Blood viscosity and blood pressure: role of temperature and hyperglycemia

We planned a study to research the relations among blood pressure (BP), viscosity, and temperature in healthy subjects and among BP, viscosity, and glucose in diabetics. With simple random sampling method, 53 healthy and 29 diabetes mellitus (DM) type II subjects were selected. Parameters were determined with capillary viscometer and glucometer at 22 degrees C, 36.5 degrees C, and 39.5 degrees C in healthy subjects, and at 22 degrees C on diabetic patients during OGTT with 75 g of glucose. Statistical evaluations of the data were made with regression analysis, Student t test, Spearman's correlation, and analysis of variance. When temperature decreased from 36.5 degrees C to 22 degrees C, blood viscosity increased 26.13%. This increase resulted in a 20.72% decrease in blood flow rate. According to the Hagen-Poiseuille equation, the required BP increase for compensation of the resulting tissue ischemia was 20.72%. Also, a 34.73% decrease in erythrocyte deformability and 18.71% increase in plasma viscosity were seen. When temperature increased from 36.5 degrees to 39.5 degrees C, blood viscosity decreased 10.38%. This caused 11.15% decrease in blood flow rate, and 11.15% decrease in BP, according to the equation. Erythrocyte deformability increase of 9.92% and plasma viscosity decrease of 4.99% arose from the temperature rise. There is a correlation between total data for temperatures and viscosities (r = -0.84, P < .001). When the mean value of blood glucose increased from 100 to 400 mg/dL, viscosity increased 25% (r= 0.59, P = .002). In this state, blood flow rate decrease was 20% and BP increase for physiological compensation was 25%. Consequently, temperature, glucose and viscosity levels of blood are important factors for BP.