الفهرس 
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Abstract
Background: Left atrial pressure and its surrogate, pulmonary capillary wedge pressure (PCWP) are important for determining diastolic function. The role of transthoracic echocardiography (TTE) in assessing diastolic function is well established in awake subjects. Current guidelines recommend assessment of left ventricular diastolic function with transthoracic echocardiography (TTE) in awake, spontaneously breathing patients utilizing two-dimensional, spectral and tissue Doppler and color M-mode techniques (Paulus et al., 2007& Nagueh et al., 2009). There are few data, however, investigating the reliability of these measurements for diastolic assessment under general anaesthesia, or with the use of transoesophageal echocardiography (TOE). This is most likely due to the inherent difficulties to measure of left atrial filling pressures during cardiac surgery, either directly or indirectly using pulmonary capillary wedge pressure (PCWP) as a surrogate pressure. We have designed two studies to investigate the application of echocardiography in estimation PCWP in anaesthetized and mechanically ventilated patients during cardiac surgery.
The objective of the retrospective study was to identify whether pulmonary capillary wedge pressure can be estimated in anaesthetized patients receiving mechanical ventilation, using transoesophageal echocardiography. A retrospective validation study investigated a 10-patient cohort with variable haemodynamic conditions, and a 102-patient series in which a single measurement was made during stable haemodynamic conditions. Concurrent echocardiographic Doppler and pulmonary artery catheter wedge pressure measurements were performed. In the 10-patient cohort, the systolic fraction of Doppler measurements in the pulmonary vein (r = - 0.32, p = 0.035) and the E ⁄ A ratio (r = 0.56, p = 0.0009) were correlated with the wedge pressure. In all cases, the limits of agreement exceeded 10 mmHg, and sensitivity or specificity for detecting wedge pressure 15 mmHg was poor. This study demonstrates proof of concept that using transoesophageal echocardiography for estimating the pulmonary artery wedge pressure may not be sufficiently accurate for clinical use.
The objective of the prospective study was to assess the accuracy of predicting PCWP by TTE and transoesophageal echocardiography (TEE) during coronary artery surgery. Methods: In 27 adult patients undergoing on-pump coronary artery surgery, simultaneous echocardiographic and hemodynamic measurements were obtained immediately before anesthesia (TTE), after anesthesia and mechanical ventilation (TTE and TEE), during conduit harvest (TEE), and after separation from cardiopulmonary bypass (TEE). Results: Twenty patients had an ejection fraction (EF) of 0.5 or greater. With the exception of E/e′ and S/D ratios, echocardiographic values changed over the echocardiographic studies. In patients with low EF, E velocity, deceleration time, pulmonary vein D, S/D, and E/e′ ratios correlated well with PCWP before anesthesia. After induction of anesthesia using TTE or TEE, correlations were poor. In normal EF patients, correlations were poor for both TEE and TTE at all five stages. The sensitivity and specificity of echocardiographic values were not high enough to predict raised PCWP except for a fixed curve pattern of interatrial septum (area under the curve 0.89 for PCWP ≥17, and 0.98 for ≥18 mmHg) and S/D less than 1 (area under the curve 0.74 for PCWP ≥17, and 0.78 for ≥18 mmHg). Conclusion: Doppler assessment of PCWP was neither sensitive nor specific enough to be clinically useful in anesthetized patients with mechanical ventilation. The fixed curve pattern of the interatrial septum was the best predictor of raised PCWP.