What are the perioperative considerations for a patient with impaired renal function (eGFR of 37) undergoing surgery with general anesthesia?

Perioperative Management for eGFR 37 with General Anesthesia

A patient with an eGFR of 37 mL/min/1.73 m² (Stage 3b CKD) faces significantly elevated cardiovascular and renal risks during surgery, and your primary goals are maintaining adequate renal perfusion pressure, avoiding nephrotoxic agents, and implementing goal-directed fluid therapy to prevent acute kidney injury and reduce mortality. 1

Risk Stratification

Your patient is at substantially increased risk for perioperative complications:

• An eGFR <60 mL/min/1.73 m² correlates significantly with major adverse cardiovascular events including myocardial infarction, stroke, and heart failure progression 1
• Even temporary worsening of renal function increases 30-day mortality 3.7-fold, while persistent worsening increases it 7.3-fold 1
• Additional risk factors that compound perioperative acute kidney injury include: age >56 years, emergency surgery, active heart failure, ascites, hypertension, intraperitoneal surgery, and diabetes 1

Preoperative Optimization

Calculate precise renal function using the CKD-EPI formula and assess urinary albumin-creatinine ratio 1, 2

Adjust all medication dosages according to eGFR to prevent drug accumulation and toxicity:

• Avoid morphine, codeine, and meperidine entirely (active metabolites accumulate) 1
• Use with extreme caution and reduce doses: hydrocodone, oxycodone, hydromorphone 1
• Preferred opioids with no active metabolites: fentanyl, sufentanil, methadone 1
• Avoid tramadol and tapentadol completely 1

Continue ACE inhibitors or ARBs if prescribed for diabetic kidney disease or albuminuria - these are renoprotective and should not be stopped without nephrology consultation 3, 2

Intraoperative Hemodynamic Management

Maintain mean arterial pressure (MAP) between 60-70 mmHg, or >70 mmHg if the patient has pre-existing hypertension 4, 3, 2

Implement goal-directed fluid therapy with stroke volume monitoring to optimize cardiac output and maintain adequate renal perfusion pressure (MAP minus central venous pressure >60 mmHg) 4, 3, 2

Avoid hypovolemia aggressively - even brief hypotensive episodes can precipitate acute kidney injury in patients with baseline renal impairment 4, 2

Minimize central venous pressure as elevated CVP impairs renal perfusion and is a critical hemodynamic factor in worsening renal function 3

Nephrotoxic Agent Avoidance

Eliminate or minimize all nephrotoxic medications:

• NSAIDs must be avoided or used with extreme caution due to direct nephrotoxic effects 4, 3
• Aminoglycosides should be avoided 3
• If contrast media is required, use low-osmolar or iso-osmolar agents only and do not exceed the maximum contrast dose (contrast volume/eGFR ratio) 3, 2

Contrast-Induced Nephropathy Prevention (if applicable)

If your patient requires contrast-enhanced procedures:

Hydrate with isotonic saline (1 mL/kg/h for 12 hours before and after) or sodium bicarbonate (3 mL/kg for 1 hour before, then 1 mL/kg/h for 6 hours after) 1, 3, 2

Consider N-acetylcysteine (600 mg orally twice daily) as an adjunct given its low cost and toxicity profile, though evidence for benefit remains inconclusive 1, 3

Minimize contrast volume and use the lowest effective dose 3, 2

Anesthetic Agent Selection

For local anesthetics, use lidocaine or mepivacaine as these are safe in CKD 2

Reduce epinephrine dose in local anesthetics due to hypertension risk 2

For sedation, diazepam is optimal (0.1-0.8 mg/kg orally) as it is hepatically metabolized and requires no dose adjustment 2

Postoperative Monitoring

Monitor renal function closely with regular assessment of:

• Urine output continuously 4, 2
• Serum creatinine daily 4, 2
• Define acute kidney injury as a rise in serum creatinine of 44 μmol/L (0.5 mg/dL) or 25% relative rise from baseline within 48 hours 1, 3

Maintain adequate hydration and continue avoiding nephrotoxic medications in the postoperative period 4

Critical Pitfalls to Avoid

Never discontinue ACE inhibitors/ARBs without nephrology consultation - these medications are protective in CKD patients 2

Do not rely solely on serum creatinine for assessing renal function as it is affected by weight, race, sex, age, muscle mass, and protein intake 3

Avoid loop diuretics unless absolutely necessary as they are strongly associated with worsening renal function, particularly when combined with spironolactone 5

Do not underestimate cardiovascular risk - cardiovascular disease is the most common cause of death in patients with renal disease 6