[Hot topics in obstetric anesthesia]. / "Hot topics" aus der geburtshilflichen Anästhesie.

In 2019 the annual conference of the scientific working group on obstetric anesthesiology of the German Society of Anesthesiology and Intensive Care Medicine (DGAI) took place in the usual manner. Emergency situations, such as the challenge of a preclinical birth or the recognition and treatment of an amniotic fluid embolism were discussed. In addition, topics on the correct treatment of a female patient with a known addictive disorder were of great interest as well as the discussion on the question when a transfusion should be performed in postpartum anemia and which risks accompany the increasing prevalence of obesity, especially during pregnancy. A further hot topic was the deliberation on the prevalence and differential diagnostic clarification of neurological complications after epidural anesthesia. In connection with the topic of birth, exciting and practice relevant topics for all anesthetists confronted with this field were presented and discussed. The essential aspects are summarized in this article.

A numerical simulation of neural fields on curved geometries.

Despite the highly convoluted nature of the human brain, neural field models typically treat the cortex as a planar two-dimensional sheet of ne;urons. Here, we present an approach for solving neural field equations on surfaces more akin to the cortical geometries typically obtained from neuroimaging data. Our approach involves solving the integral form of the partial integro-differential equation directly using collocation techniques alongside efficient numerical procedures for determining geodesic distances between neural units. To illustrate our methods, we study localised activity patterns in a two-dimensional neural field equation posed on a periodic square domain, the curved surface of a torus, and the cortical surface of a rat brain, the latter of which is constructed using neuroimaging data. Our results are twofold: Firstly, we find that collocation techniques are able to replicate solutions obtained using more standard Fourier based methods on a flat, periodic domain, independent of the underlying mesh. This result is particularly significant given the highly irregular nature of the type of meshes derived from modern neuroimaging data. And secondly, by deploying efficient numerical schemes to compute geodesics, our approach is not only capable of modelling macroscopic pattern formation on realistic cortical geometries, but can also be extended to include cortical architectures of more physiological relevance. Importantly, such an approach provides a means by which to investigate the influence of cortical geometry upon the nucleation and propagation of spatially localised neural activity and beyond. It thus promises to provide model-based insights into disorders like epilepsy, or spreading depression, as well as healthy cognitive processes like working memory or attention.

Effect of Vorapaxar Alone and in Combination with Aspirin on Bleeding Time and Platelet Aggregation in Healthy Adult Subjects.

The effect of the protease-activated receptor-1 (PAR-1) antagonist vorapaxar on human bleeding time is not known. This was a randomized, two-period, open-label trial in healthy men (n = 31) and women (n = 5). In period 1, subjects received 81 mg aspirin q.d. or a vorapaxar regimen achieving steady-state plasma concentrations equivalent to chronic 2.5 mg q.d. doses, for 7 days. In period 2, each group added 7 days of the therapy alternate to that of period 1 without washout. Bleeding time and platelet aggregation using arachidonic acid, ADP, and TRAP agonists were assessed. Bleeding time geometric mean ratio (90% CI) for vorapaxar/baseline was 1.01 (0.88-1.15), aspirin/baseline was 1.32 (1.15-1.51), vorapaxar + aspirin/vorapaxar was 1.47 (1.26-1.70), and vorapaxar + aspirin/aspirin was 1.12 (0.96-1.30). Unlike aspirin, vorapaxar did not prolong bleeding time compared with baseline. Bleeding time following administration of vorapaxar with aspirin was similar to that following aspirin alone.

Prevalence factors associated with equine herpesvirus type 1 infection in equids with upper respiratory tract infection and/or acute onset of neurological signs from 2008 to 2014.

The objective of the present case-control study was to determine prevalence factors associated with the detection of equine herpesvirus type 1 (EHV-1) by quantitative PCR (qPCR) in horses presented to veterinarians with clinical signs related to an upper respiratory tract infection and/or acute onset of neurological disease from March 2008 to December 2014. Nasal secretions and whole blood from 4228 equids with acute onset of fever, respiratory signs and/or neurological deficits were tested by qPCR for EHV-1. Categorical analyses were performed to determine the association between observations and EHV-1. A total of 117/4228 (2.7 per cent) equids tested qPCR-positive for EHV-1, with most of the isolates belonging to the non-neuropathogenic genotype (N752). EHV-1 PCR-positive equids were over-represented in racing horses. Depression, anorexia, nasal discharge and coughing were significantly less frequently reported in the EHV-1 qPCR-positive equids compared with the EHV-1 qPCR-negative cases. Neurological deficits were more frequently reported in the EHV-1 qPCR-positive cases. This study provides contemporary information on the frequency of EHV-1 detection by qPCR in blood and nasal secretions from horses with fever, respiratory signs and neurological deficits.

[Acute perioperative hemodilution without using hydroxyethyl starch : hemodynamic alterations under "controlled" hypovolemia]. / Akute perioperative Hämodilution ohne Verwendung von Hydroxyethylstärke : Hämodynamische Veränderungen unter "kontrollierter" Hypovolämie.

BACKGROUND: Up to now hydroxyethyl starch preparations have frequently been used to compensate for volume deficits accompanying blood withdrawal during acute normovolemic hemodilution. This approach was questioned with respect to the current limitations for use of hydroxyethyl starch solutions imposed by the European Medicines Agency. Because crystalloids distribute evenly across the whole extracellular compartment, 80 % of the infused solution will be "lost" to the interstitial space. Thus, a physiological adjustment of blood loss caused by hemodilution with crystalloids alone (1:5 ratio) seems hardly feasible and according to current data perhaps not even desirable. A 3:1 ratio (crystalloids versus blood loss) as applied in the current study can be regarded as a practical compromise between physiological needs and recommendations according to the literature (1.4:1) but will lead to moderate hypovolemia the hemodynamic consequences of which are not well described. AIM: The current study investigates the hemodynamic impact of a hemodilution with crystalloids under the precondition of a 3:1 substitution ratio compared to withdrawn blood. METHODS: In the context of acute perioperative hemodilution 10 otherwise healthy women graded I and II on the American Society of Anesthesiologists (ASA) classification scheduled for open gynecological cancer surgery underwent an average blood withdrawal of 1097 ± 285 ml which was substituted by an average of 3430 ± 806 ml of Ringer's lactate. The resulting deficit in blood volume was exactly quantified by a double tracer technique. Hemodynamic changes were evaluated by a combination of thermodilution and pulse contour analysis (PiCCO system®). Subsequently, the remaining volume deficit was compensated by 245 ± 64 ml of a 20 % albumin solution and hemodynamic parameters were again evaluated. RESULTS: When infusing Ringer's lactate in a 3:1 ratio compared to the actual blood loss, the blood volume decreased by 12 %. The volume effect of Ringer's lactate proved to be 17 %. While mean arterial pressure and heart rate remained constant, key hemodynamic parameters changed relevantly during the time course. A significant rise in cardiac output and myocardial contractility could be observed which was accompanied by a decrease in systemic vascular resistance. In contrast, cardiac preload and the parameters representing pulmonary vascular permeability remained unaltered. The infusion of 245 ± 64 ml of a 20 % albumin solution nearly completely restituted blood volume and led to an insignificant rise in systemic vascular resistance but did not normalize cardiac output or myocardial contractility. CONCLUSION: In the study population, the loss of intravascular fluid during perioperative haemodilution could be compensated by an increase in cardiac performance. However, whether patients with a reduced cardiac capacity (i.e. older patients) are capable to improve their cardiac output sufficiently in order to compensate hypovolemia accompanying perioperative haemodilution with crystalloids remains questionable.

Vascular content, tone, integrity, and haemodynamics for guiding fluid therapy: a conceptual approach.

BACKGROUND: Despite many clinical trials and investigative efforts to determine appropriate therapeutic intervention(s) for shock, this topic remains controversial. The use of i.v. fluid has represented the cornerstone for the treatment of hypoperfusion for two centuries. METHODS: As a part of International Acute Dialysis Quality Initiative XII Fluids Workgroup meeting, we sought to incorporate recent advances in our understanding of vascular biology into a more comprehensive yet accessible approach to the patient with hypoperfusion. In this workgroup, we attempted to develop a framework that incorporates key aspects of the vasculature into a diagnostic approach. RESULTS: The four main components of our proposal involve the assessment of the blood flow (BF), vascular content (vC), the vascular barrier (vB), and vascular tone (vT). Any significant perturbation in any of these domains can lead to hypoperfusion at both the macro- and micro-circulatory level. We have termed the BF, vC, vB, and vT diagnostic approach the vascular component (VC) approach. CONCLUSIONS: The VC approach to hypoperfusion has potential advantages to the current diagnostic system. This approach also has the distinct advantage that it can be used to assess the systemic, regional, and micro-vasculature, thereby harmonizing the approach to clinical vascular diagnostics across these levels. The VC approach will need to be tested prospectively to determine if this system can in fact improve outcomes in patients who suffer from hypoperfusion.

Heartworm-positive dogs recover without complications from surgical sterilization using cardiovascular sparing anesthesia protocol.

Expedited home placement of heartworm-positive shelter dogs is desirable and may outweigh the perceived increase in anesthetic risk for pre-adoption sterilization; however, this issue has not been addressed in the literature. Our goal was to determine whether heartworm-positive dogs suffered clinically evident perioperative complications after sterilization under general anesthesia. Anticipated complications could result from anesthesia-induced changes in pulmonary vascular resistance and cardiac output leading to signs of thromboembolic disease and even death from dislodged parasites. The medical records of 15 hemodynamically stable, intact, heartworm-positive, mixed-breed shelter dogs with no or mild clinical signs were examined. Pre-operative evaluation of patients included a complete blood count, clinical chemistry profile, heartworm antigen and microfilariae screen, electrocardiogram, and thoracic radiographs. The anesthetic protocol for heartworm-positive dogs included acepromazine (0.01-0.05 mg/kg), butorphanol (0.1mg/kg IM) and meloxicam (0.2mg/kg IM), or carprofen (2mg/kg SQ) in the preanesthetic period; tiletamine/zolazepam (3-6 mg/kg IV) or ketamine/diazepam (3-6mg/kg/0.25-5mg/kg IV) to effect for induction; maintenance on isoflurane or sevoflurane and oxygen. A lidocaine testicular block was performed on 11 males. All dogs were monitored postoperatively for a minimum of 24h and then daily until discharge. There were no clinically evident perioperative complications in heartworm-positive dogs. Purposeful pre-operative evaluation of heartworm-positive dogs while utilizing cardiovascular-sparing anesthetic protocols may allow clinicians to proceed with sterilization of hemodynamically stable heartworm-positive shelter dogs prior to heartworm treatment.

Placental syncytiotrophoblast maintains a specific type of glycocalyx at the fetomaternal border: the glycocalyx at the fetomaternal interface in healthy women and patients with HELLP syndrome.

Recent studies showed that considerable amounts of glycosaminoglycans are released into maternal blood during normal pregnancy and in hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome. Maternal endothelia and the syncytiotrophoblast layer have been discussed as a possible origin of these glycocalyx components. Our study aimed to visualize the glycocalyx on the syncytiotrophoblast by electron microscopy, to analyze its structure and composition by immunohistochemistry, and to determine potential differences between healthy women and women with HELLP syndrome. For electron microscopy, a cotyledon was fixed by perfusion of the intervillous space with a 2% lanthanum-nitrate glutaraldehyde solution followed by immersion fixation in the same fixative. For immunohistochemistry, sections of 16 placentas (HELLP patients/healthy women, n = 8 each) were stained with monoclonal antibodies against the main glycocalyx constituents syndecan 1, hyaluronic acid, and heparan sulfate. Semiquantitative evaluation of staining intensity focused on the apical surface of the syncytiotrophoblast and fetal intravillous endothelia as possible localizations of a placental glycocalyx. Electron microscopy revealed a glycocalyx of approximately 250 nm, covering the syncytiotrophoblast layer. This was found to contain large amounts of syndecan 1, but neither hyaluronic acid nor heparan sulfate as major components. Intravillous fetal endothelium did not express any of the investigated glycosaminoglycans. Healthy women and patients with HELLP showed no differences concerning glycocalyx composition and thickness of the syncytiotrophoblast. The composition of the "placental" glycocalyx differs from the adult and fetal vascular glycocalyx. Obviously, the human placental syncytiotrophoblast maintains a special kind of glycocalyx at the fetomaternal interface.

Increased serum concentrations of circulating glycocalyx components in HELLP syndrome compared to healthy pregnancy: an observational study.

Severe inflammation has been shown to induce a shedding of the endothelial glycocalyx (EGX). Inflammatory cytokines, such as tumor necrosis factor α (TNF-α), impede the thickness of the EGX. While a controlled inflammatory reaction occurs already in normal pregnancy, women with hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome had an exaggerated inflammatory response. This study investigates the shedding of the glycocalyx during normal pregnancy and in women with HELLP syndrome. Glycocalyx components (syndecan 1, heparan sulfate, and hyaluronic acid) were measured in serum of healthy women throughout pregnancy (4 time points, n = 26), in women with HELLP syndrome (n = 17) before delivery and in nonpregnant volunteers (n = 10). Serum concentrations of TNF-α and soluble TNF-α receptors (sTNF-Rs) were assessed once in all 3 groups. Syndecan 1 serum concentrations constantly rose throughout normal pregnancy. Immediately before delivery, a 159-fold increase was measured compared to nonpregnant controls (P < .01). Even higher amounts were observed in patients with HELLP prior to delivery (median 12 252 ng/mL) compared to healthy women matched by gestational age (median 5943 ng/mL; P < .01). Relevantly, increased serum levels of heparan sulfate, hyaluronic acid, and sTNF-Rs were only detected in patients with HELLP (P < .01). These findings suggest that considerable amounts of syndecan 1 are released into maternal blood during uncomplicated pregnancy. The HELLP syndrome is associated with an even more pronounced shedding of glycocalyx components. The maternal vasculature as well as the placenta has to be discussed as a possible origin of circulating glycocalyx components.

Dynamical energy analysis for built-up acoustic systems at high frequencies.

Standard methods for describing the intensity distribution of mechanical and acoustic wave fields in the high frequency asymptotic limit are often based on flow transport equations. Common techniques are statistical energy analysis, employed mostly in the context of vibro-acoustics, and ray tracing, a popular tool in architectural acoustics. Dynamical energy analysis makes it possible to interpolate between standard statistical energy analysis and full ray tracing, containing both of these methods as limiting cases. In this work a version of dynamical energy analysis based on a Chebyshev basis expansion of the Perron-Frobenius operator governing the ray dynamics is introduced. It is shown that the technique can efficiently deal with multi-component systems overcoming typical geometrical limitations present in statistical energy analysis. Results are compared with state-of-the-art hp-adaptive discontinuous Galerkin finite element simulations.