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Biomedical subjects

O D Timmons

Publications and source records attributed to O D Timmons.

11 recordsLinked to original sources
PubMed1996

The impact of extracorporeal membrane oxygenation on survival in pediatric patients with acute respiratory failure. Pediatric Critical Care Study Group.

OBJECTIVE: Extracorporeal membrane oxygenation (ECMO) has been used with increasing frequency in the treatment of acute respiratory failure in pediatric patients. Our objective in this study was to test the hypothesis that ECMO improves outcome in pediatric patients with acute respiratory failure. DESIGN: Multicenter, retrospective cohort analysis. SETTING: Forty one pediatric intensive care units participated in the study under the auspices of the Pediatric Critical Care Study Group. PATIENTS: All pediatric patients admitted to the participating institutions with acute respiratory failure during 1991 were included. Patients with congenital heart disease, contraindications to ECMO, or incomplete data were excluded, yielding a data set of 331 patients from 32 hospitals. INTERVENTIONS: Conventional mechanical ventilation, high-frequency ventilation, and extracorporeal membrane oxygenation. MEASUREMENTS AND MAIN RESULTS: Multivariate logistic regression analysis was used to identify factors associated with survival. In a second analysis, pairs of ECMO and non-ECMO patients, matched by severity of disease and respiratory diagnosis, were compared. The use of ECMO (p = .0082), but not the use of high-frequency ventilation, was associated with a reduction in mortality. Other factors independently associated with mortality included oxygenation index (p < .0001), Pediatric Risk of Mortality score (PRISM) (p < .0001) and the Paco2 (p = .045). In 53 diagnosis- and risk-matched pairs, there was a significantly lower mortality rate (26.4% vs. 47.2%; p < .01) in the ECMO-treated patients. When all patients were stratified into mortality risk quartiles on the basis of oxygenation index and PRISM score, the proportion of deaths among ECMO-treated patients in the 50% to 75% mortality risk quartile was less than half the proportion in the non-ECMO treated patients (28.6% vs. 71.4% p < .05)> No effect was seen in the other quartiles. CONCLUSIONS: The use of ECMO was associated with an improved survival in pediatric patients with respiratory failure. The lack of association of outcome with treatment in the ECMO-capable hospital or with another tertiary technology (i.e. high-frequency ventilation) suggests that ECMO itself was responsible for the improved outcome. Further studies of this procedure are warranted but require broad-based multi-institutional participation to provide sufficient statistical power and sensitivity to demonstrate efficacy.

Acute Disease↗
PubMed1995

Inhaled nitric oxide prevents the increase in pulmonary vascular permeability caused by hydrogen peroxide.

Given the interest in using inhaled nitric oxide (NO.) to treat acute lung injury and the importance of oxygen radicals in its pathogenesis, we studied the effects, in buffer-perfused isolated rabbit lungs, of inhaled NO. (24 ppm) on the injury caused by generating hydrogen peroxide with glucose and glucose oxidase (GOX). Experiments were performed at a constant pulmonary arterial pressure. GOX substantially augmented vascular permeability, as demonstrated by an increase in the lung-to-perfusate 125I-labeled albumin ratio, lavage-to-perfusate 125I-albumin ratio, wet-to-dry lung weight ratio, and pulmonary vascular filtration coefficient. Lungs treated with inhaled NO. before perfusion with GOX had lung-to-perfusate and lavage-to-perfusate 125I-albumin ratios that were not significantly different from control values and intermediate between the control and GOX groups. Inhaled NO. also prevented the increase in wet-to-dry lung weight ratio and pulmonary vascular filtration coefficient caused by GOX.. Thus inhaled NO. substantially reduced in the isolated lung the increase in pulmonary vascular permeability produced by the intravascular generation of hydrogen peroxide.

Administration, Inhalation↗
PubMed1995

Predicting death in pediatric patients with acute respiratory failure. Pediatric Critical Care Study Group. Extracorporeal Life Support Organization.

OBJECTIVE: To estimate mortality risk in pediatric patients with acute hypoxemic respiratory failure (AHRF). DESIGN: Retrospective chart review. SETTING: Forty-one pediatric ICUs. SUBJECTS: Four hundred seventy children with AHRF. We defined AHRF as mechanical ventilation with positive end-expiratory pressure > or = 6 cm H2O and fraction of inspired oxygen greater than or equal to 0.5 for 12 or more hours. MEASUREMENTS: Physiologic and treatment variables were recorded every 12 h for 14 days. Cases were randomly assigned to score development and score validation subsets. Variables were assessed for their association with mortality in the development subset by logistic regression analysis. The analysis generated a series of logistic equations, which we called the Pediatric Respiratory Failure (PeRF) score, to estimate mortality risk at 12-h intervals over the first 7 days of treatment for AHRF. The predictive ability of the score was assessed in the validation subset by receiver operating characteristic curve area and goodness-of-fit chi 2. RESULTS: Mortality of the collected cases was 43%. The PeRF score included age, operative status, Pediatric Risk of Mortality score, fraction of inspired oxygen, respiratory rate, peak inspiratory pressure, positive end-expiratory pressure, PaO2, and PaCO2. Area under the receiver operating characteristic curve was 0.769 at entry and increased to greater than 0.8 after 36 h. When the score was applied to the validation subset of patients, goodness-of-fit chi 2 showed no significant difference between estimated and actual mortality between 0 and 96 h. CONCLUSIONS: The PeRF Score accurately estimated mortality risk in this retrospectively sampled group of high-risk pediatric patients with AHRF. This score may be useful in studies of newer therapies for pediatric AHRF, though prospective validation is necessary before it could be used to make clinical decisions.

Adolescent↗
PubMed1994

Advances in the critical care of poisoned paediatric patients.

Recent improvements in paediatric intensive care may potentially improve outcome for severely poisoned children. The application of advanced techniques of critical care to the poisoned paediatric patient encompasses a wide variety of therapeutic and technical innovations that are primarily directed towards support of the cardiopulmonary system and removal of toxins. New extracorporeal removal techniques such as continuous arterio-venous haemofiltration have not substantively increased our ability to remove toxins except in rare instances. Exotic techniques such as extracorporeal membrane oxygenation remain in the background for use in rare instances only, with little clear data on the relative risks and benefits of applying them.

Chelation Therapy↗
PubMed1993

Modes of death in the pediatric intensive care unit: withdrawal and limitation of supportive care.

OBJECTIVE: To determine the frequency of withdrawal or limitation of supportive care for children dying in a pediatric intensive care unit (ICU). DESIGN: Retrospective review of medical records. SETTING: Pediatric ICU in a tertiary care children's hospital. PATIENTS: All children dying in the pediatric ICU over a 54-month period (n = 300). INTERVENTIONS: Medical record review. MEASUREMENTS AND MAIN RESULTS: Data recorded for each patient included diagnosis, mode of death, and whether the child was brain dead. Each patient was assigned to one of the following mode of death categories: brain dead; active withdrawal of supportive care (meaning removal of the endotracheal tube); failed cardiopulmonary resuscitation; allowed to die without cardiopulmonary resuscitation (do-not-resuscitate status). A total of 300 patients were identified. Diagnoses included postoperative congenital heart disease (n = 56), head trauma (n = 38), near-miss sudden infant death syndrome (n = 28), pneumonia (n = 22), sepsis (n = 21), near-drowning (n = 21), various anoxic insults (n = 20), multiple trauma (n = 17), and patients with other diagnoses (n = 77). Mode of death was active discontinuation of support in 95 (32%) patients, do-not-resuscitate status in 78 (26%), brain death in 70 (23%), and failed cardiopulmonary resuscitation in 57 (19%). CONCLUSIONS: In a large, multidisciplinary pediatric ICU, the most common mode of death was active withdrawal of support. In addition, more than half (173/300, 58%) of children dying in the pediatric ICU underwent either active withdrawal or limitation (do-not-resuscitate status) of supportive care.

Brain Death↗
PubMed1991

Mortality rates and prognostic variables in children with adult respiratory distress syndrome.

In a retrospective chart review of cases of adult respiratory distress syndrome in our pediatric intensive care unit from 1987 to 1990, we attempted to identify the physiologic variables predictive of death. We identified 44 children with adult respiratory distress syndrome; the mortality rate was 75%. We found significant differences between survivors and nonsurvivors in intrapulmonary venous admixture (Qsp/Qt), mean airway pressure (Paw), alveolar-arterial oxygen tension difference (P(A-a)O2), oxygenation index, and peak inspirator pressure; Qsp/Qt greater than 0.5, Paw greater than 23 cm H2O, and P(A-a)O2 greater than 470 mm Hg were 93%, 90%, and 81% predictive of death, respectively, in this study population. Sensitivity and specificity were enhanced when we linked multiple predictors, but this linkage was seldom successful because few patients had more than one positive predictor. We propose to use the individual predictors that we have identified as randomization criteria in a future trial of extracorporeal membrane oxygenation for pediatric cases of adult respiratory distress syndrome.

Adolescent↗
PubMed1990

Effects of serum and endotoxin in experimental lung injury.

Lipopolysaccharide (LPS) is in large part responsible for the lung injury that occurs in the sepsis syndrome. Recent work has shown the ability of LPS alone to induce injury in endothelial monolayers, though the LPS effect is enhanced in the presence of serum. We previously demonstrated that low-dose LPS (50 ng/mL) can lead to lung injury in an isolated perfused rabbit lung model. To examine the effect of serum on LPS-induced injury rabbit lungs were perfused with increasing doses of rabbit serum in the presence and absence of LPS. There was no increase in total weight gained by the lung,Qf, with either 5% serum, 10% serum, or 10% serum with LPS. However vascular permeability as measured by hydraulic conductance was increased with increasing doses of serum. This effect was not enhanced by the addition of LPS. These results provide evidence that serum alone may cause lung injury, perhaps through the activation of complement or other mediators.

Animals↗