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Renal Dysfunction and Perioperative Acute Kidney Injury

Renal dysfunction is linked to increased postoperative morbidity and mortality. An estimated glomerular filtration rate (eGFR) below 50 ml.min⁻¹.1.73 m², classified as stage 3a chronic kidney disease, is associated with excess morbidity. A rise in creatinine of 44 µmol·L⁻¹ has been associated with an odds ratio of 6.5 for death and an increased length of hospital stay by 3.5 days. One in three cases of acute kidney injury (AKI) occurs perioperatively.

KDIGO Classification Criteria for Acute Kidney Injury

Stage 1

• Serum creatinine increase: 1.5–1.9 times baseline or ≥ 26.5 µmol·L⁻¹ (0.3 mg·dL⁻¹)
• Urine output: < 0.5 mL·kg⁻¹·h⁻¹ for 6–12 h

Stage 2

• Serum creatinine increase: 2.0–2.9 times baseline
• Urine output: < 0.5 mL·kg⁻¹·h⁻¹ for ≥ 12 h

Stage 3

• Serum creatinine increase: 3.0 times baseline or ≥ 353.6 µmol·L⁻¹ (4.0 mg·dL⁻¹)
• Urine output: < 0.3 mL·kg⁻¹·h⁻¹ for ≥ 24 h or anuria ≥ 12 h

Defining CKD

Chronic kidney disease (CKD) is diagnosed based on eGFR values (< 90 ml.min⁻¹.1.73 m²) from two or more creatinine measurements taken at least 90 days apart. Episodes shorter than this are termed acute kidney disease, which might precede chronic disease even if eGFR subsequently exceeds 90 ml.min⁻¹.1.73 m².

Pathophysiology

Perioperative renal dysfunction involves multiple factors:

• Arterial Hypotension: Reduces the normal net pressure of 25 mmHg that drives ultrafiltration through the glomerulus, decreasing with lower cardiac output.
• Inflammation, Vascular Injury, and Tubular Obstruction: Often accompany reduced ultrafiltration.
• Intercellular Tight Junction Disruption: Leads to cell shedding into the tubular lumen and loss of transmembrane ion channel polarity.
• Elevated Intratubular Pressure: Decreases glomerular filtration and activates tubule-glomerular feedback, causing pre-glomerular vasoconstriction.

Major Risk Factors for Perioperative AKI

Patient Factors

• Chronic kidney disease
• Heart failure
• Hypertension
• Peripheral arterial disease
• Obstructive pulmonary disease
• Diabetes mellitus
• Alcoholism
• Male gender
• Obesity
• Age > 65 years

Surgical Factors

• Emergency surgery
• Non-renal solid organ transplant
• Cardiac bypass time
• Aortic cross clamp

Other Factors

• Acute illness
• Sepsis
• Multi-organ dysfunction
• Nephrotoxic drugs:
  • ACE inhibitors
  • Angiotensin receptor blockers
  • Diuretics
  • Radio-opaque intravenous contrast

Prevention Strategies

Preoperative

• Modify risk factors
• Ensure patients are hydrated and euvolemic
• Remove nephrotoxic drugs

Intraoperative

• Maintain cardiac output and renal perfusion
  • Avoid prolonged intraoperative hypotension
• Avoid fluid overload
  • Use goal-directed fluid therapy to achieve target hemodynamic goals
• Fluid choice
  • Avoid semi-synthetic colloids; prefer balanced solutions over 0.9% saline to prevent hyperchloremic acidosis

Postoperative

• Monitor postoperative oliguria carefully; avoid unnecessary fluid infusions
• Recognize that no drugs effectively prevent AKI
  • Dopamine and fenoldopam are still used but lack evidence for preventing AKI
• Ensure adequate renal function indicated by urine output > 400 mL/day without diuretic drugs, which correlates with reduced need for renal support.

Links

• Renal Physiology
• ICU and renal disease
• Renal protection
• Renal transplant
• Contrast nephropathy
• Anaesthesia and renal disease

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References:

1. Golden, D. B., Corbett, J. M., & Forni, L. G. (2015). Peri‐operative renal dysfunction: prevention and management. Anaesthesia, 71(S1), 51-57. https://doi.org/10.1111/anae.13313
2. Allman K, Wilson I, O’Donnell A. Oxford Handbook of Anaesthesia. Vol. 4. Great Clarendon Street, Oxford, OX2 6DP, United Kingdom: Oxford University Press; 2016. Allman et al. – Oxford Handbook of Anaesthesia.pdf
3. Butterworth J, Mackey D, Wasnick J. Morgan and Mikhail’s Clinical Anesthesiology, 7th Edition. 7th edition. New York: McGraw Hill Medical; 2022. Butterworth et al. – 2022 – Morgan and Mikhail’s Clinical Anesthesiology, 7th .pdf

Summaries:

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© 2025 Francois Uys. All Rights Reserved.

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