Static and dynamic components of esophageal and central venous pressure during intra-abdominal hypertension.

OBJECTIVE: To investigate the effects of intra-abdominal hypertension on esophageal and central venous pressure considering values obtained at end-expiration (i.e., in static conditions) and during tidal volume delivery (i.e., in dynamic conditions).
DESIGN: Retrospective (pigs) and prospective, randomized, controlled (rats) trial.
SETTING: Animal laboratory of a university hospital.
SUBJECTS: Six female pigs and 15 Sprague Dawley male rats.
INTERVENTIONS: During anesthesia and paralysis, animals' abdomens were inflated with helium.
MEASUREMENTS AND MAIN RESULTS: Abdominal pressure was measured by intraperitoneal catheter. In pigs, esophageal pressure and central venous pressure were continuously measured while inflating the abdomen together with hemodynamic assessment. In rats, the abdomen was inflated after the random application of three levels of positive end-expiratory pressure. Data are shown as mean +/- SD. At end-expiration, esophageal pressures were similar before and after abdominal inflation (p = .177). In contrast, the dynamic component significantly rose after intra-abdominal hypertension, from 3.2 +/- 0.7 cm H2O to 10.0 +/- 2.3 cm H2O (p < .001), and was correlated with peritoneal pressure (linear regression, R2 = .708, p < .001). Positive end-expiratory pressure significantly influenced static esophageal pressure during intra-abdominal hypertension (p = .002) but not dynamic pressures. Static central venous pressure rose with intra-abdominal hypertension from 4.1 +/- 1.5 cm H2O to 6.7 +/- 1.8 cm H2O (p = .043), more so the dynamic component (from 2.9 +/- 0.8 cm H2O to 9.3 +/- 3.1 cm H2O, p = .02). Dynamic changes of esophageal pressures correlated with dynamic changes of central venous pressure (linear regression, R2 = .679, p < .001). Mean values of central venous pressure significantly increased with intra-abdominal hypertension from 7.7 +/- 1.5 cm H2O to 12.7 +/- 2.6 cm H2O (p = .006), whereas transmural central venous pressure and intrathoracic blood volume did not change significantly.
CONCLUSIONS: Dynamic changes of esophageal pressure occurred during intra-abdominal hypertension, whereas end-expiratory pressure was affected by high positive end-expiratory pressure levels. Provided that central venous pressure changes reflect esophageal pressure, central venous pressure itself cannot be relied on to guide resuscitation in patients with intra-abdominal hypertension, particularly when abdominal pressures are changing over short periods of time.