Ingrid Meex

Cerebral tissue oxygen saturation during therapeutic hypothermia in post-cardiac arrest patients

AIM OF THE STUDY This observational study was performed to assess the cerebral tissue oxygen saturation during and after therapeutic hypothermia in comatose patients after out-of-hospital cardiac arrest. METHODS We performed a prospective observational study on the cerebral tissue oxygen saturation (SctO(2)) in post-cardiac arrest patients treated with therapeutic hypothermia (TH) between March 2011 and April 2012. SctO(2) (measured by near-infrared spectroscopy) was non-invasively and continuously measured in 28 post-cardiac arrest patients during hypothermia and active rewarming. RESULTS At the start of mechanically induced TH, SctO(2) was 68% (65-72) and PaCO(2) was 47.2 mmHg (36.9-51.4). SctO(2) and PaCO(2) significantly decreased to 59% (57-64; p=0.006) and 36.6 mmHg (33.9-44.7; p=0.002), respectively, within the first 3h of mechanically induced TH. Cerebral tissue oxygen saturation was significantly lower in non-survivors (n=10) compared with survivors (n=18) at 3h after induction of hypothermia (p=0.02) while the decrease in PaCO(2) was similar in both groups. During TH maintenance, SctO(2) gradually returned to baseline values (69% (63-72)) at 24h, with no differences between survivors and non-survivors (p=0.65). Carbon dioxide remained within the range of mild hypocapnia (32-38 mmHg) throughout the hypothermic period. During rewarming, SctO(2) further increased to 71% (67-78). CONCLUSIONS Induction of TH in comatose post-CA patients changes the balance between oxygen delivery and supply. The decrease in SctO(2) was less pronounced in patients surviving to hospital discharge.

Feasibility of absolute cerebral tissue oxygen saturation during cardiopulmonary resuscitation

IntroductionCurrent 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.MethodsRecent 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.ResultsOur 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.ConclusionsBoth 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.

An observational near-infrared spectroscopy study on cerebral autoregulation in post-cardiac arrest patients: Time to drop ‘one-size-fits-all’ hemodynamic targets?

AIMS A subgroup of patients with ROSC after cardiac arrest (CA) with disturbed cerebral autoregulation might benefit from higher mean arterial pressures (MAP). We aimed to (1) phenotype patients with disturbed autoregulation, (2) investigate whether these patients have a worse prognosis, (3) define an individual optimal MAP per patient and (4) investigate whether time under this individual optimal MAP is associated with outcome. METHODS Prospective observational study in 51 post-CA patients monitored with near infrared spectroscopy. RESULTS (1) 18/51 patients (35%) had disturbed autoregulation. Phenotypically, a higher proportion of patients with disturbed autoregulation had pre-CA hypertension (31±47 vs. 65±49%, p=0.02) suggesting that right shifting of autoregulation is caused by chronic adaptation of cerebral blood flow to higher blood pressures. (2) In multivariate analysis, patients with preserved autoregulation (n=33, 65%) had a significant higher 180-days survival rate (OR 4.62, 95% CI [1.06:20.06], p=0.04]. Based on an index of autoregulation (COX), the average COX-predicted optimal MAP was 85 mmHg in patients with preserved and 100 mmHg in patients with disturbed autoregulation. (3) An individual optimal MAP could be determined in 33/51 patients. (4) The time under the individual optimal MAP was negatively associated with survival (OR 0.97, 95% CI [0.96:0.99], p=0.02). The time under previously proposed fixed targets (65, 70, 75, 80 mmHg) was not associated with a differential survival rate. CONCLUSION Cerebral autoregulation showed to be disturbed in 35% of post-CA patients of which a majority had pre-CA hypertension. Disturbed cerebral autoregulation within the first 24h after CA is associated with a worse outcome. In contrast to uniform MAP goals, the time spent under a patient tailored optimal MAP, based on an index of autoregulation, was negatively associated with survival.

Hemodynamic targets during therapeutic hypothermia after cardiac arrest: A prospective observational study ☆

AIM In analogy with sepsis, current post-cardiac arrest (CA) guidelines recommend to target mean arterial pressure (MAP) above 65 mmHg and SVO2 above 70%. This is unsupported by mortality or cerebral perfusion data. The aim of this study was to explore the associations between MAP, SVO2, cerebral oxygenation and survival. METHODS Prospective, observational study during therapeutic hypothermia (24h - 33 °C) in 82 post-CA patients monitored with near-infrared spectroscopy. RESULTS Forty-three patients (52%) survived in CPC 1-2 until 180 days post-CA. The mean MAP range associated with maximal survival was 76-86 mmHg (OR 2.63, 95%CI [1.01; 6.88], p = 0.04). The mean SVO2 range associated with maximal survival was 67-72% (OR 8.23, 95%CI [2.07; 32.68], p = 0.001). In two separate multivariate models, a mean MAP (OR 3.72, 95% CI [1.11; 12.50], p=0.03) and a mean SVO2 (OR 10.32, 95% CI [2.03; 52.60], p = 0.001) in the optimal range persisted as independently associated with increased survival. Based on more than 1625000 data points, we found a strong linear relation between SVO2 (range 40-90%) and average cerebral saturation (R(2) 0.86) and between MAP and average cerebral saturation for MAPs between 45 and 101 mmHg (R(2) 0.83). Based on our hemodynamic model, the MAP and SVO2 ranges associated with optimal cerebral oxygenation were determined to be 87-101 mmHg and 70-75%. CONCLUSION we showed that a MAP range between 76-86 mmHg and SVO2 range between 67% and 72% were associated with maximal survival. Optimal cerebral saturation was achieved with a MAP between 87-101 mmHg and a SVO2 between 70% and 75%. Prospective interventional studies are needed to investigate whether forcing MAP and SVO2 in the suggested range with additional pharmacological support would improve outcome.

Increase in cerebral oxygenation during advanced life support in out-of-hospital patients is associated with return of spontaneous circulation

IntroductionBy maintaining sufficient cerebral blood flow and oxygenation, the goal of cardiopulmonary resuscitation (CPR) is to preserve the pre-arrest neurological state. To date, cerebral monitoring abilities during CPR have been limited. Therefore, we investigated the time-course of cerebral oxygen saturation values (rSO2) during advanced life support in out-of-hospital cardiac arrest. Our primary aim was to compare rSO2 values during advanced life support from patients with return of spontaneous circulation (ROSC) to patients who did not achieve ROSC.MethodsWe performed an observational study to measure rSO2 using Equanox™ (Nonin, Plymouth, MI) from the start of advanced life support in the pre-hospital setting.ResultsrSO2 of 49 consecutive out-of-hospital cardiac arrest patients were analyzed. The total increase from initial rSO2 value until two minutes before ROSC or end of advanced life support efforts was significantly larger in the group with ROSC 16% (9 to 36) compared to the patients without ROSC 10% (4 to 15) (P = 0.02). Mean rSO2 from the start of measurement until two minutes before ROSC or until termination of advanced life support was higher in patients with ROSC than in those without, namely 39% ± 7 and 31% ± 4 (P = 0.05) respectively.ConclusionsDuring pre-hospital advanced life support, higher increases in rSO2 are observed in patients attaining ROSC, even before ROSC was clinically determined. Our findings suggest that rSO2 could be used in the future to guide patient tailored treatment during cardiac arrest and could therefore be a surrogate marker of the systemic oxygenation state of the patient.

Regional cerebral oximetry during cardiopulmonary resuscitation: useful or useless?

BACKGROUND Approximately 375,000 people annually experience sudden cardiac arrest (CA) in Europe. Most patients who survive the initial hours and days after CA die of postanoxic brain damage. Current monitors, such as electrocardiography and end-tidal capnography, provide only indirect information about the condition of the brain during cardiopulmonary resuscitation (CPR). In contrast, cerebral near-infrared spectroscopy provides continuous, noninvasive, real-time information about brain oxygenation without the need for a pulsatile blood flow. It measures transcutaneous cerebral tissue oxygen saturation (rSO2). This information could supplement currently used monitors. Moreover, an evolution in rSO2 monitoring technology has made it easier to assess rSO2 in CA conditions. OBJECTIVE We give an overview of the literature regarding rSO2 measurements during CPR and the current commercially available devices. We highlight the feasibility of cerebral saturation measurement during CPR, its role as a quality parameter of CPR, predictor of return of spontaneous circulation (ROSC) and neurologic outcome, and its monitoring function during transport. DISCUSSION rSO2 is feasible in the setting of CA and has the potential to measure the quality of CPR, predict ROSC and neurologic outcome, and monitor post-CA patients during transport. CONCLUSION The literature shows that rSO2 has the potential to serve multiple roles as a neuromonitoring tool during CPR and also to guide neuroprotective therapeutic strategies.

Low hemoglobin levels are associated with lower cerebral saturations and poor outcome after cardiac arrest

PURPOSE Post-cardiac arrest (CA) patients have a large cerebral penumbra at risk for secondary ischemic damage in case of suboptimal brain oxygenation during ICU stay. The aims of this study were to investigate the association between hemoglobin, cerebral oxygenation (SctO2) and outcome in post-CA patients. METHODS Prospective observational study in 82 post-CA patients. Hemoglobin, a corresponding SctO2 measured by NIRS and SVO2 in patients with a pulmonary artery catheter (n=62) were determined hourly during hypothermia in the first 24h of ICU stay. RESULTS We found a strong linear relationship between hemoglobin and mean SctO2 (SctO2=0.70×hemoglobin+56 (R(2) 0.84, p=10(-6))). Hemoglobin levels below 10g/dl generally resulted in lower brain oxygenation. There was a significant association between good neurological outcome (43/82 patients in CPC 1-2 at 180 days post-CA) and admission hemoglobin above 13g/dl (OR 2.76, 95% CI 1.09:7.00, p=0.03) or mean hemoglobin above 12.3g/dl (OR 2.88, 95%CI 1.02:8.16, p=0.04). This association was entirely driven by results obtained in patients with a mean SVO2 below 70% (OR 6.25, 95%CI 1.33:29.43, p=0.01) and a mean SctO2 below 62.5% (OR 5.87, 95%CI 1.08:32.00, p=0.03). CONCLUSION Hemoglobin levels below 10g/dl generally resulted in lower cerebral oxygenation. Average hemoglobin levels below 12.3g/dl were associated with worse outcome in patients with suboptimal SVO2 or SctO2. The safety of a universal restrictive transfusion threshold of 7g/dl can be questioned in post-CA patients.

Cerebral tissue oxygen saturation values in volunteers and patients in the lateral decubitus and beach chair positions: a prospective observational study.

BackgroundThe objective of this study was to describe changes in cerebral tissue oxygen saturation (SctO2) due to changes in body position in healthy volunteers and in patients undergoing surgery under general anesthesia in the beach chair position (BCP) and lateral decubitus position (LDP).MethodsIn this prospective observational study, SctO2 was measured in 85 awake volunteers serially positioned every 15 min, beginning with the supine position (SP) and followed by the beach chair, supine, and lateral decubitus positions. Cerebral tissue oxygen saturation was also measured supine and in either the BCP or the LDP in 195 patients (according to surgical preference) undergoing elective arthroscopic shoulder surgery. We measured the lowest stable SctO2 values in each position as well as changes in blood pressure and heart rate.ResultsIn healthy volunteers, the median (interquartile range [IQR]) lowest stable SctO2 value in the SP was 69 [66-71] %. A change in position to the BCP caused a small but statistically significant decrease in the median [IQR] lowest SctO2 value to 67 [65-70] % (P = 0.028 compared with baseline). This decrease was associated with an increase in median [IQR] arterial pressure from 83 [78-88] mmHg in the SP to 85 [81-93] mmHg in the BCP (P < 0.001 compared with baseline). In patients undergoing surgery in the BCP, the median [IQR] lowest stable SctO2 value was 55 [51-59] %, which was significantly lower (P < 0.001) than the median [IQR] lowest SctO2 value in patients in the LDP (66 [62-69] %). More patients in the BCP group (57%) showed SctO2 values ≤ 55% and/or a decrease of ≥ 20% from baseline (57%) compared with the LDP group (5% and 6%, respectively; P < 0.001 for each comparison).ConclusionsMore than 55% of patients undergoing arthroscopic shoulder surgery in the BCP experience cerebral desaturation events. In volunteers without anesthesia, no desaturation events were observed. The clinical importance of these findings needs further investigation.RésuméContexteL’objectif de cette étude était de décrire les changements de la saturation en oxygène cérébral tissulaire (SctO2) provoqués par les changements de position du corps chez des volontaires sains et des patients subissant une chirurgie sous anesthésie générale en position assise (PAs - beach chair position) et en décubitus latéral (DL).MéthodeDans cette étude observationnelle prospective, on a mesuré la SctO2 de 85 volontaires sains éveillés repositionnés en série toutes les 15 minutes, en commençant en position allongée (PAl) puis en position assise, puis allongée à nouveau, et finalement en décubitus latéral. La saturation en oxygène cérébral tissulaire a également été mesurée en position allongée et en PAs ou en DL chez 195 patients (selon la préférence chirurgicale) subissant une arthroscopie non urgente de l’épaule. Nous avons mesuré les valeurs stables de SctO2 les plus basses dans chaque position ainsi que les changements de tension artérielle et de fréquence cardiaque.RésultatsChez les volontaires sains, la valeur stable moyenne (écart interquartile [ÉIQ]) la plus basse de SctO2 en PAl était 69 [66-71] %. Un changement en PAs a provoqué une réduction, faible mais significative d’un point de vue statistique, de la valeur médiane [ÉIQ] la plus basse de SctO2 à 67 [65-70] % (P = 0,028 comparativement aux valeurs de base). Cette réduction a été associée à une augmentation de la tension artérielle médiane [ÉIQ] de 83 [78-88] mmHg en PAl à 85 [81-93] mmHg en PAs (P < 0,001 comparativement aux valeurs de base). Chez les patients subissant une chirurgie en PAs, la valeur médiane [ÉIQ] stable la plus basse de SctO2 était de 55 [51-59], soit significativement plus basse (P < 0,001) que la valeur médiane [ÉIQ] stable la plus basse telle que mesurée chez les patients en DL (66 [62-69] %). La plupart des patients du groupe PAs (57 %) ont montré des valeurs de SctO2 ≤ 55 % et/ou une réduction ≥ 20 % par rapport aux valeurs de base (57 %) comparativement au groupe DL (5 % et 6 %, respectivement; P < 0,001 pour chaque comparaison).ConclusionPlus de 55 % des patients subissant une arthroscopie de l’épaule dans le groupe PAs ont subi des épisodes de désaturation cérébrale. Chez les volontaires sains n’ayant pas subi d’anesthésie, aucun épisode de désaturation n’a été observé. L’importance clinique de ces résultats nécessite des recherches plus approfondies.

Accuracy of continuous thermodilution cardiac output monitoring by pulmonary artery catheter during therapeutic hypothermia in post-cardiac arrest patients

PURPOSE Thermodilution continuous cardiac output measurements (TDCCO) by pulmonary artery catheter (PAC) have not been validated during therapeutic hypothermia in post-cardiac arrest patients. The calculated cardiac output based on the indirect Fick principle (FCO) using pulmonary artery blood gas mixed venous oxygen saturation (FCO-BG-SvO2) is considered as the gold standard. Continuous SvO2 by PAC (PAC-SvO2) has also not been validated previously during hypothermia. The aims of this study were (1) to compare FCO-BG-SvO2 with TDCCO, (2) to compare PAC-SvO2 with BG-SvO2 and finally (3) to compare FCO with SvO2 obtained via PAC or blood gas. METHODS We analyzed 102 paired TDCCO/FCO-BG-SvO2 and 88 paired BG-SvO2/PAC-SvO2 measurements in 32 post-cardiac arrest patients during therapeutic hypothermia. RESULTS TDCCO was significantly although poorly correlated with FCO-BG-SvO2 (R2 0.21, p<0.01) without systematic bias (-0.15±1.76 l/min). Analysis according to Bland and Altman however showed broad limits of agreement ([-3.61; 3.45] l/min) and an unacceptable high percentage error (105%). None of the criteria for clinical interchangeability were met. Concordance analysis showed that TDCCO had limited trending ability (R2 0.03). FCO based on PAC-SvO2 was highly correlated with FCO-BG-SvO2 (R2 0.72) with a small bias (-0.08±0.72 l/min) and slightly too high percentage error (44%). CONCLUSION Our results show an extreme inaccuracy of TDCCO by PAC in post-cardiac arrest patients during therapeutic hypothermia. We found a reasonable correlation between BG-SvO2 and PAC-SvO2 and subsequently between FCO calculated with SvO2 obtained either via blood gas or PAC. The decision to start or titrate inotropics should therefore not be guided by TDCCO in this setting.

Cerebral saturation monitoring during cardiopulmonary resuscitation should be used as dynamic, rather than static, information

With great interest we read the paper of Parnia et al.1 The uthors report a significantly higher overall mean rSO2 in patients ith return of spontaneous circulation (ROSC) in comparison with on-survivors (respectively 35 ± 5 vs 18 ± 0.4). First of all, both hese values are extremely low, despite the fact that all patients ad in-hospital cardiac arrest, and shorter delays to treatment (and igher overall mean rSO2) are expected compared to patients with ut of hospital arrest.2 The reason for these low values might be elated to the used near-infrared spectroscopy (NIRS) technology INVOS® is a relative O2 saturation monitoring). Secondly, the difference in rSO2 between survivors and nonurvivors is the highest during the final 5 min of resuscitation. This s not a surprising observation, since increasing rSO2 is a precuror of the onset of ROSC and at ROSC, the difference in rSO2 is or sure the greatest compared to rSO2 values in patients who ever had ROSC (and therefore worse hemodynamics without any ncrease in rSO2 during the whole cardiopulmonary resuscitation CPR)). We are not sure whether the slow increase in rSO2 observed efore ROSC might not be explained by the use of a “relative” NIRS echnology (with a proprietary averaging algorithm), not providing absolute” saturation values. The authors confirmed that their findings indicate that rSO2 in ardiac arrest is a dynamic measurement and that any decrease or