Peritoneal pH during laparoscopy is dependent on ambient gas environment: helium and nitrous oxide do not cause peritoneal acidosis

Underneath Images and Robots, Looking Deeper into the Pneumoperitoneum: A Narrative Review

Laparoscopy offers numerous advantages over open procedures, minimizing trauma, reducing pain, accelerating recovery, and shortening hospital stays. Despite other technical advancements, pneumoperitoneum insufflation has received little attention, barely evolving since its inception. We explore the impact of pneumoperitoneum on patient outcomes and advocate for a minimally invasive approach that prioritizes peritoneal homeostasis. The nonlinear relationship between intra-abdominal pressure (IAP) and intra-abdominal volume (IAV) is discussed, emphasizing IAP titration to balance physiological effects and surgical workspace. Maintaining IAP below 10 mmHg is generally recommended, but factors such as patient positioning and surgical complexity must be considered. The depth of neuromuscular blockade (NMB) is explored as another variable affecting laparoscopic conditions. While deep NMB appears favorable for surgical stillness, achieving a balance between IAP and NMB depth is crucial. Temperature and humidity management during pneumoperitoneum are crucial for patient safety and optical field quality. Despite the debate over the significance of temperature drop, humidification and the warming of insufflated gas offer benefits in peritoneal homeostasis and visual clarity. In conclusion, there is potential for a paradigm shift in pneumoperitoneum management, with dynamic IAP adjustments and careful control of insufflated gas temperature and humidity to preserve peritoneal homeostasis and improve patient outcomes in minimally invasive surgery.

The "Dark Side" of Pneumoperitoneum and Laparoscopy

Laparoscopic surgery has been one of the most common procedures for abdominal surgery at pediatric age during the last few decades as it has several advantages compared to laparotomy, such as shorter hospital stays, less pain, and better cosmetic results. However, it is associated with both local and systemic modifications. Recent evidence demonstrated that carbon dioxide pneumoperitoneum might be modulated in terms of pressure, duration, temperature, and humidity to mitigate and modulate these changes. The aim of this study is to review the current knowledge about animal and human models investigating pneumoperitoneum-related biological and histological impairment. In particular, pneumoperitoneum is associated with local and systemic inflammation, acidosis, oxidative stress, mesothelium lining abnormalities, and adhesion development. Animal studies reported that an increase in pressure and time and a decrease in humidity and temperature might enhance the rate of comorbidities. However, to date, few studies were conducted on humans; therefore, this research field should be further investigated to confirm in experimental models and humans how to improve laparoscopic procedures in the spirit of minimally invasive surgeries.

Luminal microbiota related to Crohn's disease recurrence after surgery

BACKGROUND

Microbial factors are likely to be involved in the recurrence of Crohn's disease (CD) after bowel resection. We investigated the luminal microbiota before and longitudinally after surgery, in relation to disease recurrence, using 16S metagenomic techniques.

METHODS

In the prospective Post-Operative Crohn's Endoscopic Recurrence (POCER) study, fecal samples were obtained before surgery and 6, 12, and 18 months after surgery from 130 CD patients. Endoscopy was undertaken to detect disease recurrence, defined as Rutgeerts score ≥i2, at 6 months in two-thirds of patients and all patients at 18 months after surgery. The V2 region of the 16S rRNA gene was sequenced using Illumina MiSeq. Cluster analysis was performed at family level, assessing microbiome community differences between patients with and without recurrence.

RESULTS

Six microbial cluster groups were identified. The cluster associated with maintenance of remission was enriched for the Lachnospiraceae family [adjusted OR 0.47 (0.27-0.82), P = .007]. The OTU diversity of Lachnospiraceae within this cluster was significantly greater than in all other clusters. The cluster enriched for Enterobacteriaceae was associated with an increased risk of disease recurrence [adjusted OR 6.35 (1.24-32.44), P = .026]. OTU diversity of Enterobacteriaceae within this cluster was significantly greater than in other clusters.

CONCLUSIONS

Luminal bacterial communities are associated with protection from, and the occurrence of, Crohn's disease recurrence after surgery. Recurrence may relate to a higher abundance of facultatively anaerobic pathobionts from the Enterobacteriaceae family. The ecologic change of depleted Lachnospiraceae, a genus of butyrate-producing bacteria, may permit expansion of Enterobacteriaceae through luminal environmental perturbation.

Effects of propofol on the inflammatory response during robot-assisted laparoscopic radical prostatectomy: a prospective randomized controlled study

Robot-assisted laparoscopic radical prostatectomy (RALRP) is a minimally invasive procedure; however, some amount of surgical trauma that can trigger systemic inflammation remains. Moreover, pneumoperitoneum during RALRP induces ischemia–reperfusion injury (IRI). Propofol, an anesthetic, is known to have anti-inflammatory and antioxidant properties. In the present study, we compared the effects of propofol with those of desflurane on inflammation and IRI during RALRP via measurements of different biomarkers and evaluation of perioperative renal function. Fifty patients were randomized to receive either desflurane (n = 25) or propofol (n = 25) with remifentanil during RALRP. Serum levels of interleukin (IL)-6 (IL-6), tumor necrosis factor alpha, C-reactive protein, and nitric oxide were measured 10 min after anesthesia induction (T1), 100 min after carbon dioxide (CO₂) insufflation (T2), and 10 min after CO₂ deflation (T3). Perioperative urine outputs and the serum creatinine level at 24 h after surgery were also recorded. We found that IL-6 levels at T2 and T3 were higher than those at T1 in both groups, although the increases were significant attenuated only in the propofol group. The other parameters showed no differences among the three time points in both groups. The intraoperative urine output was significantly higher in the propofol group than in the desflurane group, while the creatinine level showed no significant changes in either group. Our findings suggest that propofol can not only attenuate the inflammatory response during and after pneumoperitoneum in patients undergoing RALRP but also prevent oliguria during pneumoperitoneum.

Effect of pneumoperitoneum with warmed humidified or standard-temperature carbon dioxide during laparoscopy on core body temperature, cardiorespiratory and thromboelastography variables, systemic inflammation, peritoneal response, and signs of postoperative pain in healthy mature dogs

OBJECTIVE To evaluate effects of pneumoperitoneum created with warmed humidified CO₂ (WHCO₂) during laparoscopy on core body temperature, cardiorespiratory and thromboelastography variables, systemic inflammation, peritoneal response, and signs of postoperative pain in healthy mature dogs. ANIMALS 6 mature purpose-bred dogs. PROCEDURES In a randomized crossover study, each dog was anesthetized twice, and pneumoperitoneum was created with standard-temperature CO₂ (STCO₂; 22°C and 0% relative humidity) and WHCO₂ (37°C and 98% relative humidity). Data were collected during each procedure, including core body temperature, cardiorespiratory and thromboelastography variables, and inflammatory biomarkers. Peritoneal biopsy specimens were collected and evaluated with scanning electron microscopy. Dogs were assessed for signs of postoperative pain. RESULTS Mean core body temperature was significantly lower (35.2°C; 95% confidence interval, 34.5° to 35.8°C) with WHCO₂ than with STCO₂ (35.9°C; 95% confidence interval, 35.3° to 36.6°C) across all time points. Cardiac index increased during the procedure for both treatments but was not significantly different between treatments. Thromboelastography variables did not differ significantly between treatments as indicated by the coagulation index. Subjective evaluation of peritoneal biopsy specimens revealed mesothelial cell loss with STCO₂. There was no significant difference in circulating C-reactive protein or interleukin-6 concentrations. There was a significant increase in the number of postoperative pain scores > 0 for the WHCO₂ treatment versus the STCO₂ treatment. CONCLUSIONS AND CLINICAL RELEVANCE Analysis of these data suggested that effects on evaluated variables attributable to the use of WHCO₂ for creating pneumoperitoneum in healthy mature dogs undergoing laparoscopy did not differ from effects for the use of STCO₂.

Anesthesia for Endoscopy

Anesthesia for endoscopic surgery can be challenging depending on surgical manipulations and patient comorbidity. Anesthetists must understand the possible systemic changes and complications that are associated with endoscopic surgery. Pneumoperitoneum induces vasoconstriction, reduces cardiac output, and decreases functional residual capacity in the cardiopulmonary system. Both hypoventilation caused by the thoracoscopic procedure and CO2 insufflation increase Paco2. To prevent the problems associated with high Paco2, monitoring of end-tidal CO2 (ETco2) and capability of positive pressure ventilation are crucial. Sudden changes of ETco2 should be monitored closely. Endoscopic surgery should be a less invasive procedure; however, appropriate analgesia remains necessary.

Attenuation of Oxidative Stress by Ischemic Preconditioning in an Experimental Model of Intraabdominal Hypertension

PURPOSE

Increased intra-abdominal pressure, as used in laparoscopic surgery or seen in intraabdominal hypertension (IAH), is associated with tissue ischemia and oxidative stress. Ischemic preconditioning (IP) is a method successfully used in liver and transplant surgery, in order to attenuate the detrimental effects of ischemia and reperfusion. In this experimental study, we tested the ability of IP to modify oxidative stress induced by extremely high intraabdominal pressures.

METHODS

Twenty-five female pigs were studied and divided in three groups: a control group, a pneumoperitoneum group (with pressure of 30 mmHg), and an ischemic preconditioning group (initially subjected to preconditioning with pressure of 25 mmHg for 15 min and desufflation for 15 min and then to pneumoperitoneum as in pneumoperitoneum group). Blood samples were obtained at identical time intervals in the three groups. Total oxidative capacity, total antioxidative capacity and total nitric oxide (NO), nitrite and nitrate concentrations were measured and compared between groups.

RESULTS

IP increased total antioxidative capacity (p = .045) and protective mediators like nitrite (p = .022). It was also associated with a trend toward lower levels of total oxidative capacity at the end of the abdominal desufflation period but statistical significance was not met.

CONCLUSIONS

IP attenuated oxidative stress induced by IAH, mainly by increasing antioxidative capacity and the levels of protective mediators. The fact that IP was effective, even when used at extremely high levels of intraabdominal pressure, reinforces the interest on this method but further studies are needed to clarify its mechanism of action and potential clinical applications.

Warm, humidified carbon dioxide gas insufflation for laparoscopic appendicectomy in children: a double-blinded randomized controlled trial

OBJECTIVE

To investigate clinical benefits of warm, humidified carbon dioxide (CO(2)) insufflation for acute laparoscopic appendicectomy on postoperative pain and recovery in children (age 8-14 years).

BACKGROUND

Conventional CO(2) insufflation leads to desiccation-related peritoneal inflammation and injury, which is preventable with warm, humidified CO2 gas. We hypothesized that reduced peritoneal desiccation would improve patient-centered outcomes in children after laparoscopic appendicectomy.

METHOD

A double-blinded, randomized controlled trial was conducted. Intervention group participants received warm (37°C), humidified (98% relative humidity) CO(2) gas insufflation, whereas control participants received standard room temperature (20°C) gas with 0% relative humidity. Perioperative analgesia and anesthesia were standardized. Postoperative opiate usage was converted to morphine equivalent daily dosages (MEDD) for comparison, and pain intensity at rest and on moving was rated by participants using visual analog scales. Postoperative recovery and return to normal activities was assessed using a questionnaire on day 10.

RESULTS

Between February 2010 and March 2011, a total of 190 participants were randomized. Both intervention and control groups were matched at baseline. Postoperative MEDD and pain scores were also similar. There were no differences in postoperative recovery parameters.

CONCLUSIONS

Warm, humidified CO(2) insufflation for acute laparoscopic appendicectomy has no short-term clinical benefits on postoperative outcomes in pediatric patients (ClinicalTrials.gov trial identifying code: NCT01027455).

Optimizing working-space in laparoscopy: measuring the effect of mechanical bowel preparation in a porcine model

BACKGROUND

Adequate working space is a prerequisite for safe and efficient minimal access surgery. No objective data exist in literature about the effect of mechanical bowel preparation (MBP) on working space in laparoscopic surgery. We objectively measured this effect with computed tomography in a porcine laparoscopy model.

METHODS

Using standardized anesthesia, twelve 20-kg pigs without MBP and eight 20-kg pigs with MBP were studied with computed tomography at intra-abdominal pressure (IAP) levels of 0, 5, 10, and 15 mmHg. Volumes and dimensions of the pneumoperitoneum were measured on reconstructed CT images and compared between the pigs with and those without MBP.

RESULTS

A reproducible and statistically significant increase of approximately 500 ml in pneumoperitoneum volume was found in the MBP group at all levels of IAP. This represents a 43 % relative increase at a pneumoperitoneum pressure of 5 mmHg, 21 % at IAP 10 mmHg, and 18 % at IAP 15 mmHg. Peak inspiratory pressure was lower at IAP 0 and 5 mmHg in the MBP group. Anteroposterior diameter in the group with MBP was lower at 0 mmHg, but abdominal dimensions were similar in both groups at all other IAPs. This shows that the gain in working space is due to a diminished volume of the intra-abdominal content and not to compression or displacement of the bowel.

CONCLUSIONS

MBP increases working space by reducing bowel content. Especially at low intra-abdominal working pressures, the increase in working space associated with MBP could represent an important benefit in challenging laparoscopic surgery.

Oxidative stress in laparoscopic versus open abdominal surgery: a systematic review

BACKGROUND

Any form of trauma, including surgery, is known to result in oxidative stress. Increased intra-abdominal pressure during pneumoperitoneum and inflation-deflation may cause ischemia reperfusion and, hence, oxidative stress may be greater during laparoscopic surgery. The aim of this study was to systemically review the literature to compare oxidative stress in laparoscopic and open procedures.

METHODS

A systematic search of the Medline, Pub Med, EMBASE, and Cochrane databases was performed with the following keywords: pneumoperitoneum AND surger $ OR laparoscop $ AND oxida $. The search was limited to articles published between 1980 and August 2010.

RESULTS

The initial search identified 197 papers. After review of the abstracts, 17 papers met the inclusion criteria. Six more papers were identified through the reference lists. It was not possible to perform a meta-analysis due to heterogeneity of patient data, patient selection criteria, and diversity of biomarkers used. The majority of studies demonstrated greater immediate oxidative stress after open surgery. There was, however, a paucity of studies comparing open versus laparoscopic surgery with regards to tissue oxidative stress.

CONCLUSION

Laparoscopic surgery seems to produce less systemic oxidative stress. However the effect of pneumoperitoneum on local oxidative stress and tissue hypoxia and its clinical significance need further investigation.

A prospective case-control study of the local and systemic cytokine response after laparoscopic versus open colonic surgery

BACKGROUND

There is a sequential, high concentration cytokine response after major abdominal surgery. The magnitude of this response has been directly linked to postoperative metabolic derangement, ileus, adhesions, and oncological outcomes. We aimed to compare the local and systemic cytokine response in laparoscopic and open colonic surgery and relate this to postoperative recovery parameters.

METHODS

Using a prospectively collected patient database, we compared a Study Group (n = 50) of patients undergoing elective laparoscopic colonic resection with a Control Group (n = 25) of patients undergoing equivalent open colonic surgery within an ERAS program. Patients were matched for age, gender, BMI, ASA, Cr Possum, side of resection, diagnosis, and histologic stage. Plasma and peritoneal fluid concentrations of IL-6, IL-8, IL-10, and TNFα were measured at 20-24 h after surgery. The Surgical Recovery Score was determined pre-operatively and at 3, 7, 30, and 60 d postoperatively. All data were prospectively collected, and a priori definitions were used for discharge parameters, complications, and complication severity.

RESULTS

Peritoneal fluid IL-6 concentration was lower after laparoscopic surgery. There were no significant differences in the other cytokines measured, or in any postoperative recovery outcomes. Significant correlations were found between cytokine levels and discharge criteria achievement, day stay, postoperative complications, and the Surgical Recovery Score.

CONCLUSION

With the exception of a lower peritoneal IL-6 level, the systemic and peritoneal cytokine response at 20-24 h is similar after laparoscopic versus open colonic resection within an ERAS program, with corresponding equivalent rates of postoperative recovery.

Application of stereology to study the effects of pneumoperitoneum on peritoneum

BACKGROUND

Scanning electron microscopy is unable to provide sufficient data to obtain definitive results for research into the morphologic effect of pneumoperitoneum on peritoneum. To overcome this difficulty, we adopted stereology to examine the effect of the type of gas insufflated, pressure, duration, and gas flow on morphologic alterations of peritoneum.

METHODS

Fifty SD rats were divided into ten groups. One group served as control. Pneumoperitoneum was established at 5 mmHg and 1.0 l/min gas flow for 1, 2 or 3 h with CO2 (in groups C1h, C2h, and C3h, respectively) or with He (in groups H1h, H2h, and H3h, respectively). CO2 pneumoperitoneum was further established at 8 mmHg and 1.0 l/min gas flow for 1 h (group C8p), at 5 mmHg and 2.0 l/min gas flow for 1 h (group C2f), and at 5 mmHg and 3.0 l/min gas flow for 1 h (group C3f). After the procedures, five specimens were sampled from anterior peritoneum and measured by stereological and electron-microscopic techniques.

RESULTS

Groups H1h and C1h, H2h and C2h, and H3h and C3h, respectively, were the same in terms of area fraction of basal lamina exposed and diameter of mesothelial cells (P>0.05). The magnitudes of peritoneal trauma in groups C2h, C3h, C8p, C2f, and C3f were significantly higher than that in group C1h (P<0.01), and the same result was observed in groups H2h and H3h against group H1h (P<0.01), and in group C3f against group C2f (P<0.01). Furthermore, the area fractions of basal lamina exposed in groups C3h and H3h were remarkably higher than those in groups C2h and H2h, respectively (P<0.01). The mechanism of basal lamina exposure comprises mesothelial cell desquamation and plasmatorrhexis.

CONCLUSIONS

Peritoneal morphologic trauma during pneumoperitoneum can be attributed to the pressure, duration, and gas flow instead of the type of gas insufflated.

Systematic review of oxidative stress associated with pneumoperitoneum

Background

There have been several reports of ischaemic complications after routine laparoscopy. The aim of this review was to investigate the relationship between this oxidative stress and pneumoperitoneum.

Methods

Medline, Medline in-process, The Cochrane Library, PubMed and EMBASE were searched for papers on oxidative stress and pneumoperitoneum, from 1947 to March 2008 with no language restriction or restriction on trial design. Papers that did not investigate pneumoperitoneum as a causative factor, or did not report outcome measures related to oxidative stress, were excluded.

Results

A total of 73 relevant papers were identified: 36 animal studies, 21 human clinical trials, nine case reports, five review articles and two comments. Pneumoperitoneum causes a reduction in splanchnic blood flow, resulting in biochemical evidence of oxidative stress in a pressure- and time-dependent manner. There is evidence that the use of carbon dioxide for insufflation is contributory. Several measures proposed to minimize the oxidative stress have shown promise in animal studies, but few have been evaluated in the clinical setting.

Conclusion

There is an increasing body of evidence, mainly from animal studies, that pneumoperitoneum decreases splanchnic perfusion with resulting oxidative stress. It is now appropriate to investigate the clinical significance of pneumoperitoneum-associated oxidative stress.

Maternal and fetal near-term sheep cytokine responses to carbon dioxide pneumoperitoneum

It is known that carbon dioxide (CO2) pneumoperitoneum induces fetal acidosis in pregnant ewes. Our aim was to determine changes of the levels of maternal and fetal cytokines interleukin-6, interleukin-8, and tumor necrosis factor alpha after CO2 pneumoperitoneum in pregnant ewes. Eight ewes with singleton pregnancies of 120 to 140 days gestation were anesthetized and intubated. Insufflation produced modest but significant maternal arterial hypercapnia (an increase of 10.7 mm Hg; P<0.001) and acidosis (a decrease in mean pH of 0.1.04; P=0.0005). Fetal pCO2 was increased by 15.3 mm Hg on average and pH was decreased by 0.11 U on average immediately after desufflation (both P<0.001). No significant difference was observed in the concentration of cytokine in the maternal or fetal blood samples. These results suggest that respiratory acidosis does not lead to the elevation of cytokines in pregnant ewes and fetuses, which may contribute to premature labor.

Effects of adding small amounts of oxygen to a carbon dioxide-pneumoperitoneum of increasing pressure in rabbit ventilation models

OBJECTIVE

To evaluate the metabolic consequences of the addition of oxygen to the CO(2)-pneumoperitoneum.

DESIGN

Prospective randomized study in rabbits. After 30 minutes of ventilation pneumoperitoneum was maintained for 90 minutes with pure CO(2) or CO(2) with 2% or 6% of oxygen. The intraperitoneal pressure was increased from 10 to 15 and 20 mm Hg every 30 minutes. Ventilation rate was either fixed or a progressive hyperventilation. End points were changes in arterial blood gases (Pco(2), Po(2)), pH, acid-base balance (actual base excess [ABE], standard bicarbonate [SBC], standard base excess [SBE], hydrogen carbonate [HCO(3)(-)], concentration of total carbon dioxide [Tco(2)]); oxygen and oximetry (oxyhemoglobin [O(2)Hb], oxygen saturation [So(2)], reduced hemoglobin [RHb], total oxygen concentration [To(2)], and oxygen tension at half saturation assessing hemoglobin oxygen affinity [p50]); and lactate concentrations assayed every 15 minutes.

SETTING

University research center.

ANIMALS

Twenty-four adult female New Zealand white rabbits.

INTERVENTION(S)

Anesthesia, mechanical ventilation, and pneumoperitoneum.

RESULT(S)

The effects of CO(2)-pneumoperitoneum on all end points increased with the elevated intraperitoneal pressure and were more pronounced when ventilation was fixed. Changes were less when 2% or 6% of oxygen had been added to the CO(2)-pneumoperitoneum. With use of logistic regression, the addition of oxygen, intraperitoneal pressure, and ventilation were found to be independent variables affecting Pco(2), pH, ABE, SBE, HCO(3)(-), O(2)Hb, So(2), p50, and end-tidal CO(2).

CONCLUSION(S)

The metabolic consequences of the combined effect of increased intraperitoneal pressure and CO(2)-pneumoperitoneum were less when 2% to 6% of oxygen was added or when animals were hyperventilated. We suggest that metabolic and mesothelial hypoxemia caused by CO(2) absorption can be reduced by adding small amounts of oxygen and by hyperventilation.

Meta-analysis of the effect of warm humidified insufflation on pain after laparoscopy

Background

Studies on the use of warmed and humidified insufflation (WHI) in laparoscopic abdominal procedures to reduce pain have been inconclusive owing to small sample sizes.

Methods

An electronic database search identified all randomized controlled trials (RCTs) on adults undergoing elective laparoscopic abdominal surgery under general anaesthesia in which the exposure group had WHI and the control group had standard cold and dry carbon dioxide. The outcome measure was pain by visual analogue score or morphine usage.

Results

Seven RCTs were included. Patients in the WHI group experienced a significant reduction in pain score at 6 h (P = 0·006), 1 day (P = 0·010) and 3 days (P &lt; 0·001) after operation, and in morphine usage on day 2 (P = 0·040).

Conclusion

WHI reduces pain after laparoscopy.

Laparoscopic peritoneal dialysis catheter implantation using a Tenckhoff trocar under local anesthesia with nitrous oxide gas insufflation

BACKGROUND

Laparoscopic implantation of peritoneal dialysis catheters has many advantages over conventional methods. The ability to perform laparoscopy with the patient under local anesthesia allows renal failure patients, who ordinarily might not be considered candidates for general anesthesia, an opportunity to undergo this procedure.

METHODS

Using local anesthesia and nitrous oxide pneumoperitoneum, 175 catheters were implanted in long musculofascial tunnels under laparoscopic guidance to minimize the risk of catheter migration and flow dysfunction.

RESULTS

Nitrous oxide pneumoperitoneum was well tolerated, allowing all procedures to be safely completed with the patients under local anesthesia. The overall 1- and 2-year catheter survival rates were 92.7% and 91.3%, respectively. The incidence of catheter tip migration and omental entrapment was 1.7% and 2.9%, respectively. Temporary pericatheter leak occurred in 7.4% of cases.

CONCLUSIONS

Nitrous oxide insufflation enables safe performance of laparoscopic surgery with the patient under local anesthesia. Patients benefit from a minimally invasive technique with the assurance of obtaining successful long-term catheter function.

Effects of simulated carbon dioxide and helium peumoperitoneum on proliferation and apoptosis of gastric cancer cells

AIM

To investigate the effects of carbon dioxide (CO(2)) and helium insufflation administered at different pressures on the growth and apoptosis of cultured human gastric cancer cells.

METHODS

The gastric cancer cells MKN-45 were exposed to a CO(2) and helium environment maintained at different pressures (0, 5, 10 and 15 mmHg). The cells were exposed to simulated pneumoperitoneum environment for 4 h, and pH of the culture media was measured after it was moved to normal conditions for 0, 2, 4, 6 and 8 h. Proliferation viability of MKN-45 was examined by 3-[4,5Dimethylthiazol-2-yl],5-diphenyltetrazolium bromide or triazolyl blue (MTT) assay after it was moved to normal conditions. Apoptotic ratio was measured by Annexin V-FITC/PI double labelled staining.

RESULTS

The pH of media was acid and recovered to normal after 4 h in the CO(2) group while it was basic in the helium group. There was no difference between CO(2) groups (under 10 mmHg ) and control group (P > 0.05) in the proliferative viability of the cells. The cultured cells exposed to 15 mmHg CO(2) environment grew more slowly than control group from 4 to 7 d (P < 0.01 ) while there was no difference from 1 to 3 d (P > 0.05). The proliferative viability in helium group was not obviously different from the control group (P > 0.05). The apoptotic ratio of the cultured cells was markedly higher than that of the control group (P < 0.01) at 10 and 15 mmHg CO(2) insufflation pressure. In helium group, the apoptotic ratio was not obviously different from the control group (P > 0.05).

CONCLUSION

There is no obvious effect in the proliferation and apoptosis of MKN-45 cells under 10 mmHg CO(2) insufflation pressure and helium in any pressure. Fifteen mmHg CO(2) insufflation pressure can inhibit the proliferation of the cells and improve apoptosis.

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.

Peritoneal and systemic pH during pneumoperitoneum with CO2 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, CO(2), 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 CO(2) 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 CO(2), 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 CO(2) 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 CO(2) 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 CO(2) 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.

Acidification during carbon dioxide pneumoperitoneum is restricted to the gas-exposed peritoneal surface: effects of pressure, gas flow, and additional intraperitoneal fluids

BACKGROUND

There are varying data regarding the degree and extent of abdominal acidification during laparoscopy. The aim of this study was to determine the extent of peritoneal acidification during carbon dioxide insufflation and the effects of different pressures, insufflation rates, and free intraperitoneal fluids.

MATERIALS AND METHODS

Sixteen male Sprague-Dawley rats weighing 250-300 g were anesthetized and a two-point pH probe was inserted in the abdominal cavity. After closure of the abdominal wall, each group of 4 rats was subjected to one of four insufflation regimens: low pressure (2 mm Hg, no leakage); high pressure (10 mm Hg, no leakage); leakage (2 mm Hg, leakage 0.5 mL/min); and fluid (2 mm Hg, 10 mL intraperitoneal 0.9% NaCl). During insufflation peritoneal pH was continuously measured.

RESULTS

Carbon dioxide insufflation significantly decreased the peritoneal pH to <7.0 only in areas exposed to the insufflation gas. Neither changes in pressure nor insufflation rate had major effects on the peritoneal pH. The addition of 10 mL normal saline into the abdominal cavity significantly enhanced the pH change during insufflation. conclusion: Acidification associated with carbon dioxide pneumoperitoneum is limited to the area of inspection and manipulation. The increased acidification following injection of normal saline could offer a useful mechanism to alter the inflammatory response.

Prospective randomized trial of heated humidified versus cold dry carbon dioxide insufflation during laparoscopic gastric bypass

BACKGROUND

The replacement of cold dry carbon dioxide with heated humidified gas for insufflation during complex laparoscopic procedures has been reported to decrease hypothermia and peritoneal cell desiccation, with a resultant decrease in postoperative pain and narcotic use and a shortened recovery, but may prevent the paralysis of the peritoneal polymorphonuclear cell cytokine cascade and add to the cost of the procedure. We report our outcomes comparing carbon dioxide insufflation with different characteristics during laparoscopic gastric bypass.

METHODS

Fifty consecutive patients were randomized to undergo laparoscopic gastric bypass with either cold-dry or heated-humidified carbon dioxide insufflation. Statistical analysis of variance between groups was determined by Levine's t test with the Greenhouse-Geisser correction, at a significance level of P <.05.

RESULTS

The two groups were similar for preoperative gender, age, weight, body mass index, and baseline C-reactive protein. The intraoperative room and patient core temperature, liters of insufflation used, lens cleanings, operating time, recovery room time, and narcotics used were not significantly different. The postoperative subjective analog shoulder pain score was significantly less (P = .025) for the heated-humidified group at 18 hours, but not at 6, 12, 24, or 48 hours. The abdominal pain scores and overall narcotic use, postoperative C-reactive protein, and length of stay were not significantly different between the two groups.

CONCLUSION

Heated-humidified insufflation resulted in a transient reduction in subjective shoulder pain at 18 hours postoperatively, but no reduction in abdominal pain or narcotics used. We were unable to verify any clinically significant difference between the two groups comparing heated-humidified and cold-dry insufflation after laparoscopic gastric bypass.

Effect of acidosis on expression of mesothelial cell plasminogen activator inhibitor type-1

BACKGROUND

Abdominal mesothelial cells are exposed to carbon dioxide during laparoscopy. Previous data indicate that carbon dioxide increases release and expression of plasminogen activator inhibitor type-1 (PAI-1) and induces acidification.

METHODS

To assess the impact resulting from a range of pH, human mesothelial cells were exposed to culturing media balanced to pH levels of 6.0 to 8.0 for 90 min. Samples from cell media were withdrawn at several time points. Concentrations of PAI-1 and PAI-1 activity were measured using enzyme-linked immunoassay techniques. To focus on the effect of clinically relevant pH, cells were subjected to pH 6.4 and 7.4. Samples were withdrawn for PAI-1 assessments and for PAI-1 mRNA analyses.

RESULTS

During exposure to various levels of pH, PAI-1 secretion and activity were variable. However, 5 h after exposure, greater concentration and activity of PAI-1 were observed in acidified cultures. More PAI-1 mRNA was isolated after exposure of cells to a pH of 6.4, apparently indicating transcriptional regulation.

CONCLUSIONS

Mesothelial cells seem to respond to acidification by an increased release and production of PAI-1 in vitro.