Charles G. Pond

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.

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.

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 myocardial ischemia : its relation to anatomic pattern of coronary artery stenosis

Background:Recently, the frequency of intraoperative myocardial ischemic episodes in patients with steal-prone coronary anatomy, compared with other groups of patients undergoing coronary artery surgery (CABG), has been characterized. Because the relationship between anatomic distribution of coronary stenosis and myocardial ischemic episodes over the entire perioperative period has not been well defined, the authors sought to examine this relationship in 100 adult patients undergoing CABG surgery. Methods:Continuous electrocardiographic (ECG) monitoring was performed in the pre-, intra-, and postoperative periods, quantifying the frequency (episodes/hour of monitoring [epis/h]) and duration (minutes/hour of monitoring [min/h]) of ECG ischemic episodes defined as a reversible ST segment shift ≥ 1 mm at J + 60 ms of ≥ 1 min duration. Based on preoperative coronary angiography, patients were categorized into the following groups: group 1 (n = 40), steal-prone coronary anatomy (occluded major coronary artery and ≥ 50% stenosis of the artery supplying the collateral vessels); group 2 (n = 17), left main or equivalent coronary stenosis (≥ 50% stenosis of left main coronary artery ≥ 70% proximal stenosis of the left anterior descending and circumflex coronary arteries); and group 3 (n = 43), coronary artery stenosis ≥ 70% not fitting the preceding categories. Results:Compared with group 3, patients in group 1 had more frequent and longer ECG ischemlc events preoperatively, and were nearly two times more likely (relative risk 1.82, 95% confidence interval 1.07–3.10) to develop an ischemic event during this period. There were no differences in the relative risk, frequency, or duration of an ischemic episode between groups 1 and 3 during the intraoperative and postoperative periods, or between groups 1 and 2 or groups 2 and 3 during any perioperative period. In group 2 patients, the frequency of ischemic epis/h was less intra- compared with preoperatively, while, in group 3, the ischemic epis/h decreased postoperatively compared with the intraoperative period. The duration of ischemic episodes (min/h) in group 3, however, increased postoperatively compared with the pre- and intraoperative periods, while, in group 2, the duration of ischemic episodes (min/h) was less intraoperatively compared with the preoperative period. Ninety-seven percent of preoperative ECG ischemic episodes occurred without symptoms. Postoperative myocardial infarction occurred in three patients in group 3, two in group 2, and one in group 1. There were no perioperative deaths. Conclusion:These data indicate that, compared with patients with non-left main or equivalent coronary stenosis, those with steal-prone coronary anatomy have more frequent and longer ECG ischemic episodes preoperatively. The data also indicate that there are no other differences in the risk, frequency, or duration of ischemic episodes between groups perioperatively. Thus, different distributions of coronary artery stenosis may be associated with changes in the perioperative characteristics of ECG ischemic episodes.

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.