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

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

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

Automated control for investigation of the insufflation-ventilation interaction in experimental laparoscopy

In laparoscopic surgery the abdominal cavity is insufflated with pressurized carbon dioxide gas to create workspace. This pressure is exerted through the diaphragm onto the lungs, competing with ventilation and hampering it. In clinical practice the difficulty of optimizing this balance can lead to the application of harmfully high pressures. This study set out to create a research platform for the investigation of the complex interaction between insufflation and ventilation in an animal model. The research platform was constructed to incorporate insufflation, ventilation and relevant hemodynamic monitoring devices, controlling insufflation and ventilation from a central computer. The core of the applied methodology is the fixation of physiological parameters by applying closed-loop control of specific ventilation parameters. For accurate volumetric measurements the research platform can be used in a CT scanner. An algorithm was designed to keep blood carbon dioxide and oxygen values stable, minimizing the effect of fluctuations on vascular tone and hemodynamics. This design allowed stepwise adjustment of insufflation pressure to measure the effects on ventilation and circulation. A pilot experiment in a porcine model demonstrated adequate platform performance. The developed research platform and protocol automation have the potential to increase translatability and repeatability of animal experiments on the biomechanical interactions between insufflation and ventilation.

Comparison of the effect of general anesthesia and spinal anesthesia technique combined with general anesthesia on intraabdominal volume during gynecological laparoscopy

PURPOSE

We aimed to investigate the effect of spinal anesthesia which will be performed simultaneously with general anesthesia on the site of operation with the same pressure.

MATERIAL AND METHOD

This study was conducted as a randomized, prospective clinical study on 40 patients who were randomly divided into two groups. Twenty women underwent general anesthesia (Group GA) and 20 women underwent spinal anesthesia with general anesthesia (Group SGA). For all cases, preoperative height, weight, waist circumference, body mass index (kg/m² ), the distance between both spina iliaca anterior superior, the distance of the intersection of both ribs with an imaginary line drawn over the anterior axillary line, suprapubic bone-umbilical, umbilical-xiphoid, and suprapubic bone-xiphoid distance from the midline of the abdomen were measured. Moreover, while the patient was lying in the neutral position on the operating table, the height of the highest point of the abdomen to the operating table was also measured. These measurements were repeated at intra-abdominal pressure (IAP) 14 and 25 mmHg. The amount of intra-abdominal insufflated CO₂ was also recorded at IAP 14 and 25 mmHg.

RESULTS

When the intra-abdominal insufflation volumes of both groups were compared at 14 and 25 mmHg, respectively, there was no statistical difference (p: 0.54, p: 0.40). When 14 and 25 mmHg were compared in all cases, a statistically significant difference was observed in other measurements except in xiphoid-umbilical distance (p < 0.05).

CONCLUSION

We found that spinal anesthesia combined with GA had no effect on the abdominal volume and anthropometric measurements in laparoscopic procedures.

The effect of different levels of pneumoperitoneum pressures on regional cerebral oxygenation during robotic assisted laparoscopic prostatectomy

Background/aim

This study aimed to evaluate the effect of low- and high-pressure pneumoperitoneum pressures applied during robotic-assisted laparoscopic prostatectomy (RALP) using near-infrared spectroscopy (NIRS) on regional cerebral oxygenation saturation (rSO₂).

Materials and methods

The prospective, comparative, and observational study included patients aged 18–80 years, with the American Society of Anesthesiologists (ASA) physical status I-II, who would undergo elective RALP. The patients were divided into two groups (12 mmHg of pneumoperitoneum pressure group, n=22 and 15 mmHg of pneumoperitoneum pressure group, n=23). Patients’ demographic data, durations of anesthesia, surgery, pneumoperitoneum, and Trendelenburg position, intraoperative estimated blood loss, fluid therapy, urine output, hemodynamic and respiratory data, and rSO₂ values were recorded at regular intervals.

Results

The rSO₂ values increased significantly during the pneumoperitoneum combined with steep Trendelenburg position (from t3 to t6 ) and at the end of the surgery ( t7 ) in both groups, compared to the values 5 min after the onset of pneumoperitoneum in the supine position ( t2 ) (P < 0.05), but no statistical significance was observed between the two groups. No cerebral desaturation was observed in any of our patients. Hemodynamic and respiratory parameters were preserved in both groups. The blood lactate levels were significantly higher in patients operated at high-pressure pneumoperitoneum, compared to those with low-pressure pneumoperitoneum (P < 0.05).

Conclusion

We believe that low-pressure pneumoperitoneum, especially in robotic surgeries, such as robotic-assisted laparoscopic prostatectomy (RALP), can be applied safely.

Can We Routinely Employ the Use of Low-Pressure Gynaecological Laparoscopy? A Systematic Review

Clinicians have learnt valuable lessons throughout the COV-SARS-2 pandemic, many of which have produced solutions that we aim to continue to implement within the foreseeable future. Optimising patients' surgical pathways to reduce the length of stay and complications is an area of particular importance, both for maximal utilisation of available resources and for reduction of the exposure of inpatient and elective patients to an increased risk of infection within healthcare facilities. The aim of this review was to investigate the possible implications of using low-pressure laparoscopic gynaecological surgery versus standard- or high-pressure pneumoperitoneum surgeries. The primary outcome was postoperative pain, with secondary outcomes including duration of surgery, length of inpatient stay and rate of complications. MEDLINE, Embase and Cochrane CENTRAL were searched from inception to December 2020. We searched for published randomised control trials comparing low-pressure laparoscopic surgery (≤8 mmHg) to at least one additional standardised pneumoperitoneum pressure (≥12 mmHg and/or ≥15 mmHg). A total of 203 studies were reviewed, five of which were included in this analysis. Studies comparing low-pressure laparoscopic surgery against gasless abdominal cavities were excluded. The meta-analysis of the results was pooled and calculated within RevMan 5.0 software (Cochrane, London, England). Studies using a visual analogue scale (1-10) to compare low versus standard pneumoperitoneum pressures did not display a significant diminution of postoperative pain at ≤ 6 or 24 hours: -0.30 [95% CI -0.63, 0.03] and -0.66 [95% CI -1.35, 0.02], respectively. Studies additionally demonstrated worse visualisation of the surgical field within the low-pressure group (risk ratio 10.31; 95% CI, 1.29-82.38 I2 = 0%). Studies measuring postoperative pain using a numerical rating scale displayed significant pain reduction at all hours measured (p ≤ 0.01). The rate of intraoperative complications was 1% for all groups measured. Cumulative analysis of the duration of surgery did not differ significantly between groups (p = 0.99). The pandemic has revealed new issues that must be addressed by clinicians to promote the safety of patients and the efficiency of inpatient stay. This review has paved the way for new possibilities and innovative approaches to address the issue of optimising patient surgical pathways; however, at present, we cannot give a firm justification for the use of low-pressure gynaecological laparoscopy. Reasons for this include the minimal reduction in pain scores between low, standard and high pneumoperitoneum pressures, leading to a mixture of statistically significant results, as well as a reduction in the visualisation of the surgical field and the small population sizes in the reviewed papers. Additional research is required to further explore the potential clinical benefits of gynaecological laparoscopy to ensure its effective ambulatory use within mainstream surgical operations.

Modeling intra-abdominal volume and respiratory driving pressure during pneumoperitoneum insufflation-a patient-level data meta-analysis

During pneumoperitoneum, intra-abdominal pressure (IAP) is usually kept at 12-14 mmHg. There is no clinical benefit in IAP increments if they do not increase intra-abdominal volume IAV. We aimed to estimate IAV (ΔIAV) and respiratory driving pressure changes (ΔP_RS) in relation to changes in IAP (ΔIAP). We carried out a patient-level meta-analysis of 204 adult patients with available data on IAV and ΔP_RS during pneumoperitoneum from three trials assessing the effect of IAP on postoperative recovery and airway pressure during laparoscopic surgery under general anesthesia. The primary endpoint was ΔIAV, and the secondary endpoint was ΔP_RS. The endpoints' response to ΔIAP was modeled using mixed multivariable Bayesian regression to estimate which mathematical function best fitted it. IAP values on the pressure-volume (PV) curve where the endpoint rate of change according to IAP decreased were identified. Abdomino-thoracic transmission (ATT) rate, that is, the rate ΔP_RS change to ΔIAP was also estimated. The best-fitting function was sigmoid logistic and linear for IAV and ΔP_RS response, respectively. Increments in IAV reached a plateau at 6.0 [95%CI 5.9-6.2] L. ΔIAV for each ΔIAP decreased at IAP ranging from 9.8 [95%CI 9.7-9.9] to 12.2 [12.0-12.3] mmHg. ATT rate was 0.65 [95%CI 0.62-0.68]. One mmHg of IAP raised ΔP_RS 0.88 cmH₂O. During pneumoperitoneum, IAP has a nonlinear relationship with IAV and a linear one with ΔP_RS. IAP should be set below the point where IAV gains diminish.NEW & NOTEWORTHY We found that intra-abdominal volume changes related to intra-abdominal pressure increase reached a plateau with diminishing gains in commonly used pneumoperitoneum pressure ranges. We also found a linear relationship between intra-abdominal pressure and respiratory driving pressure, a known marker of postoperative pulmonary complications.

Pressure-Volume Curve during Capnoperitoneum in Cats

Laparoscopy is a growing field in veterinary medicine, although guidelines are lacking. The objective of this study was to evaluate the pressure-volume curve during capnoperitoneum in cats. A total of 59 female cats were scheduled for routine laparoscopy. Pressure and volume data were recorded and processed, and the yield point of the curve was calculated using a method based on a capacitor discharging function. For the remaining 40 cats, a linear-like pressure-volume curve was observed until a yield point with a mean cutoff pressure (COP) of 6.44 ± 1.7 mmHg (SD) (range, 2.72-13.00 mmHg) and a mean cutoff volume (COV) of 387 ± 144.35 mL (SD) (range, 178.84-968.43 mL) was reached. The mean mL/kg CO₂ value in cats was 208 ± 34.69 mL/kg (range, 100.00-288.46 mL/kg). The COV correlated with COP and body weight but not with body condition score (BCS). COP correlated only with the COV. This study suggests that feline patients have a pressure-volume curve similar to that of canine patients, and the same pressure limit recommendations can be used for both species. After a yield point of 6.44 mmHg is reached, the increment in volume decreases exponentially as the intra-abdominal pressure (IAP) increases.

Effect of an individualized versus standard pneumoperitoneum pressure strategy on postoperative recovery: a randomized clinical trial in laparoscopic colorectal surgery

Background

It remains uncertain whether individualization of pneumoperitoneum pressures during laparoscopic surgery improves postoperative recovery. This study compared an individualized pneumoperitoneum pressure (IPP) strategy with a standard pneumoperitoneum pressure (SPP) strategy with respect to postoperative recovery after laparoscopic colorectal surgery.

Methods

This was a multicentre RCT. The IPP strategy comprised modified patient positioning, deep neuromuscular blockade, and abdominal wall prestretching targeting the lowest intra-abdominal pressure (IAP) that maintained acceptable workspace. The SPP strategy comprised patient positioning according to the surgeon's preference, moderate neuromuscular blockade and a fixed IAP of 12 mmHg. The primary endpoint was physiological postoperative recovery, assessed by means of the Postoperative Quality of Recovery Scale. Secondary endpoints included recovery in other domains and overall recovery, the occurrence of intraoperative and postoperative complications, duration of hospital stay, and plasma markers of inflammation up to postoperative day 3.

Results

Of 166 patients, 85 received an IPP strategy and 81 an SPP strategy. The IPP strategy was associated with a higher probability of physiological recovery (odds ratio (OR) 2·77, 95 per cent c.i. 1·19 to 6·40, P = 0·017; risk ratio (RR) 1·82, 1·79 to 1·87, P = 0·049). The IPP strategy was also associated with a higher probability of emotional (P = 0·013) and overall (P = 0·011) recovery. Intraoperative adverse events were less frequent with the IPP strategy (P &lt; 0·001) and the plasma neutrophil–lymphocyte ratio was lower (P = 0·029). Other endpoints were not affected.

Conclusion

In this cohort of patients undergoing laparoscopic colorectal surgery, an IPP strategy was associated with faster recovery, fewer intraoperative complications and less inflammation than an SPP strategy. Registration number: NCT02773173 (http://www.clinicaltrials.gov).

Effects of intra-abdominal pressure on laparoscopic working space in domestic rabbits (Oryctolagus cuniculus)

OBJECTIVE

To assess the effects of 3 intra-abdominal pressures (IAPs) on pneumoperitoneal (laparoscopic working space) volume in domestic rabbits (Oryctolagus cuniculus).

ANIMALS

6 female New Zealand White rabbits.

PROCEDURES

A Latin-square design was used to randomly allocate sequences of 3 IAPs (4, 8, and 12 mm Hg) to each rabbit in a crossover study. Rabbits were anesthetized, subumbilical cannulae were placed, and CT scans were performed to obtain baseline measurements. Each IAP was achieved with CO₂ insufflation and maintained for ≥ 15 minutes; CT scans were performed with rabbits in dorsal, left lateral oblique, and right lateral oblique recumbency. The abdomen was desufflated for 5 minutes between treatments (the 3 IAPs). Pneumoperitoneal volumes were calculated from CT measurements with 3-D medical imaging software. Mixed linear regression models evaluated effects of IAP, rabbit position, and treatment order on working space volume.

RESULTS

Mean working space volume at an IAP of 8 mm Hg was significantly greater (a 19% increase) than that at 4 mm Hg, and was significantly greater (a 6.9% increase) at 12 mm Hg than that at 8 mm Hg. Treatment order, but not rabbit position, also had a significant effect on working space. Minor adverse effects reported in other species were observed in some rabbits.

CONCLUSIONS AND CLINICAL RELEVANCE

A nonlinear increase in abdominal working space was observed with increasing IAP. Depending on the type of procedure and visual access requirements, IAPs > 8 mm Hg may not provide a clinically important benefit for laparoscopy in rabbits.

Abdominal wall elasticity of children during pneumoperitoneum

OBJECTIVE

Laparoscopic surgery in children is often hampered by limited working space. This is partially compensated by stretching the child's abdominal wall. The volume of space that can be gained and changes to abdominal wall elasticity with respect to age are unknown. In the current research, we studied the extent of abdominal wall elasticity while establishing pneumoperitoneum in children.

METHODS

One hundred and sixty three children less than 18 years of age, undergoing elective laparoscopic surgery were recruited for the study. After induction of general anesthesia with a standardized muscle relaxant dose, a length of 5 cm was marked above, below and lateral to the umbilicus. The length of the marking was measured under increasing intraabdominal pressure (IAP of 0, 4, 6, 8, 10, 12 mmHg). The measurements were repeated to assess the effect of prestretching. The patients were divided into two groups: infants (less than one year of age) and older children (more than one year of age).

RESULTS

Depending on the age and axes of the measurements, a child's abdomen stretches up to 17% on average, with induction of pneumoperitoneum. The percentage of stretch tapers off as the IAP approaches peak pressure. As children become older, the longitudinal abdominal wall elasticity decreases, but the transverse abdominal wall elasticity increases. Regardless of age, prestretching results in a statistically significant increase in the elasticity over the transverse and lower sagittal abdominal wall.

CONCLUSION

A child's abdominal wall has considerable expandability. The characteristics of elasticity change depending on the axis and age. Prestretching can improve intraabdominal working space. This knowledge is helpful in port position design for minimally invasive surgery in children.

LEVEL OF EVIDENCE

Level II.

Abdominal Compliance and Laparoscopy: A Review

Background and Objectives

Creating and maintaining a pneumoperitoneum to perform laparoscopy is governed by gas laws and the limiting physical constraints of the abdomen.

Methods

A review of how gas, biomechanical and physical properties affect the abdomen and a systematic structured Medline and PubMed search was conducted to identify relevant studies related to the topic.

Results

Abdominal compliance is a measure of ease of abdominal expansion and is determined by the elasticity of the abdominal wall and diaphragm. It is the change in intra-abdominal volume per change in intra-abdominal pressure. Caution should be exercised with pressures exceeding 12 millimeters mercury since this is defined as intra-abdominal hypertension.

Conclusions

Abdominal compliance has its limits, is unique for each patient and pressure-volume curves cannot be easily predicted. Using the lowest possible pressure to accomplish the surgical task without compromising surgical outcome is the desired goal. The clinical importance is caution and knowing there is a point where more pressure does not increase working space and only increases pressure.

An individualised versus a conventional pneumoperitoneum pressure strategy during colorectal laparoscopic surgery: rationale and study protocol for a multicentre randomised clinical study

Background

A recent study shows that a multifaceted strategy using an individualised intra-abdominal pressure titration strategy during colorectal laparoscopic surgery results in an acceptable workspace at low intra-abdominal pressure in most patients. The multifaceted strategy, focused on lower to individualised intra-abdominal pressures, includes prestretching the abdominal wall during initial insufflation, deep neuromuscular blockade, low tidal volume ventilation settings and a modified lithotomy position. The study presented here tests the hypothesis that this strategy improves outcomes of patients scheduled for colorectal laparoscopic surgery.

Methods

The Individualized Pneumoperitoneum Pressure in Colorectal Laparoscopic Surgery versus Standard Therapy (IPPCollapse-II) study is a multicentre, two-arm, parallel-group, single-blinded randomised 1:1 clinical study that runs in four academic hospitals in Spain. Patients scheduled for colorectal laparoscopic surgery with American Society of Anesthesiologists classification I to III who are aged > 18 years and are without cognitive deficits are randomised to an individualised pneumoperitoneum pressure strategy (the intervention group) or to a conventional pneumoperitoneum pressure strategy (the control group). The primary outcome is recovery assessed with the Post-operative Quality of Recovery Scale (PQRS) at postoperative day 1. Secondary outcomes include PQRS score in the post anaesthesia care unit and at postoperative day 3, postoperative complications until postoperative day 28, hospital length of stay and process-related outcomes.

Discussion

The IPPCollapse-II study will be the first randomised clinical study that assesses the impact of an individualised pneumoperitoneum pressure strategy focused on working with the lowest intra-abdominal pressure during colorectal laparoscopic surgery on relevant patient-centred outcomes. The results of this large study, to be disseminated through conference presentations and publications in international peer-reviewed journals, are of ultimate importance for optimising the care and safety of laparoscopic abdominal surgery. Selection of patient-reported outcomes as the primary outcome of this study facilitates the translation into clinical practice. Access to source data will be made available through anonymised datasets upon request and after agreement of the Steering Committee of the IPPCollapse-II study.

Trial registration

ClinicalTrials.gov, NCT02773173. Registered on 16 May 2016. EudraCT, 2016-001693-15. Registered on 8 August 2016.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3255-1) contains supplementary material, which is available to authorized users.

A multifaceted individualized pneumoperitoneum strategy for laparoscopic colorectal surgery: a multicenter observational feasibility study

BACKGROUND

While guidelines for laparoscopic abdominal surgery advise using the lowest possible intra-abdominal pressure, commonly a standard pressure is used. We evaluated the feasibility of a predefined multifaceted individualized pneumoperitoneum strategy aiming at the lowest possible intra-abdominal pressure during laparoscopic colorectal surgery.

METHODS

Multicenter prospective study in patients scheduled for laparoscopic colorectal surgery. The strategy consisted of ventilation with low tidal volume, a modified lithotomy position, deep neuromuscular blockade, pre-stretching of the abdominal wall, and individualized intra-abdominal pressure titration; the effect was blindly evaluated by the surgeon. The primary endpoint was the proportion of surgical procedures completed at each individualized intra-abdominal pressure level. Secondary endpoints were the respiratory system driving pressure, and the estimated volume of insufflated CO₂ gas needed to perform the surgical procedure.

RESULTS

Ninety-two patients were enrolled in the study. Fourteen cases were converted to open surgery for reasons not related to the strategy. The intervention was feasible in all patients and well-accepted by all surgeons. In 61 out of 78 patients (78%), surgery was performed and completed at the lowest possible IAP, 8 mmHg. In 17 patients, IAP was raised up to 12 mmHg. The relationship between IAP and driving pressure was almost linear. The mean estimated intra-abdominal CO₂ volume at which surgery was performed was 3.2 L.

CONCLUSION

A multifaceted individualized pneumoperitoneum strategy during laparoscopic colorectal surgery was feasible and resulted in an adequate working space in most patients at lower intra-abdominal pressure and lower respiratory driving pressure. ClinicalTrials.gov (Trial Identifier: NCT03000465).

Ultrasound detection of diaphragm position in the region for lung monitoring by electrical impedance tomography during laparoscopy

BACKGROUND AND AIMS

During laparoscopic surgery, a capnoperitoneum is created to optimize the operating space for surgeons. One effect of this is abdominal pressure which alters the physiological thoraco-abdominal configuration and pushes the diaphragm and lungs cranially. Since the lung image acquired by electrical impedance tomography (EIT) depends on the conditions within the thorax and abdomen, it is crucial to know the diaphragm position to determine the effect of diaphragm shift on EIT thorax image.

METHODS

The presence of diaphragm in the region of EIT measurement was determined by ultrasound in 20 patients undergoing laparoscopic surgery. Data were obtained in the supine position during spontaneous breathing in a mechanically ventilated patient under general anesthesia with muscle relaxation and in a mechanically ventilated patient under general anesthesia with muscle relaxation during capnoperitoneum.

RESULTS

The diaphragm was shifted cranially during capnoperitoneum. The diaphragm detection rate rose by 10% during capnoperitoneum at the fifth intercostal space, from 55% to 65% and by 10% from 0% at mid-sternal level compared to mechanical ventilation without capnoperitoneum.

CONCLUSION

The diaphragm was detected in the area contributing to the creation of the thoracic EIT image. Considering the cranial shift of diaphragm caused by excessive intra-abdominal pressure, the impedance changes in the abdomen and the principle of EIT, we assume there could be a significant impact on EIT image of the thorax acquired during capnoperitoneum. For this reason, for lung monitoring using EIT during capnoperitoneum, the manufacturer's recommendation for electrode belt position is not appropriate. The study was registered in ClinicalTrials.gov with an identifier NCT03038061.

Influence of body weight and body conformation on the pressure-volume curve during capnoperitoneum in dogs

OBJECTIVE To evaluate the pressure-volume relationship during capnoperitoneum in dogs and effects of body weight and body conformation. ANIMALS 86 dogs scheduled for routine laparoscopy. PROCEDURES Dogs were allocated into 3 groups on the basis of body weight. Body measurements, body condition score, and body conformation indices were calculated. Carbon dioxide was insufflated into the abdomen with a syringe, and pressure was measured at the laparoscopic cannula. Volume and pressure data were processed, and the yield point, defined by use of a cutoff volume (COV) and cutoff pressure (COP), was calculated. RESULTS 20 dogs were excluded because of recording errors, air leakage attributable to surgical flaws, or trocar defects. For the remaining 66 dogs, the pressure-volume curve was linear-like until the yield point was reached, and then it became visibly exponential. Mean ± SD COP was 5.99 ± 0.805 mm Hg. No correlation was detected between yield point, body variables, or body weight. Mean COV was 1,196.2 ± 697.9 mL (65.15 ± 20.83 mL of CO₂/kg), and COV was correlated significantly with body weight and one of the body condition indices but not with other variables. CONCLUSION AND CLINICAL RELEVANCE In this study, there was a similar COP for all dogs of all sizes. In addition, results suggested that increasing the abdominal pressure after the yield point was reached did not contribute to a substantial increase in working space in the abdomen. No correlation was found between yield point, body variables, and body weight.

Design of Virtual Fixtures for Robotic Cholecystectomy

BACKGROUND AND OBJECTIVE

With the ongoing developments in robotic surgery, the associated adverse events need to be carefully evaluated. Virtual fixtures (VFs), a safety design feature against unintended motion during robotic surgery, have been proposed, but the methodology for designing VFs remains experimental. In this study, we propose a novel methodology for designing VFs for robotic cholecystectomy.

MATERIALS AND METHODS

Laparoscopic cholecystectomy (LC) was performed in 24 patients with cholecystitis. Active working space (AWS), the distance between instrument heads (DBIH), motion speed of bilateral hands, and instrument heads were calculated and analyzed.

RESULTS

DBIH was 14.78 ± 6.94 cm. Diameter of right and left AWS was 15.81 ± 3.69 cm and 15.33 ± 1.52 cm, respectively. DBIH was found to significantly correlate with the surgeon's experience. Bilateral AWS was found to be significantly associated with body circumference at Murphy's point level. However, no association was observed between bilateral AWS and surgeon's experience.

CONCLUSIONS

A novel methodology to build VFs for designing VFs for robotic cholecystectomy is established. Surgeon's experience appears to play an important role in determining the DBIH during robotic laparoscopic cholecystectomy, but does not affect bilateral AWS.

The Intraocular Pressure under Deep versus Moderate Neuromuscular Blockade during Low-Pressure Robot Assisted Laparoscopic Radical Prostatectomy in a Randomized Trial

Background

This study aimed to determine whether continuous deep neuromuscular blockade (NMB) improves the surgical conditions and facilitates robotic-assisted laparoscopic radical prostatectomy (RALRP) under low intra-abdominal pressure (IAP) to attenuate the increase in intraocular pressure (IOP) during CO₂ pneumoperitoneum in the steep Trendelenburg (ST) position.

Methods

Sixty-seven patients undergoing RALRP were randomly assigned to a moderate NMB group (Group M), including patients who received atracurium infusion until the end of the ST position, maintaining a train of four count of 1–2; and the deep NMB group (Group D), including patients who received rocuronium infusion, maintaining a post-tetanic count of 1–2. IOP was measured in all patients at nine separate time points. All RALRPs were performed by one surgeon, who rated the overall and worst surgical conditions at the end of the ST position.

Results

The highest IOP value was observed at T4 (60 min after the ST position) in both Group M (23.3 ± 2.7 mmHg) and Group D (19.8 ± 2.1 mmHg). RALRP was accomplished at an IAP of 8 mmHg in 88% Group D patients and 25% Group M patients. The overall surgical condition grade was 4.0 (3.0–5.0) in Group D and 3.0 (2.0–5.0) in Group M (P < 0.001).

Conclusion

The current study demonstrated that continuous deep NMB may improve surgical conditions and facilitate RALRP at a low IAP, resulting in significant attenuation of the increase on IOP. Moreover, low-pressure pneumoperitoneum, facilitated by deep NMB still provided acceptable surgical conditions.

Trial Registration

ClinicalTrials.gov NCT02109133

Abdominal compliance: A bench-to-bedside review

Abdominal compliance (AC) is an important determinant and predictor of available workspace during laparoscopic surgery. Furthermore, critically ill patients with a reduced AC are at an increased risk of developing intra-abdominal hypertension and abdominal compartment syndrome, both of which are associated with high morbidity and mortality. Despite this, AC is a concept that has been neglected in the past.AC is defined as a measure of the ease of abdominal expansion, expressed as a change in intra-abdominal volume (IAV) per change in intra-abdominal pressure (IAP):AC = ΔIAV / ΔIAPAC is a dynamic variable dependent on baseline IAV and IAP as well as abdominal reshaping and stretching capacity. Whereas AC itself can only rarely be measured, it always needs to be considered an important component of IAP. Patients with decreased AC are prone to fulminant development of abdominal compartment syndrome when concomitant risk factors for intra-abdominal hypertension are present.This review aims to clarify the pressure-volume relationship within the abdominal cavity. It highlights how different conditions and pathologies can affect AC and which management strategies could be applied to avoid serious consequences of decreased AC.We have pooled all available human data to calculate AC values in patients acutely and chronically exposed to intra-abdominal hypertension and demonstrated an exponential abdominal pressure-volume relationship. Most importantly, patients with high level of IAP have a reduced AC. In these patients, only small reduction in IAV can significantly increase AC and reduce IAPs.A greater knowledge on AC may help in selecting a better surgical approach and in reducing complications related to intra-abdominal hypertension.

Optimizing working space in laparoscopy: CT measurement of the influence of small body size in a porcine model

INTRODUCTION

In our continuing research into the determinants of laparoscopic working space, the influence of small body size was investigated.

METHODS

In eight 6-kg pigs, the effects of intraabdominal CO2 pneumoperitoneum pressure (IAP), prestretching of the abdominal wall, and neuromuscular blockade (NMB) on laparoscopic working space volume and distances were studied. Computed tomography was used to measure working space during two stepwise abdominal insufflation-runs up to an IAP of 15mm Hg. Results were compared with data from earlier experiments in 20-kg pigs.

RESULTS

Cardiorespiratory parameters were stable up to an IAP of 8-10mm Hg. In 6-kg pigs working-space dimensions were five times smaller than in 20-kg pigs. Working-space volume, anteroposterior (AP) diameter and symphysis-diaphragm distance increased linearly up to an IAP of 8mm Hg. Above 8mm Hg, compliance decreased. Eighty percent of the total volume (618ml) and of AP diameter (3cm) at 15mm Hg had been achieved at an IAP of 10mm Hg. Prestretching by a first insufflation resulted in a statistically significant increase in working space volume and in AP diameter during the second insufflation. This effect was significantly larger than in 20-kg pigs. Neuromuscular blockade did not have a significant effect on working-space.

CONCLUSIONS

Working space in growing individuals is very limited. Eighty percent of the working space created by an IAP of 15mm Hg was already achieved at 10mm Hg, while cardiorespiratory side effects at an IAP of 8-10mm Hg seem acceptable. Prestretching of the abdominal wall significantly increased working space, even more so than in 20-kg pigs. As in 20-kg pigs, NMB had no significant effect on laparoscopic working space. Prestretching of the abdominal wall is a promising cheap, safe and easy strategy to increase laparoscopic working space, lessening the need for prolonged high-pressure pneumoperitoneum.

Optimizing working space in laparoscopy: CT-measurement of the effect of neuromuscular blockade and its reversal in a porcine model

OBJECTIVE

The objective of this paper was to determine the effect of neuromuscular blockade (NMB) on working space in a porcine laparoscopy model.

BACKGROUND

Conflicting results on the effect of NMB on laparoscopic working space are found in literature. Almost all studies are limited by absence of objective assessment of working space or use surrogate outcomes.

METHODS

In a standardized porcine laparoscopy model, laparoscopic working-space dimensions with and without NMB were investigated in 16 animals using computed tomography at intra-abdominal pressures of 0, 5, 10, and 15 mmHg during multiple runs of abdominal insufflation.

RESULTS

No statistically significant effect of NMB on abdominal dimensions and laparoscopic working-space volume was found during CO2 pneumoperitoneum. In contrast, the effect of pre-stretching of the abdominal wall by a previous abdominal insufflation was found to be significant.

CONCLUSIONS

This experimental study confirms the results from several clinical studies that NMB does not influence laparoscopic working space. Studies dealing with working space during laparoscopy should take note of pre-stretching bias.

Optimizing working space in laparoscopy: CT measurement of the effect of pre-stretching of the abdominal wall in a porcine model

BACKGROUND

Determinants of working space in minimal access surgery have not been well studied. Using computed tomography (CT) to measure volumes and linear dimensions, we are studying the effect of a number of determinants of CO2 working space in a porcine laparoscopy model. Here we report the effects of pre-stretching of the abdominal wall.

METHODS

Earlier we had noted an increase in CO2 pneumoperitoneum volume at repeat insufflation with an intra-abdominal pressure (IAP) of 5 mmHg after previous stepwise insufflation up to an IAP of 15 mmHg. We reviewed the data of this serendipity group; data of 16 pigs were available. In a new group of eight pigs, we also explored this effect at repeat IAPs of 10 and 15 mmHg. Volumes and linear dimensions of the CO2 pneumoperitoneum were measured on reconstructed CT images and compared between the initial and repeat insufflation runs.

RESULTS

Previous stepwise insufflation of the abdomen with CO2 up to 15 mmHg significantly (p < 0.01) increased subsequent working-space volume at a repeat IAP of 5 mmHg by 21 %, 7 % at a repeat IAP of 10 mmHg and 3 % at a repeat IAP of 15 mmHg. The external anteroposterior diameter significantly (p < 0.01) increased by 0.5 cm (14 %) at repeat 5 mmHg. Other linear dimensions showed a much smaller change. There was no statistically significant correlation between the duration of the insufflation run and the volume increase after pre-stretching at all IAP levels.

CONCLUSIONS

Pre-stretching of the abdominal wall allows for the same surgical-field exposure at lower IAPs, reducing the negative effects of prolonged high-pressure CO2 pneumoperitoneum on the cardiorespiratory system and microcirculation. Pre-stretching has important scientific consequences in studies addressing ways of increasing working space in that its effect may confound the possible effects of other interventions aimed at increasing working space.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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