[A relationship between plasma ANP concentration and hemodynamics during PEEP--evaluation by transesophageal ECHO...

This study was undertaken to find which cardiac function indices as judged by transesophageal ECHO cardiography (TEE) would accurately predict the plasma ANP levels during PEEP. Fourteen patients who underwent orthopedic surgery were the subjects of the study. PEEP 10 cmH2O or 15 cmH2O was added with a PEEP valve during mechanical ventilation under general anesthesia. The cardiac function indices were measured using a 5 MHz TEE probe and plasma ANP levels were evaluated by radioimmunoassay. There were significant reductions in the left atrial diameter, cardiac output and pulmonary venous flow during PEEP, while A/R and CVP were significantly increased. The plasma ANP concentration decreased significantly from 39.2 +/- 4.8 pg.ml-1 at pre PEEP period to 26.8 +/- 3.1 pg.ml-1 at PEEP 15 cmH2O (mean +/- SE, P less than 0.05). However, we could not find any significant correlation between the cardiac function indices and ANP levels. The secretion of ANP from the heart is regulated mainly by stretch tension of the atrium. PEEP increases the pericardial pressure. Therefore, it seems to be difficult to predict the stretch tension of the atrium using TEE under PEEP.