Objective:

To investigate differences in norepinephrine (NE) trajectories following initiation of arginine vasopressin (AVP) in septic shock based on body mass index (BMI).

Approach:

• Data Re-analysis: Data was re-analysed using absolute NE dose (mcg/min) to eliminate the influence of body weight on the NE dose metric.
• Statistical Analysis: Mixed-effects modelling was utilized to evaluate NE trajectories across BMI groups, controlling for baseline covariates.
• Body Composition Metrics: Exploratory analysis included body composition metrics such as fat-free mass (FFM) and the ratio of extracellular water to total body water (ECW/TBW).

Key Findings:

• Normal weight patients received lower median NE infusion rates compared to obese patients (33 vs. 40 mcg/min, p = 0.019).
• BMI-dependent differences in NE trajectories persisted when using absolute dosing, indicating that weight normalization may mask severity of shock.
• No significant interactions were found between FFM index or ECW/TBW ratio and NE trajectories, suggesting differences in vasopressin sensitivity.

Interpretation:

BMI influences NE response patterns during AVP treatment in septic shock, independent of weight normalization and body composition metrics.

Limitations:

• The sample size was modest, which may limit the strength of the conclusions drawn.
• BIA parameters may be influenced by fluid overload in critically ill patients.

Conclusion:

Further research with larger cohorts and more robust assessment techniques is necessary to clarify the role of body composition in AVP responsiveness.