Potential pharmacobiological and hormonal effects on resuscitation

Objectives

Studies have now clearly shown sex-related differences in the clinical presentations of women (vs men) with out-of-hospital cardiac arrest (OOHCA) and, more importantly, differences in the ability to resuscitate them. Presumably, these observations indicate potential pharmacobiological and/or hormonal factors. However, almost all out-of-hospital cardiac arrests (OOHCAs) occur in postmenopausal women aged >60 years. The purpose of this investigation was therefore to delineate any further stratification in sex-related differences when examining the outcomes of younger women and men (<50 years old) prospectively entered into a very large OOHCA registry.

Methods

A prospective, population-based, 7-year study of all adult (>18 years) OOHCAs in an urban-EMS system with centralized protocols and medical direction using Utstein-style data guidelines. In terms of ability to resuscitate, the endpoints evaluated were return of spontaneous circulation (ROSC) and short-term survival (SURV) for those <50 years of age vs those >50 years.

Results

Of the nearly 10,000 consecutive OOHCAs studied, 3926 were women (with 839 <50 years) and 5519 were men (with 1653 <50 years). Although OOHCAs for women were witnessed less often, were fewer in ventricular fibrillation (VF) presentations (21% vs 29% for men) and were less frequent with bystander CPR, they still achieved ROSC (46% vs 39%; P < 0.001) and SURV (21% vs 17%; P < 0.001) more often than men, especially if they were <50 years of age (ROSC = 52% for women vs 41% for men, P < 0.001; SURV = 28% vs 17%; P < 0.001). Also, for younger women, VF SURV was 31% vs 16% for men (P < 0.001) while VF SURV for older patients was 29% vs 20%. For pulseless electrical activity (PEA) cases, SURV was 29% vs 18% (P < 0.001) for younger ages, but was not different for the older women and men (18% vs 19%). For asystole presentations, it was 21% vs 11% (younger group; P < 0.001) and was 10% for both women and men >50 years of age.

Conclusion

Relative to men, younger women (<50 years of age) are strikingly easier to resuscitate from cardiac arrest than older counterparts, especially with PEA and asystole presentations. Regardless of eventual neurological outcomes, these findings significantly strengthen the argument that there may be either hormonal and/or pharmacobiological differences between men and women that facilitate the ability to resuscitate. While these findings still ostensibly suggest genetic links to ROSC (and possible sex-related differences in the effects and dosing of interventions), the data here now strongly infer hormonal (e.g. estrogenic) differences as a key factor in these observations.