24-hour survival prediction of initial blood pH for non-traumatic out-of-hospital cardiac arrest patients in the Emergency Department of Nakornping Hospital

Abstract

Background: A major reduction in tissue perfusion during cardiac arrest can lead to metabolic acidosis, which causes a decrease in blood pH.  Blood gas analysis, as one of the cardiopulmonary resuscitation parameters, may be effective in predicting ROSC and 24-hour survival.

Objectives: This study aims to investigate the associations between the initial blood pH during ongoing cardiopulmonary resuscitation of out-of-hospital cardiac arrest (OHCA) patients and the likelihood of return of spontaneous circulation (ROSC) and 24-hour survival.

Methods: Patients with OHCA who more than 15 years old were enrolled in this prospective observational cohort study. From October 2020 to August 2021, data from Nakornping Hospital's emergency department was collected, including the sex, age, date and time, pre-hospital CPR duration, witness arrest, cardiac origin, bystander CPR, shockable rhythm and initial blood pH.

Results: A total of 79 patients with out-of-hospital cardiac arrest (OHCA) were included. Univariable logistic regression analysis revealed several factors significantly associated with return of spontaneous circulation (ROSC), including prehospital chest compression duration ≥20 minutes compared to 0 minutes (Odds Ratio [OR] 6.9; 95% Confidence Interval [CI] 2.11–22.57; p 0.001), initiation of chest compression by a bystander (OR 0.26; p 0.021), and initial blood pH ≥ 7.0 (OR 3.75; 95% CI 1.46–9.64; p 0.006). Factors associated with 24-hour survival included prehospital chest compression duration of 1–19 minutes and ≥20 minutes (OR 8.86 and 13.12; 95% CI 1.66–47.20 and 2.54–67.61; p 0.011 and 0.002, respectively), as well as initial blood pH ≥6.8, ≥6.9, and ≥7.0 (OR 11.35, 4.88, and 5.56; 95% CI 1.42–90.73, 1.46–16.28, and 1.85–16.66; p 0.022, 0.010, and 0.002, respectively). However, multivariable analysis identified only one statistically significant factor: prehospital chest compression duration of 1–19 minutes and ≥20 minutes, which remained independently associated with 24-hour survival (AOR 6.48,  95% CI 1.12–37.41 and AOR and 8.03, 95% CI1.28–50.19; p 0.037 and 0.026, respectively).

Conclusions: From this study, the association between the Initial blood pH and the likelihood of ROSC and 24-hour survival was inconclusive. Further research is needed.