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Ann Thorac Surg 1999;67:1078-1082
© 1999 The Society of Thoracic Surgeons

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Original Articles

Effect of internal thoracic artery preparation on blood loss, lung function, and pain

^a Department of Thoracic and Cardiovascular Surgery, JWG University Hospital, Frankfurt/Main, Germany
^b Department of Pulmology, Johann Wolfgang Goethe University Hospital, Frankfurt/Main, Germany

Accepted for publication October 15, 1998.

Address reprint requests to Dr Wimmer-Greinecker, Department of Thoracic and Cardiovascular Surgery, University Hospital Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
Background. Postoperative blood loss, respiratory distress, and pain after coronary artery operation were assessed in a prospective, randomized, clinical study comparing two techniques of internal thoracic artery preparation.

Methods. In group A (n = 57) the internal thoracic artery was dissected with the entire surrounding connective tissue after opening the pleura, using routine lateral pleural drainage. In group B (n = 55) a venoarterial pedicle was prepared without surrounding muscle leaving the pleura intact. We assessed blood loss, clinical outcome, lung function, location, intensity, and quality of pain 6 days and 3 months after the operation.

Results. Significantly higher blood loss was observed in group A (A, 608 ± 58 mL; B, 470 ± 48 mL; p = 0.027). Forced expiratory volume in 1 second was significantly decreased in group A 6 days after surgery (A, 76.0% ± 1.6%; B, 83.2% ± 1.6%; p = 0.020). The forced expiratory volume in 1 second correlated to inspiratory vital capacity, which confirmed the advantage of the venoarterial technique (A, 0.771 ± 0.021; B, 0.832 ± 0.020; p = 0.003). Vital capacity was significantly higher in the venoarterial group at 3 months (A, 85.2% ± 2.1%; B, 98.5% ± 1.2%; p = 0.009), but not on postoperative day 6. The incidence of pleural effusion and atelectasis was significantly higher in group A (effusion: A, 52.6%; B, 23.6%; p = 0.002; atelectasis: A, 42.1%; B, 20.0%, p = 0.015). Sternal pain (A, 36.8%; B, 9.1%; p = 0.001) and suspenders pain (A, 33.3%; B, 7.3%; p = 0.001) occurred more often in group A. When using a multidimensional pain score, patients in group A experienced significantly sharper (6 days: A, 6.7 ± 0.3; B, 3.3 ± 0.2; p = 0.018; 3 months: A, 3.5 ± 0.3; B, 1.4 ± 0.3; p = 0.046) and more annoying pain (6 days: A, 7.6 ± 0.2; B, 2.7 ± 0.1; p = 0.036; 3 months: A, 6.6 ± 0.3; B, 2.3 ± 0.2; p = 0.040).

Conclusions. These results demonstrate that the venoarterial preparation technique is superior to conventional internal thoracic artery preparation regarding postoperative blood loss, lung function, and pain.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
The internal thoracic artery (ITA) is the graft of choice for myocardial revascularization owing to superior graft patency and increased long-term survival compared with saphenous vein bypass grafting [1–5]. However, studies dealing with these subjects were performed regardless of ITA preparation technique.

There are various methods for ITA harvesting. Most authors prepare the ITA conventionally as a musculofascial pedicle. The ITA can also be harvested as a semiskeletonized vessel as described by Horii and Suma [6] by performing lysis of the endothoracic fascia leaving the pleura intact, or as an entirely skeletonized vessel [7] by harvesting of a generous pedicle containing veins, fat, lymphatics, and fascia, and denuding the ITA by bipolar cautery secondarily.

Several studies have been conducted to compare the postoperative course in patients after coronary artery bypass grafting. Patients who received saphenous vein grafts versus ITA grafts showed a higher incidence of pleuropulmonary complications [8], pleural effusions, and chest tube drainage [9, 10], as well as a greater need for secondary thoracotomy [10], a higher incidence of postoperative pain [8], and intercostal neuralgia [11].

The aim of the present study was to compare the clinical outcome of patients after ITA preparation with two different ITA harvesting techniques considering postoperative blood loss, pulmonary function, and pain.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

 
In a prospective, randomized, clinical trial we studied 112 consecutive patients undergoing coronary artery bypass grafting with one ITA graft. Two different techniques of ITA harvesting were applied. In group A (n = 57) the ITA was dissected conventionally as a wide pedicle with surrounding tissue and parts of the endothoracic fascia. In that group, incision of the pleura and lateral pleural drainage was performed routinely. In group B (n = 55) the ITA was prepared as a venoarterial pedicle without muscular support according to the method described by Horii and Suma [6]. We tried to avoid opening the pleural space in that group. In both groups, ITA dissection was completed before heparinization and cannulation for cardiopulmonary bypass. In both methods, dissection of the ITA was performed in large part with electrocautery, and side branches were occluded with hemoclips. For exposing and harvesting the ITA, a Chevalier retractor (Delacroix, France) was used. Cardiopulmonary bypass was instituted using a capillary membrane oxygenator. No topical cooling of the heart was performed.

Patients with prior cardiac surgery, abnormal lung function (chronic obstructive pulmonary disease), abnormal clotting parameters or coagulation disorders, abnormal left ventricular function (ejection fraction less than 40%), diabetes, degenerative alterations of the vertebral column, or psychiatric disturbances were not included.

All examinations were performed 1 day before and 6 days and 3 months after operation. Chest tube drainage was documented until 12 hours postoperatively. Management of postoperative bleeding consisted of autologous retransfusion of the first 500 mL of chest tube blood. If blood loss exceded 500 mL, fresh-frozen plasma and packed red blood cells were administered individually, and chest tube blood was processed in a cell-saving device and retransfused under laboratory monitoring. On termination of cardiopulmonary bypass and administration of protamine, activated clotting time was maintained between 100 and 120 seconds.

Body plethysmography was performed to assess lung function. The following parameters were compared between groups: vital capacity (VC), forced expiratory volume in 1 second (FEV₁), and FEV₁/VC%. At each examination, arterial blood gas analysis was performed (PO₂, PCO₂, O₂ saturation, and hemoglobin).

To monitor pleural effusion and atelectasis, a chest roentgenogram was performed routinely 1 day before the operation and 1 day, 6 days, and 3 months postoperatively. Pleural effusion was considered relevant when exceeding the phrenocostal angle, and atelectases were recorded when showing a clear radiologic shadow of a width of more than 5 mm. Roentgenograms were examined by the same radiologist.

All patients received the same postoperative analgesia consisting of oral nonsteroid antiphlogistics during the first 3 days (paracetamol, 3 x 500 mg).

Localization of pain was classified as sternal, shoulder, or suspenders pain. The latter was defined as bilateral parasternal pain being expressed over more than half the height of the thorax.

Postoperative pain quality and intensity was evaluated using a multidimensional pain score [12]. Pain quality was divided into a subscale of 7 topics, each consisting of three adjectives, to which patients had to allot a numeric score (1 to 4 points; Table 1).

This study was approved by the local institutional human research committee on May 29, 1996. Written informed consent was obtained from each patient.

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
One hundred twelve consecutive patients were studied (group A, n = 57; group B, n = 55). Demographic data collected for each patient included age, sex, nicotine use, left ventricular function, number of grafts, aortic cross-clamp time, and cardiopulmonary bypass time. There was no significant difference between groups concerning these baseline variables (Table 2). Additional aortic valve replacement was performed in 8 patients in group A and in 7 patients in group B (not significant).

There was no mortality in either group, and no sternal infection or instability was observed.

Postoperative blood loss
Postoperative blood loss within the first 12 hours (Fig 1) was significantly higher in group A than in group B (A, 608 ± 58 mL; B, 470 ± 48 mL; p = 0.027). There was no significant difference in postoperative application of fresh-frozen plasma and packed red blood cells between the two groups. Reexploration of the chest because of bleeding was necessary in 1 patient in group A and in 2 patients in group B (not significant).

View larger version (28K): [in this window] [in a new window]   Fig 1. Postoperative blood loss.

Repeated assessment of arterial blood gas analysis showed no significant difference.

Radiologic assessment
The incidence of pleural effusions was significantly higher in group A versus group B 6 days after operation (A, 52.6%; B, 23.6%; p = 0.002) (Fig 2); Atelectasis (A, 42.1%; B, 20.0%; p = 0.015) was seen more often in group A than in group B. No significant difference was seen 3 months postoperatively (Fig 3).

View larger version (26K): [in this window] [in a new window]   Fig 2. Pleural effusion.

View larger version (29K): [in this window] [in a new window]   Fig 3. Postoperative atelectasis.

When using a multidimensional pain score to evaluate pain quality, group A patients suffered from significantly sharper (stabbing) pain at 6 days (A, 6.7 ± 0.3; B, 3.3 ± 0.2; p = 0.018) and 3 months after surgery (A, 3.5 ± 0.3; B, 1.4 ± 0.3; p = 0.046) and more annoying (troublesome) pain (6 days: A, 7.6 ± 0.2; B, 2.7 ± 0.1; p = 0.036; 3 months: A, 6.6 ± 0.3; B, 2.3 ± 0.2; p = 0.040). Sudden pain was expressed significantly less in group B 3 months postoperatively (A, 4.0 ± 0.3; B, 1.2 ± 0.3; p = 0.008). Rhythmical, persistent, electrifying, and thermal pain showed no significant differences between groups.

	Comment

Top Abstract Introduction Patients and methods Results Comment References

 
The composition of patient groups (Table 2) is sufficiently balanced to elucidate the effect of surgical technique per se on postoperative variables.

The ITA is widely accepted as the graft of choice for myocardial revascularization, but the technique of ITA preparation has been discussed rarely. Several authors consider the venoarterial technique disadvantageous because of the anatomic localization of the ITA in the anterior mediastinum after chest closure. There is concern that a closed pleura might inflict increased tension on the graft by forcing it against the sternum [13]. Furthermore, the ITA may be harmed during eventual reopening of the chest. This problem may be solved by placing the ITA into a pericardial and pleural incision, allowing it to slide under the lung [14]. We dissect the peripleural fat in the upper mediastinum, thereby creating a tunnel for safe placement of the ITA. In most cases, the lung covers the ITA pedicle, even if the pleura remains closed. In addition, limited chest wall trauma by harvesting the ITA venoarterially may better maintain sternal perfusion as documented by Parish and associates [15], resulting in a reduction of sternal wound infections. In the present study, no sternal infections were observed in either group.

A potentially prolonged cutdown time for the venoarterial technique has been discussed as well. Our own experience showed no marked time difference between the techniques examined.

The present data show that the venoarterial technique is superior to the conventional technique with respect to postoperative bleeding. This may be owing to reduced trauma of the surrounding musculofascial tissue. The intact pleura may even cause tamponade effects contributing to reduced blood loss.

There is evidence that impairment of pulmonary function in patients undergoing coronary artery bypass grafting is more pronounced when ITA grafts [5, 9, 16, 17] are used. Previous reports comparing patients with saphenous vein versus ITA grafts suggest that the reasons for poor lung function may include pleurotomy, chest wall distortion because of the use of a retractor, and even postoperative pain. Cohen and coworkers [8] have evidence that postoperative FEV₁ is reduced with and without ITA harvesting. However, the present results indicate a significant reduction of FEV₁ and FEV₁/VC ratio only in patients who were operated on conventionally, implying that the ITA preparation technique does influence postoperative lung function. In our opinion, reduced FEV₁ and even FEV₁/VC ratio is determined substantially by postoperative pain in the early postoperative course. There was no difference between groups in the 3-month follow-up. Matsumoto and associates [16] demonstrated that pleurotomy does not affect postoperative FEV₁. However, in that study the pulmonary function test was performed 20 to 30 days after operation and may not be influenced by postoperative pain.

Pleural effusion and atelectasis of the lower lobes, which were significantly more frequent in group A, contribute to reduced lung volume, and may be associated with the postoperative decrease of FEV₁ and FEV₁/VC ratio.

Controversy exists about the effect of pleurotomy on postoperative pulmonary function. Previous data demonstrated that pleurotomy in patients undergoing coronary artery bypass grafting reduces pulmonary function [17, 18] because of a higher incidence of pleural effusion and atelectasis [19, 20], increased intrapulmonary shunting [21], and increased postoperative pain owing to more extensive surgical trauma to the chest wall [8, 22]. Matsumoto and colleagues [16] compared a skeletonizing technique with a wide musculofascial pedicle and demonstrated a significant reduction of VC in the conventional group. In our standard group, a significant decrease of VC was documented 3 months postoperatively as compared with the venoarterial group. Opening of the pleural space leads to extensive adhesions of the lung, resulting in pulmonary restriction and decreased VC in the long term.

In the present study, assessment of postoperative pain quality and intensity was performed using a multidimensional pain score [12]. The subscale and description of pain quality were translated from German into the English language, and may not be exactly identical to the German implication.

Severe postoperative pain in patients undergoing coronary artery bypass grafting who received ITA grafts compared with saphenous vein grafts has been documented in previous studies [8]. Using a numeric rating scale, Cohen and associates [8] demonstrated significantly more postoperative pain in patients undergoing ITA harvesting and reported that age, smoking, and sex had no effect on postoperative pain. Our data also show that patients receiving an ITA graft in the standard fashion suffer significantly more often from stabbing and troublesome pain. They also experience sternal and suspenders pain significantly more often, probably because of chest wall trauma and damage to intercostal nerves.

Differentiation of whether the venoarterial pedicle or the closed pleura has more impact on the improved results in group B remains difficult. We assume that the preparation of a wide ITA pedicle with surrounding tissue and parts of the endothoracic fascia has more influence on blood loss and postoperative pain, whereas a closed pleural cavity has a greater positive effect on postoperative lung function. Both facts do have an additive impact on postoperative outcome though, and evaluation of groups separating these matters would require larger numbers of patients.

The findings of this study have important clinical implications, in that the venoarterial method is superior to the conventional technique in terms of postoperative bleeding, lung function, and pain. We recommend that the venoarterial technique should be performed routinely.

	References

Top Abstract Introduction Patients and methods Results Comment References

 

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