Characteristic alterations of the peritoneum after carbon dioxide pneumoperitoneum

Objective: Any route of entry into the abdomen contributes to alterations of the intraperitoneal organs with different clinical consequences. Characteristic alterations of the peritoneum after CO₂ pneumoperitoneum used in laparoscopic surgery is examined. Methods: A CO₂ pneumoperitoneum with an intraperitoneal pressure of 6 mmHg was applied for 30 min in 32 nude mice. In the course of 4 days, the animals were killed and the peritoneal surface of the abdominal wall was studied by means of scanning electron microscopy. Results: Already 2 h after release of the pneumoperitoneum, mesothelial cells were bulging up. The intercellular clefts thereby increased in size, and the underlying basal lamina became visible. This reaction peaked after 12 h. Subsequently, peritoneal macrophages and lymphocytes filled all gaps, thereby recovering the basal lamina. Conclusion: The morphologic integrity of the peritoneum is temporarily disturbed by a CO₂ pneumoperitoneum. Received: 9 March 1998/Accepted: 24 July 1998     

Intraperitoneal immunity and pneumoperitoneum

Background: Carbon dioxide (CO₂) pneumoperitoneum has been implicated as a possible factor in depressed intraperitoneal immunity. Using in vitro functional assays, CO₂ has been shown to decrease the function of peritoneal macrophages harvested from insufflated mice. However, an effective in vivo assessment is lacking. Listeria monocytogenes (LM), an intracellular pathogen, has served as a well-established in vivo model to study cell-mediated immune responses in mice. This study examines the immune competence of mice based on their ability to clear intraperitoneally administered LM following CO₂ vs helium (He) insufflation. Methods: Eighty-five mice (C57Bl/6, males, 4–6 weeks old) were divided between the following four treatment groups: CO₂ insufflation, He insufflation, abdominal laparotomy (Lap), and control (anesthesia only). Immediately postoperatively, each group was inoculated percutaneously and intraperitoneally with a sublethal dose (.015 × 10⁶ org) of virulent LM (EGD strain). Half of the animals were killed on postoperative day 3 and half on day 5. Spleens and livers (sites of bacterial predilection) were harvested, homogenized, and plated on TSB agar. The amount of bacteria (1 × 10⁶ LM/spleen and liver) from each group was then compared. Statistical significance was set at p≤ 0.05. Results: Control animals had nominal bacteria on day 3 (0.016 × 10⁶ LM/spleen and liver), and the bacterial burden remained low at day 5 (0.038 × 10⁶ LM/spleen and liver) postchallenge. On day 3, the bacterial burden was significantly higher in the CO₂ group (5.46 × 10⁶ LM/spleen and liver) as compared to He (0.093 × 10⁶ LM/spleen and liver) and controls. The Lap group (3.44 × 10⁶ LM/spleen and liver) had significantly more bacteria than the controls. There were no significant differences between any of the groups on day 5. Conclusions: In this animal model, CO₂ pneumoperitoneum impaired cell-mediated intraperitoneal immunity significantly more than He pneumoperitoneum and controls on day 3. Also on day 3, laparotomy caused impairment of intraperitoneal immunity when compared to controls. Finally, intraperitoneal immunosuppression resolved by day 5. Received: 22 July 1998/Accepted: 3 March 1999     

Effect of carbon dioxide pneumoperitoneum and wound closure technique on port site tumor implantation in a rat model

Background The purpose of this study was to evaluate the effects of carbon dioxide (CO₂) pneumoperitoneum and wound closure technique on port site tumor implantation.Methods A standard quantity of rat mammary adenocarcinoma (SMT2A)was allowed to grow in a flank incision in Wistar-Furth rats (n = 90) for 14 days. Thereafter, 1-cm incisions were made in each animal in three quadrants. There were six control animals. The experimental animals were divided into a 60-min CO₂ pneumoperitoneum group (n = 42) and a no pneumoperitoneum (n = 42) group. The flank tumor was lacerated transabdominally in the experimental groups. The three wound sites were randomized to closure of (a) skin; (b) skin and fascia; and (c) skin, fascia, and peritoneum. The abdominal wounds were harvested en bloc on postoperative day 7.Results Histologic comparison of the port sites in the pneumoperitoneum and no-pneumoperitoneum groups did not demonstrate a statistically significant difference in tumor implantation for any of the closure methods. Evaluation of the closure techniques showed no statistical difference between the pneumoperitoneum group and the no-pneumoperitoneum group in the incidence of port site tumor implantation. Within the no-pneumoperitoneum group, there was a significant increase (p = 0.03) in tumor implantation with skin closure alone vs all three layers. Additionally, when we compared all groups by closure technique, the rate of tumor implantation was found to be significantly higher (p = 0.01) for skin closure alone vs closure of all three layers.Conclusions This study suggests that closure technique may influence the rate of port site tumor implantation. The use of a CO₂ pneumoperitoneum did not alter the incidence of port site tumor implantation at 7 days postoperatively.     

Effects of carbon dioxide vs helium pneumoperitoneum on hepatic blood flow

Background: Elevated intraabdominal pressure due to gas insufflation for laparoscopic surgery may result in regional blood flow changes. Impairments of hepatic, splanchnic, and renal blood flow during peritoneal insufflation have been reported. Therefore we set out to investigate the effects of peritoneal insufflation with helium (He) and carbon dioxide (CO₂) on hepatic blood flow in a porcine model. Methods: Twelve pigs were anesthetized and mechanically ventilated with a fixed tidal volume after the stabilization period. Peritoneal cavity was insufflated with CO₂ (n= 6) or He (n= 6) to a maximum intraabdominal pressure of 15 mmHg. Hemodynamic parameters, gas exchange, and oxygen content were studied at baseline, 90 mm and 150 min after pneumoperitoneum, and 30 min after desufflation. Determination of hepatic blood flow with indocyanine green was made at all measured points by a one-compartment method using hepatic vein catheterization. Results: A similar decrease in cardiac output was observed during insufflation with both gases. Hepatic vein oxygen content decreased with respect to the baseline during He pneumoperitoneum (p < 0.05), but it did not change during CO₂ insufflation. Hepatic blood flow was significantly reduced in both the He and CO₂ pneumoperitoneums at 90 min following insufflation (63% and 24% decrease with respect to the baseline; p < 0.001 and p < 0.05, respectively) being this decrease marker in the He group (p= 0.02). Conclusions: These findings suggest that helium intraperitoneal insufflation results in a greater impairment on hepatic blood flow than CO₂ insufflation. Received: 27 March 1996/Accepted: 19 January 1997     

Effect of carbon dioxide pneumoperitoneum on bacteremia and severity of peritonitis in an experimental model

Background: Laparoscopy is increasingly used in conditions complicated by peritonitis. A theoretical concern is that carbon dioxide pneumoperitoneum may increase bacteremia. Method: In 60 rats peritonitis was induced by cecostomy. Animals were randomly allocated to pneumoperitoneum (PP) and control groups. Blood cultures and intraabdominal swabs were assessed. A peritonitis severity score (PSS) was computed based on histology from peritoneal biopsy. Results: One hour after cecostomy neither in abdominal swabs nor in blood samples bacteria were reproduced in PP and control groups. Three hours after cecostomy the frequency of positive blood cultures was 80% and 20% in PP and control groups, respectively (p < 0.0001). Six hours after cecostomy the frequency of positive blood cultures was 100% in each group (p > 0.05). One hour after cecostomy the mean peritoneal severity score was significantly higher in the PP group than in the control group, but there was not any significant difference between groups 3 and 6 h after cecostomy. The mean peritoneal severity scores were found to be significantly increased with time when the PP groups compared with each other. Conclusion: In rats, pneumoperitoneum can't cause a more severe peritonitis but it does induce an increase in the rate of bacteremia within the early 6-h period of peritonitis. Received: 14 April 1997/Received: 18 September 1997     

The effect of carbon dioxide pneumoperitoneum on free radicals

Background: Carbon dioxide is usually preferred as the insufflating agent for laparoscopic surgery because it is readily available, noncombustible, and chemically stable. It is still questionable, however, if CO₂ pneumoperitoneum has any effect on free radicals and lipid peroxidation. The purpose of this study was to investigate the possible effects of CO₂ pneumoperitoneum on free radicals and lipid peroxidation in the erythrocytes of rats. Methods: Fifty male Sprague-Dawley rats were divided into five equal groups: controls, a sham-operation group, and three groups of 5, 10, or 15 mmHg pneumoperitoneum with CO₂. At the end of the procedure, blood was collected and the erythrocytes were separated from the plasma. The resultant supernatant fractions of erythrocytes were assayed for superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA). Results: SOD activities of the 5 and 10 mmHg pneumoperitoneum groups were significantly lower than those of the sham operation group. SOD activity was greater in the 15 mmHg pneumoperitoneum group than in any of the other groups, and this activity was significantly different from that seen in the 5 and 10 mmHg pneumoperitoneum groups (p < 0.05). No significant changes were observed in the CAT activities of the study groups (p > 0.05). MDA level was increased in the 5 mmHg pneumoperitoneum group; this result was statistically different from the control and 15 mmHg pneumoperitoneum groups (p < 0.05). No significant differences were found in the CAT activities for the study groups. On the other hand, the SOD activities of the 5 and 10 mmHg pneumoperitoneum groups were significantly lower than those of the sham and the 15 mmHg pneumoperitoneum group (p < 0.05 for all comparisons). Conclusions: These results indicate that CO₂ pneumoperitoneum applied with 5–10 mmHg pressure increases the formation of free oxygen radicals by inhibiting SOD activity and that the accumulation of free radicals elevates the level of MDA, a metabolite of lipid peroxidation. The effect of CO₂ pneumoperitoneum on free radicals and lipid peroxidation is pressure-dependent in rats. The mechanism underlying this pressure dependency is still under investigation. Received: 16 December 1999/Accepted: 14 February 2000/Online publication: 10 May 2000     

The adverse hemodynamic effects of anesthesia, head-up tilt, and carbon dioxide pneumoperitoneum during laparoscopic cholecystectomy

Background: The increased intra-abdominal pressure during pneumoperitoneum, together with the head-up tilt used in upper abdominal laparoscopies, would be expected to decrease venous return to the heart. The goal of our study was to determine whether laparoscopy impairs cardiac performance when preventive measures to improve venous return are taken, and to analyze the effects of positioning, anesthesia, and increased intra-abdominal pressure. Methods: Using invasive monitoring, hemodynamic changes were investigated in 15 ASA class I or II patients under isoflurane–fentanyl anesthesia during laparoscopic cholecystectomy. Before laparoscopy, the patients received an intravenous (IV) infusion of colloid solution if cardiac filling pressures were low, and their legs were wrapped from toes to groin with elastic bandages. Measurements were taken while the patients were awake in the supine (baseline) and head-up tilt (15–20°) positions, and after the induction of anesthesia in the same positions. Measurements were repeated at regular intervals during laparoscopy (intra-abdominal pressure at 13–16 mmHg), after deflation of the gas, and in the recovery room. Results: With the passive head-up tilt in awake and anesthetized patients, the cardiac index (CI), stroke index (SI), central venous pressure (CVP), and pulmonary capillary wedge pressure (PCWP) decreased, and systemic vascular resistance increased. With the patient under anesthesia, SI decreased, but CI did not change significantly as a result of the compensatory increase in heart rate. Carbon dioxide (CO₂) insufflation at the start of laparoscopy produced increases in CVP and PCWP as well as mean systemic and mean pulmonary arterial pressures without changes in CI or SI. Toward the end of the laparoscopy, CI decreased by 15%. The hemodynamic values returned to nearly prelaparoscopic levels after deflation of the gas, and CI was elevated during the recovery period, whereas systemic vascular resistance was decreased in comparison with the baseline. Conclusions: By correcting relative dehydration and preventing the pooling of blood, CI decreased less than 20% during pneumoperitoneum as compared with the baseline awake level. The head-up positioning accounts for many of the adverse effects in hemodynamics during laparoscopic cholecystectomy. Received: 6 November 1998/Accepted: 8 July 1999     

Alterations in hemodynamics and left ventricular contractility during carbon dioxide pneumoperitoneum

Background: Carbon dioxide (CO₂) pneumoperitoneum has been shown to adversely affect hemodynamics in patients. This study specifically examines the potential contribution of altered left ventricular contractility (LVC) to hemodynamic changes observed during CO₂ pneumoperitoneum. Methods: In a canine model, LV volumes, LV pressure, and intrathoracic and central venous pressures were recorded both at basal intra-abdominal pressure (IAP) and after CO₂ insufflation to produce IAPs of 5–25 mmHg. Results: At IAPs greater than 15 mmHg, cardiac output and LV end-diastolic volume decreased. Mean arterial pressure and heart rate were unchanged. LVC, quantified using the linear Frank-Starling relationship, was not affected by increases in IAP. Conclusions: This study is the first to quantify LVC during CO₂ pneumoperitoneum and demonstrates no changes in contractility over IAPs from 5 to 25 mmHg. In the dog model, any hemodynamic alterations induced by CO₂ pneumoperitoneum are secondary to altered LV preload and not alterations in contractility or LV afterload. Received: 8 March 1996/Accepted: 23 April 1996     

Hemodynamic changes in the inferior caval vein during pneumoperitoneum

Background: Laparoscopic procedures of increasing difficulty and duration are becoming more and more common. This may cause significant challenges to the circulatory system and possibly influence thrombogenicity. Methods: Experimental study of carbon dioxide pneumoperitoneum in pigs. Results: Inferior caval vein blood flow remained unchanged, whereas inferior caval vein pressure increased during pneumoperitoneum. Inferior caval vein, pulmonary, and systemic vascular resistance increased during pneumoperitoneum and remained increased after exsufflation. Conclusions: Pneumoperitoneum leads to an increased inferior caval vein pressure, which could cause a dilation of peripheral veins. The similar patterns of vascular resistance in the inferior caval vein, pulmonary artery, and systemic arteries (a gradual increase remaining elevated after exsufflation) suggest a common humoral factor or increased sympathetic nerve activity. Received: 2 April 1996/Accepted: 7 June 1996     

The clinical impact of warmed insufflation carbon dioxide gas for laparoscopic cholecystectomy

Background: Reports suggest that the insufflation of cold gas to produce a pneumoperitoneum for laparoscopic surgery can lead to an intraoperative decrease in core body temperature and increased postoperative pain. Methods: In a randomized controlled trial with 20 patients undergoing laparoscopic cholecystectomy, the effect of insufflation using carbon dioxide gas warmed to 37°C (group W) was compared with insufflation using room-temperature cold (21°C) gas (group C). Intraoperative body core and intra-abdominal temperatures were determined at the beginning and end of surgery. Postoperative pain intensity was evaluated using a visual analog scale and recording the consumption of analgesics. Results: There were no significant group-specific differences during the operation, neither in body temperature (group W: 36.1 ± 0.4°C vs group C: 35.7 ± 0.6°C) nor in intra-abdominal temperature (group W: 35.9 ± 0.3°C vs group C: 35.6 ± 0.6°C). Postoperatively, the two groups did not differ in pain susceptibility and need of analgesics. Conclusion: The use of carbon dioxide gas warmed to body temperature to produce a pneumoperitoneum during short-term laparoscopic surgery has no clinically important effect. Received: 13 August 1999/Accepted: 24 September 1999/Online publication: 9 August 2000     

Does pneumoperitoneum during laparoscopy increase bacterial translocation?

Background: To evaluate the impact of laparoscopy in the presence of peritonitis, this study was designed to assess bacteremia caused by E. coli–induced peritonitis with a carbon dioxide pneumoperitoneum in a rat model. Methods: Sixty Sprague-Dawley rats were divided into inoculum groups (no E. coli, 10⁶ colony-forming units [CFU] E. coli, and 10⁸ CFU E. coli), followed by induction of a carbon dioxide pneumoperitoneum or no pneumoperitoneum. Fifteen-minute-interval blood cultures were obtained to determine time of bacteremia development. Statistical assessment to determine significant differences among groups was done using ANOVA and t-test analysis. Results: A total of 20 animals with E. coli introduced into the peritoneum and a carbon-dioxide-induced pneumoperitoneum had more frequent positive blood cultures at all time intervals compared to identical inoculum subgroups without a pneumoperitoneum. ANOVA revealed a significant difference in bacteremia within the same concentration inoculum groups in animals receiving a pneumoperitoneum vs none (p < 0.01). Bacteremia increased significantly as inoculum concentrations increased (25% with 10⁶ E. coli inoculum vs 80% with 10⁸ E. coli), especially among the insufflated subgroups (45% with 10⁶ E. coli vs 100% with 10⁸ E. coli) over 180 min (p < 0.01). Conclusion: Carbon dioxide pneumoperitoneum increases the incidence of E. coli bacterial translocation from the peritoneum into the bloodstream in this rat model. Received: 30 April 1996/Accepted: 5 July 1996     

An in vitro model fails to demonstrate aerosolization of tumor cells

Background: We investigated the ability of pressurized CO₂ gas to aerosolize B16 melanoma (B16) tumor cells in an in vitro model. Methods: The experimental apparatus consisted of an 18.9-L plastic cylindrical vessel and a compliant latex pouch was attached to the top. Two 5-mm ports penetrated the vessel; insufflation and desufflation were carried out through them. A culture dish containing 20 million B16 cells in liquid culture media was placed at the base within the container. In the first experiment, the vessel was insufflated with CO₂ gas to a static pressure of 15 or 30 mm Hg with the outflow port closed. After 10 min, the outflow port was opened and the gas was desufflated through a collecting device containing sterile culture medium. In a second experiment, a continuous flow of CO₂ through the vessel was maintained after a pressure of 15 or 30 mm Hg was established. A total of 10 L CO₂ was cycled through the vessel. In both experiments, 24 determinations were carried out at each pressure. Each experimental culture dish was microscopically scanned for 2 weeks for the presence of tumor cells. The third and fourth experiments tested for the presence of aerosolized nonviable tumor cells in the expelled gas. Using the model described above, after 10 mins of 30 mm Hg static pressure, the CO₂ gas was expelled directly onto a glass slide and cytofixed. Alternately, after 10 mins at 30 mm Hg static pressure, the gas was expelled through a saline-filled Soluset (Abbott Laboratories), centrifuged, and the residue cytofixed onto a glass slide. Each of the five slides per experiment were examined microscopically for the presence of cells. Results: In the first and second experiments, no cells or growth were observed in any of the 96 experimental dishes. In experiments three and four, no cells were detected on any of the slides. Conclusions: It was not possible with this model to aerosolize tumor cells in a pressurized CO₂ environment. Our results suggest that aerosolization of tumor cells is not the mechanism of port site recurrences after laparoscopic surgery for malignant disease. Received: 16 September 1996/Accepted: 6 October 1997     

Oxidative stress in lung tissue induced by CO2 pneumoperitoneum in the rat

Background: Clinical trials have found that the pneumoperitoneum has potentially hazardous side effects. The biochemical basis of organ injury induced by pneumoperitoneum is, however, not well defined. Since oxidative stress is believed to play an important role in many pathological conditions, we set out to examine oxidative stress markers in the lung, liver, kidney, and pancreas by using a rat model of laparoscopy with CO₂ pneumoperitoneum and comparing it to a group with gasless laparoscopy. Methods: Malondialdehyde (for lipid peroxidation), protein-bound carbonyls (for protein oxidation), reduced and oxidized glutathione, and the neutrophil marker myeloperoxidase were evaluated in tissue homogenates at 2 h, 6 h, and 18 h after laparoscopy. Immunoblotting was used to analyze the modification of lung proteins by 4-hydroxynonenal at 6 h. Results: Significant lipid peroxidation was found selectively in lungs at 2 h and 6 h after CO₂ pneumoperitoneum. This was accompanied by a loss of glutathione but only minor protein oxidation. Further, lung proteins were clearly modified by the aldehydic product of lipid peroxidation 4-hydroxynonenal. Myeloperoxidase in lungs increased continuously up to 18 h in both experimental groups, but there were higher levels in the group with pneumoperitoneum. Conclusion: Oxidative stress is likely to contribute to the impairment of pulmonary function after laparoscopic operations using a CO₂ pneumoperitoneum. Received: 22 November 1999/Accepted: 22 March 2000/Online publication: 10 July 2000     

The effects of pneumoperitoneum on gastric blood flow and traditional hemodynamic measurements

Background: The purpose of this study was to investigate the effects of increasing intraabdominal pressure (IP) on gastric blood flow, as measured by gastric tonometry and traditional hemodynamic measurements. Methods: Nine swine were anesthetized, intubated, and ventilated. Arterial and pulmonary artery catheters were placed by cutdown, a trocar was placed in the abdomen, and a gastric tonometer was placed in the stomach. Serial measurements of arterial and mixed venous blood gases, cardiac output, wedge pressure, lactic acid, and gastric intramucosal pH (pH_i) were collected at intraperitoneal pressures of 0, 8, 10, 12, 14, 16, and 18 mm Hg after 30 min equilibration. Statistical analysis included Pearson correlation and Student's t test. Results: Increasing levels of IP were correlated with decreased arterial pH (p < 0.00003), increased mixed venous CO₂ (p < 0.003), decreased intramucosal pH (p < 0.014), and increased arterial CO₂ (p < 0.015). Gastric pH_i differed significantly from baseline at IP levels of 16 mm Hg (p < 0.004) and 18 mm Hg (p < 0.01). No significant effects were observed on cardiac output or arterial lactate. No significant effects were observed in a control group that had been insufflated to 8 mm Hg and held constant over 3 h. Conclusions: In this model, gastric blood flow is adversely affected by increasing IP with pronounced effects in excess of 15 mm Hg. These results suggest that gastric tonometry may be used to monitor the adverse effects of pneumoperitoneum. Gastric pH_i may be an earlier indicator of altered hemodynamic function during laparoscopy than traditional measures. Received: 25 March 1997/Accepted: 30 June 1997     

Fatal carbon dioxide embolism as an unreported complication of retroperitoneoscopy

Retroperitoneoscopy has gained popularity because it offers a safe alternative to the more debilitating open approach and avoids postoperative ileus. However, this type of procedure carries certain disadvantages in terms of intraperitoneal effusions and hemodynamic changes. Major complications are exceptional. We describe the case of a 52-year-old man who died of carbon dioxide embolism during elective totally extraperitoneal (TEP) inguinal hernioplasty for symptomatic left indirect inguinal hernia. With the patient under general anesthesia, the retroperitoneal space was gained through a 1.5-cm incision made below the umbilicus. During the dissection, the patient collapsed and could not be resuscitated. At autopsy, air bubbles were admixed with blood in the epicardial veins, but no injury to vessels was demonstrated. We conclude that carbon dioxide embolism usually is caused by direct puncture of major vessels during intra-abdominal procedures. However, when this complication occurs during retroperitoneoscopy, it seems related to pressure-forced entry of carbon dioxide into the venous plexus. Received: 13 July 1998/Accepted: 20 January 1999     

The influence of different insufflation pressures during carbon dioxide pneumoperitoneum on the development of pulmonary metastasis in a mouse model

Background: The effects of different insufflation pressures on the development of pulmonary metastasis was investigated in a mouse laparoscopy model. Methods: BALB/C mice intravenously inoculated with colon 26 cells were randomized to one of five treatment groups (10 mice per group): pneumoperitoneum at different pressures of 5, 10 or 15 mmHg; full laparotomy for 60 min; or anesthesia control. Cancer nodules on the lung surface 19 days postoperatively were compared between groups. Results: (a) As compared with the control group, pneumoperitoneum at 10 and 15 mmHg and laparotomy enhanced the growth of pulmonary metastases (p < 0.01). (b) The growth of metastases also was greater in laparotomy group mice than in mice undergoing pneumoperitoneum at 5 and 10 mmHg (p < 0.05). Conclusions: These results suggest that the effects of different insufflation pressures on the growth of pulmonary metastases are not identical, and that pneumoperitoneum with high pressure may promote pulmonary metastases similar to those with laparotomy. Received: 4 November 1999/Accepted: 20 December 1999/Online publication: 25 April 2000     

Duration of postlaparoscopic pneumoperitoneum

Background: Patients who present with abdominal pain after recent laparoscopic surgery present a diagnostic dilemma when pneumoperitoneum is present. Previous studies do not define the duration of postlaparoscopic pneumoperitoneum. In this study, we attempted to define the duration of laparoscopic pneumoperitoneum and to identify factors which affect resolution time. Methods: We followed 57 patients who underwent laparoscopic cholecystectomy (34), inguinal herniorraphy (20), or appendectomy (three). Serial abdominal films were taken until all residual gas was resolved. Results: Thirty patients resolved their pneumoperitoneum within 24 h; 16 patients resolved between 24 h and 3 days; nine patients resolved between 3 and 7 days; two patients resolved between 7 and 9 days. Mean resolution time for all patients was 2.6 ± 2.1 days. There was no apparent difference in resolution time between the three types of procedures; however, the sample size may be insufficient. Duration of the pneumoperitoneum did not correlate with gender, age, weight, initial volume of CO₂ used, length of time for the procedure, or postoperative complications. Sixteen patients had bile spillage during cholecystectomy which significantly reduced the duration of postoperative pneumoperitoneum (p < 0.008), resulting in a mean resolution time of 1.3 ± 0.9 days. While 14 patients reported postoperative shoulder pain, no correlation was found between the presence or duration of shoulder pain and the extent or duration of pneumoperitoneum. Conclusions: We conclude that the residual pneumoperitoneum following laparoscopic surgery resolves within 3 days in 81% of patients and within 7 days in 96% of patients. The resolution time was significantly less in patients sustaining intraoperative bile spillage during cholecystectomy. There was no correlation found between postoperative shoulder pain and the presence or duration of the pneumoperitoneum. Received: 22 March 1996/Accepted: 12 July 1996     

The influence of laparotomy and laparoscopy on tumor growth in a rat model

Background: The effects of laparotomy and laparoscopy with different gases on subcutaneous and intraperitoneal tumor growth have not been evaluated yet. Methods: Tumor growth of colon adenocarcinoma DHD/K12/TRb was measured in rats after laparotomy, laparoscopy with CO₂ or air, and in control group. Cell kinetics were determined after incubation with carbon dioxide or air in vitro and tumor growth was measured subcutaneously and intraperitoneally after surgery in vivo. Results: In vitro, tumor cell growth increased significantly after incubation with air and CO₂. In vivo, intraperitoneal tumor weight was increased after laparotomy (1,203 ± 780 mg) and after laparoscopy with air (1,085 ± 891 mg) and with CO₂ (718 ± 690 mg) compared to control group (521 ± 221 mg) (p < 0.05). Subcutaneous tumor growth was promoted after laparotomy (71 ± 35 mg) and even more after laparoscopy with air (82 ± 45 mg) and CO₂ (99 ± 55 mg) compared to control group (36 ± 33 mg). Conclusions: Insufflation of air and CO₂ promote tumor growth in vitro. In vivo, intraperitoneal tumor growth seems to be promoted primarily by intraperitoneal air and subcutaneous tumor growth by CO₂. Received: 7 November 1996/Accepted: 3 December 1996     

Portal venous flow during CO2 pneumoperitoneum in the rat

Backround: CO₂ gas insufflation is routinely used to extend the abdominal wall. The resulting pneumoperitoneum has a number of local and systemic effects on the organism. Portal blood flow, which plays an important role in hepatic function and cell-conveyed immune response, is one of the affected parameters. Methods: An established animal model (rat) of laparoscopic surgery was modified by implanting a perivascular flow probe. Hemodynamics in the portal vein were then measured during increasing intraabdominal pressure generated by carbon dioxide insufflation. Results: Using this technique, an adequate flowmetry of the portal vein was achieved in all animals. The creation of a CO₂ pneumoperitoneum with increasing intraabdominal pressure led to a linear decrease in portal venous flow. Conclusions: Elevated intraabdominal pressure caused by carbon dioxide insufflation may compromise hepatic function and cell-conveyed immune response during laparoscopic surgery. Received: 28 January 1998/Accepted: 22 June 1998     

Port site tumor recurrence rates in a murine model of laparoscopic splenectomy decreased with increased experiencerid=""id=""Presented at the sixth International Congress of the European Association of Endoscopic Surgery (E.A.E.S.), Rome, Italy, 5 June 1998

Background: The etiology of port site tumor recurrences following laparoscopic surgery for cancer remains unknown. A recent study from our laboratory using a murine splenic tumor model suggests that it is poor surgical technique (i.e., crushing of the tumor) rather than the CO₂ pneumoperitoneum that is responsible for these tumors. However, in that experiment, no intraabdominal procedure was carried out. We subsequently performed a preliminary study in which we compared the rate of port site tumor recurrences after laparoscopic-assisted splenectomy (LAS) vs open splenectomy (OS) using the murine splenic tumor model. In this study, we found significantly more port and incisional tumors after laparoscopic splenectomy. The reasons for this finding are unclear. Further analysis of the data showed that the incidence of port tumors in the LAS group decreased dramatically from the first to the second trial, suggesting that the experience of the surgeon may play a role. The purpose of the current study was to carry out further trials to determine if the lower rate of port tumor recurrence in the laparoscopic group will persist with increased surgical experience. Methods: Splenic tumors were established in female Balb/C mice (n= 128) via a subcapsular injection of a 0.1-cc suspension containing 10⁵ C-26 colon adenocarcinoma cells via a left flank incision at the initial procedure. Seven days later, the animals with isolated splenic tumors (95%) were randomized to one of two groups—open splenectomy (OS) or laparoscopic-assisted splenectomy (LAS). Three ports were placed in similar locations in all animals. The OS mice underwent an open splenectomy via a subcostal incision and anesthesia for 20 min. The LAS mice underwent laparoscopic mobilization of the spleen using a three-port technique, followed by an extracorporeal splenectomy via a subcostal incision. Seven days after splenectomy, the mice were killed and inspected for abdominal wall tumor implants. The experiment was carried out in four separate trials. Results: When the results of the four trials were combined, there was no significant difference in the incidence of animals with at least one port tumor recurrence between the OS vs the LAS group (25% vs 35.2%; p= 0.30, power = 0.91). However, the overall incidence of port site tumors (number of ports with tumors/total number of ports for each group) was significantly higher in the laparoscopic-assisted group than in the open group (18.5% vs 9.5%; p= 0.03). It was noted that the incidence of port tumor recurrence (PTR) in the LAS group dropped significantly from the first to the latter three trials (second, third, and fourth trials combined) (36.1% vs 13.5%; p < 0.006) while it did not change significantly in the OS group. In the latter three trials, there was no significant difference in the number of animals with PTR between the LAS and the OS group (13.5% vs 9.8%; p= 0.43). Conclusions: Overall, there was no significant difference between the OS and the LAS groups in number of animals with port tumor recurrence or subcostal wound tumor recurrence. However, there were more port tumors in the laparoscopic-assisted group. The reasons for these findings are unclear. The laparoscopic mobilization was quite difficult; it required excessive splenic manipulation, which may have liberated tumor cells from the primary lesion and facilitated port tumor formation. With increased experience, less manipulation was required to complete the mobilization. Of note, the incidence of port tumors in the LAS group decreased significantly from the first to the subsequent three trials; therefore, it is possible that surgical technique is a factor in port tumor formation. The CO₂ pneumoperitoneum may also be a factor, but this seems less likely. Received: 10 September 1999/Accepted: 4 April 2000/Online publication: 9 August 2000