Microtubule sliding activity of a kinesin-8 promotes spindle assembly and spindle length control

Molecular motors play critical roles in the formation of mitotic spindles, either through controlling the stability of individual microtubules, or by cross-linking and sliding microtubule arrays. Kinesin-8 motors are best known for their regulatory roles in controlling microtubule dynamics. They contain microtubule-destabilizing activities, and restrict spindle length in a wide variety of cell types and organisms. Here, we report for the first time on an anti-parallel microtubule-sliding activity of the budding yeast kinesin-8, Kip3. The in vivo importance of this sliding activity was established through the identification of complementary Kip3 mutants that separate the sliding activity and microtubule destabilizing activity. In conjunction with kinesin-5/Cin8, the sliding activity of Kip3 promotes bipolar spindle assembly and the maintenance of genome stability. We propose a “slide-disassemble” model where Kip3’s sliding and destabilizing activity balance during pre-anaphase. This facilitates normal spindle assembly. However, Kip3’s destabilizing activity dominates in late anaphase, inhibiting spindle elongation and ultimately promoting spindle disassembly

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

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Pupillary abnormalities in non-selected critically ill patients: an observational study

International audienceBackground: Repeated pupillary examination is a key element of neurologic surveillance in intensive care units (ICU). However, in non-selected critically ill patients, the clinical interest of monitoring pupillary diameter and light reflex is poorly documented. We aimed to determine the prevalence and the etiologies of pupillary abnormalities (PAs) in this ICU patient population. Methods: We performed a prospective, observational study in a medical university affiliated ICU over a 6-month period. All patients with at least one pupillary examination were included. PA was defined as areflexia and/or anisocoria present at the time of ICU admission or occurring during the ICU stay. Results: During the study period, we included 297 patients who had 6 +/- 9 pupillary examinations per day (totaling 11,360 pupillary assessments). The majority of patients (n=161, 54%) were admitted to the ICU for acute respiratory or cardiovascular failure. A total of 128 PAs were recorded in 109 patients: 78 areflexia alone (61%), 33 anisocoria alone (26%) and 17 (13%) with associated anisocoria and areflexia. The main causes of PAs were related to acute brain ischemia (n=41, 32%) and sedation/analgesia (n=50, 39%). Among the PAs, 59 (46%) were present upon ICU admission. The etiologies of the PAs at admission did not differ from those occurring during ICU stay (P=NS). Interestingly, 9 (7%) PAs were attributed to ipratropium nebulization in patients with chronic obstructive pulmonary disease exacerbation. Conclusions: The high prevalence of PAs, frequently associated with both brain organic lesions and drug side effects, highlights the clinical interest of pupillary surveillance in non-selected critically ill patients

Effects of methylene blue on microcirculatory alterations following cardiac surgery: A prospective cohort study

International audienceBACKGROUND: Methylene blue is used as rescue therapy to treat catecholamine-refractory vasoplegic syndrome after cardiac surgery. However, its microcirculatory effects remain poorly documented. OBJECTIVE: We aimed to study microcirculatory abnormalities in refractory vasoplegic syndrome following cardiac surgery with cardiopulmonary bypass and assess the effects of methylene blue. DESIGN: A prospective open-label cohort study. SETTING: 20-Bed ICU of a tertiary care hospital. PATIENTS: 25 Adult patients receiving 1.5 mg kg-1 of methylene blue intravenously for refractory vasoplegic syndrome (defined as norepinephrine requirement more than 0.5 μg kg-1 min-1) to maintain mean arterial pressure (MAP) more than 65 mmHg and cardiac index (CI) more than 2.0 l min-1 m-2. MAIN OUTCOME MEASURES: Complete haemodynamic set of measurements at baseline and 1 h after the administration of methylene blue. Sublingual microcirculation was investigated by sidestream dark field imaging to obtain microvascular flow index (MFI), total vessel density, perfused vessel density and heterogeneity index. Microvascular reactivity was assessed by peripheral near-infrared (IR) spectroscopy combined with a vascular occlusion test. We also performed a standardised measurement of capillary refill time. RESULTS: Despite normalised CI (2.6 [2.0 to 3.8] l min-1 m-2) and MAP (66 [55 to 76] mmHg), patients with refractory vasoplegic syndrome showed severe microcirculatory alterations (MFI \textless 2.6). After methylene blue infusion, MFI significantly increased from 2.0 [0.1 to 2.5] to 2.2 [0.2 to 2.8] (P = 0.008), as did total vessel density from 13.5 [8.3 to 18.5] to 14.9 [10.1 to 14.7] mm mm-2 (P = 0.02) and perfused vessel density density from 7.4 [0.1 to 11.5] to 9.1 [0 to 20.1] mm mm-2 (P = 0.02), but with wide individual variation. Microvascular reactivity assessed by tissue oxygen resaturation speed also increased from 0.5 [0.1 to 1.8] to 0.7 [0.1 to 2.7]% s-1 (P = 0.002). Capillary refill time remained unchanged throughout the study. CONCLUSION: In refractory vasoplegic syndrome following cardiac surgery, we found microcirculatory alterations despite normalised CI and MAP. The administration of methylene blue could improve microvascular perfusion and reactivity, and partially restore the loss of haemodynamic coherence. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT04250389

Improving the prognostic value of ∆PCO(2) following cardiac surgery: a prospective pilot study

International audienceConflicting results have been published on prognostic significance of central venous to arterial PCO(2) difference (∆PCO(2)) after cardiac surgery. We compared the prognostic value of ∆PCO(2) on intensive care unit (ICU) admission to an original algorithm combining ∆PCO(2), ERO(2) and lactate to identify different risk profiles. Additionally, we described the evolution of ∆PCO(2) and its correlations with ERO(2) and lactate during the first postoperative day (POD1). In this monocentre, prospective, and pilot study, 25 patients undergoing conventional cardiac surgery were included. Central venous and arterial blood gases were collected on ICU admission and at 6, 12 and 24 h postoperatively. High ∆PCO(2) (≥ 6 mmHg) on ICU admission was found to be very frequent (64% of patients). Correlations between ∆PCO(2) and ERO(2) or lactate for POD1 values and variations were weak or non-existent. On ICU admission, a high ∆PCO(2) did not predict a prolonged ICU length of stay (LOS). Conversely, a significant increase in both ICU and hospital LOS was observed in high-risk patients identified by the algorithm: 3.5 (3.0-6.3) days versus 7.0 (6.0-8.0) days (p = 0.01) and 12.0 (8.0-15.0) versus 8.0 (8.0-9.0) days (p \textless 0.01), respectively. An algorithm incorporating ICU admission values of ∆PCO(2), ERO(2) and lactate defined a high-risk profile that predicted prolonged ICU and hospital stays better than ∆PCO(2) alone

Outcome of primary graft dysfunction rescued by venoarterial extracorporeal membrane oxygenation after heart transplantation

International audienceBACKGROUND: Primary graft dysfunction remains the leading cause of 30-day mortality after heart transplantation. Few data have been published about the clinical outcome of severe primary graft dysfunction treated with venoarterial extracorporeal membrane oxygenation (VA-ECMO). AIM: To evaluate the prevalence and outcome of severe primary graft dysfunction requiring VA-ECMO, and to identify factors associated with hospital mortality. METHODS: We performed an observational analysis of our institutional database of VA-ECMO for primary graft dysfunction after heart transplantation. Patients with severe primary graft dysfunction, according to the International Society for Heart and Lung Transplantation classification, were included. The primary outcome was survival to hospital discharge. Risk factors for in-hospital mortality were searched with multiple logistic regression analysis using backward stepwise variable elimination. RESULTS: Of the 397 patients who had heart transplantation between January 2007 and December 2018, 60 (15.1%) developed severe primary graft dysfunction requiring VA-ECMO. The median age was 52 (interquartile range 39-59) years, and 73.3% were male. Thirty-nine (65.0%) patients were weaned after a mean duration of VA-ECMO support of 7.2±6.0 days. Thirty-two (53.3%) patients were alive at hospital discharge. Inotropic support in the recipient before heart transplantation (odds ratio [OR] 3.88, 95% confidence interval [CI] 1.04-14.44; P=0.04), total ischaemic time (OR 0.99, 95% CI 0.99-1.00; P=0.01) and 48-hour total blood transfusion (OR 1.14, 95% CI 1.04-1.26; P=0.01) were independent predictors of in-hospital mortality. CONCLUSIONS: Severe primary graft dysfunction requiring VA-ECMO is frequent after heart transplantation. Survival to hospital discharge after VA-ECMO for severe primary graft dysfunction is satisfactory in such a critically ill population

Prediction of intraoperative hypotension from the linear extrapolation of mean arterial pressure

International audienceBACKGROUND: Hypotension prediction index (HPI) software is a proprietary machine learning-based algorithm used to predict intraoperative hypotension (IOH). HPI has shown superiority in predicting IOH when compared to the predictive value of changes in mean arterial pressure (ΔMAP) alone. However, the predictive value of ΔMAP alone, with no reference to the absolute level of MAP, is counterintuitive and poor at predicting IOH. A simple linear extrapolation of mean arterial pressure (LepMAP) is closer to the clinical approach. OBJECTIVES: Our primary objective was to investigate whether LepMAP better predicts IOH than ΔMAP alone. DESIGN: Retrospective diagnostic accuracy study. SETTING: Two tertiary University Hospitals between May 2019 and December 2019. PATIENTS: A total of 83 adult patients undergoing high risk non-cardiac surgery. DATA SOURCES: Arterial pressure data were automatically extracted from the anaesthesia data collection software (one value per minute). IOH was defined as MAP \textless 65 mmHg. ANALYSIS: Correlations for repeated measurements and the area under the curve (AUC) from receiver operating characteristics (ROC) were determined for the ability of LepMAP and ΔMAP to predict IOH at 1, 2 and 5 min before its occurrence (A-analysis, using the whole dataset). Data were also analysed after exclusion of MAP values between 65 and 75 mmHg (B-analysis). RESULTS: A total of 24 318 segments of ten minutes duration were analysed. In the A-analysis, ROC AUCs to predict IOH at 1, 2 and 5 min before its occurrence by LepMAP were 0.87 (95% confidence interval, CI, 0.86 to 0.88), 0.81 (95% CI, 0.79 to 0.83) and 0.69 (95% CI, 0.66 to 0.71) and for ΔMAP alone 0.59 (95% CI, 0.57 to 0.62), 0.61 (95% CI, 0.59 to 0.64), 0.57 (95% CI, 0.54 to 0.69), respectively. In the B analysis for LepMAP these were 0.97 (95% CI, 0.9 to 0.98), 0.93 (95% CI, 0.92 to 0.95) and 0.86 (95% CI, 0.84 to 0.88), respectively, and for ΔMAP alone 0.59 (95% CI, 0.53 to 0.58), 0.56 (95% CI, 0.54 to 0.59), 0.54 (95% CI, 0.51 to 0.57), respectively. LepMAP ROC AUCs were significantly higher than ΔMAP ROC AUCs in all cases. CONCLUSIONS: LepMAP provides reliable real-time and continuous prediction of IOH 1 and 2 min before its occurrence. LepMAP offers better discrimination than ΔMAP at 1, 2 and 5 min before its occurrence. Future studies evaluating machine learning algorithms to predict IOH should be compared with LepMAP rather than ΔMAP

Veno-arterial extracorporeal membrane oxygenation for drug intoxications: A single center, 14-year experience

International audienceBACKGROUND AND AIM OF THE STUDY: Acute cardiovascular failure remains a leading cause of death in severe poisonings. Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) has been increasingly used as a rescue therapeutic option for those cases refractory to optimal conventional treatment. We sought to evaluate the outcomes after VA-ECMO used for drug intoxications in a single-center experience. METHODS: We performed an observational analysis of our prospective institutional database. The primary endpoint was survival to hospital discharge. RESULTS: Between January 2007 and December 2020, 32 patients (mean age: 45.4 ± 15.8 years; 62.5% female) received VA-ECMO for drug intoxication-induced refractory cardiogenic shock (n = 25) or cardiac arrest (n = 7). Seven (21.8%) patients developed lower limb ischemia during VA-ECMO support. Twenty-six (81.2%) patients were successfully weaned after a mean VA-ECMO support of 2.9 ± 1.3 days. One (3.1%) patient died after VA-ECMO weaning for multiorgan failure and survival to hospital discharge was 78.1% (n = 25). In-hospital survivors were discharged from hospital with a good neurological status. Survival to hospital discharge was not statistically different according to sex (male = 75.0% vs. female = 80.0%; p = .535), type of intoxication (single drug = 81.8% vs. multiple drugs = 76.1%; p = .544) and location of VA-ECMO implantation (within our center = 75% vs. peripheral hospital using our Mobile Unit of Mechanical Circulatory Support = 100%; p = .352). Survival to hospital discharge was significantly lower in patients receiving VA-ECMO during on-going cardiopulmonary resuscitation (42.8% vs. 88.0%; p = .026). CONCLUSIONS: VA-ECMO appears to be a feasible therapeutic option with a satisfactory survival rate and acceptable complications rate in poisonings complicated by refractory cardiogenic shock or cardiac arrest

The motor domain of the kinesin Kip2 promotes microtubule polymerization at microtubule tips

Kinesins are microtubule-dependent motor proteins, some of which moonlight as microtubule polymerases, such as the yeast protein Kip2. Here, we show that the CLIP-170 ortholog Bik1 stabilizes Kip2 at microtubule ends where the motor domain of Kip2 promotes microtubule polymerization. Live-cell imaging and mathematical estimation of Kip2 dynamics reveal that disrupting the Kip2-Bik1 interaction aborts Kip2 dwelling at microtubule ends and abrogates its microtubule polymerization activity. Structural modeling and biochemical experiments identify a patch of positively charged residues that enables the motor domain to bind free tubulin dimers alternatively to the microtubule shaft. Neutralizing this patch abolished the ability of Kip2 to promote microtubule growth both in vivo and in vitro without affecting its ability to walk along microtubules. Our studies suggest that Kip2 utilizes Bik1 as a cofactor to track microtubule tips, where its motor domain then recruits free tubulin and catalyzes microtubule assembly.ISSN:0021-9525ISSN:1540-814

Elaboration of a French version of the Duke Activity Status Index questionnaire and performance to predict functional capacity

International audienceBACKGROUND: Guidelines recommend detecting poor functional capacity (VO(2max) \textless 14 ml.kg(-1).min(-1)) to assess preoperative cardiac risk. This screening is performed via a cardiopulmonary exercise test (CPET), the self-reported inability to climb two flights of stairs, or the use of the Duke Activity Status Index (DASI) questionnaire, which has shown a significant correlation with VO(2max) and postoperative outcomes. The objectives of the present study were: 1) to create a French version of the DASI questionnaire (FDASI); 2) to assess its diagnostic performance in predicting functional capacity. METHODS: Consecutive adult patients undergoing CPET for medical or preoperative evaluation were prospectively included between May 2020 and March 2021. All patients were asked to complete FDASI as a self-questionnaire and report their inability to climb two flights of stairs. RESULTS: 122 patients were included. Test-retest reliability was 0.88 and 23 (19%) patients experienced a VO(2)(max) \textless 14 ml.kg(-1.)min(-1). There was a significant positive relationship between FDASI and VO(2max): r(2) = 0.32; p \textless  0.001. ROC(AUC) was 0.81 [95%CI: 0.73-0.89]. The best FDASI score threshold was 36 points, leading to sensitivity and specificity values of 87% [74-100] and 68% [56-79], respectively. Besides, sensitivity and specificity were 35% [17-56] and 92% [86-97] for the self-reported inability to climb two flights of stairs. CONCLUSION: A FDASI score of 36 represents a reliable threshold the clinicians could routinely use to identify patients with a VO(2max) \textless 14 ml.kg(-1.)min(-1). FDASI could advantageously replace the self-reported inability to climb two flights of stairs