PURPOSE:Systolic blood pressure variation (SPV) and pulse pressure variation (PPV) are often used as dynamic indices for the prediction of volume responsiveness in critically ill patients. They may also better predict volume responsiveness than traditional methods of intravascular volume estimation such as central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP). The goal of our study was to determine the effect of heart rate (HR) and tidal volume (TV) on systolic blood pressure variation.
METHODS:We prospectively studied baseline and post intervention SPV in 24 patients after elective coronary artery bypass surgery. Study patients were hemodynamically stable with baseline HR <90bpm and had epicardial pacing wires in place. Heart rate and radial artery pulsewave tracing were obtained to determine the presence of SPV. Cardiac pacing wires inserted during surgery were used to increase the HR from baseline by 20 bpm for approximately 3 min and 3 consecutive measurements of SPV obtained. SPV was also determined after decreasing TV from the customary 10cc/kg used in our institution to 6cc/kg after 3 min of observation at the lower TV. Results were analyzed using SPSS Version 13.0 (SPSS Inc., Chicago, IL, USA). The Wilcoxon signed rank test was used to detect differences in pairs of observations before and after intervention.
RESULTS:See Table 1.
CONCLUSION:We were unable to detect any significant effects of changes in heart rate on SPV. However, decreasing the tidal volume from 10cc/kg to 6cc/kg resulted in significant changes in SPV.
CLINICAL IMPLICATIONS:Ventilatory tidal volume should be taken into consideration when using SPV to assess intravascular volume status or fluid responsiveness in postoperative coronary bypass patients.
DISCLOSURE:Jeffrey Drees, No Financial Disclosure Information; No Product/Research Disclosure Information