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Can Surgery Be Made Safer?

By: Charles E MeischEndoscopic consultantNBS Group Supply (Medical Device Division).257 Livingston AvenueNew Brunswick, NJ 089011-888-800-8192

Surgery is the branch of medicine dealing with manual operative procedures for the correction ofdeformities, defects, injuries, and the diagnosis of certain diseases. Traditionally, these proceduresrequired open surgery known as a laparotomy. Within the last few years Minimally Invasive Surgery,specifically Laparoscopy which deals with the abdomen, has become a replacement for many openprocedures.

Studies have shown major benefits to the patient in terms of reduced post operative pain, increased postoperative comfort, reduced hospital stay, quicker return to normal physical activities and ultimately aquicker return to work. Improved comes is and reduced wound complications associated with large scarsare also major advantages associated with this technique.

Many of the general procedures are performed using a rigid scope that is placed into the abdominalcavity with the use of small trocars. A mini scope can be inserted allowing direct visual observation. Thisallows the placement of additional trocars that enable the insertion of micro instruments for the repair,removal, or diagnosis of problems without the need for large surgical cutting of the abdomen.

What is taparoscopy?

Laparoscopy is abdominal exploration using a type of Endoscope called a Laparoscope. Laparoscopy isa technique which permits the examination and surgical treatment of viscera and organs within theperitoneal cavity. It is becoming popular, rapidly replacing many procedures that traditionally requiredopen laparotomy.

To improve visualization of the peritoneal cavity and facilitate instrument manipulation duringlaparoscopy, the abdominal cavity must first be filled with an insufflating gas producing apneumoperitoneum. Laproscopic insufflators are specialized pressure-limiting gas flow regulators thatmake it easy to establish and maintain a pneumoperitoneum. To establish the pneumoperitoneum, oneend of a piece of low pressure tube ranging in length from approximately 8 to 10 feet is connected to theinsufflator outlet port. The other end of the tube is connected to an Insufflation needle know as a Veressneedle. A Laproscopic procedure usually begins with the insertion of the Veress needle into the inferiorportion of the umbilicus, since this region of the abdominal wall is usually devoid of major blood vesselsand nerves. Furthermore, inter-abdominal structures usually do not adhere to the region of theabdominal wall except in patients who have previously undergone surgery.

Three liters of gas is usually sufficient to produce a space in the peritoneum cavity to allow for adequatevisibility. The exact amount of gas used to establish a pneumoperitoneum depends on the size of theabdominal cavity, development of abdominal musculature elasticity of the abdominal wall, as well as thedegree of gas leakage and rate of reabsorbing.

Once the pneumoperitoneum is established, the veress needle is removed from the peritoneal cavity.Then a trocar in a sleeve is used to enlarge the needle puncture. After completely penetrating theabdominal wall, the trocar is removed, followed by insertion of the Laparoscope. This is done throughthe trocar sleeve. Additional trocar punctures are often needed to allow a number of instruments to be

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Page 2 of5used in the peritoneum cavity without removing the Laparoscope. Upon completion of the procedure,most of the Insuffiation gas is expelled manually depressing the abdominal wall through an existingtrocar sleeve. The body innocuously absorbs any gas remaining in the abdomen.

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Blind insertion of Insufflation with a Veress needle can cause serious complications. If the Veress needlewas accidentally inserted into a blood vessel, Insufflation could cause the formation of a gas embolism.The introduction of gas through a Veress needle that has not completely penetrated the abdominal wallcould also produce a subcutaneous or subfascial emphysea. Moreover, the insertion of any sharp objectinto the abdomen can perforate the section of the bowel that is adhered to the peritoneum possiblycausing peritonitis.

Filling the abdomen with gas after visually confirming safe interperitoneal placement Significantlyreduces the number of complications associated with the Veress needle. Rather than use a Veressneedle to insufflate the peritoneal cavity, some surgeons prefer to puncture the abdominal wall with atrocar for creation of the pneumoperitoneum. Once the trocar has penetrated the abdominal wall, theLaparoscope can be immediately inserted through the trocar sleeve to insure proper interperitonealplacement. As a result this procedure enables the surgeon to reduce the number of blind insertionsusing a Veress needle and trocar to one trocar only.

Twenty years ago the concept of this procedure would never even have been considered. Almostanything we use or rely on has changed, most have evolved. The same thing has happened in themedical device industry. Some medical procedures performed today were not thought possible then.

The introduction of Endoscopic surgery also involved the use of scopes to help doctors see areas theydidn't have access to in the past. Endoscopic surgery started in the Gynecological area and movedquickly into the Urological area. The use of rigid telescopes to see areas that normally would requireopen surgery reduced costs and lowered infection rates. After several years, general surgeons started tobecome interested in these newer techniques using rigid endoscopes. In the early 1980s, generalsurgeons started to use endoscopes for purposes other than diagnosis. They called upon themanufacturers to develop more sophisticated equipment that could reach further into areas than anyonecould realize. These new smaller Endoscopes were necessary. Everything was being downsized orbeing made smaller so that they could reach areas that were harder to reach without open surgery.

Surgeons then began to realize that these instruments were not only useful for diagnosis but could alsobe used immediately to resolve certain problems. After the late 1980's, Endoscopes and Endoscopicprocedures became the norm rather than the exception. Companies evolved to try to solve andsupplement the lack of supply.

The difference between the United States and Europe was the accessories. The US wanted as manydisposable accessories as possible while Europe did not see the need to dispose of the accessories dueto costs. In the US, the market for insuffiators and accessories continued to increase.

For instance, colecystectomy procedures are estimated to be 800,000 per year; Myomectomy 125,000procedures per year; appendectomy 115,000 per year; Nissen Fundoldoplication 100,000 per year.

Other procedures are now being preformed such as, bowel resection, hysterectomy, bladdersuspension, endometriosis, splenectomy, and adrenaletomy along with gastric bypasses and manymore. These procedures can now be done endoscopically.

The primary concern for all manufacturers was the creation of smoke generated by electronic knives orlasers in the pneumoperitoneum (see figure 1).

As laproscopic procedures evolve and become more complicated,the original insuffiators could only produce 9.9 liters per minute. Allused C02 gas which is relatively inert is easily absorbed into thebody. Newer units were made to increase the flow, but not thepressure.

Original insufflators used silicone tubing (generally one-quarterinch 1.0.) that flowed from the insufflator, through the tube and intothe patient. Recently, within the last 10 years, it became obviousthat putting a foreign gas into the body should be filtered and anybodily fluid that could accidentally be pushed up through the tube

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Industry News Page 3 of5should be stopped prior to going into the insufflator. Once into the F,0g re 1insufflator, it becomes very difficult to cfean and recondition these I Uvery expensive units. Most Endoscopic companies who sell insufflators now offer them with disposabletubing containing filters. The filters are usually rated at .1 micron but can be anywhere from .1 to .3microns and they are all suppose to be hydrophobic.

The 9.9 liters per minute insufflators were sufficient when using an ordinary gas filter, and inserting it intothe line allowing it to filter the gas and also stop any backflow of fluid from getting into the insufflator. Asprocedures increase in complexity, insufflators were made capable of delivering increased liters per minof gas. This was necessary due to longer procedures, and the use of multiple trocars.

The most common problem is finding a filter that can perform to flow rates upward of 40 liters perminute.

This is a very high flow from the original 9.9 units. Insufflators work differently. They do not just allow gasto flow from a machine to a patient. They are critical in nature. They allow the gas to cycle approximatelyevery 1.8 to 2 seconds at relatively high pressure against the filter and there are mechanisms in theinsufflators that sense the backpressure of the abdomen. Once set, the backpressure will stop theinsufflation process until it senses the need to re-inflate.

The false reading on an insufflator due to the lack of flow caused by the filter, the blocking of the filter, orother obstacle in the pathway may not allow for an accurate pneumoperitoneum to be achieved, ormaintained.

When using low flow insufflators (by low flow 9.9 UM to 15 UM), most people bought standard off theshelf gas filters.

They seemed to work fine, however once you get up into the 20,30 or 40 UM range, specialized filters needed to be develop. Notall companies have pursued this. Some have and developedunique filters (see Figure 2). As the gas cycles, it does not directlyhit a flat filter membrane (flat meaning the filter housing itself is flatin nature encompassing the membrane). After careful testing, itwas determined that a baffle system was necessary to allow largecycles of gas enough time to get through the filter and not causeexcessive back pressure which would prematurely shut off theinsufflator. The baffled or bulbous shaped back of the filter allowsa reservoir of gas to build up and then migrate through the filtermembrane prior to the next cycfe. Without this, the cycles create Figure 2excessive back pressure. This can cause problems with theoperation of the equipment and false shut downs along with overpressure alarms.

Membranes themselves have also evolved. Filter companies have been working on gas filters that arehydrophobic both in the respiratory and in the Insufflation area for some time. Filters are available thatproduce the optimum amount of flow at the least amount of cost. Using a flat filter on a high flowinsufflator at 1.8 to 2 cycfes per second can damage and most likely never let the gas pass through thefilter or achieve the rated filter micron size?

The only way to do this is to allow the gas to enter the buffered area that was developed (See figure 1).Any filter that is used should carry an ULPA or HEPA rating. Any filter manufacturer that will not supplyyou with the test data to prove this should not be used.

Insufflators have also evolved from the 9.9 UM to 30 UM or even higher flow rates.

They all function in a similar nature and contain sophisticatedelectronic feedback devices. Once set, these new high flow unitswill fill the peritoneum to the appropriate pressure and maintain itas the body absorbs some of the gas. Trocars may also leaksome gas (see figure 3). Aside from the geometry of the filter itselftesting will cfearly show that trying to push a high flow of gasthrough a 1/4 inch hole with no reservoir becomes virtuallyimpossible. With any unit purchased, a specification sheet withtest criteria proving flow through the filter at the advertised flow

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Industry News Page 4 of5rate should be requested of the manufacturer. Figure 3

Along with the geometry of the filter housing, filter membranes also evolved. Industry discovered thataerosol droplets can bypass filters causing malfunction of insufflators. This also increases maintenance,physically restricts the passage of airflow, and more seriously may lead to bacterial growth in theinsufflator.

During the late 1950's, membrane technology began to expand. Osmotic transfer of salts across themembrane began in the area of de-salini-zation and has lead into kidney dialysis. A hypothesis wasformed that a membrane could be designed that would pass air but would not pass water and also filterout aerosols and bacteria from the air stream. This membrane would be an analogous to a child's toy formaking soap bubbles which uses a water film formed in a hoop. When a child blows into the hoop apressure differential across the hoop causes the film to bulge out and form a bubble. For moreinformation on thin films refer to 1: Strength of Materials Part 2 by Timoshenko; or 2:Advanced Strengthof Materials by Denhartog.

Reducing the hoops diameter increases the differential pressure (not force) needed to distort the film,thereby creating a very fine net the size of the original hoop. With the differential pressure increase thetotal force across the net is higher. Another characteristic that must be considered is the hydrophobicity.Air would be free to move through the net until the net was touched by a liquid which would form a filmblocking the movement of air until the differential pressure across the net was too great or the liquid wasevaporated. Obviously, the net would have to be some material which would cause liquid to form a filmacross the intercies. The specific composition of membranes with these properties is generally a tradesecret of the membrane manufacturer. However, the most common material is Teflon. The Teflon sheetis either mechanically perforated or is stretched to form tears or holes in the material. Other methods areto coat any netlike substrate with a chemical, generally a silicone compound. The effect of this is tocreate a hydrophobic membrane that allows free flow of air until the membrane is wetted. At this pointair-flow would be stopped as long as pressure differential is below the maximum level. Air-flow throughthe filter must be maintained by the membrane. The membrane must have sufficient small intercies tostop or entrap aerosol fluids and microbes. The microbes are generally considered to be carried by theaerosol fluids. The membrane must be capable of being secured either mechanically or by heat sealinginto the exit area of the filter.

Test results of new membranes were extremely encouraging. They allowed air-flow at a normal rate untilliquid covered one side in which case the filter shut down. This saved the insufflator from beingdamaged. The bacteriological testing showed that these membranes stopped pathogens and aerosolsas well as any commercial microbial filters and met HEPA and ULPA criteria.

Surgery was not at a stand still during the development of the new filters and membranes. New surgicaltools were introduced that were micro in size along with both laser and electrical knives. Both of thesetools minimized bleeding by cauterizing while cutting, however they produced dense smoke in theabdomen.

No one really knew what the smoke consisted of, but most agreedthat it was best kept out of the air. The solution was to develop anew type of filter that could be connected to an exit port of a trocarand capture the smoke. Lab tests showed that in the presence ofthis dense smoke, filters not designed for smoke elimination couldshut down in 30 seconds. Analysis of the smoke showed it tocontain proteins, peptides, amino acids and other breakdownparticles. In other tests, electron microscopic studies showed alayer of these breakdown products had formed over the surface ofthe membrane blocking airflow. Filter companies have spent atremendous amount of time and money to develop an inexpensive G.ourto?sY:.f~~l5:~rpJ.!1t:,,,· _yet disposable smoke evacuator. A filter that combines fluidstoppage along with smoke and bacterial filtration to cleanse the Figure 4expelled gas is now available (see figure 4). It is obvious that thisis needed to control cross contamination and infection and to protect operating personnel from smokecaused by laser and electro surgery. The designs have been rigorously tested and prove reliable.(additional information on the devices shown in this article can be obtained by contacting themanufacturers or the author directly.) In the future, technology will continue to improve. This is justanother stepping stone in the final attempt of surgeons to alleviate discomfort, shorten hospital stays,curtail cross contamination, and protect operating room personnel.

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