The pan-RAF-MEK non degrading molecular glue NST-628 is a potent and brain penetrant inhibitor of the RAS-MAPK pathway with activity across diverse RAS- and RAF-driven cancers

Alterations in the RAS-MAPK signaling cascade are common across multiple solid tumor types and is a driver for many cancers. NST-628 is a potent pan-RAF-MEK molecular glue that prevents phosphorylation and activation of MEK by RAF, overcoming the limitations of traditional RAS-MAPK inhibitors and leading to deep durable inhibition of the pathway. Cellular, biochemical, and structural analysis of RAF-MEK complexes show that NST-628 engages all isoforms of RAFand prevents the formation of BRAF-CRAF heterodimers, a differentiated mechanism from all current RAF inhibitors. With a potent and durable inhibition of the RAF-MEK signaling complex as well as high intrinsic permeability into the brain, NST-628 demonstrates broad efficacy in cellular and patient-derived tumor models harboring diverse MAPK pathway alterations, including orthotopic intracranial models. Given its functional and pharmacokinetic mechanisms that are differentiated from previous therapies , NST-628 is positioned to make an impact clinically in an areas of unmet patient need.

A closed translocation channel in the substrate-free AAA+ ClpXP protease diminishes rogue degradation

AAA+ proteases degrade intracellular proteins in a highly specific manner. E. coli ClpXP, for example, relies on a C-terminal ssrA tag or other terminal degron sequences to recognize proteins, which are then unfolded by ClpX and subsequently translocated through its axial channel and into the degradation chamber of ClpP for proteolysis. Prior cryo-EM structures reveal that the ssrA tag initially binds to a ClpX conformation in which the axial channel is closed by a pore-2 loop. Here, we show that substrate-free ClpXP has a nearly identical closed-channel conformation. We destabilize this closed-channel conformation by deleting residues from the ClpX pore-2 loop. Strikingly, open-channel ClpXP variants degrade non-native proteins lacking degrons faster than the parental enzymes in vitro but degraded GFP-ssrA more slowly. When expressed in E. coli, these open channel variants behave similarly to the wild-type enzyme in assays of filamentation and phage-Mu plating but resulted in reduced growth phenotypes at elevated temperatures or when cells were exposed to sub-lethal antibiotic concentrations. Thus, channel closure is an important determinant of ClpXP degradation specificity.

Electroencephalography for predicting antidepressant treatment success: A systematic review and meta-analysis

BACKGROUND

Patients suffering from major depressive disorder (MDD) regularly experience non-response to treatment for their depressive episode. Personalized clinical decision making could shorten depressive episodes and reduce patient suffering. Although no clinical tools are currently available, machine learning analysis of electroencephalography (EEG) shows promise in treatment response prediction.

METHODS

With a systematic review and meta-analysis, we evaluated the accuracy of EEG for individual patient response prediction. Importantly, we included only prediction studies that used cross-validation. We used a bivariate model to calculate prediction success, as expressed by area-under the curve, sensitivity and specificity. Furthermore, we analyzed prediction success for separate antidepressant interventions.

RESULTS

15 studies with 12 individual patient samples and a total of 479 patients were included. Research methods varied considerably between studies. Meta-analysis of results from this heterogeneous set of studies resulted in an area under the curve of 0.91, a sensitivity of 83 % (95 % CI 74-89 %), and a specificity of 86 % (95 % CI 81-90 %). Classification performance did not significantly differ between treatments. Although studies were all internally validated, no externally validated studies have been reported. We found substantial risk of bias caused by methodological shortcomings such as non-independent feature selection, though performance of non-biased studies was comparable.

LIMITATIONS

Sample sizes were relatively small and no study used external validation, increasing the risk of overestimation of accuracy.

CONCLUSIONS

Electroencephalography can predict the response to antidepressant treatment with high accuracy. However, future studies with more rigorous validation are needed to produce a clinical tool to guide interventions in MDD.

PROSPERO REGISTRATION NUMBER

CRD42021268169.

Optimization of a urea-containing series of nicotinamide phosphoribosyltransferase (NAMPT) activators

NAD⁺ is a crucial cellular factor that plays multifaceted roles in wide ranging biological processes. Low levels of NAD⁺ have been linked to numerous diseases including metabolic disorders, cardiovascular disease, neurodegeneration, and muscle wasting disorders. A novel strategy to boost NAD⁺ is to activate nicotinamide phosphoribosyltransferase (NAMPT), the putative rate-limiting step in the NAD⁺ salvage pathway. We previously showed that NAMPT activators increase NAD⁺ levels in vitro and in vivo. Herein we describe the optimization of our NAMPT activator prototype (SBI-0797812) leading to the identification of 1-(4-((4-chlorophenyl)sulfonyl)phenyl)-3-(oxazol-5-ylmethyl)urea (34) that showed far more potent NAMPT activation and improved oral bioavailability.

Negative-Stain Electron Microscopy Reveals Dramatic Structural Rearrangements in Ni-Fe-S-Dependent Carbon Monoxide Dehydrogenase/Acetyl-CoA Synthase

The Ni-Fe-S-containing A-cluster of acetyl-coenzyme A (CoA) synthase (ACS) assembles acetyl-CoA from carbon monoxide (CO), a methyl group (CH3+), and CoA. To accomplish this feat, ACS must bind CoA and interact with two other proteins that contribute the CO and CH3+, respectively: CO dehydrogenase (CODH) and corrinoid Fe-S protein (CFeSP). Previous structural data show that, in the model acetogen Moorella thermoacetica, domain 1 of ACS binds to CODH such that a 70-Å-long internal channel is created that allows CO to travel from CODH to the A-cluster. The A-cluster is largely buried and is inaccessible to CFeSP for methylation. Here we use electron microscopy to capture multiple snapshots of ACS that reveal previously uncharacterized domain motion, forming extended and hyperextended structural states. In these structural states, the A-cluster is accessible for methylation by CFeSP.

Crystallographic Characterization of the Carbonylated A-Cluster in Carbon Monoxide Dehydrogenase/Acetyl-CoA Synthase

The Wood–Ljungdahl pathway allows for autotrophic bacterial growth on carbon dioxide, with the last step in acetyl-CoA synthesis catalyzed by the bifunctional enzyme carbon monoxide dehydrogenase/acetyl-CoA synthase (CODH/ACS). ACS uses a complex Ni–Fe–S metallocluster termed the A-cluster to assemble acetyl-CoA from carbon monoxide, a methyl moiety and coenzyme A. Here, we report the crystal structure of CODH/ACS from Moorella thermoacetica with substrate carbon monoxide bound at the A-cluster, a state previously uncharacterized by crystallography. Direct structural characterization of this state highlights the role of second sphere residues and conformational dynamics in acetyl-CoA assembly, the biological equivalent of the Monsanto process.

A Stable Ferryl Porphyrin at the Active Site of Y463M BthA

BthA is a diheme enzyme that is a member of the bacterial cytochrome c peroxidase superfamily, capable of generating a highly unusual Fe(IV)Fe(IV)═O oxidation state, known to be responsible for long-range oxidative chemistry in the enzyme MauG. Here, we show that installing a canonical Met ligand in lieu of the Tyr found at the heme of MauG associated with electron transfer, results in a construct that yields an unusually stable Fe(IV)═O porphyrin at the peroxidatic heme. This state is spontaneously formed at ambient conditions using either molecular O₂ or H₂O₂. The resulting data illustrate how a ferryl iron, with unforeseen stability, may be achieved in biology.

Structural insight into metallocofactor maturation in carbon monoxide dehydrogenase

The nickel-dependent carbon monoxide dehydrogenase (CODH) employs a unique heterometallic nickel-iron-sulfur cluster, termed the C-cluster, to catalyze the interconversion of CO and CO₂ Like other complex metalloenzymes, CODH requires dedicated assembly machinery to form the fully intact and functional C-cluster. In particular, nickel incorporation into the C-cluster depends on the maturation factor CooC; however, the mechanism of nickel insertion remains poorly understood. Here, we compare X-ray structures (1.50-2.48 Å resolution) of CODH from Desulfovibrio vulgaris (DvCODH) heterologously expressed in either the absence (DvCODH^-CooC) or presence (DvCODH^+CooC) of co-expressed CooC. We find that the C-cluster of DvCODH^-CooC is fully loaded with iron but does not contain any nickel. Interestingly, the so-called unique iron ion (Fe_u) occupies both its canonical site (80% occupancy) and the nickel site (20% occupancy), with addition of reductant causing further mismetallation of the nickel site (60% iron occupancy). We also demonstrate that a DvCODH variant that lacks a surface-accessible iron-sulfur cluster (the D-cluster) has a C-cluster that is also replete in iron but lacks nickel, despite co-expression with CooC. In this variant, all Fe_u is in its canonical location, and the nickel site is empty. This D-cluster-deficient CODH is inactive despite attempts to reconstitute it with nickel. Taken together, these results suggest that an empty nickel site is not sufficient for nickel incorporation. Based on our findings, we propose a model for C-cluster assembly that requires both CooC and a functioning D-cluster, involves precise redox-state control, and includes a two-step nickel-binding process.

A widely distributed diheme enzyme from Burkholderia that displays an atypically stable bis-Fe(IV) state

Bacterial diheme peroxidases represent a diverse enzyme family with functions that range from hydrogen peroxide (H2O2) reduction to post-translational modifications. By implementing a sequence similarity network (SSN) of the bCCP_MauG superfamily, we present the discovery of a unique diheme peroxidase BthA conserved in all Burkholderia. Using a combination of magnetic resonance, near-IR and Mössbauer spectroscopies and electrochemical methods, we report that BthA is capable of generating a bis-Fe(IV) species previously thought to be a unique feature of the diheme enzyme MauG. However, BthA is not MauG-like in that it catalytically converts H2O2 to water, and a 1.54-Å resolution crystal structure reveals striking differences between BthA and other superfamily members, including the essential residues for both bis-Fe(IV) formation and H2O2 turnover. Taken together, we find that BthA represents a previously undiscovered class of diheme enzymes, one that stabilizes a bis-Fe(IV) state and catalyzes H2O2 turnover in a mechanistically distinct manner.

Substrate Binding Mode and Molecular Basis of a Specificity Switch in Oxalate Decarboxylase

Oxalate decarboxylase (OxDC) catalyzes the conversion of oxalate into formate and carbon dioxide in a remarkable reaction that requires manganese and dioxygen. Previous studies have shown that replacing an active-site loop segment Ser¹⁶¹-Glu¹⁶²-Asn¹⁶³-Ser¹⁶⁴ in the N-terminal domain of OxDC with the cognate residues Asp¹⁶¹-Ala¹⁶²-Ser-¹⁶³-Asn¹⁶⁴ of an evolutionarily related, Mn-dependent oxalate oxidase gives a chimeric variant (DASN) that exhibits significantly increased oxidase activity. The mechanistic basis for this change in activity has now been investigated using membrane inlet mass spectrometry (MIMS) and isotope effect (IE) measurements. Quantitative analysis of the reaction stoichiometry as a function of oxalate concentration, as determined by MIMS, suggests that the increased oxidase activity of the DASN OxDC variant is associated with only a small fraction of the enzyme molecules in solution. In addition, IE measurements show that C–C bond cleavage in the DASN OxDC variant proceeds via the same mechanism as in the wild-type enzyme, even though the Glu¹⁶² side chain is absent. Thus, replacement of the loop residues does not modulate the chemistry of the enzyme-bound Mn(II) ion. Taken together, these results raise the possibility that the observed oxidase activity of the DASN OxDC variant arises from an increased level of access of the solvent to the active site during catalysis, implying that the functional role of Glu¹⁶² is to control loop conformation. A 2.6 Å resolution X-ray crystal structure of a complex between oxalate and the Co(II)-substituted ΔE162 OxDC variant, in which Glu¹⁶² has been deleted from the active site loop, reveals the likely mode by which the substrate coordinates the catalytically active Mn ion prior to C–C bond cleavage. The “end-on” conformation of oxalate observed in the structure is consistent with the previously published V/K IE data and provides an empty coordination site for the dioxygen ligand that is thought to mediate the formation of Mn(III) for catalysis upon substrate binding.

Intrathecal fentanyl added to bupivacaine and morphine for cesarean delivery may induce a subtle acute opioid tolerance

BACKGROUND

Previous studies have demonstrated that the addition of intrathecal fentanyl to a spinal anesthetic for cesarean delivery improves intraoperative analgesia. However, intrathecal fentanyl may induce acute tolerance to opioids. The objective of this study was to investigate whether the addition of intrathecal fentanyl to spinal anesthesia with intrathecal morphine increases postoperative analgesic requirements and pain scores.

METHODS

In this randomized, double-blinded study, 40 women having elective cesarean delivery were enrolled. Patients received spinal anesthesia with hyperbaric bupivacaine 12 mg, morphine 200 μg, and fentanyl 0, 5, 10 or 25 μg. Each patient received intravenous patient-controlled analgesia morphine for 24h postoperatively. Outcome measures included postoperative morphine usage and pain scores, as well as intraoperative pain, nausea, hypotension and vasopressor use.

RESULTS

Total morphine use over the 24-h post-spinal study period was similar among the study groups (P=0.129). Postoperative pain scores were higher in patients receiving fentanyl 5, 10 and 25 μg compared to fentanyl 0 μg control group (P=0.003).

CONCLUSIONS

The study results suggest that intrathecal fentanyl may induce acute tolerance to intrathecal morphine. However, because there was no difference in postoperative analgesia requirement and the difference in pain scores was small, the clinical significance of this finding is uncertain.

Efficacy and tolerability of vildagliptin vs. pioglitazone when added to metformin: a 24-week, randomized, double-blind study

AIM

The aim of this study was to compare the efficacy and tolerability of vildagliptin vs. pioglitazone as add-on therapy in patients with type 2 diabetes inadequately controlled with metformin monotherapy.

METHODS

This 24-week, multicentre, double-blind, randomized, active-controlled study compared vildagliptin (100 mg daily, given as equally divided doses, n = 295) and pioglitazone (30 mg daily, given as a single q.d. dose, n = 281) in patients with inadequate glycaemic control (A1C 7.5-11%) while receiving a stable metformin dose (> or =1500 mg daily). The adjusted mean changes from baseline to study endpoint (AMDelta) in A1C, fasting plasma glucose (FPG), fasting lipids and body weight were compared by analysis of covariance.

RESULTS

When added to a stable dose of metformin (mean dose at baseline >2000 mg/day), both vildagliptin and pioglitazone decreased A1C (AMDelta = -0.9 +/- 0.1% and -1.0 +/- 0.1%, respectively) from identical baseline values (8.4 +/- 0.1%). The between-group difference in AMDelta A1C was 0.1 +/- 0.1%, and non-inferiority of vildagliptin to pioglitazone was established at both 0.4 and 0.3% margins for upper limit of the 95% confidence intervals. Pioglitazone decreased FPG (AMDelta = -2.1 +/- 0.1 mmol/l) to a greater extent than vildagliptin (AMDelta = -1.4 +/- 0.1 mmol/l), but only pioglitazone increased body weight (AMDelta = +1.9 +/- 0.2 kg: between-group difference = -1.6 +/- 0.3 kg, p < 0.001). Adverse events (AEs) were reported by 60% of vildagliptin-treated patients and by 56.4% of pioglitazone-treated patients; serious AEs were reported by 2.0 and 4.6% of patients receiving vildagliptin and pioglitazone respectively. Mild hypoglycaemia was reported by one patient (0.3%) in the vildagliptin group and by no patients receiving pioglitazone.

CONCLUSIONS

When added to metformin, the efficacy of vildagliptin is non-inferior to that of pioglitazone. The treatments were similarly well tolerated, but only pioglitazone increased body weight.

Local infiltration of epinephrine-containing lidocaine with bicarbonate reduces superficial bleeding and pain during labor epidural catheter insertion: a randomized trial

BACKGROUND

Superficial bleeding after labor epidural catheter placement is a common phenomenon. In addition to delaying securing the epidural catheter, it may loosen the adhesive catheter dressing. The primary aim of this study was to determine whether skin infiltration with epinephrine-containing rather than plain lidocaine reduces superficial bleeding after catheter placement. Secondary objectives were to determine whether adding epinephrine and/or sodium bicarbonate affected infiltration pain.

METHODS

After institutional review board approval and informed consent, 80 healthy women receiving epidural analgesia during labor were randomly assigned in a double-blind manner to four local anesthetic mixtures (n=20 in each group): group L: lidocaine 1.5%, group LB: lidocaine 1.5% with 8.4% sodium bicarbonate, group LE: lidocaine 1.5% with epinephrine 1:200000, and group LEB: lidocaine 1.5% with epinephrine 1:200000 and 8.4% sodium bicarbonate. Clinical endpoints included the amount of superficial bleeding at the catheter site, pain during local anesthetic infiltration and epidural catheter movement during labor.

RESULTS

Demographic data were similar among the groups. The addition of epinephrine to lidocaine significantly reduced superficial bleeding. Solutions containing epinephrine were well tolerated and caused no cardiovascular disturbances. The addition of epinephrine did not increase pain, while bicarbonate reduced it [verbal score (scale 0-10) 3.6+/-2.2 vs. 2.6+/-1.8; P=0.04]. There were no differences in epidural catheter movement among the groups; no catheters became displaced during labor.

CONCLUSION

Local infiltration of epinephrine-containing lidocaine before epidural catheter insertion reduces superficial bleeding and the addition of bicarbonate decreases pain during skin infiltration.

A survey of labor patient-controlled epidural anesthesia practice in California hospitals

BACKGROUND

Patient-controlled epidural analgesia (PCEA) offers many advantages over continuous epidural infusions for labor analgesia including fewer physician interventions, improved analgesia and satisfaction, and reduced local anesthetic doses. However, anesthesiologists have been slow to adopt this technique, first described in 1988. No previous studies have evaluated specific labor patient-controlled epidural analgesia practices in the United States. The aim of this study was to determine labor epidural and patient-controlled epidural analgesia practices among California hospitals.

METHODS

Following institutional review board exemption approval, an online survey was created using freeonlinesurveys.com. An anonymous survey was sent via e-mail to 230 California Society of Anesthesiologists' members chosen at random to represent their hospitals' labor analgesia practices.

RESULTS

We received 133 replies from the 230 survey requests sent, a 58% response rate. The median labor epidural rate among the hospitals involved was 65% (range 0-95%). Overall, only 25% of California hospitals use patient-controlled epidural analgesia for analgesia in labor, with greater use among hospitals with dedicated obstetric anesthesia coverage and larger numbers of deliveries. Reasons given for not using patient-controlled epidural analgesia include cost, clinician preference, safety concerns and the inconvenience of change.

CONCLUSIONS

Despite the potential advantages of patient-controlled epidural analgesia over continuous epidural infusions for labor analgesia, patient-controlled epidural analgesia has not been widely adopted in California hospitals. Education regarding this technique is needed to encourage its increased use.

“Ultra-light” patient-controlled epidural analgesia during labor: effects of varying regimens on analgesia and physician workload

BACKGROUND

Patient-controlled epidural analgesia (PCEA) offers many advantages over continuous epidural infusions for maintenance of labor analgesia. Some of these benefits may depend on the PCEA settings. This study evaluated several regimens for "ultra-light" (0.125%) PCEA with basal continuous infusion (CI) in labor with goals of minimizing physician interventions while providing good analgesia.

METHODS

Two hundred and twenty ASA I-II women receiving epidural analgesia during active labor (cervical dilation <5 cm) were randomly assigned in a double-blind manner to four treatment groups (n=30 in each). Analgesia was maintained with a PCEA/CI pump using bupivacaine 0.0625% + sufentanil 0.35 microg/mL. PCEA settings were: group A: CI 10 mL/h, PCEA bolus 6 mL, 8-min lockout; group B: CI 10 mL/h, PCEA bolus 12 mL, 16-min lockout; group C: CI 15 mL/h, PCEA bolus 6 mL, 8-min lockout; group D: CI 15 mL/h, PCEA bolus 12 mL, 16-min lockout.

RESULTS

In groups A, B, C and D, 76, 77, 75 and 85% of parturients respectively, required no physician rescue boluses. Pain scores were low and maternal satisfaction was high in all groups, with minimal differences among them. Spontaneous vaginal delivery occurred in 78% of patients overall, instrumental (forceps or vacuum) delivery in 10% and cesarean section in 12%.

CONCLUSIONS

These ultra-light PCEA regimens provided excellent analgesia with minimal physician workload and a high spontaneous delivery rate. Use of moderate to high-volume, ultra-light PCEA/CI techniques should facilitate provision of labor analgesia in busy obstetric units.

Correction of intraoperative coagulopathy in a patient with neurofibromatosis type I with intravenous desmopressin (DDAVP)

A patient with the genetic condition neurofibromatosis type I and no known coagulopathy undergoing cesarean delivery, had diffuse uterine and surgical site bleeding that was not correctable by oxytocin, methylergonovine and PGF2 alpha. Despite good uterine tone, hemorrhage continued from the uterus and the surrounding tissues, persisting even after surgical ligation of the uterine arteries. With no change in her condition, which was behaving clinically as a coagulopathy, an infusion of desmopressin acetate (DDAVP) was begun. The patient's bleeding promptly resolved shortly after infusion of this agent. A review of relevant literature suggests that platelet reactivity of patients with neurofibromatosis type 1 is attenuated in some in vitro conditions. Thus, there may be some theoretical basis for using DDAVP in patients with neurofibromatosis type 1 who have bleeding problems with no other known source, such as in the case presented here.

Effects of insulin-sensitising agents in mice with hepatic insulin resistance

AIMS/HYPOTHESIS

The metabolic abnormalities of insulin resistance are ameliorated by insulin sensitisers via different mechanisms. Metformin decreases hepatic glucose output, whereas rosiglitazone (RSG) is an agonist for peroxisome proliferator activated receptor (PPAR)gamma, highly expressed in fat. To gain insight into the mechanisms of action of these drugs, we compared their actions in two models of insulin resistance: the obese, hyperglycaemic ob/ob mouse and the liver specific insulin receptor knockout (LIRKO) mouse.

METHODS

Control, ob/ob, and LIRKO mice were divided into three groups that received metformin (300 mg/kg body weight/day), RSG (3 mg/kg body weight/day), or placebo for 3 weeks.

RESULTS

In the presence of the severe hepatic insulin resistance of the LIRKO mouse, neither metformin nor RSG had any significant effect on glucose or insulin tolerance tests. On the other hand, RSG decreased serum concentrations of total cholesterol, LDL, and HDL in LIRKO mice. Adipocyte PPARgamma gene and protein expression, and adipocyte size were all increased in LIRKO mice treated with RSG, whereas fat-cell size in control animals was decreased by RSG.

CONCLUSION/INTERPRETATION

TZDs probably improve some lipid parameters of the dysmetabolic syndrome associated with diabetes mellitus even in the presence of absolute hepatic insulin resistance, but both metformin and TZDs require an operating insulin signalling system in the liver for their effects in glucose homeostasis.

Phenylephrine added to prophylactic ephedrine infusion during spinal anesthesia for elective cesarean section

BACKGROUND

Because ephedrine infusion (2 mg/min) does not adequately prevent spinal hypotension during cesarean delivery, the authors investigated whether adding phenylephrine would improve its efficacy.

METHODS

Thirty-nine parturients with American Society of Anesthesiologists physical status I-II who were scheduled for cesarean delivery received a crystalloid preload of 15 ml/kg. Spinal anesthesia was performed using 11 mg hyperbaric bupivacaine, 2.5 microg sufentanil, and 0.1 mg morphine. Maternal heart rate and systolic blood pressure were measured at frequent intervals. A vasopressor infusion was started immediately after spinal injection of either 2 mg/min ephedrine plus 10 microg/min phenylephrine or 2 mg/min ephedrine alone. Treatments were assigned randomly in a double-blind fashion. The infusion rate was adjusted according to systolic blood pressure using a predefined algorithm. Hypotension, defined as systolic blood pressure less than 100 mmHg and less than 80% of baseline, was treated with 6 mg ephedrine bolus doses.

RESULTS

Hypotension occurred less frequently in the ephedrine-phenylephrine group than in the ephedrine-alone group: 37% versus 75% (P = 0.02). Ephedrine (36+/-16 mg, mean +/- SD) plus 178+/-81 microg phenylephrine was infused in former group, whereas 54+/-18 mg ephedrine was infused in the latter. Median supplemental ephedrine requirements and nausea scores (0-3) were less in the ephedrine-phenylephrine group (0 vs. 12 mg, P = 0.02; and 0 vs. 1.5, P = 0.01, respectively). Umbilical artery pH values were significantly higher in the ephedrine-phenylephrine group than in the group that received ephedrine alone (7.24 vs. 7.19). Apgar scores were similarly good in both groups.

CONCLUSION

Phenylephrine added to an infusion of ephedrine halved the incidence of hypotension and increased umbilical cord pH.

Walking with labor epidural analgesia: the impact of bupivacaine concentration and a lidocaine-epinephrine test dose

BACKGROUND

Regional analgesia techniques for labor that permit ambulation are popular among parturients. This study evaluated the influence of bupivacaine bolus concentration and a 3-ml 1.5% lidocaine-epinephrine test dose, on analgesic effectiveness and the ability to walk after block placement.

METHODS

Using a randomized double-blind study design, epidural analgesia was initiated in 60 parturients undergoing labor as follows: Group TD/B.0625 received a 3-ml lidocaine-epinephrine test dose + 12 ml bupivacaine, 0.0625%; group TD/B.125 received a 3-ml test dose + 12 ml bupivacaine, 0.125%; group B.0625 received 15 ml bupivacaine, 0.0625% (no test dose); and group B.125 received 15 ml bupivacaine, 0.125% (no test dose). Initial boluses in all groups contained 10 microg sufentanil. Bupivacaine, 0.0625%, with 0.33 microg/ml sufentanil was infused throughout labor at 13.5-15 ml/h. Analgesia balance, proprioception, motor block, and patient ability to stand and walk were evaluated at various intervals.

RESULTS

A bolus of 0.125% bupivacaine containing sufentanil, without a previous test dose, proved to be optimal with respect to analgesia and early ambulation. When a test dose was given before bupivacaine, 0.125%, fewer women walked within 1 h of block placement. Bupivacaine, 0.0625%, with sufentanil, with or without a test dose, provided inadequate analgesia, necessitating additional bupivacaine, which impaired the ability to walk. A high percentage of women in all groups (73-93%) walked at some stage during labor.

CONCLUSIONS

Omitting a lidocaine-epinephrine test dose and using 0.125% bupivacaine for the initial bolus should permit ambulation in the early postblock period for most parturients who elect this option.

Progression of microalbuminuria to proteinuria in type 1 diabetes: nonlinear relationship with hyperglycemia

While small clinical trials have shown that improved glycemic control reduces the risk of progression of microalbuminuria to proteinuria, two recent clinical trials did not confirm this finding. We sought to reconcile the contradictory evidence by examining the dose-response relationship between hyperglycemia and progression of microalbuminuria to proteinuria in individuals with type 1 diabetes and microalbuminuria (n = 312) who were followed for 4 years with repeated assessments of urinary albumin excretion. Since 33 patients did not participate in follow-up (10.6%), data for 279 patients were analyzed. Urinary albumin excretion level worsened to proteinuria in 40 (4.1 per 100 person-years). To examine the dose-response relationship, baseline HbA1c was divided into four roughly equal groups using the cut points 8, 9, and 10%. The incidence rate varied significantly among the four groups (P = 0.008). Among those with HbA1c <8.0%, the incidence rate of progression was only 1.3 per 100 person-years, while it was 5.1, 4.2, and 6.7 per 100 person-years in the three other groups. We used generalized additive models to examine the dose-response curve using HbA1c as a continuous variable and found that the risk of progression rises steeply between an HbA1c of 7.5-8.5% and then remains approximately constant across higher levels. In conclusion, the results of this study suggest that, in patients with microalbuminuria, the risk of progression to overt proteinuria can be reduced by improved glycemic control only if the HbA1c is maintained below 8.5%. Moreover, below that value, the risk declines as the level of HbA1c decreases.

Maternal sensitivity during infancy and subsequent life events relate to attachment representation at early adulthood

A prospective longitudinal research study of 86 prematurely born children from birth to age 18 years provided empirical evidence for continuity from infancy experience to representations of attachment at age 18 years. Young adults whose representation of attachment was dismissing had been objectively observed during infancy, 16-17 years earlier, to receive less sensitive maternal care than those infants who were later judged at early adulthood to have secure or preoccupied representations. Infancy experience alone did not differentiate young adults with secure representations from those with preoccupied representations. Rather, adverse life events through age 12, particularly parental divorce, reduced the likelihood of secure representations and increased the likelihood of preoccupied representations. The absence of adverse life events did not increase the likelihood of security for those who had not experienced early sensitive caregiving.

Maternal sensitivity during infancy and subsequent life events relate to attachment representation at early adulthood

A prospective longitudinal research study of 86 prematurely born children from birth to age 18 years provided empirical evidence for continuity from infancy experience to representations of attachment at age 18 years. Young adults whose representation of attachment was dismissing had been objectively observed during infancy, 16-17 years earlier, to receive less sensitive maternal care than those infants who were later judged at early adulthood to have secure or preoccupied representations. Infancy experience alone did not differentiate young adults with secure representations from those with preoccupied representations. Rather, adverse life events through age 12, particularly parental divorce, reduced the likelihood of secure representations and increased the likelihood of preoccupied representations. The absence of adverse life events did not increase the likelihood of security for those who had not experienced early sensitive caregiving.

Randomized comparison of intravenous nitroglycerin and magnesium sulfate for treatment of preterm labor

OBJECTIVE

To compare the safety and efficacy of high-dose intravenous (IV) nitroglycerin with those of IV magnesium sulfate for acute tocolysis of preterm labor.

METHODS

Thirty-one women with preterm labor before 35 weeks' gestation were assigned randomly to IV magnesium sulfate or IV nitroglycerin for tocolysis. Preterm labor was defined as the occurrence of at least two contractions in 10 minutes, with cervical change or ruptured membranes. Acute tocolysis was defined as tocolysis for up to 48 hours. Magnesium sulfate was administered as a 4-g bolus, then at a rate of 2-4 g/h. Nitroglycerin was administered as a 100-microg bolus, then at a rate of 1- to 10-microg/kg/min. The primary outcome measure was achievement of at least 12 hours of successful tocolysis.

RESULTS

Thirty patients were available for analysis. There were no significant differences in gestational age, cervical dilation, or incidence of ruptured membranes between groups at the initiation of tocolysis. Successful tocolysis was achieved in six of 16 patients receiving nitroglycerin, compared with 11 of 14 receiving magnesium sulfate (37.5 versus 78.6%, P = .033). Tocolytic failures (nitroglycerin versus magnesium sulfate) were due to persistent contractions with cervical change or rupture of previously intact membranes (five of 16 versus two of 14), persistent hypotension (four of 16 versus none of 14), and other severe side effects (one of 16 versus one of 14). Maternal hemodynamic alterations were more pronounced in patients who received nitroglycerin, and 25% of patients assigned to nitroglycerin treatment had hypotension requiring discontinuation of therapy.

CONCLUSION

Tocolytic failures were more common with nitroglycerin than with magnesium sulfate. The hemodynamic alterations noted in patients receiving nitroglycerin, including a 25% incidence of persistent hypotension, might limit the usefulness of IV nitroglycerin for the acute tocolysis of preterm labor.

Obstetric postanesthesia care unit stays: reevaluation of discharge criteria after regional anesthesia

BACKGROUND

Obstetric patients may have long postanesthesia care unit (OB-PACU) stays after surgery because of residual regional block or other conditions. This study evaluated whether modified discharge criteria might allow for earlier discharge without compromising patient safety.

METHODS

Data were prospectively collected for 6 months for all patients (N=358) who underwent cesarean section or tubal ligation and recovered in the OB-PACU. Regional anesthesia was used in 94% of patients. The duration of anesthesia and PACU stays, the presence and treatment of events in the PACU, and the regression of neural blockade were recorded. Discharge from the OB-PACU required a 60-min minimum stay, stable vital signs, adequate analgesia, and ability to flex the knees. After completion of prospective data collection, events that kept patients in the PACU after 60 min were reevaluated as to whether patients needed to stay in the PACU for medical reasons. "Needed to stay" events included bleeding, cardiorespiratory problems, sedation, dizziness, and pain. "Safe to leave" conditions included pruritus, nausea, and residual neural blockade. The cumulative duration of OB-PACU stays not clearly justifiable for medical reasons was calculated.

RESULTS

Residual block and spinal opioid side effects accounted for the majority of "unnecessary" stays. Annually, 429 h of PACU time could have been saved using the revised criteria. Complications did not develop subsequently in any patient deemed "safe to leave."

CONCLUSIONS

In many obstetric patients, the duration of PACU stays could safely be shortened by continuing observation in a lower-acuity setting. This may result in greater flexibility and more efficient use of nursing personnel.

Intrathecal sufentanil produces sensory changes without hypotension in male volunteers

BACKGROUND

Intrathecally administered sufentanil is frequently associated with hypotension and sensory changes in women undergoing labor. In this study, the authors examined whether intrathecally administered sufentanil has similar effects in pain-free individuals with low concentrations of progesterone (i.e., male volunteers).

METHODS

Ten male volunteers were randomly assigned to receive an intrathecal injection of either 10 microg sufentanil or saline in a double-blind fashion. Blood pressure, heart rate, oxyhemoglobin saturation, and temperatures from the body core and skin of the calf and ipsilateral great toe were recorded. Cold and pin prick sensation, motor block, and visual analogue scores for sedation, pruritus, and nausea also were assessed. Current perception thresholds using the Neurometer current perception threshold instrument (Neurotron, Inc., Baltimore, MD) were determined for three frequencies (2,000, 250, and 5 Hz, corresponding to stimulation of Abeta, Adelta, and C fibers, respectively) on the upper and lower extremities.

RESULTS

Pruritus and sensory changes to pin prick and cold occurred in the sufentanil group but not the saline group. Neither group had a significant change in blood pressure, heart rate, oxyhemoglobin saturation, sedation, or core temperature. There was a clinically insignificant difference in the calf minus toe temperature index between the saline and sufentanil groups. There was a small increase in the current perception thresholds at 250 Hz in the sufentanil group.

CONCLUSIONS

Intrathecally administered sufentanil did not affect blood pressure in male volunteers. The other effects of sufentanil, however, were similar to those observed in women undergoing labor. This suggests that the hypotension occurring in these women after intrathecally administered sufentanil is secondary to relief of pain, rather than to a sympathectomy.

Anserine bursitis and non-insulin dependent diabetes mellitus

OBJECTIVE

To determine the relationship between non-insulin dependent diabetes mellitus (NIDDM), knee pain, and anserine bursitis, and its relation to sex, age, or body mass index (BMI).

METHODS

Ninety-four consecutive patients with NIDDM, 66 women and 28 men, and 57 nondiabetic patients, 36 women and 22 men, were examined at an outpatient clinic of a tertiary care hospital. Date of onset in patients with NIDDM was noted, and serum was analyzed for either hemoglobin A1C (HbA1C) or glycosylated hemoglobin (GHb) in 69 of these patients. Anserine bursitis was diagnosed if knee pain and tenderness at the bursal site were found on examination.

RESULTS

On examination 34 (36%) patients with NIDDM were found to have anserine bursitis. Of these, 31 (91%) were women and 3 (9%) were men (p < 0.05). Age, BMI, duration of diabetes, HbA1C or GHb, and age of onset of diabetes were found not to differ significantly between patients with and those without anserine bursitis.

CONCLUSION

A relationship exists between NIDDM, knee pain, and anserine bursitis unrelated to age, BMI, duration and control of diabetes, and age at the diagnosis of diabetes.

Intrathecal sufentanil for labor analgesia does not cause a sympathectomy

BACKGROUND

Intrathecal sufentanil (ITS) is frequently used to provide analgesia during labor. Decreases in blood pressure and sensory changes in this circumstance suggest that ITS may have a local anesthetic effect and thus cause a sympathectomy. To determine whether ITS given to laboring women causes a sympathectomy, the authors evaluated central and lower extremity temperature changes after ITS administration. These findings were compared with those in a control group of women having spinal anesthesia with bupivacaine for elective cesarean section in whom an extensive sympathectomy was expected.

METHODS

Twenty parturients classified as American Society of Anesthesiologists' physical status 1 or 2 had temperatures measured centrally, at the calf, and at the great toe at frequent intervals after receiving 10 microg ITS for labor analgesia (sufentanil group, n = 10), or hyperbaric bupivacaine 12 mg in their spinal anesthetic for cesarean section (bupivacaine group, n = 10). Calf-to-toe temperature indices (C-T) were calculated by subtracting toe temperature from calf temperature. A decrease in this index means that the toe had warmed compared with the calf and is an indication of vasodilation and a sympathectomy.

RESULTS

There was no significant change in the C-T indices or central temperature in the sufentanil group, but the C-T indices and central temperature decreased significantly in the bupivacaine group.

CONCLUSIONS

The decreases in the C-T index and central temperature in the bupivacaine group indicate the presence of a sympathectomy. The lack of change in the C-T indices and central temperature in the sufentanil group indicates that no significant vasodilation occurred. Therefore, the decrease in blood pressure seen after ITS administration for labor analgesia is unlikely to be the result of a sympathectomy.

Unusual spontaneous hepatic vein to paraumbilical vein shunt in a patient with Budd-Chiari syndrome and cirrhosis: a case report

A very unusual portosystemic shunt was identified using color flow Doppler sonography in an adult male with Budd-Chiari syndrome and cirrhosis secondary to a hypercoagulability state. Hepatofugal blood flow was demonstrated between the middle hepatic vein and a recanalized paraumbilical vein, resulting clinically in prominent periumbilical veins. The clinical and radiological features are described.

Changes in the position of epidural catheters associated with patient movement

BACKGROUND

Epidural catheter movement has been noted with change of patient position and can result in inadequate anesthesia. This study was designed to measure movement and to develop a technique that minimizes catheter displacement.

METHODS

In 255 parturients requesting epidural anesthesia for labor or cesarean section, a multiorificed lumbar epidural catheter was inserted with the patient in the sitting flexed position. The distance to the epidural space, length of catheter inserted, and amount of catheter position change as the patient moved from the sitting flexed to sitting upright and then to the lateral decubitus position were measured before the catheter was secured to the skin. Adequacy of analgesia, the need for catheter manipulation, and whether the patient was considered obese were noted. Data were grouped according to body mass index (BMI): < 25, 25-30, and > 30 kg/m2.

RESULTS

The groups did not differ with respect to the length of catheter initially inserted or changes in catheter position between initial taping and removal. The distance to the epidural space differed significantly among the groups, increasing with greater BMI. Catheters frequently appeared to be drawn inward with position change from the sitting flexed to lateral decubitus position, with the greatest change seen in patients with BMI > 30. Only nine catheters were associated with inadequate analgesia, four of which were replaced. No analgesic failures occurred in the BMI > 30 group. In patients judged by the anesthesiologist to be obese or to have an obese back, BMI was greater, and distance to the epidural space and the magnitude of catheter movement with position change were greater than in those who were not obese.

CONCLUSIONS

Epidural catheters moved a clinically significant amount with reference to the skin in all BMI groups as patients changed position. If catheters had been secured to the skin before position change, many would have been pulled partially out of the epidural space. To minimize the risk of catheter displacement, particularly in obese patients, we recommend that multiorificed catheters be inserted at least 4 cm into the epidural space and that patients assume the sitting upright or lateral position before securing the catheter to the skin.

Intrathecal sufentanil for labor analgesia: do sensory changes predict better analgesia and greater hypotension?

Sensory changes and hypotension occur after intrathecal sufentanil (ITS) is given during labor. The goal of this study was to determine whether sensory changes are predictive of hemodynamic changes or duration of pain relief. We also examined whether sensory and hemodynamic changes relate to the concentration of ITS administered. Forty-five ASA physical status I and II women in active labor were randomly assigned to receive 10 micrograms ITS diluted in either 1, 2, or 3 mL of normal saline (15 in each group). An observer blinded to treatment recorded verbal pain scores, blood pressure, and sensory changes to light touch, pinprick, and cold at frequent intervals. Excellent analgesia was obtained in 42 of 45 patients. There were no differences among the groups with respect to the number of patients with sensory changes, the duration of analgesia or sensory changes, the quality of analgesia, or the severity of hypotension. The groups were therefore combined for further analyses. Among this combined group, the duration of analgesia was 99 +/- 7 min (mean +/- SE). Cold, pinprick, and light touch sensation were decreased in 66%, 50%, and 33% of patients, respectively. Motor block was absent in all patients. The duration and quality of analgesia were similar in subjects with and without sensory changes. Systolic blood pressure decreased 23 +/- 2 mm Hg (P < 0.05) during the first 30 min after ITS, and six patients were given ephedrine. The magnitude of blood pressure change was not affected by the diluent volume or the presence of sensory changes. Because sensory changes were not predictive of the duration or quality of analgesia or the degree of hemodynamic change, we conclude that analgesia with ITS is predominantly mediated via spinal cord opioid receptors rather than by a local anesthetic-type conduction blockade.

Direct right atrial catheter insertion with video-assisted thoracic surgery

Chronic gastrointestinal disorders may require support with long-term total parenteral nutrition via a central venous catheter. Central venous access may be problematic because of infection or thrombosis of previous catheters. We report a case where video-assisted thoracic surgical catheter insertion directly into the right atrium provided a successful and safe method of long-term central venous access for parenteral nutrition.

Conservative therapy in an ERCP-induced abdominal abscess

We describe a 30 year-old man who presented with an abdominal abscess as an unusual complication of endoscopic retrograde cholangiopancreatography with papillotomy. His presenting symptom was recurrent vomiting, while fever, abdominal pain, and leukocytosis were not significant. The abscess was observed with repeated computerized tomographic scans and completely regressed with intravenous antibiotic treatment over a three week period, leading to complete remission.

A patient with hypoparathyroidism, dysmorphic features and mental retardation

There have been various reports in the medical literature concerning children with syndromes of congenital hypoparathyroidism, seizures, dysmorphic features and mental retardation. We describe a patient with hypoparathyroidism, mental retardation, micrognathia, deep-set eyes and pes cavus in a 31-year-old man. This combination of abnormalities in an adult is unique.

Ketorolac and spinal morphine for postcesarean analgesia

This study was designed to compare spinal morphine (SM), ketorolac (K), and a combination of the two drugs with respect to analgesic efficacy and side effects in postcesarean patients. Forty-eight parturients having bupivacaine spinal anesthesia for cesarean delivery randomly received in a double-blind manner either: SM: 0.1 mg or SM: 0.2 mg (but no K); SM: 0.1 mg plus K 60 mg intravenously (i.v.) one hour after spinal injection, and 30 mg i.v. every 6 h for three doses or i.v. K dosed as previously described (but no SM). Analgesia and side effects were evaluated during the first 20 h. Forty-eight women were studied. There were no significant differences in analgesia among the groups, although patients receiving SM: 0.1 mg tended to have less satisfactory intraoperative analgesia. Pruritus was common in all patients receiving SM whereas patients who received K had the lowest overall scores for severity of side effects. No serious complications occurred and all groups expressed similarly high satisfaction at the 24 h visit. We conclude that there is no advantage to combining SM and K, and that K provides satisfactory postcesarean analgesia with few side effects.

Prevention of hypotension after spinal anesthesia for cesarean section: six percent hetastarch versus lactated Ringer's solution

This study was designed to determine whether preoperative administration of 6% hetastarch decreases the incidence and severity of hypotension after spinal anesthesia for cesarean section. Forty nonlaboring ASA class I and II women having nonurgent cesarean sections were randomized to receive either 500 mL of 6% hetastarch plus 1 L lactated Ringer's solution (LR) (n = 20), or 2 L of LR (n = 20) prior to induction of spinal anesthesia. Hypotension occurred in 45% of patients who received hetastarch vs 85% of those who received only LR (P < 0.05), and minimum systolic blood pressure was lower in the LR group than in the hetastarch group (85 +/- 12 vs 93 +/- 12 mm Hg [mean +/- SD]; P < 0.05). In addition, the LR group had a higher maximum heart rate (115 +/- 17 vs 104 +/- 16 bpm), a shorter mean time to hypotension (7 +/- 4 vs 10 +/- 7 min), and required more 5-mg doses of ephedrine for treatment of hypotension (0 vs 2 [median]; P < 0.05) than the hetastarch group. Neonatal outcome, as determined by Apgar scores and cord blood gas analyses, was good and similar in both groups. We conclude that 6% hetastarch plus LR is more effective than LR alone and that its routine use before spinal anesthesia for cesarean section should be considered.

Placental transfer and neonatal effects of epidural sufentanil and fentanyl administered with bupivacaine during labor

BACKGROUND

This randomized double-blind investigation was designed to study the placental transfer and neonatal effects of epidural sufentanil and fentanyl infused with bupivacaine for labor analgesia.

METHODS

Healthy parturient women (n = 36) received epidural bupivacaine alone (group B) or with fentanyl (group B-F) or sufentanil (group B-S). Group B received a 12-ml bolus of 0.25% bupivacaine followed by a 10 ml/h infusion of 0.125% bupivacaine. Groups B-F and B-S received a 12-ml bolus of 0.125% bupivacaine with 75 micrograms fentanyl or 15 micrograms sufentanil, respectively, followed by 10 ml/h of 0.125% bupivacaine with fentanyl 1.5 micrograms/ml or sufentanil 0.25 micrograms/ml. Maternal venous (MV) and umbilical arterial (UA) and umbilical venous (UV) bupivacaine and opioid plasma concentrations were determined. Neonatal assessment included Apgar scores, umbilical cord blood gas analyses, and neurobehavioral testing at delivery and at 2 and 24 h of life using the Neurologic and Adaptive Capacity Score (NACS).

RESULTS

The mean total dose of fentanyl was 136.6 +/- 13.1 micrograms (SEM), and of sufentanil, 23.8 +/- 1.8 micrograms. Although administered in a ratio of 5.7:1, fentanyl and sufentanil MV plasma concentrations were in the ratio of 27:1. UV/MV ratios were 0.37 for fentanyl and 0.81 for sufentanil. Fentanyl was detected in most UA samples, whereas sufentanil was present in only one sample. Neonatal condition was good and generally similar in all groups, with the exception of a lower NACS at 24 h in group B-F.

CONCLUSIONS

Although the degree of placental transfer of sufentanil appeared greater than that of fentanyl, lower MV sufentanil concentrations resulted in less fetal exposure to sufentanil. The lower NACS at 24 h in group B-F may reflect the continued presence of fentanyl in the neonate.

Spinal versus epidural anesthesia for cesarean section: a comparison of time efficiency, costs, charges, and complications

Spinal anesthesia recently has gained popularity for elective cesarean section. Our anesthesia service changed from epidural to spinal anesthesia for elective cesarean section in 1991. To evaluate the significance of this change in terms of time management, costs, charges, and complication rates, we retrospectively reviewed the charts of patients who had received epidural (n = 47) or spinal (n = 47) anesthesia for nonemergent cesarean section. Patients who received epidural anesthesia had significantly longer total operating room (OR) times than those who received spinal anesthesia (101 +/- 20 vs 83 +/- 16 min, [mean +/- SD] P < 0.001); this was caused by longer times spent in the OR until surgical incision (46 +/- 11 vs 29 +/- 6 min, P < 0.001). Length of time spent in the postanesthesia recovery unit was similar in both groups. Supplemental intraoperative intravenous (i.v.) analgesics and anxiolytics were required more often in the epidural group (38%) than in the spinal group (17%) (P < 0.05). Complications were noted in six patients with epidural anesthesia and none with spinal anesthesia (P < 0.05). Average per-patient charges were more for the epidural group than for the spinal group. Although direct cost differences between the groups were negligible, there were more substantial indirect costs differences. We conclude that spinal block may provide better and more cost effective anesthesia for uncomplicated, elective cesarean sections.

Parturient's posture during epidural puncture affects the distance from skin to epidural space

STUDY OBJECTIVE

To assess the factors affecting the distance from skin to epidural space.

DESIGN

Prospective observational study of consecutive cases over a 2-year period.

SETTING

Inpatient obstetric unit in a French university hospital.

PATIENTS

2,123 consecutive term parturients who received epidural anesthesia for cesarean section or epidural analgesia for labor and vaginal delivery.

INTERVENTIONS

At the time of epidural puncture, the interspace used and the patient's posture (sitting or left lateral decubitus) were recorded, and the distance from the skin to the epidural space (DS-ES) was measured to the nearest 0.5 cm using a marked epidural needle.

MEASUREMENTS AND MAIN RESULTS

The relationship between patient factors [height, weight, body mass index (BMI; weight/height2), presence of scoliosis] and technical factors (interspace, patient's posture at puncture) versus DS-ES was investigated using multiple regression analysis. DS-ES correlated positively with the parturient's weight and BMI. In addition, DS-ES was significantly greater when epidural puncture was performed in the lateral position as compared with the sitting position.

CONCLUSION

Both the patient's weight and position during epidural needle placement are important factors influencing DS-ES. A change from the sitting to the lateral position may increase DS-ES, causing catheter dislodgment and consequent inadequate analgesia. Clinical studies relating DS-ES to inadequate analgesia must take these factors into account.