The effect of thermal baths on oedema of the lower limbs might be explained by physical mechanisms of hydrostatic pressure resulting from the use of a deep bath and a centripetal underwater jet, by which the veins and lymph ducts are drained every day. The purpose of this experiment is to demonstrate the existence of hormonal mechanisms which would account for the diuretic effect of thermal baths. One of the effects observed with hydrotherapy is the physiological diuresis that follows each bath, this diuresis would appear to depend at least in part on the atrial natriuretic factor (ANF). The criteria by which assessment can be made essentially biological: ANF level and its biological effects on blood and urine; aldosterone level; plasma renin activity (PRA); creatinine clearance; hematocrit; proteinemia; and blood and urine electrolyte balance. The inclusion criteria are: subjects selected at random and willing cooperate. The criteria for exclusion are disease states which modify ANF kinesis: congestive heart failure, cardiac rhythm disorders, decompensated cirrhosis of liver, obesity, treatment antihypertensive drugs.

METHODS:

Thirty patients were put through the same experimental sequence, as follows: emptying of the bladder and ingestion of 200 cc of water; seated rest fort 30 mn, after which (to): blood sample; urine sample; ingestion of 200 cc of water; deep bath for 20 mn, i.e. the basic hydro treatment in phlebology at Barbotan. The deep bath is specific to Barbotan and the patient is subjected to maximum immersion in water at a mesothermal temperature of 34.5 degrees C, followed by (t1): blood and urine sample; ingestion of 200 cc of water; supine rest for 90 mn, followed by (t2): blood and urine sample.

RESULTS:

Data from twenty-eight patients were usable. In this protocol, we use variance analysis with repeated measurements and a 95% confidence limit. The mean value of the principal parameters studies are set out in the following table; these value are accompanied by the degree of significance of the modification at (t1) and (t2). Our experimentation with thirty patients showed that the big thermal bath at Barbotan produces a highly significant increase in ANF secretion, resulting in the diuresis observed after the use of the bath. The antagonist effect of AFN on the renin--angiotensin-aldosterone system was corroborated: we found decreased aldosterone, PRA and creatinine clearance, and increased diuresis and natriuresis. The renal and cardiovascular effects observed after extended immersion in the Barbotan bath (increased diuresis, tachycardia and hypotension, transitory venous vasoplegia and ephemeral vasodilatation of the surface capillaries) are the result of increased ANF secretion. [formula: see text] Supine rest immediately after the bath is essential. This sustains the enhanced ANF and thus reinforces its renal effects, while reducing adverse cardiovascular effects such as the orthostatic hypotension and venous vasoplegia that are normally observed after use of the bath. Moreover, by reducing venular and lymphatic pressure, clinostatism facilitate interstitial to intravascular tissue fluid exchanges and thus helps to drain oedema from the legs. It is striking to note that the hydrotherapy prescribed at Barbotan les Thermes has always included the three most potent factors for ANF release: deep immersion in the big bath, immediate supine rest, and walking. Physiological diuresis has thus been induced empirically as an essential part of the treatment of lower limb phlebopathies.