Background:Diabetes is often associated with orthostatic hypotension and temperature intolerance. Studies have examined either one stress or the other and not both to see if the stresses are additive.Material/Methods:Eight subjects with Type 1 and 12 subjects with Type 2 diabetes and 15 controls were tested for orthostatic intolerance during a vertical tilt in a thermally neutral environment (22°C) and a warm room (42°C). Blood pressure, cardiac output, stroke volume, heart rate, skin blood flow and skin and body temperature were recorded.Results:All subjects experienced reductions in their cardiac output and blood pressure when tilted. In the warmer environment, significant impairments in the compensatory blood pressure response and redistribution of cardiac output were found in subjects with diabetes. When tilted to the vertical posture, subjects with diabetes experienced reductions of about 10 mmHg in systolic blood pressure in the cool environment, and a reduction of 21 mmHg when tilted in the warm environment. The fall in the systolic pressure in the subjects with diabetes was accompanied by corresponding reductions in stroke volume and cardiac output (from 5.06 L/min to 4.75 L/min) but no change in the heart rate. To compensate for a vertical tilt, skin blood flow was reduced by about half in the controls but there was only a small vasoconstriction in the subjects with diabetes.Conclusions:Individuals with Type 1 and Type 2 diabetes, while showing some loss in orthostatic tolerance in a cool environment, showed significant clinical impairment associated with heat exposure.

Keywords: Dizziness - physiopathology, Blood Flow Velocity, Blood Pressure, Body Temperature, Diabetes Mellitus, Type 1 - physiopathology, Diabetes Mellitus, Type 2 - physiopathology, Dizziness - physiopathology, Hot Temperature, Reference Values, Skin - blood supply, Skin Temperature