Systolic pressure variation as diagnostic method for hypovolemia during anesthesia for cardiac surgery

An accurate predictor of effective intravascular volume is of paramount importance for patients submitted to major surgical procedures. A new method to evaluate intravascular volume based on systolic blood pressure variations (SPV), (difference between the maximum and minimum systolic values during controlled respiratory cycle) and its variable delta down (dDown) has shown to be a sensitive indicator of ventricular preload. As SPV is not routinely used in clinical practice our purpose was to evaluate the accuracy of this parameter in evaluating volume status of patients submitted to cardiac surgery.

As from specially developed software, blood pressure variation was transmitted in real time from operating room monitor to a network-connected computer. After the adaptation of this system, nine patients submitted to cardiac surgery were evaluated. Variables were recorded in two moments: T0 (before volume replacement) and TP (after volume replacement). At the same time, conventional hemodynamic parameters were also studied and compared to systolic pressure variation.

Primary study results have shown that SPV (systolic pressure variation), in its dDown component, presents the best variation consistency after volume replacement with starch. Remaining hemodynamic parameters evaluated, although pointing to clear cardiovascular improvement after replacement, are highly variable among the patients and even on expander's response.

Results have shown that SPV is a sensitive method to evaluate intravascular volume status in patients under mechanical ventilation, when correlated to central venous pressure, pulmonary capillary wedge pressure and systolic index variations.