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Ann Thorac Surg 1996;61:789-793
© 1996 The Society of Thoracic Surgeons
Departments of Surgery, The University of Tennessee, College of Medicine, and Veterans Affairs Medical Center, Memphis, Tennessee
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Abstract |
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Methods. From January 1980 to May 1995, we performed coronary artery bypass procedures on 20 patients with SCI; 4 were tetraplegic and the remainder were paraplegic. The indication for operation was angina: unstable (13), exertional (4), or postinfarctional (3). Bowel and bladder care was given immediately before operation; operating room tables were double padded and a pelvic wrap was used to protect the back. Electric wheelchairs were used for early mobilization.
Results. Vasomotor instability from cardiopulmonary bypass was not present in patients with SCI. Pharmacologic support was required in the operating room by 4 patients for low vascular resistance, but in only one case in the intensive care unit. One patient required ventilatory support for more than 24 hours. All patients were able to cough effectively. No thoracic wound complications occurred. There were three operative deaths, all in patients with multiple risk factors. The acute hospital stay averaged 9.3 days; patients were then transferred to an SCI unit for rehabilitation, where upper-extremity weight bearing was restricted for 2 to 4 weeks.
Conclusions. Patients should not be denied coronary artery bypass procedures because of an SCI, but their special needs must be managed properly.
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Introduction |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentReferences |
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Spinal cord injuries (SCI) are an important nationwide healthcare problem, most often affecting otherwise healthy individuals. Currently, there are approximately 240,000 individuals with an SCI in this country; between 7,000 and 8,000 new severe cases occur each year. The life expectancy of an individual with SCI, once low, has risen dramatically in the last several decades with improved medical management of comorbid conditions (eg, urosepsis, renal failure, and pulmonary complications) [1, 2]. Specialized rehabilitation programs are returning most patients with SCI to their home or other residence in the community, where the majority of them consider their quality of life to be average or better. Longevity, however, is not without problem. Multiple risk factors for coronary heart disease (CHD), such as increased percentage of body fat, sedentary life-style, and lipid abnormalities, are common in individuals with an SCI [3]. However, there is little information available on the prevalence of CHD in this population [4]. This risk of CHD in individuals with SCI is at least as high as that in the general population. Several studies have documented an increased incidence of death due to CHD in an SCI patient compared with that expected from general population studies [1, 5]. As the chronic SCI population ages, the ability to detect and treat myocardial ischemia will become an increasingly important issue.
The physiologic derangements of patients with SCI undergoing coronary artery operations raise special problems with regard to their response to cardiopulmonary bypass (eg, response to blood flow and vasomotor manipulations) and their perioperative management. We report our experience at a single institution over a 15-year period in operative treatment of CHD in patients with chronic SCI.
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Material and Methods |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentReferences |
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All patients in this study were men; the mean age was 57.8 years (range, 38 to 71 years). All had a permanent SCI of at least 10 years' duration; 13 were more than 20 years from their injury, with the longest at 47 years. Four patients were tetraplegic and the remainder were paraplegic (Table 1
). All had achieved some level of partial independence; some were completely independent and gainfully employed. Indications for coronary artery bypass operations were angina (13 unstable, 5 exertional) or acute myocardial infarction with complications (3). There was an average of 3.9 risk factors per patient (range, 1 to 7) among 19 patients evaluated using the standard criteria of the Veterans Affairs Cardiac Surgery Risk Assessment Program. These included peripheral vascular disease (10), prior myocardial infarction (9), diabetes mellitis (8), current smoker (7), cerebrovascular disease (4), left main disease (3), emergent or urgent operation (3), creatinine greater than 2.0 mg • dL-1/end-stage renal failure (3/2), acute myocardial infarction (3), reoperation (2), preoperative nitroglycerin (2), resting electrocardiogram changes (2), diuretic use (2), chronic obstructive pulmonary disease (2), hypertension/left ventricular hypertrophy (2), preoperative intraaortic balloon pump use (1), and congestive heart failure (1). Left ventricular function was normal in 9, mildly reduced in 3 (ejection fraction 0.45 to 0.54), and moderately reduced in 6 (ejection fraction 0.35 to 0.44). All patients underwent coronary artery grafting alone except 1, who also had a left ventricular aneurysmectomy. In 8 patients, the left internal mammary artery was used for grafting. Nine patients had a preoperative urinary tract infection; in 4, a decubitus was present.
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Bowel and bladder care was given immediately before operation, and bowel care was resumed at about the third postoperative day. An appropriately placed sheepskin pelvic wrap (to avoid operative sites) was used for all tetraplegic patients and for any paraplegic patient with decubitus. The operating table was routinely double padded with foam rubber, and all pressure points (ie, shoulder, elbow, hip, sacrum) were additionally padded and repeatedly checked.
Paraplegics, by necessity, become dependent on their upper extremities and upper-body strength to carry out routine activities of daily living. It is frightening to them to lose this ability, as is necessary for a time after sternotomy to prevent sternal healing problems. Preoperative education in the use of lifts and moving techniques that minimize upper-body weight bearing was given to allay anxiety due to loss of independence. Instructions for a specific rehabilitation program and a time frame for regaining independence were helpful.
Operation
Anesthesia was induced with high-dose narcotics, pancuronium bromide, and a hypnotic agent; phenylephrine was used when hypotension occurred during induction. Cardiopulmonary bypass was established in a standard manner at flow rates of 2.2 to 2.4 L/m2, maintaining a mean arterial pressure of 40 to 60 mm Hg and using phenylephrine infusion for hypotension. Blood was added to the bypass circuit to maintain a hematocrit of at least 18%, and crystalloid was added when the reservoir volume dropped below 800 mL. Systemic hypothermia to 28°C was used. Myocardial protection was accomplished with cold crystalloid cardioplegia until 1985; after that time, cold blood cardioplegia was used.
The use of the internal mammary artery as a graft was at the surgeon's discretion; otherwise, all were reversed saphenous vein grafts.
Postoperative Care
Air flotation beds were used immediately upon leaving the operating room, as were frequent position changes, to prevent pressure necrosis of the skin. Ventilator support was discontinued using a standard protocol. When the patient was sufficiently alert to raise his head, he was extubated if a maximum inspiratory force of -20 cm H2O and a tidal volume of 10 mL/kg were obtained. Tracheobronchial toilet then was initiated; incentive spirometer, aerosolized bronchodilators with positive pressure, and nasotracheal suction were all used as needed to aid an ineffective cough effort. Aggressive diuresis and an upright position were also helpful in maintaining adequate pulmonary function. Patients were transferred from the Thoracic Service to the SCI unit at about the seventh day (mean, 9.3 days; median, 7 days) after operation; thereafter, rehabilitation was continued until their discharge.
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Results |
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No discernible differences from other patients were noted during cardiopulmonary bypass with respect to volume requirements, flow manipulation, or support of vascular resistance. Autonomic hyperreflexia was not seen.
Excluding the 2 patients who died in the immediate perioperative period (less than 24 hours), 8 patients required pharmacologic support during separation from cardiopulmonary bypass. In 4, the support was an alpha-adrenergic agent (phenylephrine in 3, norepinephrine in 1) given for a low mean arterial pressure due to low systemic vascular resistance. Only 1 of these patients required continued support in the intensive care unit for 24 hours for low vascular resistance. Five patients required inotropic support to aid left ventricular function, but none longer than 48 hours. There was no difference in the need for pharmacologic support of the peripheral vascular resistance between patients with different levels of SCI. Likewise, the patient's age or time between SCI and bypass operation had no impact on the need for support of vascular resistance.
All patients immediately surviving the operation (n = 18), except 1, were extubated within the first 24 hours. A 71-year-old patient with multiple risk factors, including hemodialysis for end-stage renal disease and hypoventilation-obesity syndrome, required ventilator support for 14 days. He ultimately recovered and did well despite a prolonged hospital course. All patients, regardless of the level of SCI, were able to cough. In 3 patients, clinically significant atelectasis developed, requiring intensified tracheobronchial toilet and a longer intensive care unit stay; pneumonia developed in 1 of these patients. There was no correlation between the level of SCI and the subsequent development of postoperative pulmonary problems.
Eleven complications, other than pulmonary, were observed in 9 surviving patients. Urinary tract infection, recurrent or new, was the most common infectious complication, occurring in 6 patients. In 1 patient, a new sacral decubitus ulcer developed, and in another, an ulcer that was present before operation worsened; both patients had prolonged hospital stays. Superficial subcutaneous infections of the chest wound occurred in 2 patients; no deep sternal or mediasternal infection occurred. There were no complications of the vein harvest site.
The operative mortality rate in this group was 15% (3 of 20). Two patients died immediately after operation (less than 24 hours); both had multiple risk factors and were operated on emergently for complications from an evolving myocardial infarction. Both died of cardiac failure. One patient died more than 2 months after successful coronary revascularization; he experienced severe hemolytic anemia of unknown cause requiring multiple blood transfusions, glomerulonephritis leading to renal insufficiency, and urosepsis. Of the 17 patients discharged, all are currently alive and well. One patient had repeat cardiac catheterization 5 years after operation, showing patent grafts, and 1 underwent angioplasty 10 years after his bypass operation. One patient has had recurrence of angina 1 year after operation, but his symptoms are well controlled on medical therapy.
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Comment |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentReferences |
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The diagnosis of CHD in SCI, however, may be difficult. Many cardiac pain fibers accompany sympathetic afferents entering the spinal cord, primarily within the first four thoracic segments [8]. Injury to the high thoracic or cervical cord impairs or prevents pain fibers from reaching higher centers. Thus, a person with a high SCI who has cardiac ischemia may have a blunted or absent experience of cardiac pain. We found, however, that all patients in our series had recognizable angina (or angina equivalent) or the usual clinical findings of a myocardial infarction. For patients with SCI who have suspected silent ischemia or atypical symptoms, noninvasive testing for ischemic cardiac disease can be used successfully. Several alternatives to the standard treadmill and bicycle are available [3, 9, 10].
With the ever-increasing number of long-term SCI survivors, management of ischemic heart disease in these patients is an important clinical problem. Ethical issues may exist. In a reported case of cardiac operation in a patient with SCI, Begelman and Anderson [11] raised the ethical consideration of whether resources are best used by performing cardiac operation in a patient with chronic paraplegia; they concluded that in a similar situation, they would again offer such a procedure. We strongly agree, and think it would be inappropriate to withhold operative treatment based on an SCI alone. Most of these individuals, regardless of their level of SCI, have a favorable estimate of their quality of life. All surviving patients in our series have returned to their preoperative level of independence, and most report an improved quality of life (personal communications).
Operative care of a patient with SCI begins before entering the operating room. Concurrent medical problems should all be addressed to minimize the risk; specifically, infection of the urinary tract and breakdown of the skin and soft tissues of the pelvic and sacral area should be treated. Education about avoidance of weight bearing on the upper extremities, use of the electric wheelchair, appropriate transfer techniques, rehabilitation plans, and an expected time frame to regain the preoperative level of independence help allay many of the apprehensions that patients with SCI have. Sternal closure using, perhaps, ten wires or an orthopedic cable system to strengthen the sternal closure beyond that which is satisfactory for the usual postoperative patient may be helpful in allowing earlier upper-extremity weight bearing. We believe that at least 2 to 4 weeks of inpatient rehabilitation (to allow sternal wound healing) is important. Familiarity with the special needs of the patient with SCI, both physical and psychological, is essential.
We could detect no difference in the response to cardiopulmonary bypass in patients with SCI; excessive use of alpha-adrenergic drugs or the need for additional volume in the bypass circuit to counteract a low vascular resistance was not seen. Moreover, standard doses of alpha- and beta-adrenergic drugs produced expected changes in the peripheral vascular resistance, and there was no exaggerated response to standard doses of intravenous nitroprusside or nitroglycerin during or after bypass.
We have noted an unsatisfactory quality of the venous conduit (eg, small diameter, poor distensibility) in some patients with longstanding high thoracic or cervical cord injuries. There seems to be a tendency for the saphenous veins to become atrophied, presumably from atrophy of the lower-extremity muscles and loss of the effects of gravity in these bedbound or chairbound patients. In patients with high cord injuries of more than 20 years' duration, we routinely search for an adequate venous conduit preoperatively using ultrasound imaging, to better plan our revascularization.
Postoperative management of patients with SCI undergoing coronary artery operations was remarkably similar to our experience with patients without SCI. Alterations in pulmonary function in patients with SCI have been investigated extensively and vary with the level of SCI [12]. Forced vital capacity, forced expiratory volume in 1 second, and expiratory reserve volume are all reduced, whereas residual volume is increased [13]. Despite these derangements, separation from ventilatory support and extubation were not difficult, even in patients with high cord lesions. All patients could cough and clear secretions, attributable, in part, to the chronic nature of their injuries and adaptation over the years.
Urinary tract infection, a frequent preoperative impediment, was common postoperatively and represents a continuing problem for the individual with SCI [14]. Bacteremia with contamination of the fresh mediastinal wound is possible. Most of these patients have a continuing need for indwelling bladder catheters; therefore, we routinely treat any bacteriuria that occurs in a patient with SCI for the first 4 to 6 weeks after operation.
Despite our heightened awareness of and specific maneuvers to avoid pressure necrosis of the skin, we were not able to avoid this complication completely. With more frequent position changes and the earlier use of flotation beds, we have not had a skin pressure problem in our last 12 patients.
Spinal cord injury may be an important risk factor in terms of survival after coronary artery operations. The 15% mortality rate in this group of patients is substantially higher than that reported in most other series of coronary artery bypass grafting in patients aged 38 to 71 years. It is not possible to reach a conclusion regarding recommendations for individual operability from this small group of patients; however, all 3 patients who died were operated upon for complications of an acute myocardial infarction (100% mortality). This is a high-risk group of patients (average 3.9 major risk factors per patient in our series) to subject to coronary operations. Because of their SCI, they may have been misdiagnosed or medically managed longer before being referred for operation, resulting in operation later in the course of their disease than if they had no SCI. However, comorbid conditions unavoidable in the patient with SCI may always place them in a higher-risk group for coronary operations. Larger numbers of patients with SCI undergoing bypass operations will be needed to resolve these issues.
In summary, coronary artery bypass procedures can be carried out reasonably safely in patients with SCI and should not be denied solely on the basis of an SCI. However, the special perioperative needs of the patient with SCI must be managed properly. The response to cardiopulmonary bypass and the benefit from coronary revascularization do not appear to be affected by an SCI.
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Footnotes |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentReferences |
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Address reprint requests to Dr Walker, Cardiopulmonary Surgical Consultants, 525 North State of Franklin Rd, Suite 9, Johnson City, TN 37604.
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentReferences |
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