Re-expansion of atelectasis during general anaesthesia: a computed tomography study

Effect of different lung recruitment strategies and airway device on oscillatory mechanics in children under general anaesthesia

BACKGROUND

Atelectasis has been reported in 68 to 100% of children undergoing general anaesthesia, a phenomenon that persists into the recovery period. Children receiving recruitment manoeuvres have less atelectasis and fewer episodes of oxygen desaturation during emergence. The optimal type of recruitment manoeuvre is unclear and may be influenced by the airway device chosen.

OBJECTIVE

We aimed to investigate the different effects on lung mechanics as assessed by the forced oscillation technique (FOT) utilising different recruitment strategies: repeated inflations vs. one sustained inflation and different airway devices, a supraglottic airway device vs. a cuffed tracheal tube.

DESIGN

Pragmatic enrolment with randomisation to the recruitment strategy.

SETTING

We conducted this single-centre trial between February 2020 and March 2022.

PARTICIPANTS

Seventy healthy patients (53 boys) aged between 2 and 16 years undergoing general anaesthesia were included.

INTERVENTIONS

Forced oscillations (5 Hz) were superimposed on the ventilator waveform using a customised system connected to the anaesthesia machine. Pressure and flow were measured at the inlet of the airway device and used to compute respiratory system resistance and reactance. Measurements were taken before and after recruitment, and again at the end of surgery.

MAIN OUTCOME MEASURES

The primary endpoint measured is the change in respiratory reactance.

RESULTS

Statistical analysis (linear model with recruitment strategy and airway device as factors) did not show any significant difference in resistance and reactance between before and after recruitment. Baseline reactance was the strongest predictor for a change in reactance after recruitment: prerecruitment Xrs decreased by mean (standard error) of 0.25 (0.068) cmH 2 O s l -1 per  1 cmH 2 O -1  s l -1 increase in baseline Xrs ( P  < 0.001). After correcting for baseline reactance, the change in reactance after recruitment was significantly lower for sustained inflation compared with repeated inflation by mean (standard error) 0.25 (0.101) cmH 2 O ( P  = 0.0166).

CONCLUSION

Although there was no significant difference between airway devices, this study demonstrated more effective recruitment via repeated inflations than sustained inflation in anaesthetised children.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry: ACTRN12619001434189.

Manual and ventilator hyperinflation parameters used by intensive care physiotherapists in Sri Lanka: An online survey

INTRODUCTION

Hyperinflation is a common procedure to clear secretion, increase lung compliance and enhance oxygenation in mechanically ventilated patients. Hyperinflation can be provided as manual hyperinflation (MHI) or ventilator hyperinflation (VHI), where outcomes depend upon the methods of application. Hence it is crucial to assess the application of techniques employed in Sri Lanka due to observed variations from recommended practices.

OBJECTIVE

This study is aimed to evaluate the application and parameters used for MHI and VHI by physiotherapists in intensive care units (ICUs) in Sri Lanka.

METHODOLOGY

An online survey was conducted among physiotherapists who are working in ICUs in Sri Lanka using WhatsApp groups and other social media platforms.

RESULTS

A total of 96 physiotherapists responded. The survey comprised of three sections to obtain information about socio-demographic data, MHI practices and VHI practices. Most of the respondents (47%) worked in general hospitals and 74% of participants had a bachelor's degree in physiotherapy; 31.3% had 3-6 years of experience; 93.8% used hyperinflation, and 78.9% used MHI. MHI was performed routinely and as needed to treat low oxygen levels, abnormal breath sounds, and per physician orders while avoiding contraindications. Self-inflation bags are frequently used for MHI (40.6%). Only a few participants (26%) used a manometer or tracked PIP. In addition to the supine position, some participants (37.5%) used the side-lying position. Most physiotherapists followed the recommended MHI technique: slow squeeze (57.3%), inspiratory pause (45.8%), and quick release (70.8%). VHI was practised by 19.8%, with medical approval and it was frequently performed by medical staff compared to physiotherapists. Treatment time, number of breaths, and patient positioning varied, and parameters were not well-defined.

CONCLUSION

The study found that MHI was not applied with the recommended PIP, and VHI parameters were not identified. The study indicates a need to educate physiotherapists about current VHI and MHI practice guidelines.

Change in stroke volume during alveolar recruitment maneuvers through transient continuous positive airway pressure or stepwise increase in positive end expiratory pressure in anesthetized patients: a prospective randomized double-blind study

PURPOSE

Intraoperative alveolar recruitment maneuvers (ARM) used during protective ventilation strategy may have severe adverse hemodynamic effects, reported mainly during abrupt continuous positive airway pressure (CPAP). Stepwise increase and decrease in positive end expiratory pressure (PEEP) may be used. We compared the hemodynamic effects of these two maneuvers.

METHODS

We enrolled patients scheduled for intermediate to high-risk surgery with continuous arterial pressure and stroke volume (esophageal Doppler) monitoring in a prospective, single-centre, randomized, double-blind study. After induction of anesthesia, we ensured preload independence of stroke volume before an ARM was randomly performed: 30 cm H2O CPAP for 30 sec (CPAP group) or stepwise increase in PEEP from 8 to 20 cm H2O with inspiratory pressure of 10 cm H2O followed by a stepwise decrease in PEEP from 20 to 8 cm H2O (STEP group). The primary outcome was the relative variation in stroke volume.

RESULTS

Thirty-five patients were included in the CPAP and STEP groups. Mean (standard deviation) relative variation in stroke volume was -57 (24)% in the CPAP group and -32 (24)% in the STEP group (difference, -25; 95% confidence interval, -37 to -14; P < 0.001). Changes in systolic, mean, and diastolic arterial pressure over time were not different between groups. The ARM was stopped because of a systolic arterial pressure < 70 mm Hg in four patients in the CPAP group and in one patient in the STEP group.

CONCLUSIONS

Alveolar recruitment maneuvers through stepwise increase and decrease in PEEP have a better hemodynamic tolerance than transient CPAP.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT04802421); first submitted 15 March 2021.

PEEP-Induced Lung Recruitment Maneuver Combined with Prone Position for ARDS: A Single-Center, Prospective, Randomized Clinical Trial

Background: Prone position (PP) and the positive end-expiratory pressure (PEEP)-induced lung recruitment maneuver (LRM) are both efficient in improving oxygenation and prognosis in patients with ARDS. The synergistic effect of PP combined with PEEP-induced LRM in patients with ARDS remains unclear. We aim to explore the effects of PP combined with PEEP-induced LRM on prognosis in patients with moderate to severe ARDS and the predicting role of lung recruitablity. Methods: Patients with moderate to severe ARDS were consecutively enrolled. The patients were prospectively assigned to either the intervention (PP with PEEP-induced LRM) or control groups (PP). The clinical outcomes, respiratory mechanics, and electric impedance tomography (EIT) monitoring results for the two groups were compared. Lung recruitablity (recruitment-to-inflation ratio: R/I) was measured during the PEEP-induced LRM procedure and was used for predicting the response to LRM. Results: Fifty-eight patients were included in the final analysis, among which 28 patients (48.2%) received PEEP-induced LRM combined with PP. PEEP-induced LRM enhanced the effect of PP by a significant improvement in oxygenation (∆PaO2/FiO2 75.8 mmHg vs. 4.75 mmHg, p < 0.001) and the compliance of respiratory system (∆Crs, 2 mL/cmH2O vs. -1 mL/cmH2O, p = 0.02) among ARDS patients. Based on the EIT measurement, PP combined with PEEP-induced LRM increased the ventilation distribution mainly in the dorsal region (5.0% vs. 2.0%, p = 0.015). The R/I ratio was measured in 28 subjects. The higher R/I ratio was related to greater oxygenation improvement after LRM (Pearson's r = 0.4; p = 0.034). Conclusions: In patients with moderate to severe ARDS, PEEP-induced LRM combined with PP can improve oxygenation and dorsal ventilation distribution. R/I can be useful to predict responses to LRM.

Bibliometric Evaluation of the 100 Top-Cited Articles on Anesthesiology

This review is a bibliometric analysis based on anesthesiology, which is a medical specialty that deals with a patient's complete preoperative, intraoperative, and postoperative care. The objective of the review attempts to analyze the bibliometric characteristics of the 100 most top-cited articles on anesthesiology. The meta-data of the study were collected from the Core Collection of Web of Science database. A title search option was employed, and "Anesthesia" and "Anesthesiology" were typed in two different search boxes separated with the Boolean operator ''OR''. Further, the data were sorted by highest citation order; later, "article" was selected from the filter of document type, and all other types of documents were excluded. Finally, downloaded the bibliographic details of the 100 top-cited articles. VOSviewer Software (version 1.6.10 by van Eck and Waltman) was used for bibliometric network analysis for co-authors and keywords. Pearson chi-square test was used for statistical analysis. The 100 top-cited articles were published between the years of 1971 and 2018. These articles gained a maximum of 1006 to a minimum of 276 citations with an average of 384.57 cites/article. Open accessed articles gained a slightly higher ratio of citations, while more than half of the articles were published in the two leading journals of "Anesthesiology" and "Anesthesia and Analgesia". There was no statistically significant difference in both citation analysis among open and closed access journals and Anesthesia vs Non-Anesthesia journals. Thirty-six articles were published in journals not specifically related to Anesthesia. Most of the top-cited articles were contributed by the United States, whereas Surgery and General Anesthesia were the two most occurred keywords.  We conclude that all the top-cited articles in anesthesiology were contributed by authors who belonged to the developed nations and the United States outclassed the rest of the world. This bibliometric analysis would be valuable to practitioners, academics, researchers, and students to understand the dynamics of progress in the field of anesthesiology.

The impact of inspiratory pressure level on prevention of ventilator-associated pneumonia: A double-blind, randomized clinical trial

BACKGROUND

Atelectasis and pneumonia are highly prevalent in patients under mechanical ventilation. Studies indicate that using ventilation with an open lung concept improves recovery, decreases ventilator-related pneumonia, decreases mortality and leads to faster weaning from the ventilator. Therefore, this study investigated the effect of higher airway pressure on ventilator-associated pneumonia.

METHODS

This randomized clinical trial was conducted on 120 patients under mechanical ventilation. The patients were divided into two groups based on ventilator pressure: the control group (pressure level 20) and the intervention group (pressure level 30). Demographic data, disease severity, the incidence of ventilator-associated pneumonia, organ damage, days connected to the ventilator, length of hospitalization in ICU, and mortality were compared between the two groups.

RESULTS

There was no significant difference in demographic data and disease severity between the two groups. The average Clinical Pulmonary Infection Score in the intervention group was significantly lower than the control group (P = 0.02). The intervention group's average Sequential Organ Failure Assessment score was significantly lower than the control group (p = 0.016).

CONCLUSIONS

High-pressure levels can decrease ventilator-associated pneumonia and organ failure. It is recommended that the study be repeated with a larger, more diverse population.

Effects of two alveolar recruitment manoeuvres (sustained inflation and stepwise) followed by positive end-expiratory pressure on cardiac output (measured with lithium dilution), invasive blood pressure and arterial oxygen tension in isoflurane-anaesthetised goats

Alveolar recruitment manoeuvres (ARM) performed during general anaesthesia improve oxygenation; however cardiovascular depression may be observed. The aim of the study was to compare the effects of sustained inflation (SI) and stepwise ARMs on cardiac output (CO), mean arterial blood pressure and arterial oxygen tension (PaO2) in ten mechanically ventilated goats anaesthetised with isoflurane. In the SI ARM, peak inspiratory presure (PIP) was increased to 30 cmH2O and sustained for 20 s. In the stepwise ARM, the PIP was increased by 5 cmH2O each minute for three minutes from 10 to 25 cmH2O. Both ARMs were followed by positive end-expiratory pressure of 5 cmH2O. Paired lithium dilution CO measurements and arterial blood samples were obtained before and after each ARM. The order of the ARM was randomised and each goat was subjected to both techniques. Data was reported as median and interquartile range (IQR). Significance was set at 0.05. The median change in CO (measured by subtracting values after and before ARM) was -0.15 L min-1 (IQR -0.51; 0.03) and - 0.90 L min-1 (IQR -1.69; -0.58) for SI and stepwise ARM respectively (p = 0.04). The median change in PaO2 was 3 kPa (IQR -2.7; 7.6) and 0.4 kPa (IQR -3.4; 5.5) for SI and stepwise ARM respectively (p = 0.03). In conclusion, SI ARM causes less impact on CO and provides a better improvement in PaO2 compared to stepwise ARM in goats.

Recruitment Maneuver to Reduce Postoperative Pulmonary Complications after Laparoscopic Abdominal Surgery: A Systematic Review and Meta-Analysis

Background: Lung-protective ventilation strategies are recommended for patients undergoing mechanical ventilation. However, there are currently no guidelines to follow regarding recruitment maneuvers (RMs). We attempted to identify the effects of RMs on patients undergoing laparoscopic abdominal surgery. Methods: We searched for randomized controlled trials (RCTs) in PubMed, the Cochrane Library databases, Embase, Web of Science and the ClinicalTrials.gov registry for trials published up to December 2021. The primary outcome was postoperative pulmonary complications (PPCs). The secondary outcomes consisted of the static lung compliance, driving pressure (DP), intraoperative oxygenation index (OI), OI in the post-anesthesia care unit (PACU), mean arterial pressure (MAP) and heart rate (HR). Seventeen RCTs with a total of 3480 patients were examined. Results: Patients who received RMs showed a considerable reduction in PPCs (risk ratio (RR) = 0.70; 95% confidence interval (CI): 0.62 to 0.79; p < 0.01), lower DP (weighted mean difference (WMD) = −3.96; 95% CI: −5.97 to −1.95; p < 0.01), elevated static lung compliance (WMD = 10.42; 95% CI: 6.13 to 14.71; p < 0.01) and improved OI (intraoperative: WMD = 53.54; 95% CI: 21.77 to 85.31; p < 0.01; PACU: WMD = 59.40; 95% CI: 39.10 to 79.69; p < 0.01) without substantial changes in MAP (WMD = −0.16; 95% CI −1.35 to 1.03; p > 0.05) and HR (WMD = −1.10; 95% CI: −2.29 to 0.10; p > 0.05). Conclusions: Recruitment maneuvers reduce postoperative pulmonary complications and improve respiratory mechanics and oxygenation in patients undergoing laparoscopic abdominal surgery. More data are needed to elucidate the effect of recruitment maneuver on the circulatory system.

Comparison of Different Tidal Volumes for Ventilation in Patients with an Acute Traumatic Cervical Spine Injury

Background

There is scant literature comparing high tidal volume ventilation (HTV) over low tidal volume (LTV) ventilation in acute traumatic cervical spinal cord injury (CSCI).

Objective

The aim of this prospective randomized controlled parallel-group, single-blinded study was to compare the effect of two different tidal volumes (12-15 mL/kg and 6-8 mL/kg) in CSCI on days to achieve ventilator-free breathing (VFB), PaO2/FIO2 ratio, the incidence of complications, requirement of vasopressor drugs, total duration of hospital stay, and mortality.

Materials and Methods

We enrolled patients with acute high traumatic CSCI admitted to the neurotrauma intensive care unit within 24 h of injury, requiring mechanical ventilation. Participants were randomized to receive either HTV, 12-15 mL/kg (group H) or LTV, 6-8 mL/kg (group L) tidal volume ventilation.

Results and Conclusions

A total of 56 patients, 28 in each group were analyzed. Patient demographics and injury severity were comparable between the groups. VFB was achieved in 23 and 19 patients in groups H and L, respectively. The median number of days required to achieve VFB was 3 (2, 56) and 8 (2, 50) days, P = 0.33; PaO2: FIO2 ratio was 364.0 ± 64 and 321.0 ± 67.0, P = 0.01; the incidence of atelectasis was 25% and 46%, P = 0.16, respectively, in group H and group L. The hemodynamic parameters and the vasopressor requirement were comparable in both groups. There was no barotrauma. The duration of hospital stay (P = 0.2) and mortality (P = 0.2) was comparable in both groups. There was no significant difference in days to achieve ventilator-free breathing with HTV (12-15 mL/kg) ventilation compared to LTV (6-8 mL/kg) ventilation in acute CSCI. The PaO2:FiO2 ratio was higher with the use of 12-15 mL/kg. No difference in mortality and duration of hospital stay was seen in either group.

Tidal Volume and Positive End-Expiratory Pressure and Postoperative Hypoxemia during General Anesthesia: A Single Center Multiple Cross-over Factorial Cluster Trial

BACKGROUND

Intraoperative mechanical ventilation is a major component of general anesthesia. The extent to which various intraoperative tidal volumes and positive end-expiratory pressures (PEEP) on postoperative hypoxia and lung injury remains unclear. We hypothesized that adult patients having orthopedic surgery, ventilation using different tidal volumes and PEEP levels affects the oxygenation within first hour in the postoperative care unit.

METHODS

We conducted a 2 by 2 factorial cross-over cluster trial at the Cleveland Clinic Main Campus. We enrolled patients having orthopedic surgery with general anesthesia who were assigned to factorial clusters with tidal volumes of 6 or 10 ml/kg of predicted body weight and to PEEP of 5 or 8 cm H20 in one-week clusters The primary outcome was the effect of tidal volume or PEEP on time-weighted average peripheral oxygen saturation divided by the fraction of inspired oxygen (SpO2/FiO2 ratio) during the initial postoperative hour.

RESULTS

We enrolled 2860 patients who had general anesthesia for orthopedic surgery from September 2018 through October 2020. The interaction between tidal volume and PEEP was not significant (p = 0.565). The mean (SD) time-weighted average of SpO2/FiO2 ratio was 353 (47) and not different in patients assigned to high and low tidal volume (estimated effect 3.5% (97.5%CI: -0.4%,7.3%;P=0.042), and for those assigned to high and low PEEP (-0.2% (97.5%CI: -4.0%,3.6%;P=0.906). We did not find significant difference in ward SpO2/FiO2 ratio, pulmonary complications, and duration of hospitalization among patients assigned to various tidal volumes and PEEP levels.

CONCLUSION

Among adults having major orthopedic surgery, pulse oximetry oxygenation is similar with tidal volumes between 6 and 10 ml/kg and PEEP between 5 and 8 cm H20. Our results suggest that any combination of tidal volumes between 6 and 10 ml/kg and PEEP between 5 vs. 8 mL cmH20 can be used safely for orthopedic surgery.Trial Registration ClinicalTrials.gov Identifier: NCT03657368.

Comparison of the efficacy of two alveolar recruitment manoeuvres in improving the lung mechanics and the degree of atelectasis in anaesthetized healthy sheep

The aim of the present study was to evaluate whether the application of two types of alveolar recruitment manoeuvres (ARMs) followed by a positive end-expiratory pressure (PEEP) improved lung mechanics and the degree of atelectasis caused by general anaesthesia. Twenty-one female Merino sheep were divided into three groups: sustained inflation ARM (ARMsust), stepwise ARM (AMRstep), and control (without ARM). Sheep received detomidine-morphine for premedication, propofol for induction, and isoflurane during general anaesthesia in a volume-controlled mode with 100% oxygen during the first 15 min of anaesthesia and 40% the rest of the study. The right jugular vein and metacarpal artery were catheterised for mixed venous and arterial blood sample collection, respectively. The quasistatic compliance (Cqst), oxygenation parameters, and shunt fraction (Qs/Qt) were monitored before ARM application (TpreARM), and at 10 (T10) and 60 min (T60) after ARM application. A pulmonary histopathological study was conducted on five animals from each group. A significant increase in Cqst was observed in both ARM groups at T10 compared to TpreARM (ARMsust: P = 0.001; ARMstep: P = 0.002), although only the ARMsust group showed significant differences compared to the control group. The ARMstep group presented a significant improvement in oxygenation parameters and Qs/Qt fraction (T10: 4.84 (3.26-16.48)%, P = 0.048; T60: 4.40 (4.31-14.16)%, P = 0.004) compared with TpreARM (21.48 (20.61-28.32)%). The ARMstep group had the highest percentage of alveolar area and the most homogeneous values. In conclusion, the application of a stepwise ARM followed by PEEP improved atelectasis caused by isoflurane anaesthesia in healthy sheep.

Comparison of Intra-operative Pressure-Controlled Ventilation and Volume-Controlled Ventilation in Bariatric Surgery: A Prospective Randomized Study

Background: Mechanical ventilation may be particularly challenging in obese patients undergoing laparoscopic bariatric surgery. The present study aimed to compare the effects of pressure-controlled ventilation (PCV) with those of volume-controlled ventilation (VCV) on peripheral tissue oxygenation (PTO), respiratory function, hemodynamic status, and ventilation-related complications in patients undergoing laparoscopic bariatric surgery.

Methods: A total of 100 patients with obesity who underwent gastric plication or sleeve gastrectomy were recruited for the study, and 60 patients (n=32, in group PCV; n=28, in group VCV) were ultimately enrolled. Data on peri-operative PTO (arterial blood gas [ABG] analysis and tissue oxygen saturation [StO₂]) and respiratory functions were recorded for each patient, along with post-operative hemodynamic status, fluid intake, urinary output, Numeric Pain Rating Scale (NPRS) score , and complications.

Results: The two groups were similar in pH, partial pressure of oxygen, partial pressure of carbon dioxide, oxygen saturation, and lactate values at baseline, intra-operative and post-operative periods. The peri-operative StO₂ values were also similar between the two groups at all times. The two groups were identical in terms of preoperative values for respiratory function tests and post-operative hemodynamic status, fluid intake, urinary output, pain scores, and complication rates.

Conclusions: In conclusion, the choice of the mechanical ventilation mode did not appear to influence oxygen delivery, respiratory function, hemodynamic status, post-operative pain, or ventilation-related complications in obese patients undergoing laparoscopic bariatric surgery.

Evaluation of the Effect of the Inspired Oxygen Fraction on Blood Oxygenation during Inhalant Anaesthesia in Horses: A Systematic Review with Meta-Analysis

In anaesthetized horses, pronounced ventilation/perfusion mismatching often occurs. Several authors have investigated the effect of lower inspired oxygen fractions (FiO₂) to reduce formation of absorption atelectasis. This systematic review compared the effects of low (<0.6) and high (>0.8) FiO₂ on the arterial oxygen tension (PaO₂), the alveolar-to-arterial oxygen tension difference (P(A-a)O₂), and the PaO₂/FiO₂ ratio in horses during inhalation anaesthesia. Using the Systematic Review Protocol for Animal Intervention Studies, four experimental and one clinical investigations were deemed suitable for inclusion. A meta-analysis was performed on the four experimental studies. The PaO₂ was significantly lower (p = 0.0007, mean difference -23.54 kPa, 95% CI -37.18, -9.90) with a lower FiO₂. However, the P(A-a)O₂ was also significantly lower (p < 0.00001, mean difference -20.80 kPa, 95% CI -26.28, -15.32) when using a low FiO₂. For the PaO₂/FiO₂ ratio, only one study fitted the inclusion criteria, so no meta-analysis was performed. It is concluded that, while only a limited number of studies are available, the use of a higher FiO₂ in horses during inhalation anaesthesia will result in higher levels of PaO₂, but also a larger P(A-a)O₂ difference. Further studies are needed to increase the level of evidence on this subject.

Recruitment maneuvers in patients undergoing thoracic surgery: a meta-analysis

OBJECTIVE

Pulmonary atelectasis is a common postoperative complication that may lead to intrapulmonary shunt, refractory hypoxemia, and respiratory distress. Recruitment maneuvers may relieve pulmonary atelectasis in patients undergoing thoracic surgery. This meta-analysis of randomized controlled trials (RCTs) is to evaluate the effectiveness and safety of recruitment maneuvers in patients undergoing thoracic surgery.

METHODS

We performed a literature search on the PubMed, Embase, and Cochrane Library databases and the ClinicalTrials.gov registry for trials published before April 2021. We investigated postoperative pulmonary atelectasis incidence, intrapulmonary shunt fraction, static lung compliance, and mean arterial pressure.

RESULTS

Six RCTs involving 526 patients were reviewed. Patients receiving a recruitment maneuver exhibited a significant decrease in intrapulmonary shunt fraction [weighted mean difference (WMD) - 0.02, 95% CI - 0.03 to - 0.01], improved static lung compliance (WMD 2.16; 95% CI 1.14-3.18), and PaO₂/FIO₂ ratio (WMD 31.31; 95% CI 12.11-50.52) without a significant difference in mean arterial pressure (WMD - 0.64; 95% CI - 4.92 to 3.64). The incidence pulmonary atelectasis favored recruitment maneuver group, but was not statistically significant (RR 0.55; 95% CI 0.27-1.12).

CONCLUSIONS

Recruitment maneuvers may be a viable treatment for reducing intra-pulmonary shunt and improving static lung compliance and PaO₂/FIO₂ ratio without the disturbance of hemodynamics in patients undergoing thoracic surgery.

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.

Definition and clinical evaluation of a recruiting airway pressure based on the specific lung elastance in anesthetized dogs

OBJECTIVE

To determine the specific lung elastance (SE_L) in anesthetized dogs and to evaluate the efficacy of a SE_L-based recruiting airway pressure (RP_aw) at improving global and regional lung aeration.

STUDY DESIGN

Retrospective and prospective clinical study.

ANIMALS

A total of 28 adult dogs were included in the retrospective study and six adult dogs in the prospective study.

METHODS

Retrospective study: SE_L and SE_L-based RP_aw were determined using previously published data. In mechanically ventilated dogs undergoing thoracic computed tomography (CT), SE_L was calculated as ΔP_L/(V_T/EELV), where ΔP_L is the driving transpulmonary pressure, V_T is the tidal volume and EELV is the end-expiratory lung volume. The ratio of lung to respiratory system elastance (E_L/E_rs) was determined. SE_L and E_L/E_rs were used to calculate the SE_L-based RP_aw. Prospective study: dogs underwent thoracic CT at end-expiration and at end-inspiration using the SE_L-based RP_aw, and global and regional aeration was determined. For analysis of regional aeration, lungs were divided into cranial, intermediate and caudal regions. Regional compliance was also calculated. A p value <0.05 was considered significant.

RESULTS

The SE_L and E_L/E_rs were 12.7 ± 3.1 cmH₂O and 0.54 ± 0.07, respectively. The SE_L-based RP_aw was 29.1 ± 7.6 cmH₂O. In the prospective study, the RP_aw was 28.2 ± 1.3 cmH₂O. During RP_aw, hyperinflation increased (p = 0.0003) whereas poorly aerated (p < 0.0001) and nonaerated (p = 0.01) tissue decreased. Normally aerated tissue did not change (p = 0.265). Regional compliance was higher in the intermediate (p = 0.0003) and caudal (p = 0.034) regions compared with the cranial region. Aeration did not differ between regions (p > 0.05).

CONCLUSIONS AND CLINICAL RELEVANCE

An SE_L-based RP_aw reduces poorly and nonaerated lung tissue in anesthetized dogs. In nonsurgical anesthetized dogs, an RP_aw near 30 cmH₂O is effective at improving lung aeration.

The role of ultrasonographic lung aeration score in the prediction of postoperative pulmonary complications: an observational study

Background

Postoperative pulmonary complications (PPCs) are important contributors to mortality and morbidity after surgery. The available predicting models are useful in preoperative risk assessment, but there is a need for validated tools for the early postoperative period as well. Lung ultrasound is becoming popular in intensive and perioperative care and there is a growing interest to evaluate its role in the detection of postoperative pulmonary pathologies.

Objectives

We aimed to identify characteristics with the potential of recognizing patients at risk by comparing the lung ultrasound scores (LUS) of patients with/without PPC in a 24-h postoperative timeframe.

Methods

Observational study at a university clinic. We recruited ASA 2–3 patients undergoing elective major abdominal surgery under general anaesthesia. LUS was assessed preoperatively, and also 1 and 24 h after surgery. Baseline and operative characteristics were also collected. A one-week follow up identified PPC+ and PPC- patients. Significantly differing LUS values underwent ROC analysis. A multi-variate logistic regression analysis with forward stepwise model building was performed to find independent predictors of PPCs.

Results

Out of the 77 recruited patients, 67 were included in the study. We evaluated 18 patients in the PPC+ and 49 in the PPC- group. Mean ages were 68.4 ± 10.2 and 66.4 ± 9.6 years, respectively (p = 0.4829). Patients conforming to ASA 3 class were significantly more represented in the PPC+ group (66.7 and 26.5%; p = 0.0026). LUS at baseline and in the postoperative hour were similar in both populations. The median LUS at 0 h was 1.5 (IQR 1–2) and 1 (IQR 0–2; p = 0.4625) in the PPC+ and PPC- groups, respectively. In the first postoperative hour, both groups had a marked increase, resulting in scores of 6.5 (IQR 3–9) and 5 (IQR 3–7; p = 0.1925). However, in the 24th hour, median LUS were significantly higher in the PPC+ group (6; IQR 6–10 vs 3; IQR 2–4; p < 0.0001) and it was an independent risk factor (OR = 2.6448 CI95% 1.5555–4.4971; p = 0.0003). ROC analysis identified the optimal cut-off at 5 points with high sensitivity (0.9444) and good specificity (0.7755).

Conclusion

Postoperative LUS at 24 h can identify patients at risk of or in an early phase of PPCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01236-6.

Recruitment maneuvers to reduce pulmonary atelectasis after cardiac surgery: A meta-analysis of randomized trials

BACKGROUND

Pulmonary atelectasis is a common postoperative complication that may lead to intrapulmonary shunt, refractory hypoxemia, and respiratory distress. Recruitment maneuvers may relieve pulmonary atelectasis in patients undergoing cardiac surgery. We conducted a meta-analysis of randomized controlled trials to evaluate the effectiveness of recruitment maneuvers in these patients.

METHODS

We conducted a search in PubMed, Embase, Cochrane Library, and the ClinicalTrials.gov registry for trials published before March 2020. Individual effect sizes were standardized, and a meta-analysis was performed to calculate a pooled effect size by using random-effects models. Pulmonary atelectasis was assessed postoperatively. Secondary outcomes included hypoxic events, arterial oxygen tension (Pao₂)/inspired oxygen fraction (Fio₂) ratio, cardiac index, mean arterial pressure, and postoperative complications including pneumothorax and pneumonia.

RESULTS

We reviewed 16 trials involving 1455 patients. Patients receiving recruitment maneuvers had a reduced incidence of pulmonary atelectasis (group with recruited pressure >40 cmH₂O: risk ratio [RR], 0.20; 95% confidence interval [CI], 0.07-0.57; group with recruited pressure <40 cmH₂O: RR, 0.54; 95% CI, 0.33-0.89), reduced incidence of hypoxic events (RR, 0.23; 95% CI, 0.14-0.37), reduced incidence of pneumonia (RR, 0.42; 95% CI, 0.18-0.95), and improved Pao₂/Fio₂ ratio (weighted mean difference [WMD]; 58.87, 95% CI, 31.24-86.50) without disturbing the cardiac index (WMD, 0.22; 95% CI, -0.18 to 0.61) or mean arterial pressure (WMD, -0.30, 95% CI, -3.19 to 2.59) as compared with those who received conventional mechanical ventilation. The incidence of pneumothorax was nonsignificant between the groups.

CONCLUSIONS

Recruitment maneuvers may reduce postoperative pulmonary atelectasis, hypoxic events, and pneumonia and improve Pao₂/Fio₂ ratios without hemodynamic disturbance in patients undergoing cardiac surgery.

Lung ultrasound score to determine the effect of fraction inspired oxygen during alveolar recruitment on absorption atelectasis in laparoscopic surgery: a randomized controlled trial

Background

Although the intraoperative alveolar recruitment maneuver (RM) efficiently treats atelectasis, the effect of Fio₂ on atelectasis during RM is uncertain. We hypothesized that a high Fio₂ (1.0) during RM would lead to a higher degree of postoperative atelectasis without benefiting oxygenation when compared to low Fio₂ (0.4).

Methods

In this randomized controlled trial, patients undergoing elective laparoscopic surgery in the Trendelenburg position were allocated to low- (Fio₂ 0.4, n = 44) and high-Fio₂ (Fio₂ 1.0, n = 46) groups. RM was performed 1-min post tracheal intubation and post changes in supine and Trendelenburg positions during surgery. We set the intraoperative Fio₂ at 0.4 for both groups and calculated the modified lung ultrasound score (LUSS) to assess lung aeration after anesthesia induction and at surgery completion. The primary outcome was modified LUSS at the end of the surgery. The secondary outcomes were the intra- and postoperative Pao₂ to Fio₂ ratio and postoperative pulmonary complications.

Results

The modified LUSS before capnoperitoneum and RM (P = 0.747) were similar in both groups. However, the postoperative modified LUSS was significantly lower in the low Fio₂ group (median difference 5.0, 95% CI 3.0–7.0, P < 0.001). Postoperatively, substantial atelectasis was more common in the high-Fio₂ group (relative risk 1.77, 95% CI 1.27–2.47, P < 0.001). Intra- and postoperative Pao₂ to Fio₂ were similar with no postoperative pulmonary complications. Atelectasis occurred more frequently when RM was performed with high than with low Fio₂; oxygenation was not benefitted by a high-Fio_2.

Conclusions

In patients undergoing laparoscopic surgery in the Trendelenburg position, absorption atelectasis occurred more frequently with high rather than low Fio₂. No oxygenation benefit was observed in the high-Fio₂ group.

Trial registration

ClinicalTrials.gov, NCT03943433. Registered 7 May 2019,

The effects of a recruitment manoeuvre with positive end-expiratory pressure on lung compliance in patients undergoing robot-assisted laparoscopic radical prostatectomy

The effects of a recruitment manoeuvre (RM) with positive end-expiratory pressure (PEEP) on lung compliance (C_LUNG) are not well characterised in robot-assisted laparoscopic radical prostatectomy (RARP). Patients were allocated to group R (n = 10; with an RM) or C (n = 9; without an RM). An RM involved sustained inflation of 30 cmH₂O for 30 s. The lungs were ventilated with volume-controlled ventilation with tidal volume of 7 mL kg^-1 of predicted body weight and fraction of inspired oxygen of 0.5. End-tidal carbon dioxide pressure was maintained at normocapnia. Patients were in the horizontal lithotomy position (pre-op). After pneumoperitoneum, patients underwent RARP in a steep Trendelenburg lithotomy position at a PEEP level of 0 cmH₂O (RARP0). An RM was used in the R group but not in the C group. Patients were then ventilated with 5 cmH₂O PEEP for 1 h after RARP0 (RARP5.1) and 2 h after RARP0 (RARP5.2). Oesophageal pressure and airway pressure were measured for calculating C_LUNG and chest wall compliance. C_LUNG significantly decreased from pre-op to RARP0 and did not significantly increase from RARP0 to RARP5.1 and RARP5.2 in either group. C_LUNG differed significantly between groups at RARP5.1 and RARP5.2 (103 ± 30 vs. 68 ± 11 mL cm^-1 H₂O and 106 ± 35 vs. 72 ± 9 mL cm^-1 H₂O; P < 0.05). In patients undergoing RARP, with the addition of RM, the C_LUNG was effectively increased from the horizontal lithotomy position to the steep Trendelenburg lithotomy position under pneumoperitoneum.

Effect of an ultrasound-guided lung recruitment manoeuvre on postoperative atelectasis in children: A randomised controlled trial

BACKGROUND

Ultrasound-guided alveolar recruitment, regardless of the technique, could be more effective because it facilitates real-time monitoring of the expansion of collapsed alveoli.

OBJECTIVES

To evaluate and compare the effects of an ultrasound-guided lung recruitment manoeuvre with those of a conventional recruitment manoeuvre on the occurrence of postoperative atelectasis and clinical outcomes in children.

DESIGN

A randomised controlled trial.

SETTING

Tertiary children's hospital.

PATIENTS

Children aged 6 years or less.

INTERVENTION

Children scheduled for simple, superficial procedures underwent lung ultrasound after tracheal intubation (T1), at the end of surgery (T2) and before discharge from the postanaesthesia care unit (T3). Following lung ultrasound evaluation at T1 and T2, the conventional recruitment manoeuvre with a maximal airway pressure of 30 cmH2O was performed in the control group, while an ultrasound-guided recruitment manoeuvre was performed in the ultrasound group.

MAIN OUTCOME MEASURES

The primary outcome was the incidence of significant atelectasis at T3.

RESULTS

The incidences of atelectasis at T3 were 20.9 and 11.6% in the control (n = 43) and ultrasound groups (n = 43), respectively (odds ratio [OR], 2.012; 95% confidence interval [CI], 0.614 to 6.594; P = 0.249). The lung ultrasound scores were better in the ultrasound group than in the control group at T2 and T3, and the incidence of postoperative desaturation was higher in the control group than in the ultrasound group (16.3 vs. 2.3%; OR, 0.12; 95% CI 0.01 to 1.04; P = 0.05). The median airway pressure required for full lung expansion in the ultrasound group was 35 cmH2O at T1 and T2. Other postoperative outcomes were similar between groups.

CONCLUSION

Ultrasound-guided lung recruitment may be more effective than the conventional procedure in terms of the prevention of intra-operative atelectasis and postoperative desaturation; however, its beneficial effects on postoperative atelectasis remain unclear. An inspiratory airway pressure of more than 30 cmH2O is required for full recruitment of alveoli in healthy children.

CLINICAL TRIAL REGISTRY

ClinicalTrials.gov (NCT03453762).

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.

Perioperative Transthoracic Lung Ultrasound for Assessment of Pulmonary Outcome in Adolescent Idiopathic Scoliosis Patients: Prospective, Observational Pilot Study

The purpose of study was to evaluate the perioperative lung ultrasound findings of patients undergoing scoliosis correction. LUS examination was performed examined three 3 times for each patient: 20 min after starting mechanical ventilation of the lungs(preoperative), after surgery when the patient was placed in the supine position(postoperative), and 20 min after arrival in the post-anaesthesia care unit. Arterial blood gas analyses, mechanical ventilation parameters, peripheral oxygen saturation(SpO2) were also checked. Twenty-six patients completed the study. The changes of LUS score(20 min) was significantly negatively correlated with the partial pressure of arterial oxygen(PaO2)/fraction of inspired oxygen(FiO2) ratio change(P = 0.039, r = −0.40). The change in mean convex side LUS score was significantly greater than that of the concave side as determined by two-factor repeated measures analysis of variance(p = 0.001). Multiple regression analysis revealed perioperative LUS change was the significant factor related to the oxygen index change (p = 0.042). One case of pneumothorax was diagnosed and pleural thickening more than 5 mm was detected in 8 patients and five patients of those were diagnosed pleural effusion and performed thoracentesis after surgery. Postoperative increase of LUS score was related with deteriorating of oxygenation at one day after surgery, and it suggests that lung ultrasound allows prediction of postoperative hypoxia and facilitates the diagnosis of pulmonary complications at operation room in AIS patients.

Respiratory complications of anaesthesia

Postoperative pulmonary complications are a major determinant of outcome for patients and consume huge resources within hospital, particularly in critical care. Prediction and anticipation of postoperative pulmonary complications are vital for patient selection and, in some cases, for informed patient consent. Being able to assess the likelihood of postoperative pulmonary complications also allows research into methods to reduce them by allowing allocation of patients to the appropriate arms of research trials. Some patients have pre-operative characteristics or belong to patient groups such as those with chronic obstructive pulmonary disease or obstructive sleep apnoea, where techniques and evidence-based guidance to avoid or reduce complications are becoming established. Intra-operative ventilation and the use of lung-protective ventilation may be helpful during major surgery, but studies looking at reduced tidal volumes, recruitment and levels of positive end-expiratory pressure, have this far only led to a degree of consensus in terms of tidal volume, although parameters that predispose to postoperative pulmonary complications are becoming clearer. Optimal postoperative care in terms of analgesia, positioning, physiotherapy and mobilisation is another developing area. Techniques such as continuous positive airways pressure, non-invasive ventilation and high-flow nasal humidified oxygen appear to show some benefit, but the exact roles, pressures and timings of each are currently being explored. Much remains to be researched and developed into evidence-based practice.

Effect of combining a recruitment maneuver with protective ventilation on inflammatory responses in video-assisted thoracoscopic lobectomy: a randomized controlled trial

BACKGROUND

We hypothesized that the addition of a recruitment maneuver to protective ventilation (PVRM) would result in lower pulmonary and systemic inflammatory responses than traditional ventilation or protective ventilation (PV) alone in patients undergoing lung surgery.

METHODS

Sixty patients who underwent scheduled thoracoscopic lobectomy were randomly assigned to three groups: traditional ventilation, PV, or PVRM. Ventilations were performed using a tidal volume of 10 mL/kg for the traditional ventilation group and either 8 mL/kg (two-lung) or 6 mL/kg (one-lung, OLV) with a positive end-expiratory pressure of 5 cm H₂O for the PV and PVRM groups. The RM was performed 10 min after the start of OLV. Fiberoptic bronchoalveolar lavage (BAL) was performed twice in dependent and non-dependent lungs: before the start and immediately after the end of OLV. Blood samples were collected at the same time points. The levels of cytokines, including TNF-α, IL-1β, IL-6, IL-8, and IL-10, were measured.

RESULTS

After OLV, the level of TNF-α in the BAL fluid of dependent lungs was significantly higher in the PV than in the PVRM group (P = 0.049), whereas IL-1β, IL-6, IL-8, and IL-10 levels were not significantly different among the groups. In non-dependent lung BAL fluid, no cytokines were significantly different among the groups. After OLV, IL-10 serum levels were significantly higher in the traditional ventilation than in the PVRM group (P = 0.027).

CONCLUSIONS

Lower inflammatory responses in the ventilated lung and serum were observed with PVRM than with traditional ventilation or PV alone. Larger multi-center clinical trials are warranted to confirm the effects of different ventilatory strategies on postoperative outcomes.

Breath-Hold Diving

Breath-hold diving is practiced by recreational divers, seafood divers, military divers, and competitive athletes. It involves highly integrated physiology and extreme responses. This article reviews human breath-hold diving physiology beginning with an historical overview followed by a summary of foundational research and a survey of some contemporary issues. Immersion and cardiovascular adjustments promote a blood shift into the heart and chest vasculature. Autonomic responses include diving bradycardia, peripheral vasoconstriction, and splenic contraction, which help conserve oxygen. Competitive divers use a technique of lung hyperinflation that raises initial volume and airway pressure to facilitate longer apnea times and greater depths. Gas compression at depth leads to sequential alveolar collapse. Airway pressure decreases with depth and becomes negative relative to ambient due to limited chest compliance at low lung volumes, raising the risk of pulmonary injury called "squeeze," characterized by postdive coughing, wheezing, and hemoptysis. Hypoxia and hypercapnia influence the terminal breakpoint beyond which voluntary apnea cannot be sustained. Ascent blackout due to hypoxia is a danger during long breath-holds, and has become common amongst high-level competitors who can suppress their urge to breathe. Decompression sickness due to nitrogen accumulation causing bubble formation can occur after multiple repetitive dives, or after single deep dives during depth record attempts. Humans experience responses similar to those seen in diving mammals, but to a lesser degree. The deepest sled-assisted breath-hold dive was to 214 m. Factors that might determine ultimate human depth capabilities are discussed. © 2018 American Physiological Society. Compr Physiol 8:585-630, 2018.

Specific anesthesia-induced lung volume changes from induction to emergence: a pilot study

BACKGROUND

Studies aimed at maintaining intraoperative lung volume to reduce post-operative pulmonary complications have been inconclusive because they mixed up the effect of general anesthesia and the surgical procedure. Our aims were to study: (1) lung volume during the entire course of anesthesia without the confounding effects of surgical procedures; (2) the combination of three interventions to maintain lung volume; and (3) the emergence phase with focus on the restored activation of the respiratory muscles.

METHODS

Eighteen ASA I-II patients undergoing ENT surgery under general anesthesia without muscle relaxants were randomized to an intervention group, receiving lung recruitment maneuver (LRM) after induction, 7 cmH₂ O positive end-expiratory pressure (PEEP) during anesthesia and continuous positive airway pressure (CPAP) during emergence with 0.4 inspired oxygen fraction (FiO₂ ) or a control group, ventilated without LRM, with 0 cmH₂ O PEEP, and 1.0 FiO₂ during emergence without CPAP application. End-expiratory lung volume (EELV) was continuously estimated by opto-electronic plethysmography. Inspiratory and expiratory ribcage muscles electromyography was measured in a subset of seven patients.

RESULTS

End-expiratory lung volume decreased after induction in both groups. It remained low in the control group and further decreased at emergence, because of active expiratory muscle contraction. In the intervention group, EELV increased after LRM and remained high after extubation.

CONCLUSION

A combined intervention consisting of LRM, PEEP and CPAP during emergence may effectively maintain EELV during anesthesia and even after extubation. An unexpected finding was that the activation of the expiratory muscles may contribute to EELV reduction during the emergence phase.

Effect of Bronchoconstriction-induced Ventilation-Perfusion Mismatch on Uptake and Elimination of Isoflurane and Desflurane

BACKGROUND

Increasing numbers of patients with obstructive lung diseases need anesthesia for surgery. These conditions are associated with pulmonary ventilation/perfusion (VA/Q) mismatch affecting kinetics of volatile anesthetics. Pure shunt might delay uptake of less soluble anesthetic agents but other forms of VA/Q scatter have not yet been examined. Volatile anesthetics with higher blood solubility would be less affected by VA/Q mismatch. We therefore compared uptake and elimination of higher soluble isoflurane and less soluble desflurane in a piglet model.

METHODS

Juvenile piglets (26.7 ± 1.5 kg) received either isoflurane (n = 7) or desflurane (n = 7). Arterial and mixed venous blood samples were obtained during wash-in and wash-out of volatile anesthetics before and during bronchoconstriction by methacholine inhalation (100 μg/ml). Total uptake and elimination were calculated based on partial pressure measurements by micropore membrane inlet mass spectrometry and literature-derived partition coefficients and assumed end-expired to arterial gradients to be negligible. VA/Q distribution was assessed by the multiple inert gas elimination technique.

RESULTS

Before methacholine inhalation, isoflurane arterial partial pressures reached 90% of final plateau within 16 min and decreased to 10% after 28 min. By methacholine nebulization, arterial uptake and elimination delayed to 35 and 44 min. Desflurane needed 4 min during wash-in and 6 min during wash-out, but with bronchoconstriction 90% of both uptake and elimination was reached within 15 min.

CONCLUSIONS

Inhaled methacholine induced bronchoconstriction and inhomogeneous VA/Q distribution. Solubility of inhalational anesthetics significantly influenced pharmacokinetics: higher soluble isoflurane is less affected than fairly insoluble desflurane, indicating different uptake and elimination during bronchoconstriction.

Anesthetic Considerations in Patients Undergoing Bariatric Surgery: A Review Article

Context

This article discusses the anesthetic considerations in patients undergoing bariatric surgery in the preoperative, intraoperative, and postoperative phases of surgery.

Evidence Acquisition

This review includes studies involving obese patients undergoing bariatric surgery. Searches have been conducted in PubMed, MEDLINE, EMBASE, Google Scholar, Scopus, and Cochrane Database of Systematic Review using the terms obese, obesity, bariatric, anesthesia, perioperative, preoperative, perioperative, postoperative, and their combinations.

Results

Obesity is a major worldwide health problem associated with many comorbidities. Bariatric surgery has been proposed as the best alternative treatment for extreme obese patients when all other therapeutic options have failed.

Conclusions

Anesthetists must completely assess the patients before the surgery to identify anesthesia- related potential risk factors and prepare for management during the surgery.

Changes in Stroke Volume Induced by Lung Recruitment Maneuver Predict Fluid Responsiveness in Mechanically Ventilated Patients in the Operating Room

Background

Lung recruitment maneuver induces a decrease in stroke volume, which is more pronounced in hypovolemic patients. The authors hypothesized that the magnitude of stroke volume reduction through lung recruitment maneuver could predict preload responsiveness.

Methods

Twenty-eight mechanically ventilated patients with low tidal volume during general anesthesia were included. Heart rate, mean arterial pressure, stroke volume, and pulse pressure variations were recorded before lung recruitment maneuver (application of continuous positive airway pressure of 30 cm H2O for 30 s), during lung recruitment maneuver when stroke volume reached its minimal value, and before and after volume expansion (250 ml saline, 0.9%, infused during 10 min). Patients were considered as responders to fluid administration if stroke volume increased greater than or equal to 10%.

Results

Sixteen patients were responders. Lung recruitment maneuver induced a significant decrease in mean arterial pressure and stroke volume in both responders and nonresponders. Changes in stroke volume induced by lung recruitment maneuver were correlated with those induced by volume expansion (r2 = 0.56; P &lt; 0.0001). A 30% decrease in stroke volume during lung recruitment maneuver predicted fluid responsiveness with a sensitivity of 88% (95% CI, 62 to 98) and a specificity of 92% (95% CI, 62 to 99). Pulse pressure variations more than 6% before lung recruitment maneuver discriminated responders with a sensitivity of 69% (95% CI, 41 to 89) and a specificity of 75% (95% CI, 42 to 95). The area under receiver operating curves generated for changes in stroke volume induced by lung recruitment maneuver (0.96; 95% CI, 0.81 to 0.99) was significantly higher than that for pulse pressure variations (0.72; 95% CI, 0.52 to 0.88; P &lt; 0.05).

Conclusions

The authors’ study suggests that the magnitude of stroke volume decrease during lung recruitment maneuver could predict preload responsiveness in mechanically ventilated patients in the operating room.

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.

Indications for manual lung hyperinflation (MHI) in the mechanically ventilated patient with chronic obstructivepulmonary disease

Manual lung hyperinflation (MHI) can enhance secretion clearance, improve total lung/thorax compliance and assistin the resolution of acute atelectasis. To enhance secretion clearance in the intubated patient, the evidence highlights the need to maximize expiratory flow. Chronic pulmonary diseases such as chronic obstructive pulmonary disease(COPD) have often been cited as potential precautions and/or contra-indications to the use of manual lung hyperinflation (MHI). There is an absence of evidence on the effects of MHI in the patient with COPD. Research on the effects of mechanical ventilation in the patient with COPD providesa useful clinical examination of the effect of positive pressure on cardiac and pulmonary function. The potential effects of MHI in the COPD patient group were extrapolated on the basis of the MHI and mechanical ventilation literature. There is the potential for MHI to have both detrimental and beneficial effects on cardiac and pulmonary functionin patients with COPD. The potential detrimental effects of MHI may include either, increased intrinsic peep throughinadequate time for expiration by the breath delivery rate, tidal volume delivered or through the removal of appliedextemal PEEP thereby causing more dynamic airway compression compromising downward expiratory flow, which may also retard bronchial mucus transport. MHI may also increase right ventricular after load through raised intrathoracic pressures with lung hyperinflation, and may therefore impair right ventricular function in patients with evidence of cor pulmonale. There is the potential for beneficial effectsfrom MHI in the intubated COPD patient group (i.e., secretion clearance), but further research is required, especially on the effect of MHI on inspiratory and expiratory flowrate profiles in this patient group. The more controlled delivery of lung hyperinflation through the use of the mechanical ventilator may be a more optimal means of providinglunghyperinflation and shouldbe furtherinvestigated.

Application of CO2 waveform in the alveolar recruitment maneuvers of hypoxemic patients during one-lung ventilation

Deterioration of gas exchange during one-lung ventilation (OLV) is caused by both total collapse of the nondependent lung and partial collapse of the dependent lung. Alveolar recruitment maneuver improves lung function during general anesthesia. The objective of this study was to investigate whether there is an indirect relationship between the changes of CO2 expirogram and the selective lung recruitment. To further improve the oxygenation and gas exchange, we compare adjust setting of ventilated parameters based on CO2 expirogram and a preset setting of ventilated parameters during OLV in patients undergoing right-side thoracic surgery.Thirty patients met the requirements criteria that were studied at 3 time points: during two-lung ventilation (TLV), during OLV with preset ventilation parameters (OLV-PP), and during OLV with adjustable ventilation parameters (OLV-AP) that are in accordance with CO2 expirogram. Adjustable ventilation parameters such as tidal volume (VT), respiratory rate (RR), positive end-expiratory pressure (PEEP), and the ratio of inspiratory to expiratory were adjusted by utilizing the phase III slopes of CO2 expirogram, which together with the relationship between the changes of CO2 expirogram and the selective lung recruitment.During OLV, the phase III slopes of CO2 expirogram in patients with pulse oxymetry (SpO2) decreased less than 93% after the OLV-PP, and were absolutely different from that during TLV. After OLV-AP, the phase III slopes of CO2 expirogram and SpO2 were similar to those during TLV. During OLV, however, parameters of ventilation setting in both OLV-PP and OLV-AP are obviously different.This study indicates that alveolar recruitment by utilizing CO2 expirogram probably improves SpO2 level during one-lung ventilation.

Performance of manual hyperinflation: consistency and modification of the technique by intensive care unit nurses during physiotherapy

AIMS AND OBJECTIVES

To assess the consistency and safety of manual hyperinflation delivery by nurses of variable clinical experience using a resuscitator bag during physiotherapy treatment.

BACKGROUND

Manual hyperinflation involves the delivery of larger than normal gas volumes to intubated patients and is routinely used by nurses in collaboration with physiotherapists for the management of retained sputum. The aim is to deliver slow deep breaths with an inspiratory hold without unsafe airway pressures, lung volumes or haemodynamic changes. In addition, nursing staff should be able to 'feel' differences in resistance and adjust their technique accordingly.

DESIGN

Prospective observational study utilising the simulation of a mechanically ventilated patient.

METHODS

Thirty-three nurses delivered manual hyperinflation to a SimMan3G mannequin who had three distinct lung scenarios applied (normal; asthma; Acute Respiratory Distress Syndrome) in randomised order during simulated physiotherapy treatment. Respiratory rate, tidal volume (Vt ), mean inspiratory flow rate (Vt /Ti), and peak airway pressure data were generated.

RESULTS

Over all scenarios, mean respiratory rate = 12·3 breaths/minute, mean Vt  = 638·6 mls, mean inflation time = 1·3 seconds and peak airway pressure exceeded 40 cm H2 O in 41% of breaths, although only in 10% of breaths during the 'normal' lung scenario.

CONCLUSIONS

Experienced nurses were able to manually hyperinflate 'normal' patients in a simulated setting safely. Despite their knowledge of barotrauma, unsafe airway pressures were delivered in some scenarios.

RELEVANCE TO CLINICAL PRACTICE

Training with regard to safe airway pressures, breath hold and adequate volumes is recommended for all nurses undertaking the procedure. Nurses and physiotherapists must closely monitor the patient's condition during manual hyperinflation thereby recognising changes with regard to lung compliance and airway resistance, with nurses responding by altering their technique. The addition of a pressure manometer in the circuit may improve patient safety when performing manual hyperinflation.

Predictive Factors of Atelectasis Following Endoscopic Resection

BACKGROUND AND AIM

Atelectasis is one of the pulmonary complications associated with anesthesia. Little is known about atelectasis following endoscopic procedures under deep sedation. This study evaluated the frequency, risk factors, and clinical course of atelectasis after endoscopic resection.

METHODS

A total of 349 patients who underwent endoscopic resection of the upper gastrointestinal tract at a single academic tertiary referral center from March 2010 to October 2013 were enrolled. Baseline characteristics and clinical data were retrospectively reviewed from medical records. To identify atelectasis, we compared the chest radiography taken before and after the endoscopic procedure.

RESULTS

Among the 349 patients, 68 (19.5 %) had newly developed atelectasis following endoscopic resection. In univariate logistic regression analysis, atelectasis correlated significantly with high body mass index, smoking, diabetes mellitus, procedure duration, size of lesion, and total amount of propofol. In multiple logistic regression analysis, body mass index, procedure duration, and total propofol amount were risk factors for atelectasis following endoscopic procedures. Of the 68 patients with atelectasis, nine patients developed fever, and six patients displayed pneumonic infiltration. The others had no symptoms related to atelectasis.

CONCLUSIONS

The incidence of radiographic atelectasis following endoscopic resection was nearly 20 %. Obesity, procedural time, and amount of propofol were the significant risk factors for atelectasis following endoscopic procedure. Most cases of the atelectasis resolved spontaneously with no sequelae.