Pneumoperitoneum deteriorates intratidal respiratory system mechanics: an observational study in lung-healthy patients

Driving pressure during general anesthesia for minimally invasive abdominal surgery (GENERATOR)-study protocol of a randomized clinical trial

BACKGROUND

Intraoperative driving pressure (ΔP) has an independent association with the development of postoperative pulmonary complications (PPCs) in patients receiving ventilation during general anesthesia for major surgery. Ventilation with high intraoperative positive end-expiratory pressure (PEEP) with recruitment maneuvers (RMs) that result in a low ΔP has the potential to prevent PPCs. This trial tests the hypothesis that compared to standard low PEEP without RMs, an individualized high PEEP strategy, titrated to the lowest ΔP, with RMs prevents PPCs in patients receiving intraoperative protective ventilation during anesthesia for minimally invasive abdominal surgery.

METHODS

"DrivinG prEssure duriNg gEneRal AnesThesia fOr minimally invasive abdominal suRgery (GENERATOR)" is an international, multicenter, two-group, patient and outcome-assessor blinded randomized clinical trial. In total, 1806 adult patients scheduled for minimally invasive abdominal surgery and with an increased risk of PPCs based on (i) the ARISCAT risk score for PPCs (≥ 26 points) and/or (ii) a combination of age > 40 years and scheduled surgery lasting > 2 h and planned to receive an intra-arterial catheter for blood pressure monitoring during the surgery will be included. Patients are assigned to either an intraoperative ventilation strategy with individualized high PEEP, titrated to the lowest ΔP, with RMs or one with a standard low PEEP of 5 cm H2O without RMs. The primary outcome is a collapsed composite endpoint of PPCs until postoperative day 5.

DISCUSSION

GENERATOR will be the first adequately powered randomized clinical trial to compare the effects of individualized high PEEP with RMs versus standard low PEEP without RMs on the occurrence of PPCs after minimally invasive abdominal surgery. The results of the GENERATOR trial will support anesthesiologists in their decisions regarding PEEP settings during minimally invasive abdominal surgery.

TRIAL REGISTRATION

GENERATOR is registered at ClinicalTrials.gov (study identifier: NCT06101511) on 26 October 2023.

The Impact of Pneumoperitoneum on Mean Expiratory Flow Rate: Observational Insights from Patients with Healthy Lungs

BACKGROUND/OBJECTIVES

Surgical pneumoperitoneum (PP) significantly impacts volume-controlled ventilation, characterized by reduced respiratory compliance, elevated peak inspiratory pressure, and an accelerated expiratory phase due to an earlier onset of the airway pressure gradient. We hypothesized that this would shorten expiratory time, potentially increasing expiratory flow rate compared to pneumoperitoneum conditions. Calculations were performed to establish correlations between respiratory parameters and the mean increase in expiratory flow rate relative to baseline.

METHODS

Mechanical ventilation parameters were recorded for 67 patients both pre- and post-PP. Ventilator settings were standardized with a tidal volume of 6 mL/kg, a respiratory rate of 12 breaths per minute, a PEEP of 3 cmH2O, an inspiratory time of 2 s, and an inspiratory-to-expiratory ratio of 1:1.5 (I:E).

RESULTS

The application of PP increased both peak inspiratory pressure and mean expiratory flow rate by 28% compared to baseline levels. The elevated intra-abdominal pressure of 20 cmH2O resulted in a 34% reduction in dynamic chest compliance, a 50% increase in elastance, and a 20% increase in airway resistance. The mean expiratory flow rate increments relative to baseline showed a significant negative correlation with elastance (p = 0.0119) and a positive correlation with dynamic compliance (p = 0.0028) and resistance (p = 0.0240).

CONCLUSIONS

A PP of 20 cmH2O resulted in an increase in the mean expiratory flow rate in the conventional I:E ratio in the volume-ventilated mode. PP reduces lung and chest wall compliance by elevating the diaphragm, compressing the thoracic cavity, and increasing airway pressures. Consequently, the lungs and chest wall stiffen, requiring greater ventilatory effort and accelerating expiratory flow due to increased airway resistance and altered pulmonary mechanics. Prolonging the inspiratory phase through I:E ratio adjustment helps maintain peak inspiratory pressures closer to baseline levels, and this method enhances the safety and efficacy of mechanical ventilation in maintaining optimal respiratory function during laparoscopic surgery.

The Association of Intraoperative driving pressure with postoperative pulmonary complications in open versus closed abdominal surgery patients - a posthoc propensity score-weighted cohort analysis of the LAS VEGAS study

BACKGROUND

It is uncertain whether the association of the intraoperative driving pressure (ΔP) with postoperative pulmonary complications (PPCs) depends on the surgical approach during abdominal surgery. Our primary objective was to determine and compare the association of time-weighted average ΔP (ΔP_TW) with PPCs. We also tested the association of ΔP_TW with intraoperative adverse events.

METHODS

Posthoc retrospective propensity score-weighted cohort analysis of patients undergoing open or closed abdominal surgery in the 'Local ASsessment of Ventilatory management during General Anaesthesia for Surgery' (LAS VEGAS) study, that included patients in 146 hospitals across 29 countries. The primary endpoint was a composite of PPCs. The secondary endpoint was a composite of intraoperative adverse events.

RESULTS

The analysis included 1128 and 906 patients undergoing open or closed abdominal surgery, respectively. The PPC rate was 5%. ΔP was lower in open abdominal surgery patients, but ΔP_TW was not different between groups. The association of ΔP_TW with PPCs was significant in both groups and had a higher risk ratio in closed compared to open abdominal surgery patients (1.11 [95%CI 1.10 to 1.20], P <  0.001 versus 1.05 [95%CI 1.05 to 1.05], P <  0.001; risk difference 0.05 [95%CI 0.04 to 0.06], P <  0.001). The association of ΔP_TW with intraoperative adverse events was also significant in both groups but had higher odds ratio in closed compared to open abdominal surgery patients (1.13 [95%CI 1.12- to 1.14], P <  0.001 versus 1.07 [95%CI 1.05 to 1.10], P <  0.001; risk difference 0.05 [95%CI 0.030.07], P <  0.001).

CONCLUSIONS

ΔP is associated with PPC and intraoperative adverse events in abdominal surgery, both in open and closed abdominal surgery.

TRIAL REGISTRATION

LAS VEGAS was registered at clinicaltrials.gov (trial identifier NCT01601223 ).

Intraabdominal Pressure Targeted Positive End-expiratory Pressure during Laparoscopic Surgery: An Open-label, Nonrandomized, Crossover, Clinical Trial

BACKGROUND

Pneumoperitoneum for laparoscopic surgery is associated with a rise of driving pressure. The authors aimed to assess the effects of positive end-expiratory pressure (PEEP) on driving pressure at varying intraabdominal pressure levels. It was hypothesized that PEEP attenuates pneumoperitoneum-related rises in driving pressure.

METHODS

Open-label, nonrandomized, crossover, clinical trial in patients undergoing laparoscopic cholecystectomy. "Targeted PEEP" (2 cm H2O above intraabdominal pressure) was compared with "standard PEEP" (5 cm H2O), with respect to the transpulmonary and respiratory system driving pressure at three predefined intraabdominal pressure levels, and each patient was ventilated with two levels of PEEP at the three intraabdominal pressure levels in the same sequence. The primary outcome was the difference in transpulmonary driving pressure between targeted PEEP and standard PEEP at the three levels of intraabdominal pressure.

RESULTS

Thirty patients were included and analyzed. Targeted PEEP was 10, 14, and 17 cm H2O at intraabdominal pressure of 8, 12, and 15 mmHg, respectively. Compared to standard PEEP, targeted PEEP resulted in lower median transpulmonary driving pressure at intraabdominal pressure of 8 mmHg (7 [5 to 8] vs. 9 [7 to 11] cm H2O; P = 0.010; difference 2 [95% CI 0.5 to 4 cm H2O]); 12 mmHg (7 [4 to 9] vs.10 [7 to 12] cm H2O; P = 0.002; difference 3 [1 to 5] cm H2O); and 15 mmHg (7 [6 to 9] vs.12 [8 to 15] cm H2O; P < 0.001; difference 4 [2 to 6] cm H2O). The effects of targeted PEEP compared to standard PEEP on respiratory system driving pressure were comparable to the effects on transpulmonary driving pressure, though respiratory system driving pressure was higher than transpulmonary driving pressure at all intraabdominal pressure levels.

CONCLUSIONS

Transpulmonary driving pressure rises with an increase in intraabdominal pressure, an effect that can be counterbalanced by targeted PEEP. Future studies have to elucidate which combination of PEEP and intraabdominal pressure is best in term of clinical outcomes.

The Effect of sevoflurane, desflurane and propofol on respiratory mechanics and integrated pulmonary index scores in laparoscopic sleeve gastrectomy. A randomized trial

Objectives:

To compare the effects of sevoflurane, desflurane, and propofol on respiratory mechanics, and integrated pulmonary index (IPI) scores in patients undergoing laparoscopic sleeve gastrectomy.

Methods:

A total of 60 patients with a body mass index of ≥40 kg/m², who underwent laparoscopic sleeve gastrectomy between September 2015 and September 2016 at Fatih Sultan Mehmet Health Application and Research Center, Istanbul, Turkey were included in this randomized prospective study. After induction, anesthesia was maintained by sevoflurane in group S, desflurane in group D, and propofol in group P. Peak inspiratory pressure (PIP), plateau pressure (P_plateau), compliance (Cdyn), respiratory resistance (Rrs), and IPI values were recorded. Mann-Whitney U, Kruskal-Wallis, Dunn’s, Friedman, and Fisher-Freeman-Halton tests were performed for statistical analysis. A p value of <0.05 was considered statistically significant.

Results:

A significant increase was found in PIP in group S (T₁: 25; T₂: 27 cmH₂O), and group D (T₁: 25; T₂: 29,5 cmH₂O) during pneumoperitoneum. Dynamic compliance decreased in all groups during pneumoperitoneum. In group S, the decrease in Cdyn was also statistically significant after pneumoperitoneum (T₁: 43.65; T₅: 41.25 ml/cmH₂O). Comparison between groups the values of PIP, P_plateau, Cdyn, Rrs, and IPI were similar.

Conclusion:

In morbidly obese patients, sevoflurane, desflurane, and propofol are similar in terms of the intraoperative respiratory mechanics, and perioperative respiratory parameters provided with IPI.

Modified 2-port laparoscopic herniorrhaphy with Kirschner wire in children: A retrospective review

BACKGROUND

Pediatric inguinal hernia is one of the most common diseases in children, and laparoscopy is the main surgical method. This study aims to evaluate the efficacy of a new modified 2-port laparoscopic herniorrhaphy with Kirschner wire (TLHK) for inguinal hernia in children.

METHODS

A total of 5304 children with inguinal hernia hospitalized at the Jiangmen Center Hospital from June 2003 to May 2016 were enrolled in this retrospective study. Four thousand one hundred thirty-five children underwent TLHK that comprised the observation group, while 1169 received single incision laparoscopy (SIL) as the control group (CG). A propensity score matched cohort study was conducted between these groups. We included all patients who were diagnosed as inguinal hernia and matched comparators with a proportion of 1:1. The propensity score was calculated using logistic regression with forward stepwise selection in 4 variables. The patients' operative details, intra- and postoperative complications, and postoperative hospital stay were analyzed. The follow-up lasted from 1 month to 2 years.

RESULTS

Among 5304 potential patients, the propensity score identified 270 (135 TLHK cases and 135 comparators) patients. The age, sex, body mass index, and the hernia type and location did not differ between CG and TLHK. TLHK group had a shorter operative time (unilateral: 17.4 ± 3.35 minutes vs 20.7 ± 3.71 minutes; bilateral: 20.4 ± 5.17 minutes vs 25.2 ± 5.43 minutes), less complications (2.10% vs 2.65%), lower recurrence rate (0% vs 4.44%), and similar hospital stay (2.3 ± 1.1 vs 2.1 ± 1.3) as compared with CG. No iliac vessel injury, spermatic cord vessels injury, vas deferens injury, or iatrogenic cryptorchidism occurred in either of the groups.

CONCLUSION

TLHK is a safe and feasible treatment for inguinal hernia in children due to less invasion and less recurrence rate than SIL.

Individualized lung recruitment maneuver guided by pulse-oximetry in anesthetized patients undergoing laparoscopy: a feasibility study

BACKGROUND

We conducted this study to test whether pulse-oximetry hemoglobin saturation (SpO₂ ) can personalize the implementation of an open-lung approach during laparoscopy. Thirty patients with SpO₂  ≥ 97% on room-air before anesthesia were studied. After anesthesia and capnoperitoneum the FIO₂ was reduced to 0.21. Those patients whose SpO₂ decreased below 97% - an indication of shunt related to atelectasis - completed the following phases: (1) First recruitment maneuver (RM), until reaching lung's opening pressure, defined as the inspiratory pressure level yielding a SpO₂ ≥ 97%; (2) decremental positive end-expiratory (PEEP) titration trial until reaching lung's closing pressure defined as the PEEP level yielding a SpO₂  < 97%; (3) second RM and, (4) ongoing ventilation with PEEP adjusted above the detected closing pressure.

RESULTS

When breathing air, in 24 of 30 patients SpO₂ was < 97%, PaO₂ /FIO₂  ˂ 53.3 kPa and negative end-expiratory transpulmonary pressure (P_TP-EE ). The mean (SD) opening pressures were found at 40 (5) and 33 (4) cmH₂ O during the first and second RM, respectively (P < 0.001; 95% CI: 3.2-7.7). The closing pressure was found at 11 (5) cmH₂ O. This SpO₂ -guided approach increased P_TP-EE (from -6.4 to 1.2 cmH₂ O, P < 0.001) and PaO₂ /FIO₂ (from 30.3 to 58.1 kPa, P < 0.001) while decreased driving pressure (from 18 to 10 cmH₂ O, P < 0.001). SpO₂ discriminated the lung's opening and closing pressures with accuracy taking the reference parameter P_TP-EE (area under the receiver-operating-curve of 0.89, 95% CI: 0.80-0.99).

CONCLUSION

The non-invasive SpO₂ monitoring can help to individualize an open-lung approach, including all involved steps, from the identification of those patients who can benefit from recruitment, the identification of opening and closing pressures to the subsequent monitoring of an open-lung condition.

Low-pressure pneumoperitoneum with abdominal wall lift in laparoscopic total mesorectal excision for rectal cancer: Initial experience

AIM

To evaluate the safety and feasibility of a new technology combining low-pressure pneumoperitoneum (LPP) and abdominal wall lift (AWL) in laparoscopic total mesorectal excision (TME) for rectal cancer.

METHODS

From November 2015 to July 2017, 26 patients underwent laparoscopic TME for rectal cancer using LPP (6-8 mmHg) with subcutaneous AWL in Qilu Hospital of Shandong University, Jinan, China. Clinical data regarding patients’ demographics, intraoperative monitoring indices, operation-related indices and pathological outcomes were prospectively collected.

RESULTS

Laparoscopic TME was performed in 26 cases (14 anterior resection and 12 abdominoperineal resection) successfully, without conversion to open or laparoscopic surgery with standard-pressure pneumoperitoneum. Intraoperative monitoring showed stable heart rate, blood pressure and paw airway pressure. The mean operative time was 194.29 ± 41.27 min (range: 125-270 min) and 200.41 ± 20.56 min (range: 170-230 min) for anterior resection and abdominoperineal resection, respectively. The mean number of lymph nodes harvested was 16.71 ± 5.06 (range: 7-27). There was no positive circumferential or distal resection margin. No local recurrence was observed during a median follow-up period of 11.96 ± 5.55 mo (range: 5-23 mo).

CONCLUSION

LPP combined with AWL is safe and feasible for laparoscopic TME. The technique can provide satisfactory exposure of the operative field and stable operative monitoring indices.

Respiratory complications after colonic procedures in chronic obstructive pulmonary disease: does laparoscopy offer a benefit?

BACKGROUND

Patients with severe chronic obstructive pulmonary disease (COPD) are at a higher risk for postoperative respiratory complications. Despite the benefits of a minimally invasive approach, laparoscopic pneumoperitoneum can substantially reduce functional residual capacity and raise alveolar dead space, potentially increasing the risk of respiratory failure which may be poorly tolerated by COPD patients. This raises controversy as to whether open techniques should be preferentially employed in this population.

METHODS

The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database from 2011 to 2014 was used to examine the clinical data from patients with COPD who electively underwent laparoscopic and open colectomy. Patients defined as having COPD demonstrated either functional disability, chronic use of bronchodilators, prior COPD-related hospitalization, or reduced forced expiratory reserve volumes on lung testing (FEV1 <75%). Demographic data and preoperative characteristics were compared. Linear and logistic regressions were utilized to perform multivariate analysis and determine risk-adjusted outcomes.

RESULTS

Of the 4397 patients with COPD, 53.8% underwent laparoscopic colectomy (LC) while 46.2% underwent open colectomy (OC). The LC and OC groups were similar with respect to demographic data and preoperative comorbidities. Equivalent frequencies of exertional dyspnea (LC 35.4 vs OC 37.7%, P = 0.11) were noted. After multivariate risk adjustment, OC demonstrated an increased rate of overall respiratory complications including pneumonia, reintubation, and prolonged ventilator dependency when compared to LC (OR 1.60, 95% CI 1.30-1.98, P < 0.01). OC was associated with longer length of stay (10 ± 8 vs. 6.7 ± 7 days, P < 0.01) and higher readmission (OR 1.36, 95% CI 1.09-1.68, P < 0.01) compared to LC.

CONCLUSION

Despite the potential risks of laparoscopic pneumoperitoneum in the susceptible COPD population, a minimally invasive approach was associated with lower risk of postoperative respiratory complications, shorter length of stay, and decrease in postoperative morbidity.

Long-term outcomes and propensity score matching analysis: rectal cancer resection for patients with elevated preoperative risk

BACKGROUND

It is still controversial about the treatment strategy for rectal cancer patients with elevated operative risk and elder rectal cancer patients.

METHODS

This study presented a retrospective single center experience in rectal cancer proctectomy for high operative risk patients. High operative risk patient was defined as Cr-POSSUM > 5% combined with associated risk factors. 220 in 1477 consecutive patients met the inclusion criteria.

RESULTS

132 patients were selected (66:66) after propensity score matching. The total complication rate between conventional open rectal resection (71 %) and laparoscopic surgery (41%) was significantly different (p = 0.0005). There is a significantly positive correlation between open surgery and advanced Dindo Classification (p = 0.02). Cr-POSSUM is positively correlated with Dindo Classification (p = 0.01). There was no significant difference in survival rate among stage I∼II, different age groups or different Cr-POSSUM score sub-groups. However, stage III-IV tumor patients in laparoscopic group experienced improved overall survival rate. (p < 0.0001). For patients with preoperative pulmonary or renal disease, patients in laparoscopic group also had better long term prognosis (p = 0.03, p = 0.049).

CONCLUSIONS

The results demonstrate the potential advantages of laparoscopic rectal cancer resection for high operative risk patients, especially for the patients with preoperative respiratory or renal disease and stage III cancer.