OBJECTIVETo assess the possibility of using arterial pressure waveform or pulse oximetry plethysmographic waveform variation to estimate the pulmonary arterial wedge pressure (PAWP).

METHODSFourteen American Society of Anesthesiologists grade I - II patients aged 33 - 69 years and weighing 62.0 +/- 9.5 kg scheduled for elective abdominal tumor surgery were studied. Their hemoglobin exceeded 120 g/L and hematocrit exceeded 35 percent. Pre-operative acute hypervolemic hemodilution was applied immediately after general anesthestic induction and tracheal intubation. PAWP, systolic pressure variation (SPV), delta down (dDown), SPV(plet), dDown(plet) and other hemodynamic parameters were measured and recorded when total fluid volume (crystalloid and colloid) infused reached 10 ml/kg and 20 ml/kg and again at the end of the operation. Central venous pressure was maintained at 10 - 12 mm Hg during operation. Systolic blood pressure at the end of Valsalva maneuver (airway pressure was kept at 22 mm Hg) and the systolic pressure before the Valsalva manoeuvre during apnea were used to calculate arterial pressure ratio (APR).

RESULTSAPR, SPV, dDown, SPV(plet) and dDown(plet) all correlated well with PAWP (r = 0.717, -0.695, -0.680, -0.522 and -0.624 respectively, P < 0.01). There was a closer linear correlation between APR and PAWP than between the other parameters. The regression equation was PAWP (mm Hg) = 0.207 x APR (%) - 0.382.

CONCLUSIONDuring positive pressure mechanical ventilation, APR, SPV, dDown, SPV(plet) and dDown(plet) can be used to estimate PAWP effectively.