A 65-year-old woman was hospitalized in the intensive care unit in a coma. Has been suffering from type II diabetes for 10 years. The last 2 weeks were observed pronounced polyuria, polydipsia. Serum glucose - 30 mmol/l, arterial blood pH - 7.3. Blood plasma osmolarity is 350 mOsm / l. The patient was diagnosed with diabetic hyperosmolar coma. What is the main pathogenetic mechanism of coma?