Comparison of volume-controlled and pressure-controlled ventilation in steep Trendelenburg position for robot-assisted laparoscopic radical prostatectomy

Changes of endotracheal tube cuff pressure and its indicators in laparoscopic resection of colorectal neoplasms: an observational prospective clinical trial. comment on: BMC anesthesiology. 2024 Nov 13;24(1):413

It is important to consider some of the study variables which may influence the interpretation of the paper from Cai et al. on endotracheal tube cuff pressures during laparoscopic colorectal surgery. These include cuff compliance, tracheal diameter, peritoneal insufflation pressures and the use of volume control ventilation. CLINICAL TRIAL NUMBER: Not applicable.

Effect of ventilation mode on postoperative pulmonary complications among intermediate- to high-risk patients undergoing abdominal surgery: A randomized controlled trial

BACKGROUND

The effect of different mechanical ventilation modes on pulmonary outcome after abdominal surgery remains unclear. We evaluated the effects of three common ventilation modes on postoperative pulmonary complications (PPCs) among intermediate- to high-risk patients undergoing abdominal surgery.

METHODS

This randomized clinical trial enrolled adult patients at intermediate or high risk of PPCs who were scheduled for abdominal surgery. Participants were randomized to receive one of three modes of mechanical ventilation modes: volume-controlled ventilation (VCV), pressure-controlled ventilation (PCV), and pressure-control with volume-guaranteed ventilation (PCV-VG). Lung-protective ventilation strategy was implemented in all groups. The primary outcome was the incidence of a composite of pulmonary complications within the first 7 postoperative days. Pulmonary complications within 30 postoperative days, the severity grade of PPCs, and other secondary outcomes were also analyzed.

RESULTS

A total of 1365 patients were randomized and 1349 were analyzed. The primary outcome occurred in 98 (21.8%) in the VCV group, 95 (22.1%) in the PCV group, and 101 (22.5%) in the PCV-VG group (P = 0.865). Additionally, there were no statistically significant differences among the three groups in terms of the incidence of pulmonary complications within postoperative 30 days, severity grade of PPCs, and other secondary outcomes.

CONCLUSION

In intermediate- to high-risk patients undergoing abdominal surgery, the choice of ventilation mode did not affect the risk of PPCs.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, entry ChiCTR1900025880.

Continuous estimation of respiratory system compliance and airway resistance during pressure-controlled ventilation without end-inspiration occlusion

BACKGROUND

Assessing mechanical properties of the respiratory system (Cst) during mechanical ventilation necessitates an end-inspiration flow of zero, which requires an end-inspiratory occlusion maneuver. This lung model study aimed to observe the effect of airflow obstruction on the accuracy of respiratory mechanical properties during pressure-controlled ventilation (PCV) by analyzing dynamic signals.

METHODS

A Hamilton C3 ventilator was attached to a lung simulator that mimics lung mechanics in healthy, acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD) models. PCV and volume-controlled ventilation (VCV) were applied with tidal volume (VT) values of 5.0, 7.0, and 10.0 ml/kg. Performance characteristics and respiratory mechanics were assessed and were calibrated by virtual extrapolation using expiratory time constant (RCexp).

RESULTS

During PCV ventilation, drive pressure (DP) was significantly increased in the ARDS model. Peak inspiratory flow (PIF) and peak expiratory flow (PEF) gradually declined with increasing severity of airflow obstruction, while DP, end-inspiration flow (EIF), and inspiratory cycling ratio (EIF/PIF%) increased. Similar estimated values of Crs and airway resistance (Raw) during PCV and VCV ventilation were obtained in healthy adult and mild obstructive models, and the calculated errors did not exceed 5%. An underestimation of Crs and an overestimation of Raw were observed in the severe obstruction model.

CONCLUSION

Using the modified dynamic signal analysis approach, respiratory system properties (Crs and Raw) could be accurately estimated in patients with non-severe airflow obstruction in the PCV mode.

The intraoperative management of robotic-assisted laparoscopic prostatectomy

PURPOSE OF REVIEW

Robotic-assisted laparoscopic radical prostatectomy has become the second most commonly performed robotic surgical procedure worldwide, therefore, anesthesiologists should be aware of the intraoperative pathophysiological consequences. The aim of this narrative review is to report the most recent updates regarding the intraoperative management of anesthesia, ventilation, hemodynamics and central nervous system, during robotic-assisted laparoscopic radical prostatectomy.

RECENT FINDINGS

Surgical innovations and the advent of new technologies make it imperative to optimize the anesthesia management to provide the most holistic approach possible. In addition, an ageing population with an increasing burden of comorbidities requires multifocal attention to reduce the surgical stress.

SUMMARY

Total intravenous anesthesia (TIVA) and balanced general anesthesia are similar in terms of postoperative complications and hospital stay. Reversal of rocuronium is associated with shorter hospital stay and postanesthesia recovery time. Adequate PEEP levels improve oxygenation and driving pressure, and the use of a single recruitment maneuver after the intubation reduces postoperative pulmonary complications. Restrictive intravenous fluid administration minimizes bladder-urethra anastomosis complications and facial edema. TIVA maintains a better autoregulation compared with balanced general anesthesia. Anesthesiologists should be able to optimize the intraoperative management to improve outcomes.

Ventilation strategy during urological and gynaecological robotic-assisted surgery: a narrative review

Robotic-assisted surgery has improved the precision and accuracy of surgical movements with subsequent improved outcomes. However, it requires steep Trendelenburg positioning combined with pneumoperitoneum that negatively affects respiratory mechanics and increases the risk of postoperative respiratory complications. This narrative review summarises the state of the art in ventilatory management of these patients in terms of levels of positive end-expiratory pressure (PEEP), tidal volume, recruitment manoeuvres, and ventilation modes during both urological and gynaecological robotic-assisted surgery. A review of the literature was conducted using PubMed/MEDLINE; after completing abstract and full-text review, 31 articles were included. Although different levels of PEEP were often evaluated within a protective ventilation strategy, including higher levels of PEEP, lower tidal volume, and recruitment manoeuvres vs a conventional ventilation strategy, we conclude that the best PEEP in terms of lung mechanics, gas exchange, and ventilation distribution has not been defined, but moderate PEEP levels (4-8 cm H2O) could be associated with better outcomes than lower or highest levels. Recruitment manoeuvres improved intraoperative arterial oxygenation, end-expiratory lung volume and the distribution of ventilation to dependent (dorsal) lung regions. Pressure-controlled compared with volume-controlled ventilation showed lower peak airway pressures with both higher compliance and higher carbon dioxide clearance. We propose directions to optimise ventilatory management during robotic surgery in light of the current evidence.

Perioperative lung function following flow controlled ventilation for robot-assisted prostatectomies in steep trendelenburg position: an observational study

BACKGROUND

Steep Trendelenburg position combined with capnoperitoneum can lead to pulmonary complications and prolonged affection of postoperative lung function. Changes in pulmonary function occur independent of different modes of ventilation and levels of positive end-expiratory pressure (PEEP). The effect of flow-controlled ventilation (FCV) has not been evaluated yet. We perioperatively measured spirometric lung function parameters in patients undergoing robot-assisted prostatectomy under FCV. Our primary hypothesis was that there is no significant difference in the ratio of the maximal mid expiratory and inspiratory flow (MEF50/MIF50) after surgery.

METHODS

In 20 patients, spirometric measurements were obtained preoperatively, 40, 120, and 240 min and 1 and 5 days postoperatively. We measured MEF50/MIF50, vital capacity (VC), forced expiratory volume in 1 s (FEV1), and intraoperative ventilation parameters.

RESULTS

MEF50/MIF50 ratio increased from 0.92 (CI 0.73-1.11) to 1.38 (CI 1.01-1.75, p < 0.0001) and returned to baseline within 24 h, while VC and FEV1 decreased postoperatively with a second nadir at 24 h and only normalized by the fifth day (p < 0.0001). Compared to patients with PCV, postoperative lung function changes similarly.

CONCLUSION

Flow-controlled ventilation led to changes in lung function similar to those observed with pressure-controlled ventilation. While the ratio of MEF50/MIF50 normalized within 24 h, VC and FEV1 recovered within 5 days after surgery.

Surgical bleeding in patients undergoing posterior lumbar inter-body fusion surgery: a randomized clinical trial evaluating the effect of two mechanical ventilation mode types

BACKGROUND

The purpose of the study was to compare the effect of using volume-controlled ventilation (VCV) versus pressure-controlled ventilation (PCV) on blood loss in patients undergoing posterior lumbar inter-body fusion (PLIF) surgery.

METHODS

In a randomized, single-blinded, parallel design, 78 patients, candidates for PLIF surgery, were randomly allocated into two groups of 39 to be mechanically ventilated using VCV or PCV mode. All the patients were operated in prone position by one surgeon. Amount of intraoperative surgical bleeding, transfusion requirement, surgeon satisfaction, hemodynamic parameters, heart rate, and blood pressure were measured as outcomes.

RESULTS

PCV group showed slightly better outcomes than VCV group in terms of mean blood loss (431 cc vs. 465 cc), transfusion requirement (0.40 vs. 0.43 unit), and surgeon satisfaction (82.1% vs. 74.4%); however, the differences were not statistically significant. Diastolic blood pressure 90 and 105 min after induction were significantly lower in PCV group (P = 0.043-0.019, respectively); however, blood pressure at other times, hemoglobin levels, and mean heart rate were similar in two groups.

CONCLUSIONS

In patients undergoing posterior lumbar inter-body fusion surgery, mode of ventilation cannot make significant difference in terms of blood loss; however, some minor benefits in outcomes may lead to the selection of PCV rather than VCV. More studies with larger sample size, and investigating more factors may be needed.

Lung mechanics during video-assisted abdominal surgery in Trendelenburg position: a cross-sectional propensity-matched comparison between classic laparoscopy and robotic-assisted surgery

BACKGROUND

Video-assisted surgery has become an increasingly used surgical technique in patients undergoing major thoracic and abdominal surgery and is associated with significant perioperative respiratory and cardiovascular changes. The aim of this study was to investigate the effect of intraoperative pneumoperitoneum during video-assisted surgery on respiratory physiology in patients undergoing robotic-assisted surgery compared to patients undergoing classic laparoscopy in Trendelenburg position.

METHODS

Twenty-five patients undergoing robotic-assisted surgery (RAS) were compared with twenty patients undergoing classic laparoscopy (LAS). Intraoperative ventilatory parameters (lung compliance and plateau airway pressure) were recorded at five specific timepoints: after induction of anesthesia, after carbon dioxide (CO₂) insufflation, one-hour, and two-hours into surgery and at the end of surgery. At the same time, arterial and end-tidal CO₂ values were noted and arterial to end-tidal CO₂ gradient was calculated.

RESULTS

We observed a statistically significant difference in plateau pressure between RAS and LAS at one-hour (26.2 ± 4.5 cmH₂O vs. 20.2 ± 3.5 cmH₂O, p = 0.05) and two-hour intervals (25.2 ± 5.7 cmH₂O vs. 17.9 ± 3.1 cmH₂O, p = 0.01) during surgery and at the end of surgery (19.9 ± 5.0 cmH₂O vs. 17.0 ± 2.7 cmH₂O, p = 0.02). Significant changes in lung compliance were also observed between groups at one-hour (28.2 ± 8.5 mL/cmH₂O vs. 40.5 ± 13.9 mL/cmH₂O, p = 0.01) and two-hour intervals (26.2 ± 7.8 mL/cmH₂O vs. 54.6 ± 16.9 mL/cmH₂O, p = 0.01) and at the end of surgery (36.3 ± 9.9 mL/cmH₂O vs. 58.2 ± 21.3 mL/cmH₂O, p = 0.01). At the end of surgery, plateau pressures remained higher than preoperative values in both groups, but lung compliance remained significantly lower than preoperative values only in patients undergoing RAS with a mean 24% change compared to 1.7% change in the LAS group (p = 0.01). We also noted a more significant arterial to end-tidal CO₂ gradient in the RAS group compared to LAS group at one-hour (12.9 ± 4.5 mmHg vs. 7.4 ± 4.4 mmHg, p = 0.02) and two-hours interval (15.2 ± 4.5 mmHg vs. 7.7 ± 4.9 mmHg, p = 0.02), as well as at the end of surgery (11.0 ± 6.6 mmHg vs. 7.0 ± 4.6 mmHg, p = 0.03).

CONCLUSION

Video-assisted surgery is associated with significant changes in lung mechanics after induction of pneumoperitoneum. The observed changes are more severe and longer-lasting in patients undergoing robotic-assisted surgery compared to classic laparoscopy.

Assessment of Perioperative Atelectasis Using Lung Ultrasonography in Patients Undergoing Pneumoperitoneum Surgery in the Trendelenburg Position: Aspects of Differences according to Ventilatory Mode

BACKGROUND

During robotic gynecologic pneumoperitoneum surgery in the Trendelenburg position, aeration loss leads to perioperative atelectasis. Recently developed ventilator mode pressure-controlled ventilation volume-guaranteed (PCV-VG) mode could provide adequate ventilation with lower inspiratory pressure compared to volume-controlled ventilation (VCV); we hypothesized that PCV-VG mode may be beneficial in reducing perioperative atelectasis via low tidal volume (V_T) of 6 mL/kg ventilation during robotic gynecologic pneumoperitoneum surgery in the Trendelenburg position. We applied lung ultrasound score (LUS) for detecting perioperative atelectasis. We aimed to compare perioperative atelectasis between VCV and PCV-VG with a low V_T of 6 mL/kg during pneumoperitoneum surgery in the Trendelenburg position using LUS.

METHODS

Patients scheduled for robotic gynecologic surgery were randomly allocated to the VCV (n = 41) or PCV-VG group (n = 41). LUS, ventilatory, and hemodynamic parameters were evaluated at T1 (before induction), T2 (10 minutes after induction in the supine position), T3 (10 minutes after desufflation of CO₂ in the supine position), and T4 (30 minutes after emergence from anesthesia in the recovery room).

RESULTS

Eighty patients (40 with PCV-VG and 40 with VCV) were included. Demographic data showed no significant differences between the groups. The total LUS has changed from baseline to T4, 0.63 (95% confidence interval [CI], 0.32, 0.94) to 1.77 (95% CI, 1.42, 2.21) in the VCV group and 0.86 (95% CI, 0.56, 1.16) to 1.43 (95% CI, 1.08, 1.78) in the PCV-VG group (P = 0.170). In both groups, total LUS increased significantly compared to the baseline values.

CONCLUSION

Using a low V_T of 6 mL/kg during pneumoperitoneum surgery in the Trendelenburg position, our study showed no evidence that PCV-VG ventilation was superior to VCV in terms of perioperative atelectasis.

TRIAL REGISTRATION

Clinical Research Information Service Identifier: KCT0006404.

Changes in dead space components during pressure-controlled inverse ratio ventilation: A secondary analysis of a randomized trial

Background

We previously reported that there were no differences between the lung-protective actions of pressure-controlled inverse ratio ventilation and volume control ventilation based on the changes in serum cytokine levels. Dead space represents a ventilation-perfusion mismatch, and can enable us to understand the heterogeneity and elapsed time changes in ventilation-perfusion mismatch.

Methods

This study was a secondary analysis of a randomized controlled trial of patients who underwent robot-assisted laparoscopic radical prostatectomy. The inspiratory to expiratory ratio was adjusted individually by observing the expiratory flow-time wave in the pressure-controlled inverse ratio ventilation group (n = 14) and was set to 1:2 in the volume-control ventilation group (n = 13). Using volumetric capnography, the physiological dead space was divided into three dead space components: airway, alveolar, and shunt dead space. The influence of pressure-controlled inverse ratio ventilation and time factor on the changes in each dead space component rate was analyzed using the Mann-Whitney U test and Wilcoxon’s signed rank test.

Results

The physiological dead space and shunt dead space rate were decreased in the pressure-controlled inverse ratio ventilation group compared with those in the volume control ventilation group (p < 0.001 and p = 0.003, respectively), and both dead space rates increased with time in both groups. The airway dead space rate increased with time, but the difference between the groups was not significant. There were no significant changes in the alveolar dead space rate.

Conclusions

Pressure-controlled inverse ratio ventilation reduced the physiological dead space rate, suggesting an improvement in the total ventilation/perfusion mismatch due to improved inflation of the alveoli affected by heterogeneous expansion disorder without hyperinflation of the normal alveoli. However, the shunt dead space rate increased with time, suggesting that atelectasis developed with time in both groups.

Equal Ratio Ventilation Reduces Blood Loss During Posterior Lumbar Interbody Fusion Surgery

STUDY DESIGN

A prospective randomized double-blinded study.

OBJECTIVE

The aim of this study was to compare the effect of two different ventilator modes (inspiratory to expiratory ratio [I:E ratio] of 1:1 and 1:2) on intraoperative surgical bleeding in patients undergoing posterior lumbar interbody fusion (PLIF) surgery.

SUMMARY OF BACKGROUND DATA

During PLIF surgery, a considerable amount of blood loss is anticipated. In the prone position, engorgement of the vertebral vein increases surgical bleeding. We hypothesized that equal ratio ventilation (ERV) with I:E ratio of 1:1 would lower peak inspiratory pressure (PIP) in the prone position and consequentially decrease surgical bleeding.

METHODS

Twenty-eight patients were randomly assigned to receive either ERV (ERV group, n = 14) or conventional ventilation with I:E ratio of 1:2 (control group, n = 14). Hemodynamic and respiratory parameters were measured at 5 minutes after anesthesia induction, at 5 minutes after the prone position, at the time of skin closure, and at 5 minutes after turning to the supine position.

RESULTS

The amount of intraoperative surgical bleeding in the ERV group was significantly less than that in the control group (975.7 ± 349.9 mL vs. 1757.1 ± 1172.7 mL, P = 0.030). Among other hemodynamic and respiratory parameters, PIP and plateau inspiratory pressure (Pplat) were significantly lower and dynamic lung compliance (Cdyn) was significantly higher in the ERV group than those of the control group throughout the study period, respectively (all P < 0.05).

CONCLUSION

Compared to conventional ratio ventilation, ERV provided lower PIP and reduced intraoperative surgical blood loss in patients undergoing PLIF surgery.Level of Evidence: 2.

Protective mechanical ventilation with optimal PEEP during RARP improves oxygenation and pulmonary indexes

BACKGROUND

This trial aimed to evaluate the effects of a protective ventilation strategy on oxygenation/pulmonary indexes in patients undergoing robot-assisted radical prostatectomy (RARP) in the steep Trendelenburg position.

METHODS

In phase 1, the most optimal positive end-expiratory pressure (PEEP) was determined in 25 patients at 11 cmH₂O. In phase 2, 64 patients were randomized to the traditional ventilation group with tidal volume (VT) of 9 ml/kg of predicted body weight (PBW) and the protective ventilation group with VT of 7 ml/kg of PBW with optimal PEEP and recruitment maneuvers (RMs). The primary endpoint was the intraoperative and postoperative PaO₂/FiO₂. The secondary endpoints were the PaCO₂, SpO₂, modified clinical pulmonary infection score (mCPIS), and the rate of complications in the postoperative period.

RESULTS

Compared with controls, PaO₂/FiO₂ in the protective group increased after the second RM (P=0.018), and the difference remained until postoperative day 3 (P=0.043). PaCO₂ showed transient accumulation in the protective group after the first RM (T2), but this phenomenon disappeared with time. SpO₂ in the protective group was significantly higher during the first three postoperative days. Lung compliance was significantly improved after the second RM in the protective group (P=0.025). The mCPIS was lower in the protective group on postoperative day 3 (0.59 (1.09) vs. 1.46 (1.27), P=0.010).

CONCLUSION

A protective ventilation strategy with lower VT combined with optimal PEEP and RMs could improve oxygenation and reduce mCPIS in patients undergoing RARP.

TRIAL REGISTRATION

ChiCTR ChiCTR1800015626 . Registered on 12 April 2018.

Hemodynamic outcome of different ventilation modes in laparoscopic surgery with exaggerated trendelenburg: a randomised controlled trial

Purpose

To compare hemodynamic effects of two different modes of ventilation (volume-controlled and pressure-controlled volume guaranteed) in patients undergoing laparoscopic gynecology surgeries with exaggerated Trendelenburg position.

Methods

Thirty patients undergoing laparoscopic gynecology operations were ventilated using either volume-controlled (Group VC) or pressure-controlled volume guaranteed mode (Group PCVG) (n = 15 for both groups). Hemodynamic variables were measured using Pressure Recording Analytical Method by radial artery cannulation in addition to peak and mean airway pressures and expired tidal volume.

Results

The only remarkable finding was a more stable cardiac index in Group PCVG, where other hemodynamic parameters were similar. Expired tidal volume increased in Group VC while peak airway pressure was lower in Group PCVG.

Conclusion

PCV-VG causes less hemodynamic perturbations as measured by Pressure Recording Analytical Method (PRAM) and allows better intraoperative hemodynamic control in exaggerated Trendelenburg position in laparoscopic surgery.

Characteristics of patients undergoing robotic-assisted prostatectomy. Observational study

Introduction: Prostatectomy is the standard treatment for patients with clinically localized prostate cancer. Currently, robot-assisted radical prostatectomy (RARP) is widely used for its advantages, as it provides better visualization, precision, and reduced tissue manipulation. However, RARP requires a multidisciplinary approach in which anesthesia and analgesia management are especially important. Objective: This study aims to describe our experience delivering anesthesia for the first cases of patients undergoing RARP in a teaching hospital in Bogotá, Colombia. Methodology: An observational study was conducted. We included all patients undergoing RARP from September 2015 to December 2019 at Fundación Santa Fe de Bogotá. All patients with incomplete data were excluded. Patient demographics were recorded, and significant perioperative events were reviewed. Results: A total of 301 patients were included. At our institution, the mean age for patients undergoing RARP was 61.4 ± 6.7 years. The mean operative time was 205 ± 43 min and mean blood loss was 300 [200-400] mL. Only 6 (2%) patients required transfusion. Age and BMI were not associated with clinical outcomes. Conclusions: An adequate perioperative approach in RARP is important to minimize complications, which in this study and in this institution were infrequent.

Use of volume controlled vs. pressure controlled volume guaranteed ventilation in elderly patients undergoing laparoscopic surgery with laryngeal mask airway

Background

The peak inspiratory pressure (PIP) is crucial in mechanical ventilation with supraglottic airway device (SAD). Pressure-controlled ventilation volume-guaranteed (PCV-VG), delivering a preset tidal volume with the lowest required airway pressure, is being increasingly used during general anesthesia. In this study, we compared respiratory mechanics and circulatory parameters between volume-controlled ventilation (VCV) and PCV-VG in elderly patients undergoing laparoscopic surgery using the laryngeal mask airway supreme (LMA).

Methods

Eighty participants scheduled for laparoscopic surgery were enrolled in this prospective, randomized clinical trial. The participants were randomly assigned to receive VCV or PCV-VG. PIP, dynamic compliance (Cdyn) and mean inspiratory pressure (Pmean) were recorded at 5 min after induction of anesthesia (T1), 5 min after pneumoperitoneum(T2), 30 and 60 min after pneumoperitoneum (T3 and T4). Data including other respiratory variables, hemodynamic variables, and arterial blood gases were also collected. The difference in PIP between VCV and PCV-VG was assessed as the primary outcome.

Results

PIP was significantly lower at T2, T3, and T4 in both groups compared with T1 (all P <  0.0001), and it was significantly lower in the PCV-VG group than the VCV group at T2, T3, and T4 (all P <  0.001). Cydn was decreased at T2, T3, and T4 in two groups compared with T1 (all P <  0.0001), but it was higher in PCV-VG group than in VCV group at T2, T3, and T4 (all P <  0.0001). There were on statistically significant differences were found between the groups for other respiratory and hemodynamic variables.

Conclusion

In elderly patients who underwent laparoscopic surgery using an LMA, PCV-VG was superior to VCV in its ability to provide ventilation with lower peak inspiratory pressure and greater dynamic compliance.

Lung-protective properties of expiratory flow-initiated pressure-controlled inverse ratio ventilation: A randomised controlled trial

Background

Expiratory flow-initiated pressure-controlled inverse ratio ventilation (EF-initiated PC-IRV) reduces physiological dead space. We hypothesised that EF-initiated PC-IRV would be lung protective compared with volume-controlled ventilation (VCV).

Methods

Twenty-eight men undergoing robot-assisted laparoscopic radical prostatectomy were enrolled in this randomised controlled trial. The EF-initiated PC-IRV group (n = 14) used pressure-controlled ventilation with the volume guaranteed mode. The inspiratory to expiratory (I:E) ratio was individually adjusted by observing the expiratory flow-time wave. The VCV group (n = 14) used the volume control mode with a 1:2 I:E ratio. The Mann–Whitney U test was used to compare differences in the serum cytokine levels.

Results

There were no significant differences in serum IL-6 between the EF-initiated PC-IRV (median 34 pg ml^-1 (IQR 20.5 to 63.5)) and VCV (31 pg ml^-1 (24.5 to 59)) groups (P = 0.84). The physiological dead space rate (physiological dead space/expired tidal volume) was significantly reduced in the EF-initiated PC-IRV group as compared with that in the VCV group (0.31 ± 0.06 vs 0.4 ± 0.07; P<0.001). The physiological dead space rate was negatively correlated with the forced vital capacity (% predicted) in the VCV group (r = -0.85, P<0.001), but not in the EF-initiated PC-IRV group (r = 0.15, P = 0.62). Two patients in the VCV group had permissive hypercapnia with low forced vital capacity (% predicted).

Conclusions

There were no differences in the lung-protective properties between the two ventilatory strategies. However, EF-initiated PC-IRV reduced physiological dead space rate; thus, it may be useful for reducing the ventilatory volume that is necessary to maintain normocapnia in patients with low forced vital capacity (% predicted) during robot-assisted laparoscopic radical prostatectomy.

Effect of Various Modes of Mechanical Ventilation in Laparoscopic Cholecystectomies on Optic Nerve Sheath Diameter and Cognitive Functions

Aim: In this study, we aim at investigating the effects of volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) modes on changes in the optic nerve diameter and cognitive functions in laparoscopic cholecystectomy operations. Materials and Methods: Sixty patients who underwent laparoscopic cholecystectomy were randomly divided into two groups based on the mode of mechanical ventilation provided: Group P; PCV, Group V; VCV. Optic nerve sheath diameter was measured when the patient was awake (T0), in the 10th minute after induction (T1), in the 10th minute after the initiation of gas insufflation (T2), when maximum gas pressure was reached in the reverse-Trendelenburg position (T3), and pre-extubation (T4). Partial oxygen saturation (PaO₂), PCO₂, end-tidal carbon dioxide (ETCO₂), and peak airway pressure (pPEAK) were also recorded. A Mini-Mental State Examination (MMSE) was conducted on patients preoperatively and in the postoperative third month. Results: Between the groups, a statistically significant difference was found in Group P compared with Group V in terms of optic nerve diameter at measurement times T1 (P < .05). In the intragroup comparison, a significant difference was found in the initial values in all measurements except for measurement times T0 and T4 in both Group P and Group V (P < .05). pPEAK values were identified to be statistically significantly lower in Group P than Group V at all measurement times (P < .05). No difference was identified in the MMSE scores in the intergroup and intragroup comparisons. Conclusion: Laparoscopic cholecystectomy increases the optic nerve diameter due to the mechanical and systemic effects of the operation, and the PCV mode can be preferred. Clinical Trial Number: NCT04413903.

Ventilation and outcomes following robotic-assisted abdominal surgery: an international, multicentre observational study

BACKGROUND

International data on the epidemiology, ventilation practice, and outcomes in patients undergoing abdominal robotic-assisted surgery (RAS) are lacking. The aim of the study was to assess the incidence of postoperative pulmonary complications (PPCs), and to describe ventilator management after abdominal RAS.

METHODS

This was an international, multicentre, prospective study in 34 centres in nine countries. Patients ≥18 yr of age undergoing abdominal RAS were enrolled between April 2017 and March 2019. The Assess Respiratory Risk in Surgical Patients in Catalonia (ARISCAT) score was used to stratify for higher risk of PPCs (≥26). The primary outcome was the incidence of PPCs. Secondary endpoints included the preoperative risk for PPCs and ventilator management.

RESULTS

Of 1167 subjects screened, 905 abdominal RAS patients were included. Overall, 590 (65.2%) patients were at increased risk for PPCs. Meanwhile, 172 (19%) patients sustained PPCs, which occurred more frequently in 132 (22.4%) patients at increased risk, compared with 40 (12.7%) patients at lower risk of PPCs (absolute risk difference: 12.2% [95% confidence intervals (CI), 6.8-17.6%]; P<0.001). Plateau and driving pressures were higher in patients at increased risk, compared with patients at low risk of PPCs, but no ventilatory variables were independently associated with increased occurrence of PPCs. Development of PPCs was associated with a longer hospital stay.

CONCLUSIONS

One in five patients developed one or more PPCs (chiefly unplanned oxygen requirement), which was associated with a longer hospital stay. No ventilatory variables were independently associated with PPCs.

CLINICAL TRIAL REGISTRATION

NCT02989415.

Pronounced haemodynamic changes during and after robotic-assisted laparoscopic prostatectomy: a prospective observational study

OBJECTIVES

Robotic-assisted laparoscopic prostatectomy (RALP) is typically conducted in steep Trendelenburg position (STP). This study investigated the influence of permanent 45° STP and capnoperitoneum on haemodynamic parameters during and after RALP.

DESIGN

Prospective observational study.

SETTING

Haemodynamic changes were recorded with transpulmonary thermodilution and pulse contour analysis in men undergoing RALP under standardised anaesthesia.

PARTICIPANTS

Informed consent was obtained from 51 patients scheduled for elective RALP in a University Medical Centre in Germany.

INTERVENTIONS

Heart rate, mean arterial pressure, central venous pressure (CVP), Cardiac Index (CI), systemic vascular resistance (SVR), Global End-Diastolic Volume Index (GEDI), global ejection fraction (GEF), Cardiac Power Index (CPI) and stroke volume variation (SVV) were recorded at six time points: 20 min after induction of anaesthesia (T1), after insufflation of capnoperitoneum in supine position (T2), after 30 min in STP (T3), when controlling Santorini's plexus in STP (T4), before awakening in supine position (T5) and after 45 min in the recovery room (T6). Adverse cardiac events were registered intraoperatively and postoperatively.

RESULTS

All haemodynamic parameters were significantly changed by capnoperitoneum and STP during RALP and partly normalised at T6. CI, GEF and CPI were highest at T6 (CI: 3.9 vs 2.2 L/min/m²; GEF: 26 vs 22%; CPI: 0.80 vs 0.39 W/m²; p<0.001). CVP was highest at T4 (31 vs 7 mm Hg, p<0.001) and GEDI at T6 (819 vs 724 mL/m², p=0.005). Mean SVR initially increased (T2) but had decreased by 24% at T6 (p<0.001). SVV was highest at T5 (12 vs 9%, p<0.001). Two of the patients developed cardiac arrhythmia during RALP and one patient suffered postoperative cardiac ischaemia.

CONCLUSIONS

RALP led to pronounced perioperative haemodynamic changes. The combination of increased cardiac contractility and heart rate reflects a hyperdynamic situation during and after RALP. Anaesthesiologists should be aware of unnoticed pre-existing heart failure to worsen during STP in patients undergoing RALP.

Effect of Different Levels of Positive End-Expiratory Pressure (PEEP) on Respiratory Status during Gynecologic Laparoscopy

Background

During gynecologic laparoscopy, pneumoperitoneum, and the position of the patient's head can lead to pathophysiologic changes in cardiovascular and respiratory systems, complicating the management of anesthesia in these patients. One of the strategies for improving the respiratory status of patients undergoing laparoscopy is the use of Positive End-Expiratory Pressure (PEEP).

Objectives

This study aimed to evaluate the effect of different levels of PEEP on the respiratory status of patients undergoing gynecologic laparoscopy.

Methods

In this clinical trial, 60 patients with ASA I were randomly assigned to three groups to control anesthesia: ZEEP (PEEP 0 cmH₂O; 20 cases), PEEP₅ (PEEP 5 cmH₂O; 20 cases), and PEEP₁₀ (PEEP 10 cmH₂O; 20 cases). Respiratory and hemodynamic variables of patients were compared before general anesthetic induction and immediately after CO₂ insufflation at intervals of 5, 10, 20, 30, and 60 min and the end of the operation in the three study groups.

Results

The PEEP application improved pH, PaCO₂, and PaO₂ levels at the end of pneumoperitoneum compared to baseline when compared with the non-use of PEEP (ZEEP group). Also, the frequency of dysrhythmia in the use of PEEP in controlled ventilation was significantly lower in patients with PEEP₁₀ (P < 0.05). The application of PEEP₅ resulted in similar effects to PEEP₁₀ in the levels of respiratory variables.

Conclusions

The PEEP application is associated with improved arterial blood gas in patients with gynecologic laparoscopy. The use of PEEP₁₀ has a greater effect on the improvement of respiratory parameters and complications of pneumoperitoneum.

Temporal Changes in Ventilator Settings in Patients With Uninjured Lungs: A Systematic Review

In patients with uninjured lungs, increasing evidence indicates that tidal volume (VT) reduction improves outcomes in the intensive care unit (ICU) and in the operating room (OR). However, the degree to which this evidence has translated to clinical changes in ventilator settings for patients with uninjured lungs is unknown. To clarify whether ventilator settings have changed, we searched MEDLINE, Cochrane Central Register of Controlled Trials, and Web of Science for publications on invasive ventilation in ICUs or ORs, excluding those on patients <18 years of age or those with >25% of patients with acute respiratory distress syndrome (ARDS). Our primary end point was temporal change in VT over time. Secondary end points were changes in maximum airway pressure, mean airway pressure, positive end-expiratory pressure, inspiratory oxygen fraction, development of ARDS (ICU studies only), and postoperative pulmonary complications (OR studies only) determined using correlation analysis and linear regression. We identified 96 ICU and 96 OR studies comprising 130,316 patients from 1975 to 2014 and observed that in the ICU, VT size decreased annually by 0.16 mL/kg (-0.19 to -0.12 mL/kg) (P < .001), while positive end-expiratory pressure increased by an average of 0.1 mbar/y (0.02-0.17 mbar/y) (P = .017). In the OR, VT size decreased by 0.09 mL/kg per year (-0.14 to -0.04 mL/kg per year) (P < .001). The change in VTs leveled off in 1995. Other intraoperative ventilator settings did not change in the study period. Incidences of ARDS (ICU studies) and postoperative pulmonary complications (OR studies) also did not change over time. We found that, during a 39-year period, from 1975 to 2014, VTs in clinical studies on mechanical ventilation have decreased significantly in the ICU and in the OR.

Comparison of volume-controlled, pressure-controlled, and pressure-controlled volume-guaranteed ventilation during robot-assisted laparoscopic gynecologic surgery in the Trendelenburg position

Background: Pressure-controlled ventilation volume-guaranteed (PCV-VG) is being increasingly used for ventilation during general anesthesia. Carbon dioxide (CO₂) pneumoperitoneum in the Trendelenburg position is routinely used during robot-assisted laparoscopic gynecologic surgery. Here, we hypothesized that PCV-VG would reduce peak inspiratory pressure (Ppeak), compared to volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV). Methods: In total, 60 patients were enrolled in this study and randomly assigned to receive VCV, PCV, or PCV-VG. Hemodynamic variables, respiratory variables, and arterial blood gases were measured in the supine position 15 minutes after the induction of anesthesia (T0), 30 and 60 minutes after CO₂ pneumoperitoneum and Trendelenburg positioning (T1 and T2, respectively), and 15 minutes after placement in the supine position at the end of anesthesia (T3). Results: The Ppeak was higher in the VCV group than in the PCV and PCV-VG groups (p=0.011). Mean inspiratory pressure (Pmean) was higher in the PCV and PCV-VG groups than in the VCV group (p<0.001). Dynamic lung compliance (Cdyn) was lower in the VCV group than in the PCV and PCV-VG groups (p=0.001). Conclusion: Compared to VCV, PCV and PCV-VG provided lower Ppeak, higher Pmean, and improved Cdyn, without significant differences in hemodynamic variables or arterial blood gas results during robot-assisted laparoscopic gynecologic surgery with Trendelenburg position.

Volume-Controlled Versus Dual-Controlled Ventilation during Robot-Assisted Laparoscopic Prostatectomy with Steep Trendelenburg Position: A Randomized-Controlled Trial

Dual-controlled ventilation (DCV) combines the advantages of volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV). Carbon dioxide (CO₂) pneumoperitoneum and steep Trendelenburg positioning for robot-assisted laparoscopic radical prostatectomy (RALRP) has negative effects on the respiratory system. We hypothesized that the use of autoflow as one type of DCV can reduce these effects during RALRP. Eighty patients undergoing RALRP were randomly assigned to receive VCV or DCV. Arterial oxygen tension (PaO₂) as the primary outcome, respiratory and hemodynamic data, and postoperative fever rates were compared at four time points: 10 min after anesthesia induction (T1), 30 and 60 min after the initiation of CO₂ pneumoperitoneum and Trendelenburg positioning (T2 and T3), and 10 min after supine positioning (T4). There were no significant differences in PaO₂ between the two groups. Mean peak airway pressure (Ppeak) was significantly lower in group DCV than in group VCV at T2 (mean difference, 5.0 cm H₂O; adjusted p < 0.001) and T3 (mean difference, 3.9 cm H₂O; adjusted p < 0.001). Postoperative fever occurring within the first 2 days after surgery was more common in group VCV (12%) than in group DCV (3%) (p = 0.022). Compared with VCV, DCV did not improve oxygenation during RALRP. However, DCV significantly decreased Ppeak without hemodynamic instability.

Impact of the modality of mechanical ventilation on bleeding during pituitary surgery: A single blinded randomized trial

BACKGROUND

Bleeding modifies the surgeon's view of the field during transsphenoidal endoscopic pituitary surgery. Since ventilation can alter venous return, we compared the effect of volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) on intraoperative bleeding.

METHODS

Eighty-six patients were randomized to VCV or PCV in this single blinded study; comparisons concerned 42 in the PCV group and 43 in the VCV group.

RESULTS

Intraoperative bleeding, the primary endpoint, did not differ between groups whether analysis focused on 7 levels of the score, from minimal bleeding to bleeding with significant change in the conduct of surgical procedure (P = .89) or on a stratification into 3 categories, mild, moderate, and major (P = .47). Median [interquartile range] peak airway pressure was lower in the PCV group (13.5 [12.5-15] vs 16.3 [14.4-19.1] cm H2O, P < .001) while mean airway pressures were similar (P = .08). Means ± SD of tidal volumes were lower in the VCV group when expressed as absolute values (470.6 ± 84 vs 434.7 ± 71.7 ml, P = .05) or as tidal volume/theoretical ideal weight ratio (6.7 [6.5-7] vs 7.2 [6.9-7.9], P < .001). The 2 groups were similar for postoperative complications and number of patients cured.

CONCLUSION

In conclusion, ventilation mode does not influence intraoperative bleeding during transsphenoidal pituitary surgery.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT01891838; July 3, 2013.

Lung ultrasound score-based perioperative assessment of pressure-controlled ventilation-volume guaranteed or volume-controlled ventilation in geriatrics: a prospective randomized controlled trial

Purpose

Recent studies have shown the potential benefits of pressure-controlled ventilation-volume guaranteed (PCV-VG) compared to volume-controlled ventilation (VCV), but the results were not impressive. We assessed the effects of PCV-VG versus VCV in elderly patients by using lung ultrasound score (LUS).

Patients and methods

Elderly patients (aged 65-90 years) scheduled for hip joint surgery were randomly assigned to either the PCV-VG or VCV group during general anesthesia. LUS and mechanical ventilator parameters were evaluated before induction, 30 mins after a semi-lateral position change, during supine repositioning before awakening, and 15 mins after arrival to the post-anesthesia care unit (PACU). Pulmonary function tests were performed before and after surgery. Other recovery indicators were also assessed in the PACU.

Results

A total of 76 patients (40 for PCV-VG and 36 for VCV) were included this study. Demographic data showed no significant difference between the two groups. In both groups, LUSs before induction were significantly lower than those at other time points. LUSs of the VCV group were significantly increased during perioperative periods compared with the PCV-VG group (p=0.049). Visualized LUS modeling suggested an intuitive difference in the two groups and unequal distribution in lung aeration. Higher dynamic compliance and lower inspiratory peak pressure were observed in the PVC-VG group compared to the VCV group (33.54 vs 27.36, p<0.001; 18.93 vs 21.19, p<0.001, respectively). Postoperative forced vital capacity of the VCV group was lower than that of PCV-VG group, but this result was not significant (2.06 vs 1.79, respectively; p=0.091). The other respiratory data are comparable between the two groups.

Conclusion

The PCV-VG group showed better LUS compared with the VCV group. Moreover, LUS modeling in both groups suggests non-homogeneous and positional change in lung aerations during surgery.

Clinical trial registration

This study was registered at the UMIN clinical trials registry (unique trial number: UMIN000029355; registration number: R000033510).

Effect of prolonged inspiratory time on gas exchange during robot-assisted laparoscopic urologic surgery

BACKGROUND

Gas exchange disturbance may develop during urologic robotic laparoscopic surgery with the patient in a steep Trendelenburg position. This study investigated whether prolonged inspiratory time could mitigate gas exchange disturbances including hypercapnia.

METHODS

In this randomized cross-over trial, 32 patients scheduled for robot-assisted urologic surgery were randomized to receive an inspiratory to expiratory time ratio (I:E) of 1:1 for the first hour of pneumoperitoneum followed by 1:2 for last period of surgery (group A, n = 17) or I:E of 1:2 followed by 1:1 (group B, n = 15). Arterial blood gas analysis, airway pressure and hemodynamic variables were assessed at four time points (T1: 10 min after induction of general anesthesia, T2: 1 h after the initiation of pneumoperitoneum, T3: 1 h after T2 and T4: at skin closure). The carry over effect of initial I:E was also evaluated over the next hour through arterial blood gas analysis.

RESULTS

There was a significant decrease in partial pressure of oxygen in arterial blood (PaO₂) for both groups at T2 and T3 compared to T1 but in group B the PaO₂ at T4 was not decreased from the baseline. Partial pressure of carbon dioxide in arterial blood (PaCO₂) increased with I:E of 1:2 but did not significantly increase with I:E of 1:1; however, there were no differences in PaO₂ and PaCO₂ between the groups.

CONCLUSION

Decreased oxygenation by pneumoperitoneum was improved and PaCO₂ did not increase after 1 h of I:E of 1:1; however, the effect of equal ratio ventilation longer than 1 h remains to be determined. There was no carryover effect of the two different I:E ratios.

International multicenter observational study on assessment of ventilatory management during general anaesthesia for robotic surgery and its effects on postoperative pulmonary complication (AVATaR): study protocol and statistical analysis plan

INTRODUCTION

Robotic-assisted surgery (RAS) has emerged as an alternative minimally invasive surgical option. Despite its growing applicability, the frequent need for pneumoperitoneum and Trendelenburg position could significantly affect respiratory mechanics during RAS. AVATaR is an international multicenter observational study aiming to assess the incidence of postoperative pulmonary complications (PPC), to characterise current practices of mechanical ventilation (MV) and to evaluate a possible association between ventilatory parameters and PPC in patients undergoing RAS.

METHODS AND ANALYSIS

AVATaR is an observational study of surgical patients undergoing MV for general anaesthesia for RAS. The primary outcome is the incidence of PPC during the first five postoperative days. Secondary outcomes include practice of MV, effect of surgical positioning on MV, effect of MV on clinical outcome and intraoperative complications.

ETHICS AND DISSEMINATION

This study was approved by the Institutional Review Board of the Hospital Israelita Albert Einstein. The study results will be published in peer-reviewed journals and disseminated at international conferences.

TRIAL REGISTRATION NUMBER

NCT02989415; Pre-results.

Anaesthetic issues in robotic-assisted minimally invasive surgery

Over the past decade there has been an exponential increase in the number of robotic-assisted surgical procedures performed in Australia and internationally. Despite this growth, there are no level I or II studies examining the anaesthetic implications of these procedures. Available observational studies provide insight into the significant challenges for the anaesthetist. Most anaesthetic considerations overlap with those of non-robotic surgery. However, issues with limited patient access and extremes of positioning resulting in physiological disturbances and risk of injury are consistently demonstrated concerns specific to robotic-assisted procedures.

Comparisons of Pressure-controlled Ventilation with Volume Guarantee and Volume-controlled 1:1 Equal Ratio Ventilation on Oxygenation and Respiratory Mechanics during Robot-assisted Laparoscopic Radical Prostatectomy: a Randomized-controlled Trial

Background: During robot-assisted laparoscopic radical prostatectomy (RALP), steep Trendelenburg position and carbon dioxide pneumoperitoneum are inevitable for surgical exposure, both of which can impair cardiopulmonary function. This study was aimed to compare the effects of pressure-controlled ventilation with volume guarantee (PCV with VG) and 1:1 equal ratio ventilation (ERV) on oxygenation, respiratory mechanics and hemodynamics during RALP. Methods: Eighty patients scheduled for RALP were randomly allocated to either the PCV with VG or ERV group. After anesthesia induction, volume-controlled ventilation (VCV) was applied with an inspiratory to expiratory (I/E) ratio of 1:2. Immediately after pneumoperitoneum and Trendelenburg positioning, VCV with I/E ratio of 1:1 (ERV group) or PCV with VG using Autoflow mode (PCV with VG group) was initiated. At the end of Trendelenburg position, VCV with I/E ratio of 1:2 was resumed. Analysis of arterial blood gases, respiratory mechanics, and hemodynamics were compared between groups at four times: 10 min after anesthesia induction (T1), 30 and 60 min after pneumoperitoneum and Trendelenburg positioning (T2 and T3), and 10 min after desufflation and resuming the supine position (T4). Results: There were no significant differences in arterial blood gas analyses including arterial oxygen tension (PaO₂) between groups throughout the study period. Mean airway pressure (Pmean) were significantly higher in the ERV group than in the PCV with VG group T2 (p<0.001) and T3 (p=0.002). Peak airway pressure and hemodynamic data were comparable in both groups. Conclusion: PCV with VG was an acceptable alternative to ERV during RALP producing similar PaO₂ values. The lower Pmean with PCV with VG suggests that it may be preferable in patients with reduced cardiovascular function.

What is the proper ventilation strategy during laparoscopic surgery?

The main stream of intraabdominal surgery has changed from laparotomy to laparoscopy, but anesthetic care for laparoscopic surgery is challenging for clinicians, because pneumoperitoneum might aggravate respiratory mechanics and arterial oxygenation. The authors reviewed the literature regarding ventilation strategies that reduce deleterious pulmonary physiologic changes during pneumoperitoneum for laparoscopic surgery under general anesthesia and make appropriate recommendations.

Effects of positive end-expiratory pressure on intracranial pressure during pneumoperitoneum and Trendelenburg position in a porcine mode

Background/aim: This study was undertaken to evaluate the effects of positive end-expiratory pressure (PEEP) levels on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) and to determine the appropriate PEEP level during steep Trendelenburg position combined with pneumoperitoneum.Materials and methods: Ten pigs were included in this study. Pneumoperitoneum and Trendelenburg position were maintained and PEEP titration was initiated. Arterial pressure, heart rate, arterial blood gas, ICP, and CPP were recorded at the following time points: baseline (T0), 30 min after positioning and pneumoperitoneum (T1), PEEP 5 (T2), PEEP 10 (T3), PEEP 15 (T4), and PEEP 20 (T5).Results: MAP significantly increased at T1 compared to T0 and decreased at T4 and T5 compared to T1. ICP was 9.5 mmHg and CPP was 69.3 mmHg at T0. CO2 insufflation and steep Trendelenburg position did not cause any significant difference in ICP and CPP. ICP increased and CPP decreased significantly at T4 and T5 compared to both T0 and T1. PaO2 and PaO2/FiO2 decreased significantly at T1 and T2 compared to T0, while both increased significantly at T3, T4, and T5 compared to T1.Conclusion: PEEP of 10 cmH2O was effective for providing oxygenation while preserving hemodynamic stability, ICP, and CPP in this model.

Comparison of pressure vs. volume controlled ventilation on oxygenation parameters of obese patients undergoing laparoscopic cholecystectomy

Background & Objective:

There is no special guideline for the best ventilation mode during laparoscopic anesthesia in obese patients and there are too many studies with different controversial points. The aim of this study was to compare the effect of pressure controlled ventilation (PCV) vs. volume controlled ventilation (VCV) on respiratory and oxygenation parameters in patients undergoing laparoscopic cholecystectomy.

Methods:

Seventy patients with 30 <BMI<40 and ASA physical status I-II were studied in this randomized prospective trial. Anesthesia was started with VCV and after creation of pneumoperitoneum; the patients were randomized into PCV or VCV groups. Ventilation parameters were adjusted to a CO2 target of 35-40 mmHg. Hemodynamic and oxygenation parameters and respiratory parameters like plateau, mean airway and peak pressure were recorded for all patients during the study.

Results:

Patients in VCV group needed higher tidal volume and respiratory rate to maintain target CO₂ in 35 and 55 minutes after the study. Plateau pressure and mean airway pressure in two groups didn’t have significant difference between two groups but peak airway pressure in 35 and 55 minutes after pneumoperitoneum was significantly higher in VCV group than PCV group. There were no significant differences between two groups regarding PO₂, PCO₂ and pH, except 35 and 55 minutes after pneumoperitoneum. In mentioned times, patients in PCV group had significantly higher PO₂ levels compared to VCV group.

Conclusion:

Despite some beneficial effects regarding plateau, mean airway pressure and oxygenation parameters with PCV, there was no significant clinical difference between PCV and VCV in obese patients undergoing laparoscopic cholecystectomy.

Effects of recruitment manoeuvre on perioperative pulmonary complications in patients undergoing robotic assisted radical prostatectomy: A randomised single-blinded trial

Robotic-assisted laparoscopic radical prostatectomy (RARP) needs a steep Trendelenburg position and a relatively high CO2 insufflation pressure, and patients undergoing RARP are usually elderly. These factors make intraoperative ventilatory care difficult and increase the risk of perioperative pulmonary complications. The aim was to determine the efficacy of recruitment manoeuvre (RM) on perioperative pulmonary complications in elderly patients undergoing RARP. A total of 60 elderly patients scheduled for elective RARP were randomly allocated to two groups after induction of anaesthesia; positive end expiratory pressure (PEEP) was applied during the operation without RM in the control group (group C) and after RM in the recruitment group (group R). The total number of patients who developed intraoperative desaturation or postoperative atelectasis was significantly higher in group C compared to group R (43.3% vs. 17.8%, P = 0.034). Intraoperative respiratory mechanics, perioperative blood gas analysis, and pulmonary function testing did not show differences between the groups. Adding RM to PEEP compared to PEEP alone significantly reduced perioperative pulmonary complications in elderly patients undergoing RARP.

Airway Resistance in Patients with Obstructive Sleep Apnea Syndrome Following Robotic Prostatectomy

BACKGROUND

Because minimally invasive surgery can improve postoperative recovery, it became the preferred technique for patients with significant comorbidities. However, steep Trendelenburg position and abdominal CO2-insufflation can lead to a significant increase in upper airway resistance and an alteration of overall lung function. In particular, patients who already suffer from an obstructive airway disease like obstructive sleep apnea syndrome (OSAS) might be at risk for postoperative airway complications. Therefore, we perioperatively performed spirometric tests in patients with OSAS undergoing robotic surgery in steep Trendelenburg position.

METHODS

Twenty patients with OSAS were enrolled in the study. A day before surgery lung function measurements were performed and repeated preoperatively, 40, 120, and 240 minutes and 1 and 5 days postoperatively. We measured vital capacity (VC), forced expiratory volume in 1 second (FEV1), maximal mid expiratory and inspiratory flow (MEF50, MIF50), arterial oxygen saturation, and nasal flow.

RESULTS

The ratio of MEF50 to MIF50, as an indicator of upper airway resistance, was increased significantly postoperatively and normalized within 24 hours (p < 0.0001), while FEV1 and VC were significantly reduced and recovered only partially as much as the fifth postoperative day (p < 0.0001).

CONCLUSION

Airway resistance increased following robotic radical prostatectomy in Trendelenburg position in patients with OSAS. Two separate major effects can be observed. A significant increase of the upper airway resistance, which improved to preoperative conditions within 24 hours, and a reduction in FEV1 and VC, which recovered only partially as much as the fifth postoperative day.

Comparison of volume controlled ventilation and pressure controlled ventilation in patients undergoing robot-assisted pelvic surgeries: An open-label trial

Background and Aims:

Although volume controlled ventilation (VCV) has been the traditional mode of ventilation in robotic surgery, recently pressure controlled ventilation (PCV) has been used more frequently. However, evidence on whether PCV is superior to VCV is still lacking. We intended to compare the effects of VCV and PCV on respiratory mechanics and haemodynamic in patients undergoing robotic surgeries in steep Trendelenburg position.

Methods:

This prospective, randomized trial was conducted on sixty patients between 20 and 70 years belonging to the American Society of Anesthesiologist Physical Status I–II. Patients were randomly assigned to VCV group (n = 30), where VCV mode was maintained through anaesthesia, or the PCV group (n = 30), where ventilation mode was changed to PCV after the establishment of 40° Trendelenburg position and pneumoperitoneum. Respiratory (peak and mean airway pressure [AP_peak, AP_mean], dynamic lung compliance [C_dyn] and arterial blood gas analysis) and haemodynamics variables (heart rate, mean blood pressure [MBP] central venous pressure) were measured at baseline (T₁), post-Trendelenburg position at 60 min (T₂), 120 min (T₃) and after resuming supine position (T₄).

Results:

Demographic profile, haemodynamic variables, oxygen saturation and minute ventilation (MV) were comparable between two groups. Despite similar values of AP_mean, AP_peak was significantly higher in VCV group at T2 and T3 as compared to PCV group (P < 0.001). C_dyn and PaCO₂ were also better in PCV group than in VCV group (P < 0.001 and 0.045, respectively).

Conclusion:

PCV should be preferred in robotic pelvic surgeries as it offers lower airway pressures, greater C_dyn and a better-preserved ventilation-perfusion matching for the same levels of MV.

Respiratory dynamics and dead space to tidal volume ratio of volume-controlled versus pressure-controlled ventilation during prolonged gynecological laparoscopic surgery

BACKGROUND

Laparoscopic operations have become longer and more complex and applied to a broader patient population in the last decades. Prolonged gynecological laparoscopic surgeries require prolonged pneumoperitoneum and Trendelenburg position, which can influence respiratory dynamics and other measurements of pulmonary function. We investigated the differences between volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) and tried to determine the more efficient ventilation mode during prolonged pneumoperitoneum in gynecological laparoscopy.

METHODS

Twenty-six patients scheduled for laparoscopic radical hysterectomy combined with or without laparoscopic pelvic lymphadenectomy were randomly allocated to be ventilated by either VCV or PCV. Standard anesthesic management and laparoscopic procedures were performed. Measurements of respiratory and hemodynamic dynamics were obtained after induction of anesthesia, at 10, 30, 60, and 120 min after establishing pneumoperitoneum, and at 10 min after return to supine lithotomy position and removal of carbon dioxide. The logistic regression model was applied to predict the corresponding critical value of duration of pneumoperitoneum when the Ppeak was higher than 40 cmH₂O.

RESULTS

Prolonged pneumoperitoneum and Trendelenburg position produced significant and clinically relevant changes in dynamic compliance and respiratory mechanics in anesthetized patients under PCV and VCV ventilation. Patients under PCV ventilation had a similar increase of dead space/tidal volume ratio, but had a lower Ppeak increase compared with those under VCV ventilation. The critical value of duration of pneumoperitoneum was predicted to be 355 min under VCV ventilation, corresponding to the risk of Ppeak higher than 40 cmH₂O.

CONCLUSIONS

Both VCV and PCV can be safely applied to prolonged gynecological laparoscopic surgery. However, PCV may become the better choice of ventilation after ruling out of other reasons for Ppeak increasing.

Physiopathology and clinical considerations of laparoscopic surgery in the elderly

OBJECTIVE

The marked improvements in medical technology and healthcare, lead an increasing number of elderly patients to take advantage of even complex surgical. Recently, laparoscopic surgery has been accepted as a minimally invasive treatment to reduce the morbidity after conventional surgery, and a number of studies have demonstrated the feasibility of laparoscopy with significant advantages also in the elderly. On the other side, the laparoscopic procedure has some drawbacks, including prolonged operation time and impact of carbon dioxide pneumoperitoneum on circulatory and respiratory dynamics. This paper will review the physiopathological implications of laparoscopy, as well as the current literature concerning the most common laparoscopic procedures that are increasingly performed in elderly patients.

MATERIALS AND METHODS

A systematic review of the current literature was performed using the search engines EMBASE and PubMed to identify all studies reporting the physiopathological implications of laparoscopy in the elderly. The MeSH search terms used were "laparoscopy in the elderly", "physiopathology of laparoscopy", and "pneumoperitoneum". Multiple combinations of the keywords and MeSH terms were used with particular reference to elderly patients.

RESULTS

Although laparoscopy is minimally invasive in its dissection techniques, the increased physiologic demands present particular challenges among elderly patients.

CONCLUSIONS

Laparoscopy and its safety in the elderly patients remains a challenge and the evaluation of this approach is therefore mandatory. Although many studies have demonstrated the applicability and advantages of the laparoscopy also in the geriatric population, with low rates of morbidity and mortality, in elderly patients undergoing general surgical procedures the physiologic demands of laparoscopy should be carefully considered.

Comparison of volume-controlled ventilation and pressure-controlled ventilation volume guaranteed during laparoscopic surgery in Trendelenburg position

STUDY OBJECTIVE

To analyze the effects of pressure-controlled ventilation-volume guaranteed (PCV-VG) and volume controlled ventilation (VCV) on airway pressures and respiratory and circulatory indicators during laparoscopic surgery in Trendelenburg position.

DESIGN

Prospective randomized comparative clinical study.

SETTING

Tertiary hospital.

PATIENTS

Forty ASA physical status 1 and 2 patients who underwent elective laparoscopic surgery in Trendelenburg position.

INTERVENTIONS

Patients were randomly allocated to either VCV group (n=20) or the PCV-VG group (n=20). After induction of anesthesia, for both modes of ventilation, the target tidal volume (VT) was 8mL/kg and the respiratory rate was adjusted to avoid hypercarbia.

MEASUREMENTS

The peak and mean inspiratory pressures, dynamic compliance, exhaled VT, oxygenation index and physiological dead space were calculated and recorded at T1, 5minutes after induction of anesthesia in supine position, T2, 5minutes after stabilization of pneumoperitoneum, T3 and T4, 15 and 60minutes after 30° Trendelenburg position with pneumoperitoneum respectively.

MAIN RESULTS

PCV-VG group had significantly lower peak inspiratory pressure and greater dynamic compliance than VCV group (P<.001).

CONCLUSIONS

In patients who underwent laparoscopic surgery in Trendelenburg position, PCV-VG was superior to VCV in its ability to provide ventilation with lower peak inspiratory pressure and greater dynamic compliance.

Effect of the Prolonged Inspiratory to Expiratory Ratio on Oxygenation and Respiratory Mechanics During Surgical Procedures

Prolonged inspiratory to expiratory (I:E) ratio ventilation has been researched to reduce lung injury and improve oxygenation in surgical patients with one-lung ventilation (OLV) or carbon dioxide (CO2) pneumoperitoneum. We aimed to confirm the efficacy of the 1:1 equal ratio ventilation (ERV) compared with the 1:2 conventional ratio ventilation (CRV) during surgical procedures. Electronic databases, including PubMed, Embase, Cochrane Central Register of Controlled Trials, Web of Science, and Google Scholar were searched.Prospective interventional trials that assessed the effects of prolonged I:E ratio of 1:1 during surgical procedures. Adult patients undergoing OLV or CO2 pneumoperitoneum as specific interventions depending on surgical procedures. The included studies were examined with the Cochrane Collaboration's tool. The data regarding intraoperative oxygenation and respiratory mechanics were extracted, and then pooled with standardized mean difference (SMD) using the method of Hedges. Seven trials (498 total patients, 274 with ERV) were included. From overall analysis, ERV did not improve oxygenation at 20 or 30 minutes after specific interventions (SMD 0.193, 95% confidence interval (CI): -0.094 to 0.481, P = 0.188). From subgroup analyses, ERV provided significantly improved oxygenation only with laparoscopy (SMD 0.425, 95% CI: 0.167-0.682, P = 0.001). At 60 minutes after the specific interventions, ERV improved oxygenation significantly in the overall analysis (SMD 0.447, 95% CI: 0.209-0.685, P < 0.001) as well as in the subgroup analyses with OLV (SMD 0.328, 95% CI: 0.011-0.644, P = 0.042) and laparoscopy (SMD 0.668, 95% CI: 0.052-1.285, P = 0.034). ERV provided lower peak airway pressure (Ppeak) and plateau airway pressure (Pplat) than CRV, regardless of the type of intervention. The relatively small number of the included articles and their heterogeneity could be the main limitations. ERV improved oxygenation at all of the assessment points during laparoscopy. In OLV, oxygenation improvement with ERV was observed 1 hour after application. ERV could be beneficial to reduce the Ppeak and Pplat.

Respiratory gas exchange during robotic-assisted laparoscopic radical prostatectomy

STUDY OBJECTIVE

Robotic-assisted laparoscopic prostatectomy requires patients to be secured in a steep Trendelenburg position for several hours. Added to the CO2 pneumoperitoneum that is created, this positioning invariably restricts diaphragmatic and chest wall excursion, which can adversely affect respiratory gas exchange. This study sought to measure the extent of respiratory gas change during this procedure.

DESIGN

Retrospective, institutional review board approved.

SETTING

Operating room.

PATIENTS

N = 186 males, American Society of Anesthesiologists 2-3, with prostatic carcinoma undergoing robotic-assisted laparoscopic radical prostatectomy.

INTERVENTIONS

Arterial blood gases and noninvasive respiratory measurements were recorded for those patients (n = 32) in whom a radial arterial catheter had been inserted intraoperatively, specifically timed to different phases of the procedure: supine lithotomy, steep Trendelenburg, and return to supine. Ventilatory parameters were standardized.

MEASUREMENTS

Systemic blood pressure, heart rate, respiratory rate, Pao2, Paco2, oxygen saturation as measured by pulse oximetry, and end-tidal carbon dioxide pressure.

MAIN RESULTS

Although no patients developed perioperative respiratory complications, the Pao2 invariably fell (395 vs 316 mm Hg; P = .001) while the patients were in steep Trendelenburg, and the Paco2-end-tidal carbon dioxide pressure rose (10.0 vs 13.4 mm Hg; P < .0001). Upon return to supine, patients' respiratory measurements promptly returned to within 15% of baseline. Subgroup analysis for high-BMI vs low-BMI patients as well as for patients with pulmonary disease and/or a smoking history showed similar individual effects and only small, although significant, respiratory gas exchange aberrations.

CONCLUSIONS

Positioning patients with a CO2 pneumoperitoneum in steep Trendelenburg for several hours imposes restriction of diaphragmatic and chest wall movement sufficient for respiratory gas exchange to be adversely affected. Return of function to within 15% of baseline occurred within minutes after return to supine and release of the CO2 pneumoperitoneum. No patients during the study period developed pulmonary complications that required alteration in their level of care.