Effects of volume therapy on splanchnic perfusion and myocardial oxygenation after cardiac surgery

Aims: The present study was designed to analyse the effects of two fluid strategies on splanchnic perfusion and myocardial oxygenation after cardiac surgery.

Methods: 20 patients were studied and were stratified retrospectively by the median of the amount of postoperative volume replacement. Group low-volume received less than 1850mL fluid therapy, group high-volume received more than 1850mL during the first 10 hours of intensive care treatment. Fluid therapy was guided by filling pressures. Each patient was equipped with a nasogastric tube for tonometric determination of gastric pCO₂, a fiberoptic pulmonary artery catheter and a polarographic intramyocardial oxygen catheter.

Results: Haemodynamics were not different between groups upon ICU-admission. In group low-volume stroke volume index and cardiac index increased continuously throughout the study, while in group high-volume an increase was only observed during the first 5 hours. The arterial to gastric difference of CO₂ and filling pressures showed no between group differences. Myocardial oxygenation showed a steady increase in group low-volume from 29mmHg (22/33) (Median (25%/75%)) upon admittance to the ICU to 41mmHg (27/58) 10 hours later (p<0.001), whereas there was no increase in group high volume (p=0.406) with lower myocardial pO₂-values (22mmHg (19/36) admittance to the ICU; 32mmHg (21/41) 10 hours later). Ventilation was prolonged in group high-volume.

Conclusion: This suggest that fluid loading without a beneficial effect on haemodynamics may not only be ineffective in improving splanchnic perfusion but may have detrimental effects on myocardial oxygenation and pulmonary function. Fluid therapy should be titrated according to individual physiological responses.