Acute Kidney Injury

Acute Kidney Injury

Definition

1. Increase in the serum creatinine concentration from baseline (>26 mmol/L within 48 hours)
2.  Percentage serum creatinine increase >50%
3. Oliguria of less than 0.5 mL/kg per hour for more than six hours (or <500mL/day for an adult). Normal UOP is approximately 1mL/kg/hour = 1500mL/day for a 60kg adult.

History

1. Consider these things for all patients. Remember, kidney injury in the hospital is often tied into another problem (infection, heart failure, medications).
2. decreased or no urine output, flank pain, edema, hypertension, or discolored urine? Hesistancy, frequency?
3. weakness and easy fatiguability (from anemia), anorexia, vomiting, diarrhea, mental status changes or seizures, and edema?
4. fever, cough, dysuria? Bleeding (i.e. melena, blood per rectum)?*new/changed doses in medications?
5. Does the patient have medical problems that pre-dispose to CKD (i.e. HIV, diabetes, HTN)

Exam

1. Vital signs (including orthostatics), CVA tenderness, Prostate exam

Investigations

1. Urinalysis, including microscopic analysis of centrifuged sediment to look for cells.
2. BUN and creatinine. Calculated FENa if urine electrolytes available.
3. Electrolytes if available
4. Abdominal ultrasound (rule out obstruction, assess size and echotexture of kidneys).
5. Monitor urine output (UOP). Strongly consider catheterization, especially in setting of enlarged prostate or full bladder on exam. Etiologies U/A, sediment, Indices

Etiologies

1. Prerenal*

• Hypovolemia (bleeding, diarrhea)
• Systemic vasodilation (infection)
• Decreased cardiac output (heart failure)
• Renal vasoconstriction (ACEI, NSAIDS, cirrhosis)
• Large vessel (thrombosis, embolism, dissection) 

2 Intrinsic

• Acute Tubular Necrosis (ATN)*
• Ischemia: prolonged pre-renal
• Toxins: drugs (aminoglycosides), pigments (rhabdo), protein
• Acute Interstital Nephritis
• Allerigc: sulfa, b-lactams, NSAIDs, traditional meds
• Infection: pyelonephritis
• Infiltrative: sarcoid, lymphoma, leukemia
• Renovascular (small vessel)
• Glomerulonephritis*

3 Post RENAL

• Bladder neck: BPH, prostate CA, schisto*
• Ureteral: malignancy, LAD, nephrolithiasis
• Tubular: precipitation of crystal

Treatment Options

1. Consider fluid boluses if you think the patient is dehydrated and has prerenal AKI.
2.  Goal UOP to at least 100mL/hour (but listen to lungs to assess for fluid overload)
3. If patient is bleeding, check PT/INR; consider blood transfusion.
4. Monitor for uremia (i.e. mental status changes, vomiting), and electrolyte drerangement
5. Stop all nephrotoxic agents, such as NSAIDs or aminoglycosides, and adjust meds to GFR.

Indications for urgent dialysis:

1.  Acid-base disturbance (academia)
2. Electrolyte disorder (usually hyperkalemia)
3. Intoxication (methanol, ethylene glycol, lithium, salicylates)
4. Overload of volume (pulmonary edema)
5. Uremia (pericarditis, encephalopathy, severe bleeding)

Signs and Sxs of Uremia

1 General

Nausea, anorexia, malaise, fetor uremicus, metallic taste, pruritis, uremic frost

2 Neurologic

Encephalopathy (change in mental status, decreased memory and attention), seizures, neuropathy

3 Cardiovascular

Pericarditis, HTN, volume overload, CHF, cardiomyopathy, hyperlipidemia, accelerated atherosclerosis

4 Hematologic

Anemia, bleeding (due to platelet dysfunction)

5 Metabolic

Hyperkalemia, hyperphosphatemia, acidosis, hypocalcemia, secondary hyperparathyroidism, osteodystrophy