Background: In hemorrhagic shock, the alterations in arterial vascular tone, which are primarily regulated by adrenosympathetic influences are compensatory responses to bleeding.
Objective: The aim of this study was to evaluate vascular tone expressed by the volume elastic modulus (Ev) as a clinical monitor to detect the hypovolemic state.
Methods: Thirteen patients with hemorrhagic shock were studied. The initial Ev measurement was performed at arrival, and subsequent measurements were obtained 4 and 12 hours after arrival. Patients were divided into two groups by cluster analysis by using the Ev values at arrival and 4 hours after arrival. Circulatory parameters, the clinical course, and fluid were compared.
Results: The Ev values were identical at admission (cluster I vs. II: 456.4+/-197.1 vs 566.1+/-234.1 mm Hg, mean +/- SD). After 4 hours of fluid resuscitation, all patients were recovered from shock. In cluster I, the Ev remained high at 4 hours (523.4+/-75.1 mm Hg) and invasive treatments for hemostasis were required. In cluster II, the Ev significantly decreased at 4 hours (182.8+/-70.7 mm Hg, p < 0.01) and clinical courses were eventless thereafter. During 4 to 12 hours, more fluid was given in cluster I (p < 0.05). At 12 hours after arrival, the Ev values were identical in both clusters.
Conclusion: These data demonstrate that the Ev increases in hemorrhagic shock. Furthermore, normotensive hypovolemic conditions generated by persistent bleeding can be detected by measuring the Ev.