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3 CPR by first responders improves acid-base balance and prognosis in out-of-hospital non-traumatic cardiac arrest
  1. A Hernández-Tejedor,
  2. E Corral,
  3. R de Elías,
  4. R Suárez
  1. SAMUR-PC, Madrid, Spain


Background Early basic-CPR has been shown to be effective. However, its effect on homeostasis in non-traumatic out-of-hospital cardiac arrest (OHCA) is unknown. We analyze pathophysiological and prognostic consequences of basic-CPR performed by first responders (FR) previous to EMS arrival.

Method Prospective observational cohort study including all patients treated for OHCA by an EMS from 2015 to 2017. Basic-CPR by FR and venous blood gas by Epocal (Ottawa, Canada) at the beginning of advanced-CPR were covariates. Dependent variables included analytical values and final outcomes (ROSC and final neurological condition CPC grades I–II). Statistical analysis: Kolmogorov-Smirnov/Lilliefors test of normality, bivariate (T-test and Chi-square-test) and multivariate (logistic regression and recursive partitioning) analysis and association measures (odds ratio-OR).

Results Our EMS attended 749 OHCA. Eighty-seven cases were excluded due to lack of data on gasometry (52)/FR (35). We analyzed 662 cases (137 women, 65.1±16.1 years-old), 46.1% were shockable rhythms and 63% received basic-CPR. pH was 7.13±0.15 in CPR-by-FR-cases and 7.06±0.18 in non-CPR-by-FR-cases (p<0.001). PvCO2 69±23 vs 77±25 mmHg (p<0.001), base excess −6.6±5.4 vs −8.6±6.6 mmol/L (p<0.001) and lactate 6.4±2.9 vs 7.1±3.3 mmol/L (p=0.008). CPR-by-FR (OR 1.83, CI95% 1.30–2.56, p<0.001) and shockable-rhythm (OR 3.32, CI95% 2.37–4.65, p<0.001) were independently associated with higher pH. ROSC occurred in 62.8% of CPR-by-FR-cases and 54.7% of non-CPR-by-FR-cases; OR 1.40, CI95% 1.02–1.93, p=0.039). Recovery CPC I–II occurred in 27.1% of CPR-by-FR-cases and 19.2% of non-CPR-by-FR-cases; OR 1.57, CI95% 1.06–2.30, p=0.022).

Conclusion Basic-CPR by FR slows down metabolic and respiratory acidosis. This entails better outcomes. These data reinforce universal CPR training programs.


  1. Shin J, Lim YS, Kim K, Lee HJ, Lee SJ, Jung E, et al. Initial blood pH during cardiopulmonary resuscitation in out-of-hospital cardiac arrest patients: a multicentre observational registry-based study. Critical Care 2017;21:322.

  2. Corral E, Casado MI, García-Ochoa MJ, Suárez R. Looking a ‘metabolic watch’. The analytical parameters found at the beginning of the resuscitation are predictors of the neurological prognostic in the prehospital cardiac arrest. Resuscitation 2015;96(Suppl 1);148.

Conflict of interest None.

Funding None.

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