SWAP Score for Out of Hospital Cardiac Arrest

The SWAP (Shockable, Witnessed, Age, pH) score is a prognostication tool for patients arriving to the ED after out of hospital cardiac arrest. It was designed to rapidly assess the predicted neurological outcome in patients actively receiving CPR upon arrival. Through logistic regression, four independent variables were produced with binary non-weighted scores of one or zero depending on patient characteristics.

Study enrollment involved patients that had been assessed by basic life support crews in the field and then transferred to the emergency department while actively being resuscitated without evidence of ROSC in the field. The four variables isolated include 3 clinical parameters (shockable rhythm, witnessed cardiac arrest, and age over 60) and 1 bloodwork result (pH < 7 on arrival to ED). While increasing SWAP scores were associated with worse neurologic outcomes, scores of 4 were 100% specific in predicting poor neurological outcome which is the finding of highest utility.

Limitations of this study include is that it has yet to be externally validated, involves time-sensitive bloodwork, and may lack generalizability in many healthcare settings. Specifically for generalizability, within most North American settings OHCA is managed exclusively in the pre-hospital environment until ROSC is achieved, thereby making this Taiwanese study patient population quite different. For now, the SWAP score is another more objective tool used to guide clinician gestalt for duration of resuscitation and degree of resource allocation in possibly futile situations.

Variable & Associated Points
• Shockable initial rhythm (Yes 0, No +1)
• Witnessed cardiac arrest or collapse (Yes 0, No +1)
• Age > 60 (Yes +1, No 0)
• Initial pH ≤ 7 (Yes +1, No 0)