Association between low pH and unfavorable neurological outcome among out-of-hospital cardiac arrest patients treated by extracorporeal CPR: a prospective observational cohort study in Japan

Abstract

Background: We aimed to identify the association of pH value in blood gas assessment with neurological outcome among out-of-hospital cardiac arrest (OHCA) patients treated by extracorporeal cardiopulmonary resuscitation (ECPR). Methods: We retrospectively analyzed the database of a multicenter prospective observational study on OHCA patients in Osaka prefecture, Japan (CRITICAL study), from July 1, 2012 to December 31, 2016. We included adult OHCA patients treated by ECPR. Patients with OHCA from external causes such as trauma were excluded. We conducted logistic regression analysis to identify the odds ratio (OR) and 95% confidence interval (CI) of the pH value for 1 month favorable neurological outcome adjusted for potential confounders including sex, age, witnessed by bystander, CPR by bystander, pre-hospital initial cardiac rhythm, and cardiac rhythm on hospital arrival.

The association between low pH value and unfavorable neurological outcome among the out-of-hospital cardiac arrest patient treated by extra-corporeal CPR: sensitivity analysis

“…Third, we agree with the concern that the blood test results including pH value might influence on the decision-making of the implementation of extracorporeal cardio-pulmonary resuscitation, and it could be a selection bias as mentioned in limitation part [ 1 ]. However, this potential selection would not change the results of this study.…”

“…We would like to thank Dr. Romain Jouffroy and his team for their interest and giving some suggestions for our research to investigate the association between pH value and neurological outcome among the out-of-hospital cardiac arrest (OHCA) patients treated by extracorporeal cardiopulmonary resuscitation (ECPR) [ 1 , 2 ].…”

“…First, Dr. Romain and his team suggested that the time duration from OHCA occurrence to the blood test or no flow duration should be in the analysis as a covariate. Basically, we believe that it is unnecessary to adjust the low or no flow time duration to estimate the association between the pH value and outcome, because we think pH value is the representative of the duration and the quality of the resuscitation as described in the original article [ 1 ], and we assumed that the duration was not a confounder but a “parent” of the association between pH value and outcome in the causal inference. Further, they also suggested that categorization of the pH value to three groups could not reflect the pathophysiology accurately, and it should be treated as a continuous variable.…”

Development and Validation of a Clinical Score to Predict Neurological Outcomes in Patients With Out-of-Hospital Cardiac Arrest Treated With Extracorporeal Cardiopulmonary Resuscitation

“…Based on the previous studies 8 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 and the opinion of the emergency medicine experts in our research group (Y.O., T. Kiguchi, T.I., T.Y., T.M., T.N., M.K., N.N., S.Y., S.K., S.O., T. Kitamura, and T.I. ), we selected the following variables as potential predictors of in-hospital mortality: age, witnessed by bystander, CPR by bystander, shockable rhythm on hospital arrival, time from emergency call to hospital arrival, and initial serum pH value.…”

Association between low pH and unfavorable neurological outcome among out-of-hospital cardiac arrest patients treated by extracorporeal CPR: do not dismiss confounders!

“…In the May issue of the Journal, Okada et al [1] reported in a multi-institutional observational study an association between low pH value (< 7.03) before the implementation of extracorporeal cardiopulmonary resuscitation (ECPR) and 1-month unfavorable neurological outcome among out-of-hospital cardiac arrest (OHCA) patients treated with ECPR. They also suggested that pH value may be helpful to consider the candidate for ECPR.…”