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Arch Dis Child 85:252-255 doi:10.1136/adc.85.3.252
  • Archimedes

Towards evidence based medicine for paediatricians

In order to give the best care to patients and families, paediatricians need to integrate the highest quality scientific evidence with clinical expertise and the opinions of the family.1 Archimedes seeks to assist practising clinicians by providing “evidence based” answers to common questions which are not at the forefront of research but are at the core of practice.

A word of warning. The topic summaries are not systematic reviews, though they are as exhaustive as a practising clinician can produce. They make no attempt to statistically aggregate the data, nor search the grey, unpublished literature. WhatArchimedes offers is practical, best evidence based answers to practical, clinical questions.

The format of Archimedes may be familiar. A description of the clinical setting is followed by a structured clinical question. (These aid in focusing the mind, assisting searching,2 and gaining answers.3) A brief report of the search used follows—this has been performed in a hierarchical way, to search for the best quality evidence to answer the question.4 A table provides a summary of the evidence and key points of the critical appraisal. For further information on critical appraisal, and the measures of effect (such as number needed to treat, NNT), books by Sackett et al and Moyer et al may help.5 6 To pull the information together, a commentary is provided. But to make it all much more accessible, the clinical bottom line is highlighted.

Readers wishing to submit their own questions—with best evidence answers—are encouraged to read the Instructions for Authors athttp://www.archdischild.com

Critical appraisal note: evidence of equivalence versus no evidence of difference

When a randomised study compares two therapies and finds no difference in an important outcome between the two, does this provide evidence of equivalence or merely an absence of evidence of effectiveness? The practical answer requires integration of the study with clinical expertise.  If a dichotomous outcome is present (dead versus not, hospitalised versus sent home) then a variety of measures can be generated. Of these, those which give information of the risk reduction (relative, absolute, or its inverse; the number needed to treat) are useful. With continuous outcome measures, estimates of difference can also be produced, but may be more difficult to interpret. A confidence interval can be produced for each of these measures, within whose limits the true effect is likely to fall. This degree of uncertainty is the first element to be considered in the question. As a rule of thumb, if a study cannot exclude a 20% difference between the treatments, it is probably not evidence of equivalence.  The second element requires knowledge of the disease and outcome. If the outcome is fatal, disfiguring or had serious morbidity, perhaps a greater degree of certainty is required. There is also the rest of the clinical literature on the subject—does this result agree with the general tenor of evidence or does it stick out?  Combining these aspects—precision, importance, and congruence—allows an answer to the question of equivalence versus lack of difference.

References

Are routine chest x rays helpful in the management of febrile neutropenia?

Scenario

A friendly, coryzal 5 year old girl with acute lymphocytic leukemia attends with another episode of febrile neutropenia. According to departmental protocol, her admission includes a chestx ray. You wonder as to the value of this routine irradiation.

Structured clinical question

In a 5 year old girl with febrile neutropenia [patient] does routine chest radiography [intervention] assist in management decisions or diagnose occult pneumonia [outcome]?

Search

Secondary sources—nil. SumSearch—“neutropenia” AND “radiography” AND filter “diagnosis”. Search results—67 individual articles found, three relevant.

Summary

See table 1-1.

Table 1-1

Commentary

There is no good quality study addressing the use of chest radiographs in uncomplicated febrile neutropenia. Two of these studies are consistent with clinical feeling—lack of abnormal signs or symptoms in children with febrile neutropenia rules out pneumonia. The meth-odological weaknesses would tend to favour this—with one study having clinical features as part of the reference standard, and the second tending to fail to perform chest radiography on children without symptoms. The third study only gives data on respiratory signs (ignoring symptoms) and has a subsequently reduced sensitivity and improved specificity.

Clinical bottom line

  • Pneumonia was uncommon in children with febrile neutropenia (∼3%)

  • An absence of respiratory signs and symptoms made pneumonia very unlikely

  • Routine chest x rays seem unnecessary.

Authors

Clare Collins (Research Fellow, Oxford Vaccine Group, Oxford) [clare.collins{at}paediatrics.ox.ac.uk] Matthew Fenton (Registrar in Paediatric Oncology, John Radcliffe Hospital, Oxford) Bob Phillips (Junior Fellow, Centre for Evidence-based Medicine)

References

  1. 1-1.
  2. 1-2.
  3. 1-3.

Does dexamethasone improve blood pressure in hypotensive ill neonates?

Scenario

A 25 week gestation baby, birth weight 695 g is ventilated for respiratory distress syndrome. Invasive blood pressure monitoring at 2 hours of age showed a mean of 23–25 mm Hg. The blood pressure did not improve over the next 24 hours, in spite of three intravenous boluses of 0.9% saline and concurrent infusions of dopamine and dobutamine at 15 μg/kg/min.

A colleague suggests that dexamethasone might help to improve the baby's blood pressure.

Structured clinical question

In hypotensive preterm infants [patient] does treatment with dexamethasone [intervention] increase blood pressure [outcome]?

Search

Secondary sources—nil. Search strategy—“hypotension” AND “(dexamethasone OR steroid)” AND “newborn” AND “(clinical trial)”. Search results—three articles found, two relevant.

Summary

See table 2-2.

Table 2-2

Commentary

The study by Gassmaier and Weston was well constructed in terms of randomisation, blinding, and intention to treat analysis. Dexamethasone administration, after treatment with volume boluses, dopamine, and adrenaline infusion, improved BP such that adrenaline was discontinued in 63% babies (compared with 11% of placebo group).

The paper by Bourchier and Weston supports the idea that bolus steroids are a useful adjunct to conventional treatments for hypotension in sick, ventilated preterm infants. Dopamine and hydrocortisone both appeared to be effective (p = 0.108) in the treatment of hypotension refractory to treatment with fluid bolus. However, if five babies received hydrocortisone, one additional baby remained hypotensive, compared with similar babies who received dopamine. Confidence intervals for this NNT are wide (3, 45), suggesting a larger study would show statistical difference at the 5% level.

Dexamethasone appears to be a useful adjunct to the commonly used pathway for treating hypotension in neonates (fluid bolus ± dopamine ± dobutamine).

Although no adverse events related to steroid use are reported in either paper, no long term follow up is reported and caution is warranted as there is emerging evidence of increased risk of cerebral palsy, following postnatal dexamethasone use in babies at risk for chronic lung disease (Shinwell et al,Arch Dis Child Fetal Neonatal Ed2000;83:F177–F181), without improvement in mortality (Halliday and Ehrenkranz. Early postnatal (<96 hours) corticosteroids for preventing chronic lung disease in preterm infants.Cochrane Database of Systematic Reviews, Issue 1, 2001).

Clinical bottom line

  • Dexamethasone improved blood pressure in ill, ventilated neonates.

Author

Richard Nicholl (Consultant Neonatologist) [DrNicholl{at}aol.com] on behalf of The Northwick Park Neonatal Journal Club, Northwest London NHS Hospitals Trust

References

  1. 2-1.
  2. 2-2.

Does nebulised adrenaline reduce admission rate in bronchiolitis?

Scenario

A 4 month old infant attends the emergency department in the late morning with bronchiolitis. It is the first episode of wheeze. Clinically, there is moderate indrawing and recession, tachypnoea (RR = 50), reasonable air movement on auscultation, and the oxygen saturation is 94% in air. You want to admit the infant, but the mother is breast feeding and keen to get home by 3 pm, when her other children get home from school. You have heard that in North America, nebulised adrenaline has been used in some cases and admission has been avoided.

Structured clinical question

In an infant with bronchiolitis [patient] does nebulised adrenaline (compared to other treatments) [intervention] reduce the need for admission [outcome]?

Search

Secondary sources—Cochrane Library (2001): “bronchiolitis”, two systematic reviews (one irrelevant—anticholinergics and wheeze);Clinical Evidence (Issue 4): “child health—bronchiolitis”, two systematic reviews (one irrelevant—adrenaline not included); DARE: “bronchiolitis”, five systematic reviews (three irrelevant; two relevant SRs were by same authors—one referenced in Cochrane and one referenced in journal).

PubMed clinical queries: “bronchiolitis” AND “epinephrine” [therapy, sensitive]—eight references (three irrelevant to question).

MedLine [1966 to Dec 2000] (Ovid): “bronchiolitis” OR “bronchitis” AND [“epinephrine (exp)” or “catecholamines”]; LIMIT to “clinical trial”—13 references (eight irrelevant to question).

Five papers addressed the question of nebulised adrenaline and bronchiolitis (one of them specifically answering the question).

Summary

See table 3-3.

Table 3-3

Commentary

There is only one study (Menon et al) that specifically answers the question; this study shows a reduction in hospital admission, and the study group is similar to the patient in the clinical scenario.

A systematic review that includes adrenaline as one of a number of bronchodilators fails to show significant differences in outcomes compared to placebo. However, adrenaline has an α adrenergic action which is thought to be important in bronchiolitis (as well as the β adrenergic bronchodilatory effects it has). The positive effect of adrenaline may therefore have been diluted in the systematic review by the inclusion of agents that have little or no effect.

The Menon et al study compared adrenaline with salbutamol, which is not routinely used in the UK in this condition. For this reason, data on studies comparing adrenaline to placebo in bronchiolitis are also presented. Studies comparing the two show a benefit of adrenaline over placebo as well as benefit over pure β adrenergic agonists.

It is thought that the α adrenergic properties of adrenaline are important in bronchiolitis, as the vasoconstriction of the pulmonary vessels reduces mucosal oedema and exudate, thereby reducing airway obstruction.

The regime used was 3 ml of 1/1000 adrenaline nebulised at arrival and 30 minutes later. The infants were then observed for at least two hours.

Currently, a multicentre trial in the UK comparing nebulised adrenaline with placebo is under discussion.

Clinical bottom line

  • Nebulised adrenaline probably reduced hospital admission in bronchiolitis

  • Nebulised adrenaline appeared superior to salbutamol and placebo in relieving symptoms in bronchiolitis.

Author

Maud Meates (Consultant Paediatrician, North Middlesex Hospital, London) [mmeates{at}doctors.org.uk]

References

  1. 3-1.
  2. 3-2.
  3. 3-3.
  4. 3-4.
  5. 3-5.

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