Obesity: an anaesthetic challenge

Anesthesia and Analgesia for the Obese Parturient

Obesity is a worldwide epidemic and is associated with an increased risk of hypertension, diabetes, and obstructive sleep apnea. Pregnant patients with obesity experience a higher risk of maternal and fetal complications. Anesthesia also poses higher risks for obese parturients and may be more technically challenging due to body habitus. Safe anesthesia practice for these patients must take into consideration the unique challenges associated with the combination of pregnancy and obesity.

Postoperative Recovery Outcomes for Obese Patients Undergoing General Anesthesia: A Meta-Analysis of Randomized Controlled Trials

Purpose

This study was performed to assess the postoperative recovery outcomes in obese patients undergoing general anesthesia.

Methods

The eligible studies were identified from PubMed, EmBase, and the Cochrane library until December 2020. The standard mean differences (SMDs) with 95% confidence intervals (CIs) were used to calculate the role of desflurane, sevoflurane, and propofol on recovery outcomes, and the analyses using the random-effects model.

Results

Eleven randomized controlled trials involving 713 obese patients undergoing general anesthesia were selected for final meta-analysis. We noted desflurane was associated with a shorter time to eye-opening than sevoflurane (SMD: −0.86; 95% CI, −1.43 to −0.28; P = 0.003). The use of desflurane with shorter time to extubation as compared with propofol (SMD: −1.13; 95% CI, −1.52 to −0.73; P < 0.001) or sevoflurane (SMD: −1.19; 95% CI, −2.15 to −0.22; P = 0.016), while sevoflurane was associated with longer time to extubation as compared with propofol (SMD: 1.47; 95% CI, 1.03 to 1.91; P < 0.001). Desflurane were associated with shorter time to stating name as compared with propofol (SMD: −1.40; 95% CI, −2.32 to −0.48; P = 0.003) or sevoflurane (SMD: −2.09; 95% CI, −3.33 to −0.85; P = 0.001). In addition, desflurane was associated with a longer time for orientation to place as compared with propofol (SMD: 0.65; 95% CI, 0.22 to 1.07; P = 0.003), while desflurane with shorter time for orientation to place as compared with sevoflurane (SMD: −0.88; 95% CI, −1.46 to −0.30; P = 0.003).

Conclusions

The use of desflurane could provide better recovery outcomes in obese patients undergoing general anesthesia. Further large-scale trials should be comparison the long-term effectiveness of various anesthetics.

Comparison of the effectiveness of two-handed mask ventilation techniques (C-E versus V-E) in obese patients requiring general anesthesia in an Indian population

Background:

Two-handed mask ventilation techniques are often used in cases of difficult mask ventilation scenarios. A comparison of two methods of two-handed techniques in terms of tidal volume was undertaken in the context of the obese population.

Aims and Objectives:

To determine and compare the effectiveness of mask ventilation in obese Indian adult subjects by using either the C-E technique or the V-E technique after induction of general anaesthesia.

Material and Methods:

This was a randomised interventional study conducted on eighty obese patients. They were randomized into Group A ventilated with C-E technique and Group B with V-E technique. Expired tidal volume (VTe), Peak inspiratory pressure (PIP), SpO₂, EtCO₂ and vital signs were noted.

Results:

The BMI and hemodynamic parameters were comparable between the two groups. The expired tidal volume of 702 ± 77 mL with the V-E technique was significantly more than the C-E technique, which was 492 ± 71 mL. The ventilatory failure rate with the C-E technique was 15% and 0% with the V-E technique. There was no significant difference between the peak airway pressures for the two techniques: 20.3 ± 1.5 mm H₂O for Group A and 20.5 ± 1.2 mm H₂O for Group B.

Conclusions:

Mask ventilation with the two-handed V-E technique is associated with better tidal volumes and reduced failure rates in the obese population. So the V-E technique should be attempted first as a rescue measure in obese adult patients if the return of spontaneous breathing and tracheal intubation is impossible.

Impact of weight on stone-free rate during percutaneous nephrolithotomy

Background

To assess Impact of weight on stone-free rate during percutaneous nephrolithotomy.

Methods

Hundred and twenty-three PNL procedures were done between January 2016 and July 2017. The patients were divided into four groups according to the World Health Organization (WHO) classification of body mass index (BMI): < 25 ((group 1, average)), 25–29.9 (group 2, overweight), 30–39.9 (group 3, obese), and ≥ 40 kg/m2 (group 4, morbidly obese). All groups were compared as regarding preoperative variables, intra-operative procedure and postoperative results.

Results

The non-obese groups were younger in age than obese and morbid obese groups (P = 0.005). The difference in BMI was statistically significant between non-obese and obese groups (P = 0.0001). Most of females gender were obese and morbid obese (P = 0.0001) and most of the obese patients had left-sided renal stone (P = 0.001). Most of overweight and obese groups had radiopaque stones (P = 0.02). There were no statistically significant differences between all groups as regarding co-morbidity, stone size, stone locations, and hydronephrosis grade. Operative time (P = 0.034), length of hospital stay (P value = 0.014) and fluoroscopy time (P = 0.0001) were statistically significant differences between all groups. Number of accesses, access site, postoperative hemoglobin drop, post- operative complications, fate of residual stones and stone-free rate were not statistically significant differences between all groups. BMI was correlated with mean fluoroscopy time and mean hospitalization duration in our study as the time of hospitalization and time of x-ray exposure increase with obesity.

Conclusion

PNL is a safe and effective procedure for obese patients. BMI do not predict clearance post PNL.

Is obesity associated with poorer outcomes in patients undergoing minimally invasive mitral valve surgery?

OBJECTIVES

METHODS

This is a retrospective cohort study of all patients undergoing MIMVS ± concomitant procedures over an 8-year period. Patients were stratified into 2 groups: BMI ≥ 30 kg/m2 and BMI ˂ 30 kg/m2, as per World Health Organization definitions. Baseline characteristics, operative and postoperative outcomes and 5-year survival were compared.

RESULTS

We identified 296 patients (BMI ≥30, n = 41, median 35.3, range 30–43.6; BMI &lt;30, n = 255, median 26.2, range 17.6–29.9). The groups were well matched with regard to baseline characteristics. There was only 1 in-hospital mortality, and this was in the BMI &lt; 30 group. There was no difference in repair rate for degenerative disease (100% vs 96.3%, P &gt; 0.99 respectively) or operative durations [cross-clamp: 122 min interquartile range (IQR) 100–141) vs 125 min (IQR 105–146), P = 0.72, respectively]. There were only 6 conversions to sternotomy, all in non-obese patients. There was no significant difference in any other perioperative or post-operative outcomes. Using the Kaplan–Meier analysis, there was no significant difference in 5-year survival between the 2 groups (95.8% vs 95.5%, P = 0.83, respectively).

CONCLUSIONS

In patients having MIMVS, there is insufficient evidence to suggest that obesity affects either short- or mid-term outcomes. Obesity should therefore not be considered as a contraindication to this technique for experienced teams.

Efficacy and safety of mini percutaneous nephrolithotomy in obese patients

Purpose

We aimed to evaluate the effect of obesity on surgical outcomes of mini percutaneous nephrolithotomy (Mini-PNL).

Methods

Hundred and eighty two Mini-PNL procedures were performed between May 2013 and January 2015 and their results were evaluated retrospectively. Patients were classified as non-obese (BMI, 18.5–30 kg/m²) and obese (≥30 kg/m²) groups. Obese and non-obese patients were compared according to pre-operative demographic values, intra-operative surgery techniques and post-operative results.

Results

BMI values of 133 patients were lower than 30 kg/m² while 49 patient’s BMI values were higher than 30 kg/m². There were no significant difference between operation time, fluoroscopy time, number of access and access sites when two groups were compared. No significant difference was found in total length of hospital stay, hemoglobin drop, and complication rates. Stone-free rates were 70.7 % in the non-obese and 71.4 % in the obese group (p = 0.9).

Conclusions

Mini-PNL procedure is a safe and effective treatment modality, which should be strongly considered for obese patients with appropriate sized stones.

Lumbar Ultrasound Image Feature Extraction and Classification with Support Vector Machine

Needle entry site localization remains a challenge for procedures that involve lumbar puncture, for example, epidural anesthesia. To solve the problem, we have developed an image classification algorithm that can automatically identify the bone/interspinous region for ultrasound images obtained from lumbar spine of pregnant patients in the transverse plane. The proposed algorithm consists of feature extraction, feature selection and machine learning procedures. A set of features, including matching values, positions and the appearance of black pixels within pre-defined windows along the midline, were extracted from the ultrasound images using template matching and midline detection methods. A support vector machine was then used to classify the bone images and interspinous images. The support vector machine model was trained with 1,040 images from 26 pregnant subjects and tested on 800 images from a separate set of 20 pregnant patients. A success rate of 95.0% on training set and 93.2% on test set was achieved with the proposed method. The trained support vector machine model was further tested on 46 off-line collected videos, and successfully identified the proper needle insertion site (interspinous region) in 45 of the cases. Therefore, the proposed method is able to process the ultrasound images of lumbar spine in an automatic manner, so as to facilitate the anesthetists' work of identifying the needle entry site.

Obesity in laparoscopic surgery

Since the 1980s, minimally invasive techniques have been applied to an increasing number and variety of surgical procedures with a gradual increase in the complexity of procedures being successfully performed laparoscopically. In the past, obesity was considered a contraindication to laparoscopy due to the higher risk of co-morbid conditions such as diabetes, hypertension, coronary artery disease and venous thromboembolism. Performing laparoscopic gynaecological procedures in morbidly obese patients is no longer a rare phenomenon; however, it does necessitate changes in clinical practice patterns. Understanding of the physiological changes induced by laparoscopy, particularly in obese patients, is important so that these may be counteracted and adverse outcomes avoided. Laparoscopy in obese patients confers certain advantages such as shorter hospital stay, less post-operative pain and fewer wound infections. In addition to these benefits, minimal-access surgery has been demonstrated as safe and effective in obese patients; however, specific surgical strategies and operative techniques may need to be adopted.

Effect of clonidine versus dexmedetomidine on pain control after laparoscopic gastric sleeve: A prospective, randomized, double-blinded study

BACKGROUND

The use of opioids in surgeries for morbidly obese patients could cause respiratory depression. Therefore, alternative analgesics are needed to improve anesthetic management for obese patients. The objective of this study was to compare the effect of dexmedetomidine and clonidine on pain as well as analgesic consumption at 24 h postoperatively in patients undergoing laparoscopic gastric sleeve. The secondary objective was to compare patients' and surgeons' satisfaction.

MATERIALS AND METHODS

A total of 60 obese and morbidly obese patients scheduled to undergo laparoscopic gastric sleeve were randomly assigned into two groups. 10 min after induction of general anesthesia, one group received 0.8-1.2 μg/kg/30 min intravenous (IV) clonidine through 500 mL lactated Ringer's solution and placebo (normal saline solution) through syringe pump. The second group received IV dexmedetomidine through syringe pump at a rate 0.5-0.8 μg/kg/h and placebo through 500 mL lactated Ringer's solution. Data on pain, analgesic consumption, and return to normal activity in addition to patients' and surgeons' satisfaction were collected.

RESULTS

Both groups were similar with respect to demographic and intraoperative hemodynamic characteristics. Fentanyl consumption, surgery duration and hospital stay were similar for the two groups. Pain scores on walking were significantly lower in the clonidine group at 12 h postoperatively (P = 0.014) compared with dexmedetomidine group. The number of patients who consumed pethidine was significantly lower in the clonidine group at 12 h postoperatively (P = 0.045).

CONCLUSION

This study concluded that clonidine and dexmedetomidine yielded similar outcomes with a difference in pain and analgesic consumption at 12 h postoperatively.

Carbon dioxide monitoring during laparoscopic-assisted bariatric surgery in severely obese patients: transcutaneous versus end-tidal techniques

Various factors including severe obesity or increases in intra-abdominal pressure during laparoscopy can lead to inaccuracies in end-tidal carbon dioxide (PETCO2) monitoring. The current study prospectively compares ET and transcutaneous (TC) CO2 monitoring in severely obese adolescents and young adults during laparoscopic-assisted bariatric surgery. Carbon dioxide was measured with both ET and TC devices during insufflation and laparoscopic bariatric surgery. The differences between each measure (PETCO2 and TC-CO2) and the PaCO2 were compared using a non-paired t test, Fisher's exact test, and a Bland-Altman analysis. The study cohort included 25 adolescents with a mean body mass index of 50.2 kg/m2 undergoing laparoscopic bariatric surgery. There was no difference in the absolute difference between the TC-CO2 and PaCO2 (3.2±3.0 mmHg) and the absolute difference between the PETCO2 and PaCO2 (3.7±2.5 mmHg). The bias and precision were 0.3 and 4.3 mmHg for TC monitoring versus PaCO2 and 3.2 and 3.2 mmHg for ET monitoring versus PaCO2. In the young severely obese population both TC and PETCO2 monitoring can be used to effectively estimate PaCO2. The correlation of PaCO2 to TC-CO2 is good, and similar to the correlation of PaCO2 to PETCO2. In this population, both of these non-invasive measures of PaCO2 can be used to monitor ventilation and minimize arterial blood gas sampling.

Obese patients: respiratory complications in the post-anesthesia care unit

INTRODUCTION

Obesity has been associated with respiratory complications, and the majority of these complications occur in the Post-Anesthesia Care Unit (PACU). The aim of this study was to evaluate the outcome and incidence of adverse respiratory events (AREs) in obese patients during their stay in the PACU METHODS: We conducted a prospective control study that included 27 obese patients matched with an equal number of patients with body mass index (BMI)<30 (non-obese control group); the 2 groups of patients were similar in respect to gender distribution, age, and type of surgery and had been admitted into the PACU after elective surgery (May 2011). The AREs were identified during PACU stay. Descriptive analysis of variables was performed, and the Mann-Whitney U test, Chi-square test, or Fisher's exact test were used for comparisons. Associations with AREs were studied using univariate and multivariate logistic regression models.

RESULTS

There was a higher frequency of STOP-BANG ≥3 (89% vs. 11%, P<.001) among obese patients and they were less frequently scheduled to undergo high-risk surgery (7% vs. 41%, P=.005) and major surgery (4% vs. 15%, P=.008). Obese patients had more frequent AREs in the PACU (33% vs. 7%, P<.018). Multivariate analysis identified obesity and residual neuromuscular blockade as independent risk factors for the occurrence of AREs. Stay in the PACU was longer for obese patients (120min vs. 84min, P<.01).

CONCLUSIONS

Obesity was considered an independent risk factor for AREs in the PACU. Obese patients stayed longer in the PACU, but they did not stay longer in the hospital.

Anesthesia considerations in the obese gravida

Obesity is associated with serious morbidity during pregnancy, and obese women also are at a high risk of developing complications during labor, leading to an increased risk for instrumental and Cesarean deliveries. The engagement of the obstetrical anesthetist in the management of this group of high-risk patients should be performed antenatally so that an appropriate management strategy can be planned in advance to prevent an adverse outcome. Good communication between all care providers is essential. The obese patient in labor should be encouraged to have a functioning epidural catheter placed early in labor. Apart from providing analgesia and alleviating physiological derangements during labor, the presence of a functioning epidural catheter can also be used to induce anesthesia quickly in the event of an emergency cesarean section, thus avoiding a general anesthesia, which has exceedingly high risks in the obese parturient. Successful management of the obese patient necessitates a comprehensive strategy that encompasses a multidisciplinary and holistic approach from all care-providers.

Special populations critical care considerations of the morbidly obese pregnant patient

The critically ill pregnant patient poses a unique challenge to the clinician, requiring a thorough understanding of normal and abnormal maternal and fetal physiology associated with pregnancy. The morbidly obese patient presents even greater challenges to the clinician, and morbidity and mortality are proportionately increased. Because increased numbers of obese pregnant women are now admitted to intensive care units, practitioners must be aware of the physiology associated with both pregnancy and obesity. A multidisciplinary approach is imperative to prevent both maternal and fetal morbidity and mortality for these very complex patients, especially when they are admitted to the ICU with critical illness.

Clinical outcomes in obese and normal-weight children undergoing ultrasound for suspected appendicitis

BACKGROUND

Obesity constitutes an independent predictor for a nondiagnostic screening ultrasound (US) in suspected appendicitis. Furthermore, the imaging route consisting of the screening US with a second US if necessary has a significantly lower diagnostic accuracy in the obese children (83%) than their lean counterparts (93%). However, the effect of this association on clinical outcomes in the obese population is unknown.

OBJECTIVES

In children presenting to the emergency department (ED) undergoing US for suspected appendicitis, the objective was to examine if there is a significant difference in the proportions of those with a "desirable outcome" in the obese group versus their normal-weight counterparts.

METHODS

This was a reanalysis of a recent prospective cohort study conducted at a tertiary care pediatric ED. A consecutive sample of 263 previously healthy children 4-17 years of age undergoing screening US for suspected appendicitis was enrolled. Study patients were divided into obese (body mass index-for-age percentiles [BMI-FAP] ≥ 85%) and normal-weight groups. The main outcome was the proportion of children with the desirable outcome in the obese and normal-weight groups. Desirable outcomes for patients with a nondiagnostic screening US were defined as either 1) nonperforated appendicitis or alternate surgical diagnosis undergoing appropriate surgical procedure within 24 hours of assessment without a computed tomography (CT) scan or 2) no appendicitis, discharged from the ED within 24 hours without a CT scan. Secondary outcomes included hospitalization, CT imaging for any reason within 30 days of initial presentation, length of hospital stay, return visits, time to and length of surgery, and complications.

RESULTS

Of the 263 patients, 76 (28.9%) were obese, and 187 had a normal weight. Ninety-nine children (37.6%) had appendicitis (obese = 24, normal-weight = 75). The desirable outcome was achieved in 46 (64.5%) of the obese patients versus 137 (73.3%) of the normal-weight children (95% confidence interval [CI] for the difference = -0.21 to 0.04). Compared to the normal-weight children, the obese children had similar hospitalization rates (44.7% vs. 45.5%), median length of hospital stay (20.5 hours vs. 23.0 hours), and return ED visit rates (11.8% vs. 9.1%). The median time to surgery (obese = 10.5 hours, normal-weight = 9.0 hours), complications (obese = 25%, normal-weight = 21.3%), perforations (obese = 33%, normal-weight = 31%), and length of surgery (obese 80 [±37] minutes, normal-weight 67 [±25] minutes) were also similar. The rate of CT within 30 days of initial presentation was higher in the obese compared to the normal-weight group (13/76 or 17.1% vs. 13/187 or 6.9%, 95% CI = 0.02 to 0.23).

CONCLUSIONS

Previously healthy obese children undergoing screening US for suspected appendicitis experienced comparable clinical outcomes to their normal-weight counterparts. However, they were three times more likely to receive a CT scan during their investigation. These results argue for continuing current practice of using the screening US in this population, followed by a CT if clinically warranted upon reexamination.

The airways and gastric contents in obese patients

BACKGROUND AND OBJECTIVES

The objective of this study was to review the literature and to question the concept that obese patients should be considered as having a potential full stomach and, therefore, question how the airways, considered as of difficult access due to obesity, should be approached during anesthetic induction.

CONTENTS

Classically, obese patients are viewed as having a potential full stomach, leading to conducts to protect the airways during anesthetic induction. Frequently, awake intubation or rapid sequence intubation is performed. However, this concept is based on a single study, which has been cited by other authors. Obese patients are also considered difficult to intubate, raising the concern on the successful approach of the airways. However, studies in the literature question this concept, leading to questioning of the techniques used to access the airways.

CONCLUSIONS

Studies in the literature demonstrate that gastric emptying is not slowed in obese patients as previously believed, and gastric contents are not greater in this patient population; intubation can, therefore, be safely done after anesthesia. Although obesity alone does not lead to failure to intubate, other signs can be used to predict difficult intubations.

[Evaluation of tracheal intubation conditions in morbidly obese patients: a comparison of succinylcholine and rocuronium]

OBJECTIVE

To compare tracheal intubation conditions in morbidly obese patients 60 seconds after administration of succinylcholine or rocuronium doses based on real weight or ideal weight.

METHOD

We evaluated patients with a body mass index (BMI) of 40 kg x m(-2) or more but no other indications of difficult-intubation risk. Induction was performed under fentanyl and propofol at doses calculated based on real weight. Patients were assigned to 1 of 4 groups for tracheal intubation. Group 1 received 1 mg of succinylcholine per kilogram of ideal weight, group 2 received 1 mg of succinylcholine per kilogram of real weight, group 3 received 0.6 mg of rocuronium per kilogram of ideal weight, and group 4 received 0.6 mg of rocuronium per kilogram of real weight. Tracheal intubation was performed 60 seconds later and intubation conditions were recorded using a clinical scoring system.

RESULTS

Eighty patients with a mean BMI of 47.5 kg x m(-2) were enrolled. The difficult intubation rate was 3.75%. All patients were intubated. Laryngoscopy conditions and position and movement of vocal cords were similar in all 4 groups. Reaction to cuff inflation revealed intergroup differences; group 3 presented slight limb movements, diaphragm movement, and sustained cough for more than 10 seconds.

CONCLUSION

These results suggest that administration of succinylcholine calculated based on real weight or ideal weight and rocuronium based on real weight can provide clinically acceptable conditions for tracheal intubation in morbidly obese patients with no other difficult-intubation criteria.

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery medical guidelines for clinical practice for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice are systematically developed statements to assist health-care professionals in medical decision making for specific clinical conditions. Most of the content herein is based on literature reviews. In areas of uncertainty, professional judgment was applied. These guidelines are a working document that reflects the state of the field at the time of publication. Because rapid changes in this area are expected, periodic revisions are inevitable. We encourage medical professionals to use this information in conjunction with their best clinical judgment. The presented recommendations may not be appropriate in all situations. Any decision by practitioners to apply these guidelines must be made in light of local resources and individual patient circumstances. The American Society for Parenteral & Enteral Nutrition fully endorses sections of these guidelines that address the metabolic and nutritional management of the bariatric surgical patient.

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice are systematically developed statements to assist healthcare professionals in medical decision making for specific clinical conditions. Most of the content herein is based on literature reviews. In areas of uncertainty, professional judgment was applied. These guidelines are a working document that reflects the state of the field at the time of publication. Because rapid changes in this area are expected, periodic revisions are inevitable. We encourage medical professionals to use this information in conjunction with their best clinical judgment. The presented recommendations may not be appropriate in all situations. Any decision by practitioners to apply these guidelines must be made in light of local resources and individual patient circumstances. The American Society for Parenteral & Enteral Nutrition fully endorses sections of these guidelines that address the metabolic and nutritional management of the bariatric surgical patient.

Childhood body mass index and perioperative complications

BACKGROUND

Our aim was to describe the incidence of quality assurance events between overweight/obese and normal weight children.

METHODS

This is a retrospective review of the quality assurance database of the Mott Children's Hospital, University of Michigan for the period January 2000 to December 2004. Using directly measured height and weight, we computed the body mass index (BMI) in 6094 children. Overweight and obesity were defined using age and gender-specific cut off according to the National Center for Health Statistics (NCHS)/Centers for Disease Control and Prevention (CDC) (2000) growth charts. Frequency of quality assurance events were compared between normal weight, overweight, and obese children.

RESULTS

There were 3359 males (55.1%) and 2735 females (44.9%). The mean age for the entire population was 11.9 +/- 5.2 while the mean BMI was 21.6 +/- 6.7 kg x m(-2). The overall prevalence of overweight and obesity was 31.6%. Obesity was more prevalent in boys than girls (P = 0.016). Preoperative diagnoses of hypertension, type II diabetes, and bronchial asthma were more common in overweight and obese than normal weight children (P = 0.0001 for hypertension, P = 0.001 for diabetes and P = 0.014 for bronchial asthma). Difficult airway, upper airway obstruction in the postanesthesia care unit (PACU) and PACU stay longer than 3 h and need for two or more antiemetics were more common in overweight and obese than normal weight children (P = 0.001). There was no significant difference in the incidence of unplanned hospital admission following an outpatient surgical procedure between normal weight and overweight/obese children.

DISCUSSION

Studies on perioperative aspects of childhood overweight and obesity are rare. Our report shows a high prevalence of overweight and obesity in this cohort of pediatric surgical patients. Certain perioperative morbidities are more common in overweight and obese than in normal weight children. There is a need for prospective studies of the impact of childhood overweight and obesity on anesthesia and surgical outcome.

Outcome of percutaneous nephrolithotomy: effect of body mass index

OBJECTIVE

The surgical management of renal and upper ureteral calculi presents unique challenges in obese patients. We reviewed our recent experience with percutaneous nephrolithotomy (PNL) in obese patients to determine the safety and outcome of this procedure in such group of patients.

PATIENTS AND METHODS

The surgical records of 1121 patients treated with PNL between 2000 and 2004 were reviewed. Patients were stratified into four groups according to the World Health Organization classification of body mass index (BMI): <25 (average), 25-29.9 (overweight), 30-39.9 (obese), and >40 kg/m(2) (morbidly obese). The outcomes of PNL in these four groups were compared.

RESULTS

A total of 1287 procedures were performed on 1155 renal units (1.1 procedures per renal unit). The overall stone-free rate was 85.1% and the mean hospital stay was 3.3+/-2.6 d. Major complications were seen in 72 patients (6.4%). No statistically significant differences were found in decrease in haemoglobin concentration, hospital stay, and complication rate among the four study groups. The need for auxiliary procedures and stone-free rates were comparable.

CONCLUSIONS

PNL in obese and morbidly obese patients yields a stone-free rate that is comparable to that achieved in nonobese patients. The complication rate and length of hospital stay are also similar.

Effect of vital capacity manoeuvres on arterial oxygenation in morbidly obese patients undergoing open bariatric surgery

BACKGROUND

Arterial oxygenation may be compromised in morbidly obese patients undergoing bariatric surgery. The aim of this study was to evaluate the effect of a vital capacity manoeuvre (VCM), followed by ventilation with positive end-expiratory pressure (PEEP), on arterial oxygenation in morbidly obese patients undergoing open bariatric surgery.

METHODS

Fifty-two morbidly obese patients (body mass index >40 kg m-2) undergoing open bariatric surgery were enrolled in this prospective and randomized study. Anaesthesia and surgical techniques were standardized. Patients were ventilated with a tidal volume of 10 mL kg-1 of ideal body weight, a mixture of oxygen and nitrous oxide (FiO2 = 40%) and respiratory rate was adjusted to maintain end-tidal carbon dioxide at a level of 30-35 mmHg. After abdominal opening, patients in Group 1 had a PEEP of 8 cm H2O applied and patients in Group 2 had a VCM followed by PEEP of 8 cm H2O. This manoeuvre was defined as lung inflation by a positive inspiratory pressure of 40 cm H2O maintained for 15 s. PEEP was maintained until extubation in the two groups. Haemodynamics, ventilatory and arterial oxygenation parameters were measured at the following times: T0 = before application of VCM and/or PEEP, T1 = 5 min after VCM and/or PEEP and T2 = before abdominal closure.

RESULTS

Patients in the two groups were comparable regarding patient characteristics, surgical, haemodynamic and ventilatory parameters. In Group 1, arterial oxygen partial pressure (PaO2) and arterial haemoglobin oxygen saturation (SaO2) were significantly increased and alveolar-arterial oxygen pressure gradient (A-aDO2) decreased at T2 when compared with T0 and T1. In Group 2, PaO2 and SaO2 were significantly increased and A-aDO2 decreased at T1 and T2 when compared with T0. Arterial oxygenation parameters at T1 and T2 were significantly improved in Group 2 when compared with Group 1.

CONCLUSION

The addition of VCM to PEEP improves intraoperative arterial oxygenation in morbidly obese patients undergoing open bariatric surgery.

Perioperative care of patients undergoing bariatric surgery

The epidemic of obesity in developed countries has resulted in patients with extreme (class III) obesity undergoing the full breadth of medical and surgical procedures. The popularity of bariatric surgery in the treatment of extreme obesity has raised awareness of the unique considerations in the care of this patient population. Minimizing the risk of perioperative complications that contribute to morbidity and mortality requires input from several clinical disciplines and begins with the preoperative assessment of the patient. Airway management, intravenous fluid administration, physiologic responses to pneumoperitoneum during laparoscopic procedures, and the risk of thrombotic complications and peripheral nerve injuries in extremely obese patients are among the factors that present special intraoperative challenges that affect postoperative recovery of the bariatric patient. Early recognition of perioperative complications and education of the patient regarding postoperative issues, including nutrition and vitamin supplementation therapy, can improve patient outcomes. A suitable physical environment and appropriate nursing and dietetic support provide a safe and dignified hospital experience. This article reviews the multidisciplinary management of extremely obese patients who undergo bariatric surgery at the Mayo Clinic.

Perioperative management of special populations: obesity

Surgeons and hospitals must be aware of the special considerations for treating obese patients. Obesity involves increased incidence of several comorbidities, such as coronary heart disease and hyper-tension, which increase perioperative risk. Obesity has been identified as an independent risk factor for surgical site infection and the obese population has a higher than normal incidence of perioperative deep venous thrombosis and pulmonary embolism. For these and other reasons, medical professionals must make thorough evaluations to properly identify and address medical comorbidities and other issues associated with obese patients. Medical professionals must, for example, use invasive arterial monitoring for severely obese patients and ensure that operating room tables can accommodate obese patients.

How to inform a morbidly obese patient on the specific risk to develop postoperative pulmonary complications using evidence-based methodology

BACKGROUND AND OBJECTIVE

Patients have the right to be informed about the expected benefits and risks of medical and surgical procedures. Ideally this information should be scientifically based and presented to the patient in time. In morbidly obese patient undergoing general anaesthesia, postoperative pulmonary complications are an important cause of postoperative morbidity and mortality. A 46-yr-old female with a body mass index of 89.8 kg m(-2) was scheduled to undergo radical abdominal surgery for cervix carcinoma. In order to inform her accurately on the risk of developing postoperative pulmonary complications, we undertook to answer the following question: What is the risk to develop postoperative pulmonary complications in a morbidly obese patient about to undergo abdominal surgery under general anaesthesia?

METHODS

A Medline search was conducted from 1966 to 2004 with respect to postoperative pulmonary complications in abdominal surgery of morbidly obese patients. Altogether, 213 articles were found, of which seven were selected. Additionally, seven cross-references and or related articles were used.

RESULTS

For obese patients who undergo abdominal surgery under general anaesthesia, the likelihood to develop atelectasis is 10.4 +/- 4.8% (P < 0.001) with a correlation coefficient of 0.28-0.34 (P < 0.05). The likelihood to develop atelectasis and pneumonia taken together is 29.3% with an adjusted odds ratio of 2.82 (95% confidence interval 1.66-4.78; P = 0.0001).

CONCLUSION

Considering the positive correlation coefficient and the high body mass index of this patient she has a risk of at least 29.3% to develop pneumonia and/or atelectasis, which should affect the anaesthetic strategy in this patient.

Anesthesia for Pediatric Obesity

This article discusses the unique anesthetic implications of obesity, with an emphasis on children and adolescents. It also touches on the issues surrounding bariatric surgery in the morbidly obese adolescent population. Adolescent bariatric surgery is moving to the forefront as a treatment modality because weight-loss programs alone are not keeping pace with the growth of the problem. Bariatric surgery offers the potential to achieve the weight reductions necessary to reverse the debilitating and costly comorbidities of obesity.

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.

Obesity: physiologic changes and challenges during laparoscopy

OBJECTIVE

The purpose of this report was to describe the evidence for the benefits of laparoscopic surgery in obese patients, to review the physiologic abnormalities that are associated with obesity, and to explore surgical techniques that will enable surgeons to perform laparoscopy successfully in obese patients.

STUDY DESIGN

This article is a review of the available literature on obesity, the physiologic changes that occur in obese patients, and the impact of these changes on laparoscopy outcomes.

RESULTS

Obesity is associated with sudden death and a wide range of morbid conditions such as hypertension, atherosclerosis, angina, chronic obstructive disease, and diabetes mellitus. Recent studies have demonstrated that obese patients who undergo laparoscopy have shorter hospital stays, less postoperative pain, and fewer wound infections when compared with obese patients who undergo laparotomy. Laparoscopy patients also have fewer postoperative ileus and fevers.

CONCLUSION

With thorough preparation and careful preoperative evaluation, laparoscopy can be performed safely and is the preferred surgical method in obese patients.

Percutaneous stone surgery in the obese: outcome stratified according to body mass index

OBJECTIVE

To report our experience of percutaneous surgery for treating renal pelvicalyceal stones over 6 years, to show that this approach is feasible and safe in obese and morbidly obese patients, as the prevalence of obesity and stone disease has risen in the last 20 years.

PATIENTS AND METHODS

We retrospectively reviewed the results of 223 percutaneous nephrolithotomies (PCNLs) by one urologist between 1995 and 2001. Patients were stratified into four groups according to the World Health Organization classification of body mass index (BMI), i.e. <25, 25-29.9 (overweight), 30-39.9 (obese) and > 40 kg/m(2) (morbidly obese). The outcomes of surgery in these four groups were compared.

RESULTS

There were no statistically significant differences in operative duration, decrease in haemoglobin concentration, postoperative analgesic use, hospital stay and stone-free rates; nor was there a higher complication rate in patients who were obese.

CONCLUSION

The outcome of PCNL is independent of the patients' BMI and results can be favourable in most patients. We therefore advocate treating obese patients with symptomatic stone disease based on individual status, using percutaneous surgery where appropriate.

The influence of body mass index on the prevalence of complications after vaginal and abdominal hysterectomy

AIM OF STUDY

To investigate the association between obesity and peri- or postoperative complications after hysterectomy for nonmalignant bleeding disorders.

MATERIAL AND METHODS

Data from 444 vaginal hysterectomies and 503 abdominal hysterectomies indicated by benign bleeding disorders were drawn from a regional database. Data on peri- or postoperative complications and postoperative stay were related to preoperative body mass index (BMI).

RESULTS

Obesity was related to longer operation time for vaginal as well as abdominal hysterectomy and to large perioperative blood loss for vaginal hysterectomy only. No association was found between BMI and serious complications such as ileus, infection or hematomas except for a higher prevalence of wound hematoma after abdominal hysterectomy in underweight and normal weight patients. Neither was any association found between BMI and use of blood transfusion, reoperation or prolonged postoperative stay.

CONCLUSION

Vaginal and abdominal hysterectomy have a significant risk of complications, but obese patients did not experience an increased risk of serious morbidity compared to normal weight women. Obesity per se is not a contraindication of vaginal or abdominal hysterectomy in otherwise healthy women.

The impact of body mass on management of patients with renal colic

OBJECTIVE

To study the impact of body mass on diagnosis and initial response to medical treatment in patients presenting with renal colic.

PATIENTS AND METHODS

One hundred and sixty-five consecutive patients presenting with symptoms of renal colic have been examined. Patients were divided in 3 groups according to their body mass index: normal-weight (BMI < or = 24.9 kg/m2), overweight (BMI 25.0-29.9 kg/m2) and obese (BMI > or = 30 kg/m2). Diagnosis of renal colic was based on history, clinical examination, presence of hematuria in a urine sample, appearance of a stone on a plain radiograph, and/or presence of hydronephrosis in ultrasonography. In addition, previous history of renal colic, time to seek medical advice and time to pain relief following administration of medications were examined.

RESULTS

Mean body mass index did not differ between patients with a history of < or = 1, 1-5 and > or = 5 renal colics (P = 0.65). Prevalence rates of appearance of either lithiasis or hydronephrosis vs normal findings on the Kidney-Ureter-Bladder plain radiograph or ultrasonography were not different between normal-weight, overweight and obese subjects (P = 0.38 and P = 0.90 respectively). The time to seek for medical advice and the response to treatment were not different between the study groups (P = 0.24 and P = 0.53 respectively).

CONCLUSION

Body mass does not have any impact on diagnosis, time to seek for medical advice or response to treatment in patients with renal colic.

Comparison of end-tidal and transcutaneous measures of carbon dioxide during general anaesthesia in severely obese adults

BACKGROUND

Patients with severe obesity (body mass index (BMI) greater than 35 kg x m(-2)) present difficulties for end-tidal carbon dioxide (FE'(CO(2))) monitoring. Previous studies suggest that transcutaneous (TC) carbon dioxide measurements could be valuable, so we compared FE' and TC measures with Pa(CO(2)) in severely obese patients during anaesthesia.

METHODS

We studied patients with severe obesity (BMI >or=40 kg x m(-2)) undergoing gastric bypass surgery. Carbon dioxide was measured with both FE' and TC devices. The difference between each measure (FE'(CO(2)) and TC-CO(2)) and the Pa(CO(2)) was averaged for each patient to provide one value, and data compared with a non-paired, two-way t-test, Fisher's exact test.

RESULTS

We studied 30 adults (aged 18-54 yr, mean 41, SD 8.0 yr; weight: 115-267 kg, mean 162, SD 35 kg). The absolute difference between the TC-CO(2) and Pa(CO(2)) was 0.2 (0.2) (mean, SD) kPa while the absolute difference between the FE'(CO(2)) and Pa(CO(2)) was 0.7 (0.4) kPa (P<0.0001). The bias and precision were +0.1 (0.3) kPa for TC vs arterial carbon dioxide and -0.7 (0.4) kPa for FE' vs arterial carbon dioxide.

CONCLUSIONS

Transcutaneous carbon dioxide monitoring provides a better estimate of Pa(CO(2)) than FE'(CO(2)) in patients with severe obesity.

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.

Childhood obesity: a challenge for the anaesthetist?

The definition of childhood obesity has not been standardized in the past, making studies difficult to compare. In spite of this, the increase in the incidence of childhood obesity is evident and has now reached epidemic proportions. Obese children experience few of the medical complications seen in obese adults. Respiratory physiology appears to be most affected, the degree of which is determined by the level of obesity. Although there is a considerable amount of information on the anaesthetic management of the obese adult, very little has been written concerning the obese child. There is less pathology in the obese child when compared with the adult but some evidence shows a higher likelihood of a critical incident occurring when anaesthetizing such children. This shows that we need to be as worried about anaesthetizing the obese child as we are for the obese adult. This concern should increase with increasing body mass index.

A pilot study of patient-led identification of the midline of the lumbar spine

The midline of the lumbar spine is usually identified by palpation of the spinous processes. Placement of an epidural or spinal needle is more difficult when these bony landmarks are impalpable. This pilot study investigated the ability of 50 healthy volunteers to identify the midline of their own backs, using light touch or proprioception. The midline as identified in this manner was compared with the 'gold standard' as defined by the interspinous line. Sensation to light touch was the most accurate, with 90% of the volunteers able to identify the midline to within 6.5 mm. Proprioception using a finger to touch the midline was less accurate. This study was carried out on volunteers with palpable spinous processes but suggests that, in certain circumstances, a patient-led identification of the midline may be of value.

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.

Randomized comparison of isoflurane and sevoflurane for laparoscopic gastric banding in morbidly obese patients

STUDY OBJECTIVE

To compare the efficacy and recovery profile of sevoflurane and isoflurane as the main anesthetics for morbidly obese patients.

DESIGN

Randomized, blinded study.

SETTING

Inpatients.

PATIENTS

30 ASA physical status II and III obese patients [body mass index (BMI) > 35 kg/m(2)] undergoing laparoscopic gastric banding for morbid obesity.

INTERVENTIONS

After standard intravenous induction of general anesthesia and tracheal intubation, anesthesia was maintained with either sevoflurane or isoflurane as the main anesthetics. The end-tidal concentrations of the volatile drugs were adjusted to maintain systolic arterial blood pressure within +/-20% from baseline values. When the surgeon started the skin suture, the end-tidal concentration of the inhalational drug was reduced to 0.5 minimum alveolar concentration in both groups. At the last skin suture, the inhalational drug was discontinued and the vaporizator was removed to allow blinded evaluation of the emergence times.

MEASUREMENTS AND MAIN RESULTS

No differences in anesthetic exposure, hemodynamic parameters, incidence of untoward events, or postoperative pain relief were reported between the two groups. Extubation, emergence, and response times were shorter after sevoflurane [6 min (3-15 min), 8 min (5-18 min), and 12 (6-25 min)] than isoflurane [10 min (6-26 min), 14 min (6-21 min), and 21 min (14-41 min)] (p = 0.001, p = 0.03, and p = 0.0005, respectively). The median time for postanesthesia care unit discharge was 15 minutes (25th-75th percentiles: 10-18 min) after sevoflurane and 27 minutes (25th-75th percentiles: 20-30 min) after isoflurane (p = 0.0005).

CONCLUSIONS

Sevoflurane provides a safe and effective intraoperative control of cardiovascular homeostasis in morbidly obese patients undergoing laparoscopic gastric banding, with the advantage of a faster recovery and earlier discharge from the postanesthesia care unit than isoflurane.

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.

Anaesthesia for LSCS in a morbidly obese patient

The management of a morbidly obese parturient with a body mass index of 88 is reported. She developed asthma during the pregnancy. Lumbar epidural anaesthesia was successfully used for an elective caesarean section and tubal ligation.