A Comparison of Systolic Blood Pressure Variations and Echocardiographic Estimates of End-Diastolic Left Ventricular Size in Patients After Aortic Surgery

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As suggested by experimental studies, systolic pressure variation (SPV), the difference between maximum and minimum values of systolic blood pressure after a single positive pressure breath, may be a fair indicator of left ventricular preload. SPV was quantified in 21 patients who had undergone abdominal aortic surgery and were sedated under mechanical ventilation. The aim of the study was to assess the ability of this parameter to qualitatively estimate left ventricular preload measured using transesophageal echocardiography. All patients had preoperative radionuclide ejection fraction >45%. Postoperative mechanical ventilatory patterns were the same for all patients: tidal volume = 10 mL/kg; respiratory frequency = 12–14 breathsimin; and zero end-expiratory pressure mode. Left ventricular dimensions at end-diastole correlated well with the magnitude of both SPV (r = 0.80) and its delta down (dDown) component (i.e., the degree by which systolic pressure decreases with each mechanical breath) (r = 0.83). Once the first measurement was completed, volume loading with two increments of 250 mL of human albumin 5% was performed in all but three patients. Each volume loading step caused a significant increase in the end-diastolic area (EDa) index (7.0 ± 1.6 to 8.5 ± 1.6 cm2/m2) and cardiac index (CI) (3.1 ± 0.9 to 4.1 ± 0.9 L.min−1·m−2) and a concomitant significant decrease in the SPV (8.6 ± 4.5 to 6.1 ± 3.7 mm Hg) and its dDown component (5.9 ± 4.1 to 2.9 ± 2 mm Hg). The initial (preinfusion) dDown values showed a significant linear correlation to the increase in EDa (r = 0.63) and CI (r = 0.55) in response to the infusion of 500 mL of colloid solution. Thus the higher the initial dDown, the greater was the change in EDa and CI after volume loading. These findings confirm the results of animal studies that demonstrate the usefulness of SPV to estimate left ventricular filling. They suggest that, in mechanically ventilated patients after vascular noncardiac surgery, pressure waveform analysis is a simple means of cardiovascular assessment that provides reliable information concerning preload estimation and the response to left ventricular volume loading.

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