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Biomedical subjects

P Viars

Publications and source records attributed to P Viars.

At least 145 records · Page 8Linked to original sources
PubMed1988

Myocardial contusion in patients with blunt chest trauma as evaluated by thallium 201 myocardial scintigraphy.

Fifty five patients suffering from blunt chest trauma were studied to assess the diagnosis of myocardial contusion using thallium 201 myocardial scintigraphy. Thirty-eight patients had consistent scintigraphic defects and were considered to have a myocardial contusion. All patients with scintigraphic defects had paroxysmal arrhythmias and/or ECG abnormalities. Of 38 patients, 32 had localized ST-T segment abnormalities; 29, ST-T segment abnormalities suggesting involvement of the same cardiac area as scintigraphic defects; 21, echocardiographic abnormalities. Sixteen patients had segmental hypokinesia involving the same cardiac area as the scintigraphic defects. Fifteen patients had clinical signs suggestive of myocardial contusion and scintigraphic defects. Almost 70 percent of patients with blunt chest trauma had scintigraphic defects related to areas of myocardial contusion. When thallium 201 myocardial scintigraphy directly showed myocardial lesion, two-dimensional echocardiography and standard ECG detected related functional consequences of cardiac trauma.

Adult↗
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↗
PubMed1988

Ventilatory effects of continuous epidural infusion of fentanyl.

The effects of a continuous epidural administration of fentanyl on pain and on ventilation were studied in eight patients scheduled for orthopedic surgery of the knee. In each subject, epidural fentanyl was given by a bolus dose of 1 microgram.kg-1, followed by a continuous infusion of 1 microgram.kg-1.h-1 over 18 hours. Ventilatory measurements were performed during quiet breathing and during CO2 stimulation tests before surgery. After surgery measurements were made before epidural administration of fentanyl; 1, 2, 5, 18 hours after the start of epidural fentanyl infusion; and 6 hours after its discontinuation. Adequate pain relief was achieved in all patients during fentanyl administration. No significant change in ventilation was noted during quiet breathing. The slope of the ventilatory response to CO2 (VE/PaCO2) decreased significantly from 1.46 +/- 0.2 to 0.75 +/- 0.1 L.min-1.mm Hg-1 (mean +/- SEM; P less than 0.05) one hour after the onset of fentanyl administration, and remained stable throughout the infusion. Eighteen hours after the onset of epidural fentanyl infusion, VE/PaCO2 was still 0.76 +/- 0.14 L.min-1.mm Hg-1. At the end of fentanyl administration, plasma fentanyl levels measured in six patients had progressively increased from 0.42 +/- 0.02 ng.ml one hour after the onset of the infusion to 1.54 +/- 0.19 ng.ml at the end of the infusion. These results suggest that a continuous epidural administration of fentanyl is a technique of analgesia that can provide adequate pain relief but which is associated with ventilatory depression. However, with the doses used in this study, the ventilatory depression remained moderate and of no demonstrable clinical consequence.

Adult↗
PubMed1987

[High frequency jet ventilation].

High frequency jet ventilation (HFJV) is a new ventilation technique which ensures satisfactory gas exchanges with tidal volumes of about 2 ml . kg-1. A gas mixture under high pressure is "chopped up" by an electrically-controlled solenoid valve and delivered to the patient by an injection system. A specific heater-humidifier is required for optimal humidity and warmth of the gas mixture. HFJV creates a positive end-expiratory pressure effect in the alveoles, and the increase of mean intratracheal pressure observed accurately reflects the increase of mean alveolar pressure. Convection by direct alveolar ventilation plays a determinant role in CO2 clearance under HFJV, the other gas transport mechanisms being accessory. In respiratory failure with shock HFJV is better tolerated haemodynamically than conventional ventilation. The main indications of the new technique are ENT surgery, thoracic and tracheal surgery, lithotripsy, broncho-pleural and oesophago-tracheal fistulae and circulatory shock.

Anesthesia↗
PubMed1987

Transoesophageal echocardiographic monitoring of left ventricular function.

Technical advances in echocardiography, especially the introduction of oesophageal probes, have led to the extension of its indications to the field of anaesthesia and intensive care. Transoesophageal echocardiography (TEE) provides high quality imaging of the left ventricle in patients on ventilators. In addition, manipulation of the probe is performed near the patient's head and so does not interfere with the surgeon's job. This enables echocardiographic monitoring of left ventricular function throughout the operation. The information so obtained not only provides data about anatomical changes which is sometimes invaluable, but also allows quantification of left ventricular function which is the main advantage for anaesthetists. The images allow study of regional and global left ventricular contraction and the deduction of certain parameters of ventricular performance. The ability to perform real time monitoring of ventricular function throughout anaesthesia and the immediate postoperative period is all the more valuable in patients with limited cardiac and coronary reserve. This new method of monitoring gives a better understanding of the physiopathology of peroperative cardiac events and provides information which may guide the conduct of the anaesthesia and postoperative care.

Echocardiography↗
PubMed1987

[Motor block induced by spinal injection of pethidine. Quantification and comparison with lidocaine].

Intrathecal pethidine (or meperidine) at a dose of 1 mg.kg-1 has proved to be effective and useful for surgical procedures by producing a spinal nerve block due to its local anaesthetic properties. Motor blockade was assessed by dynamometric measurement of the dorsal flexion of foot in ten ASA I patients after subarachnoid pethidine, and in seven ASA I patients after subarachnoid 5% lidocaine at the same dosage. Measurements were made every 5 min during the first 30 min, then every 15 min until complete motor block recovery was obtained. Values were expressed as a percentage of the initial muscle strength registered before lumbar puncture. The two drugs gave a dramatic and similar decrease in muscle strength (92 vs 95%; NS). However, the delay of maximal effect was significantly longer with pethidine than with lidocaine (33.5 +/- 14 min vs 19 +/- 5.6 min; p less than 0.05). The duration of the motor blockade was similar for both drugs (116 vs 106 min) and the 25%-75% time intervals were identical (32 +/- 14 min vs 33 +/- 12.6 min). Two severe respiratory depressions were observed with pethidine, which were rapidly reversible by intravenous naloxone. Numerous other minor side-effects occurred more frequently with meperidine than with lidocaine. It was concluded that dynamometry gave an accurate description of motor blockade induced by spinal anaesthesia.

Adult↗
PubMed1987

Continuous i.v. infusion of labetalol for postoperative hypertension. Haemodynamic effects and plasma kinetics.

Labetalol is a combined alpha- and beta-adrenoreceptor blocking agent. A loading dose may be used to antagonize sympathetic overactivity rapidly after surgery and be followed by a continuous infusion to achieve a stable effect. The haemodynamic effects and pharmacokinetics of this method of labetalol administration were studied in six rewarmed, extubated and sedated patients 15 +/- 2 h after aortobifemoral bypass surgery. Patients were monitored with radial and thermistor-tipped pulmonary artery catheters. Labetalol 1.5 mg kg-1 was injected i.v. over 5 min and a maintenance infusion of 0.2 mg kg-1 h-1 was started 30 min later and continued for 5.5 h. Within 5 min of the loading dose, i.v. labetalol induced significant (P less than 0.05) decreases in mean arterial pressure (-32 +/- 11%), in heart rate (-20 +/- 11%) and in cardiac index (-26 +/- 15%) that lasted throughout the infusion. Changes in systemic vascular resistance were not uniform, but an increase was not observed in any patient. Mean stroke volume index and ventricular filling pressures were not significantly affected by labetalol administration. The mean measured steady state plasma concentration (Css) (264 +/- 46 ng ml-1) was higher than predicted (170 ng ml-1) because the clearance (13.1 +/- 2.4 ml kg-1 min-1) was lower than that used to calculate the infusion rate. We conclude that labetalol is an effective antihypertensive agent in the postoperative period. A Css can be achieved rapidly by such i.v. administration and this offers the advantage of inducing rapid and stable haemodynamic effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

High frequency jet ventilation: the influence of different methods of injection on respiratory parameters.

Fourteen critically ill patients with ventilatory failure were ventilated with HFJV using a constant driving pressure of 3 atm and a constant I:E ratio of 0.43. In six (group I) HFJV, using a frequency of 100 b.p.m., was delivered via a proximal injector cannula. Four injector cannulae (i.d. 1.8, 1.6, 1.4 and 1.2 mm, respectively) were used at random. In eight patients (group II), HFJV using three frequencies (100, 300 and 600 b.p.m.) was administered either via a 1.8-mm i.d. proximal injector cannula (proximal injection), for via a Hi-Lo jet tracheal tube (distal injection). The following indices were measured in vivo: mean airway pressure (Paw), mean pulmonary volume above apnoeic FRC (delta V), mean alveolar pressure (clamps method) and arterial blood-gas tensions. Injected volume (Vinj), entrainment (E) and tidal volume (VT) were measured in vitro using a water-sealed spirometer. Operating pressure (the pressure in the connecting tube) was measured directly using a high pressure calibrated transducer. In group I, Paw, delta V, PaO2, Vinj and VT significantly decreased whereas operating pressure and E significantly increased when the internal diameter of the injector cannula was reduced. In group II, Paw, delta V, E, VT and operating pressure significantly decreased, whereas Vinj increased and PaO2 and PaCO2 remained unchanged, when proximal injection was switched to distal injection. In both groups, a significant relationship was found between operating pressure and E. At a constant driving pressure, operating pressure increased with narrow injector cannulae and increased frequency, and decreased when proximal injection was switched for distal injection.

Adolescent↗
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↗
PubMed1987

Hormonal response to captopril pre-treatment during sodium nitroprusside-induced hypotension in man.

To assess the hormonal response to captopril pre-treatment during sodium nitroprusside (SNP) -induced hypotension, 12 patients were studied during a spinal surgical procedure. Haemodynamic data, plasma-renin activity, aldosterone, adrenaline and noradrenaline levels were measured. Patients were randomly allocated to two groups: Group I, control patients; Group II, 3 mg kg-1 captopril pre-treated patients. SNP requirement for the same level (mean arterial pressure (MAP) = 55 mmHg) and duration of hypotension (88.5 +/- 28.7 vs. 95.2 +/- 22.5 min) was significantly lower in Group II than in Group I (16.5 +/- 14.2 mg vs. 39.3 +/- 16.7 mg; P less than 0.05) and a lower SNP infusion rate was required to induce and to maintain hypotension. In Group II patients, MAP remained significantly lower than the control and Group I values for 30 min after SNP withdrawal. Cardiac index (CI) remained stable in both groups. Heart rate was not modified in Group II during hypotension. Plasma-renin activity rose more dramatically in Group II patients than in Group I both during hypotension (13.9 +/- 7.5 vs. 2.8 +/- 0.9 ng ml-1 h-1; P less than 0.05) and after hypotension (23.4 +/- 15.4 vs. 2.2 +/- 0.8 ng ml-1 h-1; P less than 0.05). Plasma catecholamine levels increased in both groups during hypotension and remained raised in captopril patients after SNP withdrawal. It can be concluded that recovery from hypotension may be delayed when using captopril and that sympathoadrenal activity induced by hypotension is not substantially altered by captopril pre-treatment, suggesting that sympathetic blockade might not be the mechanism by which captopril reduces SNP requirement during controlled hypotension for surgical procedure in man.

Adult↗
PubMed1987

[Transurethral surgery and persistent urinary infection: effect of a single preoperative dose of cefuroxime].

To evaluate the efficacy of cefuroxime, a second generation cephalosporin, in minimizing the risk of per and postoperative infection complications in patients with urinary tract infection undergoing transurethral surgery, 86 patients (ASA I, II) with persistent urinary tract infection despite antibiotic therapy were studied. A double blind protocol was followed. Patients were randomly assigned to receive 10 minutes before surgery either I.V. cefuroxime (1.5 g) (group C, n = 39) or placebo (group P, n = 47) the incidence of positive peroperative systematic blood cultures was lower in group C (9.7%) than in group P (25.2%) (p less than 0.001). The incidence of postoperative blood cultures taken when clinical septic signs were present, was significantly lower in group C (0%) than in group P (21.7%) (p less than 0.05). However neither the incidences of both postoperative urinary tract infection at the 48th postoperative hour and the clinical signs of bacteraemia including fever nor the average length of hospitalization were significantly different in the 2 groups. This lack of significant clinical benefit was not explained by the pharmacokinetic properties of this antibiotic. Thus, preoperative administration of a single dose of cefuroxime, reduces the incidence of per and postoperative bacteraemias in ASA I-II patients with persistent urinary tract infection.

Adolescent↗
PubMed1987

[Prevention of anuria in uretero-sigmoidostomy without catheter].

The development of anuria following catheter-less uretero-sigmoidostomy performed between 1977 and 1982 has led to a modification of the intra-operative and post-operative intensive care. During the period 1983 to 1985, the systematic intra-operative administration of furosemide immediately after performing the uretero-colonic anastomosis, the use of intra- and post-operative filling with control of filling pressures by a pulmonary arterial catheter, resulting in considerable diuresis, have been able to prevent anuria following this type of surgery.

Anuria↗
PubMed1986

Prevention of vasospasm in subarachnoid haemorrhage. A controlled study with nimodipine.

A prospective randomized double blind study was conducted in 70 patients suffering from subarachnoid haemorrhage, due to aneurysm rupture, to determine if the use of nimodipine reduces the severity of ischaemic deficits secondary to vasospasm. At the end of the study, two patients had severe deficit or died in the treated group, while 10 had a bad outcome in the placebo group. Angiographic vasospasm was not significantly different in its frequency or its severity between the two groups. However, the association of extensive and diffuse vasospasm was less frequent in the nimodipine group. This study confirms the effectiveness of Nimodipine in reducing the occurrence of neurological deficit due to vasospasm, even if this action is not observed in all cases.

Adolescent↗
PubMed1986

[Hemodynamic effect of the clamping of the carotid in the surgically treated coronary patient].

To determine both the incidence of myocardial ischaemia and haemodynamic response to carotid cross-clamping in coronary artery disease, 30 patients undergoing carotid endarterectomy were studied with a clear history of effort related disabling angina pectoris. Myocardial ischaemia was detected by a recording of lead CM5 of the electrocardiogram. A radial arterial and a thermodilution pulmonary catheter were inserted to obtain haemodynamic measurements before and after carotid cross-clamping and unclamping. Anaesthesia was induced with increments of thiopental, fentanyl 6 micrograms X kg-1 and pancuronium. Additional fentanyl (2 micrograms X kg-1) was injected before skin incision and before carotid cross-clamping. Carotid cross-clamping results in a significant increase in both mean arterial blood pressure and capillary wedge pressure. Two patients experienced myocardial ischaemia with ST segment depression during carotid cross-clamping. Nitroglycerin infusion led to the improvement of ST segment depression. When halothane was additionally administered to patients who developed hypertension in response to carotid cross-clamping, arterial blood pressure returned to normal value. These results indicate that carotid cross-clamping increases determinants of myocardial oxygen demand and may cause myocardial ischaemia in patients suffering from angina pectoris.

Aged↗
PubMed1986

[A case of spinal extradural hematoma during the insertion of an epidural catheter].

An epidural haematoma was observed after epidural lumbar puncture in a 75-year old patient receiving 5,000 units calcium heparinate every 12 h as antithrombotic therapy. The diagnosis was suspected by the occurrence of sudden pain and bleeding through the epidural catheter, followed by a complete paraplegia. The diagnosis was confirmed by contrast myelography. Early surgery did not improve the neurological deficit. This case report emphasized that anticoagulant therapy must be discontinued before epidural anaesthesia.

Aged↗