Eye symptoms, visual evoked potentials and EEG during intravenous infusion of glycine

Disturbance of vision is a complication that may occur from absorption of the glycine solution used to irrigate the bladder during transurethral operations. We examined for a possible dose-response relationship between glycine dose, eye symptoms and neurophysiological changes after repeated intermittent intravenous infusions of 4.4 g of glycine for up to 22 g over 1 h in 10 male volunteers. The serum glycine concentration increased from 230 +/- 75 to 5,232 +/- 1,088 mumol/l (mean +/- s.d.) during the infusions. We found an increase in diastolic arterial pressure but no significant changes in systolic pressure, heart rate or mental status. Five of the volunteers developed blurring of vision which lasted for 10-30 min. The visual evoked potentials (VEP) of these subjects showed an increase of the P100 and N70 latencies which started after no more than 4.4 g of glycine had been administered. The amplitude of the VEP was preserved and the main frequency of the EEG did not change, indicating that VEP changes were not due to cortical dysfunction. There was no dose-response relationship between glycine infusion and eye symptoms but a sub-group of volunteers responded with both visual disturbances and VEP changes.