Whole blood serotonin levels are markedly elevated in patients on dialytic therapy

The normal range for whole blood serotonin levels in chronic renal failure patients has not been defined. As serotonin may be implicated in platelet abnormalities, hypo- and hypertension and itch in dialysis patients, serotonin whole blood levels were measured in a group of patients with chronic renal failure and/or who were dialysis dependent. The levels were elevated in 12 patients with moderate (mean serum creatinine 335 ± 54 umol/1) chronic renal failure (270 ± 46 µg/1) compared to 11 normals (163 ± 17 µg/1. p < 0.05; quoted normal range < 300 u.g/1) but did not correlate with serum creatinine levels. There was a marked elevation in serotonin levels in dialyzed patients, including those on hemodialysis (polysulfone, n = 6, 747 ± 234 µg/1: cuprophane membranes, n = 6, 708 ± 198 µg/1). hemodiafiltration (n = 12. 695 ± 130 µg/1) and especially peritoneal dialysis (n = 6. 1,148 ± 162 µg/1). All results were significant (p < 0.01) compared to normals and compared to the nondialyzed group (p < 0.05). The level of serotonin decreased during hemodialysis regardless of the membrane used. There was no positive correlation of serotonin levels with pruritus or hypertension, although there was a negative correlation with systolic blood pressure. The reference range for serotonin whole blood levels needs to be broadened when considering dialyzed patients.