[Orthostatic hypotension in tetraplegic patients (author's transl)].

Blood pressure regulation was studied in nine patients with tetraplegia following total cervical section. Ten minutes after placing the patients in an inclined position at 30 degrees there was a marked reduction in blood pressure, an increase in heart rate, and absence of increased peripheral resistance. Valsalva's maneuver was pathological in all cases (lack of overshoot). Circulating catecholamines were measured in five cases and were low in decubitus and did not react to orthostatism. Plasma renin and aldosterone levels were at the upper limits of normal and reacted strongly to orthostatism. Marked hypersensitivity to exogenous angiotensin and noradrenaline was observed in all cases. These modifications result from section of the sympathetic efferent pathways. High plasma renin levels and their increase during orthostatism are not incompatible with these findings and probably result from intervention of renal baroreceptors. Whatever the mechanism involved, this increase in plasma renin activity could play an important role in the control of blood pressure in tetraplegic patients.