Autonomic dysfunction and hemodynamics in vitamin B12 deficiency.

Orthostatic hypotension in patients with cobalamin (Cbl) deficiency has been reported previously in isolated cases but we are not aware of detailed systematic studies of hemodynamic and autonomic nervous system function in patients with cobalamin deficiency. We investigated hemodynamic and autonomic responses to 60 degrees passive head up tilt (HUT) in 21 patients with vitamin B12 deficiency, 21 healthy age-matched control subjects and 9 age-matched patients with diabetes mellitus (DM) and established diabetic neuropathy. To systematically assess hemodynamic and autonomic nervous system function, we performed measurements of heart rate, beat-to-beat systolic and diastolic blood pressure, stroke index, cardiac index, total peripheral resistance index, total power, low (LF) and high (HF) frequency oscillatory component of heart rate variability, LF/HF ratio and spontaneous baroreflex sensitivity. As compared to controls, we found a significant fall of systolic blood pressure during 60 consecutive beats directly after head up tilt; furthermore, a significantly blunted fall of stroke index, cardiac index and a lack of increase of total peripheral resistance index for the duration of tilt in patients with diabetes mellitus and in patients with vitamin B12 deficiency. As compared to controls, we observed an altered response of spectral indices of sympathetic activation and vagal withdrawal and an impaired modulation of baroreflex sensitivity during head up tilt suggestive of a complex modification in the neural control activities in patients with cobalamin deficiency, which was comparable to that observed in patients with diabetes mellitus and established autonomic neuropathy. The results suggest that vitamin B12 deficiency causes autonomic dysfunction with similar hemodynamic consequences and patterns of autonomic failure as seen in diabetic autonomic neuropathy. Defective sympathetic activation may be the cause for orthostatic hypotension, which is occasionally seen in patients with vitamin B12 deficiency. It is concluded that patients with orthostatic hypotension should be screened for cobalamin deficiency.