Comparison of a Valveless Trocar System and Conventional Insufflation in Pediatric Urologic Surgery

Abstract

Background:

Conventional operative insufflation uses a one-way trocar to handle instruments while maintaining pneumoperitoneum. In 2007, the AirSeal^® valveless trocar insufflation system was introduced, which maintains stable pneumoperitoneum while continuously evacuating smoke. Although this device has been validated in adult patients, it has not been extensively validated in the pediatric population.

Materials and Methods:

A retrospective cohort study of pediatric urology patients aged 0 to 21 who underwent laparoscopic pyeloplasty between March 2016 and October 2021 was performed. Intraoperative physiologic parameters, procedure characteristics, postoperative outcomes, and demographics of each patient in whom either AirSeal insufflation system (AIS) or conventional insufflation system (CIS) was utilized were obtained from hospital records. Data were compared across the AIS and CIS cohorts. The primary outcomes were intraoperative anesthetic and physiologic parameters, including end tidal carbon dioxide, oxygen saturation, body temperature, positive inspiratory pressure, systolic blood pressure, and heart rate.

Results:

There were no significant differences in the anesthetic and physiologic parameters in the AIS and CIS groups. In addition, no differences in demographics, procedural characteristics, or complication rates were found between the cohorts.

Conclusion:

The AirSeal valveless trocar insufflation system demonstrates comparable intraoperative anesthetic and physiologic outcomes compared to conventional one-way valve insufflation in pediatric laparoscopic pyeloplasty. Certain surgeon-related qualitative metrics are underappreciated in this study, however, including improved visualization with vigorous suctioning and pressure maintenance with frequent instrument exchanges. Surgeon experience may mask the benefits of these characteristics as it pertains to quantitative surgical outcomes such as estimated blood loss, operative time, and perioperative complications.

Introduction

Adequate insufflation is critical for visualization and operative manipulation during laparoscopy. Pneumoperitoneum in laparoscopic surgeries is achieved through insufflation with carbon dioxide (CO₂), which is colorless, highly diffusible, rapidly reabsorbed, and rapidly excreted.¹ Unstable pneumoperitoneum may contribute to an increased risk of intraoperative complications and extend the duration of operative and anesthetic time.

Conventional insufflation uses a one-way trocar through which instruments are handled while maintaining pneumoperitoneum. This closed system is associated with several limitations.² First, CO₂ gas lost during the exchange of instruments must be constantly replaced. One-way trocars are also associated with moisture collection on the laparoscopic lens, impairing visibility of the surgical field. In addition, surgical smoke from the use of electrocautery must be manually evacuated with a suction device, increasing operative time. Difficulties with retrieving intact specimens and transferring needles have also been reported.³ Finally, the one-way valve may lead to elevated intraperitoneal CO₂ levels, with potentially harmful side-effects, including alterations in heart rate (HR), cardiac contractility, and vascular resistance.⁴ In infants, potential adverse effects of pneumoperitoneum include reduced urine output and alterations in cerebral oxygenation and blood flow.⁵

In 2007, a valveless trocar insufflation system (AirSeal^®; SurgiQuest, Milford, CT) was introduced to counteract the limitations of conventional insufflation. This system comprised a valveless trocar (AirSeal Access Port), three-lumen tubing, and the AirSeal Intelligent Flow System consisting of insufflation, filtration, and recirculation.⁶ This low-impact strategy is designed to maintain stable pneumoperitoneum regulated by a CO₂ pressure sensor, while continuously evacuating smoke. Prospective randomized trials have reported significantly less variability in pressure readings, lower end-tidal CO₂ (EtCO₂) levels, decreased operative time, and reduced trocar manipulations for specimen or needle retrieval.^6
–8

While the benefits of AirSeal are well-established in the adult population, it has not been extensively studied in pediatric subjects. Stable pneumoperitoneum is critical in infants and children in whom anatomic limitations (particularly the small peritoneal volume) challenge visualization and instrument manipulation, with risk for subcutaneous emphysema and masked pneumothorax. The purpose of this study is to formally assess for differences in intraoperative anesthetic and physiologic parameters of the AirSeal valveless trocar insufflation system when compared to conventional insufflation in pediatric subjects who have undergone laparoscopic/robotic pyeloplasty.

Materials and Methods

Between March 2016 and October 2021, a retrospective, single-center analysis was conducted to evaluate the safety of the SurgiQuest AirSeal valveless trocar insufflation system in pediatric subjects who have undergone laparoscopic urologic surgery. This study was conducted at The Bristol-Myers Squibb Children's Hospital at Robert Wood Johnson University Hospital by three surgeons performing laparoscopic or robot-assisted laparoscopic urologic procedures. Institutional Review Board approval was obtained. Inclusion criteria were pediatric subjects (up to age 21) who had undergone laparoscopic or robot-assisted laparoscopic urologic procedures performed at our institution. The two cohorts consisted of subjects in whom pneumoperitoneum was achieved through the valveless trocar using the AirSeal insufflation system (AIS) and those in whom pneumoperitoneum was achieved through closed, one-way valves using the conventional insufflation system (CIS).

Patients underwent standard evaluation and management by experienced anesthesiologists in the preoperative and intraoperative period. All patients received standard care with endotracheal intubation and positive pressure ventilation. Ventilation was delivered under pressure-controlled ventilator settings with a target tidal volume of 6 to 8 mL/kg. Patients in the study arm were insufflated using a 5, 8, or 12-mm AirSeal Access Port (SurgiQuest) connected to the AirSeal IFS insufflator (SurgiQuest). Endopath XCEL (Ethicon, Somerville, NJ) and Endotip (Storz, Cluver City, CA) trocars were used for secondary ports for instrumentation. Of note, these trocars generally have an outer diameter slightly larger than the manufacturer's noted diameter (e.g., a 5 mm port has an outer diameter greater than 5 mm).

Conventional insufflation patients had their procedures performed using Endopath XCEL and Endotip trocars with insufflation through a 6 or 11 mm assistant port connected to a standard insufflation system (Storz). All operations were performed at an intraperitoneal pressure ranging from 8 to 10 mmHg with a flow rate of 40 L/min.

Patient information was obtained from our institution's electronic medical record. Perioperative outcomes were obtained from electronic records as well as written intraoperative anesthesia reports documenting ventilator settings and physiologic parameters. Collected patient demographic information included age, race, gender, and body mass index (BMI). The primary outcomes were intraoperative anesthetic and physiologic parameters, including ETCO₂, arterial oxygen saturation (SaO₂), core temperature, peak inspiratory pressure (PIP), systolic blood pressure (SBP), HR, and intraoperatively administered intravenous fluids such as crystalloids, antibiotics, and additional sedation. Secondary outcomes included procedural characteristics such as perioperative complication rates, estimated blood loss, and hospital length of stay. Records were also reviewed for documentation of subcutaneous emphysema.

ETCO₂ was measured as an indicator of arterial partial pressure of CO₂ and systemic CO₂ absorption as well as risk of respiratory depression, respiratory acidosis, hypoxia, and malignant hyperthermia.⁹ Intraoperative SaO₂ measurement serves as an early detector of hypoxemia and related complications such as hypoventilation.¹⁰ Intraoperative core temperature was evaluated for detection of hypothermia and hyperthermia, as well as common inflammatory concerns such as fever, intraventricular hemorrhage, and mismatched blood transfusions.¹¹ PIP served as an indicator for risk of hyperventilation and barotrauma with poor compliance.¹² SBP and HR are components of cardiac output for monitoring of circulatory perfusion. Procedural characteristics were recorded by the intraoperative anesthesiologist for all patients in hand-written reports. An experienced anesthesiologist assisted with review of intraoperative reports. Perioperative complications were categorized by grade using the Clavien-Dindo classification.

Ethical approval

Our research complies with the Journal of Endourology and Committee on Publication Ethics guidelines on ethical publishing.

Statistical analysis

Sample size was determined through convenience sampling of patients at our institution who satisfied inclusion criteria. The primary outcome of intra- and postoperative complication rate (subdivided by Clavien-Dindo grade) was assessed by two-sided Fisher's exact test.

Continuous variables (age, BMI, duration, length of stay (LOS), SaO₂, PIP, SBP, and HR) were tested for normality using the Shapiro-Wilks test with a cutoff of 0.01. Continuous normal variables were reported as means (SD), while non-normal variables were reported as median (IQR). Categorical data (race, gender, positioning) were reported as n (%).

Repeatedly monitored intraoperative data, including core temperature, SaO₂, PIP, SBP, and HR, were quantified by taking the single-case average recorded value over the duration of each case, then comparing the means of the single-case averages between the two cohorts by two sided, two-sample t-tests, p-values.

Due to the small sample size, categorical variables were compared with Fisher's exact tests. Continuous normal variables were assessed using two-sided t-tests, while continuous non-normal variables were assessed using the Kruskal-Wallis test. p-Values <0.05 were deemed significant. All analyses were performed using R software version 3.6.2 (https://cran.r-project.org).

Results

Twenty-six pediatric patients who underwent laparoscopic pyeloplasty were included in the study, with accrual from March 2016 to October 2021. The AIS arm had 14 patients. The CIS arm had 12 patients. Patient demographic data and surgery characteristics are presented in Table 1. There were no significant differences in demographic or surgical data, including race, BMI, procedure type, or patient positioning. The average age at surgery was 8.82 years (range of 3.66–15.6) in the AIS arm, and 8.88 years (range of 4.62–17.6) in the CIS arm. Of the 14 patients in the AIS cohort, 4 (28.6%) were insufflated with a 5 mm AirSeal trocar, 6 (37.5%) with an 8 mm trocar, and 4 (28.6%) with a 12 mm trocar. Average procedure durations were 237 minutes (range of 216–272) for the AIS group and 219 minutes (range of 191–245) for the CIS group (p = 0.22).

Table 1.

Patient Demographics, Procedures, and Positioning

	Overall	AirSeal^®	Conventional	p
	N = 26	N = 14	N = 12	p
Median age (IQR), years	8.87 (3.66–16.6)	8.82 (3.66–15.6)	8.88 (4.62–17.6)	0.643
Gender				0.683
Female	9 (34.6%)	4 (28.6%)	5 (41.7%)
Male	17 (65.4%)	10 (71.4%)	7 (58.3%)
Race				0.294
African American	7 (26.9%)	3 (21.4%)	4 (33.3%)
Asian	2 (7.69%)	0 (0.00%)	2 (16.7%)
Other	5 (19.2%)	4 (28.6%)	1 (8.33%)
Caucasian	12 (46.2%)	7 (50.0%)	5 (41.7%)
Median BMI (IQR)	17.2 (15.8–20.3)	17.3 (16.4–22.3)	16.5 (15.0–19.1)	0.266
Procedure: pyeloplasty	26 (100%)	14 (100%)	12 (100%)	.
Positioning				1
L lateral decubitus	8 (30.8%)	4 (28.6%)	4 (33.3%)
R lateral decubitus	18 (69.2%)	10 (71.4%)	8 (66.7%)
Median duration (IQR), minutes	228 (201–269)	237 (216–272)	219 (191–245)	0.217

BMI = body mass index.

Primary and secondary endpoints are presented in Table 2. There were no significant differences in the estimated blood loss (p = 1.0) or hospital length of stay (p = 0.931). ETCO₂ was consistent across both cohorts (p = 0.672), with an average of 39.1 mmHg (SD = 2.79 mmHg) in AIS patients and an average of 38.6 mmHg (SD = 3.01 mmHg) in CIS patients. There was no significant difference in the intraoperative SaO₂ (p = 0.067), average core temperature (p = 0.17), PIP (p = 0.75), SBP (p = 0.63), HR (p = 0.60), or administered IV fluids (p = 0.86).

Table 2.

Procedural Data and Outcomes

	Overall	AirSeal	Conventional	p
	N = 26	N = 14	N = 12
Median estimated blood loss (IQR)	25.0 (5.00–42.5)	22.5 (2.50–47.5)	25.0 (5.00–25.0)	1
Median LOS (IQR)	1.00 (1.00–2.00)	1.00 (1.00–2.00)	1.00 (1.00–2.00)	0.931
Mean ETCO₂ (SD)	38.9 (2.84)	39.1 (2.79)	38.6 (3.01)	0.672
Median IntraopSaO₂ (IQR)	100 (99.9–100)	99.9 (99.5–100)	100 (100.0–100)	0.067
Mean IntraopTemp (SD)	36.1 (0.61)	35.9 (0.52)	36.2 (0.68)	0.173
Mean PIP (SD)	20.4 (4.78)	20.7 (4.36)	20.0 (5.54)	0.752
Mean SBP (SD)	103 (13.6)	102 (14.9)	104 (12.4)	0.63
Mean HR (SD)	103 (20.0)	101 (19.9)	105 (20.8)	0.597
Median IVF (IQR)	800 (500–1575)	950 (512–1500)	775 (462–1650)	0.857
CompGrade				0.203
1	1 (3.85%)	1 (7.14%)	0 (0.00%)
3b	2 (7.69%)	0 (0.00%)	2 (16.7%)
None	23 (88.5%)	13 (92.9%)	10 (83.3%)
Specific complications
Grade I
Fever		1	0
Grade IIIb
Incisional hernia		0	1
Hydronephrosis		0	1

ETCO₂ = end-tidal carbon dioxide; LOS = length of stay; PIP = peak inspiratory pressure; SBP = systolic blood pressure

There was no significant difference in complication rate or severity between the AIS and CIS cohorts (p = 0.11). Thirteen of 14 (92.9%) AIS patients and 10 of 12 (83.3%) CIS patients had no perioperative complications. The complication in the AIS cohort was fever. The two complications in the CIS cohort were hydronephrosis which necessitated ureteral stent exchange and an incisional hernia. No patients were noted to have clinically significant subcutaneous emphysema.

Discussion

Pneumoperitoneum causes a multitude of changes in hemodynamic parameters, including a decrease in venous return, preload, and cardiac output and an increase in HR, mean arterial pressure, systemic venous resistance, and pulmonary vascular resistance.¹³ These changes may warrant more invasive measurements by the anesthesia provider. Other challenges that must be overcome by surgical teams include condensation on the camera, difficulty extracting specimens, and risk of losing needles during passage.³ The introduction of the AirSeal valveless trocar insufflation system was a promising advancement in laparoscopic surgery, as it helped mitigate these concerns. Of particular importance in pediatric patients is the smaller peritoneal volume, which can collapse under suction. In contrast, AirSeal allows for maintenance of pneumoperitoneum even with vigorous suctioning.¹⁴

Risks associated with AirSeal use in comparison to conventional insufflation have been previously documented. In 2013, Horstmann et al. reported a significantly higher incidence of subcutaneous emphysema in patients insufflated using AirSeal.⁷ Conversely, a 2021 systematic review of AirSeal use in laparoscopic surgery reported no differences in total complications, severe (Clavien-Dindo scores ≥2) complications, or rate of conversion to laparotomy.⁶ Likewise, only one of eight studies for which data were available reported significantly increased blood loss in AirSeal-insufflated patients undergoing laparoscopic renal surgery.⁸

In 2016, Miyano et al. published, to our knowledge, the first study to report on the use of AirSeal in the pediatric population undergoing laparoscopic appendectomy, which demonstrated a significantly lower intraperitoneal pressure in comparison to conventional insufflation. This difference was accompanied by a significantly lower mean SBP and mean ETCO₂, while all other parameters were similar between groups. In the present study, no significant differences were observed across all parameters, including blood loss, ETCO₂, perioperative complications, HR, or SaO₂. Miyano et al. also noted that their mean operative times were relatively short (72.2–76.2 minutes), which limited the scope of their analysis.

In the current study, the substantially greater overall mean operative time (201–269 minutes) allowed a more robust analysis of the effects of AirSeal. The greater procedure lengths in our study reduce the influence of variance in single-cases, and thus provide for more accurate characterization of intraoperative parameters. In addition, the range of subjects' ages in the work by Miyano et al. is much narrower than that of our study. The prior work examined patients ranging from age 3 to 14 years, while our study encompasses the entire range of pediatric ages, with patients in both cohorts ranging from <1 to 21 years old.¹⁵ This, however, comes with the important caveat that there are significant physiologic differences among this age range and these results may not be generalizable to all pediatric subpopulations.

In comparison to studies of adults, the results we present here are similar in terms of the complication rates associated with AirSeal use. A 2017 study by Annino et al. prospectively compared 122 consecutive patients split into two cohorts who underwent robotic partial nephrectomy with conventional (n = 55) or AirSeal (n = 67) insufflation.¹⁶ Similar to the current study, Annino et al. reported no differences in postoperative complications and no cases of subcutaneous emphysema. In 2021, Desroches et al. reported the results of a multi-institutional, randomized controlled trial comparing the use of AirSeal vs conventional insufflation for robotic partial nephrectomy in 202 patients, with a maximum intraperitoneal pressure of 15 mmHg.¹⁷ This study reported no significant differences in ETCO₂, subcutaneous emphysema rates, or estimated blood loss in the AirSeal group when compared to the conventional group.

An important consideration when utilizing AirSeal for laparoscopic surgery is its cost effectiveness. There are currently no studies in the literature that specifically delineate the differences in financial burden associated with CIS vs AIS. A rudimentary look at costs charged to our hospital by ConMed© shows that regardless of size of the AirSeal port, the cost of said device is ∼80 USD. This, however, only accounts for the disposable components of the AIS and does not consider the upfront and operating costs of the insufflator itself along with any reduced costs resulting from improvement in qualitative surgical metrics. A more detailed analysis is beyond the scope of our study.

This single-center study has several limiting factors which warrant future efforts in examining the safety and efficacy of AirSeal in the pediatric population. The study's retrospective nature limited the data available for analysis, such as our inability to compare intra-abdominal pressure and insufflation settings due to a lack of documentation. Our institution's use of paper charts for intraoperative anesthesia records, along with interprovider variability in charting, presented challenges in data interpretation. The small sample size for this study limits our conclusions on operative complication rates. Operative complications that can be directly sourced to the laparoscopic process are rare, and true incidence cannot be fully captured without a much larger sample. Finally, while the average procedure length was substantial, the range of procedure times does create variability. Differing procedure lengths caused patients to have inconsistent quantities of data points for continuously monitored intraoperative variables (e.g., HR).

As a result, single-case averages calculated from shorter procedures foster greater variance and less reliability. Nonetheless, this study represents an important documentation of the safety of the use of AirSeal in pediatric patients over a broad range of ages and procedures. While this work cannot definitively establish the safety profile of AirSeal systems in pediatric patients, it does indicate that only limited differences exist in complication rates when compared to standard insufflation. Future work must investigate both the safety and efficacy of AirSeal in pediatric urologic surgery through prospective reviews or randomized controlled trials, to elicit a clearer understanding of the role of AirSeal in this patient population.

Conclusion

The AirSeal valveless trocar insufflation system demonstrated comparable intraoperative safety compared to conventional insufflation using a one-way valve in pediatric laparoscopic urologic surgery. Future prospective studies are needed for evaluation of additional outcomes of interest, including the financial burden that comes with its utilization.

Footnotes

Authors' Contributions

A.L.C.: methodology, formal analysis, investigation, data curation, writing—original draft, and writing—review and editing. S.K.D.: writing—review and editing and supervision. J.L.P.: formal analysis, data curation, and writing—review and editing. G.L.: conceptualization, methodology, investigation, data curation, and writing—original draft. M.M.: investigation and writing—original draft. B.A.: investigation and resources. E.T.T.: validation and data curation. U.S.: writing—review and editing and supervision. J.B.: conceptualization, writing—review and editing, and supervision. H.A.: conceptualization, writing—review and editing, and supervision. S.E.: conceptualization, writing—review and editing, supervision, and project administration.

Author Disclosure Statement

S.E. reports a relationship with Intuitive Surgical, Inc., that includes consulting or advisory and speaking and lecture fees.

Funding Information

No funding was received for this article.

Abbreviations Used

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