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Biomedical subjects

B Riou

Publications and source records attributed to B Riou.

At least 37 records · Page 2Linked to original sources
PubMed2002

Effects of halothane and isoflurane on the contraction, relaxation and energetics of rat diaphragmatic muscle.

BACKGROUND: The inotropic effects of halogenated anaesthetics on diaphragmatic muscle remain a matter of debate. Their effects on its relaxation are poorly understood, although diaphragmatic relaxation is recognized as an important physiological process that may interfere with diaphragmatic performance, fatigue and arterial blood flow. METHODS: The effects of halothane and isoflurane (1 or 2 x minimum alveolar concentration [1 or 2 MAC]) on contraction and relaxation of rat diaphragm muscle strips (n = 40) were studied in vitro from force-velocity curves obtained at various loads from isotonic to isometric conditions. From these curves we determined the peak power output and the curvature. Data are mean (SD) percentage of baseline values. RESULTS: At I MAC, isoflurane and halothane induced no significant inotropic and lusitropic effects. At 2 MAC, isoflurane induced a negative inotropic effect (active force, 93(5)% of baseline). Halothane and isoflurane induced a significant decrease in the peak power output at 2 MAC (88(8) and 86(9)% of baseline; P < 0.05), without significant changes in the curvature of the force-velocity curve. At 2 MAC isoflurane under high loads and halothane under low loads induced moderate negative lusitropic effects. CONCLUSION: Halothane and isoflurane induced very moderate inotropic and lusitropic effects, suggesting that the decrease in diaphragm function observed in vivo is not related to a direct effect on diaphragmatic contractility.

Anesthetics, Inhalation↗
PubMed2002

[Acute dyspnoea in elderly patients].

There is a natural physiological decline in pulmonary function and the cardiovascular system with age. In emergency medicine, acute dyspnoea is a common problem among elderly patients. Some causes, such as pulmonary embolism and diastolic heart failure, are probably under-diagnosed. A good clinical history and examination are as important as arterial blood gas analysis, chest radiography and electrocardiography. Few studies have examined acute dyspnoea in elderly patients, except in the setting of pneumonia. Establishing the underlying diagnosis is often difficult because of atypical presentation and the interaction between cardiac and pulmonary underlying functions. This topic describes several respiratory and cardiac diseases presenting as acute dyspnoea, especially "cardiac asthma" and pulmonary embolism. The clinical usefulness of new investigations such as cardiac and lung echography, pulmonary function tests, serum Brain Natriuretic Peptide and thoracic CT scan are discussed. Further studies looking at acute dyspnoea in elderly patients are needed.

Acute Disease↗
PubMed2001

Coronary and aortic vasoreactivity protection with endothelin receptor antagonist, bosentan, after ischemia and hypoxia in aged rats.

This study investigated the effects of bosentan, a dual endothelin ET(A) and ET(B) receptor antagonist, during hypoxia-reoxygenation of senescent aorta and during ischemia-reperfusion of senescent heart. Isolated aortic rings and isolated hearts from adult and senescent rats were submitted, respectively, to hypoxia/reoxygenation (20/30 min) and to low-flow ischemia/reperfusion (45/30 min), without or with bosentan (10(-5) M). In the aorta, bosentan treatment prevented the impairment of relaxation in response to acetylcholine after hypoxia-reoxygenation at both ages. In the heart, coronary flow recovery during reperfusion, which is lower in senescents than in adults (48% vs. 76% of baseline value, respectively; P<0.05) was fully prevented by bosentan. Prevention of endothelial dysfunction during reoxygenation of hypoxic aorta and of coronary vasoconstriction during reperfusion of ischemic heart with a dual endothelin ET(A) and ET(B) receptor antagonist suggests a role of endothelin in the vulnerability of aorta to hypoxia-reoxygenation, and of coronary arteries to ischemia-reperfusion, especially during aging.

Acetylcholine↗
PubMed2001

Initial imaging assessment of severe blunt trauma.

OBJECTIVES: Total body computed tomography (CT) scan is increasingly used in traumatised patients, but the need for an initial rapid imaging assessment beforehand remains unknown. To address this problem, we assessed the value of an initial imaging assessment (chest X-ray, pelvic X-ray, abdominal ultrasonography) in severely traumatised patients in a prospective study. DESIGN AND SETTING: Prospective study of a cohort in a level 1 trauma centre of an university teaching hospital. PATIENTS AND INTERVENTIONS: 400 patients with severe blunt trauma. Within 30 min of arrival in the hospital, these patients underwent a rapid imaging assessment at the bedside, including chest and pelvic X-ray, and an abdominal ultrasonography. The decision taken for each imaging technique (chest drainage or thoracotomy, pelvic angiography, and laparotomy, respectively) was judged as appropriate or inappropriate. MEASUREMENTS AND RESULTS: Emergency chest drainage or thoracotomy was performed in 78 cases (78 appropriate), pelvic angiography in 8 cases (5 appropriate) and immediate laparotomy in 48 cases (47 appropriate). Emergency treatment was decided in 108 patients, and the decisions were considered appropriate in 392 (98%, 95% CI: 97%-99%) cases. Three variables (heart rate, systolic arterial pressure and Glasgow Coma Scale) were independent predictors of the need for an emergency decision, but among patients who had none of these criteria, 16% required an emergency decision. CONCLUSIONS: A simple and rapid initial imaging assessment enabled appropriate emergency decisions before further imaging assessment was performed. We recommend that every patient with severe blunt trauma receive this initial assessment.

Abdominal Injuries↗
PubMed2001

Validity of applying TRISS analysis to paediatric blunt trauma patients managed in a French paediatric level I trauma centre.

OBJECTIVE: Using a weighted combination of the Revised Trauma Score (RTS), the Injury Severity Score (ISS), the type of injury (blunt or penetrating) and patient age, the TRISS method is used to calculate the probability of survival (ps) in trauma patients. The goal of this study was to compare the ability of the American Major Trauma Outcome Study (MTOS) norm for adult blunt trauma patients (ADULT) and the specific norm for paediatric patients (PED) to estimate the ps of injured children using TRISS methodology. DESIGN: Retrospective analysis using a paediatric trauma patient database. SETTING: A French level 1 paediatric trauma centre. PATIENTS: Four hundred seven consecutive paediatric blunt trauma patients, treated over a 3-year period. MEASUREMENTS: The observed and expected survivals were compared, using the M, W and Z scores, with both ADULT and PED. The W score is the number of survivors more or less than expected from the MTOS predictions for 100 patients. A Z score, which measures the significance of W, between -1.96 and +1.96, indicates no significant difference between observed and expected survivors. A value of M less than 0.88 indicates a disparity in the severity match between the study group and the MTOS group. We calculated the standardised W score (Ws), which represents the W score that would have been observed if the case mix of severity was identical to that of the MTOS group. Accordingly, a standardised Z score (Zs) was also calculated. In addition, we calculated the area under the receiver operating curve (aROC) using both norms, while calibration was also assessed by calculation of the Hosmer-Lemeshow goodness-of-fit tests. RESULTS: Using PED, the number of actual survivors (n = 364) was not significantly different from the MTOS (n = 358). The value of M, 0.65, indicated a disparity in the severity match between the study group and the MTOS group, due to a higher proportion of patients with lower ps (TRISS < 0.95, 52 vs 27%). We was +1.06% (95% confidence interval -0.34 to 2.08) and Zs was 1.48, indicating no significant difference from the MTOS. Using ADULT, the number of observed survivors (n = 364) was significantly higher than that expected (n = 354), with a W score of +2.70% (Z = +1.98, p < 0.05). There was a disparity in the severity match (M = 0.67) between the study group and the MTOS group, due to a higher proportion of patients with lower ps. Ws was +1.32% (95% confidence interval -0.12 to 2.37) and Zs = +1.79 (NS), indicating no significant difference from the MTOS. The Hosmer-Lemeshow statistics indicated that ADULT (Cg = 7.24, p = 0.51; Hg = 4.45, p = 0.81) and PED (Cg = 6.08, p = 0.64; Hg = 3.55, p = 0.90) provided sufficient goodness-of-fit. There was no significant difference in the aROC of the TRISS between the two norms (0.935 +/- 0.050 vs 0.936 +/- 0.050; NS). CONCLUSION: Both adult and paediatric norms were equally good predictors of the probability of survival of injured children, provided that Ws and Zs are used when there is a disparity in the severity match between the study group and the MTOS group.

Adolescent↗
PubMed2001

[Barotrama during apnea testing for the determination of brain death].

We describe three cases of tension pneumothorax occurring during apnea testing for the determination of brain death. Every case needed needle thoracostomy for emergency chest deflation and/or a chest tube to be inserted rapidly. Moreover, haemodynamic and oxygenation parameters were impaired in each of the patients after these pneumothorax. This was uneventful for the two first patients (organs harvesting was contra-indicated or not consented by the patient's family), but might be responsible for damaging lungs in the third patient and consequently loosing the pulmonary graft. Limitation of oxygen insufflation up to 8 L.min-1 with a 12 F oxygen supply tubing inserted within 5 cm into the endotracheal tube should be recommended to avoid this iatrogenic complication.

Adult↗
PubMed2001

Postoperative titration of intravenous morphine.

BACKGROUND AND OBJECTIVE: Intravenous morphine titration is used to obtain postoperative pain relief, but few studies have assessed the appropriate regimen. In a quality programme, we performed a prospective non-randomized study of morphine titration in a postanaesthesia care unit (PACU). METHODS: Four regimens of morphine titration were studied: every 10 (group 1, n = 400) or 5 min (group 2, n = 400) with a maximum of five intravenous boluses; every 5 min, without any limitation in the number of boluses (groups 3 and 4, n = 400 each); in groups 1, 2, and 3, subcutaneous morphine was administered 4 h after titration. In group 4, administration of subcutaneous morphine was allowed only 2 h after titration. A visual analogue pain scale (VAPS) > 30 mm was required to administer morphine and pain relief was defined as a VAPS < or = 30 mm. RESULTS: After morphine titration, VAPS was lower and the number of patients with pain relief was greater in patients from groups 3 and 4. Patients from group 4 had the lowest VAPS (26 +/- 17 mm) and the highest percentage of pain relief (73%) at the end of the PACU period. The number of sedated patients increased in groups 3 (62%) and 4 (61%) compared with group 1 (27%). No significant differences in morphine-related adverse effects were observed. CONCLUSION: Intravenous morphine titration every 5 min with an unlimited number of boluses and early subcutaneous administration provided the best analgesic regimen.

Adult↗
PubMed2001

Extracellular calcium modulates the effects of protamine on rat myocardium.

UNLABELLED: We studied the effects of protamine (10-300 microg. mL(-1)) as well as its interaction with heparin in rat left ventricular papillary muscles in vitro at calcium concentrations of 0.5 and 1 mM under low (isotony) and high (isometry) loads. Protamine induced a negative inotropic effect that was less pronounced at calcium 0.5 mM (active force at protamine 300 microg/mL, 84 +/- 20 vs 57 +/- 15% of baseline, P: < 0.05); whereas at calcium 1 mM there was a marked contracture of the muscle. For the smallest concentrations of protamine and at calcium 0.5 mM, we observed a moderate positive inotropic effect that was suppressed by nifedipine. Protamine induced a negative lusitropic effect under low load and decreased postrest potentiation, suggesting an impairment in the functions of the sarcoplasmic reticulum. Heparin was able to inhibit and reverse the negative inotropic effect of protamine. The negative inotropic effect of protamine is enhanced by an increase in extracellular calcium concentration. This negative inotropic effect is probably related to calcium overload and impairment in sarcoplasmic reticulum functions, and heparin can block these effects. IMPLICATIONS: The negative inotropic effect of protamine is enhanced by an increase in extracellular calcium concentration. This negative inotropic effect is probably related to calcium overload and impairment in sarcoplasmic reticulum functions, and heparin can block these effects.

Animals↗
PubMed2001

The chronic inhibition of angiotensin-converting enzyme impairs postoperative renal function.

UNLABELLED: Postoperative renal impairment can increase postoperative mortality and morbidity. We sought to identify preoperative risk factors responsible for postoperative renal impairment in patients undergoing aortic surgery. This prospective study included 249 patients admitted for aortic surgery. Preoperative and postoperative glomerular filtration rates (GFRs) were assessed with pre- and postoperative creatinine clearance measurements. Postoperative renal impairment was defined as a 20% decrease in GFR between Day 0 (before surgery) and Day 7 +/-1 day (after surgery). Preoperative and intraoperative variables considered as potentially responsible for postoperative renal impairment were tested. Chronic treatment with angiotensin-converting enzyme inhibitors (ACEIs) was the only factor significantly associated with postoperative renal impairment (odds ratio [95% confidence interval] = 2.01 [1.05-3.83]). Chronic preoperative ACEI treatment is significantly associated with postoperative renal impairment. Inhibition of renal compensatory mechanisms caused by renin angiotensin system blockade might be responsible for the observed decrease in renal function in patients chronically treated with ACEIs undergoing aortic surgery. However, age and preoperative renal dysfunction were not associated with a postoperative decrease in GFR, but they were associated with a postoperative creatinine clearance <60 mL/min. IMPLICATIONS: The aim of this study was to identify preoperative risk factors responsible for postoperative renal impairment in vascular surgery. Chronic angiotensin-converting enzyme inhibitor treatment was the only factor significantly associated with postoperative renal impairment. Inhibition of renal compensatory mechanisms caused by renin angiotensin system blockade might be responsible for the observed decreased renal function.

Aged↗
PubMed2001

Effects of dantrolene on rat diaphragm muscle during postnatal maturation.

BACKGROUND: Dantrolene is the only known effective treatment for malignant hyperthermia. However, its effects on diaphragm muscle during postnatal maturation remain unknown. METHODS: The effects of dantrolene (10(-8) to 10(-4) M) were investigated in vitro on diaphragm muscle strips in adult rats and in postnatal rats aged 3, 10, and 17 days, and compared with those of ryanodine (10(-8) to 10(-6) M). The authors studied contraction and relaxation under isotonic and isometric conditions (29 degrees C, Krebs-Henseleit solution, tetanic stimulation at 50 Hz). Data are mean +/- SD. RESULTS: During postnatal maturation, the authors observed a progressive increase in active force developed per cross-sectional area (from 34 +/- 25 to 69 +/- 32 mN/mm2; P < 0.05) and maximum shortening velocity (from 2.9 +/- 0.5 to 4.9 +/- 1.4 Lmax/s; P < 0.05). Dantrolene induced a negative inotropic effect in diaphragm muscles in isotonic and isometric conditions in all groups, but this effect was significantly less marked in the 3-day-old rats compared with older rats. Dantrolene did not induce significant lusitropic effects during postnatal maturation. Developmental changes in the pharmacologic response to dantrolene were more rapid than those of ryanodine. CONCLUSION: Dantrolene induced less pronounced negative inotropic effects on the diaphragm in neonatal rats as compared with adult rats. Our study suggests that developmental changes in the pharmacologic response to dantrolene are more rapid than those of ryanodine.

Aging↗
PubMed2001

Distribution of the probability of survival is a strategic issue for randomized trials in critically ill patients.

BACKGROUND: Many randomized clinical trials in trauma have failed to demonstrate a significant improvement in survival rate. Using a trauma patient database, we simulated what could happen in a trial designed to improve survival rate in this setting. METHODS: The predicted probability of survival was assessed using the TRISS methodology in 350 severely injured trauma patients. Using this probability of survival, the authors simulated the effects of a drug that may increase the probability of survival by 10-50% and calculated the number of patients to be included in a triad, assuming alpha = 0.05 and beta = 0.10 by using the percentage of survivors or the individual probability of survival. Other distributions (Gaussian, J shape, uniform) of the probability of survival were also simulated and tested. RESULTS: The distribution of the probability of survival was bimodal with two peaks (< 0.10 and > 0.90). There were major discrepancies between the number of patients to be included when considering the percentage of survivors or the individual value of the probability of survival: 63,202 versus 2,848 if the drug increases the probability of survival by 20%. This discrepancy also occurred in other types of distribution (uniform, J shape) but to a lesser degree, whereas it was very limited in a Gaussian distribution. CONCLUSIONS: The bimodal distribution of the probability of survival in trauma patients has major consequences on hypothesis testing, leading to overestimation of the power. This statistical pitfall may also occur in other critically ill patients.

Adolescent↗
PubMed2001

Effectiveness of epidural blood patch in the management of post-dural puncture headache.

BACKGROUND: Lumbar epidural blood patch (EBP) is a common treatment of post-dural puncture headache, but its effectiveness and mode of action remain a matter of debate. The aim of this study was to assess both the effectiveness and the predictive factors of failure of EBP on severe post-dural puncture headache. METHODS: This prospective observational study includes all patients treated in the authors' hospital with EBP for incapacitating post-dural puncture headache, from 1988 to 2000. The EBP effect was classified into complete relief (disappearance of all symptoms), incomplete relief of symptoms (clinically improved patients who recovered sufficiently to perform normal daily activity), and failure (persistence of severe symptoms). The following data were analyzed using a logistic regression to identify predictive factors of failure of EBP: (1) patient characteristics; (2) circumstances of dural puncture; (3) delay between dural puncture and EBP; and (4) the volume of blood injected for EBP. RESULTS: A total of 504 patients were analyzed. The frequency rates of complete relief, incomplete relief of symptoms, and failure after EBP were 75% (n = 377), 18% (n = 93), and 7% (n = 34), respectively. In a multivariate analysis, only the diameter of the needle used to perform dura mater puncture (odds ratio = 5.96; 95% confidence interval, 2.63-13.47; P < 0.001) and a delay in EBP less than 4 days (odds ratio = 2.63; 95% confidence interval, 1.06-6.51; P = 0.037) were independent significant risk factors for a failure of EBP. CONCLUSIONS: Epidural blood patch is an effective treatment of severe post-dural puncture headache. Its effectiveness is decreased if dura mater puncture is caused by a large bore needle.

Adult↗
PubMed2001

Myocardial and coronary effects of propofol in rabbits with compensated cardiac hypertrophy.

BACKGROUND: Myocardial effects of propofol have been previously investigated but most studies have been performed in healthy hearts. This study compared the cardiac effects of propofol on isolated normal and hypertrophic rabbits hearts. METHODS: The effects of propofol (10-1,000 microM) on myocardial contractility, relaxation, coronary flow and oxygen consumption were investigated in hearts from rabbits with pressure overload-induced left ventricular hypertrophy (LVH group, n = 20) after aortic abdominal banding and from sham-operated control rabbits (SHAM group, n = 10), using an isolated and erythrocyte-perfused heart model. In addition, to assess the myocardial and coronary effects of propofol in more severe LVH, hearts with a degree of hypertrophy greater than 140% were selected (severe LVH group, n = 7). RESULTS: The cardiac hypertrophy model induced significant left ventricular hypertrophy (136+/-21%, P < 0.05). The pressure-volume relation showed normal systolic function but an altered diastolic compliance in hypertrophic hearts. Propofol only decreased myocardial contractility and relaxation at supratherapeutic concentrations (> or = 300 microM) in SHAM and LVH groups. The decrease in myocardial performances was not significantly different in SHAM and LVH groups. Propofol induced a significant increase in coronary blood flow which was not significantly different between groups. In severe LVH group, the degree of hypertrophy reached to 157+/-23%. Similarly, the effects of concentrations of propofol were not significantly different from the SHAM group. CONCLUSIONS: Propofol only decreased myocardial function at supratherapeutic concentrations. The myocardial and coronary effects of propofol were not significantly modified in cardiac hypertrophy.

Anesthetics, Intravenous↗
PubMed2001

Minimum alveolar concentration of volatile anesthetics in rats during postnatal maturation.

BACKGROUND: Although neonatal rats have become widely used as experimental laboratory animals, minimum alveolar concentration (MAC) values of volatile anesthetics in rats during postnatal maturation remain unknown. METHODS: We determined MAC values of volatile anesthetics in spontaneously breathing neonatal (2-, 9-, and 30-day-old) and adult Wistar rats exposed to increasing (in 0.1-0.2% steps) concentrations of halothane, isoflurane, or sevoflurane (n = 12-20 in each group), using the tail-clamp technique. MAC and its 95% confidence intervals were calculated using logistic regression and corrected for body temperature (37 degrees C). RESULTS: In adult rats, inspired MAC values corrected at 37 degrees C were as follows: halothane, 0.88% (confidence interval, 0.82-0.93%); isoflurane, 1.12% (1.07-1.18%); and sevoflurane, 1.97% (1.84-2.10%). In 30-day-old rats, the values were as follows: halothane, 1.14% (1.07-1.20%); isoflurane, 1.67% (1.58-1.76%); and sevoflurane, 2.95% (2.75-3.15%). In 9-day-old rats, inspired MAC values were as follows: halothane, 1.68% (1.58-1.78%); isoflurane, 2.34% (2.21-2.47%); and sevoflurane, 3.74% (3.64-3.86%). In 2-day-old rats, inspired MAC values were as follows: halothane, 1.54% (1.44-1.64%); isoflurane, 1.86% (1.72-2.01%); and sevoflurane, 3.28% (3.09-3.47%). CONCLUSION: As postnatal age increases, MAC value significantly increases, reaching the greatest value in 9-day-old rats, and decreases thereafter, and at 30 days is still greater than the adult MAC value.

Age Factors↗
PubMed2001

Interaction of protamine with alpha- and beta-adrenoceptor stimulations in rat myocardium.

BACKGROUND: Protamine alters the inotropic responses to beta-adrenoceptor stimulation, but its mechanism of action is not well-understood. Moreover, its interaction with alpha-adrenoceptor stimulation and the lusitropic (relaxation) response to beta-adrenoceptor stimulation remain unknown. METHODS: The effects of protamine (10 or 100 microg/ml) on the responses induced by phenylephrine and isoproterenol were studied in rat left ventricular papillary muscles. Inotropic and lusitropic effects were studied under low and high loads. The authors also studied the interaction of protamine with forskolin (50 microm) and dibutyryl 3',5'-cAMP (0.5 mm). Data are mean percentage of baseline active force +/- SD. RESULTS: In control groups, phenylephrine (135 +/- 17%, P < 0.05) and isoproterenol (185 +/- 44%, P < 0.05) induced a positive inotropic effect. Isoproterenol induced positive lusitropic effects under low and high loads. Protamine abolished the inotropic responses to alpha- (102 +/- 23%, not significant) and beta-adrenoceptor stimulations (99 +/- 17%, not significant) but did not modify the lusitropic responses to isoproterenol. Protamine abolished the inotropic responses to forskolin (89 +/- 6 vs. 154 +/- 20%, P < 0.05) and markedly decreased that of dibutyryl 3',5'-cAMP (132 +/- 31 vs. 167 +/- 30%, P < 0.05) but did not modify their lusitropic responses. CONCLUSIONS: Protamine abolished the inotropic responses to alpha- and beta-adrenoceptor stimulations but preserved the lusitropic responses to beta-adrenoceptor stimulation. Although protamine may act at several sites on the adrenoceptor stimulation cascade, one of its main sites of action is situated downstream from cAMP-mediated phosphorylation.

Adrenergic alpha-Agonists↗