A comparison of fluid instillation volumes to assess intra-abdominal pressure using Kron's methods

BACKGROUND: Intra-abdominal pressure (IAP) measurement has become an important tool in the assessment of critically ill patients. The World Society of the Abdominal Compartment Syndrome consensus guidelines recommend using a maximum volume of 25 mL of sterile saline instilled into the bladder for intermittent IAP measurements. It is postulated that the volume of fluid instilled may have an impact on the estimation of IAP. METHODS: This study sought to compare measured bladder pressures after the instillation of 25, 10, and 0 mL volumes of sterile saline using measurement analysis. Measurement was performed using the modified Kron technique, and treatment allocation was applied by prospective, alternate patient treatment allocation. Transvesical IAP measurements were undertaken using volumes from 0 mL to 25 mL. Recordings were taken with the catheter unclamped, clamped, 10 mL instillation, and 25 mL instillation. This measurement analysis was conducted in a mixed intensive care unit at a Level I trauma hospital over a period of 14 weeks. IAP measurements were performed on 37 patients with varying disease processes using 25, 10, and 0 mL of sterile saline instilled into the bladder. RESULTS: Medical, surgical, and trauma patients were distributed equally across the treatment groups. Twenty-three patients were male, and the mean age was 58 years ± 18 years. The concordance correlation coefficient between 25 mL and 10 mL was 0.95. The concordance correlation coefficient between 25 mL and no fluid with an unclamped and clamped catheter was 0.55. CONCLUSION: In a general intensive care unit population, measured intra-urinary bladder pressure measurements using a volume of 10 mL fluid instillation provides comparable results to using 25 mL fluid. LEVEL OF EVIDENCE: Diagnostic study, level II.