Acute Kidney Injury

Passing through London I picked up my August copy of Clinical Medicine (Journal of the Royal College of Physicians). In it there is an article about acute kidney injury (AKI) by Alison Prescott et al [Donal O’Donoghue the national clinical director for kidney care is the senior author]. The article is titled “Acute Kidney Injury: top ten tips”. The article cites the National Confidential Enquiry into Patient Outcomes and Death(NCEPOD)’s report “Adding insult to injury”. One key finding in the report was that 30% of patients had predictable and avoidable AKI. Worse, only 50% of patients had predictable and avoidable AKI.

Prescott et al discuss the 10 tips for prevention, identification, and management of AKI. In the article most of the recommendations are about improving administrative aspects of AKI – better coding, changing hospital policies, better responsiveness to laboratory values etc. Still, the article does raise the question: what are the tips for managing AKI? So, here is my take:

1. Recognize and manage the risk of AKI

Recognizing patients at highest risk of AKI is probably the most important tip. I recently attended a lecture by Barry Brenner at the Brigham. He discussed his two hit hypothesis for kidney injury. Kidney injury occurs most often when the patient has a hit on top of existing kidney injury or disease. An example of this is contrast nephrotoxicity – most common among patients with pre-existing kidney impairment and diabetes mellitus. Recognizing the patient at risk and minimizing the risk by either avoiding the 2^nd hit or by minimizing it’s impact (for example, using hydration, N-acetyl cysteine, etc.) is key.

2. Early recognition and early referral

In my opinion the definition of AKI still remains too complex. A simple definition would be >0.5 mg/dL increase in serum creatinine in a clinical context commensurate with the possibility of acute kidney injury.  If one recognizes AKI early then there is tremendous value in early referral to a nephrologist. The nephrologists value early in the injury process is to ameliorate some of the enablers of kidney injury – for example by making sure that the patient is volume replete, recommend adjustment of medication doses, and institute treatment (for example, use corticosteroids for a drug-induced interstitial nephritis).

3. Try to determine if the AKI is reversible

Many forms of AKI can be reversed by immediate action. For example, AKI from obstruction can ne reversed if an ultrasound of the kidney is done and hydronephrosis demonstrated. Likewise, if one considers the possibility of abdominal compartment syndrome (pressures > 25 mmHg), emergency surgical decompression can be pursued. AKI from an allergic interstitial nephritis or from an acute glomerulonephritis is potentially reversible.  Determining the cause might require a kidney biopsy.

4. Treat the complications of AKI

Studies demonstrate a high mortality associated with hospital acquired AKI. It’s unlikely the AKI itself is the major cause of this increased mortality. Rather, complications of AKI such as electrolyte abnormalities or fluid abnormalities or very high levels of drugs or their metabolites make an important contribution. Frequent monitoring of potassium levels and avoiding excessive volume expansion are important. Worse, only 50% of patients had predictable and avoidable AKI.

5. Don’t let go

Here I agree with the Prescott paper. There is consensus that in some patients renal injury results in residual renal damage. Making sure that one documents AKI in the discharge note. Following these patients in the clinic and instituting nephroprotective strategies makes sense. I don’t see every patient in follow-up, but only those in whom kidney function has not retured to baseline - this is a common sense recommendation but it’s surprising how often it's not done.