Background: Transurethral holmium YAG laser resection of the prostate (HoLR-P) and transurethral electrovaporization of the prostate (TUV-P) have recently received increasing attention as an effective minimally invasive approach for the treatment of prostatic hypertrophy. However, less information is available regarding the intraoperative changes in the serum Na+ and blood hemoglobin levels during either HoLR-P or TUV-P.

Methods: Intraoperative changes in serum Na+ and blood hemoglobin levels were investigated in 17 patients undergoing transurethral resection of the prostate (TUR-P, n = 7), HoLR-P (n = 7) or TUV-P (n = 3). The 3% D-sorbitol solution was used as the irrigating fluid in all the patients.

Results: In three patients, severe hyponatremia (118-123 mEq x l(-1)) developed abruptly (< or = 15 min) at various time points during TUR-P with (n = 1) or without (n = 2) cystostomy. However, no clinical symptoms were observed after development of the hyponatremia in those awake patients. No large (> 10 mEq x l(-1)) decreases in the Na+ level were observed in any of the patients undergoing HoLR-P or TUV-P. In patients undergoing TUR-P and HoLR-P, percent changes in serum Na+ level significantly correlated with those in blood hemoglobin level, but not with the resection time; the slopes were significantly larger than unity.

Conclusions: The TUR syndrome is less likely to occur during HoLR-P or TUV-P. During TUR-P, the onset of severe hyponatremia appears to be unpredictable, and may not necessarily be accompanied by clinical symptoms. Frequent measurements of the serum Na+ level appear essential for early detection of severe hyponatremia.