PRINCIPLES AND TECHNIQUES OF ABDOMINAL ACCESS AND

PHYSIOLOGY OF PNEUMOPERITONEUM 1 PRINCIPLES AND TECHNIQUES OF ABDOMINAL ACCESS AND PHYSIOLOGY OF PNEUMOPERITONEUM Jon C. Gould, MD, FACS, and Ancil Philip, MD Abdominal Access in Laparoscopic Surgery When compared with the open approach to many abdominal operations, the laparoscopic technique is often associated with decreased morbidity and a quicker recovery. Unfortunately, there are also specific complications related to the laparoscopic approach that would not necessarily be seen with a laparotomy. Many of the most significant complications occur very early in the operation during the act of attaining abdominal access. There are three general types of laparoscopic access, with many variations and modifications. The Veress needle technique is the oldest and most traditional method of laparoscopic entry. The direct trocar insertion technique involves direct penetration of the fascia and peritoneum by the trocar. Finally, in the open or Hasson technique, a minilaparotomy is performed so that the initial trocar can be placed under direct visualization. veress needle access Molloy and colleagues assessed 155,987 gynecologic procedures and reported that the Veress needle was used in 81% of them. 1 In addition, of the 17,216 general surgery procedures assessed, the Veress needle was used in 48%, whereas in the remaining 52%, other methods were used. Kelling first described preliminary insufflation of the peritoneal cavity prior to trocar placement in 1901. 2 The Veress technique remains popular today. In the Veress technique, gas is insufflated until an adequate volume has been added to create space in the peritoneal cavity between the abdominal wall and the intra-abdominal as well as the retroperitoneal organs. Once insufflation is complete, a sharp trocar is placed into the peritoneal cavity. In the blind technique, a bladed trocar is inserted into the insufflated peritoneal cavity without direct visualization. A modification of this technique involves the use of a trocar into which a laparoscope can be inserted. Visualization of the abdominal wall layers and the insufflated peritoneal cavity is possible because of the clear tip of these optical-viewing trocars. Janos Veress first introduced the spring-loaded needle currently used to introduce pneumoperitoneum, originally to induce pneumothorax. 3 Modern needles are 12 to 15 cm long, with an external diameter of 2 mm. The outer cannula of a Veress needle consists of a beveled needle point for cutting through tissues. A spring-loaded inner stylet is located within the outer cannula [see Figure 1]. The tip of the inner stylet is dull, protecting the viscera from injury by the sharp outer cannula. Direct pressure on the tip of the Veress needle pushes the dull stylet into the shaft of the outer cannula. When the tip of the needle enters a space such as the peritoneal cavity, the dull inner stylet springs forward. Technique The location on the abdominal wall selected for initial Veress placement depends on a variety of factors. The type of procedure, location of previous incisions, and patient s body habitus may all have an influence. The initial trocar does not always need to be placed through the same incision as the Veress needle, although this is the most common practice. The advantage to using the same site includes the fact that easy Veress placement and insufflation in a particular location provides some level of reassurance that this is a safe site. Prior to insertion of the Veress needle, it is a good practice to ensure that the stomach is decompressed with a gastric tube as gas is often insufflated into the stomach during induction of anesthesia. A large, gas-filled stomach can be injured by the Veress needle or primary trocar. The distended stomach may also displace other intra-abdominal organs, putting these at increased risk for injury. The abdominal wall is relatively thin in the periumbilical location, and the umbilicus is tethered to the fascia, making this an ideal location for initial Veress access. An alternative location (e.g., subcostal) or a different technique (open Hassan) may be best in patients with a prior midline incision near the umbilicus. Insertion of the Veress needle and primary trocar through a site in the left upper quadrant is recommended by some surgeons to decrease the risk of complications related to intra-abdominal adhesions. 4,5 The Figure 1 Veress needle. DOI 10.2310/7800.2203

PHYSIOLOGY OF PNEUMOPERITONEUM 2 left upper quadrant insertion site (Palmer point) is located 3 cm below the middle of the left costal margin. 6 Anatomic studies indicate that the abdominal wall is uniformly thin in this location and the distance from the skin to the retroperitoneal structures is greater than 11 cm in most patients. 7 For the periumbilical Veress needle insertion, a skin incision is made, typically of sufficient size to easily accommodate the intended trocar to be placed at this site. Penetrating towel clips can be placed in the skin near the incision and used to elevate the abdominal wall. This maneuver helps create some space between the anterior aspect of the peritoneal cavity and the intra-abdominal contents as well as the retroperitoneal major vascular structures. It also minimizes the chance for downward pressure with the Veress needle to push the fascia closer to these vital structures. In obese patients, there is a tendency for the skin and subcutaneous fat to be lifted instead of the fascia with this towel clip maneuver. Because of this, a slightly larger incision is sometimes necessary. The base of the umbilicus or the fascia itself should be grasped. Now that the fascia is elevated, the surgeon takes the Veress needle and advances it at a right angle to the fascia. The needle is advanced until there is a perceptible change in force as the needle penetrates the fascia and enters the peritoneal cavity. An audible click is usually heard or felt as the spring-loaded tip advances into the peritoneal cavity. A surgeon should feel or hear two clicks as a Veress needle is placed through the abdominal wall. The retracted blunt needle tip will suddenly extend after it passes through the anterior rectus abdominus fascia and again when it enters the peritoneal cavity. 8 In the waggle test, the hub of the Veress needle should move freely about a fulcrum point located within the anterior abdominal wall. Lack of free movement suggests that the needle tip has entered an intraperitoneal or retroperitoneal structure and the needle should be partially withdrawn. Opponents of this maneuver point out that, if done forcefully, it is likely to enlarge an injury to a fixed vessel or viscus. 9 It is also likely, however, to alert surgeons to the possibility of retroperitoneal placement before insufflation. Drop test A syringe partially filled with saline is attached to the Veress needle. The first maneuver is to aspirate the syringe. The appearance of blood indicates that a blood vessel was entered. The needle can be removed and reinserted, with the procedure continuing in the absence of hemodynamic instability. 10 The aspiration of enteric fluid indicates that the needle has been placed into bowel. It is best to leave this needle in place to identify the specific segment of bowel that has been injured. Options at this point include converting to an open procedure or inserting a second Veress needle in a different location and establishing access in this alternate location. The location of the Veress needle should be ascertained and any bowel injury immediately repaired. In the event that no obvious perforation is found, several options exist. The procedure could be aborted at this point followed by close clinical observation (may be considered in laparoscopic incisional hernia procedures where a permanent prosthetic will be placed into the peritoneal cavity). A laparotomy could be made to continue the search for the possible bowel injury. The final option is to continue with the procedure laparoscopically as planned. The risk with the latter approach is of delayed peritonitis from an unrecognized bowel injury, and caution should be employed if this option is selected. Any signs of postoperative peritonitis or early sepsis should be taken seriously and investigated thoroughly in theses cases. In the absence of blood or enteric fluid, saline is then injected. The inability to inject saline suggests that the tip of the needle may be in a tissue plane. Next, the saline drop test is performed to further assess the location of the tip of the needle [see Figure 2]. A drop of saline is placed in the hub of the needle while maintaining abdominal wall elevation. The passage of saline through the needle is consistent with the tip of the needle being located in the peritoneal cavity. It is important to realize that a successful drop test does not rule out the possibility that the tip of the needle is in bowel. 11 Insufflation Once these placement tests are completed to the satisfaction of the surgeon, the gas tubing is connected to the Veress needle, and insufflation is commenced at a low rate of flow (5 mm Hg) while continuing to elevate the abdominal wall. Once insufflation is initiated, it is important to note both the flow rates and the intra-abdominal pressure. The measured pressure will vary according to the length and size of the needle, depth of anesthesia, patient s body habitus, and location of the tip of the needle. A flow rate of zero and a pressure of 20 mm Hg or more indicate that the tip of the needle is not situated freely within the peritoneal cavity. The most likely locations include the abdominal wall or an intra-abdominal organ such as the omentum. In the latter case, lifting the abdominal wall further and slightly angulating the needle may free the tip to allow insufflation to proceed. The needle should not be advanced further without withdrawing it completely and beginning the entire sequence described above from the beginning because of the risk of penetrating the retroperitoneum. Once insufflation is begun, the strongest predictor of intraperitoneal placement seems to be an initial filling pressure of less than 10 mm Hg. 12 If the initial intra-abdominal pressure is low and flow seems to be occurring through the needle, the flow rate on the insufflator can be set to a higher rate. Many high-flow insufflators can accommodate flow rates up to 40 L/min, but flow rates in excess of 1 to 2 L/min are rarely Figure 2 Saline drop test.

PHYSIOLOGY OF PNEUMOPERITONEUM 3 exceeded through the long, narrow Veress needle. During insufflation, it is important to continue to observe the abdominal wall morphology, flow rates, volume insufflated, intra-abdominal pressure, and patient s vital signs. Eccentric elevation of the abdominal wall may suggest extraperitoneal insufflation or insufflation into a visceral structure such as the stomach or another piece of small or large bowel. Percussion for tympany is a useful maneuver for ensuring uniform insufflation of the abdominal cavity. Trocar insertion After an adequate volume of gas has been insufflated, the Veress needle is removed. In the blind technique for initial trocar insertion, a bladed trocar is inserted through an adequately sized incision. The operating table should be set to a height that allows the surgeon to adequately control the force and vector of initial trocar placement. When the table is placed too high, the surgeon must elevate his or her arm, resulting in reduced control and perhaps a greater risk of injury. Countertraction on the abdominal wall should be maintained to minimize the chance of intra-abdominal injury from the trocar blade. Bladed trocars are equipped with a spring-loaded safety shield that retracts when passed through the abdominal wall. Bladed configurations vary by manufacturer, and the recommended technique for trocar insertion differs as well. Trocars with a three- or four-sided blade shaped like a pyramid are placed by steadily rotating the trocar back and forth as the blade is advanced. Disadvantages to these trocars include the large size of the fascia defect created. Incisional trocar-site hernias may be more common with pyramidal than with conical or flat trocar blades. In one comparative study, the risk of incisional hernia was more than 10 times greater when a disposable pyramidal device was used than when access was gained with a reusable conical trocar cannula system (1.83 versus 0.17%). 13 Potential advantages to the pyramidal-bladed trocars may include the possibility that less force is required to access the abdominal cavity than other blade configurations. 14 Conical flat-bladed trocars [see Figure 3] are placed with direct axial pressure and little rotation. The advantage to bladed trocars with this configuration is that for smaller trocars, the fascia defect is so small that it does not need to be closed at the end of the case. During bladed trocar insertion, a perceptible change in the insertion force signals entry into the peritoneal cavity. This is often accompanied by an audible click as the blade retracts. Advancement of the trocar is halted at this point. The bladed trocar is removed from its outer cannula. If the insufflation port on the cannula is opened, an audible hiss of escaping gas indicates that the tip of the cannula is located in the insufflated peritoneal cavity. The laparoscope is then inserted through this port, both to confirm the successful placement of the cannula in the peritoneal cavity and to rule out intra-abdominal injury from either Veress needle or trocar insertion. If the cannula is located in the peritoneal cavity, the gas tubing is connected to the gas port of the cannula, and insufflation commences through this port to the set pressure (typically 15 mm Hg). The remaining cannulas are then placed under direct visualization from within the peritoneal cavity. The Veress technique can also be used to place a primary optical-viewing trocar. Optical trocars can be bladed or bladeless [see Figure 4]. As is the case for the bladed trocars, insertion techniques vary according to trocar tip configuration. 15 direct trocar insertion In the direct insertion technique, the primary trocar is placed without preinsufflation. This can be performed with either a bladed trocar and a blind technique or an optical trocar under some measure of direct visualization. Theoretical advantages include decreased time to establish abdominal laparoscopic access. 16 Potential disadvantages may include a higher rate of trocar-related intra-abdominal injuries. Several published series evaluating the direct trocar placement technique have demonstrated that very low rates of injury are possible. 17 This technique is safe in the hands of experienced laparoscopists those most likely to publish their results. For inexperienced surgeons, the direct access technique is likely associated with unnecessary increased risk when compared with alternative techniques. 1,18,19 Technique If a bladed trocar is selected, it is important to ensure that the patient is completely relaxed, that the skin incision is sufficiently large, and that adequate countertraction on the fascia is maintained during placement. When a bladed trocar with a safety shield is used as described above, a change in resistance signifies that the tip of the trocar may be in the peritoneal cavity. Prior to the initiation of insufflation, the laparoscope should be inserted into the cannula. If the Figure 3 Conical flat-bladed trocar. Figure 4 Nonbladed optical trocar.

PHYSIOLOGY OF PNEUMOPERITONEUM 4 peritoneal cavity has been safely entered, insufflation can commence at a high rate of flow. If the cannula has not entered the peritoneal cavity, it should be removed and the sequence above reinitiated from the beginning or an alternate technique such as a Veress or open access technique selected. Optical trocars can also be placed with a direct technique. Once again, the patient needs to be completely relaxed, an adequate skin incision should be made, and adequate countertraction should be applied. A gradual twisting motion is employed, and distinct layers of the abdominal wall can be seen during entry. 20 open (hasson) access In an effort to decrease the incidence of injuries associated with the blind penetration of the abdominal cavity during laparoscopy, Hasson proposed a blind minilaparotomy technique. 21 He developed a reusable device similar to a standard laparoscopic port with a cork-shaped sleeve on the outside. The sleeve could be slid up or down on the cannula shaft depending on the thickness of the patient s abdominal wall. Sutures in the fascia were used to anchor the outer sleeve and to create an airtight seal. Disposable Hasson cannulas are currently available. Hasson-type cannulas that are fixed to the abdominal wall between a balloon and a dense foam cuff are also commercially available [see Figure 5]. Regardless of the configuration of the cannula, the basic method for peritoneal access in the open technique remains the same. In the open technique, the peritoneal cavity is entered under direct visualization. Theoretical advantages to the open technique may include a decreased likelihood of injury to adherent bowel, 5,22 although this has been a matter of debate. Major vascular injuries during initial trocar insertion are likely minimized with the open technique, although they can still occur. Potential disadvantages may include increased operative time (especially in obese patients) and an increased risk of late port-related complications such as hematoma, wound infection, or hernia. 7 Leakage of gas around the cannula is occasionally a problem, but balloon-tipped cannulas and high-flow insufflators prevent these issues from being clinically significant. Technique The periumbilical location is most often chosen for initial Hasson cannula placement. An adequately sized incision is made, and the abdominal wall fascia is identified. Two Kocher clamps are secured to the fascia on either side of the midline linea alba. The Kocher clamps are elevated, and the abdominal fascia is incised vertically in the midline. An Figure 5 Hassan cannula. approximately 1.5 to 2.0 cm defect is created in the fascia. If the defect is too large, air leakage may be a problem. Depending on the patient s body habitus, it may be easy to become lost in the preperitoneal space. Entry into the peritoneal cavity should be confirmed visually. Two heavy sutures should be placed in either side of the fascial defect prior to releasing the fascia from the Kocher clamps. The Hasson cannula with its blunt obturator is advanced into the peritoneal cavity, and the sutures are firmly attached to the fixation obturator. Gas is insufflated through the cannula at a high rate of flow, and the laparoscope is inserted. If gas leaks excessively around the cannula, there are several techniques for addressing this. The first option is to remove the stay sutures and secure these to the cannula more firmly. A penetrating towel clip can be used to seal the skin around the cannula. The cannula can be removed, and another fascial suture can be placed and tied to decrease the size of the fascial opening. Finally, a balloon-tipped fixation trocar can be placed to seal the leak. complications Insertion of the Veress needle and primary trocar for initial entry remains the most hazardous part of laparoscopy, accounting for 40% of all laparoscopic complications and the majority of the fatalities. 23 Despite decades of research and development to find safer methods for initial laparoscopic entry, major vessel injuries have been reported using virtually all types of trocar insertion methods. The overall morbidity and mortality rates related to laparoscopic access are low. The life-threatening complications include injury to the bowel, bladder, major abdominal vessels, and anterior abdominal wall vessel. Injuries to the bowel (1.8 per 1,000 cases) are most common, followed by injuries to the abdominal vessels (0.9 per 1,000 cases). 24 A recent Cochrane review included 17 randomized, controlled trials concerning 3,040 individuals undergoing laparoscopy. Overall, there was no evidence of advantage using any single abdominal access technique in terms of preventing major complications. However, there were two advantages with direct trocar entry when compared with Veress needle entry in terms of avoiding extraperitoneal insufflation (odds ratio [OR] 0.06, 95% confidence interval [CI] 0.02 to 0.23) and failed entry (OR 0.22, 95% CI 0.08 to 0.56). There was also an advantage with radially expanding access system (Step bladeless trocars, Covidien, Norwalk, CT) trocar entry when compared with standard trocar entry in terms of trocar site bleeding (OR 0.06, 95% CI 0.01 to 0.46). Finally, there was an advantage of not lifting the abdominal wall before Veress needle insertion when compared with lifting in terms of failed entry without an increase in the complication rate (OR 5.17, 95% CI 2.24 to 11.90). However, studies were limited to small numbers, excluding many patients with previous abdominal surgery and women with a raised body mass index, who often had unusually high complication rates. The authors concluded that there appears to be no evidence of benefit in terms of the safety of one technique over another. However, the included studies were small and cannot be used to confirm the safety of any particular technique. 25 Vascular Injury Vascular injury can occur regardless of the method of access, largely because of the relatively close proximity of the

PHYSIOLOGY OF PNEUMOPERITONEUM 5 abdominal wall to the great vessels that are located retroperitoneally, which, in thin individuals, can be as little as 2 cm. 26 Most vascular injuries (up to 80%) occur at the initial access. 5 Recent studies have suggested that the incidence of major vascular injury is slightly higher with the closed technique (Veress and direct trocar insertion) as opposed to the open (Hasson) technique. Molloy and colleagues study suggests that the open technique decreased the rate of vascular injury to 0.01% compared with a rate of 0.04% associated with closed techniques using a Veress needle. 1 A recent systematic review specifically evaluating injuries related to Veress needle insertion included 38 selected articles, 696,502 laparoscopies, and 1,575 injuries (0.23%). Of these injuries, 98 (6.2%) involved blood vessels, 8 (8.1%) of which were injuries to major retroperitoneal vessels. 27 Although the incidence of major vascular injuries is low, the mortality rate arising from these lesions reportedly ranges between 8 and 17%. 28 It is difficult to determine the exact prevalence of iatrogenic injury during laparoscopy because certain complications are not usually reported, 29 for obvious reasons. Vessel injuries attributable to trocars are usually more obvious and catastrophic than injuries related to Veress needle insertion. Transmural vessel injury related to trocars is the rule rather than the exception. 30 When recognized, the trocar and cannula should be left in place and a conventional vascular repair performed. An expanding retroperitoneal hematoma, hemodynamic instability in the face of active bleeding, and active intra-abdominal hemorrhage that cannot be managed laparoscopically are all indications for conversion to laparotomy and exploration or vascular repair. Trocarrelated major vascular injuries reported to the Food and Drug Administration (FDA) by the medical device industry between 1993 and 1996 were reviewed. 31 Of the 408 injuries reported, 26 resulted in death and 87% occurred despite the use of trocars with safety shields. The most common site of injury was the aorta (23%), followed by the vena cava (15%). A more recent review of FDA reports focused on two optical access devices that purported to provide a degree of safety by allowing the operator to insert a clear but sharp trocar with a laparoscope positioned within it. 32 In that report, 37 major vascular injuries of the aorta, vena cava, and iliac vessels were described, and four deaths were described in relation to vascular injury. These reports seem to validate the notion that safety shields, designed to protect vessels and viscera, do not provide such protection and justify the FDA decision to forbid the term in product labeling. From these reports, it also seems as if in some cases, the diagnosis of major vascular injury may be delayed, usually because of retroperitoneal bleeding, with symptoms manifesting in the recovery room. Abdominal wall vascular complications are typically managed with devices designed to facilitate fascial closure of laparoscopic port sites (suture passers) when possible. It is important to visualize all trocar sites after each trocar is removed at the end of the case to minimize the possibility that an abdominal wall vessel has been injured but has not yet bled because of tamponade by the trocar itself. 33 Visceral Injury Although studies have suggested that the open technique of initial trocar placement may be associated with a lower incidence of major vascular injuries, the same cannot be said for visceral injuries. 34 The incidence of this complication is about 0.05% of all open access procedures. 35 The main difference between bowel injuries occurring during the open technique compared with the closed technique is that with the open procedure, it is more likely that the injury will be immediately obvious and repaired without delay. Veress needle injuries to the large and small bowel may be associated with a higher incidence of peritonitis and other complications than injuries to the stomach, which can often be managed conservatively. 10 If it is suspected that the Veress needle has penetrated the bowel, the needle should be left in place and a second needle placed in another location. Once abdominal access is established, the location of the needle should be ascertained, and repair of any injuries should proceed as appropriate related to the nature of the injury. Physiology of Pneumoperitoneum The introduction and widespread acceptance of laparoscopy have created new challenges for anesthesia providers. Laparoscopic surgery and carbon dioxide (CO 2 ) insufflation have introduced unique management concerns and physiologic consequences for patients. When one considers the fact that many patients undergoing laparoscopic surgery are likely to be sent home shortly following the procedure, it becomes important for surgeons to understand these physiologic consequences and potential ramifications as well. cardiovascular effects Intraoperative Position Patient position is important during laparoscopic surgery to help facilitate visualization of the operative field. For upper abdominal surgery, the reverse Trendelenburg position (head up) can enhance exposure of the operative field. The extreme reverse Trendelenburg position with the aid of a padded footboard has been advocated in bariatric surgery as a means of maximizing exposure. In lower abdominal and pelvic surgery, the Trendelenburg position (head down) enhances operative exposure. It has been demonstrated that intraabdominal volume varies as a patient s position changes. 36 When compared with the supine position in laparoscopic surgery, the Trendelenburg position is associated with increased intra-abdominal volume, and the reverse Trendelenburg position is associated with decreased volume. Decreased intra-abdominal volume may correlate with impaired visualization for the surgeon, possibly extending the operative time and impacting the ultimate outcome in other ways (e.g., increasing doses of muscle relaxation in a quest to see better and poorly visualized anatomy). An increase in intra-abdominal pressure up to 12 to 15 mm Hg decreases venous return, which results in reduced preload and cardiac index (CI), without adequate intravascular volume loading. The common belief is that changes in body position, especially the reverse Trendelenburg position, intensify these negative effects of pneumoperitoneum, whereas the Trendelenburg position has a positive effect on venous return and hence cardiac output (CO). These physiologic effects are likely minimized in euvolemic patients. 37 Invasive hemodynamic monitoring can be used to determine the hemodynamic consequences of laparoscopic surgery in healthy

PHYSIOLOGY OF PNEUMOPERITONEUM 6 volunteers. Joris and colleagues determined that CO decreased by as much as 50% of the preoperative value after the beginning of the laparoscopy and that systemic vascular resistance (SVR) increased accordingly. 38 Hirvonen and colleagues conducted a similar study but took measures to prevent the peripheral pooling of blood, which can happen with the reverse Trendelenburg position, and increased intraabdominal pressure related to pneumoperitoneum. 39 Before laparoscopy, the patients received an intravenous infusion of colloid solution if cardiac filling pressures were low and their legs were wrapped from toes to groin with elastic bandages. A 20% decrease in CO and a 30% decrease in stroke volume (SV) were observed during laparoscopic cholecystectomy in healthy subjects when compared with preoperative values. With the change in position from the supine to the reverse Trendelenburg position in awake and anesthetized patients, the CI, stroke index (SI), central venous pressure (CVP), and pulmonary capillary wedge pressure (PCWP) decreased and SVR increased. In robotic prostatectomy, where patients are placed in a steep (40 ) Trendelenburg position for several hours, it has been demonstrated that mean arterial pressure (MAP) and CVP increased significantly. 40 First, the observed increase in pressure is the result of increased hydrostatic pressure at the external auditory meatus caused by the tilting of the table. In addition, because MAP increased by a greater absolute amount than CVP, at least part of the observed increase in MAP must also be caused by increased CO, SVR, or both. Several additional investigators have demonstrated that placing the patient in the Trendelenburg position is associated with an increase in the CVP, with the CO remaining the same or increasing. 41,42 The induction of pneumoperitoneum has been reported to reduce, elevate, and have no effect on CO in different reports. 37,43,44 Position as an independent factor on the hemodynamic profile is much less studied than the hemodynamic consequences of pneumoperitoneum. Pneumoperitoneum Insufflation of the peritoneal cavity with CO 2 during laparoscopic surgery leads to an increase in the intra-abdominal pressure. Drawing conclusions on the effect of pneumoperitoneum alone on hemodynamic function is difficult as a result of the confounding variables of study methodology, anesthesia, position of the patient, surgical stimulus, and condition of the patient. The effects of pneumoperitoneum on cardiac physiology have been found to depend on the magnitude of the pressure increase, intravascular volume, and underlying cardiovascular status of the patient. The creation of pneumoperitoneum to an intra-abdominal pressure of less than 20 mm Hg in the supine position is generally associated with an increase in the MAP and SVR, although the clinical impacts of these changes are determined by a variety of patient-specific factors. 45,46 Older animal studies have looked at the impact of pneumoperitoneum in relation to intravascular volume status. It has been demonstrated that at very high intra-abdominal pressures in a dog model, CO decreased by 53% in hypovolemic dogs and by 15% in normovolemic dogs but increased by 50% in hypervolemic dogs. 47,48 At low and normal right atrial pressures (low and normal volume status), the inferior vena cava (IVC) is compressed and collapses, causing a decrease in venous return. In hypovolemic dogs, the poor cardiac performance is postulated to be further compounded by the increase in total peripheral resistance related to the compression of the splanchnic arterioles by the increased intra-abdominal pressure. On the other hand, at high right atrial pressures (hypervolemic status), the venous return to the heart is actually augmented as the IVC resists compression. CO in these animals is likely increased related to the Starling mechanism. In humans, the effects of varying pneumoperitoneum-induced changes in intra-abdominal pressure have been studied at much lower pressures. 49,50 Invasive monitoring and echocardiography were used to evaluate the hemodynamic changes as the intra-abdominal pressure increased from low (7 mm Hg) to higher (15 mm Hg) in healthy patients undergoing elective laparoscopic cholecystectomy. At low insufflation and intra-abdominal pressures, an overall mild increase in MAP, SV, and CO was observed. At 15 mm Hg insufflation pressure, the SV and CO were observed to decrease to a similar degree. There are few published data on the effect of higher insufflation pressures in humans during laparoscopy. In 100 healthy women undergoing elective gynecologic procedures, initial insufflation to an intra-abdominal pressure of 30 mm Hg was attained prior to insertion of the primary trocar. Heart rate, blood pressure, and pulmonary compliance were measured at 15 versus 30 mm Hg. A significant increase in MAP and a decrease in pulmonary compliance were observed at 30 mm Hg compared with 15 mm Hg. 51 Unfortunately, CO and other hemodynamic parameters were not evaluated. Bradyarrhythmias have been reported to occur with the induction of pneumoperitoneum. These arrhythmias are most likely related to the vagal stimulation induced by peritoneal stretching on insufflation. 52 In one recent study of patients undergoing laparoscopic urologic surgery, 28% of patients developed bradycardia perioperatively compared with 0% of patients randomly assigned to a treatment group to receive a dose of atropine prior to pneumoperitoneum induction. 53 Treatment of bradycardia on induction of pneumoperitoneum consists of immediate cessation of surgical stimulation, abdominal deflation, and the administration of anticholinergic drugs such as glycopyrrolate or atropine. Carbon Dioxide CO 2 is the preferred gas for abdominal insufflation in laparoscopy as a result of its lack of flammability, solubility, and ready availability. CO 2 insufflation results in diffusion of CO 2 into the blood and an increase in its elimination through the lungs. The CO 2 load is greatest during extraperitoneal insufflation (e.g., preperitoneal inguinal hernia repair) compared with intraperitoneal insufflation. 54 The cardiovascular effects of hypercarbia seen during laparoscopic procedures are not as significant when compared with the effects of patient position and pneumoperitoneum provided that the arterial carbon dioxide tension (PaCO 2 ) is kept below 50 torr by controlled ventilation (increased ventilation to increase CO 2 exchange and decrease PaCO 2 ). Hypercarbia has effects on the myocardium (myocardial irritability with transient arrhythmias, increased contractility), central nervous system (increased sympathetic tone), and periphery (vasodilation with a decrease in the SVR). The net effect is the negligible hemodynamic consequences of hypercarbia. 55 Studies comparing CO 2 pneumoperitoneum to pneumoperitoneum created with

PHYSIOLOGY OF PNEUMOPERITONEUM 7 alternative gases such as nitric oxide and helium have demonstrated that the hemodynamic effects are independent of the type of gas insufflated. 56 CO 2 embolism is a potentially fatal complication caused by the insufflation of CO 2 directly into the circulation. CO 2 embolism occurs most frequently on the induction of pneumoperitoneum but can occur at any point in the operation. 57 Certain procedures, such as laparoscopic hepatectomy, are very commonly associated with small CO 2 gas embolisms that are usually subclinical, although clinically significant CO 2 embolism is still a major concern in these cases. 58 Cardiovascular collapse can occur rapidly with a large CO 2 embolism. Gas obstructs the right ventricular outflow tract, resulting in cyanosis, increased venous pressure, ventricular arrhythmias, and a decrease in the end-tidal carbon dioxide tension (PCO 2 ). Immediate recognition of the problem is essential. Treatment consists of the immediate cessation of insufflation, positioning the patient in the head-down left lateral position, hyperventilation, and even aspiration of gas from the right atrium through a central venous catheter. respiratory effects The respiratory effects of laparoscopic surgery include those of pneumoperitoneum and positioning and are superimposed on the effects caused by the anesthetic itself. Lung volumes and compliance are decreased during laparoscopic surgery. Effect of Pneumoperitoneum The increase in intra-abdominal pressure caused by pneumoperitoneum also affects the pulmonary system by impeding diaphragmatic movement, leading to a decrease in the functional residual capacity (FRC) of the lung. Compliance is also decreased, mostly as a result of a cephalad displacement of the diaphragm and the chest wall. This disturbance in compliance is immediately reversible on abdominal deflation. 59 Airway pressures increase during CO 2 pneumoperitoneum because of decreased compliance and the need to increase minute ventilation to excrete the increased CO 2 load absorbed from the peritoneal cavity. Hasukic and colleagues measured pulmonary function tests in postoperative patients who underwent laparoscopic cholecystectomy. 60 Pulmonary function tests demonstrated a decrease in forced expiratory volume in 1 second (FEV 1 ) and forced vital capacity (FVC). In spite of these documented effects of pneumoperitoneum of pulmonary function, studies have shown that the pulmonary status of patients after a laparoscopic procedure is actually less detrimentally affected than when compared with the open procedure. 61 Oxygenation Increasing pneumoperitoneum also causes an increase in alveolar dead space, leading to potential hypoxemia. 62 This leads to ventilator-perfusion mismatching and intrapulmonary shunting. The risk of hypoxemia is counteracted by controlled mechanical ventilation during laparoscopic surgery with increased tidal volumes and the addition of positive end-expiratory pressure (PEEP). 40 Carbon Dioxide Absorption and Excretion CO 2 is the most common gas used to obtain pneumoperitoneum during laparoscopic surgery. It is absorbed into the bloodstream, where it is finally excreted by the lungs. Most of the CO 2 combines with water found in the red blood cells to form carbonic acid. Carbonic acid further breaks down into hydrogen, which is carried by hemoglobin, and bicarbonate, which diffuses into the plasma. A small amount of CO 2 does get dissolved directly in the bloodstream and is transported to the lungs for excretion. 63 Subcutaneous emphysema is a frequent occurrence and is commonly caused by leakage around an abdominal insufflating port. Extensive subcutaneous emphysema can be associated with significant respiratory acidosis, necessitating prolonged postoperative ventilation. 64 pain after laparoscopic surgery Laparoscopic surgery has been shown to cause less postoperative pain when compared with the equivalent open technique for many operations. Some examples of common general surgery procedures where laparoscopic surgery has been shown to reduce postoperative pain include cholecystectomy, hemicolectomy, appendectomy, and inguinal hernia repair. 65 67 In addition to incisional and visceral pain, laparoscopic surgery has been associated with shoulder tip pain. This referred pain is thought to be caused by the increased intra-abdominal pressure caused by the laparoscopic gas, resulting in diaphragmatic stretching and phrenic nerve irritation. As a result, shoulder tip pain is unique to laparoscopy and usually dissipates in 1 to 3 days as the CO 2 is absorbed into the systemic circulation. One method to reduce shoulder tip pain is by employing a lower pressure during the procedure; however, this can reduce the size of the surgical field. 68 Other techniques, such as intraperitoneal irrigation with local anesthesia, have shown promising results. 69 nausea and vomiting after laparoscopic surgery A common complaint by patients who have undergone a laparoscopic procedure is postoperative nausea and vomiting (PONV). This can be seen in as many as 40 to 75% of patients and can delay discharge of patients, especially during outpatient surgery. 70 Patients rank vomiting as the number one complication of surgery they want to avoid and rank nausea in the top five. When patients are given the option of allocating $100 out of pocket to the prevention of postoperative complications, they choose to allocate approximately $30 for the prevention of PONV. 71 The etiology of PONV from a purely surgical standpoint (not taking into account the effects of anesthetic gas) is likely attributable to a combination of peritoneal gas insufflation and bowel manipulation. 72 Postoperative opioids, female sex, history of motion sickness, history of migraine, duration of the operation, and a previous history of PONV have all been demonstrated in a predictive model as significant independent variables with marked association with PONV. 73 The newest guidelines delineated in the 2008 consensus guidelines for the management of PONV suggest that the clinical team should evaluate the patient s risk for PONV, reduce baseline risk factors for PONV, evaluate the patient s preferences, and determine the cost-effectiveness of antiemetic prophylaxis before deciding to administer PONV prophylaxis to the patient. 74 Other than identifying patients at the greatest risk for PONV, guidelines include reducing baseline risk factors (avoid general anesthesia when possible, use propofol for induction and maintenance of anesthesia, avoid nitrous oxide and volatile anesthetics, minimize opioids and

PHYSIOLOGY OF PNEUMOPERITONEUM 8 neostigmine, and maintain adequate hydration) and administering antiemetics prophylactically in moderate- and high-risk patients in the appropriate dose and at the appropriate time. A recently published economic analysis of routine prophylaxis of PONV in all surgical patients determined that the study site hospital s net profit increases linearly with increased PONV prophylaxis administration. Economic analysis showed that PONV prophylaxis was economically beneficial for the hospital when weighed against the expense generated by treating patients returning to the hospital with PONV. 75 Financial Disclosures: None Reported References 1. Molloy D, Kaloo PD, Cooper M, et al. Laparoscopic entry: a literature review and analysis of techniques and complications of primary port entry. Aust N Z J Obstet Gynaecol 2002;42:246 53. 2. Gunning J. The history of laparoscopy. J Reprod Med 1974;12:222 6. 3. Veress J. Neues Instrument zur Asfuhrung von Brustoder Bauchpunktionen and Pneumothoraxbehandlung. Dtsch Med Wochenshr 1938;41:1480 1. 4. Agarwala N, Liu CY. Safe entry techniques during laparoscopy: left upper quadrant entry using the ninth intercostal space a review of 918 procedures. J Minim Invasive Gynecol 2005;12:55 61. 5. Howard FM, El-Minawi AM, DeLoach VE. Direct laparoscopic cannula insertion at the left upper quadrant. J Am Assoc Gynecol Laparosc 1997;4:595 600. 6. Palmer R. Safety in laparoscopy. J Reprod Med 1974;13:1 5. 7. Giannios NM, Rohlck KE, Gulani V, et al. Left upper quadrant laparoscopic instrument placement: effects of insertion angle and body mass index on distance to posterior peritoneum by magnetic resonance imaging. Am J Obstet Gynecol 2009;201:522. 8. Vilos GA, Ternamian A, Dempster J, et al. Laparoscopic entry: a review of techniques, technologies, and complications. J Obstet Gynaecol Can 2007;29:433 65. 9. Brosens I, Gordon A. Bowel injuries during gynaecological laparoscopy: a multinational survey. Gynecol Endosc 2001;10:141 5. 10. Crist DW, Gadacz DW. Complications of laparoscopic surgery. Surg Clin North Am 1993;73:265 89. 11. Nuzzo G, Giuliante F, Tebala GD, et al. Routine use of open technique in laparoscopic operations. J Am Coll Surg 1997;184: 58 62. 12. Vilos AG, Vilos GA, Abu-Rafea B, et al. Effect of body habitus and parity on the initial Veress intraperitoneal (VIP) CO 2 insufflation pressure during laparoscopic access in women. J Minim Invasive Gynecol 2006;13: 108 13. 13. Leibl BJ, Schmedt CG, Schwarz J, et al. Laparoscopic surgery complications associated with trocar tip design: review of literature and own results. J Laparoendosc Adv Surg Tech A 1999;9:135 40. 14. Tarnay CM, Glass KB, Munro MG. Entry force and intra-abdominal pressure associated with six laparoscopic trocar±cannula systems: a randomized comparison. Obstet Gynecol 1999;94:83 8. 15. Sabeti N, Tarnoff M, Kim J, et al. Primary midline peritoneal access with optical trocar is safe and effective in morbidly obese patients. Surg Obes Relat Dis 2009;5:610 4. 16. Tinelli A, Malvasi A, Istre O, et al. Abdominal access in gynaecological laparoscopy: a comparison between direct optical and blind closed access by Veress needle. Eur J Obstet Gynecol Reprod Biol 2010;148:191 4. 17. Mlyncek M, Truska A, Garay J. Laparoscopy without the use of the Veress needle: results in a series of 1,6000 procedures. Mayo Clin Proc 1994;69:1146 8. 18. Woolcott R. The safety of laparoscopy performed by direct trocar insertion and carbon dioxide insufflation under vision. Aust N Z J Obstet Gynaecol 1997;37:216 9. 19. Kaali SG, Barad DH. Incidence of bowel injury due to dense adhesions at the sight of direct trocar insertion. J Reprod Med 1992;37:617 8. 20. Rabl C, Palazzo F, Aoki H, et al. Initial laparoscopic access using an optical trocar without pneumoperitoneum is safe and effective in the morbidly obese. Surg Innov 2008; 15:126 31. 21. Hasson HM. Modified instrument and method for laparoscopy. Am J Obstet Gynecol 1971;110:886 7. 22. Mayol J, Garcia-Aguilar J, Ortiz-Oshiro E, et al. Risks of the minimal access approach for laparoscopic surgery: multivariate analysis of morbidity related to umbilical trocar insertion. World J Surg 1997;21:529 33. 23. Fuller J, Ashar BS, Carey-Corrado J. Trocarassociated injuries and fatalities: an analysis of 1399 reports to the FDA. J Minim Invasive Gynecol 2005;12:302 7. 24. Shirk GJ, Johns A, Redwine DB. Complications of laparoscopic surgery: how to avoid them and how to repair them. J Minim Invasive Gynecol 2006;13:352 9. 25. Ahmed G, Duffy JMN, Phillips K, et al. Laparoscopic entry techniques. Cochrane Database Syst Rev 2008;16(2):CD006583. 26. Hurd WW, Bude RO, DeLancey JO, et al. The relationship of the umbilicus to the aortic bifurcation: implications for laparoscopic technique. Obstet Gynecol 1992;80:48 51. 27. Azevedo JL, Azevedo OC, Miyahira SA, et al. Injuries caused by Veress needle insertion for creation of pneumoperitoneum: a systematic literature review. Surg Endosc 2009;23: 1428 32. 28. Olsen DO. Laparoscopic cholecystectomy. Am J Surg 1991;161:339 44. 29. Chapron CM, Pierre F, Lacroix S, et al. Major vascular injuries during gynecologic laparoscopy. J Am Coll Surg 1997;185: 461 5. 30. Wolfe WM, Pasic R. Transuterine insertion of Veress needle in laparoscopy. Obstet Gynecol 1990;75:456 7. 31. Bhoyrul S, Vierra MA, Nezhat CR, et al. Trocar injuries in laparoscopic surgery. J Am Coll Surg 2001;192:677 83. 32. Sharp HT, Dodson MK, Draper ML, et al. Complications associated with optical-access laparoscopic trocars. Obstet Gynecol 2002; 99:553 5. 33. Hurd WW, Pearl ML, DeLancey JO, et al. Laparoscopic injury of abdominal wall blood vessels: a report of three cases. Obstet Gynecol 1993;82:673 6. 34. Chapron C, Cravello L, Chopin N, et al. Complications during set-up procedures for laparoscopy in gynecology: open laparoscopy does not reduce the risk of major complications. Acta Obstet Gynecol Scand 2003;82:1125 9. 35. McMahon AJ, Baxter JN, O Dwyer PJ. Preventing complications of laparoscopy. Br J Surg 1993;80:1592 4. 36. Mulier JP, Dillemans B, Cauwenberge SV. Impact of the patient s body position on the intraabdominal workspace during laparoscopic surgery. Surg Endosc 2010;24: 1398 402. 37. Wilcox S, Vandam LD. Alas, poor Trendelenburg and his position! A critique of its uses and effectiveness. Anesth Analg 1988;67:574 8. 38. Joris JL, Noirot DP, Legrand MJ, et al. Hemodynamic changes during laparoscopic cholecystectomy. Anesth Analg 1993;76: 1067 71. 39. Hirvonen EA, Poikolainen EO, Pääkkönen ME, et al. The adverse hemodynamic effects of anesthesia, head-up tilt, and carbon dioxide pneumoperitoneum during laparoscopic cholecystectomy. Surg Endosc 2000;14: 272 7. 40. Kalmar AF, Foubert L, Hendrickx JFA et al. Influence of steep Trendelenburg position and CO 2 pneumoperitoneum on cardiovascular, cerebrovascular, and respiratory homeostasis during robotic prostatectomy. Br J Anaesth 2010;104:433 9. 41. Meininger D, Westphal K, Bremerich DH, et al. Effects of posture and prolonged pneumoperitoneum on hemodynamic parameters during laparoscopy. World J Surg 2008; 32:1400 5. 42. Kelman GR, Swapp GH, Smith I, et al. Cardiac output and arterial blood-gas tension during laparoscopy. Br J Anaesth 1972; 44:1155 62. 43. Hofer CK, Zalunardo MP, Klaghofer R, et al. Changes in intrathoracic blood volume associated with pneumoperitoneum and positioning. Acta Anaesthesiol Scand 2002;46: 303 8. 44. Odeberg S, Ljungqvist O, Svenberg T, et al. Haemodynamic effects of pneumoperitoneum and the influence of posture during anesthesia for laparoscopic surgery. Acta Anaesthesiol Scand 1994;38:276 83. 45. Grabowski JE, Talamini MA. Physiological effects of pneumoperitoneum. J Gastrointest Surg 2009;13:1009 16. 46. Dorsay DA, Greene FL, Baysinger CL. Hemodynamic changes during laparoscopic cholecystectomy monitored with transesophageal echocardiography. Surg Endosc 1995;9: 128 34. 47. Kashtan J, Green JF, Parsons EQ, et al. Hemodynamic effect of increased abdominal pressure. J Surg Res 1981;30:249 55. 48. Ivankovich AD, Miletich DJ, Albrecht RF, et al. Cardiovascular effects of intraperitoneal insufflation with carbon dioxide and nitrous oxide in the dog. Anesthesiology 1975;42: 281 7. 49. Dexter SP, Vucevic M, Gibson J, et al. Hemodynamic consequences of high- and low-pressure capnoperitoneum during laparoscopic cholecystectomy. Surg Endosc 1999; 13:376 81. 50. McLaughlin JG, Scheeres DE, Dean RJ, et al. The adverse hemodynamic effects of laparoscopic cholecystectomy. Surg Endosc 1995; 9:121 4.

PHYSIOLOGY OF PNEUMOPERITONEUM 9 51. Abu-Rafea B, Vilos GA, Vilos AG, et al. High-pressure laparoscopic entry does not adversely affect cardiopulmonary function in healthy women. J Minim Invasive Gynecol 2005;12:475 9. 52. Myles PS. Bradyarrhythmias and laparoscopy; a prospective study of heart rate changes with laparoscopy. Aust N Z J Obstet Gynaecol 1991;31:171 3. 53. Aghamohammadi H, Mehrabi S, Mohammad Ali, et al. Prevention of bradycardia by atropine sulfate during urological laparoscopic surgery: a randomized controlled trial. Urol J 2009;6:92 5. 54. Liem MSL, Kallewaard JW, de Smet AM, et al. Does hypercarbia develop faster during laparoscopic herniorrhaphy than during laparoscopic cholecystectomy? Assessment with continuous blood gas monitoring. Anesth Analg 1995;81:1243 9. 55. Cullen DJ, Eger EI. Cardiovascular effects of carbon dioxide in man. Anesthesiology 1974;41:345 9. 56. Bongard FS, Pianim NA, Leighton TA, et al. Helium insufflation for laparoscopic operation. Surg Gynecol Obstet 1993;177:140 6. 57. Yacoub OF, Cardona I, Coveller LA, et al. Carbon dioxide embolism during laparoscopy. Anesthesiology 1982;57:533 5. 58. Jayaraman S, Khakhar A, Yang H, et al. The association between central venous pressure, pneumoperitoneum, and venous carbon dioxide embolism in laparoscopic hepatectomy. Surg Endosc 2009;23:2369 73. 59. Fahy BG, Barnas GM, Nagle SE, et al. Changes in lung and chest wall properties and abdominal insufflation of carbon dioxide are immediately reversible. Anesth Analg 1996; 82:601 5. 60. Hasukic S, Mesic D, Dizdarevic E, et al. Pulmonary function after laparoscopic and open cholecystectomy. Surg Endosc 2002; 16:163 5. 61. Schwenk W, Bohm B, Witt C, et al. Pulmonary function following laparoscopic or conventional colorectal resection: a randomized controlled evaluation. Arch Surg 1999;134: 6 12. 62. Gutt CN, Oniu T, Mehrabi A, et al. Circulatory and respiratory complications of carbon dioxide insufflation. Dig Surg 2004;21: 95 105. 63. Wagner PD, Powell FL, West JB. Ventilation, blood flow and gas exchange. In: Mason RJ, Broaddus VC, Martin T, et al., editors. Murray and Nadel s textbook of respiratory medicine. 5th ed. Philadelphia: Saunders Elsevier; 2010. p 53 88. 64. Gottlieb A, Sprung J, Zheng XM, et al. Massive subcutaneous emphysema and severe hypercarbia in a patient during endoscopic transcervical parathyroidectomy using carbon dioxide insufflation. Anesth Analg 1997;84:1154 6. 65. Lujan JA, Parrilla P, Robles R, et al. Laparoscopic cholecystectomy vs. open cholecystectomy in the treatment of acute cholecystitis. Arch Surg 1998;133:173 5. 66. Lourenco T, Murray A, Grant A, et al. Laparoscopic surgery for colorectal cancer: safe and effective? A systematic review. Surg Endosc 2008;22:1146 60. 67. Sauerland S, Jaschinski T, Neugebauer EA. Laparoscopic versus open surgery for suspected appendicitis. Cochrane Database Syst Rev 2010;(10):CD001546. 68. Gurusamy KS, Samraj K, Davidson BR. Low pressure versus standard pressure pneumoperitoneum in laparoscopic cholecystectomy. Cochrane Database Syst Rev 2009;(2): CD006930 69. Palmes D, Rottgermann S, Classen C, et al. Randomized clinical trial of the influence of intraperitoneal local anesthesia on pain after laparoscopic surgery. Br J Surg 2007;94: 824 32. 70. Watcha MF, White PF. Postoperative nausea and vomiting: its etiology, treatment, and prevention. Anesthesiology 1992;77:162. 71. Macario A, Weinger M, Carney S, et al. Which clinical anesthesia outcomes are important to avoid? The perspective of patients. Anesth Analg 1999;89:652 8. 72. Smith I. Anesthesia for laparoscopy with emphasis on outpatient laparoscopy. Anesthesiol Clin North Am 2001;19:21 41. 73. Palazzo M, Evans R. Logistic regression analysis of fixed patient factors for postoperative sickness: a model for risk assessment. Br J Anaesth 1993;70:135 40. 74. Gan TJ, Meyer TA, Apfel CC, et al. Society for Ambulatory Anesthesia guidelines for the management of postoperative nausea and vomiting. Anesth Analg 2007;105:1615 28. 75. Dzwonczyk R, Weaver TE, Puente EG, et al. Postoperative nausea and vomiting prophylaxis from an economic point of view. Am J Ther 2010 Jul 10. [Epub ahead of print]