Review
The role of evidence based medicine in neurotrauma

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Abstract

The introduction of evidence based medicine de-emphasised clinical experience and so-called “background information” and stressed the importance of evidence gained from clinical research when making clinical decisions. For many years randomised controlled trials have been seen to be the only way to advance clinical practice, however, applying this methodology in the context of severe trauma can be problematic. In addition, it is increasingly recognised that considerable clinical experience is required in order to critically evaluate the quality of the evidence and the validity of the conclusions as presented. A contemporary example is seen when considering the role of decompressive craniectomy in the management of neurotrauma. Although there is a considerable amount of evidence available attesting to the efficacy of the procedure, considerable clinical expertise is required in order to properly interpret the results of these studies and the implications for clinical practice. Given these limitations the time may have come for a redesign of the traditional pyramid of evidence, to a model that re-emphasises the importance of “background information” such as pathophysiology and acknowledges the role of clinical experience such that the evidence can be critically evaluated in its appropriate context and the subsequent implications for clinical practice be clearly and objectively defined.

Introduction

It is over 20 years since the introduction of evidence based medicine when it was announced that a new paradigm was emerging. This paradigm shift de-emphasised intuition and unsystematic clinical experience when considering clinical decision making and stressed the importance of examining evidence from clinical research [1]. The levels of evidence were stratified according to strength and a pyramid constructed with the meta-analysis of randomised controlled trials placed at the apex and seen to provide the highest level of evidence. Clinical judgement and background information such as pathophysiology were relegated to the base of the pyramid and were deemed to provide the lowest level of evidence (Fig. 1).

For many years a well designed randomised controlled trial published in a reputable medical journal was seen to be the only way to advance clinical practice and there can be no doubt that within the field of neurosurgery there are notable examples. These include the International Subarachnoid Aneurysm Trial (ISAT) investigating the role of coiling versus clipping of intracranial aneurysms [2], the Clifton studies investigating the role of hypothermia in traumatic brain injury (TBI) [3], [4] and the Medical Research Council Corticosteroid Randomization After Significant Head injury (MRC CRASH) study that investigated the role of steroids in the field of TBI [5]. It is however becoming increasingly apparent that there may be some limitations when attempting to apply this approach across all aspects of clinical practice, not least in the context of neurotrauma where surgery is often performed as a life saving intervention [6], [7]. In addition, it is increasingly recognised that considerable clinical experience is required not only to critically evaluate the quality of the evidence but also to assess the validity of the conclusions that are often presented by the investigators. Indeed it has been suggested that even the most rigorous trials have methodological flaws such that the conclusions of many studies are either exaggerated or indeed incorrect [8]. Given these limitations the time may have come for another paradigm shift that re-emphasises the importance of a clear understanding of pathophysiology and acknowledges the role of clinical experience such that the evidence can be critically evaluated in its appropriate context.

A contemporary example of this issue is seen when considering the role of decompressive craniectomy in the management of neurotrauma [9]. There is currently a great deal of evidence available regarding clinical efficacy of the procedure however considerable expertise is required in order interpret this evidence and the impact that it should have on clinical practice.

The aim of this narrative review is to highlight the importance of so called “background information” when considering the surgical management of severe TBI and this includes the underlying pathophysiology of the condition and the contemporary medical management. Thereafter the evidence currently available for clinical efficacy will be critically evaluated.

Section snippets

Pathophysiology

There are two important concepts that require consideration when managing patients with severe TBI. The first is the neuroexcitatory cascade and the second is the Monro–Kellie doctrine.

Decompressive craniectomy

By temporarily removing a large section of the calvarium, decompressive craniectomy challenges the Monro–Kellie doctrine by expanding the “rigid box” and providing extra space into which the injured brain can expand. The aims of the procedure are to reduce ICP and prevent death due to brainstem compression following tonsillar herniation, to reduce secondary brain injury due to impaired cerebral perfusion, and to improve clinical outcome.

Currently there would appear to be sufficient evidence

Reducing mortality

In the context of trauma numerous non-randomised cohort studies have demonstrated that surgical decompression can control intractable intracranial hypertension in situations where the patient is thought unlikely to survive without surgical intervention [6], [7], [32], [33], [34]. Likewise in the context of ischaemic stroke where the use of ICP monitoring is less widespread, decompressive surgery has been shown to be beneficial in the setting of deteriorating consciousness levels and pupillary

Decompressive craniectomy: Critical examination of the evidence

There is little doubt that these were well organised, multicentre studies based on genuine clinical equipoise and they do provide the only level one evidence for clinical efficacy of decompressive craniectomy in the adult population.

The hypothesis of the DECRA study was that early decompressive surgery would lower the ICP, improve cerebral perfusion and thereby prevent secondary brain injury. This hypothesis was based on the clear association between raised ICP and poor outcome following TBI

Conclusions

There can be little doubt that an evidence based approach in medicine provides valuable information on which to base clinical practice, however it is becoming increasingly apparent that there are limitations when attempting to apply this approach across certain aspects of surgery, not least in the context of a lifesaving intervention. It is also apparent that some of the conclusions presented do not always hold up to closer scrutiny.

In the context of decompressive craniectomy for severe TBI

Conflicts of Interest/Disclosures

The authors declare that they have no financial or other conflicts of interest in relation to this research and its publication.

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