Estimation of Cardiac Preload Changes by Systolic Pressure Variation in Pigs Undergoing Pneumoperitoneum

Background: Variations in systolic pressure arterial waveform (SPV) and its component have been shown to be a reasonable indicator of left ventricular preload. Creation of a pneumoperitoneum (PMOP) by insufflation of CO2 increases intrathoracic pressure, leading to overestimation of preload as assessed by pressure methods. The purpose of this study was to compare SPV with other standard methods in anaesthetized pigs.

Methods: We measured SPV and its DeltaDown component (deltaDown), pulmonary artery occlusion pressure (PAOP) and left ventricular short-axis cross-sectional area using transthoracic echocardiography (TTE) in 7 pigs, at baseline, after 12 mmHg PMOP and after an intravascular load with 10 ml/kg hydroxylethylstarch (HES).

Results: PMOP increased SPV from 12.9+/-4.9 to 16.9+/-5.5 mmHg (P<0.05) and decreased pulmonary compliance, with no change in PAOP or end-diastolic area assesssed by TTE. Intravascular volume loading significantly decreased SPV from 16.9+/-5.5 to 11.2+/-4.9 mmHg and deltaDown from 9.9+/-7.1 to 5.2+/-4.5 (P<0.05), and increased PAOP and end-diastolic area. Significant correlation between changes in deltaDown and EDA was noted following HES (r=0.78, P<0.05).

Conclusion: In anaesthetized pigs, the creation of a PMOP alters SPV, likely by decreasing lung compliance. Once PMOP is established, changes in cardiac preload could be estimated by SPV analysis.