Renal, Endocrine, Metabolic, and Gastrointestinal Critical Care
Renal
Acute kidney injury is staged by creatinine rise and urine output; creatinine lags behind injury, so oliguria and fluid overload often lead. Treat hyperkalemia with calcium for cardiac membrane stabilization, insulin with dextrose, nebulized albuterol, and removal by dialysis when refractory. Severe fluid overload, acidosis, and uremia are dialysis indications.
Endocrine and metabolic
In diabetic ketoacidosis, begin with isotonic fluid, then insulin at 0.05-0.1 units/kg per hour. If potassium is below 3.3 mmol/L, give potassium before insulin. Corrected sodium = measured sodium + 1.6 x (glucose - 100)/100. Cerebral edema presents with headache, bradycardia, hypertension, or declining consciousness and is treated with hyperosmolar therapy and reduced fluid rate. Bicarbonate is reserved for severe acidosis. Adrenal crisis requires stress-dose hydrocortisone; thyroid storm requires beta-blockade and antithyroid therapy. Inborn errors of metabolism often present with hyperammonemia and acidosis.
Gastrointestinal
Consider necrotizing enterocolitis in preterm infants, hepatic encephalopathy with elevated ammonia, and pancreatitis with epigastric pain and elevated lipase. Stress ulcer prophylaxis is not universal.
Traps
Do not correct chronic hyponatremia rapidly because of osmotic demyelination risk. Distinguish SIADH from cerebral salt wasting using volume status. Do not start insulin in DKA before confirming potassium is safe. Rapid fluid boluses in DKA increase cerebral edema risk.
Worked rule
A glucose of 600 mg/dL with sodium 130 mmol/L gives corrected sodium of 130 + 8 = 138 mmol/L; falling corrected sodium during therapy suggests developing cerebral edema.