Heat-washout - an objective method for diagnosing neuropathy and atherosclerosis in diabetic patients

The heat-washout method is an objective method that measures cutaneous blood flow rate (BFR) in ml (100 g. min)(-1), previously found useful for measuring toe BFR in non-diabetic patients with claudication.

The method is used for evaluating the presence of a veno-arteriolar reflex (VAR) in the forefoot and signs of atherosclerosis in the first toe in type 2 diabetics.

Nine type 2 diabetics for +10 years, peripheral neuropathy, median age 62, and 9 healthy subjects without diabetes, median age 52 were examined for the presence of a VAR in the forefoot. A VAR was present when BFR decreased 25% or more with the foot 50 cm below heart level. Examinations for atherosclerosis were made in the pulp of the first toe. An increase in BFR of 50% or more with the foot 50 cm below heart level indicated the presence of atherosclerosis.

The VAR was significantly attenuated in type 2 diabetics with neuropathy compared to controls, (P<0·01). Only one patient with known neuropathy and diabetes showed a reflex compared to eight out of nine controls (P<0·01). The VAR was correlated to the vibration perception threshold measured with biothesiometry (r = -0·661, P = 0·0003). Two patients with type 2 diabetes and neuropathy without clinical sign of peripheral artery disease (PAD) had an abnormal response similar to that seen in subjects with intermittent claudication.

The heat-washout method seems useful as and objective method for evaluating as well the presence of a VAR as atherosclerosis in type 2 diabetics.