Brain Tissue Oxygen-Based Therapy and Outcome After Severe Traumatic Brain Injury: A Systematic Literature Review

Abstract

Observational clinical studies demonstrate that brain hypoxia is associated with poor outcome after severe traumatic brain injury (TBI). In this study, available medical literature was reviewed to examine whether brain tissue oxygen (PbtO2)-based therapy is associated with improved patient outcome after severe TBI. Clinical studies published between 1993 and 2010 that compared PbtO2-based therapy combined with intracranial and cerebral perfusion pressure (ICP/CPP)-based therapy to ICP/CPP-based therapy alone were identified from electronic databases, Index Medicus, bibliographies of pertinent articles, and expert consultation. For analysis, each selected paper had to have adequate data to determine odds ratios (ORs) and confidence intervals (CIs) of outcome described by the Glasgow outcome score (GOS). Seven studies that compared ICP/CPP and PbtO2- to ICP/CPP-based therapy were identified. There were no randomized studies and no comparison studies in children. Four studies, published in 2003, 2009, and 2010 that included 491 evaluable patients were used in the final analysis. Among patients who received PbtO2-based therapy, 121(38.8%) had unfavorable and 191 (61.2%) had a favorable outcome. Among the patients who received ICP/CPP-based therapy 104 (58.1%) had unfavorable and 75 (41.9%) had a favorable outcome. Overall PbtO2-based therapy was associated with favorable outcome (OR 2.1; 95% CI 1.4-3.1). Summary results suggest that combined ICP/CPP- and PbtO2-based therapy is associated with better outcome after severe TBI than ICP/CPP-based therapy alone. Cross-organizational practice variances cannot be controlled for in this type of review and so we cannot answer whether PbtO2-based therapy improves outcome. However, the potentially large incremental value of PbtO2-based therapy provides justification for a randomized clinical trial.

The Role of Invasive Monitoring in Traumatic Brain Injury

“…Studies [26,27] have since confirmed that low PbtO2 of less than 10 for 15 min are associated with worse clinical outcomes and some prospective studies as well as multiple non-randomized studies comparing ICP/CPP-driven protocols versus ICP/CPP and PbtO2-driven protocols, and a pooled analysis of these that included 491 patients suggests that there is a twofold likelihood of better outcomes with the PbtO2 and ICP/CPP-driven protocols [28]. There is still no class 1 evidence, but an ongoing randomized clinical trial in TBI patients will hopefully shed some light on this.…”

Unraveling the complexities of invasive multimodality neuromonitoring

“…49 Despite its complicated dependence on multiple physiological factors, brain hypoxia is an independent predictor of poor outcome in brain-injured patients, 38,44,45 and PbtO 2 threshold-based treatment strategies may improve outcomes. 4,41 Monitoring devices for PbtO 2 measure local tissue oxygen tension and may not reflect global brain oxygenation. In addition, probe placement can cause local tissue injury, leading to falsely low measurements.…”

Systematic and Comprehensive Literature Review of Publications on Direct Cerebral Oxygenation Monitoring

“…It has also been emphasized that the surgeon/physician in charge of pbtO2 monitoring must have experience in data interpretation: "It is equally important that the clinician understands relevant aspects of brain oxygen physiology and head trauma pathophysiology to enable correct interpretation of the monitored data and therefore to direct an appropriate therapeutic response that is likely to benefit, not harm, the patient" [348]. Three reviews have underlined the known fact of a lack of a randomized trial to prove the utility of pbtO2 monitoring which, speaking from a strictly scientific point of view, is needed to recommend its unrestricted routine use [200,273,325]. In keeping with this view a recent comprehensive pbtO2 review concludes that the current scientific literature implies that: "...…”