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     

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     

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     

Intraperitoneal tumor growth is influenced by pressure of carbon dioxide pneumoperitoneum

Background: Several studies have indicated that the carbon dioxide (CO₂) pneumoperitoneum during laparoscopy plays a role in the pathogenesis of port-site metastases. An experimental animal study was performed to investigate the impact of various pneumoperitoneum pressures on peritoneal tumor growth. Methods: In this study, 36 male WAG rats were randomized into three groups; two groups with different pneumoperitoneum pressures (16 mmHg and 4 mmHg) and one group of gasless controls. After a pneumoperitoneum of 0.5 × 10⁶ ml was established, 531 tumor cells were injected intra-abdominally and the pneumoperitoneum was maintained for 60 min. Peritoneal tumor growth was assessed on day 11 at autopsy. Results: Peritoneal tumor growth in the 16-mmHg group was significantly greater than in the 4-mmHg group (p= 0.039) and the gasless group (p= 0.004). Conclusions: High-pressure CO₂ pneumoperitoneum stimulates intra-abdominal tumor growth. The use of low insufflation pressures in laparoscopic cancer surgery should be considered. Received: 1 December 1998/Accepted: 10 July 1999/Online publication: 9 August 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     

Time-related changes in hemodynamic parameters and pressure-derived indices of left ventricular function in a porcine model of prolonged pneumoperitoneum

Background: Advanced laparoscopic procedures require prolonged pneumoperitoneum. Increased intra-abdominal pressure causes a number of hemodynamic changes including a drop in cardiac output, but it is unclear whether there is a direct effect on cardiac contractility. In this experimental study, we sought to determine whether there is a direct impact of pneumoperitoneum on cardiac contractility. We also examined the time-related changes taking place during the insufflation period. Methods: Six young pigs were anesthetized and mechanically ventilated. Pneumoperitoneum was established by insufflating carbon dioxide to a pressure of 15 mmHg and maintained for a period of 180 min. Hemodynamic parameters including left ventricular dP/dT were invasively recorded every 15 min. All hemodynamic changes were statistically evaluated, and parameters were correlated with time. Results: Cardiac output decreased with insufflation from a baseline of 3.37 ± 0.34 lt/min and reached the lowest value at 165 min of pneumoperitoneum (2.86 ± 0.30 l/min; p= 0.023). Systemic vascular resistance (SVR) significantly increased from 2236 ± 227 dyne/s/cm⁵ to a maximum of 3774 ± 324 dyne/s/cm⁵ (p= 0.005). Left ventricular dP/dT maximum did not change significantly with insufflation. The decrease in cardiac output strongly correlated with the increase in SVR (r=−0.949). Time of insufflation correlated with cardiac output (r=−0.762) and dP/dT maximum (r=−0.727). Conclusions: Pneumoperitoneum at 15 mmHg negatively affects cardiac output without significantly affecting cardiac contractility. A significant increase in SVR appears to be the driving event for the decreased cardiac output. Prolonged pneumoperitoneum may have an additional negative effect on hemodynamic parameters. Received: 5 January 2000/Accepted: 4 May 2000/Online publication: 26 July 2000     

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     

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     

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     

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     

Hemodynamic and pulmonary changes during and after laparoscopic cholecystectomy

Background: The cardiopulmonary changes experienced by patients who undergo laparoscopic cholecystectomy (LC) and the prognostic value of patient characteristics are not well understood. Methods: Cardiorespiratory changes were investigated in 120 patients undergoing LC or open cholecystectomy (OC). The results and their relation to patient variables were statistically evaluated. Results: The most significant cardiorespiratory changes were (A-a)PO₂ increase during OC; decrease of pH and compliance and increase of peak airway pressure during LC; impairment of arterial blood gas mean values and respiratory muscle strength; atelectasis and pneumonia (five cases) after OC; and lamellar atelectasis (two cases) after LC. Significant adverse prognostic factors related to intra- and postoperative LC cardiorespiratory changes were ASA class greater than I, FEF_75–85% < 900 ml, and PaO₂ < 10.4 kPa (PPV, 71.4% and 46.6%, respectively). Conclusions: LC carries no significant cardiorespiratory changes provided that intraoperative monitoring of hemodynamics and respiratory parameters is done for the study of blood gas values in all patients at risk.     

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     

Hepatic and portal vein blood flow during carbon dioxide pneumoperitoneum for laparoscopic hepatectomy

Background: Laparoscopy under carbon dioxide (CO₂) pneumoperitoneum has many advantages. However, the risks of CO₂ pneumoperitoneum during laparoscopic hepatectomy (LH) have not been defined. Methods: The hemodynamics of the hepatic vein were examined during CO₂ pneumoperitoneum both pre- and posthepatectomy in eight pigs. Portal blood flow was measured with Doppler ultrasound during laparoscopic cholecystectomy in 10 human patients. Results: Experimentally, elevated intraabdominal pressure (IAP) with CO₂ insufflation produced significant increases in CO₂ partial pressure and echogenicity of the hepatic vein in the posthepatectomy group. Clinically, elevated IAP caused significant narrowing of the portal vein and significant decreases in portal blood velocity. The mean portal flow was significantly decreased with elevation of IAP >10 mmHg. Conclusions: LH with CO₂ pneumoperitoneum may lead to embolism caused by CO₂ bubbling through the hepatic vein. Elevated IAP may cause a decrease in hepatic blood flow and induce severe liver damage, especially in patients with poor liver function. Gasless laparoscopy using abdominal wall lifting should be employed in LH to avoid the risks of CO₂ embolism and liver damage. Received: 28 March 1997/Accepted: 12 September 1997     

Feasibility of therapeutic pneumoperitoneum in a large animal model using a microvaporisator

Background: Multimodal therapy is used increasingly in advanced gastrointestinal tumors. Potential benefits of using an intraoperative adjuvant therapy during laparoscopy for cancer have been documented in animal studies. The aim of this study was to develop a device that could deliver such an intraoperative drug therapy. Methods: We developed a micropump suitable for minimally invasive surgery procedures that allowed microdroplets of therapeutic substance to be distributed into the pneumoperitoneum (CO₂), creating a ``therapeutic pneumoperitoneum.' A closed-loop control system regulates drug delivery according to the gas flow. In vitro, the micropump is able to aerosolize various aqueous and ethanol solutions, including cytostatic and bacteriostatic drugs and adhesion-modulating agents. The size of the microdroplets has been optimized to prevent visual artifacts. Results: The micropump was tested in an animal model (pig). The system was inserted into a 5-mm trocar. After insufflation of a 12-mm CO₂ pneumoperitoneum, laparoscopic sigmoid colon resections could be performed with no special difficulties. No fog developed, and no system-related complication was observed. At autopsy, the active principle was distributed to all exposed peritoneal surfaces. Conclusions: As opposed to conventional peritoneal washing, therapeutic pneumoperitoneum reaches the entire peritoneal surface, allowing an optimal drug distribution. Drug diffusion into the tissues is enhanced by the intraperitoneal pressure. Precise determination of the instantaneous and total drug quantity is possible. Therefore, this drug delivery system has several advantages over conventional irrigation. Its potential domains of application are locoregional cancer therapy, prevention of port-site recurrences, immunomodulation, analgesia, peritonitis, and prevention of postoperative adhesions. Received: 27 May 1998/Accepted: 5 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     

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 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     

Influence of acute hemorrhage and pneumoperitoneum on hemodynamic and respiratory parameters

Background: We examined the questions of whether resuscitated (compensated) acute hemorrhage enhances the negative effects of carbopneumoperitoneum on hemodynamic and respiratory parameters and whether pneumoperitoneum with helium has any advantages under these circumstances. Our investigation focused on the influence of acute hemorrhage with different gases on the cardiovascular and respiratory system as well as on hepatic and renal blood flow in a porcine model. Methods: Cardiac and hemodynamic function were monitored via implantation of catheters in pulmonary artery, femoral vein, and artery. Renal and hepatic blood flow were recorded using a transonic volume flow meter placed at the renal and hepatic artery and portal vein. Twelve animals were randomly assigned to one insufflation gas (carbon dioxide [CO₂] or helium [He]). Following baseline recordings, acute hemorrhage (20 ml/kg) was induced by continuous bleeding over 30 min. Animals then received a colloidal solution (20 ml/kg 6% hydroxyethylstarch solution) over 30 min. Pneumoperitoneum of 12 mmHg was established, and all parameters were measured after 30 min of adaptation. The major endpoints of the study were cardiac output (CO), arterial pressure (MAP), systemic vascular resistance (SVR), and central venous pressure (CVP), as well as blood flow in hepatic and renal artery and portal vein. Results: While CO and hemodynamic parameter as well as hepatic and renal blood flow were markedly reduced after hemorrhage, they returned nearly to their previous levels after resuscitation. Pneumoperitoneum with 12 mmHg did not further depress the cardiovascular system or reduce hepatic and renal blood flow. Pneumoperitoneum did not alter hepatic or renal blood flow. Pneumoperitoneum with helium did not substantially change the reaction of the cardiovascular system after resuscitated hemorrhage. Conclusions: If hemorrhage is compensated by proper resuscitation and hypovolemia is avoided, laparoscopic surgery with pneumoperitoneum of 12 mmHg appears to be not harmful. Using helium as the insufflating gas had no clear advantage over the carbon dioxide model. Received: 30 July 1997/Accepted: 24 October 1997     

Lack of neurohumoral response to pneumoperitoneum for laparoscopic cholecystectomy

Background: Pneumoperitoneum (PP) for laparoscopic surgery induces prompt changes in circulatory parameters. The rapid onset of these changes suggests a reflex origin, and the present study was undertaken to evaluate whether release of vasopressor substances could be responsible for these alterations. The influence of two different anesthesia techniques was also evaluated. Methods: American Society of Anesthesiologists (ASA) class I patients, scheduled for laparoscopic cholecystectomy, were investigated. The first group (n= 10) was anesthetized intravenously. The second group (n= 6) had inhalation anesthesia. Plasma vasopressin, catecholamines, and plasma renin activity were investigated as neurohumoral vasopressor markers of circulatory stress. The general stress response to surgery was assessed by analysis of plasma cortisol. Results: Induction of pneumoperitoneum caused no apparent activation of vasopressor substances, although several hemodynamic parameters responded promptly. Conclusion: The hemodynamic alterations, seen at the establishment of PP during stable anesthesia, cannot be explained by elevation of vasopressor substances in circulating blood. Received: 7 April 1997/Accepted: 3 December 1997