Changes in the volume status of haemodialysis patients are reflected in sublingual microvascular perfusion

Background. After the introduction of sidestream darkfield imaging (SDF) of the microcirculation, it has become clear that in sepsis, microcirculatory alterations can exist in the absence of systemic haemodynamic abnormalities. However, it is unclear whether this phenomenon also occurs in the treatment of end-stage kidney disease (ESKD) where alterations in the volume status of patients occur during dialysis. We tested the hypothesis that volume changes during dialysis directly affect the perfusion of the microcirculation in a group of adult haemodialysis patients. Secondly, we evaluated microcirculatory response to autotransfusion using the Trendelenburg position (TP). Methods. Patients who were on chronic intermittent haemodialysis were assessed for sublingual microvascular flow by SDF imaging pre- and post-TP, performed before and after ultrafiltration (UF). Sublingual microvascular flow was estimated using a semi-quantitative microvascular flow index (MFI) in small (diameter <25 mu m, which includes capillaries), medium (25-50 mu m) and large-sized (50-100 mu m) microvessels (no flow: 0, intermittent flow: 1, sluggish flow: 2 and continuous flow: 3). Changes were evaluated with the non-parametric paired Wilcoxon test. P <0.05 was judged to indicate a significant difference. Results. Thirty-nine adult patients took part in the study. The underlying diseases causing ESKD were predominantly hypertension (HT, n = 10), diabetes mellitus (DM, n = 7) or both (n = 3). At the start of UF, microvascular flow did not change significantly by TP. After completion of UF, MFI had decreased significantly in all types of microvessels (P <0.001). After UF (median volume extraction 2.491), MFI was lower than that at the start of UF and increased in most patients after TP (P <0.001) in all categories of vessels. Changes were most prominent in the smallest microvessels. Conclusions. Sublingual microvascular perfusion is reduced by UF and can be restored temporarily using autotransfusion by TP due to increased venous return. SDF imaging is able to detect these volume changes. SDF imaging and TP could become a useful bedside toot to evaluate the patient's (microvascular) volume status and response to therapy in dialysis or intradialytic hypotension