[Pathophysiology and treatment of acute hypotension occurring during hemodialysis (author's transl)].

We have recorded, by invasive techniques, the hemodynamic and biological parameters during a conventional haemodialysis session (HD), in patients exhibiting acute (Gr. I, n : 8) or progressive arterial pressure decrease (gr II, n : 6). The HD conditions are similar in both series. The sequence of events are as follows: 1. Ultrafiltration induces hypovolemia which is not counterbalanced because there is a delay in fluid transfer from extravascular to vascular space and a shift of fluid from vascular to extravascular compartment since the vascular space is hypotonic. 2. These mechanisms produce a decrease of filling pressures in all patients (gr. I and II) but, in the patients of gr. I, a sudden drop of cardiac output, cardiac index, aggravated by an absence of increase or even a decrease of vascular resistances and of the heart rate. 3. The injection of hypertonic NaCl induces a rapid rise of plasma osmolality producing a fluid transfer from extravascular to vascular compartment with simultaneously a correction of filling pressures, cardiac index and arterial pressure. 4. A difference in preload between both groups could explain in part the difference of their hemodynamic comportment but not why some patients of group II exhibit a good left ventricular work index on contrary to gr. I patients.