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General information
Glycine is an amino acid that is used in a 1.5% solution for bladder irrigation during transurethral prostatectomy and sometimes continuously for 24 hours after surgery. It has also been used to irrigate renal stone fragments after percutaneous ultrasonic lithotripsy [ ] and to distend the uterus during transcervical resection of endometrium [ ].
Systemic absorption of the irrigating fluid occurs during these procedures. For example, plasma glycine concentrations rise immediately after prostatectomy and return to normal within 24 hours [ ]. The half-life of glycine in the serum is dose dependent, being twice as long (100 minutes) when the volume of irrigant absorbed exceeded 1500 ml [ ]. After intravesical administration of 10–91 g of glycine in 17 patients undergoing transurethral resection of the prostate and intravenous infusion of 15–22 g in 18 volunteers the half-life varied from 26 to 245 minutes, being longer at higher doses [ ].
The increased glycine and fluid load can cause a variety of circulatory and nervous system disturbances, which are often referred to as the transurethral resection syndrome. The lack of a consistent definition and varying degrees of awareness of mild forms of this complication may explain the different figures given for the incidence of the syndrome in prospective studies, varying from 2% to 10% of all transurethral resections performed. Many urologists claim they have not encountered the transurethral resection syndrome for many years [ ]. However, the incidence and severity of symptoms of the transurethral resection syndrome on absorption of increasing volumes of glycine solution have been described [ ]. Hyponatremia and nausea are common features [ ]. Transitory blindness occasionally occurs [ ].In one case death occurred because of rapid absorption of glycine through a surgical defect in the posterior bladder wall [ ].
The fact that glycine can act as an inhibitory neurotransmitter may explain why absorption of glycine-containing irrigating fluid from the pelvic cavity or directly into the blood during transurethral prostate resection has been linked to loss of sight and vivid postoperative hallucinations [ ]. Ammonia production due to accumulation of glycine in tissues and the neuroinhibitory effects of glycine should be considered to be susceptibility factors when deciding on glycine as an irrigating fluid [ ].
It has been recommended that glycine irrigation should be confined to the time of operation, and an adequate diuresis should be ensured postoperatively [ ].
Glycine has also been used to irrigate the knee during arthroscopic electrosurgery [ ] and during arthroscopy of other joints [ ].
Since it has been suggested that schizophrenia is associated with reduced glutamate neurotransmission via N-methyl-D-aspartate (NMDA) glutamate receptors, and since glycine potentiates NMDA receptor-mediated neurotransmission, oral glycine has been used in the treatment of schizophrenia as an adjunct to therapy with conventional antipsychotic drugs [ , ]. The response was related to serum glycine concentrations [ ].
Oral glycine, 8 g initially followed by 4 g 4-hourly, has been used to treat salicylate overdose [ ].
Drug studies
Observational studies
The signs and symptoms of the transurethral resection syndrome were evaluated and recorded during and after 273 transurethral prostatic resections performed at two hospitals between 1984 and 1993. Glycine solution was used as the irrigant and ethanol served as a tracer for fluid absorption. The incidence and severity of symptoms related to the syndrome increased progressively as more glycine solution was absorbed. Patients who absorbed up to 300 ml of glycine solution had an average of 1.3 such symptoms; the average was 2.3 when 1000–2000 ml were absorbed, 3.1 when 2000–3000 ml were absorbed, and 5.8 for volumes greater than 3000 ml. Nausea and vomiting occurred significantly more often when 1000–2000 ml were absorbed compared with no absorption. Confusion and arterial hypotension were other prominent signs of fluid absorption. Extravasation resulted in higher risks of bradycardia, hypotension, and failed spontaneous diuresis postoperatively than intravascular absorption.
Nausea after glycine irrigation can be partly explained by the toxic effects of glycine and its secondary metabolites in addition to the effects of water intoxication and hyponatremia [ ] and is occasionally due to cerebral edema (see below).
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