Anaesthesia for minimally invasive surgery in children

Pediatric robotic surgery: issues in management-expert consensus from the Italian Society of Pediatric and Neonatal Anesthesia and Intensive Care (SARNePI) and the Italian Society of Pediatric Surgery (SICP)

BACKGROUND

Pediatric robotic-assisted surgeries have increased in recent years; however, guidance documents are still lacking. This study aimed to develop evidence-based recommendations, or best practice statements when evidence is lacking or inadequate, to assist surgical teams internationally.

METHODS

A joint consensus taskforce of anesthesiologists and surgeons from the Italian Society of Pediatric and Neonatal Anesthesia and Intensive Care (SARNePI) and the Italian Society of Pediatric Surgery (SICP) have identified critical areas and reviewed the available evidence. The taskforce comprised 21 experts representing the fields of anesthesia (n = 11) and surgery (n = 10) from clinical centers performing pediatric robotic surgery in the Italian cities of Ancona, Bologna, Milan, Naples, Padua, Pavia, Perugia, Rome, Siena, and Verona. Between December 2020 and September 2021, three meetings, two Delphi rounds, and a final consensus conference took place.

RESULTS

During the first planning meeting, the panel agreed on the specific objectives, the definitions to apply, and precise methodology. The project was structured into three subtopics: (i) preoperative patient assessment and preparation; (ii) intraoperative management (surgical and anesthesiologic); and (iii) postoperative procedures. Within these phases, the panel agreed to address a total of 18 relevant areas, which spanned preoperative patient assessment and patient selection, anesthesiology, critical care medicine, respiratory care, prevention of postoperative nausea and vomiting, and pain management.

CONCLUSION

Collaboration among surgeons and anesthesiologists will be increasingly important for achieving safe and effective RAS procedures. These recommendations will provide a review for those who already have relevant experience and should be particularly useful for those starting a new program.

Pediatric Challenges in Robot-Assisted Kidney Transplantation

Kidney transplantation is universally recognized as the gold standard treatment in patients with End-stage Kidney Disease (ESKD, or according to the latest nomenclature, CKD stage 5). Robot-assisted kidney transplantation (RAKT) is gradually becoming preferred technique in adults, even if applied in very few centra, with potentially improved clinical outcomes compared with open kidney transplantation. To date, only very few RAKT procedures in children have been described. Kidney transplant recipient patients, being immunocompromised, might be at increased risk for perioperative surgical complications, which creates additional challenges in management. Applying techniques of minimally invasive surgery may contribute to the improvement of clinical outcomes for the pediatric transplant patients population and help mitigate the morbidity of KT. However, many challenges remain ahead. Minimally invasive surgery has been consistently shown to produce improved clinical outcomes as compared to open surgery equivalents. Robot-assisted laparoscopic surgery (RALS) has been able to overcome many restrictions of classical laparoscopy, particularly in complex and demanding surgical procedures. Despite the presence of these improvements, many challenges lie ahead in the surgical and technical–material realms, in addition to anesthetic and economic considerations. RALS in children poses additional challenges to both the surgical and anesthesiology team, due to specific characteristics such as a small abdominal cavity and a reduced circulating blood volume. Cost-effectiveness, esthetic and functional wound outcomes, minimal age and weight to undergo RALS and effect of RAKT on graft function are discussed. Although data on RAKT in children is scarce, it is a safe and feasible procedure and results in excellent graft function. It should only be performed by a RAKT team experienced in both RALS and transplantation surgery, fully supported by a pediatric nephrology and anesthesiology team. Further research is necessary to better determine the value of the robotic approach as compared to the laparoscopic and open approach. Cost-effectiveness will remain an important subject of debate and is in need of further evaluation as well.

A prospective single-center observational study to assess the efficacy of the second-generation supraglottic airway device I-gel in laparoscopic surgeries in children

Background and Aims:

Supraglottic airways used in pediatric surgeries are associated with a lesser number of postanesthesia respiratory complications. However, there is limited literature on the use of i-gel for pediatric laparoscopic surgery. The aim of this study is to assess the adequacy of ventilation of i-gel for pediatric laparoscopic surgery and note any associated adverse event.

Material and Methods:

This is a single-centered prospective observational study including 119 children, aged 6 months to 18 years, scheduled for laparoscopic surgery, during a 9-month period, in a tertiary care center. I-gel was used for positive pressure ventilation, and if the post-insertion oropharyngeal seal pressure was <25 cm H₂O, it was replaced with a tracheal tube. Adequacy of ventilation and adverse events were noted.

Results:

Data from 102 cases were analyzed (17 cases excluded: tracheal intubation in 11; missing data in 6 cases). The mean oropharyngeal seal pressure was 34.2 ± 5.2 cm H₂O and mean airway pressure was 16.1 ± 2.4 cm H₂O. The adverse events included transient cough (10.7%), sore throat (4.9%), and desaturation (3.9%). There was no sign of respiratory distress during the recovery and no intervention was required in any child postoperatively.

Conclusion:

I-gel provided adequate ventilation of the lungs in children undergoing laparoscopic surgery with no major adverse event.

Anesthetic considerations and goals in robotic pediatric surgery: a narrative review

The morphosis from open surgeries to minimally invasive procedures is in greater part owing to the development of robotics. There has been a hiking popularity of robotic assistance for surgeries in recent years. Though a minimally invasive approach for surgery, it poses major challenges for an anesthesiologist that compound further for pediatric patients. The need of the hour for an anesthesiologist is to have a scrupulous knowledge and understanding of the associated anatomical and physiological considerations in case of pediatric patients. Major anesthetic concerns include restricted patient access, physiologic changes of pneumoperitoneum and different operative positions, risk of hypothermia, efficient fluid and peri-operative pain management. Timely anticipation, cautious observation for peri-operative complications and quick intervention to manage the same are warranted to provide high-quality anesthetic care. This simply implies that as robotic surgery plans to stretch up-to zenith, anesthesiologists shall strive to ace their part in robotic pediatric anesthesia as well. With an efficient and dynamic teamwork, robotic-assisted surgeries hold the potential to turn wonders for the future of surgery.

Changes in cerebral and renal oxygenation during laparoscopic pyloromyotomy

Although a laparoscopic approach may be preferred over open procedures for abdominal surgery, there are limited data on the effect of laparoscopic procedures on cerebral and renal oxygenation in neonates and young infants. Here, we evaluated the effect in neonates and infants. In this two-center prospective observational study, we evaluated changes in cerebral and renal regional oxygen saturation (rSO₂) in infants during laparoscopic pyloromyotomy. Intraoperative hemodynamic and respiratory parameters and rSO₂ were recorded. For the primary outcome, these parameters were compared at incision and at the end of pneumoperitoneum. The study cohort included 25 infants with a mean age of 40 ± 10 days and weight of 4.0 ± 0.6 kg. IAP at the beginning of laparoscopy was 10 ± 2 mmHg (range 7-15 mmHg). Although both cerebral and renal rSO₂ decreased from incision compared to the end of laparoscopy, the decrease reached statistical significance only for cerebral rSO₂ (81 ± 12 to 76 ± 16, p = 0.033). Similarly, the increase in fractional tissue oxygen extraction (FTOE) was only statistically significant for cerebral FTOE (0.18 ± 0.12 to 0.23 ± 0.16, p = 0.037). No change in hemodynamic or respiratory parameters was found. Although there was a decrease in cerebral rSO₂ and increase in cerebral FTOE during pneumoperitoneum, the values did not decrease below those noted before anesthetic induction.

Role of Robotics in Children: A brave New World!

CONTEXT

The key in the evolution towards minimally invasive surgery is the availability of appropriate equipment, especially when procedures involve children. While robotic procedures in adults continue to struggle to prove measurable advantages compared with open or classical laparoscopic ones, the use of the robotic platform (RP) in pediatric urology is steadily increasing.

OBJECTIVE

To review the contemporary literature regarding the use of robotic-assisted (RA) urologic interventions in children.

EVIDENCE ACQUISITION

A nonsystematic review of the literature was conducted through PubMed database between 2002 and 2017, with an emphasis on large series.

EVIDENCE SYNTHESIS

A few major challenges must be considered before using the RP in children: anesthesia, placement of trocars, and technical difficulties related to small space. To date, only the robot-assisted pyeloplasty is recognized as safe and efficient with an equivalent outcome compared to the open or classical laparoscopy; this was supported by large multicentric studies, which are not available for most of the other procedures.

CONCLUSIONS

RA procedure in children has been proven safe and effective. Still in its infancy, further data over time is likely to prove different RA procedures to be equivalent to open or laparoscopy in terms of outcome.

PATIENT SUMMARY

The advent of the robotic platform means an evolution towards minimizing surgical trauma for the child. Currently, the available platforms designed for adults are adapted to work in children. However, it might be expected in the future that new technologies will improve the technical possibilities to improve the robotic platform for minimally invasive surgery in children. To date, a few applications are considered safe and efficient (in experienced hands), considering that the team has to be aware of some challenges to overcome regarding anesthesia, material, and technique adaptation to the patient. The most accepted robotic applications in children comprises of the robot-assisted pyeloplasty, hemi-nephrectomy, and ureteric reimplantation.

Open versus minimally invasive surgical approaches in pediatric urology: Trends in utilization and complications

OBJECTIVE

Minimally invasive surgery (MIS) techniques are anecdotally reported to be increasingly used, but little objective data supports this. Our objective was to assess trends in MIS utilization across various procedures in pediatric urology and to compare postoperative complication rates between MIS and open procedures.

METHODS

We analyzed the 1998-2012 Nationwide Inpatient Sample. We identified children (<18 years old) undergoing open and MIS inpatient procedures and any in-hospital post-operative complications that occurred during that postoperative hospitalization. We utilized propensity score matching and multivariable logistic regression to adjust for confounding factors.

RESULTS

We identified 163,838 weighted encounters in the "overall cohort," 70,273 of which were at centers performing more than five MIS procedures over the years studied. Use of MIS techniques increased significantly over time for several procedures, most prominently for nephrectomy (Fig.). The overall rate of complications was lower in patients undergoing MIS compared with open surgery (6% vs. 11%, p < 0.001). Specialized centers had a significantly lower overall rate of complications than unspecialized centers (9% vs. 12%, p < 0.001). Within specialized centers, MIS had lower complication rates than open procedures (7% vs. 9%, p < 0.001); this finding was consistent even after adjusting for other factors (OR 0.71, p = 0.02).

DISCUSSION

Limitations include that these data may not be generalizable to encounters not in the sample pool. As a large, retrospective, administrative database, NIS may be affected by miscoding bias - rendering our analysis sensitive to the accuracy of procedure coding in NIS. Although the accuracy level of NIS is high for an administrative database, it is possible at least some portion of our cohort may be incorrectly coded. Further, the NSQIP complications we identified may represent associated comorbidities and not true postoperative complications, as NIS does not provide temporal relationships between different diagnosis codes. Despite these limitations, we note that the NIS database is rigorously monitored and audited for coding accuracy and, therefore, represents a reasonably reliable panorama of the characteristics of an inpatient surgical cohort. However, it is important to note that the choice of operative modality is, undoubtedly, multifactorial and patient/setting-specific.

CONCLUSIONS

There is increasing use of MIS for pediatric urology procedures, although utilization rates vary among procedures. MIS was associated with a lower postoperative complication rate than for open procedures. Higher-volume MIS centers have a lower complication rate than lower-volume centers.

Pediatric anesthesia for minimally invasive surgery in pediatric urology

Laparoscopic or robotic minimally invasive approaches have become the standard of care for many urological pediatric surgical procedures. Anesthetic concerns for conventional and robotic laparoscopy are similar since they both require insufflations of CO₂ to allow visualization of surgical field and perform surgery. Even if required insufflation pressures and volumes are lower in pediatric patients (given the small size of the abdomen and laxity of the abdominal walls), the associated increase of intra-abdominal pressure, along with absorption of CO₂ and surgical positioning requirement, may result in neurendocrine and mechanical impact capable to mine cardiopulmonary function. Moreover, laparoscopic approach may require specific positioning. A correct positioning is essential to allow the surgical team to optimally and safely access to the patient. The knowledge of patient's health status, along with the multiple physiologic changes that can occur and specific potential complications, allow the anesthesiologist to provide a safer an aesthesia.

Effects of carbon dioxide insufflation on regional cerebral oxygenation during laparoscopic surgery in children: a prospective study

BACKGROUND AND OBJECTIVES

Laparoscopic surgery has become a popular surgical tool when compared to traditional open surgery. There are limited data on pediatric patients regarding whether pneumoperitoneum affects cerebral oxygenation although end-tidal CO2 concentration remains normal. Therefore, this study was designed to evaluate the changes of cerebral oxygen saturation using near-infrared spectroscope during laparoscopic surgery in children.

METHODS

The study comprised forty children who were scheduled for laparoscopic (Group L, n=20) or open (Group O, n=20) appendectomy. Hemodynamic variables, right and left regional cerebral oxygen saturation (RrSO2 and LrSO2), fraction of inspired oxygen, end-tidal carbon dioxide pressure (PETCO2), peak inspiratory pressure (Ppeak), respiratory minute volume, inspiratory and end-tidal concentrations of sevoflurane and body temperature were recorded. All parameters were recorded after anesthesia induction and before start of surgery (T0, baseline), 15min after start of surgery (T1), 30min after start of surgery (T2), 45min after start of surgery (T3), 60min after start of surgery (T4) and end of the surgery (T5).

RESULTS

There were progressive decreases in both RrSO2 and LrSO2 levels in both groups, which were not statistically significant at T1, T2, T3, T4. The RrSO2 levels of Group L at T5 were significantly lower than that of Group O. One patient in Group L had an rSO2 value <80% of the baseline value.

CONCLUSIONS

Carbon dioxide insufflation during pneumoperitoneum in pediatric patients may not affect cerebral oxygenation under laparoscopic surgery.

[Effects of carbon dioxide insufflation on regional cerebral oxygenation during laparoscopic surgery in children: a prospective study]

BACKGROUND AND OBJECTIVES

Laparoscopic surgery has become a popular surgical tool when compared to traditional open surgery. There are limited data on pediatric patients regarding whether pneumoperitoneum affects cerebral oxygenation although end-tidal CO2 concentration remains normal. Therefore, this study was designed to evaluate the changes of cerebral oxygen saturation using near-infrared spectroscope during laparoscopic surgery in children.

METHODS

The study comprised forty children who were scheduled for laparoscopic (Group L, n=20) or open (Group O, n=20) appendectomy. Hemodynamic variables, right and left regional cerebral oxygen saturation (RrSO2 and LrSO2), fraction of inspired oxygen, end-tidal carbon dioxide pressure (PETCO2), peak inspiratory pressure (Ppeak), respiratory minute volume, inspiratory and end-tidal concentrations of sevoflurane and body temperature were recorded. All parameters were recorded after anesthesia induction and before start of surgery (T0, baseline), 15min after start of surgery (T1), 30min after start of surgery (T2), 45min after start of surgery (T3), 60min after start of surgery (T4) and end of the surgery (T5).

RESULTS

There were progressive decreases in both RrSO2 and LrSO2 levels in both groups, which were not statistically significant at T1, T2, T3, T4. The RrSO2 levels of Group L at T5 were significantly lower than that of Group O. One patient in Group L had an rSO2 value <80% of the baseline value.

CONCLUSIONS

Carbon dioxide insufflation during pneumoperitoneum in pediatric patients may not affect cerebral oxygenation under laparoscopic surgery.

Perioperative care of infants with pyloric stenosis

Pyloric stenosis (PS) is one of the most common surgical conditions affecting neonates and young infants. The definitive treatment for PS is surgical pyloromyotomy, either open or laparoscopic. However, surgical intervention should never be considered urgent or emergent. More importantly, emergent medical intervention may be required to correct intravascular volume depletion and electrolyte disturbances. Given advancements in surgical and perioperative care, morbidity and mortality from PS should be limited. However, either may occur related to poor preoperative resuscitation, anesthetic management difficulties, or postoperative complications. The following manuscript reviews the current evidence-based medicine regarding the perioperative care of infants with PS with focus on the preoperative assessment and correction of metabolic abnormalities, intraoperative care including airway management (particularly debate related to rapid sequence intubation), maintenance anesthetic techniques, and techniques for postoperative pain management. Additionally, reports of applications of regional anesthesia for either postoperative pain control or as an alternative to general anesthesia are discussed. Management recommendations are provided whenever possible.

Robotic cardiac surgery: an anaesthetic challenge

Robotic cardiac surgery with the da Vinci robotic surgical system offers the benefits of a minimally invasive procedure, including a smaller incision and scar, reduced risk of infection, less pain and trauma, less bleeding and blood transfusion requirements, shorter hospital stay and decreased recovery time. Robotic cardiac surgery includes extracardiac and intracardiac procedures. Extracardiac procedures are often performed on a beating heart. Intracardiac procedures require the aid of peripheral cardiopulmonary bypass via a minithoracotomy. Robotic cardiac surgery, however, poses challenges to the anaesthetist, as the obligatory one-lung ventilation (OLV) and CO2 insufflation may reduce cardiac output and increase pulmonary vascular resistance, potentially resulting in hypoxaemia and haemodynamic compromise. In addition, surgery requires appropriate positioning of specialised cannulae such as an endopulmonary vent, endocoronary sinus catheter, and endoaortic clamp catheter under the guidance of transoesophageal echocardiography. Therefore, cardiac anaesthetists should have a working knowledge of these systems, OLV and haemodynamic support.

Cardiac considerations in the operative management of the patient with Duchenne or Becker muscular dystrophy

Duchenne muscular dystrophy/Becker muscular dystrophy (DMD/BMD) is a progressive multisystem neuromuscular disorder. In addition to the skeletal muscle, the myocardium in the DMD/BMD patient is dystrophin deficient which results in a progressive cardiomyopathy. The myopathic myocardium poses significant risk of increased morbidity and mortality at the time of major surgical procedures. Careful attention must be given to the DMD/BMD patient during the intraoperative and postoperative period. Anesthesia selection is critical and anesthetics should be avoided which have been shown to be harmful in this patient population. Preanesthesia assessment should include cardiac consultation and detailed preoperative evaluation. Intraoperative management needs to insure that the weakened myocardium is not compromised by physiologic changes such as hypotension or major fluid shifts. Finally, attention to the cardiac status of the patient must continue into the postoperative period. The surgical care of the DMD/BMD patient requires a multispecialty approach to insure operative success.

Laparoscopic transperitoneal repair of pediatric diaphragm eventration using an endostapler device

BACKGROUND

Minimally invasive repairs of pediatric diaphragm eventration have been well described via a thoracoscopic approach, oftentimes requiring single-lung ventilation and tube thoracostomy, with the disadvantage of not being able to clearly visualize what lies beneath the diaphragm. We describe a novel pediatric diaphragm eventration repair using a laparoscopic transperitoneal approach and an endostapler device. We also describe our initial experience with this technique.

PATIENTS AND METHODS

Four pediatric diaphragmatic eventration patients underwent laparoscopic transperitoneal repair using an endostapler device. Repairs were performed in both male and female patients with right-sided eventrations. We approach the repair in a transperitoneal fashion using inverting sutures at the apex of the diaphragm to create tension toward the pelvis. Subsequently, an endostapler is used to remove the redundant portion of diaphragm, leaving a repaired, taut diaphragm.

RESULTS

The median age at operation was 10.5 months. The median operative time was 70 minutes. There was no mortality, surgical complications, or recurrence at a median follow-up of 17 months.

CONCLUSIONS

This laparoscopic approach allows for clear visualization of the intraabdominal organs and, at least in our early experience, a very simple, straightforward operation. Additionally, with the use of the endostapler, the redundant, often weakened diaphragm is removed, leaving the native, healthy diaphragm behind, resulting in a reliable and reproducible repair. This repair should be considered as a feasible alternative approach to the more traditional open and thoracoscopic repairs.

Optimizing working space in porcine laparoscopy: CT measurement of the effects of intra-abdominal pressure

BACKGROUND

Several factors may affect volume and dimensions of the working space in laparoscopic surgery. The precise impact of these factors has not been well studied. In a porcine model, we used computed tomographic (CT) scanning for measuring working space volume and distances. In a first series of experiments, we studied the relationship between intra-abdominal pressure (IAP) and working space.

METHODS

Eleven 20 kg pigs were studied under standardized anesthesia and volume-controlled ventilation. Cardiorespiratory parameters were monitored continuously, and blood gas samples were taken at different IAP levels. Respiratory rate was increased when ETCO₂ exceeded 7 kPa. Breath-hold CT scans were made at IAP levels of 0, 5, 10, and 15 mmHg. Insufflator volumes were compared to CT-measured volumes. Maximum dimensions of pneumoperitoneum were measured on reconstructed CT images.

RESULTS

Respiratory rate had to be increased in three animals. Mild hypercapnia and acidosis occurred at 15 mmHg IAP. Peak inspiratory pressure rose significantly at 10 and 15 mmHg. CT-measured volume increased relatively by 93 % from 5 to 10 mmHg IAP and by 19 % from 10 to 15 mmHg IAP. Comparing CT volumes to insufflator volumes gave a bias of 76 mL. The limits of agreement were -0.31 to +0.47, a range of 790 mL. The internal anteroposterior diameter increased by 18 % by increasing IAP from 5 to 10 mmHg and by 5 % by increasing IAP from 10 to 15 mmHg. At 15 mmHg, the total relative increase of the pubis-diaphragm distance was only 6 %. Abdominal width did not increase.

CONCLUSIONS

CT allows for precise calculation of the actual CO₂ pneumoperitoneum volume, whereas the volume of CO₂ released by the insufflator does not. Increasing IAP up to 10 mmHg achieved most gain in volume and in internal anteroposterior diameter. At an IAP of 10 mmHg, higher peak inspiratory pressure was significantly elevated.

[Air embolism during laparoscopic surgery in an infant girl with Cornelia de Lange syndrome]

Cornelia de Lange syndrome involves multiple malformations with particular phenotypic features (craniofacial abnormalities such as microcephaly or hypertrichosis with synophrys; cutaneous abnormalities such as hirsutism, and limb anomalies) and it is associated with a high percentage of mental retardation and complications such as digestive tract abnormalities, cardiac defects, and endocrine disorders. We report the case of a 2-month-old infant girl who underwent a laparoscopic antireflux procedure, with closure of a diaphragmatic hernia and a gastric stoma. The medical history included repeated episodes of aspiration pneumonia and hypertension. Early in the procedure, 2 episodes of sudden desaturation, hypotension, and bradycardia with a probable diagnosis of air embolism. The complications resolved with specific treatment. Anesthetic management for laparoscopic surgery in these patients is truly complex and must be informed by a thorough understanding of the disease and complications that may develop.

Thoracoscopic Repair of a Right-Sided Congenital Diaphragmatic Hernia

The presentation of a congenital diaphragmatic hernia (CDH) beyond infancy is rare, as it is a common cause for severe respiratory distress in the newborn. In contrast to the newborn period, delayed diagnosis of right-sided congenital diaphragmatic hernia (RCDH) is known as it causes less severe symptoms than left-sided CDH. A case of an 8-month-old girl is reported. Chest x-ray and ultrasound examination of the diaphragm for symptoms of pneumonia revealed an RCDH. Thoracoscopic repair could be performed. The further course was uneventful. Thoracoscopic repair of a RCDH proved in this case to be feasible and safe beyond the newborn period. It avoided the morbidity of a major thoracotomy or laparotomy and provided an excellent cosmetic result. To our knowledge, this is the first report of thoracoscopic repair of RCDH.

Chirurgie cœlioscopique chez l'enfant

In the last two decades, laparoscopy surgery has been progressively adopted to children. Cardiorespiratory changes induced have been understood and controlled. Abdominal and urological surgery have widely benefited from this technique. Immediate postoperative period is simpler. The risk of small bowel obstruction by bands and adhesions is limited. Nevertheless, laparoscopy is not indicated for all pathologies. In neonatal surgery, more studies are necessary. Maybe the future is robotic surgery.

Laparoscopic surgery: pitfalls due to anesthesia, positioning, and pneumoperitoneum

BACKGROUND

Laparoscopic procedures are increasing in number and extensiveness. Many patients undergoing laparoscopic surgery have coexisting disease. Especially in patients with cardiopulmonary comorbidity, pneumoperitoneum and positioning can be deleterious. This article reviews possible pitfalls related to the combination of anesthesia, positioning of the patient, and the influence of pneumoperitoneum in the course of laparoscopic interventions.

METHODS

A literature search using Medline's MESH terms was used to identify recent key articles. Cross-references from these articles were used as well.

RESULTS

Patient positioning and pneumoperitoneum can induce hemodynamic, pulmonary, renal, splanchnic, and endocrine pathophysiological changes, which will affect the entire perioperative period of patients undergoing laparoscopic procedures.

CONCLUSION

Perioperative management for the estimation and reduction of risk of morbidity and mortality due to surgery and anesthesia in laparoscopic procedures must be based on knowledge of the pathophysiological disturbances induced by the combination of general anesthesia, pneumoperitoneum, and positioning of the patient.