Quantum Theory Cannot Violate a Causal Inequality.

Within quantum theory, we can create superpositions of different causal orders of events, and observe interference between them. This raises the question of whether quantum theory can produce results that would be impossible to replicate with any classical causal model, thereby violating a causal inequality. This would be a temporal analog of Bell inequality violation, which proves that no local hidden variable model can replicate quantum results. However, unlike the case of nonlocality, we show that quantum experiments can be simulated by a classical causal model, and therefore cannot violate a causal inequality.

Eigenstate thermalization on average.

We consider conditions under which an isolated quantum system approaches a microcanonical equilibrium state. A key component is the eigenstate thermalization hypothesis, which proposes that all energy eigenstates appear thermal. We introduce a weaker version of this requirement, applying only to the average distinguishability of eigenstates from the thermal state, and investigate its necessity and sufficiency for thermalization.

Channels, measurements, and postselection in quantum thermodynamics.

We analyze the benefit, in terms of extracting work, of having a single use of a quantum channel or measurement in quantum thermodynamics. This highlights a connection between unital and catalytic channels, and some subtleties concerning the conditional work cost of implementing a measurement given that a certain result was obtained. We also consider postselected measurements and show that any nontrivial postselection leads to an unbounded work benefit.

Addition of dexamethasone to local infiltration analgesia in elective total knee arthroplasty: double-blind, randomized control trial.

BACKGROUND AND OBJECTIVES: Total knee arthroplasty is associated with significant pain, and effective analgesia is beneficial to patient satisfaction and functional outcomes. Studies have demonstrated that dexamethasone may have a facilitatory role on the action of local anesthesia, but this effect, when added to a local infiltration analgesia (LIA) mixture for patients having knee arthroplasty, is underexplored. Our hypothesis was that the addition of dexamethasone to local anesthetic infiltration would improve analgesic outcomes following total knee arthroplasty. METHODS: We performed a double-blind, randomized controlled trial of 140 patients undergoing elective, unilateral, total knee arthroplasty. Patients were randomly allocated to receive either 2 mL of saline 0.9% or 2 mL of dexamethasone 4 mg/mL added to a LIA mixture. Our primary outcome was 24 hours of oral morphine equivalent consumption. Our secondary outcomes included short-term and long-term analgesic and functional outcomes and adverse events. RESULTS: A total of 72 patients were included in the saline group and 68 were included in the dexamethasone group. We found comparable 24 hours of morphine consumption between saline and dexamethasone groups, with a median of 60 (IQR 40-105 (range 16-230)) mg and 56 (IQR 41-75 (range 0-300)) mg, respectively (p=0.096). Dexamethasone was associated with a statistically significant reduction in total inpatient opioid consumption, incidence of requiring rescue patient-controlled analgesia, length of hospital stay, and postoperative nausea, compared with saline. Patients in the dexamethasone group had a greater range of joint movement and distance walked on postoperative day 1 than the saline group. There were no differences in rest or active pain scores, timed up and go or 3-month outcomes. CONCLUSIONS: Dexamethasone 8 mg was associated with no improvements in 24 hours of morphine consumption but was associated with modest improvements in short-term analgesia, short-term function, length of stay and postoperative nausea. There were no long-term benefits in the use of dexamethasone in LIA for patients undergoing total knee arthroplasty. TRIAL REGISTRATION NUMBER: NCT02760043.

Reference Frames Which Separately Store Noncommuting Conserved Quantities.

Even in the presence of conservation laws, one can perform arbitrary transformations on a system if given access to a suitable reference frame, since conserved quantities may be exchanged between the system and the frame. Here we explore whether these quantities can be separated into different parts of the reference frame, with each part acting as a "battery" for a distinct quantity. For systems composed of spin-1/2 particles, we show that the components of angular momentum S_{x}, S_{y}, and S_{z} (noncommuting conserved quantities) may be separated in this way, and also provide several extensions of this result. These results also play a key role in the quantum thermodynamics of noncommuting conserved quantities.

Intrathecal Morphine and Pulmonary Complications after Arthroplasty in Patients with Obstructive Sleep Apnea: A Retrospective Cohort Study.

BACKGROUND: Intrathecal morphine is commonly and effectively used for analgesia after joint arthroplasty, but has been associated with delayed respiratory depression. Patients with obstructive sleep apnea may be at higher risk of postoperative pulmonary complications. However, data is limited regarding the safety of intrathecal morphine in this population undergoing arthroplasty. METHODS: This retrospective cohort study aimed to determine the safety of intrathecal morphine in 1,326 patients with documented or suspected obstructive sleep apnea undergoing hip or knee arthroplasty. Chart review was performed to determine clinical characteristics, perioperative events, and postoperative outcomes. All patients received neuraxial anesthesia with low-dose (100 µg) intrathecal morphine (exposure) or without opioids (control). The primary outcome was any postoperative pulmonary complication including: (1) respiratory depression requiring naloxone; (2) pneumonia; (3) acute respiratory event requiring consultation with the critical care response team; (4) respiratory failure requiring intubation/mechanical ventilation; (5) unplanned admission to the intensive care unit for respiratory support; and (6) death from a respiratory cause. The authors hypothesized that intrathecal morphine would be associated with increased postoperative complications. RESULTS: In 1,326 patients, 1,042 (78.6%) received intrathecal morphine. The mean age of patients was 65 ± 9 yr and body mass index was 34.7 ± 7.0 kg/m. Of 1,326 patients, 622 (46.9%) had suspected obstructive sleep apnea (Snoring, Tired, Observed, Pressure, Body Mass Index, Age, Neck size, Gender [STOP-Bang] score greater than 3), while 704 of 1,326 (53.1%) had documented polysomnographic diagnosis. Postoperatively, 20 of 1,322 (1.5%) patients experienced pulmonary complications, including 14 of 1,039 (1.3%) in the exposed and 6 of 283 (2.1%) in the control group (P = 0.345). Overall, there were 6 of 1 322 (0.5%) cases of respiratory depression, 18 of 1,322 (1.4%) respiratory events requiring critical care team consultation, and 4 of 1,322 (0.3%) unplanned intensive care unit admissions; these rates were similar between both groups. After adjustment for confounding, intrathecal morphine was not significantly associated with postoperative pulmonary complication (adjusted odds ratio, 0.60 [95% CI, 0.24 to 1.67]; P = 0.308). CONCLUSIONS: Low-dose intrathecal morphine, in conjunction with multimodal analgesia, was not reliably associated with postoperative pulmonary complications in patients with obstructive sleep apnea undergoing joint arthroplasty.

Effect of intravenous dexamethasone on the anaesthetic characteristics of peripheral nerve block: a double-blind, randomised controlled, dose-response volunteer study.

BACKGROUND: Intravenous dexamethasone is thought to prolong the duration of peripheral nerve block, but the dose-response relationship remains unclear. The aim of this volunteer study was to evaluate the dose-response effect of i.v. dexamethasone on the prolongation of median nerve block. METHODS: In a double-blind, randomised controlled study, 18 volunteer subjects received two median nerve blocks separated by a washout period. One block was conducted alongside an infusion of saline and the other alongside i.v. dexamethasone 2, 4, or 8 mg. The primary outcome was time to return of normal pinprick sensation. Secondary outcomes included thermal quantitative sensory testing (QST) for the time to return of cold detection threshold (CDT), warm detection threshold (WDT), cold pain threshold (CPT), heat pain threshold (HPT), area under QST curves, grip strength, and the incidence of adverse effects. RESULTS: The primary outcome, time to recovery of pinprick sensation, was similar between volunteers receiving saline or i.v. dexamethasone, regardless of dose (P=0.99). The time to recovery of QST milestones was similar between groups, although area under QST curves indicated prolongation of CDT (0 vs 8 mg, P=0.002) and WDT (0 vs 2 mg, P=0.008; 0 vs 4 mg, P=0.001; 0 vs 8 mg, P<0.001). There was no difference in motor recovery or adverse effects. CONCLUSIONS: Intravenous dexamethasone failed to significantly prolong the duration of pinprick anaesthesia regardless of dose. However, area under QST curve analysis indicated a dose-independent prolongation of CDT and WDT, the clinical significance of which is unclear. CLINICAL TRIAL REGISTRATION: NCT02864602 (clinicaltrials.gov).

Intermittent bolus versus continuous infusion popliteal sciatic nerve block following major foot and ankle surgery: a prospective randomized comparison.

BACKGROUND AND OBJECTIVES: Foot and ankle surgery is associated with severe pain that can be reduced with continuous popliteal sciatic nerve block. We tested the hypothesis that programmed intermittent bolus (PIB) delivery of local anesthetic provides superior analgesia to a continuous infusion (CI) regimen. METHODS: 60 patients undergoing major foot and ankle surgery were randomized to receive PIB (10 mL of ropivacaine 0.2% every 2 hours) or CI (5 mL/hour) continuous popliteal sciatic nerve block with patient-controlled regional analgesia (5 mL every 30 min as needed) provided for all. Primary outcome was the average of static and dynamic numerical rating scale (NRS) pain scores through 48 hours. Secondary outcomes included rest and movement NRS pain scores at different timepoints, opioid consumption, local anesthetic consumption, intensity of sensory and motor block, patient satisfaction and the incidence of opioid-related side effects. RESULTS: There was no significant difference in the primary outcome of average NRS pain score through 48 hours, opioid consumption or the volume of local anesthetic administered. Patients in group PIB had significantly decreased strength of toe dorsiflexion at 6 hours (p=0.007) and 12 hours (p=0.001) and toe plantarflexion at 12 hours (p=0.004). Patient satisfaction and the incidence of side effects was similar between groups. CONCLUSIONS: Both CI and PIB regimens provided excellent analgesia, low opioid consumption and high patient satisfaction. While there was no difference in analgesic outcomes, PIB dosing resulted in a more profound motor block. TRIAL REGISTRATION NUMBER: NCT02707874.

Addition of dexamethasone to local infiltration analgesia in elective total hip arthroplasty: a double-blind, randomized control trial.

BACKGROUND AND OBJECTIVES: Pain following total hip arthroplasty is significant, and effective analgesia is associated with an improvement in functional outcomes. Dexamethasone may facilitate the action of local anesthesia, but its role as an additive to a local infiltration analgesia (LIA) mixture in hip arthroplasty settings has not been investigated. We hypothesized that the addition of dexamethasone to local anesthetic infiltration improves analgesic outcomes following total hip arthroplasty. METHODS: We performed a double-blind, randomized control trial of 170 patients undergoing total hip arthroplasty. Patients were randomized to receive LIA mixed with either 2 mL of saline 0.9% or 2 mL of dexamethasone 4 mg/mL. The primary outcome was 24 hours oral morphine consumption. Secondary outcomes included short-term and long-term analgesic and functional outcomes and adverse events. RESULTS: 85 patients were included in each arm. 24 hours morphine consumption was similar between saline and dexamethasone groups, with a median (IQR (range)) of 75 (45-105 (0-240)) and 62.5 (37.5-102.5 (0-210)) mg, respectively (p=0.145). However, patients receiving dexamethasone had significantly reduced opioid consumption for their total in-hospital stay, but not at any other time points examined. Functional outcomes were similar between groups. The incidence of postoperative nausea and vomiting was reduced in patients receiving dexamethasone. CONCLUSIONS: The addition of 8 mg dexamethasone to LIA did not reduce 24 hours morphine consumption but was associated with limited improvement in short-term analgesic outcomes and a reduction in postoperative nausea and vomiting. Dexamethasone had no effect on functional outcomes or long-term analgesia. TRIAL REGISTRATION NUMBER: NCT02760043.

Outcome Selection and Methodological Quality of Major and Minor Shoulder Surgery Studies: A Scoping Review.

BACKGROUND: Core outcome sets aim to select and standardize the choice of important outcomes reported in clinical trials to encourage more effective data synthesis, increase the reliability of comparing results, and minimize reporting bias. A core outcome set for elective shoulder surgery has yet to be defined, and therefore a systematic assessment of outcomes and methodology is necessary to inform the development of a core outcome set. QUESTIONS/PURPOSES: The purpose of this study was to examine randomized controlled trials (RCTs) of patients having elective major or minor shoulder surgery to (1) identify the outcome domains reported; (2) determine specific outcome measurement tools that were utilized; and (3) assess the work for methodological quality and risk of bias. METHODS: We conducted a scoping review (a review that identifies the nature and extent of research evidence) to explore the reported outcome domains, outcome tools, and methodological quality from RCTs conducted in shoulder surgery. We considered both major shoulder surgery (defined as arthroplasty, rotator cuff repair, stabilization procedures, biceps tenodesis, or Bankart repairs) and minor shoulder surgery (simple arthroscopy, capsular plication, lateral clavicular excisions, or subacromial decompression). We queried 10 electronic databases for studies published between January 2006 and January 2015. Studies were included if they were prospective, randomized controlled, clinical trials enrolling patients who received an elective shoulder surgical intervention. We extracted data relating to trial characteristics, primary outcomes, tools used to measure these outcomes as well as methodological quality indicators. We assessed indicators of methodological quality by exploring (1) the reproducibility of power analyses; and (2) whether the primary outcomes were powered to minimum clinically important differences. Risk of bias was also assessed with the Jadad score with scores between 0 (very high risk of bias) and 5 (very low risk). Findings were qualitatively analyzed and reported according to systematic and scoping review guidelines. We included 315 studies involving 30,232 patients; 266 studies investigated anesthetic, analgesic, or surgical interventions. RESULTS: Of the 315 studies included, the most common outcome domains evaluated were analgesic (n = 104), functional (n = 87), anesthetic (n = 56), and radiologic (n = 29) outcomes, with temporal patterns noted. Studies of major shoulder surgery most commonly reported functional primary outcome domains, whereas minor shoulder surgery studies most frequently reported analgesic primary outcome domains. There were 85 different primary outcome tools utilized, which included 20 functional, 20 anesthetic, 13 analgesic, and 12 radiologic. A methodological quality assessment revealed that 24% of studies had reproducible power analyses, 13% were powered to minimum clinically important differences, and risk of bias assessment demonstrated a median (interquartile range [range]) Jadad score of 4 (3-5 [1-5]). CONCLUSIONS: A wide range of outcome domains and outcome assessment tools are in common use in contemporary trials of patients undergoing elective surgery. Although some diversity is important to allow the assessment of patient populations that may have different goals, the large number of tools in common use may impair the ability of future meta-analyses to pool results effectively or even for systematic reviews to synthesize what is known. The limitations of methodological quality in RCTs may be improved by researchers following standard guidelines and considering the minimum clinically important differences in their trials to be of greater use to clinicians and their patients. LEVEL OF EVIDENCE: Level I, therapeutic study.

Transmuscular quadratus lumborum versus lumbar plexus block for total hip arthroplasty: A retrospective propensity score matched cohort study.

BACKGROUND AND AIMS: Cadaveric studies have shown that injectate from transmuscular quadratus lumborum block (QLB) can spread to the lumbar plexus. Our aim was to compare analgesic efficacy of transmuscular QLB with lumbar plexus block (LPB) for patients undergoing total hip arthroplasty (THA). MATERIAL AND METHODS: Thirty patients receiving transmuscular QLB were propensity score matched with 30 patients receiving LPB for age, sex, ASA score, BMI, operative time, preoperative oxycodone, and intraoperative opioid use. The primary outcome was postoperative opioid consumption during the first 24 postoperative hours. Secondary outcomes included static pain scores at 0-12, 12-24, and 24-48 h intervals, opioid consumption at 0-12, 12-24, and 24-48 h intervals and the length of hospital stay. The incidence of severe adverse events was also compared. RESULTS: Opioid consumption (median [IQR]) in the first 24 h was similar between the transmuscular QLB and LPB patient groups-33.6 mg (22.9-48.5) versus 32.8 mg (24.8-58.3) intravenous morphine equivalents. There was no difference between groups in static pain scores or opioid consumption during any time interval up to 48 h postoperatively. Length of hospital stay (median [IQR]) was similar between the transmuscular QLB and LPB groups-55.6 h (53.7-60.3) versus 57.9 h (54.3-79.1). CONCLUSIONS: This study suggests that transmuscular QLB provides similar analgesia to LPB following THA. Prospective studies are needed to confirm this.

Quantum reference frames and their applications to thermodynamics.

We construct a quantum reference frame, which can be used to approximately implement arbitrary unitary transformations on a system in the presence of any number of extensive conserved quantities, by absorbing any back action provided by the conservation laws. Thus, the reference frame at the same time acts as a battery for the conserved quantities. Our construction features a physically intuitive, clear and implementation-friendly realization. Indeed, the reference system is composed of the same types of subsystems as the original system and is finite for any desired accuracy. In addition, the interaction with the reference frame can be broken down into two-body terms coupling the system to one of the reference frame subsystems at a time. We apply this construction to quantum thermodynamic set-ups with multiple, possibly non-commuting conserved quantities, which allows for the definition of explicit batteries in such cases.This article is part of a discussion meeting issue 'Foundations of quantum mechanics and their impact on contemporary society'.

Anatomic Study of Innervation of the Anterior Hip Capsule: Implication for Image-Guided Intervention.

BACKGROUND AND OBJECTIVES: The purpose of this cadaveric study was to determine the pattern of anterior hip capsule innervation and the associated bony landmarks for image-guided radiofrequency denervation. METHODS: Thirteen hemipelvises were dissected to identify innervation of the anterior hip capsule. The femoral (FN), obturator (ON), and accessory obturator (AON) nerves were traced distally, and branches supplying the anterior capsule documented. The relationships of the branches to bony landmarks potentially visible with ultrasound were identified. RESULTS: The anterior hip capsule received innervation from the FNs and ONs in all specimens and the AON in 7 of 13 specimens. High branches of the FN (originating above the inguinal ligament) were found exclusively in 12 specimens and passed between the anterior inferior iliac spine and the iliopubic eminence. The ONs were innervated exclusively by high branches (proximal to the division), by low branches (from the posterior branch), and by both in 4, 5, and 4 specimens, respectively. The most consistent landmark was the inferomedial acetabulum (radiographic "teardrop"). When present, the AON coursed over the iliopubic eminence before innervating the anterior hip capsule. CONCLUSIONS: Branches of the FNs and ONs consistently provided innervation to the anterior hip capsule. The AON also contributed innervation in many specimens. The relationship of the articular branches from these 3 nerves to the inferomedial acetabulum and the space between the anterior inferior iliac spine and iliopubic eminence may suggest potential sites for radiofrequency ablation.

Comparing classical and quantum equilibration.

By using a physically relevant and theory independent definition of measurement-based equilibration, we show quantitatively that equilibration is easier for quantum systems than for classical systems, in the situation where the initial state of the system is completely known (a pure state). This shows that quantum equilibration is a fundamental aspect of many quantum systems, while classical equilibration relies on experimental ignorance. When the state is not completely known (a mixed state), this framework also shows that quantum equilibration requires weaker conditions.

Thermodynamics of quantum systems with multiple conserved quantities.

Recently, there has been much progress in understanding the thermodynamics of quantum systems, even for small individual systems. Most of this work has focused on the standard case where energy is the only conserved quantity. Here we consider a generalization of this work to deal with multiple conserved quantities. Each conserved quantity, which, importantly, need not commute with the rest, can be extracted and stored in its own battery. Unlike the standard case, in which the amount of extractable energy is constrained, here there is no limit on how much of any individual conserved quantity can be extracted. However, other conserved quantities must be supplied, and the second law constrains the combination of extractable quantities and the trade-offs between them. We present explicit protocols that allow us to perform arbitrarily good trade-offs and extract arbitrarily good combinations of conserved quantities from individual quantum systems.

Rapid spatial equilibration of a particle in a box.

We study the equilibration behavior of a quantum particle in a one-dimensional box, with respect to a coarse-grained position measurement (whether it lies in a certain spatial window or not). We show that equilibration in this context indeed takes place and does so very rapidly, in a time comparable to the time for the initial wave packet to reach the edges of the box. We also show that, for this situation, the equilibration behavior is relatively insensitive to the precise choice of position measurements or initial condition.