Acute hypoxemic respiratory failure in children: case mix and the utility of respiratory severity indices.

OBJECTIVE: Acute hypoxemic respiratory failure (AHRF) is a common reason for emergency pediatric intensive care. An objective assessment of disease severity from acute physiological parameters would be of value in clinical practice and in the design of clinical trials. We hypothesised that there was a difference in the best early respiratory indices in those who died compared with those who survived. DESIGN: A prospective observational study of 118 consecutive AHRF admissions with data analysis incorporating all blood gases. SETTING: A pediatric intensive care unit in a national children's hospital. INTERVENTIONS: None. RESULTS: Mortality was 26/118, 22% (95 % confidence interval 18-26%). There were no significant differences in the best alveolar-arterial oxygen tension gradient (A-aDO2, torr), oxygenation index (OI), ventilation index (VI), or PaO2/FIO2 during the first 2 days of intensive care between the survivors and non-survivors. Only the mean airway pressure (MAP, cm H2O) used for supportive care was significantly different on days 0 and 1 (p < 0.05) with higher pressure being used in non-survivors. Multiple logistic regression analysis did not identify any gas exchange or ventilator parameter independently associated with mortality. Rather, all deaths were associated with coincident pathology or multi-organ system failure, or perceived treatment futility due to pre-existing diagnoses instead of unsupportable respiratory failure. When using previously published predictors of outcome (VI > 40 and OI > 40; A-aDO2 > 450 for 24 h; A-aDO2 > 470 or MAP > 23; or A-aDO2 > 420) the risk of mortality was overestimated significantly in the current population. CONCLUSION: The original hypothesis was refuted. It appears that the outcome of AHRF in present day pediatric critical care is principally related to the severity of associated pathology and now no longer solely to the severity of respiratory failure. Further studies in larger series are needed to confirm these findings.

Thoracic electrical bioimpedance: a non-invasive measure of cardiac output for porcine research.

A comparison of two techniques for measuring cardiac output, thermodilution (TD) and thoracic electrical bioimpedance (TEB), was undertaken in a porcine model. Eight anaesthetized large white pigs were studied. A total of 436 paired measurements were performed over a range of cardiac outputs from 1.7 to 15.1 l/min as measured by thermodilution. The Pearson product moment correlation coefficient was r = 0.963 with P < 0.001. Analysis by Bland and Altman statistics revealed a mean difference (bias) of -0.02 l/min and the limits of agreement were +/- 1.6 l/min, similar to figures found in human comparative studies. These results confirm that thoracic electrical bioimpedance is a valid method of measuring cardiac output in pigs. It has significant advantages compared to thermodilution, in particular it is cheap, simple to use, non-invasive and provides continuous data.

Validation of thoracic electrical bioimpedance as a porcine research tool.

We have compared the accuracy of two methods of measuring cardiac output, thoracic electrical bioimpedance (TEB) and thermodilution (TD), in pigs. We studied four anaesthetized pigs, producing 145 paired cardiac output values over a range of TD cardiac outputs of 2.6-12.6 litre min-1. TEB cardiac output was less than that measured by TD, by a constant factor throughout the observed range of values, because of differences in porcine thoracic shape. The Pearson product moment correlation coefficient suggested a good correlation (r = 0.984, P < 0.001). More importantly, analysis by the Bland and Altman statistical method suggested a high level of agreement, with 95% confidence intervals of +/- 1.0 litre min-1. These results suggest that TEB can be used as a satisfactory method to measure cardiac output in porcine models.

Steroids for intubated croup masking airway haemangioma.

Recently, the beneficial role of steroids for acute laryngotracheobronchitis has been more clearly defined for both intubated and unintubated patients. However, corticosteroids also improve the clinical signs of airway haemangiomata. Two patients are described who illustrate how this can be a source of diagnostic confusion.