The passive leg-raising maneuver is a reversible fluid-loading procedure used to predict fluid responsiveness in mechanically ventilated patients. The aim of the present study was to determine whether intra-abdominal hypertension (which impairs venous return) reduces the ability of passive leg raising to detect fluid responsiveness in critically ill ventilated patients.Design:
A prospective study.Setting:
The medical and surgical intensive care unit of a university medical center.Patients:
Forty-one mechanically ventilated patients with a pulse pressure variation of >12%.Interventions:
Stroke volume was continuously monitored by esophageal Doppler. Intra-abdominal pressure was measured via bladder pressure. After a passive leg-raising maneuver and a return to baseline, fluid loading with 500 mL of saline was performed. Hemodynamic parameters were recorded at each step. Nonresponders to volume loading were not analyzed (10 patients). Thirty-one patients were classified into two groups according to their response to passive leg raising: responders to passive leg raising (at least a 12% increase in stroke volume) and nonresponders to passive leg raising.Measurements and Main Results:
Sixteen patients (52%) were responders to passive leg raising, and 15 (48%) were nonresponders to passive leg raising (i.e., false negatives). At baseline, the median intra-abdominal pressure was significantly higher in the nonresponders to passive leg raising than in the responders to passive leg raising (20 [6.5] vs. 11.5 [5.5], respectively; p < .0001). The area under the receiver-operating characteristic curve was 0.969 ± 0.033. An intra-abdominal pressure cutoff value of 16 mm Hg discriminated between responders to passive leg raising and nonresponders to passive leg raising with a sensitivity of 100% (confidence interval, 78–100) and a specificity of 87.5% (confidence interval, 61.6–98.1). An intra-abdominal pressure of ≥16 mm Hg was the only independent predictor of nonresponse to passive leg raising in a multivariate analysis (odds ratio, 2.6 [confidence interval, 1.1–6.6]; p = .04).Conclusions:
An intra-abdominal pressure of ≥16 mm Hg seems to be responsible for false negatives to passive leg raising. Hence, the intra-abdominal pressure should be measured in critically ill ventilated patients, especially before performing passive leg raising.