Higher hematocrit level associated with higher 5-aminolevulinic acid-induced perioperative blood pressure change

5-aminolevulinic acid (5-ALA) is used for photodynamic diagnosis-assisted surgeries. Hypotension is among 5-ALA-related adverse effects. 5-ALA metabolism requires iron. The red cell life span is 120 days and heme iron is daily recycled. Higher hematocrit is likely to correlate with higher recycled iron. We previously reported 5-ALA-induced hemodynamics in urological surgery. This analysis aimed to determine the association between 5-ALA-induced perioperative systolic blood pressure (SBP) changes and the hematocrit.

This retrospective study enrolled consecutive patients who underwent transurethral resection of bladder tumor from August 2018 to December 2020. The patients were classified into the 5-ALA-pretreated patients (5-ALA group; n = 26) and non-pretreated patients (control group; n = 97). We evaluated the correlation between SBP change rates and hematocrit levels. The primary analyses included the difference in correlations between the two groups. Subsequently, the correlations were analyzed in the 5-ALA group and control group, respectively.

The correlations significantly differed between the two groups preoperatively (P<0.001), during surgery (P = 0.014), postoperatively (P = 0.001), and on the following morning (P = 0.002). The correlations between SBP changes and the hematocrit in the 5-ALA group were significant before patients entered the operation room (Spearman's rank correlation coefficient [rS]=-0.449, P = 0.024), before anesthesia induction (rS=-0.584, P = 0.002), during surgery (rS=-0.401, P = 0.047), after operation (rS=-0.658, P<0.001), and on the following morning (rS=-0.547, P = 0.004). Those in the control group were not significant.

The hematocrit levels were significantly correlated with perioperative 5-ALA-induced SBP changes. The association was again observed the next day. Higher hematocrit may be a factor for 5-ALA-induced hemodynamic changes.