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Ann Thorac Surg 1995;59:361-372
© 1995 The Society of Thoracic Surgeons
Section of Cardiothoracic Surgery, University of Nebraska Medical Center, Omaha, Nebraska
Accepted for publication September 16, 1994.
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Abstract |
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 TopFootnotes Abstract IntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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Introduction |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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Be not the first by whom the new are tried, Nor yet the last to lay the old aside.
Alexander Pope, 1711 [1]
The development of methods to protect the myocardium during open heart operation has closely paralleled the growth and success of the field of cardiac surgery itself. Indeed, today's excellent surgical results are a direct consequence of careful basic and clinical research efforts by a variety of investigators worldwide. Since the first cardioplegic solution was described in 1955
by Melrose and associates [2], increasingly sophisticated techniques have come and gone as the field has developed and experience has grown.
For the busy clinical surgeon, keeping current on the medical literature about this changing field of myocardial protection is not an easy task. Since 1966, more than 4,500 articles and numerous books have been published in the world's literature directly concerning this critical aspect of cardiac surgery; more than one-third of these publications have appeared in the past 5 years (Medline search, produced by the National Library of Medicine, Bethesda, Maryland. MeSH headings used: Heart arrest, induced or cardioplegic solutions; and/or hypothermia, induced). However, what is the impact of this vast quantity of published studies on the current clinical practice and techniques of myocardial protection? A variety of surveys of surgical practice have appeared since 1975 covering mostly coronary artery bypass grafting (CABG) and transplantation [3–11], but none have addressed in detail the topic of myocardial protection as applied by a large segment of practicing cardiac surgeons. For this reason, we surveyed all United States board-certified thoracic surgeons on their current methods of cardiac preservation and this article presents the results of that survey.
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Material and Methods |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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The survey was designed in four parts: (1) demographic information; (2) congenital (pediatric) heart surgical techniques; (3) adult (acquired) heart surgical techniques; (4) future trends. The results from the respondents answering the congenital heart surgery section are not included in this article and will appear in a separate publication. The survey questions were all multiple choice asking for specific information designed to be quickly answered in hopes that the survey would be promptly returned with a high response rate. Questions about operative mortality and major morbidity statistics, although interesting, would have required an extensive case review by each respondent and, therefore, were excluded. For purposes of the survey, respondents were asked to choose answers indicating their usual methods for their ``average'' patient, recognizing the fact that most surgeons seldom have an ``average'' patient in today's patient population.
Surgeons who used cardioplegic solutions were asked whether their solution closely resembled one of the previously published formulations listed at the end of the survey. Specific ``named'' formulations listed included the Buckberg blood cardioplegic solution [12, 13] and a number of named crystalloid solutions as summarized by Hearse and associates [14]. The information obtained in this survey was compared, when possible, to results found in prior surveys of cardiac surgical techniques during the past 19 years [3–11], but no statistical analysis was attempted comparing our data with this diverse group of published results.
The response for the entire survey population in each question was cross-referenced to the response to each question by various demographic groups. Groups compared were those based on the year of completion of cardiac surgery fellowship, type of practice (university-based, etc), geographic location, and by total number of open heart operations performed yearly. 
2 was used to determine whether there was a significant difference in the response to a question by a selected group when compared with the entire population response or specific group response. A p value less than 0.05 was considered to represent a significant difference. The Bonferroni inequality was used to adjust the p value when multiple tests were done on the same data.
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Results |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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Demographics
The 936 surgeons responding to the acquired heart disease portion of the survey represent a broad geographic cross-section of the United States, as illustrated by the percentage of respondents in each of the practice locations shown in Figure 1
. The number of thoracic surgeons practicing in each area that were sent surveys are: East 964, Midwest 926, South 1,491, and West 945. Also, 67 surgeons were practicing in Alaska, Hawaii, District of Columbia, and Puerto Rico (not shown on the map in Fig 1) and were sent surveys. Based on the zip code listed for the primary hospital of each respondent, techniques described herein are representative of those used in at least 506 hospitals. This number may underestimate the total number of respondent hospitals, as more than one hospital may be located in the same zip code region.
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Patient Population
The type of surgical cases treated by respondents answering the acquired heart disease section demonstrates that the vast majority (82.5%) operate on adult acquired problems only. For the remaining surgeons, 14.8% have a 75%/25% adult/congenital case mix, 2.4% have a 50%/50% adult/congenital case mix, and only 0.3% have a 25%/75% adult/congenital case mix. When stratified based on type of surgical practice, respondents in private practice and private practice with a university affiliation predominantly treat adult-acquired heart disease, with 87.2% of this group operating only on the adult-acquired population and just 1.5% operating only on a congenital heart population. However, for university-based surgeons, 57.1% have only an adult-acquired heart disease population and 7.9% perform only congenital heart surgery (p < 0.001 compared with private practice or private practice with a university affiliation). The remainder of university-based surgeons (35.0%) operate on both patient types.
The yearly acquired heart disease caseload for respondents is: less than 50 patients for 5.3% of surgeons, 50 to 100 patients for 19.0% of surgeons, 101 to 200 patients for 47.5% of surgeons, and more than 200 patients for 28.2% of surgeons. If the median number of patients is assumed for each volume grouping of caseloads, then the total number of acquired open heart operations performed yearly by the group of 947 respondents answering this particular question is approximately 149,000 patients, for a mean 157.3 operations/year/surgeon. Geographically, surgeons in the East report having the highest caseloads with more than one-third (35.1%) operating on more than 200 patients yearly (p = 0.034 compared with the rest of the respondents), compared with 31.6% of southern area surgeons, 24.6% of midwestern area surgeons, and 20.7% of western area surgeons.
From the most recent published data, the National Center for Health Statistics estimates that 392,000 coronary bypass grafting procedures were performed in 1990 and 64,000 adult cardiac valve procedures were performed in 1989, for a total of approximately 456,000 patients yearly [15]. Therefore, based on their caseload estimates, our sample of thoracic surgeons perform approximately 32.7% of the adult-acquired heart disease operations each year in the United States. Consequently, we feel that this survey should provide an accurate reflection of the current techniques used in routine clinical practice.
Almost all acquired heart disease surgeons perform CABG as well as valve operations, although CABG is by far the most common. Of the respondents, 0.1% perform CABG only. For the remainder, 45.3% have a 90%/10% CABG/valve case mix, 50.5% have a 75%/25% CABG/valve case mix, 3.3% have a 50%/50% CABG/valve case mix, and 0.9% have a 25%/75% CABG/valve case mix. As expected, the average age of these patients is high with most presenting in their seventh decade. The average patient age is less than 50 years for 0.4% of surgeons, 51 to 60 years for 3.5%, 61 to 70 years for 81.4%, 71 to 80 years for 14.4%, and greater than 80 years for 0.3%.
Information Sources
Each respondent was asked to choose their five most commonly consulted sources to obtain information about myocardial protection for use in their clinical practice, and these are listed as follows by percentage of surgeons: The Annals of Thoracic Surgery, 96.2; The Journal of Thoracic and Cardiovascular Surgery, 93.0; national thoracic surgery meetings, 80.1; informally from colleagues, 55.6; textbooks and monographs, 36.3; Journal of Cardiac Surgery, 32.3; Circulation, 17.8; local conferences, 10.7; Chest, 8.9; Journal of Cardiovascular Surgery, 7.9; Journal of the American College of Cardiology, 6.6; national cardiology meetings, 5.5; manufacturer's representatives, 4.5; American Journal of Cardiology, 4.2; Thoracic and Cardiovascular Surgeon, 1.4; and Scandinavian Journal of Thoracic and Cardiovascular Surgery, 1.2. In addition, various other sources were written in with each representing only a few respondents (less than 1% of all surgeons) and these are listed with decreasing frequency of choice: Seminars in Thoracic and Cardiovascular Surgery, Journal of Extra-Corporeal Technology, Circulation Research, personal research, Texas Heart Institute Journal, European Journal of Cardio-Thoracic Surgery, Journal of Heart and Lung Transplantation, Annals of Vascular Surgery, Surgical Forum, and discussions with their perfusionist.
Preoperative Patient Preparation
The use of various pharmacologic means to optimize a patient's condition just before cardiopulmonary bypass is a common clinical practice among respondents. Intraoperative intravenous nitroglycerin was the most commonly used agent with 61.1% of respondents using it routinely whereas the remainder (38.9%) did not. Routine administration of a single large bolus of intravenous steroids just before going on bypass is used by 21.4% of surgeons, whereas 78.6% do not use this agent in this manner. For the patient with a low ejection fraction, 14.9% of respondents electively use a preoperative low-dose inotropic agent infusion (such as dobutamine) prophylactically to enhance ventricular function, whereas the majority (85.1%) do not use this method.
The administration of an intravenous crystalloid solution containing glucose, insulin, and potassium to patients undergoing cardiac operation before their procedure has been advocated in various publications [16, 17]. For our respondents, the vast majority (97.1%) use glucose, insulin, and potassium rarely (less than 20% of patients), whereas 2.2% use it selectively (20% to 80% of patients) and only 0.7% always use it (more than 80% of patients).
Patient Monitoring
Intraoperative monitoring of patients plays an increasingly important role in modern cardiac surgical practice. The pulmonary artery (Swan-Ganz) catheter for invasive monitoring is very commonly used by our respondents. The percentage of all respondents using a pulmonary artery catheter for their patients is: 83.9% use it for more than 75% of cases, 4.3% use it for 51% to 75% of patients, 2.6% use it for 26% to 50% of patients, 3.7% use it for 10% to 25% of patients, and 5.6% rarely use it (less than 10% of patients). When stratified for respondent practice location, surgeons in the East more commonly use a pulmonary artery catheter, with 93.2% using it more than 75% of the time (p < 0.001 compared with the remainder of the respondents). For the other geographic areas, the catheter usage rate is 84.7% for the Midwest, 82.8% for the South, and 77.7% for the West.
Measuring myocardial septal temperature during the ischemic period is practiced routinely by 38.5% of surgeons, whereas 61.5% do not. Of the respondents who follow septal temperature, the preferred myocardial temperature for 33.5% is 6° to 10°C, 53.8% prefer 11° to 15°C, 6.7% prefer 16° to 20°C, and 6.0% prefer more than 20°C. Measurement of myocardial pH during the ischemic period is rarely used by our respondents, with only 3.3% of surgeons routinely using this technique, whereas the rest (96.7%) do not.
Cardiopulmonary Bypass
The type of oxygenator chosen for cardiopulmonary bypass has changed dramatically over the years as technology has advanced. For our overall respondent group, the membrane oxygenator is the clear favorite of 95.2% of surgeons for the majority of patients, whereas only 4.8% use the bubble oxygenator. However, for surgeons performing a lower volume of cases (less than 50 patients yearly), a membrane oxygenator is chosen less often and is used on 79.6% of patients and a bubbler is used on 20.5% (p < 0.001 compared with the rest of the surgeons).
The mean systemic blood pressure our respondents prefer to maintain most of the time while on cardiopulmonary bypass varies: 30 to 50 mm Hg for 4.4%, 51 to 60 mm Hg for 40.9%, 61 to 70 mm Hg for 37.4%, 71 to 80 mm Hg for 8.9%, 81 to 90 mm Hg for 1.0%, and more than 90 mm Hg for 0.1%. However, 7.3% of surgeons state that they are not concerned about systemic pressures but rather just make sure that the pump flow rate is adequate. For aortic inflow temperatures for more than 50% of patients, most surgeons prefer moderate hypothermia: 6.3% use 20° to 24°C, 66.6% use 25° to 29°C, 17.1% use 30° to 32°C, and 10.0% use more than 32°C. During the ischemic period, most surgeons (75.8%) do not lower the pump flow rate to decrease noncoronary collateral flow, whereas 24.2% of respondents use this method.
The preferences of respondents for venting the left heart during cardiopulmonary bypass is shown in Table 1. Of the two most common routes for venting (aortic root [AR] and right superior pulmonary vein [RSPV]), 60.3% of surgeons who always vent prefer the AR, whereas only 44.5% of the selectively vent group and 32.6% of the rarely vent group prefer this route. The RSPV is more commonly the vent site of choice for the surgeon who vents less frequently.
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Cardioplegic Solution Delivery
The introduction of retrograde cardioplegic solution delivery in the late 1980s provided an alternative route that has been widely accepted by cardiac surgeons, as indicated by our respondents' preferences shown in Figure 2. For the surgeons using retrograde cardioplegic solution delivery (or antegrade/retrograde combination), Figure 3 illustrates the percentage of cases in which they use this methodfig 3.
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summarizes the preferences for several other aspects of cardioplegic solution deliverytab 2.
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. Geographically, western area surgeons most commonly choose (82.4%) blood cardioplegic solutions (p = 0.012 compared with the other combined groups), with eastern area surgeons next at 79.9% (p = 0.04 compared with the other combined groups), midwestern area surgeons 69.1%, and southern area surgeons choosing blood solutions least with 64.6% (p < 0.001 compared with the other combined groups). The rest of the surgeons in each geographic area use crystalloid solutions, making the South the area most inclined toward ``clear'' solutions with 35.4% of respondents. The length of time surgeons have used their current cardioplegic solution varies greatly: less than 1 year 6.7%, 1 to 3 years 32.7%, 4 to 8 years 38.9%, and more than 8 years 22.0%.
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. Geographically, the Buckberg formulation is preferred by 44.4% of western surgeons, 42.1% of eastern surgeons, 37.5% of midwestern surgeons, and 34.1% of southern surgeons, although these differences are not statistically significant. Based on the number of responses in each category, it is apparent that some surgeons use a blood solution on some patients and a crystalloid solution on others.
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Special Protective Measures
Some local method to enhance myocardial protection is used by the majority of respondents, as summarized in Table 4tab 4. One or more methods to promote topical cardiac hypothermia are used by 88.0% of responding surgeons, with slush being the most common method used.
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Continuous Warm Blood Cardioplegia
Use of continuous warm blood cardioplegia (CWBC) (Toronto method), the newest special method of delivering cardioplegic solution, is summarized in Table 5. However, the adoption of this technique varies somewhat based on how long respondents have been in practice. Although in the overall group 10.0% use this method, the older surgeons tend to use CWBC methods more frequently, when broken down by the year of completion of cardiac surgery fellowship: 1980 to present, 8.5% use CWBC; 1970 to 1979, 10.9% use CWBC; 1960 to 1969, 14.9% use CWBC; and 1950 to 1959, 20.0% use CWBC. The small number of respondents in the oldest surgeon group (only 20 respondents completed their fellowship before 1960) precluded the difference from being statistically significant. Geographically, there are also differences in preference for this new technique: 17.3% of eastern surgeons (p = 0.004 compared with the rest) often use CWBC compared with 15.4% in the West, 7.4% in the South, and 4.9% in the Midwest (p = 0.006 compared with the rest of the respondents).
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lists the estimated frequency of a number of these problems in our respondents' practicestab 6. The incidence of postoperative atrial arrhythmias among the patients of the respondents is displayed in Figure 5. To prevent postoperative atrial arrhythmias in CABG patients, 19.0% of respondents use prophylactic digoxin, 15.3% use prophylactic ß-adrenergic blocking agents, 7.8% use prophylactic digoxin and ß-adrenergic blocking agents together, and 57.9% use no prophylactic drugs.
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. Although 78.4% of all respondents reported that they were completely or very satisfied with their present method of myocardial protection, surgeons performing a lower volume of operations (less than 50 yearly) were generally less satisfied, with only 54.5% completely or very satisfied (p < 0.001 compared with the rest of the respondents) and 6.5% were somewhat dissatisfied (only 1.3% of the overall group were somewhat dissatisfied). With more operative volume, the percentage of completely or very satisfied surgeons increased: 50 to 100 patients yearly, 73.4%; 101 to 200 patients yearly, 80.1%; and more than 200 patients yearly, 82.7%.
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Respondent Special Comments
Two hundred ninety-two special comments were written in on the returned surveys. Most related to very positive or negative views on CWBC, such as: ``In my opinion, CWBC (Toronto method) is a major advance in myocardial protection.'' However, negative views were equally expressed. Other written comments discussed the importance of retrograde cardioplegic methods, although some questioned the effectiveness of this route in protecting the right ventricle. Finally, a number of respondents remarked on the importance of conducting this nationwide survey of myocardial protection.
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Comment |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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. Seven of these surveys [3–7, 9, 11] have dealt wholly or in part with standard myocardial protection practices. Two surveys have dealt exclusively with donor heart preservation [8, 10], which was a topic not included on the current survey and consequently transplant preservation will not be discussed.
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The average number of operations performed yearly per surgeon has risen over the years. In 1977, the average surgeon was performing 100 operations yearly [3]; by 1981 this number was up to 137 operations per surgeon [4]. In 1986, the average surgeon performed a range of 100 to 150 operations yearly [7]. Now in the present survey, surgeons perform a mean of 157 operations per year. This gradual increasing caseload presumably results from an increasing patient population, but equally important are the significant advances in perioperative patient management that have decreased operative time, thereby allowing surgeons to comfortably perform more operations per day.
Cardiopulmonary Bypass
Venting the left heart has been and still is a controversial subject. Surprisingly, there has been little variation over the years as to the percentage of cardiac surgeons who vent routinely: 1977, 64.3% [3]; 1981, 52.9% [4]; 1991, 58.5% [9]; and 69.2% in the current survey. However, the anatomic site chosen for left heart venting has varied. In 1977, surgeons most commonly chose the RSPV 58% of the time, the left ventricular apex (LVA) 33%, and the AR was chosen by only 1% [3]. By 1981, 78% chose the RSPV, 13% used the LVA, and 7% chose the AR [4]. In the present survey, 38% choose the RSPV, 1% use the LVA, but 53% now choose the AR. This change to the simpler technique using the AR for venting probably reflects increased reliance of surgeons on better myocardial protection from more efficacious cardioplegic solutions, as well as investigative studies questioning the need for complete left heart venting for uncomplicated coronary artery bypass operations [18, 19]. In the 1977 survey [3], there was a significant correlation between the use of left heart venting and annual caseloads, with the busier, higher caseload surgeon less likely to vent. However, now in the present survey this variation in venting practices based on caseload no longer exists and venting practices are remarkably uniform among all demographic groups.
The choice of the type of oxygenator used has shifted dramatically over the years as technology has advanced. In 1977, 94% of surgeons routinely used the bubble oxygenator, whereas only 6% used a membrane oxygenator [3]. By 1982, routine membrane oxygenator use was only up to 10% [5]. However, a decade and many technological advances later, the present survey finds the membrane oxygenator used by 95% of surgeons. Aside from the technology changes and the price of membrane systems declining to that almost equivalent with the bubble oxygenator, we suspect that the surgical literature, which generally favors the membrane and its less deleterious effects on various elements of the blood [20, 21], has influenced surgeons to prefer this oxygenator.
Cardiac Exposure
Undoubtedly the greatest single advance in the entire field of myocardial protection is the development and adoption of cardioplegic techniques to allow exposure of the heart for the operative repair. Evolution of these various methods is well described in the monograph by Hearse and associates [22] and by other authors that followed. From the 1977 survey [3], we find anoxic arrest or ventricular fibrillation usually combined with some type of hypothermia to be the technique of choice by 94% of surgeons, with only a few (6%) using the rediscovered technique of high potassium-induced cardioplegia. In the span of only 4 years by 1981, cardioplegia had taken cardiac surgeons by storm with 92% using it [4]; 99% of surgeons were using cardioplegic techniques 1 year later in 1982 [5], and this has remained the technique of choice until the present. Figure 6 graphically displays the changes that have occurred, as documented by surveys over the last two decadesfig 6.
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). Nevertheless, surgeons tend to continue to use the same techniques (including cardioplegic methods) that they were taught in their cardiac surgery fellowships. According to a 1991 survey of cardiac training programs [9], 24.5% of these programs use crystalloid cardioplegia, and the rest use blood methods, very similar to the percentages from the current survey of individual surgeons.
Presently almost three-fourths (72.2%) of all cardiac surgeons use blood cardioplegia, with the Buckberg formulation being the favorite. Those 29.8% of respondent surgeons who use a crystalloid solution overwhelmingly favor the St. Thomas' Hospital formulation (see Table 3), the only one that is widely available as a commercially premixed solution (Plegisol; Abbott Laboratories, Abbott Park, IL). Aside from earlier research studies [14, 26] suggesting that this is the most effective crystalloid cardioplegic formulation, it has been suggested that the issue of the potential legal liability for accuracy of formulation of individual hospital-produced cardioplegic solutions as well as the reduced cost of a commercially manufactured solution have encouraged many crystalloid cardioplegia surgeons to adopt Plegisol to their practice.
Cardioplegic Solution Delivery
The use of the coronary venous circulation to deliver oxygenated solutions is not a new concept, but its clinical use was resurrected and promoted in the early 1980s by Menasché and associatesAu: ref #? as well as other investigators, as recently summarized by Chitwood [27]. By 1987, Beggerly and associates [7] in their coronary surgery survey found that only 2.6% of surgeons had ever used retrograde cardioplegia for CABG. However, during this time multiple studies were appearing in the literature that documented excellent clinical results and introduced easier retrograde delivery techniques, thereby encouraging the practicing surgeon to try this new delivery method on patients [27]. Obviously, retrograde cardioplegia delivery impressed much of the surgical community with its efficacy and ease of use such that the majority (60%) of respondents now regularly use a combination of antegrade and retrograde cardioplegia techniques. Although most surgeons use this technique selectively, 29% use retrograde on almost all cases (see Fig 3). The rapid adoption of this new technique into common practice speaks well of the adaptability and the innovative attitude of today's cardiac surgeon.
The preferred temperature of the delivered cardioplegic solution has changed little over the years since this technique was readopted. In 1981, 96.1% of surgeons preferred their solution to be less than 12°C and 81.5% wanted it to be 4° to 6°C [4]. By 1991, ``most'' preferred their solution to be less than 10°C and over ``half'' wanted the temperature to be less than 4°C [9]. The current survey results are surprisingly similar, with 92.6% preferring their solution to be less than 12°C and 58.2% liking it less than 6°C.
Continuous Warm Blood Cardioplegia
The most recent innovative approach to myocardial protection is the use of CWBC, as developed at the University of Toronto and first described in 1991 [28]. The initial publications were based on retrospective clinical studies [28, 29] and demonstrated good myocardial protection with all types of cardiac operations. The first mailing of our survey on myocardial protection was sent to cardiac surgeons at the end of 1991 just as the initial enthusiastic articles from Toronto were being published. It was not until after all completed surveys were received in mid-1992 that the first prospective, randomized trials comparing CWBC with conventional hypothermic cardioplegia techniques were beginning to be reported [30–33]. These and other subsequent studies generally report good results with CWBC but this technique, as originally described, appears to offer no clear advantages over current intermittent hypothermic methods. However, the results with CWBC in these prospective studies have raised a number of concerns about increased risks of neurologic injury, low systemic vascular resistance necessitating large doses of vasoconstrictors, fluid and potassium overload, hyperglycemia, increased bleeding, and difficult coronary visualization requiring temporary interruption of coronary perfusion with the attendant risk of myocardial damage from normothermic ischemic episodes.
Therefore, the respondents to the present survey relayed their impressions in early 1992 about this new technique with no knowledge of the results of randomized trials of CWBC that were presented or published later that year. In this setting, it is not surprising that there were a significant number of surgeons (10.0%) who had adopted CWBC to their practice and an equal number who enthusiastically looked forward to its use. Still, three-fourths of respondents remained cautious and skeptical about CWBC as anything more than a passing fad. Many surgeons currently may share the concerns recently voiced by Buckberg in an editorial about CWBC [34], who urged caution before embracing this new technique. Laboratory and clinical studies need to answer many of the questions still remaining about the role of warm heart techniques in routine practice.
Cross-Referencing
All responses to questions were cross-referenced to the demographic and caseload information obtained at the beginning of the survey. The most striking finding from this exercise is the remarkable uniformity of myocardial protection practice techniques that transcended practice type, location, case volume, or years of training. However, there were some interesting exceptions that merit discussion. The more senior cardiac surgeons who have been out of their fellowship the most years were the surgeons who tended to have the highest use of the newest technique, CWBC, with twice the percentage using this method compared with the overall respondent population. One possible explanation for this finding might be that as a group they feel the most confident about their own cardiac surgical abilities and therefore are the most comfortable trying newer, innovative techniques. However, this statement is contrary to the popular notion that older individuals (surgeons) are more resistant to change. Nevertheless, one might argue that older, more experienced surgeons know more about the field and can recognize more readily a superior technique and therefore quickly adopt it. Only time and further studies will tell whether some of the older surgeons have chosen wisely with this method.
The location of practice demonstrates some interesting differences. Surgeons in the eastern region have the highest yearly caseloads, have the highest routine usage of pulmonary artery catheters, and among geographic groups have the highest rate of adopting CWBC. On the other hand, surgeons from the western region have the highest blood cardioplegia usage rate and most tend to favor the use of the Buckberg blood cardioplegia formulation that was developed at University of California, Los Angeles. Most of these specific geographic preferences can probably be explained by surgeons following techniques taught to them at their regional training programs, as most surgeons tend to enter into practice in the same general area of the country as they did their surgery fellowship.
Finally, with regard to stratification by caseload, the surgeons performing the lowest yearly volume of operations have the lowest use of membrane oxygenators and are the most likely to use warm blood reperfusion solutions (HSR). One explanation might be that low-volume programs tend to use more bubble oxygenators because of apparent reduced costs (now this generally is not a factor) and perhaps more importantly the need for somewhat less initial training and repeated use for their perfusionists to maintain their skills with a bubble oxygenator. The tendency of lower caseload surgeons to more commonly use HSR (compared with the higher volume surgeons) may relate to a perceived need for additional myocardial protection to make sure every case does well, as only a few problem cases can rapidly change their statistical results. Alternatively, the higher case volume surgeons may believe that adding HSR takes too much time and therefore, they have eliminated it on all but the most difficult cases.
Overall, the vast majority of respondents (78.4%) were completely or very satisfied with their present methods of myocardial protection. However, the level of satisfaction was directly related to the volume of operations performed yearly. That is, the greater the caseload, the greater the percentage of satisfied surgeons and the less dissatisfaction. One might postulate that with frequent practice the busier surgeons and their perfusionists become more comfortable and perhaps more facile with the various daily demands for meticulous attention to the details of effective myocardial protection in increasingly more impaired hearts. Therefore, their overall level of satisfaction with their methods tends to be greater than that of the lower caseload surgeon.
A large mail survey of this type has a number of inherent drawbacks. Answers to some questions, such as those related to complication rates as in Table 6, rely on the memory of the surgeons and their willingness to admit to themselves what are their actual morbidity rates. Some of the questions may be misinterpreted or the respondents may believe that the possible multiple choice answers are not sufficient to relay their answer adequately. Several respondents thought that certain important topics were not included in the survey questions. Finally, there is always the worry that the sample of respondents is not representative of the practices of the whole group. That is, surgeons who vigorously support or are even ``pushing'' a particular technique such as CWBC might be more inclined to respond to the survey to have their ``voice'' heard, and consequently, this may skew the survey results to their side. Hopefully, the large response to this survey (32.2% total response rate representing practice data for 32.7% of all acquired heart disease operations performed yearly) will dilute out any such influences on the results.
After reviewing the small mountain of survey data representing the practice techniques of approximately one-third of the US thoracic surgeons, what basic facts have we learned about current cardiac surgical practice? Although no single method of myocardial protection is practiced nationwide, there are some predominant themes: (1) Cardioplegic arrest of the heart continues to be the method of myocardial protection preferred by the overwhelming majority of surgeons, 97.6% in the current survey. This percentage of surgeons has remained essentially unchanged since 1982. (2) There has been a continuing trend away from crystalloid cardioplegic solutions to those containing blood, which is currently used by more than 70% of surgeons. (3) The retrograde administration of cardioplegic solutions has been rapidly adopted into routine practice by US thoracic surgeons despite its relatively recent clinical introduction in the mid-1980s. (4) CWBC methods are gaining some disciples (10%) but the majority of surgeons (75%) have adopted a somewhat skeptical ``wait and see'' attitude toward this new method. (5) Most thoracic surgeons (78%) are very satisfied with their present methods of myocardial protection; only 2% are dissatisfied. (6) Thoracic surgeons continue to be very interested in the topic of myocardial protection, as indicated by their remarkably high response rate over the years (always more than 30%) to mail surveys covering this field. (7) Despite their general satisfaction with current myocardial protection techniques, the majority of surgeons feel that there is still much to learn from research in this field.
The results of this survey represent the collective experience of a large segment of the US cardiac surgical population, and provides the interested reader a means of self-assessment for comparison with his or her peers. In addition, these findings may have significant implications for the design and direction of cardiac surgical training programs, so that they continue to improve and evolve along with the critically important field of myocardial protection. Finally, large surveys of this type may aid in the future development of realistic and accurate consensus statements and perhaps even practice guidelines in the changing field of cardiac surgery.
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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Address reprint requests to Dr Robinson, Division of Cardiothoracic Surgery, University of South Florida, 12902 Magnolia Dr, Tampa, FL 33612-9497.
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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P. Ruengsakulrach and B. F. Buxton Anatomic and hemodynamic considerations influencing the efficiency of retrograde cardioplegia Ann. Thorac. Surg., April 1, 2001; 71(4): 1389 - 1395. [Abstract] [Full Text] [PDF]
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R. Bessho and D. J. Chambers Experimental study of intermittent crossclamping with fibrillation and myocardial protection: Reduced injury from shorter cumulative ischemia or intrinsic protective effect? J. Thorac. Cardiovasc. Surg., September 1, 2000; 120(3): 528 - 537. [Abstract] [Full Text] [PDF]
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