Pressure gradient across the pulmonary artery anastomosis during lung transplantation.

BACKGROUND: Perioperative monitoring of pulmonary artery (PA) pressures in lung transplant recipients is critical. This report characterizes an intraoperative gradient across the PA anastomosis in a series of patients undergoing bilateral sequential lung transplantation. METHODS: Hemodynamic measurements were obtained in a series of 10 patients before anesthetic induction, during one-lung ventilation/perfusion of the newly transplanted first lung with the PA catheter proximal and distal to the anastomosis and after arrival in the intensive care unit. The following measurements were recorded: central venous pressure, cardiac output, PA occlusion pressure, and systemic and pulmonary arterial pressures (systolic, diastolic, mean). RESULTS: Although a systolic pressure gradient of more than 10 mm Hg across the anastomosis was observed in all patients, there was a significant variation in systolic (13 to 59 mm Hg), diastolic (2 to 10 mm Hg), and mean (5 to 27 mm Hg) PA gradients. Mean proximal systolic PA pressure measurements (56.2 +/- 20.6 mm Hg) were greater when compared to measurements obtained distal to the anastomosis (28.6 +/- 10.1 mm Hg, p = 0.001) and to those obtained in the postoperative period (32.1 +/- 9.7 mm Hg, p = 0.004). CONCLUSIONS: The present study demonstrates that during single-lung ventilation and perfusion, the PA pressure measured proximally may not reflect accurately the pressure distal to the vascular anastomosis.

Predictors, frequency, and indications for cardiopulmonary bypass during lung transplantation in adults.

The records for 162 lung transplantations performed in 158 patients were reviewed with regard to the predictors for, frequency of, and indications for using cardiopulmonary bypass during the procedure. There were a total of 8 en bloc double-lung transplantations, 83 single-lung transplantations, and 71 bilateral single-lung transplantations. Bypass was used electively for all double en bloc and three of the bilateral sequential lung transplantation procedures and for 26 unilateral lung replacement procedures in patients with pulmonary hypertension. Of the remaining patients, 1 single-lung transplant recipient required bypass for correction of a surgical mishap and 18 bilateral single-lung recipients required bypass during replacement of the second lung. No preoperative predictors for the need of bypass could be identified. Among the bilateral sequential lung recipients, the use of bypass did not seem to adversely affect outcome, as expressed in terms of the time until extubation, the time spent in the intensive care unit, and the time required to reach a room air oxygen tension greater than 60 mm Hg.

Use of a Doppler pulmonary artery catheter for continuous measurement of right ventricular pump function and contractility during single lung transplantation.

Despite numerous technologic advances in intraoperative monitoring, the only methods routinely available for assessment of right ventricular function in lung transplant recipients are continuous measurement of right heart pressures and intermittent thermodilution determination of cardiac output and ejection fraction. Additional data may now be obtained with transesophageal echocardiography, although this technology is expensive and not widely available and requires diverting attention from a potentially unstable patient for data acquisition and analysis. Recently, a Doppler pulmonary artery catheter was introduced that measures beat-to-beat pulmonary artery blood flow-velocity, cross sectional area, and volume flow. Because of data indicating that acceleration of blood in the pulmonary artery (measured as the first derivative of either the velocity or flow waveform) is a sensitive indicator of right ventricular contractility, we have used waveforms obtained with the catheter for assessment of right ventricular pump function (stroke volume and peak pulmonary artery flow rate) and contractility in heart surgery patients. We report here our experience with this method in two patients undergoing left single lung transplantation.

Comparison of cardiac output measured by intrapulmonary artery Doppler, thermodilution, and electromagnetometry.

A Doppler pulmonary artery catheter system (Doppler cardiac output monitor or DOPCOM) that continuously measures instantaneous and mean cardiac output was recently introduced. Because thermodilution (TD) flow measurements may not represent an adequate standard, the present study was designed to compare TD and DOPCOM cardiac output measurements with aortic electromagnetic (EM) flow in cardiac surgical patients. Twenty-one patients scheduled for elective coronary artery bypass grafting were enrolled in the study. Simultaneous measurement of cardiac output by all three methods was performed before cardiopulmonary bypass, after cardiopulmonary bypass with the aorta cannulated and volume intermittently infused, and after decannulation. Analysis of all data demonstrated fair TD and EM correlation (r = 0.80), with minimal bias (0.03 +/- 1.21 L/min) and a median absolute error of 0.53 L/min; DOPCOM and EM data showed moderate correlation (r = 0.64), a bias of -0.61 +/- 1.50 L/min, and a median absolute error the same as TD (0.51 L/min). However, distribution of DOPCOM values was heavily skewed by 3 patients in whom flow measurements immediately after cardiopulmonary bypass were markedly different between the DOPCOM and electromagnetometry, probably because of malposition of the Doppler transducers secondary to partial catheter withdrawal during bypass. Consistent with this theory was the finding that before CPB, the DOPCOM was significantly better than TD in predicting EM flow (median absolute error: DOPCOM, 0.12 L/min, and TD, 0.48 L/min; p = 0.04). Our data suggest that, in general, the DOPCOM shows similar precision to TD for predicting EM flow measurements, although the DOPCOM may underestimate actual flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Perioperative evaluation of a new mixed venous oxygen saturation catheter in cardiac surgical patients.

Fiberoptic pulmonary artery flotation catheters have gained clinical acceptance for continuous monitoring of mixed venous oxygen saturation (SvO2), especially in the management of hemodynamically unstable patients. Therefore, the performance of the oximetry system used is extremely important. The accuracy and stability of a new two-wavelength oximetry pulmonary artery catheter and SAT-2 oximeter were assessed in adult patients during and following cardiac surgery. After in vitro calibration of the system, the catheter was inserted through the right internal jugular vein and positioned in the pulmonary artery prior to induction of anesthesia. During the study period, the system was updated for hemoglobin changes of 1.8 g/dL or more. In vivo SvO2 values obtained by the oximetry catheter were compared with those determined with a reference oximeter from simultaneously drawn mixed venous blood specimens at different intervals. A total of 604 paired data points from 52 patients were analyzed, 572 (94.7%) of which were within the 95% confidence interval. Overall bias was -1.7% +/- 3.5% (SD). The results suggest that over the time course of the study, in vivo SvO2 values obtained with the two-wavelength catheter and the SAT-2 oximeter closely approximated SvO2 measured with a reference oximeter from mixed venous blood samples (r = 0.917; SEE 3.5%) in cardiac surgical patients in whom marked physiological changes occur.

Inaccuracy of cardiac output by thermodilution during acute tricuspid regurgitation.

We have been comparing cardiac output measured with a novel Doppler pulmonary artery catheter to that measured by thermodilution and aortic electromagnetometry in cardiac surgical patients. We report here our observation of a nearly twofold increase in thermodilution cardiac output after the acute intraoperative onset of tricuspid regurgitation that was not confirmed by the novel catheter or direct measurement of aortic blood flow. We conclude that in some patients, acute tricuspid regurgitation may lessen the reliability of thermodilution cardiac output.