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Biomedical subjects

J F Baron

Publications and source records attributed to J F Baron.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1991

Low molecular weight hydroxyethyl starch 6% compared to albumin 4% during intentional hemodilution.

Intentional normovolemic hemodilution was chosen as the model to compare a 6% low molecular weight hydroxyethyl starch (LMW HES) to 4% albumin. The study ran over the plasma exchange period for 24 h. Nine patients, scheduled for abdominal aortic surgery, were included in each group. After basal measurements, blood was withdrawn and simultaneously replaced by either 4% albumin (Group 1) or 6% LMW HES (Group 2) to achieve a final hematocrit of approximately 30%. Hemodynamic blood oxygen gas and hormonal plasma levels were determined before hemodilution then at 30 min, 1, 2, 3, and 24 h after the end of hemodilution. Basal value for total blood volume was 4377 +/- 162 ml in group 1 and 4138 +/- 315 ml in group 2. As in both groups the decrease in blood cell volume was exactly compensated by the increase in plasma volume, no significant change in total blood volume (respectively 4432 +/- 159 and 4305 +/- 267 ml) was observed. Throughout the study, in both groups, no significant change in mean arterial and right atrial pressures was observed. In group 2 (LMW HES), a significant increase of pulmonary capillary wedge pressure was noted 120 min after hemodilution. After hemodilution, despite a significant decrease in arterial oxygen O2 content, systemic oxygen transport did not significantly vary until 24 h in relation to the increased cardiac index. An increase in O2 extraction was observed after the exchange but no further increase was observed until the 24 h. No significant changes either in global O2 consumption or in lactate concentration were detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Combined epidural and general anesthesia versus general anesthesia for abdominal aortic surgery.

The goal of this randomized study of high-risk surgical patients was to determine whether intraoperative thoracic epidural anesthesia in combination with light general anesthesia alters postoperative morbidity when compared to a standard technique of "balanced" general anesthesia. A total of 173 patients scheduled for abdominal aortic reconstruction were admitted to the study; 86 were to receive "balanced" general anesthesia (group 1) and 87 thoracic epidural anesthesia in combination with light general anesthesia (group 2). Preoperative evaluation included standard clinical tools, dipyridamole thallium gammatomography, and radionuclide angiography. In these patients, all of whom had peripheral artery disease, there were no significant differences in associated coronary artery disease, hypertension, and cardiovascular treatment. The distribution of left ventricular ejection fraction and the number of patients with thallium redistribution were not statistically different between the two groups. During the postoperative period, group 1 received analgesia of subcutaneous morphine (n = 35), epidural fentanyl (n = 30), or epidural bupivacaine (n = 21). In group 2, 6 patients with a nonfunctioning epidural catheter due to technical failure received a balanced general anesthesia and were eliminated from the study. During the postoperative period, group 2 received analgesia of subcutaneous morphine (n = 26), epidural fentanyl (n = 25), or epidural bupivacaine (n = 30). Cardiovascular morbidity did not differ between the two groups: 22 patients in group 1 and 19 patients in group 2 had a major postoperative cardiac event.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Independent role of arterial O2 tension in local control of coronary blood flow.

The aim of this study of a blood-perfused isolated rabbit heart preparation was to differentiate the effects on coronary resistance of large changes in arterial O2 tension (arterial PO2 = 45-400 Torr) from the effects of variations in arterial O2 content or myocardial O2 delivery. Standard stored human blood was resuspended in Krebs-Henseleit buffer and was oxygenated to obtain normal PO2, high PO2, and low PO2. Hemoglobin concentrations were adjusted to obtain the same arterial O2 content (CaO2) for the three PO2s. In a first set of experiments, in which coronary blood flow (CBF) was free and adapted to a constant perfusion pressure, switching from control [138 +/- 17 (SE) Torr] to high PO2 blood (380 +/- 27 Torr) induced a significant decrease in CBF and myocardial O2 consumption (MVO2). Switching from control (125 +/- 3 Torr) to low PO2 blood (49 +/- 5 Torr) induced a significant increase in CBF and MVO2. In a second set of experiments, the switch from control (159 +/- 5 Torr) to high PO2 (389 +/- 32 Torr) was performed in a preparation in which CBF and consequently O2 delivery were constant. Under these conditions, the increase in perfusion pressure demonstrated that PO2 affected coronary resistance, even though the O2 delivery was constant. No significant change in myocardial performance was observed in any of these experimental procedures. These results show that arterial PO2 may affect coronary blood flow regulation independently of any mediation by the autonomic nervous system and of any associated changes in O2 content or O2 delivery.

Animals↗
PubMed1990

[Postoperative cardiac insufficiency. The value of enoximone].

The authors discuss the physiopathological mechanisms of intra and postoperative cardiac failure and the different means of treatment. A distinction is made between the intra and postoperative periods: the factors which predispose to cardiac failure are different and the immediate postoperative period would seem to be the most dangerous in patients with reduced coronary or contractile reserves. Enoximone is a valuable and effective inotropic agent in this situation.

Acute Disease↗
PubMed1989

[Ischemia, myocardial infarction and epidural anesthesia in patients with coronary disease].

In patients with coronary artery disease, the beneficial effects of epidural anesthesia are well known and often emphasized. Thus, several studies have shown a decrease in the determinants of myocardial oxygen consumption, and an improvement in regional and global left ventricular performance. The disadvantages of epidural anesthesia in patients with coronary artery disease are also well known, however, rarely reported. These detrimental effects are dominated by a decrease in arterial pressure which in turn may compromise the coronary perfusion pressure and induce myocardial ischemia. These 2 case reports illustrate the occurrence of myocardial complications in relation to epidural anesthesia. These case reports contrast with data from the literature showing a beneficial influence of epidural anesthesia on the myocardium. However, the severity of the coronary artery disease in these 2 reported patients may explain this discrepancy. These case reports pointed out that the decrease in arterial pressure is not the exclusive mechanism by which myocardial ischemia may be observed during epidural anesthesia since an hemodynamically-unrelated ischemic episode is described. The treatment of myocardial ischemia during epidural anesthesia is illustrated by these 2 case reports. A relationship between myocardial ischemia and myocardial infarction is discussed from these observations.

Aged↗
PubMed1989

[Monitoring of mixed venous oxygen saturation in aortic surgery: value and limits].

This study aimed to determine perioperative changes in mixed venous oxygen saturation (SvO2) in patients undergoing aortic surgery. Continuous SvO2 monitoring was carried out using an Oximetrix pulmonary catheter. Fourteen patients were randomly assigned to 2 groups, group I (n = 7) patients being given a thoracic epidural anaesthetic with a supplementary general anaesthetic, and group II (n = 7) a general anaesthetic as usual. In both groups, SvO2 increased at induction. In group I patients, SvO2 decreased during surgery to less than 60% (n = 2) and less than 70% (n = 4). This fall was corrected by volume loading and intravenous ephedrine. The intraoperative decrease in SvO2 occuring in 2 group II patients was due to a fall in haematocrit in one, and a propranolol infusion in the other. Although patients in group I were all extubated early after the end of surgery (85 +/- 35 min), the lowest value of SvO2 after extubation was always greater than 60%. Patients undergoing aortic surgery under thoracic epidural anaesthesia can be extubated early, without markedly depressing peripheral reserves in oxygen extraction.

Anesthesia, Epidural↗