Quantitative monitoring of brain function, vital signs, and hormonal response during acute insulin-induced hypoglycemia.

Acute insulin-induced hypoglycemia provokes changes in central nervous system activity and release of counterregulatory hormones. The clinical relationship between central nervous system activity, hormone secretion, and vital signs has not to our knowledge been previously reported. We used computerized electroencephalographic (CEEG) analysis to monitor 5 nondiabetic subjects during acute insulin-induced hypoglycemia (0.75 U/kg intravenous push). Their glucose nadir was 38 +/- 6 mg/dl (mean +/- 1 SD). A three-phase pattern of change in CEEG power in response to hypoglycemia was observed: phase 1 was characterized by an increase in total CEEG power (natural log of activity = 9.1 +/- 1.3 microV2) over baseline (8.7 +/- 1.2 microV2) in the theta, delta, and beta frequency bands. This phase preceded and coincided with the glucose nadir. During phase 2, power in all frequency bands fell significantly below baseline. A nadir in CEEG power (8.0 +/- 1.6 microV2) occurred 40 to 55 minutes after insulin injection as glucose levels were rising. During phase 3 there was a return to baseline in CEEG power and frequency spectra. Heart rate increase just before phase 1; peak heart rate (91 +/- 8 beats/min) coincided with peak CEEG power and was significantly higher than basal rate (71 +/- 11, P less than 0.05). A significant increase in respiratory rate occurred during phase 1 of the CEEG and persisted through phase 2. A significant decrease in mean blood pressure (nadir = 73 +/- 6 mm Hg) below preinsulin blood pressure (81 +/- 8 mm Hg, P less than 0.05) coincided with the nadir of CEEG power in phase 2.(ABSTRACT TRUNCATED AT 250 WORDS)