🧪 Renal Function

🧪 Renal Function

Renal function refers to the ability of the kidneys to filter blood, eliminate waste products, and maintain fluid, electrolyte, and acid-base balance. It also plays a key role in the clearance of many drugs, including anticoagulants and contrast agents.

📊 Key Measurements

Serum Creatinine (sCr): primary marker; influenced by age, muscle mass
Estimated Glomerular Filtration Rate (eGFR):
- Calculated via CKD-EPI or MDRD formulas
- Normal >90 mL/min/1.73 m²
Creatinine Clearance (CrCl):
- Useful for drug dosing (e.g., dabigatran)
- Calculated via Cockcroft-Gault formula

💉 Clinical Relevance

💊 Drug Clearance

Renal function determines elimination of:
- Dabigatran, enoxaparin, vancomycin, contrast media
Impaired renal function increases risk of toxicity or delayed drug clearance
Always assess before:
- Contrast-enhanced imaging
- Anticoagulant dosing
- Nephrotoxic antibiotics

🧠 Neurosurgery Context

Dabigatran: requires renal dose adjustment; reversal urgency ↑ in renal impairment
Contrast-induced nephropathy: risk with repeated CT/MRI contrast in elderly or ICU patients
Surgery planning: electrolyte control, fluid balance, uremia-related bleeding risk

⚠️ Red Flags

Rapid rise in serum creatinine
Oliguria (<0.5 mL/kg/h)
Elevated BUN/creatinine ratio
Acid-base or electrolyte disturbances (↑K⁺, ↓HCO₃⁻)

✅ Best Practice

Always document baseline renal function pre-intervention
Use eGFR/CrCl to adjust drug doses
In patients >70 years or on nephrotoxic agents, monitor daily renal profile
Avoid contrast or nephrotoxins when possible in acute impairment

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