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Eur J Cardiothorac Surg 2005;27:361-366
© 2005 Elsevier Science NL
a Thoracic Surgery Department, Evangelisches Krankenhaus Duisburg-Nord, Fahrner Str. 133, Duisburg 47169, Germany
b Chest Surgery department, Faculty of Medicine, Cairo University, Cairo, Egypt
c Cardiothoracic Surgery departments, Faculty of Medicine, Cairo University, Cairo, Egypt
Received 3 September 2004; received in revised form 19 November 2004; accepted 22 November 2004.
* Corresponding author. Tel.: +49 203 508 5996; fax: +49 203 508 1913. (E-mail: boseila{at}gmx.de).
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Abstract |
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 Top Abstract 1. Introduction2. Patients and methods3. Results4. Discussion5. ConclusionReferences |
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Key Words: Manubriotomy • Sternotomy • Myasthenia gravis • Pulmonary function
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1. Introduction |
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TopAbstract1. Introduction2. Patients and methods3. Results4. Discussion5. ConclusionReferences |
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The aim of this work was to assess the effects of manubriotomy versus median sternotomy as a route for thymectomy, as regards their effects on the postoperative respiratory status, which is already affected due to the myasthenic affection of the patients.
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2. Patients and methods |
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TopAbstract1. Introduction2. Patients and methods3. Results4. Discussion5. ConclusionReferences |
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Inclusion criteria were the presence of myasthenia gravis for surgical excision, which is MGFA class IIa or more, regardless of age or sex.
Exclusion criteria were the presence of chest deformities, associated pulmonary and cardiac pathology, the presence of a thymoma, and the presence of a myasthenic crisis, or the need for preoperative plasmapheresis.
To establish the diagnosis of myasthenia, all patients had undergone a careful neurological work-up prior to surgery that included physical examination, chest CT, and positive electromyography test.
Patient records were examined for the following parameters: age at onset of disease and at operation, duration of disease until surgery, patient sex, preoperative medication, medically optimized preoperative level of symptoms, pre- and postoperative pulmonary functions, operating time, duration of respiratory ventilation, length of stay in the intensive care unit and overall length of hospitalization, and postoperative complications.
2.1. Clinical assessment of the severity of the disease
The respective levels of symptoms were graded according to the MGFA classification as shown in Table 1 [4].
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Group A included patients who underwent thymectomy through a median sternotomy.
Group B included patients who underwent thymectomy through a manubriotomy.
Pulmonary functions were performed using Sensormedix 2200 pulmonary function lab. Flow volume loop, pre- and postbronchodilator was performed for every patient before surgery. Forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), peak expiratory flow rate (PEFR), peak inspiratory flow rate (PIFR) were chosen as major airway function indices, and the mean forced expiratory flow during the middle half of the forced vital capacity (FEF 25–75) represented the small airway function.
Preoperative anticholinesterase and glucocorticoid medications were administered till the morning of surgery, as prescribed by the patient's neurologist with the goal of maximizing muscle strength.
During anesthesia, the administration of muscle blocking agents was avoided. Intravenous opioids were used cautiously, because inadequate analgesia can lead to severe postoperative respiratory compromise. As regards prophylactic antibiotics, no aminoglycosides or tetracyclines or penicillins were used as they could potentiate the myasthenic effects. The operation was performed under general anesthesia using a single lumen tube.
An incision is made from 1 to 2cm below the sternal notch extending to the third or fourth intercostal spaces. The manubrium should be completely divided and the sternotomy is carried to the level of the third or fourth interspace. At this level, the sternum may be transversely transected by means of an oscillating saw if it deems necessary in the course of the operation to gain complete access.
With the sternum retracted, adequate visualization of the thymus and its cervical extensions is obtained for performance of a total thymectomy. Initially the phrenic nerves are identified. With sharp and blunt dissection the overlying mediastinal pleurae are pushed to the sides to bring the thymus and innominate vein into view. The mobilization starts with dissection of the right inferior horn off the pericardium with its associated pericardial fat pad. The right superior horn is then freed circumferentially in its middle portion up to the thyrothymic ligament. By using a right-angled clamp and blunt dissection technique, the middle portion of the right lobe and associated fatty tissue are pulled back from the area above the phrenic nerve up to the junction of the innominate vein and superior vena cava and the lateral arterial blood supply is ligated and divided. The mediastinal pleura is not intenionally opened during the course of the dissection. This completes one-half of the resection. The same steps are carried out on the left side. Separate margins are taken for frozen section analysis to make sure no thymic tissue is left behind.
This approach permits excellent visualization of the thymus gland, its vascular attachments, and all peripheral tissues in the mediastinal region limited by the thyroid gland superiorly, between the phrenic nerves laterally, and pericar dial sac and mediastinal pleura inferiorly.
In both groups, the maximal resection of the thymus gland and ectopic tissue was deemed mandatory for surgical success and improvement of the disease, and every effort was done to achieve it.
Patients were extubated in the operating room if possible. The prerequisite was enough muscle power to breathe spontaneously with satisfactory gas exchange.
After surgery, all patients were taken directly from the operating room to the intensive care unit. In the postoperative period, the patients were administered intravenous neostigmine, based on their preoperative total daily dose of pyridostigmine in a ratio of 1:60 neostigmine to pyridostigmine. Patients were changed from intravenous neostigmine to oral pyridostigmine as soon as they were able to take medications by mouth.
The following variables were monitored postoperatively: hemodynamic and respiratory parameters, and the duration of postoperative intubation and ventilation.
Three and 10 days postoperatively pulmonary functions were performed according to the preoperative scheme.
2.2. Statistics
Associations between qualitative variables were tested using 
2 and Fisher's exact test. The Student's t-test for equality of means with 2—Tail significance was also used. All values are presented as mean±standard deviation (SD), and the standard error of mean was calculated, and P-values were used, where the level of significance was set at P<0.05.
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3. Results |
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TopAbstract1. Introduction2. Patients and methods3. Results4. Discussion5. ConclusionReferences |
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4. Discussion |
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TopAbstract1. Introduction2. Patients and methods3. Results4. Discussion5. ConclusionReferences |
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4.1. Maximal thymectomy
The beneficial effect of thymectomy is thought to be maximized by the removal of all thymic tissue, including ectopic thymic tissue [7].
Anatomic studies [8,9] have proven that islets of ectopic thymic tissue can be present in mediastinal and cervical fat. Thus, the extended transsternal approach and the transcervical–transsternal approach have been advocated to maximize the completeness of thymectomy and improve results. Through their ‘maximal’ thymectomy through the ‘extended’ transsternal approach, Jaretzki and associates in 1988 [7] reported very good long-term results in their patients with a 46% remission rate.
Bril and colleagues reported in 1998 [5] an excellent long-term (8.4 years) remission rate (44.2%) with the improved transcervical thymectomy advocated by Cooper and associates in [10], which matches the results after en bloc transcervical–transsternal ‘maximal’ thymectomy of Jaretzki et al. [7] with their long-term remission rate of 46% after 3.3 years.
The partial sternum-splitting (manubriotomy) technique seemed to be a rational compromise between the extended incisions for cervicomediastinal thymectomy, which is very invasive, and the limited incision for transcervical thymectomy, which might not allow for a complete thymectomy. Gracey and associates [11] reported about thymectomy through a manubriotomy with good immediate postoperative results. They stated that only 9.4% of their patients needed postoperative mechanical ventilation, and that these were preoperatively in Osserman classes IIb and IIc, with significant bulbar symptoms (equivalent to classes III and IV MGFA clinical classification). Different authors stated that partial sternotomy permits excellent visualization of the thymus gland, its vascular attachments, and all peripheral tissues in the mediastinal region limited by the thyroid gland superiorly, between the phrenic nerves laterally, and pericardial sac and mediastinal pleura inferiorly. They also stated that the results are very similar to the literature data [12–14].
4.2. Pulmonary status after thymectomy
Evaluation of preoperative pulmonary functions in myasthenic patients is considered vital as these might indicate the necessity for postoperative mechanical ventilation, and for special precautions postoperatively for prevention of postoperative pulmonary complications.
There are four particularly helpful risk factors in predicting the need for postoperative mechanical ventilation in patients undergoing thymectomy: duration of myasthenia gravis, history of chronic respiratory disease, pyridostigmine dosage above 750mg/day, and preoperative vital capacity of less than 2.9l [15]. Loach considered a vital capacity below 2.0l as a predictor for the need of postoperative mechanical ventilation [16]. This could not be correlated with our results as we excluded patients with associated pulmonary pathology and the presence of myasthenic crisis, and none of our patients needed pyridostigmine in a dose higher than 360mg/day.
Fact is, patients with myasthenia gravis face major pulmonary problems as part of their disease process, as the myasthenic forced vital capacities are significantly lower than those for normal subjects. Due to expiratory weakness, cough efficacy is reduced and may lead to postoperative pulmonary complications [17].
The preoperative data of the patients in our study have demonstrated the same findings in the form of a FVC of 69.6% and an FEV1 of 70.8% of predicted values.
The risk of postoperative respiratory insufficiency was estimated to be 50% higher for patients after transsternal thymectomy [18].
This increased risk with median sternotomy for thymectomy is related to impaired pulmonary mechanics after a major chest incision. Splinting of the chest, damage to the phrenic nerves, mediastinal infection, a higher pain medication requirement, and postoperative pulmonary complications such as atelectasis and pneumonia have all been cited as disadvantages to the trans-sternal approach [19].
The data from our study show that the postoperative pulmonary status of the patients undergoing thymectomy through a manubriotomy approach was significantly better than those who had a median sternotomy approach. This was reflected by the necessity of postoperative ventilation, the duration of postoperative ventilation, and the duration of ICU stay.
The pathophysiology of myasthenia gravis entails the autoimmune mediated binding of antibodies to the acetylcholine receptors, followed by their lysis by complement-mediated factors. Striking clinical improvement may occur after thymectomy without any change in measurable immune parameters, including the absence of change in serum levels of auto antibodies [20]. This observation can explain the significant improvement in the pulmonary function parameters in this study, namely the FEV1 done 10 days postoperatively. Despite the expected deterioration in FVC and FEV1 due to pain following median sternotomy or manubriotomy the mean FEV1% increased from 70.8 to 72.5% with a P-value <0.001. An explanation to this early postoperative improvement in the pulmonary functions is the optimization of therapy during the postoperative intensive care unit stay.
Ten days postoperatively pulmonary functions showed that the FVC and PIFR were significantly higher postoperatively in the manubriotomy group than in the median sternotomy group. At the same time the forced expiratory volume in the first second (FEV1); the peak expiratory flow rate (PEFR), and the mean forced expiratory flow during the middle half of the forced vital capacity (FEF 25–75) showed better values in the manubriotomy group, although not statistically significant.
4.3. Mortality and morbidity after thymectomy
In our study, as well as in recent other studies, no mortality was encountered irrespective of surgical approach [21–23]. Morbidity rates have differed, depending on the approach chosen for thymectomy.
As argued by the proponents of the transsternal approach, diminished morbidity rates after transcervical and thoracoscopic thymectomy are unlikely to compensate for the perceived disadvantage of leaving behind thymic tissue in the anterior mediastinum which is not readily accessible through these approaches [24].
Transsternal thymectomy with extensive resection of the parathymic fat pad carries a substantial risk of nerve damage. In myasthenic patients with already compromised respiratory muscle function, nerve palsies may amount to catastrophic injuries [7].
Several investigators reported on the postoperative complications after transsternal thymectomy in detail. They had a phrenic nerve palsy rate of 5%, and a recurrent nerve palsy rate of 3%. Impaired wound healing occurred at a rate of 9.3–16% in the form of sternal fistula, wound infection, seroma, and hematoma, keloid formation, and defective wound healing. Atelectasis and pneumonia occurred at a rate of 8–14%. Thromboses related complications occurred at a rate of 1–2.7% [24].
Jaretzki and associates [7] rated the risk of postoperative empyema, deep sternal wound infection, sternal wound dehiscence, chylothorax, and pulmonary embolism at 1% each.
Pego-Fernandes and associates in 2002 [12] reported their complications with a partial sternotomy in 478 myasthenia patients. There were four patients who needed postoperative ventilation, one patient developed osteomyelitis of the sternal bone, and five patients had subcutaneous fluid collection.
As regards postoperative complications in our median sternotomy approach group, the incidence was similar to the reviewed literature reports, with mediastinitis being 7%, pneumonitis 15.4%, and phrenic nerve palsy in 3.8% (1 patient). This was higher than in the manubriotomy group, where mediastinitis was not encountered, the incidence of pneumonitis was reduced to 8.3% and phrenic nerve palsy did not occur. All these mentioned complications affect indirectly the pulmonary status of the patients, which is of specific concern for the myasthenic patients who may have global respiratory muscle weakness [1].
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5. Conclusion |
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TopAbstract1. Introduction2. Patients and methods3. Results4. Discussion5. ConclusionReferences |
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Controlled prospective studies are necessary to compare and evaluate the different less invasive but complete thymectomy techniques.
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References |
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TopAbstract1. Introduction2. Patients and methods3. Results4. Discussion5. ConclusionReferences |
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This article has been cited by other articles:
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  L. Chalabreysse, A. Orsini, C. Vial, and F. Tronc Microscopic thymoma Interactive CardioVascular and Thoracic Surgery, February 1, 2007; 6(1): 133 - 135. [Abstract] [Full Text] [PDF]
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 M. Zielinski and J. Kuzdzal Safety of complete median sternotomy approach for thymectomy Eur. J. Cardiothorac. Surg., September 1, 2005; 28(3): 504 - 504. [Full Text] [PDF]
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