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F Brunet

Publications and source records attributed to F Brunet.

81 records · Page 5Linked to original sources
PubMed1986

Mechanisms of decreased left ventricular preload during continuous positive pressure ventilation in ARDS.

Continuous positive pressure ventilation is associated with a reduction in left ventricular preload and cardiac output, but the mechanisms responsible are controversial. The decrease in left ventricular preload may result exclusively from a decreased systemic venous return due to increased pleural pressure, or from an additional effect such as decreased left ventricular compliance. To determine the mechanisms responsible, we studied the changes in cardiac output induced by continuous positive pressure ventilation in eight patients with the adult respiratory distress syndrome. We measured cardiac output by thermodilution, and biventricular ejection fraction by equilibrium gated blood pool scintigraphy. Biventricular end-diastolic volumes were then calculated by dividing stroke volume by ejection fraction. As positive end-expiratory pressure increased from 0 to 20 cm H2O, stroke volume and biventricular end-diastolic volumes fell about 25 percent, and biventricular ejection fraction remained unchanged. At 20 cm H2O positive end-expiratory pressure, volume expansion for normalizing cardiac output restored biventricular end-diastolic volumes without markedly changing biventricular end-diastolic transmural pressures. The primary cause of the reduction in left ventricular preload with continuous positive pressure ventilation appears to be a fall in venous return and hence in right ventricular stroke volume, without evidence of change in left ventricular diastolic compliance.

Adult↗
PubMed1984

Oxygen consumption during septic shock. Effects of inotropic drugs.

Septic shock may be defined as a clinical entity wherein a patient has an inadequate peripheral metabolism in the presence of circulating bacteria. The demands for metabolic requirements of the tissues and hence for oxygen transport to these tissues are then markedly high. The average response to increased metabolism in such patients is a percentage increase in cardiac output that is comparable to the percentage increase in oxygen consumption while oxygen extraction rate does not change or even decreases in severe or/and advanced septic shock. This emphasizes the high priority placed by the body on the ability to increase blood flow from the heart in the presence of increased metabolic demands due to sepsis. Concerning the myocardium, oxygen consumption is low in hyper- and hypodynamic states of septic shock, probably and partially due to marked arterial vasodilatation. However, in hypodynamic states, the lower value of perfusion pressure may account for a decrease in myocardial oxygen supply, especially in subendocardial areas and may be responsible for myocardial ischaemia, more especially as myocardial oxygen extraction as well as systemic oxygen extraction is impaired. The goal of therapeutics is to improve oxygen availability through: (1) maintenance of haemoglobin levels and (2) increases in stroke volume using inotropic drugs since these drugs may produce a rise in myocardial oxygen supply higher than their drug-induced increase in oxygen requirements in hypodynamic states of septic shock.

Blood Pressure↗
PubMed1984

[Valve replacement, a possible factor in myocardial deterioration].

Cardiopulmonary bypass (CPB) may be a cause of myocardial damage in a small number of patients undergoing valve replacement (4 out of 1576 valve replacements). The responsibility of CPB can only be presumed when: the degree of myocardial dysfunction after surgery can be quantified, other causes of myocardial dysfunction are excluded. the type of valvular disease is taken into consideration. Variations in load after correction of certain lesions (mitral regurgitation) makes changes of LV systolic function difficult to interpret. The first case concerned a 23 year old patient operated for aortic regurgitation (Björk prosthesis) under local and general hypothermia and followed-up for 1 year after surgery. Ventricular extrasystoles and left bundle branch block were observed during surgery and radiological and echocardiographic LV dilatation persisted with deterioration of echographic, isotopic, haemodynamic and angiographic parameters of LV function: ejection fraction fell from 62% before surgery to 35% with diffuse hypokinesia and persistent LV dilatation (191 vs 188 ml). In the absence of prosthetic valve dysfunction, associated valve lesions or coronary artery disease, LV deterioration was attributed to CPB and inadequate myocardial protection. In two other cases (60 and 62 years) correction of aortic stenosis (Starr 1260) with coronary perfusion was followed by cardiac failure with left bundle branch block, deterioration of LV function, and death after 3 years in one case and precarious survival at 10 years in the other. In a fourth case (mixed mitral valve disease corrected by a Starr prosthesis under aortic clamping), the variation of cardiac load before and after surgery made changes in LV function difficult to interpret. (ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Superparamagnetic iron oxide: clinical time-response study.

Superparamagnetic iron oxide (AMI 25) is a promising new contrast agent for imaging the reticuloendothelial-system. Iron oxide crystals possess a large magnetic susceptibility and enhance proton relaxation rates, especially transverse relaxation (T2). In order to guide the clinical utilization of this contrast media we analyzed 4 patients with malignant lesions of the liver before and after slow intravenous administration (20 mumol Fe/kg) of AMI 25. We performed two magnetic resonance (MR) sequences at different times using a 0.35 T magnet. MR signal-to-noise ratio (SNR) of the reticuloendothelial system (particularly the liver SNR) decrease promptly. The maximum decrease in SNR (67-72% for the liver, 46-65% for the spleen, 23-41% for the bone marrow) is observed 3 h after injection (P less than 0.01). However, except the peak of contrast enhancement in T1-weighted sequences of splenic tissue, the curve describes a plateau within 30 min and 6 h, allowing a delay between injection and imaging. T2-weighted sequences give a greater contrast-to-noise ratio (CNR) by adding the spontaneous tumor contrast to the effect yielded by AMI 25. These results suggest that images must be acquired between 1 and 6 h after intravenous administration of superparamagnetic iron oxide.

Aged↗