Observational pilot study of intra-abdominal pressure in different head of bed positions

The 2013 World Society of the Abdominal Compartment (WSACS) Guidelines state that intra-abdominal pressure (IAP) should be measured in the supine position. Since patients in the intensive care are preferably nursed in an elevated head of bed position, measuring IAP in more upright positions is more practical. However, measured IAP increases in more upright positions. This study aimed to evaluate automated IAP measurement in different HOB elevations in postoperative cardiothoracic surgery patients. Single-center observational study. ICU of a university hospital. 37 postoperative cardiothoracic surgery patients admitted to the ICU. IAP was measured by the Accuryn Monitoring System in 0°, 15°, 30°, 45° and 60° HOB elevation. IAP measurements in 37 patients were analyzed. Mean IAP at 0° was 9.3 (SD 2.2). Mean IAP increased to 17.9 mmHg (SD 2.9) at 60°. A repeated measures ANOVA was conducted with a pairwise comparison for post-hoc analysis. Mean difference in IAP per 15° HOB elevation was: + 1.8 mmHg (95% CI 1.4-2.2) for 0°-15°, + 2.4 mmHg (2.0-2.8) for 15°-30°, + 2.2 mmHg (1.9-2.5) for 30°-45°, and + 2.1 mmHg (1.8-2.4) for 45°-60°. This pilot study demonstrates the increase of IAP by approximately 2 mmHg per 15 degree increase in HOB elevation in automated measurements in postoperative cardiothoracic patients. This finding may facilitate more routine measurements of IAP and thereby earlier signalling of increases in IAP. Future studies should focus on validating these results in larger ICU populations.