Renal Replacement Therapy: Anesthetic Considerations

Introduction^1-3

• RRT is used to support patients with acute kidney injury (AKI) and end-stage kidney disease (ESRD) when the kidneys can no longer maintain normal solute clearance, electrolyte balance, or fluid and acid-base regulation.
• Patients receiving RRT often have cardiovascular disease (CVD), anemia, and other chronic metabolic abnormalities that increase their risk of preoperative complications.
• As more patients live longer with advanced kidney disease, anesthesiologists frequently encounter patients on chronic HD, PD, or continuous RRT (CRRT) in both elective and emergent surgical settings.
• Safe perioperative management requires understanding dialysis timing, the physiologic effects of different RRT modalities, and how renal failure alters drug metabolism and hemodynamic control.

RRT^1-3

Definition

• RRT is used to provide solute clearance, electrolyte correction, and regulation of fluid and acid-base balance when the kidneys are unable to maintain homeostasis. This can be done through intermittent or continuous modalities.

Indications

• RRT is indicated when medical management is unable to correct severe metabolic abnormalities such as hyperkalemia, metabolic acidosis, or symptomatic uremia.
• Other indications include refractory volume overload, ingestion of dialyzable toxins from medications or accidental poisonings (e.g., lithium, salicylates, methanol, and ethylene glycol), and complications of renal failure such as encephalopathy or pericarditis.
• In chronic kidney disease (CKD), RRT is initiated for progressive uremic symptoms, uncontrolled electrolyte disturbances that remain refractory to medical therapy, or persistent fluid imbalance.

Acute vs Chronic RRT

• Acute RRT
  • Acute RRT is initiated for AKI or an acute exacerbation of CKD.
  • The primary goals of acute RRT include stabilization of electrolyte abnormalities, acid-base disturbances, and fluid overload.
  • CRRT is often selected for critically ill or hemodynamically unstable patients because it provides gradual solute and fluid removal, thereby improving hemodynamic tolerance.
• Chronic RRT
  • Chronic RRT provides long-term therapy for ESRD, typically through scheduled HD or home PD.
  • Common comorbidities include CVD, anemia, bone-mineral disorders such as secondary hyperparathyroidism and renal osteodystrophy, and chronic electrolyte abnormalities such as hyperkalemia, hypocalcemia, and hyperphosphatemia.

Modalities of RRT^2-4

General Principles of HD and PD^2,4,5

HD

• HD removes fluid and solutes rapidly, which can lead to rapid changes in blood pressure, electrolyte levels, and acid-base status.
• These shifts depend on the degree of ultrafiltration and the dialysate composition, making a review of recent laboratory values essential before administering anesthesia.
• Heparin is commonly given during HD and may increase perioperative bleeding risk.
• The patient’s fistula or graft must be protected from blood pressure cuffs, intravenous (IV) lines, and compression to avoid thrombosis or access damage.
• HD performed within 24 hours of surgery usually optimizes potassium, volume status, and uremic toxin levels.
• Post-HD, patients may present with hypovolemia or vasodilation, increasing the risk of hypotension during induction.

PD

• PD removes waste and fluid slowly through dialysate exchanges across the peritoneal membrane, resulting in gradual physiologic changes.
• Slower shifts make PD better tolerated in patients with reduced cardiac reserve.
• Intraperitoneal dialysate raises intra-abdominal pressure, reduces lung volumes, and may increase airway pressures during mechanical ventilation.
• Draining the abdomen before induction can improve ventilation, improve diaphragmatic movement, and reduce airway pressures.
• Dialysate glucose concentration can affect both fluid removal and blood glucose levels.
• The PD catheter must be handled with proper sterile technique to reduce the risk of infection and contamination.
• PD does not significantly clear anesthetic medications, so dosing is similar to that of patients with chronic kidney disease.
• Peritonitis should be suspected in patients with fever, abdominal pain, or cloudy dialysate.

Anesthetic Considerations

Preoperative Evaluation

• A recent dialysis session is important because it helps optimize potassium, acid-base status, and volume before anesthesia.^1,2
• Preoperative labs should include electrolytes, bicarbonate, blood urea nitrogen/creatinine, hemoglobin, and glucose, with special attention to potassium, as hyperkalemia can lead to arrhythmias.^1,2
• Volume status must be assessed carefully. Patients may present hypovolemic after HD or slightly hypervolemic if PD exchanges were incomplete.^2,4
• The dialysis access site (arteriovenous (AV) fistula or graft) must be examined for bruit, thrill, and patency, and the access limb must be avoided for blood pressure cuffs and IV placement.^1,2
• Patients on PD should have their abdomen evaluated for residual dialysate, as this may affect ventilation. Abdominal drainage may be performed before induction if needed.^4,5
• A thorough medication history should include antihypertensives, phosphate binders, and anemia therapy, as these medications may influence hemodynamics, electrolyte balance, and oxygen-carrying capacity. It is also important to identify any residual heparin from recent HD, as it can increase perioperative bleeding risk.^2,6
• Peritonitis must be considered in PD patients with abdominal pain, fever, or cloudy dialysate, as it can change antibiotic management and perioperative planning.^4,5

Intraoperative Management

• Patients receiving RRT require individualized intraoperative management due to altered drug clearance, fluid and electrolyte instability, autonomic dysfunction, and limited physiologic reserve.^2,7
• Local or regional anesthesia is preferred when possible to minimize exposure to renally cleared agents and to improve postoperative analgesia.^1,2
• For procedures requiring general anesthesia, induction and maintenance should be carefully titrated because these patients can experience profound hypotension due to vasodilation or hypovolemia post-dialysis.^1,2
• Balanced anesthesia using inhalation agents, total intravenous anesthesia, or a combination of techniques can be used safely. However, opioids and renally-cleared agents such as morphine, meperidine, and certain neuromuscular blockers (e.g., pancuronium, vecuronium) should be avoided or dose-adjusted because of the risk of metabolite accumulation and respiratory depression.^6,7
• Cisatracurium is preferred for neuromuscular blockade because it is metabolized independently of renal function.^2,7
• Using multimodal analgesia such as acetaminophen, regional anesthesia when safe, and low-dose ketamine can reduce the need for opioids.^2,6
• Intraperitoneal fluid in PD can reduce lung volumes; therefore, these patients may require slightly higher airway pressures during ventilation.^4,5
• Fluid management should be conservative, with careful titration to avoid both hypovolemia and volume overload, especially in patients with limited cardiac function.^2,7
• Patients with advanced kidney disease often have autonomic dysfunction and impaired ability to tolerate fluid shifts, making hemodynamic monitoring necessary.^2,7
• If the patient is actively receiving CRRT, pump settings, such as ultrafiltration rate and dialysate flow, can alter drug clearance and fluid status; therefore, close coordination with the ICU team is essential to maintain stability.^1,2
• The limb with an AV fistula or graft should be kept free from compression, and patient positioning should avoid pressure on the PD catheter.^1,2

Postoperative Considerations

• Electrolytes, especially potassium, should be rechecked postoperatively due to unpredictable intraoperative shifts in volume and acid-base status.^2,7
• Patients may need to restart HD or PD depending on their fluid balance, electrolytes, and overall metabolic status.^1,2
• Patients receiving PD should be assessed for catheter patency, signs of peritonitis, and whether postoperative exchanges should be continued or held temporarily.^5,7
• Patients who have an AV fistula or graft should have the access site inspected for a palpable thrill, an audible bruit, and evidence of thrombosis or infection.^1,2
• Multimodal analgesia with nonopioid agents, regional techniques, and use of short-acting opioids is recommended.^2,6
• Gabapentinoids, nonsteroidal anti-inflammatory drugs, and renally cleared opioids should be avoided.^2,6