Search PubMed⌕ Search

Biomedical subjects

J F Baron

Publications and source records attributed to J F Baron.

At least 19 recordsLinked to original sources
PubMed1996

Autologous blood donation with recombinant human erythropoietin in cardiac surgery: the Japanese experience.

Four units of predonated autologous blood (AB) is considered sufficient to cover the blood requirements of 95% of patients undergoing elective cardiac surgery, thus avoiding the risks associated with allogeneic blood transfusion. A review of six Japanese studies was undertaken to summarize the potential for recombinant human erythropoietin (rHuEPO) to facilitate donation of AB by patients scheduled for cardiac surgery. Intravenous (i.v.) administration of rHuEPO improved the anemia associated with AB donation, an effect that was further enhanced by i.v. iron supplementation. Once weekly subcutaneous (s.c.) administration of rHuEPO facilitated the donation of AB and reduced allogeneic blood requirements in patients scheduled for cardiac surgery, suggesting that rHuEPO could be administered on an outpatient basis. rHuEPO was of particular benefit in anemic patients, eliminating exposure to allogeneic blood in the majority of patients. In conclusion, rHuEPO facilitates the donation of AB and reduces allogeneic blood requirements of patients scheduled for cardiac surgery.

Administration, Oral↗
PubMed1995

Mechanisms of postoperative prolonged plasma volume expansion with low molecular weight hydroxethy starch (HES 200/0.62, 6%).

OBJECTIVE: To define the mechanisms of the stable and prolonged post-operative plasma volume expansion observed with Hydroxyethyl Starches (HES) and to determine whether a partial intravascular hydrolysis of large molecules contribute to reinforce the colloid-osmotic effect. DESIGN: Prospective, pharmacologic study using single dose of drug. SETTING: University-based, post-anesthesia care unit. PATIENTS: The protocol was performed during the post-operative period, in 10 patients after stable recovery from general anesthesia for carotid endarterectomy. INTERVENTIONS: HES 200/0.62 (500 ml) was infused over 30 min. Standard hemodynamic and biological variables, HES concentration and colloid osmotic pressure were obtained at each measurement. Plasma volume was calculated using 51Cr-labelled RBCs. Patterns of changes in number average molecular weight (MWn) and weight average MW (MWw) were measured using gel permeation chromatography. Measurements were obtained at control, end of infusion, 1 h, 3 h, 6 h and 24 h after infusion. MEASUREMENTS AND MAIN RESULTS: Plasma volume increased by 693 ml (+21%) after the infusion of HES and remained constant over 24 h. HES concentration progressively decreased to reach a value of 35% of the peak at 24 h. MWn and MWw, initially decreased when compared with the dose solution and changed little in the 24 h study period. Diuresis significantly decreased at 3 h up to 24 h. Plasma albumin decreased after infusion and then progressively increased to reach a significantly higher value at 24 h than after infusion. CONCLUSION: Initial plasma volume expansion and decrease in HES concentration agree with previously-published data. Maintenance of plasma volume expansion over 24 h was not related to a partial intravascular hydrolysis. Low elimination rate of HES, extravascular mobilization of albumin and post-operative renal adaptations were possibly the 3 main mechanisms to explain a prolonged plasma volume expansion with HES 200/0.62, 6%.

Aged↗
PubMed1995

[Effects of platelet-rich plasma on hemostasis and transfusion requirement in vascular surgery].

OBJECTIVE: To assess the effect of intraoperative autologous platelet-rich plasma (PRP) transfusion on haemostasis, blood loss and blood requirements during vascular surgery. STUDY DESIGN: Randomized clinical trial. PATIENTS: Twenty patients undergoing elective abdominal infrarenal aortic aneurysmectomy, using autologous transfusion techniques (predonation programme and/or preoperative normovolaemic haemodilution and/or intraoperative use of a cell-saver), were randomly allocated either into the PRP group (n = 10) or the Control group (n = 10). METHOD: In patients of PRP group, 10 mL.kg-1 of PRP were obtained over 40 to 50 min, prior to induction of anaesthesia, and compensated simultaneously with an equivalent amount of hydroxyethyl starch. Each PRP unit was transfused to its donor after aortic declamping. Blood samples were obtained before induction, before incision, at wound closing and at the end of PRP unit transfusion for determination of biological variables. RESULTS: The PRP units transfused in the patients of PRP group contained 755 +/- 117 mL of plasma with a platelet count of 62 +/- 31 G.L-1. The intra and postoperative blood losses were similar in both groups (1622 +/- 758 and 233 +/- 322 mL respectively in PRP group vs 1890 +/- 1331 and 291 +/- 303 mL respectively in Control group). In both groups, three patients required an additional transfusion of homologous blood. The results of biological tests (haematocrit, platelet and white cell counts, prothrombin time, aPTT, thrombin time, fibrinogen, D-dimers, proteins, calcium) were also similar between groups at the various times of sampling. The reinfusion of the PRP unit did not increase the platelet count. CONCLUSIONS: This study demonstrates that intraoperative infusion of autologous PRP does not decrease blood loss and homologous transfusion requirements in patients undergoing elective abdominal infrarenal aortic aneurysmectomy. This result can be related to the relatively moderate enrichment in platelets obtained with the centrifugation speed used in this study.

Aortic Aneurysm, Abdominal↗
PubMed1995

Mechanisms of increased myocardial contractility with hypertonic saline solutions in isolated blood-perfused rabbit hearts.

Hypertonic saline improves organ perfusion and animal survival during hemorrhagic shock because it expands plasma volume and increases tissue oxygenation. Because both decreased and increased myocardial performance have been reported with hypertonic saline, the effects of hyperosmolarity and the mechanism accounting for it were investigated in isolated blood-perfused rabbit hearts. Coronary blood flow (CBF), myocardial contractility, relaxation, and oxygen consumption were measured during administration of blood perfusates containing 140-180 mmol sodium concentrations ([Na+]). In two other series of experiments, the role of Na(+)-Ca2+ exchange in the inotropic effect of hyperosmolarity (160 mmol sodium concentration) and hypertonicity (sucrose) were also investigated. Hypertonic [Na+] induced a significant increase in contractility and relaxation, combined with a coronary vasodilation. Myocardial oxygen consumption (MVO2) increased at all hypertonic [Na+] without significant change in coronary venous oxygen tension (PVO2) and content (CVO2). Amiloride (0.3 mmol) inhibited the improved contractility observed with 160 mmol sodium. Similar Na(+)-Ca2+ exchanger blockade did not inhibit the inotropic effect of sucrose. These results confirm the positive inotropic effect of hypertonic [Na+]. The inhibition of this improvement by amiloride suggests that calcium influx through the sarcolemna could be the major mechanism of this effect.

Amiloride↗
PubMed1994

Dipyridamole-thallium scintigraphy and gated radionuclide angiography to assess cardiac risk before abdominal aortic surgery.

BACKGROUND: Because many patients with atherosclerotic disease of the abdominal aorta also have coronary artery disease, assessment of cardiac risk before abdominal aortic surgery has received much attention. Our prospective study was designed to identify predictors of cardiac risk in consecutive patients evaluated preoperatively with dipyridamole-thallium single-photon-emission computed tomography (SPECT) to assess myocardial perfusion and radionuclide angiography to measure left ventricular ejection fraction. METHODS: Clinical and scintigraphic data were collected prospectively during hospitalization in 457 consecutive patients undergoing elective abdominal aortic surgery. Adverse cardiac outcomes were predicted with multivariate analyses. RESULTS: Eighty-six patients (19 percent) had one or more of the following postoperative complications: prolonged myocardial ischemia (61 patients), myocardial infarction (22), congestive heart failure (20), and severe ventricular tachyarrhythmia (2). Twenty patients died postoperatively (4.4 percent), half of them from cardiac causes. Information about myocardial perfusion obtained from dipyridamole-thallium SPECT did not accurately predict adverse cardiac outcomes. The best correlates of cardiac complications were definite clinical evidence of coronary artery disease (odds ratio, 2.6; 95 percent confidence interval, 1.6 to 4.3) and age greater than 65 years (odds ratio, 2.3; 95 percent confidence interval, 1.4 to 3.6). Measurement of the ejection fraction was useful only in the prediction of left ventricular failure. Age greater than 65 years was the only predictor of death (odds ratio, 26.4; 95 percent confidence interval, 3.5 to 200.0). CONCLUSIONS: The presence of definite clinical evidence of coronary artery disease and older age were the most important preoperative predictors of an adverse cardiac outcome after abdominal aortic surgery. These results suggest that the routine use of dipyridamole-thallium SPECT and radionuclide angiography for screening before abdominal aortic surgery may not be justified.

Aged↗
PubMed1994

Aprotinin to decrease bleeding and intraoperative blood transfusion requirements during descending thoracic and thoracoabdominal aortic aneurysmectomy using cardiopulmonary bypass.

The purpose of this retrospective study was to assess the efficacy of aprotinin, an antifibrinolytic agent, in reducing bleeding and blood transfusion requirements in patients undergoing descending thoracic or thoracoabdominal aortic aneurysmectomy using cardiopulmonary bypass (CPB). Sixty-nine consecutive patients underwent thoracic or thoracoabdominal aneurysmectomy using CPB in a 2-year period. None of the 29 patients operated on in 1990 (group 1) received aprotinin, whereas all 40 patients operated on in 1991 (group 2) were placed on a high-dose regimen of aprotinin. There were no significant differences between the two groups. Administration of aprotinin was associated with a decrease in CPB time (p = 0.02), surgical duration (p = 0.05) and intraoperative blood loss (p = 0.008) as well as a reduction in intraoperative packed red cells (p = 0.01), Cell-Saver units (p = 0.05), fresh-frozen plasma units (p = 0.002), and platelet concentrate (p = 0.01) requirements. These data suggest that aprotinin is effective in reducing bleeding and blood transfusion requirements during descending thoracic or thoracoabdominal aortic aneurysmectomy using CPB.

Adult↗
PubMed1994

Effects of propofol and thiopental on coronary blood flow and myocardial performance in an isolated rabbit heart.

BACKGROUND: Some clinical and experimental studies suggest that propofol decreases myocardial contractility and relaxation, whereas others report preserved cardiac function. To investigate the effects of propofol on intrinsic contractility and relaxation, increasing concentrations of propofol were infused in isolated blood-perfused rabbit hearts. Equimolar concentrations of thiopental were infused as a reference group. METHODS: Coronary blood flow, left ventricular contractility and relaxation (as maximal positive and negative left ventricular pressure derivatives [dP/dtmax and dP/dtmin], respectively), and myocardial oxygen consumption (MvO2) were measured during infusion of 10-1,000 microM propofol in blood-perfused hearts. To determine whether the effects of propofol depend on the heart's perfusate, propofol also was infused in isolated buffer-perfused rabbit hearts. In addition, the effects of propofol solvent were investigated in blood- and buffer-perfused preparations. RESULTS: In blood-perfused preparations, coronary blood flow increased with propofol concentrations greater than 30 microM and with 300 and 1,000 microM thiopental. Left ventricular dP/dtmax and dP/dtmin remained unchanged with propofol and decreased with concentrations of thiopental equal to or greater than 30 microM. MvO2 increased with 1,000 microM propofol, whereas coronary venous oxygen tension and content remained unchanged. MvO2 decreased with thiopental associated with a significant increase in coronary venous oxygen tension and content. In six buffer-perfused hearts, basal coronary blood flow was much greater and MvO2 less than in blood-perfused hearts. Left ventricular dP/dtmax and dP/dtmin decreased with 30, 100, and 300 microM propofol. Propofol vehicle did not change coronary blood flow, myocardial performance, or MvO2 of blood- or buffer-perfused hearts. CONCLUSIONS: When compared to a reference drug such as thiopental, propofol did not depress the myocardial performance of blood-perfused rabbit hearts. The type of the perfusate (blood vs. buffer), however, had a major influence on the myocardial effects of propofol.

Animals↗
PubMed1994

A comparison of systolic blood pressure variations and echocardiographic estimates of end-diastolic left ventricular size in patients after aortic surgery.

As suggested by experimental studies, systolic pressure variation (SPV), the difference between maximum and minimum values of systolic blood pressure after a single positive pressure breath, may be a fair indicator of left ventricular preload. SPV was quantified in 21 patients who had undergone abdominal aortic surgery and were sedated under mechanical ventilation. The aim of the study was to assess the ability of this parameter to qualitatively estimate left ventricular preload measured using transesophageal echocardiography. All patients had preoperative radionuclide ejection fraction > 45%. Postoperative mechanical ventilatory patterns were the same for all patients: tidal volume = 10 mL/kg; respiratory frequency = 12-14 breaths/min; and zero end-expiratory pressure mode. Left ventricular dimensions at end-diastole correlated well with the magnitude of both SPV (r = 0.80) and its delta down (dDown) component (i.e., the degree by which systolic pressure decreases with each mechanical breath) (r = 0.83). Once the first measurement was completed, volume loading with two increments of 250 mL of human albumin 5% was performed in all but three patients. Each volume loading step caused a significant increase in the end-diastolic area (EDa) index (7.0 +/- 1.6 to 8.5 +/- 1.6 cm2/m2) and cardiac index (CI) (3.1 +/- 0.9 to 4.1 +/- 0.9 L.min-1 x m-2) and a concomitant significant decrease in the SPV (8.6 +/- 4.5 to 6.1 +/- 3.7 mm Hg) and its dDown component (5.9 +/- 4.1 to 2.9 +/- 2 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

[Mid-term results of cardiomyoplasty].

Cardiomyoplasty (CMP) is a technique of circulatory assistance using a pediculated latissimus dorsi muscle wrapped around the heart and electrically stimulated during systole. Sixty-four patients, aged 15 to 69 years (average 50.8 +/- 13 years) with cardiac failure underwent CMP between January 1985 and July 1993. The causes of cardiac failure were : ischaemic heart disease (39 cases), dilated cardiomyopathy (18 cases), cardiomyopathy following valvular heart disease (2 cases), cardiac tumours (4 cases) and congenital heart disease (1 case). Twenty-four patients underwent an associated surgical procedure. Intra and postoperative intra-aortic balloon pumping was required in 27 cases. Hospital mortality (before latissimus dorsi stimulation) was 20.3% (13/64 cases). Evaluation of the survivors 12 months after surgery showed an improvement in functional class (1.,5 versus 3.3 before CMP ; p < 0.05), in isotopic ejection fraction (27 +/- 3% versus 17 +/- 6%, p < 0.05) and cardiac index (2.87 +/- 0.63 l/min/m2 versus 2.38 +/- 0.41 l/min/m2, p < 0.05). There was no significant change in cardiac filling pressures. The number of hospital admissions for congestive cardiac failure in operated patients was 0.4 per patient per year, compared with 2.5 per patient per year (p < 0.05) before CMP. The preoperative predictive factors for late mortality were: permanent functional Class IV (NYHA), severe cardiac dilatation (cardio-thoracic ratio greater than 0.60; left ventricular end diastolic dimension > 75 mm), an isotopic left ventricular ejection fraction < 15%, severe biventricular cardiac failure and irreversible pulmonary hypertension. The actuarial 4 year survival rate was 68.3%.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1993

[Value of thallium-dipyridamole myocardial scintigraphy in coronary patients in non cardiac surgery].

Cardiac assessment is of particular importance in patients with documented or suspected coronary artery disease (CAD) as well as in all those patients undergoing vascular surgery. Use of dipyridamole thallium scintigraphy (DTS) in this population could help to detect significant coronary artery narrowing, together with the location and quantification of the areas of myocardium in jeopardy. Such information might lead to changing the surgical procedure, or to starting other treatment, such as coronary angioplasty or bypass graft surgery, thereby diminishing the morbidity and mortality associated with surgery in these high-risk patients. The ability of DTS to predict acute postoperative ischaemic events has been suggested by several studies. Various shortcomings of DTS used as a preoperative screening test have been pointed out in some recent papers. Therefore it is concluded that: 1) DTS should not be used as a routine preoperative test in vascular surgical patients. DTS is not accurate enough when used in patients without any clinical findings suggestive of CAD, 2) DTS may prove more useful in stratifying patients with an intermediate probability of developing cardiac complications. In such patients, the test will not provide a linear "all or nothing" result, but, when taken together with the clinical findings and the nature of the surgical procedure, a complex stratification, 3) Because of progress in the perioperative management of high-risk patients, positive findings on preoperative DTS may not correlate perfectly with perioperative cardiac events, 4) As several factors influence thallium uptake after dipyridamole, DTS does not have a perfect specificity, thus leading to order an excessive number of coronary angiographies. Some patients will be seen as having a false-positive DTS, 5) Preoperative screening DTS leads to cardiac catheterization and hence to revascularisation, independently of symtomatology. Further studies must be undertaken to determine whether this approach will improve short and long term patient survival.

Coronary Disease↗
PubMed1992

Transesophageal echocardiographic assessment of left ventricular function in response to labetalol for control of postoperative hypertension.

Although labetalol (LAB), the combination of an alpha- and beta-adrenergic blocking agent, is thought to be effective and safe for the control of postoperative hypertension, no study has focused on changes in left ventricular (LV) function when this drug was used to control postoperative hypertension. Therefore, this study determined the effects of LAB on hemodynamics and LV function assessed by 2D transesophageal echocardiography (TEE) in 17 patients undergoing abdominal aortic surgery who experienced a postoperative hypertensive episode. Postoperatively, patients were transferred while still intubated and under fentanyl sedation to the postanesthesia care unit where a TEE probe was inserted to provide a short-axis view of the LV. When their systolic blood pressure increased above 165 mmHg for more than 4 minutes, LAB was given in a dose of 0.75 mg/kg IV, over 2 minutes. If the blood pressure was not lowered to within 10% of the preoperative values, additional doses of LAB were given. Control of hypertension was obtained in all patients and was associated with a significant decrease in heart rate (90 +/- 19 to 70 + 13 bpm), cardiac index (4.52 +/- 1.65 to 3.36 +/- 1.55 L/min/m2), and mixed venous oxygen saturation (73 +/- 10 to 63 +/- 10%). With the lower blood pressure, end-diastolic area increased, indicating myocardial depression. In conclusion, LAB can be used to effectively control hypertension during the early postoperative period after abdominal aortic surgery. However, the reduction of blood pressure is achieved principally by the negative inotropic effect of LAB, which predominates over its vasodilator action.

Adult↗
PubMed1992

[Pharmacology of low molecular weight hydroxyethyl starch].

In the last ten years, the practice of plasma volume expansion has changed significantly. Most clinicians have put a stop to the use of fresh frozen plasma because of growing concerns about hepatitis and AIDS transmission. Today, natural and synthetic colloids and crystalloids are used to a great extent. Although clinical practice varies from one institution to another, the most widely observed change was a major increase in the administration of human serum albumin (HSA). As a result, the cost of plasma volume expansion became so high that it justified finding safe and cheaper alternatives to HSA. Low molecular weight, hydroxyethylstarch (HES) are the synthetic colloids which are closest to HSA. HES are modified natural polymers whose physico-chemical properties are defined by their molecular weight and molar substitution ratio. Average molecular weights of these poly-dispersed solutions are approximately 200 to 250 kd (in weight) and 60 kd (in number). Hydroxyethylation, which slows down hydrolysis by alpha-amylase, is best quantified by the molar substitution ratio between the proportions of hydroxyethyl-ether and glucose. HES have pharmacokinetic properties which are independent of molecular weight and directly related to the molar substitution ratio. The two HES available in France are Elohes and Lomol, Elohes, at a concentration of 6%, has a colloid-osmotic effect close to that of plasma. It induces an initial plasma volume expansion greater than that of the infused volume, and has a long lasting effect (24 h) related to its molar substitution ratio (0.62). Lomol, at a concentration of 10%, is hyperoncotic.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodilution↗
PubMed1992

Dipyridamole-thallium-201 scintigraphy in the diagnosis and prognosis of coronary artery disease in patients undergoing noncardiac surgery.

Although most of the published studies using DTS as a preoperative screening test show various shortcomings, the following conclusions can be drawn: 1. DTS should not be used as a routine preoperative test in vascular surgical patients. DTS possesses insufficient accuracy when used in patients without clinical findings suggestive of CAD. 2. DTS may prove more useful in stratifying patients with an intermediate probability of developing cardiac complications. In such a population the test will not offer an "all or nothing" linear results, but rather, when included with the clinical findings and the nature of the surgical procedure, a complex stratification. 3. Because of progress in the perioperative management of high-risk patients, positive findings on preoperative DTS may not correlate perfectly with perioperative cardiac occurrences. 4. Because several factors influence thallium uptake after dipyridamole, DTS does not have perfect specificity, which leads to the prescribing of an excessive number of coronary angiographies. Some patients will be seen as having a false-positive DTS test. 5. The use of DTS as a preoperative screening test leads to cardiac catheterization and hence to revascularization independent of symptomatology. Studies must be undertaken to determine whether this approach will improve short- and long-term patient survival.

Coronary Disease↗