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Biomedical subjects

J F Baron

Publications and source records attributed to J F Baron.

At least 73 records · Page 4Linked to original sources
PubMed1989

Normovolemic hemodilution and lumbar epidural anesthesia.

This randomized study was designed to determine the cardiovascular effects of normovolemic hemodilution and lumbar epidural anesthesia in patients scheduled for vascular surgery. The patients were randomly assigned to three different groups: group 1 (N = 10) included patients undergoing lumbar epidural anesthesia without hemodilution; group 2 (N = 10) consisted of patients with normovolemic hemodilution without epidural anesthesia; and in group 3 (N = 10) normovolemic hemodilution was produced during lumbar epidural anesthesia. The three groups included several patients with a history of either myocardial infarction or stable mild angina or treated and controlled hypertension. In group 1, the level of epidural anesthesia reached T-9 +/- 1. After lumbar epidural anesthesia and 7 mL/kg colloid infusion, pulmonary capillary wedge pressure increased slightly but significantly above baseline, without significant changes either in mean arterial pressure or in cardiac index. In group 2, the same colloid infusion as in group 1 when infused before normovolemic hemodilution increased pulmonary capillary wedge pressure and cardiac index without significant effects on arterial blood pressure. Normovolemic hemodilution using a colloid solution decreased hemoglobin concentration (18%) and increased cardiac index significantly (9%). No significant change in systemic oxygen transport or in total body oxygen consumption was observed. In group 3, with anesthesia to T-9 +/- 1, hemodynamic changes were as observed in group 1. After normovolemic hemodilution, hemoglobin concentration decreased significantly (15%), whereas cardiac index increased significantly (15%) without significant changes either in mean arterial pressure or in heart rate. Systemic oxygen transport and total body oxygen consumption did not change significantly. No patient experienced chest pain or electrocardiographic evidence of myocardial ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Epidural↗
PubMed1988

Forearm vascular tone and reactivity during lumbar epidural anesthesia.

Forearm vascular tone and sympathetic reactivity were investigated in ten unpremedicated patients during two levels of epidural sensory blockade, neither of which levels was high enough to block cardiac sympathetic pathways. An 8-MHz pulsed Doppler blood flowmeter was used to determine brachial artery diameter and flow characteristics. Measurements were made before and during sympathetic stimulation induced by a contralateral isometric handgrip. The lower level of sensory blockade (T11) in the absence of sympathetic stimulation was associated with decreases in right atrial pressure, brachial artery diameter (3.9 +/- 0.2 vs 4.2 +/- 0.2 mm, P less than 0.05) and brachial blood flow (42 +/- 5 vs 66 +/- 7 ml.min-1, p less than 0.001), whereas forearm vascular resistance increased significantly (2.2 +/- 0.3 vs 1.5 +/- 0.2 mm Hg.ml-1.min-1, P less than 0.01). Neither heart rate nor mean arterial pressure changed. At the higher level of blockade (T7), right atrial pressure and systemic arterial pressure decreased further without change in heart rate. Brachial artery diameter (3.8 +/- 0.2 mm) remained unchanged while brachial blood flow additionally decreased (30 +/- 3 ml.min, P less than 0.05), and forearm vascular resistances further increased (3.0 +/- 0.2 mm Hg.ml-1.min-1, P less than 0.01). Changes in heart rate and in mean arterial pressure associated with isometric exercise were similar before and during epidural anesthesia at both levels of epidural blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Left ventricular global and regional function during lumbar epidural anesthesia in patients with and without angina pectoris. Influence of volume loading.

The influence of lumbar epidural anesthesia without cardiac sympathectomy on global and regional left ventricular function was investigated prior to surgery in eight normal subjects (group 1) and in ten patients suffering from stable mild effort-related angina (group 2). In both groups, epidural blockade was performed with 10 ml 0.5% plain bupivacaine. To differentiate the effects due to epidural blockade from those related to volume expansion, three sets of measurements were obtained: control, epidural blockade without volume loading, and epidural blockade with volume loading (500 ml lactated Ringer's solution). Radionuclide angiography was used to determine cardiac output, left ventricular ejection fraction, end systolic and end diastolic volumes, and to analyse left ventricular wall motion. Peak systolic pressure-end systolic volume ratio was used as an index of myocardial contractility. Seventy-two hours postoperatively, a thallium 201 myocardial scintigraphy obtained after iv dipyridamole detected myocardial defects in all patients with a history of angina. These defects were fully redistributed in eight out of ten patients. Throughout the procedure, patients with a history of angina exhibited neither chest pain nor ECG evidence of myocardial ischemia. At control, left ventricular ejection fraction (LVEF) and systolic pressure-volume ratio (SPVR) were lower in group 2 than in group 1 (LVEF: 0.54 +/- 0.02 vs. 0.64 +/- 0.02, P less than 0.01), (SPVR: 2.3 +/- 0.2 vs. 3.3 +/- 0.4 mmHg/ml, P less than 0.05). In addition, 19 hypokinetic sectors were found in group 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Effects of high-frequency jet ventilation on arterial baroreflex regulation of heart rate.

Fifteen anesthetized mechanically ventilated patients recovering from multiple trauma were studied to compare the effects of high-frequency jet ventilation (HFJV) and continuous positive-pressure ventilation (CPPV) on arterial baroreflex regulation of heart rate. Systolic arterial pressure and right atrial pressure were measured using indwelling catheters. Electrocardiogram (ECG) and mean airway pressure were continuously monitored. Lung volumes were measured using two linear differential transformers mounted on thoracic and abdominal belts. Baroreflex testing was performed by sequential intravenous bolus injections of phenylephrine (200 micrograms) and nitroglycerin (200 micrograms) to raise or lower systolic arterial pressure by 20-30 Torr. Baroreflex regulation of heart rate was expressed as the slope of the regression line between R-R interval of the ECG and systolic arterial pressure. In each mode of ventilation the ventilatory settings were chosen to control mean airway pressure and arterial PCO2 (PaCO2). In HFJV a tidal volume of 159 +/- 61 ml was administered at a frequency of 320 +/- 104 breaths/min, whereas in CPPV a tidal volume of 702 +/- 201 ml was administered at a frequency of 13 +/- 2 breaths/min. Control values of systolic arterial pressure, R-R interval, mean pulmonary volume above apneic functional residual capacity, end-expiratory pulmonary volume, right atrial pressure, mean airway pressure, PaCO2, pH, PaO2, and temperature before injection of phenylephrine or nitroglycerin were comparable in HFJV and CPPV. Baroreflex regulation of heart rate after nitroglycerin injection was significantly higher in HFJV (4.1 +/- 2.8 ms/Torr) than in CPPV (1.96 +/- 1.23 ms/Torr).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Influence of venous return on baroreflex control of heart rate during lumbar epidural anesthesia in humans.

The role of variation of venous return on baroreflex control of heart rate during lumbar epidural anesthesia was investigated in 12 unpremedicated patients. Group 1 patients (n = 6) received 8 ml of 0.5% plain bupivacaine in the epidural space (L3-4) (mean upper level of analgesia at T10). Group 2 patients (n = 6) received 8 ml of saline at the same level in the epidural space. Following the epidural injection, phenylephrine (PHE) and nitroglycerin (NTG) were employed to alter the stimulation of baroreceptor sites before and during application of lower body positive pressure (LBPP). Plasma bupivacaine, catecholamines, renin activity, and vasopressin were assayed. In contrast to saline, epidural bupivacaine induced a decrease in systolic arterial and right atrial pressures (-11 +/- 4 and -3.2 +/- 0.7 mmHg, respectively, mean +/- SEM) without change in heart rate, an increase in baroreflex slopes during PHE and NTG injections (+5.9 +/- 1.6 ms/mmHg and +2.8 +/- 0.9 ms/mmHg, respectively), and a decrease in plasma norepinephrine (-248 +/- 89 pg/ml). The application of LBPP restored hemodynamic and reflex variables to preepidural analgesia values, whereas plasma catecholamines decreased further. Plasma renin activity and vasopressin were not modified at any time in either groups. This study indicates that lumbar epidural anesthesia enhances cardiac vagal tone mainly through a decrease in venous return.

Adult↗
PubMed1985

Influence of caloric intake on the respiratory mode during mandatory minute volume ventilation.

Mandatory minute volume ventilation has been proposed as a method for weaning patients from ventilators. The purpose of this study was to delineate the influence of caloric intake on spontaneous ventilation in patients receiving mandatory minute volume ventilation. While the value of such ventilation remained unchanged, eight patients were studied at the following three different levels of daily caloric intake: (1) level A, mean of 223 kcal/sq m; (2) level B, mean of 1,380 kcal/sq m; and (3) level C, mean of 2,100 kcal/sq m. We performed gas exchange measurements and a 24-hour recording of ventilation with a monitoring system providing distinction between spontaneous and mechanical cycles. We found that the ventilatory mode was markedly dependent upon the nutritional intake; the percentage of spontaneous ventilation over 24 hours increased from 11 +/- 7 percent (+/- SE) during diet A to 50 +/- 9 percent during diet B and 79 +/- 8 percent during diet C. This increment paralleled the increase in production of carbon dioxide with caloric intake. We suggest therefore that the patient's ability to breathe spontaneously when receiving mandatory minute volume ventilation should be interpreted according to caloric intake.

Aged↗
PubMed1983

[Contamination of an oxygen delivery circuit by compressed air].

Routine checking of the FIO2 of a mixture delivered by a ventilator revealed large discrepancies between the FIO2 assigned and that effectively delivered, the latter being low. Measurements of FIO2 at the wall outlets showed the O2 delivery pipeline to be contaminated by compressed air. By disconnecting all the ventilators supplied by this pipeline one after the other, one ventilator, or rather its blender, was found responsible.

Air↗
PubMed1983

Total IgE, specific IgE and prick-tests against foods in common migraine--a prospective study.

A prospective study of total IgE, specific IgE against 12 common foods, and prick-tests with 11 common food allergens was performed on 50 consecutive migraine sufferers. Total IgE levels were found above 100 kU/l for seven patients, but five of them were atopic. Prick-tests and RAST were positive for four and six patients (class 1), respectively. Food challenge on these six patients did not cause any migraine attacks. This study thus indicates a very low frequency of allergic dietary migraine to common foods.

Adolescent↗