Real-Time Measurement of Xenon Concentration in a Binary Gas Mixture Using a Modified Ultrasonic Time-of-Flight Anesthesia Gas Flowmeter: A Technical Feasibility Study

BACKGROUND: Xenon (Xe) is an anesthetic gas licensed for use in some countries. Fractional concentrations (%) of gases in a Xe:oxygen (O2) mixture are typically measured using a thermal conductivity meter and fuel cell, respectively. Speed of sound in such a binary gas mixture is related to fractional concentration, temperature, pressure, and molar masses of the component gases. We therefore performed a study to assess the feasibility of developing a novel single sterilizable device that uses ultrasound time-of-flight to measure both real-time flowmetry and fractional gas concentration of Xe in O2. METHODS: For the purposes of the feasibility study, we adapted an ultrasonic time-of-flight flowmeter from a conventional anesthetic machine to additionally measure real-time fractional concentration of Xe in O2. A total of 5095 readings of Xe % were taken in the range 5%–95%, and compared with simultaneous measurements from the gold standard of a commercially available thermal conductivity Xe analyzer. RESULTS: Ultrasonic measurements of Xe (%) showed agreement with thermal conductivity meter measurements, but there was marked discontinuity in the middle of the measurement range. Bland-Altman analysis (95% confidence interval in parentheses) yielded: mean difference (bias) 3.1% (2.9%–3.2%); lower 95% limit of agreement −4.6% (−4.8% to −4.4%); and upper 95% limit of agreement 10.8% (10.5%–11.0%). CONCLUSIONS: The adapted ultrasonic flowmeter estimated Xe (%), but the level of accuracy is insufficient for clinical use. With further work, it may be possible to develop a device to perform both flowmetry and binary gas concentration measurement to a clinically acceptable degree of accuracy. Accepted for publication August 17, 2018. Funding: None. Conflicts of Interest: See Disclosures at the end of the article. Some preliminary data from the first part of this study were presented as a poster at the European Society of Anaesthesia Annual Conference, Geneva, Switzerland, June 5, 2017. Reprints will not be available from the authors. Address correspondence to David J. Williams, FRCA, Department of Anaesthetics, Morriston Hospital, Swansea SA6 6NL, United Kingdom. Address e-mail to davidjwilliams@doctors.org.uk. © 2018 International Anesthesia Research Society

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Regional Anesthesia and Readmission Rates After Total Knee Arthroplasty

BACKGROUND: Total knee arthroplasty is a commonly performed procedure and an important contributor to national health care spending. Reducing the incidence of readmission could have important consequences for patient well-being and relevant financial implications. Whether regional anesthesia techniques are associated with decreased readmission rates and costs among privately insured patients remains unknown. METHODS: Using administrative claims data, we identified 138,362 privately insured patients 18–64 years of age who underwent total knee arthroplasty between 2002 and 2013. We then examined whether the use of a nerve block was associated with decreases in readmission rates and related costs during the 90 days after discharge. Our analyses were adjusted for potential confounding variables including medical comorbidities and previous use of opioids and other medications. RESULTS: After adjusting for patient demographics, comorbidities, and preoperative medication use, the adjusted 90-day readmission rate was 1.8% (95% confidence interval [CI], 1.1–2.4) among patients who did not receive a block compared to 1.7% (95% CI, 1.1–2.4) among patients who did (odds ratio, 0.99; 95% CI, 0.91–1.09; P = .85). The adjusted readmission-related postoperative cost for patients who did not receive a block was $561 (95% CI, 502–619) and $574 (95% CI, 508–639) for patients who did (difference, $13; 95% CI, −75 to 102; P = .74). This lack of statistically significant differences held for subgroup and sensitivity analyses. CONCLUSIONS: Nerve blocks were not associated with improved measures of long-term postoperative resource use in this younger, privately insured study population. Accepted for publication August 24, 2018. Funding: E.C.S. was supported by the National Institute on Drug Abuse (K08DA042314). Conflicts of Interest: See Disclosures at the end of the article. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website (https://ift.tt/KegmMq). This work was presented at the Medical Student Anesthesia Research Fellowship (MSARF) symposium at the annual American Society of Anesthesiologists meeting, Boston, MA, October 22, 2017. Reprints will not be available from the authors. Address correspondence to Eric C. Sun, MD, PhD, Department of Anesthesiology, Perioperative and Pain Medicine, H3580, Stanford University Medical Center, Stanford, CA 94305. Address e-mail to esun1@stanford.edu. © 2018 International Anesthesia Research Society

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Predicting the Size of a Left Double-Lumen Tube for Asian Women Based on the Combination of the Diameters of the Cricoid Ring and Left Main Bronchus: A Randomized, Prospective, Controlled Trial

BACKGROUND: There are limited data about how to choose the correct size of a double-lumen tube (DLT). It is especially difficult to select an appropriate DLT for Asian women because of their small stature. The primary aim of this study was to compare the overall accuracy of the DLT selected based on the combination of transverse diameter of cricoid ring and the equivalent diameter of the left main bronchus (ED-LMB) with that based on the ED-LMB alone for Asian women. METHODS: In this study, 80 consecutive and blinded female patients were assigned randomly to 2 groups. The overall accuracy of the selection of DLT was compared between the Combined group and LMB group. The accuracy of the selection of tracheal segment and bronchial segment was also compared between the 2 groups. The postoperative hoarseness and sore throat were investigated by blinded assessors. RESULTS: The overall accuracy of selection of the DLTs was higher in the Combined group than that in the LMB group (87.5% vs 60.0%; P = .010). The accuracy of selection of tracheal segment was also higher in the Combined group (92.5% vs 67.5%; P = .010). The accuracy of selection of bronchial segment was similar between the groups (95.0 % vs 86.1%; P = .246). The severity of sore throat was higher in the LMB group at 24 hours after the operation (P = .001). CONCLUSIONS: The correct size of DLT for Asian women should be selected based on the combination of transverse diameter of cricoid ring and the ED-LMB. Accepted for publication August 29, 2018. Funding: None. The authors declare no conflicts of interest. Clinical trial number and registry URL: ChiCTR-INR-17013040, https://ift.tt/2IBXrA2. Reprints will not be available from the authors. Address correspondence to Dong Youjing, PhD, Shengjing Hospital, China Medical University, No. 36 Sanhao St, Heping District, 110004 Shenyang, China. Address e-mail to dongyj@sj-hospital.org. © 2018 International Anesthesia Research Society

https://ift.tt/2pCC0X0

Predosing Chemical Stability of Admixtures of Propofol, Ketamine, Fentanyl, and Remifentanil

Admixtures of propofol–ketamine, propofol–ketamine–fentanyl, and propofol–ketamine–remifentanil were subjected to various clinically relevant conditions to study their chemical stability. A novel high-performance liquid chromatography-mass spectrometry method revealed no degradation of any compound by incubation at 37°C, constant mixing, or table-top storage for 6- and 24-hour time periods, except variable recovery of both propofol and fentanyl in the admixtures of propofol–ketamine–fentanyl suggesting possible degradation. Accepted for publication August 1, 2018. Funding: US Army Medical Research and Materiel Command. The authors declare no conflicts of interest. The views expressed in this article are those of the authors and do not reflect the official policy of the Uniformed Services University, Departments of the Army, Navy, or Air Force, Department of Defense, Department of Veterans Affairs, or the US Government. Reprints will not be available from the authors. Address correspondence to Peter Bedocs, MD, PhD, Defense and Veterans Center for Integrative Pain Management, Henry M. Jackson Foundation, 11300 Rockville Pike, Suite 709, Rockville, MD 20852. Address e-mail to peter.bedocs.ctr@usuhs.edu. © 2018 International Anesthesia Research Society

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Resident Competency and Proficiency in Combined Spinal–Epidural Catheter Placement Is Improved Using a Computer-Enhanced Visual Learning Program: A Randomized Controlled Trial

BACKGROUND: Physician educators must balance the need for resident procedural education with clinical time pressures as well as patient safety and comfort. Alternative educational strategies, including e-learning tools, may be beneficial to orient novice learners to new procedures and speed proficiency. We created an e-learning tool (computer-enhanced visual learning [CEVL] neuraxial) to enhance trainee proficiency in combined spinal–epidural catheter placement in obstetric patients and performed a randomized controlled 2-center trial to test the hypothesis that use of the tool improved the initial procedure performed by the anesthesiology residents. METHODS: Anesthesiology residents completing their first obstetric anesthesiology rotation were randomized to receive online access to the neuraxial module (CEVL group) or no access (control) 2 weeks before the rotation. On the first day of the rotation, residents completed a neuraxial procedure self-confidence scale and an open-ended medical knowledge test. Blinded raters observed residents performing combined spinal–epidural catheter techniques in laboring parturients using a procedural checklist (0–49 pts); the time required to perform the procedure was recorded. The primary outcome was the duration of the procedure. RESULTS: The CEVL group had significantly shorter mean (±standard deviation) procedure time compared to the control group 22.5 ± 4.9 vs 39.5 ± 7.1 minutes (P

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Red Blood Cell Transfusion in Pediatric Orthotopic Liver Transplantation: What a Difference a Few Decades Make

BACKGROUND: Liver transplantation in children is often associated with coagulopathy and significant blood loss. Available data are limited. In this observational retrospective study, we assessed transfusion practices in pediatric patients undergoing liver transplantation at a single institution over the course of 9 years. METHODS: Data were retrospectively collected from patient medical records at the Children's Hospital of Pittsburgh of University of Pittsburgh Medical Center. All patients who underwent liver transplantation from January 2008 to June 2017 were included. Primary and secondary outcomes were volume of red blood cells (RBCs) transfused and mortality, respectively. RESULTS: From January 2008 to June 2017, there were 278 liver transplants in 271 patients. The number of primary transplants were 259, second retransplants 15, and third retransplants 4. Average age at transplantation was 6.9 years. Biliary atresia, maple syrup urine disease, urea cycle defect, and liver tumor were the leading indications accounting for 66 (23.7%), 45 (16.2%), 24 (8.6%), and 23 (8.3%) of transplants, respectively. Seventy-six cases (27.3%) did not require RBC transfusions. Among those transfused, 181 (89.6%) of the cases required 12 months of age (0.12 BV). By diagnosis, the group requiring the highest median volume transfusion was patients with total parenteral nutrition–related liver failure (3.41 BV) followed by patients undergoing repeat transplants (0.6 BV). Comparison of primary versus repeat transplants shows a trend toward higher volume transfusions in third transplants (median, 2.71 BV), compared to second transplants (0.43 BV) and primary transplants (0.18 BV). Four of 271 patients (1.5%) died during admission involving liver transplantation. Nine of 271 patients (3.3%) died subsequently. Total mortality was 4.8%. CONCLUSIONS: In contrast to historically reported trends, evaluation of current transfusion practices reveals that most patients undergoing liver transplantation receive

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Statistical Versus Clinical Significance in Subclavian Vein Cross-Sectional Area: Is a 0.10-cm2 Difference Really Meaningful or Just an Example of False Precision?

No abstract available

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Ultrasound-guided lumbar plexus block using three different techniques: a comparison of ultrasound image quality

Abstract

Purpose

The purpose of this study was to compare the ultrasound image quality at three different transducer positions for ultrasound-guided lumbar plexus block (LPB).

Methods

This prospective comparative study included 30 patients who underwent total hip arthroplasty under general anesthesia in combination with LPB. Using the same ultrasound machine settings for each patient, a transverse view of the lumbar plexus (LP) at the L3–4 vertebral level was obtained with a convex transducer placed at three different positions: immediately lateral to the dorsal midline (medial position), almost 5 cm lateral to the dorsal midline (paravertebral position), and at the abdominal transverse flank (shamrock position). Ultrasound-guided LPB with catheter insertion was performed via in-plane needle insertion with the transducer randomly assigned to one of the three positions. The echo intensity (EI) ratio of the LP to psoas major muscle (PMM), the EI of the LP and PMM, and the ultrasound visibility score of the needle, local anesthetic, and catheter were recorded.

Results

The LP/PMM EI ratio was significantly higher at paravertebral position (1.4 ± 0.2) than at medial position (1.2 ± 0.2; p = 0.003) and shamrock position (1.3 ± 0.2; p = 0.040). The EI of the LP and PMM was highest at shamrock position (p < 0.001). During the block procedure, the ultrasound visibility score of the needle and local anesthetic was significantly higher at paravertebral position than at medial position.

Conclusion

Under the conditions of this study, the contrast between LP and PMM is significantly higher at paravertebral position than at medial position and at the abdominal transverse flank (shamrock position). LP and PMM at the shamrock position appear significantly brighter among the three probe positions in sonograms.

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Predictors for sustained new-onset atrial fibrillation in critically ill patients: a retrospective observational study

Abstract

Purpose

Although new-onset atrial fibrillation (AF) is frequently observed in the intensive care unit (ICU), the incidence and predictors for sustained new-onset AF have not been investigated, except for cardiac surgery patients. We have evaluated potential predictors for sustained new-onset AF in a mixed ICU.

Methods

In this retrospective observational study, we screened non-cardiac surgery patients who were admitted to the ICU between January 2010 and December 2013 and had been hospitalized for > 24 h in the ICU. We collected information about heart rhythm 6 h after the onset of AF. We compared detailed patient characteristics between patients with sinus rhythm (SR) and those with sustained AF at 6 h after the onset of AF. Additionally, we applied variable selection using backward elimination based on Akaike's Information Criterion (AIC). Calibration was performed based on the Hosmer–Lemeshow test.

Results

New-onset AF occurred in 151 of 1718 patients and 99 patients converted to SR at 6 h. Backward elimination identified predictors as follows (AIC = 175.3): CHADS₂ score, elective surgery, infection on ICU admission, serum potassium > 4.0 mmol/L, male sex, mechanical ventilation, and diagnostic grouping. The model showed good calibration for sustenance of AF at 6 h after the onset using the Hosmer–Lemeshow Chi-square value of 4.36 (degrees of freedom = 4, p = 0.360) indicating a good fit.

Conclusions

These predictors might be useful in future interventional studies to identify patients who are likely to sustain new-onset AF.

https://ift.tt/2xUjfmo

In vitro changes in the proportion of protein-unbound-free propofol induced by valproate

Abstract

Purpose

It has been reported that oral valproate (VPA) reduces the dose of propofol required for sedation. As  a potential reason for this, it is considered that VPA displaces serum protein-bound propofol and increases the proportion of protein-unbound-free propofol. To examine this hypothesis, the present in vitro study investigated the influence of VPA on the proportion of protein-unbound-free propofol in human serum samples.

Methods

Serum samples were collected from 10 healthy volunteers, who were not taking any medication. VPA (final concentration: 0.05, 0.1 or 1 mg/mL) and propofol (final concentration: 1 or 5 µg/mL) were mixed with serum samples with normal (4.0 g/dL) or low (2.5 g/dL) albumin concentrations. Then, protein-unbound-free propofol was extracted from the samples, and its concentration was measured using high-performance liquid chromatography. We compared the proportion of protein-unbound-free propofol in each of the VPA-containing samples with that in serum samples without VPA (control).

Results

In the serum samples with normal albumin concentrations, 1 mg/mL VPA significantly increased the proportion of protein-unbound-free propofol at 1 and 5 µg/mL propofol. Furthermore, in the serum samples with low albumin concentrations, the proportion of protein-unbound-free propofol was significantly increased by both 0.1 and 1 mg/mL VPA at propofol concentrations of 1 and 5 µg/mL.

Conclusion

VPA might increase the proportion of protein-unbound-free propofol in human serum via displacement reactions.

https://ift.tt/2P8Xjur