Hypoglycemia

General anesthesia deletes the warning system - The neurogenic signs are what a patient would otherwise report. Asleep, they are gone, and the first thing you see is neuroglycopenic: unexplained confusion, a seizure, or a patient who will not wake up.

Check the glucose, don't reason about it - Point-of-care glucose is the answer to delayed emergence, an unexplained intraoperative seizure, or new confusion in PACU. Whipple's triad confirms it - symptoms, a measured glucose under 55 mg/dL drawn at the time of symptoms, and relief with correction.

Treatment ladder - Severe or unconscious: IV dextrose followed by a glucose infusion. Awake and able to swallow: a rapidly absorbed carbohydrate such as fruit juice. No IV access: glucagon 1 mg IM, or intranasal with the newer formulations. Follow with a complex carbohydrate once awake and recheck glucose frequently - one correction is not the end of it.

Which agents actually cause it - Insulin, sulfonylureas, and meglitinides. Metformin very rarely does. Also worth scanning the med list for pentamidine, disopyramide, quinolones, non-selective beta-blockers, regular salicylates, and the diuretic plus ACE inhibitor plus beta-blocker combination when a patient bottoms out for no obvious reason.

Hypoglycemia unawareness - Repeated episodes blunt the autonomic response so neuroglycopenic symptoms arrive before any warning. Type 1 diabetics on intensive insulin therapy are about three times as likely to have hypoglycemia as type 2 diabetics.

Prolonged fasting is the setup - Glycogenolysis holds glucose for only 8 to 12 hours before stores are depleted and gluconeogenesis takes over. Alcohol use, malnourishment, liver disease, sepsis, and renal failure remove that reserve, so a long NPO window in those patients is a real risk, not a theoretical one.

Pseudohypoglycemia - Chronically hyperglycemic patients become symptomatic at glucose levels inside the normal range because the set point has moved. The symptoms are real even when the number is not low.

Post-bariatric patients - Roux-en-Y gastric bypass produces postprandial hyperinsulinemic hypoglycemia, and repeated episodes in this group commonly erode the autonomic warning symptoms.

Insulinoma workup - Draw insulin, proinsulin, and C-peptide during the episode. Low C-peptide with high insulin means exogenous insulin; high C-peptide with high insulin means a secretagogue or an endogenous tumor. Localize with abdominal CT or MRI. An insulinoma should also prompt a MEN workup - know about the other endocrine tumors before you plan the anesthetic.

The cost of missing it - Prolonged severe hypoglycemia causes cardiac arrhythmias, cardiac arrest, multiorgan failure, and permanent neurologic injury.

Hypoglycemia is a plasma glucose below 70 mg/dL, though symptoms often do not appear until 55 mg/dL or lower. The brain makes almost no glucose of its own and depends on a continuous arterial supply, so the defenses are layered: endogenous insulin secretion falls first, then pancreatic alpha cells release glucagon, then the adrenal medulla releases epinephrine, with cortisol and growth hormone recruited in prolonged episodes.

Symptoms split into neurogenic - tremor, palpitations, anxiety, hunger, diaphoresis, paresthesias - and neuroglycopenic - behavioral change, confusion, fatigue, seizure, coma. Drugs are the most common cause: insulin, sulfonylureas, and meglitinides. Non-drug causes include alcohol, which blocks gluconeogenesis once glycogen is spent, plus sepsis, end-stage liver disease, renal failure, adrenal insufficiency, insulinoma, and IGF-2-secreting non-islet cell tumors.