Impaired orthostatic response in patients with type 2 diabetes mellitus after 48 hours of bed rest.

Objective: To compare the effect of bed rest on orthostatic responses of patients with type 2 diabetes mellitus and nondiabetic control subjects.

Methods: Six patients with type 2 diabetes and 6 non-diabetic control subjects underwent 48 hours of bed rest and 48 hours of ambulatory activity in randomized order. A 10-minute tilt test was conducted before and after each period of hospitalization, and cardiovascular responses to 80 degrees head-up tilt were analyzed with use of a 2-factorial (study group and bed rest condition) analysis of variance design. We hypothesized that patients with diabetes would experience more severe changes in orthostatic response after bed rest.

Results: No significant differences in orthostatic responses were observed before bed rest between control subjects and patients with diabetes. After bed rest, control subjects had a greater (P = .01) increase in heart rate during tilt in comparison with before bed rest (before versus after bed rest, 9 +/- 4 versus 24 +/- 7 beats/min) and maintained their blood pressure during tilt. After bed rest, patients with diabetes did not have a compensatory increase in heart rate and had a greater (P = .02) decline in systolic blood pressure during tilt in comparison with before bed rest (before versus after bed rest, -7 +/- 10 versus -21 +/- 11 mm Hg). Their arm and leg skin vasomotor responses (laser Doppler flowmetry) during tilt were not altered after bed rest and were similar to those in control subjects before and after bed rest.

Conclusion: Cardiac neuropathy in patients with type 2 diabetes may prevent a compensatory heart rate response after bed rest deconditioning and result in a more severe orthostatic response. A greater decrease in blood pressure with upright tilt is evident after a relatively short period of bed rest.