Performance of non-invasive stroke volume variation during passive leg raising as a predictor of hypotension following induction of spinal anesthesia for elective cesarean delivery: a single cohort study.

BACKGROUND: Spinal anesthesia for cesarean delivery is accompanied by hypotension in up to 70% of cases. To date, there is no gold standard for predicting hypotension after spinal anesthesia for cesarean delivery. The Clearsight™ device is a non-invasive system that uses a digital cuff to calculate stroke volume. We hypothesized that stroke volume variation induced with passive leg raising before spinal anesthesia for elective cesarean delivery could predict the occurrence of hypotension. METHODS: We conducted a prospective observational study, including third trimester parturients undergoing elective cesarean delivery with spinal anesthesia. We analyzed the stroke volume variation performance for predicting hypotension. Stroke volume was collected in the semi-recumbent position (baseline) and during passive leg raising before spinal anesthesia. Systolic arterial blood pressure measurement was followed for 15 min after spinal anesthesia. Hypotension was defined as a ≥20% decrease from the baseline measurement. All parturients received appropriate hypotension prophylaxis. RESULTS: Data from 42 parturients were analyzed. Hypotension occurred in 45%. The area-under-the curve for predicting hypotension using the stroke volume variation was 0.83 (95% CI 0.68 to 0.98; P=0.001). The best cut-off value for predicting hypotension was 7%, having a sensitivity of 87% (95% CI 0.70 to 0.99) and a specificity of 83% (95% CI 0.69 to 0.97). CONCLUSION: In our study of third trimester parturients undergoing cesarean delivery and receiving appropriate hypotension prophylaxis, a digital non-invasive monitoring device of stroke volume variation analysis was useful for predicting the occurrence of hypotension after spinal anesthesia.

Clearsight™ use for haemodynamic monitoring during the third trimester of pregnancy - a validation study.

BACKGROUND: We assessed the validity of Clearsight™ as a non-invasive cardiac output and stroke volume monitoring device, comparing it with transthoracic echocardiography measurements during the third trimester of pregnancy. METHODS: Measurements obtained from Clearsight™ were compared with those from echocardiography as the gold standard. The precision and accuracy of the Clearsight™ was measured using the Bland and Altman method. Clinical agreement with echocardiography was assessed using the agreement tolerability index. RESULTS: Measurements were recorded from 44 pregnant women with a median [IQR range] gestational age of 33 [30-37] weeks. We found that Clearsight™ measurements presented a systematic overestimation of cardiac output, with mean bias [CI 95%] of 2.7 [2.3-3.0] L/min, with limits of agreement of  -0.1 to 5.4 L/min. It overestimated stroke volume, with a bias of 29.5 [25.0-33.4] mL and a limit of agreement of -1.6 to 60.1 mL. In addition, the analysis of cardiac output showed a percentage of error of 41% and intra-class correlation [CI 95%] of 0.37 [0.17 to 0.53, P <0.001]. For stroke volume, the percentage of error was 40% and intra-class correlation 0.16 [-0.1 to 0.34; P=0.27]. We found that agreement tolerability index scores were unacceptable. We evaluated the ability of the device to track changes in cardiac output by inducing a left lateral decubitus position, but the analysis was inconclusive. CONCLUSION: The agreement between Clearsight™ and the echocardiography measurements of cardiac output and stroke volume were not within an acceptable range in the third trimester of pregnancy.

Spontaneous shear flow in confined cellular nematics.

In embryonic development or tumor evolution, cells often migrate collectively within confining tracks defined by their microenvironment 1,2. In some of these situations, the displacements within a cell strand are antiparallel 3, giving rise to shear flows. However, the mechanisms underlying these spontaneous flows remain poorly understood. Here, we show that an ensemble of spindle-shaped cells plated in a well-defined stripe spontaneously develop a shear flow whose characteristics depend on the width of the stripe. On wide stripes, the cells self-organize in a nematic phase with a director at a well-defined angle with the stripe's direction, and develop a shear flow close to the stripe's edges. However, on stripes narrower than a critical width, the cells perfectly align with the stripe's direction and the net flow vanishes. A hydrodynamic active gel theory provides an understanding of these observations and identifies the transition between the non-flowing phase oriented along the stripe and the tilted phase exhibiting shear flow as a Fréedericksz transition driven by the activity of the cells. This physical theory is grounded in the active nature of the cells and based on symmetries and conservation laws, providing a generic mechanism to interpret in vivo antiparallel cell displacements.

Diagnostic point-of-care ultrasound: applications in obstetric anaesthetic management.

Complications during pregnancy are not frequent, but may occur abruptly. Point-of-care ultrasound is a non-invasive, non-ionising diagnostic tool that is available at the bed-side when complications occur. This review covers the use of ultrasound in various clinical situations. Gastric ultrasound can identify stomach contents that put the woman at risk for pulmonary aspiration. In the future, this tool will probably be used routinely before induction of anaesthesia to determine the presence of stomach contents above a particular risk threshold. Difficult tracheal intubation, and the potential for 'can't intubate, can't oxygenate', is more frequent in pregnant women. Point-of-care ultrasound of the airway allows accurate identification of the cricothyroid membrane, permitting rapid and safer establishment of front-of-neck airway access. Combined cardiac and lung ultrasound can determine the potential risk:benefit of fluid administration in the pregnant patient. Such prediction is of critical importance, given the tendency of pregnant women to develop pulmonary oedema. Combined echocardiography and lung ultrasound can be combined with ultrasound of the leg veins to differentiate between the various causes of acute respiratory failure, and guide treatment in this situation. Finally, as shown in the general population, multi-organ point-of-care ultrasound allows early diagnosis of the main causes of circulatory failure and cardiac arrest at the bed-side. As the importance of point-of-care ultrasound in critical patients is increasingly recognised, it is emerging as an important tool in the therapeutic armoury of obstetric anaesthetists.

Turbulent Dynamics of Epithelial Cell Cultures.

We investigate the large length and long time scales collective flows and structural rearrangements within in vitro human bronchial epithelial cell (HBEC) cultures. Activity-driven collective flows result in ensembles of vortices randomly positioned in space. By analyzing a large population of vortices, we show that their area follows an exponential law with a constant mean value and their rotational frequency is size independent, both being characteristic features of the chaotic dynamics of active nematic suspensions. Indeed, we find that HBECs self-organize in nematic domains of several cell lengths. Nematic defects are found at the interface between domains with a total number that remains constant due to the dynamical balance of nucleation and annihilation events. The mean velocity fields in the vicinity of defects are well described by a hydrodynamic theory of extensile active nematics.

Can point-of-care ultrasound predict spinal hypotension during caesarean section? A prospective observational study.

Spinal anaesthesia for elective caesarean section is associated with maternal hypotension, secondary to alteration of sympathetic tone and hypovolemia, in up to 70% of cases. Measurement of the subaortic variation in the velocity time integral (VTI) after passive leg raising allows prediction of fluid responsiveness. Our objective, in this prospective single-centre observational study, was to assess the ability of change in VTI after 45° passive leg raising to predict hypotension after spinal anaesthesia. Ultrasound measurements were performed just before elective caesarean section. Anaesthesia, intravenous coloading and prophylactic vasopressor treatment were standardised according to current guidelines. We studied 40 women. Hypotension occurred in 17 (45%) women. The area (95%CI) under the receiver operating characteristics (ROC) curve for the prediction of spinal hypotension was 0.8 (0.6-0.9; p = 0.0001). Seventeen women had a change in VTI with leg elevation ≤ 8%, which was predictive for not developing hypotension, and 11 had a change ≥ 21%, predictive for hypotension. The grey zone between 8% and 21%, with inconclusive values, included 12 women. We suggest that cardiac ultrasound provides characterisation of the risk of hypotension following spinal anaesthesia at elective caesarean section, and therefore may allow individualised strategies for prevention and management.

Rapid diagnostic test and use of antibiotic against methicillin-resistant Staphylococcus aureus in adult intensive care unit.

Ventilator-associated pneumonia (VAP) due to methicillin-resistant Staphylococcus aureus (MRSA) is associated with excess mortality and costs. Molecular biology test allows rapid identification of MRSA in sputum with high negative predictive value. We hypothesized that use of a rapid diagnostic test in patients with suspected VAP was associated with reduced use of antibiotics directed against MRSA. This retrospective, observational study was conducted in a polyvalent intensive care unit (ICU) of a university hospital. We compared two periods: before (2007-2010) and after (2010-2015) the implementation of a rapid diagnostic test, which uses RT-PCR to detect pathogens in 60 minutes. The primary endpoint was the effect on the empirical use of anti-MRSA antibiotics. The second endpoint was the effect of this strategy on the cost regarding antibiotic treatment. The first group included 120 suspected VAP (88 patients) and the second group 121 suspected VAP (89 patients). Empirical use of vancomycin and linezolid decreased by 50 % between the two periods. Twenty-seven VAP (22 %) were treated with an anti-MRSA treatment between 2007 and 2010, and 13 (11 %) between 2010 and 2015 (p = 0.04). The mean cost of anti-MRSA treatment by patients in the first group was 63 ± 223 €, and 13 ± 52 € in the second group (p < 0.001). This study shows that a rapid diagnostic test was associated with reduced use and cost of anti-MRSA antibiotics in patients with suspected VAP. These results should be confirmed by further multicenter prospective studies.

[Meningitis to Candida albicans at the adult, use of the new diagnosis methods]. / Méningite à Candida albicans chez l'adulte, apport des nouveaux moyens diagnostiques.

Candida albicans or non-albicans are a frequent source of infection but seldom displayed in cerebrospinal fluid although responsible of an important number of nosocomial meningitis. Diagnosis is difficult which often delays treatment, which in turn hinders prognostic. This clinical case shows a patient afflicted with a deadly C. albicans meningitis and allows us to focus on new diagnostic tools and advice against this infection.

[Ischemic heart failure making the diagnosis of a Vaquez disease: a rare event]. / Choc cardiogénique ischémique révélateur d'une maladie de Vaquez, un événement rare.

We present the case of a 46-year-old patient without any past medical history, admitted to our ICU for cardiogenic shock complicating acute coronary syndrome. The blood tests found polycethemia, a polycethemia vera was suspected and confirmed by genetic analysis. Ischemic heart failure as an initial symptom of polycethemia vera and its treatment by arterial bleeding is a rare event that we describe in this article.

Emergence of collective modes and tri-dimensional structures from epithelial confinement.

Many in vivo processes, including morphogenesis or tumour maturation, involve small populations of cells within a spatially restricted region. However, the basic mechanisms underlying the dynamics of confined cell assemblies remain largely to be deciphered and would greatly benefit from well-controlled in vitro experiments. Here we show that confluent epithelial cells cultured on finite population-sized domains, exhibit collective low-frequency radial displacement modes as well as stochastic global rotation reversals. A simple mathematical model, in which cells are described as persistent random walkers that adapt their motion to that of their neighbours, captures the essential characteristics of these breathing oscillations. As these epithelia mature, a tri-dimensional peripheral cell cord develops at the domain edge by differential extrusion, as a result of the additional degrees of freedom of the border cells. These results demonstrate that epithelial confinement alone can induce morphogenesis-like processes including spontaneous collective pulsations and transition from 2D to 3D.

Perfect nematic order in confined monolayers of spindle-shaped cells.

Elongated, weakly interacting, apolar, fibroblast cells (mouse fibroblasts NIH-3T3) cultured at confluence align together, forming large domains (correlation length ∼ 500 µm) where they are perfectly ordered. We study the emergence of this mesoscopic nematic order by quantifying the ordering dynamics in a two-dimensional tissue. Cells are initially very motile and the monolayer is characterized by anomalous density fluctuations, a signature of far-from-equilibrium systems. As the cell density increases because of proliferation, the cells align with each other forming these large oriented domains while, at the same time, the cellular movements and the density fluctuations freeze. Topological defects that are characteristic of nematic phases remain trapped at long times thereby preventing the development of infinite domains. When confined within adhesive stripes of given widths (from 30 µm to 1.5 mm) cells spontaneously align with the domain edges. This orientation then propagates toward the pattern center. For widths smaller than the orientation correlation length, cells perfectly align in the direction of the stripe. Experiments performed in cross-shaped patterns show that in the situation of two competing populations, both the number of cells and the degree of alignment impact the final orientation.