Clinical InvestigationsCerebral Arterio-venous pCO2 Difference, Estimated Respiratory Quotient, and Early Posttraumatic Outcome: Comparison With Arterio-venous Lactate and Oxygen DifferencesChieregato, Arturo MD*; Marchi, Maurizia MD†; Fainardi, Enrico MD, PhD‡; Targa, Luigi MD*Author Information *Unità Operativa di Anestesia e Rianimazione, Azienda USL di Cesena, Cesena †Unità Operativa di Anestesia e Rianimazione ‡Unità Operativa di Neuroradiologia, Azienda Ospedaliera-Universitaria di Ferrara, Ferrara, Italy Reprints: Arturo Chieregato, MD, Unità Operativa di Anestesia e Rianimazione, Ospedale M. Bufalini, viale Ghirotti 286, 47023, Cesena, Italy (e-mail: [email protected]). Received for publication August 18, 2006; accepted March 26, 2007 Journal of Neurosurgical Anesthesiology: October 2007 - Volume 19 - Issue 4 - p 222-228 doi: 10.1097/ANA.0b013e31806589f6 Buy Metrics Abstract Arterio-venous pCO2 difference (AVDpCO2) and estimated respiratory quotient, the ratio between AVDpCO2 and arterio-venous O2 difference, may be potentially useful estimators of irreversible posttraumatic global cerebral ischemia. Our aim was to evaluate their relevance, along with arterio-venous lactate difference (AVDL) and lactate oxygen index (LOI), in early outcome prediction. The retrospective study involved 55 patients with severe head injury, admitted consecutively in a multidisciplinary intensive care unit of a general hospital. A retrograde jugular catheter was placed as soon as possible, allowing for 324 simultaneous arterio-jugular samples to be taken throughout the first 48-hour postinjury. Early brain death (within 48 h) was assumed to be due to early global ischemia. A multivariate model including clinical and radiologic descriptors and jugular bulb variables showed that a widening of AVDL and LOI was associated with early brain death. Whereas in the patients who died, a progressive worsening of AVDpCO2 and estimated respiratory quotient, associated with corresponding changes in AVDL and LOI were observed, in patients who survived the widening of AVDpCO2 normalized along with that of arterio-venous O2 difference. These findings suggest that the isolated measurement of widening AVDpCO2 is not specific for global cerebral ischemia, but its observation over time could be potentially more useful. © 2007 Lippincott Williams & Wilkins, Inc.