Microalbuminuria and nerve conduction velocity in type-I diabetics during conventional therapy and during continuous i.v. insulin infusion.

The objective of this study was to follow the development of microalbuminuria and nerve conduction velocity under continuous i.v. insulin therapy over a limited period of 4 months. For this purpose, 8 labile type I diabetics were selected (age 33 +/- 8 years, duration of diabetes 16 +/- 9 years) and treated conventionally with two insulin injections daily over 4 months. Afterwards, the same patients were treated with continuous i.v. insulin infusion and finally again with two injections daily over 4 months each. This procedure allowed each diabetic to serve as his own control. HbA1, microalbuminuria, nerve conduction velocity and relative refractory period of the ulnar nerve were checked at monthly intervals. During the continuous i.v. infusion over 4 months, blood sugar values were significantly lower, glucosuria had disappeared almost completely and the glycosylated hemoglobin had fallen to near normal values. The mean rate of albumin excretion was 16 +/- 5 micrograms/min at rest and 76 +/- 26 micrograms/min during exercise (normal: 3.9 +/- 0.4 and 4.8 +/- 1.2 microgram/min, respectively) and did not change significantly. Nerve conduction velocity in the ulnar nerve rose significantly under i.v. insulin therapy from 47.9 +/- 0.6 m/sec to 52 +/- 0.6 m/sec. Similarly, the relative refractory period of the same nerve fell significantly from 3.7 +/- 0.2 to 1.9 +/- 0.1 msec (i.e. to within normal range). It is concluded that functional disturbances of peripheral nerve can regress by improved blood sugar control with continuous i.v. insulin infusion over 4 months. On the other hand, incipient microangiopathy measured as microalbuminuria remains unchanged over the same period of time. If an improvement is at all possible, considerably longer periods of euglycemia are likely to be necessary.