Singing-induced hypotension: a complication of a high spinal cord lesion.

Cardiovascular autonomic control was studied in a patient with an incomplete high spinal cord lesion who presented with the symptoms of severe dizziness during debating and singing but not during orthostasis. The marked falls in blood pressure upon singing and orthostasis (45 degrees passive head-up tilt) were comparable in magnitude but different in time course. The fall in blood pressure upon graded Valsalva manoeuvres, however, was comparable to singing in magnitude and time course; similarly, 20 and 30 mmHg strain evoked complaints of dizziness. These differential circulatory responses upon orthostasis versus singing and Valsalva in tetraplegic patients have not been described before. We suggest that rapidly developing hypotension such as that induced by a moderate Valsalva strain represents the instantaneous mechanical effects of a raised intrathoracic pressure with lack of abdominal compression on the cardiovascular system when baroreflex vasomotor modulation is disrupted.