Elsevier

Resuscitation

Volume 90, May 2015, Pages 121-126
Resuscitation

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

https://doi.org/10.1016/j.resuscitation.2015.03.001Get rights and content

Abstract

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 24 h 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.

Introduction

In healthy individuals, cerebral autoregulation maintains cerebral perfusion across a broad range of changes in mean arterial pressure (MAP) with a presumed lower threshold between 50–60 mmHg.1 Current post-cardiac arrest (CA) guidelines recommend targeting a MAP above 65 mmHg.2 However, some post-CA patients might benefit from resuscitation to a higher MAP in order to preserve cerebral perfusion due to a rightward shift of cerebral autoregulation.3 Aiming for the same one-size-fits-all hemodynamic targets among all patients may potentially be harmful due to cerebral hypoperfusion in patients with a right-shifted autoregulation or due to excessive use of fluids and vasopressive agents in patients with preserved autoregulation. Moreover, experimental data revealed the possible influence of therapeutic hypothermia on the preservation of cerebral autoregulation, rendering it even more difficult to predict the optimal MAP ensuring adequate cerebral perfusion in individual patients.4 Post-CA patients have a large cerebral penumbra at risk for secondary ischemic damage in case of suboptimal brain oxygenation. Brain tissue oxygen saturation (SctO2) can be measured non-invasively with near-infrared spectroscopy.5 The present study was performed to investigate the relationship between MAP and SctO2 in individual post-CA patients. Specific aims were (1) to investigate whether patients with preserved autoregulation have a better prognosis, (2) to compare patient characteristics of patients with preserved versus disturbed autoregulation, (3) to define an individual optimal MAP per patient and (4) to investigate whether the percentage of time under the predicted individual optimal MAP is associated with outcome.

Section snippets

Study population

All comatose survivors after non-traumatic CA treated in our tertiary care hospital (Ziekenhuis Oost-Limburg, Genk, Belgium) are prospectively enrolled in our database (n = 82). The present study includes all patients with continuous MAP and SctO2 monitoring recorded every 2 s during the first 24 h of ICU stay between 2011 and 2013. Data from 31 patients, with recordings at a longer than 2 s time interval were excluded for the present analysis, leaving a study population of 51 patients. Patients

Study population

Fifty-one patients were included in the study. Baseline characteristics are summarized in Table 1. Twenty-five patients (49%) had a good outcome defined as survival in CPC 1–2 at 180 days post-CA.

Cerebral autoregulation

Cerebral autoregulation was classified as disturbed in 18/51 (35%) of the patients. Chronic arterial hypertension was more frequent in patients with disturbed autoregulation (31 ± 47 vs 65 ± 49%, p = 0.02). There were no other significant baseline differences between patients with preserved and disturbed

Discussion

First, we showed that cerebrovascular autoregulation is disturbed in approximately one third of post-CA patients during therapeutic hypothermia. Presumably, in most patients, we should interpret the disturbed autoregulation as a right-shift of its lower limits. Two-thirds of these patients had chronic arterial hypertension pre-cardiac arrest suggesting that the right shifting of the lower threshold of autoregulation may be caused by protective chronic adaption of the cerebral blood flow to

Sources of funding

No financial disclosures.

Conflict of interest statement

None declared.

Acknowledgements

This study is part of the Limburg Clinical Research Program (LCRP) UHasselt-ZOL-Jessa, supported by the foundation Limburg Sterk Merk, Hasselt University, Ziekenhuis Oost-Limburg and Jessa Hospital.

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      Autoregulation may also be right-shifted which increases CePP requirements for achieving adequate CBF, contributing to secondary ischemic brain injury when CePP falls below a pathologically elevated lower limit of autoregulation.23 Dysfunctional cerebral autoregulation is observed in many patients after resuscitation and this phenomenon is associated with poor outcomes.36,37 Nishizawa et al.38 described autoregulation to be absent three days post-arrest in eight comatose patients.

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    A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2015.03.001.

    1

    KA and CG equally contributed to this paper.

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