Prolongation of spinal duration by escalating doses of intrathecal epinephrine in lower limb arthroplasty.

Aim: The optimal dose of low-dose intrathecal epinephrine in the absence of intrathecal opioids is unknown. Materials & methods: Prospective, randomized, double blind clinical trial of patients undergoing lower limb arthroplasties. The primary end point was spinal block duration measured via motor and sensory block duration. Results: 30 patients undergoing lower limb arthroplasty were randomized into one of six groups with varying intrathecal epinephrine doses 0-100 mcg. There was a direct linear effect between motor block duration and intrathecal epinephrine dose with higher doses being associated with longer block duration (p = 0.011). Mean motor block duration was 3.74 ± 1.13, 3.36 ± 0.47, 3.39 ± 0.60, 4.06 ± 0.98 and 5.20 ± 1.41 h for the EPI0, EPI25, EPI50, EPI75 and EPI100 groups respectively. Conclusion: This study reveals that low-dose intrathecal epinephrine (75-100 mcg) in the absence of intrathecal opioids can be reliably used to prolong motor block duration in lower limb arthroplasty. Clinical Trial Registration: NCT02619409 (ClinicalTrials.gov).

What is this summary about? Here, we summarize the results of the addition of a medicine called epinephrine to a type of anesthesia called spinal anesthesia which involves injection of medication into the fluid surrounding the spinal cord. The study was to determine the optimal amount of epinephrine needed to prolong the effect of spinal anesthesia for patients undergoing replacements of their hips and/or knees. What were the results? The study showed that the addition of low-dose epinephrine to spinal anesthesia prolongs the motor block ­ or inability to move the leg ­ in a linear fashion with higher doses of epinephrine associated with longer motor block. Our results did not show a significant difference in sensory block, or the inability to feel the leg. What do the results mean? The study shows that the addition of low-dose epinephrine to spinal anesthesia can reliably prolong the effect of the anesthesia which may be needed in more complicated hip or knee surgeries.

Paravertebral anesthetic nerve block for pain control after peroral endoscopic myotomy.

BACKGROUND: Excess post-operative opioid medication use can delay recovery and is associated with long-term misuse, addiction, and overdose. We aimed to explore the effect of pre-procedural thoracic paravertebral nerve block (PNB) on pain-related outcomes after POEM. METHODS: In this retrospective cohort study, consecutive patients who did and did not receive a PNB prior to POEM were compared. The outcomes were peak and cumulative pain scores, total opioid use during hospitalization, and length of stay. After adjusting for confounders, the associations between nerve block and the outcomes of interest were explored. RESULTS: Forty-nine consecutive patients were enrolled; 25 patients received a block whereas the subsequent 24 did not. There were no differences in baseline characteristics between the study groups. In unadjusted analyses, there was no significant difference between patients who did and did not undergo PNB in peak pain score (7.8 vs. 8.7, p=0.14), cumulative pain score in the first 12 hours (area under curve 66.5 vs. 75.8, p=0.22), median total opioid use (38.9 mg morphine equivalent dosing vs. 42, p=1.00), and median length of hospitalization (26.5 hours vs. 24, p=0.35). In multivariable regression models, PNB was not associated with a reduction in pain scores, opioid use, or hospitalization. There were no adverse events related to the block. CONCLUSIONS: In this exploratory, observational study, paravertebral nerve block immediately before POEM did not result in a statistically significant reduction in pain-related outcomes or hospitalization. Additional observational studies may elucidate whether higher anesthetic doses or longer acting formulations would be of value.

Impact of a multidisciplinary multimodal opioid minimization initiative in kidney transplant recipients.

Opioid use after kidney transplant has been shown to be a risk factor for chronic opioid use, which leads to an increased risk of mortality. The purpose of this study was to evaluate the early impact of a multimodal pain regimen and education quality improvement program on opioid use after kidney transplant 2 months after implementation. This was a retrospective, single-center analysis of post-operative opioid use, comparing the average daily Morphine milligram equivalents (MME) of the patients who received education on opioids and a multimodal pain regimen (preoperative TAP/QL block, scheduled APAP and gabapentin) compared to a historical control group. Despite having no differences in pre-transplant opioid exposure, daily and overall inpatient opioid utilization was significantly reduced in the multimodal pain protocol cohort (38.6 vs 8.0 MME/day; P < .001); 5% of patients in the multimodal pain protocol cohort were discharged with an opioid prescription, compared to 96% of controls (P < .001). Our early results demonstrate that a multimodal pain protocol can effectively and dramatically reduce short-term opioid utilization in kidney transplant recipients.

Multivalent interactions between CsoS2 and Rubisco mediate α-carboxysome formation.

Carboxysomes are bacterial microcompartments that function as the centerpiece of the bacterial CO2-concentrating mechanism by facilitating high CO2 concentrations near the carboxylase Rubisco. The carboxysome self-assembles from thousands of individual proteins into icosahedral-like particles with a dense enzyme cargo encapsulated within a proteinaceous shell. In the case of the α-carboxysome, there is little molecular insight into protein-protein interactions that drive the assembly process. Here, studies on the α-carboxysome from Halothiobacillus neapolitanus demonstrate that Rubisco interacts with the N terminus of CsoS2, a multivalent, intrinsically disordered protein. X-ray structural analysis of the CsoS2 interaction motif bound to Rubisco reveals a series of conserved electrostatic interactions that are only made with properly assembled hexadecameric Rubisco. Although biophysical measurements indicate that this single interaction is weak, its implicit multivalency induces high-affinity binding through avidity. Taken together, our results indicate that CsoS2 acts as an interaction hub to condense Rubisco and enable efficient α-carboxysome formation.

Post-Reperfusion Syndrome in Liver Transplantation: Does a Caval Blood Flush Vent Help?

BACKGROUND Post-reperfusion syndrome (PRS) during liver transplantation can range from a benign event to a profound hemodynamic excursion from baseline with significant morbidity. Multiple variables can be responsible for the diverse presentations. Over time, our group noticed that a blood flush of the liver graft via a caval vent (in addition to a standard chilled flush via the portal vein) appeared to result in a milder reperfusion effect. Attenuation of PRS via caval vent seemed to minimize hemodynamic instability and reduce metabolic derangements associated with reperfusion. MATERIAL AND METHODS This was a prospective observational pilot study of standard practice with the addition of lab values and hemodynamic evaluations. We methodically observed normal clinical flow in 20 adult orthotopic liver transplant recipients. We analyzed blood and fluid samples at set time intervals during the peri-reperfusion phase. RESULTS Sixteen out of 20 patients received a blood flush via caval venting. Mean arterial pressure (MAP) and heart rate were better preserved in the patient population that received a caval blood flush vent. Elevations in central venous pressure (CVP) were similar between the 2 groups. Lab values (blood gas, electrolyte, and hemoglobin) of the patients' blood were similar, with no notable differences. Analysis of the initial blood flushed through the liver graft proved to be hypothermic, acidotic, and hyperkalemic. CONCLUSIONS Pre-reperfusion caval venting in liver transplantation (in addition to a portal vent and a chilled LR/albumin portal flush solution) appears to have favorable hemodynamic effects. The literature on this technique is sparse and larger studies are needed.

Tracing a protein's folding pathway over evolutionary time using ancestral sequence reconstruction and hydrogen exchange.

The conformations populated during protein folding have been studied for decades; yet, their evolutionary importance remains largely unexplored. Ancestral sequence reconstruction allows access to proteins across evolutionary time, and new methods such as pulsed-labeling hydrogen exchange coupled with mass spectrometry allow determination of folding intermediate structures at near amino-acid resolution. Here, we combine these techniques to monitor the folding of the ribonuclease H family along the evolutionary lineages of T. thermophilus and E. coli RNase H. All homologs and ancestral proteins studied populate a similar folding intermediate despite being separated by billions of years of evolution. Even though this conformation is conserved, the pathway leading to it has diverged over evolutionary time, and rational mutations can alter this trajectory. Our results demonstrate that evolutionary processes can affect the energy landscape to preserve or alter specific features of a protein's folding pathway.

Kinetic and structural comparison of a protein's cotranslational folding and refolding pathways.

Precise protein folding is essential for the survival of all cells, and protein misfolding causes a number of diseases that lack effective therapies, yet the general principles governing protein folding in the cell remain poorly understood. In vivo, folding can begin cotranslationally and protein quality control at the ribosome is essential for cellular proteostasis. We directly characterize and compare the refolding and cotranslational folding trajectories of the protein HaloTag. We introduce new techniques for both measuring folding kinetics and detecting the conformations of partially folded intermediates during translation in real time. We find that, although translation does not affect the rate-limiting step of HaloTag folding, a key aggregation-prone intermediate observed during in vitro refolding experiments is no longer detectable. This rerouting of the folding pathway increases HaloTag's folding efficiency and may serve as a general chaperone-independent mechanism of quality control by the ribosome.

Anesthesia for subcutaneous implantable cardioverter-defibrillator implantation: Perspectives from the clinical experience of a U.S. panel of physicians.

BACKGROUND AND OBJECTIVE: Worldwide adoption of the subcutaneous implantable cardioverter-defibrillator (S-ICD) for preventing sudden cardiac death continues to increase, as longer-term evidence demonstrating the safety and efficacy of the S-ICD expands. As a relatively new technology, comprehensive anesthesia guidance for the management of patients undergoing S-ICD placement is lacking. This article presents advantages and disadvantages of different periprocedural sedation and anesthesia options for S-ICD implants including general anesthesia, monitored anesthesia care, regional anesthesia, and nonanesthesia personnel administered sedation and analgesia. METHODS: Guidance, for approaches to anesthesia care during S-ICD implantation, is presented based upon literature review and consensus of a panel of high-volume S-ICD implanters, a regional anesthesiologist, and a cardiothoracic anesthesiologist with significant S-ICD experience. The panel developed suggested actions for perioperative sedation, anesthesia, surgical practices, and a decision algorithm for S-ICD implantation. CONCLUSIONS: While S-ICD implantation currently requires higher sedation than transvenous ICD systems, the panel consensus is that general anesthesia is not required or is obligatory for the majority of patients for the experienced S-ICD implanter. The focus of the implanting physician and the anesthesia services should be to maximize patient comfort and take into consideration patient-specific comorbidities, with a low threshold to consult the anesthesiology team.

A Retrospective Study Evaluating the Effect of Low Doses of Perineural Dexamethasone on Ropivacaine Brachial Plexus Peripheral Nerve Block Analgesic Duration.

Objective: Examination of the effectiveness of perineural dexamethasone administered in very low and low doses on ropivacaine brachial plexus block duration. Design: Retrospective evaluation of brachial plexus block duration in a large cohort of patients receiving peripheral nerve blocks with and without perineural dexamethasone in a prospectively collected quality assurance database. Setting: A single academic medical center. Methods: A total of 1,942 brachial plexus blocks placed over a 16-month period were reviewed. Demographics, nerve block location, and perineural dexamethasone utilization and dose were examined in relation to block duration. Perineural dexamethasone was examined as none (0 mg), very low dose (2 mg or less), and low dose (greater than 2 mg to 4 mg). Continuous catheter techniques, local anesthetics other than ropivacaine, and block locations with fewer than 15 subjects were excluded. Associations between block duration and predictors of interest were examined using multivariable regression models. A subgroup analysis of the impact of receiving dexamethasone on block duration within each block type was also conducted using a univariate linear regression approach. Results: A total of 1,027 subjects were evaluated. More than 90% of brachial plexus blocks contained perineural dexamethasone (≤4 mg), with a median dose of 2 mg. Increased block duration was associated with receiving any dose of perineural dexamethasone (P < 0.0001), female gender (P = 0.022), increased age (P = 0.048), and increased local anesthetic dose (P = 0.01). In a multivariable model, block duration did not differ with very low- or low-dose perineural dexamethasone after controlling for other factors (P = 0.420). Conclusion: Perineural dexamethasone prolonged block duration compared with ropivacaine alone; however, duration was not greater with low-dose compared with very low-dose perineural dexamethasone.

Comparison of analgaesia with lumbar epidurals and lumbar plexus nerve blocks in patients receiving multimodal analgaesics following primary total hip arthroplasty: a retrospective analysis.

PURPOSE: Significant post-operative pain occurs after hip arthroplasty. In a prior study, lumbar plexus nerve blocks provided comparable analgaesia to lumbar epidurals; however, multimodal analgaesics were not used consistently. METHODS: This study assessed a randomly selected cohort of 48 patients undergoing primary hip arthroplasty who received a regional anaesthesia technique for post-operative pain. Twenty-four patients with lumbar epidurals and 24 with single-injection lumbar plexus nerve blocks were reviewed using electronic medical records. Post-operative opiate consumption was the primary endpoint. Secondary endpoints were participation in physical therapy, side effects, and time to discharge. Descriptive statistics were calculated to describe patients in the different groups. Opiate consumption was compared using linear mixed models. Multivariable models were examined for both primary and secondary endpoints. RESULTS: In comparison with patients receiving lumbar epidural catheters, patients with lumbar plexus blocks consumed less opiates post-operatively at 24-36 and 36-48 hours (P = 0.037 and 0.002, respectively); it did not differ at zero to 12 hours or 12-24 hours post-operatively. Patients with lumbar plexus blocks had earlier times to first ambulation (28.5 ± 3.29 vs 21.9 ± 1.76 h; P = 0.043). However, differences by block type were not observed for ambulation distance, level of assistance to ambulate or time of discharge orders. CONCLUSIONS: Following primary total hip arthroplasty, lumbar plexus nerve blocks provide effective post-operative analgaesia with decreased opiate consumption compared with lumbar epidural catheters. Lumbar plexus blocks also promote earlier post-operative ambulation and are compatible with post-operative prophylactic anticoagulants.

Thoracolumbar interfascial plane (TLIP) block: a pilot study in volunteers.

PURPOSE: Regional anesthesia has been shown to improve outcomes in several recent studies. The transversus abdominis plane (TAP) block provides anesthesia to the abdominal wall by introducing local anesthetic to the ventral rami of the thoracolumbar nerves. This work quantifies the area of anesthesia obtained after performing the novel thoracolumbar interfascial plane block (analogous to the TAP block but intended for the back) which targets the sensory component of the dorsal rami of the thoracolumbar nerves. METHODS: Ten participants underwent bilateral ultrasound-guided injections of 0.2% ropivacaine 20 mL into the fascial plane between the multifidus and longissimus muscles. After five and 20 min, respectively, the area of anesthesia was plotted on the participant's back. Anesthesia was defined as loss of point discrimination to pinprick. RESULTS: Participants reported a mean (SD) area of anesthesia surrounding the needle injection site of 137.4 (71.0) cm(2) and 217.0 (84.7) cm(2) at five and 20 min after injection, respectively. The mean (SD) cephalad and caudal spread of local anesthetic from the site of injection was 6.5 (1.8) cm and 3.9 (1.2) cm, respectively. There were no complications or adverse events reported. CONCLUSION: This report shows that a reproducible area of anesthesia can be obtained by ultrasound-guided injection of local anesthetic in the fascial plane between the multifidus and longissimus muscles of the thoracolumbar spine. The area of anesthesia consistently covered the midline and had a predictable spread. This project was registered with clinicaltrials.gov (NCT02297191).

Discovery of multiple hidden allosteric sites by combining Markov state models and experiments.

The discovery of drug-like molecules that bind pockets in proteins that are not present in crystallographic structures yet exert allosteric control over activity has generated great interest in designing pharmaceuticals that exploit allosteric effects. However, there have only been a small number of successes, so the therapeutic potential of these pockets--called hidden allosteric sites--remains unclear. One challenge for assessing their utility is that rational drug design approaches require foreknowledge of the target site, but most hidden allosteric sites are only discovered when a small molecule is found to stabilize them. We present a means of decoupling the identification of hidden allosteric sites from the discovery of drugs that bind them by drawing on new developments in Markov state modeling that provide unprecedented access to microsecond- to millisecond-timescale fluctuations of a protein's structure. Visualizing these fluctuations allows us to identify potential hidden allosteric sites, which we then test via thiol labeling experiments. Application of these methods reveals multiple hidden allosteric sites in an important antibiotic target--TEM-1 ß-lactamase. This result supports the hypothesis that there are many as yet undiscovered hidden allosteric sites and suggests our methodology can identify such sites, providing a starting point for future drug design efforts. More generally, our results demonstrate the power of using Markov state models to guide experiments.

Zinc deficiency augments leptin production and exacerbates macrophage infiltration into adipose tissue in mice fed a high-fat diet.

Zinc (Zn) deficiency and obesity are global public health problems. Zn deficiency is associated with obesity and comorbid conditions that include insulin resistance and type 2 diabetes. However, the function of Zn in obesity remains unclear. Using a mouse model of combined high-fat and low-Zn intake (0.5-1.5 mg/kg), we investigated whether Zn deficiency exacerbates the extent of adiposity as well as perturbations in metabolic and immune function. C57BL/6 mice were randomly assigned to receive either a high-fat diet (HFD) or a control (C) diet for 6 wk, followed by further subdivision into 2 additional groups fed Zn-deficient diets (C-Zn, HFD-Zn), along with a C diet and an HFD, for 3 wk (n = 8-9 mice/group). The extent of visceral fat, insulin resistance, or systemic inflammation was unaffected by Zn deficiency. Strikingly, Zn deficiency significantly augmented circulating leptin concentrations (HFD-Zn vs. HFD: 3.15 ± 0.16 vs. 2.59 ± 0.12 µg/L, respectively) and leptin signaling in the liver of obese mice. Furthermore, gene expression of macrophage-specific markers ADAM8 (A disintegrin and metalloproteinase domain-containing protein 8) and CD68 (cluster of differentiation 68) was significantly greater in adipose tissue in the HFD-Zn group than in the HFD group, as confirmed by CD68 protein analysis, indicative of increased macrophage infiltration. Inspection of Zn content and mRNA profiles of all Zn transporters in the adipose tissue revealed alterations of Zn metabolism to obesity and Zn deficiency. Our results demonstrate that Zn deficiency increases leptin production and exacerbates macrophage infiltration into adipose tissue in obese mice, indicating the importance of Zn in metabolic and immune dysregulation in obesity.

Kinetic analysis of the bypass of a bulky DNA lesion catalyzed by human Y-family DNA polymerases.

1-Nitropyrene (1-NP), a mutagen and potential carcinogen, is the most abundant nitro polyaromatic hydrocarbon in diesel exhaust, which reacts with DNA to form predominantly N-(deoxyguanosin-8-yl)-1-aminopyrene (dG(AP)). If not repaired, this DNA lesion is presumably bypassed in vivo by any of human Y-family DNA polymerases kappa (hPolκ), iota (hPolι), eta (hPolη), and Rev1 (hRev1). Our running start assays demonstrated that each of these enzymes was indeed capable of traversing a site-specifically placed dG(AP) on a synthetic DNA template but that hRev1 was stopped after lesion bypass. The time required to bypass 50% of the dG(AP) sites (t(50)(bypass)) encountered by hPolη, hPolκ, and hPolι was determined to be 2.5 s, 4.1 s, and 106.5 s, respectively. The efficiency order of catalyzing translesion synthesis of dG(AP) (hPolη > hPolκ > hPolι ≫ hRev1) is the same as the order for these human Y-family enzymes to elongate undamaged DNA. Although hPolη bypassed dG(AP) efficiently, replication by both hPolκ and hPolι was strongly stalled at the lesion site and at a site immediately downstream from dG(AP). By employing presteady state kinetic methods, a kinetic basis was established for polymerase pausing at these DNA template sites. Besides efficiency of bypass, the fidelity of those low-fidelity polymerases at these pause sites was also significantly decreased. Thus, if the translesion DNA synthesis of dG(AP)in vivo is catalyzed by a human Y-family DNA polymerase, e.g., hPolη, the process is certainly mutagenic.