Arterial Pressure Variation in Elective Noncardiac Surgery: Identifying Reference Distributions and Modifying Factors.

BACKGROUND: Assessment of need for intravascular volume resuscitation remains challenging for anesthesiologists. Dynamic waveform indices, including systolic and pulse pressure variation, are demonstrated as reliable measures of fluid responsiveness for mechanically ventilated patients. Despite widespread use, real-world reference distributions for systolic and pulse pressure variation values have not been established for euvolemic intraoperative patients. The authors sought to establish systolic and pulse pressure variation reference distributions and assess the impact of modifying factors. METHODS: The authors evaluated adult patients undergoing general anesthetics for elective noncardiac surgery. Median systolic and pulse pressure variations during a 50-min postinduction period were noted for each case. Modifying factors including body mass index, age, ventilator settings, positioning, and hemodynamic management were studied via univariate and multivariable analyses. For systolic pressure variation values, effects of data entry method (manually entered vs. automated recorded) were similarly studied. RESULTS: Among 1,791 cases, per-case median systolic and pulse pressure variation values formed nonparametric distributions. For each distribution, median values, interquartile ranges, and reference intervals (2.5th to 97.5th percentile) were, respectively, noted: these included manually entered systolic pressure variation (6.0, 5.0 to 7.0, and 3.0 to 11.0 mmHg), automated systolic pressure variation (4.7, 3.9 to 6.0, and 2.2 to 10.4 mmHg), and automated pulse pressure variation (7.0, 5.0 to 9.0, and 2.0 to 16.0%). Nonsupine positioning and preoperative ß blocker were independently associated with altered systolic and pulse pressure variations, whereas ventilator tidal volume more than 8 ml/kg ideal body weight and peak inspiratory pressure more than 16 cm H2O demonstrated independent associations for systolic pressure variation only. CONCLUSIONS: This study establishes real-world systolic and pulse pressure variation reference distributions absent in the current literature. Through a consideration of reference distributions and modifying factors, the authors' study provides further evidence for assessing intraoperative volume status and fluid management therapies.