Feasibility of absolute cerebral tissue oxygen saturation during cardiopulmonary resuscitation

Abstract

Introduction: Current monitoring during cardiopulmonary resuscitation (CPR) is limited to clinical observation of consciousness, breathing pattern and presence of a pulse. At the same time, the adequacy of cerebral oxygenation during CPR is critical for neurological outcome and thus survival. Cerebral oximetry, based on near-infrared spectroscopy (NIRS), provides a measure of brain oxygen saturation. Therefore, we examined the feasibility of using NIRS during CPR.

Methods: Recent technologies (FORE-SIGHT™ and EQUANOX™) enable the monitoring of absolute cerebral tissue oxygen saturation (SctO2) values without the need for pre-calibration. We tested both FORE-SIGHT™ (five patients) and EQUANOX Advance™ (nine patients) technologies in the in-hospital as well as the out-of-hospital CPR setting. In this observational study, values were not utilized in any treatment protocol or therapeutic decision. An independent t-test was used for statistical analysis.

Results: Our data demonstrate the feasibility of both technologies to measure cerebral oxygen saturation during CPR. With the continuous, pulseless near-infrared wave analysis of both FORE-SIGHT™ and EQUANOX™ technology, we obtained SctO2 values in the absence of spontaneous circulation. Both technologies were able to assess the efficacy of CPR efforts: improved resuscitation efforts (improved quality of chest compressions with switch of caregivers) resulted in higher SctO2 values. Until now, the ability of CPR to provide adequate tissue oxygenation was difficult to quantify or to assess clinically due to a lack of specific technology. With both technologies, any change in hemodynamics (for example, ventricular fibrillation) results in a reciprocal change in SctO2. In some patients, a sudden drop in SctO2 was the first warning sign of reoccurring ventricular fibrillation.

Conclusions: Both the FORE-SIGHT™ and EQUANOX™ technology allow non-invasive monitoring of the cerebral oxygen saturation during CPR. Moreover, changes in SctO2 values might be used to monitor the efficacy of CPR efforts.

Figure 1

Cerebral tissue oxygen saturation (SctO2 (%)) (monitored with FORE-SIGHT™ technology) during out-of-hospital cardiac arrest (patient 1). After 15 minutes of BLS, first measured SctO₂ values were 31% and 38% over the left (grey line) and right (black line) fontal region, respectively. Defibrillation (dotted arrow) resulted in ROSC and an immediate increase in SctO₂ to 60% (left) and 69% (right). During preparation for transport, ventricular fibrillation (arrow) reoccurred and was accompanied with an immediate decrease in SctO₂. Again, defibrillation (dotted arrow) resulted in sinus rhythm and SctO₂ values above 65%. BLS, basic life support; CPR, cardiopulmonary resuscitation; Defib, defibrillation; VF, ventricular fibrillation.

Figure 2

Cerebral tissue oxygen saturation (SctO₂ (%)) (monitored with EQUANOX Advance™ technology) in a patient (patient 6) who collapsed at ER entrance. The sensor was applied after six minutes of CPR and two defibrillation attempts. SctO₂ started at 50% and increased to 60%, right before ventricular fibrillation reoccurred (arrows). When ROSC was achieved, SctO₂ increased immediately above 70%. CPR, cardiopulmonary resuscitation; ROSC, return of spontaneous circulation; VF, ventricular fibrillation.

Figure 3

Cerebral tissue oxygen saturation (SctO₂ (%)) (monitored with FORE-SIGHT™ technology) and arterial blood pressure (mmHg) in an in-hospital cardiac arrest patient (patient 3). After 14 minutes of BLS by a trained caregiver, first measured SctO₂ values were 48% and 52% over the left (grey line) and right (black line) fontal region, respectively. Switch of person giving CPR (arrows) resulted in increased cerebral oxygen saturations. Parallel fluctuations were observed between SctO₂ and systolic blood pressure (thin black line). After cessation of CPR, SctO₂ decreased to values between 30% and 35%. BLS, basic life support; CPR, cardiopulmonary resuscitation.

Figure 4

Cerebral tissue oxygen saturation (SctO₂ (%)) (monitored with EQUANOX Advance™ technology) during out-of-hospital cardiac arrest (patient 7). The starting SctO₂ value (after 20 minutes of BLS) was 3%, but rose quickly to 21%. The highest measured value during CPR was 38%. A decrease in SctO₂ was observed during rhythm assessment (every 2 minutes). CPR was stopped 50 minutes after arrival of the medical emergency team, without obtaining ROSC. After termination of CPR, SctO₂ decreased rapidly. BLS, basic life support; CPR, cardiopulmonary resuscitation; ROSC, return of spontaneous circulation.