The assessment of the microcirculatory effects of dobutamine using mercury in silastic strain gauge plethysmography in man.

Adverse changes in the microcirculation are currently considered as the most likely common pathway of organ failure, dramatically manifest in the multiple organ failure syndrome. We have investigated 28 patients presenting with gross cardiovascular instability due to septic shock or haemorrhage, using standard invasive methods of monitoring (Physiological Profile). We combined this study with a computer assisted mercury-in-rubber strain gauge plethysmography (MSG) measurement, for a parallel (non-invasive) assessment of peripheral microcirculatory function. We started the investigation on patient arrival in ICU and continued it during their resuscitation regime, which essentially consisted of fluid loading together with inotropic support, where necessary. We found highly significant changes in isovolumetric venous pressure (Pvi), determined by the MSG technique, when we compared survivors (27.29 +/- 1.65 mmHg, mean +/- s.e.m.) with non-survivors (39.5 +/- 2.97 mmHg, P less than 0.001). To investigate the role of dobutamine in patient improvement we compared the Pvi values obtained from the MSG studies and demonstrated a significant decrease from the initial value (38.2 +/- 2.4 mmHg) to the final one (25.4 +/- 2.4 mmHg), obtained after weaning the patients off dobutamine. Marked cyclic changes in limb circumference (vasomotion) were also observed and their appearance correlated well with accepted parameters of cardiovascular instability. We propose that changes in both Pvi and Vm are useful indices of microvascular hypoperfusion which is probably the underlying cause of pathology in both patient groups.