Intravascular volume depletion in a 24-hour porcine model of intra-abdominal hypertension.

BACKGROUND: The purpose of the study was to examine hemodynamic parameters and intravascular volume in a porcine model in the presence of intra-abdominal hypertension (IAH) lasting for 24 hours. METHODS: Twelve pigs (52.5 +/- 4.9 kg) were studied over a period of 24 hours. In six animals, the intra-abdominal pressure was increased to 30 mm Hg via carbon dioxide-pneumoperitoneum. The others served as controls. Using the double-indicator dilution technique, intrathoracic blood volume (ITBV), total circulating blood volume, and cardiac output (CO) were measured. Standard parameters (e.g., central venous pressure [CVP]), were also recorded. RESULTS: In the presence of IAH, ITBV and total circulating blood volume were significantly reduced to 55% and 67% of control values. CO decreased to 27% and CVP increased fourfold. CONCLUSION: IAH leads to significant intravascular volume depletion that is not reflected by the CVP. Assessment of CO and ITBV in the presence of a critically increased intra-abdominal pressure is therefore recommended.

Evaluation of two novel methods for the direct and continuous measurement of the intra-abdominal pressure in a porcine model.

OBJECTIVE: Intravesical bladder pressure (IVP) measurement is considered to be the gold standard for the assessment of intra-abdominal pressure (IAP). However, this method is indirect, discontinuous, and potentially infectious and relies on a physiological bladder function. This study evaluated two novel methods for direct, continuous IAP measurement. DESIGN AND SETTING: Experimental study in an animal research laboratory. SUBJECTS: 18 male domestic pigs. INTERVENTIONS: CO(2) was insufflated to increase the IAP to 30 mmHg for 18 and 24 h in six animals each. Another six animals served as controls. A piezoresistive (PRM) and an air-capsule (ACM) pressure measurement probe were placed intra-abdominally and of IAP was measured every 1 h (PRM/ACM) or every 2 h (IVP). The mean difference between insufflator readings and IAP values and limits of agreement (mean difference +/-2 SD) were calculated. MEASUREMENTS AND RESULTS: In the presence of applied pressure IVP and PRM remained significantly below insufflator readings while ACM values showed no difference. Mean difference (and limits of agreement) were 4.5 (-2.1 to 11.1 mmHg), 1.6 (-8.0 to 11.2 mmHg), and 0.5 (-4.5 to 5.4 mmHg) for IVP, PRM, and ACM. The mean measurement-to-measurement drift of the ACM values was 9.0+/-10.2 mmHg. CONCLUSIONS: In this model agreement of PRM and ACM with insufflator readings was comparable to IVP. As both methods may be advantageous regarding continuous straightforward measurement of IAP, the employment in further experimental and clinical investigations is suggested.

A porcine model of the abdominal compartment syndrome.

The purpose of this study was to investigate whether an intra-abdominal pressure (IAP) of 30 mmHg lasting 24 h in a porcine model will lead to a condition comparable with the abdominal compartment syndrome (ACS) in humans. We examined 12 intubated and anesthetized domestic pigs with a mean body weight of 52.5 +/- 4.9 kg. Using a CO2 pneumoperitoneum, the IAP was increased to 30 mmHg (study group, n = 6) for an investigation period of 24 h. In the control group, the IAP remained unchanged. Investigated parameters were cardiac output (CO), peak inspiratory pressure (PIP), urine output (UO), as well as serum alanine aminotransferase (ALT), lactate, lipase, and alkaline phosphatase (AP). Additionally, histopathological examinations were performed. In the study group, CO was significantly reduced compared with the control group. All animals of this group became anuric and their PIP exceeded 40 cm H2O. Furthermore, ALT, AP, lipase, and lactate were significantly increased. Histopathologically, high-grade atelectasis in the lower lobes of the lung together with medium grade liver necrosis, medium grade proximal tubular epithelial necrosis, and medium grade mucosal bowel damage were observed. In this porcine model, an intra-abdominal pressure of 30 mmHg led to a condition comparable with the ACS. Because function or integrity of additional organ systems was impaired, an IAP of 30 mmHg has to be considered a predisposition for the multi-organ dysfunction syndrome in this porcine model.