The influence of food on postural hypotension in three groups with chronic autonomic failure--clinical and therapeutic implications.

The effect of a balanced liquid meal on supine and postural blood pressure (BP) responses was investigated in three groups of patients with chronic autonomic failure; 10 with associated neurological impairment (multiple system atrophy (MSA), Shy-Drager syndrome) and seven without (of which five had pure autonomic failure (PAF); and two had a deficiency of the enzyme dopamine beta hydroxylase, DBH-deficiency). All had marked postural hypotension. Subjects with normal autonomic function were also studied. In MSA and PAF food lowered supine BP substantially, with a more rapid and greater fall in PAF. After food, the levels of BP reached were considerably lower because of the reduced supine BP and many had to be returned to the horizontal position earlier than before. Ingestion of a similar volume of water alone had no effect in MSA or PAF. In DBH deficiency, food had variable but minimal effects on BP while supine and during head-up tilt. In subjects with normal autonomic function food did not affect BP. The BP responses to food thus varied in the three groups with chronic autonomic failure. The influence of food on both supine and postural BP therefore should be considered in the clinical and laboratory assessment of autonomic dysfunction and in relation to therapeutic approaches, designed to alleviate postural hypotension.