Lasers in urology

Ever since Mulvany first described use of Ruby laser for lithotripsy, urologists have been exploiting every possible application of this technology. Laser lithotripsy in the 1980s and now laser prostatectomy in the 1990s have dominated laser usage in urology. Applications of lasers for superficial lesions (e.g., condylomata acuminata and carcinoma of penis) have found an established role. Interests in laser welding, photodynamic therapy and fluorescence continues to grow and evolve. The laser industry at the same time is striving to provide more efficient lasers. High power lasers (Holmium:YAG, KTP:YAG) and laser machines combining double wavelengths (Nd:YAG and KTP, Ho: YAG and Nd:YAG) are commercially available. Diode lasers with their portability and reliability qualities can now provide high output powers in various wavelengths. Here, we have reviewed different lasers, laser tissue interaction and clinical laser applications relevent to urology.     

Prosthetic arteriovenous fistulas and venous anastomotic stenosis: influence of a high flow velocity on the development of intimal hyperplasia

OBJECTIVE: To search a sensitive parameter for the early diagnosis of primary open angle glaucoma (POAG). METHOD: A system of computerized image analysis was used to acquire images of the optic nerve head of patients with POAG, suspect glaucoma (SG) and of normal persons. Each of these groups contained 31 eyes of 31 cases. The mean relative depths of disc rim and cup at different areas in the optic nerve head were measured. All these patients were followed up for four to six months, and the changes of the mean depths of every sector were compared between each pair of the three groups with statistic analysis. RESULTS: The mean depth of the neural rim and cup of each sector and that of total rim and total cup of POAG and SG patients were all deeper than that of normal controls. The mean depths of neural rim of the superior sector, inferior sector and the total rim area of POAG were deeper than that of SG patients. Compared to their first measurements, the changes of mean depths of neural rim of superior sector and total neural rim area of POAG patients were more prominent than that of normal controls and SG. We also compared the relative depth of the total rim area in the different areas in the optic nerve head with other two dimensional optic disc parameters such as cup/disc ratio, etc. CONCLUSION: Our study suggests that three-dimensional stereoscopic measurement of the surface of optic nerve head and follow-up be of paramount importance in the early diagnosis of POAG patients.     

Effect of 2,3,7,8-tetrachlorodibenzo-rho-dioxin on renal function in the rat

X-ray microanalysis of air dried and ultrathin frozen and frozen dried sections of human sperm cells has indicated a large deviation of elemental composition between cells in a single sample and between samples. Analysis of air dried cells indicates a similar subcellular elemental distribution to that found in sectioned material. Sodium to potassium ratios are found to be similar in both preparations. Air drying is considered a valid method for the preparation of sperm cells for analysis.     

Impaired endothelium-dependent relaxation in isolated resistance arteries of spontaneously diabetic rats

1. Previous studies have shown that endothelium-dependent relaxation in the aorta of spontaneously diabetic bio bred rats (BB) is impaired. 2. We have investigated noradrenaline (NA) contractility, endothelium-dependent acetylcholine (ACh) and bradykinin (BK) relaxation, and endothelium-independent sodium nitroprusside (SNP) relaxation in mesenteric resistance arteries of recent onset BB rats and established insulin treated BB rats, compared to their age-matched non diabetic controls. 3. There was no significant difference in the maximum contractile response or sensitivity to noradrenaline in either of the diabetic groups compared to their age-matched controls. 4. Incubation with the nitric oxide synthetase inhibitor NG-nitro-L-arginine (L-NOARG) resulted in a significant increase in maximum contractile response to noradrenaline in the recent onset age-matched control group (P < 0.05). Analysis of the whole dose-response curve (using ANOVA for repeated measures with paired t test) showed a significant left-ward shift following the addition of L-NOARG (P < 0.001). A similar but less marked shift (P < 0.01) was evident in vessels from recent onset diabetics. An overall shift in both sensitivity and maximum response was also evident in the age-matched non diabetic controls of the insulin-treated group (P < 0.05). However, by contrast, there was no significant change in sensitivity in the insulin-treated diabetic rats. 5. ACh-induced endothelium-dependent relaxation was significantly impaired in the recent onset diabetic rats compared to their age-matched controls (47 +/- 11% versus 92 +/- 2%, P < 0.05, n = 6), and in the insulin treated diabetic rats (34 +/- 5% versus 75 +/- 6%, P < 0.05, n = 6). The relaxation responses to BK also were significantly impaired in the diabetic rats compared to their age-matched controls (recent onset: 20 +/- 3% versus 72 +/- 7%, P < 0.05, n = 6; insulin treated: 12 +/- 9% versus 68 +/- 7%, P < 0.05, n = 7). 6. Incubation with either the nitric oxide synthetase substrate, U-arginine, or the free radical scavenging enzyme superoxide dismutase (150 mu ml-1) failed to improve the attenuated response of acetylcholine-induced relaxation in the diabetic vessels. 7. Endothelium-dependent relaxation mediated by ACh and BK was significantly attenuated in both the diabetic and control vessels after incubation with L-NOARG. 8. Pretreatment with a cyclo-oxygenase inhibitor, indomethacin, significantly enhanced the relaxation to ACh in both the recent onset and insulin treated diabetic rats (42 +/- 10%, n = 7 versus 64 +/- 7%, n = 7, P < 0.05, and 40 +/- 5%, n = 7 versus 65 +/- 9%, n = 6, P < 0.05). 9. Following endothelium removal, there was a marked impairment in endothelium-dependent relaxation responses to ACh and BK in both the diabetic and control vessels. 10. Incubation with the thromboxane A2 receptor antagonist SQ29548, did not significantly improve the ACh endothelium-dependent relaxation response in the diabetic vessels. 11. Endothelium-independent relaxation to sodium nitroprusside was significantly impaired in the first group of diabetic vessels studied; however, subsequent studies showed no impairment of the sodium nitroprusside response in the diabetic vessels. 12. In conclusion, the ability of the endothelium to regulate vascular contractility is reduced in recent onset diabetic vessels, and significantly impaired in established insulin treated diabetics. Relaxation to the endothelium-dependent vasodilators ACh and BK was impaired in both the recent onset and the established insulin treated diabetics, and the ACh response was significantly improved following pretreatment with indomethacin, suggesting a role for a cyclo-oxygenase-derived vasoconstrictor. Preliminary studies with a thromboxane A2, receptor antagonist, SQ29548 did not significantly improve the impaired relaxation to ACh, indicating that the vasoconstrictor prostanoid is not thromboxane A2.     

Respiratory effects of intravenous midazolam

Thirty-four healthy, young-adult patients receiving intravenous midazolam for third-molar surgery had their respiratory parameters measured by respiratory inductive plethysmography. Tidal volume and minute volume showed significant changes during the initial 5-10 minutes of sedation, the changes being maximal during the first 5 minutes from the completion of injection of midazolam. The measurement of phase angle, an indicator of respiratory asynchrony, showed no significant change from normal, although a few patients showed some asynchrony of breathing, suggesting some amount of respiratory obstruction. A few patients showed a short period of apnoea and a small fall in the oxygen saturation. None of these changes caused any clinical concerns. It is suggested that the absence of stimulation after injection of midazolam, particularly in the initial few minutes, may contribute to the potential onset of respiratory problems.