Sizes of pure and doped helium droplets from single shot x-ray imaging.

Advancements in x-ray free-electron lasers on producing ultrashort, ultrabright, and coherent x-ray pulses enable single-shot imaging of fragile nanostructures, such as superfluid helium droplets. This imaging technique gives unique access to the sizes and shapes of individual droplets. In the past, such droplet characteristics have only been indirectly inferred by ensemble averaging techniques. Here, we report on the size distributions of both pure and doped droplets collected from single-shot x-ray imaging and produced from the free-jet expansion of helium through a 5 µm diameter nozzle at 20 bars and nozzle temperatures ranging from 4.2 to 9 K. This work extends the measurement of large helium nanodroplets containing 109-1011 atoms, which are shown to follow an exponential size distribution. Additionally, we demonstrate that the size distributions of the doped droplets follow those of the pure droplets at the same stagnation condition but with smaller average sizes.

Aggregation of solutes in bosonic versus fermionic quantum fluids.

Quantum fluid droplets made of helium-3 (3He) or helium-4 (4He) isotopes have long been considered as ideal cryogenic nanolabs, enabling unique ultracold chemistry and spectroscopy applications. The droplets were believed to provide a homogeneous environment in which dopant atoms and molecules could move and react almost as in free space but at temperatures close to absolute zero. Here, we report ultrafast x-ray diffraction experiments on xenon-doped 3He and 4He nanodroplets, demonstrating that the unavoidable rotational excitation of isolated droplets leads to highly anisotropic and inhomogeneous interactions between the host matrix and enclosed dopants. Superfluid 4He droplets are laced with quantum vortices that trap the embedded particles, leading to the formation of filament-shaped clusters. In comparison, dopants in 3He droplets gather in diffuse, ring-shaped structures along the equator. The shapes of droplets carrying filaments or rings are direct evidence that rotational excitation is the root cause for the inhomogeneous dopant distributions.

Angular Momentum in Rotating Superfluid Droplets.

The angular momentum of rotating superfluid droplets originates from quantized vortices and capillary waves, the interplay between which remains to be uncovered. Here, the rotation of isolated submicrometer superfluid ^{4}He droplets is studied by ultrafast x-ray diffraction using a free electron laser. The diffraction patterns provide simultaneous access to the morphology of the droplets and the vortex arrays they host. In capsule-shaped droplets, vortices form a distorted triangular lattice, whereas they arrange along elliptical contours in ellipsoidal droplets. The combined action of vortices and capillary waves results in droplet shapes close to those of classical droplets rotating with the same angular velocity. The findings are corroborated by density functional theory calculations describing the velocity fields and shape deformations of a rotating superfluid cylinder.

Two Transcutaneous Stimulation Techniques in Shoulder Pain: Transcutaneous Pulsed Radiofrequency (TPRF) versus Transcutaneous Electrical Nerve Stimulation (TENS): A Comparative Pilot Study.

Objective: To compare the safety and efficacy of 2 transcutaneous stimulation techniques, transcutaneous pulsed radiofrequency (TPRF) versus transcutaneous electrical nerve stimulation (TENS), in chronic shoulder tendonitis. Design: A prospective, randomized, and double-blind clinical trial. Setting: Academic pain service of a city hospital. Subjects: Fifty patients with sonography-confirmed shoulder tendonitis. Methods: Fifty patients were randomly allocated into two groups for electrical stimulation treatment with 3-month follow-ups: Group 1 (n=25), TENS and Group 2 (n=25), TPRF. Both groups underwent either treatment for 15 minutes every other day, three times total. Our primary goals were to find any treatment comfort level, adverse event, and changes in Constant-Murley shoulder (CMS) scores. The secondary goals were finding the changes in pain, enjoyment of life, and general activity (PEG) scores. Results: For primary goals, no adverse events were noted throughout this study. No differences were found between groups for treatment tolerability (3.20 + 0.87 vs. 2.16 + 0.75). Statistically significant lower PEG scores were noticeable with the TPRF group after the course (12.73 + 5.79 vs. 24.53 + 10.21, p=0.013). Their statistical significance lasted for 3 months although the difference gap diminished after 1 month. CMS scores were significantly higher in the TPRF group (70.84 + 6.74 vs. 59.56 + 9.49, p=0.007) right after treatment course but the significance did not last. Conclusions: In treating chronic shoulder tendinitis using two transcutaneous stimulation techniques, both TPRF and TENS are safe and effective. TPRF is superior to TENS.

Experience of Immediate Ambulation and Early Discharge After Tumescent Anesthesia and Propofol Infusion in Cosmetic Breast Augmentation.

INTRODUCTION: Current cosmetic breast augmentation relies on general anesthesia that normally requires 40 min to total recovery. With experience, the surgical procedure can be completed expediently in 20 min under tumescent anesthesia and propofol full sedation to achieve immediate postoperative ambulation and home discharge readiness, and thus improve patient satisfaction and reduce cost. We retrospectively examined the outcomes of the protocol. MATERIALS AND METHODS: Per protocol, 1200 female patients underwent simple cosmetic breast augmentation accomplished with tumescent anesthesia, immediate mobilization, and early home discharge readiness after surgery. The following records were analyzed: vital sign stability during mobilization in the first 30 cases (primary goal), duration of surgery and anesthesia, frequency of intraoperative opioid use, frequency of ambulation needing assistance, Verbal Analog Scores and incidences of pain, orthostatic intolerance events, incidences of postoperative nausea and vomiting or anti-emetic use, and complications at follow-up visits (secondary goal). RESULTS: Hemodynamics during immediate postoperative mobilization demonstrated no statistically significant fluctuations and/or orthostatic intolerance requiring interventions. The mean duration of surgery was 20.4 ± 4.1 min. The mean duration of anesthesia was 25.2 ± 6.8 min. All patients tolerated immediate postoperative ambulation well. Adverse postoperative events were scarce. Only 9.1% reported postoperative pain, and 5.7% reported postoperative nausea and vomiting. One percent had transit post-ambulation dizziness needing supine positioning for less than 3 min. The average time to meet home-readiness criteria was 4.7 min, and there was no incidence of hematoma, infection, or complaints at follow-ups. CONCLUSIONS: For simple cosmetic breast augmentation, instead of general anesthesia and 40 min of recovery time, a tumescent anesthetic technique can be used for immediate postoperative ambulation and a 4.7-min home discharge readiness without a decrease in anesthesia quality and safety. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Metoclopramide improves the quality of tramadol PCA indistinguishable to morphine PCA: a prospective, randomized, double blind clinical comparison.

OBJECTIVE: Multimodal analgesia has been effectively used in postoperative pain control. Tramadol can be considered "multimodal" because it has two main mechanisms of action, an opioid agonist and a reuptake inhibitor of norepinephrine and serotonin. Tramadol is not as commonly used as morphine due to the increased incidence of postoperative nausea and vomiting (PONV). As metoclopramide is an antiemetic and an analgesic, it was hypothesized that when added to reduce PONV, metoclopromide may enhance the multimodal feature of tramadol by the analgesic property of metoclopramide. Therefore, the effectiveness of postoperative patient-controlled analgesia (PCA) with morphine was compared against PCA with combination of tramadol and metoclopramide. DESIGN: A prospective, randomized, double blind clinical trial. SETTING: Academic pain service of a university hospital. SUBJECTS: Sixty patients undergoing elective total knee arthroplasty with general anesthesia. METHODS: Sixty patients were randomly divided into Group M and Group T. In a double-blinded fashion, Group M received intraoperative 0.2 mg/kg morphine and postoperative PCA with 1 mg morphine per bolus, whereas Group T received intraoperative tramadol 2.5 mg/kg and postoperative PCA with 20 mg tramadol plus 1 mg metoclopramide per bolus. Lockout interval was 5 minutes in both groups. Pain scale, satisfaction rate, analgesic consumption, PCA demand, and side effects were recorded by a blind investigator. RESULTS: These two groups displayed no statistically significant difference between the items and variables evaluated. CONCLUSIONS: This combination provides analgesia equivalent to that of morphine and can be used as an alternative to morphine PCA.

Tramadol 2.5 mg x kg(-1) appears to be the optimal intraoperative loading dose before patient-controlled analgesia.

PURPOSE: We previously established that a 5 mg x kg(-1) intraoperative dose can reduce the nausea/vomiting associated with tramadol patient-controlled analgesia (PCA). This study was conducted to identify the most appropriate initial dose to improve the quality of tramadol PCA. METHODS: During general anesthesia, 60 patients undergoing knee arthroplasty were randomly allocated to receive 1.25 mg x kg(-1) (Group I), 2.5 mg x kg(-1) (Group II), 3.75 mg x kg(-1) (Group III), or 5 mg x kg(-1) (Group IV) tramadol. The emergence condition was recorded. The titration of additional tramadol 20 mg + metoclopramide 1 mg doses by PCA every five minutes was performed in the postanesthesia care unit (PACU) until the visual analogue scale (VAS) score was < or = 3. An investigator blinded to study group recorded the VAS and side effects every ten minutes. RESULTS: In the PACU, significantly more tramadol (8.4 +/- 3.1 vs 4.3 +/- 2.1, 2.5 +/- 1.8, and 0.4 +/- 0.3, P < 0.05), and a higher incidence (15/15 vs 5/15, 3/15, and 2/15, P < 0.05) of PCA use was observed in Group I compared to Groups II-IV. VAS was significantly higher in Group I than in Groups II-IV at zero and ten minutes (P < 0.05). Unexpected delayed emergence anesthesia (> 30 min) was observed in Group III (n = 1) and in Group IV (n = 2). Sedation was more important in Groups III and IV than in Groups I and II (P < 0.05). CONCLUSION: When considering efficacy and side-effect profile, 2.5 mg x kg(-1) of tramadol is the optimal intraoperative dose of this drug to provide effective postoperative analgesia with minimal sedation.

Metoclopramide decreases emesis but increases sedation in tramadol patient-controlled analgesia.

PURPOSE: To evaluate the clinical benefits and disadvantages of adding metoclopramide to tramadol for patient-controlled analgesia (PCA). METHODS: Forty adult patients, undergoing elective arthroplasties, were recruited into this prospective, randomized, double-blind study. During general anesthesia all patients received 2.5 mg x kg(-1) of tramadol as a loading dose at the beginning of wound closure. In the postanesthesia care unit (PACU) patients were randomly allocated to receive PCA containing either 20 mg tramadol + 1 mg metoclopramide per millilitre (n = 20, Group T+M) or tramadol 20 mg per millilitre (n = 20, Group T). The PCA setup was 1 mL/bolus with a lockout interval of five minutes. A blinded investigator assessed the vital signs, visual analogue scale, and severity of postoperative nausea and/or vomiting in the PACU. The PCA demand and delivery, overall satisfaction rate and adverse effects were recorded in the PACU and on postoperative days one and two. RESULTS: Nausea/vomiting scores were more severe (1.7 +/- 1.0 vs 0.2 +/- 0.5, 2.3 +/- 1.2 vs 0.6 +/- 0.6, 1.9 +/- 0.9 vs 0.2 +/- 0.5, at 12 hr, 18 hr, 24 hr, respectively, P < 0.05) and more frequent (7/20 vs 1/20, 5/20 vs 0/20 for nausea and vomiting respectively, P < 0.05) on postoperative day one in Group T compared to Group T+M. However, the incidence of sedation was higher in Group T+M (7/20 vs 1/20, P < 0.05). CONCLUSIONS: The incidence and severity of nausea/vomiting decreased if metoclopramide was added to tramadol for PCA. An increased incidence of sedation was noticed with this drug combination.

Can neostigmine reduce propofol injection pain?

BACKGROUND: Neostigmine has been found to cause peripheral analgesia. We used venous retention technique to evaluate whether neostigmine displayed peripheral analgesic effect in reducing propofol injection pain. METHODS: In a double blind fashion, 105 patients were randomly allocated to receive either 1 ml 0.5 mg neostigmine (Group N, n = 35), 1 ml 2% lidocaine (Group L, n = 35), or 1 ml normal saline (Group C, n = 35) as pretreatment to reduce pain on propofol injection. A pediatric T-connector linking with the i.v. catheter port was used for injection. Venous occlusion was made possible with a tourniquet before the intravenous administration of one of the three drugs. The tested drug was allowed to retain for one minute and then the tourniquet was released for propofol injection. Pain and side effect assessments were made after propofol injection. RESULTS: The incidence of propofol injection pain was 85% in normal saline group, 46% in neostigmine group and 6% in lidocaine group (P < 0.05 among groups). The tested drugs arrayed in order of increasing magnitude of intensity of pain upon propofol injection were lidocaine (mean rank 34.20), neostigmine (mean rank 50.42) and normal saline (mean rank 76.81) in sequence (P < 0.05 among groups). CONCLUSIONS: With one-minute venous retention, 0.5 mg neostigmine (1 ml) could produce peripheral analgesia to some degree in reducing propofol injection pain. However, its analgesic effect was inferior to 1 ml of 2% lidocaine.