Abstract

PIP: According to a report by Jens Jordan and colleagues, tap water has substantial pressor effects. They reported that 480 ml of Nashville tap water raised systolic blood pressure in seated, healthy, middle-aged people by 11 mmHg and in patients with orthostatic hypotension due to chronic autonomic failure by more than 30 mmHg. The pressor effects began a few minutes after the water had been drunk, peaked at about 20 minutes, and remained raised for a further 25 minutes before returning to baseline values by 80 minutes. However, these findings were questioned by Senard and colleagues, who gave 500 ml of Toulouse tap water to patients with Parkinson's disease and autonomic failure but did not observe a rise in blood pressure. The author comments that both reports did not provide the composition of the tap water, which raises the possibility that the pressor effects might have been due to chemicals or electrolytes in the water. Thus, the precise mechanisms causing the pressor response to tap water still remain to be determined. Even so, there are various implications arising from the observations especially in the elderly and in patients with autonomic failure.