Endovascular laser–tissue interactions and biological responses in relation to endovenous laser therapy

Endovenous laser treatment (ELT) has evolved into a frequently employed modality for the treatment of leg varicose veins. Due to the very high complete response rates, minimal complications and side effects, and the possibility to monitor therapeutic outcome noninvasively by duplex ultrasound, a considerable amount of reports have been published on clinical and translational studies, whereas disproportionally few studies have been performed to elucidate the molecular and cellular basis for post-ELT vessel obliteration. Consequently, this review addresses the putative molecular and cellular mechanisms responsible for varicose vein obliteration following laser irradiation in the context of endovenous laser–tissue interactions. First, the histological profile of laser-treated varicose veins is summarized, and an account is given of the temporal and spatial dynamics of cells involved in inflammation and remodeling in the heat-affected vein segment. Inasmuch as thrombotic occlusion of the venous lumen blocks circulatory access to the affected vessel segment and thermal damage in the vascular wall causes most cells to die, the majority of cells involved in inflammation and remodeling have to be recruited. Second, the (possible) biochemical triggers for the chemotactic attraction of immune cells and fibroblasts are identified, comprising (1) thermal coagula, (2) thrombi, (3) dead and dying cells in the vein wall, and (4) thermally denatured extracellular matrix proteins in the vein wall. The molecular biology underlying the chemotactic signaling and subsequent obliterative remodeling is elucidated. Finally, the relative contribution of every biochemical trigger to obliterative remodeling is addressed.     

Comparison of laser fiber degradation and perioperative outcomes following holmium laser enucleation of the prostate using 550 and 1000 µm fiber diameters

Objective

To compare perioperative and post-operative outcomes for holmium laser enucleation of the prostate (HoLEP) between cases performed with a 550 µm or 1000 µm fiber.

Methods

We retrospectively reviewed the most recent 50 patients undergoing HoLEP with a 550 µm fiber and the most recent 50 patients with a 1000 µm fiber. The length of exposed laser fiber after stripping was measured pre- and post-enucleation, with the difference being our primary outcome of degradation length. We compared operative and clinical characteristics between patients undergoing HoLEP using 550 and 1000 µm laser fibers.

Results

All 100 patients met inclusion for analysis. Overall, the 550 µm fiber experienced more degradation than the 1000 µm fiber (2.9 vs 1.9 cm, respectively; p?=?0.01). The 1000 µm fiber utilized significantly less energy compared to the 500 µm fiber (81 vs 109 kJ, respectively; p?<?0.01). In addition, operations performed with the 1000 versus the 500 µm fiber were overall shorter (79 vs 88 min, respectively; p?=?0.03), although both groups had statistically similar times for enucleation (45 vs 51 min, respectively; p?=?0.42) and morcellation (10 vs 9 min, respectively; p?=?0.50). These findings occurred in the context of statistically similar prostate weight enucleated and bladder stones treated between groups. Post-operatively patients experienced no difference in blood loss or dysuria.

Conclusions

Use of the 1000 µm fiber resulted in significantly less fiber degradation, energy requirement, and total operative time during HoLEP, in spite of similar prostate size and time required for enucleation and morcellation. Different fiber diameters do not appear to affect post-operative blood loss or dysuria.

     

KTP laser and nitinol alloy stents: Are they compatible?

BACKGROUND/OBJECTIVE: Nitinol alloy stents are in frequent use in recanalizing malignant airway stenoses. Potassium titanyl phosphate (KTP) is one of the lasers of choice in removal of obstructing airway lesions. There is a paucity of research regarding the safety of these advances working together. STUDY DESIGN/MATERIALS AND METHODS: In vitro study involving direct contact application of KTP laser with nitinol alloy stents under microscope guidance in varying gaseous environments. RESULTS: Stent damage can occur once power settings exceed one watt. Complete stent destruction occurs regardless of gaseous environment at a mere three watts of power. CONCLUSIONS: Our results suggest that KTP laser is unsafe to use in the presence of a nitinol alloy stent, regardless of the gaseous environment.     

Bilateral loss of light reflex and accommodation following 360° peripheral retinal laser therapy

We report a case of bilateral loss of pupillary light reflex and accommodation following 360° peripheral retinal laser therapy. A 24 years old male underwent prophylactic laser barrage for peripheral retinal lattice degenerations. Soon after the procedure, he developed bilateral loss of pupillary light reflex and accommodation. The patient faced difficulty while doing near work. On instillation of 0.125% pilocarpine, both pupils demonstrated the phenomenon of denervation supersensitivity. Damage to the short ciliary nerves was the most likely mechanism responsible for this adverse outcome.     

Does low-level laser therapy affect the survival of patients with head and neck cancer?

Lasers in Medical Science - Low-level laser therapy (LLLT) is used in patients with head and neck cancer (HNC) for treatment-related mucositis. There is conflicting evidence as to whether LLLT...     

Correction to: Q‑S laser micro‑drilling and multipass full‑beam Q‑S laser for tattoo removal — a case series

Lasers in Medical Science -     

Measurement of tear resistance after manual capsulorhexis and femtosecond laser–assisted capsulotomy of crystalline lenses

Lasers in Medical Science - In this study, the tear resistance of porcine lens capsules after continuous curvilinear capsulorhexis (CCC) and femtosecond (fs)-laser-assisted capsulotomy for cataract...     

Microleakage and scanning electron microscopy evaluation of all-in-one self-etch adhesives and their respective nanocomposites prepared by erbium:yttrium–aluminum–garnet laser and bur

The aim of this study was to evaluate the microleakage of all-in-one self-etch adhesives and their respective nanocomposites in class V cavities prepared by erbium:yttrium–aluminum–garnet (Er:YAG) laser and bur. Class V cavities were prepared on both buccal and lingual surfaces of 72 premolars by Er:YAG laser or bur and divided into six groups (n = 24). The occlusal margins were enamel and the cervical margins were cementum. The groups were as follows: group 1 Er:YAG laser preparation (E) + Xeno V (X) + CeramX (C); group 2 bur preparation (B) + X + C; group 3 E + AdheSE One (A) + Tetric EvoCeram (T); group 4 B + A + T; group 5 E + Clearfil S3 Bond (CSB) + Clearfil Majesty Esthetic (CME); group 6 B + CSB + CME. All teeth were stored in distilled water at 37°C for 24 h, then thermocycled 500 times (5–55°C). Ten teeth from each group were chosen for the microleakage investigation and two teeth for the scanning electron microscopy (SEM) evaluation. The teeth that were prepared for the microleakage test were immersed in 0.5% basic fuchsin dye for 24 h. After immersion, the teeth were sectioned and observed under a stereomicroscope for dye penetration. Data were analyzed by Kruskal–Wallis and Mann–Whitney U tests (P < 0.05). Bur-prepared cavities presented less microleakage in all groups for enamel (P < 0.05); however, in cervical margins, there were no differences between laser-prepared and bur-prepared cavities in the Xeno V + CeramX and AdheSE One + Tetric EvoCeram groups (P > 0.05). SEM observations of restorative material–dentin interfaces seemed to correspond with those of the microleakage test. Microleakage at the cervical interfaces was greater than that at the occlusal interfaces. Er:YAG laser-prepared class V cavities yielded more microleakage in occlusal margins with all-in-one self-etch adhesives and the respective manufacturer’s nanocomposites.     

Should open excisions and sutured incisions be treated differently? A review and meta-analysis of animal wound models following low-level laser therapy

Although low-level laser therapy (LLLT) was discovered already in the 1960s of the twentieth century, it took almost 40 years to be widely used in clinical dermatology/surgery. It has been demonstrated that LLLT is able to increase collagen production/wound stiffness and/or improve wound contraction. In this review, we investigated whether open and sutured wounds should be treated with different LLLT parameters. A PubMed search was performed to identify controlled studies with LLLT applied to wounded animals (sutured incisions—tensile strength measurement and open excisions—area measurement). Final score random effects meta-analyses were conducted. Nineteen studies were included. The overall result of the tensile strength analysis (eight studies) was significantly in favor of LLLT (SMD?=?1.06, 95% CI 0.66–1.46), and better results were seen with 30–79 mW/cm² infrared laser (SMD?=?1.44, 95% CI 0.67–2.21) and 139–281 mW/cm² red laser (SMD?=?1.52, 95% CI 0.54–2.49). The overall result of the wound contraction analysis (11 studies) was significantly in favor of LLLT (SMD?=?0.99, 95% CI 0.38–1.59), and the best results were seen with 53–300 mW/cm² infrared laser (SMD?=?1.18, 95% CI 0.41–1.94) and 25–90 mW/cm² red laser (SMD?=?1.6, 95% CI 0.27–2.93). Whereas 1–15 mW/cm² red laser had a moderately positive effect on sutured wounds, 2–4 mW/cm² red laser did not accelerate healing of open wounds. LLLT appears effective in the treatment of sutured and open wounds. Statistical heterogeneity indicates that the tensile strength development of sutured wounds is more dependent on laser power density compared to the contraction rate of open wounds.     

Low-level laser therapy can reduce lipopolysaccharide-induced contractile force dysfunction and TNF-α levels in rat diaphragm muscle

Our objective was to investigate if low-level laser therapy (LLLT) could improve respiratory function and inhibit tumor necrosis factor (TNF-α) release into the diaphragm muscle of rats after an intravenous injection of lipopolysaccharide (LPS) (5 mg/kg). We randomly divided Wistar rats in a control group without LPS injection, and LPS groups receiving either (a) no therapy, (b) four sessions in 24 h with diode Ga–AsI–Al laser of 650 nm and a total dose of 5.2 J/cm², or (c) an intravenous injection (1.25 mg/kg) of the TNF-α inhibitor chlorpromazine (CPZ). LPS injection reduced maximal force by electrical stimulation of diaphragm muscle from 24.15 ± 0.87 N in controls, but the addition of LLLT partly inhibited this reduction (LPS only: 15.01 ± 1.1 N vs LPS + LLLT: 18.84 ± 0.73 N, P < 0.05). In addition, this dose of LLLT and CPZ significantly (P < 0.05 and P < 0.01, respectively) reduced TNF-α concentrations in diaphragm muscle when compared to the untreated control group.     

Effect of Nd∶YAG laser on experimental disc degeneration part I. Biochemical and radiographical analysis

Summary Intervertebral disc herniation is an important health problem from both the social and economic aspect. It is often accompanied by a decrease in the content of water and proteoglycan (PG). The present study was undertaken to elucidate the effect of neodymium-yttrium-aluminum-garnet (NdYAG) laser on degenerated disc tissue.In this study a ventral disc herniation model in guinea pigs was performed to study the effects of NdYAG laser on degenerated disc with low water and PG content. Effect of NdYAG laser on degenerated cervical disc tissue is examined from the aspects of biochemistry and radiology. In the acute period water, PG, and collagen content decreased due to the ablative effect of NdYAG laser on disc tissue. When changes in the degenerated disc in the post-laser chronic period were compared with degenerated disc findings, statistically significant changes could not be be found.From the results of this study, there is no question that the NdYAG laser offers many potential benefits, it remains to be proven whether or not this is of real benefit in the treatment of patients with degenerated disc disease.This study was presented in part at the 8th National Congress of the Turkish Neurosurgical Society, Marmaris, May 8–12, 1994.     

High-power helium–neon laser irradiation inhibits the growth of traumatic scars in vitro and in vivo

This study explored the inhibitory effect of the high-power helium–neon (He–Ne) laser on the growth of scars post trauma. For the in vitro study, human wound fibroblasts were exposed to the high-power He–Ne laser for 30 min, once per day with different power densities (10, 50, 100, and 150 mW/cm²). After 3 days of repeated irradiation with the He–Ne laser, fibroblast proliferation and collagen synthesis were evaluated. For in vivo evaluation, a wounded animal model of hypertrophic scar formation was established. At postoperative day 21, the high-power He–Ne laser irradiation (output power 120 mW, 6 mm in diameter, 30 min each session, every other day) was performed on 20 scars. At postoperative day 35, the hydroxyproline content, apoptosis rate, PCNA protein expression and FADD mRNA level were assessed. The in vitro study showed that the irradiation group that received the power densities of 100 and 150 mW/cm² showed decreases in the cell proliferation index, increases in the percentage of cells in the G0/G1 phase, and decreases in collagen synthesis and type I procollagen gene expression. In the in vivo animal studies, regions exposed to He–Ne irradiation showed a significant decrease in scar thickness as well as decreases in hydroxyproline levels and PCNA protein expression. Results from the in vitro and in vivo studies suggest that repeated irradiation with a He–Ne laser at certain power densities inhibits fibroblast proliferation and collagen synthesis, thereby inhibits the growth of hypertrophic scars.     

Investigation of endovenous laser ablation of varicose veins in vitro using 1.885-μm laser radiation

This paper presents the results of endovenous laser ablation (EVLA) of varicose veins in vitro using radiation of a solid-state laser based on the crystal LiYF₄:Tm, with a wavelength of 1.885 μm and power output of around 3 W. An experimental series with saline solution and red blood cell (RBC) suspension in the venous lumen was performed to identify the impact of a heated carbonized layer precipitated on the fiber end face versus the efficiency of EVLA. Results of these experiments confirmed that the presence of a heated carbonized layer on the fiber end face increases the efficiency of EVLA.     

Morphology of resin–dentin interfaces after Er,Cr:YSGG laser and acid etching preparation and application of different bonding systems

The goal of this study was to show the modifications in the ultrastructure of the dentin surface morphology following different surface treatments. The stability of the adhesive compound with dentin after laser preparation compared with conventional preparation using different bonding agents was evaluated. An Er,Cr:YSGG laser and 36% phosphoric acid in combination with various bonding systems were used. A total of 100 caries-free human third molars were used in this study. Immediately after surgical removal teeth were cut using a band saw and 1-mm thick dentin slices were created starting at a distance of 4 mm from the cusp plane to ensure complete removal of the enamel. The discs were polished with silicon carbide paper into rectangular shapes to a size of 6 × 4 mm (±0,2 mm).The discs as well as the remaining teeth stumps were stored in 0.9% NaCl at room temperature. The specimens were divided into three main groups (group I laser group, group II etch group, group III laser and etch group) and each group was subdivided into three subgroups which were allocated to the different bonding systems (subgroup A Excite, subgroup B Scotchbond, subgroup C Syntac). Each disc and the corresponding tooth stump were treated in the same way. After preparation the bonding composite material was applied according to the manufacturers' guidelines in a hollow tube of 2 mm diameter to the disc as well as to the corresponding tooth stump. Shear bond strength testing and environmental scanning electron microscopy were used to assess the morphology and stability of the resin-dentin interface. The self-etching bonding system showed the highest and the most constant shear values in all three main groups, thus enabling etching with phosphoric acid after laser preparation to be avoided. Thus we conclude that laser preparation creates a surface texture that allows prediction of the quality of the restoration without the risk of negative influences during the following treatment steps. This can easily and repeatedly be achieved.