Does taking endurance into account improve the prediction of weaning outcome in mechanically ventilated children?

INTRODUCTION: We conducted the present study to determine whether a combination of the mechanical ventilation weaning predictors proposed by the collective Task Force of the American College of Chest Physicians (TF) and weaning endurance indices enhance prediction of weaning success. METHOD: Conducted in a tertiary paediatric intensive care unit at a university hospital, this prospective study included 54 children receiving mechanical ventilation (> or = 6 hours) who underwent 57 episodes of weaning. We calculated the indices proposed by the TF (spontaneous respiratory rate, paediatric rapid shallow breathing, rapid shallow breathing occlusion pressure [ROP] and maximal inspiratory pressure during an occlusion test [Pimax]) and weaning endurance indices (pressure-time index, tension-time index obtained from P(0.1) [TTI1] and from airway pressure [TTI2]) during spontaneous breathing. Performances of each TF index and combinations of them were calculated, and the best single index and combination were identified. Weaning endurance parameters (TTI1 and TTI2) were calculated and the best index was determined using a logistic regression model. Regression coefficients were estimated using the maximum likelihood ratio (LR) method. Hosmer-Lemeshow test was used to estimate goodness-of-fit of the model. An equation was constructed to predict weaning success. Finally, we calculated the performances of combinations of best TF indices and best endurance index. RESULTS: The best single TF index was ROP, the best TF combination was represented by the expression (0.66 x ROP) + (0.34 x Pimax), and the best endurance index was the TTI2, although their performance was poor. The best model resulting from the combination of these indices was defined by the following expression: (0.6 x ROP) - (0.1 x Pimax) + (0.5 x TTI2). This integrated index was a good weaning predictor (P < 0.01), with a LR+ of 6.4 and LR+/LR- ratio of 12.5. However, at a threshold value < 1.3 it was only predictive of weaning success (LR- = 0.5). CONCLUSION: The proposed combined index, incorporating endurance, was of modest value in predicting weaning outcome. This is the first report of the value of endurance parameters in predicting weaning success in children. Currently, clinical judgement associated with spontaneous breathing trials apparently remain superior.

Can generic paediatric mortality scores calculated 4 hours after admission be used as inclusion criteria for clinical trials?

INTRODUCTION: Two generic paediatric mortality scoring systems have been validated in the paediatric intensive care unit (PICU). Paediatric RISk of Mortality (PRISM) requires an observation period of 24 hours, and PRISM III measures severity at two time points (at 12 hours and 24 hours) after admission, which represents a limitation for clinical trials that require earlier inclusion. The Paediatric Index of Mortality (PIM) is calculated 1 hour after admission but does not take into account the stabilization period following admission. To avoid these limitations, we chose to conduct assessments 4 hours after PICU admission. The aim of the present study was to validate PRISM, PRISM III and PIM at the time points for which they were developed, and to compare their accuracy in predicting mortality at those times with their accuracy at 4 hours. METHODS: All children admitted from June 1998 to May 2000 in one tertiary PICU were prospectively included. Data were collected to generate scores and predictions using PRISM, PRISM III and PIM. RESULTS: There were 802 consecutive admissions with 80 deaths. For the time points for which the scores were developed, observed and predicted mortality rates were significantly different for the three scores (P < 0.01) whereas all exhibited good discrimination (area under the receiver operating characteristic curve >or=0.83). At 4 hours after admission only the PIM had good calibration (P = 0.44), but all three scores exhibited good discrimination (area under the receiver operating characteristic curve >or=0.82). CONCLUSIONS: Among the three scores calculated at 4 hours after admission, all had good discriminatory capacity but only the PIM score was well calibrated. Further studies are required before the PIM score at 4 hours can be used as an inclusion criterion in clinical trials.

Influence of respiratory system impedance on volume and pressure delivered at the Y piece in ventilated infants.

OBJECTIVES: Tidal volume (VT) delivered to infants' airways are overestimated and pressure underestimated when measured in the ventilator and not at the Y piece. This study aimed at evaluating the influence of respiratory system impedance on expiratory VT (VTE) and pressure measurement difference. DESIGN: Prospective observational study. SETTING: Pediatric intensive care unit at a university hospital. PATIENTS: Data were collected between February 2000 and October 2001 for 30 infants (range, 1-23 months) ventilated in the pressure-controlled or volume-controlled mode. INTERVENTIONS: Measurements of VTE, pressure obtained at the same time at the Y piece and on the ventilator Servo 300, were collected in ventilated infants. Respiratory system impedance was calculated from data obtained at the Y piece. Circuit compliance was measured in vitro. VTEs were corrected for compressible volume. MEASUREMENTS AND RESULTS: VTEs were overestimated by the Servo 300 in the pressure-controlled and volume-controlled modes (from 5% to 62% of the value displayed on Servo 300). Maximal inspiratory pressures were underestimated by the Servo 300 in the pressure-controlled mode (difference from -2 to +19 cm H(2)O). Measurement difference increased with increasing respiratory system impedance. Ventilator VTE corrected for circuit compliance did not offer a sufficiently accurate estimation of VTE at the Y piece. CONCLUSIONS: VT and pressure measurements must be performed at the Y piece, especially in infants with increased respiratory system impedance (i.e., decreased respiratory system compliance or increased resistance). Correcting VTE for circuit compliance cannot replace measurement of VT at the Y piece.

Combined antithrombin and protein C supplementation in meningococcal purpura fulminans: a pharmacokinetic study.

PURPOSE: To document in patients with meningococcal purpura fulminans (PF), the effects of a combined supplementation with antithrombin (AT) and protein C (PC) plasma concentrates and to estimate the pharmacokinetics and dose requirements of each inhibitor. DESIGN: Retrospective study of 15 patients. SETTING. One paediatric and one adult ICU in a university hospital. INTERVENTIONS: In addition to standard intensive care, all patients received a 100 IU/kg loading dose of AT and PC concentrates, followed by a continuous infusion (AT: 100-150 IU.kg.day; PC: 100 IU.kg.day in adults, and 400 IU/kg in infants). MEASUREMENTS: Clinical data, coagulation, and fibrinolysis parameters, AT and PC activities, and free protein S (PS) levels were sequentially measured. Restitution ratio, median increment after supplementation, and half-life of clearance from plasma were calculated for the two plasma substitutes. RESULTS. At admission, all patients had a severe decrease in AT, PC, and PS levels. The supplementation regimen induced a substantial increase in AT and PC activities, peaking at H18 and H48, respectively. The supplementation procedure did not modify free PS levels. The median values of AT and PC restitution ratio, increment in plasma activity observed after 100 IU/kg concentrate, and apparent half-life of clearance from plasma were 0.85 U.ml.U.kg and 0.59 U.ml.U.kg, 23% and 21%, 16 h and 6 h, respectively. CONCLUSION: If AT and PC concentrates are to be given in fulminant meningococcemia, the doses of supplementation should be at least 150 IU/kg AT and 250 IU/kg PC as loading dose and 150 IU/kg AT and 200 IU/kg PC as daily maintenance therapy. Taking into account the individual variability in inhibitor deficiency and restitution ratio, repeated measurements of plasma levels are mandatory to obtain a patient-based adjustment of the supplementation.

Infantile subdural hematomas due to traffic accidents.

The most common cause of subdural hematomas (SDH) in infants is shaken-baby syndrome (SBS). The pathogenesis and natural history of infantile SDH (ISDH) are poorly documented, because in SBS, the date of shaking is usually imprecise and the assault is often repeated. Victims of traffic accidents (TA) form a study group close to experimental conditions, because the trauma is unique, witnessed and dated. We reviewed 18 cases of SDH due to TA in infants under the age of 24 months. Our goal was to investigate the clinical and radiological data and natural history of SDH. A subdural collection was found on the day of trauma in 7 cases. In 3 of these, the collection was already hypodense. The perifalcine region was the most frequent site of intracranial bleeding. Blood hyperdensity was always found on CT scans performed during the first week, and turned hypodense on about the 9th day. Three patients had retinal hemorrhage, of a type distinct from that found in SBS. Drainage of the SDH was required in 14 cases after a mean delay of 13.5 +/- 5.8 days after trauma. Four patients also required a ventriculoperitoneal shunt because of associated hydrocephalus. Our data suggest that impaired CSF drainage plays a large role in the pathogenesis of ISDH. The fact that a single and recent trauma can result in mixed-density ISDH can be of great importance in forensic medicine.