Validation of Stroke Work and Ventricular Arterial Coupling As Markers of Cardiovascular Performance During Resuscitation

Background: Resuscitation regimens based on stroke work index (SWI) and ventricular-arterial coupling (VAC) are controversial. The Signal Interpretation and Monitoring (SIMON) system continuously collects and stores physiologic intensive care unit (ICU) bedside data at 3- to 5-second intervals. The purpose of this study was to demonstrate the capabilities of a completely automated data management system by further evaluating SWI-based resuscitation.

Methods: This study was a retrospective review of all severely injured patients requiring a pulmonary artery catheter (PAC) for acute postinjury resuscitation. Patients with a severe head injury were excluded. Hemodynamic (HD) data (21 million datapoints) were densely acquired and archived by SIMON. Mean values of HD variables were compared between survivors and nonsurvivors. Receiver operator characteristic (ROC) curves were constructed for HD variables. Threshold values which maximized sensitivity and specificity were determined.

Results: Eighty-eight patients over a 19-month time period met criteria and were included in the analysis. SWI was significantly greater in survivors versus nonsurvivors (4421 +/- 1278 versus 3163 +/- 1066 mm Hg . mL/m, p = 0.0008). VAC was quantified by the ratio (RATIO) of afterload (Ea) to contractility (Ees). RATIO (Ea/Ees) in survivors was significantly better than in nonsurvivors (1.9 +/- 1.1 vs. 2.9 +/- 1.0, p = 0.002). ROC curves identified threshold values of 3250 mm Hg x mL/m for SWI and 2.1 for RATIO (AUC = 0.78 and 0.82, respectively).

Conclusion: Previous work demonstrating the use of SWI and VAC as resuscitation guidelines was supported through the use of a powerful ICU data management system (SIMON). The emergence of these "new vital signs" may change the way injured patients are evaluated and resuscitated in the ICU.