Scour Damage Detection and Structural Health Monitoring of a Laboratory-Scaled Bridge Using a Vibration Energy Harvesting Device.

A vibration-based bridge scour detection procedure using a cantilever-based piezoelectric energy harvesting device (EHD) is proposed here. This has an advantage over an accelerometer-based method in that potentially, the requirement for a power source can be negated with the only power requirement being the storage and/or transmission of the data. Ideally, this source of power could be fulfilled by the EHD itself, although much research is currently being done to explore this. The open-circuit EHD voltage is used here to detect bridge frequency shifts arising due to scour. Using one EHD attached to the central bridge pier, both scour at the pier of installation and scour at another bridge pier can be detected from the EHD voltage generated during the bridge free-vibration stage, while the harvester is attached to a healthy pier. The method would work best with an initial modal analysis of the bridge structure in order to identify frequencies that may be sensitive to scour. Frequency components corresponding to harmonic loading and electrical interference arising from experiments are removed using the filter bank property of singular spectrum analysis (SSA). These frequencies can then be monitored by using harvested voltage from the energy harvesting device and successfully utilised towards structural health monitoring of a model bridge affected by scour.

Effect of Epidural Infusion Bolus Delivery Rate on the Duration of Labor Analgesia: A Randomized Clinical Trial.

BACKGROUND: Programmed intermittent boluses of local anesthetic have been shown to be superior to continuous infusions for maintenance of labor analgesia. High-rate epidural boluses increase delivery pressure at the catheter orifice and may improve drug distribution in the epidural space. We hypothesized that high-rate drug delivery would improve labor analgesia and reduce the requirement for provider-administered supplemental boluses for breakthrough pain. METHODS: Nulliparous women with a singleton pregnancy at a cervical dilation of less than or equal to 5 cm at request for neuraxial analgesia were eligible for this superiority-design, double-blind, randomized controlled trial. Neuraxial analgesia was initiated with intrathecal fentanyl 25 µg. The maintenance epidural solution was bupivacaine 0.625 mg/ml with fentanyl 1.95 µg/ml. Programmed (every 60 min) intermittent boluses (10 ml) and patient controlled bolus (5 ml bolus, lockout interval: 10 min) were administered at a rate of 100 ml/h (low-rate) or 300 ml/h (high-rate). The primary outcome was percentage of patients requiring provider-administered supplemental bolus analgesia. RESULTS: One hundred eight women were randomized to the low- and 102 to the high-rate group. Provider-administered supplemental bolus doses were requested by 44 of 108 (40.7%) in the low- and 37 of 102 (36.3%) in the high-rate group (difference -4.4%; 95% CI of the difference, -18.5 to 9.1%; P = 0.67). Patient requested/delivered epidural bolus ratio and the hourly bupivacaine consumption were not different between groups. No subject had an adverse event. CONCLUSIONS: Labor analgesia quality, assessed by need for provider- and patient-administered supplemental analgesia and hourly bupivacaine consumption was not improved by high-rate epidural bolus administration.

The Effect of Prophylactic Phenylephrine and Ephedrine Infusions on Umbilical Artery Blood pH in Women With Preeclampsia Undergoing Cesarean Delivery With Spinal Anesthesia: A Randomized, Double-Blind Trial.

BACKGROUND: Spinal anesthesia for cesarean delivery is associated with a high incidence of hypotension. Phenylephrine results in higher umbilical artery pH than ephedrine when used to prevent or treat hypotension in healthy women. We hypothesized that phenylephrine compared to ephedrine would result in higher umbilical artery pH in women with preeclampsia undergoing cesarean delivery with spinal anesthesia. METHODS: This study was a randomized double-blind clinical trial. Nonlaboring women with preeclampsia scheduled for cesarean delivery with spinal anesthesia at Prentice Women's Hospital of Northwestern Medicine were randomized to receive prophylactic infusions of phenylephrine or ephedrine titrated to maintain systolic blood pressure >80% of baseline. Spinal anesthesia consisted of hyperbaric 0.75% bupivacaine 12 mg, fentanyl 15 µg, and morphine 150 µg. The primary outcome was umbilical arterial blood pH and the secondary outcome was umbilical artery base excess. RESULTS: One hundred ten women were enrolled in the study and 54 per group were included in the analysis. There were 74 and 72 infants delivered in the ephedrine and phenylephrine groups, respectively. The phenylephrine:ephedrine ratio for umbilical artery pH was 1.002 (95% confidence interval [CI], 0.997-1.007). Mean [standard deviation] umbilical artery pH was not different between the ephedrine 7.20 [0.10] and phenylephrine 7.22 [0.07] groups (mean difference -0.02, 95% CI of the difference -0.06 to 0.07; P = .38). Median (first, third quartiles) umbilical artery base excess was -3.4 mEq/L (-5.7 to -2.0 mEq/L) in the ephedrine group and -2.8 mEq/L (-4.6 to -2.2mEq/L) in the phenylephrine group (difference -0.6 mEq/L, 95% CI of the difference -1.6 to 0.3 mEq/L; P = .10). When adjusted for gestational age and infant gender, umbilical artery pH did not differ between groups. There were also no differences in the umbilical artery pH stratified by magnesium therapy or by the severity of preeclampsia. CONCLUSIONS: We were unable to demonstrate a beneficial effect of phenylephrine on umbilical artery pH compared with ephedrine. Our findings suggest that phenylephrine may not have a clinically important advantage compared with ephedrine with regard to improved neonatal acid-base status when used to prevent spinal anesthesia-induced hypotension in women with preeclampsia undergoing cesarean delivery.

Is dexamethasone associated with recurrence of ovarian cancer?

BACKGROUND: Basic science studies suggest that perioperative immune impairment may augment the risk of cancer recurrence after otherwise potentially curative surgery. Despite its immunosuppressant properties, dexamethasone is commonly given to oncologic patients in an effort to reduce postoperative nausea and vomiting. We therefore tested the hypothesis that perioperative dexamethasone administration increases the risk of ovarian cancer recurrence. METHODS: Women who had primary ovarian cytoreductive surgery between January 1997 and October 2007 were identified using a database maintained by the division of Gynecologic Oncology at Northwestern University. Tumor recurrence in women given perioperative systemic dexamethasone (4-10 mg) was compared with those who did not receive dexamethasone. The primary outcome was the propensity-matched time to cancer recurrence. Recurrence was defined by a carcinoantigen 125 >21 U/mL or computerized tomography evidence of the disease followed by tissue confirmation. Median difference and 95% confidence interval between the propensity-matched groups were calculated using a 10,000 sample bootstrap. RESULTS: Among 260 women having primary cytoreductive surgery for ovarian cancer that met our inclusion criteria, 102 subjects were given perioperative systemic dexamethasone. Cancer recurrence was observed in 178 subjects, and the overall unadjusted median (IQR) time to recurrence was 18 (7-50) months. Eighty-seven cases and 87 controls were propensity matched to adjust for confounding covariates. After propensity matching the groups for confounding covariates, the median (IQR) time to recurrence in the dexamethasone group was 23 (6-46) compared with 18 (8-53) months in the control group (P = 0.63) with a median (95% confidence interval) difference of time to recurrence between the dexamethasone and the control group of 5 (-8 to 17) months. CONCLUSION: We could not find evidence for an association between perioperative systemic dexamethasone administration and ovarian cancer recurrence after primary cytoreductive surgery. Our results do not support avoiding low-dose perioperative dexamethasone for prevention of postoperative nausea, vomiting, and pain in ovarian cancer patients.

The effect of ketamine on hypoventilation during deep sedation with midazolam and propofol: a randomised, double-blind, placebo-controlled trial.

BACKGROUND: Hypoventilation is a major cause of morbidity and mortality in patients having procedures under sedation. Few clinical strategies have been evaluated to reduce intraoperative hypoventilation during surgical procedures under deep sedation. OBJECTIVE: The primary objective of this investigation was to examine the effect of ketamine on hypoventilation in patients receiving deep sedation for surgery with midazolam and propofol. DESIGN: The study was a randomised, placebo-controlled, double-blind clinical trial. SETTING: Intraoperative. PATIENTS: Healthy women undergoing breast surgery. INTERVENTION: Randomised to receive ketamine (0.5 mg kg bolus, followed by an infusion of 1.5 µg kg min) or isotonic saline. MAIN OUTCOME MEASURE: Duration of hypercapnia measured continuously with a transcutaneous carbon dioxide (TCO2) monitor. RESULTS: Fifty-four participants were recruited. Patient and surgical characteristics were similar between the study groups. The median percentage of the sedation time with TCO2 more than 6.7 kPa in participants in the ketamine group, 1.2% (95% confidence interval, CI, 0 to 83), was less than that in the isotonic saline group (65%, 95% CI, 0 to 88; P = 0.01). Severe hypoventilation (TCO2 >8.0 kPa) was also less in the ketamine group, median 0% (95% CI, 0 to 11.7) compared with 28% (95% CI, 0 to 79.3; P = 0.0002) for the isotonic saline group. The ketamine group required less airway manoeuvres (chin lift) to keep the SaO2 greater than 95% median (95% CI) [0 (0 to 3) compared with 3 (0 to 16) in the isotonic saline group] (P = 0.004). CONCLUSION: Ketamine decreased the duration and severity of hypercapnia in patients undergoing deep sedation with propofol. The addition of ketamine may reduce hypoventilation and adverse effects in patients having procedures under sedation. TRIAL REGISTRATION: clinicaltrials.gov identifier: NCT01535976.

The association between frequency of self-reported medical errors and anesthesia trainee supervision: a survey of United States anesthesiology residents-in-training.

BACKGROUND: Poor supervision of physician trainees can be detrimental not only to resident education but also to patient care and safety. Inadequate supervision has been associated with more frequent deaths of patients under the care of junior residents. We hypothesized that residents reporting more medical errors would also report lower quality of supervision scores than the ones with lower reported medical errors. The primary objective of this study was to evaluate the association between the frequency of medical errors reported by residents and their perceived quality of faculty supervision. METHODS: A cross-sectional nationwide survey was sent to 1000 residents randomly selected from anesthesiology training departments across the United States. Residents from 122 residency programs were invited to participate, the median (interquartile range) per institution was 7 (4-11). Participants were asked to complete a survey assessing demography, perceived quality of faculty supervision, and perceived causes of inadequate perceived supervision. Responses to the statements "I perform procedures for which I am not properly trained," "I make mistakes that have negative consequences for the patient," and "I have made a medication error (drug or incorrect dose) in the last year" were used to assess error rates. Average supervision scores were determined using the De Oliveira Filho et al. scale and compared among the frequency of self-reported error categories using the Kruskal-Wallis test. RESULTS: Six hundred four residents responded to the survey (60.4%). Forty-five (7.5%) of the respondents reported performing procedures for which they were not properly trained, 24 (4%) reported having made mistakes with negative consequences to patients, and 16 (3%) reported medication errors in the last year having occurred multiple times or often. Supervision scores were inversely correlated with the frequency of reported errors for all 3 questions evaluating errors. At a cutoff value of 3, supervision scores demonstrated an overall accuracy (area under the curve) (99% confidence interval) of 0.81 (0.73-0.86), 0.89 (0.77-0.95), and 0.93 (0.77-0.98) for predicting a response of multiple times or often to the question of performing procedures for which they were not properly trained, reported mistakes with negative consequences to patients, and reported medication errors in the last year, respectively. CONCLUSIONS: Anesthesiology trainees who reported a greater incidence of medical errors with negative consequences to patients and drug errors also reported lower scores for supervision by faculty. Our findings suggest that further studies of the association between supervision and patient safety are warranted. (Anesth Analg 2013;116:892-7).

The prevalence of burnout and depression and their association with adherence to safety and practice standards: a survey of United States anesthesiology trainees.

BACKGROUND: The prevalence of burnout and depression in anesthesiology residents has not been determined. It is also unknown whether anesthesiology resident burnout/depression may affect patient care and safety. The primary objective of this study was to determine the prevalence of burnout and depression in anesthesiology residents in the United States. We hypothesized that residents at high risk of burnout and/or depression would report more medical errors as well as a lower rate of following principles identified as the best practice of anesthesiology. METHODS: A cross-sectional survey was sent to 2773 anesthesiology residents in the United States. The questionnaire was divided into 5 parts examining trainees' demographic factors, burnout (Maslach Burnout Inventory), depression (Harvard depression scale), 10 questions designed to evaluate best practice of anesthesiology, and 7 questions evaluating self-reported errors. Best practices and self-reported error rates were compared among subjects with a high risk of burnout only, high risk of depression only, high risk of burnout and depression, and low risk of burnout and depression. Pairwise comparisons were considered significant at P < 0.004 and confidence intervals (CIs) reported at 99.6%. RESULTS: There were 1508 (54%) resident responds. High burnout risk was found in 41% (575 of 1417) of respondents. Working >70 hours per week, having >5 drinks per week, and female gender were associated with increased burnout risk. Twenty-two percent (298 of 1384) screened positive for depression. Working >70 hours of work per week, smoking, female gender, and having >5 drinks per week were associated with increased depression risk. Two hundred forty (17%) respondents scored at high risk of burnout and depression, 321 (23%) at high risk of burnout, 58 (4%) at high risk of depression only, and 764 (56%) at low risk of burnout or depression. Median best practice scores (maximum = 30) for residents at high risk of burnout (difference -2; 99.6% CI, -1 to -2; P < 0.001) or high risk of burnout and depression (difference -4; 99.6% CI, -3 to -6; P < 0.001) were lower than scores of residents at low risk for burnout or depression. Thirty-three percent of respondents with high burnout and depression risk reported multiple medication errors in the last year compared with 0.7% of the lower-risk responders (P < 0.001). CONCLUSION: Burnout, depression, and suicidal ideation are very prevalent in anesthesiology residents. In addition to effects on the health of anesthesiology trainees, burnout and depression may also affect patient care and safety.

Factors affecting admission to anesthesiology residency in the United States: choosing the future of our specialty.

BACKGROUND: Admission to an anesthesiology residency in the United States is competitive, and the odds associated with a successful match based on the applicants' characteristics have not been determined. The objective of this study was to examine factors associated with admission to anesthesiology residency in the United States. METHODS: The study was a retrospective cohort evaluation of the 2010 to 2011 residency applicants. Applicants' characteristics and objective factors used to select trainees were extracted. The primary outcome was a successful match to an anesthesiology residency. Data were analyzed using conditional inference tree analysis and propensity score matching. RESULTS: Data available from 1,976 applications were examined corresponding to 58% of the national sample. The odds (99% CI) for successful match were 3.6 (3.1-4.2) for U.S. medical school graduates, 2.6 (2.3 to 3.0) for applicants with United States Medical Licensing Examination Step 2 scores more than 210, and 1.2 (1.1 to 1.3) for female applicants. The odds (99% CI) for a successful match for international and U.S. graduate applicants younger than 29 yr was 3.3 (2.0-5.4) and (1.9 to 4.2), respectively, even after propensity matching for medical school, exam scores, and gender. The average applicant had no peer-reviewed scholarly productivity. CONCLUSION: Although anesthesiology residency acceptance was primarily associated with U.S. medical school attendance and United States Medical Licensing Examination Step 2 scores, our study suggest an influence of age and gender bias in the selection process. Peer-reviewed scholarly production among applicants and prior graduate education did not appear to influence candidate selection.

Publication bias in the anesthesiology literature.

BACKGROUND: Publication bias occurs because positive finding studies are more likely to be published. The dearth of studies of negative or equivalence findings can erroneously affect future research and potentially clinical care of patients. We hypothesized that positive studies were more likely to be published than negative studies in anesthesiology journals with a higher impact and circulation. METHODS: A PubMed search for controlled trials in humans published in peer-reviewed anesthesiology journals during 2008 and 2009 was performed. Fourteen anesthesiology journals and 1163 studies were evaluated. The average clinical trial impact factor (average citations per article) for each journal was determined. The quartiles for the clinical trial impact factor for the journals included in the analysis were 4, 6.1, and 9.1. Studies were scored by 2 raters as positive or negative results of the primary stated outcome. Factors previously associated with publication were also extracted. The primary outcome, the proportion of positive and negative studies in the journals in the upper quartile of the clinical trial impact factor to the lower quartiles was compared using the Fisher exact test. The odds ratio for the effect of positive study results adjusted for other characteristics associated with publication was determined using binary logistic regression. A multinomial logistic regression model was fitted for the journals with an impact factor in the upper quartile with adjustment for study trial registration, origin of publication, positive study findings, reporting of treatment blinding, reporting of subject withdrawals, study sponsorship, and description of the randomization method. RESULTS: Positive finding studies were identified in 72% (425 of 588) of articles in journals with a clinical trial impact factor >9.1 compared with 53% (308 of 575) in journals <9.1 (P < 0.001). After adjusting for factors associated with publication, positive study results had an odds ratio (95% confidence interval) of 2.28 (1.76-3.01) for publication in an anesthesiology journal in the upper quartile. Multinomial logistic regression identified positive study findings associated with an increased likelihood of publication in 3 of the 4 anesthesiology journals with a clinical trial impact factor >9.1. CONCLUSION: This study reports the presence of publication bias in the anesthesiology literature especially in higher clinical trial impact factor journals. Publication bias can have potential implications for future research and the clinical care of patients. Authors should be encouraged to submit negative studies to high impact journals and the journals should be encouraged to evaluate the editorial process as the cause of publication bias.

High incidence of burnout in academic chairpersons of anesthesiology: should we be taking better care of our leaders?

BACKGROUND: Burnout is a work-related psychologic syndrome characterized by emotional exhaustion, low personal accomplishment, and depersonalization. METHODS: By using an instrument that included the MBI-HHS Burnout Inventory, we surveyed academic anesthesiology chairpersons in the United States. Current level of job satisfaction compared with 1 and 5 yr before the survey, likelihood of stepping down as chair in the next 2 yr, and a high risk of burnout were the primary outcomes. RESULTS: Of the 117 chairs surveyed, 102 (87%) responded. Nine surveys had insufficient responses for assessment of burnout. Of 93 chairs, 32 (34%) reported high current job satisfaction, which represented a significant decline compared with that reported for 1 yr (P = 0.009) and 5 yr (P = 0.001) before the survey. Of 93 chairs, 26 (28%) reported extreme likelihood of stepping down as a chair in 1-2 yr. There was no association of age (P = 0.16), sex (P = 0.82), or self-reported effectiveness (P = 0.63) with anticipated likelihood of stepping down, but there was a negative association between the modified efficacy scale scoρrgr; = -0.303, P = 0.003) and likelihood of stepping down. Of 93 chairs, 26 (28%) met the criteria for high burnout and an additional 29 (31%) met the criteria for moderately high burnout. Decreased current job satisfaction and low self-reported spousal/significant other support were independent predictors of high burnout risk. CONCLUSION: Fifty-one percent of academic anesthesiology chairs exhibit a high incidence/risk of burnout. Age, sex, time as a chair, hours worked, and perceived effectiveness were not associated with high burnout; however, low job satisfaction and reduced self-reported spousal/significant other support significantly increased the risk.

A randomized comparison of the use of an optical compared with a rigid laryngoscope on the success rate of novices performing tracheal intubation.

Proficiency in tracheal intubation is a difficult skill to acquire, especially when using a rigid laryngoscope. We compared success in tracheal intubation by novices using an optical laryngoscope with that achieved with a rigid laryngoscope. After structured training in laryngoscopy and 5 consecutive successful intubation attempts using both the optical and rigid laryngoscope on a high-fidelity mannequin, trainees were randomly assigned to perform their first 2 tracheal intubations using either an optical or rigid laryngoscope using the standard Macintosh blade. The success rate for intubation was higher using the optical laryngoscope (23 of 30 attempts) compared with the rigid laryngoscope (8 of 30 attempts, P < 0.001). Intubation time was shorter using the optical laryngoscope (35 seconds; 95% confidence interval, 27-44 seconds) compared with the rigid laryngoscope (75 seconds; 95% confidence interval, 59-90 seconds) in successfully intubated patients (P < 0.001). Our study demonstrated greater successful tracheal intubation and reduced intubation time during the first two attempted intubations by novices using an optical compared with a rigid laryngoscope.

A dose-ranging study of the effect of transversus abdominis block on postoperative quality of recovery and analgesia after outpatient laparoscopy.

BACKGROUND: Postoperative pain can delay functional recovery after outpatient surgery. Multimodal analgesia can improve pain and possibly improve quality of recovery. In this study, we evaluated the dose-dependent effects of a preoperative transversus abdominis plane (TAP) block on patient recovery using the Quality of Recovery 40 (QoR-40) questionnaire after ambulatory gynecological laparoscopic surgery. Global QoR-40 scores range from 40 to 200, representing very poor to outstanding quality of recovery, respectively. METHODS: Healthy women undergoing outpatient gynecological laparoscopy were randomly allocated to receive a preoperative TAP block using saline, ropivacaine 0.25%, or ropivacaine 0.5%. Needle placement for the TAP blocks was performed using ultrasound guidance and 15 mL of the study solution was injected bilaterally by a blinded investigator. QoR-40 score and analgesic use were assessed 24 hours postoperatively. The primary outcome was global QoR-40 score at 24 hours after surgery. Data were analyzed using the Kruskal-Wallis test. Post hoc pairwise comparisons were made using the Dunn test with P values and 95% confidence intervals Bonferroni corrected for 6 comparisons. RESULTS: Seventy-five subjects were enrolled and 70 subjects completed the study. The median (range) for the QoR-40 score after the TAP block was 157 (127-193), 173 (133-195), and 172 (130-196) for the saline group and 0.25% and 0.5% ropivacaine groups, respectively. The median difference (99.2% confidence interval) in QoR-40 score for 0.5% bupivacaine (16 [1-30], P=0.03) and 0.25% bupivacaine (17 [2-31], P=0.01) was more than saline but not significantly different between ropivacaine groups (-1 [-16 to 12], P=1.0). Increased global QoR-40 scores correlated with decreased area under the pain score time curve during postanesthesia recovery room stay (ρ=-0.56, 99.2% upper confidence limit [UCL]=-0.28), 24-hour opioid consumption (ρ=-0.61, 99.2% UCL=-0.34), pain score (0-10 scale) at 24 hours (ρ=-0.53, 99.2% UCL=-0.25), and time to discharge readiness (ρ=-0.65, 99.2% UCL=-0.42). The aforementioned variables were lower in the TAP block groups receiving ropivacaine compared with saline. CONCLUSIONS: The TAP block is an effective adjunct in a multimodal analgesic strategy for ambulatory laparoscopic procedures. TAP blocks with ropivacaine 0.25% and 0.5% reduced pain, decreased opioid consumption, and provided earlier discharge readiness that was associated with better quality of recovery.

Comparison of SNAP™ II and BIS Vista indices during normothermic cardiopulmonary bypass under isoflurane anesthesia.

OBJECTIVE: Processed EEG monitoring during cardiopulmonary bypass (CPB) may help determine loss of consciousness and depth of anesthesia. This study compared the SNAP(™) II and BIS Vista monitors in patients undergoing isoflurane anesthesia with normothermic CPB. METHODS: 40 subjects undergoing CPB with isoflurane anesthesia were enrolled. Subjects were premedicated with 1-2 mg midazolam approximately 5 min prior to acquisition of baseline index values and anesthesia induced with midazolam and fentanyl. Anesthesia was maintained with isoflurane, midazolam, and fentanyl and a cis-atracurium infusion. SNAP(™) II (version 1.2.9 algorithm 1.88) and BIS Vista (application version 3.00 platform version 2.03) indices were recorded at baseline, pre-induction, post-intubation, incision, start of CPB, every 15 min during CPB, end of CPB, and end of case. Agreement between methods was determined using Pearson correlation and the Bland-Altman method with repeated observa- tions. RESULTS: Twenty-four male and 12 female subjects completed the analysis. The correlation between SNAP(™) II and BIS Vista index values was 0.61 (P < 0.005). A linear relationship between the difference in the indices and the average index values was observed following the induction of anesthesia. In awake subjects, the bias between the SNAP(™) II and BIS Vista was 5 (95% CI 3-7). The limits of agreement were 23 (95% CI 19-26) and -13 (95% CI -9--16). During anesthesia, the mean difference on a log scale was 0.11 (95% CI 0.09-0.12). The limits of agreement were 0.43 (95% CI 0.40-0.45) and -0.21 (95% CI -0.18--0.24). The antilog of the mean difference demonstrated that the SNAP(™) II value was 28% (95% CI 24-33%) higher than the BIS Vista value following induction of anesthesia. CONCLUSIONS: The SNAP(™) II monitor demonstrates a consistently positive bias during cardiopulmonary bypass under isoflurane anesthesia compared with the BIS Vista.

Postoperative hypoxemia in morbidly obese patients with and without obstructive sleep apnea undergoing laparoscopic bariatric surgery.

INTRODUCTION: The increased incidence of morbid obesity has resulted in an increase of bariatric surgical procedures. Obstructive sleep apnea (OSA) is a commonly encountered comorbidity in morbidly obese patients. Sedatives, analgesics, and anesthetics alter airway tone, and airway obstruction and death have been reported in patients with OSA after minimal doses of sedatives and anesthetics, yet there is a lack of consensus regarding the care of these patients. In this study, we sought to determine whether obese patients with polysomnography-confirmed diagnosis of OSA were at significantly greater risk for postoperative hypoxemic episodes in the first 24 h after laparoscopic bariatric surgery than morbidly obese patients without a diagnosis of OSA. METHODS: Adult subjects (Body Mass Index, 35-75 kg/m(2)) scheduled to undergo laparoscopic bariatric surgery were studied. A finger pulse oximetry probe was placed preoperatively and oxygen saturation (Spo(2)) was recorded continuously. All subjects underwent preoperative polysomnography testing within 4 wk of surgery. Anesthetic management was standardized, using propofol for induction and desflurane and remifentanil for maintenance of anesthesia. Patient-controlled analgesia programmed to deliver morphine, 1 mg. every 10 minutes, was used for pain management postoperatively. Hypoxemic episodes were scored as Spo(2) >4% below the polysomnography study baseline and lasting for more than 10 s. RESULTS: Eight men and 32 women were enrolled and 1 subject had incomplete data. Thirty-one of the 40 subjects had polysomnography-confirmed OSA. Eight subjects used home continuous positive airway pressure devices nightly, and six of these used their device postoperatively. Preoperatively, subjects with OSA had lower nadir Spo(2) during the polysomnography study and a larger number had an apnea/hypopnea index >10 episodes per hour compared with the non-OSA group. In the first 24 h postoperatively, there was no difference in the median Spo(2) with and without oxygen therapy, between OSA and non-OSA groups. The number of episodes of oxygen desaturation >4% below the polysomnography study baseline value and the mean number of desaturation episodes per hour did not differ between the groups. CONCLUSIONS: In morbidly obese subjects, in the first 24 h after laparoscopic bariatric surgery, OSA does not seem to increase the risk of postoperative hypoxemia. Our data confirm that morbidly obese subjects, with or without OSA, experience frequent oxygen desaturation episodes postoperatively, despite supplemental oxygen therapy suggesting that perioperative management strategies in morbidly obese patients undergoing laparoscopic bariatric surgery should include measures to prevent postoperative hypoxemia.

The accuracy of blood loss estimation after simulated vaginal delivery.

BACKGROUND: Visual blood loss estimation often underestimates blood loss. In this study we sought to determine the effect of calibrated drape markings on blood loss estimation in a simulated vaginal delivery. METHODS: Subjects were randomized to estimate simulated blood loss (300, 500, 1000, and 2000 mL) in calibrated or noncalibrated vaginal delivery drapes and then crossover. RESULTS: Visual blood loss estimation with noncalibrated drapes underestimated blood loss, with worsening accuracy at larger volumes (16% error at 300 mL to 41% at 2000 mL). The calibrated drape error was <15% at all volumes. CONCLUSIONS: Calibrated vaginal delivery drapes improve blood loss estimation.

Gastric emptying of water in obese pregnant women at term.

BACKGROUND: Healthy nonpregnant and pregnant patients may ingest clear liquids until 2 h before induction of anesthesia without adversely affecting gastric volume. In this study, we compared gastric emptying in obese, term, nonlaboring pregnant women (prepregnancy body mass index >35 kg/m2) after the ingestion of 50 and 300 mL of water. METHODS: Gastric emptying was assessed in 10 obese, term pregnant volunteers using both serial gastric ultrasound examinations and acetaminophen absorption in a crossover study design. After an overnight fast, volunteers ingested 1.5 g acetaminophen and 50 or 300 mL water (randomly assigned) on two occasions separated by at least 2 days. Serial gastric antrum cross-sectional areas were determined using gastric ultrasound imaging and the half-time to gastric emptying (T([1/2])) was calculated. Areas under the plasma acetaminophen concentration versus time curve (AUC), peak concentrations (C(max)), and time to peak concentration (t(max)) for 50 mL and 300 mL ingestions were compared. RESULTS: Mean prepregnancy body mass index was 41 +/- 9 kg/m(2). Gastric emptying T([1/2]) was not different after ingestion of 300 mL water compared with 50 mL (23 +/- 11 min vs 32 +/- 15 min). There were no differences between acetaminophen AUCs at 60, 90, or 120 min, C(max) or t(max) after ingestion of 300 mL compared with 50 mL of water. CONCLUSIONS: Gastric emptying in obese, nonlaboring term pregnant women is not delayed after ingestion of 300 mL compared with 50 mL of water. Gastric antral volume after ingestion of 300 mL of water is similar to the baseline fasting level at 60 min.

An in vitro evaluation of the pressure generated during programmed intermittent epidural bolus injection at varying infusion delivery speeds.

STUDY OBJECTIVE: Programmed intermittent bolus injection of epidural anesthetic solution results in decreased anesthetic consumption and better patient satisfaction compared with continuous infusion, presumably by better spread of the anesthetic solution in the epidural space. It is not known whether the delivery speed of the bolus injection influences analgesia outcomes. The objective of this in vitro study was to determine the pressure generated by a programmed intermittent bolus pump at 4 infusion delivery speeds through open-ended, single-orifice and closed-end, multiorifice epidural catheters. DESIGN: In vitro observational study. SETTING: Not applicable. PATIENTS: Not applicable. INTERVENTIONS: A CADD-Solis Pain Management System v3.0 with Programmed Intermittent Bolus Model 2110 was connected via a 3-way adapter to an epidural catheter and a digital pressure transducer. Pressures generated by delivery speeds of 100, 175, 300, and 400 mL/h of saline solution were tested with 4 epidural catheters (2 single orifice and 2 multiorifice). These runs were replicated on 5 pumps. Analysis of variance was used to compare the mean peak pressures of each delivery speed within each catheter group (single orifice and multiorifice). MAIN RESULTS: Thirty runs at each delivery speed were performed with each type of catheter for a total of 240 experimental runs. Peak pressure increased with increasing delivery speeds in both catheter groups (P<.001). Peak pressures were higher with the multiorifice catheter compared with the single-orifice catheter at all delivery speeds (P<.001, for all). CONCLUSION: Using a pump designed for programmed intermittent infusion boluses, the delivery speed of saline solution through epidural catheters was directly related to the peak pressures. Future work should evaluate whether differences in the delivery speed of anesthetic solution into the epidural space correlate with differences in the duration and quality of analgesia during programmed intermittent epidural bolus delivery.

The effect of sevoflurane versus desflurane on the incidence of upper respiratory morbidity in patients undergoing general anesthesia with a Laryngeal Mask Airway: a meta-analysis of randomized controlled trials.

STUDY OBJECTIVE: To compare the incidence of upper airway morbidity with sevoflurane versus desflurane in patients undergoing general anesthesia with a Laryngeal Mask Airway (LMA). DESIGN: Systematic review and meta-analysis of randomized controlled trials (RCTs). SETTING: Operating room of an academic medical center. MEASUREMENTS: A systematic review of RCTs of patients receiving general anesthesia with a LMA was performed. Sevoflurane and desflurane were used for maintenance of anesthesia in the RCTs. A wide search was performed to identify RCTs comparing desflurane with sevoflurane on the incidence of upper respiratory adverse events in patients undergoing surgery with a LMA. The primary outcomes were incidence of cough and laryngospasm. A random-effects model was used to perform quantitative analysis. MAIN RESULTS: Data originating from 7 studies comprising 657 subjects were analyzed. The confidence interval (CI) was large relative to a clinically significant difference in the incidence of overall cough and laryngospasm in patients receiving desflurane versus sevoflurane (odds ratio [OR; 95% CI] of 1.44 [0.49 - 4.1] and 3.06 [0.43 - 21.62]), respectively. The incidence of cough at emergence was greater in subjects receiving desflurane compared with sevoflurane (OR [95% CI] of 2.43 [1.2 - 4.7], number needed to harm [NNH] = 9.0); however, the analysis was limited by the presence of an asymmetric funnel plot suggesting the possibility of publication bias. CONCLUSIONS: There is a lack of evidence that desflurane causes a greater incidence of upper airway adverse events than sevoflurane in patients undergoing general anesthesia with a LMA.

The effect of intravenous dexamethasone and lidocaine on propofol-induced vascular pain: a randomized double-blinded placebo-controlled trial.

Background. The mechanism for pain associated with intravenous administration of propofol is believed to be related to the release of nitric oxide. We hypothesized that pain following propofol injection would be reduced by pretreatment with dexamethasone. Methods. One hundred fourteen female subjects received 5 mL of preservative-free saline, 0.5 mg · kg(-1) of lignocaine hydrochloride 10 mg · mL(-1) or 0.25 mg · kg(-1) of dexamethasone, intravenously, following exsanguination and occlusion of the veins of the arm. This was followed by a 0.5 mg · kg(-1) injection of propofol. Pain scores, facial grimacing, arm withdrawal, and vocalization were recorded prior to and at 15 and 30 seconds following the injection of propofol. Results. The incidence of moderate to severe pain following the injection of propofol was significantly decreased with both lidocaine and dexamethasone. Hand withdrawal was also significantly decreased in comparison to saline. Conclusion. Low dose dexamethasone is commonly used as an antiemetic, and, in larger doses, it has been demonstrated to provide prolonged postoperative analgesia. At higher analgesic doses, dexamethasone may also reduce pain associated with the injection of propofol. This effect is probably related to the effect of the steroid on nitric oxide production associated with intravenous propofol injection.

Desflurane/fentanyl compared with sevoflurane/fentanyl on awakening and quality of recovery in outpatient surgery using a laryngeal mask airway: a randomized, double-blinded controlled trial.

STUDY OBJECTIVE: To compare time to awakening and upper airway morbidity between desflurane and sevoflurane using a Laryngeal Mask Airway (LMA) and a balanced anesthetic regimen inclusive of opioids. DESIGN: Randomized, double-blinded, placebo-controlled clinical trial. SETTING: Ambulatory surgery unit of a university hospital. PATIENTS: 80 subjects receiving general anesthesia for outpatient gynecological surgery using a LMA. INTERVENTIONS: Desflurane/fentanyl or sevoflurane/fentanyl were used for anesthetic maintenance. MEASUREMENTS: Patients were randomly assigned to receive desflurane or sevoflurane. The primary outcome was time to awakening as determined by an observer who was blinded to study group allocation. Secondary outcomes included the frequency of sore throat, cough, and pain perioperatively and at 2 and 24 hours postoperatively. Quality of recovery (QoR; via QoR-40 questionnaire) at 24 hours also was determined. MAIN RESULTS: The median (IQR) time to eye opening following desflurane was 6.8 (5.0 - 9.8) minutes versus 11.8 (8.8 - 14.6) minutes following sevoflurane (P < 0.001), or a difference of 5.0 (99% CI 2.3 - 6.8) minutes. The median difference in response to verbal commands was 5.3 (99% CI 2.4 - 7.1) minutes. The frequency of cough, laryngospasm, sore throat, and hoarseness did not differ between groups. Quality of recovery at 24 hours was better in the desflurane group: difference in medians 6 (99% CI 0 - 12; P = 0.003). CONCLUSIONS: Desflurane retains faster awakening properties than does sevoflurane when used in combination with fentanyl as part of anesthetic maintenance in outpatient surgery with a LMA. The balanced anesthetic maintenance regimen seems to reduce the potential airway reactivity properties of desflurane.