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Biomedical subjects

R C Tasker

Publications and source records attributed to R C Tasker.

At least 19 recordsLinked to original sources
PubMed2001

Neurocritical care and traumatic brain injury.

The majority of severely head injured children will not require neurosurgery. For the pediatrician, the central question must be whether medical interventions are effective in limiting morbidity and treating the problem of cerebral oedema. However, in order to address this issue we need to give some thought to the system of care in which we practice, how we assess the severity of brain injury and whether, in regard to pathophysiology, responses in children are significantly different from those seen in adults. In this regard, this review highlights some of the recent pediatric neurocritical care literature and provides, for the clinician, a framework on which to base ones medical management of severe traumatic brain injury occurring in childhood.

Brain Injuries↗
PubMed2001

Acute neurology and neurophysiology of haemolytic-uraemic syndrome.

Involvement of the central nervous system (CNS) is found in around 30% of children with haemolytic-uraemic syndrome (HUS). This complication is the single most common cause of mortality and also a major contributor to the morbidity associated with HUS. We reviewed 22 children with HUS and acute CNS involvement. Both global and focal derangements occurred, and in survivors, early regional EEG abnormalities-especially those in the occipital and temporal areas-were prognostically useful.

Acute Disease↗
PubMed2000

Time course of severe respiratory syncytial virus infection in mechanically ventilated infants.

The time course of intensive care for severe respiratory syncytial virus (RSV) lower respiratory tract illness may be predicted by the severity of gas exchange during the first 48 h of mechanical ventilation. To test this hypothesis, two studies were undertaken in RSV-positive mechanically ventilated patients who did not have chronic lung disease, congenital heart disease or immunodeficiency. First, a retrospective criteria-generating review of 45 infants was carried out. In these infants, more severe lower airway disease, as demonstrated by four-quadrant consolidation on chest X-ray, was associated with 'best' alveolar arterial oxygen gradients (AaDO2, torr) and mean airway pressure (MAP, cm H2O) values as follows: first 24h, AaDO2 > 400 and MAP > 10 (positive and negative predictive values 100% and 97%, respectively); second 24 h, AaDO2 > or = 300 and MAP > 10 (positive and negative predictive values 91% and 100%, respectively). The second study, a prospective, hypothesis-testing, analysis of length-of-stay in 44 infants stratified according to the above AaDO2 and MAP criteria demonstrated that the duration of intensive care was longer in the severe group: median (interquartile range in days) 17 (15-39) vs 7 (4-8) (p < 0.01). We suggest that, in mechanically ventilated infants with RSV, the time course of intensive care is predictable based on early clinical features and respiratory parameters. Therefore reports on the effectiveness of special therapies using intensive care stay as a measure of outcome should be interpreted with respect to these observations before drawing conclusions about efficacy.

Humans↗
PubMed2000

Hypercarbia and mild hypothermia, only when not combined, improve postischemic bioenergetic recovery in neonatal rat brain slices.

In the immature brain, postischemic metabolism may be influenced beneficially by the effect of inducing hypercarbia or hypothermia. With use of 31P nuclear magnetic resonance spectroscopy, intracellular pH (pHi) and cellular energy metabolites in ex vivo neonatal rat cerebral cortex were measured before, during, and after substrate and oxygen deprivation in in vitro ischemia. Early postischemic hypothermia (fall in temperature -3.2 +/- 1.0 degrees C) delayed the normalization of pHi after ischemia by inducing an acid shift in pHi (P < 0.01). Postischemic hypercarbia (Krebs-Henseleit bicarbonate buffer equilibrated with 10% carbon dioxide in oxygen) and hypothermia induced separate, but potentially additive, reversible decreases in pHi, each of approximately -0.16 pH unit (P < 0.05). When these postischemic perturbations were applied in isolation, there was significant improvement of approximately 20% in the recovery of beta-ATP (P < 0.05). In combination, however, hypercarbia and hypothermia worsened recovery in ATP by approximately 20% (P < 0.05). In control tissue, which had not been exposed to ischemia, ATP content was also significantly reduced by co-administration of the two treatments (P < 0.05), an effect that persisted even after discontinuing the perturbing conditions. Therefore, in this vascular-independent neonatal preparation, early postischemic modulation of metabolism by hypercarbia or hypothermia appears to confer improved bioenergetic recovery, but only if they are not administered together.

Adenosine Triphosphate↗
PubMed2000

Neurological critical care.

Of utmost importance in the practice of neurological critical care is the treatment of cerebral edema, when possible, and the control of life-threatening seizures. In this regard, severe traumatic head injury and refractory status epilepticus are useful clinical therapeutic paradigms. Evidence-based treatment established for these conditions has, by necessity, a wider application to other much less frequent causes of coma and acute neurological illness managed in the intensive therapy unit. Therefore, this review of pediatric neurocritical care literature in 1999 highlights central clinical reports of the medical management of severe traumatic brain injury, the benzodiazepines used in the treatment of status epilepticus, and the emerging or recently appreciated encephalopathies occurring in children.

Brain Diseases↗
PubMed1999

Persistent pulmonary hypertension of the term neonate: a strategy for management.

UNLABELLED: The management of 32 consecutive term infants referred with persistent pulmonary hypertension of the newborn were reviewed. Despite indices suggesting severe cardiorespiratory failure with a median alveolar-arterial oxygen gradient of 591 torr (inter-quartile range 432-618) and oxygenation index of 31 (18-44), all but one patient responded to conventional treatment with inhaled nitric oxide and high frequency oscillatory ventilation. CONCLUSION: Patients should be referred early to centres where maximal conventional support can be offered before consideration for extracorporeal membrane oxygenation.

Administration, Inhalation↗
PubMed1999

Multicenter randomized controlled trial of the effects of inhaled nitric oxide therapy on gas exchange in children with acute hypoxemic respiratory failure.

OBJECTIVES AND BACKGROUND: To determine whether inhaled nitric oxide (iNO) therapy can attenuate the progression of lung disease in acute hypoxemic respiratory failure, we performed a multicenter, randomized, masked, controlled study of the effects of prolonged iNO therapy on oxygenation. We hypothesized that iNO therapy would improve oxygenation in an acute manner, slow the rate of decline in gas exchange, and decrease the number of patients who meet pre-established oxygenation failure criteria. STUDY DESIGN: A total of 108 children (median age 2.5 years) with severe acute hypoxemic respiratory failure from 7 centers were enrolled. After consent was obtained, patients were randomized to treatment with iNO (10 ppm) or mechanical ventilation alone for at least 72 hours. Patients with an oxygenation index >/=40 for 3 hours or >/=25 for 6 hours were considered treatment failures and exited the study. RESULTS: Patient age, primary diagnosis, pediatric risk of mortality score, mode of ventilation, and median oxygenation index (35 +/- 22 vs 30 +/- 15; iNO vs control; mean +/- SEM) were not different between groups at study entry. Comparisons of oxygenation indexes during the first 12 hours demonstrated an acute improvement in oxygenation in the iNO group at 4 hours (-10.2 vs -2.7, mean values; P <.014) and at 12 hours (-9.2 vs -2.8; P <.007). At 12 hours 36% of the control group met failure criteria in contrast with 16% in the iNO group (P <.05). During prolonged therapy the failure rate was reduced in the iNO group in patients whose entry oxygenation index was >/=25 (P <.04) and in immunocompromised patients (P <.03). CONCLUSIONS: We conclude that iNO causes an acute improvement in oxygenation in children with severe AHRF. Two subgroups (immunocompromised and an entry oxygen index >/=25) appear to have a more sustained improvement in oxygenation, and we speculate that these subgroups may benefit from prolonged therapy.

Administration, Inhalation↗
PubMed1998

Timing of recovery of lung function after severe hypoxemic respiratory failure in children.

OBJECTIVE: To describe the timing of recovery of lung function after severe acute hypoxemic respiratory failure (AHRF) in children. DESIGN: A serial observational follow-up study of clinical and lung function measurements up to 53 months after acute illness. SETTING: University pediatric intensive care unit in a national children's hospital. PATIENTS: Five critically ill children aged 5-14 years. INTERVENTIONS: None RESULTS: Clinical recovery: each patient required a 3-5 month convalescence before being able to attend full-time school because of lethargy and dyspnea. All patients developed wheeze 3-12 months after illness and four received long-term bronchodilator therapy. Lung function recovery: for both the forced vital capacity (FVC) and forced vital capacity in the first second (FEV1) four patients had abnormally low values, regaining only 60-70% of predicted values for their height and sex, and all of this improvement had occurred by 6-12 months after illness. Beyond this interval, patients remained on their same FVC and FEV1 centile. FEV1/FVC ratios were consistently within the normal range, indicating a predominantly restrictive defect. Changes in peak expiratory flow exhibited a time course of improvement similar to the other lung function tests. CONCLUSION: In children, pulmonary recovery after severe AHRF may occur for 6-12 months. A 1-year follow-up could offer a rational single point for assessment of outcome and long-term counselling of child and parents.

Adolescent↗
PubMed1998

Combined lung injury, meningitis and cerebral edema: how permissive can hypercapnia be?

We describe a patient with combined meningococcal septicemia and meningitis, cerebral edema and acute respiratory distress syndrome, in whom we balanced the conflicting carbon dioxide strategies for optimal pulmonary and neurological management using jugular oxygen saturation (SjvO2) monitoring to identify the upper limit of "tolerable" hypercapnia. Our observations suggest that significant acidosis was not well tolerated; however, cautious induction of pH down to 7.32 and an arterial carbon dioxide tension (PaCO2) < 5.9 kPa was tolerated acutely without significant cerebral hyperemia. Moreover, with the development of metabolic compensation and normal pH, higher levels of PaCO2 could be permitted. In similar cerebro-pulmonary circumstances we suggest that these findings warrant consideration. Alternatively, invasive monitoring of SjvO2 could be undertaken so that patient-specific criteria for permissive hypercapnia can be determined.

Acidosis, Respiratory↗
PubMed1998

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.

Acute Disease↗