Evaluation of intra-abdominal pressure after laparoscopic and open gastric bypass

The impact of minimally invasive surgical approaches on surgical-site infections

We performed a literature review to describe the risk of surgical-site infection (SSI) in minimally invasive surgery (MIS) compared to standard open surgery. Most studies reported decreased SSI rates among patients undergoing MIS compared to open procedures. However, many were observational studies and may have been affected by selection bias. MIS is associated with reduced risk of surgical-site infection compared to standard open surgery and should be considered when feasible.

A prospective randomized double-blind study comparing the dose-response curves of epidural ropivacaine for labor analgesia initiation between parturients with and without obesity

Background: Previous studies have explored the median effective concentration (EC50) of ropivacaine for labor epidural analgesia in parturients with obesity. However, the clinical relevance of the 90% effective concentration (EC90) remains unclear. This study aimed to determine and compare the dose-response curve of epidural ropivacaine for labor analgesia between parturients with and without obesity. Methods: Parturients were divided into two groups based on body mass index (BMI): group N, consisting of parturients with BMI <30 kg/m2, and group O, consisting of parturients with BMI >30 kg/m2. Within each group, the patients were randomized to receive one of five concentrations (0.0375%, 0.075%, 0.1125%, 0.15%, or 0.1875%) of epidural ropivacaine for labor analgesia. Analgesia was induced with a loading dose of 15 mL of the assigned concentration. Visual analogue scale (VAS) scores were recorded at baseline and 30 min post-dose to calculate the response (%) using the formula [(baseline VAS pain score-VAS pain score at 30 min)/baseline VAS pain score] ×100%. The EC50 and EC90 values were determined via nonlinear regression analysis. Results: The EC50 and EC90 values of ropivacaine were 0.061% (95% confidence interval [CI], 0.056%-0.066%) and 0.177% (95% CI, 0.152%-0.206%) in group N and 0.056% (95% CI, 0.051%-0.061%) and 0.161% (95% CI, 0.138%-0.187%) in group O, respectively. No significant differences were observed in the EC50 and EC90 values between the two groups (p-values = 0.121 and 0.351, respectively. Conclusion: In conclusion, within the parameters of this study, our findings suggest that obesity, characterized by a mean BMI value of 30.9, does not significantly influence the EC50 and EC90 values of epidural ropivacaine for labor analgesia. Further investigations are warranted to elucidate the dose-response relationship between ropivacaine and obesity with higher BMI values. Clinical trial registration: https://www.chictr.org.cn/showproj.html?proj=190747, Identifier ChiCTR2300073273.

Impact of Morbid Obesity on Post-esophagectomy Leak Rate: a NSQIP Analysis

BACKGROUND

Morbid obesity is becoming more prevalent and is a known risk factor for esophageal cancer. Esophagectomy in this population is technically more challenging than the non-obese, thus increasing the risks of surgery. This study hypothesizes that higher body mass index (BMI) is associated with higher anastomotic leak rates after esophagectomy.

METHODS

This study is a retrospective review of patients undergoing esophagectomy in the National Surgical Quality Improvement Program (NSQIP) Targeted Esophagectomy database from 2016 to 2019. Patients were stratified by BMI < 35 versus BMI > 35, with the primary outcome being leak post-esophagectomy. Univariate analyses were performed for demographics and post-operative outcomes, and multivariate analyses were performed specifically for the primary outcome of anastomotic leak (all diagnoses and malignancy/dysplasia subgroup). This study was approved by the Institutional Review Board.

RESULTS

Of 4165 patients, 439 (10.5%) had a BMI > 35. Patients with BMI > 35 were often younger (mean age 60 vs 64 years, p < 0.001), White (p < 0.001), female (p < 0.001), non-smoker (p < 0.001), diabetic (p < 0.001), with hypertension (p < 0.001), and ASA ≥ 3 (p < 0.001). There were no differences between BMI groups with regard to indication for esophagectomy (malignancy/dysphasia vs other), conversion to open, mortality, or length of stay. The BMI > 35 cohort reported higher operative times (p < 0.001), open operative approach (p = 0.04), superficial surgical site infection (p < 0.001), return to operating room (p = 0.01), and leak (13.5% vs 10.1%, p = 0.01). BMI > 35 was not an independent predictor of leak for all diagnoses; however, the subgroup analysis of esophagectomy for malignancy/dysplasia demonstrated that BMI > 35 was predictive of leak (OR 1.42, 95% CI 1.05-1.91), as well as operative time and hypertension.

CONCLUSION

Patients with a BMI > 35 and who undergo esophagectomy have a higher rate of anastomotic leak. BMI > 35 was also an independent predictor of leak when esophagectomy was performed for malignancy/dysplasia, but not for all diagnoses. The risk of anastomotic leak should be considered in morbidly obese patients undergoing esophagectomy, particularly for malignancy.

Effects of pneumoperitoneum and patient position on intracranial pressure in obese patients undergoing laparoscopic cholecystectomy

Background/Aim: Optic nerve sheath diameter (ONSD) measurement is one of the non-invasive techniques used for intracranial pressure (ICP) measurement. ICP changes have been evaluated based on ONSD measurements during many laparoscopic surgeries. However, such analyses in the obese patient populations are limited. This study aimed at investigating the effects of pneumoperitoneum and reverse Trendelenburg and head-up position on ICP based on ONSD measurements in obese patients undergoing laparoscopic cholecystectomy. Methods: This observational study included 60 female patients who were scheduled for laparoscopic cholecystectomy. Obese patients with a body mass index (BMI) of 30 and above were assigned to Group 1, while BMI < 30 patients were assigned to Group 2. The first ONSD measurement was performed just before insufflation (T1). The second measurement was taken 5 min after insufflation (T2), the third measurement 5 min after placing patients in the reverse Trendelenburg and head-up position (T3), and the last measurement 5 min after the deflation while the reverse Trendelenburg and head-up position was maintained (T4). Results: ONSD measurements at the T2 and T3 time points in Group 1 patients were higher than in Group 2 patients (P = 0.012 versus P = 0.020). Both measurement values were higher in obese patients. In Group 1 patients, T2 and T3 measurements were significantly higher than T1 and T4 measurements (T2 > T1; P < 0.001, T2 > T4; P < 0.001, T3 > T1; P < 0.001, and T3 > T4; P < 0.001). No significant difference between T2 and T3 and between T1 and T4 measurements were found. In Group 2 patients, T2 measurements were significantly higher than the T1, T3, and T4 measurements, while T3 measurements were significantly higher than T1 and T4 measurements (T2 > T1; P < 0.001, T2 > T3; P = 0.022, T2 > T4; P < 0.001, T3 > T1; P < 0.001, and T3 > T4; P = 0.048). No significant difference between T1 and T4 measurements was noted. Conclusion: Laparoscopic cholecystectomy does not cause an increase in ICP of obese patients with limited pneumoperitoneum pressure, reverse Trendelenburg and head-up position, and controlled anesthesia.

Renal Compression in Heart Failure: The Renal Tamponade Hypothesis

Renal dysfunction is one of the strongest predictors of outcome in heart failure. Several studies have revealed that both reduced perfusion and increased congestion (and central venous pressure) contribute to worsening renal function in heart failure. This paper proposes a novel factor in the link between cardiac and renal dysfunction: "renal tamponade" or compression of renal structures caused by the limited space for expansion. This space can be limited either by the rigid renal capsule that encloses the renal interstitial tissue or by the layer of fat around the kidneys or by the peritoneal space exerting pressure on the retroperitoneal kidneys. Renal decapsulation in animal models of heart failure and acute renal ischemia has been shown effective in alleviating pressure-related injury within the kidney itself, thus supporting this concept and making it a potentially interesting novel treatment in heart failure.

The Effects of Perioperative Factors on Early Postoperative Morbidity in Bariatric Surgery

PURPOSE

This study aims to examine the predictive role of obesity-type-related indexes and perioperative intraabdominal pressure measurements for early postoperative complications following bariatric surgery.

MATERIALS AND METHODS

Sixty-seven female patients with obesity who underwent bariatric surgery (laparoscopic sleeve gastrectomy or gastric bypass) were included in this study. Obesity-related indexes (BMI, waist/hip ratio, and waist/height ratio) were calculated using patient data. Intraoperative hemodynamic measurements and intraabdominal pressure measurements were done at the beginning and at the end of the operation. Intraabdominal pressure measurements were done using both bladder port and trocar port. Patients were followed for early postoperative complications.

RESULTS

Among 67 patients included, 22 developed early postoperative complications (32.8%), mostly pulmonary (20.9%). Trans-trocar IAP measured at the beginning of the operation emerged as the single independent predictor of postoperative complications (OR, 40.3; p = 0.002). Based on ROC analysis, AUC for predicting complications was 0.955 (p < 0.01). Optimal cutoff point (≥ 14.5 mmHg) was associated with 100% sensitivity and 82% specificity. In addition, there were weak but significant positive correlations between trans-trocar IAP-beginning and BMI (r = 0.443, p < 0.001), waist/hip ratio (r = 0.434, p < 0.001), and waist/height ratio (r = 0.539, p < 0.001).

CONCLUSION

Findings of this study suggest that a high baseline intraabdominal pressure predicts a higher risk for early postoperative complications following bariatric surgery. This information would help improve patient care. Further large studies are warranted.

Obesity and anastomotic leak rates in colorectal cancer: a meta-analysis

PURPOSE

Anastomotic leak (AL) following colorectal cancer resection is associated with considerable morbidity and mortality with an impact on recurrence rates and survival. The impact of obesity on AL rates is debated. This meta-analysis aims to investigate the relationship between obesity and AL.

METHODS

A search was conducted of the PubMed/MEDLINE, and Web of Science databases and included studies were split into Western and Asian groups based on population-specific body mass index (BMI) ranges for obesity. A meta-analysis was performed to assess the impact of obesity on AL rate following colorectal cancer resection.

RESULTS

Two thousand three hundred and four articles were initially screened. Thirty-one studies totaling 32,953 patients were included. Patients with obesity had a statistically significant increase in AL rate in all Western and Asian study groups. However, this increase was only clinically significant in the rectal anastomotic subgroups-Western: 10.8% vs 8.4%, OR 1.57 (1.01-2.44) and Asian: 9.4% vs 7.4%, OR 1.58 (1.07-2.32).

CONCLUSIONS

The findings of this analysis confirm that obesity is a significant risk factor for anastomotic leak, particularly in rectal anastomoses. This effect is thought to be primarily mediated via technical difficulties of surgery although metabolic and immunological factors may also play a role. Obesity in patients undergoing restorative CRC resection should be discussed and considered as part of the pre-operative counselling.

Non-invasive measurement of pulse pressure variation using a finger-cuff method in obese patients having laparoscopic bariatric surgery

Pulse pressure variation (PPV) is a dynamic cardiac preload variable used to predict fluid responsiveness. PPV can be measured non-invasively using innovative finger-cuff systems allowing for continuous arterial pressure waveform recording, e.g., the Nexfin system [BMEYE B.V., Amsterdam, The Netherlands; now Clearsight (Edwards Lifesciences, Irvine, CA, USA)] (PPV_Finger). However, the agreement between PPV_Finger and PPV derived from an arterial catheter (PPV_ART) in obese patients having laparoscopic bariatric surgery is unknown. We compared PPV_Finger and PPV_ART at 6 time points in 60 obese patients having laparoscopic bariatric surgery in a secondary analysis of a prospective method comparison study. We used Bland–Altman analysis to assess absolute agreement between PPV_Finger and PPV_ART. The predictive agreement for fluid responsiveness between PPV_Finger and PPV_ART was evaluated across three PPV categories (PPV < 9%, PPV 9–13%, PPV > 13%) as concordance rate of paired measurements and Cohen’s kappa. The overall mean of the differences between PPV_Finger and PPV_ART was 0.5 ± 4.6% (95%-LoA − 8.6 to 9.6%) and the overall predictive agreement was 72.4% with a Cohen’s kappa of 0.53. The mean of the differences was − 0.7 ± 3.8% (95%-LoA − 8.1 to 6.7%) without pneumoperitoneum in horizontal position and 1.1 ± 4.8% (95%-LoA − 8.4 to 10.5%) during pneumoperitoneum in reverse-Trendelenburg position. The absolute agreement and predictive agreement between PPV_Finger and PPV_ART are moderate in obese patients having laparoscopic bariatric surgery.

Anaesthesia for laparoscopic surgery

Laparoscopic surgery has become increasingly common with reduced postoperative pain and faster recovery. Clinicians managing patients undergoing abdominal laparoscopic surgery should appreciate the physiological changes which mainly arise from patient positioning and the effects of pneumoperitoneum.

Theoretical Analysis of the Relative Impact of Obesity on Hemodynamic Stability During Acute Hemorrhagic Shock

Background:

Evidence suggests that morbid obesity may be an independent risk factor for adverse outcomes in patients with traumatic injuries.

Objectives:

In this study, a theoretic analysis using a derivation of the Guyton model of cardiovascular physiology examines the expected impact of obesity on hemodynamic changes in Mean Arterial Pressure (MAP) and Cardiac Output (CO) during Hemorrhagic Shock (HS).

Patients and Methods:

Computer simulation studies were used to predict the relative impact of increasing Body Mass Index (BMI) on global hemodynamic parameters during HS. The analytic procedure involved recreating physiologic conditions associated with changing BMI for a virtual subject in an In Silico environment. The model was validated for the known effect of a BMI of 30 on iliofemoral venous pressures. Then, the relative effect of changing BMI on the outcome of target cardiovascular parameters was examined during simulated acute loss of blood volume in class II hemorrhage. The percent changes in these parameters were compared between the virtual nonobese and obese subjects. Model parameter values are derived from known population distributions, producing simulation outputs that can be used in a deductive systems analysis assessment rather than traditional frequentist statistical methodologies.

Results:

In hemorrhage simulation, moderate increases in BMI were found to produce greater decreases in MAP and CO compared to the normal subject. During HS, the virtual obese subject had 42% and 44% greater falls in CO and MAP, respectively, compared to the nonobese subject. Systems analysis of the model revealed that an increase in resistance to venous return due to changes in intra-abdominal pressure resulting from obesity was the critical mechanism responsible for the differences.

Conclusions:

This study suggests that obese patients in HS may have a higher risk of hemodynamic instability compared to their nonobese counterparts primarily due to obesity-induced increases in intra-abdominal pressure resulting in reduced venous return.

Interventions for protecting renal function in the perioperative period

BACKGROUND

Various methods have been used to try to protect kidney function in patients undergoing surgery. These most often include pharmacological interventions such as dopamine and its analogues, diuretics, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, N-acetyl cysteine (NAC), atrial natriuretic peptide (ANP), sodium bicarbonate, antioxidants and erythropoietin (EPO).

OBJECTIVES

This review is aimed at determining the effectiveness of various measures advocated to protect patients' kidneys during the perioperative period.We considered the following questions: (1) Are any specific measures known to protect kidney function during the perioperative period? (2) Of measures used to protect the kidneys during the perioperative period, does any one method appear to be more effective than the others? (3) Of measures used to protect the kidneys during the perioperative period,does any one method appear to be safer than the others?

SEARCH METHODS

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 2, 2012), MEDLINE (Ovid SP) (1966 to August 2012) and EMBASE (Ovid SP) (1988 to August 2012). We originally handsearched six journals (Anesthesia and Analgesia, Anesthesiology, Annals of Surgery, British Journal of Anaesthesia, Journal of Thoracic and Cardiovascular Surgery, and Journal of Vascular Surgery) (1985 to 2004). However, because these journals are properly indexed in MEDLINE, we decided to rely on electronic searches only without handsearching the journals from 2004 onwards.

SELECTION CRITERIA

We selected all randomized controlled trials in adults undergoing surgery for which a treatment measure was used for the purpose of providing renal protection during the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 72 studies for inclusion in this review. Two review authors extracted data from all selected studies and entered them into RevMan 5.1; then the data were appropriately analysed. We performed subgroup analyses for type of intervention, type of surgical procedure and pre-existing renal dysfunction. We undertook sensitivity analyses for studies with high and moderately good methodological quality.

MAIN RESULTS

The updated review included data from 72 studies, comprising a total of 4378 participants. Of these, 2291 received some form of treatment and 2087 acted as controls. The interventions consisted most often of different pharmaceutical agents, such as dopamine and its analogues, diuretics, calcium channel blockers, ACE inhibitors, NAC, ANP, sodium bicarbonate, antioxidants and EPO or selected hydration fluids. Some clinical heterogeneity and varying risk of bias were noted amongst the studies, although we were able to meaningfully interpret the data. Results showed significant heterogeneity and indicated that most interventions provided no benefit.Data on perioperative mortality were reported in 41 studies and data on acute renal injury in 44 studies (all interventions combined). Because of considerable clinical heterogeneity (different clinical scenarios, as well as considerable methodological variability amongst the studies), we did not perform a meta-analysis on the combined data.Subgroup analysis of major interventions and surgical procedures showed no significant influence of interventions on reported mortality and acute renal injury. For the subgroup of participants who had pre-existing renal damage, the risk of mortality from 10 trials (959 participants) was estimated as odds ratio (OR) 0.76, 95% confidence interval (CI) 0.38 to 1.52; the risk of acute renal injury (as reported in the trials) was estimated from 11 trials (979 participants) as OR 0.43, 95% CI 0.23 to 0.80. Subgroup analysis of studies that were rated as having low risk of bias revealed that 19 studies reported mortality numbers (1604 participants); OR was 1.01, 95% CI 0.54 to 1.90. Fifteen studies reported data on acute renal injury (criteria chosen by the individual studies; 1600 participants); OR was 1.03, 95% CI 0.54 to 1.97.

AUTHORS' CONCLUSIONS

No reliable evidence from the available literature suggests that interventions during surgery can protect the kidneys from damage. However, the criteria used to diagnose acute renal damage varied in many of the older studies selected for inclusion in this review, many of which suffered from poor methodological quality such as insufficient participant numbers and poor definitions of end points such as acute renal failure and acute renal injury. Recent methods of detecting renal damage such as the use of specific biomarkers and better defined criteria for identifying renal damage (RIFLE (risk, injury, failure, loss of kidney function and end-stage renal failure) or AKI (acute kidney injury)) may have to be explored further to determine any possible benefit derived from interventions used to protect the kidneys during the perioperative period.

Recent advances in laparoscopic surgery

Laparoscopic surgery has been widely adopted and new technical innovation, procedures and evidence based knowledge are persistently emerging. This review documents recent major advancements in laparoscopic surgery. A PubMed search was made in order to identify recent advances in this field. We reviewed the recent data on randomized trials in this field as well as papers of systematic review. Laparoscopic cholecystectomy is the most frequently performed procedure, followed by laparoscopic bariatric surgery. Although bile duct injuries are relatively uncommon (0.15%-0.6%), intraoperative cholangiography still plays a role in reducing the cost of litigation. Laparoscopic bariatric surgery is the most commonly performed laparoscopic gastrointestinal surgery in the USA, and laparoscopic Nissen fundoplication is the treatment of choice for intractable gastroesophageal reflux disease. Recent randomized trials have demonstrated that laparoscopic gastric and colorectal cancer resection are safe and oncologically correct procedures. Laparoscopic surgery has also been widely developed in hepatic, pancreatic, gynecological and urological surgery. Recently, SILS and robotic surgery have penetrated all specialties of abdominal surgery. However, evidence-based medicine has failed to show major advantages in SILS, and the disadvantage of robotic surgery is the high costs related to purchase and maintenance of technology. Laparoscopic surgery has become well developed in recent decades and is the choice of treatment in abdominal surgery. Recently developed SILS techniques and robotic surgery are promising but their benefits remain to be determined.

Anesthetic implications of obesity in the surgical patient

The obese patient presents many challenges to both anesthesiologist and surgeon. A good understanding of the pathophysiologic effects of obesity and its anesthetic implications in the surgical setting is critical. The anesthesiologist must recognize increased risks and comorbidities inherent to the obese patient and manage accordingly, optimizing multisystem function in the perioperative period that leads to successful outcomes. Addressed from an organ systems approach, the purpose of this review is to provide surgical specialists with an overview of the anesthetic considerations of obesity. Minimally invasive surgery for the obese patient affords improved analgesia, postoperative pulmonary function, and shorter recovery times at the expense of a more challenging intraoperative anesthetic course. The physiologic effects of laparoscopy are discussed in detail. Although laparoscopy's physiologic effects on various organ systems are well recognized, techniques provide means for compensation and reversing such effects, thereby preserving good patient outcomes.

The relationship between volume and outcome after bariatric surgery: a nationwide study in Taiwan

BACKGROUND

This study purposed to explore the impact of hospital volume and surgeon volume on hospital resource utilization after bariatric surgery and to identify the predictors of length of stay (LOS) and hospital treatment cost in a nationwide population in Taiwan.

METHODS

This population-based cohort study retrospectively analyzed 2,674 bariatric surgery procedures performed from 1997 to 2008. Hospitals were classified as low- and high-volume hospitals if their annual number of bariatric surgeries were <35 and ≥ 35, respectively. Surgeons were classified as low- and high-volume surgeons if their annual number of bariatric surgeries were <15 and ≥ 15, respectively. Hierarchical linear regression models were used to predict LOS and hospital treatment cost.

RESULTS

The mean LOS was 7.67 days and the LOS for high-volume hospitals/surgeons was, on average, 28%/31% shorter than that for low-volume hospitals/surgeons. The mean hospital treatment cost was US$2,344.08, and the average hospital costs for high-volume hospitals/surgeons were 10%/13% lower than those for low-volume hospitals/surgeons. Advanced age, male gender, high Charlson co-morbidity index, and current treatment in a low-volume hospital, by a low-volume surgeon, and via open gastric bypass were significantly associated with long LOS and high hospital treatment cost (P < 0.001).

CONCLUSIONS

The data suggest that annual surgical volume is the key factor in hospital resource utilization. The results improve the understanding of medical resource allocation for this surgical procedure and can help to formulate public health policies for optimizing hospital resource utilization for related diseases.

Impact of morbid obesity on epidural anesthesia complications in labor

OBJECTIVE

We sought to determine whether morbid obesity is associated with increased maternal hypotension or fetal heart rate (FHR) abnormalities after epidural anesthesia placement during labor.

STUDY DESIGN

This was a retrospective cohort study of women undergoing epidural anesthesia during labor at term from April 2008 through July 2010.

RESULTS

A total of 125 morbidly obese patients were matched for age and race with 125 normal-weight patients. Morbidly obese patients had more frequent persistent systolic (16% vs 4%, P = .003) and diastolic (49% vs 29%, P = .002) hypotension and more prolonged (16% vs 5%, P = .006) and late (26% vs 14%, P = .03) FHR decelerations. Increasing body mass index was associated with persistent systolic (odds ratio, 1.06; 95% confidence interval, 1.02-1.10) and diastolic (odds ratio, 1.04; 95% confidence interval, 1.01-1.06) hypotension after controlling for epidural bolus dose and hypertensive disorders.

CONCLUSION

Morbidly obese women have more hypotension and prolonged FHR decelerations following epidural anesthesia during labor at term.

Effects of preoperative inspiratory muscle training in obese women undergoing open bariatric surgery: respiratory muscle strength, lung volumes, and diaphragmatic excursion

OBJECTIVE

To determine whether preoperative inspiratory muscle training is able to attenuate the impact of surgical trauma on the respiratory muscle strength, in the lung volumes, and diaphragmatic excursion in obese women undergoing open bariatric surgery.

DESIGN

Randomized controlled trial.

SETTING

Meridional Hospital, Cariacica/ES, Brazil.

SUBJECTS

Thirty-two obese women undergoing elective open bariatric surgery were randomly assigned to receive preoperative inspiratory muscle training (inspiratory muscle training group) or usual care (control group).

MAIN MEASURES

Respiratory muscle strength (maximal static respiratory pressure--maximal inspiratory pressure and maximal expiratory pressure), lung volumes, and diaphragmatic excursion.

RESULTS

After training, there was a significant increase only in the maximal inspiratory pressure in the inspiratory muscle training group. The maximal expiratory pressure, the lung volumes and the diaphragmatic excursion did not show any significant change with training. In the postoperative period there was a significant decrease in maximal inspiratory pressure in both the groups. However, there was a decrease of 28% in the inspiratory muscle training group, whereas it was 47% in the control group. The decrease in maximal expiratory pressure and in lung volumes in the postoperative period was similar between the groups. There was a significant reduction in the measures of diaphragmatic excursion in both the groups.

CONCLUSION

The preoperative inspiratory muscle training increased the inspiratory muscle strength (maximal inspiratory pressure) and attenuated the negative postoperative effects of open bariatric surgery in obese women for this variable, though not influencing the lung volumes and the diaphragmatic excursion.

Increasing abdominal pressure with and without PEEP: effects on intra-peritoneal, intra-organ and intra-vascular pressures

BACKGROUND

Intra-organ and intra-vascular pressures can be used to estimate intra-abdominal pressure. The aim of this prospective, interventional study was to assess the effect of PEEP on the accuracy of pressure estimation at different measurement sites in a model of increased abdominal pressure.

METHODS

Catheters for pressure measurement were inserted into the stomach, urinary bladder, peritoneal cavity, pulmonary artery and inferior vena cava of 12 pigs. The pressures were recorded simultaneously at baseline, during 10 cm H20 PEEP, external abdominal pressure (7 kg weight) plus PEEP, external abdominal pressure without PEEP, and again under baseline conditions. RESULTS (MEAN +/- SD): PEEP alone increased diastolic pulmonary artery and inferior vena cava pressure but had no effect on the other pressures. PEEP and external abdominal pressure increased intraperitoneal pressure from 6 +/- 1 mm Hg to 9 +/- 2 mm Hg, urinary bladder pressure from 6 +/- 2 mm Hg to 11 +/- 2 mm Hg (p = 0.012), intragastric pressure from 6 +/- 2 mm Hg to 11 +/- 2 mm Hg (all p

CONCLUSIONS

Our data suggest that pressure changes induced by external abdominal pressure were not modified by changing PEEP between 0 and 10 cm H20.

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MESH Headings

• Abdomen/physiology
• Animals
• Female
• Models, Animal
• Peritoneal Cavity/physiology
• Positive-Pressure Respiration
• Pressure
• Pulmonary Artery/physiology
• Stomach/physiology
• Swine
• Urinary Bladder/physiology
• Vena Cava, Inferior/physiology

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Silicone-ring Roux-en-Y gastric bypass in the treatment of obesity: effects of laparoscopic versus laparotomic surgery on respiration

BACKGROUND

The objective of this study was to compare the effects of silicone-ring Roux-en-Y gastric bypass carried out by laparoscopy versus that accomplished by laparotomy on pulmonary function.

METHODS

A total of 26 women (body mass index (BMI) 35-49 kg/m(2)) were studied candidates for silicone-ring Roux-en-Y gastric bypass carried out by laparoscopy (LG; n = 13) and laparotomy (or open surgery (OG); n = 13). Smokers, patients having lung disease, and those unable to carry out the tests properly were excluded. The physical therapy was standardized for both the groups. Respiratory evaluation was carried out during the preoperative period and on the second postoperative day by using spirometry and other tests that evaluated respiratory muscle strength and diaphragmatic mobility. Pain was evaluated by the visual analog scale on the second postoperative day. The statistical analysis was carried out with parametric or nonparametric tests, depending on the distribution of variables, considering p < 0.05 as statistically significant.

RESULTS

Patients were similar with respect to age, BMI, and waist-to-hip ratio. A decrease in all variables was observed for both the groups in the postoperative period, although this decrease was less pronounced in the LG group. Pain intensity was also lower in the LG group. The length of hospital stay was 2 days, and there were no pulmonary complications.

CONCLUSION

As there were no differences in the incidence of pulmonary complications and the length of hospital stay between the groups, the results showed that silicone-ring Roux-en-Y gastric bypass carried out by laparoscopy caused less pain and impairment of pulmonary function in the postoperative period.

Interventions for protecting renal function in the perioperative period

BACKGROUND

A number of methods have been used to try to protect kidney function in patients undergoing surgery. These include the administration of dopamine and its analogues, diuretics, calcium channel blockers, angiotensin converting enzyme inhibitors and hydration fluids.

OBJECTIVES

For this review, we selected randomized controlled trials which employed different methods to protect renal function during the perioperative period. In examining these trials, we looked at outcomes that included renal failure and mortality as well as changes in renal function tests, such as urine output, creatinine clearance, free water clearance, fractional excretion of sodium and renal plasma flow.

SEARCH STRATEGY

We searched the Cochrane Central register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 2), MEDLINE (1966 to June, 2007), and EMBASE (1988 to June, 2007); and handsearched six journals (Anesthesia and Analgesia, Anesthesiology, Annals of Surgery, British Journal of Anaesthesia, Journal of Thoracic and Cardiovascular Surgery, and Journal of Vascular Surgery).

SELECTION CRITERIA

We selected all randomized controlled trials in adults undergoing surgery where a treatment measure was used for the purpose of renal protection in the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 53 studies for inclusion in this review. As well as data analysis from all the studies, we performed subgroup analysis for type of intervention, type of surgical procedure, and pre-existing renal dysfunction. We undertook sensitivity analysis on studies with high and moderately good methodological quality.

MAIN RESULTS

The review included data from 53 studies, comprising a total of 2327 participants. Of these, 1293 received some form of treatment and 1034 acted as controls. The interventions mostly consisted of different pharmaceutical agents, such as dopamine and its analogues, diuretics, calcium channel blockers, ACE inhibitors, or selected hydration fluids. The results indicated that certain interventions showed minimal benefits. All the results suffered from significant heterogeneity. Hence we cannot draw conclusions about the effectiveness of these interventions in protecting patients' kidneys during surgery.

AUTHORS' CONCLUSIONS

There is no reliable evidence from the available literature to suggest that interventions during surgery can protect the kidneys from damage. There is a need for more studies with high methodological quality. One particular area for further study may be patients with pre-existing renal dysfunction undergoing surgery.

Use and outcomes of laparoscopic versus open gastric bypass at academic medical centers

BACKGROUND

A large outcome study of laparoscopic gastric bypass has not been done because of difficulty in differentiating between open and laparoscopic procedures in the absence of a specific ICD-9 procedural code for the laparoscopic operation. The University HealthSystem Consortium (UHC) clinical database recently added a specific procedural code for laparoscopic gastric bypass. The goal of this study was to compare the use and outcomes of laparoscopic versus open gastric bypass at academic centers.

STUDY DESIGN

Using ICD-9 diagnosis and procedure codes, we obtained data from the UHC clinical database for all patients who underwent laparoscopic or open Roux-en-Y gastric bypass for treatment of morbid obesity between 2004 and 2006 (n = 22,422). The main outcomes measures were demographics, comorbidities, length of hospital stay, 30-day readmission, morbidity, observed and expected (risk-adjusted) mortality, and costs.

RESULTS

There were 16,357 patients who underwent laparoscopic gastric bypass and 6,065 patients who underwent open gastric bypass. Laparoscopic gastric bypass patients had a shorter length of hospital stay (2.7 days versus 4.0 days, p < 0.01); lower overall complications (7.4% versus 13.0%, p < 0.01); lower rates of pneumonia, venous thrombosis, leak, wound infection, and pulmonary complications; costs were also lower. The observed-to-expected in-hospital mortality ratio was similar between groups (1.0 versus 1.0).

CONCLUSIONS

This nationwide analysis of academic medical centers between 2004 and 2006 showed that bariatric surgery has shifted to a predominately laparoscopic approach. In addition, laparoscopic gastric bypass is as safe as open gastric bypass and is considerably associated with a lower 30-day morbidity.

What Happens to Patients who Do Not Follow-Up after Bariatric Surgery?

Loss of follow-up is a concern when tracking long-term clinical outcomes after bariatric surgery. The results of patients who are “lost to follow-up” are not known. After bariatric surgery, the lack of follow-up may result in less weight loss for patients. This study investigated the hypothesis that there are differences between patients who do not automatically return for their annual follow-up and those that do return. Patients who were greater than 14 months postoperative after laparoscopic gastric bypass were contacted if they had not returned for their annual appointment. They were seen in clinic and/or a phone interview was performed for follow-up. These patients (Group A) were compared with patients who returned to see us for their annual appointment (Group B) without us having to notify them. There were 105 consecutive patients, with 48 patients who did not automatically return for their annual appointment. Only six of these patients could not ultimately be contacted. There was no difference in preoperative body mass index between the two groups. Percentage excess body weight loss was greater in Group B (76 vs 65%; P < 0.003). More patients had successful weight loss (defined as within 50% of ideal body weight) in Group B (50 [88%] vs 28 [67%]; P < 0.02). We found that a significant number of patients will not comply with regular follow-up care after laparoscopic gastric bypass unless they are prompted to do so by their bariatric clinic. These patients have worse clinical outcome ( i.e., less weight loss). Caution should be taken when examining the results of any bariatric study where there is a significant loss to follow-up.

Unexpected pathology during laparoscopic bariatric surgery

BACKGROUND

The popularity of bariatric surgery has increased in recent years with the escalating incidence of morbid obesity in our society. The improvement in minimally invasive technology and the increased number of laparoscopic bariatric procedures being performed have resulted in the discovery of unexpected pathology not suspected preoperatively. The authors hypothesized that the occurrence of unexpected pathology is not associated with immediate adverse outcomes during laparoscopic bariatric procedures.

METHODS

From December 2002 to June 2004, 398 patients underwent laparoscopic bariatric surgery for morbid obesity. A retrospective chart review was performed to determine the incidence of unexpected findings and their effect on patient results.

RESULTS

Nine unexpected pathologic lesions were found in eight patients (2%). The findings included lesions on the small bowel (n = 3), stomach (n = 4), and liver (n = 2). In all cases except one (for which a biopsy was performed), the abnormalities were found and removed laparoscopically. The final pathology showed gastric leiomyomas (n = 2), gastric gastrointestinal stromal cell tumors (n = 2), ectopic pancreatic tissue (n = 2), arteriovenous malformation (n = 1), biliary adenoma (n = 1), and fibrosed hemangioma (n = 1). The planned bariatric procedures were completed for all the patients without incident. No complications occurred postoperatively, and all were discharged in 1 to 3 days (mean, 2 days).

CONCLUSIONS

Unexpected findings occur with relative frequency during laparoscopic bariatric procedures. Biopsy or removal of these lesions usually does not increase complications nor preclude continuation of the planned bariatric procedure.

Challenges of laparoscopic colectomy in the obese patient: a review

BACKGROUND

Perioperative care of clinically severely obese patients presents numerous unique challenges. These patients have distinctive issues with regard to cardiovascular, pulmonary, and thromboembolic complications. In addition, hospital equipment must be able to accommodate the body habitus of this population.

METHODS

A Medline search using the terms "morbid obesity," "colon resection," "obesity comorbidities," "laparoscopic colectomy," "perioperative challenges," and "risk factors" was performed for English-language articles. Further references were obtained through cross-referencing the bibliography cited in each publication.

RESULTS

The authors discussed the most relevant challenges surgeons encounter in the perioperative setting when treating obese patients.

COMMENTS

The management of the morbidly obese patient requires meticulous preoperative, intraoperative, and postoperative care. Colorectal surgeons should be familiar with obesity-related problems when treating colorectal disease processes in this patient population. The associated comorbid illnesses in this population, as well as the technical difficulties regularly posed by them, make laparoscopic colectomy a more challenging procedure than normally encountered in the nonobese patient population.

Three-year follow-up of a prospective randomized trial comparing laparoscopic versus open gastric bypass

OBJECTIVE

To analyze long-term weight loss, changes in comorbidities and quality of life, and late complications after laparoscopic and open gastric bypass.

SUMMARY BACKGROUND DATA

Early results from our prospective randomized trial comparing the outcome of laparoscopic versus open gastric bypass demonstrated less postoperative pain, shorter length of hospital stay, fewer wound-related complications, and faster convalescence for patients who underwent laparoscopic gastric bypass.

METHODS

Between May 1999 and March 2001, 155 morbidly obese patients were enrolled in this prospective trial, in which 79 patients were randomized to laparoscopic gastric bypass and 76 to open gastric bypass. Two patients in the laparoscopic group required conversion to open surgery; their data were analyzed within the laparoscopic group on an intention-to-treat basis. The 2 groups were well matched for body mass index, age, and gender. Outcome evaluation included weight loss, changes in comorbidities and quality of life, and late complications.

RESULTS

The mean follow-up was 39+/-8 months. There were no significant differences in the percent of excess body weight loss between the 2 groups at the 3-year follow-up (77% for laparoscopic versus 67% for open). The rate of improvement or resolution of comorbidities was similar between groups. Improvement in quality of life, measured by the Moorehead-Ardelt Quality of Life Questionnaire, was observed in both groups without significant differences between groups. Late complications were similar between groups except for the rate of incisional hernia, which was significantly greater after open gastric bypass (39% versus 5%, P<0.01), and the rate of cholecystectomy, which was greater after laparoscopic gastric bypass (28% versus 5%, P=0.03).

CONCLUSIONS

In this randomized trial with a 3-year follow-up, we found that laparoscopic gastric bypass was equally effective as open gastric bypass with respect to weight loss and improvement in comorbidities and quality of life. A major advantage at long-term follow-up for patients who underwent laparoscopic gastric bypass was the reduction in the rate of incisional hernia.

Obese parturients have lower epidural local anaesthetic requirements for analgesia in labour †

BACKGROUND

There are no studies comparing local anaesthetic requirements for obese and normal parturients. Obesity has been associated with a higher incidence of Caesarean section and higher levels of epidural block have also been found in obese obstetric patients, suggesting they may require less local anaesthetic. The aim of our study was to estimate the minimum local analgesic concentration (MLAC) of bupivacaine for obese and non-obese parturients.

METHODS

Otherwise healthy parturients (n=32) requesting epidural analgesia were enrolled in this up-down sequential allocation study. Women were in active labour (3-6 cm cervical dilatation) with visual analogue pain scores (VAPS) >40/100 mm. Subjects with BMI >30 kg m(-2) were allocated to the obese group and BMI < or = 30 kg m(-2) were allocated to the normal group. The initial epidural dose for both groups was 20 ml 0.1% w/v bupivacaine (20 mg), with a dosing increment of 0.01% w/v VAPS < or = 10/100 mm defined effective analgesia. The MLAC was estimated using up-down reversals and probit regression with P<0.05 as significant.

RESULTS

Groups were similar except for BMI and weight (P<0.001). Local anaesthetic requirements were significantly (P<0.001) reduced by a factor of 1.68 (95% CI 1.32-2.29) in the obese group, with significantly higher initial level of block (P<0.001).

CONCLUSION

We found obese parturients to have significantly decreased epidural bupivacaine analgesic requirements. A contributing factor to obese patients having more difficult labours may be that relatively larger doses of local anaesthetic are administered than actually required. It may be worth considering lowering the concentrations and doses with which we initiate analgesia in obese parturients.

The impact of laparoscopy on bariatric surgery

The rising popularity of bariatric surgery over the past several years is attributable in part to the development of laparoscopic bariatric surgery. Morbidly obese patients have associated comorbid conditions that may predispose them to postoperative morbidity. The laparoscopic approach to bariatric surgery offers a minimally invasive option that reduces the physiologic stress and provides clinical benefits, as compared with the open approach. This review summarizes the impact of laparoscopic surgery on bariatric surgery, the various risk factors that could potentially predispose morbidly obese patients to postoperative morbidity, the fundamental differences between laparoscopic and open bariatric surgery, and the physiology of reduced tissue injury associated with laparoscopic bariatric surgery.

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.

Effect of prolonged pneumoperitoneum on intraoperative urine output during laparoscopic gastric bypass

BACKGROUND

Intraoperative oliguria is common during laparoscopic operations. The objective of this study was to evaluate the effects of prolonged pneumoperitoneum during laparoscopic gastric bypass (GBP) on intraoperative urine output and renal function.

METHODS

104 patients with a body mass index between 40 and 60 kg/m2 were randomly assigned to laparoscopic (n = 54) or open (n = 50) GBP. Intraoperative urine output was recorded at 30-min intervals. Blood urea nitrogen and creatinine levels were measured at baseline and on postoperative days 1, 2, and 3. Levels of antidiuretic hormone, aldosterone, and plasma renin activity were also measured in a subset of laparoscopic (n = 22) and open (n = 24) GBP patients at baseline, 2 hours after surgical incision, and in the recovery room.

RESULTS

The laparoscopic and open groups were similar in age, gender, and body mass index. There was no significant difference in amount of intraoperative fluid administered between groups (5.4 +/- 1.6 L, laparoscopic versus 5.8 +/- 1.7 L, open), but operative time was longer in the laparoscopic group (232 min versus 200 min, p < 0.01). Urinary output during laparoscopic GBP was 64% lower than during open GBP at 1 hour after surgical incision (19 mL versus 55 mL, p < 0.01) and continued to remain lower than that of the open group by 31-50% throughout the operation. Postoperative blood urea nitrogen and creatinine levels remained within the normal range in both groups. Serum levels of antidiuretic hormone, aldosterone, and plasma renin activity peaked at 2 hours after surgical incision with no significant difference between the two groups.

CONCLUSION

Prolonged pneumoperitoneum during laparoscopic gastric bypass significantly reduced intraoperative urine output but did not adversely alter postoperative renal function.

Systemic stress response after laparoscopic and open gastric bypass

BACKGROUND

The magnitude of the systemic stress response is proportional to the degree of operative trauma. We hypothesized that laparoscopic gastric bypass (GBP) is associated with reduced operative trauma compared with open GBP, resulting in a lower systemic stress response.

STUDY DESIGN

Forty-eight patients with a body mass index of 40 to 60 were randomly assigned to laparoscopic (n = 26) or open (n = 22) GBP Blood samples were measured at baseline and at 1, 24, 48, and 72 hours postoperatively. Metabolic (insulin, glucose, epinephrine, norepinephrine, dopamine, ACTH, cortisol), acute phase (C-reactive protein), and cytokine (interleukin [IL]-6, IL-8, tumor necrosis factor [TNF]-alpha) responses were measured. Catabolic response was also measured by calculating the nitrogen balance at 24 and 48 hours postoperatively.

RESULTS

The two groups of patients were similar in terms of age, gender, and preoperative body mass index. The mean operative time was longer for laparoscopic GBP than for open GBP (229 +/- 50 versus 207 43 minutes). After laparoscopic and open GBP, plasma concentrations of insulin, glucose, epinephrine, dopamine, and cortisol increased; IL-8 and TNF-alpha remained unchanged; and negative nitrogen balances occurred at 24 and 48 hours. There was no significant difference in these parameters between groups. Concentrations of norepinephrine, ACTH, C-reactive protein, and IL-6 levels also increased, but these levels were significantly lower after laparoscopic GBP than after open GBP (p < 0.05).

CONCLUSIONS

Systemic stress response after laparoscopic GBP is similar to that after open GBP, except that concentrations of norepinephrine, ACTH, C-reactive protein, and IL-6 are lower after laparoscopic than after open GBP. These findings may suggest a lower degree of operative injury after laparoscopic GBP.