What intra‑operative renal protective strategies should be employed for a high‑risk surgical patient with chronic kidney disease, diabetes, and hypertension undergoing major vascular, cardiac, or prolonged abdominal surgery?

Intraoperative Renal Protective Strategies for High-Risk Surgical Patients

Hemodynamic Optimization: The Cornerstone of Renal Protection

Maintain mean arterial pressure (MAP) between 60-70 mmHg in normotensive patients and >70 mmHg in patients with pre-existing hypertension to preserve renal perfusion pressure. 1, 2, 3 This is the single most important intervention with proven efficacy to prevent acute kidney injury (AKI). 4

Goal-Directed Fluid Therapy

Implement goal-directed fluid therapy using stroke volume monitoring to guide fluid administration, vasopressors, and inotropes. 1, 2, 3 This approach consistently demonstrates reduced complication rates and length of stay in cardiac and major surgery. 1

• Monitor cardiac index, systemic venous oxygen saturation, and urine output using standardized algorithms rather than informal clinical judgment. 1
• Quantified hemodynamic goals are essential during procedures with risk of hemodynamic instability (hemorrhagic surgery, major vascular/cardiac surgery, emergency surgery). 1

Fluid Management Strategy

Aim for a mildly positive fluid balance of 1-2 liters by the end of surgery using isotonic crystalloids. 1, 2, 3 This represents a critical shift from older "zero-balance" strategies.

Evidence Behind This Recommendation

• A large multicenter RCT of 3000 patients undergoing major abdominal surgery demonstrated that zero-balance fluid restriction significantly increased AKI incidence compared to a modestly liberal regimen (1.6 kg weight gain vs 0.3 kg). 1
• While zero-balance strategies reduced complications in older meta-analyses, the most recent high-quality evidence prioritizes renal protection. 1

Fluid Type Selection

Use isotonic crystalloids exclusively; avoid hydroxyethyl starch (HES) and albumin for routine intraoperative fluid administration. 1

• The FDA issued a black box warning for HES use in critically ill patients, which includes high-risk surgical patients. 1
• Retrospective studies demonstrate HES 130/0.4 is associated with increased postoperative AKI risk. 1
• Pathological tubular changes related to HES have been documented in patients who later develop chronic kidney disease. 1
• Balanced crystalloid solutions reduce AKI incidence compared to hyperchloremic solutions like 0.9% saline. 4

Nephrotoxic Agent Avoidance

Strictly avoid all nephrotoxic medications including NSAIDs, aminoglycosides, and minimize contrast media exposure during the perioperative period. 2, 3

Specific Medication Management

• Hold metformin on the morning of surgery to reduce lactic acidosis risk, particularly in patients with renal impairment. 1
• Continue ACE inhibitors or ARBs if prescribed for diabetic kidney disease with albuminuria, as discontinuation may worsen renal outcomes. 2, 3
• Adjust all medication dosages according to estimated GFR to prevent drug accumulation. 3

Glycemic Control

Target intraoperative blood glucose <180 mg/dL rather than intensive control (<110 mg/dL). 2 Moderate glycemic control reduces AKI risk by 38% compared to no control, while intensive control increases hypoglycemia risk without additional renal benefit. 2

Biomarker-Guided Early Detection

Consider using novel biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL) for early identification of patients developing kidney stress to guide intervention strategies. 1 While all cardiac surgery patients may benefit from biomarker monitoring, this is particularly important in moderate-to-high risk groups where traditional risk scores have poor discrimination. 1

Perfusion-Specific Considerations

For Cardiac Surgery with Cardiopulmonary Bypass (CPB)

Maintain adequate CPB flow rates to ameliorate impaired renal oxygenation during bypass. 1 Increased CPB flow improves renal oxygenation and may reduce postoperative renal dysfunction. 1

For Major Vascular Surgery

• Major vascular surgery carries significantly higher risk of postoperative renal complications compared to other procedures. 3
• The surgical technique for IVC anastomosis (piggyback vs bicaval replacement) may impact AKI development, though data are mixed. 1

Critical Pitfalls to Avoid

Do not rely solely on serum creatinine for intraoperative renal function assessment. 2 Creatinine is affected by weight, race, sex, age, muscle metabolism, and protein intake, making it an unreliable real-time indicator. 2

Avoid aggressive fluid resuscitation without hemodynamic monitoring. 2 Increased central venous pressure from excessive fluid administration paradoxically worsens renal function. 2

Do not use traditional "renoprotective" agents like dopamine, fenoldopam, or N-acetylcysteine. 1 Prospective randomized trials have demonstrated inconsistent or absent nephroprotective effects for these agents. 1

Monitoring Requirements

• Continuously monitor urine output, targeting >0.5 mL/kg/hour. 1
• Track lactate levels and oxygen debt as indicators of tissue perfusion adequacy. 1
• Maintain protective lung ventilation with low tidal volumes during mechanical ventilation. 1

Risk Stratification Context

The following factors compound perioperative AKI risk and should trigger aggressive implementation of all protective strategies: 3

• Age >56 years
• Emergency surgery
• Active heart failure
• Ascites
• Pre-existing hypertension
• Diabetes mellitus
• Baseline eGFR <60 mL/min/1.73 m²
• Intraperitoneal surgery

Patients with six or more risk factors experience a 10% incidence of perioperative AKI with a hazard ratio of 46 compared to those with fewer than three risk factors. 3