Microsphere intestinal blood flow analysis during pneumoperitoneum using carbon dioxide and helium

Background Pneumoperitoneum has been associated with a decreased flow in the superior mesenteric artery and portal venous system. Intestinal blood flow was studied during a 2-h pneumoperitoneum with carbon dioxide (CO₂) or helium in a porcine model using colored microspheres.Methods For this study, 12 pigs were divided into two groups (6 CO₂ and 6 helium). Different colored microspheres were injected directly into the left ventricle before, 40, 80, and 120 min after insufflation with either gas at a pressure of 15 mmHg. Microsphere concentration was measured in the mucosa and muscularis/serosa layers of the jejunum, cecum, and sigmoid colon to calculate blood flow.Results Intestinal perfusion initially increases with insufflation and returns to near baseline levels during pneumoperitoneum of 2 h. The effect of helium on tissue perfusion is similar to that of carbon dioxide.Conclusions Intestinal perfusion does not change significantly during prolonged pneumoperitoneum at a pressure of 15 mmHg with CO₂ or helium.Podium presentation at the 2004 meeting of the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES), Denver, Colorado, USA, 31 March-3 April, 2004     

Effects of carbon dioxide vs helium pneumoperitoneum on hepatic blood flow

Background: Elevated intraabdominal pressure due to gas insufflation for laparoscopic surgery may result in regional blood flow changes. Impairments of hepatic, splanchnic, and renal blood flow during peritoneal insufflation have been reported. Therefore we set out to investigate the effects of peritoneal insufflation with helium (He) and carbon dioxide (CO₂) on hepatic blood flow in a porcine model. Methods: Twelve pigs were anesthetized and mechanically ventilated with a fixed tidal volume after the stabilization period. Peritoneal cavity was insufflated with CO₂ (n= 6) or He (n= 6) to a maximum intraabdominal pressure of 15 mmHg. Hemodynamic parameters, gas exchange, and oxygen content were studied at baseline, 90 mm and 150 min after pneumoperitoneum, and 30 min after desufflation. Determination of hepatic blood flow with indocyanine green was made at all measured points by a one-compartment method using hepatic vein catheterization. Results: A similar decrease in cardiac output was observed during insufflation with both gases. Hepatic vein oxygen content decreased with respect to the baseline during He pneumoperitoneum (p < 0.05), but it did not change during CO₂ insufflation. Hepatic blood flow was significantly reduced in both the He and CO₂ pneumoperitoneums at 90 min following insufflation (63% and 24% decrease with respect to the baseline; p < 0.001 and p < 0.05, respectively) being this decrease marker in the He group (p= 0.02). Conclusions: These findings suggest that helium intraperitoneal insufflation results in a greater impairment on hepatic blood flow than CO₂ insufflation. Received: 27 March 1996/Accepted: 19 January 1997     

Liver histology alterations during carbon dioxide pneumoperitoneum in a porcine model

Background This study aimed to investigate the time course changes in liver histology during carbon dioxide (CO₂) pneumoperitoneum in a large animal model. Methods For this study, 14 white pigs were anesthetized. Liver biopsies performed 0, 1, and 2 h after establishment of CO₂ pneumoperitoneum (at 12 mmHg) and after peritoneal desufflation were sent for histologic examination. Heart rate, mean blood pressure, hepatic artery flow, portal vein flow, and aortic flow were recorded in 10-min increments. Three animals served as control subjects. Results A statistically significant time course increase was observed in portal inflammation, intralobular inflammation, edema, sinusoidal dilation, sinusoidal hyperemia, centrilobular dilation, centrilobular hyperemia, pericentrilobular ischemia, and focal lytic necrosis scores. There were no significant changes in the control group. This eliminated an effect of anesthesia only. The portal vein flow increased as much as 21%, and the hepatic artery flow decreased as much as 31% of baseline, but these differences did not attain statistical significance. Aortic flow remained relatively stable. Conclusion Histomorphologic changes occurred, indicating liver tissue injury during CO₂ pneumoperitoneum at an intraabdominal pressure of 12 mmHg in the porcine model. Portal vein flow increased, and hepatic artery flow decreased, whereas aortic flow remained relatively unaffected in this experiment. Presented in part orally at the 10th World Congress of Endoscopic Surgery, Berlin, September 2006     

Hemodynamic and pulmonary changes during open, carbon dioxide pneumoperitoneum, and abdominal wall-lifting cholecystectomy

Background: Carbon dioxide (CO2) pneumoperitoneum effects are still controversial. The aim of this study was to investigate cardiopulmonary changes in patients subjected to different surgical procedures for cholecystectomy. Methods: In this study, 15 patients were assigned randomly to three groups according to the surgical procedure to be used: open cholecystectomy (OC), CO2 pneumoperitoneum cholecystectomy (PP), and laparoscopic gasless cholecystectomy (abdominal wall lifting [AWL]), respectively. A pulmonary artery catheter was used for hemodynamic monitoring in all patients. A subcutaneous multiplanar device (Laparo Tenser) was used for abdominal wall lifting. To avoid misinterpretation of results, conventional anesthesia was performed with all parameters, and the position of the patients held fixed thoroughout surgery. The following parameters were analyzed: mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), cardiac index (CI), stroke volume index (SVI), central venous pressure (CVP), systemic vascular resistances index (SVRI), mean pulmonary arterial pressure (MPAP), pulmonary capillary wedge pressure (PCWP), pulmonary vascular resistances index (PVRI), peak inspiratory pressure (PIP), end-tidal CO2 pressure (ETCO)2, CO2 arterial pressure (PaCO2), and arterial pH. Results: All the operations were completed successfully. The Laparo Tenser allowed good exposition of the surgical field. A slight impairment of the cardiopulmonary functions, with reduction of SVRI, MAP, and CI and elevation of pulmonary pressures and vascular resistance, followed induction of anesthesia. However, these effects tended to normalize in the OC and AWL groups over time. In contrast, CO2 insufflation produced a complex hemodynamic and pulmonary syndrome resulting in increased right- and left side filling pressures, significant cardiac index reduction, derangement of the respiratory mechanics, and respiratory acidosis. All of these effects normalized after desufflation. Conclusions: Cardiopulmonary adverse effects of general anesthesia were significant but transitory and normalized during surgery. Carbon dioxide pneumoperitoneum caused a significant impairment in cardiopulmonary functions. In high-risk patients, gasless laparoscopy may be preferred for reliability and absence of cardiopulmonary alterations. apd: 21 December 2000     

Hemodynamic effects of helium vs carbon dioxide pneumoperitoneum in an experimental model of acute heart failure

Background  The systemic absorption of carbon dioxide (CO₂) during abdominal insufflation can lead to hypercarbia and acidosis, which contribute to the systemic hemodynamic effects of the pneumoperitoneum (PnP). In several animal and clinical studies, the use of helium (He) as a substitute for CO₂ prevented the development of hypercarbia. One of the common comorbid conditions in which the use of a CO₂ PnP may cause adverse effects is heart failure. The aim of our study was to evaluate and compare the hemodynamic effects of CO₂ and He PnP in an animal model of acute heart failure (AHF). Methods  Hemodynamic and blood gas parameters were measured in 10 domestic pigs during two periods of He and CO₂ insufflation of 30 min duration each, with a 30-min stabilization period between insufflations. The model of AHF was created by sodium pentobarbital injections, and measurements were repeated with both CO₂ and He PnP. The animals were ventilated with constant minute ventilation. Results  Cardiac output had a tendency to decrease during PnP, but these changes were more pronounced with CO₂ PnP in normal the heart (from 2.84±0.65 to 2.18±0.68 L/min, p=0.06) and with He PnP during AHF (from 1.78 ±0.49 to 1.32±0.34 L/min, p=0.016). Systemic vascular resistance increased in every insufflation, but this elevation was not statistically significant. CO₂ and He insufflation caused significant increase of PaCO₂ in the nonfailed heart. During AHF, He insufflation did not elevate PaCO₂. Conclusions  In an experimental model of acute heart failure, insufflation with He did not have any advantage over CO₂. The hemodynamic response to CO₂ and He PnP during normal conditions and under conditions of failed cardiac function support the hypothesis that the hemodynamic response to PnP is a result of a combination of pressure and CO₂ absorption; Furthermore, it appears that increased intraabdominal pressure is the more crucial factor. Online publication: 7 May 2001 Presented in poster format at the annual meeting of the Society of American Gastrointestinal Endoscopic Surgeons (SAGES), San Antonio, TX, USA. 24–27 March 1999     

Hemodynamic changes in the inferior caval vein during pneumoperitoneum

Background: Laparoscopic procedures of increasing difficulty and duration are becoming more and more common. This may cause significant challenges to the circulatory system and possibly influence thrombogenicity. Methods: Experimental study of carbon dioxide pneumoperitoneum in pigs. Results: Inferior caval vein blood flow remained unchanged, whereas inferior caval vein pressure increased during pneumoperitoneum. Inferior caval vein, pulmonary, and systemic vascular resistance increased during pneumoperitoneum and remained increased after exsufflation. Conclusions: Pneumoperitoneum leads to an increased inferior caval vein pressure, which could cause a dilation of peripheral veins. The similar patterns of vascular resistance in the inferior caval vein, pulmonary artery, and systemic arteries (a gradual increase remaining elevated after exsufflation) suggest a common humoral factor or increased sympathetic nerve activity. Received: 2 April 1996/Accepted: 7 June 1996     

Inferior vena caval blood flow and cardiac hemodynamics during carbon dioxide pneumoperitoneum

Background: The effects of carbon dioxide pneumoperitoneum on venous return and cardiac hemodynamics during laparoscopic surgery were studied. Methods: Twelve adult pigs underwent placement of an electromagnetic flow meter across the infrarenal vena cava (IVC) as well as placement of Swan Ganz and arterial monitoring catheters. Measurements of the flow through infrarenal IVC, cardiac output (CO), pulmonary capillary wedge pressure (PCWP), mean arterial pressure (MAP), and heart rate were recorded at baseline, 5 and 60 min following insufflation to 15 mmHg with CO₂, and 5 min following desufflation. Stroke volumes and systemic vascular resistance (SVR) were calculated as well. Results: Flow through the IVC dropped by 24 and 31% at 5 and 60 min (p=0.03 and 0.02, respectively). Paradoxically, cardiac output rose by 14 and 28% at 5 and 60 min (p=0.03 at 60 min). Central venous and pulmonary capillary wedge pressures rose transiently by 35 and 36% at 5 min before returning to baseline (p<0.01). Mean arterial pressure and heart rate remained relatively constant during insufflation. Systemic vascular resistance diminished from 938 dynes/cm/s prior to insufflation to its nadir at 60 min of 650 dynes/cm/s (p<0.01). Conclusions: These observations suggest potentially complex interactions between the mechanical and systemic effects of the CO₂ pneumoperitoneum on venous return. Transient elevations in cardiac filling pressures occur by an unknown mechanism, and a generalized enhanced inotropic state mediated via increased sympathetic outflow is observed in this hypercapnic anesthetized animal model.Presented at the Society of American Endoscopic Gastrointestinal Surgeons, Nashville, Tennessee, April 19, 1994     

经食管超声心动图监测腹腔镜手术患者肾血流量的准确性

Objective To determine the accuracy of renal blood flow assessment by transesophageal echocardiography (TEE) during carbon dioxide (CO2) pneumoperitoneum.Methods The left renal arterial diameter (RAD) and the Doppler velocity time integral (VTI) were measured by TEE before peumoperitoneum (T0, baseline), at 1, 5, 10, 15, 20 and 30 min of pneumoperitoneum and 1 and 5 min after deflation in 35 patients undergoing elective laparoscopic cholecystectomy. The left renal blood flow (LRBF) and the left renal blood perfusion resistance (LRPR) were calculated according to the following formulae: LRBF = 1/4π x RAD2 x VTI x HR, LRPR = MAP/LRBF.Three months later, the TEE images of 10 cases were randomly selected and reviewed by the same and another research team member to check the repeatability and consistency of the LRBF determination during operation, respectively. The quality of the TEE images was evaluated by another specialist.Results Before pneumoperitoneum, 94% of the TEE images were rated as satisfactory. There was no significant difference between the qualities of the TEE images obtained before and during pneumoperitoneum. The variabilities between the RADs measured by TEE during and 3 months after operation were 9.28% by the same team member and 8.71% by another team member. The variabilities between the VTIs measured by TEE during and 3 months after operation were 5.61% by the same team member and 6.25% by another team member. The linear regression analysis of the LRBF showed that the slope and the intercept were 1.05 and 31.4 ml/min respectively by the same member and 0.92 and 47.3 ml/min respectively by another member. The LRBF was decreased during pneumoperitoneum and the LRPR was increased.Conclusion TEE can be used to accurately monitor the changes in renal blood flow during CO2 pneumoperitoneum.     

腹腔镜胆囊切除术中二氧化碳气腹对脑血流的影响

目的 观察腹腔镜期间二氧化碳气腹对患者脑血流的影响。方法 选择行腹腔镜胆囊切除术患者３０例,ＡＳＡⅠ～Ⅱ级、于气腹前、气腹后１０、３０ｍｉｎ分别采取桡动脉血管颈内静脉血,测定ＰａＯ２、ＰａＣＯ２、ＳａＯ３、颈内静脉血氧分压（ＰｉｖＯ２）和血氧和度（ＳｕｖＯ２）等值。结果与气腹前比较,气腹后１０ｍｉｎ、３０ｍｉｎ的ＳｕｖＯ２、颈内静脉血氧含量（ＣｕｖＯ２）和ＰａＣＯ２无显著性增加（Ｐ〈０．０１）,脑     

腹膜后腹腔镜手术中二氧化碳气腹对糖尿病患者脑血流的影响

目的采用经颅多普勒超声(TCD)对患者术中脑血流进行无创动态监测,观察腹膜后腹腔镜人工CO2气腹对糖尿病患者脑血流的影响。方法选择择期行腹膜后腹腔镜肾囊肿去顶术2型糖尿病患者20例,记录气腹前(T1)、气腹后10 min(T2)、30 min(T3)、60 min(T4)和停气腹后20min(T5)的平均脑血流速度(Vm)和搏动指数(PI)[PI=(Vs-Vd)/Vm]。结果T3与T4时颈内动脉颅内段(ICA)、大脑中动脉(MCA)和基底动脉(BA)的Vm比T1时明显增加(P<0.05),T2～T4时ICA、MCA、BA的PI值比T1时明显升高(P<0.05)。结论2型糖尿病患者在行腹膜后腹腔镜手术时,气腹持续时间超过30 min就会对脑血流产生影响。     

腹腔镜下妇科肿瘤切除术中二氧化碳气腹对患者脑血流的影响

目的 观察妇科肿瘤患者腹腔镜手术期间二氧化碳(CO2)气腹对患者脑血流的影响.方法 选择妇科肿瘤行腹腔镜手术的患者40例,美国麻醉医师协会(ASA)分级Ⅰ～Ⅱ级,无心、脑系统疾病,于气腹前、气腹后头低臀高位20 min分别采取桡动脉和颈内静脉血,测定动脉血氧分压(PaO2)、动脉血二氧化碳分压(PaCO2)、动脉血氧饱和度(SaO2)、颈内静脉血氧分压(PjvO2)和颈内静脉血氧饱和度(SjvO2)等值.结果 气腹前SjvO2为(66±7)％,气腹后20min的SjvO2为(84±6)％,颈内静脉血氧含量(CjvO2)气腹前为(9.4±1.6)％,气腹后20 min为(11.6±1.8)％,PaCO2气腹前为(4.2±0.4) kPa,气腹后20 min为(5.3±0.4) kPa,均显著增加(P＜0.01),脑动静脉血氧含量差(Ca-jvDO2)气腹前为(5.1±1.2)％,气腹后为(2.4±0.9)％,显著减少(P＜0.01).结论 妇科肿瘤患者腹腔镜手术期间,CO2气腹对脑循环产生显著影响,脑血流(CBF)显著增加,Ca-jvDO2明显减少.这种变化提示可能存在脑细胞缺氧.     

Effect of increasing cardiac preload,sympathetic antagonism,or vasodilation on visceral blood flow during pneumoperitoneum

Background and aims An impaired visceral perfusion caused by pneumoperitoneum may contribute to morbidity after laparoscopic surgery. The following three therapeutic concepts: increasing cardiac preload, controlled vasodilation, or selective sympathetic antagonism, were evaluated regarding a possible increase of visceral blood flow during pneumoperitoneum with carbon dioxide.Methods Forty three pigs were assigned to treatment with an increase of preload and vasodilation (group A) or selective sympathetic antagonism with esmolol (group B). In both groups, pigs were assigned to head-up, head-down, or supine position. Perfusion of the vena porta and renal artery was measured by transonic volume flow meters and documented before capnoperitoneum, after induction of a 14-mmHg capnoperitoneum in each body position, after controlled vasodilation with sodium nitroprusside, and after controlled increase of intravascular volume by colloidal infusion.Results Increasing intravascular volume improved portal blood flow in all body positions (p<0.05), but not renal blood flow. Medication of esmolol did not alter the measured parameters in any body position compared to control. Vasodilation with sodium nitroprusside reduced renal blood flow in supine and in head-up position.Conclusion An optimal intravascular volume was most effective in improving portal blood flow during capnoperitoneum in this trial. Esmolol had no negative effects on portal and renal blood flow. Patients with renal dysfunction might be treated carefully with sodium nitroprusside during capnoperitoneum.     

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

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

Haemodynamic, acid-base and blood volume changes during prolonged low pressure pneumoperitoneum in rabbits

Background. The anaesthetic management of small infants duringadvanced laparoscopic surgery can be complicated by the majorpathophysiological effects of increased intra-abdominal pressure.In this study haemodynamic, acid–base and blood volumechanges were investigated during pneumoperitoneum in a smallanimal model. Methods. Ten fasted, anaesthetized, mechanically ventilatedand multi-catheterized New Zealand rabbits were randomized tocarbon dioxide pneumoperitoneum (PP, duration 210 min, pressure8 mm Hg) or control group. Cardiac index was determined usingtrans-cardiopulmonary thermodilution and total blood volumewas measured by thermal-dye dilution with indocyanine greenusing a fibreoptic monitor system. Results. In PP cardiac index (CI), central venous oxygen saturation(SCV_O2), total blood volume (TBV) and base excess (BE) decreasedsignificantly during the study whereas all variables remainedconstant in the control group. After release of PP the measuredvariables did not return to baseline within 30 min [PP, baselinevs study end: CI 108 (22) vs 85 (14) ml kg^–1 min^–1,SCV_O2 81.4 (8.9) vs 56.7 (9.8)%, TBV 318 (69) vs 181 (54) ml,BE –1.9 (2.7) vs –8.7 (1.8) mmol litre^–1;P<0.01]. Conclusion. Our animal model suggests that a decrease in CI,metabolic acidosis and hypovolaemia could occur after prolongedlow pressure pneumoperitoneum in small infants, which is possiblynot detectable by the standard monitor setting. Therefore, theroutine use of an extended monitoring including measurementof central venous oxygen saturation and acid–base parametersshould be considered during and soon after operation, when pneumoperitoneumwill last longer than 2 h.     

Insufflation profile and body position influence portal venous blood flow during pneumoperitoneum

Background: We investigated changes in portal venous blood flow (PVBF) during carbon dioxide (CO₂) pneumoperitoneum to evaluate the effects of different insufflation profiles and body positions. Methods: An established rat model was extended by implanting a portal vein flow probe that would enable us to measure PVBF for 60 min [t₀–t₆₀] in animals subjected to a CO₂ pneumoperitoneum with an intraabdominal pressure (IAP) of 9 mmHg. Forty-eight male Sprague-Dawley rats were randomized into the following four experimental and two control groups: decompression group D1 (n = 8), desufflation for 1 min every 14 min; decompression group D2 (n = 8), desufflation for 5 min, after 27 min; position group P1 (n = 8), 35° head-up position; position group P2 (n = 8), 35° head-down position; negative control group C1 (n = 8), no insufflation; positive control group C2 (n = 8), constant IAP of 9 mmHg for 60 min. Results: Pneumoperitoneum and body positions, respectively, reduced PVBF [t₁–t₆₀] significantly (p < 0.001) by 32.0% C2, 32.8% D1, 31.1% D2, 40.8% P1, and 48.5% P2, as compared to PVBF at t₀ in each group. There was a significant difference in PVBF reduction between P1 and P2 and also between C2 and both P1 and P2 (p < 0.04). Conclusions: CO₂ pneumoperitoneum reduces PVBF significantly (>30%). Extreme body positions (35° tilt) significantly intensify PVBF reduction. PVBF reduction is significantly more dramatic in subjects placed in a 35° head-down position. Short desufflation periods did not improve mean PVBF, but it may have beneficial immunological and oncological effects that warrant further investigation. Presented at the annual meeting of the European Association for Endoscopic Surgery (EAES), Lisbon, Portugal, 2002.     

Alterations in hemodynamics and left ventricular contractility during carbon dioxide pneumoperitoneum

Background: Carbon dioxide (CO₂) pneumoperitoneum has been shown to adversely affect hemodynamics in patients. This study specifically examines the potential contribution of altered left ventricular contractility (LVC) to hemodynamic changes observed during CO₂ pneumoperitoneum. Methods: In a canine model, LV volumes, LV pressure, and intrathoracic and central venous pressures were recorded both at basal intra-abdominal pressure (IAP) and after CO₂ insufflation to produce IAPs of 5–25 mmHg. Results: At IAPs greater than 15 mmHg, cardiac output and LV end-diastolic volume decreased. Mean arterial pressure and heart rate were unchanged. LVC, quantified using the linear Frank-Starling relationship, was not affected by increases in IAP. Conclusions: This study is the first to quantify LVC during CO₂ pneumoperitoneum and demonstrates no changes in contractility over IAPs from 5 to 25 mmHg. In the dog model, any hemodynamic alterations induced by CO₂ pneumoperitoneum are secondary to altered LV preload and not alterations in contractility or LV afterload. Received: 8 March 1996/Accepted: 23 April 1996     

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

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

Hemodynamic and tissue blood flow responses to long-term pneumoperitoneum and hypercapnia in the pig

Background Increased peritoneal blood flow may influence the ability of cancer cells to adhere to and survive on the peritoneal surface during and after laparoscopic cancer surgery. Carbon dioxide (CO₂) pneumoperitoneum is associated with a marked blood flow increase in the peritoneum. However, it is not clear whether the vasodilatory effect in the peritoneum is related to a local or systemic effect of CO_2. Methods In this study, 21 pigs were exposed to pneumoperitoneum produced with either CO₂ (n = 7) or helium (He) (n = 7) insufflation at 10 mmHg for 4 h, or to two consecutive levels of hypercapnia (7 and 11 kPa) (n = 7) produced by the addition of CO₂ to the inhalational gas mixture. Tissue blood flow measurements were performed using the colored microsphere technique. Results Blood flow in peritoneal tissue increased during CO₂, but not He, pneumoperitoneum, whereas it did not change at any level of hypercapnia alone. There was no change in blood flow in most organs at the partial pressure of CO₂ (PaCO₂) level of 7 kPa. However, at a PaCO₂ of 11 kPa, blood flow was increased in the central nervous system, myocardium, and some gastrointestinal organs. The blood flow decreased markedly in all striated muscular tissues during both levels of hypercapnia. Conclusion The effect of CO₂ on peritoneal blood flow during laparoscopic surgery is a local effect, and not attributable to central hemodynamic effects of CO₂ pneumoperitoneum or high systemic levels of CO₂.     

Effect of carbon dioxide pneumoperitoneum on tissue blood flow in the peritoneum,rectus abdominis,and diaphragm muscles

Background: Changes in local blood flow may play a role in the pathogenesis of port-site metastasis. This study aimed to investigate the effect of pneumoperitoneum induced by carbon dioxide (CO₂) on the blood flow in the peritoneum and abdominal wall muscle layers, which are target structures for this phenomenon. Methods: The study was performed on domestic farm swine of both genders weighing 20 to 25 kg. Intraabdominal pressures (IAP) of 0, 5, and 10 mmHg were produced by either CO₂ (n = 9) or helium (He) (n = 6) insufflations. The colored microsphere technique was used to measure blood flow distributions in the parietal peritoneum, rectus abdominis, and diaphragm muscles. Results: Insufflation of CO₂ was associated with a threefold increase in blood flow of the parietal peritoneum at both 5 and 10 mmHg IAP (p < 0.001 for both pressure levels). In contrast, insufflation of He caused a significant decrease in blood flow in the parietal peritoneum at both 5 and 10 mmHg (p < 0.05). In the rectus abdominis and diaphragm muscles, blood flow remained unchanged after insufflation of CO₂ at both 5 and 10 mmHg IAP. However, after insufflation of He, there was a substantial decrease in blood flow both in the rectus abdominis and diaphragm muscles at both 5 mmHg (p < 0.01 and p < 0.05, respectively) and 10mmHg (p < 0.001 and p < 0.01, respectively). Conclusions: Despite high intraabdominal pressure, tissues surrounding the abdominal cavity, particularly the peritoneum, respond to insufflation of CO₂ with increased blood flow, which may favor the growth of tumor cells.