Impact of carbon dioxide and helium insufflation on cardiorespiratory function during prolonged pneumoperitoneum in an experimental rat model

BACKGROUND: Experimental studies on laparoscopic surgery are often performed in rats. However, the hemodynamic and respiratory responses related to the pneumoperitoneum have not been studied extensively in rats. Therefore, the aim of this study was to investigate in spontaneously breathing rats the effects of CO2 and helium, insufflation pressure, and duration of pneumoperitoneum on blood pressure, arterial pH, pCO2, pO2, HCO3-, base excess, and respiratory rate. METHODS: Five groups of 9 Brown Norway rats were anesthetized and underwent CO2 insufflation (6 or 12 mmHg), helium insufflation (6 or 12 mmHg), or abdominal wall lifting (gasless control) for 120 min. Blood pressure was monitored by an indwelling carotid artery catheter. Baseline measurements of mean arterial pressure (MAP), respiratory rate, arterial blood pH, pCO2, pO2, HCO3-, and base excess were recorded. Blood gases were analyzed at 5, 30, 60, 90, and 120 min during pneumoperitoneum, and MAP and respiratory rate were recorded at 5 and 15 min and at 15-min intervals thereafter for 2 h. RESULTS: CO2 insufflation (at both 6 and 12 mmHg) caused a significant decrease in blood pH and increase in arterial pCO2. Respiratory compensation was evident since pCO2 returned to preinsufflation levels during CO2 insufflation at 12 mmHg. There was no significant change in blood pH and pCO2 in rats undergoing either helium insufflation or gasless procedures. Neither insufflation pressure nor the type of insufflation gas had a significant effect on MAP over time. CONCLUSION: The cardiorespiratory changes during prolonged pneumoperitoneum in spontaneously breathing rats are similar to those seen in clinical practice. Therefore, studies conducted in this animal model can provide valuable physiological data relevant to the study of laparoscopic surgery.     

Effectors of hypercarbia during experimental pneumoperitoneum.

Hypercarbia occurs during laparoscopy with carbon dioxide (CO2) insufflation. This may be due to increased ventilatory dead space after expansion of the peritoneal cavity with impairment of diaphragmatic excursion, or to increased absorption of CO2 from the peritoneum. To separate these effects, the authors examined the consequences of different insufflating gases and of diminished tissue perfusion on hypercarbia and dead space during pneumoperitoneum. Helium was chosen as an alternate insufflating gas because it is both inert and minimally absorbed. Eight swine (18 to 20 kg) were anesthetized, paralyzed, and mechanically ventilated at constant minute volume. Pneumoperitoneum with helium was maintained at 15 mm Hg for 45 minutes. After desufflation and stabilization for 1 hour, pneumoperitoneum was repeated with CO2. The sequence was again repeated after hemorrhagic shock to constant mean arterial pressure of 50 mm Hg. Data was analyzed by analysis of variance; significance levels are P < 0.01 unless otherwise listed. Arterial PCO2 increased significantly with CO2 insufflation within 15 minutes in normotensive animals and within 30 minutes during hypotension. Arterial pH decrease with CO2 pneumoperitoneum was significant in both groups at 30 minutes. Mixed venous PCO2 also increased with CO2 pneumoperitoneum within 30 minutes. Hypotension did not alter these changes. No significant changes were seen with helium pneumoperitoneum. Neither helium nor CO2 pneumoperitoneum significantly altered dead space. The authors make the following conclusions: 1) Absorption of CO2 from the abdomen during CO2 pneumoperitoneum produces respiratory acidosis, which is not seen with helium insufflation; 2) Pneumoperitoneum does not significantly increase dead space with either gas; 3) Transperitoneal absorption of CO2 is only partly related to perfusion because significant hypercarbia occurs during hemorrhagic shock.     

Peritoneal and systemic pH during pneumoperitoneum with CO<Subscript>2</Subscript> and helium in a pig model

Background Local peritoneal effects of laparoscopic gases might be important in peritoneal biology during and after laparoscopic surgery. The most commonly used gas, CO₂, is known to be well tolerated, but also causes changes in acid-base balance. Helium is an alternative gas for laparoscopy. Although safe, it is not widely used. In this study a method for monitoring peritoneal pH during laparoscopy was evaluated and peritoneal pH during CO₂ and helium pneumoperitoneum was studied as well as its systemic reflection in arterial pH. Methods For these experiments 20 pigs were used, with ten exposed to pneumoperitoneum with CO₂, and ten to helium. Peritoneal and sub-peritoneal pH were continuously measured before and during gas insufflation, during a 30-minute period with a pneumoperitoneum and during a 30-minute recovery period. Arterial blood-gases were collected immediately before gas insufflation, at its completion, at 30 minutes of pneumoperitoneum and after the recovery period. Results Peritoneal pH before gas insufflation was in all animals 7.4. An immediate local drop in pH (6.6) occurred in the peritoneum with CO₂ insufflation. During pneumoperitoneum pH declined further, stabilising at 6.4, but was restored after the recovery period (7.3). With helium, tissue pH increased slightly (7.5) during insufflation, followed by a continuous decrease during pneumoperitoneum and recovery, reaching 7.2. Systemic pH decreased significantly with CO₂ insufflation, and increased slightly during helium insufflation. Systemic pH showed co-variation with intra-peritoneal pH at the the end of insufflation and after 30 minutes of pneumoperitoneum. Conclusions Insufflation of CO₂ into the peritoneal cavity seemed to result in an immediate decrease in peritoneal pH, a response that might influence biological events. This peritoneal effect also seems to influence systemic acid-base balance, probably due to trans-peritoneal absorption.     

Heated, humidified CO2 gas is unsatisfactory for awake laparoscopy.

BACKGROUND: The necessity for general anesthesia represents an impediment to using a laparoscopic approach for some procedures that are otherwise performed with the patient under local anesthesia using a conventional open technique. Heating and humidifying the insufflation gas reportedly reduces perioperative pain associated with a CO2 pneumoperitoneum, thus enabling awake laparoscopy. METHODS: Two cases are reported herein of laparoscopy performed with the patient under local anesthesia using heated, humidified CO2 gas for the pneumoperitoneum. RESULTS: Both patients experienced pain with insufflation of heated, humidified CO2 gas of sufficient magnitude that the procedure could not be performed. The CO2 gas was washed out and replaced with helium gas insufflation with complete resolution of pain. The laparoscopic procedures were accomplished without further discomfort with local anesthesia and using a helium gas pneumoperitoneum. CONCLUSIONS: Heated, humidified CO2 gas insufflation does not reduce pain sufficiently to permit satisfactory performance of laparoscopy with local anesthesia, especially when full volume insufflation is required. Cold, dry helium gas produces no pain. The theory that cold, dry insufflation gas is a source of peritoneal pain during laparoscopy needs to be reassessed.     

Abdominal insufflation with CO2 causes peritoneal acidosis independent of systemic pH.

We have shown that the inflammation-attenuating effects of CO(2) pneumoperitoneum during laparoscopy are not due to changes in systemic pH. However, acidification of peritoneal macrophages in an in vitro CO(2) environment has been shown to reduce LPS-mediated cytokine release. We tested the hypothesis that the peritoneum is locally acidotic during abdominal insufflation with CO(2)--even when systemic pH is corrected. Rats (n = 20) were anesthetized and randomized into two groups: continued spontaneous ventilation (SV) or intubation and mechanical ventilation (MV). All animals were then subjected to abdominal insufflation with CO(2). Mean arterial pH among SV rats decreased significantly from baseline after 15 and 30 minutes of CO(2) pneumoperitoneum (7.329 --> 7.210 --> 7.191, P < 0.05), while arterial pH among MV rats remained relatively constant (7.388 --> 7.245 --> 7.316, P = NS). In contrast, peritoneal pH dropped significantly from baseline and remained low for both groups during CO(2) abdominal insufflation (SV 6.74 --> 6.41 --> 6.40, P < 0.05; MV 6.94 --> 6.45 --> 6.45, P < 0.05). In a second experiment, rats (n = 10) were randomized to receive abdominal insufflation with either CO(2) or helium. Abdominal insufflation with helium did not significantly affect peritoneal pH (7.10 --> 7.02 --> 6.95, P = NS), and the decrease in pH among CO(2)-insufflated animals was significant compared with helium-insufflated animals (P < 0.05). Peritoneal pH returned to baseline levels in all groups within 15 minutes of desufflation in both experiments. A significant local peritoneal acidosis occurs during laparoscopy which is specifically attributable to the use of CO(2) and which is independent of systemic pH. These data provide additional evidence that localized peritoneal acidosis is central to the mechanism of CO(2)-mediated attenuation of the inflammatory response following laparoscopic surgery.     

Peritoneal acidosis mediates immunoprotection in laparoscopic surgery

BACKGROUND: We have shown previously that abdominal insufflation with CO(2) increases serum levels of IL-10 and TNFalpha and increases survival among animals with lipopolysaccharide (LPS)-induced sepsis, even after a laparotomy. We demonstrated previously that the effect of CO(2) is not from changes in systemic pH, although the peritoneum is locally acidotic during abdominal insufflation with CO(2) even when systemic pH is corrected. We hypothesized that acidification of the peritoneum via means other than CO(2) insufflation would produce alterations in the inflammatory response similar to those associated with CO(2) pneumoperitoneum. METHODS: In total, 42 rats were randomized into 7 groups (n = 6): 1) LPS only, 2) anesthesia control, 3) helium pneumoperitoneum, 4) CO(2) pneumoperitoneum, 5) buffered mild acid lavage, 6) buffered strong acid lavage, and 7) buffered strong acid lavage + helium pneumoperitoneum. Animals received anesthesia with vaporized isoflurane (except the LPS-only group) and their respective abdominal treatment (pneumoperitoneum and/or lavage) for 30 min followed immediately by stimulation with systemic LPS (1 mg/kg, IV). Blood was harvested via cardiac puncture 60 min after LPS injection, and serum levels of IL-10 and TNFalpha levels were determined by enzyme-linked immunosorbent assay. RESULTS: Mean peritoneal pH decreased (P < .05) after CO(2) pneumoperitoneum, buffered strong acid lavage, and buffered strong acid lavage + helium pneumoperitoneum, and it decreased (P = .1) after helium pneumoperitoneum alone and buffered mild acid lavage. IL-10 levels were increased (P < .01), and TNFalpha levels decreased (P < .001) among animals with acidic peritoneal cavities compared with animals with pH-normal peritoneal cavities. Decreasing peritoneal pH correlated with both increasing IL-10 levels (r = -.465, P < .01) and decreasing TNFalpha levels (r = 0.448, P < .01). Among animals with peritoneal acidosis, there were no differences in levels of IL-10 or TNFalpha regardless of insufflation status (P > .05 for both cytokines). CONCLUSIONS: Acidification of the peritoneal cavity whether by abdominal insufflation or by peritoneal acid lavage increases serum IL-10 and decreases serum TNFalpha levels in response to systemic LPS challenge. The degree of peritoneal acidification correlates with the degree of inflammatory response reduction. These results support the hypothesis that pneumoperitoneum-mediated attenuation of the inflammatory response after laparoscopic surgery occurs via a mechanism of peritoneal cell acidification.     

Helium Pneumoperitoneum Ameliorates Hypercarbia and Acidosis Associated with Carbon Dioxide Insufflation during Laparoscopic Gastric Bypass in Pigs

Background: In the morbidly obese patient undergoing laparoscopic gastric bypass (LGBP), insufflation with carbon dioxide to 20 mmHg for prolonged periods may induce significant hypercarbia and acidosis with attendant sequelae. We hypothesize that the use of helium as an insufflating agent results in less hypercarbia and acidosis. Methods: The study was performed between May and November 2002. A Paratrend 7 fiberoptic probe was placed via a carotid artery catheter in 5 adult Yorkshire swine as continuous pH and pCO₂ levels were measured. Animals were ventilated to a constant pCO₂, after which LGBP was performed. Blood gas values were measured during the procedure and for 1 hour after release of pneumoperitoneum. Helium was used for insufflation in 3 of the pigs and CO₂ in 2. Comparison of arterial pH and pCO₂ were made between groups. Results: Mean maximum pCO₂ for the control group (CO₂ insufflation) was 99.75 ± 22.98 mmHg, while for the experimental group (helium insufflation) was 52.86 ± 6.27mmHg (P=.036). Mean low pH for the groups were 7.10 ± .056 and 7.36 ± .015 (P =.004) respectively. Normalization of pCO₂ in the helium group occurred at a mean of 14.58 min (SD 13.3 min) after release of pneumoperitoneum, while in the control group levels did not normalize (mean final pCO₂= 71.5 mmHg). Conclusions: Helium pneumoperitoneum in LGBP is associated with less intraoperative hypercarbia and acidosis than is the use of CO₂. In addition, pCO₂ returns to normal more rapidly postoperatively with the use of helium insufflation. Study of helium insufflation in humans undergoing LGBP is needed to prove its benefits in the clinical setting.     

Mechanism of decreased in vitro murine macrophage cytokine release after exposure to carbon dioxide: relevance to laparoscopic surgery.

OBJECTIVE: The objective of this study was to determine the effect of carbon dioxide (CO2) on the function of peritoneal macrophages. SUMMARY BACKGROUND DATA: Laparoscopic surgery is associated with minimal pain, fever, and low levels of inflammatory cytokines. To understand the mechanisms involved, the authors investigated the effect of different gases on murine peritoneal macrophage intracellular pH and correlated these alterations with alterations in LPS-stimulated inflammatory cytokine release. METHODS: Peritoneal macrophages were incubated for 2 hours in air, helium, or CO2, and the effect of the test gas on immediate or next day lipopolysaccharide (LPS)-stimulated tumor necrosis factor (TNF) and interleukin-1 release compared. Cytosolic pH of macrophages exposed to test gases was measured using single-cell fluorescent imaging. The in vivo effects of test gases were determined in anesthetized rats during abdominal insufflation. RESULTS: Macrophages incubated in CO2 produced significantly less TNF and interleukin-1 in response to LPS compared to incubation in air or helium. Cytokine production returned to normal 24 hours later. Exposure to CO2, but not air or helium, caused a marked cytosolic acidification. Pharmacologic induction of intracellular acidification to similar levels reproduced the inhibitory effect. In vitro studies showed that CO2 insufflation lowered tissue pH and peritoneal macrophage LPS-stimulated TNF production. CONCLUSIONS: The authors propose that cellular acidification induced by peritoneal CO2 insufflation contributes to blunting of the local inflammatory response during laparoscopic surgery.     

Effects of prolonged pneumoperitoneum on hemodynamics and acid-base balance during totally endoscopic robot-assisted radical prostatectomies

Laparoscopic techniques have become a standard approach for diagnostic and therapeutic procedures in many surgical disciplines. Recent progress in endoscopic surgery is based on the integration of computer-enhanced telemanipulation systems. Because robot-assisted radical prostatectomies take up to 10 hours, the present study was performed to evaluate the effects of prolonged intraperitoneal CO2 insufflation on hemodynamics and gas exchange in 15 patients with prostate cancer. When CO2 insufflation was initiated, peak inspiratory pressure increased and reached significant values after a 1.5-hour period of intraperitoneal CO2 insufflation. With the release of CO2, peak inspiratory pressure decreased close to baseline values. A significant increase in heart rate was observed after a 4-hour period of increased intraabdominal pressure. Mean arterial blood pressure and central venous pressure remained stable during CO2 insufflation. Minute ventilation was adjusted according to repeated blood gas analyses to maintain pH, base excess (BE), bicarbonate (HCO3?), and PaCO2 within physiologic ranges. The present data show, that prolonged CO2 insufflation during totally endoscopic robot-assisted radical prostatectomy results in only minor changes in hemodynamics and acid-base status. Because of the limited experience with long-term pneumoperitoneum, we consider invasive haemodynamic monitoring and repeat blood gas analysis essential for such operations.     

Short-term impact of carbon dioxide, helium, and gasless laparoscopic donor nephrectomy on renal function and histomorphology in donor and recipient

BACKGROUND: Laparoscopic donor nephrectomy has the potential to increase the number of living kidney donations by reducing donor morbidity. However, studies have shown that raised intraabdominal pressure can result in transient renal dysfunction. Therefore, laparoscopically procured kidneys might be at higher risk for suffering a period of ischemia during pneumoperitoneum. The objective of this study was to investigate the short-term impact of pneumoperitoneum used for laparoscopic donor nephrectomy on renal function and histomorphology in donor and recipient. METHODS: EXPERIMENT 1: KIDNEY DONOR: Initially, 36 brown Norway (BN) rats were randomized for three procedures: 2 h of carbon dioxide (CO2) insufflation (8 mmHg), 2 h of helium insufflation (8 mmHg), and 2 h of gasless technique (0 mmHg). After this, a unilateral nephrectomy was performed in all the animals. EXPERIMENT 2: RECIPIENT: Subsequently, 36 donor BN rats were subjected to a similar insufflation protocol, but after nephrectomy, a syngeneic kidney transplantation (BN-BN) was performed. Urine and blood samples were collected on postoperative days 1, 3, 7, and 14 for determination of renal function. Subsequently, donor and recipient kidneys were removed for histomorphologic and immunohistochemical analysis. RESULTS: In both donors and recipients, no significant changes in serum creatinine, proteinuria, or glomular filtration were detected between the CO2, the helium, and the gasless control groups. In both experiments, histologic analysis of Kidney specimens did not show any deleterious effects from abdominal gas insufflation. Although kidney grafts exposed to CO2 showed significantly higher numbers of CD45+ leukocytes 3 days after transplantation, immunohistochemical analysis did not show significant differences in number of infiltrating cells (CD4, CD8, ED1, OX6, OX62) between the two insufflation groups and the gasless control subjects. CONCLUSIONS: Abdominal gas insufflation does not have an adverse effect on the renal function of the kidney donor 1 week after laparoscopic donor nephrectomy. No differences in renal function or histomorphology were detected between syngeneic kidney grafts exposed to pneumoperitoneum and gasless control subjects.     

Arterial to end-tidal carbon dioxide tension difference during laparoscopic colorectal surgery

BACKGROUND: Determination of end-tidal carbon dioxide pressure (PET(CO2)) is effective to confirm adequate ventilation, because arterial to end-tidal carbon dioxide tension difference (deltaa-ET(CO2)) does not change normally during operation. But deltaa-ET(CO2) may change during laparoscopic surgery, because peritoneal insufflation of CO2 will increase CO2 production and reduce functional residual volume. Changes in deltaa-ET(CO2) were reported in laparoscopic cholecystectomy with cardiovascular complication, but there is controversy about how deltaaET(CO2) will change in more complicated and long laparoscopic surgery. In this prospective study, we examined changes in deltaa- ET(CO2) during laparoscopic colorectal surgery. METHODS: Fifty patients received combined general and epidural anesthesia. CO2 pneumoperitoneum was initiated after obtaining arterial blood for gas analysis. Mechanical ventilation was used to maintain PET(CO2) at a stable value between 30 and 40 mmHg during the procedure. Arterial blood gas analysis was performed 10, 60, 120 minutes after CO2 insufflation, and 10 minutes after the termination of insufflation. RESULTS: The mean +/- SD for deltaa-ET(CO2) was 5.8 +/- 4.1 before pneumoperitoneum, 7.1 +/- 4.8, 8.1 +/- 5.4, 6. 4 +/- 4.9 in 10, 60, 120 minutes after pneumoperitoneum, and 6.4 +/- 4.9 in 10 minutes after the termination of pneumoperitoneum. deltaa-ET(CO2) increased significantly during pneumoperitoneum, but did not increase further even if CO2 insufflation was longer than 60 minutes. CONCLUSIONS: In laparoscopic colorectal surgery, Pa(CO2) should be checked for at least the first 60 minutes to confirm adequate ventilation.     

Morphology of the murine peritoneum after pneumoperitoneum vs laparotomy

BACKGROUND: Although there have been studies of the effects of pneumoperitoneum on the peritoneal cavity, we still do not know whether the morphologic changes to the peritoneum are different for pneumoperitoneum vs laparotomy. Using scanning electron microscopy, we examined the murine peritoneum after pneumoperitoneum vs laparotomy and compared the changes. METHODS: Forty-five mice were anesthetized with diethyl ether and divided into seven groups. Pneumoperitoneum was established at 5 mmHg for 30 min with carbon dioxide (CO(2)) (n = 9), helium (n = 9), and air (n = 9). One group underwent laparotomy for 30 min (n = 9), and a control group underwent anesthesia only (n = 3). CO(2) pneumoperitoneum was further established at 10 mmHg for 30 min (n = 3) and at 5 mmHg for 60 min (n = 3). After the procedures, the peritoneum was resected from the mesenterium of the small intestine in each animal and examined by scanning electron microscope for morphologic changes of the mesothelial cells. RESULTS: Bulging up of the mesothelial cells was evident immediately after pneumoperitoneum, whereas detachment of the mesothelial cells was present immediately after laparotomy. Bulging up of the mesothelial cells was reduced at 24 h after CO(2) pneumoperitoneum and fully resolved at 72 h in all pneumoperitoneum groups, whereas the mesothelial cells remained detached at 72 h in the laparotomy group. Intercellular clefts were found immediately after helium pneumoperitoneum and were present at 24 h and 72 h after helium pneumoperitoneum, but they were not seen after air pneumoperitoneum and were only evident after CO(2) pneumoperitoneum at 10 mmHg. Depression of the mesothelial cell surface was observed when pneumoperitoneum lasted 60 min. CONCLUSION: Morphologic peritoneal alterations after pneumoperitoneum differed from those after laparotomy and were influenced by the type of gas, amount of pressure, and duration of insufflation. These peritoneal changes after pneumoperitoneum may be associated with a specific intraperitoneal tumor spread after laparoscopic cancer surgery.     

Cardiopulmonary changes during laparoscopy and vessel injury: comparison of CO2 and helium in an animal model

BACKGROUND: Injury of venous vessels during elevated intraperitoneal pressure is thought to cause possible fatal gas embolism, and helium may be dangerous because of its low solubility. METHODS: Twenty pigs underwent laparoscopy with either CO2 (n=10) or helium (n=10) with a pressure of 15 mm Hg and standardized laceration (1 cm) of the vena cava inferior. After 30 s, the vena cava was clamped, closed endoscopically by a running suture and unclamped again. During the procedure changes of cardiac output (CO), heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), pulmonary artery pressure (PAP), pulmonary artery wedge pressure (PAWP), end tidal CO2 pressure (PETCO2), and arterial blood gas analyses (pH, pO2 and pCO2) were investigated. RESULTS: No animal died during the experimental course (mean blood loss during laceration: CO2, 157+/-50 ml; helium, 173+/-83 ml). MAP and CO values showed a decrease after laceration of the vena cava in both groups that had already been completely compensated for before suturing. PETCO2 increased significantly after CO2 insufflation (P<0.01), while helium showed no effect. Laceration of the vena cava caused no significant changes in PETCO2 values in either group. Significant acidosis and an increase of pCO2 were only found in the CO2 group. CONCLUSIONS: The incidence of gas embolism during laparoscopy and accidental vessel injury seems to be very low. With the exception of acidosis and an increase of PETCO2 in the CO2 group, there were no differences in cardiopulmonary function between insufflation of CO2 and helium.     

Long-term impact of pneumoperitoneum used for laparoscopic donor nephrectomy on renal function and histomorphology in donor and recipient rats

OBJECTIVE: To investigate the long-term impact of pneumoperitoneum used for laparoscopic donor nephrectomy on renal function and histomorphology in donor and recipient. SUMMARY BACKGROUND DATA: Laparoscopic donor nephrectomy has the potential to increase the number of living kidney donations by reducing donor morbidity. However, function of laparoscopically procured kidneys might be at risk due to ischemia as a consequence of elevated intra-abdominal pressure during laparoscopy. METHODS: In experiment 1, 30 Brown Norway rats were randomized to three procedures: 2 hours of CO2 insufflation, 2 hours of helium insufflation, and 2 hours of gasless laparoscopy. After this, a unilateral nephrectomy was performed in all animals. Another six rats were used as controls. In experiment 2, 36 donor Brown Norway rats were subjected to a similar insufflation protocol, but after nephrectomy a syngeneic renal transplantation was performed. All rats had a follow-up period of 12 months. Urine and blood samples were collected each month for determination of renal function. After 1 year, donor and recipient kidneys were removed for histomorphologic and immunohistochemical analysis. RESULTS: In donors as well as in recipients, no significant changes in serum creatinine, proteinuria, or glomerular filtration rate were detected between the CO2, the helium, and the gasless control group after 1 year. No histologic abnormalities due to abdominal gas insufflation were found. Immunohistochemical analysis did not show significant differences in the number of infiltrating cells (CD4, CD8, ED1, OX62, and OX6) and adhesion molecule expression (ICAM-1) between the three groups. CONCLUSIONS: Abdominal gas insufflation does not impair renal function in the donor 1 year after LDN. One year after transplantation, no differences in renal function or histomorphology were detected between kidney grafts exposed to either pneumoperitoneum or a gasless procedure.     

Helium pneumoperitoneum reduces tumor recurrence after curative laparoscopic liver resection in rats in a tumor-bearing small animal model

BACKGROUND: After exposure of neoplastic tissue to helium, a significant reduction of tumor growth has been detected in experimental studies, both in vitro and in vivo. This tumor-suppressive effect of helium is controversly discussed in the literature. It was therefore the aim of this study to investigate the influence of pneumoperitoneum with CO2, room air, or helium in a tumor-bearing small animal model comparing laparoscopic partial hepatic resection for hepatocellular carcinoma with conventional open partial hepatectomy. METHODS: One-hundred forty-eight male American Cancer Institute rats underwent partial hepatectomy for curative resection of previously induced hepatocellular carcinoma (Morris hepatoma 3924A). Resection was performed either in open laparotomy (n = 30) or laparoscopically under the employment of CO2 (n = 30), room air (n = 30), or helium (n = 30) for the pneumoperitoneum. Twenty-eight animals served as controls receiving anesthesia but no tumor resection. All animals were sacrificed on postoperative days 21, 35, or 56 for autopsy and evaluation of possible tumor recurrence and metastasis. RESULTS: Significant reduction of postoperative tumor recurrence and metastasis was observed in the group of animals receiving laparoscopic tumor resection under helium insufflation compared to open surgery or laparoscopic resection with air pneumoperitoneum. CONCLUSIONS: The results of this study suggest a suppressive effect of helium pneumoperitoneum on postoperative tumor growth and metastatic spread. Furthermore, tumor exposure to room air appears to have a stimulative influence on tumor recurrence and metastasis compared to a pneumoperitoneum established with CO2.     

"Low-pressure" laparoscopic cholecystectomy in high risk patients (ASA III and IV): our experience

The insufflation pressure used for laparoscopic cholecystectomy is usually 12-15 mm Hg, and a pneumoperitoneum with carbon dioxide has a significant effect on both cardiovascular and respiratory function. These effects are transient in young, healthy patients, but may be dangerous in ASA III and IV patients with a poor cardiac reserve. This study was designed to assess the feasibility of performing laparoscopic cholecystectomy at 6.5-8 mm Hg insufflation pressure in "high-risk" patients. Thirteen patients, 10 ASA III and 3 ASA IV, with cholelithiasis, were included in this study The insufflation pressure was 6.5-8 mm Hg, with a 10 degrees anti-Trendelenburg position. The cardiovascular and blood gas variables studied were: mean arterial blood pressure, heart rate, respiratory rate, and end-tidal CO2 pressure. The authors reported no conversions and no intra- or postoperative complications. During insufflation heart rate and mean arterial blood pressure increased minimally if compared with laparoscopic cholecystectomy at 12-15 mm Hg. Pa CO2 increased after insufflation (+5 mm Hg), and the end-tidal CO2 pressure gradient was moderate (3.5 mm Hg) and unchanged during surgery. A low-pressure pneumoperitoneum is feasible for laparoscopic cholecystectomy and minimizes the adverse haemodynamic effects of peritoneal insufflation.     

Metabolic and immunologic consequences of laparoscopy with helium or carbon dioxide insufflation: a randomized clinical study

Background : Previous studies using animal models have demonstrated that carbon dioxide (CO₂) pneumoperitoneum during laparoscopy is associated with adverse physiological, metabolic, immunological and oncological effects, and many of these problems can be avoided by the use of helium insufflation. The present study was performed in patients to compare the effect of helium and CO₂ insufflation on intraperitoneal markers of immunological and metabolic function. Methods : Eighteen patients undergoing elective upper gastrointestinal laparoscopic surgery were randomized to have insufflation achieved by using either helium (n = 8) or CO₂ (n = 10) gas. Intraperitoneal pH was monitored continuously during surgery, and peritoneal macrophage function was determined by harvesting peritoneal macrophages at 5 min and 30 min after commencing laparoscopy, and then assessing their ability to produce tumour necrosis factor‐α (TNF‐α), and their phagocytic function. Results : Carbon dioxide laparoscopy was associated with a lower intraperitoneal pH at the commencement of laparoscopy, although this difference disappeared as surgery progressed. The production of TNF‐α was better preserved by CO₂ laparoscopy, but the insufflation gas used did not affect macrophage phagocytosis. Patients undergoing helium laparoscopy required less postoperative analgesia. Conclusion : The choice of insufflation gas can affect intraperitoneal macrophage function in the clinical setting, and possibly acid–base balance. The present study suggested no immunological advantages for the clinical use of helium as an insufflation gas. The outcomes of the present study, however, are different to those obtained from previous laboratory studies and further research is needed to confirm this outcome.     

Laparoscopic-type environment enhances mesothelial cell fibrinolytic activity in vitro via a down-regulation of plasminogen activator inhibitor-1 activity

BACKGROUND: Fewer intraperitoneal adhesions have been observed after laparoscopic surgery compared with conventional techniques. The aim of this study is to assess the effect of the pneumoperitoneum on mesothelial cell fibrinolytic activity by use of an in vitro model. METHODS: Human peritoneal mesothelial cells were seeded onto 24-well plates and incubated in carbon dioxide or helium at 5 mm Hg for 4 hours or standard culture conditions. Supernatant was removed for analysis at 0, 24, 48, and 72 hours after gas incubation and analyzed for plasminogen activator activity, total tissue plasminogen activator (tPA), and total plasminogen activator inhibitor-1 (PAI-1) concentrations by use of an enzyme-linked immunosorbent assay. The effect of different insufflation pressures (0, 7, and 14 mm Hg) was also examined. RESULTS: Enhanced plasminogen activator activity was observed at 48 hours and 72 hours from cells exposed to CO(2) (P<.04 each) and helium (P<.05 each) compared with control. This was associated with a decrease in PAI-1 concentrations at 48 and 72 hours in both the CO(2) and helium groups compared with control (P<.03 each, CO(2) vs control; and P<.04 each, helium vs control). No changes in tPA levels were observed. Changes in insufflation pressures did not affect plasminogen activator activity. CONCLUSIONS: These results suggest that incubation of human mesothelial cells with both CO(2) and helium in the absence of oxygen enhances mesothelial cell fibrinolytic activity because of a reduction in PAI-1 concentrations. These changes may participate in the observed reduction in adhesions after laparoscopic surgery relative to open surgery.     

The effects of preperitoneal carbon dioxide insufflation on cardiopulmonary function in pigs.

BACKGROUND AND OBJECTIVES: Although considerable experimental and clinical knowledge exists on the physiology of pneumoperitoneum, insufflation of the preperitoneal space has not been extensively studied. The purpose of this study is to evaluate the physiology associated with preperitoneal carbon dioxide (CO2) insufflation in a porcine model. METHODS: Eleven pigs weighing 35 to 45 kg were anesthetized and placed on mechanical ventilation. A pulmonary artery catheter and an arterial line were inserted. Balloon dissection of the preperitoneal space and insufflation to 10 mm Hg for 1.5 hours, followed by an increase to 15 mm Hg for an additional 1.5 hours, was performed. Hemodynamic and arterial blood gas values were determined every 15 minutes throughout the stabilization and three-hour insufflation period. Hemodynamic parameters and blood gas values were analyzed using one-way analysis of variance with respect to insufflation time and pressure. RESULTS: Analysis of hemodynamics (CO, CVP, PAD, PAS, PCWP) did not demonstrate statistical significance with respect to time. However, there was a statistical difference in CO (p=.01), CVP (p<.01), and PCWP (p=.034) when comparing a pressure of 15 mm Hg to a pressure of 10 or 0 mm Hg. The other parameters did not demonstrate significant differences among the three pressure groups. Arterial PCO2 and pH were highly significant with respect to time (p<.01 and P<.01, respectively) and among the pressure groups (p<.01 and P<.01, respectively). CONCLUSIONS: Insufflation of the preperitoneal space with CO2 gas does not cause significant alterations in hemodynamics and blood gas changes at a pressure of 10 mm Hg. However, when a pressure of 15 mm Hg is used to insufflate this space, there is evidence of decreased pH and cardiac output, with elevated CVP and CO2 retention. This correlates with greater pneumodissection of the gas within the layers of the abdominal wall when elevated pressures are used.