O78 Membrane depolarization in motor nerves of critical ill patients is related to insulin resistance

Abstract

Objectives Critical illness polyneuropathy/myopathy (CIP/CIM) features depolarization of the resting membrane potential and reduced membrane excitability in motor nerve and muscle.1–3 Since CIP/CIM shows an increased Insulin resistance,4 and Insulin is one agonist of the Na-K-pump controlling resting membrane potential,5 we like to prove if Insulin resistance is correlated with motor nerve resting membrane polarisation in critical ill patients. Methods ICU patients were classified as ICU-control and CIM/CIP patients related to electrophysiological exam. Electrophysiological excitability studies recording the recovery-of-excitability at baseline and during Insulin clamp condition (euglycemic-hyperinsulinemic clamp) were conducted, to prove resting membrane polarization at baseline and after high dosage of Insulin (steady state).6 Insulin sensitivity Index (ISI), as marker of Insulin resistance, was calculated during steady state condition. Results Two ICU-control and six CIM/CIP patients were enrolled. The resting membrane polarization during steady state condition was significantly correlated to ISI (R2 = 0.858; p = 0.001), where pronounced Insulin resistance correlates with pronounced membrane depolarization. Membrane repolarization after Insulin stimulation of Na-K-pump fails in CIM/CIP patients with severe Insulin resistance, compared to ICU control patients with a less severe Insulin resistance. Discussion Resting membrane depolarization in critically ill patients is correlated to Insulin resistance, where membrane repolarization induced by Insulin seems to fail in CIM/CIP patients showing the most severe Insulin resistance,4 but not in ICU-control patients. Conclusions Insulin resistance in critical ill patients, besides affecting glucose metabolism, also influences motor nerve dysfunction. Significance We prove the link between muscle dysfunction and disturbed Glucose metabolism in CIM/CIP patients.