Nd:YAG laser bipolar dissector--preliminary results.

We have developed a laser bipolar dissector (LBD) which uses the 1,064 nm Nd:YAG wavelength. The laser emits from the inner surface of the distal 7 mm of each probe made of synthetic sapphire. With low laser power (15-25 W), the bipolar provides hemostatic cutting of larger blood vessels. Animal experiments were carried out using New Zealand white rabbits. The LBD hemostatically cut through veins up to 5 mm and arteries up to 2 mm in diameter. Rebleeding did not occur. Transection of parenchymal organs such as liver and lung was easily performed with complete hemostasis. In chronic experiments a partial hepatectomy with splenectomy and left nephrectomy was performed using the LBD alone without any ligation. Up to 3 weeks postoperatively there were no direct complications related to using the LBD. In conclusion the LBD could perform a hemostatic transection of large vessels and might have clinical application in the dissection of vascular parenchymal organs.

Clinical application of the Nd:YAG laser bipolar dissector in intra-abdominal surgery.

A laser bipolar dissector (LBD) using a 1064 nm Nd:YAG laser energy source that provides hemostatic dissection using low-powered laser energy (15-25 W) has been developed. Clinical applications have included a partial hepatectomy (n = 5), a cholecystectomy (n = 4), an appendectomy, lymphnode dissection, and division of adhesions. The LBD was effective in resection of noncirrhotic liver and reduced the number of ligations required. There were no direct complications related to using the LBD. Operative time and blood loss were difficult to compare to conventional methods. The LBD may have applications for partial hepatectomies and other intra-abdominal operations.

Endoscopic contact Nd:YAG laser resectional vaporization (ECLRV) and esophageal dilatation (ED) in advanced malignant obstruction of the esophagus.

Malignant esophageal obstruction in patients with advanced and metastatic carcinoma is unsuitable for surgery. Palliative treatment must provide adequate swallowing with minimum complications in these often seriously ill patients. Twenty consecutive patients underwent endoscopic Nd:YAG contact laser resection and vaporization (ECLRV) and esophageal dilatation (ED) for advanced esophageal carcinoma since August, 1985. Average duration of the disease when first referred was 7.2 months. Tumor cell type was either squamous cell carcinoma (n = 11) or adenocarcinoma (n = 9). Tumor location was distal (n = 14), middle (n = 5), or upper (n = 2). Mean tumor length was 7.5 cm. Mean preoperative luminal diameter was 1 mm, with total obstruction in ten (50%) patients. The operative procedure in all patients was under general anesthesia with endotracheal tube intubation. Rigid and flexible endoscopes were both used as indicated. Mean postoperative luminal diameter was 15 mm. All but four were able to swallow fluids on the first postoperative day, followed by semisolids the next day without discomfort. Minor perforation was noted in three cases and managed in two conservatively. One more patient had difficulty in swallowing due to extra-esophageal compression, in spite of a technically successful laser therapy. Percutaneous endoscopic gastrostomy (PEG) was carried out in eight cases. Eleven patients were retreated successfully for recurrent obstruction and two were treated more than twice, at a mean of six-week intervals. Endoscopic contact laser resectional vaporization with esophageal dilatation was relatively safe and provided an improved quality of life in this preliminary study group, providing a mean survival of 18.5 weeks (range 2-50 weeks).

Laserthermia. A new method of interstitial local hyperthermia using the contact Nd:YAG laser.

Laserthermia is a new method of delivering interstitial local hyperthermia using a synthetic contact probe with a computer-controlled Nd:YAG laser to deliver both pulsed and continuous laser energy. The system allows an easily controllable increase in temperature (for example, from 42 to 43 degrees C) over a fixed period of time (for example, 20 minutes) to be delivered to tissue. A single or multiple channel system can be used depending on the volume of tissue to be treated. Tumor necrosis appears to be related to avascular infarction. Early clinical results support the beneficial therapeutic effects of Laserthermia in its oncologic applications.

Contact YAG laser system in abdominal surgery, in particular hepatic and pancreatic surgery.

The SLT contact Nd:YAG laser system offers a new method of obtaining a hemostatic incision through the anterior abdominal wall and a surgical tool for performing various intraabdominal resectional procedures. Advantages include reduction in intraoperative bleeding, reduced tissue damage, and tactile sensation with a reduction in laser power requirements. Sterile disposable laser scalpels, fibers, synthetic sapphire probes, and a user friendly laser system offer a new dimension in intraabdominal surgery, especially relating to liver and pancreatic surgery. Potentially, all general surgical procedures could use the SLT contact laser, which may, in the future, replace conventional electrocautery and the surgical steel scalpel. Cost containment and improved quality of care will probably be the driving forces for its acceptance.

Laser surgery in colonic and anorectal lesions.

Endoscopic laser therapy for diseases of gastrointestinal tract in general, and lesions of colon, rectum, and anus in particular, is in its infancy. Advances are expected to be made to define those lesions that are amenable to lasers and those that are not. In this process, it is hoped that the relative merits and demerits of the various modes of endoscopic therapy might be brought to light. With the advent of contact Nd:YAG laser technology, it is increasingly realized that such a mode of operation could be used to great advantage in both endoscopic and open surgery related to lower-gastrointestinal tract diseases. Furthermore, contact Nd:YAG laser therapy definitely appears to be efficient and safe and compares favorably with other therapies available. How such an effective modality should be sequenced in combination with other available therapies has yet to be worked out. There is more to be done in this arena, which holds high promises.

Splenic resection with the Contact Nd:YAG laser system.

Splenic resection in the dog was proven to have decreased blood loss (52%), decreased operating time (44%), and decreased surgical manipulation using the SLT Contact Nd:YAG Laser System with the synthetic sapphire probe, as compared with the noncontact CO2 laser. Tissue damage and hematologic changes were minimal and equivalent in both laser systems. The overall ease of use and operating technique was subjectively better with the contact Nd:YAG laser, and the danger of scattered and reflective beam damage was eliminated. The contact Nd:YAG laser with the synthetic sapphire probes offers a significant advantage over the noncontact CO2 laser in the resection of splenic tissue. Future applications in pediatric surgery now need to be evaluated.

Hematoporphyrin derivative uptake and photodynamic therapy in pancreatic carcinoma.

Little information is currently available concerning the uptake of porphyrins by pancreatic tumors, or the effect of photodynamic therapy (PDT) on pancreatic cancer. In Syrian golden hamsters (n = 33), the organ distribution of 125I-labeled dihematoporphyrin ether (DHE) was studied in a pancreatic cancer model. In the same animal model the effect of PDT was studied using a gold vapor laser for energy delivery 3 hr after the injection of DHE (n = 7). DHE was 2.4 times more concentrated in the pancreatic tumor than in the nontumorous pancreas at 3 hr. Simultaneously there was a considerable accumulation of DHE in the surrounding gastrointestinal tract, causing perforation of the duodenum and jejunum with resultant death in four (57%) animals after PDT. Photodynamic therapy caused extensive tumor necrosis without any obvious effect on the nontumor-bearing pancreas. Damage to the surrounding tissue in the hamster indicates that precautions should be taken if PDT is to be used clinically in pancreatic cancer. Intratumoral injection of DHE may give higher drug concentrations with greater specificity for tumor treatment.

Microcirculatory effects of somatostatin in acute pancreatitis.

Somatostatin, a 28-amino-acid inhibitory polypeptide has been advocated for the treatment of upper gastrointestinal bleeding and acute pancreatitis. This study examines the effect of somatostatin in acute hemorrhagic pancreatitis in piglets (n = 12), weighing 8-12 kg. Six animals served as controls, and received only fluid resuscitation (0.9%, NaCl, 20 ml/kg/h). Six animals received somatostatin treatment consisting of a 15 micrograms/kg bolus i.v. given simultaneously with the induction of pancreatitis, and treatment continued with an intravenous infusion (15 micrograms/kg/h) for 5 h. Cardiac output, heart rate, blood pressure, arterial pO2, hematocrit and serum amylase were recorded before and each hour during the experiment. Regional blood flow in the gastrointestinal area was measured using the microsphere method. The microspheres labelled with three different isotopes were administered before the experiment and at 2 and 5 h, respectively. There was a significant decrease in the cardiac output (p less than 0.05) and an increase in systemic blood pressure in the somatostatin-treated group (p less than 0.025). Pancreatic blood flow decreased by 43% following somatostatin infusion. The decreases at 2 and 5 h were highly significant (p less than 0.005). Blood flow to the mucosal but not muscular region of the stomach was decreased by somatostatin. This study suggests that somatostatin might be harmful in acute pancreatitis due to its adverse effects on pancreatic blood flow and cardiac output. However, somatostatin may be effective in reducing gastrointestinal bleeding. If the drug is used clinically, careful monitoring of the cardiac output is necessary.

Laser pancreatectomy. A comparison between dog and pig.

Total pancreatectomy was performed in dogs (n = 5) and pigs (n = 6) using a contact Nd:YAG laser with a wave length of 1060 nm. The fiber was connected to a laser scalpel, and a 1.0-mm-diameter sapphire tip was used. The power was set at 10-12 W with a pulse time of 9.9 s. The animals were followed postoperatively (p.o.) for 1 week, and no mortality, infection, or any other complication were observed. Total pancreatectomy was significantly faster to perform in pigs than in dogs (P less than 0.001). The number of ligatures (P less than 0.05) and the amount of bleeding (P less than 0.05) were significantly less in pigs than in dogs. The present paper describes the anatomy of the pancreas in dogs and pigs, and also the technical procedure of total pancreatectomy in both species is presented. In conclusion, total pancreatectomy is easier to perform in pigs than in dogs. Furthermore, the anatomy of the pancreas in the pig resembles much that in man.

Laserthermia: a new computer-controlled contact Nd: YAG system for interstitial local hyperthermia.

Contact Nd:YAG laser surgery is assuming a greater importance in endoscopic and open surgery, allowing coagulation, cutting, and vaporization with greater precision and safety. A new contact probe allows a wider angle of irradiation and diffusion of low-power laser energy (less than 5 watts), using the interstitial technique for producing local hyperthermia. Temperature sensors that monitor continuously can be placed directly into the surrounding tissue or tumor. Using a computer program interfaced with the laser and sensors, a controlled and stable temperature (e.g., 42 degrees C) can be produced in a known volume of tissue over a prolonged period of time (e.g., 20-40 min). This new laserthermia system, using a single low-power Nd:YAG laser for interstitial local hyperthermia, may offer many new advantages in the experimental treatment and clinical management of carcinoma. A multiple system is now being developed.

Acid reduction by intragastric contact Nd:YAG laser photoradiation in rats.

Gastric acid reduction in the treatment of duodenal ulcers occurs following extragastric vagotomy, antrectomy, or seromyotomy. This study examines the effects of intraluminal LCV and/or pyloric MA using laser photoradiation in Sprague-Dawley rats. Groups were compared to sham-operation and truncal vagotomy with pyloroplasty (TVP) regarding gastric acid secretion, plasma gastrin, pancreatic polypeptide, and histology, including immunocytochemistry for G-cells. All operative procedures reduced acid output (P less than 0.001) both immediately and at 8 weeks, with LCV being more effective than TVP or MA. Moreover, LCV with MA was no more beneficial than LCV alone. Plasma gastrin increased slightly following TVP but not following the LCV group in the acute study, and no difference was seen in the chronic group. Histologically, the depth of laser penetration was optimum with no perforations. Although the G-cells were destroyed following the laser photoradiation, they reappeared in lesser numbers at 8 weeks. Laser photoradiation of the intramural nerve plexuses on the lesser curve of the stomach by intragastric mucosal myotomy is effective in reducing gastric acid and may have a clinical and therapeutic role with flexible fiberoptic gastroscopy.

Proximal pancreatectomy: a comparison of electrocautery and contact and noncontact Nd:YAG laser techniques in the dog.

Proximal pancreatectomy with duodenal preservation is technically difficult. It has often been performed experimentally in pancreatic transplantation studies. Preservation of the pancreaticoduodenal vessels and duodenum provides an excellent method of testing various operative techniques in pancreatic surgery which may lead to further clinical applications. The present study has compared the conventional noncontact Nd:YAG laser technique with electrocautery and a new contact Nd:YAG laser technique for proximal pancreatectomy. There were five dogs in each group, and the pancreatic duct was left open to drain into the abdominal cavity after pancreatic transection in all of the animals. Resection with the contact laser caused significantly less blood loss (109 +/- 74 ml) than the noncontact laser (228 +/- 81 ml), (p less than 0.05). A greater number of ligatures were used in the noncontact laser group (11 +/- 3 ligatures) as compared with the electrocautery group (2.2 +/- 1.6 ligatures) and the contact laser group (5.2 +/- 2.8 ligatures), (p less than 0.005). Noncontact laser and electrocautery resection techniques resulted in necrotizing pancreatitis and death in two animals. The new contact laser system provides a safe and effective method of performing pancreatic surgery.

Techniques of liver resection. Comparison of suction knife, ultrasonic dissector, and contact neodymium-YAG laser.

Liver resections were performed in 18 pigs with an inexpensive disposable plastic suction knife, an ultrasonic dissector, or a contact neodymium (Nd)-YAG laser. Technical aspects and intraoperative and postoperative data were compared. Intraoperative blood loss was less with the suction knife (112 +/- 28 mL) than with the ultrasonic dissector (149 +/- 45 mL) or Nd-YAG laser (174 +/- 25 mL). Operating time was similar in all groups. The number of ligatures used in the Nd-YAG laser group (12 +/- 1) was significantly less than in the ultrasonic dissector (27 +/- 2) or suction knife (32 +/- 2) groups. In the ultrasonic dissector group, there was an increase in postoperative white blood cell count and liver enzyme levels compared with the other two groups. Light microscopy revealed dilated bile ducts in the ultrasonic dissector resection group, which may reflect biliary stasis. There were no significant differences in mortality among the three experimental groups. Results indicated that the ultrasonic dissector and the contact laser method were not substantially better than an inexpensive, easily modified plastic suction catheter in performing a major nonanatomic liver resection in piglets.

Laserthermia: a computer-controlled contact Nd:YAG system for interstitial local hyperthermia.

Contact Nd:YAG laser surgery is assuming a role of greater importance in endoscopic and open surgery, allowing coagulation, cutting, and vaporization with greater precision and safety. A synthetic sapphire probe allows a wider angle of irradiation and diffusion of low power laser energy (less than 5 W) using an interstitial technique for producing local hyperthermia. Sensors placed directly into surrounding tissue or tumor continuously monitor temperature, and a pertinent computer program produces a controlled and stable temperature (e.g., 42 degrees C) over a period of time (e.g., 20-40 min). The Laserthermia system (Surgical Laser Technologies, Inc., Malvern, PA), using the Nd:YAG laser, offers many advantages in the experimental and clinical treatment of carcinoma by local interstitial hyperthermia.

Prostaglandin deficiency by itself is not the cause of mepirizole-induced duodenal ulcers in rats.

The purpose of these studies was to determine the role played by endogenous prostaglandins in the development of gastric ulcers produced by indomethacin, and of duodenal ulcers produced by mepirizole in rats. Indomethacin (10 mg/kg subcutaneously) produced gastric ulcers, whereas mepirizole (100 mg/kg subcutaneously) produced exclusively duodenal ulcers. Both drugs, given at ulcerogenic doses, reduced the gastric and duodenal generation of PGE2, PGF2 alpha, 6-keto-PGF1 alpha, and thromboxane B2. In this regard, the extent of reduction was more pronounced after indomethacin than after mepirizole. Despite this greater inhibition of prostaglandin synthesis by indomethacin, this drug did not produce duodenal ulcers, whereas mepirizole was duodenoulcerogenic. In addition, mepirizole increased gastric acid secretion by 74%, whereas indomethacin had no effect on acid secretion. Oral administration of 16,16-dimethyl PGE2, given at nonantisecretory doses (0.5-5 micrograms/kg), prevented formation of indomethacin-induced gastric ulcers, whereas antisecretory doses were required to prevent formation of mepirizole-induced duodenal ulcers. We conclude that a reduction of prostaglandin formation in the duodenal mucosa is not by itself sufficient to induce duodenal ulcers. We hypothesize that three changes, produced by mepirizole, must be present for duodenal ulcers to develop: increased gastric acid secretion, decreased duodenal bicarbonate secretion (as demonstrated earlier), and decreased duodenal content of prostaglandins. The decreased prostaglandin formation, although not causing duodenal ulcers, may lower the resistance of duodenal mucosa to the hyperacidity induced by mepirizole. On the other hand, in the case of gastric ulcers following administration of indomethacin, a decrease in gastric mucosal levels of prostaglandins may play a more important role than changes in gastric acidity.

Metabolic and immune effects of dietary arginine supplementation after burn.

The effect of supplemental dietary arginine on metabolism and immunity was studied in 36 burned guinea pigs (30% of total body surface area) with previously placed catheter gastrostomies. The animals were randomized into four groups. After an initial three-day adaptation period, all groups received continuous isonitrogenous, isocaloric (175 kcal [735 kJ]/kg/d), and isovolemic intragastric tube feedings until postburn day (PBD) 14. Groups A, B, C, and D received 0%, 1%, 2%, and 4%, respectively, of total energy intake as arginine given in the form of crystalline arginine hydrochloride with 22%, 21%, 20%, and 18%, respectively, of total energy as whey protein. The average body weight after burn decreased equally in all groups. Resting metabolic expenditure on PBD 6 was higher in groups B (151% +/- 6% of preburn) and C (156% +/- 7%) than in groups A (131% +/- 4%) and D (136% +/- 3%). Ear-thickness response to dinitrofluorobenzene challenge on PBD 12 showed the best response in group C. The mortality rates of groups A, B, C, and D were 56%, 29%, 22%, and 56%, respectively. This study suggests that oral dietary arginine supplementation up to 2% of energy intake may be beneficial after burn injury.

An experimental study of the effects of electrocautery and various lasers on gastrointestinal tissue.

It is possible that in the future, lasers will replace electrocautery in gastrointestinal surgical procedures. Few studies exist that compare the tissue effects of electrocautery with newer laser modalities. In this study, the tissue effects of electrocautery, noncontact Nd:YAG, contact Nd:YAG, and CO2 lasers were studied in the stomach, small bowel, colon, liver, and pancreas in 24 rats. At light microscopic examination, all tissue damage was thermal in nature, irrespective of the modality used. Furthermore, an independent observer was unable to distinguish which method has been used in most tissues. Tissue effects were similar in the stomach, small intestine, and colon after use of all the modalities. The CO2 laser caused slightly less damage than the other methods (p less than 0.05), but with use of this modality, hemostasis could not be achieved in the liver and pancreas. The contact Nd:YAG laser caused moderate damage with excellent hemostasis in all tissue. The noncontact Nd:YAG caused significantly more tissue damage than all other methods (p less than 0.01), especially in the liver and pancreas. The results suggest that the new contact laser system provides an effective method of performing gastrointestinal surgery with especially good hemostatic effects on liver and pancreatic resections.

Photoradiation therapy in early gastrointestinal cancer.

Endoscopic photodynamic therapy has been used in the treatment of 19 cases of upper gastrointestinal cancer of which six were superficial esophageal and 13 were early gastric cancer. Six patients subsequently underwent surgical resection. Residual tumors were found in the resected specimens of one esophageal carcinoma and in the two early gastric carcinomas. Technical problems resulted in one failure. Follow-up ranged from 4 months to 3 years and 11 months with no tumor recurrence in either the operated or unoperated patients. Other delivery systems are currently under investigation.