From the Guidelines
The patient's worsening acute kidney injury (AKI) despite normal urine sodium and osmolality with ongoing fluid administration suggests a potential intrinsic kidney injury rather than a pre-renal cause, and I recommend immediately stopping the continuous fluids and reassessing the patient's volume status. The patient likely has adequate intravascular volume given the normal urine sodium, and continued fluid administration may be worsening the kidney injury through volume overload, as suggested by the KDIGO guideline which recommends not using diuretics to prevent AKI, but suggests their use in the management of volume overload 1. A nephrology consultation should be obtained urgently to guide further management.
Diagnostic Workup
Additional diagnostic workup should include:
- A comprehensive metabolic panel
- Complete blood count
- Urinalysis with microscopy
- Urine protein-to-creatinine ratio
- Renal ultrasound to evaluate for obstruction Consider checking for nephrotoxic medications, such as aminoglycosides, that may be contributing to the AKI and discontinue them if possible, as recommended by the KDIGO guideline which suggests not using aminoglycosides for the treatment of infections unless no suitable, less nephrotoxic, therapeutic alternatives are available 1.
Management
Diuretic therapy with furosemide may be appropriate if volume overload is confirmed, as suggested by the KDIGO guideline which recommends not using diuretics to prevent AKI, but suggests their use in the management of volume overload 1. The normal urine sodium and osmolality in the setting of worsening kidney function suggests that the kidneys are still concentrating urine appropriately but are suffering from an intrinsic injury, possibly acute tubular necrosis, glomerulonephritis, or interstitial nephritis. Close monitoring of intake and output, daily weights, and serial creatinine measurements is essential to guide further management, and protocol-based management of hemodynamic and oxygenation parameters may be beneficial in preventing the development or worsening of AKI in high-risk patients, as suggested by the KDIGO guideline 1.
From the Research
Causes of Worsening Acute Kidney Injury (AKI)
- Despite receiving continuous intravenous (IV) fluids, AKI can worsen due to various factors, including fluid overload, which is increasingly shown to be detrimental to both renal outcomes and survival 2, 3.
- The use of synthetic colloids has been associated with no survival benefit and increased risk of AKI, whereas crystalloids, particularly balanced solutions, are preferred as they may reduce the risk of hyperchloremic acidosis and kidney injury 2, 3, 4.
- In patients with established AKI who are unresponsive to fluid administration, fluid restriction is the treatment of choice, and an optimal strategy might involve a timely period of guided fluid resuscitation with appropriate solutions, followed by an appropriate fluid balance 3, 4.
Fluid Management in AKI
- The goal of fluid therapy in critical care medicine is to restore hemodynamic stability and vital organ perfusion while avoiding interstitial edema, and decisions regarding fluid management in critically ill patients with AKI are difficult due to accompanying oliguria and body fluid overload 3, 4.
- Newer dynamic preload indexes, such as stroke volume variation and pulse pressure variation, have been shown to be more reliable indicators for accurate evaluation of fluid responsiveness in critically ill patients than static pressure measurements 3.
- Combining both static and dynamic measures to assess fluid balance, fluid responsiveness, and effects of fluid therapy is an area requiring ongoing study to translate this theory into clinically useful practice at the bedside 4.
Treatment of AKI
- Management of AKI is founded on treating the underlying cause, but supportive care, including fluid management, vasopressor therapy, and kidney replacement therapy, is also crucial 5, 6.
- Blood pressure targets are often higher in AKI, and these can be achieved with fluids and vasopressors, some of which may be more kidney-protective than others 5.
- Initiation of kidney replacement therapy is controversial, and studies have not consistently demonstrated any benefit to early start dialysis 5.