MICROVASCULAR MONITORING USING THE MERCUR Y IN SILASTIC STRAIN-GAUGE PLETHYSMOGRAPHY (MSG)

Mercury in silastic strain gauge plethysmography (MSG) is a noninvasiv e method for assessing microvascular parameters in peripheral limbs. M SG allows measurement of capillary filtration coefficient (Kf), isovol umetric venous pressure (P-vi), venous pressure (P-v) and arterial inf low (Q(a)) into the limb, respectively. We used MSG in combination wit h invasive monitoring techniques (pulmonary artery flotation catheters and arterial catheters) to study 36 critically ill patients in either hemorrhagic or septic shock. We observed marked increases in P-vi in both patient groups which correlated with outcome. On admission, both groups showed elevated values for P-vi, survivors 37.7+/-2.6, nonsurvi vors 33.7+/-3.5 mm Hg (means+/-SEM) when compared with a control group of young healthy students (22.1+/-0.82 mm Hg). Survivors showed a dec rease in P-vi to 27.3+/-1.7 mm Hg, whereas in nonsurvivors P-vi increa sed to 39.5+/-3.0 at the last measurement taken. The changes in P-vi d epended only fluid replacement (F) had a lower P-vi (31.3+/-2.9 mm Hg) than patients needing inotropic support with dobutamine (D, P-vi=38.2 +/-2.4 mm Hg) to fulfill our therapeutic goals (DO2>550 ml . min(-1) . m(-2), VO2>150 ml . min(-1) . m(-2) and mixed venous lactate <1.5 mmo l/l). After treatment P-vi did not change significantly in the F group (31.3+/-1.8), the D group however showed a significant decrease in P- vi to 25.4+/-2.42, which did not differ from the normal value. We rega rd P-vi as an indicator of insufficient microvascular flow. MSG appear s to be a noninvasive method for assessing the microcirculation, which could enable early detection of microvascular failure, particularly v aluable for critically ill patients.