OP06 Is intra-arrest cerebral oxygen saturation associated with return of spontaneous circulation in out-of-hospital cardiac arrest patients? – A prospective feasibility study

<h3>Background</h3> Near-infrared spectroscopy (NIRS) has emerged as a non-invasive technique to measure regional cerebral oxygen saturation (rSO2) during cardiopulmonary resuscitation (CPR). Previous studies indicate an association between rSO2 during out-of-hospital cardiac arrest (OHCA) and return of spontaneous circulation (ROSC). This study reports, for the first time in a UK prehospital setting, the association between rSO2 during CPR and achieving ROSC in non-traumatic OHCA patients. <h3>Methods</h3> A prospective observational study was conducted at East Anglian Air Ambulance (EAAA) between 01/06/2023 and 31/05/2024 primarily to determine the feasibility of using NIRS in OHCA. Patients aged &gt;18 years who were undergoing CPR for non-traumatic OHCA were included. rSO2 was measured during the phase of external chest compressions using a portable, non-invasive NIRS device. Logistic regression was used to test the association between maximum rSO2 during CPR and ROSC. <h3>Results</h3> During the study period EAAA attended 529 OHCA patients. After exclusions, 112 patients were included in the final analysis. 32 (28.6%) achieved ROSC. Maximum rSO2 was higher in patients who achieved ROSC compared to those who did not (figure 1). The odds ratio for achieving ROSC was 1.08 (95% CI 1.05-1.13, <i>p</i>&lt;0.001) for each percentage point increase in maximum rS02. <h3>Conclusion</h3> Application of NIRS to measure rSO2 in OHCA is achievable in a UK prehospital setting. The rSO2 measured during arrest is associated with ROSC. rSO2 readings may provide useful information about patient prognosis; or be used as a target for goal-directed optimisation of cerebral oxygenation to improve neurological outcomes from OHCA.