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.     

Gas embolism during laparoscopic cholecystectomy

Advancements in laparoscopic surgery have resulted in decreased length of hospitalization, reduced postoperative pain, and better cosmesis following general surgical procedures. Carbon dioxide gas embolism is a rare occurrence that can be fatal. We report the case of a patient with a venous gas embolism during laparoscopic cholecystectomy. A 63-year-old woman presented with intermittent right upper quadrant pain, and her abdominal ultrasound showed a possible gallbladder polyp. A laparoscopic cholecystectomy was planned. A Veress needle was placed in the right upper quadrant to initiate abdominal access. Shortly after carbon dioxide insufflation, the patient's hemodynamic status deteriorated, her oxygen saturation dropped, and her end-tidal CO2 decreased. Gas insufflation was immediately stopped, and the patient was resuscitated. She stabilized quickly, and the procedure was performed without further event. She did well postoperatively and was discharged home the next day. Carbon dioxide embolism during laparoscopy, albeit rare, can be a fatal complication of the procedure. Whenever sudden changes in hemodynamic stability occur, venous gas embolism should be considered. As laparoscopic techniques and applications are expanded, the general surgeon must be aware of this entity.     

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.     

Carbon dioxide embolization: is it a complication of laparoscopic cholecystectomy?

The occurrence of pulmonary gas embolism in patients undergoing laparoscopic cholecystectomy is reported in the medical literature. Severe intraoperative complications or the patient's death were correlated to gas embolism during laparoscopic procedures. However, the careful retrospective study or the autoptic exam of such casualties have always showed an erroneus direct puncture of vessels or the straight insertion of the Veress needle into a parenchymal organ. It is obvious that the direct gas injection into a vein or into parenchymal organs is a primary cause of gas embolism, as well as the high flow insufflation of gas into the peritoneal cavity in concomitance with the lesion of major abdominal vessel's wall. Gas embolism may occur each time the vein internal pressure is lower than the external pressure and not only during a laparoscopic procedure when carbon dioxyde is inflated into the peritoneal cavity, but also during open surgery such as major liver resections, neurosurgery, vascular or cardiac surgery. The review of large series of laparoscopic cholecystectomies reported in the international literature, as well as our own clinical experience in this field, together with the results of laboratory animal studies based on the experimental insufflation or injection of carbon dioxyde, show that gas embolism must not be considered as a complication of laparoscopic surgery. Due to the above mentioned risks with the use of the Veress needle, the surgeon should revalue alternative means in creating the pneumoperitoneum.     

Capnography in the early diagnosis of carbon dioxide embolism during laparoscopy

Venous embolism of carbon dioxide occurred during elective diagnostic laparoscopy in a healthy adult female. The diagnosis of gas embolism was made on the basis of the sudden abrupt onset of systolic and diastolic murmurs. The continuously recorded end-tidal carbon dioxide concentration (FETCO2) increased abruptly from 3.8 to 4.2 per cent and then slowly decreased to 4.0 per cent over the subsequent 30 seconds. CO2 insufflation was terminated immediately following the establishment of the diagnosis. The patient recovered uneventfully. A transient but rapid rise in FETCO2 is suggested as a useful early sign of venous CO2 embolism during laparoscopy.     

Safety of the Veress needle in pediatric laparoscopy

PURPOSE: To better establish the complication rate with the Veress needle technique for establishing a pneumoperitoneum in pediatric laparoscopy. PATIENTS AND METHODS: We reviewed all pediatric laparoscopy cases performed by a single surgeon from 1996 to 2003. There were 257 patients ranging in age from 4 months to 19 years. Infraumbilical placement of the Veress needle was used to create a pneumoperitoneum. All instances of preperitoneal insufflation, vessel/viscus injury, and forced conversion to open surgery were recorded. The length of time required to establish pneumoperitoneum was reported in the last 139 patients. RESULTS: The average length of time required to gain access to the peritoneum was <2 minutes. Of these procedures, 138 were performed for nonpalpable undescended testicles, 101 for varicoceles, 13 for duplication anomalies, and 5 for intersex disorders. There were 18 cases (7.0%) of preperitoneal insufflation. No cases resulted in vessel/visceral injury, conversion to open surgery, conversion to use of the Hassan trocar technique, or inability to complete the procedure because of complications in establishing a pneumoperitoneum. In all cases of preperitoneal insufflation, proper access was achieved by pulling the needle out and reinserting it at a different angle, with pneumoperitoneum being achieved easily in each case. CONCLUSION: The use of the Veress needle to establish pneumoperitoneum in children of all ages is safe, fast, and efficacious.     

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.     

The influence of CO2 versus helium insufflation or the abdominal wall lifting technique on the systemic immune response

BACKGROUND: Both laparoscopic and conventional surgery result in activation of the systemic immune response; however, the influence of the laparoscopic approach, using CO2 insufflation, is significantly less. Little is known about the influence of alternative methods for performing laparoscopy, such as helium insufflation and the abdominal wall lifting technique (AWLT), and the systemic immune response. METHODS: Thirty-three patients scheduled for elective cholecystectomy were randomly assigned to undergo laparoscopy using either CO2 or helium for abdominal insufflation or laparoscopy using only the AWLT. The postoperative inflammatory response was assessed by measuring the white blood cell count, C-reactive protein (CRP) and interleukin-6 (IL-6). The postoperative immune response was assessed by measuring monocyte HLA-DR expression. RESULTS: CRP levels were significantly higher 1 day after helium insufflation when compared with CO2 insufflation; however, no differences were observed 2 days after surgery. The AWLT resulted in significantly higher levels of CRP both 1 and 2 days after surgery when compared with either CO2 or helium insufflation. A small increase in postoperative IL-6 levels was observed in all groups, but no significant differences were seen between the groups. After both helium insufflation and AWLT a significant decrease in HLA-DR expression was observed, in contrast to the CO2 group. CONCLUSION: Carbon dioxide used for abdominal insufflation seems to limit the postoperative inflammatory response and to preserve parameters reflecting the immune status. These findings may be of importance in determining the preferred method of laparoscopy in oncologic surgery.     

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.     

Impact of laparoscopic gases on peritoneal microenvironment and essential parameters of cell function

Several experimental studies confirm the hypotheses that laparoscopic gases influence the development of tumor metastases [12, 14, 23]. The mechanism for this alteration of malignant tumor growth is still unknown. One reason might be an influence of the in sufflation gas on essential cell function regulating parameters. To investigate the changes of the intra- and extracellular milieu, four parameters—extra- and intracellular pH, intracellular free calcium levels, and tissue oxygen partial pressure—were measured during insufflation with carbon dioxide (CO2), helium (He), or a nonhypoxic gas mixture consistent of 80% CO2 and 20% O2. Study design (In vitro experiments) Intracellular calcium and pH levels were measured in DHD/K12/TRb colon adenocarcinoma cells using fluorescence imaging microscopy. (In vivo experiments) Tissue oxygen partial pressure was measured using a flexible micro catheter (Licox CMP) implanted in the abdominal wall of rats. After establishing the pneumoperitoneum an optical system and an aspirator were inserted to control the position of the micro catheter and to aspirate wound exudates for pH measurements of the wound fluid. Results: Creating of pneumoperitoneum with both CO2 and helium caused a decrease in partial pressure of oxygen in the abdominal wall to about 5 mm Hg whereas insufflation with a nonhypoxic gas mixture (80% CO2 and 20% O2) induced no significant changes. The intra- and extra cellular pH values dramatically decreased during CO2 insufflation (7.4 to 6.2) in vitro. Helium caused a pH increase up to 7.6. Free intracellular calcium was enhanced during CO2 insufflation, whereas helium insufflation did not cause any changes in [Ca2+]i. Nevertheless, a significant decrease of [Ca2+]i was observed during reoxygenation following helium-induced hypoxia. Conclusion: Our study demonstrates that insufflation with either CO2 or He causes significant changes of intra- and extracellular parameters regulating essential cell functions such as oxidative phosphorylation to produce ATP, cell proliferation, or onset of apoptosis.     

A 5-mm open-entry technique achieves safe, single-step, cosmetic laparoscopic entry.

BACKGROUND AND OBJECTIVE: The rare but serious complications of blind Veress needle insertion during laparoscopy include bowel and vascular injury. To reduce these risks, a novel method of open laparoscopy was introduced into our clinical practice, and its efficacy was evaluated. METHODS: This is a retrospective evaluation of a novel 5-mm-open laparoscopic technique in a university hospital-based endoscopy practice in 65 consecutive patients undergoing laparoscopy with a single surgeon. RESULT: A 71% success rate was achieved using the 5-mm open-entry laparoscopic technique. No complications occurred during any of the laparoscopic procedures, but 29% reverted to a standard 5-mm Veress needle technique. The success of the open-entry technique was independent of prior abdominal surgery, subject age, or body mass index (BMI). CONCLUSION: The 5-mm open-entry technique is safe, fast, and cosmetic. It is easily mastered and may be converted to a standard Veress needle technique if peritoneal entry is not achieved.     

Impact of pneumoperitoneum on expression of E-cadherin, CD44v6 and CD54 (ICAM-1) on HT-29 colon-carcinoma cells

INTRODUCTION: The mechanism of potential tumor cell spread and growth during laparoscopy is poorly understood. Nevertheless, different experimental studies reported a stimulation of tumor cell growth and an increased metastatic potential of carcinoma cells using carbon dioxide as an insufflation medium. Adhesion molecules do play an important and regulatory function in the process of metastatic spread and invasion of cancer cells. Therefore we investigated the influence of CO2 and Helium insufflation on the in-vitro expression of E-Cadherin, CD44v6 and CD54 (ICAM-1) on HT-29 colon carcinoma cells. METHODS: HT-29 carcinoma cells were exposed to either CO2 or helium insufflation. Expression of E-Cadherin, CD44v6 and CD54 (ICAM-1) on HT-29 colon carcinoma cells were measured 1, 12, 24, 48 and 96 h after CO2 and helium insufflation using flowcytometry (FACScan). Data were analyzed by Friedman-test. RESULTS: HT-29 cell line showed a short decrease in E-Cadherin expression after CO2 exposure while helium insufflation had no influence. In contrasts to these findings the expression of CD44v6 and CD54 on HT-29 cells were not influenced significantly by either CO2 or helium. CONCLUSION: CO2 seems only to have a minor influence on the expression of E-Cadherin while expression of other adhesion molecules did not change after CO2 incubation. The alternative gas helium did not cause any significant changes of the expression of either E-Cadherin, CD44v6 and CD54. Further investigations are needed to elucidate the changes of the metastatic potential of tumor cells after laparoscopic and open procedures.     

Helium vs carbon dioxide gas Insufflation with or without saline lavage during laparoscopy

BACKGROUND: Helium is an inert gas that, if used for insufflation during laparoscopy, may be followed by less postoperative pain than carbon dioxide (CO2) insufflation, due to a more limited effect on intraabdominal pH and metabolism. Saline lavage has also recently been shown to reduce postoperative pain following laparoscopic surgery. To evaluate these possibilities and to better define the clinical safety of helium insufflation, we undertook a prospective randomized trial comparing CO2 and helium insufflation with or without saline lavage in patients undergoing elective laparoscopic upper abdominal surgery. METHODS: From January to November 2000, 173 patients undergoing elective laparoscopic cholecystectomy or fundoplication were randomized to undergo laparoscopy with either CO2 or helium insufflation. Within each group, patients were further randomized to undergo peritoneal lavage with 2 L of 0.9% saline at the end of the surgical procedure. This yielded the following four patient groups; CO2 (group 1, n = 47), CO2 + saline lavage (group 2, n = 43), helium (group 3, n = 43) and helium + saline lavage (group 4, n = 40). Patients were blinded to their randomization, and post-operative assessment was also performed by a blinded investigator, who applied a standardized scoring system to assess postoperative pain. RESULTS: The study groups were well matched for age, sex, weight, American Society of Anesthesiologists (ASA) status, duration of surgery, and volume of gas utilized, and 81% of patients were discharged within 48 h. There were no differences in the incidence of postoperative complications among the study groups, and postoperative pain scores were not significantly different when all four groups were compared. When helium (groups 3 and 4) was compared with CO2 (groups 1 and 2), no differences in pain score were seen. When no lavage (groups 1 and 3) was compared with lavage (groups 2 and 4), less pain was found in the group undergoing saline peritoneal lavage (mean 4-h pain score, 5.9 vs 5.2; 24-h pain score, 4.8 vs 4.1; p > 0.05). CONCLUSIONS: The use of helium insufflation for laparoscopic surgery, while not associated with any significant adverse sequelae, was not associated with less postoperative pain in this trial. The use of saline peritoneal lavage was associated with less pain in the early postoperative period.     

Venous gas embolism — a comparison of carbon dioxide and helium in pigs

Purpose

The use of helium for insufflation during laparoscopic surgery avoids hypercarbia and acidosis associated with absorbed CO₂, but the effects of helium gas embolism are unknown. We compared the effects of CO₂ with He gas embolism on survival, haemodynamic variables, oxygenation, and ventilation in pigs.

Methods

Anaesthetized juvenile pigs were given progressively larger boluses of either CO₂ (n=5) or He (n=4) into the right atrium. Measurements of haemodynamic vanables, oxygenation, and P_ETCO₂ were made before and after each gas injection.

Results

All animals survived injections of 300 ml CO₂ while no animal survived more than 120 ml He (P < 0.01). Mean arterial pressure decreased more after 60 ml He (99 ±14 to 44 ±20 mmHg) than after 60 ml CO₂ (110 ±12 to 88 ±14 mmHg, P < 0.001). Cardiac output did not change at any injection volume. The P_ETCO₂ decreased more after 60 ml He (30 ±2 to 3 ±6 mmHg) than after 60 ml CO₂ (35 ±3 to 30 ±3 mmHg, P < 0.001). Only the He group showed a decrease in PaO₂ (190 ±51 to 68 ±22 mmHg at 60 ml, P < 0.05).

Conclusion

Helium gas embolism has a greater deleterious effect than CO₂ gas embolism on survival, MAR P_ETCO₂, and PaO₂. These different effects of gas embolism should be recognized when considering the use of helium or other insoluble gases for abdominal laparoscopic insufflation.     

Endoscopic endocrine neck surgery with carbon dioxide insufflation: the effect on intracranial pressure in a large animal model

BACKGROUND: Endoscopic endocrine neck surgery requires insufflation with carbon dioxide (CO(2)) at 10 to 15 mm Hg, which may decrease the cerebral venous return and increase intracranial pressure. This study evaluated the effect of CO(2) neck insufflation on intracranial pressure (ICP) and hemodynamic parameters. METHODS: Fifteen pigs underwent endoscopic thyroid dissection. Insufflation was performed with CO(2) at 0 (sham), 10, 15, and 20 mm Hg and with helium at 20 mm Hg with 3 pigs in each group. ICP, mean arterial pressure, central venous pressure (CVP), cardiac output, and blood gas were measured at baseline, 30, 60, and 120 minutes. RESULTS: There were no differences in mean ICP between the sham group and CO(2) insufflation at 10 mm Hg. Mean ICP increased significantly with CO(2) at 15 and 20 mm Hg and with helium at 20 mm Hg. A significant increase in CVP occurred in pigs operated with CO(2) at 20 mm Hg. We observed jugular vein collapse under all insufflation pressures; however, pigs operated at 10 mm Hg were able to maintain an intermittent blood flow. CONCLUSIONS: A severe increase in ICP occurs with insufflation pressures higher than 15 mm Hg, possibly as a result of decreased cervical venous blood flow. Carbon dioxide insufflation up to 10 mm Hg does not alter ICP and is recommended for clinical application in endoscopic neck surgery.     

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.     

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.