Renal & Respiratory Support

Epidemiology & Risk Factors

• CSA-AKI occurs in 20–30% of cardiac surgery patients; 2–5% require RRT
• Risk Factors: Preoperative CKD, diabetes, advanced age, prolonged CPB (>120 min), low CO, perioperative nephrotoxins, re-operation
• KDIGO Classification: Stage 1 (Cr ↑ 1.5–1.9× or ↑ ≥0.3 mg/dL), Stage 2 (Cr ↑ 2.0–2.9×), Stage 3 (Cr ↑ ≥3× or RRT)
• Prevention: Goal-directed hemodynamic optimization, avoid nephrotoxins (aminoglycosides, NSAIDs, contrast), maintain adequate perfusion pressure (MAP >65), consider RIPC (remote ischemic preconditioning)

Indications for RRT in CVICU

• Refractory hyperkalemia (K⁺ >6.5 despite medical therapy)
• Severe metabolic acidosis (pH <7.1 unresponsive to treatment)
• Refractory volume overload (diuretic-resistant pulmonary edema)
• Uremic complications (encephalopathy, pericarditis, bleeding)
• Severe AKI with oliguria (<0.5 mL/kg/hr for >12h) in setting of hemodynamic instability
• CRRT preferred over IHD in hemodynamically unstable patients (most CVICU patients)

CRRT Modalities & Targets

Prescription Targets

• Effluent dose: 20–25 mL/kg/hr (KDIGO guideline; prescribe 25–30 to account for downtime)
• Blood flow rate: 150–250 mL/min
• Anticoagulation: Regional citrate (preferred; avoids systemic anticoagulation) or systemic heparin
• Monitor: Ionized calcium (citrate), filter life, electrolytes q4–6h, fluid balance
• Net ultrafiltration: Titrate to clinical targets (typically 50–150 mL/hr for fluid removal)

Key Principles

• Post-CPB patients are typically fluid-overloaded from priming volume, cardioplegia, and crystalloid administration
• Diuretic strategy: Furosemide bolus or infusion (1–20 mg/hr); add metolazone for synergy; thiazide for distal blockade
• Target negative fluid balance once hemodynamically stable (POD 1–3)
• Albumin 25% as colloid for intravascular volume; avoid in hyperoncotic state
• Electrolyte targets: K⁺ 4.0–4.5, Mg²⁺ >2.0, ionized Ca²⁺ 1.1–1.3 mmol/L, phosphate 2.5–4.5