A feasibility study evaluating the role of cerebral oximetry in predicting return of spontaneous circulation in cardiac arrest

Regional cerebral oxygen saturation after cardiac arrest in 60 patients--a prospective outcome study

INTRODUCTION

Non-invasive near-infrared spectroscopy (NIRS) offers the possibility to determine regional cerebral oxygen saturation (rSO2) in patients with cardiac arrest. Limited data from recent studies indicate a potential for early prediction of neurological outcome.

METHODS

Sixty cardiac arrest patients were prospectively enrolled, 22 in-hospital cardiac arrest (IHCA) and 38 out-of-hospital cardiac arrest (OHCA) patients respectively. NIRS of frontal brain was started after return of spontaneous circulation (ROSC) during admission to ICU and was continued until normothermia. Outcome was determined at ICU discharge by the Pittsburgh Cerebral Performance Category (CPC) and 6 months after cardiac arrest.

RESULTS

A good outcome (CPC 1-2) was achieved in 23 (38%) patients, while 37 (62%) had a poor outcome (CPC 3-5). Patients with good outcome had significantly higher rSO2 levels (CPC 1-2: rSO2 68%; CPC 3-5: rSO2 58%; p<0.01). For good and poor outcome median rSO2 within the first 24h period was 66% and 59% respectively and for the following 16h period 68% and 59% (p<0.01). Outcome prediction by area of rSO2 below a critical threshold of rsO2=50% within the first 40h yielded 70% specificity and 86% sensitivity for poor outcome.

CONCLUSION

On average, rSO2 within the first 40h after ROSC is significantly lower in patients with poor outcome, but rSO2 ranges largely overlap between outcome groups. Our data indicate limited potential for prediction of poor outcome by frontal brain rSO2 measurements.

Cerebral oximetry with blood volume index in asystolic pediatric cerebrospinal fluid malfunctioning shunt patients

Pediatric cerebrospinal fluid shunt malfunctions can present with varying complaints. The primary cause is elevated intracranial pressure (ICP). Malfunctioning sites are the proximal or distal sites[1-4]. A rare presenting complaint is cardiac arrest. Immediate ICP reduction is the only reversible option for this type of cardiac arrest.

Cerebral oximetry and cerebral blood flow monitoring in 2 pediatric survivors with out-of-hospital cardiac arrest

In pediatric out-of-hospital cardiac arrest (POHCA), cardiovascular monitoring tools have improved resuscitative endeavors and cardiovascular outcomes but with still poor neurologic outcomes. Regarding cardiac arrest in patients with congenital heart disease during surgery, the application of cerebral oximetry with blood volume index (BVI) during the resuscitation has shown significant results and prognostic significance. We present 2 POHCA patients who had cerebral oximetry with BVI monitoring during their arrest and postarrest phase in the emergency department and its potential prognostic aspect.Basic procedures include left and right cerebral oximetry with BVI monitoring at every 5-second interval during cardiac arrest, resuscitation, and postarrest in 2 POHCA patients in the pediatric emergency department.Regional cerebral tissue oxygen saturation (rSo2) with BVI readings in these 2 POHCA survivors demonstrated interesting cerebral physiology, blood flow, and potential prognostic outcome. In 1 patient, the reference range of cerebral rSo2 with positive blood flow during arrest and postarrest phases consistently occurred. This neurologic monitoring had its significance when the resuscitation effectiveness was used and end-tidal CO2 changes were lost. The other patient's cerebral rSo2 with simultaneous BVI readings and trending showed the effectiveness of the emergency medical services (EMS) resuscitation.Cerebral oximetry with cerebral blood flow index monitoring in these POHCA survivors demonstrates compelling periarrest and postarrest cerebral physiology information and prognostication. Cerebral oximetry with cerebral BVI monitoring during these arrest phases has potential as a neurologic monitor for the resuscitative intervention's effectiveness and its possible neurologic prognostic application in the pediatric OCHA patients.

A pilot study examining the role of regional cerebral oxygen saturation monitoring as a marker of return of spontaneous circulation in shockable (VF/VT) and non-shockable (PEA/Asystole) causes of cardiac arrest

BACKGROUND

Non-invasive monitoring of cerebral perfusion and oxygen delivery during cardiac arrest is not routinely utilized during cardiac arrest resuscitation. The objective of this study was to investigate the feasibility of using cerebral oximetry during cardiac arrest and to determine the relationship between regional cerebral oxygen saturation (rSO2) with return of spontaneous circulation (ROSC) in shockable (VF/VT) and non-shockable (PEA/asystole) types of cardiac arrest.

METHODS

Cerebral oximetry was applied to 50 in-hospital and out-of-hospital cardiac arrest patients.

RESULTS

Overall, 52% (n=26) achieved ROSC and 48% (n=24) did not achieve ROSC. There was a significant difference in mean±SD rSO2% in patients who achieved ROSC compared to those who did not (47.2±10.7% vs. 31.7±12.8%, p<0.0001). This difference was observed during asystole (median rSO2 (IQR) ROSC versus no ROSC: 45.0% (35.1-48.8) vs. 24.9% (20.5-32.9), p<0.002) and PEA (50.6% (46.7-57.5) vs. 31.6% (18.8-43.3), p=0.02), but not in the VF/VT subgroup (43.7% (41.1-54.7) vs. 42.8% (34.9-45.0), p=0.63). Furthermore, it was noted that no subjects with a mean rSO2<30% achieved ROSC.

CONCLUSIONS

Cerebral oximetry may have a role as a real-time, non-invasive predictor of ROSC during cardiac arrest. The main utility of rSO2 in determining ROSC appears to apply to asystole and PEA subgroups of cardiac arrest, rather than VF/VT. This observation may reflect the different physiological factors involved in recovery from PEA/asytole compared to VF/VT. Whereas in VF/VT, successful defibrillation is of prime importance, however in PEA and asytole achieving ROSC is more likely to be related to the quality of oxygen delivery. Furthermore, a persistently low rSO2 <30% in spite of optimal resuscitation methods may indicate futility of resuscitation efforts.

Detection of a spontaneous pulse in photoplethysmograms during automated cardiopulmonary resuscitation in a porcine model

INTRODUCTION

Reliable, non-invasive detection of return of spontaneous circulation (ROSC) with minimal interruptions to chest compressions would be valuable for high-quality cardiopulmonary resuscitation (CPR). We investigated the potential of photoplethysmography (PPG) to detect the presence of a spontaneous pulse during automated CPR in an animal study.

METHODS

Twelve anesthetized pigs were instrumented to monitor circulatory and respiratory parameters. Here we present the simultaneously recorded PPG and arterial blood pressure (ABP) signals. Ventricular fibrillation was induced, followed by 20 min of automated CPR and subsequent defibrillation. After defibrillation, pediatric-guidelines-style life support was given in cycles of 2 min. PPG and ABP waveforms were recorded during all stages of the protocol. Raw PPG waveforms were acquired with a custom-built photoplethysmograph controlling a commercial reflectance pulse oximetry probe attached to the nose. ABP was measured in the aorta.

RESULTS

In nine animals ROSC was achieved. Throughout the protocol, PPG and ABP frequency content showed strong resemblance. We demonstrate that (1) the PPG waveform allows for the detection of a spontaneous pulse during ventilation pauses, and that (2) frequency analysis of the PPG waveform allows for the detection of a spontaneous pulse and the determination of the pulse rate, even during ongoing chest compressions, if the pulse and compression rates are sufficiently distinct.

CONCLUSIONS

These results demonstrate the potential of PPG as a non-invasive means to detect pulse presence or absence, as well as pulse rate during CPR.

Cerebral oximetry and cardiac arrest

Cerebral oximetry is a Food and Drug Administration-approved technology that allows monitoring of brain oxygen saturation in accessible superficial brain cortex regions, which are amongst the most vulnerable in regard to ischemic or hypoxic injury. Since most oxygen in the area of interest is located in the venous compartment, the determined regional brain oxygen saturation approximately reflects the local balance between oxygen delivery and oxygen consumption. Major systemic alterations in blood oxygen content and oxygen delivery will be accompanied by corresponding changes in regional brain saturation. This systematic review, which is based on a Medline search, focuses on the characteristic changes in regional cerebral oxygen saturation that occur, when global oxygen supply to the brain ceases. It further highlights the potential application of cerebral oximetry in the management of cardiac arrest victims, the predictability of clinical outcome after global cerebral ischemia, and it also indicates possible potentials for the management of cerebral reperfusion after having instituted return of spontaneous circulation.

Optical characterization of two-layered turbid media for non-invasive, absolute oximetry in cerebral and extracerebral tissue

We introduce a multi-distance, frequency-domain, near-infrared spectroscopy (NIRS) method to measure the optical coefficients of two-layered media and the thickness of the top layer from diffuse reflectance measurements. This method features a direct solution based on diffusion theory and an inversion procedure based on the Levenberg-Marquardt algorithm. We have validated our method through Monte Carlo simulations, experiments on tissue-like phantoms, and measurements on the forehead of three human subjects. The Monte Carlo simulations and phantom measurements have shown that, in ideal two-layered samples, our method accurately recovers the top layer thickness (L), the absorption coefficient (µ a ) and the reduced scattering coefficient (µ' s ) of both layers with deviations that are typically less than 10% for all parameters. Our method is aimed at absolute measurements of hemoglobin concentration and saturation in cerebral and extracerebral tissue of adult human subjects, where the top layer (layer 1) represents extracerebral tissue (scalp, skull, dura mater, subarachnoid space, etc.) and the bottom layer (layer 2) represents cerebral tissue. Human subject measurements have shown a significantly greater total hemoglobin concentration in cerebral tissue (82±14 µM) with respect to extracerebral tissue (30±7 µM). By contrast, there was no significant difference between the hemoglobin saturation measured in cerebral tissue (56%±10%) and extracerebral tissue (62%±6%). To our knowledge, this is the first time that an inversion procedure in the frequency domain with six unknown parameters with no other prior knowledge is used for the retrieval of the optical coefficients and top layer thickness with high accuracy on two-layered media. Our absolute measurements of cerebral hemoglobin concentration and saturation are based on the discrimination of extracerebral and cerebral tissue layers, and they can enhance the impact of NIRS for cerebral hemodynamics and oxygenation assessment both in the research arena and clinical practice.

Prevalence and factors correlating with hyperoxia exposure following cardiac arrest--an observational single centre study

Purpose of the study

Arterial hyperoxia during care in the intensive care unit (ICU) has been found to correlate with mortality after cardiac arrest (CA). We examined the prevalence of hyperoxia following CA including pre-ICU values and studied differences between those exposed and those not exposed to define predictors of exposure.

Materials and methods

A retrospective analysis of a prospectively collected cohort of cardiac arrest patients treated in an Australian tertiary hospital between August 2008 and July 2010. Arterial blood oxygen values and used fractions of oxygen were recorded during the first 24 hours after the arrest. Hyperoxia was defined as any arterial oxygen value greater than 300 mmHg. Chi-square test was used to compare categorical data and Mann–Whitney U-test to continuous data. Statistical methods were used to identify predictors of hyperoxia exposure.

Results

Of 122 patients treated in the ICU following cardiac arrest 119 had one or several arterial blood gases taken and were included in the study. Of these, 49 (41.2%) were exposed to hyperoxia and 70 (58.8%) were not during the first 24 hours after the CA. Those exposed had longer delays to return of spontaneous circulation (26 minutes vs. 10 minutes) and a longer interval to ICU admission after the arrest (4 hours compared to 1 hour). Location of the arrest was an independent predictor of exposure to hyperoxia (P-value = 0,008) with out-of-hospital cardiac arrest patients being more likely to have been exposed (65%), than those with an in-hospital (21%) or ICU (30%) cardiac arrest. Out-of-hospital cardiac arrest patients had higher oxygen concentrations to the fraction of inspired oxygen ratios.

Conclusions

Hyperoxia exposure was more common than previously reported and occurred more frequently in association with out-of-hospital cardiac arrest, longer times to ROSC and delays to ICU admission.

Feasibility of absolute cerebral tissue oxygen saturation during cardiopulmonary resuscitation

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.