Issue 180 Item 15 Vasodilatory Response to Hypercapnia Impaired in Diabetics

Insulin-dependent diabetics have an impaired cerebral vasodilatory response to hypercapnia under propofol anesthesia, and the impairment is related to the severity of diabetes.

Whether vasoregulation is intact in diabetic patients and whether it is affected by disease severity "remains controversial," Dr. Yuji Kadoi and colleagues from Gunma University School of Medicine write in the October issue of Stroke: Journal of the American Heart Association.

They studied 30 diabetic and 30 age-matched nondiabetic controls consecutively scheduled for elective surgery.
Transcranial Doppler studies revealed significant between-group differences in absolute and relative CO2 reactivity after induction of anesthesia (p < 0.01 for both). Absolute CO2 reactivity was 2.8 for controls versus 2.1 for diabetics, while relative CO2 reactivity was 6.2 for controls and 4.5 for diabetics.

There were also significant differences between diabetics with and without retinopathy in absolute and relative CO2 reactivity (p = 0.002).

"It is not clear why the presence of retinopathy was associated with abnormal cerebrovascular CO2 reactivity," the authors say. "However, it has been reported that retinal circulation might represent the cerebrovascular circulation because the retina develops from the forebrain."

An additional finding that absolute CO2 reactivity was inversely correlated with glycosylated hemoglobin suggests that "controlled plasma glucose is important to prevent the progression of impaired cerebral autoregulation. Stroke 2003;34:2399-2403.