Use of speckle-tracking strain in preload-dependent patients, need for cautious interpretation!

BACKGROUND: In critical patients, left ventricular ejection fraction and fractional shortening are used to reflect left ventricular systolic function. An emerging technique, two-dimensional-strain echocardiography, allows assessment of the left ventricle systolic longitudinal deformation (global longitudinal strain) and the speed at which this deformation occurs (systolic strain rate). This technique is of increasing use in critical patients in intensive care units and in the peri-operative period where preload constantly varies. Our objective, in this prospective single-center observational study, was to evaluate the effect of fluid resuscitation on two-dimensional-strain echocardiography measurements in preload-dependent critically ill patients. We included 49 patients with preload dependence attested by an increase of at least 10% in the left ventricular outflow track velocity-time integral measured by echocardiography during a passive leg raising maneuver. Echocardiography was performed before fluid resuscitation (echocardiography 1) and after preload independency achievement (echocardiography 2). RESULTS: Two-dimensional-strain echocardiography was feasible in 40 (82%) among the 49 patients. With preload dependence correction, the absolute value of global longitudinal strain and systolic strain rate was significantly increased from, respectively, - 13.3 ± 3.5 to - 18.4% ± 4.5 (p < 0.01) and - 1.11 s-1 ± 0.29 to - 1.55 s-1 ± 0.55 (p < 0.001). The fluid resuscitation affects GLS and SSR in preload-dependent patients, with a shift, for GLS, from pathological to normal values. CONCLUSION: In critically ill patients, the assessment of the systolic function by two-dimensional-strain echocardiography needs prior evaluation of preload dependency, in order to adequately interpret this variable. Future studies should assess the ability of global longitudinal strain to guide fluid management in the critically ill patients.

[Spontaneous pneumomediastinum secondary to inhalation of crack]. / Pneumomédiastin spontanée secondaire à l'inhalation de crack.

The use of cocaine causes numerous cardiovascular and pulmonary side effects. In this context, the occurrence of a pneumomediastinum represents a specific complication, often misunderstood by primary care physicians. We describe here on case of patient who suffered from subcutaneous emphysema and pneumomediastinum after smoking "crack". We emphasize the importance of always keeping in mind the possibility of illicit substance use in such cases, especially among young and healthy patients. A short observation period with outpatient follow-up is appropriate in the majority of patients. Invasive procedures have a low yield and should be based on a high degree of clinical suspicion for esophageal rupture or bronchial tree laceration.

Impact of a goal-directed therapy protocol on postoperative fluid balance in patients undergoing liver transplantation: a retrospective study.

OBJECTIVE: Liver transplantation carries major risks during the perioperative period. Few studies focused on the hemodynamics of patients undergoing liver transplantation. The present study was aimed to evaluate the impact of the implementation of a protocol including goal-directed therapy in patients undergoing liver transplantation. Our first goal was to determine its impact on the fluid balance. Secondarily, we evaluated possible improvements in the patient outcomes. STUDY DESIGN: A before and after study. PATIENTS AND METHODS: Fifty patients undergoing liver transplantation were included during two successive six-month periods. During the first period, the management of the patients was left at the discretion of the senior physicians (control group, n=25). During the second period, the patients were treated according to a predetermined protocol including a specific hemodynamic monitoring (protocol group, n=25). RESULTS: The fluid balance was negative in the protocol group and positive in the control group at 24h (-606mL vs. +3445mL, P<0.01) and 48h (-2315mL vs. +1170mL, P<0.01) after liver transplantation. The volume of the crystalloid administration was lower in the protocol group than in the control group (5000mL vs. 8000mL, P<0.01, and 1500mL vs. 6000mL, P<0.01, during surgery and 48h after liver transplantation, respectively). The duration of mechanical ventilation and postoperative ileus were significantly reduced in the protocol group, as compared with the control group, 20h vs. 94h (P<0.01) and 4days vs. 6days (P<0.01), respectively. CONCLUSION: For patients undergoing liver transplantation, the implementation of a protocol aiming to optimize hemodynamics was associated with reduced fluid balance and decreased requirement for mechanical ventilation and postoperative ileus duration.

Hanbury Brown-Twiss correlations to probe the population statistics of GHz photons emitted by conductors.

We present the first study of the statistics of GHz photons in quantum circuits, using Hanbury Brown and Twiss correlations. The super-Poissonian and Poissonian photon statistics of thermal and coherent sources, respectively, made of a resistor and a radio frequency generator, are measured down to the quantum regime at milli-Kelvin temperatures. As photon correlations are linked to the second and fourth moments of current fluctuations, this experiment, which is based on current cryogenic electronics, may become a standard for probing electron/photon statistics in quantum conductors.

Quantum partition noise of photon-created electron-hole pairs.

We show experimentally that even when no bias voltage is applied to a quantum conductor, the electronic quantum partition noise can be investigated with GHz radio frequency excitation. Using a quantum point contact configuration as the ballistic conductor we are able to make an accurate determination of the partition noise Fano factor resulting from the photon-assisted shot noise. Applying both voltage bias and rf irradiation we are able to make a definitive quantitative test of the scattering theory of photon-assisted shot noise.