Does Switching Norepinephrine to Phenylephrine in Septic Shock Complicated by Atrial Fibrillation With Rapid Ventricular Response Improve Time to Rate Control?

Background: Atrial fibrillation (AF) frequently develops during critical illness. In septic shock complicated by rapid AF, the use of phenylephrine may be advantageous secondary to its β-1 sparing properties. However, evidence supporting this strategy is lacking.

Objective: The purpose of this study is to determine the clinical effect on rate control of transitioning norepinephrine to phenylephrine in septic shock patients who develop AF with a rapid ventricular response (RVR).

Methods: A single-center retrospective study of septic shock patients admitted to the medical or surgical intensive care unit (ICU) who developed AF with RVR (heart rate >110 beats per minute [bpm]). Patients who were switched to phenylephrine were compared to those who remained on norepinephrine. The primary end point was sustained achievement of rate control. A time-varying Cox proportional hazards model was used to assess the primary end point.

Results: A total of 67 patients were included in the study, of which 28 were switched to phenylephrine. Baseline characteristics were similar between groups. The unadjusted hazard ratio for achieving rate control was significant at 1.99 (95% confidence interval [CI]: 1.19-3.34; < .01) for the phenylephrine group. The adjusted hazard ratio was 1.75 (95% CI: 0.86-3.53; = .12). There were no statistically significant differences in mortality or ICU length of stay.

Conclusion: Our study suggests a potential clinical effect on achieving rate control when switching to phenylephrine cannot be excluded. It remains unclear if there is a benefit on mortality or length of stay outcomes in critically ill patients.