High vasopressor doses are associated with decreased tissue oxygenation in critically ill patients: a secondary analysis of a prospective cohort.

BACKGROUND: Despite stabilizing macrocirculatory blood pressure, vasopressors may deleteriously affect microcirculatory perfusion in critically ill patients. As microcirculatory dysfunction is associated with adverse outcomes and objective bedside monitoring remains limited, hyperspectral imaging (HSI) has emerged as a promising noninvasive method to assess tissue oxygenation. This study investigated the association between load of vasoactive medication and microcirculatory impairment using HSI in critically ill patients.

METHODS: In this secondary analysis of the prospective HySpec-ICU study, 502 surgical ICU patients were included. HSI measurements of the hand were performed on the day of admission to determine tissue oxygenation (StO₂) and other HSI variables. Multivariable linear regression and mediation analysis were employed to investigate the association between Norepinephrine Equivalent (NEE) and StO₂ and its impact on serum lactate levels.

RESULTS: Higher NEE was independently associated with significantly lower StO₂ (B = - 0.0931, β=-0.193, p = 0.001), while MAP showed no significant correlation with StO₂. Patients in the highest NEE quartile (> 0.28) exhibited the lowest StO₂ and the highest 30-day mortality (41.8%). StO₂ partially mediated the relationship between vasopressor load and arterial lactate. StO₂ generally improved after shock reversal defined as NEE ≤ 0.05, lactate < 2mmol/l, MAP ≥ 65mmHg for at least 24 h (+ 5.8%, p < 0.001).

CONCLUSION: High vasopressor requirements are associated with impaired microcirculatory oxygenation of the hand regardless of systemic blood pressure. HSI provides an objective bedside tool to monitor these alterations, potentially identifying patients with persistent microcirculatory shock who require intensified therapy beyond macrohemodynamic targets.