Improved laparoscopic operating techniques using a digital enhancement video system

May 1998, Vol. 5, No. 2

TheJourndof the American Associationof Gynecologic Laparoscopists

Improved Laparoscopic Operating Techniques Using a Digital Enhancement Video System Rene Wenzl, M.D., Rainer Lehner, M.D., Andrea Holzer, M.D., Ursula Windberger, M.D., Harald Heinzl, Ph.D., and Udo M. Losert, Ph.D.

Abstract

We conducted a prospective, randomized trial in a piglet model to assess the advantages of a digital enhancement video system during difficult endoscopic procedures. Laparoscopic pelvic lymphadenectomy was performed with either conventional two-dimensional or digitally enhanced videoendoscopy. With equal amounts of extirpated lymph nodes, the operations performed with digitally enhanced videoendoscopy were significantly shorter (left lymphadenectomy p = 0.0001, right lymphadenectomy p = 0.001), had less blood loss and fewer false movements, and were associated with no complications, compared with those performed with a two-dimensional videosystem. Thus the accuracy of difficult laparoscopic techniques can be improved by three-dimensional visual perception. (J Am Assoc Gynecol l aparosc 5(2):175-178, 1998)

Because of its many known advantages, laparoscopic surgery is widely performed not only for diagnostic purposes but therapeutically for various indications.l~ Although the procedures are generally safe and efficient, major disadvantages are impaired visual perception of the operating field, kinematic restriction, and lack of three-dimensionalperception. Only with experience and training can surgeons become oriented in the operating field and perform difficult

manipulations such as tissue dissection and endoscopic suturing. Thus, conventional laparoscopies may require long operating time and result in significant blood loss, therefore increasing risks for patients? New videoendoscopic techniques provide a threedimensional impression of intraabdominal organs, which is a great help in orienting surgeons during operative laparoscopy. Especially in difficult phases of the operation, realistic depth perception improves

From the Departments of Obstetrics and Gynecology (Drs. Wenzl and Lehner), Anesthesiology and General Intensive Care (Dr. Holzer), and Medical Computer Science (Dr. Heinzl), and Center for Biomedical Research (Drs. Windberger and Losert), University of Vienna, Vienna, Austria. Address reprint requests to Rene Wenzl, M.D., Department of Obstetrics and Gynecology, Division of Endocrinology and Sterility Treatment, University of Vienna, Wahringer Gurtel 18-20, 1090 Vienna, Austria: fax 43 1 40400 2423. Presented at the World Congress of Gynecologic Endoscopy, Rome, Italy, June 18-22, 1997.

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the quality of surgery.6 However, published articles on these techniques are either based on simulator models or rely on expert opinion. The digital enhancement processor (Digivideo; Karl Storz Endoscopy, Tuttlingen, Germany; Figure 1) can be used in conjunction with a videocamera. This system digitally increases fine details of endoscopic images, provides good identification of structures in the operating field, and improves visualization. Digitization of the camera image, made possible by highthroughput microprocessor technology and over 500 million arithmetic operations per second, increases the image black-to-white or contrast transfer function ratio to deliver detail otherwise not available to the eye without significant straining. This provides increased image detail and higher-quality images. This system is not a three-dimensional camera, but is a way to bring out more detail in the image through digital enhancement. Similar to three-dimensional videoendoscopy, it is a tool for better orientation in threedimensional space. Materials and Methods

We performed a prospective, randomized study to compare perception during lymphadenectomy performed by conventional two-dimensional and digital-enhanced videoendoscopy with respect to operating time, blood loss, and complication rate in 16 healthy female pigs (Edelschwein breed, body weight 31 + 6 kg; 8 pigs/group). Randomization was done by envelope method before induction of anesthesia.

FIGURE 1. With the Digivideo processor the picture from the camera is transferred to the processor before it is displayed on the video screen.

Operative Procedure The procedures were carried out according to the Austrian law for animal experiments, and the study was approved by the local ethics committee. The animals were kept in accordance with guidelines of the European Convention for the Protection of Vertebrate Animal Used for Experimental and other Scientific Purposes (Strasbourg, 1986). All operations were performed by the same experienced surgeon (RW) and the same assistant (RL). With free access to water, the animals were fasted 24 hours before the operation. They were premedicated with ketamine HC120 mg/kg body weight and atropine 0.03 mg/kg body weight intramuscularly, intubated after administration of intravenous thiopentone 10 mg/kg body weight, and ventilated with oxygen-nitrous oxide by volume control. After administration of piritramide 15 mg and pancuronium bromide 4 mg, anesthesia was maintained by infusion of piritramide 100 pg/kg body weight/minute and pancuronium bromide 6.6 p/kg body weight/minute. A Veress needle was placed subumbilically, and carbon dioxide gas was insufflated intraperitoneally to a constant intraperitoneal pressure of 12 mm Hg. Four cannulas were inserted through the abdominal wall in the standard manner. One 12-mm cannula was used as an optic port in the umbilicus. Four centimeters above the symphysis, two 5-ram cannulas, one each in the left and right midclavicular lines, and one 10-mm cannula in the midline of the abdomen were used as the operating ports. For all operations we used two atraumatic graspers and one pair of scissors with the option of monopolar current (Autosuture, Vienna, Austria). Pelvic lymphadenectomy was done as described elsewhere7 on both sides beginning with the left side. Visible lymph nodes were extirpated with atraumatic technique. Detectable vessels were coagulated with monopolar current in the coagulating mode to minimize blood loss. Measured operating time on both sides started at beginning of the peritoneal incision and ended after extirpation of visible lymph nodes and complete hemostasis. False movement was considered an inadequate, time-consuming direction of one operating instrument. The number of false movements was counted by an independent observer by video documentation. Postoperatively, blood loss was measured by aspiration. At the completion of the experiment the animals were euthanatized with intravenous potassium while still under anesthesia.

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Data Analysis For statistical analysis we used Student's t test and Wilcoxon rank sum test. The chosen power value was 85% for a clinically relevant difference of reducing operating time 25% with a supposed SD of 15%. This evaluation resulted in eight pigs per group. Probability below 0.05 was considered statistically significant.

Discussion

Surgeons are accustomed to performing open operations with three-dimensional perception. This is important for accurate placement of instruments and sutures,V, s and surgery can be completed in reasonable time and with adequate technique. An essential disadvantage of conventional laparoscopy is lack of threedimensional perception, which results in longer operating time, inappropriate preparation, and risk of complications. A simulator model demonstrated that dexterity tests performed by experienced and inexperienced surgeons were improved with a three-dimensional endoscopy system. 9 It seems to be mandatory to keep operating time as short as possible. Especially in high-risk patients a short procedure and precise preparation seem to have a major effect on outcome and complication rate. In addition, as the percentage of laparoscopic surgery performed in elderly and compromised patients is increasing, surgeons and anesthesiologists must find ways to decrease intraoperative and perioperative complications? A drawback of true three-dimensional videoendoscopic systems is that surgeons and assistants have to wear special shutter glasses to achieve a flicker-free image of organs. 6 Therefore, the systems are not recommended in diagnostic or simple operating procedures because of the high learning c u r v e 6 and ocular fatigue) The Digivideo system enhances fine details of endoscopic images with a digital processor, and it is not necessary to wear special glasses; Thus it can be used in difficult operations as well as in diagnostic and less demanding procedures. In this study, the quality of the operations, as measured by the number of extirpated lymph nodes, was comparable with the two systems. However, with the Digivideo, more accurate identification of tissue planes and more exact orientation in the abdominal cavity led to improved operating technique, as shown by less blood loss and fewer complications.

Results

Laparoscopic pelvic lymphadenectomy was performed successfully in 15 pigs. In one animal operated by conventional videoendoscopy it was necessary to perform laparotomy due to massive bleeding of a common iliac artery. The number of extirpated lymph nodes was comparable in both video systems: mean + SD 10.75 + 2.49 with Digivideo and 9.62 + 1.59 with videoendoscopy. The operation was statistically significantly shorter with Digivideo (left side p = 0.0001, right side p = 0.001; Figure 2). The number of time-consuming false movements by the surgeon or assistant was statistically significantly higher during two-dimensional videoendoscopy (p = 0.0038). Median blood loss was 0.5 ml (range 0-3 ml) for Digivideo and 3 ml (range 0-200 ml) for conventional videoendoscopy (p = 0.02). In the pig with the bleeding common iliac artery, estimated blood loss was 200 ml. For this animal, only data from the laparoscopic procedure were included in statistical calculations. All other operations were completed without complications and with full hemostasis.

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References 2D left

Digivideo left

2D right

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Digivideo right

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FIGURE 2. Mean _+SD duration of lymphadenectomy.

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