Laparoscopic extraperitoneal inguinal hernia repair with spinal anesthesia and nitrous oxide insufflation

Background: Laparoscopic repair of inguinal hernia is traditionally performed under general anesthesia mainly because of the adverse effects that carbon dioxide pneumoperitoneum has on awake patients. Since a mandatory use of general anesthesia for all hernia repairs is questionable, the feasibility of laparoscopic extraperitoneal herniorraphy using spinal anesthesia combined with nitrous oxide insufflation was investigated. Methods: Over a 4-month period, February to May 1998, we performed 35 consecutive total extraperitoneal inguinal hernia procedures (24 unilateral, 11 bilateral) using spinal anesthesia and nitrous oxide extraperitoneal gas. Data on operative findings, self-reported operative and postoperative pain and discomfort (visual analog pain scale), procedure-related hemodynamics, and complications were collected prospectively. Results: All 35 procedures were completed laparoscopically without the need to convert to general anesthesia. Mean operative time was 39 ± 7 min for unilateral hernia and 65 ± 10 min for bilateral hernia. Incidental peritoneal tears occurred in 22 patients (63%) resulting in nitrous oxide pneumoperitoneum, which was well tolerated. The patients remained hemodynamically stable throughout the procedure, and operative conditions and visibility were excellent. Complications at a mean of 4 months after the procedure included seven uninfected seromas (20%), three patients with transient testicular pain, and one (3%) recurrence. Conclusions: Laparoscopic total extraperitoneal hernia repair can be safely and comfortably performed using spinal anesthesia with extraperitoneal nitrous oxide insufflation gas. This method provides a good alternative to general anesthesia. Received: 17 February 1999/Accepted: 1 July 1999     

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Background: Although many aspects of laparoscopic surgery have been determined, the question of which insufflation gas is the best arises repeatedly. The aim of this study was to review the findings on the major gases used today in order to provide information and guidelines for the laparoscopic surgeon. Methods: We reviewed the literature for clinical and laboratory studies on the currently used laparoscopic insufflation gases: carbon dioxide (CO₂), nitrous oxide (N₂O), helium (He), air, nitrogen (N₂), and argon (Ar). The following parameters were evaluated: acid–base changes, hemodynamic and respiratory sequelae, hepatic and renal blood flow changes, increase in intracranial pressure, outcome of venous emboli, and port-site tumor growth. Results: The major advantage of CO₂ is its rapid dissolution in the event of venous emboli. Hemodynamic and acid–base changes with CO₂ insufflation usually are mild and clinically negligible for most patients. Although N₂O is advantageous for procedures requiring local/regional anesthesia, it does not suppress combustion. Findings show that Ar may have unwanted hemodynamic effects, especially on hepatic blood flow. There are almost no hemodynamic or acid-base sequelae with the use of He, air, and N₂, but they dissolve slowly and carry a potential risk of lethal venous emboli. Conclusions: Clearly, CO₂ maintains its role as the primary insufflation gas in laparoscopy, but N₂O has a role in some cases of depressed pulmonary function or in local/regional anesthesia cases. Other gases have no significant advantage over CO₂ or N₂O and should be used only in protocol studies. The relation of port-site metastasis to a specific type of gas requires further research. Received: 16 January 2000/Accepted: 15 March 2000/Online publication: 22 August 2000     

Humidified gas prevents hypothermia induced by laparoscopic insufflation

Background: This experimental study evaluated whether humidification of warmed insufflated CO₂ during laparoscopic procedures would resolve the problem of laparoscopy-induced hypothermia. Methods: Changes in core temperature were quantified over a 3-h period of high-flow CO₂ insufflation in a randomized, controlled trial of five pigs. Each animal was anesthetized and studied on three occasions under standardized conditions, acting as its own control by insufflation with no gas compared with insufflation by cool dry gas and heated humidified gas. Results: Core temperatures after insufflation with heated humidified gas were no different from that of controls. After insufflation with cool dry gas, core temperature dropped by 1.8°C, which was significantly more than the 0.6°C drop experienced by control animals and those insufflated with heated humidified gas (p < 0.01). Calculations of the heat expended in evaporation of water were also performed. The temperature drop due to water evaporation alone in pigs insufflated with cool dry gas was calculated to be 1.5°C. This compares favorably with the measured 1.2°C temperature difference between these animals and the control group. Conclusions: The majority of heat lost during laparoscopic insufflation is due to water evaporation, and laparoscopic hypothermia may be prevented by using heated and humidified gas insufflation. Received: 10 December 1997/Accepted: 28 May 1998     

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     

Pathophysiological and clinical aspects of the CO2 pneumoperitoneum (CO2-PP)

Experimental studies demonstrated a severe cardiac load of the CO₂ pneumoperitoneum caused by an accelerated after- and a decreased preload. Patients displaying cardiovascular risks are therefore often rejected from laparoscopic surgery. Hence, the pathophysiological changes and the intraoperative risk of the CO₂ pneumoperitoneum in high-risk cardiopulmonary patients (NYHA II–III, n= 15) undergoing laparoscopic cholecystectomy are described. The changes in cardiac after- and preload seem to be due to the elevated intraabdominal pressure rather than transperitoneally resorbed CO₂ and are reversible by desufflation. In one patient conversion to open operation had to be performed because of a severe drop in cardiac output and right ventricle ejection fraction. Mixed oxygen saturation was predicting intraoperative worsening in this case. The described pathophysiological changes may seem to be well tolerated even in high-risk cardiac patients. Monitoring of hemodynamics should include an arterial catheter line and blood gas analyses. Pharmacologic interventions or pressureless laparoscopic procedures might not be necessary as long as laparoscopic cholecystectomy is performed. Received: 13 December 1996/Accepted: 8 January 1997     

The feasibility of laparoscopic extraperitoneal hernia repair under local anesthesia

Background: Laparoscopic preperitoneal herniorrhaphy has the advantage of being a minimally invasive procedure with a recurrence rate comparable to open preperitoneal repair. However, surgeons have been reluctant to adopt this procedure because it requires general anesthesia. Methods: In this report, we describe the technique used in the laparoscopic repair of inguinal hernias under local anesthesia using the preperitoneal approach. We also report our results with 10 inguinal hernias repaired using the same technique. Results: Ten patients underwent their primary inguinal hernia repairs under local anesthesia. None were converted to general anesthesia. Four patients received a small amount of intravenous sedation. Three patients had bilateral hernias. There were five direct and eight indirect hernias. The average operative time was 47 min. The average lidocaine usage was 28 cc. All patients were discharged within a few hours of the surgery. There were no complications. Follow-up has ranged from 1 to 6 months. There has been no recurrences to date. Conclusions: The extraperitoneal laparoscopic repair of inguinal hernia is feasible under local anesthesia. This technique adds a new treatment option in the management of bilateral inguinal hernias, particularly in the population where general anesthesia is contraindicated or even for patients who are reluctant to receive general or epidural anesthesia. Received: 22 July 1998/Accepted: 18 September 1998     

Laparoscopic surgery in newborn infants

Background: Thanks to various technical innovations and advances in instrumentation, laparoscopic surgical intervention is now possible for certain congenital anomalies in children. To test the applicability of laparoscopic surgery in neonates, we reviewed our personal experience of neonatal laparoscopic surgery, focusing on cardiopulmonary function, surgical procedures, problems with devices, and degree of associated surgical stress. Methods: We performed 65 laparoscopic procedures in neonates. Their ages ranged from 2 to 30 days old, and their body weights ranged from 1,980 to 4,780 g. All 65 laparoscopic procedures were carried out without mortality or serious morbidity. Results: As complications, we encountered four cases of hypothermia due to rapid insufflation of carbon dioxide (CO₂). We also found that relative hypercapnea (increase in end-tidal CO₂ as high as 61 mmHg) developed unless hyperventilation and a relatively high peak insufflation pressure were maintained during pneumoperitoneum. No cardiac depression developed at this insufflation pressure. Fluid and electrolyte balance during our cases of newborn laparoscopic surgery, as well as the doses and volumes of fluid and electrolytes administered, were identical to those required for open surgery. Interleukin-6 (IL-6) was measured serially to estimate the degree of associated surgical stress and was found to be significantly lower in neonates who had received laparoscopic procedures than in those who had received open procedures. Conclusion: Laparoscopic surgery can be carried out safely even in neonates. Received: 9 June 1998/Accepted: 22 September 1998     

Postoperative drowsiness and emetic sequelae correlate to total amount of carbon dioxide used during laparoscopic cholecystectomy

Background: After laparoscopy with carbon dioxide (CO₂) insufflation early postoperative recovery is often complicated with drowsiness and postoperative nausea and vomiting (PONV). Methods: 25 ASA I − II patients undergoing elective laparoscopic cholecystectomy under standardized anaesthesia were studied in a randomized, prospective study. The conventional CO₂ pneumoperitoneum was compared with the mechanical abdominal wall lift (AWL) method with minimal CO₂ insufflation with special reference to postoperative recovery. Results: Postoperative drowsiness was of a significantly longer duration with the conventional method (p < 0.001) compared with the AWL technique. There was a positive correlation with the total amount of CO₂ used and the duration of drowsiness (r = 0.75, p < 0.01). PONV was seen significantly more often in patients with CO₂ insufflation of more than 121 (p < 0.05). Conclusions: Avoiding excessive CO₂ is beneficial for smoother and more uneventful recovery after laparoscopic cholecystectomy. Received: 11 January 1996/Accepted: 29 May 1996     

Influence of nitrous oxide anesthesia on venous gas embolism with carbon dioxide and helium during pneumoperitoneum

Background: Gas embolism is a potential hazard during laparoscopic procedures. The aim of this study was to evaluate the effects of nitrous oxide (N₂O) inhalation in the case of gas embolism with carbon dioxide (CO₂) and helium during pneumoperitoneum. Methods: For this study, 20 anesthetized pigs were ventilated with N₂O (67% inspired) in O₂ (n= 10) or with halothane (0.7–1.5 inspired) in O₂ (n= 10). In each group, CO₂ (n= 5) or helium (n= 5) pneumoperitoneum was established and gas embolism induced at different rates (CO₂ at 0.5, 1, or 2 ml/kg/min; helium at 0.025, 0.05, or 0.1 ml/kg/min) through the left femoral vein a maximum of 10 min while all hemodynamic parameters were continuously monitored. Results: In the CO₂ group without N₂O, all the animals tolerated rates of 0.5 and 1 ml/kg/min over the 10 min, whereas only 3 of 4 animals in the CO₂ group with N₂O tolerated a rate of 0.5 ml/kg/min, and 2 of 4 animals a rate of 1 ml/kg/min. In the helium group without N₂O, all the animals tolerated gas embolism at all rates, whereas in the helium group with N₂O, 4 of 5 animals needed to be resuscitated at a rate of 0.1 ml/kg/min and one death occurred. Conclusions: Inhalation of N₂O worsens the negative cardiovascular effects of venous CO₂ or helium gas emboli and increases the risk of emboli-induced death when CO₂ or helium are used to establish pneumoperitoneum. The volume of venous venous helium gas emboli causing such effects is substantially smaller than that for venous CO₂ gas emboli. Received: 20 September 1999/Accepted: 1 October 2000/Online publication: 4 August 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     

Hormone-cytokine response

Background: Changes in blood hormone and cytokine were investigated in patients who underwent laparoscopic cholecystectomy via insufflation (CO₂ group) vs those who had abdominal wall-lifting (Air group). Methods: Seventeen female patients with cholecystolithiasis were randomly divided into two groups. Peripheral blood samples were obtained during perioperative period, and plasma hormone levels (ACTH, cortisol) and serum cytokine levels (TNFα, IL-1β, IL-6, IL-10) were measured. Results: The number of circulating lymphocytes significantly decreased at 1 h after surgery in both groups, but the decrease in the CO₂ group was significantly smaller than that in the Air group. There was no significant difference in hormone elevation between groups. Serum concentrations of IL-6 and IL-10 in the Air group were significantly higher than in the CO₂ group. Conclusions: CO₂ insufflation may reduce cytokine production in laparoscopic cholecystectomy. Received: 10 November 1996/Accepted: 19 February 1997     

Effect of CO2 insufflation on bacteremia and bacterial translocation in an animal model of peritonitis

Background: The widespread adoption of the laparoscopic approach has created some concern over the potential for increased risk of bacteremia and sepsis due to increased intraabdominal pressure in patients with intraabdominal infection and peritonitis. This study examines the effect of the CO₂ pneumoperitoneum on bacteremia and bacterial translocation. Methods: New Zealand white rabbits were assigned into three groups of 10 animals. In group 1, 100 ml of sterile saline was infused into the peritoneal cavity under 10 mmHg CO₂ insufflation for 1 h. Group 2 received 100 ml of saline containing 10⁹ CFU/ml (colony-forming units) E. coli strain 0163 and 10 mmHg CO₂ insufflation for 1 h. Group 3 received an identical bacterial inoculum, followed by a 10-cm midline laparotomy. Blood samples were taken for culture by cardiac puncture at various intervals during the experiment. At 6 h after being subjected to the experimental procedures, the rabbits were killed and their organs were cultured quantitatively for translocating bacteria. Results: In group 1, neither blood nor organ cultures were positive, whereas in group 2 all blood cultures became positive in 1 h, and intraperitoneally infused bacteria translocated to the lung and kidney in all rabbits. In group 3, blood cultures became positive in 1 h, all but two of the rabbits had translocated bacteria in their lungs, and kidney samples from two of the rabbits were culture-positive. Conclusions: Our results indicate that both CO₂ pneumoperitoneum and laparotomy increase the incidence of bacterial translocation from the peritoneal cavity into the bloodstream. Thus, the risk of translocation to extraperitoneal organs such as lung and kidney is increased significantly by laparoscopy. Therefore, laparoscopic surgery should be avoided or used cautiously in the setting of acute peritonitis.     

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     

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     

The effect of laparoscopy on the movement of tumor cells and metastasis to surgical wounds

Background: A variety of mechanisms have been proposed to explain tumor growth in port sites following laparoscopic cancer surgery. We devised two experimental models to determine whether carbon dioxide (CO₂) insufflation during laparoscopic surgery influences the movement of tumor cells and leads to tumor implantation and growth in surgical wounds. Methods: Model 1: Viable adenocarcinoma cells were introduced into the upper abdomen of six syngeneic immune-competent rats during laparoscopy with CO₂ insufflation; the same procedure was followed for a further six rats during gasless laparoscopy. A length of plastic tubing introduced through the anterolateral aspect of the rats' left lower abdominal wall was used to vent the insufflation gas through the abdomen of a recipient rat for 30 min. After 21 days, the peritoneal cavity and surgical wounds of the recipient rat were examined for implanted tumor. Model 2: A suspension of radiolabeled adenocarcinoma cells was introduced into the upper abdomen of five rats during laparoscopy with CO₂ insufflation and an additional five rats during gasless laparoscopy. A length of plastic tubing introduced through the anterolateral aspect of the left lower abdominal flank was used to vent the insufflation gas through phosphate-buffered saline solution. After 30 min, the solution was counted for radioactivity. Results: Tumor growth occurred at the site of both the insufflation and venting ports in the second rat in five of the six rats from the group undergoing insufflation, but it was found in none of the gasless laparoscopy group (p= 0.015). In the second model, significant transfer of tumor cells to the vented gas occurred only in the rats undergoing laparoscopy with insufflation (median, 2.71% versus 0% of the introduced labeled cells; p= 0.008). Conclusions: Carbon dioxide insufflation results in tumor dissemination during laparoscopy, leading to port site metastasis. Gasless laparoscopy may prevent this problem. Received: 17 March 1997/Accepted: 6 June 1997     

Transesophageal echocardiographic assessment of hemodynamic function during laparoscopic cholecystectomy in healthy patients

Background: This study aimed by means of transesophageal echocardiography, to evaluate hemodynamic changes induced by pneumoperitoneum in patients with normal cardiac performance. Methods: In this study, 11 ASA I–II patients (mean age, 39 years) with normal cardiac performance undergoing laparoscopic cholecystectomy were evaluated. A 5-MHz transesophageal biplane phased-array transducer connected to an echocardiographer was inserted after induction of anesthesia. Data were collected at three different times: before insufflation (T1), 10 min after insufflation (T2), and 5 min after desufflation (T3). At these same times, heart rate, systolic blood pressure, diastolic blood pressure, end-tidal carbon dioxide (CO₂), and peak airway pressure were recorded. Statistical analysis was performed using one-way and two-way analysis of variance (ANOVA). A p value less than 0.05 was considered significant. Results: End-systolic and end-diastolic diameters of the left ventricle, contractility, and performance parameters did not change significantly. Conversely, at insufflation, color Doppler area of the mitral backflow increased significantly (p < 0.05) when already present or showed up abruptly (T1: 0.22 ± 0.28 cm²; T2: 1.28 ± 1.02 cm²; T3: 0.49 ± 0.53 cm²). Conclusions: Such an event is not interpreted as a mitral insufficiency. It is possibly the result of a ``contrast effect' caused by the absorption of CO₂ microbubbles in the blood. Received: 12 April 1998/Accepted: 23 June 1999     

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     

Effect of pressure and gas type on intraabdominal, subcutaneous, and blood pH in laparoscopy

Background: According to the literature, the number of port-site metastases in laparoscopic surgery varies considerably depending on the type of gas used for the pneumoperitoneum. In order to investigate this observation we studied the changes in blood, subcutaneous, and intra-abdominal pH during laparoscopy with helium, CO₂ and room air in a rat model. In addition, we looked at the influence of intra-abdominal pressure and duration of pneumoperitoneum on the pH during the laparoscopy. Methods: pH was measured by tonometry, intra-abdominally and subcutaneously. A pH electrode was additionally placed into the subcutaneous tissue and the results compared to those measured by tonometry. Blood samples were taken from a catheter in the carotid artery. The intra-abdominal pressure was 0, 3, 6, 9 mmHg for 30 min in each case. We investigated the effect of pneumoperitoneum with CO₂, helium and air in randomized groups of 5 rats. In an additional series the pressure was held constant at 3 mmHg and the pH was measured every 30 min. Results: Due to the different absorption capacity of the peritoneum, laparoscopy with CO₂ decreases the subcutaneous pH from 7.35 to 6.81. Blood pH is reduced from 7.37 to 7.17 and the intra-abdominal pH from 7.35 to 6.24. Other, less absorbable gases induce smaller changes of blood and subcutaneous pH (only 10% of CO₂). In a variance analysis the p value is less than 0.001. The influence of duration of laparoscopy (30 min vs 90 min) on the subcutaneous pH is less compared to the influence of intra-abdominal pressure (0, 3, 6, 9 mmHg). Conclusions: Depending on the type of gas (CO₂, air, helium) used for laparoscopy blood, subcutaneous and intra-abdominal pH are influenced differently. Because lower pH is known to impair local defense mechanisms, these results may be one explanation for the higher incidence of port-site metastasis in laparoscopy with CO₂ than with other gases, as reported in the literature. Received: 11 June 1998/Accepted: 12 February 1999     

Effects of pneumoperitoneum on cardiac autonomic nervous activity evaluated by heart rate variability analysis during sevoflurane, isoflurane, or propofol anesthesia

Background: The effects of pneumoperitoneum on the activity of the cardiac autonomic nervous system have not been completely understood. Methods: In this study, 45 unpremedicated adult patients who underwent laparoscopic cholecystectomy were anesthetized with either 3.5% sevoflurane, 2% isoflurane, or 8 mg/kg/h propofol (15 patients in each group). The status of cardiac autonomic nervous activity was evaluated by heart rate variability analysis three times: once when the patient was awake, once after induction of general anesthesia, and once after insufflation for pneumoperitoneum. Intra-abdominal pressure was maintained automatically at 10 mmHg by a carbon dioxide (CO₂) insufflator. For each measurement, electrocardiogram was recorded for 256 s and played back offline to detect R-R intervals. Power spectral analysis of heart rate variability was applied, and the low-frequency (LF, 0.04–0.15 Hz) and high-frequency (HF, 0.15–0.40 Hz) bands of the spectral density of the heart rate variability were obtained from a power spectra of R-R intervals using the fast-Fourier transform algorithm. The HF/LF ratio also was analyzed. Results: Measurements of heart rate variability in the three groups showed similar change. Although the power of HF, which represents parasympathetic nervous activity, did not change, the power of LF, which represents both sympathetic and parasympathetic nervous activity, decreased during the anesthetized stage and increased during the insufflated stage. The HF/LF ratio, which represents the balance of parasympathetic and sympathetic activity, increased after induction of general anesthesia, and decreased after insufflation. Conclusions: Our results suggest that pneumoperitoneum increases sympathetic cardiac activity. The choice of general anesthetic did not seem to have a major influence on the change in the cardiac autonomic nervous system after induction of pneumoperitoneum for laparoscopic cholecystectomy. Received: 22 January 1999/Accepted: 22 March 1999     

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