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Biomedical subjects

P Viars

Publications and source records attributed to P Viars.

At least 181 records · Page 10Linked to original sources
PubMed1985

Hepatic plasma flow during sodium nitroprusside-induced hypotension in humans.

Changes in hepatic plasma flow (HPF) during sodium nitroprusside (SNP) induced hypotension were studied in 14 patients undergoing intracranial aneurysm surgery under neurolept anesthesia. Patients were monitored with the use of a radial artery catheter and a thermistor-tipped Swan-Ganz catheter. Hypotension was induced with incremental increases in the rate of SNP infusion until a stable mean arterial pressure (MAP) 35-55 mmHg had been achieved. In one group (Group A) of 10 patients, indocyanine green (ICG) clearance was determined simultaneously with hemodynamic variables, before and during SNP hypotension. In a second group (Group B) of four patients, a catheter was inserted into a hepatic vein to determine the ICG hepatic extraction (HE) coefficient. In Group A, MAP decreased from 73 +/- 10 (SD) to 41 +/- 9 mmHg, while cardiac index (CI) decreased in six patients and increased in four patients. However, the mean value of CI did not change significantly. The mean value of ICG clearance was not significantly affected by SNP hypotension. Nevertheless, a positive linear correlation existed between individual variation in CI and ICG clearance (r = 0.96). On the other hand, no correlation was noted between the change in MAP and ICG clearance. In Group B patients, the ICG HE coefficient remained unchanged during SNP hypotension, suggesting that ICG clearance varies only according to the variation in HPF. In conclusion, this study demonstrated that HPF did not decrease, despite a range of 20-60% decrease in blood pressure when CI is maintained during SNP hypotension.

Adult↗
PubMed1985

Factors influencing pulmonary volumes and CO2 elimination during high-frequency jet ventilation.

An external spirometric method using a differential linear transformer was used to measure tidal volume (VT) and to determine factors influencing CO2 elimination and HFJV-induced "PEEP effect" in 15 critically ill patients under HFJV. VT increased with increasing driving pressure (DP) and decreasing frequency (f) and was influenced little by changes in I/E ratio. CO2 elimination, as reflected by the measurement of PaCO2, was mainly influenced by the absolute level of VT rather than by the product VT X frequency (PaCO2 = 5715/VT, r = 0.75, P less than 0.05). The primary phenomenon explaining HFJV-induced "PEEP effect" was intrapulmonary gas trapping due to incomplete exhalation of the first VT administered: the spontaneous relaxation times of these first VT were longer than expiratory time allotted to the ventilatory settings. HFJV-induced "PEEP effect" increased with I/E ratio, DP, and f and was markedly influenced by the mechanical properties of the total respiratory system. At given ventilatory settings, HFJV-induced "PEEP effect" was greater in patients with a normal or elevated time constant of the total respiratory system (tau RS) than in patients with a low tau RS. These results suggest that HFJV should not be used in patients with chronic obstructive pulmonary disease and asthma, and should be preferentially administered to patients having stiff lungs or decreased chest wall compliance.

Adult↗
PubMed1985

Left ventricular dysfunction after non-cardiac surgical procedures in patients with ischemic heart disease.

In order to demonstrate the presence of postischemic ventricular dysfunction after non-cardiac surgical procedures, myocardial perfusion scintigraphy with thallium 201 and radionuclide ventriculography were performed before and 24 h after intervention in 20 patients suffering from angina pectoris. A long-term ECG recording was used in all patients to detect peroperative myocardial ischemia. In 14 of the 20 patients studied, both ventriculography and thallium scintigraphy were unchanged at the postoperative study. Comparison of pre- and postoperative radionuclide data revealed an increased deficit in one patient, both increased deficit and decreased ejection fraction in four others and a decreased ejection fraction in one other. In these five last patients, continuous ECG recording demonstrated the occurrence of peroperative ST segment depression. These results underline the part played by prolonged peroperative episodes of myocardial ischemia in the occurrence of postoperative left ventricular dysfunction.

Adult↗
PubMed1985

[Determination of total nitrogen in biological milieux by chemoluminescence: a comparison with the reference method].

An assay technique for the chemiluminescent estimation of total nitrogen in biological samples have been used for two hundred urines and gastric fluids, and results compared with those given by the traditional Kjeldahl method. Chemiluminescence is accurate, reproducible, and appear to be well correlated with Kjeldahl assay technique. Without doubt, it is advantageous to the point of samples manipulation, that need no dangerous compounds, and by the way of her swiftness and her possible automation. Lastly, according with preliminary studies, this method seem as well practicable for solid samples as for liquid samples. This assay technique is therefore usefull in current practice to investigate nitrogen balance in every patient.

Feces↗
PubMed1984

Prediction of cerebral vasospasm value of fibrinogen degradation products (FDP) in the cerebro-spinal fluid (CSF) for prediction of vasospasm following subarachnoid haemorrhage due to a ruptured aneurysm.

In a new treatment regimen with antifibrinolytic drugs in patients with aneurysmal subarachnoid haemorrhages, we have systematically controlled the level of fibrinogen degradation products (FDP) in the cerebrospinal fluid (CSF). The frequency of severe vasospasm with clinical ischaemia has been compared with the patient's initial level of FDP. Fifty patients have been included in this study. (All in Hunt and Hess's grades I or II on their arrival.) Patients with a secondary deterioration unrelated to vasospasm were excluded. The FDP levels were measured in the first three days following the bleeding and we were informed of them at the end of the study. The diagnosis of severe vasospasm was confirmed by arteriography and computed tomography (CT) and it was named "severe" when accompanied with signs of clinical ischaemia. Twenty patients developed a severe vasospasm with clinical ischaemia. In these patients, the mean value of the initial FDP level was between 80 and 320 mcg/ml compared with 20 to 80 mcg/ml for those who had not developed clinical ischaemia (p = 0.0009). Furthermore, two different groups may be discriminated by their initial FDP level: FDP greater than 80 mcg/ml; n = 23, 65% severe vasospasm; FDP less than 80 mcg/ml; n = 27.8% no severe vasospasm (p less than 0.001). These results do not imply a direct role of FDP in pathophysiological mechanisms of vasospasm, but they suggest a relationship between the clot lysis and the appearance of vasospasm with clinical ischaemia. To our knowledge this is the first time that such a predictive role can be attributed to the initial FDP level in the prognosis of vasospasm.

Female↗
PubMed1984

Metronidazole kinetics and bioavailability in patients undergoing gastrointestinal surgery.

Kinetics and bioavailability of metronidazole were studied in 17 patients admitted in our emergency care unit for gastrointestinal surgery. All were treated with intravenous metronidazole (500 mg three times a day) before, during, and for 4 days after surgery. Seven of the patients continued the intravenous regimen and seven were switched to oral therapy with the same dose and dosing interval for 4 additional days. Kinetic evaluations were performed at steady state on days 4 and 8. The main unexpected result was a consistent 51% increase in AUC with no increase in elimination t 1/2 when intravenous was changed to oral therapy. This change was accompanied by an upward 75% shift in the trough metronidazole plasma concentrations. There was no change when patients remained on intravenous metronidazole. Reduction of clearance on oral treatment appears to be the most likely explanation.

Administration, Oral↗
PubMed1984

Oxygen drive to breathing during halothane anesthesia: effects of almitrine bismesilate.

The changes in ventilation and breathing pattern induced by the substitution of pure oxygen for room air were tested in patients during stable halothane anesthesia before and after the administration of almitrine bismesilate, a specific stimulant of the peripheral chemoreceptors. Ventilation was monitored in 25 patients for 15 min while breathing an air-halothane (1.5%) mixture and while breathing then for 10 min an O2-halothane (1.5%) mixture. The maneuver was repeated in 11 of these patients after the infusion of 0.5 mg/kg of almitrine bismesilate. Before almitrine administration, O2 inhalation caused a progressive decrease of minute-ventilation (VE) reaching 94.5 +/- 1.4% (mean +/- SEM) of the initial value at the tenth minute (P less than 0.01). This decrease was secondary to a progressive increase of inspiratory and expiratory times. Almitrine bismesilate caused a significant increase in VE (+11.6%), tidal volume (+14.0%), and mean inspiratory flow (+10.0%) when breathing the air-halothane mixture. Ten minutes after O2 administration, these variables were not different from those observed before almitrine infusion. This study shows that during halothane anesthesia, hypoxic ventilatory drive is not abolished but is depressed severely. Almitrine bismesilate can restore the hypoxic ventilatory drive.

Adult↗
PubMed1984

Respiratory effects of intrathecal morphine after upper abdominal surgery.

The effects of intrathecal (IT) administration of two doses of morphine (Group 1: 2 mg, n = 9; Group 2: 5 mg, n = 10) were studied in 19 patients after upper abdominal surgery. The ventilatory variables and occlusion pressure (P0.1) were recorded during room air breathing and during CO2 rebreathing tests prior to surgery, 24 h after surgery before IT morphine (n = 12), and 3, 5, 7, 11, and 24 h after injection. During room air breathing, minute ventilation (VE) did not change significantly in Group 1 and decreased significantly 3, 5, 7, and 11 h after injection in Group 2. During the rebreathing tests, there was a significant shift to the right of the ventilatory response to CO2 in both groups. The peak of the ventilatory depression was delayed, occurring 7 h and 11 h postinjection in Groups 1 and 2, respectively. Two patients in Group 2 developed clinically significant ventilatory depression. The shallow breathing observed after surgery was not changed after analgesia. In group 2, 5, mg IT morphine was responsible for a significant decrease in f60 (respiratory frequency for a PETCO2 of 60 mmHg). P0.1 increased markedly after surgery during both room air breathing and the rebreathing tests. After IT morphine, compared with the postoperative preanalgesic values, P0.1(60) (P0.1 at a PETCO2 of 60 mmHg) did not change in Group 1 and decreased significantly in Group 2. It is concluded that IT morphine is responsible for a ventilatory depression that is delayed and seems to be dose related and that analgesia does not abolish the shallow breathing observed after upper abdominal surgery.

Abdomen↗
PubMed1984

High-frequency jet ventilation vs continuous positive airway pressure for postoperative respiratory support.

In ten patients after recovery from general anesthesia for major vascular surgery, we compared continuous positive airway pressure (CPAP) and high-frequency jet ventilation (HFJV) at the same fractional concentration of oxygen in the inspired gas, both being superimposed on spontaneous breathing. The HFJV was delivered by a ventilator ( Acutronic VS-600) through the lateral lumen of a three-lumen endotracheal tube. Mean airway pressure was increased (3, 8, and 11 mm Hg) by adjusting the driving pressure during HFJV and by the setting of the expiratory valve during CPAP. During HFJV, the frequency (10 Hz) and inspiratory-expiratory ratio (0.25) were kept constant. Control values were measured when patients breathed spontaneously without positive end-expiratory pressure. Cardiac output and transmural filling pressures remained unchanged throughout the study. Neither the arterial oxygen pressure (PaO2) nor intrapulmonary shunt (Qs/Qt) changed significantly during CPAP. The 20- to 30-percent increase in PaO2 and the 5- to 10-percent decrease in Qs/Qt during HFJV when compared to control reflected a slightly but significantly (p less than 0.05) better oxygenation. The increase in arterial carbon dioxide tension was significantly greater during CPAP than during HFJV.

Airway Resistance↗
PubMed1984

Hemodynamic consequences of increasing mean airway pressure during high-frequency jet ventilation.

Six critically ill patients with acute respiratory failure were ventilated using high-frequency jet ventilation (HFJV)-frequency 100.min-1, driving pressure 35 psi, 1.8 mm inside diameter injector cannula. Hemodynamic measurements using radial artery and Swan-Ganz catheters, esophageal pressure (EP), and mean airway pressure (Paw) were measured at four different I:E ratios: 0.25, 0.43, 0.67 and 1.0. Static respiratory compliance, using the super syringe method, was measured during intermittent positive pressure ventilation (IPPV) and during HFJV. The results suggested that decreased venous return, increased right ventricular afterload, and decreased PaCO2 accounted for the decrease in cardiac index observed during HFJV using elevated I:E ratios. These variations, related to marked increases in intrathoracic pressures, are very similar to those observed during conventional ventilation with PEEP.

Adult↗
PubMed1984

Impact of changes in operating pressure during high-frequency jet ventilation.

Fifteen critically ill patients with acute respiratory failure were ventilated with high-frequency jet ventilation (HFJV; frequency 100 breaths/min; I/E ratio 0.43; 1.8-mm internal diameter injector cannula). The patients were divided into two groups according to their initial PaO2 during intermittent positive pressure ventilation at FIO21: in eight patients (group I) the mean PaO2 was 141 +/- 34 mm Hg, and in seven patients (group II) mean PaO2 was 376 +/- 75 mm Hg. During HFJV three different operating pressures were used at random: 1.3, 1.8, and 2.3 bars. Increase in operating pressures significantly decreased PaCO2 and significantly increased mean lung volume above apneic FRC, mean airway pressure, and mean alveolar pressure in both groups. A close relationship was found between variations in mean airway pressure and mean alveolar pressure (r = 0.99, P less than 0.001). Significant increases in PaO2 with increasing operating pressures were observed only in group I. In group II, PaCO2 was significantly lower than in group I for a given operating pressure. We conclude that operating pressure is a main determinant of arterial oxygenation during HFJV because of the concomitant increases in intrathoracic pressures and lung volume. Operating pressure also influences carbon dioxide clearance, PaCO2 varies inversely with operating pressure.

Adult↗