Prospective pilot study of cerebral near infrared spectroscopy monitoring during pre-hospital anaesthesia.

BACKROUND

Near-infrared spectroscopy (NIRS) provides a non-invasive measure of cerebral tissue oxygenation. The literature on application of this method in pre-hospital setting is limited. The aims of this study were to determine the feasibility of cerebral NIRS during pre-hospital anaesthesia and to quantify the changes in front lobe regional oxygen saturation (rSO) during the pre-hospital phase.

METHODS

NIRS monitoring (Nonin SenSmart X-100) of front lobe regional oxygen saturation (rSO2) was initiated before induction of anaesthesia in 31 adult patients and continued until hospital arrival. The median age of the patients was 55 years (IQR [range] 43-63 [20-84]), and 20 (65%) of the patients were male. The indications for pre-hospital anaesthesia were neurological reasons (29%), intoxication (23%), traumatic brain injury (23%) and successful resuscitation from cardiac arrest (16%).

RESULTS

The NIRS monitoring was successful in 29 of 31 cases (94%; 95% CI: 78-99). One patient could not be monitored due to poor probe-skin contact, and 1 patient had poor contact with 1 hemisphere. Monitoring was performed for a total of 1335 minutes and was successful in both hemispheres 95% (95% CI: 94-96) of the time. The median lowest rSO was 8% (IQR [range] 2-13 [0-30]) below baseline, and median peak rSO was 7% (IQR [range] 2-11 [0-34]) above the baseline. Changes in rSO without accompanying changes in vital signs were observed.

CONCLUSION

NIRS is feasible during pre-hospital anaesthesia and substantial changes were observed in some patients. It provides data beyond the standard monitoring used in the pre-hospital setting.