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Hypoxemia during cardiopulmonary bypass
336
Ann Thorac Surg 1990;5033&7
CORRESPONDENCE
this level with judicious use of both crystalloids and vasopressors. Diabetes insipidus is usually managed with vasopressin. As our experience with organ procurement has grown, we have modified donor selection criteria to reflect variables identified to have significant impact on recipient survival. Our most recent change involves antibiotic prophylaxis to the donor and recipient following our discovery of the importance of donor mouth flora in the development of early thoracic infection after transplantation [l].To further modify ventilator and fluid management of potential donors without sufficient proof is not practical given the varied nature and location of the hospitals providing donors for our pulmonary transplant program.
Bartley P. Grifith Division of Cardiothoracic Surgery University of Pittsburgh Pittsburgh, PA 15261
We emphasize that interruption of the gas supply from whatever cause will allow liquid into the gas compartment and may cause rapid failure of bubble oxygenators.
Philip Belcher, M B , BS, FRCS Robin ]ones Department of Cardiothoracic Surgery and HeartlLung Department Brompton Hospital Fulham Rd London SW3 6HP England
Reference 1. Robblee JA, Crosby E, Keon WJ. Hypoxemia after intraluminal oxygen line obstruction during cardiopulmonary bypass. Ann Thorac Surg 1989;48:575-6.
Reference 1. Zenati M, Dowling RD, Dummer JS, et al. Influence of the donor lung on the development of early infections in lung transplant recipients. J Heart Transplant (in press).
Hypoxemia During Cardiopulmonary Bypass To the Editor: We agree that hard data on oxygenator problems and accidents are scarce and a database should be set up. However, the following points should be noted regarding the report by Robblee and associates [l].In general, if gas flow becomes interrupted, diverted, or reduced below a minimum then whatever fluid is present immediately above the gas disparger plate will enter the gas compartment by gravity. Once there, any liquid or solid phase material will affect predictability and stability of gas exchange. Manufacturers recommend continuous running of gas at approximately 1 to 1.5 L/min to prevent this occurring. If ingress occurs before bypass, clear liquids may be blown through with high gas flows; if this is not 100% effective the oxygenator must be changed. We consider the likely cause of the problem to have been interruption of the gas flow after the first bypass. It is a useful safety measure to maintain gas flow until the circuit is dismantled. When the manufacturers’ recommendations have been flouted, it is meaningless to blame the mannitol even if conditions are recreated experimentally. We encountered a somewhat different problem during a routine coronary artery operation. Shortly after completion of the first distal anastomosis an audible hissing developed. Arterial oxygen tension was then 29.4 kPa. Connections were checked but the hiss continued and arterial return blood darkened visibly. Within 8 minutes the oxygenator (William Harvey H 1700) had stopped bubbling. The patient by this point had been reventilated and bypass was stopped easily at 35°C with a systolic blood pressure of 95 to 100 mm Hg and no inotropes. The oxygenator was changed, the operation completed, and the patient extubated at the end of the procedure. There was no neurological deficit. Careful inspection revealed a circumferential crack in the Luer fitting on the gas line that had allowed blood to enter the gas compartment. We consider it fortunate that the operation was being carried out at near normothermia using an intermittent fibrillation technique; this allowed quick recovery and easy cessation of bypass.
Inadequate Flow of the Internal Mammary Artery: Another Complication of Sternal Overretraction To the Editor: The internal mammary artery is universally accepted as the conduit of choice for patients undergoing coronary artery bypass grafting. The use of the left internal mammary artery (LIMA) is recommended in almost all patients. The LIMA is harvested in the standard fashion by completely mobilizing the pedicle up to the subclavian vein and dividing all the branches. Flow is usually checked immediately after mobilization to decide if the LIMA is to be used as a pedicle or as a free graft. We recently encountered a patient who had excellent flow of his LIMA after mobilization. The mammary artery was prepared and put in a papaverine sponge to be used later. After two distal vein graft anastomoses, the LIMA to left anterior descending coronary artery anastomosis was performed. Just before the completion of the anastomosis the bulldog clamp was released and no mammary artery flow was observed. The vessel was gently probed past the clamp site without evidence of spasm, obstruction, or dissection and without obtaining any blood flow. We therefore decided to use the LIMA as a free graft. The artery was cut proximally and saline solution was instilled in the antegrade fashion without a problem. Of note is that the proximal cut end of the LIMA still did not bleed. After completion of the aortic anastomosis the cross-clamp was released. Normal sinus rythm was restored spontaneously and the patient was weaned from cardiopulmonary bypass. On closing the retractor massive bleeding was noted from the proximal cut end of the LIMA, which was then ligated. We concluded that the interruption of blood flow from the LIMA was caused by overretraction of the sternum. This must have caused stretching and kinking of the LIMA at its origin from the subclavian artery. In retrospect the retractor was opened further at the time of the distal anastomosis and after flow through the LIMA was already checked. Reported complications of overretraction of the sternum include avulsion of the innominate vein, stretching of the brachial plexus, and increased pulmonary inflation pressures. The purpose of this letter is to increase awareness of another possible complication of sternal overretraction, ie, interruption of LIMA flow. It seems logical that excessive retraction of the sternum may also decrease the flow in the LIMA. Consequently when LIMA
Ann Thorac Surg 1990;5033&7
CORRESPONDENCE
this level with judicious use of both crystalloids and vasopressors. Diabetes insipidus is usually managed with vasopressin. As our experience with organ procurement has grown, we have modified donor selection criteria to reflect variables identified to have significant impact on recipient survival. Our most recent change involves antibiotic prophylaxis to the donor and recipient following our discovery of the importance of donor mouth flora in the development of early thoracic infection after transplantation [l].To further modify ventilator and fluid management of potential donors without sufficient proof is not practical given the varied nature and location of the hospitals providing donors for our pulmonary transplant program.
Bartley P. Grifith Division of Cardiothoracic Surgery University of Pittsburgh Pittsburgh, PA 15261
We emphasize that interruption of the gas supply from whatever cause will allow liquid into the gas compartment and may cause rapid failure of bubble oxygenators.
Philip Belcher, M B , BS, FRCS Robin ]ones Department of Cardiothoracic Surgery and HeartlLung Department Brompton Hospital Fulham Rd London SW3 6HP England
Reference 1. Robblee JA, Crosby E, Keon WJ. Hypoxemia after intraluminal oxygen line obstruction during cardiopulmonary bypass. Ann Thorac Surg 1989;48:575-6.
Reference 1. Zenati M, Dowling RD, Dummer JS, et al. Influence of the donor lung on the development of early infections in lung transplant recipients. J Heart Transplant (in press).
Hypoxemia During Cardiopulmonary Bypass To the Editor: We agree that hard data on oxygenator problems and accidents are scarce and a database should be set up. However, the following points should be noted regarding the report by Robblee and associates [l].In general, if gas flow becomes interrupted, diverted, or reduced below a minimum then whatever fluid is present immediately above the gas disparger plate will enter the gas compartment by gravity. Once there, any liquid or solid phase material will affect predictability and stability of gas exchange. Manufacturers recommend continuous running of gas at approximately 1 to 1.5 L/min to prevent this occurring. If ingress occurs before bypass, clear liquids may be blown through with high gas flows; if this is not 100% effective the oxygenator must be changed. We consider the likely cause of the problem to have been interruption of the gas flow after the first bypass. It is a useful safety measure to maintain gas flow until the circuit is dismantled. When the manufacturers’ recommendations have been flouted, it is meaningless to blame the mannitol even if conditions are recreated experimentally. We encountered a somewhat different problem during a routine coronary artery operation. Shortly after completion of the first distal anastomosis an audible hissing developed. Arterial oxygen tension was then 29.4 kPa. Connections were checked but the hiss continued and arterial return blood darkened visibly. Within 8 minutes the oxygenator (William Harvey H 1700) had stopped bubbling. The patient by this point had been reventilated and bypass was stopped easily at 35°C with a systolic blood pressure of 95 to 100 mm Hg and no inotropes. The oxygenator was changed, the operation completed, and the patient extubated at the end of the procedure. There was no neurological deficit. Careful inspection revealed a circumferential crack in the Luer fitting on the gas line that had allowed blood to enter the gas compartment. We consider it fortunate that the operation was being carried out at near normothermia using an intermittent fibrillation technique; this allowed quick recovery and easy cessation of bypass.
Inadequate Flow of the Internal Mammary Artery: Another Complication of Sternal Overretraction To the Editor: The internal mammary artery is universally accepted as the conduit of choice for patients undergoing coronary artery bypass grafting. The use of the left internal mammary artery (LIMA) is recommended in almost all patients. The LIMA is harvested in the standard fashion by completely mobilizing the pedicle up to the subclavian vein and dividing all the branches. Flow is usually checked immediately after mobilization to decide if the LIMA is to be used as a pedicle or as a free graft. We recently encountered a patient who had excellent flow of his LIMA after mobilization. The mammary artery was prepared and put in a papaverine sponge to be used later. After two distal vein graft anastomoses, the LIMA to left anterior descending coronary artery anastomosis was performed. Just before the completion of the anastomosis the bulldog clamp was released and no mammary artery flow was observed. The vessel was gently probed past the clamp site without evidence of spasm, obstruction, or dissection and without obtaining any blood flow. We therefore decided to use the LIMA as a free graft. The artery was cut proximally and saline solution was instilled in the antegrade fashion without a problem. Of note is that the proximal cut end of the LIMA still did not bleed. After completion of the aortic anastomosis the cross-clamp was released. Normal sinus rythm was restored spontaneously and the patient was weaned from cardiopulmonary bypass. On closing the retractor massive bleeding was noted from the proximal cut end of the LIMA, which was then ligated. We concluded that the interruption of blood flow from the LIMA was caused by overretraction of the sternum. This must have caused stretching and kinking of the LIMA at its origin from the subclavian artery. In retrospect the retractor was opened further at the time of the distal anastomosis and after flow through the LIMA was already checked. Reported complications of overretraction of the sternum include avulsion of the innominate vein, stretching of the brachial plexus, and increased pulmonary inflation pressures. The purpose of this letter is to increase awareness of another possible complication of sternal overretraction, ie, interruption of LIMA flow. It seems logical that excessive retraction of the sternum may also decrease the flow in the LIMA. Consequently when LIMA