Eur J Cardiothorac Surg 2004;26:1192-1195
© 2004 Elsevier Science NL
Cutting lung parenchyma using the harmonic scalpel—an animal experiment
Thomas F. Molnara,*,
Zalan Szantóa,
Terezia Lászlób,
Laszlo Lukacsa,
Örs Peter Horvatha
a Thoracic Surgery Division, Department of Surgery, Faculty of Medicine, University of Pécs, Pécs, Hungary
b Department of Pathology, Faculty of Medicine, University of Pécs, Pécs, Hungary
Received 14 February 2004;
received in revised form 23 June 2004;
accepted 1 July 2004.
* Corresponding author. Tel.: +36 72 536 126; fax: +36 72 536 127. (E-mail: mft{at}iseb.pote.hu).
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Abstract
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Objective: Applicability of harmonic scalpel in lung surgery was investigated using an animal model. Methods: Air tightness, control of bleeding and features of tissue regeneration were compared in a 4-week time frame of investigation in animals in which either surgical stapler or harmonic scalpel were used for pulmonary resection. Results: No significant differences between the two methods were found on a clinical and histopathological basis. Conclusions: Complete lack of granuloma formation at the resection line and in its vicinity consequently restitutio ad integrum demonstrate the advantage of the harmonic scalpel over the stapler in the circumstances investigated. Overall the vibration transmission method was shown not to be inferior to the standard methods in peripherial lung tissue resection.
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1. Introduction
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Air tightness and secure haemostasis are two equally important criteria for any lung parenchyma resection technique as well as for bronchus amputation methods. Oversewing the cut edge surfaces is a time consuming procedure not only in open chest surgery, but also a complicated and sometimes cumbersome method in VATS. Stapling resection lines is generally considered the safest method and the gold standard when novel parenchyma resection techniques are evaluated. However, the significant number of metallic pieces from the cartridges left behind in the surgical field is a cause of concern for late complications [1]. Butressing the stapled line of the problematic lung parenchyma only partially solves the problem of using foreign material [2]. Diathermy alone, excellent for haemostasis, does not provide a sufficiently durable safety zone of air tightness according to everyday operating theatre practice. Lasers have an extensively investigated and well-established role in procedures on the tracheobronchial system endoluminally as well as in the field of parenchyma resection [3]. Argon beam coagulation [4] is under evaluation as are novel methods of thermal sealing [5], the modalities are about to become widely accepted. All of the above methods lead to local coagulation sealing and covering the resected surfaces by burning at temperatures between 150 and 400°C. The harmonic scalpel converts mechanical energy from the high-frequency friction to heat at the blade–tissue interface (Fig. 1) and thus controls bleeding by coaptive coagulation at temperatures ranging from 50 to 100°C. The cutting and coagulating effect is due to the viscoelastic nature of the tissue. Speed of resection and depth of coagulation are controlled and balanced by the power applied and the position of the blades [6]. The vessels of the liver are safely coapted and sealed by harmonic scalpel produced protein coagulation and therefore the method is widely used in hpatic surgery. In minimally invasive abdominal surgery such as sceletisation of stomach and suprarenal gland removal the application of the ultrasonic scalpel is preferred [7]. Transmitted vibration techniques, well established in diagnostic fields, are gaining favour in coronary angioplasty [6]. In spite of sporadic reports [8] the harmonic scalpel has not met with general acceptance in chest surgery. The behaviour of the lung surface exposed to high-frequency ultrasound and concomittant tissue changes have not been explored sufficiently. The present study reports short-term in vivo results and medium-term histological findings from examinations carried out in the healing phases, comparing the features of the resection lines cut by means of standard staple- and- cut devices and by the harmonic scalpel using a dog model.
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2. Materials and methods
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Two groups of beagle dogs were employed to evaluate the efficacy of the procedure and to check the safety of the lung parenchyma resection lines. The resected lungs of the animals were secured either by staplers (Group A) or using the harmonic scalpel (Group B). Eight beagle dogs weighed between 17 and 24kg were used. The mean age of the animals was 14.2 (11–15) months. The dogs were cared for in compliance with the ‘Guide for the Care and Use of Laboratory Animals’. The entire procedure and the aftercare were supervised by an independent veterinary surgeon in accordance with the Hungarian law, State Regulations and the Statute of Animal Experiments of the Pécs University.
2.1. Anaesthesia
Propofol induction (8mg/kg) followed by endotracheal intubation was ontinued by PEEP ventilation maintained with a Siemens 900C respirator (TV: 8ml/kg, 16 breaths/min). Anaesthesia was achieved with a mixture of inhaled oxygen (60%) and isoflurane (1%). Standard intraoperative monitoring was performed. Animals were extubated at the end of the procedure.
2.2. Operative procedure
A 10-cm long right lateral thoracotomy was performed above the sixth rib and 5x3-cm slices of the lower lobe were resected. The standard length of the resection line was 5cm. In Group A the resection was performed using an Endo-GIA Stapler 50 (Johnson and Johnson Ltd). In Group B the resection was performed using Ultracision Harmonic Scalpel (Johnson and Johnson Ltd). (Technical parameters:vibration frequency: 55,500Hz, blade excursions/force, 70µm/Level 3, jaw surface position: blunt) Completing the procedure airtightness of the lung surface was tested at 30watercm. Air was sucked out from the pleural space at the end of the procedure and no chest tubes were left behind. The average operative time was 10.8min. The average anaesthesia time was 21.2min.
2.3. Clinical examinations
Plain chest-X-ray was taken 8h following the procedures to confirm the absence of haemato/pneumothorax.. Standard postoperative care was given with a daily medical check-up until the end of the study, maximally 1 month. The general condition and respiratory status of the animals were checked twice a day.
2.4. Pathological examinations
Lung parenchyma specimens were harvested at weekly intervals from one dog in each group at weeks 1, 2, 3 and 4. The distal parts of the resection lines were examined immediately following the surgery. Animals were exterminated, as planned, at 1, 2, 3 and 4 weeks with i.v. potassium chloride and morphine and the lungs were removed. The resection lines were examined using light-microscopy. Histological evaluations were performed on specimens pooled in 10% formaldehyde. Paraffin-embedded sections were then submitted to haematoxylin eosin staining for light microscopy examination with 40x magnification. Special attention was paid to signs of inflammation and/or necrosis, degeneration or structural changes of the alveolar wall. Focus was on the depth of necrosis, viability, condition of the vessels and alveoli at the resection line.
Criteria adopted for comparison at the end points of the study were:
- (a) presence/lack of pneumothorax/haemothorax following the procedure/8h postop/at time of termination
- (b) condition of the lung tissue during the healing process investigated at weeks 1–4
- (c) structural changes at the resection lines of the lung and of the underlying parenchyma at seven day intervals till a total of 28 days.
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3. Results
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All the animals survived the procedure without complication. Immediate good postoperative conditions were observed and full lung expansions were confirmed by chest X-ray. Expanded, macroscopically healthy lungs without evidence of delayed air leak were found also in all animals of both groups at the different times of autopsy. Intrathoracally no abnormalities other than thin adhesions in the region of the stapling were encountered at the removal of the lungs after 2, 3 and 4 weeks. Normal pulmonary surfaces were noted in all cases of the Ultracision group. The histological evaluation showed a dynamic chain of events as time passed by (Fig. 2). There was no sign of necrosis or vascular endothelial injury at the resection surface cut by the harmonic scalpel as seen by light microscope in the specimens taken immediately after surgery. Only increased eosinophilic staining was detected at the cut surface the result of acute traumatic effect. The parenchyma next to the narrow acellular necrotic zone of the resection line was hyperaemic, but otherwise intact. In the stapled specimen there were also a narrow necrotic zone and sublethally injured alveolar septa and vessels and increased eosinophilia as well adjacent to the stapled cut surface. In the specimen ‘week 1’ exposed to the harmonic scalpel there were four different levels clearly distinguishable below the resection line. There was a superior layer, where the alveolar walls and the vascular elements were fragmented. Then came the transient zone of necrotic-haemorrhagic area containing fibrin and sludge-filled vascular lumens. Beneath this necrotic zone, there was a sublethally damaged region with marked eosinophilic staining. Intact lung parenchyma lay beneath. In the ‘week 1’ stapled lung specimen, the resection surface was covered with eosinophilic fibrin staining. There were obvious early signs of granulation. Slightly staining connective tissue was detectable after 2 weeks on the surface of the specimen cut by the harmonic scalpel. Granulation in the close vicinity of metal pieces was even more strongly expressed in the specimen of group B taken at the same time (week 2). The foreign body reaction had developed further and extended around the metal pieces. There was no significant change in week 3 in the specimen cut with the harmonic scalpel. No abnormalities other than tiny foci of atelectasis without any sign of granulation or collagenization were seen in the specimen taken 4 weeks following harmonic scalpel resection. This kind of complete recovery (restitutio ad integrum) was not seen in the 4-week-old stapled resection lines, however, the strong focal scar formation around the clips was obviously indicative of a foreign body reaction.
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Fig. 2. (a) Early reparative process in the week 1 stapled lung specimen. There is a thin layer of fibrin on the resected surface where early scar formation also is taking place. The active granulation tissue is densely infiltrated by lymphoid elements. (b) Four levels are distinguishable on the week 1 specimen of the harmonic scalpel group. There is a necrotic zone, an intensive eosinophilic sublethally injured level, above a haemorrhagic level, and the intact lung parenchyma underneath. (c) Granulation tissue and scar formation at the site of the removed metal clips are even more strongly expressed in the week 4 specimen in Group A (Stapler). The superficial lung parenchyma is replaced by a definite scar tissue. Irregular, narrowed microvascular elements are heralding the resulting vascular proliferation. (d) Lack of granulation and/or collagenization and only minimal focal atelectasis below the former resectional surface are notable features of the week 4 lung specimen in Group B (Ultrasonic scalpel).
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4. Conclusion
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Resected lung surfaces following the use of the harmonic scalpel were shown to be closed as safely as with the standard stapling device. Both the clinical status of the animals and the microscopic aspect of the lung specimen were as satisfactory after use of the harmonic scalpel as after stapling, the established satandard method.
No air escape occurred after either procedure. Regarding the pathology the complete lack of granulation as monitored microscopically in the long follow up specimen suggests a clear advantage of the harmonic scalpel. The findings obtained from the 4-week-old stapled lung specimen may offer a clue to some unfavourable events observed by others [2] as a triggering mechanism leading to rejection of metal pieces. In a dog model the harmonic scalpel was found a safe method for a highly limited peripheral lung resection. The use of the harmonic scalpel may offer a reliable alternative to the existing, accepted methods of tangential resections of subpleural lesions of the lung. We feel, that on the basis of the presented experiment on dogs the current use of the harmonic scalpel in humans in the mediastinal tumour dissection and resection, completion of lung fissures may be extended to the territory of the very periphery of the lung parenchyma.
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Acknowledgments
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Funding and competing interests: The project was funded by OTKA (No. TO37590) Hungary, the cost of the animals was partially supported by Johnson and Johnson Hungary Ltd.
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Abstract
1. Introduction
