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 β 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.

Correlation of systolic pressure variation, pulse pressure variation and stroke volume variation in different preload conditions following a single dose mannitol infusion in elective neurosurgical patients

Background: A Prospective observational study was designed assess the correlation between arterial pressure waveform derived indices and echocardiography derived stroke volume variation (SVV) at different preload conditions in patients undergoing elective craniotomies. Methods: Systolic pressure variation (SPV) and pulse pressure variation (PPV) were calculated from the arterial waveform. SVV was measured from transoesophageal echocardiography. After measuring baseline values for all three parameters, 1 g/kg of mannitol infusion (20%) was given over 15–20 min. Repeated measurements of SPV, PPV, SVV, urine output and peak airway pressure were done at the interval of 15, 30, 60, 90 and 120 min after stopping mannitol infusion. Pearson correlation coefficient (level of significance), and receiver operating characteristics curve were used for statistical analysis. Results: Significant correlation was present between SPV and SVV throughout the study. Significant correlation between SPV and PPV was present only at 90 min and 2 h after mannitol. The predictive effect of SPV and PPV in differentiating a volume loss ≥10 mL/kg was better than SVV. The best cut-off values for SPV, PPV and SVV were 12%, 9% and 20%, respectively. Conclusions: During mechanical ventilation with a tidal volume of 8 mL/kg, SPV correlated significantly with SVV at different preload conditions following mannitol infusion. PPV correlated poorly with SVV. SPV and PPV correlated only in the presence of hypovolaemia.