Please see Bibliography of References for a list of abstracts, manuscripts and posters.
Otero R, Crawford J, Rivers EP, Nwoke P, Sankey SS. Ann Emerg Med. 2006;48(4, Supplement):S99. Abstract 330.
Background: Crookes et al demonstrated that a decreased thenar muscle tissue oxygen saturation may reflect the presence of severe hypoperfusion (shock) in trauma patients better than traditional hemodynamic parameters. Near-infrared spectroscopy (NIRS) may be a novel method for rapidly and noninvasively assessing changes in tissue level oxygenation. The purpose of this study was to investigate the predictive value of NIRS measurements (StO2) as an early indicator of compromised systemic perfusion in critical patients with a variety of chief complaints in the emergency department (ED). In addition, the demographic data from this current cohort was compared to Crooke’s study of normal volunteers to evaluate the magnitude of the difference in mean StO2 .
Population: The primary site for this study was a single, urban, teaching hospital with approximately 95,000 ED evaluations. Patients enrolled were triaged to the critical care category one area (CAT 1).
Methods: This was a prospective, nonrandomized, observational, study in patients greater than 18 years old admitted to the CAT 1 area of the emergency department with various complaints classified as cardiovascular, metabolic, neurological, trauma or gastrointestinal etiology (n=250). The NIRS probe was applied to the right thenar eminence and data was collected and stored for analysis. StO2 monitoring was performed within 10 minutes of admission to CAT 1 and values were recorded at one minute. The Emergency physicians were blinded to StO2 values. Exclusion criteria included Do Not Resuscitate status, peripheral vascular disease, cardiac arrest, amputated upper extremities or skin abnormalities in monitoring site as well as refusal to participate.
Statistical analysis: After dividing the StO2 data into quartiles based upon the total population examined (n=250). Student’s t-test was used to compare the mean StO2 value against a patient’s age, blood pressure, lactate and pulse oximetry value (SpO2). Subsequently, ANOVA analysis was run for all of the continuous variables allowing pairwise comparisons. Tukey adjustment was selected for multiple comparisons.
Results: For this cohort of patients there was a statistically significant difference between the mean StO2 value and age, diastolic blood pressure and lactate level (P < 0.01, P < 0.05 and P=0.05 respectively). Differences between StO2 value, mean arterial pressure and SpO2 were marginally statistically significant (P=0.07 and P=0.08). When comparing the demographics from this study and Crooke’s group, there was a significant difference in mean age, StO2 value and blood pressure values.
Conclusion: NIRS has demonstrated with significance, that there is a decrease in systemic perfusion in critically ill patients presenting to the emergency department. There appears to be some clinical utility for monitoring selected groups of patients for early circulatory failure. Further prospective, multi-centered trials are needed.