Continuous Warm Blood Cardioplegia

ARTICLE BY NANNEllE HAGES, CST, AND A. KARlM JABR, CCP

he goal in cardiac desired coolness of temperature has li~ation,'~and tissue oxygen procedures is to been reached, the surgical proce- uptake,16as well as on pH17 and have a safe operat- dure is performed. osmotic homeo~tasis.'~Since current ing time while rnini- Whether the procedure is coro- hypothermic techniques involve mizing the ischemic nary bypass or valve replace- ischemic arrest, the has to be L period that causes ment, it is necessary to infuse more reperfused following the procedure. damage to the 6eart. Different meth- cardioplegia solution and pour This can lead to "reperfusion ods and combinations of arrest and slush about every 10 minutes. This injury."19 myocardial protection are currently intermittent cold blood cardioplegia has become safer being used throughout the country. provides a state of hypothermic due to many improvements in sur- The heart can be arrested electro- ischemic arrest. gical techniques, technol- mechanically, chemically, or physi- Hypotherrnia is used to prolong ogy, and cardiac anesthesia. How- cally. This article will introduce STs the safe period of ischemic arrest ever, the major advancement over to a new method using warm blood during cardiac surgery by reducing the past 15years has been in the cardioplegia. the heart's oxygen demands. Due to field of myocardial protection. A this effect, hypothermia has been new method of myocardial protec- Hypothermic Blood Cardioplegia the fundamental component of tion based on the concept of "warm The most common method of most methods of myocardial pro- aerobic arrest" has recently been myocardial protection is hypother- tection. However, hypothermia has described.1° mia. When a number of side effects including Both animal and human data is initiated, the heart becomes its detrimental effects on enzyme show that electromechanical work is empty. Placing a clamp across the function, energy generation, and the major determinant of myocar- ascending , an infusion of cold cell membranes. dial oxygen cons~mption.~~~~~There- (5°C) cardioplegia (mixture of blood The precise composition of the fore, if the heart is kept electro- and chemicals) is used to arrest the optimal cardioplegia solution mechanically arrested and continu- heart. This is also used as an energy remains somewhat controversial.' ously perfused with warm blood (ie, source. The cardioplegia solution is However, it is widely acknowl- aerobic arrest), then the need for used to put the heart in a kind of edged that hypothermia, hypothermia is questionable. "suspended animation," allowing introduced into clinical medicine in This new approach being used surgical procedures to be performed the early 1950s: is the single most durirlg open heart surgery to aid in while the muscle is not working. important component of myocar- myocardial protection is known as At this point in the procedure, a dial protecti~n.~-~This approach is warm continuous blood cardiople- phrenic insulating pad may be based on a large amount of data gia, normothermia, or aerobic arrest. placed behind the heart to protect indicating that myocardial This method is successfully the phrenic nerve from damage, and hypothermia significantly dimin- achieved by using an antegrade car- an ice "slush or ice cold saline fluid ishes cardiac metaboli~m.~'~Hence, dioplegia cannula as well as a retro- is poured onto the heart. A metal during ischemic cardiac arrest (ie, grade cardioplegia cannula. needle tip probe may be inserted anaerobic arrest), oxygen consump- into the myocardium to monitor tion is decreased and postoperative Technique of Warm Blood Cardio- temperature. Also, the systemic cardiac impairment should be kept plegia temperature of the patient may drift to a minimum. After routine prep and draping of to 32°C or may be actively cooled to Despite these benefits, hypother- the patient, an incision is made from 30°C. mia has several major disadvan- the sternal notch to xiphoid and a When the heart is completely tages such as its effects on enzyme median sternotomy is carried out. still, optimal amounts of cardiople- function," membrane stability,12cal- After placement of the chest retrac- gia have been infused, and the cium seq~estration,'~glucose uti- tor, the is opened and li~ation,'~ATP generation and uti- suspended with stay sutures. The surgeon asks the anesthesiol- mL of high potassium blood cardio- bypass procedures. ogist to begin heparinization at this plegia (containing the mixture pre- Using the retrograde cardiople- time. The is cannu- viously described) given antegrade gia reverses the circulation in the lated as well as the right (the through the aortic root. Then at the heart, providing a continuous flow superior and inferior vena cava are sterile field, the perfusion is of blood in the . Since the cannulated at this time for mitral switched to retrograde and the flow of blood is now from the ). Full cardiopul- remaining 500 mL is given while to the arteries, the blood cardiople- monary bypass is initiated. With the venting the aortic root. The perfu- gia has nowhere to drain. An aortic heart empty and beating, a cardio- sionists will then switch to low vent site is helpful at this time. The plegia cannula is introduced to the potassium blood cardioplegia and vent is turned on to prevent the root of the aorta and secured with a perfuse retrograde continuously heart from becoming distended as stay suture and tourniquet. The during the case at a rate of 100 well as to help with visualization. cross clamp is applied and blood mL/min. This technique can be This can be awkward at times, and cardioplegia is infused into the aorta used for all valve and coronary blood in the visual field is frustrat- (Figure 1). Cardiac arrest is invari- ably achieved within 1minute of infusion of cardioplegia solution. Oxygenated blood is mixed in a 4:l ratio with a Frems' cardioplegic solution (Frems' solution consists of 1,000 mL of dextrose in water, 100 Eq KC1,18 mEq Mg SO,, 12 mEq tromethamine, and 20 mL of CPD solution; osmolality=425mOsm/L; pH=7.95), resulting in a high potas- sium blood cardioplegia mixture. The mixture is administered at 300 mL/min for a total of 1 L, and then switched to low potassium blood cardioplegia delivered at 100 mL/min. The blood cardioplegia is delivered continuously. The low potassium blood cardioplegia (con- sists of 1,000 mL of d5w, 25 mEq KGL, 18 Eq Mg SO,, 12 mEq THAM, and 20 mL of CPD solution) is per- fused throughout the procedure unless some electrical activity is noted, which necessitates the tem- porary return to the high potassium cardioplegic solution.

Retrograde Technique When the retrograde cardioplegia technique is used, a retrograde can- nula is inserted through the right atrium, into the coronary sinus, and held secure with a pursestring suture and lightly clinched down with a tourniquet (Figure 2). The coronary sinus lies posterior, between the left atrium and the left , left of the atrioventricular groove (A-V groove) into which the cardiac veins enter. The right extremity of the coronary sinus turns forward and upward to enter the right atrium (Figure 3). The can- nula is inserted prior to the initia- Figure 1. Retrograde cardioplegia cannula system to deliver normothermic continuous tion of cardiopulmonary bypass." antegrade/retrograde cardioplegia. (Photo courtesy of Research Medical, Inc., Cardiac arrest is achieved with 500 Midvale, Utah.)

THE SURGICAL T blood cardioplegia. The low potas- sium blood cardioplegia is infused continuously for all valvular proce- dures, and the pressure, measured at the cardioplegia delivery system, must not exceed 130 mm Hg. Dur- ing coronary surgery, when cardio- plegia is flowing only down saphe- nous grafts, less than 100 mL/min ox cardioplegia is occasion- ally delivered down the vein grafts to avoid exceeding the ~ressure limit. The primary scrub person's full attention is now essential for the entire time the cross clamp is on. Particularly close attention must be paid to the operative field. The car- dioplegia is run continuously (there is no "down" time) between distal anastomoses. The surgeon will not stop to infuse the heart with cardio- plegia or add slush; the procedure continues rapidly. It is necessary to aid in the visualization as well as to prevent the chest from overflowing since fluid may build up from copi- ous irrigation or the flow may drain into the chest. The surgical team must be alert to pressure changes in the retrograde pressure monitor line. Pressure changes indicate car- dioplegia flow in the coronary sinus may be obstructed. The cannula may be pressing against the wall of the coronary sinus, the stay sutures around the cannula may be too Figure 2. Retrograde cardioplegia cannula with balloon. (Photo courtesy of tight, or the cannula may be falling Research Medical, Inc., Midvale, Utah.) out of the coronary sinus. It may be necessary to readjust the placement of the retrograde cannula.

ing. These problems can be easily The surgical technologist must be Complications overcome if the team members work ready to assist in providing Available literature suggests that together and communicate well adequate visualization during distal continuous warm blood cardiople- with one another. anastomoses. gia may have lower complication Visualization is a problem. In coronary artery bypass rates than continuous cold cardio- Among the techniques for allowing surgery, the distal anastomoses are plegia. Studies have shown the the surgeon improved visualization fashioned first according to the operative mortality is also lower in is for the scrub person to apply a severity of the disease. The low warm blood cardioplegia, although constant stream of warm saline, potassium cardioplegia is perfused this may not be statistically signifi- "warm squirt," while the surgeon is down each graft after completion of cant because of the small numbers sewing distally. Another successful anastomoses through a multiport involved in the studies." technique is to gently "blow" the cardioplegia delivery set. In the study by Lichtenstein et blood away. By connecting the suc- This technique can be easily al.,23patients undergoing coronary tion tubing to a CO, tank with a adapted for use during valvular artery bypass surgery using contin- micro filter, cool air is emitted. A surgery. In patients having an aorto- uous cold blood cardioplegia were third technique includes using a tomy (aortic valve), the coronary compared with a group receiving small vessel occluder inserted into sinus is perfused continuously continuous warm blood cardiople- the vessel to help occlude the flow. throughout the procedure. During gia. There was no significant differ- If all else fails, the flow may be mitral valve surgery, the aortic root ence in mortality between the interrupted for up to 10 minutes. is perfused continuously with warm

THE SURGICAL TECHNOLOGIST (Marshall)

Figure 3. Heart drawn out of pericardial sac. (Adapted from Netter FH.22) groups (cold 2.1% versus warm gia has two major components: con- success with this technique lies in 1.1%), but there were significant tinuous blood cardioplegia and nor- good communication skills among decreases in the usage of the intra- mothermic (warm) perfusion. Each the perfusionists, surgical technolo- aortic balloon myocardial of these components has been used gists, surgeon, and any other mem- infarction, strokes, and re-operation individually in cardiac s~rgery,2',~~ bers of the operating room team. for bleeding when the two but they had not been used The perfusionist must pay close approaches were compared by chi- together. It is this combination that attention to the pressure of the ret- squared analysi~.~Theseimproved makes the technique so effective rograde cannula and communicate clinical results were observed since continuous cardioplegia, when an increase or decrease in the moni- despite an increase in cross clamp- performed under hypothermic con- tor line. The surgical technologist ing time, but most importantly, ditions, has a number of disadvan- may need to remind the team to nearly 100% of the patients returned tages, as does normothermia when turn on the vent during retrograde to normal sinus rhythm without applied in an ischemic, contracting, and to turn it off during antegrade defibrillation. or fibrillating myocardium. If perfusion, as well as pay extremely While the present technique can electromechanical arrest can be close attention to the operative field at times be cumbersome (blood in achieved chemically as first during distals. Of course the the operative field is troublesome, suggested by Melr~se;~and if surgeon will communicate his/her particularly during coronary artery can be eliminated bv, con- frustration to all members of the bypass surgery), this is a relatively tinuous perfusion with blood, the surgical team if bloody flow makes minor problem to overcome given need for hypothermia becomes it impossible to see. the potential advantage of greatly questionable. prolonged operative time that is This new techniaue for delivervI' Summary possible with good myocardial of continuous, normothermic blood The mainstay of myocardial protec- preservation." Furthermore, similar cardioplegia is relatively easy to tion at the present time is hypother- technical problems have been over- perform, safe, and effective. It repre- mia. The initial goal of hypothermia come by surgeons using intermittent sents a new approach to the prob- was cerebral protection, but it ischemic or fibrillatory lem of maintaining myocardial pro- became the single most important tection during cardiac surgery and factor of myocardial protection. The Advantages of Continuous Warm should benefit patients with poor concept of hypothermia has been Blood Cardioplegia ventricular function. ingrained in the modern approaches Continuous warm blood cardiople- The secret to achieving optimal to heart surgery, but two of the

THE SURGICAL TECHNOLOGIST JUNE 1993 major effects of hypothermia have ment of heart disease. Circulation. 1978; FF, eds. Summit, NJ: CIBA Pharmaceu- been ignored: many changes may 57,58 (Suppl II):113-114. tical Company. 1973; 5:7. 7. Hearse PJ, Brainbridge MV, Jynge P. 23. Lichtenstein SV, Ashe K, El-Dalati H, occur on a cellular level that could Protection of the ischemic myocardium: Panos A, Slutsky AS. Warm heart result in significant cell damage, cardioplegia. New York: Raven Press. surgery. ]Thorac Cardiovasc Surg. 1989; and hypothermia itself does not 1981. ,submitted for publication. lead to a decrease in myocardial 8. Bigelow WG, Lindsay WK, Harrison 24. Lichtenstein SV, El-Dalati H, Panos A, oxygen consumption. The major RC, Gorden RA, Greenwood WF. Oxy- Slutsky AS. Long cross-clamp time with determinant of myocardial oxygen gen transport and utilization in dogs at warm heart surgery. Lancet. 1989; is electromechanical work-a beat- low body temperature. Am ]Physiol. 1(8652):1443. 1950; 160:125-130. 25. Olinger GN, Maloney PJ, Mulder JV, ing heart. Diminished myocardial 9. Reissman KR, Van Citters RL. Oxygen Buckberg GD. Coronary revasculariza- oxygen with hypothermia is actu- consumption and mechanical efficiency tion in "high versus "low-risk" ally due to a decrease in heart rate. of the hypothermic heart. ]Appl Physiol. patients. Ann Surg. 1985; 182293-301. Hypothermia is used to prolong 1956; 9:427-432. 26. Akins CW. Noncardioplegic myocar- safe periods of ischemic arrest. Sur- 10. Lee JC. Effect of hypothermia on dial preservation for coronary revascu- myocardial metabolism. Am ]Physiol. larization. ] Thorac Cardiovasc Surg. prisingly, hypothermia actually 1965; 208:1253-1258. 1984; 88:174-181. increases myocardial oxygen con- 11. Martin DR, Scott DF, Downer GL, 27. Bomfim V, Kaijser L, Bendz R, Sylven sumption per beat, due to increased Blezer FO. Primary cause of unsuccess- C, Olen C. Myocardial protection dur- contractility. ful liver and heart preservation. Cold ing . Cardiac Continuous warm blood cardio- sensitivity of the ATP-ase system. Ann metabolism and enzyme release follow- plegia is a controversial technique Surg. 1972; 175:lll-117. ing continuous blood cardioplegia. 12. McMurchie EJ, Raison JK, Cairncross Scand ]Thorac Cardiovasc Surg. 1981; because of the lack of hypothermia. KD. Temperature-induced phase 15:141-147. There are many concerns for patient changes in membranes of the heart: a 28. McGoon DW, Pestana A, Moffit EA. selection criteria, as well as the contrast between the thermal response Decreased risk of aortic valve surgery. effects on the brain. Studies from of poikilotherms and homeotherms. Arch Surg. 1965; 91:779-787. around the country are forthcoming Comp Biochem Physiol. 1973; 44B:1017- 29. Melrose DG, Dieger DB, Bentall HH, and the scientific community awaits 1026. Baker JB. Elective cardiac arrest: prelim- 13. Sakai T, Kuihara S. Effect of rapid cool- inary communications. Lancet. 1955; the results. A ing on mechanical and electrical 221-22. responses in ventricular muscle of the Editor's note: guinea pig. Physiol (London). 1985; Additional reading: Nannette Hages, CST, was first 361:361-378. Panos A, Ashe K, El-Dalati H, et al. Heart introduced to continuous warm 14. Fuhrman GJ, Furrman FA. Utilization surgery with long cross-clamp times. blood cardioplegia in 1989.The first of glucose by the hypothermic rat. Am J Clin lnvest Med. 1989; 12(5 suppl):C55. Physiol. 1963; 295:181-183. Panos A, Ashe K, El-Dalati H, et al. Clinical known patient to undergo this pro- 15. Lyons JM, Raison JK. A temperature- cedure in the United States was comparison of continuous warm (37°C) induced transition in mitochondria1 versus continuous cold (10°C) blood operated. on at that time. Upon mov- oxidation: contrast between cold- and cardioplegia in CABG surgery. Clin ing to Florida a few years later, warm-blooded animals. Comp Biochem lnvest Med. 1989; 12(5 suppl):C55. Nannette Hages, CST, was a mem- Physiol. 1970; 37:495-511. Salerno TA. Single cross-clamping period ber of the surgical team that 16. Magovem GJ, Flaherty JT, Gott VL, for the proximal and distal anastomoses Bulkely BH, Gardner TJ. Failure of in coronary surgery. An alternative to performed the first known continu- blood cardioplegia to protect ous warm blood cardioplegia in that conventional techniques. Ann Thorac myocardium at lower temperatures. Surg. 1982; 33518-520. state. Circulation. 1982; 66(Suppl I):60-67. 17. Rahn H, Reeves RB, Howell BJ. Hydro- References gen ion regulation, temperature and 1. Buckberg GD. A proposed "solution" to evolution. Am Rev Resp Dis. 1975; the cardioplegic controversy. ]Thorac 112165-172. Cardiovasc Surg. 1979; 77:803-815. 18. MacKnieht AC. Leaf A. Regulation of 2. Bigelow WG, Lindsay WK, Greenwood cellular Folumh. Physiol ~eg.1977; Nannette Hages, WF. Hypothermia. Its possible role in 57:510-573. CST, is currenfly cardiac surgery. Ann Surg. 1950; 19. Danforth WH, Naegle S, Bing RJ. Effect working on thr open 132849466. of ischemia and reoxygenation on gly- heart teum at Sara- 3. Roe BB. A history of clinical cardiople- colytic reactions and ATP in heart mus- sota Memorial Hos- gia. In: Engleman RM, Levitsky S, eds. cle. Circ Res. 1960; 8(5):965-971. pital in Sarasotn, A textbook of clinical cardioplegia. New 20. Bernhard WF, Schwarz HF, Malick NP. Florida. She prr- York: Futura. 1982; 1-7. Intermittent cold coronary perfusion as scnted this topic at 4. Griepp RB, Stinson EB, Shumway NE. an adjunct to open heart surgery. Surg the 1991 AST confer- ence in Nrw Profound local hypothermia for Gynecol Obstet. 1960; 111:744-750. 21. Buckberg GD, Brazier JR, Nelson RL, Orleans. Nannette myocardial protection during open- has been a member of heart surgery. ]Thorac Cardiovasc Surg. Goldstein SM, McConnell DH, Cooper AST and certified 1973; 66:731-741. N. Studies of the effects of hypothermia since 1981. 5. Roberts AJ. Preface. In: Roberts AJ, ed. on regional blood flow and metabolism Myocardial protection in cardiac surgery. during cardiopulmonary bypass. ]Tho- rac Cardiovasc Surg. 1977; 73(1):87-94. A. Karim labr, CCP, is a Canadian citizen, New York: Marcel Dekker. 1987; v-viii. originallyfrom Kuwait. He was one ofthe 6. Bigelow WG. The role of hypothermia 22. Netter FH. The ClBA Collection of Med- founders of the continuous warm blood cardiople- in the past, present and future manage- ical Illustrations. Shapter RK, Yonkman gia technique with SV Lichtenstein, MD.

JUNE 1993