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Ann Thorac Surg 2000;70:91-96
© 2000 The Society of Thoracic Surgeons
a Department of Cardiovascular Surgery, Guven Hospital, Ankara, Turkey
b Department of Cardiovascular Anesthesiology, Guven Hospital, Ankara, Turkey
Address reprint requests to Dr Karagoz, Cankaya Cad 4-2, Cankaya 06680, Ankara, Turkey
e-mail: karagoz{at}tr-net.net.tr
| Abstract |
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Methods. Between October 1998 and June 1999, 5 patients underwent coronary artery bypass grafting without endotracheal general anesthesia, using high thoracic epidural block to construct extension grafts with a short segment of radial artery, between the in situ left or right internal thoracic arteries and the left anterior descending (n = 4) or right coronary arteries (n = 1). There were 2 female and 3 male patients, with a mean age of 67.4 ± 8.3 years.
Results. The perioperative course of the patients was uneventful. There was no perioperative morbidity or mortality. No patient was converted to general anesthesia or to conventional operation. Control angiograms revealed patent anastomoses in all patients. In 1 patient, spasm of the radial artery graft was observed that was relieved 3 weeks later spontaneously. Mean length of hospital stay was 2.2 ± 0.4 days. All patients were symptom free and returned to normal daily life at the first postoperative month.
Conclusions. Our initial experience confirms the feasibility of performing coronary bypass grafting in the conscious patient without endotracheal general anesthesia.
| Introduction |
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Over the past several years, minimally invasive coronary artery bypass grafting has evolved from an experimental procedure to an accepted mode of therapy, albeit with some reservations [7, 8]. Despite the use of small incisions and avoidance of cardiopulmonary bypass, such operations can still be considered significantly "invasive," regarding employment of general anesthesia and placement of various indwelling catheters and tubes into the patient. Since 1993, considerable experience has accumulated in performing coronary anastomoses on the beating heart, and various aspects of minimally invasive approaches have been simplified [911]. In an attempt to further simplify and decrease the "invasiveness" of this procedure, we have been involved in considerable research regarding elimination of various steps of coronary bypass grafting without compromising the reliability of the procedure. In this respect, performing this operation without endotracheal general anesthesia was deemed feasible in certain subsets of patients. This report describes our initial experience in performing coronary bypass grafting in conscious patients without endotracheal general anesthesia.
| Material and methods |
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Patient selection criteria included presence of significant (> 70%) proximal LAD or right coronary artery stenosis, good caliber target vessel (> 1 mm), presence of an inflow graft (internal thoracic artery), and a cooperative patient. Presence of diabetes or chronic obstructive pulmonary disease (COPD), or any other variable that could present potential comorbidity, did not effect patient selection.
Patients were fully informed about the pros and cons of the surgical approach, including that this technique is new and long-term results are not yet available, and a written informed consent was obtained. The first 3 patients were referred to us with an indication of coronary bypass surgery, whereas the last 2 patients were operated on in lieu of primary percutaneous coronary angioplasty. Preoperative characteristics of the patients are depicted in Table 1. One patient presented with unstable chest pain, whereas 4 patients had stable angina pectoris. Patients continued to take their usual medications until the morning of surgery, except aspirin, which was stopped 1 week before surgery. No patient was on specific antiplatelet therapy preoperatively. No patient was given beta-blockers preoperatively, except for their usual medications.
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In the operating room, 10 mL of epidural anesthesia solution was administered epidurally as a bolus (Table 2). Fifteen minutes later, the level of the block was tested by assessing both temperature and pin prick discrimination. Loss of temperature discrimination was deemed necessary to continue the operation with epidural anesthesia. Additional bolus doses of epidural anesthesia solution were administered as needed to achieve motor block of the intercostal muscles (Table 3). Motor block of the intercostal muscles was assessed visually by monitoring the loss of intercostal movement. Sensory block level was maintained at the C6 to T8 level.
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Surgical technique
The H-graft technique was used for this procedure [11]. In all patients, a short segment of a radial artery graft was interposed between the in situ left or right internal thoracic arteries and the LAD or the right coronary artery. Radial artery harvest was accomplished by axillary block in 1 patient, and by musculocutaneous nerve block in the latter patients. A 7- to 10-cm segment of radial artery graft was harvested from the nondominant arm, and preserved in verapamil-nitroglycerin solution [12, 13]. This solution was also used as a rinsing solution during the anastomoses. In all operations, 5,000 IU of heparin was used for anticoagulation, which was reversed by protamine at the termination of the operation.
LAD grafting
A 5- to 7-cm skin incision was performed over the left fourth rib, and the left fourth costal cartilage was resected, which exposed the left internal thoracic artery (LITA). During costal cartilage resection, care was taken to leave the posterior periosteum over the pleura with careful use of raspatories, so as not to enter the pleural space. Only a self-retaining retractor (Martin, Tuttlingen, Germany) retracted the skin, and costal or sternal retraction was not used. The fat pad over the pericardium was dissected free, and the pericardium was opened just beneath the LITA and not over the LAD, as would be under general anesthesia. Traction sutures were placed on the pericardium and pulled through the incision, to avoid the displacement of the heart during respiration. Two heavy U sutures buttressed with Teflon felt were placed at 1.5 to 2 cm apart and at either side of the LAD. These sutures were pulled through the incision appropriately, to pull the anastomosis territory into sight, and to diminish cardiac displacement. With these sutures pulled up, the heart becomes wedged to the thoracotomy and stabilizes itself. The distal end of the radial artery graft was anastomosed to the LAD on the beating heart, with running 8-0 polypropylene sutures using previously described techniques [9, 10]. The radial artery graft was trimmed to adequate length, and the other end of the graft was anastomosed end-to-side to the in situ LITA with running 8-0 polypropylene sutures. The wound was closed after a Hemovac drain was placed. In case of inadvertent opening of the pleura, a chest tube was inserted.
Right coronary artery grafting
Essentially the same surgical technique was used as the LAD grafting, except that the skin incision was over the right fifth costal cartilage. With this incision, the right internal thoracic artery was located more lateral from the sternum than the position of the LITA with the above-mentioned incision for the LAD grafting. Exposure of the right coronary artery was achieved by placing two U sutures buttressed with Teflon felt at the acute margin of the heart, which were pulled cephalad. The anastomoses were constructed as described above.
Thoracic epidural analgesia with bupivacain (3.75 mg/h) and fentanyl (10 µg/h) was continued for 18 hours in 1 patient. In 4 patients, postoperative thoracic epidural analgesia was not used. Patients remained in the intensive care unit overnight, and were discharged after a control angiogram was performed at the first postoperative day. All patients were contacted at their first and fourth postoperative months.
| Results |
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Control angiograms revealed patent anastomoses in all patients. However, in 1 patient, spasm of the radial artery graft was observed. The graft was patent but apparently spastic with fair filling of the LAD. The radial artery graft spasm could not be relieved by nitroglycerin and diltiazem infusions into the LITA at the time of arteriography. The patient was on continuous thoracic epidural analgesia at the time of control angiography. Because he had complete relief of chest pain after termination of thoracic epidural analgesia, nothing further was employed and the patient was discharged at postoperative day 3 on oral diltiazem and aspirin. Three weeks later, a second control coronary angiogram revealed widely patent radial artery graft with excellent flow into the LAD.
All patients were symptom free and returned to normal daily life at the first postoperative month, and they remained symptom free at the fourth postoperative month.
| Comment |
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The advent of minimally invasive techniques for cardiac surgery inevitably affected the anesthetic approaches as well, introducing new strategies towards better analgesia, earlier extubation, improved respiratory function leading to earlier ambulation, and reduced narcotic requirements [14]. Avoidance of endotracheal intubation in coronary artery surgery, however, was never before deemed necessary or feasible.
Although endotracheal intubation is employed daily in vast numbers without significant complications; documented hemodynamic responses to tracheal intubation, tube suctioning during the intubated period, and tracheal extubation may lead to myocardial ischemia and represent a potential risk for patients with coronary artery disease [15, 16]. Furthermore, in an era of patient satisfaction, eliminating endotracheal intubation, and hence tube suctioning and extubation experience in a cardiac surgical patient, may be considered a less invasive approach.
Although not universally utilized, high thoracic epidural block has recently evolved as an important adjunct of minimally invasive coronary bypass procedures [14, 17]. In our recent practice, we had been particularly satisfied with this approach in terms of facilitating beating-heart surgery and pain control (n = 47). The infusion doses required for this purpose often yield somato-sensory block at the T2 to T8 level. Sympathetic block of the heart results in bradycardia, and there is evidence that high thoracic epidural block yields coronary artery dilatation with subsequent increase in the subendocardial blood flow [18, 19]. Internal thoracic artery dilatation can be achieved, if the block level raises to the C6 level, where the stigmata of Horners syndrome can be observed (Ganapaty S, personal communication, September 1998).
Observation of the development of Horners syndrome is a very important landmark of the conduction of high thoracic epidural anesthesia, which indicates the upper tolerable level of epidural anesthesia in the awake patient. In this approach, to achieve motor block of the respiratory muscles, high doses of anesthetic agents are introduced into the epidural space. In the spontaneously breathing conscious patient, diaphragmatic respiration suffices for adequate respiratory function, whereas the intercostal muscles are paralyzed. If the block level raises above the C4 level, diaphragm paralysis also ensues. Hence, development of Horners syndrome is an indication of the safe limits of high thoracic epidural anesthesia, and should be closely monitored. It is known that cranial spread of sensory blockade in the higher thoracic level is minimal [20], indicating that once bilateral ptosis ensues, the block level will not rise unless additional epidural solution is administered.
In the presented cases, a slight accumulation of carbon dioxide was observed during diaphragmatic respiration, without clinical significance (Fig 1). Epidural administration of fentanyl may also cause minor degrees of respiratory depression. Another potential benefit of epidural anesthesia is the preservation of the fibrinolytic system, which may reduce the incidence of postoperative arterial thrombosis, as demonstrated by Rosenfeld and associates with lower extremity vascular surgery [21]. This may counterbalance the probable procoagulant activity in patients undergoing off-pump coronary surgery [22].
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One of the main concerns of epidural catheter placement is the possibility of hematoma formation, which may have drastic effects in a heparinized patient [17]. However, the risk of hematoma formation is estimated to be very low after epidural block (1:150,000) [23]. Careful patient selection, an atraumatic technique of epidural catheter placement, willingness to postpone surgery for 24 hours if a bloody tap occurred, and a minimum time interval of 60 to 120 minutes between epidural catheter placement and heparinization are suggested to minimize hemorrhagic complications [23]. Several reports suggest the relative safety of epidural anesthesia in heparinized patients or in patients who are on anticoagulant therapy [2426]. The use of a relatively low dose of heparin (5,000 IU) in these patients is not related to the possibility of epidural hematoma formation, but is rather based on our previous experience. We have been using the same protocol of heparinization in off-pump coronary surgery since 1993.
Another theoretical concern of thoracic epidural anesthesia is the possibility of inducing bronchospasm in patients with COPD or bronchial hyperreactivity, due to sympathetic blockade of the bronchial tree [27]. In our experience, however, the perioperative course of respiratory function was uneventful in all patients, and did not differ in patients with or without COPD. It was also suggested that the sympathetic nerve supply exerts little influence in bronchomotor tone in this subset of patients [27].
Although it is not our preferred minimally invasive coronary bypass method of choice [10], the H-graft technique has proved to be very suitable for the presented approach, as there was no need for intercostal or sternal retraction with this technique [28]. Although midline sternotomy or rib cage lifting techniques could also be used in this setting [9, 10], the need for sternal or rib cage retraction in a patient breathing spontaneously may limit the use of these techniques. Also, episodes of coughing or other unpredictable acute events may be difficult to manage in an awake patient with retracted ribs or sternum. The H-graft technique is simple and straightforward to apply in the above-mentioned setting. Necessity of costal cartilage resection, the use of an interposition graft, and the necessity of a second incision to harvest this graft can be deemed as disadvantages of this strategy. Also, the possibility of a "steal" syndrome through the H-graft can be considered as a possible disadvantage of this technique [11].
Spasm of radial artery grafts is a major concern [12]. In our previous experience, we have been particularly satisfied with the use of verapamil-nitroglycerin solution [12, 13]. The reason for radial artery graft spasm observed in the case in the presented series is not clear, however. The atraumatic vascular clamp (Vascu-stat; Scanlan, St. Paul, MN) used to control back-bleeding through the graft might induce graft spasm. This case was a reoperation, and routine preventive measures of graft spasm were employed. He was also on thoracic epidural bloc, indicating that high thoracic epidural block has no effect on denervated grafts. Spontaneous relief of radial artery graft spasm is also of concern.
A most interesting observation in performing coronary bypass grafting in the conscious and spontaneously breathing patient is that under diaphragmatic respiration, the heart becomes wedged to the thoracotomy when pulled upwards, hence stabilizing the anterior surface of the heart without hemodynamic compromise. This was observed consistently in all patients who underwent LAD grafting in the awake setting. This facilitates a reliable and quick coronary anastomosis.
Our initial experience confirms the feasibility of this approach, and further technical improvements are to be expected over time. It is not the intention of this report to advocate the elimination of endotracheal intubation in routine coronary bypass surgery. The basic idea behind this approach is to facilitate the learning process towards performing cardiac surgery in a less invasive manner. Such a strategy may ultimately combine the patient comfort of percutaneous revascularization procedures with the advantages of coronary artery bypass grafting with arterial grafts.
| Acknowledgments |
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| References |
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