Transurethral resection of the prostate, serum glycine levels, and ocular evoked potentials

Complications of transurethral resection of the prostate (TURP syndrome) when glycine is used as the irrigating fluid include cardiovascular and central nervous system abnormalities that occasionally include transient blindness. Serum sodium, glycine, potassium, chloride, ammonia, osmolality, carbonate, and blood urea nitrogen of 17 patients having TURP and 10 having cystoscopic examination were measured. Electroretinograms and visually evoked potentials (VEPs) were recorded in the preanesthetic preparatory area and in the recovery room immediately after surgery. Four patients reported visual aberrations coincident with increases in serum levels of glycine from a mean before surgery of 137.7 +/- 45.1 to 7,812.2 +/- 2,486.6 microM/l, mean +/- SD, after TURP. These patients also showed a reduction of serum sodium from 138 +/- 4.5 to 122 +/- 8.6 mEq/l that correlated significantly with serum levels of glycine (rho = -0.81). There were no statistically significant changes of serum ammonia and osmolality. Electroretinograms consistently demonstrated complete loss of oscillatory potentials. Thirty hertz flicker-following was also abolished. VEPs were more variably affected with prolongation of component "P100" latency found in both groups and probably resulting from sedative effects of diazepam. Patients experiencing the TURP syndrome showed abolishment of 30 Hz flicker-following in their VEPs. The elevated serum levels of glycine may contribute directly to visual aberrations resulting from glycine's role as an inhibitory transmitter in the retina.