Autonomic neuropathy in diabetics: comparison of cardiovascular tests, neurography, and cerebral refractory period of somatosensory evoked potentials.

Circulatory regulation tests--postural heart rate response (PHRR), Valsalva ratio, and reaction to sustained muscle exercise--, sural nerve neurography and cerebral refractory period (CRP) of median nerve evoked potentials were measured in 17 diabetic inpatients and correlated with their clinical signs of autonomic neuropathy (AN) and sensorimotor polyneuropathy (SN). Non-diabetic inpatients (without cardiovascular or related nervous disease) served as controls. The data of the diabetics and non-diabetic age- and sex-matched inpatients were significantly different for the PHHR measured by the 30:15 ratio, sural nerve conduction velocity and sural nerve refractory period, and CRP. The results correlated with the corresponding anamnestic signs. The PHRR showed abnormal values much more frequently than the sural nerve neurography or the CRP. No correlation was found between the signs of AN and those of SN or CRP. This stresses the need for a circulatory regulation test (preferably PHRR) in any diabetic when planning narcosis, as only these AN tests can reliably predict an increased cardiovascular risk in individual patients.