Nicolas Libert

How did you sleep in the ICU

Patient sleep is extremely disturbed in the intensive care unit. We explored the memorization of sleep disturbances during a phone interview of 60 patients using the Basic Nordic Sleep Questionnaire. Half of them reminded sleep deprivation and one third of them had a decreased long term quality of sleep.

Epstein-Barr virus reactivation in critically ill immunocompetent patients

Background: Herpes viruses can be reactivated among immunocompetent patients in intensive care unit (ICU). Cytomegalovirus (CMV) and herpes simplex virus (HSV) have been the most studied. We hypothesized that Epstein-Barr virus (EBV) could also be reactivated in immunocompetent patients during their stay in ICU and that this would be associated with morbidity and mortality. Methods: This prospective observational study included 90 patients with an ICU stay of ≥ 5 days. CMV and HSV were considered when clinically suspected and DNA was researched in blood or bronchoalveolar lavage (BAL). EBV DNA viral quantification was performed in the blood samples. Results: EBV DNA was detected in blood of 61 patients (median length for positivity of 7.5 days). CMV DNA was detected in blood of 16 patients (median length for positivity of 13.5 days) and BAL of 6 patients. HSV1 DNA was detected in the BAL of 28 patients (median length for positivity of 7.5 days). Nineteen patients had no viral reactivation, 1 experienced only CMV, 32 had only EBV, 5 had only HSV, 6 had EBV and CMV, 14 had EBV and HSV, and 9 patients reactivated three viruses. Mortality was higher among patients with EBV reactivation (33/61 vs. 7/25, p = 0.02). Length of stay (21 vs. 10 days, p < 0.001) and length of mechanical ventilation (15 vs. 7 days, p < 0.001) were higher among patients with EBV reactivation. Conclusions: This study shows that EBV DNA is detected in blood of diverse ICU patients with ≥ 5 days of stay and that it is associated with morbidity and mortality. Larger dynamic prospective studies are needed to correlate viral reactivation with immune system evolution during ICU stay and to determine the role of polyviral reactivations.

Acute Respiratory Distress Syndrome: Performance of Ventilator at Simulated Altitude

BACKGROUND Ventilation of Acute Respiratory Distress Syndrome (ARDS) is a challenge, and there is definitely a need for lack of variations between delivered and set tidal volume (Vt). We have assessed the ability of the ventilator T-birdVS02 and LTV-1000 to deliver to a lung model with ARDS a set Vt at different simulated altitudes. METHODS We used a decompression chamber to mimic the hypobaric environment at a range of simulated cabin altitudes of 1,500, 2,500, and 3,000 m (4,000, 6,670, and 8,000 feet, respectively). Ventilators were tested with realistic parameters. Vt was set at 400 mL and 250 mL in an ARDS lung model. Comparisons of preset to actual measured values were accomplished using a t test for each altitude. RESULTS The T-birdVS02 showed a decrease in the volume delivered. Comparisons of actual delivered Vt and set Vt demonstrated a significant difference starting at 1,500 m for a Vt set of 400 mL and at 2,500 m for Vt set of 250 mL. At these altitudes, the variations between Vt set and delivered were more than 10%. With decreasing barometric pressure, the LTV-1000 showed mostly an increase in volume delivered. Comparisons of actual delivered Vt and set Vt demonstrated a significant difference at 2,500 m for a Vt set of 400 mL and at 3,000 m for Vt set of 250 mL. The delivered Vt remained within 10% of the set Vt. CONCLUSION Clinicians involved in aerial evacuations must keep in mind the performance and limitations of their ventilator system.

Inhibitors of angiogenesis: new hopes for oncologists, new challenges for anesthesiologists.

ANESTHESIOLOGISTS are involved in many aspects of cancer treatment that may interfere with perioperative care. Some of these treatment considerations may have a major impact on patient outcomes. Basic research in oncology has recently led to a wealth of knowledge about novel biologic pathways for more efficient and selective tumor cell targeting. Antiangiogenic therapy has demonstrated significant activity in patients with solid tumors, such as metastatic breast cancer, renal cell carcinoma, brain tumors, non-small-cell lung cancers, and colorectal carcinoma (table 1). By targeting vascular endothelial growth factor (VEGF), these agents have demonstrated clinical efficacy in medical oncology. However, angiogenic factors are also involved in a number of physiologic processes, including tissue remodeling and wound repair. The VEGF family consists of seven related glycoproteins (VEGF-A, B, C, D, E, and placenta growth factors 1 and 2). Commonly referred to as VEGF, VEGF-A was initially identified by its ability to increase vascular permeability. The most important effects of VEGF include endothelial cell activation, tumor growth, and cell migration. The physiologic function of VEGF is to generate new blood vessels after injury to promote collateral circulation. Its production is induced in hypoxic cells through hypoxia-inducible factor (HIF) production. Circulating VEGF then binds to VEGF receptors on endothelial cells, leading to angiogenesis. Two main anti-VEGF strategies have been developed over recent years: neutralizing anti-VEGF antibody and small molecule tyrosine kinase inhibitors (TKI) targeted against VEGF receptors. While potentially improving overall survival, inhibitors of VEGF are subject to considerable uncertainty concerning their potential toxicity. An increase in wound complications and thromboembolic events has been observed in patients who undergo surgery while receiving inhibitors of angiogenesis. This paper highlights the toxicities of VEGF inhibitors, with special focus on consequences for anesthesiologists.

Acute severe asthma: performance of ventilator at simulated altitude.

Objective Exacerbation of asthma can be seen during air transport. Severe patients, not responding to conventional therapy, require ventilator support. We evaluated the performance of two transport ventilators, built with turbine technology, the T-birdVSO2 and the LTV-1000, for use during aeromedical evacuation of acute severe asthma. We have assessed the ability of both the ventilators to deliver to an acute severe asthma model a tidal volume (Vt) set at different simulated altitudes, by changing the ambient air pressure. Methods The simulated cabin altitudes were 1500, 2500, and 3000 m (decompression chamber). Vt was set at 700 and 400 ml in an acute severe asthma lung model. Comparisons of the preset with the actual measured values were accomplished using a t-test. Results Comparisons between the actual delivered Vt and set Vt showed a significant difference starting at 1500 m for both the ventilators. The T-birdVSO2 showed a decrease in the volume delivered, with a negative variation of more than 10% compared with the Vt set. The LTV-1000 showed mostly an increase in the volume delivered. The delivered Vt remained within 10% of the set Vt. Conclusion The accuracy of Vt delivery was superior with the LTV-1000 than with the T-birdVSO2, but the higher delivered Vt of the LTV-1000 are likely to be more harmful than lower delivered Vt of the T-birdVSO2.

Full-field OCT technique for high speed event-based optical flow and particle tracking

This article introduces a method to extract the speed and density of microparticles in real time at several kHz using an asynchronous event-based camera mounted on a full-field optical coherence tomography (FF-OCT) setup. These cameras detect significant amplitude changes, allowing scene-driven acquisitions. They are composed of an array of autonomously operating pixels. Events are triggered when an illuminance change at the pixel level is significant at 1μs time precision. The event-driven FF-OCT algorithm relies on a time-based optical flow computation to operate directly on incoming events and updates the estimation of velocity, direction and density while reducing both computation and data load. We show that for fast moving microparticles in a range of 0.4 - 6.5mm/s, the method performs faster and more efficiently than existing techniques in real time. The target application of this work is to evaluate erythrocyte dynamics at the microvascular level in vivo with a high temporal resolution.

Intestinal microcirculation and mucosal oxygenation during hemorrhagic shock and resuscitation at different inspired oxygen concentrations

BACKGROUND Hypotensive resuscitation is the standard of care of hemorrhagic shock resuscitation. The optimal level of arterial pressure is debated and there is a lack of data on relationships between arterial pressure, microcirculation and tissue oxygenation. We investigated the relationship between mean arterial pressure, intestinal microcirculation and mucosal oxygen tension during hemorrhagic shock and resuscitation at different inspired oxygen fraction concentration. METHODS The study was divided into two phases: 32 mice were progressively exsanguinated and then transfused in mean arterial pressure (MAP)-titrated steps of 10 mm Hg. Mice were randomized to four experimental groups: a control group in which sham mice underwent a laparotomy and three interventional groups with a common phase of exsanguination followed by progressive resuscitation at three different inspired oxygen concentrations (FIO2) (15%, 30%, and 100%). Intestinal mucosal oxygenation (intestinal PO2) and microcirculatory parameters were recorded at each 10 mm Hg MAP step. RESULTS During exsanguination, intestinal PO2 decreased linearly with MAP levels. Microcirculatory parameters decreased nonlinearly with MAP levels while they had a linear relationship with intestinal PO2. Intestinal mucosal hypoxia (PO2 ⩽ 20 mm Hg) began at a MAP of 60 mm Hg and MAP < 60 mm Hg was associated with a high percentage of animal with intestinal hypoxia (≥32%). Combination of MAP and microcirculatory parameters was superior to MAP alone at predicting mucosal oxygenation. Inversely, during resuscitation with FIO2 = 30%, the microcirculatory parameters increased linearly with MAP levels while they had a nonlinear relationship with intestinal PO2. Hypoxia (FIO2 = 15%) was poorly tolerated. In hyperoxic group (FIO2 = 100%) intestinal PO2 became significantly higher than baseline values as soon as 50 mm Hg MAP. CONCLUSION During hemorrhagic shock, intestinal PO2 decreased linearly with MAP levels and microcirculatory parameters. Associating MAP and microcirculatory parameters allowed a better prediction of intestinal PO2 than MAP alone. A MAP < 60 mm Hg was associated with a high percentage of animal with intestinal hypoxia. Normoxic resuscitation (FIO2 = 30%) was sufficient to restore intestinal PO2.

Acute kidney injury in trauma patients

Purpose of review To review epidemiology and pathophysiology of acute kidney injury (AKI) in trauma patients and propose strategies that aim at preventing AKI after trauma. Recent findings AKI in trauma patients has been reported to be as frequent as 50% with an association to a prolonged length of stay and a raise in mortality. Among the specific risk factors encountered in trauma patients, hemorrhagic shock, rhabdomyolysis severity, age, and comorbidities are independently associated with AKI occurrence. Resuscitation with balanced solutes seems to have beneficial effects on renal outcome compared with NaCl 0.9%, particularly in the context of rhabdomyolysis. However, randomized clinical studies are needed to confirm this signal. Abdominal compartment syndrome (ACS) is rare but has to be diagnosed to initiate a dedicated therapy. Summary The high incidence of AKI in trauma patients should lead to early identification of those at risk of AKI to establish a resuscitation strategy that aims at preventing AKI.

A simulator-based study of in-flight auscultation.

Introduction The use of a stethoscope is essential to the delivery of continuous, supportive en route care during aeromedical evacuations. We compared the capability of 2 stethoscopes (electronic, Litmann 3000; conventional, Litmann Cardiology III) at detecting pathologic heart and lung sounds, aboard a C135, a medical transport aircraft. Methods Sounds were mimicked using a mannequin-based simulator SimMan. Five practitioners examined the mannequin during a fly, with a variety of abnormalities as follows: crackles, wheezing, right and left lung silence, as well as systolic, diastolic, and Austin-Flint murmur. The comparison for diagnosis assessed (correct or wrong) between using the electronic and conventional stethoscopes were performed as a McNemar test. Results A total of 70 evaluations were performed. For cardiac sounds, diagnosis was right in 0/15 and 4/15 auscultations, respectively, with conventional and electronic stethoscopes (McNemar test, P = 0.13). For lung sounds, right diagnosis was found with conventional stethoscope in 10/20 auscultations versus 18/20 with electronic stethoscope (P = 0.013). Conclusions Flight practitioners involved in aeromedical evacuation on C135 plane are more able to practice lung auscultation on a mannequin with this amplified stethoscope than with the traditional one. No benefit was found for heart sounds.

The prevalence of burnout

Dear Editor, We followed with interest the correspondence between Laurent et al. and Hawryluck and Brindley about estimates of the prevalence of burnout [1]. Of course, we do agree that burnout remains poorly defined and that relying on the Maslach Burnout Inventory (MBI) raises unresolved issues [2]. Nevertheless, in a study published in the main French journal of anesthesia, involving more than 1500 anesthetists, nurses, and intensivists, we observed that values in the three MBI subscales were correlated with the number of affected dimensions and closely linked with many markers of illbeing [3]. Moreover, a Gaussian-like distribution (Fig. 1) was testament to the continuous and progressive nature of burnout, and this paradigm contradicted the usual dichotomic handling. Our work included the Fast Alcohol Consumption Evaluation (FACE) and the Harvard Department of Psychiatry and National Depression Screening Day Scale (HANDS). According to the thresholds proposed by Maslach [3], 67% of the 241 intensivists were in burnout. Depression was observed in 36% of them, 6% were addicted to alcohol, and 4% were addicted to drugs or chemicals. Of interest, 6% had high scores in the three MBI dimensions, with a strong correlation between scores and conflicts, sleep disturbances, depression, psychiatric history, and suicidal ideations. Addiction or road accidents after a nightshift increased with the number of dimensions involved without reaching statistical significance (Fig. 1). Although the MBI cannot directly tell investigators when exhaustion or depersonalization reach clinically relevant levels, it should definitely raise the alarm when the three dimensions of the inventory together reach the thresholds suggested by Maslach. This condition was related to alarming mental and health counterparts in our cohort (Fig. 1). So, rather than ever inflating the rates of detected burnout (the “bubble” rightly highlighted by Laurent et al.), investigators should focus on new definitions of cutoff values, pointing to a subpopulation at risk not only of burnout but also meaningful complications. Moreover, to prevent severe deterioration [5], we believe caregivers should perform the MBI at least once a year as part