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Resuscitation. 2019 Jun;139:76-83. doi: 10.1016/j.resuscitation.2019.03.036. Epub 2019 Apr 1.

Initial arterial pH as a predictor of neurologic outcome after out-of-hospital cardiac arrest: A propensity-adjusted analysis.

Author information

1
Department of Cardiovascular Medicine, Cleveland Clinic Foundation, Cleveland, OH, USA.
2
Department of Internal Medicine, Cleveland Clinic Foundation, Cleveland, OH, USA.
3
Department of Cardiovascular Medicine, University of Virginia, Charlottesville, VA, USA.
4
Departments of Medicine and of Population and Quantitative Health Sciences, Case Western Reserve University, Cleveland, OH, USA; Center for Health Care Research and Policy, MetroHealth Medical Center, Cleveland, OH, USA.
5
Department of Pulmonary and Critical Care Medicine, University of Virginia, Charlottesville, VA, USA.
6
Department of Cardiovascular Medicine, Cleveland Clinic Foundation, Cleveland, OH, USA. Electronic address: menonv@ccf.org.

Abstract

BACKGROUND:

Lower pH after out-of-hospital cardiac arrest (OHCA) has been associated with worsening neurologic outcome, with <7.2 identified as an "unfavorable resuscitation feature" in consensus treatment algorithms despite conflicting data. This study aimed to describe the relationship between decremental post-resuscitation pH and neurologic outcomes after OHCA.

METHODS:

Consecutive OHCA patients treated with targeted temperature management (TTM) at multiple US centers from 2008 to 2017 were evaluated. Poor neurologic outcome at hospital discharge was defined as cerebral performance category ≥3. The exposure was initial arterial pH after return of spontaneous circulation (ROSC) analyzed in decremental 0.05 thresholds. Potential confounders (demographics, history, resuscitation characteristics, initial studies) were defined a priori and controlled for via ATT-weighting on the inverse propensity score plus direct adjustment for the linear propensity score.

RESULTS:

Of 723 patients, 589 (80%) experienced poor neurologic outcome at hospital discharge. After propensity-adjustment with excellent covariate balance, the adjusted odds ratios for poor neurologic outcome by pH threshold were: ≤7.3: 2.0 (1.0-4.0); ≤7.25: 1.9 (1.2-3.1); ≤7.2: 2.1 (1.3-3.3); ≤7.15: 1.9 (1.2-3.1); ≤7.1: 2.4 (1.4-4.1); ≤7.05: 3.1 (1.5-6.3); ≤7.0: 4.5 (1.8-12).

CONCLUSIONS:

No increased hazard of progressively poor neurologic outcomes was observed in resuscitated OHCA patients treated with TTM until the initial post-ROSC arterial pH was at least ≤7.1. This threshold is more acidic than in current guidelines, suggesting the possibility that post-arrest pH may be utilized presently as an inappropriately-pessimistic prognosticator.

KEYWORDS:

Out-of-hospital cardiac arrest; Outcomes; Prognostication; Targeted temperature management; pH

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