ORIGINAL ARTICLE Mortality and Regional Oxygen Saturation Index in Septic Shock Patients: A Pilot Study Alejandro Rodriguez, MD, PhD, Thiago Lisboa, MD, Ignacio Martín-Loeches, MD, PhD, Emili Díaz, MD, PhD, Sandra Trefler, BSc, Marcos I. Restrepo, MD, MSc, and Jordi Rello, MD, PhD Background: Peripheral muscle tissue oxygenation determined noninva- sively using near-infrared spectroscopy may help to identify tissue hypoper- fusion in septic patients. The aim of this study was to investigate regional oxygen saturation index (rSO 2 ) in the brachioradialis (forearm) muscle by comparing measurements in healthy subjects and in intensive care unit (ICU) septic shock patients, and determine whether brachioradialis muscle rSO 2 is associated with poor outcome in ICU septic shock patients. Methods: We conducted a prospective observational study in healthy vol- unteers (n = 50) and ICU septic shock patients (n = 19). Brachioradialis (forearm) rSO 2 measurements in healthy volunteers at rest and in ICU septic shock patients were compared. Pulmonary artery catheter monitoring was used in ICU patients. Results: Significant differences in rSO 2 were observed between healthy volun- teers and ICU septic shock patients at ICU admission (68.7  4.9 vs. 55.0  13.0; p  0.001). When comparing septic shock survivors and nonsurvivors, significant differences were observed in rSO 2 at baseline (64.5  8.9 vs. 47.5  10.7; p  0.01), 12 hours (67.3  9.6 vs. 45.0  14.9; p  0.01), and 24 hours (65.7  7.0 vs. 50.1  10.3; p  0.01). Lactate concentration was lower in survivors than nonsurvivors at 24 hours (12.0  7.5 mmol/L vs. 23.2  12.5 mmol/L; p  0.04). Cardiac index was greater in nonsurvivors than survivors at baseline (4.6 + 1.9 L/min/m 2 vs. 3.0 + 0.9 L/min/m 2 ; p  0.05) and 12 h (3.9 + 0.5 L/min/m 2 vs. 3.1 + 0.3 L/min/m 2 ; p  0.05). Conclusions: We observed that septic shock patients with forearm skeletal muscle rSO 2 60% throughout first 24 hours after ICU admission had significantly greater mortality rate than patients with forearm skeletal muscle rSO 2 60% throughout this critical time. Key Words: Near-infrared spectroscopy, Sepsis, Microcirculation, Tissue oxygenation, Hypoxia. (J Trauma. 2011;70: 1145–1152) H emodynamically unstable patients with shock or septic shock benefit from an early, goal-directed therapy and aggressive management. 1,2 Initial resuscitation in the inten- sive care unit (ICU), or ideally in the Emergency Department, should be aimed at obtaining an adequate hemodynamic index and thus guarantee optimal tissue perfusion. By ensur- ing prompt, early oxygen delivery to tissues, we can reverse and prevent secondary ischemic injuries that lead to multiple organ dysfunction and poor outcomes, therefore increasing morbidity and mortality. 3,4 Early detection and prevention of situations in which an imbalance between oxygen delivery (DO 2 ) and oxygen consumption (VO 2 ) occurs should be the main end point for the optimal and correct resuscitation of patients with septic shock. Noninvasive techniques such as near-infrared spectroscopy (NIRS) 5–8 have been proven to evaluate oxygen saturation and blood flow in peripheral tissues. 8 –10 Tissue oxygen saturation (StO 2 ) and oxygen sat- uration index (rSO 2 ) have been proposed as a marker of tissue perfusion depending on the device used and the location of the measurement 6 –14 Although several studies 15–18 have de- tected changes in vascular reactivity using NIRS during and after a calibrated ischemic challenge, the relationship be- tween skeletal muscle rSO 2 and mortality in septic patients has not been assessed. We hypothesized that rSO 2 measurements in skeletal muscle of resting healthy subjects may differ from rSO 2 measurements in the first 24 hours of treatment of ICU septic shock patients, that skeletal muscle rSO 2 could identify tissue oxygenation deficiency in ICU patients with septic shock, and that an rSO 2 threshold in ICU septic shock patients might distinguish survivors and nonsurvivors. The objectives of this study were (1) to compare brachioradialis rSO 2 in healthy subjects and ICU septic shock patients, (2) to determine the association between brachioradialis rSO 2 and mortality, and (3) to determine a threshold brachioradialis rSO 2 that might be useful to guide resuscitation. PATIENTS AND METHODS Prospective, observational, controlled study was con- ducted in a 30-bed medical-surgical ICU in a tertiary univer- Submitted for publication July 3, 2009. Accepted for publication February 22, 2011. Copyright © 2011 by Lippincott Williams & Wilkins From the Critical Care Department (A.R., T.L., I.M.-L., E.D., S.T.), Joan XXIII University Hospital. University Rovira i Virgili, IISPV, CIBER Enfermedades Respiratorias, Tarragona, Spain; Critical Care Department (T.L.), Clinic University Hospital, Porto Alegre, Brazil; VERDICT/South Texas Veterans Health Care System and the Department of Medicine, Division of Pulmonary and Critical Care Medicine (M.I.R.), University of Texas Health Science Center at San Antonio, San Antonio, Texas; Critical Care Department (J.R.), Vall d’Hebron University Hospital, CIBER Enfermedades Respiratorias, Bar- celona, Spain. Supported by FIS PI10/01538 Instituto de Salud Carlos III (FEDER), CIBER Enfermedades respiratorias, and AGAUR (2009/SGR/1226). Dr. Restrepo is supported by a Department of Veterans Affairs, Veterans Inte- grated Service Network 17 new faculty grant and National Health Institute Grant KL2 RR025766. The views expressed in this article are those of the authors and do not necessarily represent the views of the Department of Veterans Affairs. Presented, in part, at the 21st Annual Congress of the European Society of Intensive Care Medicine, 21–24 September, 2008, Lisbon, Portugal. Address for reprints: Alejandro Rodríguez, MD, PhD, Critical Care Department, Joan XXIII University Hospital, Carrer Dr. Mallafre Guasch 4, 43007 Tarra- gona, Spain; email: ahr1161@yahoo.es. DOI: 10.1097/TA.0b013e318216f72c The Journal of TRAUMA ® Injury, Infection, and Critical Care • Volume 70, Number 5, May 2011 1145