From the Guidelines
The patient's lab values indicate impaired kidney function, which requires careful preoperative management, and I recommend postponing elective surgery until the patient's renal function is evaluated and optimized. The BUN of 29 mg/dL and creatinine of 2.2 mg/dL suggest moderate kidney dysfunction, with an estimated glomerular filtration rate likely below 30 mL/min in an 85-year-old male 1. The CK level of 33 is normal, indicating no significant muscle damage.
Preoperative Evaluation
Prior to surgery, the patient should undergo:
- Nephrology consultation to determine the cause and chronicity of the kidney dysfunction
- Medication review to discontinue nephrotoxic drugs like NSAIDs, certain antibiotics, and adjust dosages of medications cleared by the kidneys
- Ensure adequate hydration before surgery while avoiding fluid overload
- Consider IV fluid administration with balanced crystalloids rather than normal saline to prevent further kidney stress, as suggested by the European Heart Journal study 1
Intraoperative and Postoperative Management
Intraoperatively, maintain stable blood pressure to ensure renal perfusion, and postoperatively, monitor:
- Urine output
- Electrolytes
- Kidney function closely This cautious approach is necessary because impaired kidney function increases the risk of perioperative complications including fluid and electrolyte imbalances, drug toxicity, and acute kidney injury, which could significantly impact this elderly patient's surgical outcome and recovery 1.
From the Research
Laboratory Results
- BUN: 29
- Creatinine: 2.2
- CK: 33
- Patient: 85-year-old male
- Context: Preoperative exam
Relevant Studies
- The patient's laboratory results indicate impaired kidney function, which is a concern when considering the use of metformin 2, 3, 4, 5, 6.
- Metformin is generally recommended as a first-line therapy for type 2 diabetes due to its safety, low cost, and potential cardiovascular benefits 3.
- However, the use of metformin in patients with chronic kidney disease (CKD) has been restricted due to concerns over drug accumulation and metformin-associated lactic acidosis 2, 3, 4, 5, 6.
Metformin Use in CKD
- Recent studies suggest that metformin may be safely used in patients with mild to moderate CKD (estimated glomerular filtration rate [eGFR] 30-60 mL/min/1.73m2) 3, 4, 5.
- However, prescribing metformin in patients with severe renal impairment (eGFR < 30 mL/min/1.73m2) remains a controversial issue due to the increased risk of lactic acidosis and all-cause mortality 3.
- The overall incidence of lactic acidosis in metformin users is generally low, ranging from approximately 3 to 10 per 100,000 person-years 4, 5.