Potential Utility of Near-Infrared Spectroscopy in Out-of-Hospital Cardiac Arrest: An Illustrative Case Series

Abstract

Objective. We evaluated the measurement of tissue oxygen content (StO₂) by continuous near-infrared spectroscopy (NIRS) during and following cardiopulmonary rescuscitation (CPR) and compared the changes in StO₂ and end-tidal carbon dioxide (ETCO₂) as a measure of return of spontaneous circulation (ROSC) or rearrest. Methods. This was a case series of five patients who experienced out-of hospital cardiac arrest. Patients included those who had already experienced ROSC, who were being transported to the hospital, or who were likely to have a reasonable amount of time remaining in the resuscitation efforts. Patients were continuously monitored from the scene using continuous ETCO₂ monitoring and a NIRS StO₂ monitor until they reached the hospital. The ETCO₂ and StO₂ values were continuously recorded and analyzed for comparison of the time points when patients were clinically identified to have ROSC or rearrest. Results. Four of five patients had StO₂ and EtCO₂ recorded during an episode of CPR and all were monitored during the postarrest period. Three patients experienced rearrest en route to the hospital. Downward trends were noted in StO₂ prior to each rearrest, and rapid increases were noted after ROSC. The StO₂ data showed less variance than the ETCO₂ data in the periarrest period. Conclusions. This preliminary study in humans demonstrates that StO₂ dynamically changes during periods of hemodynamic instability in postarrest patients. These data suggest that a decline in StO₂ level may correlate with rearrest and may be useful as a tool to predict rearrest in post–cardiac arrest patients. A rapid increase in StO₂ was also seen upon ROSC and may be a better method of identifying ROSC during CPR than pauses for pulse checks or ETCO₂ monitoring. Key words: resuscitation; hemodynamics; tissue oxygen content; near-infrared spectroscopy; cardiopulmonary resuscitation; return of spontaneous circulation; rearrest