How should I manage critically ill patients with acute kidney injury, chronic kidney disease, or on dialysis in the ICU?

Management of Kidney Patients in the ICU

Critically ill patients with kidney disease require tailored renal replacement therapy based on hemodynamic stability, aggressive nutritional support with protein targets ≥1.5 g/kg/day, cautious isotonic crystalloid resuscitation, and meticulous electrolyte monitoring to prevent life-threatening complications and improve survival. 1, 2, 3

Renal Replacement Therapy Selection

Hemodynamically Unstable Patients

• Continuous renal replacement therapy (CRRT) or prolonged intermittent kidney replacement therapy (PIKRT) should be used in hemodynamically unstable ICU patients as these modalities provide superior hemodynamic tolerance, slower solute shifts, and better fluid removal compared to standard intermittent hemodialysis. 1, 3
• CRRT offers 24-hour continuous treatment, making it ideal for patients who cannot tolerate the rapid fluid and electrolyte shifts of conventional 3-4 hour hemodialysis sessions. 1
• The choice between CRRT and PIKRT depends on institutional resources and expertise, as no clear survival advantage has been demonstrated for either modality. 1

Hemodynamically Stable Patients

• Intermittent hemodialysis (3-4 hours, three times weekly) can be used in patients with AKI or CKD who maintain adequate blood pressure and perfusion. 1
• For chronic dialysis patients undergoing surgery, urgent hemodialysis should be performed within 12-24 hours postoperatively to eliminate excess intraoperative fluid and correct electrolyte disturbances. 3

Treatment Selection Algorithm

• Base the decision on three factors: hemodynamic status (blood pressure stability), fluid removal needs (volume overload severity), and depurative needs (rate of catabolism and uremic toxin accumulation). 1
• Extracorporeal KRT represents the gold standard in Western ICU settings, as peritoneal dialysis is rarely used for critically ill adults. 1

Fluid Resuscitation Strategy

Initial Fluid Management

• Use isotonic crystalloids (not colloids like albumin or starches) as initial management for intravascular volume expansion in patients at risk for or with AKI. 1
• In patients with advanced CKD and suspected prerenal azotemia, administer cautious IV fluid resuscitation with isotonic saline at 0.5 mL/kg/hour despite the risk of fluid overload. 2
• Avoid hydroxyethyl starch solutions, as they impair renal function, increase bleeding risk, and increase mortality in severe sepsis without providing volume expansion advantages over crystalloids. 1

Monitoring and Adjustment

• Target urine output >0.5 mL/kg/hour and reassess volume status every 4-6 hours to avoid fluid overload. 2
• Elevated serum osmolality indicates dehydration and renal hypoperfusion, supporting the need for continued fluid resuscitation. 2
• Recognize that overzealous fluid resuscitation can worsen outcomes, particularly in conditions like malaria-induced AKI where it may precipitate acute lung injury. 1

Electrolyte Management

Critical Monitoring Parameters

• Monitor potassium, phosphate, and magnesium levels daily in all ICU patients receiving kidney replacement therapy, as these electrolytes are frequently deranged. 3, 4
• Hypophosphatemia occurs in 60-80% of ICU patients on KRT and is linked to respiratory failure and cardiac arrhythmias requiring aggressive monitoring. 3
• Hypokalemia develops in up to 25% and hypomagnesemia in 60-65% of patients on prolonged kidney replacement therapy. 3

CRRT Solution Optimization

• Dialysis solutions should contain potassium (≈4 mEq/L), phosphate, and magnesium to prevent deficiencies and reduce the need for intravenous supplementation. 3, 4
• For patients with refractory hyperkalemia despite CRRT, verify adequate blood flow rates, ensure dialysate has low or zero potassium concentration, and consider increasing CRRT dose/intensity. 4
• Maintain magnesium levels ≥0.70 mmol/L through dialysate composition rather than IV supplementation, as hypomagnesemia causes refractory hyperkalemia. 4
• Avoid exogenous intravenous potassium supplementation in CRRT patients. 4

Nutritional Support

Protein and Energy Requirements

• Medical nutrition therapy should be initiated within 48 hours of ICU admission to meet the heightened metabolic demands of critically ill kidney patients. 3
• Protein targets are ≥1.5 g/kg/day plus an additional 0.2 g/kg/day to offset amino acid and protein losses during dialysis sessions. 3
• Recognize that kidney disease causes protein-energy wasting through multiple mechanisms including anorexia from uremic toxins, chronic inflammation with increased pro-inflammatory cytokines, metabolic acidosis causing increased protein breakdown, and direct dialysis-related losses. 1

Vitamin and Micronutrient Supplementation

• Use renal-specific multivitamin formulations instead of standard multivitamins to avoid excess vitamin A and other fat-soluble vitamin toxicities. 3
• Water-soluble vitamin supplementation should include thiamine (100-300 mg/day), vitamin C (≤100 mg/day), and folate, together with trace elements such as zinc (≈50 mg/day) and selenium (≈75 µg/day) to compensate for dialysis-related losses. 3
• Vitamin C intake must not exceed 100 mg/day to prevent oxalate accumulation and related complications. 3
• Avoid high-dose glutamine supplementation as it is contraindicated in critically ill patients with kidney failure. 3

Enteral vs Parenteral Nutrition

• Provide medical nutrition therapy with a focus on avoiding high-dose parenteral glutamine and using concentrated "renal" formulas if enteral nutrition is necessary. 2
• Standard enteral nutrition formulas can be used, but disease-specific renal formulas may be preferred in certain clinical contexts. 1

AKI Recognition and Monitoring

Diagnostic Criteria

• AKI is defined by increase in serum creatinine ≥0.3 mg/dL within 48 hours, OR increase ≥50% within 7 days, OR oliguria (<0.5 mL/kg/hour) in intensive care settings. 1
• Urine output criteria are particularly applicable in ICU settings and may identify 32% more AKI patients compared to serum creatinine criterion alone. 1, 5
• Measuring total urine volume over 6-hour periods (matching nursing shifts) is equivalent to hourly measurements for AKI detection. 5

Risk Stratification

• Recognize high-risk factors including older age, sepsis, hypovolemia/shock, cardiac surgery, contrast agent infusion, diabetes mellitus, preexisting CKD, cardiac failure, and liver failure. 6
• Even mild AKI episodes are associated with 90% increased risk of developing CKD during long-term follow-up, and small increases in serum creatinine are associated with substantial increases in mortality risk. 7, 8

Nephrotoxin Avoidance

Medication Management

• Avoid nephrotoxic medications including NSAIDs, aminoglycosides, and acyclovir in high doses. 1
• Exercise caution with ACE inhibitors and angiotensin-receptor blockers, which can cause dysfunction without injury in certain contexts. 1
• Avoid contrast media exposure when possible in at-risk patients. 6

Indications for Dialysis Initiation

Earlier initiation of renal replacement therapy may be necessary in patients with:

• Persistent oliguria despite fluid resuscitation 2
• Worsening metabolic acidosis refractory to medical management 2
• Hyperkalemia refractory to medical management 2
• Refractory volume overload 6
• Uremic complications (encephalopathy, pericarditis, pleuritis) 6
• Certain toxin removal needs 6

Common Pitfalls to Avoid

• Do not rely solely on serum creatinine for AKI diagnosis in ICU patients, as it is a late marker and misses early kidney dysfunction; incorporate urine output monitoring. 9, 5
• Do not use colloids (albumin or starches) for initial volume resuscitation as they offer no survival benefit over crystalloids and may worsen kidney function. 1
• Do not overlook electrolyte supplementation in CRRT solutions, as relying on IV supplementation alone leads to persistent deficiencies and complications. 3, 4
• Do not use standard multivitamins in dialysis patients, as they contain excessive fat-soluble vitamins that accumulate and cause toxicity. 3
• Do not delay nutritional support beyond 48 hours, as protein-energy wasting develops rapidly in critically ill kidney patients. 3