Assessment of the Peripheral Microcirculation Using Computer-Assisted Venous Congestion Plethysmography in Post-Traumatic Complex Regional Pain Syndrome Type I

Abstract

In complex regional pain syndrome type I (CRPS-I), edema of the affected limb is a common finding. Therefore, the changes in macro- and microcirculatory parameters were investigated to elucidate the underlying pathophysiology. Twenty-four patients with post-traumatic CRPS-I and 25 gender- and age-matched healthy subjects were examined by means of an advanced computer-assisted venous congestion strain-gauge plethysmograph. The recording of the volume response of the forearm to a stepwise inflation of an occlusion cuff placed at the upper arm enabled the calculation of the arterial blood flow into the arm (Q_a), the vascular compliance (C), the peripheral venous pressure (P_v), the isovolumetric venous pressure (P_vi; = hydrostatic pressure needed to achieve net fluid filtration) and the capillary filtration capacity (CFC) – an index of microvascular permeability. The study revealed no difference in any of the parameters between the right and left hand of healthy subjects. In CRPS-I patients, however Q_a, P_v, P_vi and CFC were significantly (p < 0.01/0.001) elevated in the affected arm (Q_a 11.2 ± 7.0 ml min^–1 100 ml^–1, P_v 20.2 ± 8.1 mm Hg, P_vi 24.7 ± 4.2 mm Hg, CFC 0.0058 ± 0.0015 ml min^–1 100 ml^–1 mm Hg^–1) compared to the unaffected arm (Q_a 4.2 ± 2.4 ml min^–1 100 ml^–1, P_v 10.0 ± 5.1 mm Hg, P_vi 13.2 ± 3.7 mm Hg, CFC 0.0038 ± 0.0005 ml min^–1 100 ml^–1 mm Hg^–1) and the values obtained in healthy controls (Q_a 5.1 ± 1.3 ml min^–1 100 ml^–1, P_v 10.4 ± 4.3 mm Hg, P_vi 15.7 ± 3.3 mm Hg, CFC 0.0048 ± 0.0012 ml min^–1 100 ml^–1 mm Hg^–1). Whereas the values in the unaffected arm of CRPS-I patients revealed no difference in Q_a, P_v and P_vi but a lower CFC (p < 0.01) compared to those from healthy controls. These results suggest profound changes in both macro- and microvascular perfusion in the affected arm of CRPS-I patients. The high CFC contributes to the edema formation, and combined with the elevated P_vi, they are in agreement with the hypothesis of an inflammatory origin of CRPS.