The Effect of Diabetes and Limb Loss on Thermoregulation and Temperature Perception

The effect of diabetes and limb loss on thermoregul ation and temperature perception by Kathleen Joy Bates Chair of the Supervisory Committee Glenn K. Klute Department of Mechanical Engineering Elevated residual limb skin temperatures inside the prosthetic socket are a source of thermal discomfort and likely responsible for profuse sweating, both report d as significant problems for lower limb amputees (Hagberg & Branemark, 2001; Meulenbelt, Geert zen, Jonkman, & Dijkstra, 2009). Simply donning the prosthesis causes a slight increase in ski n temperature, which rises markedly during activity (Klute, Berge, Huff, & Ledoux, 2006). It t akes doffing the prosthesis for the skin temperature to return to normal because poor thermal pr operties of the liner and socket severely impede heat transfer. Two local mechanisms that ar e important for maintaining thermal comfort are thermal perception (sensation of warm or cold) and co trol of peripheral blood flow (increasing or decreasing to dissipate or preserve heat). Dia betes is the reason for the majority of amputations each year (Dillingham, Pezzin, & Mackenzie, 2002) and h s been strongly associated with altered thermoregulation (Wick et al., 2006). The goals of the proposed st udy are to design and build a research tool to measure thermal perception and blood flow and to use this device to determine if diabetic lower extremity amputees (LEAs) or tr aumatic LEAs: (1) are less sensitive to warm or cold and/or (2) have an altered microcirculatory response t a thermal stimulus. We have tested the thermal perception and microcirculatory reactivity of the lateral aspect of the distal residual limb of 2 traumatic LEAs and 3 diabetic LEAs, and the homol gous location of 4 healthy, intact controls. We measured local blood flow using a laser Dop pler flowmeter (LDF) and warm and cold detection thresholds (WDT, CDT) with quantitative senso ry testing (QST). We started at four initial temperatures (30°C, 32°C, 34°C, and 35°C) and used the Me thod of Limits algorithm with a ramp rate of 0.2 C/s (Divert, 2001; Shy et al., 2003), but modified it by holding the initial temperature and perceived temperature for three minutes to c ollect blood flow data. A linear mixed effects regression was used to compare the threshold and blood per fusion data by subject group, and a likelihood ratio test was used to distinguish trends in the shape of the variables relationship to initial temperature. The average difference in CDT tempera tures between the traumatic LEAs and controls was -1.6°C (SD = 2.6°C) and between diabetic LEAs and cont rols was -1.8°C (SD = 2.6°C). For the cold test, compared to controls, average change in bl ood perfusion was 0.5 (SD = 2.2) profusion unit (PU) more and 2.3 (SD = 2.2) PU less for diabetic s and traumatic amputees, respectively. The two amputee groups were combined for the WDT a nd change in blood perfusion because of insufficient power in both groups. For the warm test, av erage difference in WDT temperatures and change in blood perfusion for the amputees was 2.1°C ( SD = 1.2°C) greater and 13.7 (SE 18.0) PU less than the controls. Differences in warm det ection thresholds were close to significance (p=0.069). There was insignificant difference i n cold detection, vasoconstrictor response to cold stimuli, and vasodilator response to warm stimul i for traumatic LEAs and diabetic LEAs as compared to healthy non-amputee controls. We conclude that amputees may have decreased sensitivity to warm temperature and there was no noticeable trend towards a change in cold perception, vasodilation or vasoconstriction. The implications of t hese findings may mean that amputees have altered perception of warmth.