Effects of autotransfusion on sublingual microvascular perfusion in hemodialysis patients before and after ultrafiltration

Background

Passive leg raising (PLR) can be used effectively to treat hypotension associated with hypovolemia by autotransfusion. We investigated the microvascular response to autotransfusion by PLR before and after ultrafiltration in patients on hemodialysis.

Patients and methods

Patients who were on chronic intermittent hemodialysis were assessed for sublingual microvascular flow by sidestream darkfield (SDF) imaging before and 1 min after PLR (45° upward) before and after ultrafiltration (UF). Sublingual capillary flow was estimated using a semiquantitative microvascular flow index (MFI) in small (diameter 10–25 μm), medium (25–50 μm), and large-sized (50–100 μm) microvessels (0 = no flow; 1 = sludging [0–0.5 mm/s], 2 = moderate flow [0.5–1.0 mm/s], 3 = high flow [1.0–3.0 mm/s]). Changes were evaluated with nonparametric paired Wilcoxon test. Associations were determined with the sign test. P < 0.05 was judged to indicate a significant difference.

Results

Sixteen patients took part in the study. The underlying disease causing renal insufficiency was predominantly hypertension (HT, n = 6) and diabetes mellitus (n = 6). At the start of ultrafiltration, PLR did not alter the microvascular flow (P = NS). After UF (median volume extraction 2.8 l) the capillary MFI increased in most patients after PLR (P < 0.01), whereas flow was not affected in large-sized microvessels (P = NS). The change in capillary MFI before and after UF was related to the UF volume in HT patients (P = 0.01), but not in the other patients.

Conclusion

Autotransfusion by PLR improves sublingual capillary microvascular perfusion in hypovolemia after UF. SDF imaging and PLR may be a useful bedside tool to evaluate the patient's volume status. In this small dataset, the finding that derangement of microvascular perfusion after UF occurs predominantly in HT patients merits further studies.