J. Dens

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

AIMSnA 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.nnnMETHODSnProspective observational study in 51 post-CA patients monitored with near infrared spectroscopy.nnnRESULTSn(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.nnnCONCLUSIONnCerebral 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 ☆

AIMnIn 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.nnnMETHODSnProspective, observational study during therapeutic hypothermia (24h - 33 °C) in 82 post-CA patients monitored with near-infrared spectroscopy.nnnRESULTSnForty-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%.nnnCONCLUSIONnwe 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.

Regional cerebral oximetry during cardiopulmonary resuscitation: useful or useless?

BACKGROUNDnApproximately 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.nnnOBJECTIVEnWe 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.nnnDISCUSSIONnrSO2 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.nnnCONCLUSIONnThe 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

PURPOSEnPost-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.nnnMETHODSnProspective 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.nnnRESULTSnWe 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).nnnCONCLUSIONnHemoglobin 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.

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

PURPOSEnThermodilution 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.nnnMETHODSnWe analyzed 102 paired TDCCO/FCO-BG-SvO2 and 88 paired BG-SvO2/PAC-SvO2 measurements in 32 post-cardiac arrest patients during therapeutic hypothermia.nnnRESULTSnTDCCO 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%).nnnCONCLUSIONnOur 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.

Pulmonary vascular response to exercise in symptomatic heart failure with reduced ejection fraction and pulmonary hypertension

To study pulmonary vascular response patterns to exercise in heart failure with reduced ejection fraction (HFrEF) and pulmonary hypertension (PH).

Point-of-care heart-type fatty acid binding protein versus high-sensitivity troponin T testing in emergency patients at high risk for acute coronary syndrome

Background: High-sensitivity cardiac troponin testing is used to detect myocardial damage in patients with acute chest pain. Heart-type fatty acid binding protein (H-FABP) may be an alternative, available as point-of-care test. Methods: Patients (n=203) referred by general practitioners for suspected acute coronary syndrome or presenting with typical chest pain and one major cardiovascular risk factor at the emergency department were prospectively included in a single-centre cohort study. High-sensitivity cardiac troponin T (hs-TnT) and point-of-care H-FABP testing were concomitantly performed at admission and after 6h. Results: Maximal hs-TnT levels above the 99th percentile were observed in 152 patients (75%) with 127 (63%) fulfilling criteria for myocardial infarction. Upon admission, hs-TnT and H-FABP were associated with an area under the curve (95% CI) of 0.83 (0.77–0.89) and 0.79 (0.73–0.85), respectively, to predict myocardial infarction, which increased to 0.93 (0.90–0.97) and 0.88 (0.84–0.93), respectively, after 6h. The diagnostic accuracy for non-ST-segment elevation myocardial infarction was somewhat lower with an area under the curve (95% CI) of 0.80 (0.72–0.87), 0.90 (0.84–0.96), 0.73 (0.64–0.81) and 0.77 (0.67–0.86), respectively. When assessment was performed within 3h of chest pain onset, diagnostic accuracy of H-FABP versus hs-TnT was similar. Each standard deviation increase in admission H-FABP was associated with a 68% relative risk increase of all-cause mortality (p-value=0.027) during 666±155 days of follow-up. Conclusions: Point-of-care H-FABP testing has lower diagnostic accuracy compared with hs-TnT assessment in patients with high pre-test acute coronary syndrome probability, but might be of interest when assessment is possible early after chest pain onset.

The validation of simplified EEG derived from the bispectral index monitor in post-cardiac arrest patients

AIMSnWe aimed to validate retrospectively the accuracy of simplified electroencephalography (EEG) monitoring derived from the bispectral index (BIS) monitor in post-cardiac arrest (CA) patients.nnnMETHODSnSuccessfully resuscitated CA patients were transferred to the Catherization Lab followed by percutaneous coronary intervention when indicated. On arrival at the coronary care unit, bilateral BIS monitoring was started and continued up to 72u202fh. Raw simplified EEG tracings were extracted from the BIS monitor at a time point coinciding with the registration of standard EEG monitoring. BIS EEG tracings were reviewed by two neurophysiologists, who were asked to indicate the presence of following patterns: diffuse slowing rhythm, burst suppression pattern, cerebral inactivity, periodic epileptiform discharges and status epilepticus (SE). Additionally, these simplified BIS EEG tracings were analysed by two inexperienced investigators, who were asked to indicate the presence of SE only.nnnRESULTSnThirty-two simplified BIS EEG samples were analysed. Compared to standard EEG, neurophysiologists interpreted all simplified EEG samples with a sensitivity of 86%, a specificity of 100% and an interobserver variability of 0.843. Furthermore, SE was identified with a sensitivity of 80% and a specificity of 94% by two unexperienced physicians.nnnCONCLUSIONnUsing a simple classification system, raw simplified EEG derived from a BIS monitoring device is comparable to standard EEG monitoring. Moreover, investigators without EEG experience were capable to identify SE in post-CA patients. Future studies will be warranted to confirm our results and to determine the added value of using simplified BIS EEG in terms of prognostic and therapeutic implications.

A42 Post-cooling Fever in Cardiac Arrest Patients Treated with Therapeutic Hypothermia

Background: Incidence and characteristics of post-cooling fever were rarely described. In this study, we analysed the possible link between cardiac arrest (CA), therapeutic hypothermia and fever. Patients and Methods: Data of 11 post-CA pts were analysed. All hemodynamic, respiratory and laboratory data were collected. Hyperthermia was defined as a core (rectal) temperature exceeding 37.7°C, Results: Of the 11 pts, there were 5 (45%) survivors and 6 (55%) non-survivors, 2 died of hemodynamic shock (first 24hrs), 4 died due to post-ischemic brain damage. All pts were successfully cooled (33° for 24hrs). Rewarming procedure was uneventfull. Eight (89%) pts developed hyperthermia at the end of rewarming. Six (75%) of them did so immediately, while the other 2 pts developed fever 2 to 5u200ahours after rewarming. Three (37.5%) pts showed short periods of fever (2 -10hrs), while the remaining 5 (62.5%) had fever for a few days. In all patients, WBC at admission were significantly increased whereas CRP only increased after 2–3 days ICU-admission, in 8 patients this occurred simultaneously with the post-cooling fever. In 7 of these 8 pts, antibiotic treatment was initiated. In 5 of 8 pts, pneumonia, prolonged weaning and awakening, but did not influence final mortality. Conclusion: We found a 89% incidence of post-cooling fever, associated with ending of rewarming and increase in inflammatory parameters (CRP).

The impact of global hemodynamics, oxygen and carbon dioxide on epileptiform EEG activity in comatose survivors of out-of-hospital cardiac arrest

AIMnTo study the association between global hemodynamics, blood gases, epileptiform EEG activity and survival after out-of-hospital CA (0HCA).nnnMETHODSnWe retrospectively analyzed 195 comatose post-CA patients. At least one EEG recording per patient was evaluated to diagnose epileptiform EEG activity. Refractory epileptiform EEG activity was defined as persisting epileptic activity on EEG despite the use of 2 or more anti-epileptics. The time weighted average mean arterial pressure 48h (TWA-MAP48), the percentage of time with a MAP below 65 and above 85mmHg and the percentage of time with normoxia, hypoxia (<70mmHg), hyperoxia (>150mmHg), normocapnia, hypocapnia (<35mmHg) and hypercapnia (>45mmHg) were calculated.nnnRESULTSnWe observed epileptiform EEG activity in 57 patients (29%). A shockable rhythm was associated with a decreased likelihood of epileptic activity on the EEG (OR: 0.41, 95%CI 0.22-0.79). We did not identify an association between the TWA-MAP48, the percentage of time with MAP below 65mmHg or above 85mmHg, blood gas variables and the risk of post-CA epileptiform EEG activity. The presence of epileptiform activity decreased the likelihood of survival independently (OR: 0.10, 95% CI: 0.04-0.24). Interestingly, survival rates of patients in whom the epileptiform EEG resolved (n=20), were similar compared to patients without epileptiform activity on EEG (60% vs 67%,p=0.617). Other independent predictors of survival were presence of basic life support (BLS) (OR:5.08, 95% CI 1.98-13.98), presence of a shockable rhythm (OR: 7.03, 95% CI: 3.18-16.55), average PaO2 (OR=0.93, CI 95% 0.90-0.96) and% time MAP<65mmHg (OR: 0.96, CI 95% 0.94-0.98).nnnCONCLUSIONnEpileptiform EEG activity in post-CA patients is independently and inversely associated with survival and this effect is mainly driven by patients in whom this pattern is refractory over time despite treatment with anti-epileptic drugs. We did not identify an association between hemodynamic factors, blood gas variables and epileptiform EEG activity after CA, although both hypotension, hypoxia and epileptic EEG activity were predictors of survival.