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     

Production and systemic absorption of toxic byproducts of tissue combustion during laparoscopic surgery

Background: Among the potential hazards of laparoscopic surgery using electrocautery is the intraperitoneal release and subsequent absorption of byproducts of tissue combustion. In a porcine model of laparoscopic surgery with smoke production, our aims were to assess (1) the relationship between levels of intraperitoneal carbon monoxide (CO) and systemic carboxyhemoglobin (COHb) and methemoglobin (MetHb), and (2) intraperitoneal concentrations of other noxious gases, including hydrogen cyanide (HCN), acrylonitrile (Acr), and benzene (Bzn). Methods: Seven pigs underwent laparoscopic resection of three hepatic wedges using monopolar electrocautery in a CO₂ pneumoperitoneum. Sequential arterial samples were drawn to measure [COHb] and [MetHb] perioperatively, while gaseous intraabdominal [CO], [HCN], [Acr], and [Bzn] were assayed intraoperatively. Results: The mean ± SEM duration of operation was 90 ± 2 min, and electrocautery was used for 68 ± 4 min. Intraabdominal [CO] rose from 0 to 814 ± 200 ppm (p < 0.01) while [COHb] increased from 2.9 ± 0.1% to 3.5 ± 0.1% (p < 0.001). Systemic [MetHb] remained unchanged intra- and postoperatively, ranging from 0.3 to 0.7%. Intraperitoneal [HCN] rose from 0 to 5.7 ± 0.7 ppm (p < 0.001). [Acr], however, did not change significantly from preoperative values, ranging from 0 to 1.6 ± 1.0 ppm, and [Bzn] was undetectable. Conclusions: Laparoscopic tissue combustion increases intraabdominal [CO] to ``hazardous' levels leading to minimal, yet significant, elevations of [COHb]. Systemic [MetHb] and intraabdominal [HCN], [Acr], and [Bzn] are not elevated to toxic levels. Production of intraperitoneal smoke during laparoscopic electrosurgery therefore may not pose a significant threat to the patient. Received: 3 April 1997/Accepted: 22 May 1997     

Evaluation of mechanism of increased intracranial pressure with insufflation

Background: Previous studies have documented an increase in intracranial pressure with abdominal insufflation, but the mechanism has not been explained. Methods: Nine 30–35-kg domestic pigs underwent carbon dioxide insufflation at 1.5 l/min. Intracranial pressure (ICP), lumbar spinal pressure (LP), central venous pressure (CVP), inferior vena cava pressure (IVCP), heart rate, systemic arterial blood pressure, pulmonary arterial pressure, cardiac output, heart rate, respiratory rate, temperature, and end-tidal CO₂ were continuously measured. Mechanical ventilation was used to maintain a constant pCO₂. Measurements were recorded at 0, 5, 10, and 15 mmHg of abdominal pressure with animals in supine, Trendelenburg (T), and reverse Trendelenburg (RT) positions. Prior to recording measurements, the animals were allowed to stabilize for 40 min after each increase in abdominal pressure and for 20 min after each position change. Results: The animals showed a significant increase in ICP (mmHg) with each 5-mmHg increase in abdominal pressure (0 mmHg: 14 ± 1.7; 5 mmHg: 19.8 ± 2.3, p < 0.001; 10 mmHg: 24.8 ± 2.5, p < 0.001; 15 mmHg: 29.8 ± 4.7, p < 0.01). The ICP at 15 mmHg abdominal pressure increased further in the T position (39 ± 4, p < 0.01). Insufflating in the RT position did not significantly reduce the increase in ICP. The IVCP (mmHg) increased with increased abdominal pressure (0 mmHg: 11.5 ± 6.2, 15 mmHg: 22.1 ± 3.5, p < 0.01). This increase correlated with the increase in ICP and LP (r of mean pressures ≥0.95). There was no significant change in CVP. Conclusions: This study suggests that care may be needed with laparoscopy in patients at risk for increased ICP due to head injury or a space occupying lesion. The mechanism of increased ICP associated with insufflation is most likely impaired venous drainage of the lumbar venous plexus at increased intraabdominal pressure. Further studies of cerebral spinal fluid movement during insufflation are currently underway to confirm this hypothesis. Received: 28 March 1997/Accepted: 5 August 1997     

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     

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     

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     

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     

Portal venous flow during CO2 pneumoperitoneum in the rat

Backround: CO₂ gas insufflation is routinely used to extend the abdominal wall. The resulting pneumoperitoneum has a number of local and systemic effects on the organism. Portal blood flow, which plays an important role in hepatic function and cell-conveyed immune response, is one of the affected parameters. Methods: An established animal model (rat) of laparoscopic surgery was modified by implanting a perivascular flow probe. Hemodynamics in the portal vein were then measured during increasing intraabdominal pressure generated by carbon dioxide insufflation. Results: Using this technique, an adequate flowmetry of the portal vein was achieved in all animals. The creation of a CO₂ pneumoperitoneum with increasing intraabdominal pressure led to a linear decrease in portal venous flow. Conclusions: Elevated intraabdominal pressure caused by carbon dioxide insufflation may compromise hepatic function and cell-conveyed immune response during laparoscopic surgery. Received: 28 January 1998/Accepted: 22 June 1998     

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     

A prospective comparison of laparoscopic ultrasound vs intraoperative cholangiogram during laparoscopic cholecystectomy

Background: The laparoscopic ultrasound (US) probe provides a new modality for evaluating biliary anatomy during laparoscopic cholecystectomy (LC). Methods: We performed a laparoscopic US examination in 65 patients without suspected common bile duct (CBD) stones prior to the performance of a laparoscopic cholangiogram (IOC). We then compared the cost, time required, surgeon's assessment of difficulty, and interpretations of findings. Results: There was a significant difference in the cost of US versus the cost of IOC ($362 ± 12 versus $665 ± 12; p < 0.05). Surgeons who had performed >10 US (EXP) were compared with those who had performed ≤10 (NOV). There were significant differences between the EXP and NOV groups in ease of examination, visualization of biliary anatomy, and accuracy of measurement of the CBD. Conclusions: The use of laparoscopic US for the accurate evaluation of the CBD and biliary anatomy requires that the surgeon has surpassed the learning curve, which we have defined as having performed >10 US exams. Received: 1 May 1998/Accepted: 21 October 1998