Abdominal compliance, linearity between abdominal pressure and ascitic fluid volume

BACKGROUND: Drainage of ascitic fluid is a common practice in order to relief the respiratory discomfort of patients. AIM: To determine the relation between the intra-abdominal pressure (IAP) and extracted volume of the ascitic fluid, in order to calculate abdominal compliance (Cabd). SETTINGS AND DESIGN: A study was designed at AHEPA University Hospital and analysed with prospectively collected data. MATERIALS AND METHODS: Fifteen patients with tension ascites that had transcutaneous drainage with a wide catheter. The ascitic fluid removed was measured, while the IAP and a Visual Analogue Scale (VAS) score for dyspnea were recorded before and 15 min after the puncture. Cabd was calculated. STATISTICAL ANALYSIS: The data were analysed with descriptive statistics, paired Student's t-test and Pearson coefficiency. RESULTS: The predrainage IAP was 18.26 mmHg (SD 1.67 mmHg), while the postdrainage was 14.46 mmHg (SD 1.34 mmHg) (P<0.001). The mean volume of ascitic fluid removed was 1624 mL (SD 861 mL). Cabd after drainage was 414.01 mL/mmHg (SD 139.15 mL/mmHg). A linear correlation was found between ascitic fluid removal and IAP variations. The dyspnea VAS score was 7.5 (SD=0.8) before the drainage and 4.3 (SD=1.0) after the drainage (P<0.001). CONCLUSIONS: The drainage of ascitic fluid reduces IAP, facilitating in this way respiration. Moreover, IAP variation seems to be in linear relation with the volume of ascitic fluid removed. This linear relation between IAP and volume may probably predict the Cabd quite accurately and vice versa. However, larger studies are necessary to safely draw predicting ΔIAP – ΔV (Cabd) diagrams, and determine the optimal ascitic fluid removal to achieve best comforting of the patient and slower fluid reformation.