Potential utility of near-infrared spectroscopy in out-of-hospital cardiac arrest: an illustrative case series.

OBJECTIVE: We evaluated the measurement of tissue oxygen content (StO(2)) by continuous near-infrared spectroscopy (NIRS) during and following cardiopulmonary resuscitation (CPR) and compared the changes in StO(2) and end-tidal carbon dioxide (ETCO(2)) 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 ETCO(2) monitoring and a NIRS StO(2) monitor until they reached the hospital. The ETCO(2) and StO(2) 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 StO(2) and EtCO(2) 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 StO(2) prior to each rearrest, and rapid increases were noted after ROSC. The StO(2) data showed less variance than the ETCO(2) data in the periarrest period.
CONCLUSIONS: This preliminary study in humans demonstrates that StO(2) dynamically changes during periods of hemodynamic instability in postarrest patients. These data suggest that a decline in StO(2) level may correlate with rearrest and may be useful as a tool to predict rearrest in post-cardiac arrest patients. A rapid increase in StO(2) was also seen upon ROSC and may be a better method of identifying ROSC during CPR than pauses for pulse checks or ETCO(2) monitoring.