Monitoring preload during liver transplantation

Abstract

Liver transplantation is associated with major shifts incentral blood volume; therefore, monitoring preload is es-sential. Filling pressures (central venous pressure or pul-monary artery occlusion pressure) do not reflect preload[right ventricular end-diastolic volume (RVEDV) or leftventricular end-diastolic volume (LVEDV)] well becausethese pressures are affected not just by preload but alsoby changes in compliance of the heart. These compliancechanges can be quite significant because of the changesin chest volume that are the result of surgical retractionand variable pressure on the diaphragm. Then, what arethe alternative methods of preload monitoring in the op-erating room? There are only two: thermodilution deter-mination of RVEDV and transesophageal echocardio-graphic estimation of RVEDV and LVEDV. Each of thesetechniques has advantages and disadvantages.The clinical determination of the right ventricularejection fraction (RVEF) and RVEDV became possible inthe early 1980s when American Edwards Laboratoriesmarketed a pulmonary artery catheter with a fast-re-sponse thermistor and an accompanying computer.That technology was based on intermittent injection ofa cold solution as a dye, and the principle of conserva-tion of energy allowed the calculation of RVEF and rightventricular volumes.