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Coronary artery surgery
Coronary artery surgery A new technique with use of little blood, if any A simplified method of performing coronary artery surgery without the use of blood is described. Not only is the use of blood substantially decreased by this method (71 per cent of our patients did not require blood), but the time of cardiopulmonary bypass is decreased since the proximal anastomoses are performed before bypass. This method has allowed us to operate upon critically ill patients in congestive failure, with marked left ventricular impairment and an ejection fraction of 0.10 to 0.20 (normal 0.70). The mortality rate in 33 such patients was 9 per cent (three deaths).
Pablo Zubiate, M.D., F.A.C.C., Jerome Harold Kay, M.D., F.A.C.C., A. Michael Mendez, M.D., Bernard G. Krohn, M.D., Richard Hochman, M.D., and Edward F. Dunne, M.D., Los Angeles, Calif.
Aorto-coronary artery bypass surgery with saphenous vein grafts used for revascularization of the myocardium was popularized in 1967. Since the original description of the surgical technique, several papers describing various techniques of the procedure have appeared in the literature. During the past 4~ years, 1,573 patients have been operated upon for the treatment of coronary artery disease at our institution. A modified, uncomplicated technique has been used. The heart-lung machine is primed without the use of blood, and the patient's own fresh blood is used after cardiopulmonary bypass. This procedure made it possible to avoid the use of homologous blood transfusions during or after surgery From the Departments of Thoracic and Cardiovascular Surgery, Medicine, Radiology, and Anesthesiology of the Saint Vincent's Hospital and the University of Southern California School of Medicine, Los Angeles, Calif. Aided by a grant from the Children's Heart Foundation of Southern California and the Los Angeles Thoracic and Cardiovascular Foundation. Received for publication April 12, 1974. Address for reprints: Jerome Harold Kay, M.D., University of Southern California School of Medicine, 2025 Zonal Avenue, Los Angeles, Calif. 90033.
in 71 per cent of the patients undergoing operations for coronary artery disease. Method The heart-lung machine is primed with 1,000 c.c, of Ringer's lactate solution, 300 c.c, of 25 per cent salt-poor albumin, 66.7 mEq. sodium bicarbonate or 250 c.c. trishydroxymethyl-aminomethane, and 20 Gm. of mannitol. Intermittent or continuous anoxic cardiac arrest is employed. Arterial pressure is monitored with an indwelling radial artery catheter, and the central venous pressure is measured with a cannula placed percutaneously into an internal jugular vein. In the critically iII patients, the left atrial pressure is monitored after bypass and in the postoperative period by a catheter inserted into the left atrium. Anesthesia is usually accomplished with the use of sodium methohexital (Brevital sodium), pancuronium bromide (Pavulon), morphine sulphate, and succinylcholine for induction and nitrous oxide and oxygen for the maintenance of the proper anesthesia level. If the patient's hemoglobin level is 11 Gm. or more, the central venous line is connected by a gravity drainage line to
263
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Thoracic and Cardiovascular Surgery
plastic blood bags containing a citrate-phosphate-dextrose (CPD) solution. Usually 1,000 c.c, of blood is withdrawn from the patient. On occasion, 500 to 700 c.c. or 1,200 to 1,500 C.c. is withdrawn. The blood pressure, heart rate, and central venous pressure as well as the electrocardiographic patterns are monitored. The amount of blood withdrawn is replaced volume for volume with Ringer's lactate solution. Patients in congestive heart failure resulting from poor left ventricular function tolerate the withdrawal of blood extremely well, usually without volume replacement. As was anticipated, the lung compliance in these patients improves prior to bypass, and cardiopulmonary bypass is tolerated remarkably well. All surgical procedures are performed through a median sternotomy incision. The saphenous vein for grafting is obtained from the leg and thigh. The vessel is carefully prepared by injection of Ringer's lactate solution or cold 5 per cent glucose in water containing 1,000 units of heparin per 100 c.c, of solution. Upon institution of cardiopulmonary bypass, hemodilution of 40 to 50 per cent occurs. The degree of hemodilution will vary according to the patient's preoperative condition, so that patients in severe left ventricular failure with an increased extravascular water load undergo more profound hemodilution. Total body surface area and duration of cardiopulmonary bypass also influence the degree of dilution. Administration of diuretics, either furosemide (Lasix) or ethacrynic acid (Edecrin) along with mannitol during and after perfusion, return the hemoglobin concentration to approximately 10 Gm. at the end of the operation. Determination of the protein, albumin, and globulin levels in the blood before, during, and after extracorporeal circulation revealed that the variations in total proteins and albumin are minimal. This suggests that the route of mobilization and replenishment into the vascular system is probably through the thoracic duct, as mentioned by Moore.' For the operation, the patient is given 3 mg. of heparin per kilogram of body weight.
The distal portion of the ascending aorta is cannulated to return blood from the oxygenator. A Satinsky clamp is applied tangentially to the ascending aorta to exclude enough of the aorta for performance of the proximal anastomoses. A cervical biopsy punch is used to make 6 mm. openings in the excluded portion of the aorta. Then, 5-0 or 6-0 Prolene is used in a continuous overand-over fashion to create anastomoses at these sites. After all proximal anastomoses are completed, the right atrial appendage is cannulated with a %6 or Y2 inch internal diameter cannula. Blood drains into the oxygenator by gravity through this cannula and tubing. Cardiopulmonary bypass is started. After the heart has emptied itself by contracting several times, it is electrically fibrillated. The heart is more completely emptied manually, and the ascending aorta is cross-clamped just proximal to the site of the aortic cannulation. The Satinsky clamp is then removed. The distal anastomoses of the saphenous vein grafts are then completed with a continuous suture of 6-0 Prolene. Before this suture is pulled taut and tied, the clamp on the aorta is temporarily opened slowly to flush out the air from the vein graft. The cross-clamp on the ascending aorta is not removed until all the anastomoses are completed unless the period of anoxic arrest exceeds 50 minutes. The left internal mammary artery is used for grafting the left anterior descending coronary artery. The anastomosis is performed with a continuous suture of 7-0 Prolene. After the anastomoses are completed and the aortic clamp is removed, the heart fibrillates actively and in many cases starts beating spontaneously. However, electrical defibrillation is required in some patients. Cardiopulmonary bypass can be discontinued almost immediately after the routine suturing of temporary pericardial pacemaker leads to the right ventricular wall. In the immediate postperfusion period, volume replacement is guided by the central venous pressure and by palpation of the pulmonary artery for the pulmonary artery pressure. For the patient with a poorly func-
Volume 68
Coronary artery surgery
Number 2
265
August, 1974
Table I Hospital mortality rate (%)
Ejection fraction
No, of patients
No. of deaths
0.45 to 0.70 0.25 to 0.40 0.10 to 0.20
343 102 33
10
3
8
8
3
9
tioning left ventricle and an ejection fraction of 0.30 or less, the left atrial pressure is measured by insertion of a Swan-Ganz catheter into the left atrium through a small stab wound at the juncture of the right pulmonary vein and the left atrium. The balloon of this catheter is partially inflated with saline, and the catheter is pulled back to secure its position at the level of the balloon so that only the small balloon and the catheter tip remain in the left atrial chamber. The blood from the heart-lung machine is returned slowly via the arterial cannula. The patient is then given protamine sulfate, and his own CPO blood is returned either as the chest is being closed in the operating room or after the patient has arrived in the cardiac surgical care unit. Results
This method of coronary artery surgery with hemodilution has obviated the use of blood in the majority of patients. From Jan. I, 1973, to Jan. I, 1974, 477 patients were operated upon for coronary artery disease by means of this technique. This figure includes all of the patients operated upon for coronary artery disease whether the operation was done on an elective or an emergency basis, e.g., for unstable angina or for complications of acute infarction. The patients ranged in age from 35 to 79 years. They have been divided into three categories: those with an ejection fraction of 0.45 to 0.70, those with a fraction from 0.25 to 0.40, and those with an extremely poor ejection fraction of 0.10 to 0.20. Of these 477 patients, 21 died in the hospital (4 per cent) (Table I). Only 136 (29 per cent) of the 477 patients received blood from the heart-lung
machine, during the operative period, or at any time during hospitalization. A total of 517 units of blood was given to the 136 patients requiring blood. This represents an average of 3.8 units of blood for each patient requiring blood. Discussion
Data from 88 per cent of the institutions in the United States that perform cardiopulmonary bypass surgery were analyzed by Roche and Stengle." An average of nearly 8 units of blood was used per patient in 1971 in this study. The increasing use of saphenous vein bypass surgery will most likely create a larger demand upon the blood resources of this country. With the method of open-heart surgery that we have described, 341 of 477 patients (71 per cent) did not receive blood at any time for coronary artery surgery during the year 1973. These patients did well with the marked hemodilution. Buckley," Laver: Michalski," Hallowell," Hardesty,' and their associates also found that hemodilution is tolerated well. During cardiopulmonary bypass, the hemoglobin may drop to levels as low as 5 Gm., and the hematocrit may drop to a level of 15 per cent. Diuretics given during the open-heart procedure and during chest closure bring the hemoglobin level to around 10 Gm. at the time of chest closure. The blood remaining in the heart-lung machine after bypass is returned to the patient either through the aortic perfusion cannula or through intravenous tubing. Next, the patient's own CPD blood is returned. Within 2 or 3 days after operation, the hemoglobin level rises to 10.5 to II Gm. If volume replacement is required in the immediate postoperative period, 5 per cent albumin is given to patients with a hematocrit level of 22 per cent or more, whereas whole blood is given to those with a hematocrit of less than 22 per cent. Packed red cells are given to correct marked anemia with normovolemia. Hemoglobin levels at the time of discharge from the hospital usually range from 7.5 to 13 Gm. (mean 10.5 Gm.), and hematocrit
The Journal of
266
Zubiate et al.
Thoracic and Cardiovascular Surgery
levels range from 26 to 40 per cent (mean 31 per cent). The preoperative injection of iron dextran (Imferon) as advocated by Newman' has been used in a limited number of patients and would be a valuable addition to this procedure except for the complications with its use. Iron-containing medications such as ferrous sulfate (Feosol) are given orally to these patients in the postoperative period. Profound hemodilution, as used with this technique, did not appear to have a detrimental effect on the acid-base balance or on cardiac function during or after cardiopulmonary bypass. The moderate degree of anemia in the postoperative period was well tolerated by the patients who did not receive any blood transfusions. Using no blood in the majority of patients and using small amounts of blood in the remaining patients should significantly decrease the morbidity and mortality rates from serum hepatitis. An important part of this technique is the use of one large cannula in the right atrium for drainage of blood to the heart-lung machine. The avoidance of vents and suction tips or lines in a cardiotomy reservoir simplifies the procedure. Because little blood, if any, leaves this closed system during bypass, there is little need for suction of blood and therefore less trauma to the blood. The single cannula in the right atrium drains not only the cavae but also the coronary sinus. This drainage is important during the time of cardiopulmonary bypass when the heart is still beating, but it is even more important once the heart is fibrillating and the ascending aorta is no longer cross-clamped. With the heart fibrillating and the aorta not crossclamped, the profuse coronary sinus flow that results could cause marked right and left ventricular distention if not drained off to the heart-lung machine immediately. Left ventricular dilatation produced by return of the bronchial blood flow is avoided by occasionally compressing the heart manually. Since the left ventricle is not vented, some blood may go directly into the aorta proximal to the area of aortic cross-clamping,
with resultant minimal but important perfusion of the coronaries. The coronary artery flow is probably further improved by emptying the cardiac chambers manually after lowering the perfusion pressure in the aorta and reapplying an aortic cross-clamp. This technique provides good exposure of the coronary arteries to be operated upon. The heart is relaxed and the field is dry. For the 5 minutes of bypass after the aortic clamp has been removed and the heart has started beating, it is important to prevent the ventricle from producing a pressure of greater than 100 mm. Hg; the left ventricle will strain against this high a perfusion pressure. Performing the proximal anastomoses to the ascending aorta before initiating cardiopulmonary bypass is advantageous: (I) The vein graft serves as a vent of the left ventricular chamber once the ascending aorta has been cross-clamped; (2) the graft also allows for perfusion of that portion of the coronary artery in which the distal anastomosis is completed while the remaining coronary artery anastomoses are being performed. This is possible since the site of aortic cross-clamping is distal to the sites of the anastomoses of the vein grafts into the ascending aorta. The application of a tangential clamp on the ascending aorta prior to bypass, in order to perform the proximal anastomoses, is well tolerated. Furthermore, doing the proximal anastomoses prior to bypass significantly shortens the cardiopulmonary bypass time. REFERENCES Moore, F. D.: The Effects of Hemorrhage on Body Composition, N. Eng\. J. Med. 273: 567, 1965. 2 Roche, J. K., and Stengle, J. M.: Open-Heart Surgery and the Demand for Blood, J. A. M. A. 225: 1516, 1973. 3 Buckley, M. J., Austen, W. G., Goldblatt, A., and Laver, M. 8.: Severe Hemodilution and Autotransfusion for Surgery of Congenital Heart Disease, Surg, Forum 22: 160, 1971. 4 Laver, M. B., and Buckley, M. J.: Extreme Hemodilution in the Surgical Patient, International Symposium on Hemodilution Rottach-
Volume 68 Number 2
Coronary artery surgery
267
August. 1974
Egern, Germany, 1971, in Messmer, K., editor: Hemodilution: Theoretical Basis and Clinical Application, Basel, 1972, S. Karger AG, pp. 215-221. 5 Michalski, A. H., Lowenstein, E., Austen, W. G., et aI.: Patterns of Oxygenation and Cardiovascular Adjustment of Acute, Transient Normovolemic Anemia, Ann. Surg. 168: 946, 1968. 6 Hallowell, P., Bland, J. H. L., and Buckley, M. J.: Transfusion of Fresh Autologous Blood
in Open-Heart Surgery, A Method for Reducing Bank Blood Requirements, J. THORAC. CARDIOVASCo SURG. 64: 941, 1972. 7 Hardesty, R. L., Bayer, W. L., and Bahnson, H. T.: A Technique for the Use of Autologous Fresh Blood During Open-Heart Surgery, J. THORAC. CARDIOVASC. SURG. 56: 683, 1968. 8 Newman, M. M., Hamstra, R., and Block, M.: Use of Banked Autologous Blood in Elective Surgery, 1. A. M. A. 218: 861, 1971.
Pablo Zubiate, M.D., F.A.C.C., Jerome Harold Kay, M.D., F.A.C.C., A. Michael Mendez, M.D., Bernard G. Krohn, M.D., Richard Hochman, M.D., and Edward F. Dunne, M.D., Los Angeles, Calif.
Aorto-coronary artery bypass surgery with saphenous vein grafts used for revascularization of the myocardium was popularized in 1967. Since the original description of the surgical technique, several papers describing various techniques of the procedure have appeared in the literature. During the past 4~ years, 1,573 patients have been operated upon for the treatment of coronary artery disease at our institution. A modified, uncomplicated technique has been used. The heart-lung machine is primed without the use of blood, and the patient's own fresh blood is used after cardiopulmonary bypass. This procedure made it possible to avoid the use of homologous blood transfusions during or after surgery From the Departments of Thoracic and Cardiovascular Surgery, Medicine, Radiology, and Anesthesiology of the Saint Vincent's Hospital and the University of Southern California School of Medicine, Los Angeles, Calif. Aided by a grant from the Children's Heart Foundation of Southern California and the Los Angeles Thoracic and Cardiovascular Foundation. Received for publication April 12, 1974. Address for reprints: Jerome Harold Kay, M.D., University of Southern California School of Medicine, 2025 Zonal Avenue, Los Angeles, Calif. 90033.
in 71 per cent of the patients undergoing operations for coronary artery disease. Method The heart-lung machine is primed with 1,000 c.c, of Ringer's lactate solution, 300 c.c, of 25 per cent salt-poor albumin, 66.7 mEq. sodium bicarbonate or 250 c.c. trishydroxymethyl-aminomethane, and 20 Gm. of mannitol. Intermittent or continuous anoxic cardiac arrest is employed. Arterial pressure is monitored with an indwelling radial artery catheter, and the central venous pressure is measured with a cannula placed percutaneously into an internal jugular vein. In the critically iII patients, the left atrial pressure is monitored after bypass and in the postoperative period by a catheter inserted into the left atrium. Anesthesia is usually accomplished with the use of sodium methohexital (Brevital sodium), pancuronium bromide (Pavulon), morphine sulphate, and succinylcholine for induction and nitrous oxide and oxygen for the maintenance of the proper anesthesia level. If the patient's hemoglobin level is 11 Gm. or more, the central venous line is connected by a gravity drainage line to
263
The Journol of
264
Zubiate et al.
Thoracic and Cardiovascular Surgery
plastic blood bags containing a citrate-phosphate-dextrose (CPD) solution. Usually 1,000 c.c, of blood is withdrawn from the patient. On occasion, 500 to 700 c.c. or 1,200 to 1,500 C.c. is withdrawn. The blood pressure, heart rate, and central venous pressure as well as the electrocardiographic patterns are monitored. The amount of blood withdrawn is replaced volume for volume with Ringer's lactate solution. Patients in congestive heart failure resulting from poor left ventricular function tolerate the withdrawal of blood extremely well, usually without volume replacement. As was anticipated, the lung compliance in these patients improves prior to bypass, and cardiopulmonary bypass is tolerated remarkably well. All surgical procedures are performed through a median sternotomy incision. The saphenous vein for grafting is obtained from the leg and thigh. The vessel is carefully prepared by injection of Ringer's lactate solution or cold 5 per cent glucose in water containing 1,000 units of heparin per 100 c.c, of solution. Upon institution of cardiopulmonary bypass, hemodilution of 40 to 50 per cent occurs. The degree of hemodilution will vary according to the patient's preoperative condition, so that patients in severe left ventricular failure with an increased extravascular water load undergo more profound hemodilution. Total body surface area and duration of cardiopulmonary bypass also influence the degree of dilution. Administration of diuretics, either furosemide (Lasix) or ethacrynic acid (Edecrin) along with mannitol during and after perfusion, return the hemoglobin concentration to approximately 10 Gm. at the end of the operation. Determination of the protein, albumin, and globulin levels in the blood before, during, and after extracorporeal circulation revealed that the variations in total proteins and albumin are minimal. This suggests that the route of mobilization and replenishment into the vascular system is probably through the thoracic duct, as mentioned by Moore.' For the operation, the patient is given 3 mg. of heparin per kilogram of body weight.
The distal portion of the ascending aorta is cannulated to return blood from the oxygenator. A Satinsky clamp is applied tangentially to the ascending aorta to exclude enough of the aorta for performance of the proximal anastomoses. A cervical biopsy punch is used to make 6 mm. openings in the excluded portion of the aorta. Then, 5-0 or 6-0 Prolene is used in a continuous overand-over fashion to create anastomoses at these sites. After all proximal anastomoses are completed, the right atrial appendage is cannulated with a %6 or Y2 inch internal diameter cannula. Blood drains into the oxygenator by gravity through this cannula and tubing. Cardiopulmonary bypass is started. After the heart has emptied itself by contracting several times, it is electrically fibrillated. The heart is more completely emptied manually, and the ascending aorta is cross-clamped just proximal to the site of the aortic cannulation. The Satinsky clamp is then removed. The distal anastomoses of the saphenous vein grafts are then completed with a continuous suture of 6-0 Prolene. Before this suture is pulled taut and tied, the clamp on the aorta is temporarily opened slowly to flush out the air from the vein graft. The cross-clamp on the ascending aorta is not removed until all the anastomoses are completed unless the period of anoxic arrest exceeds 50 minutes. The left internal mammary artery is used for grafting the left anterior descending coronary artery. The anastomosis is performed with a continuous suture of 7-0 Prolene. After the anastomoses are completed and the aortic clamp is removed, the heart fibrillates actively and in many cases starts beating spontaneously. However, electrical defibrillation is required in some patients. Cardiopulmonary bypass can be discontinued almost immediately after the routine suturing of temporary pericardial pacemaker leads to the right ventricular wall. In the immediate postperfusion period, volume replacement is guided by the central venous pressure and by palpation of the pulmonary artery for the pulmonary artery pressure. For the patient with a poorly func-
Volume 68
Coronary artery surgery
Number 2
265
August, 1974
Table I Hospital mortality rate (%)
Ejection fraction
No, of patients
No. of deaths
0.45 to 0.70 0.25 to 0.40 0.10 to 0.20
343 102 33
10
3
8
8
3
9
tioning left ventricle and an ejection fraction of 0.30 or less, the left atrial pressure is measured by insertion of a Swan-Ganz catheter into the left atrium through a small stab wound at the juncture of the right pulmonary vein and the left atrium. The balloon of this catheter is partially inflated with saline, and the catheter is pulled back to secure its position at the level of the balloon so that only the small balloon and the catheter tip remain in the left atrial chamber. The blood from the heart-lung machine is returned slowly via the arterial cannula. The patient is then given protamine sulfate, and his own CPO blood is returned either as the chest is being closed in the operating room or after the patient has arrived in the cardiac surgical care unit. Results
This method of coronary artery surgery with hemodilution has obviated the use of blood in the majority of patients. From Jan. I, 1973, to Jan. I, 1974, 477 patients were operated upon for coronary artery disease by means of this technique. This figure includes all of the patients operated upon for coronary artery disease whether the operation was done on an elective or an emergency basis, e.g., for unstable angina or for complications of acute infarction. The patients ranged in age from 35 to 79 years. They have been divided into three categories: those with an ejection fraction of 0.45 to 0.70, those with a fraction from 0.25 to 0.40, and those with an extremely poor ejection fraction of 0.10 to 0.20. Of these 477 patients, 21 died in the hospital (4 per cent) (Table I). Only 136 (29 per cent) of the 477 patients received blood from the heart-lung
machine, during the operative period, or at any time during hospitalization. A total of 517 units of blood was given to the 136 patients requiring blood. This represents an average of 3.8 units of blood for each patient requiring blood. Discussion
Data from 88 per cent of the institutions in the United States that perform cardiopulmonary bypass surgery were analyzed by Roche and Stengle." An average of nearly 8 units of blood was used per patient in 1971 in this study. The increasing use of saphenous vein bypass surgery will most likely create a larger demand upon the blood resources of this country. With the method of open-heart surgery that we have described, 341 of 477 patients (71 per cent) did not receive blood at any time for coronary artery surgery during the year 1973. These patients did well with the marked hemodilution. Buckley," Laver: Michalski," Hallowell," Hardesty,' and their associates also found that hemodilution is tolerated well. During cardiopulmonary bypass, the hemoglobin may drop to levels as low as 5 Gm., and the hematocrit may drop to a level of 15 per cent. Diuretics given during the open-heart procedure and during chest closure bring the hemoglobin level to around 10 Gm. at the time of chest closure. The blood remaining in the heart-lung machine after bypass is returned to the patient either through the aortic perfusion cannula or through intravenous tubing. Next, the patient's own CPD blood is returned. Within 2 or 3 days after operation, the hemoglobin level rises to 10.5 to II Gm. If volume replacement is required in the immediate postoperative period, 5 per cent albumin is given to patients with a hematocrit level of 22 per cent or more, whereas whole blood is given to those with a hematocrit of less than 22 per cent. Packed red cells are given to correct marked anemia with normovolemia. Hemoglobin levels at the time of discharge from the hospital usually range from 7.5 to 13 Gm. (mean 10.5 Gm.), and hematocrit
The Journal of
266
Zubiate et al.
Thoracic and Cardiovascular Surgery
levels range from 26 to 40 per cent (mean 31 per cent). The preoperative injection of iron dextran (Imferon) as advocated by Newman' has been used in a limited number of patients and would be a valuable addition to this procedure except for the complications with its use. Iron-containing medications such as ferrous sulfate (Feosol) are given orally to these patients in the postoperative period. Profound hemodilution, as used with this technique, did not appear to have a detrimental effect on the acid-base balance or on cardiac function during or after cardiopulmonary bypass. The moderate degree of anemia in the postoperative period was well tolerated by the patients who did not receive any blood transfusions. Using no blood in the majority of patients and using small amounts of blood in the remaining patients should significantly decrease the morbidity and mortality rates from serum hepatitis. An important part of this technique is the use of one large cannula in the right atrium for drainage of blood to the heart-lung machine. The avoidance of vents and suction tips or lines in a cardiotomy reservoir simplifies the procedure. Because little blood, if any, leaves this closed system during bypass, there is little need for suction of blood and therefore less trauma to the blood. The single cannula in the right atrium drains not only the cavae but also the coronary sinus. This drainage is important during the time of cardiopulmonary bypass when the heart is still beating, but it is even more important once the heart is fibrillating and the ascending aorta is no longer cross-clamped. With the heart fibrillating and the aorta not crossclamped, the profuse coronary sinus flow that results could cause marked right and left ventricular distention if not drained off to the heart-lung machine immediately. Left ventricular dilatation produced by return of the bronchial blood flow is avoided by occasionally compressing the heart manually. Since the left ventricle is not vented, some blood may go directly into the aorta proximal to the area of aortic cross-clamping,
with resultant minimal but important perfusion of the coronaries. The coronary artery flow is probably further improved by emptying the cardiac chambers manually after lowering the perfusion pressure in the aorta and reapplying an aortic cross-clamp. This technique provides good exposure of the coronary arteries to be operated upon. The heart is relaxed and the field is dry. For the 5 minutes of bypass after the aortic clamp has been removed and the heart has started beating, it is important to prevent the ventricle from producing a pressure of greater than 100 mm. Hg; the left ventricle will strain against this high a perfusion pressure. Performing the proximal anastomoses to the ascending aorta before initiating cardiopulmonary bypass is advantageous: (I) The vein graft serves as a vent of the left ventricular chamber once the ascending aorta has been cross-clamped; (2) the graft also allows for perfusion of that portion of the coronary artery in which the distal anastomosis is completed while the remaining coronary artery anastomoses are being performed. This is possible since the site of aortic cross-clamping is distal to the sites of the anastomoses of the vein grafts into the ascending aorta. The application of a tangential clamp on the ascending aorta prior to bypass, in order to perform the proximal anastomoses, is well tolerated. Furthermore, doing the proximal anastomoses prior to bypass significantly shortens the cardiopulmonary bypass time. REFERENCES Moore, F. D.: The Effects of Hemorrhage on Body Composition, N. Eng\. J. Med. 273: 567, 1965. 2 Roche, J. K., and Stengle, J. M.: Open-Heart Surgery and the Demand for Blood, J. A. M. A. 225: 1516, 1973. 3 Buckley, M. J., Austen, W. G., Goldblatt, A., and Laver, M. 8.: Severe Hemodilution and Autotransfusion for Surgery of Congenital Heart Disease, Surg, Forum 22: 160, 1971. 4 Laver, M. B., and Buckley, M. J.: Extreme Hemodilution in the Surgical Patient, International Symposium on Hemodilution Rottach-
Volume 68 Number 2
Coronary artery surgery
267
August. 1974
Egern, Germany, 1971, in Messmer, K., editor: Hemodilution: Theoretical Basis and Clinical Application, Basel, 1972, S. Karger AG, pp. 215-221. 5 Michalski, A. H., Lowenstein, E., Austen, W. G., et aI.: Patterns of Oxygenation and Cardiovascular Adjustment of Acute, Transient Normovolemic Anemia, Ann. Surg. 168: 946, 1968. 6 Hallowell, P., Bland, J. H. L., and Buckley, M. J.: Transfusion of Fresh Autologous Blood
in Open-Heart Surgery, A Method for Reducing Bank Blood Requirements, J. THORAC. CARDIOVASCo SURG. 64: 941, 1972. 7 Hardesty, R. L., Bayer, W. L., and Bahnson, H. T.: A Technique for the Use of Autologous Fresh Blood During Open-Heart Surgery, J. THORAC. CARDIOVASC. SURG. 56: 683, 1968. 8 Newman, M. M., Hamstra, R., and Block, M.: Use of Banked Autologous Blood in Elective Surgery, 1. A. M. A. 218: 861, 1971.