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Biomedical subjects

J F Baron

Publications and source records attributed to J F Baron.

At least 37 records · Page 2Linked to original sources
PubMed1997

Tris-hydroxymethyl aminomethane and sodium bicarbonate to buffer metabolic acidosis in an isolated heart model.

Metabolic acidosis induces a decrease in the developed force of cardiac muscle by affecting every step of the excitation--contraction coupling pathway. Due to transient worsening in intracellular acidosis, the value of administering sodium bicarbonate therapeutically during acute acidosis has been questioned. An alternative therapeutic drug, Tris-hydroxymethyl aminomethane (THAM) has the advantage of diffusing into the intracellular space. This study was designed to evaluate the effects of metabolic acidosis on myocardial performance and to determine the effects of alkalinization with sodium bicarbonate, THAM, and their combination. Using a blood-perfused isolated heart preparation, left ventricular contractility and relaxation were measured at normal pH and during metabolic acidosis (pH = 7.0). Acidosis dramatically impaired myocardial contractility and relaxation. After buffering with sodium bicarbonate, although plasma bicarbonate concentration was normalized, pH remained below normal owing to an increased PaCO2. Contractility and relation were initially worsened, then slightly improved to return to control values. THAM uncompletely buffered acidosis but significantly improved contractility and relaxation. The combination of THAM with sodium bicarbonate perfectly buffered acidosis without modifying PaCO2 and significantly improved contractility. The combination of THAM with sodium bicarbonate is based on the ability of THAM to capture the CO2 produced by the sodium bicarbonate buffer. This combination achieves a perfect correction of metabolic acidosis and improves myocardial performance.

Acidosis↗
PubMed1996

[Threshold values of colloid-osmotic pressure, serum albumin or protein during perioperative period].

The water flux across the capillary membrane is directly related to a gradient of hydrostatic and colloid osmotic forces. The membrane is not an absolute barrier to proteins. Any change in the capillary permeability tends to decrease the plasmatic colloid osmotic pressure. The interstitial space includes a perimicrovascular space and a compliant connective tissue space, where oedema accumulates. The lymphatics may easily drain excess filtration, but cannot clear constituted oedema. Primarily, the risk of pulmonary oedema determines the lower limit of the colloid osmotic pressure. During the perioperative period, any extrapolation of the colloid, osmotic pressure from protidaemia or albuminaemia would be approximate. Two major conclusions can be drawn from the results of Guyton and Lindsey. First, in the absence of left ventricular failure, a 50% decrease in colloid osmotic pressure does not increase extravascular lung water. Second, in the case of left ventricular failure, when the left atrial pressure exceeds 10 mmHg, a 50% decrease in colloid osmotic pressure significantly increases the risk of pulmonary oedema. In these experiments, an impairment in capillary membrane permeability is likely. As a result, the threshold at which extravascular water starts to accumulate cannot be precisely defined. However, in the perioperative period, capillary membrane permeability is frequently altered by the acute phase reaction. Finally, in most perioperative clinical situations, a 50% decrease in colloid osmotic pressure may not require any treatment.

Blood Proteins↗
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↗
PubMed1996

[Pre- and intraoperative management of heparin cross hypersensitivity. Apropos of a case].

A patient with a Starr prosthetic heart valve for 13 years developed chronic idiopathic thrombocytopaenic purpura and a highly probable crossed allergy to heparin. As the valve needed to be replaced, cardiopulmonary bypass surgery was undertaken associating heparin with lioprost and Aprotinine. In this type of situation, aggregation of control platelets by the patient's plasma in the presence of unfractionated heparin and of low molecular weight heparin justifies the use of powerful antiplatelet agents such as lioprost which was associated with Aprotinine for its platelet protective effects. This original combination allowed successful cardiopulmonary bypass surgery under unfractionated heparin under excellent conditions with minimal blood loss. This case underlines the value of this approach for cardiopulmonary bypass surgery in patients with heparin-induced thrombocytopaenia.

Adult↗
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↗