The effect of clinically relevant pressure duration on sacral skin blood flow and temperature in patients after acute spinal cord injury

Objective: To test the effect of clinically relevant duration of pressure loading (2h) on sacral skin blood flow (SBF) and skin temperature in subjects with spinal cord injury (SCI) within 24 to 96 hours after injury compared with subjects with acute orthopedic trauma and healthy subjects. Design: Three-group, repeated-measures, inception cohort. Setting: Three acute care hospitals in southern Thailand. Participants: Convenience sample of 20 subjects with acute SCI within 24 to 96 hours after injury. Age- and sex-matched subjects with acute orthopedic trauma (n=35) and healthy subjects (n=47) served as comparison groups. Interventions: Not applicable. Main Outcome Measures: Sacral SBF and skin temperature were measured simultaneously by using a laser Doppler sensor and thermocouple sensor, respectively, with subjects lying in the lateral (baseline, no pressure, 30min), supine (pressure loading, 2h), and lateral position (recovery, no pressure, 90min). Results: Baseline skin temperature was higher in subjects with acute SCI (P<.05) compared with subjects with orthopedic trauma and healthy subjects. A relative decrease in sacral SBF occurred in subjects with acute SCI (P<.01) over 2 hours of pressure loading compared with subjects with orthopedic trauma and healthy subjects. During the same time course, subjects with acute SCI had a smaller increase in sacral skin temperature compared with subjects with orthopedic trauma and healthy subjects (P<.001). During recovery, the time to the initial sacral SBF-reactive hyperemia response was shorter in subjects with acute SCI compared with subjects with orthopedic trauma (P<.001) and healthy subjects (P=.003). Additionally, the initial positive slope of the SBF reactive hyperemia response was higher in subjects with acute SCI than subjects with orthopedic trauma (P=.005) and healthy (P=.004) subjects. Conclusions: Collectively, a negative change in SBF during pressure loading plus a shorter time to increase and greater slope for SBF after pressure release reveal microvascular dysfunction in acute SCI subjects. The clinical relevance of the protocol suggests that turning interval guidelines may require reevaluation for patients with acute SCI.