The impact of morbid obesity, pneumoperitoneum, and posture on respiratory system mechanics and oxygenation during laparoscopy

The Effect of Recruitment Maneuver on Static Lung Compliance in Patients Undergoing General Anesthesia for Laparoscopic Cholecystectomy: A Single-Centre Prospective Clinical Intervention Study

Background and Objectives: The aim of this study was to examine whether the use of an alveolar recruitment maneuver (RM) leads to a significant increase in static lung compliance (Cstat) and an improvement in gas exchange in patients undergoing laparoscopic cholecystectomy. Material and Methods: A clinical prospective intervention study was conducted. Patients were divided into two groups according to their body mass index (BMI): normal-weight (group I) and pre-obese and obese grade I (group II). Lung mechanics were monitored (Cstat, dynamic compliance-Cdin, peak pressure-Ppeak, plateau pressure-Pplat, driving pressure-DP) alongside gas exchange, and hemodynamic changes (heart rate-HR, mean arterial pressure-MAP) at six time points: T1 (induction of anesthesia), T2 (formation of pneumoperitoneum), T3 (RM with a PEEP of 5 cm H2O), T4 (RM with a PEEP of 7 cm H2O), T5 (desufflation), and T6 (RM at the end). The RM was performed by increasing the peak pressure by +5 cm of H2O at an equal inspiration-to-expiration ratio (I/E = 1:1) and applying a PEEP of 5 and 7 cm of H2O. Results: Out of 96 patients, 33 belonged to group I and 63 to group II. An increase in Cstat values occurred after all three RMs. At each time point, the Cstat value was measured higher in group I than in group II. A higher increase in Cstat was observed in group II after the second and third RM. Cstat values were higher at the end of the surgical procedure compared to values after the induction of anesthesia. The RM led to a significant increase in PaO2 in both groups without changes in HR or MAP. Conclusions: During laparoscopic cholecystectomy, the application of RM leads to a significant increase in Cstat and an improvement in gas exchange. The prevention of atelectasis during anesthesia should be initiated immediately after the induction of anesthesia, using protective mechanical ventilation and RM.

Transthoracic Echocardiography Is Possible in Morbidly Obese Patients During Bariatric Surgery

BACKGROUND

To evaluate the feasibility of an abbreviated focus-assessed transthoracic echocardiography protocol in morbidly obese patients. The purpose of this study was to evaluate whether good images could be obtained from this particularly difficult group of patients for whom acoustic imaging is often poor. Heart imaging could be helpful for cardiopulmonary screening and real-time monitoring.

METHODS

The study included 186 morbidly obese patients, who underwent laparoscopic bariatric surgery. The mean patient age was 32 years (range 21-52), and there were 95 males. The parasternal long and short axes and apical 4 and 5 chambers were evaluated.

RESULTS

In 95% of the patients, at least one view was obtained. In 78%, two views were obtained, and in 31% of the patients, all views and measurements could be performed.

CONCLUSION

In obese patients, a modified focused echocardiography examination performed by anesthesiologists in the intraoperative period of morbid obese patients is feasible. The image quality was sufficient to undergo interpretation.

Acute Respiratory Failure Complicating Endoscopic Sleeve Gastroplasty: A Case Report

Endoscopic sleeve gastroplasty (ESG) is a safe and minimally invasive procedure for the treatment of obesity. We report the case of a patient with obesity who underwent ESG complicated by postprocedural respiratory failure. During the procedure, she developed a Pao2/fraction of inspired oxygen (Fio2) ratio that necessitated postoperative mechanical ventilation. Chest radiography demonstrated massively dilated loops of bowel, cephalad displacement of both hemidiaphragms, lung volume reduction, and atelectasis. With absorption of luminal carbon dioxide, she was weaned from mechanical ventilation to supplemental oxygen, and she recovered completely. This case highlights postoperative respiratory failure associated with mechanical loading of the respiratory system following ESG.

Individualised positive end-expiratory pressure in abdominal surgery: a systematic review and meta-analysis

BACKGROUND

Individualised PEEP may optimise pulmonary compliance, thereby potentially mitigating lung injury. This meta-analysis aimed to determine the impact of individualised PEEP vs fixed PEEP during abdominal surgery on postoperative pulmonary outcomes.

METHODS

Medical databases (PubMed, Embase, Web of Science, ScienceDirect, Google Scholar, and the China National Knowledge Infrastructure) were searched for RCTs comparing fixed vs individualised PEEP. The composite primary outcome of pulmonary complications comprised hypoxaemia, atelectasis, pneumonia, and acute respiratory distress syndrome. Secondary outcomes included oxygenation (P_aO₂/FiO₂) and systemic inflammatory markers (interleukin-6 [IL-6] and club cell protein-16 [CC16]). We calculated risk ratios (RRs) and mean differences (MDs) with 95% confidence interval (CI) using DerSimonian and Laird random effects models. Cochrane risk-of-bias tool was applied.

RESULTS

Ten RCTs (n=1117 patients) met the criteria for inclusion, with six reporting the primary endpoint. Individualised PEEP reduced the incidence of overall pulmonary complications (141/412 [34.2%]) compared with 183/415 (44.1%) receiving fixed PEEP (RR 0.69 [95% CI: 0.51-0.93]; P=0.016; I²=43%). Risk-of-bias analysis did not alter these findings. Individualised PEEP reduced postoperative hypoxaemia (74/392 [18.9%]) compared with 110/395 (27.8%) participants receiving fixed PEEP (RR 0.68 [0.52-0.88]; P=0.003; I²=0%) but not postoperative atelectasis (RR 0.93 [0.81-1.07]; P=0.297; I²=0%). Individualised PEEP resulted in higher P_aO₂/FiO₂ (MD 20.8 mm Hg [4.6-36.9]; P=0.012; I²=80%) and reduced systemic inflammation (lower plasma IL-6 [MD -6.8 pg ml^-1; -11.9 to -1.7]; P=0.009; I²=6%; and CC16 levels [MD -6.2 ng ml^-1; -8.8 to -3.5]; P<0.001; I²=0%) at the end of surgery.

CONCLUSIONS

Individualised PEEP may reduce pulmonary complications, improve oxygenation, and reduce systemic inflammation after abdominal surgery.

CLINICAL TRIAL REGISTRATION

CRD42021277973.

The effect of steep head-down tilt on respiratory status in endometrial cancer patients with obesity during robot-assisted hysterectomy

•

Robot-assisted surgery with a head-down tilt of 25° or below may be safe even in patients with morbid obesity.

•

In patients with morbid obesity, a steep head-down tilt may present a risk of respiratory complications.

•

A Trendelenburg position of 20–25° is adequate to perform robot-assisted surgery for endometrial cancer.

Objective

To evaluate the effect of head-down tilt on airway pressure in gynecologic patients with obesity during robot-assisted hysterectomy.

Methods

We retrospectively reviewed the records of 27 patients with body mass index (BMI) ≥ 25 kg/m² who underwent robot-assisted hysterectomy for endometrial cancer and endometrial atypical hyperplasia using the da Vinci Xi system. Mechanical ventilation was performed using pressure-controlled ventilation (PCV). Surgery was performed at 20° (group A, n = 17) or 25° head-down tilt (group B, n = 10). Respiratory parameters, including positive end-expiratory pressure (PEEP), tidal volume (TV), mean airway pressure (P mean), and peak airway pressure (P peak), were measured before (T1) and after the head-down tilt at 1 h (T2) and 2 h (T3) during anesthesia.

Results

The median BMI was 37.5 (range 28–51) kg/m², with no between-group variation. Oxygenation was maintained intraoperatively for all patients. The expiratory carbon dioxide partial pressure was 43.6 (95% confidence interval (CI) 42.2–45.0) mmHg. The P mean peak at T2 in group B was significantly higher than in group A (P < 0.011); however, other parameters at T2 and T3 did not differ significantly between the groups. Patients with BMI ≥ 40 kg/m² had significantly higher respiratory parameters than those with BMI < 40 kg/m². In patients with BMI ≥ 40 kg/m², the mean P means and P peaks at T3 were 17.3 cmH₂O (95% CI 16.3–18.3) and 29.4 cmH₂O (95% CI 27.1–31.7), respectively.

Discussion

With careful anesthetic management during PCV, robot-assisted surgery with a head-down tilt of 25° or below may be safe, even in patients with class III obesity.

Comparison of Pressure and Volume-Controlled Mechanical Ventilation in Laparoscopic Bariatric Surgery: A Randomized Crossover Trial

Background

The number of patients with obesity undergoing various surgeries is increasing annually, and ventilation problems are highly prevalent in these patients.

Objectives

We aimed to evaluate ventilation effectiveness with pressure-controlled (PC) and volume-controlled (VC) ventilation modes during laparoscopic bariatric surgery.

Methods

In this open-label randomized crossover clinical trial, 40 adult patients with morbid obesity candidates for laparoscopic bariatric surgery were assigned to VC-PC or PC-VC groups. Each patient received both ventilation modes sequentially for 15 min during laparoscopic surgery in a random sequence. Every 5 min, exhaled tidal volume, peak and mean airway pressure, oxygen saturation, heart rate, mean arterial pressure, and end-tidal CO₂ were recorded. Blood gas analysis was done at the end of 15 min. Dynamic compliance, PaO₂/FiO₂ ratio, P (A-a) O₂ gradient, respiratory dead space, and PaCO₂-ETCO₂ gradient were calculated according to the obtained results.

Results

The study included 40 patients with a mean age of 35.13 ± 9.06 years. There were no significant differences in peak and mean airway pressure, dynamic compliance, and hemodynamic parameters (P > 0.05). There was no significant difference between the two ventilation modes in pH, PaCO₂, PaO₂, PaO₂/FIO₂, dead space volume, and D (A-a) O₂ at different time intervals (P > 0.05).

Conclusions

If low tidal volumes are used during adult laparoscopic bariatric surgery, mechanical ventilation with PC mode is not superior to VC mode.

Endotracheal tube cuff pressure during laparoscopic bariatric surgery: highs and lows

Background: Gastric calibration tubes (GCTs) are a unique component of bariatric surgery. This study aimed to assess changes in the endotracheal tube (ETT) cuff pressure during laparoscopic bariatric surgery.Methods: This was a prospective observational study consisting of 124 American Society of Anesthesiologists class I–III morbidly obese patients (body mass index > 40 kg/m2) undergoing elective laparoscopic bariatric surgery under general anesthesia. The baseline ETT cuff pressure was 28 cmH2O. Cuff pressure, peak airway pressure, and hemodynamic changes were observed during various steps of bariatric surgery. Immediate postoperative complications during the first 24 h were recorded. Results: ETT cuff pressure increased significantly from the baseline (28 cmH2O) after insertion of GCT (36.3 ± 7.3 cmH2O) and creation of carboperitoneum (33.3 ± 3.8 cmH2O). Cuff pressure decreased significantly on GCT removal (24.0 ± 3.0 cmH2O) and release of carboperitoneum (24.7 ± 3.0 cmH2O). Peak airway pressure increased from the initial baseline value of 25.1 ± 3.1 to 26.5 ± 4.5 after GCT insertion, creation of carboperitoneum (32.6 ± 4.4), attainment of reverse Trendelenburg position (32.3 ± 4.0), and subsequent return to supine position 32.5 ± 4.8.Conclusions: The endotracheal cuff pressure significantly varies during the intraoperative period. Routine monitoring and readjustment of cuff pressure are advisable in all laparoscopic bariatric surgeries to minimize the possibility of postoperative complications.

Positive end-expiratory pressure individualization guided by continuous end-expiratory lung volume monitoring during laparoscopic surgery

To determine whether end-expiratory lung volume measured with volumetric capnography (EELV_CO2) can individualize positive end-expiratory pressure (PEEP) setting during laparoscopic surgery. We studied patients undergoing laparoscopic surgery subjected to Fowler (F-group; n = 20) or Trendelenburg (T-group; n = 20) positions. EELV_CO2 was measured at 0° supine (baseline), during capnoperitoneum (CP) at 0° supine, during CP with Fowler (head up + 20°) or Trendelenburg (head down - 30°) positions and after CP back to 0° supine. PEEP was adjusted to preserve baseline EELV_CO2 during and after CP. Baseline EELV_CO2 was statistically similar to predicted FRC in both groups. At supine and CP, EELV_CO2 decreased from baseline values in F-group [median and IQR 2079 (768) to 1545 (725) mL; p = 0.0001] and in T-group [2164 (789) to 1870 (940) mL; p = 0.0001]. Change in body position maintained EELV_CO2 unchanged in both groups. PEEP adjustments from 5.6 (1.1) to 10.0 (2.5) cmH₂O in the F-group (p = 0.0001) and from 5.6 (0.9) to 10.0 (2.6) cmH₂O in T-group (p = 0.0001) were necessary to reach baseline EELV_CO2 values. EELV_CO2 increased close to baseline with PEEP in the F-group [1984 (600) mL; p = 0.073] and in the T-group [2175 (703) mL; p = 0.167]. After capnoperitoneum and back to 0° supine, PEEP needed to maintain EELV_CO2 was similar to baseline PEEP in F-group [5.9 (1.8) cmH₂O; p = 0.179] but slightly higher in the T-group [6.5 (2.2) cmH₂O; p = 0.006]. Those new PEEP values gave EELV_CO2 similar to baseline in the F-group [2039 (980) mL; p = 0.370] and in the T-group [2150 (715) mL; p = 0.881]. Breath-by-breath noninvasive EELV_CO2 detected changes in lung volume induced by capnoperitoneum and body position and was useful to individualize the level of PEEP during laparoscopy.Trial registry: Clinicaltrials.gov NCT03693352. Protocol started 1st October 2018.

Effects of an open lung ventilatory strategy on lung gas exchange during laparoscopic surgery

In general anaesthesia, early collapse of poorly ventilated lung segments with low alveolar ventilation-perfusion ratios occurs and may lead to postoperative pulmonary complications after abdominal surgery. An 'open lung' ventilation strategy involves lung recruitment followed by 'individualised' positive end-expiratory pressure titrated to maintain recruitment of low alveolar ventilation-perfusion ratio lung segments. There are limited data in laparoscopic surgery on the effects of this on pulmonary gas exchange. Forty laparoscopic bowel surgery patients were randomly assigned to standard ventilation or an 'open lung' ventilation intervention, with end-tidal target sevoflurane of 1% supplemented by propofol infusion. After peritoneal insufflation, stepped lung recruitment was performed in the intervention group followed by maintenance positive end-expiratory pressure of 12-15 cmH₂O adjusted to maintain dynamic lung compliance at post-recruitment levels. Baseline gas and blood samples were taken and repeated after a minimum of 30 minutes for oxygen and carbon dioxide and for sevoflurane partial pressures using headspace equilibration. The sevoflurane arterial/alveolar partial pressure ratio and alveolar deadspace fraction were unchanged from baseline and remained similar between groups (mean (standard deviation) control group = 0.754 (0.086) versus intervention group = 0.785 (0.099), P = 0.319), while the arterial oxygen partial pressure/fractional inspired oxygen concentration ratio was significantly higher in the intervention group at the second timepoint (control group median (interquartile range) 288 (234-372) versus 376 (297-470) mmHg in the intervention group, P = 0.011). There was no difference between groups in the sevoflurane consumption rate. The efficiency of sevoflurane uptake is not improved by open lung ventilation in laparoscopy, despite improved arterial oxygenation associated with effective and sustained recruitment of low alveolar ventilation-perfusion ratio lung segments.

Effect of the "Recruitment" Maneuver on Respiratory Mechanics in Laparoscopic Sleeve Gastrectomy Surgery

Purpose

LSG surgery is used for surgical treatment of morbid obesity. Obesity, anesthesia, and pneumoperitoneum cause reduced pulmoner functions and a tendency for atelectasis. The alveolar “recruitment” maneuver (RM) keeps airway pressure high, opening alveoli, and increasing arterial oxygenation. The aim of our study is to research the effect on respiratory mechanics and arterial blood gases of performing the RM in LSG surgery.

Materials and Methods

Sixty patients undergoing LSG surgery were divided into two groups (n = 30) Patients in group R had the RM performed 5 min after desufflation with 100% oxygen, 40 cmH₂O pressure for 40 s. Group C had standard mechanical ventilation. Assessments of respiratory mechanics and arterial blood gases were made in the 10th min after induction (T1), 10th min after insufflation (T2), 5th min after desufflation (T3), and 15th min after desufflation (T4). Arterial blood gases were assessed in the 30th min (T5) in the postoperative recovery unit.

Results

In group R, values at T5, PaO₂ were significantly high, while PaCO₂ were significantly low compared with group C. Compliance in both groups reduced with pneumoperitoneum. At T4, the compliance in the recruitment group was higher. In both groups, there was an increase in PIP with pneumoperitoneum and after desufflation this was identified to reduce to levels before pneumoperitoneum.

Conclusion

Adding the RM to PEEP administration for morbidly obese patients undergoing LSG surgery is considered to be effective in improving respiratory mechanics and arterial blood gas values and can be used safely.

Lung-protective mechanical ventilation for patients undergoing abdominal laparoscopic surgeries: a randomized controlled trial

Background

Pneumoperitoneum and Trendelenburg position in laparoscopic surgeries could contribute to postoperative pulmonary dysfunction. In recent years, intraoperative lung-protective mechanical ventilation (LPV) has been reportedly able to attenuate ventilator-induced lung injuries (VILI). Our objectives were to test the hypothesis that LPV could improve intraoperative oxygenation function, pulmonary mechanics and early postoperative atelectasis in laparoscopic surgeries.

Methods

In this randomized controlled clinical trial, 62 patients indicated for elective abdominal laparoscopic surgeries with an expected duration of greater than 2 h were randomly assigned to receive either lung-protective ventilation (LPV) with a tidal volume (Vt) of 7 ml kg^− 1 ideal body weight (IBW), 10 cmH₂O positive end-expiratory pressure (PEEP) combined with regular recruitment maneuvers (RMs) or conventional ventilation (CV) with a Vt of 10 ml kg^− 1 IBW, 0 cmH₂O in PEEP and no RMs. The primary endpoints were the changes in the ratio of PaO₂ to FiO₂ (P/F). The secondary endpoints were the differences between the two groups in PaO₂, alveolar-arterial oxygen gradient (A-aO₂), intraoperative pulmonary mechanics and the incidence of atelectasis detected on chest x-ray on the first postoperative day.

Results

In comparison to CV group, the intraoperative P/F and PaO₂ in LPV group were significantly higher while the intraoperative A-aO₂ was clearly lower. C_dyn and C_stat at all the intraoperative time points in LPV group were significantly higher compared to CV group (p < 0.05). There were no differences in the incidence of atelectasis on day one after surgery between the two groups.

Conclusions

Lung protective mechanical ventilation significantly improved intraoperative pulmonary oxygenation function and pulmonary compliance in patients experiencing various abdominal laparoscopic surgeries, but it could not ameliorate early postoperative atelectasis and oxygenation function on the first day after surgery.

Trial registration

https://www.clinicaltrials.gov/identifier: NCT04546932 (09/05/2020).

Do Small Incisions Need Only Minimal Anesthesia?-Anesthetic Management in Laparoscopic and Robotic Surgery

Laparoscopic techniques have established themselves as a major part of modern surgery. Their implementation in every surgical discipline has played a vital part in the reduction of perioperative morbidity and mortality. Precise robotic surgery, as an evolution of this, is shaping the present and future operating theatre that an anesthetist is facing. While incisions get smaller and the impact on the organism seems to dwindle, challenges for anesthetists do not lessen and could even become more demanding than in open procedures. This review focuses on the pathophysiological effects of contemporary laparoscopic and robotic procedures and summarizes anesthetic challenges and strategies for perioperative management.

Sudden Airway Collapse After Pneumoperitoneum With Undiagnosed Tracheomalacia in a Morbidly Obese 12-Year-Old Boy Undergoing Laparoscopic Cholecystectomy: A Case Report

Tracheomalacia is characterized by the collapse of the tracheal wall due to the softening of the tracheal cartilage and myoelastic tissues. We describe the case of a 12-year-old morbidly obese boy, without previous medical issues, scheduled for elective laparoscopic cholecystectomy. Immediately after pneumoperitoneum was established, mechanical ventilation could not be performed. Intraoperative exploration with flexible bronchoscopy showed that the tip of the endotracheal tube was nearly occluded by the posterior tracheal wall bulging anteriorly. Anesthesiologists should be aware of undiagnosed tracheomalacia as a cause of sudden airway collapse, even after the airway is secured with an endotracheal tube.

Comparison of the effects of different positive end-expiratory pressure levels on respiratory mechanics and oxygenation in laparoscopic surgery: A protocol for systematic review and network meta-analyses

BACKGROUND

Several studies have observed the good effects of positive end-expiratory pressure (PEEP) application in laparoscopic surgeries, such as counteracted intraoperative atelectasis, improved respiratory mechanics, and gas exchange. However, evidence of systematic comparisons of different PEEP levels is short, and the optimal level of PEEP during laparoscopy remains unknown and controversial. The study aims to compare the effects of different PEEP levels on respiratory mechanics and oxygenation in laparoscopic surgery using network meta-analyses.

METHODS

To identify relevant studies, a systematic search will be conducted among electronic databases, including PubMed, Cochrane Library, EMBASE, and Web of Science. We will include randomized controlled trials (RCTs). The risk of bias in the included RCTs will be assessed using the Cochrane bias risk tool. Network meta-analysis will be performed using STATA 15.0, and R 3.4.1 software.

RESULTS

This study is ongoing and the results will be published in a peer-reviewed journal.

CONCLUSION

The results of this study will be sent to clinicians and healthcare providers in the National Health Service, which is expected to help clinicians make more informed treatment decisions and facilitate further research on the use of PEEP during surgery.

PROSPERO REGISTRATION NUMBER

CRD42018093537.

Is intra-abdominal hypertension a risk factor for ventilator-associated pneumonia?

In the last years, there has been a significant amount of research about the impact of intra-abdominal hypertension (IAH) on the outcomes of critical care patients. IAH is increasingly recognized as potential complication in intensive care unit (ICU) patients. IAH affects all body systems, most notably the cardiac, respiratory, renal, and neurologic systems. IAH affects blood flow to various organs and plays a significant role in the prognosis of the patients. Recognition of IAH, its risk factors and clinical signs can reduce the morbidity and mortality associated. Moreover, knowledge of the pathophysiology may help rationalize the therapeutic approach. On the other hand, ICU patients present frequently ventilator- associated respiratory infections. Ventilator-associated pneumonia (VAP) is the most common healthcare-associated infection (HAI) in adult critical care units. It is associated with increased ICU stay, patient ventilator days and mortality. This paper reviews the relationship between IAH and VAP. Despite animal experimentation and physiological studies on humans, in favor of the impact of IAH to VAP, there is no definitive clinical data that IAH is associated with VAP. Microaspirations form the gastrointestinal track is a pathophysiological mechanism for VAP. This review provides data suggesting that under IAH conditions bacterial translocation might be an additional responsible mechanism for VAP in those patients that merits further investigation in the future.

Comparison of effects of low-flow and normal-flow anesthesia on cerebral oxygenation and bispectral index in morbidly obese patients undergoing laparoscopic sleeve gastrectomy: a prospective, randomized clinical trial

Introduction

The effects of low-flow anesthesia on cerebral oxygenation in high-risk, morbidly obese patients are not well known.

Aim

In this prospective randomized study, we compared the effects of low-flow (0.75 l/min) and normal-flow (1.5 l/min) anesthesia on regional cerebral oxygen saturation (rSO₂) and the bispectral index (BIS) in morbidly obese patients undergoing laparoscopic bariatric surgery.

Material and methods

Fifty-two morbidly obese patients undergoing laparoscopic bariatric surgery (sleeve gastrectomy) were enrolled in this study. Patients were randomly allocated to two study groups: low-flow and normal-flow anesthesia groups. Heart rate, mean arterial pressure, peripheral oxygen saturation, end-tidal carbon dioxide, BIS, left and right rSO₂, and duration of anesthesia and surgery were recorded.

Results

The groups were similar with respect to age, gender, height, weight, body mass index, American Society of Anesthesiology physical status, heart rate, duration of anesthesia, and procedure. Mean arterial pressure and end-tidal carbon dioxide, both before and after insufflation of carbon dioxide and after the reverse Trendelenburg position, were significantly higher in the low-flow group. BIS values and left and right rSO₂ during the preoperative and intraoperative periods were similar. Although the difference in right rSO₂ between the two groups after awakening from anesthesia was statistically significant, the results of both groups remained within the normal range and were not clinically meaningful.

Conclusions

Low-flow anesthesia is safe regarding hemodynamic and respiratory characteristics, depth of anesthesia, and regional cerebral oxygen saturation in morbidly obese patients undergoing laparoscopic bariatric surgery.

Transcranial Cerebral Oxymetric Monitoring Reduces Brain Hypoxia in Obese and Elderly Patients Undergoing General Anesthesia for Laparoscopic Cholecystectomy

The aims of this prospective, observational study were to evaluate the changes of the regional cerebral saturation (rSO2) measured by near-infrared spectroscopy during elective laparoscopic cholecystectomy under total intravenous anesthesia and the association between patient's characteristics and critical decline of rSO2. Hemodynamics, rSO2, and oxygen saturation were recorded in different time points: before the anesthesia (Tbas), 2 minutes after the induction (supine position) (Tind), 2 minutes after CO2 insufflation (supine) (TCO2), 10 minutes after CO2 insufflation (reverse Trendelenburg) (TrevT), and 2 minutes after deflation (supine) (Tpost). Average age was 53±13 (range: 22 to 79 y). In 12 of a total of 62 patients (19.4%) the rSO2 decreased >20% (20.5% to 28.4%) in TCO2 or TrevT times. Significantly higher decrease of the rSO2 was found in patients older than 65 years and those with body mass index >30 kg/m (P<0.05). Noninvasive monitoring of cerebral oxygenation could be an important part of perioperative care in obese and older patients.

Left Lateral Endosurgical Extraperitoneal Total Hysterectomy with Para-Aortic and Pelvic Lymphadenectomy: A Novel Approach for the Obese Patient with Endometrial Cancer

STUDY OBJECTIVE

To describe the left lateral extraperitoneal approach to perform complete para-aortic and pelvic lymphadenectomy and transverse total hysterectomy from left to right as a novel approach to treat obese patients with endometrial cancer. Laparoscopic management of obese patients represents a challenge for the gynecologic surgeon. The extraperitoneal approach is technically easier in the obese patient because it naturally creates a bowel-free operative field.

DESIGN

A prospective pilot bicentric and descriptive study (Canadian Task Force classification III) evaluating the feasibility and reproducibility of the transverse total hysterectomy and complete lymphadenectomy through left endoscopic extraperitoneal approach in obese patients with endometrial cancer.

SETTING

A comprehensive cancer center in Toulouse and a teaching university hospital in Madrid.

PATIENTS

Sixteen consecutive overweight or obese patients (body mass index > 25 kg/m²) with high-risk endometrial cancer.

INTERVENTIONS

Currently, the left extraperitoneal approach is routinely used to perform complete para-aortic and pelvic lymphadenectomy. It provides direct access to the left ureter and uterine pedicle. This access can be extended to the right side when performing a transverse extrafascial hysterectomy from left to right. The procedure starts from the left extraperitoneal space, where the left uterine artery is sectioned and the vesicovaginal and rectovaginal septa are developed, without opening the peritoneum. Colpotomy is performed from the left to the right side. Once the right ureter is identified, the right uterine artery can be safely transected. Alternatively, the right uterine artery can be sealed and sectioned during the right pelvic lymphadenectomy. At the end of the procedure the peritoneum is opened to complete the surgery.

MEASUREMENTS AND MAIN RESULTS

Between May 2015 and February 2016, 16 consecutive obese patients were successfully treated using this technique. Median patient age was 62 years (range, 44-78), and median body mass index was 32.5 kg/m² (range, 26-42). In 3 cases the right uterine artery was sealed during the right pelvic lymphadenectomy, in 11 cases after completing vaginal opening, and in 2 cases after peritoneal opening. The median operative time was 137.5 minutes (range, 66-260). The median blood loss was 85 mL (range, 0-260), and no blood transfusion was required in any of our 16 patients. No significant complications occurred.

CONCLUSION

The full extraperitoneal approach represents an interesting alternative strategy for the surgical treatment of obese patients with high-risk endometrial cancer.

Comparison of Arterial Oxygenation Following Head-Down and Head-Up Laparoscopic Surgery

BACKGROUND

Regarding the role of gas entry in abdomen and cardiorespiratory effects, the ability of anesthesiologists would be challenged in laparoscopic surgeries. Considering few studies in this area and the relevance of the subject, this study was performed to compare the arterial oxygen alterations before operation in comparison with after surgery between laparoscopic cholecystectomy and ovarian cystectomy.

METHODS

In this prospective cohort, 70 consecutive women aged from 20 to 60 years who were candidate for laparoscopic cholecystectomy (n = 35) and ovarian cystectomy (n = 35) with reverse (20 degrees) and direct (30 degrees) Trendelenburg positions, respectively, with ASA class I or II were enrolled. After intubation and before operation, for the first time, the arterial blood gas from radial artery in supine position was obtained for laboratory assessment. Then, the second blood sample was collected from radial artery in supine position and sent to the lab to be assessed with the same device after 30 minutes from surgery termination. The measured variables from arterial blood gas were arterial partial pressure of oxygen (PaO2) and Oxygen saturation (SpO2) alterations.

RESULTS

Total PaO2 was higher in the first measurement. The higher values of PaO2 in cholecystectomy (upward) than in ovarian cystectomy (downward) were not significant in univariate (P = 0.060) and multivariate analysis (P = 0.654). Furthermore, higher values of SpO2 in cholecystectomy (upward) than in ovarian cystectomy (downward) were not significant in univariate (P = 0.412) and multivariate analysis (P = 0.984).

CONCLUSIONS

In general, based on the results of this study, the values of PaO2 in cholecystectomy (upward) were not significantly higher than the values in cystectomy (downward) in laparoscopic surgeries when measured 30 minutes after surgery.

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 pneumoperitoneum and of an alveolar recruitment maneuver followed by positive end-expiratory pressure on cardiopulmonary function in sheep anesthetized with isoflurane-fentanyl

OBJECTIVE

To investigate the effects of pneumoperitoneum alone or combined with an alveolar recruitment maneuver (ARM) followed by positive end-expiratory pressure (PEEP) on cardiopulmonary function in sheep.

STUDY DESIGN

Prospective, randomized, crossover study.

ANIMALS

A total of nine adult sheep (36-52 kg).

METHODS

Sheep were administered three treatments (≥10-day intervals) during isoflurane-fentanyl anesthesia and volume-controlled ventilation (tidal volume: 12 mL kg^-1) with oxygen: CONTROL (no intervention); PNEUMO (120 minutes of CO₂ pneumoperitoneum); PNEUMO_ARM/PEEP (PNEUMO protocol with an ARM instituted after 60 minutes of pneumoperitoneum). The ARM (5 cmH₂O increases in PEEP of 1 minute duration until 20 cmH₂O of PEEP) was followed by 10 cmH₂O of PEEP until the end of anesthesia. Cardiopulmonary data were recorded until 30 minutes after abdominal deflation.

RESULTS

PaO₂ was decreased from 435-462 mmHg (58.0-61.6 kPa) (range of mean values in CONTROL) to 377-397 mmHg (50.3-52.9 kPa) in PNEUMO (p < 0.05). Quasistatic compliance (C_qst, mL cmH₂O^-1 kg^-1) was decreased from 0.85-0.92 in CONTROL to 0.52-0.58 in PNEUMO. PaO₂ increased from 383-385 mmHg (51.1-51.3 kPa) in PNEUMO to 429-444 mmHg (57.2-59.2 kPa) in PNEUMO_ARM/PEEP (p < 0.05) and C_qst increased from 0.52-0.53 in PNEUMO to 0.70-0.74 in PNEUMO_ARM/PEEP. Abdominal deflation in PNEUMO did not restore PaO₂ and C_qst to control values. Cardiac index (L minute^-1 m²) decreased from 4.80-4.70 in CONTROL to 3.45-3.74 in PNEUMO and 3.63-3.76 in PNEUMO_ARM/PEEP. Compared with controls, ARM/PEEP with pneumoperitoneum decreased mean arterial pressure from 81 to 68 mmHg and increased mean pulmonary artery pressure from 10 to 16 mmHg.

CONCLUSIONS AND CLINICAL RELEVANCE

Abdominal deflation did not reverse the pulmonary function impairment associated with pneumoperitoneum. The ARM/PEEP improved respiratory compliance and reversed the oxygenation impairment induced by pneumoperitoneum with acceptable hemodynamic changes in healthy sheep.

Effect of Incentive Spirometry on Postoperative Hypoxemia and Pulmonary Complications After Bariatric Surgery: A Randomized Clinical Trial

Importance

The combination of obesity and foregut surgery puts patients undergoing bariatric surgery at high risk for postoperative pulmonary complications. Postoperative incentive spirometry (IS) is a ubiquitous practice; however, little evidence exists on its effectiveness.

Objective

To determine the effect of postoperative IS on hypoxemia, arterial oxygen saturation (Sao2) level, and pulmonary complications after bariatric surgery.

Design, Setting, and Participants

A randomized noninferiority clinical trial enrolled patients undergoing bariatric surgery from May 1, 2015, to June 30, 2016. Patients were randomized to postoperative IS (control group) or clinical observation (test group) at a single-center tertiary referral teaching hospital. Analysis was based on the evaluable population.

Interventions

The controls received the standard of care with IS use 10 times every hour while awake. The test group did not receive an IS device or these orders.

Main Outcomes and Measures

The primary outcome was frequency of hypoxemia, defined as an Sao2 level of less than 92% without supplementation at 6, 12, and 24 postoperative hours. Secondary outcomes were Sao2 levels at these times and the rate of 30-day postoperative pulmonary complications.

Results

A total of 224 patients (50 men [22.3%] and 174 women [77.7%]; mean [SD] age, 45.6 [11.8] years) were enrolled, and 112 were randomized for each group. Baseline characteristics of the groups were similar. No significant differences in frequency of postoperative hypoxemia between the control and test groups were found at 6 (11.9% vs 10.4%; P = .72), 12 (5.4% vs 8.2%; P = .40), or 24 (3.7% vs 4.6%; P = .73) postoperative hours. No significant differences were observed in mean (SD) Sao2 level between the control and test groups at 6 (94.9% [3.2%] vs 94.9% [2.9%]; P = .99), 12 (95.4% [2.2%] vs 95.1% [2.5%]; P = .40), or 24 (95.7% [2.4%] vs 95.6% [2.4%]; P = .69) postoperative hours. Rates of 30-day postoperative pulmonary complications did not differ between groups (8 patients [7.1%] in the control group vs 4 [3.6%] in the test group; P = .24).

Conclusions and Relevance

Postoperative IS did not demonstrate any effect on postoperative hypoxemia, Sao2 level, or postoperative pulmonary complications. Based on these findings, the routine use of IS is not recommended after bariatric surgery in its current implementation.

Trial Registration

clinicaltrials.gov Identifier: NCT02431455.

Cardiovascular and Ventilatory Consequences of Laparoscopic Surgery

Although laparoscopic surgery accounts for >2 million surgical procedures every year, the current preoperative risk scores and guidelines do not adequately assess the risks of laparoscopy. In general, laparoscopic procedures have a lower risk of morbidity and mortality compared with operations requiring a midline laparotomy. During laparoscopic surgery, carbon dioxide insufflation may produce significant hemodynamic and ventilatory consequences such as increased intraabdominal pressure and hypercarbia. Hemodynamic insults secondary to increased intraabdominal pressure include increased afterload and preload and decreased cardiac output, whereas ventilatory consequences include increased airway pressures, hypercarbia, and decreased pulmonary compliance. Hemodynamic effects are accentuated in patients with cardiovascular disease such as congestive heart failure, ischemic heart disease, valvular heart disease, pulmonary hypertension, and congenital heart disease. Prevention of cardiovascular complications may be accomplished through a sound understanding of the hemodynamic and physiological consequences of laparoscopic surgery as well as a defined operative plan generated by a multidisciplinary team involving the preoperative consultant, anesthesiologist, and surgeon.

Assessment of Ventilation Distribution during Laparoscopic Bariatric Surgery: An Electrical Impedance Tomography Study

Introduction. The aim of the study was to assess changes of regional ventilation distribution at the level of the 3rd intercostal space in the lungs of morbidly obese patients as a result of general anaesthesia and laparoscopic surgery as well as the relation of these changes to lung mechanics. We also wanted to determine if positive end-expiratory pressure of 10 cm H₂O prevents the expected atelectasis in the morbidly obese patients during general anaesthesia. Materials and Methods. 49 patients completed the examination and were randomized to 2 groups: ventilated without positive end-expiratory pressure (PEEP 0) and with PEEP of 10 cm H₂O (PEEP 10) preceded by a recruitment maneuver with peak inspiratory pressure of 40 cm H₂O. Impedance Ratio (IR) was utilized to examine ventilation distribution changes as a result of anaesthesia, pneumoperitoneum, and change of body position. We also analyzed intraoperative respiratory mechanics and pulse oximetry values. Results. In both groups general anaesthesia caused a ventilation shift towards the nondependent lungs which was not further intensified after pneumoperitoneum. Reverse Trendelenburg position promoted homogeneous ventilation distribution. Respiratory system compliance was reduced after insufflation and improved after exsufflation of pneumoperitoneum. There were no statistically significant differences in ventilation distribution between the examined groups. Respiratory system compliance, plateau pressure, and pulse oximetry values were higher in PEEP 10. Conclusions. Changes of ventilation distribution in the obese do occur at cranial lung regions. During pneumoperitoneum alterations of ventilation distribution may not follow the direction of the changes of lung mechanics. In the obese patients PEEP level of 10 cm H₂O preceded by a recruitment maneuver improves respiratory compliance and oxygenation but does not eliminate atelectasis induced by general anaesthesia.

Relative Morbidity and Mortality of Panniculectomy-Combined Surgical Staging in Endometrial Cancer

OBJECTIVE

To examine intraoperative and postoperative complication rates for surgical staging combined with panniculectomy for endometrial cancer.

METHODS

A prospectively collected institutional surgical database was used to identify patients with endometrial cancer who underwent hysterectomy-based surgical staging between December 2008 and August 2014 (n = 551). The cases were grouped into surgical staging with panniculectomy (panniculectomy group, n = 11 [2.0%]), laparotomy without panniculectomy (laparotomy group, n = 208 [37.7%]), and laparoscopy (minimally invasive surgery group, n = 332 [60.3%]). Major complication and surgical wound complication rates within 30 days from surgery were compared.

RESULTS

The panniculectomy group had a significantly higher body mass index compared with other approaches (panniculectomy group, laparotomy group, and minimally invasive surgery group: 60.4, 35.7, and 34.1; P < 0.001) and had a high stage I disease rate (90.9%, 61.5%, and 88.3%; P < 0.001). Mean pannus weight was 5733 g (4.4% of body weight). Intraoperative major complication rates were statistically nonsignificant across the groups (0%, 7.2%, and 4.2%; P = 0.23); however, the panniculectomy group had a significantly higher postoperative major complication rate compared with other approaches (36.4%, 16.3%, and 5.1%; P < 0.001). In multivariate analysis controlling for age, ethnicity, body habitus, medical comorbidities, and tumor factors, panniculectomy remained an independent predictor for increased risk of postoperative major complications (adjusted odds ratio, 4.37; P = 0.043). Surgical mortality rates were similar across the groups (0%, 0.5%, and 0%; P = 0.44). Among superobese patients (n = 50), intraoperative and postoperative complication rates were statistically similar across the 3 groups (all, P > 0.05).

CONCLUSION

Although panniculectomy-combined surgical staging is associated with an increased risk of postoperative complications, the majority recovered uneventfully, making this approach a feasible treatment option, especially for superobese patients with endometrial cancer.

The Effects of Short-Term Propofol and Dexmedetomidine on Lung Mechanics, Histology, and Biological Markers in Experimental Obesity

BACKGROUND

Administering anesthetics to the obese population requires caution because of a variety of reasons including possible interactions with the inflammatory process observed in obese patients. Propofol and dexmedetomidine have protective effects on pulmonary function and are widely used in short- and long-term sedation, particularly in intensive care unit settings in lean and obese subjects. However, the functional and biological effects of these drugs in obesity require further elucidation. In a model of diet-induced obesity, we compared the short-term effects of dexmedetomidine versus propofol on lung mechanics and histology, as well as biological markers of inflammation and oxidative stress modulation in obesity.

METHODS

Wistar rats (n = 56) were randomly fed a standard diet (lean) or experimental diet (obese) for 12 weeks. After this period, obese animals received sodium thiopental intraperitoneally and were randomly allocated into 4 subgroups: (1) nonventilated (n = 4) for molecular biology analysis only (control); (2) sodium thiopental (n = 8); (3) propofol (n = 8); and (4) dexmedetomidine (n = 8), which received continuous IV administration of the corresponding agents and were mechanically ventilated (tidal volume = 6 mL/kg body weight, fraction of inspired oxygen = 0.4, positive end-expiratory pressure = 3 cm H2O) for 1 hour.

RESULTS

Compared with lean animals, obese rats did not present increased body weight but had higher total body and trunk fat percentages, airway resistance, and interleukin-6 levels in the lung tissue (P = 0.02, P = 0.0027, and P = 0.01, respectively). In obese rats, propofol, but not dexmedetomidine, yielded increased airway resistance, bronchoconstriction index (P = 0.016, P = 0.02, respectively), tumor necrosis factor-α, and interleukin-6 levels, as well as lower levels of nuclear factor-erythroid 2-related factor-2 and glutathione peroxidase (P = 0.001, Bonferroni-corrected t test).

CONCLUSIONS

In this model of diet-induced obesity, a 1-hour propofol infusion yielded increased airway resistance, atelectasis, and lung inflammation, with depletion of antioxidative enzymes. However, unlike sodium thiopental and propofol, short-term infusion of dexmedetomidine had no impact on lung morphofunctional and biological variables.

Obesity is associated with decreased lung compliance and hypercapnia during robotic assisted surgery

Robotic assisted surgery (RAS) represents a great challenge for anesthesiology due to the increased intraabdomial pressures required for surgical optimal approach. The changes in lung physiology are difficult to predict and require fast decision making in order to prevent altered gas exchange. The aim of this study was to document the combined effect of patient physical status, medical history and intraoperative position during RAS on lung physiology and to determine perioperative risk factors for hypercapnia. We prospectively analyzed 62 patients who underwent elective RAS. Age, co-morbidities and body mass index (BMI) were recorded before surgery. Ventilatory parameters and arterial blood gas analysis were determined before induction of anesthesia, after tracheal intubation and on an hourly basis until the end of surgery. In RAS, the induction of pneumoperitoneum was associated with a significant decrease in lung compliance from a mean of 42.5–26.7 ml cm H₂O⁻¹ (p = 0.001) and an increase in plateau pressure from a mean of 16.1 mmHg to a mean of 23.6 mmHg (p = 0.001). Obesity, demonstrated by a BMI over 30, significantly correlates with a decrease in lung compliance after induction of anesthesia (p = 0.001). A significant higher increase in arterial CO₂ tension was registered in patients undergoing RAS in steep Trendelenburg position (p = 0.05), but no significant changes in end-tidal CO₂ were recorded. A higher arterial to end-tidal CO₂ tension gradient was observed in patients with a BMI > 30 (p < 0.001). In conclusion, patients’ physical status, especially obesity, represents the main risk factor for decreased lung compliance during RAS and patient positioning in either Trendelenburg or steep Trendelenburg during surgery has limited effects on respiratory physiology.

Strategies for managing oxygenation in obese patients undergoing laparoscopic surgery

The worldwide trend toward increasing body mass index (BMI) has caused the anesthetic management of overweight, obese, and severely obese patients to become common. The increase in oxygen demand coupled with the anatomic and physiologic changes associated with excess adipose tissue make maintenance of oxygenation a major challenge during induction, maintenance and recovery from general anesthesia. It is crucial for anesthesiologists, surgeons and perioperative healthcare providers alike to have a thorough understanding of the impact of airway management and mechanical ventilation on the respiratory care of the obese in the immediate perioperative setting. In this manuscript we aim to discuss the consequences of obesity, particularly abdominal obesity, on respiratory physiology and provide suggestions on intraoperative ventilatory strategies to maintain oxygenation in the severely obese patient undergoing pneumoperitoneum.

Respiratory mechanical effects of surgical pneumoperitoneum in humans

Pneumoperitoneum for laparoscopic surgery is known to stiffen the chest wall and respiratory system, but its effects on resting pleural pressure in humans are unknown. We hypothesized that pneumoperitoneum would raise abdominal pressure, push the diaphragm into the thorax, raise pleural pressure, and squeeze the lung, which would become stiffer at low volumes as in severe obesity. Nineteen predominantly obese laparoscopic patients without pulmonary disease were studied supine (level), under neuromuscular blockade, before and after insufflation of CO2 to a gas pressure of 20 cmH2O. Esophageal pressure (Pes) and airway pressure (Pao) were measured to estimate pleural pressure and transpulmonary pressure (Pl = Pao - Pes). Changes in relaxation volume (Vrel, at Pao = 0) were estimated from changes in expiratory reserve volume, the volume extracted between Vrel, and the volume at Pao = -25 cmH2O. Inflation pressure-volume (Pao-Vl) curves from Vrel were assessed for evidence of lung compression due to high Pl. Respiratory mechanics were measured during ventilation with a positive end-expiratory pressure of 0 and 7 cmH2O. Pneumoperitoneum stiffened the chest wall and the respiratory system (increased elastance), but did not stiffen the lung, and positive end-expiratory pressure reduced Ecw during pneumoperitoneum. Contrary to our expectations, pneumoperitoneum at Vrel did not significantly change Pes [8.7 (3.4) to 7.6 (3.2) cmH2O; means (SD)] or expiratory reserve volume [183 (142) to 155 (114) ml]. The inflation Pao-Vl curve above Vrel did not show evidence of increased lung compression with pneumoperitoneum. These results in predominantly obese subjects can be explained by the inspiratory effects of abdominal pressure on the rib cage.

Changes in endotracheal tube cuff pressure during laparoscopic surgery in head-up or head-down position

BACKGROUND

The abdominal insufflation and surgical positioning in the laparoscopic surgery have been reported to result in an increase of airway pressure. However, associated effects on changes of endotracheal tube cuff pressure are not well established.

METHODS

70 patients undergoing elective laparoscopic colorectal tumor resection (head-down position, n = 38) and laparoscopic cholecystecomy (head-up position, n = 32) were enrolled and were compared to 15 patients undergoing elective open abdominal surgery. Changes of cuff and airway pressures before and after abdominal insufflation in supine position and after head-down or head-up positioning were analysed and compared.

RESULTS

There was no significant cuff and airway pressure changes during the first fifteen minutes in open abdominal surgery. After insufflation, the cuff pressure increased from 26 ± 3 to 32 ± 6 and 27 ± 3 to 33 ± 5 cmH2O in patients receiving laparoscopic cholecystecomy and laparoscopic colorectal tumor resection respectively (both p < 0.001). The head-down tilt further increased cuff pressure from 33 ± 5 to 35 ± 5 cmH2O (p < 0.001). There six patients undergoing colorectal tumor resection (18.8%) and eight patients undergoing cholecystecomy (21.1%) had a total increase of cuff pressure more than 10 cm H2O (18.8%). There was no significant correlation between increase of cuff pressure and either the patient's body mass index or the common range of intra-abdominal pressure (10-15 mmHg) used in laparoscopic surgery.

CONCLUSIONS

An increase of endotracheal tube cuff pressure may occur during laparoscopic surgery especially in the head-down position.

Effects of the pneumoperitoneum and Trendelenburg position on respiratory mechanics in the rats by the end-inflation occlusion method

PURPOSE:

To describe the consequences of the cranial displacement of the diaphgram occurring during pneumoperitoneum (Pnp) and/or Trendelenburg (Tnd) position on respiratory mechanics. Possible addictive effects and the changes of the viscoelastic respiratory system resistance were studied, which were not extensively described before.

METHODS:

The end-inflation occlusion method was applied on eight rats. It allows us to determine mechanical parameters such as respiratory system static elastance, the ohmic resistance due to frictional forces in the airways, and the additional viscoelastic impedance due to tissues deformation. Measurements during mechanical ventilation were taken in controls (supine position), after 20–25° head-down tilting (Tnd), after abdominal air insufflation up to 12 mmHg abdominal pressure in the supine position (Pnp), and combining Tnd + Pnp. Tnd and Pnp modalities were similar to those commonly applied during surgical procedures in humans.

RESULTS:

We confirmed the previously described detrimental effects on respiratory mechanics due to the diaphgram displacement during both Pnp and Tnd. The increment in the total resistive pressure dissipation was found to depend primarily on the effects on the viscoelastic characteristics of the respiratory system. Data suggesting greater effects of Pnp compared to those of Tnd were obtained.

CONCLUSION:

The cranial displacement of the diaphgram occurring as a consequence of Pnp and/or Tnd, for example during laparoscopic surgical procedures, causes an increment of respiratory system elastance and viscoelastic resistance. The analysis of addictive effects show that these are more likely to occur when Pnp + Tnd are compared to isolated Tnd rather than to isolated Pnp.

Pressure-controlled inverse ratio ventilation using laryngeal mask airway in gynecological laparoscopy

BACKGROUND

It is well documented that pressure-controlled ventilation (PCV) improves oxygenation and ventilation compared to volume-controlled ventilation and reduces peak airway pressure in gynecological laparoscopy. PCV with moderately inversed inspiratory-expiratory (I: E) ratio can successfully recruit collapsed alveoli and has been proved to be beneficial in intensive care. We tested the hypothesis that altering the I: E ratio to 1.5:1 in PCV improves ventilation during gynecological laparoscopy using laryngeal mask airway (LMA).

OBJECTIVE

To study pressure-controlled inverse ratio ventilation (PCIRV) with I: E ratio 1.5:1 as against PCV with I: E ratio 1:2 in gynecological laparoscopy with LMA using noninvasive parameters.

MATERIALS AND METHODS

Intraoperative hemodynamics and side-stream spirometry recordings were noted in 20 consecutive patients undergoing major gynecological laparoscopy with LMA. Flexible LMA or LMA supreme were used depending on normal body mass index (BMI) or high BMI, respectively.

RESULTS

REVERSING THE I: E ratio to 1.5:1 increased the tidal volume, mean airway pressures, and dynamic lung compliance significantly, all indicating better oxygenation at comparable peak airway pressures as against PCV with I: E ratio 1:2. There was no change in the end-tidal carbon dioxide. There was no auto-positive end expiratory pressure (PEEP) or change in the hemodynamics.

CONCLUSION

REVERSAL OF I: E ratio with PCV can be beneficially used with LMA in laparoscopy.

A comparison between volume-controlled ventilation and pressure-controlled ventilation in providing better oxygenation in obese patients undergoing laparoscopic cholecystectomy

Background:

The maintenance of oxygenation is a commonly encountered problem in obese patients undergoing laparoscopic cholecystectomy. There is no specific guideline on the ventilation modes for this group of patients. Although several studies have been performed to determine the optimal ventilatory settings in these patients, the answer is yet to be found. The aim of this study was to evaluate the efficacy of pressure-controlled ventilation (PCV) in comparison with volume-controlled ventilation (VCV) for maintaining oxygenation during laparoscopic cholecystectomy in obese patients.

Methods:

One hundred and two adult patients of ASA physical status I and II, Body Mass Index of 30–40 kg/m², scheduled for laparoscopic cholecystectomy were included in this prospective randomized open-label parallel group study. To start with, all patients received VCV. Fifteen minutes after creation of pneumoperitoneum, they were randomized to receive either VCV (Group V) or PCV (Group P). The ventilatory parameters were adjusted accordingly to maintain the end-tidal CO₂ between 35 and 40 mmHg. Respiratory rate, tidal volume, minute ventilation and peak airway pressure were noted. Arterial blood gas analyses were done 15 min after creation of pneumoperitoneum and at 20-min intervals thereafter till the end of the surgery. All data were analysed statistically.

Results:

Patients in Group P showed a statistically significant (P < 0.05) higher level of PaO₂ and lower value of PAO₂–PaO₂ than those in Group V.

Conclusion:

PCV is a more effective mode of ventilation in comparison with VCV regarding oxygenation in obese patients undergoing laparoscopic cholecystectomy.