Association between hemoglobin concentration and peripheral perfusion index in normovolemic patients: a prospective observational study.

To investigate the relationship between hemoglobin concentration and peripheral perfusion index (PI) in normovolemic, hemodynamically stable patients. This prospective observational study included 90 adult emergency department patients, classified as anemic (n = 45) and non-anemic (n = 45) according to World Health Organization criteria. PI was measured using standardized pulse oximetry conditions. Group comparisons were performed using appropriate statistical tests. The association between hemoglobin and PI was evaluated using Spearman correlation. A multivariable linear regression model with log-transformed PI was used to identify independent predictors, adjusting for clinically relevant variables. Model assumptions and influential observations were assessed. PI values were significantly lower in anemic patients compared with non-anemic patients (median 2.1 vs. 3.5, p < 0.001). Hemoglobin concentration showed a moderate positive correlation with PI (r = 0.425, p < 0.001). In multivariable analysis, hemoglobin remained independently associated with PI (β = 0.306, p = 0.021). The model demonstrated modest explanatory power (adjusted R²=0.069). Sensitivity analysis excluding influential observations yielded consistent findings. Hemoglobin level is independently associated with PI in normovolemic patients. Although PI primarily reflects flow-related peripheral perfusion, hemoglobin contributes to its variability. These findings suggest that anemia and peripheral perfusion are interrelated but distinct physiological parameters that should be considered together in clinical interpretation.