A maximal central venous oxygen saturation (SvO2max) for the surgical patient.

Before induction of anaesthesia, 23 patients scheduled for major abdominal surgery had blood samples drawn from a central venous catheter for oxygen saturation (SvO2) after graded infusion of isotonic saline. The infusion of saline was continued until further administration resulted in a stable SvO2 (SvO2max). The SvO2 increased from 69 (53-83) to 72 (66-83) % (median and range; P < 0.0001), when the patients received 10 (0-26) mL.kg-1, average 500 mL, of saline. At the same time central venous haematocrit decreased from 38 (32-47) to 36 (23-47) % which suggests that the intravascular volume was expanded by 420 (180-3070) mL or by 72 (18-174) % of the administered volume. The results demonstrate that volume expansion by saline can establish a maximal venous oxygen saturation in the surgical patient.