Passive leg raising (PLR) can be used effectively to treat hypotension associated with hypovolemia. Shock is associated with impairment of microvascular flow. We investigated the microvascular response to PLR in patients with shock.
Patients who were admitted to the ICU with septic shock (defined by MAP<60 mm Hg and sepsis according to standard criteria) were assessed for sublingual microvascular perfusion by orthogonal polarization spectral (OPS) imaging before and 1 minute after PLR (45 degrees upward). Perfusion was estimated using a semi-quantitative microvascular flow index (MFI) in small (diameter 10-25 μm), medium (25-50 μm), and large-sized (50-100 μm) capillaries (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)).
Ten patients (2 female, 8 male; mean age 67 years) participated in this study. Mean APACHE-II score was 23 (range 13-33). Mean lactate levels were 3.5 mmol/l. MAP and CVP inceased after PLR (table). Microvascular flow increased in parallel in most patients, i.e. flow increased predominantly in small microvessels, while flow in the larger microvessels remained relatively preserved. In 4 patients, microvascular flow hardly improved after PLR. Also, after infusion of fluids until CVP was above 10, in 3 of those 4 patients flow had still not normalized. After giving 0,5 mg nitroglycerin iv as described before, flow normalized in all cases.
Changes in sublingual microvascular perfusion after PLR reflect the recruitment of blood from the venous leg pool in shock patients. Microvascular flow improves by volume infusion in most cases. Some patients may require additional infusion of nitroglycerin to actively open the microvascular system.
OPS imaging may be a valuable bed-side tool for assessing optimal fluid resuscitation.
MAP (mean, mm Hg)CVP (mean; mm Hg)MFI small microvesselsMFI medium microvesselsMFI large microvesselsBefore PLR5040,81,92,8After PLR5781,72,63,0P<0,05P<0,01P<0,01P<0,05P<0,05
Peter Spronk, None.