusively. The rebound hyperglycemia was defined in two different ways (with or without an insulin resistance component). The exact definitions follow:
- Rebound hyperglycemia was defined as blood glucose concentration of £ 50 mg/dl (£2.8 mmol/l), followed by marked hyperglycemia of ³ 300 mg/dl (³ 16.7 mmol/l) within 4-10 h. Hyperglycemia was evident at the time of the next insulin dose, but not beyond.
- Rebound hyperglycemia with insulin resistance was defined as a blood glucose concentration of £ 50 mg/dl (£2.8 mmol/l), followed by marked hyperglycemia of ³ 300 mg/dl (³ 16.7 mmol/l) within 4-10 h. The two subsequent insulin doses had little glucose lowering effect, with blood glucose concentrations remaining > 250 mg/dl (> 13.9 mmol/l) and thus the glucose concentrations remained elevated for ³ 24 h.
From the results, of the 10,767 curves measured, 45 were consistent with rebound hyperglycemia. This number represented 0.42% of all blood glucose curves measured in the study. In addition, it was noted that blood glucose curves consistent with rebound hyperglycemia with insulin resistance were even less frequent, and were confined to four single events in four different cats. Biochemical or asymptomatic hypoglycemia did occur in 51 of the 55 cats (93%) using this intensive protocol.
The authors conclude that in spite of asymptomatic or biochemical hypoglycemia being a frequent occurrence in cats treated with glargine on a protocol designed for tight glycemic control, rebound hyperglycemia is a rare occurrence. They advise that while the dose of glargine should be reduced if the cat develops asymptomatic or clinical hypoglycemia, it should not be reduced when the blood glucose concentration is high and poorly responsive to insulin. Fluctuations in blood glucose concentrations are common in the early weeks following the initiation of treatment with glargine. (VLT)