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Abstract
To determine whether mixed venous blood gas sampling obtained by pulmonary artery catheter (PAC) is influenced by the speed of withdrawal.
Prospective, observational study.
Surgical intensive care unit at a university hospital.
Twenty-five patients in the early postoperative period of cardiac surgery.
After verification of the adequate position of the PAC, measurements of mixed venous blood gas oxygen saturation, oxygen partial pressure (PO(2)), carbon dioxide partial pressure (PCO(2)), pH and bicarbonates were obtained at two different rates of withdrawal. A slow sampling was taken at a mean speed of 3 ml/min and a fast sampling at 18 ml/min for each patient. The mean difference in venous oxygen saturation between slow and fast samplings was -0.18+/-1.3%, venous PO(2): -0.2+/-1.3 mmHg, venous PCO(2): 0.1+/-0.9 mmHg, venous pH: 0+/-0.03, venous bicarbonates: 0.03+/-0.5 mmol/l.
Using the Bland & Altman method, we showed a satisfactory agreement between slow and fast mixed venous blood gas sampling techniques when measuring PO(2), oxygen saturation, PCO(2), pH and bicarbonates though a PAC.