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Raynaud's phenomenon (RP) is seen in 5-10% of the population and generally follows an indolent course. In some cases it may be the first sign of a connective tissue disease (CTD). In patients referred to the clinician because of their RP, obviously the more severe cases, CTD, in particular scleroderma, will develop, however, in a considerable percentage. Risk factors for the evolution of CTD are (a) the severity of RP at onset, (b) a positive test for antinuclear antibodies, (c) nailfold capillary abnormalities, and (d) older age at onset. Patients with RP who are at risk for the development of CTD should be followed in order to diagnose (and treat) a developing CTD as early as possible.
The measurement of the vascular outflow resistance during reconstructive vascular operations was applied since 1989 on 45 subjects with reliable results. This measurement is an aid for decision of additional treatment increasing the outflow, like a jump- or sequential bypass or a pharmacological therapy. The principle of measurement is based on the injection of a known volume of saline in the vessel and the integration of the intravascular pressure during this injection. In the prototype used, the pressure integration was performed by means of a modified analog/digital conversion method, hereby the results could be achieved directly as numerical values. Further an automatic, microcomputer based implementation of the outflow resistance measurement, showed remarkable improvements of accuracy in laboratory tests.
A calf ergometer is presented that can be used for both static and dynamic exercise in supine, sitting or standing position. During exercise each foot is fixed firmly to a pedal. During dynamic exercise the foot pedal can rotate through an angle which can be varied from 5 to 30 degrees. External work is performed only during plantar flexion. The amount of work is determined by the moment imposed to the pedal by a constant force spring and can be calculated from electrical signals that represent the angle of rotation and the moment exerted to the pedal. During static exercise the foot pedal is secured so that it cannot move.
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Peripheral outflow resistance (OR) was assessed intraoperatively in 75 infrainguinal bypass procedures to the below knee popliteal artery (20) or a single crural artery (55). OR measurement was done after completion of the distal anastomosis. For that purpose, the graft was perfused with Ringer solution at constant flow rates of 100 and 150 ml/min using a roller pump. During infusion, arterial pressure was recorded. In this way distal (DOR) and total (TOR) outflow resistance in E/S anastomoses was calculated before and after vasodilatation with papaverine. DOR at a flow rate of 100 ml/min was found to be most discriminant as a predictor of early graft thrombosis: 1. In the limbs with a thrombosed graft at 30 days OR was significantly higher than in the limbs with a patent graft (1828 +/- 418 vs. 1472 +/- 221 mPRU; p less than 0.01, Mann-Whitney U-Test). 2. The cut-off value of 1700 mPRU, which was determined by ROC curves, was 100% sensitive and 81% specific in the group of femoro-crural grafts to predict early graft failure. A better discrimination by the application of papaverine could not be achieved. We concluded from our results that OR might be an important factor in early graft thrombosis. But still there is more experience required to select patients for primary amputation or adjunctive procedures (av-fistula, sequential graft) on the basis of the present available data.
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Rheological tests were performed in four rigorously defined groups of patients with Raynaud's phenomenon: primary family-related (n = 21), primary family-unrelated (n = 30), 'possible scleroderma' (n = 26), and scleroderma (n = 19). Whole blood and plasma viscosity, and hematocrit were significantly higher in the 'possible scleroderma' group. We conclude that the contribution of central rheological abnormalities in the pathogenesis of Raynaud's phenomenon is limited.
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In fourteen patients with primary Raynaud's phenomenon we performed a double-blind, controlled study, comparing single doses of 12.5 and 25 mg of the potassium channel opener pinacidil with placebo and the active control nifedipine in randomised order. The main response criterium was the area under the curve (AUC) of the photoelectric plethysmography (PEP) during cooling and rewarming, performed 2-3 hours after administration of the study medication. Single doses of 12.5 and 25 mg pinacidil were shown not to be superior to placebo in respect of the AUC of PEP. Nifedipine, on the contrary, was significantly better than placebo. We conclude that no efficacy can be expected from the potassium channel opener pinacidil in the treatment of primary Raynaud's phenomenon. The efficacy of nifedipine cannot be explained from central rheological effects, as total blood viscosity was the same after pinacidil, nifedipine and placebo.
Between February 1989 and June 1991 the peripheral outflow resistance was measured at 45 patients during infragenual bypass surgery. In order to find out whether there is a correlation between successful bypass grafting and measured outflow resistance, all patients were controlled regularly. There was a significant difference in mean resistance between those grafts remaining patent and those that failed. 8 out of 11 bypasses, that failed up to one month after operation, had measured peripheral resistance higher than 1.1 mmHg x min/ml. 12 out of 15 bypass grafts remained patent for more than one month and had an outflow resistance less than 0.55 mmHg x min/ml. There is no definite correlation between a measured outflow resistance from 0.55 to 1.1 mmHg x min/ml because of the low number of patients in this group. The purpose of resistance measurement during peripheral vascular surgery was to determine a final value for a decision, if additional surgical or non surgical treatment for a better runoff is necessary. In our study this value is 1.1 mmHg x min/ml. Additional treatments are the peripheral AV-fistula and a jump- or sequential-graft. Another possibility is the intra- and postoperative application of Prostaglandin, which is in an experimental study in our clinic.
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Vascular run off has an important influence on patency rates of infrapopliteal bypasses especially when prosthetic grafts are used. Construction of a distal arteriovenous fistula can improve volume and velocity of graft flow. 39 patients, 14 of them diabetic, had femoro-crural PTFE-bypasses. A distal arteriovenous fistula in common ostium technique was established in 20 cases. The patency rate (early occlusions) was improved, especially diabetic patients seemed to profit by lowering the peripheral outflow resistance, which was measured intraoperatively. The influence of arteriovenous fistulas of different calibre on bypass flow and perfusion was analysed in a circulation model.
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