A Comparison of Infusion Volumes in the Measurement of Intra-Abdominal Pressure

Bladder pressure measurement through a foley catheter is the current standard in monitoring for intra-abdominal hypertension (IAH) and abdominal compart-ment syndrome (ACS). Accurate pressure transduction requires a continuous fluid column with a small volume of transducing medium at the tip of the catheter. Infus-ing excessive fluid volume can falsely elevate the measured intra-abdominal pressure (IAP) due to bladder overdistention and can lead to intrinsic muscular con-traction. This effect can be seen with volumes as low as 60 mL. Recent expert consensus has recommended 25 mL as the maximal infusion volume; however, 50 mL is the most commonly cited volume of infusion in the literature. The purpose of this analysis was to determine the variance between IAP values using a range of volume infusions between 10 and 60 mL. Eighteen adult, surgical intensive care unit (SICU) patients who were undergoing IAP measurement for IAH or clinically indicated monitoring were enrolled in a prospective, nontreatment study. Intra-abdominal pressure measurements were obtained with stepwise increases of injectate volume from 10 to 60 mL (in 10 mL increments). Bland-Altman analyses and receiver operating characteristic (ROC) curves were used for analysis. After analysis accounting for data correlation within patients, means and standard deviations were generated for differences between 50 mL and 10, 20, 30, 40, and 60 mL bladder infusion volumes. Bland-Alt-man analyses showed good agreement between mea-surements and no significant difference in variance (mean 1.35 mm Hg) between volume comparisons. The ROC curve generated for each test volume using a diagnostic pressure value for IAH (12 mmHg) showed that a value between 11 and 12 mm Hg gave the best combination of sensitivity and specificity for all test volumes. In SICU patients, with a clinical indication for IAP monitoring, bladder infusion volumes between 10 mL and 60 mL provide consistent IAP measurements