Hyperresponsiveness to water immersion in sodium retaining cirrhotics: the role of atrial natriuretic factor.

Cirrhotics do not respond uniformly to head-out water immersion (HWI). Some cirrhotics have an exaggerated natriuresis while others are unresponsive. We studied the humoral and urinary responses to HWI in 5 cirrhotics and compared this to 5 normals on the same 20 mM sodium intake. These cirrhotics had a documented tendency to salt and water retention but had minimal or no evidence of significant ascites. Plasma levels of atrial natriuretic factor (ANF) increased during immersion in both groups. However, the rise in plasma ANF from baseline during each hour of immersion was significantly greater in the cirrhotics (p less than 0.01), than in the normal volunteers. In these cirrhotics, HWI not only corrected the pre-immersion tendency to sodium retention, but by 3 hours had produced an exaggerated natriuretic response (p less than 0.05). It is possible that the greater risk of ANF in cirrhotics is responsible for this natriuretic response. However the reason for the larger rise in cirrhotics is unclear; presumably either a greater central redistribution of plasma volume occurs in cirrhotics following immersion, or there may be greater sensitivity of the ANF release system in cirrhotics.