Serum inorganic fluoride levels in obese patients during and after enflurane anesthesia

Serum ionic fluoride levels in 24 markedly obese patients (127.6 +/- 6.0 kg) and seven nonobese control subjects (67.3 +/- 1.2 kg) were compared during and following enflurane anesthesia (less than 2.0 MAC hr). Peak serum fluoride levels were higher (28.0 +/- 1.9 vs 17.3 +/- 1.3 micrometers/L, p less than 0.01) and the rate at which fluoride levels increased was more rapid (slope 5.6 vs 2.5 micrometers/L/hr) in obese patients than in control patients. No clinical evidence of nephrotoxicity was found in either group. Vasopressin resistance tests were not performed, and thus it is inknown whether subclinical nephrotoxicity occurred in either study group. Possible reasons for increased enflurane metabolism in obesity are discussed. These possibilities include differences in fluoride ion kinetics, hepatic delivery and penetration of volatile anesthetics, and altered hepatic microsomal enzyme activity. Obesity rather than weight is an important determinant of anesthetic biotransformation.     

Perioperative outcome of esophageal fundoplication for gastroesophageal reflux disease in obese and morbidly obese patients

Background

To determine the perioperative safety of esophageal fundoplication for gastroesophageal reflux disease (GERD) in patients with body mass index (BMI) ≥35 kg/m².

Methods

A retrospective review of 4,231 patients who underwent fundoplication for GERD from 2005 to 2009 was performed. Patients were identified via National Surgical Quality Improvement Program and grouped by BMI < 35 versus BMI ≥ 35 kg/m². Univariate analysis compared 30-day outcomes.

Results

Of the 4,231 patients, 3,496 (83%) had BMI < 35 kg/m² and 735 (17%) had BMI ≥ 35 kg/m². Mean BMI for each cohort was 27.9 versus 39.1, respectively. Patients with BMI ≥ 35 kg/m² had significantly longer operative times (129.7 vs 118 minutes, P < .0001) and increased American Society of Anesthesiologists scores (2.43 vs 2.3, P = .001). The overall complication rate was 1.96%. No difference was demonstrated by BMI in complication rate or hospital length of stay. Increased American Society of Anesthesiologists score, diabetes, black race, longer operative time, and intraoperative transfusion significantly increased postoperative complication rates.

Conclusions

No increased risk is conferred to morbidly obese patients who undergo fundoplication for GERD management. This study identified independent patient risk factors for postoperative complication following esophageal fundoplication.     

Faster wash-out and recovery for desflurane vs sevoflurane in morbidly obese patients when no premedication is used

Background: The aim of this study was to compare desflurane vs sevofluranekinetics and dynamics in morbidly obese patients and their recoveryprofile when no premedication had been used. Methods: Twenty-eight unpremedicated obese patients were randomly allocatedto receive either sevoflurane (n = 14) or desflurane (n = 14)as the main anaesthetic agent. After induction of anaesthesia,either sevoflurane 2% or desflurane 6% was administered for30 min via a non-rebreathing circuit. The kinetics of sevofluraneand desflurane were determined by measuring and recording end-tidalsamples during this time. The bispectral index was used to indicatethe level of hypnosis. At the end of the procedure, the end-tidalconcentrations of sevoflurane and desflurane were recorded duringthe first 5 min after stopping their administration. Time fromdiscontinuation of the anaesthetic drugs to eye opening on verbalcommand, squeezing the observer's hand on command, extubation,stating their name, giving their correct date of birth, dischargefrom the recovery room, and duration of the surgery and anaesthesiawere also recorded. Results: The F_A/F_I ratio was significantly higher in the desflurane groupfrom the 15th to the 30th min. The wash-out phase was fasterfor desflurane during the total observation period. When desfluranewas used, recovery was also faster. Conclusions: Desflurane provides faster wash-in and wash-out than sevofluranein morbidly obese patients, and recovery is much faster afterdesflurane administration when no premedication has been used.     

Laparoscopic Roux-en-Y gastric bypass in morbidly obese and super morbidly obese patients

BACKGROUND: Our objective was to compare the outcomes after laparoscopic Roux-en-Y gastric bypass (RYGB) in morbidly obese (body mass index [BMI] <50) patients with super morbidly obese (BMI >50) patients. METHODS: A prospective analysis of 120 patients who underwent laparoscopic RYGB at a community based teaching hospital between January 2002 and August 2002 was performed. Sixty patients with BMI <50 were compared with 60 patients with BMI >50. Study endpoints included: operative time, length of stay, and overall complication rates including early (<7 days) and late (>7 days) complications. RESULTS: Mean BMI in the obese group was 44.6 (range 39 to 49) versus 58.6 (range 50 to 100) in the superobese group. Medical comorbidities, age, and sex distribution were similar in both groups. Mean operative time in the obese group was 128 minutes (range 75 to 225) versus 144 minutes (range 75 to 240) in the superobese group. The overall complication rate was 10% in the obese group versus 20% in the superobese group. (P = 0.2) With regard to the obese group, the early complication rate was 5% (n = 3). These included 2 upper gastrointestinal bleeds and 1 respiratory failure. The late complication rate in this group was also 5% (n = 3). These were all anastomotic strictures requiring endoscopic dilation. In comparison, in the superobese group, the early complication rate was 8% (n = 5). These included 2 upper gastrointestinal bleeds, 1 pneumonia, 1 superficial wound infection, and 1 small bowel obstruction. The late complication rate in this group was 12% (n = 7). These included 4 anastomotic strictures, 1 incisional hernia, 1 pulmonary embolism, and 1 anastomotic leak. There were no conversions to open gastric bypass or deaths in either group. Median length of stay in both groups was 2 days. CONCLUSIONS: Our data demonstrate no significant difference in operative times, complication rates or length of stay between morbidly obese and super morbidly obese patients undergoing laparoscopic RYGB. Laparoscopic RYGB is safe and technically feasible in the super morbidly obese patient population.     

Optimization of desflurane administration in morbidly obese patients: a comparison with sevoflurane using an 'inhalation bolus' technique

Background. The concept of an ‘inhalation bolus’can be used to optimize inhaled drug administration. We investigatedthe depth of anaesthesia, haemodynamic stability, and recoverytime in morbidly obese patients resulting from bispectral index^TM(BIS^TM)-guided sevoflurane or desflurane administration andBIS-triggered inhalation boluses of sevoflurane or desfluranecombined with titration of remifentanil. Methods. Fifty morbidly obese patients undergoing laparoscopicgastroplasty received either BIS-guided sevoflurane or desfluraneanaesthesia in combination with a remifentanil target-controlledinfusion. Intraoperative haemodynamic stability and BIS controlwere measured. Immediate recovery was recorded. Results. Intraoperatively, the BIS was between 40 and 60 fora greater percentage of time in the sevoflurane (78 (13)% ofcase time) than in the desflurane patients (64 (14)% of casetime), owing to too profound anaesthesia in the desflurane patientsat the start of the procedure. However, fewer episodes of hypotensionwere found in the desflurane group, without the occurrence ofmore hypertensive episodes. During immediate recovery, eye opening,extubation, airway maintenance, and orientation occurred soonerin the desflurane group. Conclusions. Immediate recovery was significantly faster inthe desflurane group. Overall hypnotic controllability measuredby BIS was less accurate with desflurane. Overall haemodynamiccontrollability was better when using desflurane. Fewer episodesof hypotension were found in the desflurane group. The use ofthe inhalation bolus was found to be appropriate in both groupswithout causing severe haemodynamic side effects. Minimal BISvalues were significantly lower after a desflurane bolus. Br J Anaesth 2003; 91: 638–50     

Acid aspiration prophylaxis in morbidly obese patients: famotidine vs. ranitidine

Famotidine and ranitidine were compared as agents for the prevention of acid aspiration syndrome in 32 morbidly obese patients undergoing vertical banded gastroplasty. Single-dose oral famotidine or double-dose oral ranitidine were administered on a random basis before surgery. Gastric contents were aspirated through a gastric tube, manually aided by the surgeon with the abdomen open. Mean (SD) gastric volumes were 13.8 ml (6.7) and 12.1 ml (13.0) for the famotidine and ranitidine groups, respectively. Mean (SD) gastric pH values were 6.2 (1.5) and 6.8 (1.5), respectively. There were no significant differences between the groups and no patient was considered 'at risk' (pH less than 2.5 and gastric volume greater than 25 ml). We conclude that single-dose oral famotidine and double-dose oral ranitidine are equally effective for preventing acid aspiration syndrome in morbidly obese patients.     

Serum fluoride in children anaesthetized with enflurane

The serum inorganic fluoride concentration (SF) was measured in 40 children aged 22 days to 11 yrs (five infants) undergoing enflurane anaesthesia lasting 20-200 min, at an inspiratory concentration of 0.8 or 1.0%. Regardless of age, SF peaked at 2-8 mumol l-1 after 20-40 min of enflurane exposure, and at 4-10 mumol 1-1 and 6-10 mumol l-1 after 41-90 min and 91-200 min of exposure, respectively. The highest individual value was 12.5 mumol l-1. Another 23 children, aged 1-16 yrs, received 0.8% enflurane for 60 min. The increase in SF was 3-9 mumol l-1, with no clear dependence on age. Altogether, the increase in SF was comparable to that detected in adults after anaesthesia of equal duration.     

A comparison of outcomes in morbidly obese,obese and non-obese patients undergoing primary total knee and total hip arthroplasty

Background

Obesity is a growing public health issue with the prevalence of morbid obesity, (Body Mass Index (BMI) ≥ 40 kg/m²) increasing. There is some evidence these patients have more peri- and post-operative complications and poorer outcomes when undergoing arthroplasty procedures. This audit aimed to determine and compare the outcomes of non-obese, obese and morbidly obese patients undergoing arthroplasty at our institution.

Predictive performance of 'Servin's formula' during BIS-guided propofol-remifentanil target-controlled infusion in morbidly obese patients

Background. The aim of this study was to assess the predictiveperformance of ‘Servin's formula’ for bispectralindex (BIS)-guided propofol-remifentanil target-controlled infusion(TCI) in morbidly obese patients. Methods. Twenty patients (ASA physical status II–III,age 32–64 yr) undergoing bilio-intestinal bypass surgery,were recruited. Anaesthesia was induced by using a TCI of propofolwith an initial target plasma concentration of 6 µg ml^–1,then adapted to maintain stable BIS values ranging between 40and 50. A TCI of remifentanil was added to achieve pain controland haemodynamic stability. For propofol, weight was correctedas suggested by Servin and colleagues. With ideal body weight(IBW) corrected according to formula suggested by Lemmens andcolleagues. For remifentanil, weight was corrected accordingto IBW. Arterial blood samples for the determination of bloodpropofol concentrations were collected at different surgicaltimes. The predictive performance of propofol TCI was evaluatedby examining performance accuracy. Results. Median prediction error and median absolute predictionerror were –32.6% (range –53.4%; –2.5%) and33.1% (10.8%; 53.4%), respectively. Wobble median value was5.9% (2.5%; 25.2%) while divergence median value was –1.5%h^–1 (–7.7; 33.8% h^–1). Conclusion. Significant bias between predicted and measuredplasma propofol concentrations was found while the low wobblevalues suggest that propofol TCI system is able to maintainstable drug concentrations over time. As already suggested before,a computer simulation confirmed that the TCI system performancecould be significantly improved when total body weight is used.     

Obstetric anaesthesia outcome in obese and non-obese parturients undergoing caesarean delivery: an observational study

BackgroundMaternal obesity is increasing in prevalence and is associated with an increased risk of perioperative complications. This study evaluates the impact of obesity on perioperative outcomes in parturients undergoing caesarean delivery.MethodsIn this prospective observational study of 1477 consecutive caesarean deliveries, data collected included body mass index, co-morbidities, anaesthetic technique, perioperative complications and patient satisfaction. Outcome measures included obesity prevalence, association of obesity with caesarean delivery, co-morbidities, perioperative complications and patient satisfaction and were compared between the obese and non-obese groups.ResultsThe prevalence of obesity was 54.3%, including 7.2% morbidly obese. About 61% of parturients who underwent caesarean delivery because of failure to progress in labour or previous caesarean were obese. The overall prevalence of co-morbidity was 10.2% of whom 57.3% were obese. Neuraxial anaesthesia was used in 73.4% and general anaesthesia in 26.6%, similar in obese and non-obese. The epidural failure rate was 4.3% and the spinal failure rate 2.9%. Difficulty in performing neuraxial anaesthesia was greater in obese patients (P = 0.004). There was no association between obesity and laryngoscopy grades. Patient satisfaction was similar in the obese and non-obese groups. Postoperative complications were minimal and similar.ConclusionsNeuraxial anaesthesia was effective for caesarean deliveries in obese and non-obese, in elective and emergency cases. Maternal obesity is associated with increased difficulty in performing neuraxial anaesthesia, but not with increased failure rate. Our study found no differences between obese and non-obese parturients in rate of caesarean deliveries, co-morbidities, indications for delivery or anaesthesia complications.     

Hepatic Abnormalities in Obesity: comparison between mildly obese cases and morbidly obese cases

Hepatic morphology and clinical course of mildly obese subjects with abnormal liver tests were determined in comparison with those of surgically treated morbidly obese cases. Twenty mildly obese subjects (mean body mass index, 27.9) with elevated serum transaminase levels were followed up on a low-calorie diet. Nineteen morbidly obese patients (mean body mass index, 39.2) had a surgical biopsy at gastric restrictive surgery. In these two groups, the frequency and the severity of hepatic steatosis and fibrosis were comparable, whereas intralobular cell infiltration was somewhat greater in the mildly obese group. Follow-up studies of the two groups showed remarkable improvement of serum transaminase levels, the extent of which was greater in surgically treated cases. Thus, in mildly obese subjects with abnormal liver tests, (1) hepatic histological abnormalities are not milder than those in morbidly obese cases, and (2) improvement of serum transaminase levels upon diet therapy is less satisfactory than that in morbidly obese cases treated surgically. It is suggested these two groups may not be in the same spectrum of obesity-related hepatic disorders.     

Prolonged anaesthesia with isoflurane and halothane

Hepatic function was assessed pre-operatively and on the first and sixth postoperative days in 40 healthy patients who underwent prolonged maxillofacial surgery with isoflurane or halothane anaesthesia. No major changes were observed in hepatic enzymes or bilirubin. One-stage prothrombin time and Factor VII concentrations decreased on the first postoperative day and this change was more pronounced in the halothane group. The results support the use of isoflurane rather than halothane for prolonged anaesthesia in respect of the synthesising function of the liver.     

The microcirculation during enflurane and isoflurane anaesthesia in dogs

The effects of enflurane and isoflurane of 0.75 and 1.5 MAC on capillary blood flow were studied by the microsphere (9 ± 1 μm in diameter) method in two groups of seven dogs. Simultaneously, changes in the arteriolo-venular shunt were studied by collection of venous blood at a rate of 4.8 ml · min^?1 for two minutes. Enflurane anaesthesia at 0.75 MAC decreased capillary blood flow in the thyroid glands (35% of control), left and right ventricular wall (59% and 50%), adrenal gland (59%), liver (63%), spleen (56%), pancreas (35%), omentum (20%), and small intestine (60%) and at 1.5 MAC it decreased further in the thyroid glands (15%), left and right ventricular wall (31% and 32%), adrenal gland (42%), liver (47%), spleen (31%), pancreas (23%), omentum (20%), stomach (45%), and small intestine (54%). No marked changes were noted in the brain, kidney, large intestine or skeletal muscle. The arteriolo-venular shunt was decreased in the kidney from an initial rate of 12.1 to 3.8% at 0.75 MAC and to 2.5% at 1.5 MAC enflurane. In contrast, during isoflurane anaesthesia, capillary blood flow remained unchanged, except for a decrease to the thyroid glands (43%) and right ventricular wall (74%) during 1.5 MAC anaesthesia. However, the arteriolo-venular shunt was increased in the brain from 12.0 to 29.7% and 33.0% during 0.75 and 1.5 MAC isoflurane anaesthesia, respectively. It also increased from 25.0 to 41.0% and 46.3% in the skeletal muscle, and from 8.9 to 19.9% and 17.4% in the whole systemic circulation. These data indicate that capillary blood flow is better preserved during isoflurane than during enflurane anaesthesia, but is associated with increased arteriolo-venular shunting.     

Atomised lidocaine for airway topical anaesthesia in the morbidly obese: 1% compared with 2%*

Airway anaesthesia using atomised lidocaine for awake oral fibreoptic intubation in morbidly obese patients was evaluated using two doses of local anaesthetic. In this randomised, blinded prospective study, 40 ml of atomised 1% (n = 11) or 2% (n = 10) lidocaine was administered with high oxygen flow as carrier. Outcomes included time for intubation, patient tolerance to airway manipulation, haemodynamic parameters, the bronchoscopist’s overall satisfaction, and serial serum lidocaine concentrations. Patients receiving lidocaine 1% had a longer mean (SD) time from the start of topicalisation to tracheal tube cuff inflation than those receiving lidocaine 2% (8.6 (0.9) min vs 6.9 (0.5) min, respectively; p < 0.05). Patients in the 1% cohort demonstrated increased responses to airway manipulation (p < 0.0001), reflecting lower bronchoscopist’s satisfaction scores (p < 0.03). Haemodynamic responses to topicalisation and airway manipulation were similar in both groups. Peak plasma concentration was lower in the 1% group (mean (SD) 1.4 (0.3) and 3.8 (0.5) μg.ml^?1, respectively; p < 0.001). Airway anaesthesia using atomised lidocaine for awake oral fibreoptic intubation in the morbidly obese is efficacious, rapid and safe. Compared with lidocaine 1%, the 2% dose provides superior intubating conditions.     

Wash-in and wash-out curves of sevoflurane and isoflurane in morbidly obese patients

BACKGROUND: The aim of this prospective, randomized study is to compare sevoflurane and isoflurane pharmacokinetics in morbidly obese patients. METHODS: With Ethical Committee approval and written informed consent, 14 obese patients (BMI >35 kg/m2), ASA physical status II, undergoing laparoscopic, silicone-adjustable gastric banding were randomly allocated to receive either sevoflurane (n=7) or isoflurane (n=7) as main anesthetic agents. General anesthesia was induced with 1 mg x kg-1 fentanyl, 6 mg x kg-1 sodium thiopental, and 1 mg x kg-1 succinylcholine followed by 0.4 mg kg-1 x h-1 atracurium bromide (doses were referred to ideal body weight). Intermittent positive pressure ventilation (IPPV) was applied using a Servo-900C ventilator with a nonrebreathing circuit and a 15 l x min-1 fresh gas flow (tidal volume: of 10 ml x kg-1; respiratory rate: 12 breaths/min; inspiratory to expiratory time ratio of 1:2) using an oxygen/air mixture (FiO2=50%), while supplemental boluses of thiopental or fentanyl were given as indicated in order to maintain blood pressure and heart rate values within +/-20% from baseline. After adequate placement of tracheal tube and stabilization of the ventilation parameters, 2% sevoflurane or 1.2% isoflurane was given for 30 min via a nonrebreathing circuit. End-tidal samples were collected at 1, 5, 10, 15, 20, 25 and 30 min, and measured using a calibrated infrared gas analyzer. General anesthesia was then maintained with the same inhalational agents, while supplemental fentanyl was given as indicated. After the last skin suture the inhalational agents were suspended, and the end tidal samples were collected at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5 min. Then the lungs were manually ventilated until extubation. RESULTS: No differences in age, gender and body mass index were reported between the two groups. Surgical procedure required 91+/-13 in the sevoflurane group and 83+/-32 min in the isoflurane group. The FA/FI ratio was higher in the sevoflurane group from the 5th to the 30th min. Also the washout curve was faster in the sevoflurane group during the observation period; however, the observed differences were statistically significant only 30 and 60 sec after discontinuation of the inhalational agents. CONCLUSIONS: The results of this prospective, randomized study confirmed that sevoflurane provides more rapid wash-in and wash-out curves than isoflurane also in the morbid obese patient.