Creatine Kinase Monitoring in Acute Kidney Injury
In patients with AKI, creatine kinase (CK) should NOT be routinely trended, as CK levels do not guide AKI management and are not recommended by KDIGO guidelines for AKI monitoring. 1
When to Check CK in AKI Patients
CK measurement is indicated only when rhabdomyolysis is suspected as the underlying cause of AKI, based on clinical presentation including:
- Dark or tea-colored urine suggesting myoglobinuria 2
- Severe muscle pain or weakness 2
- History of trauma, prolonged immobilization, seizures, or drug/toxin exposure 3, 4
- Unexplained AKI in young patients with risk factors 4
Standard AKI Monitoring Parameters
KDIGO guidelines recommend monitoring serum creatinine and urine output to stage and track AKI progression, not CK. 1
The frequency of creatinine monitoring should be individualized based on:
- Patients at increased risk for AKI: Monitor creatinine with frequency based on patient risk and clinical course 1
- Patients with established AKI: Monitor creatinine to stage severity according to KDIGO criteria 1
- Severe AKI (Stage 3): Monitor serum creatinine every 4-6 hours initially 5
CK Monitoring in Confirmed Rhabdomyolysis
When rhabdomyolysis is confirmed (CK >1000 U/L), CK trending has limited clinical utility for several important reasons:
Evidence Against Routine CK Trending
- CK levels do not predict mortality or need for renal replacement therapy as effectively as creatinine levels 6
- CK typically peaks between admission and day 3 in 91% of cases, making it a delayed finding 3
- Peak CK >5000 U/L has only 55% specificity for predicting AKI requiring RRT, which is inadequate for clinical decision-making 3
- Initial CK levels have no predictive ability for mortality or renal dysfunction, whereas initial creatinine values do 6
When CK Monitoring May Be Considered
If rhabdomyolysis is confirmed, daily CK measurements until trending downward may be reasonable to confirm resolution, but this should not replace standard AKI monitoring with creatinine. 3
Peak CK typically occurs within 17-24 hours of admission in trauma patients, so checking CK at admission and 24 hours later captures the peak in most cases. 4
Critical Clinical Pitfalls
- Do not use CK levels to guide fluid resuscitation decisions in AKI—base fluid management on volume status assessment and creatinine trends 5, 3
- Do not delay treatment while waiting for CK results in patients with suspected rhabdomyolysis and AKI—initiate aggressive fluid resuscitation immediately based on clinical presentation 5
- Older patients develop AKI at lower CK levels (median 1,637 U/L vs 2,604 U/L in younger patients), so absence of markedly elevated CK does not exclude clinically significant rhabdomyolysis in elderly patients 4
- CK levels should not determine timing of CRRT termination—base this decision on renal function recovery (urine output ≥1000 mL/day and creatinine ≤265 μmol/L) 7
Risk Stratification Tools
The McMahon Score calculated on admission is superior to CK for predicting need for RRT, with 68% specificity and 86% sensitivity when score ≥6, compared to peak CK which is both less specific and a delayed finding. 3