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Abstract

Introduction: Dynamic parameters are more accurate measures for predicting volume responsiveness in critically ill patients than static parameters. Pulse pressure variation (PPV) and systolic pressure variation (SPV) are dynamic hemodynamic parameters that have been validated as predictors of volume responsiveness in certain patient populations. Ultrasonographic derived brachial peak velocity variation (BPVV) is a non-invasive parameter that can be easily obtained at the bedside. In a group of post-operative cardiac surgery patients we evaluated BPVV, PPV and SPV. Methods: This was a prospective observational study. 34 patients undergoing cardiac surgery were enrolled between May of 2012 and June of 2013. Data collected included age, gender and arterial catheter location. Patients were studied in the immediate post-operative period while still under positive pressure mechanical ventilation. PPV and SPV were manually measured from a waveform printout over an average of three (3) respiratory cycles. Brachial velocity was obtained with a Sonosite M Turbo ultrasound and L25 vascular transducer. The brachial artery was identified in long axis and Doppler measurements of arterial blood flow velocities were obtained. Maximum and minimum velocities were measured over approximately three (3) respiratory cycles. This process was completed three (3) times with the results averaged to ensure accuracy. Results: A total of 34 patients were enrolled, 65% where male and 35% female. The mean age was 67. SPV and PPV was calculated from a radial arterial catheter in the vast majority of cases (94%). BPVV and SPV correlated strongly and BPVV and PPV correlated even stronger in our patient population over a broad range of blood pressures The Pearson’s correlation coefficient was 0.7 between BPVV and SPV and 0.87 between BPVV and PPV. A two-tailed t-test was used. P-values of <0.01 were obtained for both BPVV and SPV and BPVV and PPV. Conclusions: There was significant correlation between BPVV and SPV and BPVV and PPV. Given that PPV and SPV are well-established markers of fluid responsiveness, BPVV may provide an alternative noninvasive dynamic method to assist clinicians with fluid resuscitation. Further studies are required to fully validate BPVV as a marker of fluid responsiveness in clinical situations requiring fluid resuscitation.