Clinical meaning
Hypoglycemia and diabetic ketoacidosis (DKA) represent opposite ends of the glucose spectrum in diabetes management, both are medical emergencies, and the nurse must be able to rapidly distinguish between them because the treatments are exactly opposite - giving insulin to a hypoglycaemic patient or glucose to a DKA patient would be life-threatening.
Hypoglycemia is defined as a blood glucose level below 4.0 mmol/L (72 mg/dL), though symptoms may begin at slightly higher levels in patients with chronically elevated glucose. It occurs when glucose utilisation or disposal exceeds glucose availability. In diabetic patients, the most common causes are: excess insulin (dosing error, injection into exercising muscle which accelerates absorption), sulfonylurea medications, insufficient carbohydrate intake (skipped or delayed meals), increased physical activity without appropriate carbohydrate compensation, and alcohol intake (alcohol inhibits hepatic gluconeogenesis).
The pathophysiology of hypoglycemia involves glucose deprivation of the brain and the counter-regulatory hormone response. The brain depends almost exclusively on glucose as its metabolic fuel and has minimal glycogen stores - brain cells begin to malfunction within minutes of glucose deprivation. As blood glucose falls, the body activates counter-regulatory hormones: glucagon (stimulates hepatic glycogenolysis and gluconeogenesis), epinephrine/adrenaline (stimulates glycogenolysis and causes the classic adrenergic symptoms - tremor, diaphoresis, tachycardia, anxiety, pallor, hunger), cortisol, and growth hormone. The symptoms of hypoglycemia are divided into adrenergic/autonomic symptoms (tremor, sweating, tachycardia, anxiety, hunger - caused by epinephrine release) and neuroglycopenic symptoms (confusion, difficulty speaking, blurred vision, behavioural changes, seizures, loss of consciousness - caused by brain glucose deprivation).