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

Prestretching increases working space at the same insufflation pressure in dogs undergoing laparoscopic procedures

OBJECTIVE

To determine if prestretching (PS) of the abdominal wall provided improved working space during elective laparoscopic procedures in dogs.

STUDY DESIGN

Prospective cohort study.

ANIMALS

Fifty client-owned dogs undergoing elective laparoscopic procedures.

METHODS

Skin markings were used to evaluate stretching of the abdominal wall. The distance from the subumbilical port to the caudal aspect of the gallbladder was measured as a proxy for intra-abdominal working length (IWL). Prestretching was performed by insufflating to an intra-abdominal pressure (IAP) of 10 mmHg for 3 min. The abdomen was desufflated back to 6 mmHg for the remainder of the procedure. A computed volumetric value utilizing skin measurements and IWL was used as a proxy for intra-abdominal working space (IWS). Percentage changes in IWL and IWS were compared.

RESULTS

Increasing the IAP from 6 to 10 mmHg increased the IWL by 7% (IQR 9.5%) and the IWS by 10.4% (IQR 13.8%) (p = .004 and .005, respectively). Returning to 6 mmHg after prestretching resulted in a median increase in IWL of 4.4% (IQR 5.7%) and IWS of 6.9% (IQR 5.4%) compared with the initial 6 mmHg IAP measurements (p < .001 for both). Intra-abdominal working length and IWS were similar at the end of surgery compared with post-PS 6 mmHg IAP measurements.

CONCLUSION

Prestretching resulted in improved IWL and IWS, although not to the extent achieved by higher insufflation pressures. The effects of PS persisted throughout the laparoscopic procedures performed in this study.

CLINICAL SIGNIFICANCE

Prestretching can provide additional laparoscopic IWL and IWS at a lower IAP.

Impact of Standard Versus Low Pneumoperitoneum Pressure on Peritoneal Environment in Laparoscopic Cholecystectomy. Randomized Clinical Trial

BACKGROUND

High CO 2 pneumoperitoneum pressure during laparoscopy adversely affects the peritoneal environment. This study hypothesized that low pneumoperitoneum pressure may be linked to less peritoneal damage and possibly to better clinical outcomes.

MATERIALS AND METHODS

One hundred patients undergoing scheduled laparoscopic cholecystectomy were randomized 1:1 to low or to standard pneumoperitoneum pressure. Peritoneal biopsies were performed at baseline time and 1 hour after peritoneum insufflation in all patients. The primary outcome was peritoneal remodeling biomarkers and apoptotic index. Secondary outcomes included biomarker differences at the studied times and some clinical variables such as length of hospital stay, and quality and safety issues related to the procedure.

RESULTS

Peritoneal IL6 after 1 hour of surgery was significantly higher in the standard than in the low-pressure group (4.26±1.34 vs. 3.24±1.21; P =0.001). On the contrary, levels of connective tissue growth factor and plasminogen activator inhibitor-I were higher in the low-pressure group (0.89±0.61 vs. 0.61±0.84; P =0.025, and 0.74±0.89 vs. 0.24±1.15; P =0.028, respectively). Regarding apoptotic index, similar levels were found in both groups and were 44.0±10.9 and 42.5±17.8 in low and standard pressure groups, respectively. None of the secondary outcomes showed differences between the 2 groups.

CONCLUSIONS

Peritoneal inflammation after laparoscopic cholecystectomy is higher when surgery is performed under standard pressure. Adhesion formation seems to be less in this group. The majority of patients undergoing surgery under low pressure were operated under optimal workspace conditions, regardless of the surgeon's expertise.

3D printed cannulas for use in laparoscopic surgery in feline patients: A cadaveric study and case series

OBJECTIVE

To evaluate custom 3D printed laparoscopic cannulas (3DPC) in a feline cadaveric abdominal surgery model and report their use in two live feline subjects.

STUDY DESIGN

Experimental cadaver study, live subject case series.

ANIMALS

Ten feline cadavers; two feline subjects.

METHODS

Custom 3DPCs were initially modeled in a PLA filament material and then created in an autoclavable dental resin for use in live patients. The surgery time, number of surgical collisions and cannula complications were recorded during cadaver procedures before and after use of 3DPCs. Cannula complications were recorded during live procedures and patients were followed to suture removal to record any incisional complications.

RESULTS

There was a significant reduction in mean surgical time (125.6 vs. 95.2 min, p = 0.03), mean number of instrument collisions (6.8 vs. 2.6, p = 0.03), and mean number of cannula complications (10 vs. 2.2, p = 0.03) with the use of only 3DPCs during the procedure. During the live procedures the use of the 3DPCs was successful and no postoperative complications occurred at the incision sites.

CONCLUSION

The use of customized 3DPCs may improve surgical dexterity and decrease complications in advanced procedures and was not associated with any clinical complications in two cats. The use of 3DPCs in veterinary medicine may allow for wider practice of laparoscopic techniques in small animals.

A novel method for monitoring abdominal compliance to optimize insufflation pressure during laparoscopy

BACKGROUND

Abdominal compliance describes the ease of expansion of the abdominal cavity. Several studies highlighted the importance of monitoring abdominal compliance (Cab) during the creation of laparoscopic workspace to individualize the insufflation pressure. The lack of validated clinical monitoring tools for abdominal compliance prevents accurate tailoring of insufflation pressure. Oscillometry, also known as the forced oscillation technique (FOT), is currently used to measure respiratory mechanics and has the potential to be adapted for monitoring abdominal compliance. This study aimed to define, develop and evaluate a novel approach which can monitor abdominal compliance during laparoscopy using endoscopic oscillometry.

MATERIALS AND METHODS

Endoscopic oscillometry was evaluated in a porcine model for laparoscopy. A custom-built insufflator was developed for applying an oscillatory pressure signal superimposed onto a mean intra-abdominal pressure. This insufflator was used to measure the abdominal compliance at insufflation pressures ranging from 5 to 20 hPa (3.75 to 15 mmHg). The measurements were compared to the static abdominal compliance, which was measured simultaneously with computed tomography imaging.

RESULTS

Endoscopic oscillometry recordings and CT images were obtained in 10 subjects, resulting in 76 measurement pairs for analysis. The measured dynamic Cab ranged between 0.0216 and 0.261 L/hPa while the static Cab based on the CT imaging ranged between 0.0318 and 0.364 L/hPa. The correlation showed a polynomial relation and the adjusted R-squared was 97.1%.

CONCLUSIONS

Endoscopic oscillometry can be used to monitor changes in abdominal compliance during laparoscopic surgery, which was demonstrated in this study with a comparison with CT imaging in a porcine laparoscopy model. Use of this technology to personalize the insufflation pressure could reduce the risk of applying excessive pressure and limit the drawbacks of insufflation.

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.

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.

Conversion Rate in Pediatric Robotic-Assisted Surgery: Looking for the Culprit

Introduction: Robotic-assisted surgery (RAS) is increasingly used in adulthood but its application in pediatric population is limited. We report our initial experience in pediatric RAS, focusing on conversions to analyze their causes. Methods: All pediatric patients who underwent RAS between June 2015 and April 2019 were included, analyzing demographics, comorbidities, previous surgery, and intraoperative surgical and anesthetic parameters. A three-arms robotic technique was used in all cases. Additional laparoscopic ports were added, when needed. The surgical team did not change during the program, whereas the anesthesiology team varied. Results: Thirty-nine patients (23 females, 16 males; mean age ± SD = 9.33 ± 4.73 years [range = 1-16]; mean weight ± SD = 35.2 ± 20.0 kg [range = 9-85]) underwent 40 different procedures (18 gastrointestinal, 15 urogynecological, 5 oncological, and 2 miscellaneous). Three procedures (7.5%) were converted to open surgery for inadequate working space (two marked bowel distension and one insufficient hepatic retraction). Converted patients were of significant lower age (mean ± standard error of mean [SEM] = 2.97 ± 1.03 versus 9.83 ± 0.77 years, P = .01) and lower weight (mean ± SEM = 11.83 ± 1.74 versus 35.47 ± 3.16 kg, P = .03). The two groups did not differ statistically for duration of facial mask ventilation before intubation (mean ± SEM = converted 10.67 ± 2.33 versus completed 10.31 ± 0.91 minutes), neuromuscular block dosage (rocuronium; mean ± SEM = converted 0.46 ± 0.06 mg/kg versus completed 0.62 ± 0.03 mg/kg) and in the type of bowel preparation (mechanical and/or pharmacological). Discussion: Conversion rate in initial pediatric RAS program is acceptable. In children, the need for conversion is mainly because of inadequate working space, particularly in smaller children, but it seems not to be influenced by measurable anesthetic factors or different regimen for bowel preparation.

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.

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.

Differences in midline fascial forces exist following laparoscopic and open transversus abdominis release in a porcine model

INTRODUCTION

Posterior component separation herniorrhaphy via transversus abdominis release (TAR) permits midline reapproximation of large fascial defects. To date, no report delineates the reduction in tensile force to reapproximate midline fascia following TAR. We hypothesized that open and laparoscopic TAR would provide similar reductions in midline reapproximation forces in a porcine model.

METHODS

Under general anesthesia, a 20-cm midline laparotomy was created and bilateral lipocutaneous flaps were raised to expose the anterior rectus sheath. Five stainless steel hooks were placed at 1-cm intervals lateral to the midline at three locations: 5 cm above, at, and 5 cm below the umbilicus bilaterally. Baseline force measurements were taken by pulling each lateral point to midline. Laparoscopic TAR was performed unilaterally by incising the parietal peritoneum and transversus muscle lateral to the linea semilunaris. Open TAR was performed contralaterally, and force measurements were repeated. Comparisons were made to baseline and between the groups.

RESULTS

Following laparoscopic TAR, 87 % (13/15) of points showed significant reduction compared to baseline forces, whereas only 20 % (3/15) of open TAR points had significant force reductions. Compared to open TAR, three locations favored the laparoscopic approach [1 cm lateral to midline, 5 cm above the umbilicus (p = 0.04; 95 % CI 0.78-1.00), 2 cm lateral to midline at the umbilicus (p = 0.04; 95 % CI 0.80-1.00), and 1 cm lateral to midline 5 cm below the umbilicus (p = 0.05; 95 % CI 0.79-1.00)]. The mean length of TAR was longer for laparoscopic than open at 27.29 versus 19.55 cm (p < 0.0001; 95 % CI 6.46-9.02).

CONCLUSIONS

Open TAR reduced midline tensile force at few locations, suggesting that the mechanism by which TAR facilitates herniorraphy may not solely be through reductions in linea alba tensile forces. At specific locations, laparoscopic TAR provides superior reduction in midline closure force compared to open TAR, likely as a result of a longer muscle release.

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.

Failed pneumoperitoneum for laparoscopic surgery following autologous Deep Inferior Epigastric Perforator (DIEP) flap breast reconstruction: a case report

Background

Laparoscopic abdominal surgery may prove difficult in patients who have undergone previous abdominal procedures. No reports in the medical literature have presented an aborted laparoscopic procedure for failed pneumoperitoneum following autologous flap-based breast reconstruction.

Case presentation

A 55-year-old woman presented with recurrent invasive lobular carcinoma of the right breast as well as a history of ductal carcinoma in situ of the left breast. The patient desired to proceed with bilateral skin- and nipple-sparing mastectomies with right axillary lymph node biopsy, followed by immediate bilateral autologous deep inferior epigastric perforator (DIEP) flap-based breast reconstruction. Preoperatively, a computerized tomography angiogram was obtained for reconstructive preparation, which revealed a left adrenal mass. Ensuing work-up diagnosed a pheochromocytoma. Given the concern for breast cancer progression, the patient elected to proceed first with breast cancer surgery and reconstruction prior to addressing the adrenal tumor. Subsequently, 3 months later the patient was brought to the operating room for a laparoscopic left adrenalectomy for the pheochromocytoma. With complete pharmacologic abdominal relaxation, the abdomen proved too tight to accommodate sufficient pneumoperitoneum and the laparoscopy was aborted. The patient was evaluated in the outpatient setting for assessment of abdominal wall compliance at regular intervals. Five months later, the patient was taken back to the operating room where pneumoperitoneum was established without difficulty and the laparoscopic left adrenalectomy was performed without complications.

Conclusion

Pneumoperitoneum for laparoscopic surgery subsequent to autologous DIEP flap-based breast reconstruction may prove difficult as a result of loss of abdominal wall compliance. Prior to performing laparoscopy in such patients, surgeons should consider the details of the patient’s previous reconstructive procedure and assess potential risk factors for difficulty with insufflation. Lastly, careful abdominal examination should be performed to indicate whether laparoscopy for elective procedures should be delayed until abdominal wall compliance normalizes.