Venous pressure measurements in the superior and inferior vena cava: the influence of intra-abdominal pressure
Markou, N.; Grigorakos, L.; Myrianthefs, P.; Boutzouka, E.; Rizos, M.; Evagelopoulou, P.; Apostolakos, H.; Baltopoulos, G.
Hepato-Gastroenterology 51(55): 51-55
2004
ISSN/ISBN: 0172-6390 PMID: 15011830 Document Number: 2596
Background/Aims: To investigate the relationship of pressure in the inferior vena cava (Five) with a) pressure in the superior vena cava (Psvc), b) intra-abdominal pressure as measured in the urinary bladder (Pcyst). Methodology: A prospective study of 38 mechanically ventilated patients. Simultaneous measurements of Psvc, Pivc and Pcyst (151 sets of measurements) were performed. Measurements were divided in: Group A (Pcyst <10 mmHg), group B (10 mmHg ltoreqPcyst <15 mmHg), group C (Pcyst gtoreq15 mmHg). Statistical analysis was performed with paired t-test, Pearson correlation. Results are expressed in mean+-SEM. Results: In Groups A and B, Psvc and Pivc were not significantly different and they were highly correlated (10.8+-0.5 mmHg vs. 10.9+-0.5 mmHg, r=0.93 for Group A and 14.4+-0.7 mmHg vs. 14.7+-0.6 mmHg, r=0.87 for Group B). Pcyst was significantly lower than Pivc in both groups. In Group C, Pivc was significantly higher than Psvc (18.9+-0.7 mmHg vs. 16.4+-0.7 mmHg). There was no significant difference between Pivc and Pcvst (19.2+-0.6 mmHg). Pivc significantly correlated with Pcyst (r=0.78) and Psvc (r=0.7). A. When Pcyst>PsVc, Pivc was higher than Psvc (p<0.01). With Pcyst <15 mmHg, no significant difference was found between Pcyst and Pivc and they were correlated (r=0.766, p<0.05). Pressures in the superior and inferior vena cava were also correlated (r=0.764, p<0.05). With Pcyst gtoreq15 mmHg, Pivc was lower than Pcyst (p<0.01). It correlated highly with Pcyst (r=0.85, p.<0.01) and less strongly with Psvc (r=0.701, p<0.01). B. When PcystltoreqPsvc, no difference between Pivc and Psvc was observed. With Pcyst <15 mmHg, Pivc was higher than Pcyst (p<0.01) and highly correlated with Psvc (r=0.932, p<0.01). Pivc also correlated with Pcyst (r=0.69, p<0.01). With Pcyst gtoreq15 mmHg, Pivc was higher than Pcyst (p<0.01) and correlated with Psvc (r=0.74, p<0.01) and Pcyst (r=0.789, p<0.01). Conclusions: Although Psvc and Pivc are interchangeable in the absence of an increased Pcyst, when Pcyst is high, measurements of Pivc are misleading. A Pcyst>Psvc results in a "waterfall" effect, and Pivc does not accurately reflect Psvc any more.
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