Ho-YAG Laser Research Articles

Anaesthesia for daycare laser tonsillectomy using the Hayek oscillator and total intravenous anaesthesia

Twenty-four patients undergoing laser tonsillectomy as a daycare procedure have been anaesthetized by means of total intravenous anaesthesia (TIVA) and ventilated using the Hayek oscillator. There have been no patients readmitted to hospital and at follow up there have been no complaints related to surgery or anaesthesia, although pain levels appear to show the customary peak on or around the fourth day. One patient was retained in hospital overnight for observation. Both the KTP and Ho-Yag lasers have been used. Numbers were too small to give a significant view as to which laser appeared to give the best surgical results.

Nonlinear optical behavior of ocular tissue during laser irradiation

A pump (cw Ho-YAG laser) and probe (He-Ne laser) system was used to study the dynamics of the optical behavior of ocular tissue during laser heating. The nonlinear optical behavior of porcine corneal and vitreous-humor tissue was characterized in vitro by means of measurements of the radial profile of a He-Ne laser beam transmitted through the tissue. Temperature gradients in the tissue created by the absorption of pump radiation caused the probe beam to diverge. For constant laser power, the rate of divergence was made dependent on the spot size of the pump beam. The profile of the transmitted probe beam returned to its original magnitude and shape after the tissue was permitted to cool. This reversible change in optical behavior was attributed to the formation of a negative lens owing to thermally induced local gradients in the refractive index of the tissue.

Excimer and holmium yttrium aluminum garnet laser coronary angioplasty

Recently access to the coronary arteries became available to laser angioplasty because of a new technique utilizes a pulsed laser source and multifiber, “over-the-wire” guided catheters. The aim of this study was to evaluate the early and long-term results and the side effects of coronary angioplasty with an excimer or a Ho-YAG laser. Forty consecutive patients were treated with the Ho-YAG laser (group I) and 46 consecutive patients were treated with the excimer laser (group II). The primary laser angioplasty success rate was 55% and 72% (NS) for groups I and II, respectively. This success rate was highest in saphenous vein grafts. It was similar in calcified and noncalcified lesions and in total occlusions and stenoses. It tended to be lower in long lesions than in short ones (40% vs 60%; p < 0.05 and 44% vs 78%; NS for groups I and II, respectively). Laser standalone therapy was performed in 5% of patients in group I compared with 22% in group II ( p < 0.05). Failures were due to the inability of the laser catheter tip to reach the lesion, to cross the obstruction, or to obtain a significant reduction in stenosis. They were more frequent in patients in group I than in those in group II (45% vs 28%). There were no deaths, no myocardial infarctions, and no need for emergency coronary artery bypass grafting because most patients had total occlusions or a well-protected coronary artery. Complications included acute closure in 8% of patients in group I and in 17% of patients in group II and spasm in 10% and 13% of patients in groups I and II, respectively. Dissection occurred more frequently in patients in group II than in those in group I (28% vs 7%; p < 0.04). The angiographic patency rate at 6-month follow-up was 33% and 29% for patients groups I and II, respectively. Multifiber, wire-guided catheters provide easy access to the coronary arteries. Excimer laser angioplasty is effective but induces a high rate of dissections. Technical improvements are required to ablate more tissue to possibly reduce the restenosis rate. Further studies are needed to elucidate the mechanism of side effects and to reduce the restenosis rate.

閉塞性動脈硬化症に対するレーザー治療

We carried out Laser angioplasty by the metal hot tip contact method with either the Argon laser or Nd-YAG laser and by the pulse laser direct beaming method aided by the Ho-YAG laser. The study was conducted on 69 patients with arteriosclerosis obliterans who had visited our hospital with a chief complaint of intermittent claudication.The initial success rates were 86% in Argon laser, 90% in Nd-YAG laser, and 87% in Ho-YAG laser. The long-term patency after surgery were 68% in the Argon laser, 64% in the Nd-YAG laser and 84% in the Ho-YAG laser.Laser angioplasty is an effective technique for the treatment of arteriosclerosis obliterans which can be performed within a short period of time in high risk cases such as those complicated by coronary artery lesions. Combined with bypass surgery, laser angioplasty enabled complete revascularization of the target area.We proved it possible to obtain a satisfactory initial success rate and favorable long-term patency by carefully selecting the lesion through meticulous observation with the fiberoptic angioscopy.

Laser Sclerostomy Ab Externo Using Mid Infrared Lasers

ABSTRACT An ab externo fistulizing procedure (sclerostomy) was performed in vivo in 48 rabbit eyes using a pulsed (20 µs and 200 µs) Holmium:YAG (Ho:YAG) laser (2120 nm) and a pulsed (200 µs) Erbium:YAG (ErYAG) laser (2940 nm). The laser energy was delivered via an infrared transmitting fiber in contact with the sclera, with the fiber inserted into a specially sharpened retractable cannula in order to guide it into the subconjunctival space. An additional optical fiberfiber coupling system was required for the Er-YAG laser. A patent fistula (200-micrometer diameter) with formation of a filtering bleb and marked intraocular pressure reduction was achieved in nearly all cases. Significant intraoperative or postoperative complications occurred only with the 20-microsecond Ho:YAG laser. Trauma to the conjunctiva was as minimal as in a subconjunctival injection. The Er.YAG laser created a smaller thermal damage zone at the fistula walls and required significantly less laser energy than the Ho-YAG laser.