Alteration of sublingual microcirculation in anemic patients during gastric cancer surgery under goal-directed fluid therapy: a prospective cohort study.

Goal-directed fluid therapy (GDFT) relies primarily on macrocirculatory hemodynamic variables for optimizing fluid therapy. Patients undergoing gastric cancer surgery often present with anemia, which may impair microvascular endothelial function and tissue oxygenation. How preoperative anemia influences intraoperative sublingual microcirculation and macro- and micro-circulatory coherence under GDFT is not known. Patients undergoing open radical gastrectomy were divided into anemic and non‑anemic groups according to their hemoglobin (Hb) levels. All patients received GDFT guided by pulse pressure variation. Sublingual microcirculatory (microvascular flow index [MFI], proportion of perfused vessels [PPV], total and perfused vessel density) and macrocirculatory (cardiac index [CI] and mean arterial pressure [MAP]) variables were measured before (T0) and immediately after induction of general anesthesia (T1), after tumor resection (T2) and at the end of surgery (T3). Mixed linear models were used to compare intergroup differences in sublingual microcirculation over time, and to analyze the correlations between macro- and micro-circulatory variables. Correlations between preoperative Hb and changes in MFI from each intraoperative time point to T0 were additionally assessed. A total of 49 patients were analyzed in present study. MFI showed a significant group‑by‑time interaction between the two groups (P = 0.030). In anemic patients (n = 22), MFI was significantly lower than that in non‑anemic patients (n = 27) at T1 (P = 0.013), and between-group differences were no longer evident at T3 (P = 0.461) under GDFT, although MFI remained below baseline in both groups. PPV was lower in anemic patients at T2 (P = 0.010). Correlation analyses demonstrated that lower preoperative Hb levels were associated with greater reductions in ΔMFI from T1 to T0 (Pearson's r = 0.343, P = 0.016) and T2 to T0 (Spearman's ρ = 0.369, P = 0.009). No significant associations were found between macro- and micro-circulatory variables in either group. Under GDFT, anemic patients exhibited greater perioperative alterations in sublingual microcirculation, particularly after anesthesia induction and tumor resection. Lower preoperative Hb concentrations were associated with greater reductions in MFI. Further, the lack of detectable associations between macrocirculatory and sublingual microcirculatory variables suggests that conventional hemodynamic targets may not fully reflect sublingual microvascular perfusion in this vulnerable population.Trial registration number: NCT07583927.