Perioperative and Critical Care Nephrology
Core concepts
Perioperative AKI arises from hypovolemia, hypotension, sepsis, nephrotoxins, and contrast. Recognize sepsis-associated AKI (inflammation, microcirculatory dysfunction), cardiorenal syndrome, and abdominal compartment syndrome (bladder pressure).
Fluid management: balanced crystalloids preferred over normal saline in large volumes (less hyperchloremic acidosis); avoid starch. Vasopressors for mean arterial pressure targets; diuretics do not improve outcomes in AKI but manage volume. CRRT for unstable patients. Contrast-associated AKI prevention: volume expansion with isotonic fluid, minimize contrast volume.
Electrolyte emergencies in ICU: hyperkalemia, hyponatremia, and acidosis. Drug dosing in CRRT differs from intermittent HD.
Traps
Normal saline in large volumes causes hyperchloremic metabolic acidosis. Do not use dopamine for renal protection. Creatinine lags-oliguria may be the first sign. Abdominal compartment syndrome requires decompression, not just diuretics. Check bladder pressure in distended abdomen with rising creatinine.
Rule of thumb
In the ICU, if AKI plus oliguria plus hypotension, optimize volume and perfusion first; then consider CRRT if unstable or refractory.
Worked example
Postoperative patient with distended abdomen, rising creatinine, and oliguria; bladder pressure 28 mmHg. Diagnosis: abdominal compartment syndrome; management is decompression and supportive care.