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Biomedical subjects

F Piquard

Publications and source records attributed to F Piquard.

At least 55 records · Page 3Linked to original sources
PubMed1998

Normal short-term renal response to acute volume expansion in heart transplant recipients: a role for atrial natriuretic peptide?

BACKGROUND: The breakdown of blood pressure and body fluid homeostasis observed in heart transplant (Htx) recipients may partly be due, as in heart failure, to a blunted renal response to elevated atrial natriuretic peptide (ANP). METHOD: This possibility was addressed through determination of the relationship between ANP, the urinary cyclic guanosine monophosphate (cGMP), a biologic marker of ANP renal activity, and the early renal responses to 10 mL/kg isotonic saline infusion over 30 minutes in 8 control subjects and 8 matched Htx recipients. RESULTS: Urine flow, natriuresis, and urinary cGMP excretion increased similarly in both groups, resulting in elimination of, respectively, 1/2 and 2/3 of the sodium and the water load during the experiment that lasted 4 hours and 30 minutes. Plasma renin and aldosterone decreases were similar in both groups. Elevated ANP further increased in Htx after saline infusion (from 19.5 +/- 3.7 to 33.8 +/- 5.6 pmol/L, P < .001). Plasma cGMP paralleled ANP in both groups (r = 0.81; P < .001). Significant correlations were observed between plasma ANP and urinary cGMP excretion (r = 0.48, P < .025 and r = 0.43, P < .05 in Htx recipients and control subjects) and between plasma ANP and urinary sodium excretion (r = 0.64, P < .001 in Htx recipients). CONCLUSION: In spite of a relative renal hyporesponsiveness to the cardiac hormone, with higher plasma ANP being not associated with increased renal excretions in Htx recipients, ANP is likely to participate in the appropriate short-term renal response to acute volume expansion in Htx recipients.

Aldosterone↗
PubMed1997

Safety of a new transpulmonary echocontrast agent (Albunex) in repeated echocardiographic studies in patients.

BACKGROUND AND HYPOTHESIS: Multiple contrast-enhanced echocardiographic studies are to be expected in patients with cardiac ischemic disease, but the sonication process used to produce the echocontrast agent Albunex may result in new epitopes that could cause an immunogenic response. METHODS: Repeated exposures to intravenous Albunex over a period of time long enough to allow development of an eventual immune reaction were performed in 12 patients while monitoring for lymphocyte transformation, microsphere specific IgE and IgG antibodies, and systemic, pulmonary artery, capillary wedge, and right atrial pressures, as well as cardiac output, left ventricular fractional shortening, and blood gases. RESULTS: No significant 3H-thymidine incorporation and thus no specific blastic transformation of the patients' lymphocytes were observed either for high or low Albunex concentrations, corresponding to the expected hepatic and plasma concentrations of microspheres. No formation of microsphere-specific IgE and IgG antibodies was observed after the first or second Albunex exposure. Furthermore, no clinically significant hemodynamic or respiratory adverse reactions were observed in any patient. CONCLUSION: These results suggest that repeated exposures to intravenous Albunex induce no adverse effect on the cellular and humoral immune systems and on left and right heart hemodynamics in patients.

Albumins↗
PubMed1997

Contrast echocardiography in coronary artery diseased patients: effect of systemic and pulmonary artery pressures on left heart opacification after intravenous injection of Albunex.

BACKGROUND: Contrast echocardiography is a useful tool for assessing repeatedly patients with coronary artery disease. Nevertheless, elevated pulmonary artery and systemic blood pressures likely to be associated with cardiac ischemia may limit the left ventricular opacification (LVO) because of the microspheres' sensitivity to pressure. OBJECTIVE: To determine the effects of systemic and pulmonary artery blood pressures on LVO. METHODS: We performed 55 intravenous injections (0.08 and 0.22 ml/kg) of a new transpulmonary contrast agent (Albunex), during two separated exposures, into 20 cardiac ischemic patients while monitoring invasively their cardiac indexes, and intracardiac, systemic, and pulmonary artery blood pressures. LVO was graded qualitatively from faint to full. RESULTS: A logistic model with the grade of LVO as the dependent variable and a selection from among the dose, exposure, right and left atrial blood pressures, systolic systemic and pulmonary artery blood pressures (ranges 94-208 and 14-45 mmHg, respectively), cardiac index, stroke index, and pulmonary and systemic vascular resistances as the explanatory variables demonstrated that increasing the dose gives an increasing probability of LVO (P = 0.02) and that increasing the pulmonary artery pressure reduces that probability (P = 0.006). A decreased cardiac index tended also to be associated with decreased LVO. The systemic blood pressure and the pulmonary and systemic vascular resistances had no statistically significant effect on the grade of LVO. CONCLUSIONS: LVO after intravenous administration of Albunex is dose-dependent and limited by an elevated pulmonary artery pressure. These data suggest that one should use higher doses for cardiac ischemic patients with elevated pulmonary artery pressures and that use of Albunex has the potential to detect pulmonary hypertension in patients.

Adult↗
PubMed1996

Atrial natriuretic factor secretion: a role for atrial systolic ejection force?

The increase in plasma concentration of atrial natriuretic factor in heart transplant patients has not been fully elucidated. Besides an eventual pressure or volume overload leading to passive atrial distension, the atrial tension developed during atrial systole, or atrial ejection force, which may be increased by the transplantation procedure, is an important determinant of atrial natriuretic factor release. We therefore determined the plasma concentration of atrial natriuretic factor and the maximal atrial ejection force in 15 heart transplant patients and 8 controls, matched for age and body mass. Atrial ejection force, as defined as the force exerted by the left atrium to accelerate blood into the left ventricle during atrial systole, was obtained using combined two-dimensional imaging and doppler echocardiography. Serum creatinin concentrations, heart rate [91.9 (SD 13.2) vs 71.8 (SD 10.9) beats.min-1], mean arterial blood pressure [103.9 (SD 9.8) vs 87.4 (SD 5.8) mmHg, 13.85 (SD 1.31) vs 11.65 (SD 0.77) kPa], left ventricular posterior wall thickness and interventricular septum thickness were higher in heart transplant patients compared to controls. Plasma concentration of atrial natriuretic factor was also elevated in heart transplant patients [63.9 (SD 18.1) vs 34.0 (SD 3.2) pg.ml-1; P < 0.001]. In contrast, although the left atrial area was greater in heart transplant patients [28.2 (SD 4.8) vs 15.8 (SD 2.5) cm2; P < 0.001], mitral area, transmitral Doppler A-wave maximal velocity and atrial ejection force were similar in transplant and in control patients [7.7 (SD 3.5) vs 8.9 (SD 2.8) kdyn, 77 (SD 35) vs 89 (SD 28)mN]. No significant correlation was observed between concentration of atrial natriuretic factor and atrial ejection force, either in heart transplant patients or in controls. Thus, the elevated plasma concentration of atrial natriuretic factor observed in these heart transplant patients was multifactorial in origin, and was considered to depend upon an hypersecretion rather than upon a decreased clearance rate. Moreover, it is suggested that the atrial ejection force was unlikely to have participated in this enhanced release of atrial natriuretic factor.

Adult↗
PubMed1996

Effect of short-term endurance training on exercise capacity, haemodynamics and atrial natriuretic peptide secretion in heart transplant recipients.

Exercise tolerance of heart transplant patients is often limited. Central and peripheral factors have been proposed to explain such exercise limitation but, to date, the leading factors remain to be determined. We examined how a short-term endurance exercise training programme may improve exercise capacity after heart transplantation, and whether atrial natriuretic peptide (ANP) release may contribute to the beneficial effects of exercise training by minimizing ischaemia and/or cardiac and circulatory congestion through its vasodilatation and haemoconcentration properties. Seven heart transplant recipients performed a square-wave endurance exercise test before and after 6 weeks of supervised training, while monitoring haemodynamic parameters, ANP and catecholamine concentrations. After training, the maximal tolerated power and the total mechanical work load increased from 130.4 (SEM 6.5) to 150.0 (SEM 6.0) W (P < 0.05) and from 2.05 (SEM 0.1) to 3.58 (SEM 0.14) kJ.kg-1 (P < 0.001). Resting heart rate decreased from 100.0 (SEM 3.4) to 92.4 (SEM 3.5) beats.min-1 (P < 0.05) but resting and exercise induced increases in cardiac output, stroke volume, right atrial, pulmonary capillary wedge, systemic and pulmonary artery pressures were not significantly changed by training. Exercise-induced decrease of systemic vascular resistance was similar before and after training. After training arterio-venous differences in oxygen content were similar but maximal lactate concentrations decreased from 6.20 (SEM 0.55) to 4.88 (SEM 0.6) mmol.l-1 (P < 0.05) during exercise. Similarly, maximal exercise noradrenaline concentration tended to decrease from 2060 (SEM 327) to 1168 (SEM 227) pg.ml-1. A significant correlation was observed between lactate and catecholamines concentrations. The ANP concentration at rest and the exercise-induced ANP concentration did not change throughout the experiment [104.8 (SEM 13.1) pg.ml-1 vs 116.0 (SEM 13.5) pg.ml-1 and 200.0 (SEM 23.0) pg.ml-1 vs 206.5 (SEM 25.9) pg.ml-1, respectively]. The results of this study suggested that the significant improvement in exercise capacity observed after this short-term endurance training period may have arisen mainly through peripheral mechanisms, associated with the possible decrease in plasma catecholamine concentrations and reversal of muscle deconditioning and/or prednisone-induced myopathy.

Adult↗
PubMed1993

Safety and efficacy of a new transpulmonary echo contrast agent in echocardiographic studies in patients.

OBJECTIVES: This study was designed to investigate in patients the effect of a new transpulmonary echo contrast agent, made from 5% human serum albumin (Albunex), on systemic and pulmonary hemodynamics and the influence of the contrast doses on left ventricular opacification. BACKGROUND: New intravenous transpulmonary echo contrast agents are promising, allowing contrast stress echocardiography and myocardial contrast echocardiography. Nevertheless, some shortcomings still remain. Thus, the pulmonary hypertension observed in pigs after Albunex injection should be investigated in humans, and the optimal dose of contrast agent remains to be determined because previous experiments indicated that the left ventricular opacification and attenuation are dose dependent. METHODS: Albunex in doses of 0.08 and 0.22 ml/kg was successively injected intravenously in 20 catheterized patients; in 11 of them, anti-inflammatory drugs were withdrawn to avoid the blocking of an eventual thromboxane-mediated pulmonary artery hypertension. Systemic blood pressure and pulmonary artery, capillary wedge and right atrial pressures were continuously monitored. Cardiac output, left ventricular fractional shortening and blood gases were determined 5 min before and 5 and 10 min after each injection. The left ventricular opacification was qualitatively assessed by three independent observers using a grading scale from 0 to 3, with 0 indicating an absence of contrast effect and 3 indicating full opacification. RESULTS: No clinical, hemodynamic or respiratory adverse reactions were observed in any patient. Irrespective of doses, a left ventricular opacification grade > or = 2 was observed in 74% of the 35 injections that could be evaluated. This percentage increased to 94% when the higher dose group was considered alone. CONCLUSIONS: This first report of the effect of Albunex injected intravenously on pulmonary artery pressures in humans demonstrates that this contrast agent appears to be safe. The significant left ventricular opacification obtained in a majority of patients without an important increase in attenuation supports the use of the higher dose of the contrast agent.

Albumins↗
PubMed1993

Role of cardiac innervation in atrial natriuretic peptide secretion in transplanted heart recipients.

To investigate whether cardiac innervation modulates atrial natriuretic peptide (ANP) secretion, we performed acute volume expansion on eight normal and eight matched (age, weight, and total blood volume) transplanted denervated heart patients (Htx), while monitoring fluid-regulating hormone, systemic blood pressure, and echocardiographic atrial area changes. At rest, plasma ANP and guanosine 3',5'-cyclic monophosphate (cGMP) were lower in control subjects than in Htx (45 +/- 16 vs. 103 +/- 35 pg/l and 0.9 +/- 0.3 vs. 3.5 +/- 1.4 pM, respectively; P < 0.001). Plasma active renin, aldosterone, and catecholamines did not differ significantly in the two populations, whereas arginine vasopressin and cortisol were higher in controls (P < 0.01 and P < 0.005). Although volume expansion (+15%) and atrial stretch were similar in the two groups, plasma ANP and cGMP increased significantly only in the Htx group (103 +/- 35 to 189 +/- 69 pg/l and 3.5 +/- 1.4 to 5.8 +/- 1.4 pM, respectively; P < 0.001). The decrease observed for the other hormones was not significant except for arginine vasopressin and cortisol (P < 0.05 and P < 0.001) in the control group. These results support the hypothesis of an inhibitory role of cardiac innervation in biologically active ANP secretion in humans, at rest and after acute volume expansion.

Adult↗
PubMed1991

Is fetal acidosis in the human fetus maternogenic during labor? A reanalysis.

The purpose of this study was to investigate whether maternogenic fetal acidosis can occur at the time of labor and delivery and to evaluate the extent of the possible maternal contribution to fetal acidosis. We have therefore determined fetal and maternal lactate concentrations and acid-base status under various conditions in 589 women at the end of gestation and during labor. The results show that metabolic acidosis develops in all fetuses because of increased production of lactic acidosis is primarily of fetal origin: 1) the umbilical arteriovenous lactate differences were positive and large in steady-state conditions as well as in depressed newborns; 2) the conditions that could produce a net transfer of lactate from the mother to the fetus, namely a positive maternofetal gradient of lactate and proton, were rarely observed; and 3) the correlation between fetal and maternal lactate levels was very weak, with regression coefficients decreasing from near steady-state conditions to acute stress conditions, indicating that the increase in lactate in the fetus and mother occurs independently. This correlation indicates also that increased maternal lactate production under conditions of labor and delivery can make a contribution by affecting the rate of net transfer from fetus to mother. This is possible in approximately 6% of the fetuses.

Acidosis↗
PubMed1990

The effects of changes in plasma amino acid concentrations on erythrocyte amino acid content.

In order to determine the effects of large variations in plasma amino acid concentrations upon human erythrocyte amino acid content, the plasma concentration of blood samples was enhanced (x 3.8) by adding amino acids or decreased (x 0.49) by plasma dilution. Before and after incubation (30 s at 37 degrees C), the erythrocyte contents were calculated from whole blood and plasma amino acid concentrations. Large and rapid plasma concentration variations led to significant erythrocyte changes in 11 amino acids. THR, CIT, alpha AB, VAL, MET, ILE, LEU, TYR, PHE, TRP, and ARG. Relationships between erythrocyte and plasma concentrations were determined for these amino acids. These observations were examined in the light of the role played by erythrocytes in blood amino acid transport.

Amino Acids↗
PubMed1990

Lactate movements in the term human placenta in situ.

Movements of lactate through the human placenta in situ were derived from maternal and fetal blood sampling performed under conditions that approximate as closely as possible the normal fetal metabolic state. It is reported that, at the end of pregnancy, the human fetus produces lactate which is transferred to the placenta. The actuality of this lactate transfer coupled with proton transfer is discussed taking into account the results of multiple linear regression analysis determined between the umbilical arterio-venous lactate differences and fetal and maternal lactate and proton concentrations. It is finally assumed that this lactate is partly metabolized in the placenta, the remaining part being transferred from the placenta to the mother.

Adult↗
PubMed1989

Are there two biological parts in the second stage of labor?

In 228 patients, fetal blood pH, pCO2 and lactic acid were measured in two distinguishable parts of the second stage of labor. The 'first' part begins at full cervical dilatation and ends when the mother starts her first voluntary bearing down efforts. In our study, the fetal acid-base status did not change in this part, regardless of a late developing hypoxia. In contrast, higher levels of lactic acid and pCO2 and lower pH values were observed in the 'final' part of the second stage, indicating increasing acidosis. In this 'final' part, the fetuses with clinical signs of distress, as defined by an ominous Apgar score at birth, showed quicker and larger acid-base shifts than did the normal fetuses. Thus the two parts of the second stage of labor actually differ in their potential to stimulate fetal acidosis. Since such fetal acidosis may develop especially during the 'final' part of labor, we have concluded that special particular attention should be devoted to this part.

Acid-Base Equilibrium↗
PubMed1989

Does fetal acidosis develop with maternal glucose infusion during normal labor?

The actual effects of glucose infusion on fetal acid-base status were studied during 125 normal deliveries in which plasma glucose and acid-base parameters were determined after maternal infusion of either 10% glucose or Ringer's solution. After 80 minutes, mean (+/- SD) plasma glucose levels were significantly higher in the glucose group (N = 59) than in the Ringer's group (N = 66), both for the mother (183.6 +/- 46.8 versus 95.3 +/- 18.0 mg/dL) and the fetus (108.4 +/- 41.4 versus 64.8 +/- 16.2 mg/dL). Fetal plasma lactate concentrations did not differ between the glucose and the Ringer's groups, but were significantly lower in the fetuses delivered by elective cesarean section in both groups. With glucose administration, fetal pCO2 was higher and pH values were lower than in the Ringer's group. However, the magnitude of acid-base status changes, indicated by both pH and pCO2 shifts (ie, the difference between umbilical artery and scalp values), failed to differ between the two groups. In fetuses with progressing hypoxia, no differences in any of the acid-base parameters were observed between glucose and Ringer's administration. These data indicate that at a glucose infusion rate of 30 g/hour, fetal acidosis, when it occurs, results from hypoxia rather than from maternal glucose administration.

Acidosis↗
PubMed1988

The validity of fetal heart rate monitoring during the second stage of labor.

Fetal blood pH, pCO2, and lactic acid were measured before and after the final period of the second stage of labor in an attempt to better understand th validity fetal heart rate (FHR) monitoring at this time. Following a classification derived from Melchior, six FHR patterns were recognized: 0, 1, 2a, 2b, 3, and 4. In the second stage of labor, until bearing-down efforts began, the fetal acid-base status did not change regardless of the type of tracing. At the time of delivery, as compared with values measured before the beginning of the final stage, the highest shift of lactic acid, coupled with the lowest pH shift, was associated with the type 3 pattern. The most rapid increases of lactic acid and pCO2 and decreases in pH were associated with type 2b patterns. Both type 3 and 2b patterns were ominous, but low Apgar scores were more frequent in type 3 because the duration of the final stage of labor was longer. Working from the mean slopes of the shifts of biologic parameters as a function of time, theoretical limits were derived and discussed for safe duration of the final stage of labor.

Adult↗
PubMed1987

Plasma amino-acids analysis: effects of delayed samples preparation and of storage.

This paper describes changes occurring in plasma amino-acid concentrations of: samples which are not prepared for analysis immediately after blood collection and samples stored for 5 to 6 months in the form of either plasma, or of deproteinized plasma, or of deproteinized and at pH 2.2 buffered plasma. Results showed that in order to avoid these changes, plasma should be deproteinized and buffered as soon as possible after blood collection. When analysis could not be performed immediately, storage of samples in a freezer at -18 degrees C in the form of deproteinized and at pH 2.2 buffered plasma showed after 5 to 6 months the best recovery of the initial concentrations, but did not exclude all changes.

Amino Acids↗
PubMed1980

Rapid bedside estimation of plasma and whole blood lactic acid.

A rapid method for the bedside measurement of plasma, intracellular and whole blood lactates is described. The paper described a new method of measuring the L-lactate content of blood using an apparatus ("Lactate Analyzer 640", manufactured by Roche Bio-electronics, Basel) previously designed for this purpose but using aqueous solutions. A novel feature of this new method is the facility to use small blood samples (100-150 mul). We therefore believe that it will become an invaluable tool in obstetrics and neonatology.

Erythrocytes↗
PubMed1980

Spontaneous activity and food requirements for maintenance and for growth in the genetically obese Zucker rat.

This study was undertaken in order to elucidate whether, as compared with those of their lean controls, the low maintenance requirements of genetically obese Zucker rats may be explained by a lower spontaneous activity. In 6 obese and 6 lean rats, daily body weight, food intake and spontaneous activity were recorded during 6 weeks, using a seismographic recorder. The obese rats weighed more (average + 46%) and ate more (average + 42%) than the lean rats, while there was no difference between their daily activity levels. The relationship between food intake (FI) and weight gain (delta W), both expressed per 100 g body weight, was: FI (kcal/day) = 3.3 delta W (g/day) + 20.4 for lean rats and 4.9 delta W (g/day) + 17.4 for obese rats. Thus, the food requirements for maintenance obtained for delta W = O was less than for obese than for lean rats, while for a given gain in body weight, it was higher for obese rats. This did not seem to be because of a lower daily activity level in the obese than in the lean rats.

Animals↗