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Biomedical subjects

P Viars

Publications and source records attributed to P Viars.

At least 55 records · Page 3Linked to original sources
PubMed1993

Histologic aspects of pulmonary barotrauma in critically ill patients with acute respiratory failure.

OBJECTIVE: To describe histologically pulmonary barotrauma in mechanically ventilated patients with severe acute respiratory failure. DESIGN: Assessment of histologic pulmonary barotrauma. SETTING: A 14-bed surgical intensive care unit (SICU) PATIENTS: The lungs of 30 young critically ill patients (mean age 34 +/- 10 years) were histologically examined in the immediate post-mortem period. None of them were suspected of pre-existing emphysema. MEASUREMENTS AND RESULTS: Clinical events and ventilatory settings used during mechanical ventilation were compared with lung histology. Airspace enlargement, defined as the presence of either alveolar overdistension in aerated lung areas or intraparenchymal pseudocysts in nonaerated lung areas, was found in 26 of the 30 lungs examined (86%). Patients with severe airspace enlargement (2.6-40 mm internal diameter) had a significantly greater incidence of pneumothorax (8 versus 2, p < 0.05), were ventilated using higher peak airway pressures (56 +/- 18 cmH2O versus 44 +/- 10 cmH2O, p < 0.05) and tidal volumes (12 +/- 3 ml/kg versus 9 +/- 2 ml/kg, p < 0.05), were exposed significantly longer to toxic levels of oxygen (8.6 +/- 9.4 days versus 1.9 +/- 2 days at FIO2 > 0.6, p < 0.05) and lost more weight (6.3 +/- 9.2 kg versus 0.75 +/- 5.8 kg, p < 0.05) than patients with mild airspace enlargement (1-2.5 mm internal diameter). CONCLUSION: Underlying histologic lesions responsible for clinical lung barotrauma consist of pleural cysts, bronchiolar dilatation, alveolar overdistension and intraprenchymal pseudocysts. Mechanical ventilation appears to be an aggravating factor, particularly when high peak airway pressures and large tidal volumes are delivered by the ventilator.

Adult↗
PubMed1993

[Peroperative perfusion of fentanyl or sufentanil: plasma concentrations and postoperative respiratory changes].

This study was designed to assess postoperatively the time course of respiratory depression due to fentanyl (F) or sufentanil (S), as well as the plasma concentrations. Seventy patients scheduled for orthopaedic surgery lasting more than 3 hours were randomly assigned to two groups, F (n = 8) or S (n = 9). Anaesthesia was induced with etomidate (0.3 mg.kg-1), droperidol (0.15 mg.kg-1), vercuronium (0.1 mg.kg-1), a loading dose of either F (10 micrograms.kg-1) or S (1 microgram.kg-1), and maintained with 60% nitrous oxide in oxygen, and an infusion of F (6 micrograms.kg-1.h-1) or S (0.6 microgram.kg-1.h-1). Mechanical ventilation was maintained postoperatively in the recovery room until the patient could be extubated. PetCO2, SpO2, fR and F and S plasma concentrations were assessed at the end of the opioid infusion, at extubation, every hour for the first 6 hours, and thereafter every 2 h for a further 10 and 18 h. Time to extubation was the same in both groups (301 +/- 141 and 307 +/- 148 min). At the time, plasma concentrations of F and S were 1.35 +/- 0.9 ng.ml-1 and 0.14 +/- 0.07 ng.ml-1 respectively. Secondary peaks in plasma concentration (78% mean increase in comparison to the previous figure) were observed in 6 patients in group F. No similar peaks occurred in group S. Mean elimination half-life was shorter with sufentanil (457 +/- 130 min) than with fentanyl (325 +/- 132 min) (not significant). The results of this study suggest that sufentanil results less frequently in postoperative secondary peaks than fentanyl.

Adult↗
PubMed1993

[Comparison of hemodynamic effects of the laryngeal mask and the orotracheal tube].

This prospective study was designed to compare the haemodynamic response to insertion of either a laryngeal mask or an orotracheal tube. Twenty patients scheduled for orthopaedic surgery were randomly assigned to two groups : laryngeal mask group (n = 10) and orotracheal tube group (n = 10). Patients were premedicated with flunitrazepam (1 mg i.m.) and anaesthesia was induced with propofol (bolus of 2.5 mg.kg-1, followed by a continuous infusion of 10 mg.kg-1.h-1) and vecuronium (0.1 mg.kg-1). Heart rate and mean arterial pressure were assessed non-invasively before and after induction of anaesthesia and immediately after tube or laryngeal mask insertion. Orotracheal intubation elicited a significant increase in heart rate (92 +/- 16 vs 77 +/- 19 b.min-1, p < 0.05) and in mean arterial pressure (117 +/- 21 vs 85 +/- 16 mmHg, p < 0.05), whereas there was significant increase in heart rate (74 +/- 11 vs 72 +/- 12 b.min-1) and mean arterial pressure (86 +/- 8 vs 81 +/- 10 mmHg) after insertion of the laryngeal mask. In both groups, plasma catecholamine concentrations were not significantly modified after tube or laryngeal mask insertion. It is concluded that, under propofol anaesthesia, laryngeal mask insertion does not induce any significant haemodynamic response in ASA 1 patients. In the opposite, orotracheal intubation increases both heart rate and mean arterial pressure.

Adult↗
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↗
PubMed1993

[Effects of postoperative autotransfusion in prosthetic surgery of the hip with the ConstaVac device].

A new device for postoperative autotransfusion (ConstaVac, Stryker) was assessed after total hip replacement in 43 patients, mean age 63 +/- 13 years. Intraoperative blood was administered to 27 patients (63%), autologous blood only in 19, homologous blood only in 6 and both autologous and homologous blood in 2. The blood shed during an average 5-hour postoperative period had an haematocrit of 23 +/- 7% and included only few platelets (72 +/- 83 G.l-1). It did not clot as it contained there was less than 0.1 g.l-1 of fibrinogen and a high concentration of D-dimers. In 30 patients (70%), the amount of blood thus collected exceeded 200 ml. An average of 327 +/- 131 ml were subsequently retransfused to these patients. Postoperative autotransfusion induced a moderate but significant decrease in platelet counts (205 +/- 66 vs. 224 +/- 67 G.l-1, p < 0.02) and fibrinogen concentrations (2.3 +/- 0.7 vs. 2.4 +/- 0.6 g.l-1, p < 0.03), and an increase in circulating D-dimers (p < 0.001). Coagulation tests, free plasma haemoglobin and potassium concentrations were not significantly altered. Since the haematocrit of the blood lost was lower than that of the patients', the haematocrit did not increase significantly. Posttransfusion shivering occurred in two patients (7%). Bacteriological cultures of the lost blood and of venous samples obtained after postoperative autotransfusion remained sterile. Postoperative autotransfusion is a simple technique with few side-effects, which might be safely associated with other methods used to decrease the rate of homologous blood transfusion.

Adult↗
PubMed1993

Effects of thoracic extradural block on diaphragmatic electrical activity and contractility after upper abdominal surgery.

BACKGROUND: Upper abdominal surgery (UAS) induces diaphragmatic dysfunction. Thoracic extradural block (TEB) using 0.5% bupivacaine improves some pressure and motion indices of diaphragmatic function. However, no direct information on diaphragmatic activity is available after UAS. The aim of this study was to assess diaphragmatic electrical activity (Edi) after UAS before and after TEB. METHODS: A postoperative electromyogram was obtained, using intramuscular electrodes inserted by the surgeon in the costal and crural parts of the diaphragm, in 14 patients undergoing abdominal aortic surgery. Tidal changes in abdominal (VAB) and rib-cage (VRC) volumes, and gastric (delta Pgas), esophageal (delta Pes), and transdiaphragmatic (delta Pdi) pressures were used to measure tidal volume (VT) and respiratory rate and to provide indirect indices of diaphragmatic activity from the two ratios VAB/VT and delta Pgas/delta Pdi. These respiratory variables were obtained preoperatively. Postoperatively, measurements including Edi were obtained before and after a segmental epidural block, reaching a T4 level was achieved with 0.5% plain bupivacaine. RESULTS: Upper abdominal surgery induced an increase in respiratory rate (+28 +/- 15%; P < .01), associated with a decrease in VAB/VT (from 0.75 +/- 0.11 to 0.07 +/- 0.08; P < .01), delta Pgas/delta Pdi (from 0.3 +/- 0.08 to 0.01 +/- 0.19; P < .05), and VT (-30 +/- 14%; P < .01). After surgery, all patients exhibited electrical diaphragmatic activity that increased with TEB by 48 +/- 28% (P < .01) and 60 +/- 22% (P < .001) for the cural and costal segments, respectively. The ratio delta Pdi/Edi, used to evaluate diaphragmatic contractility, was not modified by TEB. Tidal volume, respiratory rate, and delta Pgas/delta Pdi returned to preoperative levels, whereas VAB/VT increased but remained different from preoperative values. CONCLUSIONS: This study demonstrates that TEB produces an increase in diaphragmatic activity, identical for the two segments of the muscle. Interruption of afferents that produce an inhibitory effect on diaphragmatic activity appears the most attractive hypothesis to explain the consequences of TEB after UAS.

Aorta, Abdominal↗
PubMed1993

Effects of etomidate on the cardiac papillary muscle of normal hamsters and those with cardiomyopathy.

BACKGROUND: Etomidate has been shown to induce no significant inotropic effect on normal myocardium, but its effects on diseased myocardium remain unknown. METHODS: The effects of etomidate (1 and 5 micrograms/ml) on the intrinsic contractility of left ventricular papillary muscle from normal hamsters and those with cardiomyopathy (strain BIO 82.62, 6 months old) were investigated in vitro (Krebs-Henseleit solution, 29 degrees C, pH 7.40, Ca++ 2.5 mM, stimulation frequency 3/min). RESULTS: The contractility of papillary muscles from hamsters with cardiomyopathy was less than that of controls, as shown by the decrease in maximum shortening velocity (-25%, P < .001), isometric active force (-45%, P < .01), peak power output (-57%, P < .01), and sarcoplasmic reticulum function (P < .01). Etomidate did not induce a significant inotropic effect, as shown by the absence of changes in maximum shortening velocity and active isometric force, except at 5 micrograms/ml in cardiomyopathic hamsters (+8 +/- 10%, P < .05). The effects of etomidate on these inotropic parameters were not different in normal and cardiomyopathic hamsters. Etomidate impaired contraction-relaxation coupling under low load in both groups, suggesting that etomidate decreased sarcoplasmic function. This impairment was less (P < .02) pronounced in cardiomyopathic muscles. The effects of etomidate on contraction-relaxation coupling under heavy load were not different between groups. In both groups, etomidate had no effect on the peak power output and the curvature of the total force-velocity curve, suggesting that it did not modify the muscle myothermal economy. CONCLUSIONS: Etomidate had only a slight effect on the intrinsic mechanical properties of hamster cardiac papillary muscles, and these effects did not depend on the pathophysiologic state of the myocardium. These results may be clinically useful as, unlike etomidate, most anesthetics depress myocardial contractility.

Animals↗
PubMed1993

Early diagnosis of traumatic thoracic aortic rupture by transesophageal echocardiography.

Traumatic aorta rupture survival depends on early diagnosis requiring aortography. Aortography is the "gold standard" method, but it is time-consuming and may be dangerous in trauma patients with multiple organ injuries. Transesophageal echocardiography is a noninvasive technology that can be performed at the bedside. We report two cases in which transesophageal echocardiography enabled us to make the early diagnosis of thoracic descending aorta rupture.

Adult↗
PubMed1993

Combined severe myocardial and pulmonary contusion: early diagnosis with transesophageal echocardiography and management with high-frequency jet ventilation: case report.

We report the case of a 27-year-old patient with blunt thoracic trauma in whom transesophageal echocardiography enabled an early diagnosis of severe myocardial contusion. Conventional mechanical ventilation dramatically enhanced cardiogenic shock because of myocardial contusion, requiring increasing doses of catecholamine. High-frequency jet ventilation produced an immediate improvement in hemodynamic status, permitting a decrease in catecholamine administration.

Adult↗
PubMed1992

Comparative arterial antithrombotic activity of clopidogrel and acetyl salicylic acid in the pig.

We investigated the comparative antithrombotic properties of clopidogrel, an analogue of ticlopidine, and aspirin, using the Folts' model on femoral arteries in 22 pigs. On each animal, clopidogrel or aspirin were used to treat the thrombotic process on the left femoral artery and to prevent this process on the right femoral artery. Sequentially: an injury and stenosis were carried out on the left femoral artery; the thrombotic process was monitored with a Doppler during a 30-min observation period for cyclic flow reductions or permanent cessation of flow; after the first cyclic flow reduction occurred, clopidogrel (5 mg kg-1) or aspirin (2.5, 5, 100 mg kg-1) were injected intravenously; if cyclic flow reductions were abolished, epinephrine (0.4 micrograms kg-1 min-1) was injected to try to restore cyclic flow reductions and/or permanent cessation of flow; then injury and stenosis were applied on the right femoral artery. Before and after injection of clopidogrel or aspirin, ear immersion bleeding times and ex-vivo platelet aggregation were performed. Clopidogrel (n = 7) abolished cyclic flow reductions were efficiently prevented, even for two injuries. Basal bleeding time (5 min 28) was lengthened (> 15 min, 30 min after clopidogrel and remained prolonged even after 24 h). ADP-induced platelet aggregation was inhibited (more than 78%). Comparatively, aspirin had a moderate and no dose-dependent effect. Aspirin 2.5 mg kg-1 (n = 6) abolished cyclic flow reductions in 2 animals, CFR reoccurred spontaneously in one animal and epinephrine restored it in a second animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Continuous positive airway pressure (CPAP) vs. intermittent mandatory pressure release ventilation (IMPRV) in patients with acute respiratory failure.

Intermittent Mandatory Pressure Release Ventilation (IMPRV) is a positive pressure spontaneous breathing ventilatory mode in which airway pressure is released intermittently and synchronously with patient's spontaneous expiration in order to provide ventilatory assistance. Eight critically ill patients free of any factor known to alter chest wall mechanics (group 1) and 8 critically ill patients whose spontaneous respiratory activity was markedly altered by a flail chest, or by a C5 quadraplegia and/or by the administration of opioids (group 2) were studied prospectively. CPAP and IMPRV were administered to each patient in a random order during a 1 h period using a CESAR ventilator. Gas flow, tidal volume, tracheal pressure, esophageal pressure, end-expiratory lung volume and hemodynamic parameters were measured. In group 1 patients, the ventilatory assistance provided by IMPRV was associated with a significant decrease in spontaneous tidal volume whereas all other respiratory parameters remained unchanged. In group 2 patients, IMPRV increased minute ventilation from 8.0 +/- 2.61/min to 12.2 +/- 1.81/min (p less than 0.05), decreased PaCO2 from 46 +/- 7.3 mmHg to 38 +/- 6.8 mmHg (p less than 0.05) and reduced respiratory frequency from 21 +/- 10 bpm to 14 +/- 5.7 bpm (p less than 0.07). These results show that IMPRV provides significant ventilatory assistance to patients with mild acute respiratory failure either by decreasing patient's contribution to minute ventilation or by increasing alveolar ventilation in presence of respiratory depression of central or peripheral origin.

Acute 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

[Tracheal intubation in patients with cervical spine injuries using a fiber optic laryngoscope].

Eleven patients, with a cervical spine injury and scheduled for elective cervical spine fusion at least 48 h after their initial trauma, were intubated using a new fiberoptic laryngoscope (Bullard). This technique uses either a semi-rigid guide independent of the laryngoscope blade, or a rigid one attached to the blade. The cervical spine was immobilized with either a collar or a halo. General anaesthesia was carried out with thiopentone, fentanyl and vecuronium bromide. Orotracheal intubation was successful at the first attempts in 10 out of the 11 patients. No mobilization of the cervical spine occurred. In the first six patients, the semi-rigid guide was used, and the rigid one in the remaining five. The anaesthetist who carried out the intubations was always the same. Using the rigid guide was easier than the semi-rigid one. This is confirmed by the time required, 44 +/- 22 sec for the rigid guide, and 97 +/- 92 sec for the semi-rigid one. In the patient in whom this technique failed at the first attempt, endotracheal intubation was carried out by the nasal route and controlled by the fiberoptic laryngoscope. This technique enables a rapid and easy orotracheal intubation in trauma patients with an immobilized cervical spine, but careful training is necessary.

Adolescent↗
PubMed1992

In vitro effects of propofol on rat myocardium.

Propofol is a short-acting intravenous induction agent that induces cardiovascular depression. However, the effects of propofol on intrinsic myocardial contractility remain debatable. Thus, we studied the effects of three concentrations of propofol (1, 3, and 10 micrograms.ml-1, respectively) and its solvent on the mechanics and energetics of isolated rat left ventricular papillary muscles. Propofol and its solvent did not induce any significant inotropic effect as shown by the lack of significant changes in maximum unloaded shortening velocity and in active isometric force. Nevertheless, propofol induced a slight decrease in isometric force (92 +/- 6%, 95 +/- 5%, and 95 +/- 4%, respectively, all P less than 0.01) under certain experimental conditions (i.e., after isometric stabilization). Using various afterloaded twitches, the peak power output and the curvature of the force-velocity curve were calculated. Propofol and its solvent did not significantly modify these two energetic parameters, indicating that it did not change myothermal economy and cross-bridge kinetics. Propofol impaired isotonic relaxation, suggesting that it decreased calcium uptake by the sarcoplasmic reticulum, whereas its solvent alone did not. However, alteration of sarcoplasmic reticulum function was moderate, since postrest potentiation and postrest recovery were unmodified after propofol. It was concluded that propofol induces moderate changes on intrinsic myocardial contractility. These results suggest that cardiovascular depression observed with propofol in vivo is not related to intrinsic myocardial depression.

Animals↗
PubMed1992

Nosocomial bronchopneumonia in the critically ill. Histologic and bacteriologic aspects.

To provide a comprehensive description of the histologic and bacteriologic characteristics of human nosocomial bronchopneumonia (BPN), the lungs of 83 critically ill patients decreased after a period of mechanical ventilation were examined in the immediate postmortem period. In addition, the accuracy of the protected minibronchoalveolar lavage (BAL) technique in the diagnosis of nosocomial BPN was evaluated. In each patient, a surgical pneumonectomy was performed at the bedside within 30 min following death. Each pulmonary lobe was sampled and bacteriologically analyzed using semiquantitative cultures in 50 patients and quantitative cultures in 33 patients. The entire lung was histologically analyzed using 5 to 10 slices per lung segment. In 69 patients, the bacteriologic result of a protected mini-BAL performed within 48 h preceding death was compared with histologic and bacteriologic results of study of the lung tissue itself. Histologic lesions of BPN were found in 43 of the 83 lungs examined. These lesions were (1) severe in the majority of patients (confluent BPN, n = 23; lung abscess, n = 6), (2) preferentially found in dependent lung segments, (3) often associated with nonspecific alveolar damage, (4) associated with positive lung cultures in 65% of patients (53% with gram-negative bacteria), (5) polymicrobial in 28% of patients, (6) characterized by a lobar bacterial burden greater than 10(3) cfu/g in 32% of cases. Using semiquantitative bacteriologic analysis, the sensitivity and the specificity of the protected mini-BAL in the diagnosis of nosocomial BPN were found to be 70 and 69%, respectively. Protected mini-BAL identified 77% of causative microorganisms of BPN.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchoalveolar Lavage Fluid↗
PubMed1992

Variation in arterial to end-tidal CO2 tension differences during anesthesia in the "kidney rest" lateral decubitus position.

The course of arterial to end-tidal carbon dioxide tension difference [P(a-ET)CO2] was evaluated during general anesthesia in 25 patients scheduled for renal surgery performed in the "kidney position." The difference between arterial PCO2 (PaCO2) corrected to body temperature, and end-tidal PCO2 (PETCO2) measured by mass spectrometry was assessed after induction of anesthesia, after placement in the lateral decubitus position with back arched over a kidney bridge ("kidney position"), and every 20 min until the patients were replaced in the supine position at the end of the surgical procedure. Heart rate, arterial blood pressure, and esophageal temperature were simultaneously recorded. After induction of anesthesia, when the patients were lying supine (T1), P(a-ET)CO2 was 4.8 +/- 3.9 mm Hg (mean +/- SD). Placing the patients in the kidney position (T2) induced a significant increase in P(a-ET)CO2 (to 7.9 +/- 3.5 mm Hg; P less than 0.01). These alterations occurred without any significant change in mean arterial blood pressure or heart rate. A progressive increase in mean P(a-ET)CO2 occurred with maintenance of anesthesia; P(a-ET)CO2 reached 8.8 +/- 4.1 mm Hg (P less than 0.05 vs T2) and 8.9 +/- 4.4 mm Hg (P less than 0.05 vs T2) at 65 and 85 min, respectively, after lateral decubitus positioning. Large variations between and within patients were observed. Although stable mean arterial pressure was maintained, these changes were associated with a significant decrease in body temperature. These results demonstrate that P(a-ET)CO2 increases when patients are placed in the kidney position and may vary with the prolongation of anesthesia in this situation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗