First Things First (assess & treat for the following)

• Definition: Acute decline in renal filtering function. Marked by decreased urine production, accumulation of normally cleared toxins or markers (e.g., K+, acids, and creatinine). Creatine (CRT) and BUN are serum markers of failed renal clearance; they take time to accumulate. Check CRT clearance.
• A more accurate term for acute renal failure (ARF) is acute kidney injury, which suggests a spectrum of renal injury and dysfunction. The RIFLE Criteria (Risk, Injury, Failure, Loss, End stage) classify ARF based on elevations of creatinine, or duration of oligo- or anuria. Progressive dysfunction is associated with increased mortality.
• In ARF urine output is usually oligo- or anuric (anuric suggests overwhelming damage to both kidneys both prerenal or intrinsic renal, or complete urinary obstruction), but it can rarely be polyuric (recovery phase ATN, interstitial nephritis, postobstructive renal failure). See “History and Physical” section.
• Immediate management
  • Define severity of renal dysfunction and attempt to classify renal failure into Prerenal (PreR), intrinsic renal (IR), or obstructive/postrenal (PostR).
  • Strict input/output charting
  • Blood tests: basic metabolic profile (K, HCO3, CRT, BUN)
  • Collect urine sample for analysis, urine electrolyte panel before interventions (e.g., diuretics)
  • Identify & aggressively treat potentially reversible causes of RF. Place bladder catheter to rule out or relieve lower urinary tract obstruction and facilitate hourly urinary output checks.
  • Assess & correct volume status & electrolyte abnormalities. This is what kills. Check EKG if hyperkalemia. See “Specific Treatment” section.
  • Avoid further renal insult such as hypovolemia, hypotension, and nephrotoxins.