Seasonal and diurnal variations of Kelvin-Helmholtz Instability at terrestrial magnetopause.

Kelvin-Helmholtz Instability is ubiquitous at Earth's magnetopause and plays an important role in plasma entry into the magnetosphere during northward interplanetary magnetic fields. Here, using one solar cycle of data from NASA THEMIS (Time History of Events and Macro scale Interactions during Substorms) and MMS (Magnetospheric Multiscale) missions, we found that KHI occurrence rates show seasonal and diurnal variations with the rate being high near the equinoxes and low near the solstices. The instability depends directly on the Earth's dipole tilt angle. The tilt toward or away from the Sun explains most of the seasonal and diurnal variations, while the tilt in the plane perpendicular to the Earth-Sun line explains the difference between the equinoxes. The results reveal the critical role of dipole tilt in modulating KHI across the magnetopause as a function of time, highlighting the importance of Sun-Earth geometry for solar wind-magnetosphere interaction and for space weather.

PROSPECT guideline for total hip arthroplasty: a systematic review and procedure-specific postoperative pain management recommendations.

The aim of this systematic review was to develop recommendations for the management of postoperative pain after primary elective total hip arthroplasty, updating the previous procedure-specific postoperative pain management (PROSPECT) guidelines published in 2005 and updated in July 2010. Randomised controlled trials and meta-analyses published between July 2010 and December 2019 assessing postoperative pain using analgesic, anaesthetic, surgical or other interventions were identified from MEDLINE, Embase and Cochrane databases. Five hundred and twenty studies were initially identified, of which 108 randomised trials and 21 meta-analyses met the inclusion criteria. Peri-operative interventions that improved postoperative pain include: paracetamol; cyclo-oxygenase-2-selective inhibitors; non-steroidal anti-inflammatory drugs; and intravenous dexamethasone. In addition, peripheral nerve blocks (femoral nerve block; lumbar plexus block; fascia iliaca block), single-shot local infiltration analgesia, intrathecal morphine and epidural analgesia also improved pain. Limited or inconsistent evidence was found for all other approaches evaluated. Surgical and anaesthetic techniques appear to have a minor impact on postoperative pain, and thus their choice should be based on criteria other than pain. In summary, the analgesic regimen for total hip arthroplasty should include pre-operative or intra-operative paracetamol and cyclo-oxygenase-2-selective inhibitors or non-steroidal anti-inflammatory drugs, continued postoperatively with opioids used as rescue analgesics. In addition, intra-operative intravenous dexamethasone 8-10 mg is recommended. Regional analgesic techniques such as fascia iliaca block or local infiltration analgesia are recommended, especially if there are contra-indications to basic analgesics and/or in patients with high expected postoperative pain. Epidural analgesia, femoral nerve block, lumbar plexus block and gabapentinoid administration are not recommended as the adverse effects outweigh the benefits. Although intrathecal morphine 0.1 mg can be used, the PROSPECT group emphasises the risks and side-effects associated with its use and provides evidence that adequate analgesia may be achieved with basic analgesics and regional techniques without intrathecal morphine.

PROSPECT guideline for tonsillectomy: systematic review and procedure-specific postoperative pain management recommendations.

Tonsillectomy is one of the most frequently performed surgical procedures; however, pain management remains challenging. Procedure-specific efficacy as well as specific risks of treatment options should guide selection of pain management protocols based on evidence and should optimise analgesia without harm. The aims of this systematic review were to evaluate the available literature and develop recommendations for optimal pain management after tonsillectomy. A systematic review utilising preferred reporting items for systematic reviews and meta-analysis guidelines with procedure-specific postoperative pain management (PROSPECT) methodology was undertaken. Randomised controlled trials published in the English language up to November 2019 assessing postoperative pain using analgesic, anaesthetic or surgical interventions were identified. Out of the 719 potentially eligible studies identified, 226 randomised controlled trials met the inclusion criteria, excluding the studies examining surgical techniques. Pre-operative and intra-operative interventions that improved postoperative pain were paracetamol; non-steroidal anti-inflammatory drugs; intravenous dexamethasone; ketamine (only assessed in children); gabapentinoids; dexmedetomidine; honey; and acupuncture. Inconsistent evidence was found for local anaesthetic infiltration; antibiotics; and magnesium sulphate. Limited evidence was found for clonidine. The analgesic regimen for tonsillectomy should include paracetamol; non-steroidal anti-inflammatory drugs; and intravenous dexamethasone, with opioids as rescue analgesics. Analgesic adjuncts such as intra-operative and postoperative acupuncture as well as postoperative honey are also recommended. Ketamine (only for children); dexmedetomidine; or gabapentinoids may be considered when some of the first-line analgesics are contra-indicated. Further randomised controlled trials are required to define risk and combination of drugs most effective for postoperative pain relief after tonsillectomy.

Analgesic effect of intravenous dexamethasone after volar plate surgery for distal radius fracture with brachial plexus block anaesthesia: a prospective, double-blind randomised clinical trial.

Rebound pain after brachial plexus block resolution and development of long-lasting pain are problems associated with volar plate fixation for distal radius fractures. The aim of this double-blind study was to evaluate the effect of a single prophylactic intravenous dose of dexamethasone in this setting. The primary endpoint was highest pain score during the first 24 hours after surgery. We included 51 adults of ASA physical status 1-2 due to undergo planned acute fixation of the radius. All received premedication with oral paracetamol and etoricoxib, and a pre-operative brachial plexus block with ropivacaine. Patients were randomly allocated into two groups: a dexamethasone group receiving 16 mg dexamethasone intravenously at start of surgery and a control group receiving 4 ml saline. After surgery, all patients received fixed doses of paracetamol, etoricoxib and oxycodone, with further oxycodone added as needed in the first 48 hours. Pain, analgesic consumption and daily function were registered at predefined times up to 1 year after surgery. Median (IQR [range]) worst pain score in the first 24 hours, as assessed by verbal numeric rating scale (0-10), was 4 (2-6 [0-7]) in the dexamethasone group compared with 8 (5-8 [2-10]) in the placebo group (p < 0.001). Average pain score, 2 (1-4 [0-5]) vs. 5 (3-6 [0-8]), p = 0.001 and rescue oxycodone consumption, 5 (0-10 [0-35]) mg vs. 10 (5-15 [0-50]) mg, p = 0.037), respectively, were both significantly lower in the dexamethasone group compared with control from 8 to 24 hours. Brachial plexus block duration was 69% longer in the dexamethasone group, 21.5 (19.1-23.4 [12.9-24.1]) hours vs. 12.7 (11.9-15.3 [7.4-26.6]) hours, p < 0.001. Two patients (9%) in the dexamethasone group compared with 12 (50%) in the placebo group experienced worst pain scores of 8-10 during the first 36 hours (p = 0.002). At 3 and 7 days postoperatively, there were no significant differences between groups for pain scores or opioid consumption. At 6 months, 27 patients (57%) reported pain at the site of surgery, with significantly higher average pain score (p = 0.024) in the placebo group. At 1 year, two patients in the dexamethasone group reported pain compared with 10 in the placebo group (p = 0.015), and worst pain score was significantly higher in the placebo group (p = 0.018). We conclude that intravenous dexamethasone improves early postoperative analgesia and may also improve clinical outcomes after 6 and 12 months.

Pre-operative brachial plexus block compared with an identical block performed at the end of surgery: a prospective, double-blind, randomised clinical trial.

We evaluated whether pre-emptive analgesia with a pre-operative ultrasound-guided infraclavicular brachial plexus block resulted in better postoperative analgesia than an identical block performed postoperatively. Fifty-two patients undergoing fixation of a fractured radius were included. All patients received general anaesthesia with remifentanil and propofol. Patients were randomly allocated into two groups: a pre-operative block or a postoperative block with 0.5 ml.kg-1 ropivacaine 0.75%. After surgery, all patients received regular paracetamol plus opioids for breakthrough pain. Mean (SD) time to first rescue analgesic after emergence from general anaesthesia was 544 (217) min in the pre-operative block group compared with 343 (316) min in the postoperative block group (p = 0.015). Postoperative pain scores were higher and more patients required rescue analgesia during the first 4 h after surgery in the postoperative block group. There were no significant differences in plasma stress mediators between the groups. Analgesic consumption was lower at day seven in the pre-operative block group. Pain was described as very strong at block resolution in 27 (63%) patients and 26 (76%) had episodes of mild pain after 6 months. We conclude that a pre-operative ultrasound-guided infraclavicular brachial plexus block provides longer and better analgesia in the acute postoperative period compared with an identical postoperative block in patients undergoing surgery for fractured radius.

A randomised controlled trial of propofol vs. thiopentone and desflurane for fatigue after laparoscopic cholecystectomy.

Fatigue may delay functional recovery after day surgery and may be more common after propofol anaesthesia. We randomly allocated 123 participants scheduled for ambulatory laparoscopic cholecystectomy to induction and maintenance of general anaesthesia with propofol or thiopentone and desflurane. Postoperative fatigue was unaffected by the allocated anaesthetic. The combined mean (SD) Identity-Consequences Fatigue Scale of 34.3 (15.1) before surgery increased in the first postoperative week: to 60.4 (21.1) on day 1, p < 0.001; to 51.1 (17.2) on day 2, p < 0.001; and to 37.5 (16.3) on day 6, p = 0.028. The mean (SD) fatigue reduced at one postoperative month to 22.4 (12.6), 35% less than the combined pre-operative level, p < 0.001. Rates of nausea, vomiting and rescue antie-mesis during the first week after propofol, compared with thiopentone and desflurane, were: 23/63 vs. 32/60, p = 0.27; 8/63 vs. 9/60, p = 0.71; and 12/63 vs. 28/60, p = 0.001, respectively. There were no differences in postoperative pain. In conclusion, fatigue after scheduled laparoscopic cholecystectomy was unaffected by anaesthesia with propofol vs. thiopentone and desflurane.

Gradual withdrawal of remifentanil infusion may prevent opioid-induced hyperalgesia.

BACKGROUND: The aim of this study was to examine if gradual withdrawal of remifentanil infusion prevented opioid-induced hyperalgesia (OIH) as opposed to abrupt withdrawal. OIH duration was also evaluated. METHODS: Nineteen volunteers were enrolled in this randomized, double-blinded, placebo-controlled, crossover study. All went through three sessions: abrupt or gradual withdrawal of remifentanil infusion and placebo. Remifentanil was administered at 2.5 ng ml(-1) for 30 min before abrupt withdrawal or gradual withdrawal by 0.6 ng ml(-1) every five min. Pain was assessed at baseline, during infusion, 45-50 min and 105-110 min after end of infusions using the heat pain test (HPT) and the cold pressor test (CPT). RESULTS: The HPT 45 min after infusion indicated OIH development in the abrupt withdrawal session with higher pain scores compared with the gradual withdrawal and placebo sessions (both P<0.01. Marginal mean scores: placebo 2.90; abrupt 3.39; gradual 2.88), but no OIH after gradual withdrawal compared with placebo (P=0.93). In the CPT 50 min after end of infusion there was OIH in both remifentanil sessions compared with placebo (gradual P=0.01, abrupt P<0.01. Marginal mean scores: placebo 4.56; abrupt 5.25; gradual 5.04). There were no differences between the three sessions 105-110 min after infusion. CONCLUSIONS: We found no development of OIH after gradual withdrawal of remifentanil infusion in the HPT. After abrupt withdrawal OIH was present in the HPT. In the CPT there was OIH after both gradual and abrupt withdrawal of infusion. The duration of OIH was less than 105 min for both pain modalities. CLINICAL TRIAL REGISTRATION: NCT 01702389. EudraCT number 2011-002734-39.

The discriminatory value of cardiorespiratory interactions in distinguishing awake from anaesthetised states: a randomised observational study.

Depth of anaesthesia monitors usually analyse cerebral function with or without other physiological signals; non-invasive monitoring of the measured cardiorespiratory signals alone would offer a simple, practical alternative. We aimed to investigate whether such signals, analysed with novel, non-linear dynamic methods, would distinguish between the awake and anaesthetised states. We recorded ECG, respiration, skin temperature, pulse and skin conductivity before and during general anaesthesia in 27 subjects in good cardiovascular health, randomly allocated to receive propofol or sevoflurane. Mean values, variability and dynamic interactions were determined. Respiratory rate (p = 0.0002), skin conductivity (p = 0.03) and skin temperature (p = 0.00006) changed with sevoflurane, and skin temperature (p = 0.0005) with propofol. Pulse transit time increased by 17% with sevoflurane (p = 0.02) and 11% with propofol (p = 0.007). Sevoflurane reduced the wavelet energy of heart (p = 0.0004) and respiratory (p = 0.02) rate variability at all frequencies, whereas propofol decreased only the heart rate variability below 0.021 Hz (p < 0.05). The phase coherence was reduced by both agents at frequencies below 0.145 Hz (p < 0.05), whereas the cardiorespiratory synchronisation time was increased (p < 0.05). A classification analysis based on an optimal set of discriminatory parameters distinguished with 95% success between the awake and anaesthetised states. We suggest that these results can contribute to the design of new monitors of anaesthetic depth based on cardiovascular signals alone.

A comparison of oxycodone prolonged-release vs. oxycodone + naloxone prolonged-release after laparoscopic hysterectomy.

BACKGROUND: Targiniq®, an oxycodone prolonged-release (PR) formulation combined with the opioid antagonist naloxone PR, aims to prevent opioid-induced constipation without impairing the analgesic efficacy. This has been confirmed during prolonged use in chronic pain or cancer patients. The purpose of our study was to compare clinical effects of oxycodone PR with oxycodone PR + naloxone PR for short-term post-operative pain management. METHODS: This randomised, double-blind, prospective study included 85 women undergoing laparoscopic hysterectomy. The two groups received either oxycodone PR 10 mg or oxycodone PR 10 mg + naloxone PR 5 mg as pre-medication and twice daily for 3 days. As rescue analgesic, the patients received oxycodone intravenous during the first 24 h post-operatively and oxycodone tablets in the 24-72-h period. Constipation, other side effects, pain and satisfaction were registered during the first 7 post-operative days. RESULTS: Demographic, pre- and perioperative variables and the use of rescue analgesics were similar in the groups. There were no significant differences in variables related to constipation. In the oxycodone PR + naloxone PR group, 25% had no defecation during the first 72 h post-operatively, compared with 20% in the oxycodone PR group (mean 1.2 ± 1.1 vs. 2.1 ± 2.4 defecations). Other opioid-induced effects and side effects showed no significant differences. Only 7% were dissatisfied with their oral pain treatment. CONCLUSION: Addition of naloxone to oxycodone PR tablets in a pain regimen administered twice daily the first three post-operative days had no significant clinical effects on constipation or other variables during the first week after hysterectomy.

Plasmoid formation in current sheet with finite normal magnetic component.

Current sheet configurations in natural and laboratory plasmas are often accompanied by a finite normal magnetic component that is known to stabilize the two-dimensional resistive tearing instability in the high Lundquist number regime. Recent magnetohydrodynamic simulations indicate that the nonlinear development of ballooning instability is able to induce the formation of X lines and plasmoids in a generalized Harris sheet with a finite normal magnetic component in the high Lundquist number regime where the linear two-dimensional resistive tearing mode is stable.

Nociceptive stimuli responses at different levels of general anaesthesia and genetic variability.

BACKGROUND: Changes in skin conductance (SC), clinical stress score (CSS), the bispectral index spectroscopy (BIS) index and the variation in the BIS index may be used to monitor responses to nociceptive stimuli. We wanted to examine these methods during noxious stimulation during general anaesthesia and if the responses were associated with variability in genes related to pain. METHODS: Sixty patients, given propofol to a BIS level of 40-50, were stimulated with standardised tetanic electrical stimuli during propofol infusion, plasma level of 3 µg/ml alone, or together with remifentanil target plasma level of 3 ng/ml or 10 ng/ml. The CSS, SC, BIS index and the variability of the BIS index were registered. The inter-individual variation in nociceptive responses was analysed for co-variation with genotypes of 89 single nucleotide polymorphisms from 23 candidate genes. RESULTS: During tetanic stimuli, CSS and SC increased significantly and were attenuated with increasing level of remifentanil, different from the BIS index and the variation in the BIS index. Polymorphisms in the P-glycoprotein (ABCB1), tachykinin 1 receptor (TACR1), dopamine receptor D3 (DRD3) and beta arrestin 2 (ARRB2) genes were associated with the co-variation in SC variables or CSS response or both during standardised nociceptive stimuli (P < 0.05). Because of no corrections for multiple testing, the genetic analyses are explorative, and associations must be tested in further studies. CONCLUSION: This exploratory study suggests genes that may be tested further with relation to nociceptive response during anaesthesia. SC and CSS may be useful tools for monitoring nociceptive response during general anaesthesia.

Dexamethasone does not reduce pain or analgesic consumption after thyroid surgery; a prospective, randomized trial.

BACKGROUND: Post-operative analgesic effect of a perioperative fixed dose glucocorticoid has been demonstrated in studies on different surgical procedures. The aim of this study was to look for analgesic and opioid sparing effect after thyroid surgery with a weight-adjusted medium dose of dexamethasone compared with placebo or a higher dose. Further, to register other effects and side effects of dexamethasone in the 0­30 days postoperative period. METHODS: One hundred and twenty patients scheduled for thyroid surgery were randomly assigned to three groups receiving either dexamethasone 0.30 mg/kg, 0.15 mg/kg or placebo. Pain scores at rest and on coughing, post-operative nausea and vomiting (PONV), consumption of opioids and anti-emetics, appetite, sleep pattern, fatigue, mood, blood sugar, wound infection and dyspepsia were recorded. RESULTS: There was no effect of either dexamethasone doses on post-operative pain or rescue opioid consumption. PONV was lower in the dexamethasone groups 2­4 h post-operatively (P < 0.01). Blood sugar increased moderately from baseline in all groups, but significantly more in the dexamethasone groups (P < 0.01 at 2 h and P < 0.001 at 4 h). Minor improvement in appetite was shown with dexamethasone, along with a tendency towards less sleep and more fatigue in the 3­30 days period for the higher dose. No effect was demonstrated on other parameters. CONCLUSION: Dexamethasone had no analgesic or opioid sparing effect in our set-up after thyroid surgery. Dexamethasone reduced the incidence of PONV and led to a modest increase in blood sugar. A medium dose seems as effective as a higher dose.

Short stay and less pain after ambulatory anterior cruciate ligament (ACL) repair: COX-2 inhibitor versus glucocorticoid versus both combined.

BACKGROUND: Many studies have demonstrated that either COX-2 antagonists or glucocorticoids are efficient analgesics after orthopaedic surgery. We wanted to evaluate if the combination of these two drugs was better than one drug alone when added to paracetamol, local anaesthesia, and cryo-cuff for outpatient anterior crucial ligament (ACL) surgery. METHODS: In a double-blind design, 89 adult patients scheduled for day-case ACL repair in general anaesthesia were randomly assigned into three groups: The COXIB group (n = 30) received either 40 mg parecoxib iv or 120 mg etoricoxib orally 1 h before surgery. The STEROID group (n = 30) received 8 mg dexamethasone iv, and the combination group (Group COMBI, n = 29) received both. RESULTS: At 24 h, Group COMBI had significantly lower visual analogue scale (0-10 cm) scores during rest (2.1 ± 1.3) (mean ± standard deviation) and movement (4.2 ± 2.5) when compared to both the COXIB group (P = 0.04) and the STEROID group (P = 0.035). The accumulated consumption of rescue opioids (5.2 ± 4,5 mg morphine) was also significantly lower at 24 h compared to the other groups (P = 0.02). Mean time to discharge from hospital was about 3 h in all groups. The pain scores in the post-anaesthetic care unit, mobilization at 24 h and 7 days, and general level of satisfaction were similar between the groups. CONCLUSION: The combination of a COX-2 inhibitor and dexamethasone results in better pain relief 24 h after surgery in patients undergoing outpatient ACL surgery, compared to COX-2 inhibitor alone or dexamethasone alone. With a dedicated multimodal pain regime, most ACL patients may be discharged within 3 h.

High-volume bariatric surgery in a single center: safety, quality, cost-efficacy and teaching aspects in 2,000 consecutive cases.

BACKGROUND: Obesity surgery is the most effective treatment for morbid obesity and the fastest growing area in surgery. Laparoscopic Roux-en-Y gastric bypass (LRYGB) is the gold standard procedure in many countries. Optimization of the treatment process is important in order to keep the morbidity rate down and cost of treatment as low as possible. METHODS: In September 2005, we established a bariatric surgery program. Until December 2010, 2,000 patients underwent LRYGB. Clinical pathways were established, with focus on safety, fast-track methodology and training of surgeons. Time recordings from all parts of the treatment, as well as clinical outcome, were prospectively registered. RESULTS: Time consumption for the total procedure in the operating theater was reduced from 102 to 54 min (P < 0.001). With only 11 min turnover between patients, the total time for one patient has been reduced to 65 min, enabling us to perform six operations in a single operating theater during ordinary daytime. Early complication rate was 2.8%, and mean hospital stay was 2.3 days. We were able to double the patients treated in 2010 compared to 2007 with only 10% increase in staff. Three surgeons were trained during the period into fully qualified senior bariatric surgeons. CONCLUSIONS: Multimodal evidence-based care within the fast-track methodology and routine time recordings was successful in order to increase the production volumes and reduce costs, without compromising the safety or quality for the patients. This kind of approach may be transferred to other types of standardized surgery.

Effect of a single dose of pregabalin on post-operative pain and pre-operative anxiety in patients undergoing discectomy.

BACKGROUND: Pregabalin acts as a membrane stabilizer and has both analgesic and anxiolytic effects. We hypothesized that one pre-operative dose of pregabalin would reduce pre-operative anxiety and post-operative pain in patients undergoing discectomy. METHODS: We performed a randomized, placebo-controlled study of 150 mg pregabalin administered before lumbar discectomy in general anaesthesia. The primary endpoint was pain at rest [visual analogue scale (VAS)] 120 min after surgery. The secondary outcomes were morphine consumption, pre-operative anxiety (VAS) and the occurrence of side effects. RESULTS: The VAS scores for pain at rest and morphine consumption were higher in the placebo group during the 4-h stay in the post-anaesthetic care unit (PACU), but did not differ significantly 24 h after surgery. Pain scores at 7 days were similar and there was no difference in the occurrence of side effects. Pre-operative anxiety was significantly lower in the pregabalin group (2.23±1.11 vs. 4.17±2.37, 95% confidence interval: 0.82-3.05, P=0.001) and there was a significant positive correlation between the pre-operative anxiety score and post-operative pain at 120 min in the pregabalin group. CONCLUSIONS: A single dose of pregabalin (150 mg) reduced post-operative pain at rest and morphine consumption during the PACU period after lumbar discectomy. Pre-operative anxiety was lower, without increased incidence of side effects.