From the Guidelines
Elevated Blood Urea Nitrogen (BUN) Indications
Elevated Blood Urea Nitrogen (BUN) levels indicate impaired renal function or dehydration.
- In such cases, patients may require adjustment or discontinuation of nephrotoxic medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen, and angiotensin-converting enzyme inhibitors (ACEIs) like lisinopril 1.
- Patients with elevated BUN levels may benefit from hydration with intravenous fluids, such as 0.9% sodium chloride solution, administered at a rate of 100-200 mL/hour for 2-4 hours, and monitoring of renal function with serial BUN and creatinine measurements 1.
- It is essential to check for hypovolaemia/dehydration and exclude the use of other nephrotoxic agents, such as NSAIDs, trimethoprim, and consider reducing the dose of ACE inhibitors or angiotensin receptor blockers (ARBs) if necessary 1.
- Small increases in BUN and creatinine are expected after initiation of ACEIs and are not considered clinically important unless rapid and substantial 1.
- Hyperkalaemia should be monitored, and if potassium rises above 5.5 mmol/L, the dose of ACEI should be halved, and blood chemistry should be monitored closely 1.
From the Research
Elevated Blood Urea Nitrogen (BUN) Indications
Elevated Blood Urea Nitrogen (BUN) levels can indicate several health issues, including:
- Renal dysfunction or kidney disease, as higher BUN levels were associated with adverse renal outcomes independent of the estimated glomerular filtration rate (eGFR) 2
- Reversible renal dysfunction in patients with decompensated heart failure, as an elevated admission BUN/creatinine ratio was associated with in-hospital improvement in renal function 3
- Pre-renal azotemia, which may be caused by hypovolemia, congestive heart failure, or septic or hypovolemic shock, resulting in a disproportionate elevation of BUN compared to creatinine 4
- Increased risk of mortality in critically ill patients admitted to the ICU, as higher admission BUN concentrations were associated with adverse long-term mortality 5
- Critical limb ischemia in peripheral arterial disease patients, as elevated BUN levels were associated with an increased risk of critical limb ischemia 6
Key Findings
- Elevated BUN levels were independently associated with renal outcomes in patients with stage 3-5 chronic kidney disease 2
- A BUN/creatinine ratio can identify patients with reversible renal dysfunction in the setting of heart failure 3
- Disproportionate elevation of BUN compared to creatinine can occur in pre-renal azotemia, often due to multiple factors such as hypovolemia, heart failure, or high protein intake 4
- Admission BUN concentration was associated with adverse long-term mortality in critically ill patients, even after correction for other factors such as APACHE2 and SAPS2 scores 5
- Elevated BUN levels were associated with an increased risk of critical limb ischemia in peripheral arterial disease patients, independent of other vascular risk factors 6