Blood Flow Response to Cold Face Stimulation Is Blunted In Patients with Sickle Cell Disease

Abstract 2655

Sickle cell disease (SCD) is characterized by repeated episodes of vaso-occlusion leading to painful episodes, acute chest syndrome, stroke, end organ damage and death. Blood flow changes that result in decreased perfusion of tissues and organs increase the risk for vaso-occlusion by increasing the residence time of deoxygenated and deformed sickled red blood cells in the capillary bed. Patients with SCD are more likely to have transient decreases in perfusion in response to sighs (unpublished data). We thus hypothesized that SCD patients would have an enhanced vasoconstriction response to other autonomic stimuli, such as the cold face stimulation test, when compared to normal controls and SCD patients who are chronically transfused. Using an IRB approved protocol, we studied 13 normal, ethnic matched, subjects (mean age 30.2 + 14 yrs), 12 SCD subjects (mean age 22.9 + 13.1 yrs) and 7 chronically transfused SCD subjects (mean age 22.5 + 11.5 yrs). Dermal capillary perfusion (DCP) measured by laser Doppler and near infrared regional oxygen saturation (rSO₂) of the hand were monitored as continuous measures of peripheral blood flow. Physiologic data including systemic vascular resistance (SVR), respiratory rate, tidal volume, heart rate and mean arterial blood pressure, as well as DCP and rSO₂, were continuously monitored and recorded digitally. A cold pack was applied to the forehead for 60 seconds and the perfusion and physiological data were recorded. Baseline physiologic values were calculated as the median from 5 min to 1 min prior to the cold face stimulation and compared to median values during the cold face stimulation. In all three populations (normal controls, chronically transfused SCD, SCD) there was a rapid decrease of DCP from baseline (−38.2%, −26.6%, −22.5% respectively) and rSO2 (−8.8%, −4.8%, −3.3% respectively) during the cold face stimulation. Thus, compared to controls, the vascular response was blunted in both SCD and transfused SCD. The blood flow changes in response to the cold face stimulation in SCD improved with chronic transfusion but did not normalize. SVR increased in all populations (17%, 16%, 9% respectively) but the response was blunted in the non-transfused SCD group. Bradycardia was observed in the control and chronically transfused SCD groups (−5.9%, −3.7%) but not in the non-transfused SCD (−0.21%). Our results indicate that, as expected, there is a decrease in peripheral blood flow during cold exposure in normal controls which also occurs in SCD and chronically transfused SCD; SVR is increased consistent with peripheral vasoconstriction. Interestingly, the peripheral blood flow response to cold face stimulation is significantly blunted in both SCD and SCD with chronic transfusion, and thus transfusion does not correct the abnormality. However, chronic transfusion in SCD normalizes the bradycardiac/parasympathetic response to cold face stimulation. In overview, these findings indicate that chronic transfusion partially improves autonomic function in SCD patients, but does not correct the abnormality in peripheral microvascular reactivity.