Lawrence C. Siegel

Variability in transfusion practice for coronary artery bypass surgery persists despite national consensus guidelines : A 24-institution study

BACKGROUND An estimated 20% of allogeneic blood transfusions in the United States are associated with cardiac surgery. National consensus guidelines for allogeneic transfusion associated with coronary artery bypass graft (CABG) surgery have existed since the mid- to late 1980s. The appropriateness and uniformity of institutional transfusion practice was questioned in 1991. An assessment of current transfusion practice patterns was warranted. METHODS The Multicenter Study of Perioperative Ischemia database consists of comprehensive information on the course of surgery in 2,417 randomly selected patients undergoing CABG surgery at 24 institutions. A subset of 713 patients expected to be at low risk for transfusion was examined. Allogeneic transfusion was evaluated across institutions. Institution as an independent risk factor for allogeneic transfusion was determined in a multivariable model. RESULTS Significant variability in institutional transfusion practice was observed for allogeneic packed red blood cells (PRBCs) (27-92% of patients transfused) and hemostatic blood components (platelets, 0-36%; fresh frozen plasma, 0-36%; cryoprecipitate, 0-17% of patients transfused). For patients at institutions with liberal rather than conservative transfusion practice, the odds ratio for transfusion of PRBCs was 6.5 (95% confidence interval [CI], 3.8-10.8) and for hemostatic blood components it was 2 (95% CI, 1.2-3.4). Institution was an independent determinant of transfusion risk associated with CABG surgery. CONCLUSIONS Institutions continue to vary significantly in their transfusion practices for CABG surgery. A more rational and conservative approach to transfusion practice at the institutional level is warranted.

Port-access coronary artery bypass grafting: A proposed surgical method

Minimally invasive surgical methods have been developed to provide patients the benefits of open operations with decreased pain and suffering. We have developed a system that allows the performance of cardiopulmonary bypass and myocardial protection with cardioplegic arrest without sternotomy or thoracotomy. In a canine model, we successfully used this system to anastomose the internal thoracic artery to the left anterior descending coronary artery in nine of 10 animals. The left internal thoracic artery was dissected from the chest wall, and the pericardium was opened with the use of thoracoscopic techniques and single lung ventilation. The heart was arrested with a cold blood cardioplegic solution delivered through the central lumen of a balloon occlusion catheter (Endoaortic Clamp; Heartport, Inc., Redwood City, Calif.) in the ascending aorta, and cardiopulmonary bypass was maintained with femorofemoral bypass. An operating microscope modified to allow introduction of the 3.5x magnification objective into the chest was positioned through a 10 mm port over the site of the anastomosis. The anastomosis was performed with modified surgical instruments introduced through additional 5 mm ports. In the cadaver model (n = 7) the internal thoracic artery was harvested and the pericardium opened by means of similar techniques. A precise arteriotomy was made with microvascular thoracoscopic instruments under the modified microscope on four cadavers. In three other cadavers we assessed the exposure provided by a small anterior incision (4 to 6 cm) over the fourth intercostal space. This anterior port can assist in dissection of the distal internal thoracic artery and provides direct access to the left anterior descending, circumflex, and posterior descending arteries. We have demonstrated the potential feasibility of grafting the internal thoracic artery to coronary arteries with the heart arrested and protected, without a major thoracotomy or sternotomy.

Minimally invasive cardiopulmonary bypass with cardioplegic arrest: A closed chest technique with equivalent myocardial protection☆☆☆★★★♢

Thoracoscopic cardiac surgery is presently under intense investigation. This study examined the feasibility and efficacy of closed chest cardiopulmonary bypass and cardioplegic arrest in comparison with standard open chest methods in a dog model. The minimally invasive closed chest group (n = 6) underwent percutaneous cardiopulmonary bypass and cardiac venting, as well as antegrade cardioplegic arrest through use of a specially designed percutaneous endovascular aortic occluder and cardioplegic solution delivery system. The control group (n = 6) underwent standard sternotomy and conventional open chest cardiopulmonary bypass, aortic crossclamping, and antegrade cardioplegia. Ischemic arrest time was 1 hour in each group. Ventricular pressures and sonomicrometer segment lengths were recorded before bypass and at 30 and 60 minutes after bypass. Left ventricular function did not differ significantly between the two groups, as demonstrated by measurements of elastance and end-diastolic stroke work. Also, the preload recruitable work area was 69% and 60% of baseline at 30 and 60 minutes after bypass in the minimally invasive group versus 65% and 62% in the conventional control group (p = not significant); the stroke work end-diastolic length relationship was 78% and 71% of baseline in the minimally invasive group at these intervals versus 77% and 74% in the conventional control group (p = not significant). Myocardial temperatures were similar throughout bypass in the two groups, and ultrastructural examination of prebypass and postbypass biopsy specimens showed no differences between groups. These results demonstrate that minimally invasive cardiopulmonary bypass with cardioplegic arrest is as feasible, safe, and effective as conventional open chest cardiopulmonary bypass. Thus current technology may allow wider clinical application of closed chest cardiac surgery.

Port-access mitral valve replacement in dogs

OBJECTIVE The objective was to assess mitral valve replacement in a minimally invasive fashion by means of port-access technology. METHODS Fifteen dogs, 28 +/- 3 kg (mean +/- standard deviation), were studied with the port-access mitral valve replacement system (Heartport, Inc., Redwood City, Calif.). Eleven dogs underwent acute studies and were sacrificed immediately after the procedure. Four dogs were allowed to recover and then were sacrificed 4 weeks after operation. Cardiopulmonary bypass was conducted by femoral cannulation with an endovascular balloon catheter for aortic occlusion, root venting, and antegrade delivery of cardioplegic solution. Catheters were inserted in the jugular vein for pulmonary artery venting and retrograde delivery of cardioplegic solution. Through the oval port, a prosthesis (St. Jude Medical, Inc., St. Paul, Minn., or CarboMedics, Inc., Austin, Texas) was inserted through the left atrial appendage and secured to the anulus with sutures. Deairing was performed. RESULTS Cardiopulmonary bypass duration was 114 +/- 24 minutes and aortic crossclamp time was 68 +/- 14 minutes. All animals were weaned from cardiopulmonary bypass in sinus rhythm. Cardiac output and pulmonary artery occlusion pressure were unchanged (2.8 +/- 0.7 L/min and 7 +/- 3 mm Hg before operation vs 2.6 +/- 0.6 L/min and 9 +/- 4 mm Hg after operation). There was no mitral regurgitation according to left ventriculography in 13 of 15 dogs. In two dogs there was interference with prosthetic valve closure by residual native anterior leaflet tissue. Pathologic examination otherwise showed normal healing without perivalvular discontinuity. Microscopic studies showed no damage to the valve surfaces. Transthoracic echocardiography of the four dogs in the long-term study showed normal ventricular and prosthetic valve function 4 weeks after the operation. CONCLUSION Mitral valve replacement with a minimally invasive method has been demonstrated in dogs. A clinical trial is in progress.

Port-access coronary artery bypass with cardioplegic arrest: acute and chronic canine studies

BACKGROUND Our goal is to perform minimally invasive coronary artery bypass grafting without sacrificing the benefits of myocardial protection with cardioplegia. METHODS Twenty-three dogs underwent acute studies and 4 dogs underwent survival studies. The left internal mammary artery was taken down using a thoracoscope. Cardiopulmonary bypass was conducted via femoral cannulas and using an endovascular balloon catheter for ascending aortic occlusion, root venting, and delivery of antegrade blood cardioplegia. Pulmonary artery venting was achieved with a jugular vein catheter. An internal mammary artery-to-coronary artery anastomosis was performed using a microscope through a 10 mm port. RESULTS All animals were weaned from cardiopulmonary bypass in sinus rhythm without inotropes. Cardiopulmonary bypass duration was 104 +/- 28 minutes and aortic clamp duration was 61 +/- 22 minutes. Cardiac output and pulmonary artery occlusion pressure were unchanged. The internal mammary artery was anastomosed to the left anterior descending artery (25) or the first diagonal (2) with patency shown in 25 of 27. One dog in the survival study had a very short internal mammary artery pedicle under tension and was euthanized for excessive postoperative hemorrhage. Three weeks postoperatively the remaining dogs had angiographically patent anastomoses, normal transthoracic echocardiograms, and histologically normal healing and patent grafts. CONCLUSIONS Endovascular cardiopulmonary bypass using a balloon catheter is effective in arresting and protecting the heart to allow thoracoscopic internal mammary artery-to-coronary artery anastomosis.

Testing Computer-controlled Infusion Pumps by Simulation

The pharmacokinetic behavior of intravenous anesthetic drugs can be described by two- or three-compartment models. Rapid achievement and maintenance of steady plasma concentrations of these drugs requires a complicated delivery scheme, perhaps best controlled by a computer. The authors developed a method of simulating the performance of a computer-controlled infusion pump from the differential equations describing drug transfer between compartments. They also derived a mathematically simple and flexible approximate solution to these equations using Eulers numerical method. They incorporated this approximate solution into a computer-controlled infusion pump for intravenous drugs. They tested their pump by simulating the administration of fentanyl to a hypothetical patient whose fentanyl pharmacokinetics were described by a three-compartment model. The exact analytical solution served as the standard of comparison. The approximation technique, using a 15-s interval between model updates, had a maximum error of 0.35 ng.ml-1, and rapidly converged on the exact solution. The simulations revealed oscillations in the system. The authors suggest that such simulations be used to evaluate computer-controlled infusion pumps prior to clinical trials of these devices.

Delayed time response of the continuous cardiac output pulmonary artery catheter.

Previous studies of the accuracy of pulmonary artery catheters (PAC) which provide continuous cardiac output (CCO) monitoring have investigated the performance during steady-state conditions. We compared the response time to hemodynamic change using a CCO PAC and an ultrasonic flow probe (UFP). In five sheep, a CCO PAC was inserted, and an UFP for measurement of CCO was placed around the pulmonary artery via a left thoracotomy. Six interventions which rapidly alter cardiac output were studied: crystalloid bolus, balloon inflation in the inferior vena cava (IVC), IVC balloon deflation, dobutamine infusion, hemorrhage, and reinfusion of blood. Cardiac output measured before and after each intervention was used to calculate the total change caused by the intervention, and the time intervals from intervention to 20%, 50%, and 80% of that change were noted. For all interventions, the time response of CCO was significantly slower than UFP. The largest differences were seen with the rapid infusion of lactated Ringers solution for which the time interval for 20% change was 7.3 +/- 2.3 min (mean +/- SD) for CCO versus 0.5 +/- 0.3 min for UFP. The time interval for 80% change was 14.5 +/- 4.1 min for CCO versus 1.8 +/- 0.9 min with UFP. The current study demonstrates clinically important time delays in the response of the CCO catheter. This delay must be considered when rapid alterations of the hemodynamic state may occur. (Anesth Analg 1996;83:1173-77)

Port-access cardiac operations with cardioplegic arrest

BACKGROUND A less invasive approach to cardiac surgery has been propelled by recent advances in video-assisted surgery. Previous obstacles to minimally invasive cardiac operations with cardioplegic arrest included limitations in operative exposure, inadequate perfusion technology, and inability to provide myocardial protection. METHODS Port-access technology allows endovascular aortic occlusion, cardioplegia delivery, and left ventricular decompression. The endoaortic clamp is a triple-lumen catheter with an inflatable balloon at its distal end. Antegrade cardioplegia is delivered through a central lumen, which also acts as an aortic root vent, a second lumen is used as an aortic root pressure monitor, and a third lumen is used for balloon inflation to provide aortic occlusion. RESULTS Experimental and clinical studies have demonstrated the feasibility of port-access coronary artery bypass grafting and port-access mitral valve procedures. Endovascular cardiopulmonary bypass using the endoaortic clamp was effective in achieving cardiac arrest and myocardial protection to allow internal mammary artery to coronary artery anastomosis in a still and bloodless field. Intracardiac procedures, such as mitral valve replacement or repair, have been successfully performed clinically. CONCLUSION The port-access system effectively achieves cardiopulmonary bypass and cardioplegic arrest, thereby enabling the surgeon to perform cardiac procedures in a minimally invasive fashion. This system provides for endovascular aortic occlusion, cardioplegia delivery, and left ventricular decompression.

Predictors of outcome in a multicenter port-access valve registry

BACKGROUND The aim of this study was to examine the predictors of outcome in patients undergoing isolated valve operation using port-access techniques. METHODS Logistic regression analysis was performed in a prospective, multi-institutional registry of patients undergoing isolated aortic valve replacement (AVR, n = 252), mitral repair (MVP, n = 491), or mitral replacement (MVR, n = 568) using port-access techniques from 1997 to 1999. RESULTS Endoaortic balloon occlusion was used in 2% (AVR), 93% (MVP), and 90% (MVR) of cases. Conversion to full sternotomy occurred in 3.8% of all cases. For all patients, early mortality was 50 of 1,311 (3.8%) and onset of new atrial fibrillation occurred in 140 of 1,311 (11%) patients. The determinants of 30-day mortality were redo, age, and MVR or AVR. The determinants of reoperation for bleeding were age, reoperation, and MVR. Age was a predictor for stroke, and age and low or medium volume center were predictors of new atrial fibrillation. CONCLUSIONS Excellent short-term results can be obtained using port-access techniques in isolated mitral or aortic valve operations. Patient outcome is not related to institutional case volume, and the primary determinants of outcome after port-access valve procedures are generally patient-related factors.

Institutional variability in red blood cell conservation practices for coronary artery bypass graft surgery

OBJECTIVE To assess whether substantial institutional variability exists in red blood cell conservation practices associated with coronary artery bypass graft (CABG) surgery. DESIGN Prospective, randomized patient enrollment and data collection. SETTING Twenty-four U.S. academic institutions participating in the Multicenter Study of Perioperative Ischemia. PARTICIPANTS A well-defined subset of primary CABG surgery patients (n = 713) expected to be at low risk for bleeding and exposure to allogeneic transfusion. INTERVENTIONS None (observational study). MEASUREMENTS AND MAIN RESULTS Frequency of use of red blood cell conservation techniques was determined among institutions. Correlation was determined between use of each technique and transfusion of allogeneic red blood cells and between use of each technique and median institutional blood loss. Significant variability (p < 0.01) was detected in institutional transfusion practice with respect to the use of predonated autologous whole blood, normovolemic hemodilution, red cell salvage, and reinfusion of shed mediastinal blood. The frequency of institutional use of these techniques was not associated with allogeneic transfusion (r2 < 0.15) or blood loss (r2 < 0.10) in the low-risk population of patients examined. CONCLUSIONS Institutions vary significantly in perioperative blood conservation practices for CABG surgery. Further study to determine the appropriate use of these techniques is warranted.