[Cigarette smoking increases the risk of developing cataract].
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Cataract↗
Biomedical subjects
M Belkin
Publications and source records attributed to M Belkin.
Evidence for the existence of low-energy laser bioeffects on the nervous system.
The reported effects of low-energy laser irradiation on the nervous system are manifested in alterations in cellular and extracellular biochemical constituents and reactions, as well as in changes in cell division rates. These bioeffects were observed in both in vivo and in vitro experiments. Other observed phenomena relate to the function of the nervous system and consist mainly of induced alteration in electrical conduction, stimulation thresholds, and behavioral effects. Clinical aspects of low-energy laser bioeffects relate mainly to pain mitigation and postponement of the posttraumatic neural degeneration processes. Many of the reported observations were obtained by experiments apparently conducted according to less than rigorous scientific criteria, and some could not be duplicated. On the whole, however, there is little doubt that low-energy laser irradiation exerts some effects on the nervous system under specific conditions of irradiation and tissue exposure via a mechanism which is probably photochemical in nature.
Action Potentials↗
Inflammation after axonal injury has conflicting consequences for recovery of function: rescue of spared axons is impaired but regeneration is supported.
Neural injury leads to tissue damage beyond that caused by the initial lesion, mainly as a result of a chain of autodestructive events triggered by the trauma. These events apparently include the activation of immune-derived cells and their products, as treatment with anti-inflammatory agents, such as corticosteroids, limits the damage and thus improves recovery. On the other hand, immune-derived substances, such as cytokines, are thought to play an important role in post-traumatic axonal regeneration. Thus, the need to reduce inflammation to limit the spread of damage appears to be in conflict with the need to permit inflammation to promote regeneration. Comprehension and resolution of this apparent conflict may lead to the development of treatment protocols aimed at rescuing axons spared by the initial injury, without hampering the potential regeneration of directly and indirectly injured axons. In this study, carried out on rats with crushed optic nerves, daily intraperitoneal injections of dexamethasone commencing prior to the injury significantly attenuated the injury-induced decrease in electrophysiological activity and reduced the area of tissue damage. On the other hand, dexamethasone treatment reduced the permissiveness of the injured nerves to neural adhesion and regrowth in vitro. This latter phenomenon was also observed in injured peripheral nerves. Results are discussed with respect to the possible establishment of an appropriate protocol for corticosteroid treatment of nerve injuries aimed at promoting neuronal rescue without compromising neuronal regeneration.
Adrenal Cortex Hormones↗
A prospective study of the determinants of vein graft flow velocity: implications for graft surveillance.
PURPOSE: Serial monitoring of vein graft peak systolic flow velocity (PSFV) has been endorsed as a technique for vein graft surveillance with low values (< 45 cm/sec) considered a marker for impending graft failure. Optimal application of this method requires an understanding of the factors affecting PSFV in normal grafts. A prospective evaluation of 46 consecutive elective infrainguinal vein grafts (6 popliteal/29 tibial/11 pedal) was undertaken to assess the major determinants of PSFV. METHODS: Factors recorded for each patient included vein graft diameter (VGD), measured outflow resistance (MOR), conduit length, outflow level (popliteal/tibial/pedal), inflow level (femoral/popliteal), systolic blood pressure, cardiac ejection fraction, the presence of a patent plantar arch, and Society for Vascular Surgery/International Society for Cardiovascular Surgery resistance scoring. MOR was measured by occluding graft inflow and infusing saline solution through a proximal graft cannula at 60 cc/min while simultaneously recording the pressure at the distal anastomosis via a separate cannula. MOR was calculated by dividing the resultant pressure by the infusion rate. MORs were expressed in resistance units and were measured before and after the infusion of papaverine (MOR(PAP). PSFVs and VGDs were measured 4 to 6 cm from the distal anastomosis 3 weeks after surgery with duplex scanning (60 degree angle with midstream sample volume). RESULTS: PSFVs ranged from 22 to 148 cm/sec and averaged 83.4 +/- 4.8 cm/sec. Pedal bypass grafts had significantly lower PSFVs (64 +/- 10 vs 89.5 +/- 5 cm/sec, p = 0.02) and significantly higher MOR(PAP)s (0.86 +/- 0.15 vs 0.51 +/- 0.05 resistance units, p = 0.05) than bypasses to the popliteal/tibial level. When subjected to univariate analysis the factors correlating with PSFV were MOR (r = -0.59, p = 0.0001), MOR(PAP) (r = -0.69, p = 0.0001) VGD (r = -0.31, p = 0.06), the Society for Vascular Surgery/International Society for Cardiovascular Surgery score (r = -0.35, p = 0.04), inflow level (r = -0.47, p = 0.002), and outflow level (r = -0.35, p = 0.03). When subjected to multiple regression analysis, only MOR(PAP) (r2 = 0.51, p = 0.001) and VGD (r2 = 0.14, p = 0.001) contributed significantly to the overall model (r2 = 0.65, p = 0.0001) with MOR(PAP)) eliminating the effect of the other variables. The multiple regression model predicts PSFV as follows: PSFV = 176 + VGD(mm) (-11.7) + MOR(PAP)) (-63.4). CONCLUSIONS: Clinically successful and hemodynamically normal vein grafts have widely variable, yet predictable flow characteristics that are influenced primarily by outflow resistance and VGD. This wide variability suggests that no single lower threshold value for PSFV is universally applicable indentifying all grafts at risk for failure. Detection of focal areas of flow acceleration within the graft may be more accurate in identifying grafts at risk for failure.
Aftercare↗
An assessment of the positive predictive value and cost-effectiveness of dipyridamole myocardial scintigraphy in patients undergoing vascular surgery.
PURPOSE: The approach to cardiac risk stratification of patients undergoing vascular surgery continues to be controversial. The success of algorithms that use clinical risk factors to determine cardiac risk have been inconsistent. Dipyridamole myocardial scintigraphy (DMS) has been accepted as a sensitive, noninvasive approach to risk stratification with excellent negative predictive value. Low positive predictive value (PPV) of abnormal DMS scans is a shortcoming that contributes to extensive preoperative cardiac evaluation and intervention with associated morbidity, mortality, and cost in most patients who undergo uncomplicated vascular procedures, regardless of DMS results. METHODS: Over 6 years, 237 patients underwent DMS before surgical management of infrarenal aortic aneurysm, aortoiliac, or infrainguinal occlusive disease. The value of multiple clinical factors and DMS were assessed retrospectively for the prediction of perioperative myocardial infarction (MI), heart-related death, or preoperative selection for myocardial revascularization. Only congestive heart failure and two or more reversible defects on DMS were statistically significant on logistic regression analysis. RESULTS: The PPV of DMS was 19% for all patients with reversible defects, 12% for patients with one reversible defect, and 36.7% for patients with two or more reversible defects. The rates of cardiac death and MI were 1.3% and 5.9%, respectively. Perioperative echocardiography revealed unchanged postinfarction ejection fraction in most patients who experienced MI. Cost-effectiveness of DMS screening was evaluated. CONCLUSIONS: The costs per MI and cardiac death averted suggest a decline in cost-effectiveness of screening with DMS over time, assuming improving cardioprotective strategies of patient care. Clinical risk factors were minimally useful in the prediction of perioperative MI, heart-related death, or need for myocardial revascularization. The PPV of DMS is low, and the majority of MIs may be clinically insignificant. The cost-effectiveness of cardiac screening with DMS may not be justifiable given current trends of health care reform.
Aged↗
Are peroneal artery bypass grafts hemodynamically inferior to other tibial artery bypass grafts?
PURPOSE: Many authors have reported excellent long-term patency rates of peroneal artery bypasses. It has been suggested, however, that the hemodynamic result of the peroneal bypass is inferior to that of other infrapopliteal artery bypasses, making it suboptimal in patients with forefoot ischemic tissue loss. A retrospective review of 118 recent infrainguinal vein grafts (36 peroneal, 27 anterior tibial, 35 posterior tibial, 20 popliteal) was undertaken to assess and compare the hemodynamic results for each group. METHODS: We reviewed the hemodynamic results of 36 peroneal bypass grafts assessed by preoperative and postoperative ankle-brachial index and transmetatarsal pulse volume recording, duplex scan-derived distal graft peak systolic flow velocity, and intraoperatively measured outflow resistance. These results were compared with a concurrent series of anterior tibial, posterior tibial, and popliteal artery bypass grafts. All but one of the infrapopliteal bypass grafts were performed for limb salvage, and 65% of patients had ischemic ulcerations or gangrene. RESULTS: There was no difference in postoperative ankle-brachial index, postoperative transmetatarsal pulse volume recording, peak systolic flow velocity, or measured outflow resistance among the four different outflow groups. All patients with peroneal bypass grafts had healed wounds within a mean follow-up period of 17 months. There were no hemodynamic failures. CONCLUSION: Peroneal artery bypass grafts achieved hemodynamic results equivalent to anterior tibial, posterior tibial, and popliteal artery bypass grafts.
Analysis of Variance↗
Correlation of venous noninvasive tests with the Society for Vascular Surgery/International Society for Cardiovascular Surgery clinical classification of chronic venous insufficiency.
PURPOSE: Noninvasive tests for the evaluation of chronic venous insufficiency (CVI) include quantitative photoplethysmography (QPG), air plethysmography, and duplex ultrasonography measurement of valve closure time (VCT). These tests have been shown to accurately identify the presence of CVI, define the disease, and locate the involved segments. However, the correlation of noninvasive assessment of CVI with the clinical severity (Society for Vascular Surgery/International Society for Cardiovascular Surgery staging) has not been addressed critically. METHOD: During an 18-month period, 74 limbs were prospectively evaluated with clinical examination, air plethysmography, QPG and duplex ultrasonography. RESULTS: We studied 52 patients with a mean age of 46 years. There were 14 stage 0 limbs, 14 stage 1, 15 stage 2, and 31 stage 3. We found significant differences (p < 0.05) between normal limbs and those with CVI only by VCT and QPG. There were also marked trends toward worsening mean values for reflux (VCT, QPG, and venous filling index) and venous hypertension (residual volume fraction) between stages 0 to 1, and 1 to 2; however, there was a large degree of overlap between all groups. No test discriminated stage 2 from 3. Assessment of calf muscle pump function with ejection fraction showed no difference between any groups. CONCLUSION: The Society for Vascular Surgery/International Society for Cardiovascular Surgery criteria for CVI staging distinguishes ulcerated limbs (stage 3) from those with nonulcerating skin changes (hyperpigmentation, brawny edema, and subcutaneous fibrosis) (stage 2). However, we were not able to distinguish these groups by available noninvasive methods. This may imply that these tests are not accurate enough or that the progression from lipodermatosclerosis to frank ulceration is not accounted for by large-vessel hemodynamic changes, but rather by microcirculatory alterations.
Adult↗
Abdominal aortic aneurysms.
The management of abdominal aortic aneurysms has undergone tremendous evolution during the past three decades, resulting in significant advances in our ability to diagnose and safety treat patients with aneurysms. Over the past several years, most research interest has been focused on the etiology of aneurysmal disease, new imaging techniques, cardiac risk stratification, and new approaches for treatment. This article reviews the current approach to diagnosing and treating patients with abdominal aortic aneurysms as well as the results which may be anticipated. In stark contrast to the treatment of nonruptured aortic aneurysms, little progress has been made in the management of ruptured aneurysms, which remain highly lethal. Early identification, prompt evaluation, and surgical repair remain the most important elements in preventing mortality.
Aortic Aneurysm, Abdominal↗
Reoperative approaches for failed infrainguinal vein grafts.
The management of patients with thrombosed vein grafts remains a formidable challenge for all vascular surgeons. Management strategies will vary based on a variety of criteria including the patients' overall condition and symptoms, the interval and etiology of graft failure, and the pathological anatomy and availability of autogenous vein. A combination of resourcefulness and adherence to established vascular surgical principles and techniques will facilitate revascularization in the great majority of patients with failed grafts.
Combined Modality Therapy↗
[Sunglasses for children as public health measure].
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Adolescent↗
Dose and temporal parameters in delaying injured optic nerve degeneration by low-energy laser irradiation.
Low-energy laser irradiation has been reported to postpone the degenerative processes in crushed optic nerves of rats, which are part of the nonregenerable mammalian central nervous system. In the present study, we evaluated the optimal irradiation parameters for this purpose. Optic nerves of 141 rats were subjected to crush injury and then irradiated through the eye, starting at different points of time before or after the injury, for different durations and periods, using various intensities of either helium-neon laser or noncoherent infrared light (904 nm). The effect was evaluated by measurements of the compound action potentials of the nerve segments between the site of injury and the optic chiasm. The compound action potential amplitude of the crushed nonirradiated nerves, as measured 2 weeks after the injury, was found to be 0.51 +/- 0.30 mV, in contrast to 3.10 +/- 1.03 mV measured in 232 normal nerves. Irradiation with a 10.5 mW helium-neon laser for 2 and 3 min once a day for 14 consecutive days resulted in maximal preservation of action potentials (1.78 +/- 0.72 and 1.95 +/- 0.71 mV, respectively). Irradiations beginning immediately prior to the injury were as effective as irradiations beginning soon after it. Irradiations for longer than 3 min or twice a day aggravated the damage. Noncoherent infrared light was ineffective or adversely affected the injured nerves. Our experiments suggest that optimal delay of posttraumatic optic nerve degeneration in rats is attainable with 10.5 mW helium-neon laser irradiations for 2 or 3 min once a day for 14 consecutive days.
Action Potentials↗
Superiority of balloon occlusion arteriography to reactive hyperemic arteriography in visualization of distal lower limb vessels.
Balloon occlusion arteriography was performed in 38 lower limbs; reactive hyperemic arteriography was also performed in 16 of these limbs. To assess the safety and utility of this technique the balloon occlusion arteriograms of all 38 patients were reviewed retrospectively by a vascular surgeon and vascular radiologist who were unaware of the patient's identity and ultimate treatment. After the arteriograms were reviewed and the outflow vessels identified, a decision was made regarding operability and optimal recipient vessel for distal bypass. Twenty-two of the 38 patients underwent balloon occlusion arteriography only, and 21/22 (95.5%) of these patients only had studies deemed adequate for surgical planning. Twelve of the 16 (75%) patients underwent both reactive hyperemic arteriography and balloon occlusion arteriography; potential distal outflow vessels not seen on reactive hyperemic arteriograms were observed on balloon occlusion arteriograms. In only 4/16 (25%) patients the balloon occlusion arteriograms did not yield additional information. No complications were associated with this technique. Approximately 8.5 g of iodine per run is used for balloon occlusion arteriography compared with approximately 37 g of iodine per run for reactive hyperemic arteriography. Balloon occlusion arteriography is a safe and accurate adjunctive technique that can be used when identification of lower limb vessels is critical.
Adolescent↗
Transesophageal echocardiography for hemodynamic management of thoracoabdominal aneurysm repair.
Maintenance of cardiovascular stability during thoracoabdominal aneurysm repair remains a formidable challenge. Transesophageal echocardiography (TEE) has been shown to be an excellent method for detecting myocardial ischemia and assessing left ventricular volume. We examined the utility of TEE in a group of 17 patients from an overall series of 33 patients who underwent thoracoabdominal aneurysm resection between 1988 and 1992. The mortality rate was 9%, whereas the incidences of myocardial infarction and paraplegia were 13% and 6%, respectively. Intraoperative management was significantly altered by TEE data in nine patients. Two patients were noted to have mitral valve insufficiency, and one had transient ischemia-induced regional wall abnormalities. In six patients, Swan-Ganz-derived filling data failed to identify severe hemodynamic alterations that were noted on TEE. Five patients were hypovolemic and hyperdynamic, whereas one was in florid congestive heart failure. Further investigation is warranted to prospectively validate this technique.
Adult↗
Long-term follow up of accidental parafoveal laser burns.
The findings after 12 years of follow-up evaluation of 2 patients who sustained accidental parafoveal and juxtafoveal Nd:YAG laser injuries are reported. In both cases, the fovea was not destroyed by the initial insult and early scar formation. Both cases demonstrated, after more than a decade, minimal visual deficit without significant late complications. In spite of early decrease in visual performance, the long-term prognosis for Q-switched Nd:YAG laser retinal lesions in which the fovea was not directly involved in the injury or its repair mechanisms is relatively benign.
Adult↗
Internal sclerostomy using laser ablation of dyed sclera in glaucoma patients: a pilot study.
Twelve eyes of 12 patients with refractory glaucoma were treated with internal sclerostomy using laser ablation of dyed sclera. The technique involves iontophoretic impregnation of the sclera at the limbal region with 1% methylene blue and subsequent delivery of a pulsed dye laser beam to the stained area through a goniolens. The red wavelength of 664 nm generated by the laser is maximally absorbed by the stained sclera and creates a through and through sclerostomy. Successful complete sclerostomy was achieved in seven eyes (58.3%) but there was some reduction of intraocular pressure (IOP) in all cases. Mean prelaser IOP (of all 12 eyes) was 36.6 mm Hg and 1 hour after therapy it was reduced to 20.0 mm Hg. At the end of the follow-up period (mean 16 months) the mean IOP was 23.7 mm Hg; five eyes (41%) maintained their IOP below 22 mm Hg, and the average number of medications per eye came down from 3.25 to 2.25 per eye. Transient corneal burns with Descemet's membrane folds adjacent to the laser impact zone were detected in eight eyes (67%). No major complications like IOP spike, hyphaema, iridodialysis, or retinal detachment have been detected. Clear cornea and dark blue scleral staining are essential for the mechanical success of this procedure. Gonioscopic laser internal sclerostomy of methylene blue dyed sclera is technically feasible and the preliminary results of IOP control in refractory glaucoma are promising. Modifications of the iontophoresis process and laser parameters are currently under investigation in order to improve these results.
Adult↗
The hemodynamics of vein graft stenosis.
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Algorithms↗