Minimal Change Disease (MCD)

Edematous but underfilled - MCD is the classic "underfill" nephrotic patient. Anasarca, effusions, and ascites on the outside; intravascular volume depletion inside. Induction doses that look reasonable for the body habitus will drop the pressure hard. Titrate and have a pressor drawn up.

Sort the volume status before you treat the edema - Nephrotic fluid status swings between underfill and overfill, and the therapy differs. Weight trend, pulse, blood pressure, and the response to diuretics are what separate them. Get this straight before giving or removing volume.

Preop labs - Serum albumin (nephrotic syndrome runs below 3 g/dL), urine protein (a 3+ dipstick is 300 mg/dL or more, correlating with 3 g or more per 24 hours), and creatinine. Adults with MCD present with hematuria, acute kidney injury, and hypertension more often than children do.

Airway and ventilation - Look for periorbital, scrotal, labial, and lower extremity edema on exam, and for pleural or pericardial effusion and ascites. Effusions and a tense abdomen cut functional residual capacity and change your ventilation plan.

Steroid burden - Treatment is high-dose prednisone: adults 1 mg/kg/day up to 80 mg/day for 4-16 weeks with a 6-month taper, children 60 mg/m2 or 2 mg/kg/day up to 60 mg/day for 4-6 weeks then a taper. Most of the morbidity in MCD comes from the drugs, not the disease — steroid toxicity, systemic infection, bone loss, and cataracts.

Infection risk - Immunoglobulin losses leave children prone to sepsis, pneumonia, and peritonitis, and steroids and steroid-sparing agents such as rituximab add to it. Strict aseptic technique on lines and invasive procedures, and treat bacterial infection early.

Thromboembolism - Nephrotic syndrome is a thrombotic state; a DVT or pulmonary embolus can be the first sign of the disease. Ambulation beats bed rest for clot risk, so plan analgesia and a positioning strategy that gets them moving early.

Diuretics on board - Furosemide, spironolactone, and metolazone are commonly running. Satisfactory diuresis is hard to achieve with an albumin below 1.5 g/dL, so albumin is sometimes given with them. Diuretic use drives volume depletion — track weight, pulse, and blood pressure rather than the edema.

NSAIDs - A recent NSAID start is a recognized precipitant of nephrotic syndrome. Pick a different multimodal analgesic for postoperative pain.

Sodium and fluid restriction - Patients with active disease are on low-sodium, fluid-restricted regimens. Carrying that through the perioperative period keeps you from re-expanding the interstitium with the fluid you give.

Minimal change disease (MCD) is the most common cause of idiopathic nephrotic syndrome in children — 70% to 90% of nephrotic children over age one, versus 10% to 15% of nephrotic adults. Light microscopy shows minimal to no change and immunofluorescence is negative; electron microscopy reveals effacement of podocyte foot processes. Loss of the size- and charge-selective glomerular filtration barrier dumps albumin into the urine.

Hypoalbuminemia drops plasma oncotic pressure and fluid sequesters into the interstitium, so the patient is edematous on the outside while intravascularly depleted — the "underfilled" phenotype typical of MCD. That is the perioperative problem: a swollen, sometimes anasarcic patient who is actually volume depleted, may be oliguric and in acute kidney injury, and is carrying immunoglobulin losses plus weeks to months of high-dose steroid.