Changes in pulmonary mechanics during laparoscopic gastroplasty in morbidly obese patients

Impact of a positive end-expiratory pressure strategy on oxygenation, respiratory compliance, and hemodynamics during laparoscopic surgery in non-obese patients: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Higher positive end-expiratory pressure (PEEP) during laparoscopic surgery may increase oxygenation and respiratory compliance. This meta-analysis aimed to compare the impact of different intraoperative PEEP strategies on arterial oxygenation, compliance, and hemodynamics during laparoscopic surgery in non-obese patients.

METHODS

We searched RCTs in PubMed, Cochrane Library, Web of Science, and Google Scholar from January 2012 to April 2022 comparing the different intraoperative PEEP (Low PEEP (LPEEP): 0-4 mbar; Moderate PEEP (MPEEP): 5-8 mbar; high PEEP (HPEEP): >8 mbar; individualized PEEP - iPEEP) on arterial oxygenation, respiratory compliance (Cdyn), mean arterial pressure (MAP), and heart rate (HR). We calculated mean differences (MD) with 95% confidence intervals (CI), and predictive intervals (PI) using random-effects models. The Cochrane Bias Risk Assessment Tool was applied.

RESULTS

21 RCTs (n = 1554) met the inclusion criteria. HPEEP vs. LPEEP increased PaO2 (+ 29.38 [16.20; 42.56] mmHg, p < 0.0001) or PaO2/FiO2 (+ 36.7 [+ 2.23; +71.70] mmHg, p = 0.04). HPEEP vs. MPEEP increased PaO2 (+ 22.00 [+ 1.11; +42.88] mmHg, p = 0.04) or PaO2/FiO2 (+ 42.7 [+ 2.74; +82.67] mmHg, p = 0.04). iPEEP vs. MPEEP increased PaO2/FiO2 (+ 115.2 [+ 87.21; +143.20] mmHg, p < 0.001). MPEEP vs. LPEP, and HPEEP vs. MPEEP increased PaO2 or PaO2/FiO2 significantly with different heterogeneity. HPEEP vs. LPEEP increased Cdyn (+ 7.87 [+ 1.49; +14.25] ml/mbar, p = 0.02). MPEEP vs. LPEEP, and HPEEP vs. MPEEP did not impact Cdyn (p = 0.14 and 0.38, respectively). iPEEP vs. LPEEP decreased driving pressure (-4.13 [-2.63; -5.63] mbar, p < 0.001). No significant differences in MAP or HR were found between any subgroups.

CONCLUSION

HPEEP and iPEEP during PNP in non-obese patients could promote oxygenation and increase Cdyn without clinically significant changes in MAP and HR. MPEEP could be insufficient to increase respiratory compliance and improve oxygenation. LPEEP may lead to decreased respiratory compliance and worsened oxygenation.

PROSPERO REGISTRATION

CRD42022362379; registered October 09, 2022.

Laparoscopic surgery: A randomised controlled trial comparing intraoperative hemodynamic parameters and arterial-blood gas changes at two different pneumoperitoneal pressure values

Background

The benefits of laparoscopic surgery are well known. However, clinic and metabolic consequences of pneumoperitoneum, achieved by insufflation of gas carbon dioxide, are still debated. Cardiovascular system suffering due to the compression of intra-abdominal venous structures can cause life-threatening complications. Increased partial pressure of carbon dioxide induces metabolic acidosis with further vascular suffering. Pneumoperitoneum reduces the pulmonary exchange volumes and bring renal suffering.

Methods

The aim of this study is to evaluate the alterations in hemodynamic and hemogasanalysis parameters during the laparoscopic surgery at different pressure settings of pneumoperitoneum in order to assess the best pressure value.

We evaluated and compared intraoperative hemodynamic and hemogasanalytic alterations in two groups of patients respectively subdue to laparoscopic cholecystectomy at a pneumoperitoneum pressure of 12 mmHg (group A) and at a pressure of 8 mmHg (group B).

Results

In both groups, after the induction of anesthesia we observed a flexion in the heart rate, with no significant difference between the two groups. During the intervention, group A showed a significantly higher respiratory rate than the group B. The average blood pressure decreased mostly in group B. The oxygen saturation increased at the end of the procedure in group A, more than in the group B. The pH value was higher in group B. The hydrogen carbonate ion settled at lower levels in group A.

Conclusion

Although significant differences between the two groups were appreciated on several parameters, they were never of such magnitude to prefer the induction of pneumoperitoneum at 8 mmHg.

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Pneumoperitoneum induces hemogasanalytic and hemodynamic alterations.

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Different settings in pneumoperitoneum pressure cause different levels of hemodynamic and hemogasanalytic alterations.

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A pneumoperitoneum pressure value that could reduce the alterations in hemodynamic and hemogasanalytic parameters while mantaining the surgical safety, has to be established.

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.

Multimorbidity and Critical Care Neurosurgery: Minimizing Major Perioperative Cardiopulmonary Complications

With increasing prevalence of chronic diseases, multimorbid patients have become commonplace in the neurosurgical intensive care unit (neuro-ICU), offering unique management challenges. By reducing physiological reserve and interacting with one another, chronic comorbidities pose a greatly enhanced risk of major postoperative medical complications, especially cardiopulmonary complications, which ultimately exert a negative impact on neurosurgical outcomes. These premises underscore the importance of perioperative optimization, in turn requiring a thorough preoperative risk stratification, a basic understanding of a multimorbid patient’s deranged physiology and a proper appreciation of the potential of surgery, anesthesia and neurocritical care interventions to exacerbate comorbid pathophysiologies. This knowledge enables neurosurgeons, neuroanesthesiologists and neurointensivists to function with a heightened level of vigilance in the care of these high-risk patients and can inform the perioperative neuro-ICU management with individualized strategies able to minimize the risk of untoward outcomes. This review highlights potential pitfalls in the intra- and postoperative neuro-ICU period, describes common preoperative risk stratification tools and discusses tailored perioperative ICU management strategies in multimorbid neurosurgical patients, with a special focus on approaches geared toward the minimization of postoperative cardiopulmonary complications and unplanned reintubation.

Non-Invasive Versus Invasive Blood Pressure Monitoring in Patients During Laparoscopic Bariatric Surgery: a Prospective Method-Comparison Study

Introduction: Intra-operative blood pressure monitoring in morbidly obese patients using standard non-invasive blood pressure (NIBP) oscillometric technique with upper arm cuffing is often inaccurate. Invasive arterial blood pressure (IABP) monitoring is the gold standard but is not without complications. The purpose of this study was done to assess the degree of agreement between the forearm and upper arm NIBP with the IABP during laparoscopic bariatric surgery. Patients and Methodsm The study was conducted in our university hospital. A total of 36 morbidly obese patients undergoing laparoscopic bariatric surgery were studied. The radial artery was cannulated for IABP monitoring on one upper limb while NIBP monitoring was done on the contralateral upper arm and forearm. The NIBP and its corresponding IABP readings were recorded at selected time points at 10 minutes post-induction; 5, 15, and 30 minutes post-insufflation and 15 minutes post- exsufflation. Results: The mean arterial pressure (MAP) has narrower limits of agreement compared to the systolic blood pressure (SBP) and diastolic blood pressure (DBP) for each method of measurement used. Forearm NIBP showed better agreement with IABP compared to upper arm NIBP. Repeated measures ANOVA showed a similar pattern of changes in SBP, DBP, and MAP measured by NIBP and IABP during the surgery. Conclusion: Similar patterns of blood pressure changes were observed with IABP, upper arm, and forearm NIBP measurements at all time points. The forearm NIBP showed better agreement to IABP as compared to upper arm NIBP and may be adequate to monitor patterns of blood pressure changes during laparoscopic bariatric surgery. Keywords: Weight loss surgery, intraoperative BP monitoring, Obesity, Hypertension, Forearm and upper arm BP monitoring, IABP, NIBP

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.

Comparative Evaluation of the Effects of Three Different Recruitment Maneuvers during Laparoscopic Bariatric Surgeries of Morbid Obese Patients on Cardiopulmonary Indices

Background:

Laparoscopic bariatric surgeries in morbid obese patients may be associated with atelectasis, hypercapnia, and hypoxemia, intra and postoperatively. Several strategies are used for the prevention of these consequences. This study aimed to examine the effects of three different recruitment maneuvers comparatively during surgery and the influence of the maneuvers on some cardiopulmonary indices.

Materials and Methods:

In a clinical trial, ninety participants of laparoscopic surgery with body mass index higher than 40 were randomly divided into three equal groups. The first group was subject to 10 cmH₂O positive end-expiratory pressure (PEEP) during surgery, the second group, after venting the pneumoperitoneum, had 5 deep breaths with a positive pressure of 40 cmH₂O, and the third group was subject to both. Some pulmonary and hemodynamic parameters were measured every 15 min and compared between three groups.

Results:

The average of peak airway pressure, plateau airway pressure, and SpO₂ static and dynamic compliance between the three groups had no meaningful differences (P > 0.05), but PaCO₂in the second group was statistically higher than the other two groups (P < 0.05).

Conclusion:

Multiple deep breaths alone are not as effective as PEEP or PEEP plus MDB in preventing adverse pulmonary effects in laparoscopic bariatric surgeries of morbid obese patients.

Intraoperative Ventilation of Morbidly Obese Patients Guided by Transpulmonary Pressure

BACKGROUND

Bariatric surgery has proven a successful approach in the treatment of morbid obesity and its concomitant diseases such as diabetes mellitus and arterial hypertension. Aiming for optimal management of this challenging patient cohort, tailored concepts directly guided by individual patient physiology may outperform standardized care. Implying esophageal pressure measurement and electrical impedance tomography-increasingly applied monitoring approaches to individually adjust mechanical ventilation in challenging circumstances like acute respiratory distress syndrome (ARDS) and intraabdominal hypertension-we compared our institutions standard ventilator regimen with an individually adjusted positive end expiratory pressure (PEEP) level aiming for a positive transpulmonary pressure (P _L) throughout the respiratory cycle.

METHODS

After obtaining written informed consent, 37 patients scheduled for elective bariatric surgery were studied during mechanical ventilation in reverse Trendelenburg position. Before and after installation of capnoperitoneum, PEEP levels were gradually raised from a standard value of 10 cm H₂O until a P _L of 0 +/- 1 cm H₂O was reached. Changes in ventilation were monitored by electrical impedance tomography (EIT) and arterial blood gases (ABGs) were obtained at the end of surgery and 5 and 60 min after extubation, respectively.

RESULTS

To achieve the goal of a transpulmonary pressure (P _L) of 0 cm H₂O at end expiration, PEEP levels of 16.7 cm H₂O (95% KI 15.6-18.1) before and 23.8 cm H₂O (95% KI 19.6-40.4) during capnoperitoneum were necessary. EIT measurements confirmed an optimal PEEP level between 10 and 15 cm H₂O before and 20 and 25 cm H₂O during capnoperitoneum, respectively. Intra- and postoperative oxygenation did not change significantly.

CONCLUSION

Patients during laparoscopic bariatric surgery require high levels of PEEP to maintain a positive transpulmonary pressure throughout the respiratory cycle. EIT monitoring allows for non-invasive monitoring of increasing PEEP demand during capnoperitoneum. Individually adjusted PEEP levels did not result in improved postoperative oxygenation.

Analysis of quality of life among asthmatic individuals with obesity and its relationship with pulmonary function: cross-sectional study

CONTEXT AND OBJECTIVE:

The combined effect of obesity and asthma may lead to significant impairment of quality of life (QOL). The aim here was to evaluate the prevalence of asthma among obese individuals, characterize the severity of impairment of quality of life and measure its relationship with pulmonary function.

DESIGN AND SETTING:

Observational cross-sectional study in public university hospital.

METHODS:

Morbidly obese individuals (body mass index &gt; 40 kg/m2) seen in a bariatric surgery outpatient clinic and diagnosed with asthma, were included. Anthropometric data were collected, the Standardized Asthma Quality of Life Questionnaire (AQLQ(S)) was applied and spirometry was performed. The subjects were divided into two groups based on the median of the score in the questionnaire (worse &lt; 4 and better &gt; 4) and were compared regarding anthropometric data and pulmonary function.

RESULTS:

Among the 4791 individuals evaluated, 219 were asthmatic; the prevalence of asthma was 4.57%. Of these, 91 individuals were called to start multidisciplinary follow-up during the study period, of whom 82 answered the questionnaire. The median score in the AQLQ(S) was 3.96 points and, thus, the individuals were classified as having moderate impairment of their overall QOL. When divided according to better or worse QOL, there was a statistically difference in forced expiratory flow (FEF) 25-75%, with higher values in the better QOL group.

CONCLUSION:

The prevalence of asthma was 4.57% and QOL was impaired among the asthmatic obese individuals. The worst QOL domain related to environmental stimuli and the best QOL domain to limitations of the activities. Worse QOL was correlated with poorer values for FEF 25-75%.

Modern Spirometry Supports Anesthetic Management in Small Animal Clinical Practice: A Case Series

Modern spirometry, like no other monitoring technique, allows insight into breath-to-breath respiratory mechanics. Spirometers continuously measure volume, airway pressure, and flow while calculating and continuously displaying respiratory system compliance and resistance in the form of loops. The aim of this case series is to show how observation of spirometric loops, similar to electrocardiogram or CO2 curve monitoring, can improve safety of anesthetic management in small animals. Spirometric monitoring cases described in this case series are based on use of the anaesthesia monitor Capnomac Ultima with a side stream spirometry sensor. The cases illustrate how recognition and understanding of spirometric loops allows for easy diagnosis of iatrogenic pneumothorax, incorrect ventilator settings, leaks in the system, kinked or partially obstructed endotracheal tube, and spontaneous breathing interfering with intermittent positive-pressure ventilation. The case series demonstrates the potential of spirometry to improve the quality and safety of anesthetic management, and, hence, its use can be recommended during intermittent positive-pressure ventilation and procedures in which interference with ventilation can be expected.

I-gel as an alternative to endotracheal tube in adult laparoscopic surgeries: A comparative study

BACKGROUND:

The tracheal tube is always considered to be the gold standard for laparoscopic surgeries. As conventional laryngoscopy guided endotracheal intubation evokes significant hypertension and tachycardia, we have used I-gel, second generation extraglottic airway device, in an attempt to overcome these drawbacks. We conducted this study to compare haemodynamic changes during insertion, efficacy of ventilation, and complications with the use of I-gel when compared with endotracheal tube (ETT) in laparoscopic surgeries.

MATERIALS AND METHODS:

A total of 60 American Society of Anaesthesiologists physical status I and II adult patients undergoing elective laparoscopic surgeries were randomly allocated to one of the two groups of 30 patients each: Group-A (I-gel) in which patients airway was secured with appropriate sized I-gel, and Group-B (ETT) in which patients airway was secured with laryngoscopy - guided endotracheal intubation. Ease, attempts and time for insertion of airway device, haemodynamic and ventilatory parameters at different time intervals, and attempts for gastric tube insertion, and perioperative complications were recorded.

RESULTS:

There was significant rise in pulse rate and mean blood pressure during insertion with use of ETT when compared to I-gel. Furthermore, time required for I-gel insertion was significantly less when compared with ETT. However ease and attempts for airway device insertion, attempts for gastric tube insertion and efficacy of ventilation were comparable between two groups.

CONCLUSION:

We concluded that I-gel requires less time for insertion with minimal haemodynamic changes when compared to ETT. I-gel also provides adequate positive-pressure ventilation, comparable with ETT. Hence I-gel can be a safe and suitable alternative to ETT for laparoscopic surgeries.

Analysis of the prevalence of atelectasis in patients undergoing bariatric surgery

BACKGROUND AND OBJECTIVE

To observe the prevalence of atelectasis in patients undergoing bariatric surgery and the influence of the body mass index (BMI), gender and age on the prevalence of atelectasis.

METHOD

Retrospective study of 407 patients and reports on chest X-rays carried out before and after bariatric surgery over a period of 14 months. Only patients who underwent bariatric surgery by laparotomy were included.

RESULTS

There was an overall prevalence of 37.84% of atelectasis, with the highest prevalence in the lung bases and with greater prevalence in women (RR=1.48). There was a ratio of 30% for the influence of age for individuals under the age of 36, and of 45% for those older than 36 (RR=0.68). There was no significant influence of BMI on the prevalence of atelectasis.

CONCLUSION

The prevalence of atelectasis in bariatric surgery is 37% and the main risk factors are being female and aged over 36 years.

Intraoperative positive end-expiratory pressure evaluation using the intratidal compliance-volume profile

BACKGROUND

Lung-protective mechanical ventilation during general surgery including the application of PEEP can reduce postoperative pulmonary complications. In a prospective clinical observation study, we evaluated volume-dependent respiratory system compliance in adult patients undergoing ear-nose-throat surgery with ventilation settings chosen empirically by the attending anaesthetist.

METHODS

In 40 patients, we measured the respiratory variables during intraoperative mechanical ventilation. All measurements were subdivided into 5 min intervals. Dynamic compliance (CRS) and the intratidal volume-dependent CRS curve was calculated for each interval and classified into one of the six specific compliance profiles indicating intratidal recruitment/derecruitment, overdistension or all. We retrospectively compared the occurrences of the respective compliance profiles at PEEP levels of 5 cm H2O and at higher levels.

RESULTS

The attending anaesthetists set the PEEP level initially to 5 cm H2O in 29 patients (83%), to 7 cm H2O in 5 patients (14%), and to 8 cm H2O in 2 patients (6%). Across all measurements the mean CRS was 61 (11) ml cm H2O(-1) (40-86 ml cm H2O(-1)) and decreased continuously during the procedure. At PEEP of 5 cm H2O the compliance profile indicating strong intratidal recruitment/derecruitment occurred more often (18.6%) compared with higher PEEP levels (5.5%, P<0.01). Overdistension was practically never observed.

CONCLUSIONS

In most patients, a PEEP of 5 cm H2O during intraoperative mechanical ventilation is too low to prevent intratidal recruitment/derecruitment. The analysis of the intratidal compliance profile provides the rationale to individually titrate a PEEP level that stabilizes the alveolar recruitment status of the lung during intraoperative mechanical ventilation.

TRIAL REGISTRATION NUMBER

DRKS00004286.

Effects of pneumoperitoneal pressure and position changes on respiratory mechanics during laparoscopic colectomy

Background

This study was designed to assess the effects of pneumoperitoneal pressure (PP) and positional changes on the respiratory mechanics during laparoscopy assisted colectomy.

Methods

Peak inspiratory pressure, plateau pressure, lung compliance, and airway resistance were recorded in PP of 10 mmHg and 15 mmHg, with the position change in 5 steps: head-down at 20°, head-down at 10°, neutral position, head-up at 10° and head-up at 20°.

Results

When the patient was placed head-down, the position change accentuated the effects of pneumoperitoneum on respiratory mechanics. However, when the patient was placed in a head-up position during pneumoperitoneum the results showed no pattern. In the 20° head-up position with the PP being 10 mmHg, the compliance increased from 30.6 to 32.6 ml/cmH₂O compared with neutral position (P = 0.002). However with the PP being 15 mmHg, the compliance had not changed compared with neutral position (P = 0.989). In 20° head-down position with the PP of 10 mmHg, the compliance was measured as 24.2 ml/cmH₂O. This was higher than that for patients in the 10° head-down position with a PP of 15 mmHg, which was recorded as 21.2 ml/cmH₂O. Also in the airway resistance, the patient in the 20° head-down position with the PP of 10 mmHg showed 15.8 cmH₂O/L/sec, while the patient in the 10° head-down position with the PP of 15 mmHg showed 16.2 cmH₂O/L/sec of airway resistance. These results were not statistically significant but still suggested that the head-down position accentuated the effects of pneumoperitoneum on respiratory mechanics.

Conclusions

Our results suggest that respiratory mechanics are affected by the patient position and the level of PP - the latter having greater effect.

Laparoscopic approach to acute abdomen from the Consensus Development Conference of the Società Italiana di Chirurgia Endoscopica e nuove tecnologie (SICE), Associazione Chirurghi Ospedalieri Italiani (ACOI), Società Italiana di Chirurgia (SIC), Società Italiana di Chirurgia d'Urgenza e del Trauma (SICUT), Società Italiana di Chirurgia nell'Ospedalità Privata (SICOP), and the European Association for Endoscopic Surgery (EAES)

BACKGROUND

In January 2010, the SICE (Italian Society of Endoscopic Surgery), under the auspices of the EAES, decided to revisit the clinical recommendations for the role of laparoscopy in abdominal emergencies in adults, with the primary intent being to update the 2006 EAES indications and supplement the existing guidelines on specific diseases.

METHODS

Other Italian surgical societies were invited into the Consensus to form a panel of 12 expert surgeons. In order to get a multidisciplinary panel, other stakeholders involved in abdominal emergencies were invited along with a patient's association. In November 2010, the panel met in Rome to discuss each chapter according to the Delphi method, producing key statements with a grade of recommendations followed by commentary to explain the rationale and the level of evidence behind the statements. Thereafter, the statements were presented to the Annual Congress of the EAES in June 2011.

RESULTS

A thorough literature review was necessary to assess whether the recommendations issued in 2006 are still current. In many cases new studies allowed us to better clarify some issues (such as for diverticulitis, small bowel obstruction, pancreatitis, hernias, trauma), to confirm the key role of laparoscopy (such as for cholecystitis, gynecological disorders, nonspecific abdominal pain, appendicitis), but occasionally previous strong recommendations have to be challenged after review of recent research (such as for perforated peptic ulcer).

CONCLUSIONS

Every surgeon has to develop his or her own approach, taking into account the clinical situation, her/his proficiency (and the experience of the team) with the various techniques, and the specific organizational setting in which she/he is working. This guideline has been developed bearing in mind that every surgeon could use the data reported to support her/his judgment.

[The role of respiratory physiotherapy in the lung function of obese patients undergoing bariatric surgery. A review]

INTRODUCTION

Obesity, considered a new worldwide epidemic, is characterised by excess adipose tissue and contributes to a series of chronic diseases and increased mortality. Obesity associated to surgical procedure in these patients makes respiratory physiotherapy a must to recover lung function and prevent postoperative pulmonary complications.

AIMS

To assess the effects of respiratory physiotherapy on the lung function of obese patients undergoing weight loss surgery.

MATERIAL AND METHODS

We conducted a literature review October 2008-June 2009 of data which had been published over the last thirty years and which was available on the Medline, Pubmed ans Scielo databases.

CONCLUSION

Pre- and postoperative respiratory physiotherapy is vital for patients undergoing weight loss surgery irrespective of technique used, as it can prevent pulmonary complications inherent in the surgical procedure and aid lung function recovery.

Effects of four intraoperative ventilatory strategies on respiratory compliance and gas exchange during laparoscopic gastric banding in obese patients

BACKGROUND

Respiratory function is impaired in obese patients undergoing laparoscopic surgery. This study was performed to determine whether repeated lung recruitment combined with PEEP improves respiratory compliance and arterial partial pressure of oxygen (Pa(O2)) in obese patients undergoing laparoscopic gastric banding.

METHODS

Sixty patients with BMI >30 kg m(-2) were randomized, after induction of pneumoperitoneum, to receive either PEEP of 10 cm H2O (Group P), inspiratory pressure of 40 cm H2O for 15 s once (Group R), Group R recruitment followed by PEEP 10 cm H2O (Group RP), or Group RP recruitment but with the inspiratory manoeuvre repeated every 10 min (Group RRP). Static respiratory compliance and Pa(O2) were determined after intubation, 10 min after pneumoperitoneum (before lung recruitment), and every 10 min thereafter (after recruitment). Results are presented as mean (SD).

RESULTS

Pneumoperitoneum decreased respiratory compliance from 48 (3) to 30 (1) ml cm H2O(-1) and decreased Pa(O2) from 12.4 (0.3) to 8.8 (0.3) kPa in all groups (P<0.01). Immediately after recruitment, compliance was 32 (1), 32 (2), 40 (2), and 40 (1) ml cm H2O(-1) and Pa(O2) was 9.1 (0.3), 9.1 (0.1), 11.9 (0.1), and 11.9 (0.1) kPa in Groups P, R, RP, and RRP, respectively (P<0.01). Ten and 20 min later, Pa(O2) in Group R decreased to 9.2 (0.1) kPa and compliance in Group PR decreased to 33 (2) ml cm H2O(-1), respectively (P<0.01).

CONCLUSIONS

Group RRP recruitment strategy was associated with the best intraoperative respiratory compliance and Pa(O2) in obese patients undergoing laparoscopic gastric banding.

Best practice recommendations for anesthetic perioperative care and pain management in weight loss surgery

OBJECTIVE

To develop evidence-based recommendations that optimize the safety and efficacy of perioperative anesthetic care and pain management in weight loss surgery (WLS) patients.

RESEARCH METHODS AND PROCEDURES

This Task Group examined the scientific literature on anesthetic perioperative care and pain management published in MEDLINE from January 1994 to March 2004. We also reviewed additional data from other sources (e.g., book chapters). The search yielded 195 abstracts, of which 35 references were reviewed in detail. Task Group consensus was used to provide recommendations when evidence in the literature was insufficient.

RESULTS

We developed anesthesia practice and patient safety advisory recommendations for preoperative evaluation, intraoperative management, and postoperative care and pain management of WLS patients. We also provided suggestions related to medical error reduction and systems improvements, credentialing, and future research.

DISCUSSION

Obesity-related comorbidities including obstructive sleep apnea place WLS patients at increased risk for complications perioperatively. Regarding perioperative safety and outcomes, conclusive evidence beyond the accepted standard of care in the reviewed literature is limited. Few reports specifically address the perioperative needs of severely obese patients. In this advisory, we synthesize current knowledge and make best practice recommendations for perioperative care and pain management in WLS patients. These recommendations require periodic review as further medical knowledge and evidence evolve.

Volumes, capacidades pulmonares e força muscular respiratória no pós-operatório de gastroplastia

INTRODUÇÃO: A gastroplastia tem sido cada vez mais indicada no tratamento de obesos mórbidos, pacientes nos quais podemos identificar alteração pronunciada de volumes e capacidades pulmonares. OBJETIVO: Avaliar o comportamento dos volumes e capacidades pulmonares, força muscular respiratória, padrão respiratório e as possíveis complicações pulmonares pós-operatórias. MÉTODO: Vinte e um pacientes (três homens) com média de idade de 39 ± 9,7 anos, média de índice de massa corpórea de 50,4 Kg/m², candidatos à gastroplastia, foram avaliados no pré-operatório, primeiro, terceiro e quinto dias de pós-operatório e submetidos a mensuração de volume corrente, capacidade vital, volume minuto, pressões máximas expiratória e inspiratória, e circunferências abdominal e torácica. Observou-se a ocorrência de complicações pulmonares pós-operatórias e mortalidade. RESULTADOS: No primeiro e terceiro dias de pós-operatório houve queda de 47% e 30,5% na capacidade vital, 18% e 12,5% no volume minuto, 28% e 21% no volume corrente, 47% e 32% no índice diafragmático, 51% e 26% na pressão inspiratória máxima, e 39,5% e 26% na pressão expiratória máxima, respectivamente (p < 0,05). No quinto dia de pós-operatório, todos os valores das variáveis analisadas apresentaram-se maiores que os do primeiro pós-operatório, evidenciando um crescimento linear, com retorno total aos seus valores pré-operatórios apenas de volume corrente, volume minuto e índice diafragmático. Houve uma incidência de complicações pulmonares pós-operatórias de 4,7% e não houve óbitos. CONCLUSÃO: Pacientes submetidos a gastroplastia apresentam redução da função pulmonar, evidenciando um comportamento bastante semelhante ao já observado no pós-operatório de outras cirurgias do andar superior do abdome.

Anesthesia in the obese patient: Pharmacokinetic considerations

The prevalence of obesity has increased 15% up to 20% and represents an important challenge for the anesthesiologist in drug-dosing management. The aim of this work is to provide an overview on physiological changes and pharmacokinetic implications of obesity for the anesthesiologist. Obesity increases both fat and lean masses; however, the percentage of fat tissue increases more than does the lean mass, affecting the apparent volume of distribution of anesthetic drugs according to their lipid solubility. Benzodiazepine loading doses should be adjusted on actual weight, and maintenance doses should be adjusted on ideal body weight. Thiopental sodium and propofol dosages are calculated on total body weight (TBW). The loading dose of lipophilic opioids is based on TBW, whereas maintenance dosages should be cautiously reduced because of the higher sensitivity of the obese patient to their depressant effects. Pharmacokinetic parameters of muscle relaxants are minimally affected by obesity, and their dosage is based on ideal rather than TBW. Inhalation anesthetics with very low lipid solubility, such as sevoflurane and desflurane, allow for quick modification of the anesthetic plan during surgery and rapid emergence at the end of surgery, hence representing very flexible anesthetic drugs for use in this patient population. Drug dosing is generally based on the volume of distribution for the loading dose and on the clearance for maintenance. In the obese patient, the volume of distribution is increased if the drug is distributed both in lean and fat tissues whereas the anesthetic drug clearance is usually normal or increased.

The physiologic effects of pneumoperitoneum in the morbidly obese

OBJECTIVE

To review the physiologic effects of carbon dioxide (CO2) pneumoperitoneum in the morbidly obese.

SUMMARY BACKGROUND DATA

The number of laparoscopic bariatric operations performed in the United States has increased dramatically over the past several years. Laparoscopic bariatric surgery requires abdominal insufflation with CO2 and an increase in the intraabdominal pressure up to 15 mm Hg. Many studies have demonstrated the adverse consequences of pneumoperitoneum; however, few studies have examined the physiologic effects of pneumoperitoneum in the morbidly obese.

METHODS

A MEDLINE search from 1994 to 2003 was performed using the key words morbid obesity, laparoscopy, bariatric surgery, pneumoperitoneum, and gastric bypass. The authors reviewed papers evaluating the physiologic effects of pneumoperitoneum in morbidly obese subjects undergoing laparoscopy. The topics examined included alteration in acid-base balance, hemodynamics, femoral venous flow, and hepatic, renal, and cardiorespiratory function.

RESULTS

Physiologically, morbidly obese patients have a higher intraabdominal pressure at 2 to 3 times that of nonobese patients. The adverse consequences of pneumoperitoneum in morbidly obese patients are similar to those observed in nonobese patients. Laparoscopy in the obese can lead to systemic absorption of CO2 and increased requirements for CO2 elimination. The increased intraabdominal pressure enhances venous stasis, reduces intraoperative portal venous blood flow, decreases intraoperative urinary output, lowers respiratory compliance, increases airway pressure, and impairs cardiac function. Intraoperative management to minimize the adverse changes include appropriate ventilatory adjustments to avoid hypercapnia and acidosis, the use of sequential compression devices to minimizes venous stasis, and optimize intravascular volume to minimize the effects of increased intraabdominal pressure on renal and cardiac function.

CONCLUSIONS

Morbidly obese patients undergoing laparoscopic bariatric surgery are at risk for intraoperative complications relating to the use of CO2 pneumoperitoneum. Surgeons performing laparoscopic bariatric surgery should understand the physiologic effects of CO2 pneumoperitoneum in the morbidly obese and make appropriate intraoperative adjustments to minimize the adverse changes.

Respiratory mechanics in morbid obese patients with chronic obstructive pulmonary disease and hypertension during pneumoperitoneum

BACKGROUND AND OBJECTIVE

To evaluate the effects of pneumoperitoneum and the reverse Trendelenburg position on respiratory mechanics and blood-gases in morbid obese patients with chronic obstructive pulmonary disease and hypertension.

METHODS

Sixteen morbid obese patients with chronic obstructive pulmonary disease and hypertension were studied. Mean arterial pressure, heart rate, respiratory resistance, dynamic respiratory compliance and peak inspiratory pressures were measured at four time points: 5 min after induction of anaesthesia (T1), 5 min after insufflation of the peritoneum (T2), 5 min after adoption of a 20 degrees reverse Trendelenburg position (T3), and 5 min after deflation of the peritoneum (T4). Arterial blood-gas status was measured at the same measuring points.

RESULTS

Respiratory compliance was 40 +/- 12, 28 +/- 8, 32 +/- 8 and 37 +/- 11 mL cm H2O(-1) in T1, T2, T3 and T4, respectively. The changes were significant at T2, T3 and T4. Airway resistance and peak inspiratory pressures showed comparable changes throughout the study with that of respiratory compliance. Haemodynamic measurements showed no clinically significant changes in this study.

CONCLUSIONS

In morbid obese patients with chronic obstructive pulmonary disease and hypertension, a 20 degrees reverse Trendelenburg position improved respiratory mechanics and oxygenation without any apparent adverse effects on haemodynamics during laparoscopic gastric banding surgery.

The effects of tidal volume and respiratory rate on oxygenation and respiratory mechanics during laparoscopy in morbidly obese patients

Morbidly obese (MO) patients undergoing laparoscopy have lower PaO(2) compared with normal-weight (NW) patients. We hypothesized that increases in tidal volume (V(T)) or respiratory rate (RR) would improve oxygenation. All measurements were performed at: 1) baseline: V(T) 600-700 mL and 10 breaths/min, 2) double V(T): V(T) 1200-1400 mL and 10 breaths/min, and 3) double rate: V(T) 600-700 mL and 20 breaths/min. We calculated static respiratory system compliance (Cst,rs) and inspiratory resistance (RI,rs). End-tidal CO(2) was measured with a mass spectrometer, and PaO(2) and PaCO(2) with a continuous blood gas monitor. Supine anesthetized MO patients had 29% lower Cst,rs than the NW patients (P < 0.05). Positioning patients head-up or head-down before pneumoperitoneum did not significantly affect Cst,rs in either group (P = 0.8). Doubling the V(T), but not RR, increased Cst,rs in both groups. Pneumoperitoneum caused large decreases in Cst,rs in both groups (both P < 0.001). During pneumoperitoneum, changing the body position, V(T), or RR did not further affect Cst,rs in either group (P > 0.7). Before pneumoperitoneum, RI,rs was higher in the MO patients compared with the NW patients regardless of body position (P = 0.01). Doubling either RR or V(T) before pneumoperitoneum did not change RI,rs in either group. After pneumoperitoneum, RI,rs increased in both the head-down and head-up positions (P < 0.05), but not in the supine position. Regardless of the conditions studied, alveolar-arterial difference in oxygen tension was always significantly higher in MO patients (P < 0.05). The alveolar-arterial difference in oxygen tension was not affected by body position, pneumoperitoneum, or the mode of ventilation. Arterial oxygenation during laparoscopy was affected only by body weight and could not be improved by increasing either the V(T) or RR.

IMPLICATIONS

Morbid obesity decreases arterial oxygenation and respiratory system compliance. During laparoscopy, arterial oxygenation is affected only by the patient's body weight. Increases in tidal volume or respiratory rate do not improve arterial oxygenation.

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

We studied the effect of morbid obesity, 20 mm Hg pneumoperitoneum, and body posture (30 degrees head down and 30 degrees head up) on respiratory system mechanics, oxygenation, and ventilation during laparoscopy. We hypothesized that insufflation of the abdomen with CO(2) during laparoscopy would produce more impairment of respiratory system mechanics and gas exchange in the morbidly obese than in patients of normal weight. The static respiratory system compliance and inspiratory resistance were computed by using a Servo Screen pulmonary monitor. A continuous blood gas monitor was used to monitor real-time PaCO(2) and PaO(2), and the ETCO(2) was recorded by mass spectrometry. Static compliance was 30% lower and inspiratory resistance 68% higher in morbidly obese supine anesthetized patients compared with normal-weight patients. Whereas body posture (head down and head up) did not induce additional large alterations in respiratory mechanics, pneumoperitoneum caused a significant decrease in static respiratory system compliance and an increase in inspiratory resistance. These changes in the mechanics of breathing were not associated with changes in the alveolar-to-arterial oxygen tension difference, which was larger in morbidly obese patients. Before pneumoperitoneum, morbidly obese patients had a larger ventilatory requirement than the normal-weight patients to maintain normocapnia (6.3 +/- 1.4 L/min versus 5.4 +/- 1.9 L/min, respectively; P = 0.02). During pneumoperitoneum, morbidly obese, supine, anesthetized patients had less efficient ventilation: a 100-mL increase of tidal volume reduced PaCO(2) on average by 5.3 mm Hg in normal-weight patients and by 3.6 mm Hg in morbidly obese patients (P = 0.02). In conclusion, respiratory mechanics during laparoscopy are affected by obesity and pneumoperitoneum but vary little with body position. The PaO(2) was adversely affected only by increased body weight.

IMPLICATIONS

Morbid obesity significantly decreases respiratory system compliance and increases inspiratory resistance. Increased body weight, and not altered mechanics of breathing, was associated with worse PaO(2) during laparoscopy.

The effects of abdominal opening on respiratory mechanics during general anesthesia in normal and morbidly obese patients: a comparative study

Morbid obesity has a profound effect on respiratory mechanics and gas exchange. However, most studies were performed in morbidly obese patients before or after anesthesia. We tested the hypothesis that anesthesia and abdominal opening could modify the elastic and resistive properties of the respiratory system. Eleven morbidly obese and eight normal-weight patients scheduled for gastric binding and cancer treatment, respectively, under laparotomy were studied. Respiratory mechanics, partitioned into its lung and chest wall components, were investigated during surgery by means of the end-inspiratory inflation occlusion method and esophageal balloon at five time points. Static respiratory and lung compliance were markedly reduced in obese patients; on the contrary, static compliance of chest wall presented comparable values in both groups. Obese patients also presented higher resistances of the total respiratory system, lung and chest wall, as well as "additional" lung resistance. Mainly in obese patients, laparotomy provoked a significant increase in lung compliance and decrease in "additional" lung resistance 1 h after the peritoneum was opened, which returned to original values after the peritoneum had been closed (P < 0.005). In obese patients, low respiratory compliance and higher airway resistance were mainly determined by the lung component.

[Abdominal compartment syndrome]

French physicians dealing with abdominal emergencies are not very familiar with the abdominal compartment syndrome (ACS). Increased abdominal pressure has deleterious consequences on local (intestine, liver, kidney) circulation, leading to death in the absence of correct treatment. Abdominal trauma and ruptured aortic aneurism are the main causes of ACS. Clinical presentation may be misleading: respiratory failure, oliguria or circulatory symptoms are often predominant. Abdominal palpation is inefficient for evaluating intra-abdominal pressure (IAP); only measurement of cystic pressure allows precise evaluation of IAP. Abdominal decompression is the treatment of choice. It must be performed as soon as IAP exceeds 25 mmHg. The procedure may be risky with a high incidence of severe complications when ischaemic territories are reperfused. Recent data underline the importance of compensation of hypovolemia before decompression. Abdominal closure may necessitate various techniques (aponevrotomy, Bogota bags, etc.). At any rate, IAP must remain low at the end of the procedure. In case of suspicion of ACS, early measurement of IAP is mandatory. If pressure is over 25 mmHg, a decompressive procedure must be initiated.

Surgical aspects and future developments of laparoscopy

Laparoscopy has revolutionized surgery and in the process influenced the practice of anesthesiology. This article reviews several minimal access procedures that have been accepted into practice, are gaining acceptance, or remain investigational. Absolute contraindications to laparoscopy have been emphasized. As the threshold for primary care physicians to refer sicker and sicker patients for surgery decreases, it is crucial for the anesthesiologist to understand physiologic stresses of pneumoperitoneum and the nuances of laparoscopic surgery. The anesthesiologist also can be recruited to adjust insufflation pressures, tweak images on monitors, rotate and position the patient, or pass balloons and bougies. With patient and surgeon expectation of no pain or nausea and early discharge, anesthetic choices become vital for the ultimate success of the procedure.

The effects of the reverse trendelenburg position on respiratory mechanics and blood gases in morbidly obese patients during bariatric surgery

Anesthesia adversely affects respiratory function, particularly in morbidly obese patients. Although many studies have been performed to determine the optimal ventilatory settings in these patients, this question has not been answered. The aim of this study was to evaluate the effect of reverse Trendelenburg position (RTP) on gas exchange and respiratory mechanics in 15 obese patients undergoing biliopancreatic diversion. A standardized anesthetic regimen was used and patients were examined at standard times: 1) after tracheal intubation, 2) after laparotomy, 3) after positioning of subcostal retractors, 4) with retractors in RTP. The measurements of respiratory mechanics were repeated for a wide range of tidal volumes by using the technique of rapid occlusion during constant flow inflation. We noted a wide alveolar-arterial oxygen difference [P(A-a)O(2)] in all patients, particularly during Phase 3. When the patients were placed in RTP, P(A-a)O(2) showed a significant improvement and a return toward baseline values. As for mechanics, total respiratory system compliance was significantly higher in RTP than in the other phases. In conclusion, our data suggest that RTP is an appropriate intraoperative posture for obese subjects because it causes minimal arterial blood pressure changes and improves oxygenation.

Extending the limits: minimally invasive surgery

Minimally invasive technology is being applied to an increasing number of surgical procedures. It remains to be seen which techniques will eventually become a 'gold standard' as has the laparoscopic cholecystectomy, and which will fall by the wayside. In the meantime, anesthesiologists must be aware of the unique requirements and complications of laparoscopic surgery.