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Biomedical subjects

A Torres

Publications and source records attributed to A Torres.

At least 487 records · Page 27Linked to original sources
PubMed1993

Serum TNF levels in neonatal sepsis and septic shock.

Tumor necrosis factor (TNF-alpha) has been implicated as a principal mediator in the pathogenesis of septic shock. TNF-alpha was measured by immunoradiometric assay in serum samples from 23 full-term infants with sepsis (15 with severe infection and 8 with septic shock) and in 20 healthy full-term newborns. Serum TNF-alpha levels were significantly higher in the group with sepsis, at the time of admission to the neonatal intensive care unit, than in the healthy neonates. The highest TNF levels were found in those newborns with septic shock, particularly in those who died. Although the method is far too slow for any clinical routine work, our results suggest that the presence of elevated serum TNF-alpha levels could be considered a sensitive and specific test for predicting septic shock and its clinical outcome.

Female↗
PubMed1993

Effect of gamma irradiation on reactivity of rinderpest virus antigen with bovine immune serum in enzyme-linked immunosorbent assays and virus neutralization and indirect fluorescent-antibody tests.

Gamma irradiation effectively inactivated gradient-purified rinderpest virus. Irradiated antigen and sera remained functional in enzyme-linked immunosorbent assays, virus neutralization tests, and indirect fluorescent-antibody tests. Irradiation, however, led to a dose-dependent decrease in reactivity, particularly significant (P < 0.05) when both reagents were irradiated. To avoid false-positive reactions, only one reagent (serum or antigen) may be irradiated.

Animals↗
PubMed1993

Effects of thyroid hormones on cardiac development in oculo.

Embryonic rat myocardium was grafted into the anterior eye chamber (in oculo) of adult host rats in a series of two experiments that studied the effects of thyroid hormones [triiodothyronine (T3) and thyroxine (T4)] on heart tissue developing without hemodynamic load. In each experiment, surgical sympathectomy of one eye chamber was used to define possible interactions between thyroid hormones and sympathetic innervation to the graft. In the first experiment, propylthiouracil (PTU, 20 mg/kg sc) greatly suppressed growth and beating rate of whole heart grafts, while excess T4 (0.1 mg/kg sc) transiently increased beating rate but not growth. In the second experiment, T3 (5 mg/21 days, slow-release pellet) failed to promote growth in ventricular grafts. However, the size of atrial grafts in surgically sympathectomized eye chambers was larger in T3-treated compared with control rats. T3 administration increased beating rate in ventricular grafts. In both experiments, thyroid hormone treatments were effective in increasing heart weight-to-body weight ratios in the host rats. The data suggest that exposure to normal levels of thyroid hormones may be necessary for optimal cardiac growth. The data also support the hypothesis that a hemodynamic load is required for thyroid hormone-induced cardiac growth.

Animals↗
PubMed1993

Regional diaphragmatic length and EMG activity during inspiratory pressure support and CPAP in awake sheep.

We examined diaphragmatic mechanics in awake sheep during quiet breathing (QB) and the randomized application of 5, 10, and 15 cmH2O continuous positive airway pressure (CPAP), inspiratory pressure support (IPS), and equal combinations of IPS and CPAP (IPS/CPAP). We measured esophageal, gastric, and transdiaphragmatic (Pdi) pressures and regional length, shortening, and electromyogram (EMG) activity of both costal and crural diaphragmatic segments. Segmental resting length normalized to QB decreased during 15 cmH2O CPAP (costal, 19.2 +/- 3.3%; crural, 7.5 +/- 2.1%; P < 0.05) and during 15/15 cmH2O IPS/CPAP (costal 25.3 +/- 4.8%, crural 9.9 +/- 2.6%; P < 0.05). Only during 15 cmH2O IPS did costal shortening fraction increase (67% QB; P < 0.05). Compared with QB, during 15 cmH2O CPAP, end-tidal CO2 increased 6 Torr, regional EMG activity increased threefold, and Pdi increased 58%. During 15 cmH2O IPS these values decreased 3 Torr, threefold, and 44% respectively, but during IPS/CPAP they remained unchanged. Expiratory gastric pressure (Exp-Pga) reached 4.3 +/- 0.4 cmH2O at 15 cmH2O CPAP, but during IPS/CPAP Exp-Pga was less (maximum of 1.7 +/- 0.4 cmH2O) than at comparable CPAP (P < 0.05), despite the shorter diaphragmatic length. We conclude that: 1) IPS alters the actions of the diaphragm during CPAP, 2) Exp-Pga is poorly coupled to diaphragmatic end-expiratory length, and 3) both IPS and the release of Exp-Pga assist active diaphragmatic shortening.

Animals↗
PubMed1993

Validation of a volumeless breath-by-breath method for measurement of respiratory quotient.

Measurement of respiratory quotient (RQ) is useful as an indicator of changes in CO2 equilibrium or metabolism. Because of technical difficulties when volumetric or mixed expired methods are applied to clinical practice, we sought to validate a method of volumeless breath-by-breath RQ measurement based on real-time analysis of inspired and alveolar concentrations of O2, CO2, and N2 alone. We derived our volumeless method from a modified three-compartment lung model and tested the validity of the model by comparing it with a standard volumetric open-circuit method. Data from 1,736 breaths from 25 healthy adult volunteers for a total of 78 epochs were collected. Inspired, end-tidal, and mixed expired gas compositions were analyzed by Raman spectroscopy, and RQ values from 0.6 to 2.4 were obtained. Linear regression of the volumeless breath-by-breath method against the open-circuit method yielded a line with a slope of 1.002 (95% confidence interval 0.928 to 1.076) and an intercept of 0.066 (95% confidence interval -0.008 to 0.146) with an R2 of 0.91 (P < 0.001). We analyzed agreement by several methods and used mathematical modeling to predict precision with variations in epoch length and breath volume, which were verified by Monte Carlo techniques. We demonstrated that RQ can be measured reliably and easily using this volumeless breath-by-breath technique.

Blood Gas Analysis↗
PubMed1993

Specificity of endotracheal aspiration, protected specimen brush, and bronchoalveolar lavage in mechanically ventilated patients.

The specificity of the different techniques used to diagnose ventilator-associated pneumonia is still a matter of controversy. To investigate the specificity of endotracheal aspiration (EA), protected specimen brush (PSB), and bronchoalveolar lavage (BAL) quantitative cultures, we studied 27 consecutive mechanically ventilated (MV) patients (> 72 h) without clinical or radiographic evidence of pulmonary infection. Comparing different thresholds for quantitative cultures (from 10(3) through 10(6) CFU/ml), the lowest rate of false positive results was obtained using 10(6) for EA, 10(5) for PSB, and 10(6) for BAL. Using 10(6) CFU/ml for EA, 10(4) CFU/ml for PSB, and 10(5) CFU/ml for BAL as cutoff points, we obtained the following specificities: 85, 85, and 78% for the three techniques, respectively. A bacterial index of 8 was the best threshold to get a low percentage of false positive results for all techniques except for EA (0% for PSB and 12% for BAL). There were reasonable qualitative agreements (PSB versus EA = 58%; BAL versus EA = 69%; and PSB versus BAL = 62%) and poor quantitative correlations between concomitantly isolated microorganisms from the three types of samples. Quantitative cultures of EA, PSB, and BAL may show a considerable percentage of false positive results at the respective cutoff points usually accepted. Increasing the thresholds for quantitative cultures, albeit loosing sensitivity, may rule out better the absence of pulmonary infection in MV patients.

Bacteria↗
PubMed1993

Gastric and pharyngeal flora in nosocomial pneumonia acquired during mechanical ventilation.

We studied the interrelations between gastric, pharyngeal, proximal, and distal airway bacterial flora in ventilator-associated pneumonia (VAP) on 36 patients with nosocomial pneumonia acquired during mechanical ventilation (MV) and 27 mechanically ventilated control subjects without pulmonary infection. Gastric, pharyngeal, and endotracheal (EA) sampling for quantitative cultures were performed upon all patients, as well as fiberoptic bronchoscopy with protected specimen brush (PSB) sampling. Mean bacterial and fungi colony counts were significantly increased in pharyngeal, EA, and PSB samples in patients with VAP compared with control subjects. The overall increase in colonization was due to gram-positive cocci in all samples. In addition, gram-negative bacilli and fungi mean counts increased significantly in PSB pneumonia samples versus control samples. However, mean gastric colonization was similar in both patients with VAP and control subjects. In the former group there was an increase in coincident microorganisms isolated from gastric, pharyngeal, and EA samples in relation to PSB samples compared with control samples. Among the different quantitative cultures analyzed, only those obtained from EA significantly correlated with PSB cultures in patients with pneumonia (r = 0.67, p = 0.001). In summary, the present study shows that the coincidence between microorganisms isolated in PSB cultures and those from gastric and oropharynx increase in MV patients with pneumonia, indicating that both reservoirs play a key role in the pathogenesis of pneumonia. Conceivably, preventing both gastric and pharyngeal colonization may reduce the incidence of ventilator-associated pneumonia. From all the noninvasive samples studied only endotracheal aspirate cultures were useful for inferring the etiology of some VAP pneumonias.

Bacteria↗
PubMed1993

Quantitative cultures of endotracheal aspirates for the diagnosis of ventilator-associated pneumonia.

Bronchoalveolar lavage (BAL) and protected specimen brushing (PSB) are the most commonly used methods for diagnosing ventilator-associated (VA) pneumonia although they require bronchoscopy. Endotracheal aspiration (EA) is a simple and less costly technique than PSB or BAL. The purpose of our study was to investigate the diagnostic value of EA quantitative cultures and to compare the results obtained using EA with those obtained using PSB and BAL in mechanically ventilated patients with or without pneumonia. We prospectively studied 102 intubated patients divided into three diagnostic categories: Group I (definite pneumonia, n = 26), Group II (uncertain status, n = 48), and Group III (control group, n = 28). All patients received prior antibiotic treatment. EA, PSB, and BAL were obtained sequentially in all patients. When comparing Group I with Group III and using 10(5) cfu/ml as a threshold, we found that EA quantitative cultures represented a relatively sensitive (70%) and relatively specific (72%) method to diagnose VA pneumonia. The specificity of BAL and PSB (87% and 93%, respectively) was better than that of EA. The negative predictive value of EA cultures was higher (72%) when compared with that obtained using PSB (34%) (p < 0.05). EA quantitative cultures correlated with PSB and BAL quantitative cultures in patients with definite pneumonia. Although EA quantitative cultures are less specific than PSB and BAL for diagnosing VA pneumonia, our results suggest that the former approach may be used to treat these patients when bronchoscopic procedures are not available.

Bacteria↗
PubMed1993

Endotoxin-induced pulmonary dysfunction is prevented by C1-esterase inhibitor.

In septic shock, hypotension, disseminated intravascular coagulation, and neutrophil activation are related to the activation of the blood coagulation contact system. This study evaluates in dogs the effect of the C1-esterase inhibitor (C1-INH), a main inhibitor of the blood coagulation contact system, on the cardiovascular and respiratory dysfunction associated with endotoxic shock. Two groups were included: controls, which received Escherichia coli endotoxin, and a C1-INH group in which C1-INH was infused before E. coli endotoxin administration. In both groups, endotoxin produced hypodynamic shock; however, the decrease in the systolic index and the ventricular systolic work indexes were greater in controls than the C1-INH group. In controls, the arterial O2 partial pressure decreased by 30% and the alveolo-arterial O2 difference increased by 625%, these parameters remained unchanged in the C1-INH group. Hypoxemia was associated with increased intrapulmonary shunt, decreased blood coagulation contact factors, and decreased C3c. In contrast, C1-INH administration prevented endotoxin-induced hypoxemia, the increase in intrapulmonary shunt, and the decrease in blood coagulation contact factors. This study shows that, in dogs with endotoxic shock, pulmonary dysfunction is associated with an activation of the blood coagulation contact phase system. An inhibition of this system by C1-INH prevented the hypoxemia induced by endotoxic shock.

Animals↗
PubMed1993

[The prescription of physical exercise in the individual with aortic prostheses. The role of Doppler exercise study].

BACKGROUND AND OBJECTIVES: Exercise Doppler echocardiography allows measure valvular gradient during exercise, that could be useful in the prescription of physical activity in patients with a prosthetic aortic valve. METHODS: Exercise Doppler echocardiography was performed in 50 patients (mean age 53 +/- 12 years) with normally-functioning aortic prosthesis. Maximal exercise was performed by supine bicycle ergometry in 35 and modified Bruce protocol in 15. Continuous wave Doppler examinations were obtained at rest, during and at maximal exercise with a nonimaging transducer. RESULTS: The mean value of workload was 6.9 +/- 2 METS and there were no complications. Gradients at peak exercise were available in 43/50 patients. Exercise induced a statistic significant increase in the heart rate (76 +/- 14 to 136 +/- 26), systolic blood pressure (128 +/- 19 to 182 +/- 19 mmHg), peak gradient (29 +/- 9 to 61 +/- 17 mmHg) and mean gradient (16 +/- 5 to 32 +/- 9 mmHg). The gradient was greater than 59 mmHg in 18/43 patients, greater than 69 mmHg in 12/43 and greater than 79 mmHg in 5/43. CONCLUSIONS: Prescription of exercise in patients with aortic prosthesis requires perform an exercise Doppler echocardiography to measure the increase of valvular gradient with the exercise in each patient, since the stress testing could be normal, it can advise a rate of physical activity that determine very high prosthetic gradients.

Adult↗
PubMed1993

Fibrinolytic activity during hemodialysis: a biocompatibility-related phenomenon.

According to recent reports, fibrinolytic activity may be enhanced during hemodialysis. The aim of this work was to study the fibrinolytic activity in uremic patients, and to evaluate the effect of membrane biocompatibility on the fibrinolytic system during hemodialysis. Tissue plasminogen activator (t-PA), t-PA antigen, plasminogen activator-inhibitor (PAI), plasminogen (PL) and alpha-2-antiplasmin (AP) were measured in 10 uremic patients on maintenance hemodialysis treated sequentially with Cuprophane and polyacrylonitrile (AN69) membranes. Blood samples were obtained before and at 15, 60 and 120 minutes after the initiation of dialysis. Blood was also collected from 20 healthy individuals who served as controls. During cuprophane dialysis, t-PA increased significantly at 60 minutes (14.8 vs. 8.4 IU/ml, P < 0.05) and at 120 minutes (13.8 P < 0.01). This was accompanied by an increase in t-PA antigen, which was significant at 15 (5.1 vs. 13.1 ng/ml), 60 (15.2) and 120 (9.6) minutes (P < 0.05) of dialysis. However, during AN69 dialysis t-PA and t-PA antigen plasma levels remained stable. No significant changes were observed in PL, AP or PAI during hemodialysis with either membrane. In conclusion, hemodialysis enhances fibrinolytic activity, which is likely the result of t-PA Ag release. Therefore, this phenomenon seems to be closely related to dialysis membrane biocompatibility.

Adult↗
PubMed1992

Six new cases of a caterpillar-induced bleeding syndrome.

We describe six new cases of a hemorrhagic diathesis induced by contact with Lonomia achelous caterpillars. Onset of clinical bleeding varied between a few hours and 10 days post-exposure. Laboratory coagulation tests showed prolonged PT, PTT and ThT; normal platelets and a marked decrease of fibrinogen, factor V, plasminogen and factor XIII (including its subunits A and S). Factors VII, II and alfa 2 anti-plasmin were variably affected. In addition, activation of the fibrinolytic system and the generation of a procoagulant effect could also be demonstrated. Two cases developed severe hemorrhagic diathesis and one of them died of a cerebral hemorrhage. Different aspects of this rare syndrome are discussed in relation to its complex physiopathology and the variability observed in all clinical and laboratory manifestations. Therapeutic recommendations and some possible hazards following replacement transfusions are also considered.

Adult↗
PubMed1992

Pulmonary aspiration of gastric contents in patients receiving mechanical ventilation: the effect of body position.

OBJECTIVE: To determine if the semirecumbent position (45-degree angle) decreases aspiration of gastric contents to the airways in intubated and mechanically ventilated patients. DESIGN: A randomized, two-period crossover trial. SETTING: Respiratory intensive care unit. PATIENTS: Nineteen patients requiring intubation and mechanical ventilation. INTERVENTIONS: Patients were studied in the supine and semirecumbent positions on two separate days. MEASUREMENTS: After technetium (Tc)-99m sulphur colloid labeling of gastric contents, sequential radioactive counts in endobronchial secretions were measured at 30-minute intervals over a 5-hour period. Samples of endobronchial secretions, gastric juice, and pharyngeal contents were obtained for qualitative bacterial cultures. RESULTS: Mean radioactive counts in endobronchial secretions were higher in samples obtained while patients were in the supine position than in those obtained while patients were in the semirecumbent position (4154 cpm compared with 954 cpm; P = 0.036). Moreover, the aspiration pattern was time-dependent for each position: For the supine position, radioactivity was 298 cpm at 30 min and 2592 cpm at 300 min (P = 0.013); for the semirecumbent position, radioactivity was 103 cpm at 30 min and 216 cpm at 300 min (P = 0.04). The same microorganisms were isolated from stomach, pharynx, and endobronchial samples in 32% of studies done while patients were semirecumbent and in 68% of studies done while patients were in the supine position. CONCLUSIONS: We conclude that the supine position and length of time the patient is kept in this position are potential risk factors for aspiration of gastric contents. Elevating the head of the bed for patients who can tolerate the semirecumbent position may be a simple, no-cost prophylactic measure.

Female↗