Longterm comparison of soft palate scars after UPPP made by CO2, contact Nd-YAG or combined CO2 and Nd-YAG laser beams

C0₂ laser, contact Nd-YAG laser and Combolaser (combined CO₂ and Nd-YAG laser beam) vary distinctively in the way they interact with target tissue. To study the quality of mature scars produced by these lasers, the ultrastructure and amount of collagen in soft palate scars after 60 uvulopalatopharyngoplasty (UPPP) operations were analysed. The CO₂ laser was used in 19, contact Nd-YAG in 21 and Combolaser in 20 operations. At a clinical follow-up examination carried out, on average, 51 (range 34–74) months postoperatively, a specimen was obtained from the soft palate scar for collagen analysis. Postoperative complaints of the patients were acknowledged. No differences between the laser groups were observed concerning the gross appearance of the scars or the amount and ultrastructure of collagen. Neither the frequency nor the quality of post-operative symptoms showed any differences between the lasers. Although the initial tissue effects are different, long-term remodelling produces nearly identical soft palate scars after the use of CO₂, contact Nd-YAG and Combolaser beams.     

Tissue changes following application of lasers to the rabbit brain

Summary The effect of CO₂ and Nd-YAG lasers on rabbit brain tissue was investigated using various energy levels. With a defocussed CO₂ laser beam the depth of damage increases with application time; the superficial extension remains nearly equal. In focussed setting the CO₂ laser produced deep, fissured incisions; surrounding reactions remain relatively low. With the Nd-YAG laser the depth of the lesion is clearly dependent on the energy applied. In contrast to the absorption of the defocussed CO₂ laser beam at the surface, the Nd-YAG laser beam penetrates rather deeply into the brain tissue and produces necroses at even greater depths. The depth effects of laser radiation are limited. The focussed CO₂ laser beam appears suitable for cutting and vaporizing brain tissue. With the defocussed Nd-YAG laser beam selected areas may be destroyed by heat with sufficiently accurate prediction of depth.

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Zusammenfassung Bei variierter Energie wurde die Einwirkung des CO₂- und des Nd-YAG-Laser auf das Hirngewebe des Kaninchens systematisch untersucht. Bei defokussiertem CO₂-Laser-Strahl nimmt bei weitgehend gleichbleibender Oberflächenausdehnung die Schädigungstiefe entsprechend der Einwirkungsdauer zu. In fokussierter Stellung führt der CO₂-Laser zu tiefen spaltförmigen Inzisionen. Die Umgebungsreaktion bleibt hierbei relativ gering. Beim Nd-YAG-Laser besteht eine klare Abhängigkeit der Läsionstiefe von der verwendeten Energie. Der Nd-YAG-Laser-Strahl dringt im Gegensatz zum defokussierten CO₂-Laser-Strahl, der oberflächlich absorbiert wird, relativ weit in das Hirngewebe ein und verursacht auch noch in größeren Tiefen Nekrosen. Die Tiefenwirkung der verwendeten Laser-Strahlung ist jedoch begrenzt. Insgesamt halten wir den fokussierten CO₂-Laser-Strahl zum Schneiden und Verdampfen von Hirngewebe für geeignet. Mit dem defokussierten Nd-YAG-Laser-Strahl hingegen lassen sich umgrenzte Areale gezielt und mit genügend genau voraussagbarer Tiefenwirkung thermisch zerstören.

     

Use of the Nd-YAG laser in neurosurgery

Summary After many years of experience, in general we prefere the Nd-YAG laser, although the CO₂ laser is an advantage in a few specific cases (lipomas, cranial synostosis). While the focused CO₂ laser may be used as a cutting instrument in less vascular tissue with little trauma to the surroundings, the Nd-YAG laser produces a homogeneous coagulation with an energy dependent depth effect. Thus, with the Nd-YAG laser residual tumour tissue can be selectively and with a predictable depth effect thermally destroyed. Because of its excellent coagulation property, the use of the Nd-YAG laser is particularly indicated in highly vascular meningeal tumours. The shrinkage of a tumour and its demarcation which is due to the varying absorption properties facilitates the dissection and allows in addition the preservation of normal tissue.     

Uvulopalatopharyngoplasty with CO2, contact ND-YAG or combined CO2 and ND-YAG laser beams

Three different surgical lasers, ie CO₂, contact Nd-YAG and Combolaser (combined simultaneous and co-axial CO₂+Nd-YAG laser beam), were used for 76 uvulopalatopharyngoplasty (UPPP) operations. The effects of different lasers on intra-operative bleeding, operation time and post-operative pain were compared. Sixty patients with obstructive sleep apnoea syndrome (OSAS) and 16 patients with socially disturbing snoring were operated on. The CO₂ laser was used in 24 patients, contact Nd-YAG was used in 27 patients and Combolaser was used in 25 patients. The Combolaser was associated with significantly less intra-operative bleeding and a shorter operation time. During the immediate recovery period, post-operative pain was most mild after operations with the CO₂ laser when graded according to need for analgesics, or by the patients' subjective evaluation. Concerning possible post-operative complaints or overall outcome of the UPPP operation, no differences were found between the lasers.     

Comparison of oedema formation after CO2 and Nd-YAG laser therapy and cryosurgery

A comparison of oedema formation, as measured by leakage of the dye Evans blue from the circulation, was carried out in the laboratory rat employing standardized lesions on the anterior abdominal wall by various regimens of CO₂ laser, Nd-YAG laser and cryosurgery over a 4 h period. The CO₂ laser at high power produced significantly less oedema than any other modality (p<0.05) while the Nd-YAG laser at high power produced significantly more (p<0.05) than any other. Nd-YAG low power, cryosurgery in one of two freezes and the CO₂ laser at low power all produced a moderate degree of oedema (no significant difference). These findings have particular clinical relevance in sites where oedema may cause major functional or cosmetic problems as in the oro-facial region. The animals remained sedated over the period of observation so that any possible discomfort was eliminated.     

The carbon dioxide laser surgical unit as an instrument for surgery of brain tumours — its advantages and disadvantages

Summary The author started in 1969 his studies on developing the practical models of the carbon dioxide laser surgical units and produced Medilaser-S, Model MEL-442 and MEL-444.By the end of 1982 the author had operated on 143 cases of brain tumour with the laser. Most of those cases were brain tumours which were difficult or impossible to remove by conventional means. The major points of this paper are as follows: The principle of the laser, the mechanism of the CO₂ laser, the biomedical features of the CO₂ laser, the advantages and disadvantages of the CO₂ laser, indications and contraindications for the use of the CO₂ laser, development of the CO₂ laser surgical units, surgical procedures and techniques of brain tumour laser surgery, adjuvant methods of laser surgery and comparison between the CO₂ laser and the Nd-YAG laser.     

Separate and combined use of Nd-YAG and carbon dioxide lasers in liver resections: A preliminary report

A series of 15 patients have undergone liver resection by laser, 10 by use of the carbon dioxide laser alone, one with the neodymium-doped yttrium aluminium garnet laser (Nd-YAG) alone, and four with combined use. Partial and anatomical liver resections have been done without mortality or haemorrhagic complications, although initial haemostasis was always difficult with the CO₂ laser alone. Bile leakage occurred in four patients, but it stopped spontaneously in three. Histology showed a necrotic zone less than 2 mm deep when the CO₂ laser was used alone, but the zone was 5–6 mm deep with the Nd-YAG laser and 1.6–1.8 mm deep when the two were used in combination. Thus, the most effective cutting, with good haemostasis and minimum damage to the underlying liver, was achieved with the combined lasers. A precise superposition of the two spots was achieved with a new handpiece prototype.     

Biophysical basis and technical requisites for the use of Nd-YAG laser in neurosurgery

Summary The different interactions between laser light and biological tissue are demonstrated for the CO₂- and the Nd-YAG-laser by histological examinations.For Neurosurgery the following results became significant: The CO₂ laser has become an important tool in contactless cutting and vaporization. The Nd-YAG-laser is suitable as a coagulator whenever the site and vascularity make the removal of a tumour difficult. For the various surgical techniques in Neurosurgery using the Nd-YAG laser, special laser attachments have been developed including micro-surgical and endoscopic instruments.     

Laser Therapy in Pulmonary Medicine

In this review, the different laser applications for diseases in the thoracic cavity are presented. The different laser types, Nd-YAG, CO₂, diode lasers and photodynamic therapy (PDT) and their indications are presented. The indications for endobronchial laser vary from benign disorders like granuloma to the more frequent ablation of endobronchial tumours. The promising use of treatment with PDT in early stage lung cancer and its adjuvant role in surgical resection of pleural malignancies is discussed. Emphasis is given to the data obtained so far for the different laser applications. Paper received 4 March 1997; accepted in final form 10 November 1997.     

Treatment of Small Congenital Nevocellular Naevi Using a Combination of Ultrapulse Carbon Dioxide Laser and Q-Switched Frequency-Doubled Nd-YAG Laser

This report describes treatment combining Ultrapulse CO₂ laser and Q-switched frequency-doubled neodymium:yttrium-aluminum-garnet (Nd-YAG) laser for a number of congenital nevocellular naevi (CNN). The Ultrapulse CO₂ laser removes the superficial component, which contains most of the color, preserving the integrity of the reticular dermis. At a later stage, any residual color is targeted using the Nd-YAG laser. To date, a total of 10 histologically proven CNNs have been treated at the Laser Suite. The median age of the patients was 18 years (range, 13–24 years). All the patients were white females. The patients accepted for treatment had relatively small lesions (mean surface area, 352 mm²; range, 50–1,092 mm²), but the lesions were either cosmetically sensitive or located in an anatomically critical area in which excision could result in a scar that would be unpredictable. The median follow-up period was 24 months. The overall results have been satisfactory, with reduction of color and no significant scarring. The minor textural and pigmentary changes were acceptable to the patients.     

Experimental study of laparoscopic selective proximal vagotomy using a carbon dioxide laser

This study investigated the effectiveness of laparoscopic selective proximal vagotomy using a CO₂ laser. Irradiation of the stomach was performed from the serosal aspect using a defocused CO₂ laser beam. In the first experiment, the inhibitory effect on cysteamine ulcers in rats was compared between surgical vagotomy and CO₂ laser vagotomy using three different irradiation fields. The results suggested that irradiation near the lesser curvature provided sufficient denervation. In the second experiment, CO₂ laser vagotomy was performed laparoscopically in dogs. The procedure lasted less than 1 h and a postoperative endoscopic Congo red test confirmed its effectiveness. Subserosal tissues including the vagus nerve branches showed degeneration and were replaced by fibrosis 3 months postoperatively, but the deeper tissues were spared. In conclusion, laparoscopic CO₂ laser vagotomy may be as effective for reducing acid secretion as standard surgical vagotomy. Its simplicity and safety suggest that a clinical trial in humans may be warranted.     

An experimental study on the effects of the steel scalpel,electrocautery and various lasers on oral tissue

The tissue effects of the steel scalpel, electrocautery, CO₂ laser and contact Nd-YAG laser were studied on rat tongue. The tip of the tongue (3 mm) was cut off and fixed for histology. The rats (6-10/method/age group) were kept alive for 2, 7 and 14 days, when the remaining tongue was resected. In each postoperative age group the effects to the epithelium and muscular layer were determined separately. Peroperative bleeding was measured and attention was paid to wound contraction and inflammatory cell infiltration.Postoperative bleeding occurred with the steel scalpel and electrocautery, but not with the lasers. A significant delay in early re-epithelialization was observed after the use of all thermal knives. Resection with steel scalpel was found to result in the smallest damage to the tissues on day 0 (P< 0.01), whereas on day 7 no significant differences were observed between scalpel, electrocautery and CO₂ laser. On the other hand there was a significant difference between scalpel and contact Nd-YAG laser (P< 0.05). On day 14 these differences were no longer significant.Wound contraction on days 7 and 14 was evident after scalpel incision and slight after thermal knives.The steel scalpel causes less tissue damage than the thermal knives, whereas the advantages of a bloodless operation can be achieved with both lasers used in this study.     

CO2-Laser in neurosurgery

Summary New technical tools in surgery are only beneficial if they offer real improvements compared to the traditional techniques or if they open absolute new indications in surgery. Therefore we have tried to find absolute indications for the use of the indifferent laser system.Due to the specific wavelength the CO₂-Laser is entirely absorbed at the surface. This specific performance allows one to use the CO₂-Laser as the most precise cutting and as a completely new vaporizing instrument. It has become an irreplaceable tool in surgery of central lesions and brain stem tumours and also for spinal cord tumours. In addition the CO₂-Laser is adaptable to the operating microscope.A gain of the same importance in the meantime is the Nd-YAG Laser, which works specially for coagulation, volume coagulation and endoscopic use.It is certain that laser surgery will evolve for beyond our imagination.     

Holmium-YAG and carbon dioxide laser ablation of normal and infarcted myocardium in the canine model

Surgical and transcatheter ablative treatment of ventricular tachycardias is based on endocardial mapping and removal of myocardial areas involved in sustaining the arrhythmia. Recently, argon and neodymium-YAG laser energy have been employed for the ablative treatment of ventricular tachycardia. In the present study the effects of holmium-YAG laser irradiation on normal and infarcted myocardium in the canine model were compared with those of the CO₂ laser. Myocardial infarction was created in 11 dogs by a two-stage left anterior descending coronary artery ligation. Laser irradiation of normal and infarcted myocardium was performed at about 1, 4 and 12 weeks following ligation, with energies of 5, 10, 20 and 30 J. A total of 218 irradiation induced craters were sectioned through the central axis and the evaporized, vacuole and denatured crater areas were morphometrically calculated. Total crater areas following holmium-YAG laser irradiation were significantly larger, with shallower penetration but larger lateral extension of evaporized, vacuole and denaturation areas. Perforations occurred only with CO₂ laser irradiation. Effects on normal and infarcted myocardium were similar and independent of infarct age. It is concluded that the holmium-YAG laser is probably more effective and safer than the CO₂ laser for myocardial ablation.     

The use of the Nd-YAG and the CO2 laser in neurosurgery

Summary Over the last 3 years 120 patients have been operated on using laser techniques. This technique was chosen where technical difficulties were anticipated due to the size, the vascular supply or the localization of the process. Although the use of laser technique requires experimental work, before it can be applied clinically some distinct advantages could be demonstrated when compared with the use of the bipolar cautery.Due to its shrinking effect the laser beam is target oriented and makes the surgical procedure safe without the use of additional instruments. The Nd-YAG laser was preferred in tumors with a rich vascular supply. Thus there was a definitely decreased need for blood transfusions in patients operated on with the laser. Even those parts of the tumors that can not easily be reached, using conventional techniques can now be eliminated by laser irradiation.The variable distance between the handpiece of the laser instrument and the target organ allows a pin point as well as a more diffuse irradiation. Since it is not necessary to touch the tissue, laser techniques are particularly useful in critical areas, e. g. close to the brainstem or the spinal cord, because they make it unnecessary to touch the tissue.The question as to whether the use of laser technique will reduce the rate of recurrent tumor growth needs further studies based on longer follow-up periods. Further technical improvements are needed to make the laser device a true microinstrument. Finally a combination of both laser types — that is the Nd-YAG laser for coagulation and the CO₂ laser for cutting -might be a definite advantage.Dedicated to Prof. Dr. Dr. h. c. K. J. Zülch on occasion of his 70th birthday.     

Histological and SEM analysis of root cementum following irradiation with Er:YAG and CO2 lasers

Recently, the Er:YAG and CO₂ lasers have been applied in periodontal therapy. However, the characteristics of laser-irradiated root cementum have not been fully analyzed. The aim of this study was to precisely analyze the alterations of root cementum treated with the Er:YAG and the CO₂ lasers, using non-decalcified thin histological sections. Eleven cementum plates were prepared from extracted human teeth. Pulsed Er:YAG laser contact irradiation was performed in a line at 40 mJ/pulse (14.2 J/cm²/pulse) and 25 Hz (1.0 W) under water spray. Continuous CO₂ laser irradiation was performed in non-contact mode at 1.0 W, and ultrasonic instrumentation was performed as a control. The treated samples were subjected to stereomicroscopy, scanning electron microscopy (SEM), light microscopy and SEM energy dispersive X-ray spectroscopy (SEM-EDS). The Er:YAG laser-treated cementum showed minimal alteration with a whitish, slightly ablated surface, whereas CO₂ laser treatment resulted in distinct carbonization. SEM analysis revealed characteristic micro-irregularities of the Er:YAG-lased surface and the melted, resolidified appearance surrounded by major and microcracks of the CO₂-lased surface. Histological analysis revealed minimal thermal alteration and structural degradation of the Er:YAG laser-irradiated cementum with an affected layer of approximately 20-μm thickness, which partially consisted of two distinct affected layers. The CO₂-lased cementum revealed multiple affected layers showing different structures/staining with approximately 140 μm thickness. Er:YAG laser irradiation used with water cooling resulted in minimal cementum ablation and thermal changes with a characteristic microstructure of the superficial layer. In contrast, CO₂ laser irradiation produced severely affected distinct multiple layers accompanied by melting and carbonization.     

Histopathological and Electrophysiological Study of CO2, Er:YAG, and CO2 + Er:YAG Laser Effect on Peripheral Nerve

Background  

The purpose of this study was to investigate the morphological, histopathological, and electrophysiological changes of peripheral nerve after CO₂ (carbon dioxide), Er:YAG (erbium:yttrium aluminum garnet), and CO₂ + Er:YAG laser irradiation. There have been no comparative reports on CO₂, Er:YAG, and CO₂ + Er:YAG laser effects on peripheral nerve.     

In vitro effects of CO2 laser irradiation on platelets: Influence of aspirin

Laser angioplasty involves intravascular laser irradiation which may affect platelets and aggregation. In this study we examined the in vitro effects of different energy doses and modes of CO₂ laser irradiation on the platelet number, function and ultrastructure. Since aspirin is used in many patients suffering from coronary artery disease, the consequences of laser irradiation on aspirin-treated platelets were studied as well.We found that CO₂ laser irradiation causes a dose-response reduction of the platelet number that is most pronounced with high energy-short duration irradiation, and a dose-response reduction in platelet aggregation which is independent of the mode of irradiation. Pretreatment with aspirin does not change the effects of laser irradiation on platelet number, while aggregation is reduced only at relatively high energy doses. Electron microscopy revealed significant intracellular injury following low energy irradiation, while progressive damage to membranes occurred in a dose-response mode, both in untreated and aspirin-treated platelets. The clinical application of our findings should be done cautiously since important in vivo factors, such as the effect of laser irradiation on the vessel wall and coagulation system, were not studied.     

A device for tracheal tube during CO2 Laser irradiation in laryngomicrosurgery

We devised that the segment of commercially available defensor II tube coming in contact with the vocal cord was concaved. We used this new tube during CO₂ laser irradiation in laryngomicrosurgery. We comed to the conclusion that it was much more superior to the conventional tube in safety and resistance of the material to Co₂ laser irradiation and in increase of the operation field.(Yamada M, Arai T, Iwata S, et al.: A device for tracheal tube during CO₂ laser irradiation in laryngomicrosurgery. J Anesth 6: 379–381, 1992)     

Effect of CO2 laser on spinal epidural fibrosis

Summary In this study the effect of CO₂ laser on spinal epidural fibrosis was examined in 24 guinea pigs which were divided into two groups. The first group was the control group, the second one the CO₂ laser group.All animals had laminectomies at 3 levels. Re-exploration was performed three months after the laminectomy. In the second group the same procedure was performed but at the end of the re-exploration, CO₂ laser irradiation of the epidural fibrotic tissue was done. The wounds in both groups were closed again. Four months later all animals were sacrificed, for verification and quantification of scar formation (postoperative fibrosis) light microscopic examinations and determination of hydroxyproline were done, using Bergman's spectrophotometric method. The differences which were observed between the two groups were statistically significant (U 134, p < 0.05).This study demonstrates the reducing effect of CO₂ laser irradiation on epidural scar formation. The findings encourage its use as an alternative method of prevention of epidural fibrosis after spinal surgery.