Cold blood cardioplegia

Current Techniques

Cold blood cardioplegia The technique of myocardial protection by means of a cardioplegic solution consisting of cold blood C.) with potassium (30 mEq. per liter) is described. A disposable cooling coil is used and a separate pump head for coronary perfusion is avoided. The aortic perfusion cannula can be used for venting of the left ventricle and subsequently for venting of air. This method was used in 125 consecutive patients undergoing coronary revascularization and in 73 consecutive pediatric cardiac surgical procedures with excellent results. (/00

Hillel Laks, M.D., New Haven, Conn., Hendrick B. Barner, M.D., and George Kaiser, M.D., St. Louis, Mo.

WeI have previously reported on the use of a cooling coil for selective hypothermic perfusion of the aortic root or coronary arteries. Although good results were obtained in patients with intermittent cold coronary perfusion, laboratory studies in dogs showed that intermittent root perfusion with cold cardioplegic solution provided better protection than intermittent cold coronary perfusion with blood." We 3 have subsequently shown in dogs subjected to 2 hours of aortic crossclamping that the protection provided by intermittent cardioplegia with cold blood to which only potassium is added (30 mEq. per liter) is equal to that provided by intermittent cardioplegia with the more complex asanguineous solution." The preoperative preparation of a complex solution is avoided, and the method of administration is simple, as will be described. In addition, between the administrations of cardioplegic solution, the aortic root cannula decompresses the left ventricle and subsequently acts as a vent for air. From the Department of Surgery, Yale University School of Medicine, New Haven, Conn., and SI. Louis University School of Medicine, SI. Louis, Mo.

Technique To provide cold blood, we devised a readily available, disposable heat exchanger, shown in Fig. I. A Y connector is inserted into the arterial line. This carries blood into a heat exchanging coil, * which is immersed in a small basin of slush that is kept at the foot of the field. A No. 14 plastic can nulat with a small piece of plastic tubing impaled I em. from the tip (Fig. I) is inserted through a purse-string suture into the ascending aorta and secured. The segment of plastic tubing assists in securing the cannula at the desired depth. If an intracardiac procedure is performed and venting of air is inportant, an air-venting needle:j: is used both to administer cardioplegic solution and subsequently to vent air. When the systemic perfusate temperature reaches 28° c., the blood is drawn through the cooling coil into a 50 m!. syringe containing 1.5 mEq. of potassium chloride (30 mEq. per liter). The cold blood at a temperature of 10° C. is then injected into the root of the aorta. The contents of the cardioplegic solution, thus made up, depend partly on the pump prime. With the prime currently used (1,300 m!. of lactated Ringer's

Received for publication July 18, 1978. Accepted for publication Oct. 31, 1978.

*Travenol 2C 2410, Travenol Laboratories, Inc., Mansfield, Mass.

Address for reprints: Hillel Laks, M.D., Yale University School of Medicine, Department of Cardiothoracic Surgery, 333 Cedar St., New Haven, Conn. 06510.

tArgyle, Division of Sherwood Medical, SI. Louis, Mo., or Jelco, Hartford, Conn. *Sarns, Inc., No. 10550, Ann Arbor, Mich.

0022-5223179/020319+04$00.40/0 © 1979 The C. V. Mosby Co.

319

The Journal of Thoracic and Cardiovascular Surgery

320 Laks, Barner, Kaiser

Fig. 1. The circuit used for cold blood potassium (CBK) cardioplegia is shown. A Y connector from the arterial line is connected to the disposable cooling coil, which is immersed in a basin of iced slush. A 50 ml. syringe containing 1.5 mEg. of potassiumchloride is used to draw up the cold blood, which is then infused into the aortic root cannula or into coronary perfusion cannulas placed in the coronary ostia.

solution, 425 ml. of 20 percent mannitol, 50 mEq. of sodium bicarbonate), the solution shown in Table I is obtained after going on bypass. Systemic hypothermia of 25° to 28° C. is achieved and maintained. Sterile crushed ice made from lactated Ringer's solution is applied to the heart with each infusion of cold blood and potassium (CBK) and may be renewed more frequently if desired. In procedures in which an incision is made in the ascending aorta, the coronary cannulas can be attached to the cold perfusion line and used for the instillation of CBK into the coronary ostia. The contents of six to eight syringes (300 to 400 ml.) are infused initially and then 200 ml. is given every 20 to 30 minutes. In the presence of significant aortic regurgitation, CBK can be infused into the aortic root while the heart is being massaged, or the coronary ostia can be cannulated directly. During coronary revascularization the cardioplegic solution is given after the completion of each distal anastomosis. Between infusions the aortic root cannula is attached to a gravity drainage line and gives excellent left ventricular decompression. After com-

pletion of the distal anastomosis, the cross-clamp is released and the proximal anastomoses are completed during rewarming. In pediatric cardiac surgical procedures, an airventing needle* is used for the administration of CBK. After release of the cross-clamp the vent is attached to a gravity drainage line for venting of air. Approximately 50 ml. is given for every 5 kilograms of body weight, and infusion is repeated every 20 to 30 minutes. The chemically-induced cardioplegia is combined with profound systemic hypothermia (20° C. tympanic membrane temperature) and with very low flows or intermittent periods of total circulatory arrest. More complicated procedures can thus be completed without the time limitation previously imposed by total circulatory arrest while still providing a quiet bloodless field.

Clinical results This method of CBK cardioplegia has been used in 125 consecutive adults undergoing coronary artery *Sarns, Inc., No. 10550, Ann Arbor, Mich.

Volume 77

Cold blood cardioplegia

Number 2

32 1

February, 1979

bypass. Aortic cross-clamp time ranged from 48 to 121 minutes (mean 83 ± 3.1). There were one hospital death, no instances of intra-aortic balloon assist, and five instances in which inotropic drugs were needed for discontinuation of cardiopulmonary bypass. Peri operative infarction was definite in three cases (2.4 percent) and possible in three cases (2.4 percent) according to electrocardiographic and enzyme criteria (isoenzymes of creatine phosphokinase and lactic dehydrogenase on postoperative days I, 2, and 3). In children, this method has been used in 73 consecutive corrective cardiac surgical procedures utilizing cardiopulmonary bypass. These include 22 ventricular septal defect repairs, eight tetralogy of Fallot repairs, five redo tetralogy repairs, six Mustard procedures, six right ventricle-pulmonary artery conduit insertions, two complete atrioventricular canal repairs, one Fontan procedure, and 23 miscellaneous corrective procedures. There have been two deaths in this series, one related to bleeding and one to pulmonary complications. Inotropic drugs were required in five patients for a low output state.

Discussion Intermittent chemically-induced cardioplegia has been shown experimentally to provide excellent myocardial protection for 2 hours in the dog." 4 It provides a quiet, bloodless field and a relaxed heart. Previously described cardioplegic solutions have included numerous components intended to aid the ischemic heart." In the clinical setting, however, preparation of such solutions is both expensive and time consuming. The cardioplegic solution has previously been delivered either with a separate pump head and heat exchanger or by compression of a plastic bag containing cold cardioplegic solution." A possible criticism of blood cardioplegia versus the use of an asanguineous solution is the presence of aggregates or rouleau formations in the cold blood. We have studied our solution at 5° C. as constituted in the operating room. We have found no red cell aggregates or rouleau formations, and the indirect Coombs' test has been negative. It is possible that our use of moderate hemodilution on cardiopulmonary bypass and the addition of mannitol to the pump prime may prevent this problem. Our experimental studies of myocardial protection using intermittently administered cold blood demonstrated that it was less effective than the intermittently administered cardioplegic solution for prolonged aortic cross-clamping." We 3 have subsequently shown that

Table I. Contents of "cold blood cardioplegia" solution drawn up into a 50 mI. syringe containing 1.5 mEq. of potassium chloride Glucose Sodium Potassium Chloride Bicarbonate Total calcium Ionized calcium

400 mg.ldl. 122 mEq.lL. 28 mEq.lL. 104 mEq.lL. 23 mEq.lL. 10.2 mg.ldl.

pH

4.87 mg./dl. 7.54

Po" Osmolarity Total protein Albumin

1.7

250 mm. Hg. 366 mOsm./Kg. 2.8 Gm./dl.

Gm.ldl.

Legend: The pump prime in this case consisted of 1,300 ml. of lactated Ringer's solution in 59< dextrose, 425 ml. of 20 percent mannitol, and 50 mEq. of sodium bicarbonate.

there is no difference in the protection afforded by CBK (30 mEq. per liter), as compared to the more complex asanguineous solutions previously described, for 2 hours of aortic cross-clamping in the dog. The amount of oxygen required by the cold arrested heart is 0.3 ml. per 100 grams of myocardium." The intermittent administration of CBK both maintains the chemical cardioplegia and hypothermia and also provides the small amount of oxygen and substrates required at this temperature, This method of providing the cardioplegic solution on the field is a simple one and avoids the preparation of a separate pump head and heat exchanger. Use of an aortic needle to decompress the left ventricle has been previously described. 7 The needle in the aorta used for the administration of CBK is attached to a gravity drainage line and gives excellent decompression of the left ventricle between each infusion of cardioplegic solution. An aortic air vent may be used for the administration of blood cardioplegic and is then attached to a gravity line for venting of air. CBK has also been used successfully in pediatric cardiac surgery. Its use with profound hypothermia and low pump flows gives a quiet bloodless field without the time constraints previously imposed by total circulatory arrest. Clinical experience has thus confirmed the excellent protection provided by CBK, The simple cooling coil allows for the administration of an easily prepared cardioplegic solution, and the aortic needle provides left ventricular decompression and venting of air. The studies of blood cardioplegia for red cell aggregates, rouleau formations , and the indirect Coombs' test were per-

322

Laks, Barner, Kaiser

formed by Dr. Joseph Bove, Director of the Yale-New Haven Hospital blood bank. We express our thanks to the perfusionists, Pat Brueggeman, St. Louis University, William B. Shaffer, Jr., Dorothy Farrell, Susan Iverson, and Judy Gatehouse, Yale University, for their assistance in developing this method of administering blood cardioplegia. REFERENCES Laks H, Barner HB, Kaiser GC: A simple method of cold coronary perfusion. Ann Thorac Surg 25:351-353, 1978 2 Laks H, Barner HB, Hahn JW, Standeven JW, Jellinek M, Menz LJ: Myocardial protection with intermittent coronary perfusion using cold blood versus a cardioplegic solution. Surg Forum 28:231-234, 1977 :::I Barner HB, Laks H, Codd JW, Standeven JW, Jellinek M, Kaiser GC, Menz LJ, Tyras DH, Pennington DG, Hahn JW, Willman VL: Cold blood as the vehicle for potassium cardioplegia (submitted for publication)

The Journal of Thoracic and Cardiovascular Surgery

4 Nelson RL, Fey KH, Follette DM, Livesay 11, Deland EC, Maloney JV Jr, Buckberg GD: Intermittent infusion of cardioplegic solution during aortic cross clamping. Surg Forum 27:241-243, 1976 5 Fisk RL, Gelfand ET, Callaghan JC: Hypothermic coronary perfusion for intraoperative cardioplegia. Ann Thorac Surg 23:58-61, 1977 6 Buckberg GD, Brazier JR, Nelson RL, Goldstein SM, McConnell DH, Cooper N: Studies of the effects of hypothermia on regional myocardial blood flow and metabolism during cardiopulmonary bypass in the adequately perfused beating, fibrillating, and arrested heart. J THORAC CARDIOVASC SURG 73:87-94, 1977 7 Harlan BJ, Kyger ER, Reul GJ Jr, Cooley DA: Needle suction of the aorta for left heart decompression during aortic cross-clamping. Ann Thorac Surg 23:259-260, 1977