By Marcus A. Banks
Calcium administration after a cardiac arrest does not appear to be beneficial, according to a presentation at the Society of Critical Care Medicine’s Critical Care Congress 2025, in Orlando, Fla.
“Maybe we’re just achieving a placebo effect for ourselves,” said meeting speaker Marilyn Bulloch, PharmD, BCPS, an associate clinical professor of pharmacy practice at Auburn University, in Alabama, by offering calcium after a cardiac arrest.
Common reasons for providing calcium are to improve contractility and vascular tone after a cardiac arrest, Dr. Bulloch noted. But even if calcium achieves those effects, its ultimate efficacy appears limited.
The COCA (Calcium for Out-of-hospital Cardiac Arrest) study, in Denmark, compared the use of calcium with placebo for responding to cardiac arrests that occurred outside the hospital (Resuscitation 2022:179:21-24). Of 391 adults, 193 received up to two doses of 5 mmol IV or intraosseous calcium chloride, given after one or two doses of epinephrine. The other 198 adults received a placebo, 9 mg/mL of sodium chloride, after the epinephrine doses.
One year after the cardiac arrest, nine patients (4.7%) were alive in the calcium group, compared with 18 people (9.1%) surviving who had received the placebo. In addition, 37 people (19%) in the calcium group achieved spontaneous circulation—circulation with no need for chest compression for at least 20 minutes—compared with 53 people (27%) in the placebo group (risk ratio, 0.72; 95% CI, 0.49-1.03; risk difference, −7.6%; 95% CI, −16% to 0.8%; P=0.09) (JAMA 2021;326:1-10), explained Dr. Bulloch.
She noted that these results do not support calcium use during out-of-hospital cardiac arrest, adding that the wide confidence intervals for spontaneous circulation suggest a need for caution in interpreting the findings.
Dr. Bulloch also discussed a retrospective review of nine years of medical records in San Francisco (Resuscitation 2023:191:109933). Of 781 patients with cardiac arrest treated in an emergency department (529 males; median age, 65 years), 308 people received calcium during their cardiac arrest treatments. “You were more likely to survive to hospital admission if you did not receive calcium.” Dr. Bulloch said. Indeed, 173 of the 308 calcium-treated patients (56.2%) survived to hospital admission, compared with 357 of the 473 patients (75.5%) who did not receive calcium.
These data are retrospective, and information on comorbidities in the calcium and non-calcium groups is not available, which are limitations both the study authors and Dr. Bulloch noted. Nevertheless, there is a growing body of evidence that offering calcium after a cardiac arrest is often not helpful, she said. However, whether the calcium is harmful—not merely unhelpful—is unknown at this time, Dr. Bulloch added.
Dr. Bulloch reported no relevant financial disclosures.
