Management of Acute Kidney Injury

Objectives

1. Clinical diagnosis of acute kidney injury.
2. Identifying the aetiology of acute kidney injury.
3. Learn the complications of acute kidney injury.
4. Management of complications of acute kidney injury.
5. Basics of renal replacement therapy in acute kidney injury.


1. Clinical diagnosis of acute kidney injury.

Usual manifestations of acute kidney injury is oliguria (Reduced urine output). With the progression of renal impairment, patients develop various complications such as acidosis/ uremia which give rise to other manifestations.

There are various criterions to diagnose AKI, you don't have to memorise those.

• Increase in S.Cr by >0.3 mg/dl (>26.5 umol/l) within 48 hours; or
• Increase in S.Cr to >1.5 times baseline, which is known or presumed to have occurred within the prior 7 days; or 
• Urine volume < 0.5 ml/kg/h for 6 hours.

2. Identifying the aetiology of acute kidney injury.

You must be already knowing that acute kidney injury can be classified as pre-renal, renal and post-renal.

Pre-renal AKI

• This is when the GFR falls due to reduced renal perfusion.
• Renal perfusion is reduced due to
• Dehydration - Vomiting/ Diarrhea
• Hypotension - Sepsis, MI

Renal/ Intrinsic Renal AKI

• This is due to diseases involving either the glomerulus or the renal interstitium.
• Examples include
• Glomerulonephritis - Post-streptococcal glomerulonephritis, Nephrotic syndrome, Vasculitis
• Interstitial nephritis - Many drugs/ toxins can cause that. (As in our example where the interstitial nephritis developed secondary to NSAID ingestion.)

Post renal AKI

• Due to obstruction

So, whenever a patient presents with AKI, you should attempt to identify the category as the treatment differs entirely.

• Pre-renal - Give fluids, Bring the blood pressure up
• Renal - Diagnose and treat the disease eg: Steroids
• Post renal - Relieve the obstruction immediately.

In the acute setting apart from physical examination a bed side US scan will be extremely helpful.

• Small kidneys - Possibility of underlying CKD
• To exclude obstruction.

The next most important investigation would be an ABG.

3. Learn the complications of acute kidney injury.

Of the complications of AKI, you have to at least know the following.

• Metabolic acidosis
• Hyperkalemia
• Fluid overload
• Uremia

4. Management of complications of acute kidney injury.

• Metabolic acidosis
• Persistent acidosis causes tissue toxicity including myocardial suppression.
• IV NaHCO3 may be required initially, and subsequent continuation of oral NaHCO3 may be necessary.
• If not responding to initial management, renal replacement therapy is indicated.
  
• Hyperkalemia


• ECG is essential.
• IV Ca gluconate should be given immediately to stabilize the myocardium.
• Medical management options include
• Driving K into cells
• Beta agonists
• Insulin dextrose
• Excrete K via urine (If there is urine output of course)
• Excrete K via gut.
• Failing medical management is an indication for renal replacement therapy.
  
  
  
• Fluid overload
• In the setting of anuria, there is no other way to get rid of the fluid except renal replacement.
  
• Uremia
• Can give rise to various manifestations including encephalopathy.
• This also is an indication for renal replacement therapy.

5. Basics of renal replacement therapy in acute kidney injury.

• There are several options for renal replacement therapy.

1. Hemodialysis
• This is the usual choice. But for this patient should have a stable blood pressure.
2. Peritoneal dialysis
• Not very effective. But when HD is not available this is a good option.
3. Continuous renal replacement therapy (CRRT)
• Done in critically ill patients when the blood pressure is not stable.

You have a lot to read!!