Effect of short-term hyperglycemia per se on nociceptive and non-nociceptive thresholds

Abstract

Previous animal and human studies have indicated that nociceptive thresholds are decreased by acute hyperglycemia. The results of these studies may be challenged due to methodological problems. We therefore conducted a double-blind, controlled, cross-over study on the effect of acute hyperglycemia on nociceptive and non-nociceptive thresholds in 10 type 1 (insulin-dependent) diabetic patients (diabetes < 5 years) without symptoms or clinical signs of peripheral neuropathy. During an overnight fast, blood glucose concentration was normalized by refract insulin injections. Then, blood glucose was kept at 6 mmol/1 for 3 h by an intravenous infusion of glucose and insulin. On one study day, blood glucose was kept at 6 mmol/1 for a further 3 h and on another day, blood glucose was elevated to 12 mmol/1 during 0.5 h by additional glucose infusion and kept at that level for 2.5 h. Sensory testing was carried out twice during the initial 3 h with euglycemia and 3 times during the following period with either hyper- or euglycemia. The test procedure included determination of pain detection and pain tolerance thresholds to heat (wrists) and pressure (fingers) as well as detection thresholds to warmth/cooling (wrist), vibration (finger), and mechanical (wrist) stimulation. The changes in neither nociceptive nor non-nociceptive thresholds showed any statistically significant differences between the 2 study days. The pressure pain detection and tolerance thresholds showed, however, minor decreases at each of the test days, probably due to cutaneous sensitization caused by the repeated measurements. Compared to baseline, the pressure pain thresholds decreased significantly on the day with hyperglycemia. None of the other thresholds showed such changes. It cannot be excluded that more pronounced or longer term hyperglycemia can cause changes in sensibility. We conclude that acute hyperglycemia (12 mmol/1) does not cause major changes in nociceptive or non-nociceptive thresholds in the upper extremity, however, pressure pain thresholds was reduced significantly with hyper glycemia.