Cerebral perfusion pressure and risk of brain hypoxia in severe head injury: a prospective observational study

Antonio J Marín-Caballos,Juan M Flores-Cordero,M Dolores Rincón-Ferrari,M Angeles Muñoz-Sánchez,Francisco Murillo-Cabezas,Jose M Domínguez-Roldán,Aurelio Cayuela-Domínguez,Julio Valencia-Anguita

doi:10.1186/cc3822

Antonio J Marín-Caballos, Juan M Flores-Cordero + Show 6 more

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https://doi.org/10.1186/cc3822

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Journal: Critical Care	Publication Date: Jan 1, 2005
Citations: 77	License type: cc-by

Affiliation: Hospital Universitario Virgen del Rocío

Abstract

IntroductionHigher and lower cerebral perfusion pressure (CPP) thresholds have been proposed to improve brain tissue oxygen pressure (PtiO2) and outcome. We study the distribution of hypoxic PtiO2 samples at different CPP thresholds, using prospective multimodality monitoring in patients with severe traumatic brain injury.MethodsThis is a prospective observational study of 22 severely head injured patients admitted to a neurosurgical critical care unit from whom multimodality data was collected during standard management directed at improving intracranial pressure, CPP and PtiO2. Local PtiO2 was continuously measured in uninjured areas and snapshot samples were collected hourly and analyzed in relation to simultaneous CPP. Other variables that influence tissue oxygen availability, mainly arterial oxygen saturation, end tidal carbon dioxide, body temperature and effective hemoglobin, were also monitored to keep them stable in order to avoid non-ischemic hypoxia.ResultsOur main results indicate that half of PtiO2 samples were at risk of hypoxia (defined by a PtiO2 equal to or less than 15 mmHg) when CPP was below 60 mmHg, and that this percentage decreased to 25% and 10% when CPP was between 60 and 70 mmHg and above 70 mmHg, respectively (p < 0.01).ConclusionOur study indicates that the risk of brain tissue hypoxia in severely head injured patients could be really high when CPP is below the normally recommended threshold of 60 mmHg, is still elevated when CPP is slightly over it, but decreases at CPP values above it.

Highlights

Higher and lower cerebral perfusion pressure (CPP) thresholds have been proposed to improve brain tissue oxygen pressure (PtiO2) and outcome
Our study indicates that the risk of brain tissue hypoxia in severely head injured patients could be really high when CPP is below the normally recommended threshold of 60 mmHg, is still elevated when CPP is slightly over it, but decreases at CPP values above it
Several retrospective reports of outcomes related to CPP observed better results when CPP was > 80 mmHg [1,2], and some prospective clinical studies have shown better outcomes when CPP was maintained above 70 mmHg [3,4,5,6]] compared to the 40% mortality rate reported for the Traumatic Coma Databank patients [7]

Summary

Introduction

Higher and lower cerebral perfusion pressure (CPP) thresholds have been proposed to improve brain tissue oxygen pressure (PtiO2) and outcome. The cerebral perfusion pressure (CPP) threshold that assures adequate cerebral perfusion still remains controversial in patients with traumatic brain injury (TBI); both higher and lower CPP thresholds have been proposed to improve outcome and brain tissue oxygen pressure (PtiO2). Several retrospective reports of outcomes related to CPP observed better results when CPP was > 80 mmHg [1,2], and some prospective clinical studies have shown better outcomes when CPP was maintained above 70 mmHg [3,4,5,6]] compared to the 40% mortality rate reported for the Traumatic Coma Databank patients [7]. Other authors observed that increasing CPP into 'supranormal values' was helpful in normalizing PtiO2 in ischemic areas [14], and others have reported a positive correlation between CPP and PtiO2, with a peak of PtiO2 at a CPP value around 78 mmHg [15]

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