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

Biochemical and Electroretinographic Characterization of the Minipig Eye in the Context of Drug Safety Investigations

Minipigs are an emerging nonrodent alternative for ocular toxicology owing to anatomical similarities in the minipig eyes when compared to humans. Ocular structures and components from Göttingen minipigs were characterized and compared to species commonly used in toxicology. Ocular reference data from Göttingen minipig including intraocular pressure, vitreous electrolyte and thiol concentration, and electroretinography (ERG) data are essential to model characterization and data interpretation during drug safety assessments. Intravitreal positive control agents including gentamicin, indocyanine green, and glycine were used to demonstrate ERG alterations caused by retinal cell toxicity, light transmission obstruction, or neurotransmission interferences, respectively. Electrolyte concentrations of the aqueous and vitreous humors from Göttingen minipigs were similar to other species including humans. The reference data presented herein supports the use of the Göttingen minipig as an alternate nonrodent species in ocular toxicology.

Blue Vision (Cyanopsia) Associated With TURP Syndrome: A Case Report

There have been many complications associated with transurethral resection of the prostate (TURP), known as TURP syndrome. Of the various irrigation fluids used for TURP, glycine irrigant has been historically popular given its relatively low cost. It is also a nonconductive solution and only slightly hypoosmolar, reducing the risk of burn injury or significant hemolysis. However, there have been many case reports of central nervous system toxicity such as transient blindness and encephalopathy related to glycine toxicity. Here, we report blue vision (cyanopsia), which has never been reported as a symptom of TURP syndrome.

Early stage development of the glycine-1 re-uptake inhibitor SCH 900435: central nervous system effects compared with placebo in healthy men

AIMS

To report the first three studies with SCH 900435, a selective glycine-1 re-uptake inhibitor in development for treating schizophrenia, using systematic evaluations of pharmacodynamics to understand the observed effects.

METHODS

Three double-blind, placebo-controlled studies (single, visual effect and multiple dose) were performed. In the single and multiple dose study SCH 900435 (0.5-30 mg) was given to healthy males and frequent pharmacokinetic and pharmacodynamic measurements were performed. The visual effects study incorporated visual electrophysiological measures of macular, retinal and intracranial visual pathway function.

RESULTS

In the single dose study (highest difference, 95% CI, P) increases in smooth pursuit eye movements (8, 12 mg (-6.09, 10.14, -2.04, 0.013), 30 mg), pupil : iris ratio (20 and 30 mg (-0.065, 0.09, -0.04, <0.0001)), VAS colour perception (30 mg (-9.48, 13.05, -5.91, <0.0001)) and changes in spontaneous reports of visual disturbance were found, while FSH (8 mg (0.42, 0.18, 0.66, 0.0015), 12, 20 mg), LH (8-30 mg (1.35, 0.65, 2.05, 0.0003)) and EEG alpha2 activity decreased (12, 20, 30 mg (0.27, 0.14, 0.41, 0.0002)). A subsequent dedicated visual effects study demonstrated that visual effects were transient without underlying electrophysiological changes. This provided enough safety information for starting a multiple ascending dose study, showing less visual symptoms after twice daily dosing and titration, possibly due to tolerance.

CONCLUSIONS

Several central nervous system (CNS) effects and gonadotropic changes resulted from administration of 8 mg and higher, providing evidence for CNS penetration and pharmacological activity of SCH 900435. Antipsychotic activity in patients, specificity of the reported effects for this drug class and possible tolerance to visual symptoms remain to be established.

Glycine 1.5% for irrigation should be abandoned

BACKGROUND

Glycine 1.5% has long maintained a dominating role as an irrigating solution for monopolar transurethral resection of the prostate (TURP), as well as for certain other transurethral procedures.

MATERIALS AND METHODS

This review summarizes the findings of systematic experimental and clinical studies in which glycine 1.5% for irrigation was infused/absorbed and the outcome compared to at least one other irrigating fluid, including the isotonic saline used for bipolar TURP.

RESULTS

There were 11 studies in animals, 3 in volunteers and 6 in patients undergoing TURP. With only one exception, which is probably due to low power, these studies either show a poorer outcome after administration or absorption of glycine solution or else that glycine 2.2% is more toxic than glycine 1.5%. The poorer outcomes consisted of more tissue damage or higher mortality (animals) or more symptoms (volunteers and patients).

CONCLUSION

The safety of monopolar TURP would be improved by replacing glycine 1.5% with some other electrolyte-free fluid. The author argues that glycine 1.5% should be abandoned completely.

Transurethral resection of the prostate syndrome: almost gone but not forgotten

Transurethral resection of the prostate (TURP) syndrome is a rare but potentially fatal syndrome with multifactorial pathophysiology that is now better understood. Unfortunately, despite this improved understanding, it is not yet obsolete and still remains a risk. Many reviews of TURP syndrome have been presented from an anesthetic perspective; this review reflects more the urologic perspective with emphasis on the importance of multidisciplinary management of this complex syndrome. We present a review of TURP syndrome that specifically assesses advances in the understanding of risk factors, pathophysiology, and techniques used to prevent this syndrome. The databases Medline, Embase, Cochrane Controlled Trial Register, and Database of Abstracts of Reviews of Effects were systematically reviewed from inception to April 2009 for the keywords TUR (P), TUR (P) syndrome, and transurethral resection of prostate. There was no language restriction for our search. Randomized controlled trials, review articles and case series were included in our search. Our review showed a declining trend in the incidence of TURP syndrome despite TURP remaining the gold standard for the management of benign prostatic obstruction. Technologic advances using an array of laser techniques, the use of bipolar circuitry, together with advances in training techniques have helped minimize the risk of development of this syndrome. This review demonstrates the complexity of TURP syndrome. Even with a greater understanding of the pathophysiology, it highlights the unpredictability of the syndrome from presenting symptoms, preventative measures, and management. TURP syndrome cannot be protocol driven and the need for vigilance, a high index of suspicion, intensive monitoring, and a multidisciplinary approach is vital.

Is using ethanol-glycine irrigating fluid monitoring and 'good surgical practice' enough to prevent harmful absorption during transurethral resection of the prostate?

OBJECTIVE

To evaluate the utility of using a tracer of 1% ethanol in 1.5% glycine for the early detection of irrigation fluid absorption during transurethral resection of the prostate (TURP).

PATIENTS AND METHODS

In all, 126 men undergoing TURP were irrigated with a solution of 1% ethanol and 1.5% glycine; their expired air was tested for ethanol every 20 min, and again at the end of the procedure. Maximum absorption by the breath-ethanol reading was compared with the serum concentration of absorbed glycine (analysed by anion-exchange chromatography).

RESULTS

Complete data on 120 men were assessed; 75% of the men absorbed irrigation fluid, with glycine levels above the normal range. The sodium levels tended to decrease with increasing glycine levels (Spearman's rank correlation coefficient, - 0.57; 120 men) and five men (4%) developed clinical features of the TUR syndrome. There was a weak correlation between breath-ethanol levels and serum glycine levels (Spearman's rank correlation coefficient, 0.54). The experience of the surgeon, the weight of the resected chips, and the operative duration were not significantly predictive of irrigation fluid absorption.

CONCLUSIONS

A rising breath-ethanol level indicates irrigation fluid absorption. However, irrigating fluid absorption is unpredictable, supporting the case for alternative, potentially safer irrigants.

Fluid absorption in endoscopic surgery

Fluid absorption is an unpredictable complication of endoscopic surgery. Absorption of small amounts of fluid (1-2 litre) occurs in 5-10% of patients undergoing transurethral prostatic resection and results in an easily overlooked mild transurethral resection (TUR) syndrome. Large-scale fluid absorption is rare but leads to symptoms severe enough to require intensive care. Pathophysiological mechanisms consist of pharmacological effects of the irrigant solutes, the volume effect of the irrigant water, dilutional hyponatraemia and brain oedema. Other less widely known factors include absolute losses of sodium by urinary excretion and morphological changes in the heart muscle, both of which promote a hypokinetic circulation. Studies in animals, volunteers and patients show that irrigation with glycine solution should be avoided. Preventive measures, such as low-pressure irrigation, might reduce the extent of fluid absorption but does not eliminate this complication. Monitoring the extent of absorption during surgery allows control of the fluid balance in the individual patient, but such monitoring is not used widely. However, the anaesthetist must be aware of the symptoms and be able to diagnose this complication. Treatment should be based on administration of hypertonic saline rather than on diuretics. New techniques, such as bipolar resectoscopes and vaporizing instead of resecting tissue, result in a continuous change of the prerequisites for fluid absorption and its consequences.