Infusion of small volumes of hypertonic saline solution (HS) seems to be of benefit in patients with impaired perfusion. The cardiorespiratory response to a 7.2% NaCl solution prepared in hydroxyethylstarch (HES) solution was investigated prospectively in patients undergoing prolonged cardiopulmonary bypass (CPB) (HS-HES group; n = 15); 6% HES 200/0.5 solution was infused in a control group (HES group; n = 15). Volume was given preoperatively to double low pulmonary artery occlusion pressure (less than 4 mm Hg) within 20 minutes. Hemodynamics, oxygen transport variables, and pulmonary gas exchange were studied before and after infusion as well as before and after CPB. Significantly less HS-HES solution (3.06 +/- 0.2 mL/kg) than 6% HES 200/0.5 solution (10.3 +/- 0.9 mL/kg) was necessary to double baseline pulmonary artery occlusion pressure. Fluid balance during CPB was negative in the HS-HES patients (-0.05 mL/kg.min CPB) and was lowest in this group even 5 hours after CPB. Mean arterial pressure, pulmonary arterial pressure, and heart rate were without differences between the groups. Changes in cardiac index (+40%) and total systemic resistance (-25%) were significantly most pronounced in the HS-HES patients, continuing even until the end of operation. Pulmonary gas exchange (arterial oxygen tension, intrapulmonary right-to-left shunting) was least compromised in these patients, particularly after bypass. Oxygen consumption was without difference between the groups; oxygen delivery increased significantly more in the HS-HES patients due to the larger increase in cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)