What are the perioperative considerations for a patient with a single kidney and a history of renal disease undergoing surgery?

Perioperative Management of Single Kidney Patients

Patients with a single kidney and renal disease require meticulous hemodynamic optimization with mean arterial pressure maintained above 60-70 mmHg, strict avoidance of nephrotoxic agents, and goal-directed fluid therapy to prevent acute kidney injury and preserve remaining renal function. 1, 2

Preoperative Risk Assessment and Optimization

Calculate Baseline Renal Function

• Measure eGFR using the CKD-EPI formula (preferred over MDRD or Cockcroft-Gault) and assess urinary albumin-creatinine ratio before any surgical procedure 3, 2
• Recognize that eGFR <60 mL/min/1.73 m² significantly increases risk of major adverse cardiovascular events including myocardial infarction, stroke, and heart failure 2
• Even temporary worsening of renal function increases 30-day mortality 3.7-fold, while persistent worsening increases it 7.3-fold 2

Identify Additional Risk Factors

• Age >56 years, emergency surgery, active heart failure, ascites, hypertension, diabetes mellitus, and peripheral arterial disease all compound the risk of perioperative acute kidney injury 1, 2
• Patients with pre-existing renal dysfunction have diabetes as an independent risk factor for developing acute renal failure perioperatively 3

Medication Management

• Continue ACE inhibitors or ARBs if prescribed for diabetic kidney disease or albuminuria during minor or ambulatory surgery, except in severe renal failure 3, 2
• Adjust all medication dosages according to eGFR to prevent drug accumulation and toxicity 2
• Stop metformin if creatinine clearance is <60 mL/min due to lactic acidosis risk, particularly in elderly patients or those on high doses 3

Intraoperative Hemodynamic Management

Blood Pressure Targets

• Maintain mean arterial pressure between 60-70 mmHg in normotensive patients and >70 mmHg in hypertensive patients to preserve renal perfusion pressure 3, 1, 2
• The trans-kidney perfusion pressure (MAP minus CVP) must remain above 60 mmHg 1
• Avoid hypotension aggressively, as blood pressure fluctuations directly compromise the single remaining kidney 3

Fluid Management Strategy

• Implement goal-directed fluid therapy with stroke volume monitoring to optimize cardiac output and maintain adequate renal perfusion 1, 2
• Use isotonic crystalloids rather than hypotonic solutions 3
• Optimize cardiac output while reducing central venous pressure to improve renal perfusion, particularly important in heart failure patients 1

Surgical Technique Considerations

• For patients with preoperative renal dysfunction (creatinine clearance <60 mL/min) undergoing cardiac surgery, off-pump CABG may reduce the risk of acute kidney injury 3
• During on-pump cardiac surgery, maintain perioperative hematocrit >19% and mean arterial pressure >60 mmHg 3
• Minimize warm ischemia time to <25-30 minutes if the single kidney requires surgical manipulation, as prolonged ischemia causes irreversible damage 3

Nephrotoxic Agent Avoidance

Eliminate High-Risk Medications

• Strictly avoid NSAIDs, aminoglycosides, and minimize contrast media exposure in the perioperative period 1, 2
• Delay surgery after coronary angiography until the effect of radiographic contrast on renal function is assessed 3

Contrast-Induced Nephropathy Prevention

• Hydrate with isotonic saline or sodium bicarbonate before and after contrast-enhanced procedures 1, 2
• Consider N-acetylcysteine as an adjunct to hydration, though evidence remains inconclusive 1, 2
• Recognize that contrast-induced nephropathy occurs in up to 15% of patients with chronic renal dysfunction, with 0.5-12% requiring hemodialysis 1

Glycemic Control

Blood Glucose Management

• The usefulness of strict glycemic control (target 81-108 mg/dL) during the perioperative period is uncertain and may increase mortality risk 3
• Target blood glucose <180 mg/dL rather than intensive control, as the NICE-SUGAR trial showed higher 90-day mortality with intensive therapy (RR 1.14) 3
• Moderate glycemic control may reduce acute kidney injury risk by 38% compared to no control 3

Postoperative Monitoring

Define and Detect Acute Kidney Injury Early

• Monitor renal function with regular assessment of urine output and serum creatinine 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, 2
• Consider newer biomarkers (urinary interleukin-18, neutrophil gelatinase-associated lipocalin) for earlier detection 1

Maintain Renal Protection

• Continue adequate hydration and avoid nephrotoxic medications in the postoperative period 2
• Cautiously reintroduce antihypertensive medications as anesthesia and analgesia are tapered, avoiding those that interact with other drugs or alter GFR 3

Critical Pitfalls to Avoid

• Do not rely solely on serum creatinine for renal function assessment, as it is affected by weight, race, sex, age, muscle metabolism, and protein intake 1
• Avoid aggressive fluid resuscitation without hemodynamic monitoring, as increased central venous pressure worsens renal function 1
• Do not use pharmacological agents (mannitol, dopamine, fenoldopam) for renal protection, as their effectiveness is uncertain and studies have been negative 3
• Recognize that the combination of tissue hypoxia and hypertension can worsen renal ischemia-reperfusion injury 1