The hemodynamic actions of insulin are blunted in the sublesional microvasculature of healthy persons with spinal cord injury.

Abstract

The aim of this study was to gain a better understanding of the hemodynamic actions of insulin on cutaneous microcirculation in persons with spinal cord injury (SCI). A prospective, open-label, nonrandomized, placebo-controlled investigation was performed in an otherwise healthy cohort of persons with SCI (n = 10) and in an age- and sex-matched cohort of control subjects whose neurologic function is intact (n = 10). Laser Doppler flowmetry characterized the peak blood perfusion unit (BPU) response (percent change from baseline) to insulin or placebo iontophoresis above and below the neurologic level of injury. Placebo iontophoresis did not result in any statistically significant changes in BPU. In the arm, insulin iontophoresis resulted in a 20% mean increase in BPU (P < 0.05) in the control group and a 9% mean increase in the SCI group (P = 0.14). In the leg, insulin iontophoresis resulted in an 81% (P < 0.01) mean increase in BPU in the control group and a 29% (P < 0.001) mean increase in BPU in the SCI group. The relative effect of insulin on the lower extremity BPU response was significantly greater (P < 0.05) in the control group compared with the SCI group (77% vs. 35%, respectively). The hemodynamic actions of insulin are markedly blunted in the sublesional microvasculature of persons with SCI, most likely as a result of impaired sublesional sympathetic nervous system control.