Dynamic Changes in Peripheral Perfusion During a Vasopressor Test in Septic Shock Patients: A Physiological Proof-of-Concept Study

Background Macrohemodynamic optimization does not always improve peripheral perfusion in patients with septic shock. The vasopressor test (VPT), a transient increase in mean arterial pressure (MAP), has been proposed to assess whether increasing MAP enhances capillary refill time (CRT); however, its physiological determinants remain unclear. Objectives To (1) evaluate CRT response to a standardized VPT, (2) explore the associations between CRT and splanchnic vascular indices, and (3) identify baseline hemodynamic predictors of CRT improvement. Methods In this prospective multicenter study, 32 septic shock patients with persistent hypoperfusion and preload unresponsiveness were assessed at baseline (MAP 65 mmHg) and during VPT (MAP 85 mmHg). CRT responders were defined as those with a decrease of ≥ 1 s. Splanchnic perfusion was evaluated using Doppler-derived renal, hepatic, and splenic resistive indices. The mean systemic filling pressure (Pmsf) was estimated using an analog model. Logistic regression identified predictors of CRT improvement, and mixed-effects models examined the relationship between stroke volume (SV) changes and CRT. Results CRT response to VPT was heterogeneous; 34% of the patients showed a ≥ 1 s decrease. CRT changes did not correlate with splanchnic resistive indices. A lower baseline Pmsf level was independently associated with improvement in CRT. Mixed models demonstrated an inverse relationship between SV changes and CRT response. Conclusions CRT improvement during VPT identified patients with preserved peripheral perfusion recruitability. Lack of correlation with splanchnic indices underscores the need for territory-specific monitoring. Maintaining a normal Pmsf following initial fluid resuscitation has emerged as a significant predictor of CRT response.