Effect of acute heat exposure on skin blood flow of the paralyzed thigh in persons with spinal cord injury

Objectives: To investigate whether increased body temperature during heat exposure promotes skin blood flow of the thigh (SBFT) in individuals with spinal cord injury at rest. Study design: A prospective study with high lesion and with low lesion. Setting: Hiroshima University, Higashi-Hiroshima, Japan. Methods: Seven male paraplegics (T5-L2) and seven able-bodied subjects volunteered to participate in the experiment. First the subject rested for 1 h at an ambient temperature (Ta) of 25°C and a relative humidity (Rh) of 50%. Thereafter, the subject moved to a climatic chamber heated to Ta of 33°C an Rh of 50–55% and was exposed to this environment for 1 h. SBFT, stroke volume, heart rate, the skin temperature of the medial thigh (Tthigh) and the tympanic membrane temperature (Tty) were assessed during the experiment. Results: The four subjects with high lesions between Th6 and Th10 (HL) showed no increase in SBFT, while the remaining three subjects with low lesion at Th11 or Th12 (LL) showed increased SBFT in the hot environment. Although Tty increased with exposure time in heat, correlation between Tty and SBFT was not significant in either paraplegic group. However, correlation between SBFT and Tthigh was highly significant in both groups. The increase in Tthigh in LL was due to increased skin blood flow in the thigh, while in HL it was considered attributable to heat transfer from the environment to the skin. Conclusion: These findings indicate that SBFT during heat exposure was largely dependent on the level of spinal cord injury. SBFT with low lesions increased during heat exposure when the sympathetic cutaneous vasomotor supply of the thigh was preserved. Spinal Cord (2000) 38, 224–228.