Vascular stability and temperature monitoring in patients prone to dialysis-induced hypotension.
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Biomedical subjects
Publications and source records attributed to F Righetto.
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Among 55 uremic patients who entered our CAPD program, 7 of them showed a reduction or loss of the ultrafiltration capacity (UF) of the peritoneal membrane (PM). They have been treated with high dose of Furosemide (F) to force residual urine output. Four appeared "responders" to drug administration with a significant increase in urine volume, Na excretion and, within a week period gained their dry body weight (BW). In the remaining 3 patients drug therapy resulted ineffective, and fluid removal was obtained by hemofiltration (HF). In both groups we noted an increase in the UF capacity of PM when their dry BW was obtained either by pharmacological or technical approach. These results support the assumption that the over-hydration status of the PM plays a major role in maintaining the UF process.
Lysagth et al have reported a semplified model of spontaneous plasmapheresis by placing between an A-V shunt a conventional plasmafilter. On the basis of this experience we tried to make a further semplification of this apparatus using a single venous puncture, obtaining by gravity sufficient transmembrane pressure for plasma separation. By alternatively lowering and elevating the system, plasma is separated from the blood and packed red cells are reinfused after a new pass through the filter with FFP or plasma substitutes.
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Plasma-exchange (PE) represents an effective therapeutic approach employed in several immunological nephropathies, poisonings and various other diseases. Hemodynamic changes during intermittent flow PE were studied--using the thermodilution technique--in 8 patients (3 male and 5 female) aged between 36 and 73 years (mean 46.4). The mean values for the following parameters were measured before, during every cycle--exchanging about 300 ml of fresh frozen plasma--and at the end of the session: mean arterial pressure (MAP), heart rate (HR), cardiac index (Cl), stroke index (SI), total peripheral resistence (TPR), central venous pressure (CVP), pulmonary arterial pressure (PAP) and pulmonary capillary wedge pressure (PCWP). During the first exchange the systemic circulation showed hemodynamic changes similar that of an acute hemorrhagic condition: decrease in MAP (from 106 to 97 mmHg), Cl (from 4.27 to 3.7 L/m'/m2), SI (from 53 to 49 ml/beat/m2) and CVP (from 6.9 to 4.4 mmHg); increase in TPR (from 1230 to 1339) dynes/sec/cm-5), while HR showed only mild changes. In the following cycles all the parameters progressively returned toward the previous values. During the first cycle the pulmonary circulation showed a decrease in PAP (from 15.5 to 13 mmHg) and PCWP (from 8.9 to 6.6 mmHg). PAP also increased constantly in the following cycles reaching at the end of the session levels which were higher than the initial ones. Our data demonstrate that in PE treatment especially when is employed a low volume of fluid, has to be substituted at every cycle in order to prevent the major hemodynamic complications i.e. hypovolemic shock and heart failure.
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Vascular instability represents the most frequent intradialytic complication of uremic patients. Catecholamine impairment, changes in plasma sodium or osmolality and, more recently, temperature (T) of dialysate have been proposed to explain this phenomenon. In order to evaluate the role of T in hemodynamic stability, we studied the effect of cooling dialysate in 5 patients (3 m, 2 f), who often experienced hypotension during dialytic sessions. Dialysate T was lowered, leading to a body T decrease of 1.5 degrees C, measured by a thermistor in the pulmonary artery. Ultrafiltration was kept constant during both "warm" (W) and "cold" (C) hemodialysis (HD). Systemic and pulmonary hemodynamic parameters were studied by thermodilution technique. The evaluation was performed in the same patients during W-HD and C-HD with the same dialysate composition. MAP showed a significant reduction during the first hour under both dialysis conditions. Subsequently a further decrease of MAP was observed in W-HD, while it remained stable in C-HD. CI and SI demonstrated similar trends, whereas HR showed no major changes. TPRI appeared significantly higher during C-HD compared to W-HD, with no clinical symptoms of hypotension. Similarly pulmonary parameters resulted in a better cardiovascular stability during C-HD. Our hemodynamic study confirms the important role played by T on intradialytic vascular stability and may explain the better control observed during hemofiltration compared to standard W-HD.
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