Time-related changes in hemodynamic parameters and pressure-derived indices of left ventricular function in a porcine model of prolonged pneumoperitoneum

Background: Advanced laparoscopic procedures require prolonged pneumoperitoneum. Increased intra-abdominal pressure causes a number of hemodynamic changes including a drop in cardiac output, but it is unclear whether there is a direct effect on cardiac contractility. In this experimental study, we sought to determine whether there is a direct impact of pneumoperitoneum on cardiac contractility. We also examined the time-related changes taking place during the insufflation period. Methods: Six young pigs were anesthetized and mechanically ventilated. Pneumoperitoneum was established by insufflating carbon dioxide to a pressure of 15 mmHg and maintained for a period of 180 min. Hemodynamic parameters including left ventricular dP/dT were invasively recorded every 15 min. All hemodynamic changes were statistically evaluated, and parameters were correlated with time. Results: Cardiac output decreased with insufflation from a baseline of 3.37 ± 0.34 lt/min and reached the lowest value at 165 min of pneumoperitoneum (2.86 ± 0.30 l/min; p= 0.023). Systemic vascular resistance (SVR) significantly increased from 2236 ± 227 dyne/s/cm⁵ to a maximum of 3774 ± 324 dyne/s/cm⁵ (p= 0.005). Left ventricular dP/dT maximum did not change significantly with insufflation. The decrease in cardiac output strongly correlated with the increase in SVR (r=−0.949). Time of insufflation correlated with cardiac output (r=−0.762) and dP/dT maximum (r=−0.727). Conclusions: Pneumoperitoneum at 15 mmHg negatively affects cardiac output without significantly affecting cardiac contractility. A significant increase in SVR appears to be the driving event for the decreased cardiac output. Prolonged pneumoperitoneum may have an additional negative effect on hemodynamic parameters. Received: 5 January 2000/Accepted: 4 May 2000/Online publication: 26 July 2000     

Intracranial pressure

Background: The effects of pneumoperitoneum on intracranial pressure (ICP) have received relatively little attention. This study was undertaken to investigate the changes in ICP occurring as a result of increased intraabdominal pressure (IAP) and positioning in animals with normal and elevated ICP. Method: Five pigs (average weight 60 lb) were studied. A subarachnoid screw was placed for ICP monitoring. End tidal CO₂ was monitored. Ventilation was performed to keep PCO₂ between 30 and 50 mmHg. Measurements of arterial blood gases, mean arterial blood pressure, and ICP were recorded at four different levels of intraabdominal pressure (IAP 0, 8, 16, and 24 mmHg), both in the supine and Trendelenburg positions. A Foley catheter was introduced into the subarachnoid space to elevate the intracranial pressure, and the same measurements were performed. Results: There was a significant and linear increase in ICP with increased IAP and Trendelenburg position. The combination of increased IAP of 16 mmHg and Trendelenburg position increased ICP 150% over control levels. Conclusions: Patient positioning and level of IAP should be taken into consideration when performing laparoscopy on patients with head trauma, cerebral aneurysms, and other conditions associated with increased ICP. Received: 19 March 1996/Accepted: 24 May 1996     

Hemodynamic consequences of high- and low-pressure capnoperitoneum during laparoscopic cholecystectomy

Background: Peritoneal insufflation to 15 mmHg diminishes venous return and reduces cardiac output. Such changes may be dangerous in patients with a poor cardiac reserve. The aim of this study was to investigate the hemodynamic effects of high (15 mmHg) and low (7 mmHg) intraabdominal pressure during laparoscopic cholestectomy (LC) Methods: Twenty patients were randomized to either high- or low-pressure capnoperitoneum. Anesthesia was standardized, and the end-tidal CO₂ was maintained at 4.5 kPa. Arterial blood pressure was measured invasively. Heart rate, stroke volume, and cardiac output were measured by transesophageal doppler. Results: There were 10 patients in each group. In the high-pressure group, heart rate (HR) and mean arterial blood pressure (MABP) increased during insufflation. Stroke volume (SV) and cardiac output were depressed by a maximum of 26% and 28% (SV 0.1 > p > 0.05, cardiac output p > 0.1). In the low-pressure group, insufflation produced a rise in MABP and a peak rise in both stroke volume and cardiac output of 10% and 28%, respectively (p < 0.05). Conclusions: Low-pressure pneumoperitoneum is feasible for LC and minimizes the adverse hemodynamic effects of peritoneal insufflation. Received: 23 May 1997/Accepted: 11 March 1998     

Prolonged pneumoperitoneum at 15 mmHg causes lactic acidosis

Background: Acute increases in intraabdominal pressure (IAP) induce systemic and regional circulatory changes. Besides, mechanical compression on the capillary beds may decrease oxygen availability to the tissues. The purpose of this clinical study was to analyze the effects of increased IAP on acid-base disturbances and plasma lactate levels during prolonged carbon dioxide pneumoperitoneum. Methods: Twenty-eight patients undergoing laparoscopic sigmoidectomy were included in this study. Fourteen of them (group A) had IAP of 15 ± 1 mmHg while the remaining 14 (group B) had IAP of 10 ± 1 mmHg. The control group included six patients undergoing conventional sigmoidectomy. Results: A progressive significant increase in PaCO₂ was observed in the laparoscopic groups (p < 0.01). Plasma lactate levels in group A significantly increased 90 min after insufflation (p < 0.05) and reached the highest value 1 h after deflation (9.9 ± 1 vs 31.9 ± 2.5 mg/dl, p < 0.005). Simultaneously, arterial pH decreased in all groups; however, at 1 h after surgery, it was significantly lower (p= 0.02) in group A. There was a significant correlation between acid concentration due to lactate and lactate concentration (GA: R ²= 0.717, p= 0.03; GB: R ²= 0.879, p= 0.006 and GC: R ²= 0.853, p= 0.008). Conclusion: High IAP causes lactic acidic accumulation in patients undergoing prolonged laparoscopic procedures. Received: 1 April 1996/Accepted: 19 November 1996     

The adverse hemodynamic effects of anesthesia, head-up tilt, and carbon dioxide pneumoperitoneum during laparoscopic cholecystectomy

Background: The increased intra-abdominal pressure during pneumoperitoneum, together with the head-up tilt used in upper abdominal laparoscopies, would be expected to decrease venous return to the heart. The goal of our study was to determine whether laparoscopy impairs cardiac performance when preventive measures to improve venous return are taken, and to analyze the effects of positioning, anesthesia, and increased intra-abdominal pressure. Methods: Using invasive monitoring, hemodynamic changes were investigated in 15 ASA class I or II patients under isoflurane–fentanyl anesthesia during laparoscopic cholecystectomy. Before laparoscopy, the patients received an intravenous (IV) infusion of colloid solution if cardiac filling pressures were low, and their legs were wrapped from toes to groin with elastic bandages. Measurements were taken while the patients were awake in the supine (baseline) and head-up tilt (15–20°) positions, and after the induction of anesthesia in the same positions. Measurements were repeated at regular intervals during laparoscopy (intra-abdominal pressure at 13–16 mmHg), after deflation of the gas, and in the recovery room. Results: With the passive head-up tilt in awake and anesthetized patients, the cardiac index (CI), stroke index (SI), central venous pressure (CVP), and pulmonary capillary wedge pressure (PCWP) decreased, and systemic vascular resistance increased. With the patient under anesthesia, SI decreased, but CI did not change significantly as a result of the compensatory increase in heart rate. Carbon dioxide (CO₂) insufflation at the start of laparoscopy produced increases in CVP and PCWP as well as mean systemic and mean pulmonary arterial pressures without changes in CI or SI. Toward the end of the laparoscopy, CI decreased by 15%. The hemodynamic values returned to nearly prelaparoscopic levels after deflation of the gas, and CI was elevated during the recovery period, whereas systemic vascular resistance was decreased in comparison with the baseline. Conclusions: By correcting relative dehydration and preventing the pooling of blood, CI decreased less than 20% during pneumoperitoneum as compared with the baseline awake level. The head-up positioning accounts for many of the adverse effects in hemodynamics during laparoscopic cholecystectomy. Received: 6 November 1998/Accepted: 8 July 1999     

Laparoscopic insufflation of the abdomen reduces portal venous flow

Background: The adverse effects of sustained elevated intraperitoneal pressure (IPP) on cardiovascular, pulmonary and renal systems have been well documented by several reported experimental and clinical studies. Alteration in the splanchnic circulation has also been reported in animal experiments, but details of the exact hemodynamic changes in the flow to solid intraabdominal organs brought on by a raised intraperitoneal pressure in the human are not available. The aim of the present study was to estimate effect of increased IPP on the portal venous flow, using duplex Doppler ultrasonography in patients undergoing laparoscopic cholecystectomy. Methods: The studies were performed using the SSD 2000 Multiview Ultrasound Scanner and the UST 5536 7.0-MHz laparoscopic transducer probe. Details of the measurements were standardized in according to preset protocol. Statistical evaluation of the data was conducted by the two-way analysis of variance (ANOVA). Results: The flow measurement data have demonstrated a significant (p < 0.001) decrease in the portal flow with increase in the intraperitoneal pressure. The mean portal flow fell from 990 ± 100 ml/min to 568 ± 81 ml/min (−37%) at an IPP of 7.0 mmHg and to 440 ± 56 mmHg (−53%) when the IPP reached 14 mmHg. Conclusions: The increased intraperitoneal pressure necessary to perform laparoscopic operations reduces substantially the portal venous flow. The extent of the volume flow reduction is related to the level of intraperitoneal pressure. This reduction of flow may depress the hepatic reticular endothelial function (possibly enhancing tumor cell spread). In contrast, the reduced portal flow may enhance cryo-ablative effect during laparoscopic cryosurgery for metastatic liver disease by diminishing the heat sink effect. These findings suggest the need for a selective policy, low pressure or gas-less techniques to positive-pressure interventions, during laparoscopic surgery in accordance with the disease and the therapeutic intent. Received: 19 March 1996/Accepted: 4 July 1997     

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     

The influence of different insufflation pressures during carbon dioxide pneumoperitoneum on the development of pulmonary metastasis in a mouse model

Background: The effects of different insufflation pressures on the development of pulmonary metastasis was investigated in a mouse laparoscopy model. Methods: BALB/C mice intravenously inoculated with colon 26 cells were randomized to one of five treatment groups (10 mice per group): pneumoperitoneum at different pressures of 5, 10 or 15 mmHg; full laparotomy for 60 min; or anesthesia control. Cancer nodules on the lung surface 19 days postoperatively were compared between groups. Results: (a) As compared with the control group, pneumoperitoneum at 10 and 15 mmHg and laparotomy enhanced the growth of pulmonary metastases (p < 0.01). (b) The growth of metastases also was greater in laparotomy group mice than in mice undergoing pneumoperitoneum at 5 and 10 mmHg (p < 0.05). Conclusions: These results suggest that the effects of different insufflation pressures on the growth of pulmonary metastases are not identical, and that pneumoperitoneum with high pressure may promote pulmonary metastases similar to those with laparotomy. Received: 4 November 1999/Accepted: 20 December 1999/Online publication: 25 April 2000     

Intermittent pneumatic sequential compression (ISC) of the lower extremities prevents venous stasis during laparoscopic cholecystectomy

Background: Fifty patients were included in a prospective randomized trial to evaluate the efficacy of intermittent sequential compression (ISC) of the lower extremities in preventing venous stasis during laparoscopic cholecystectomy. Methods: We treated 25 patients with (+ISC) and 25 without (–ISC) intermittent sequential compression. Peak flow velocity (PFV) and cross-sectional area (CSA) of the right femoral vein were measured by Doppler ultrasound before, during, and after capnopneumoperitoneum with 14 mm Hg. Results: PFV was 26.4 (8.4) cm/s and CSA was 1.03 (0.23) cm² before pneumoperitoneum was induced. During abdominal insufflation, PFV decreased to 61% of the baseline value in the (–ISC) group but remained unchanged in the (+ISC) group (t = 5.17, df = 42.8, p < 0.01). CSA was 1.06 (0.22) cm² before insufflation. It increased to 118% of the baseline in the (–ISC) group and to 108% in the (+ISC) group (t =–1.55, df = 47.1, p= 0.13). PFV and CSA returned to baseline values within 5 min after abdominal desufflation. Conclusions: ISC effectively neutralizes venous stasis during laparoscopic surgery and may decrease the risk of postoperative thromboembolic complication. Therefore, it is recommended for all prolonged laparoscopic procedures. Received: 10 April 1996/Accepted: 24 April 1997     

Pneumoperitoneum risk prognosis and correction of venous circulation disturbances in laparoscopic surgery

Background: This study was initiated to find a method of determining the prognosis for possible changes in hemodynamic and respiratory parameters in patients with pneumoperitoneum (PP). Methods: We devised a model for a pseudopneumoperitoneum (PPP), which is created by encircling the wide pneumochamber on the entire abdomen and inflating it to a preset pressure. To verify the prognostic possibilities of the proposed model, we studied the pneumotachygraphy parameters, noninvasive and invasive monitoring parameters of PPP after induction of anaesthesia, and venous circulation disturbances, as well as the medical effect of the intermittent sequential compression device. Results: In healthy patients, the restrictive lung syndrome did not approach the risky limit. In patients ≥60 years old, this syndrome was very close to the limit. In a number of patients with serious cardiovascular and pulmonary pathology, the pressure of >10 mmHg was considered to be intolerable. Lung compliance, which was the parameter most sensitive to the increased intraabdominal pressure, was 47 ± 10 at baseline, and 29 ± 4 (p > 0.05) at both PPP and real PP (14 mmHg). Conclusions: The PPP model is quite similar to the real PP and can be used for preoperative prognosis in laparoscopic surgery. The elevated intraabdominal pressure results in a significant disturbance of venous blood flow in the lower extremities. The use of the device for peristaltic pneumomassage of the lower limbs is effective in correcting negative changes in venous hemodynamics in laparoscopic surgery. Received: 28 July 1997/Accepted: 12 January 1998     

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

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

Utility of transesophageal echocardiography and pulmonary artery catheterization during laparoscopic assisted abdominal aortic aneurysm repair

Background: Advanced laparoscopic procedures are more commonly performed in elderly patients with cardiac disease. There has been limited data on the use of pulmonary artery catheters (PAC) and transesophageal echocardiography (TEE) to monitor hemodynamic changes. Methods: We prospectively studied eight patients undergoing laparoscopic assisted abdominal aortic aneurysm repair. All patients had a PAC and all but one had an intraoperative TEE. Data included heart rate (HR), temperature (temp), pulmonary artery systolic (PAS) and diastolic (PAD) pressures, mean arterial pressure (MAP), central venous pressure (CVP), pulmonary capillary wedge pressure (PCWP), cardiac index (CI), mixed venous oxygen saturation (MVO₂), and oxygen extraction ratio (O₂Ex) and was obtained prior to induction, during insufflation, after desufflation, during aortic cross-clamp, and at the end of the procedure. End diastolic area (EDA), a reflection of volume status, was measured on TEE. ANOVA was used for data analysis. Results: No changes were noted in HR, temp, PAS, PCWP, CI, MVO₂, and O₂Ex. PAD and CVP were greater during insufflation compared with baseline and aortic cross-clamp without associated changes in EDA. MAP was higher at baseline compared with all other times during the procedure. Conclusions: Insufflation increased PAD and CVP. However, volume status as suggested by EDA and PCWP did not change. These data question the reliability of hemodynamic measurements obtained from the PAC during pneumoperitoneum and suggest that TEE may be sufficient for evaluation of volume status along with the added benefit of timely detection of ventricular wall motion abnormalities. Received: 27 March 1997/Accepted: 5 July 1997     

Effect of temperature of insufflated CO2 during and after prolonged laparoscopic surgery

Background: Pneumoperitoneum with room temperature carbon dioxide (CO₂) has been shown to decrease core temperature and urine output. Methods: The effect of 37°C (warm) and room temperature (cool) CO₂ pneumoperitoneum on core temperature, urine output, and central hemodynamics was compared in 26 randomized patients undergoing prolonged laparoscopic surgery (>90 min). Results: The core temperature (p < 0.05) and cardiac index (p < 0.05) were significantly higher after warm than after cool pneumoperitoneum. Urine output was significantly higher during warm (2.3 ± 1.6 ml/kg/h) than during cool (0.9 ± 0.7 ml/kg/h) insufflation (p < 0.05). Two of 13 patients with warm and 11 of 13 patients with cool pneumoperitoneum needed mannitol to maintain adequate diuresis (p < 0.05). Conclusions: Warm insufflation probably causes a local vasodilation in the kidneys and may be beneficial to patients with borderline renal function. Received: 23 June 1997/Accepted: 16 November 1997     

Operative manometry and endoscopy during laparoscopic Heller myotomy

Background: We report our initial experience using operative esophageal manometry as an adjunct to endoscopy to determine the completeness of esophagogastric high-pressure zone (HPZ) obliteration during laparoscopic Heller myotomy. Methods: Between July 1997 and October 1998, we performed laparoscopic Heller myotomies in 20 patients (eight male, 12 female; median age, 41 years). Mean duration of symptoms was 3.2 ± 2.6 years (r= 0.5–11), and 45% of the patients had received prior dilation or toxin injection. A 16-channel esophageal manometry catheter was placed prior to anesthesia, with sites crossing the lower esophageal sphincter (LES). An endoscope was passed intraoperatively to localize the squamocolumnar junction, and the myotomy was performed. While the translucency was imaged in the area of the incision, we determined the adequacy of myotomy by visual assessment of LES and gastric cardia opening in response to endoscopic air insufflation. Manometry was then performed to detect any potential residual high pressure at the myotomized esophagogastric junction (EGJ). If it was found, the locus of persistent pressure was identified by probing along the myotomy, and residual muscle fibers were cut to yield a minimum pressure at the EGJ. Results: A persistent HPZ was identified after the initial myotomy in 10 of 20 patients (50%). A Dor fundoplasty completed the operation. The mean operating time was 2.6 ± 0.5 h (median, 2.5; r= 2–3.5 h), and the mean hospital stay was 1.6 ± 1 days (median, 1, r= 1–5 days). The mean LES pressure was 2 ± 3 mmHg immediately postmyotomy (p < 0.001 compared with preoperative value). Of 20 patients, only two have reported recurrence of dysphagia (10%). One had a recurrent HPZ on manometry, and one developed esophagitis, which resolved with omeprazole. Conclusions: Our initial experience suggests that operative esophageal manometry is a useful adjunct to upper endoscopy during laparoscopic Heller myotomy, quantitatively assuring obliteration of the nonrelaxing LES and HPZ. Received: 1 March 1999/Accepted: 30 June 1999     

Nissen and Toupet fundoplications effectively inhibit gastroesophageal reflux irrespective of natural anatomy and function

Background: The physiology of Nissen fundoplication (NF) and Toupet fundoplication (TF) is controversial. The aim of this study was to determine the contribution of elevated intragastric pressure to the antireflux mechanism after surgically created fundoplication in explanted porcine stomachs. Methods: The stomachs and 6–8 cm of distal esophagus were removed from 15 pigs and placed in anatomic position. Five NF, 2 cm in length with three interrupted sutures, were performed, taking full-thickness bites of stomach and partial-thickness bites of esophagus around a 60 French dilator. Five 270° TF 2 cm in length with six interrupted sutures were performed taking full-thickness bites of stomach and partial-thickness bites of esophagus around a 60 French dilator. Each stomach served as its own control. The pylorus was tied off and the stomach was inflated with Ringer's lactate while the pressure was monitored. Results: Before NF, reflux could be easily induced with a mean intragastric pressure of 5.5 ± 3.7 mmHg. After NF reflux could not be induced but the sutures pulled out of the stomach at a mean pressure of 36.8 ± 11.7 mmHg (p < 0.01 vs control). Before TF, reflux could easily be induced with a mean intragastric pressure of 3.0 ± 3.0 mmHg. After TF, reflux could not be induced and the sutures pulled out of the esophagus or stomach with a mean pressure of 30.8 ± 9.0 mmHg (p < 0.01 vs control). Porcine stomachs in vivo are resistant to reflux, but when explanted they reflux easily. NF and TF are so effective at interrupting reflux that the sutures tear out instead of allowing reflux. Conclusions: While not yet statistically significant, it appears that sutures tear out of the esophagus (TF) more readily than they tear out of the stomach (NF). TF and NF prevent reflux in the absence of anatomic or functional components of the lower esophageal sphincter.     

Immediate and delayed effects of laparoscopic Nissen fundoplication on pulmonary function

Background: An effort was made to assess the respiratory outcomes of laparoscopic Nissen fundoplication (LNF). Methods: Prospective follow-up of 69 patients undergoing LNF for gastroesophageal reflux disease. Outcomes included pulmonary function testing, 24-h pH recording, esophageal manometry, and symptom assessment. Results: There was an improvement (p < 0.0001) in heartburn and cough scores. There was a significant fall in spirometry (p < 0001), diffusing capacity (p < 0.0001), and respiratory muscle strength (p < 0.0001) 36 h after surgery, which had returned to baseline by 1 month. At 6 months, the patients (n= 16) with impaired preoperative diffusing capacity showed improvement (17.8 ± 3.7 to 19.8 ± 4.6 ml/min/mmHg, p= 0.0245). Conclusion: Patients undergoing LNF have impaired gas exchange before surgery which tends to improve 6 months after surgery. There is an early reversible impairment in respiratory function due to diaphragm dysfunction. Patients with a preoperative 1-s forced expired volume > 1.5, or 50% predicted, are unlikely to develop signficant early respiratory complication. Received: 22 April 1996/Accepted: 9 July 1996     

Laparoscopic insufflation with room air causes exaggerated interleukin-6 response

Background: The gut is a central organ in the postoperative stress reaction. We previously reported that measuring gut-mucosal cytokines may more accurately reflect the response to operative stress. Additionally, we have shown that the gut demonstrates a blunted cytokine response after laparoscopy as compared with laparotomy. Methods: To further investigate whether this differential response is caused by exposure of the peritoneal cavity to general atmospheric air during laparotomy, 80 A/J mice were randomized equally into four groups: CD (carbon dioxide [CO₂] pneumoperitoneum), RA (room air pneumoperitoneum), AP (anesthesia and port insertion only), and PC (pure control, no intervention). Pneumoperitoneum was established and maintained at 3 mmHg for 60 min. All the mice were killed 4 h after the intervention. Jejunal mucosa and serum samples were collected and analyzed for interleukin-6 (IL-6) levels. Results were analyzed by analysis of variance (ANOVA). Results: Gut-mucosal IL-6 in the RA group was significantly higher than in all other groups: RA, 1,354.5 ± 117.9* vs. CD, 964.3 ± 114.0 vs. AP, 960.2 ± 86.2 vs. PC, 908.0 ± 83.6; *p < 0.05. The CD group did not show a significant increase in gut-mucosal IL-6 as compared with the AP and PC groups. Similarly, RA resulted in significant increases in serum IL-6 as compared with AP and PC, whereas CD showed no significant difference: RA, 161.3 ± 66.2* vs. 95.1 ± 1 vs. AP, 10.6 ± 5.3 vs. PC, undetectable; *p < 0.05. There was no difference in serum IL-6 level between CD or any of the other groups. Conclusions: Exposure of the peritoneal cavity to atmospheric air, independently of the trauma of abdominal access, causes an exaggerated serum and gut mucosal IL-6 response 4 h after intervention. The beneficial effect of CO₂ laparoscopy may be caused by the exclusion of general atmospheric air from the peritoneal cavity. Received: 29 June 1998/Accepted: 1 November 1998     

Prevalence of gastroesophageal reflux after laparoscopic Heller myotomy

Background: There is still some controversy over the need for antireflux procedures with Heller myotomy in the treatment of achalasia. This study was undertaken in an effort to clarify this question. Methods: To determine whether Heller myotomy alone would cause significant gastroesophageal reflux (GER), we studied 16 patients who had undergone laparoscopic Heller myotomy without concomitant antireflux procedures. Patients were asked to return for esophageal manometry and 24-h pH studies after giving informed consent for the Institutional Review Board (IRB)-approved study at a median follow-up time of 8.3 months (range, 3–51). Results are expressed as the mean ± SEM. Results: Fourteen of the 16 patients reported good to excellent relief of dysphagia after myotomy. They were subsequently studied with a 24-h pH probe and esophageal manometry. These 14 patients had a significant fall in lower esophageal sphincter (LES) pressure from 41.4 ± 4.2 mmHg to 14.2 ± 1.3 mmHg, after the myotomy (p < 0.01, Student's t-test). The two patients who reported more dysphagia postoperatively had LES pressures of 20 and 25 mmHg, respectively. Two of 14 patients had DeMeester scores of >22 (scores = 61.8, 29.4), while only one patient had a pathologic total time of reflux (percent time of reflux, 8%). The mean percent time of reflux in the other 13 patients was 1.9 ± 0.6% (range, 0.1–4%), and the mean DeMeester score was 11.7 ± 4.6 (range, 0.48–19.7). Conclusions: Laparoscopic Heller myotomy is effective for the relief of dysphagia in achalasia if the myotomy lowers the LES pressure to <17 mmHg. If performed without dissection of the entire esophagus, the laparoscopic Heller myotomy does not create significant GER in the postoperative period. Clearance of acid refluxate from the aperistaltic esophagus is an important component of the pathologic gastroesophageal reflux disease (GERD) seen after Heller myotomy for achalasia. Furthermore, GERD symptoms do not correlate with objective measurement of GE reflux in patients with achalasia. Objective measurement of GERD with 24 h pH probes may be indicated to identify those patients with pathologic acid reflux who need additional medical treatment. Received: 12 May 1998/Accepted: 15 December 1998     

Newly designed retraction devices for intestine control during laparoscopic aortic surgery

Background: Recent clinical studies have demonstrated the feasibility of laparoscopic surgery for aortic occlusive and aneurysmal disease. However, transperitoneal aortic access is compromised by poor exposure in the operative field from uncontrolled bowel. The retractors that are currently available are inadequate for this task. The development of new retractors would help to facilitate laparoscopic aortic surgery. Methods: Six female piglets (28–30 kg) in each group underwent laparoscopy with pneumoperitoneum (12 mmHg). Exposure of the infrarenal aorta and cross-clamping were undertaken through a transperitoneal approach. Two paddles inserted in a polyester bilayer (mobile device, group A) or a mesh net fixed to the abdominal wall (fixed device, group B) were used to retain the bowel. Aortotomy and suturing were performed to mimic a vascular procedure. After bleeding was controlled, the intraabdominal pressure (IAP) was lowered to 6 mmHg, and retraction was assessed for 30 min. The main outcome measures were time to deploy the retractors, time to perform the vascular procedure, time to withdraw the devices, and total procedural time. Blood loss and frequency of retraction failure were also recorded. Results: Mean time to deploy the device was 22 ± 12 min in group A and 36 ± 34 min in group B (n.s.). Vascular surgery time averaged 60 ± 24 min in group A and 68 ± 16 min in group B (n.s.). The times to withdraw the nets were 3.6 ± 1.2 min and 13.5 ± 8.2 min, respectively (p < 0.05). Total surgery time was 155 ± 41 min vs 174 ± 49 min (n.s.). There were six retraction failures, five in group A and one in group B. When lower IAP was used, there was only one failure in each study group. Mean blood loss was <150 ml in both groups. There were no major complications. Conclusions: Both methods provided adequate exposure of the infrarenal aorta. Vascular surgery time and blood loss were similar for both groups. The movable device proved more usable and, at lower IAP, more effective. The results of this study demonstrate effective bowel retraction for laparoscopic aortic surgery. Received: 10 December 1998/Accepted: 13 May 1999     

Immediately recognizable benefits and drawbacks after laparoscopic colon resection for benign disease

Background: A prospective assessment of the impact of laparoscopic colon resection (LCR) was carried out in order to quantify immediately recognizable benefits and limitations of this approach. Methods: Elective LCR was attempted in 95 selected patients (mean age 64 years, range 39–81 years) presenting with benign disease of the colon. A completely intracorporeal approach was adopted. Results were compared with a control group of 90 patients who had previously undergone open colectomy (OC) by the same surgeons at the same institution. Results: There were no perioperative deaths. Intraoperative complications included difficult extraction of accidentally detached anvil (n= 1), air leak at colonoscopy (n= 2), and conversion to OC (n= 1). Operating time was significantly longer after LCR compared with OC (180 ± 10.3 vs 116 ± 97, p < 0.001). Passage of flatus (3.5 ± 1.2 days vs 4.4 ± 1.4, p < 0.5) and morbidity (4 vs 3, p= 0.48) were not significantly different in the two groups. Hospital stay was significantly shorter after LCR (5.2 ± 1.3 days vs 12.2 ± 1.9 days, p < 0.001). Theater and ward costs were, respectively, significantly increased ($ 2,829.6 ± 340 vs $ 1,422 ± 318, p < 0.001) and decreased ($ 2,600 ± 366 vs $ 6,022 ± 916, p < 0.001) in LCR patients compared with the OC group. There was no significant difference in total hospital costs ($ 10,929 ± 369 vs $ 9,944 ± 1,014). Conclusions: LCR does not appear to offer any immediately recognizable advantages. Received: 15 October 1996/Accepted: 13 December 1996