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Ann Thorac Surg 2000;70:461-465
© 2000 The Society of Thoracic Surgeons
a Division of Thoracic and Cardiovascular Surgery, Hannover Medical School, Hannover, Germany
Address reprint requests to Dr Lichtenberg, Division of Thoracic and Cardiovascular Surgery, Hannover Medical School, 30623 Hannover, Germany
e-mail: lichtenberg{at}thg.mh-hannover
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Abstract |
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Methods. Preoperative and postoperative (days 1, 3, and 5) pulmonary function and postoperative pain were assessed in 15 patients undergoing MIDCAB (group A) by using a standardized score and were compared with 15 patients admitted for CABG (group B).
Results. Total operation time (140 minutes versus 189 minutes; p < 0.001) and duration of mechanical ventilation (300 minutes versus 840 minutes; p < 0.001) were significantly less in group A. Pulmonary function was comparable between the 2 groups on postoperative day 1 (POD 1). Vital capacity was significantly greater in group A on POD 3 (59.7% versus 40.6%; p < 0.001) and on POD 5 (74.4% versus 53.9%; p < 0.001). Similar results were found for forced expiratory volume in 1 second (group A versus B on POD 3: 56.3% versus 42.2%; p < 0.05; and on POD 5: 68.4% versus 55.5%; p < 0.01). Postoperative pain was significantly higher in group A (POD 1: score 5.5 versus 3.6; POD 3: 4.0 versus 2.9; p < 0.01).
Conclusions. MIDCAB procedures lead to better preservation of pulmonary function compared with conventional CABG despite greater postoperative pain.
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Introduction |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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With a minimally invasive direct coronary artery bypass (MIDCAB) technique using a lateral minithoracotomy, and surgery on the beating heart without CPB, some of the disadvantages of CABG can be avoided. The purpose of our study was to investigate how this new technique affects postoperative pulmonary function as well as postoperative pain when compared with standard CABG.
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Material and methods |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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Pulmonary function test and postoperative pain
Preoperatively, lung function parameters (vital capacity [VC] and forced expiratory volume in 1 second [FEV1]) were evaluated using a transportable spirometer unit (LAP2, Allied Healthcare, St. Louis, MO). Each test was performed three times and the best results were selected for analysis. Tests were then repeated on postoperative day (POD) 1, 3 and 5 by a respiratory therapist. Arterial blood gas analyses (pO2 and pCO2) were determined when breathing room air preoperatively and on POD 1, 3 and 5.
Patients quantified their pain at rest and at forced inspiration during spirometry using a verbal numerical pain scale from "0" (no pain whatever) to "10" (the worst imaginable pain). This standardized test was used previously by us and other investigators [11–13]. The postoperative pain regimen was equal in both groups. The amount of used pain drugs was comparable between the groups. Standard analgetic medication with diclofenac 1.5 mg/kg was administered to all patients postoperatively 1 to 2 hours before spirometry.
Anesthesiologic management
For group A, anesthesiologic management included the use of a single-lumen tube for intubation. A bronchial blocker (6 charriere; Rüsch, Kerner, Germany) was placed in the tube to allow selective ventilation of the right lung. Anesthesia was usually achieved by the use of etomidate, fentanyl, pancuronium bromide, and sodium thiopental. Before performing the anastomosis, heparin was administered at a dosage of 100 IU/kg body weight. Depending on the intraoperative bleeding tendency, protamine was given at a dosage to antagonize either half or all of the administered heparin. In selected cases pharmacologic reduction of the heart rate was necessary and accomplished with ß-blockers (esmolol hydrochloride 0.5 to 2.0 mg/kg). All patients received prophylactic antibiotics (ceftriaxon sodium 2 g) at induction of anesthesia and for 12 hours after operation.
For group B, the differences from group A were single-lumen intubation without using a bronchial blocker. Heparin was given at a dose of 300 IU/kg. On bypass, heparin was administered additionally to keep the activated clotting time longer than 400 seconds. After CPB, heparin was antagonized completely with protamine.
Operative technique
For group A, the patient was placed in a 30-degree right lateral decubitus position, and the left hemithorax was entered through the fourth or fifth intercostal space [14]. The usual length of incision was 8 cm. The pedicle of the left internal thoracic artery (ITA) was dissected from the caudal part of the sixth rib up to the cranial origin of the ITA. Exposure was obtained by a Thora-LIFT Retractor (Auto Suture; U.S. Surgical Corp, Norwalk, CT). Side branches were cut by electrocautery or clipped. After ITA preparation, diluted papaverine was applied externally. Then the pericardium was opened and formed a cradle to lift the heart. A mechanical U-shaped stabilizer (CardioThoracic Systems, Inc, Cupertino, CA) was placed parallel to the left anterior descending artery (LAD). The LAD was then surrounded by a 4/0 polypropylene tourniquet proximal to the chosen site for the anastomosis and also distally in case of significant bleeding. The artery was opened longitudinally, and the left ITA to LAD anastomosis was performed with a running 8/0 polypropylene suture. After the anastomosis one pleural chest drain was placed through the sixth or seventh intercostal space. The wound was closed in layers. No intercostal pain catheter was used.
For group B, coronary bypass grafting was carried out through a midline sternotomy. The left ITA pedicle was mobilized after wide opening of the left pleura. Cardiopulmonary bypass was established using a single venous and arterial cannula. Moderate systemic hypothermia (32°C to 34°C) was applied and CPB was carried out with a disposable membrane oxygenator (Sorin-Biomedica; Saluggia, VC, Italy). Myocardial preservation was achieved by using cold crystalloid cardioplegia (St. Thomas Solution) every 20 minutes during the cross-clamp period. The distal coronary anastomosis were performed in standard technique. The chest was closed using six to eight steel wires (Sherwood Medical, St. Louis, MO) after one left pleural chest drain as well as a subxiphoid mediastinal drainage tube were placed through the sixth or seventh intercostal space.
Fluid drainage in both groups was monitored hourly. Daily chest roentgenograms and ultrasonographic examinations were done to evaluate diaphragmatic motion, retention of intrapleural fluid, and atelectasis. On POD 1 the subxiphoid tube was removed in all patients in group B. The pleural tube was removed in all patients of groups A and B on POD 2.
Statistical analysis
Data are expressed as mean ± SD. Patient variables were analyzed by Student’s t test for unpaired data when appropriate. Results of pain scores and blood gas analysis as well as pulmonary function parameters were analyzed with repeated measures of analysis of variance. Multiple pairwise comparisons were done using the Bonferroni t test. Probability values less than 0.05 were considered significant.
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Results |
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Comment |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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Pulmonary impairment in postoperative cardiac surgical patients with CPB has been reported previously [1–6, 10, 11, 17]. Many authors found a significant reduction of the lung function in patients having sternotomies [1] for coronary artery bypass procedure with the ITA used as conduit [4, 5, 17]. Pain, pleurotomy, and impaired pulmonary mechanics may lead to deterioration of pulmonary function in the postoperative period. The pathologic effects of extracorporeal circulatory support on the lungs have been extensively examined and described [2, 7, 9, 10, 18]. They lead to functional changes that have been designated by Baer and Osborn as "postperfusion pulmonary congestion syndrome" [7]. Complement activation [18], thrombotic occlusion of pulmonary capillaries, and insufficient coverage of the metabolic demands of lung tissue [2] lead to an increase of extravascular lung fluids as well as atelectasis and ventilation disruptions [3, 9]. These changes are responsible for degradation of lung function after ECC. Additionally, activated leukocytes and oxygen free radicals have been implicated in the pathogenesis of lung injury associated with cardiopulmonary bypass [9]. The comparison of multivessel (CABG) and single-vessel (MIDCAB) coronary diseases resulted in significantly different operation times and slightly different anesthetic management, factors potentially influencing postoperative pulmonary function that could not be controlled for in this study.
Our results indicate that after MIDCAB surgery the irritation of the intercostal nerves during the first 3 days postoperatively proved to cause pain of higher intensity than the sternotomy after CABG procedure despite systematic analgetic therapy. Similar results were described by other authors [19]. Consequently, the influence of pain leads to inadequate and shallow breathing [4]. This explains why VC and FEV1 in the MIDCAB group on the first postoperative day were not significantly different compared to the CABG procedure. Following reduction of the wound pain better recovery of lung function was observed among the MIDCAB patients on POD 3. During the rest of the study period significantly higher lung function values were documented in these patients compared to CABG patients. One can conclude that with improved pain therapy (e.g. intercostal nerve block) the lung function can be further improved significantly during the postoperative period for MIDCAB patients. However, the oxygen concentration in the blood showed no differences in both groups.
In our study, we could demonstrate that the anterolateral approach for MIDCAB procedures, causes significantly more pain in the early postoperative period with standard analgetic treatment. Nevertheless, pulmonary function measurements show a clearly faster normalization rate in MIDCAB patients, even though temporary single lung ventilation was instituted. This might reflect a longer operation time as well as more-aggravated damage of the lungs from CPB. Patients with significantly impaired pulmonary function, therefore, should preferably undergo a MIDCAB procedure if their coronary status allows for it.
We recommend a more sophisticated analgesic treatment, such as intercostal nerve block, to further accelerate the postoperative recovery of MIDCAB patients. [15]
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