Background: Rhabdomyolysis is a condition of rapid muscle breakdown resulting in myalgia, enzyme elevations, electrolyte imbalance. Released heme pigment may lead to tubular obstruction, vasoconstriction, and tubular epithelial cell injury, causing acute kidney injury (AKI) as a severe complication. Especially with predisposing conditions such as volume depletion. Early and aggressive fluid resuscitation is an essential intervention aiming at restoring renal perfusion. For patients developing severe renal impairment with complications such as life-threatening electrolyte or fluid imbalances, renal replacement therapy (RRT) will need to be initiated. This study aimed to evaluate the impact of RRT on clinical outcomes, economic and survival burden in patients with rhabdomyolysis developed acute kidney injury.

Methods: The National Inpatient Sample (2014) was used to identify adult patients hospitalized with rhabdomyolysis with acute kidney injury. We recognized rhabdomyolysis, AKI, hemodialysis (including intermittent and continuous), peritoneal dialysis, congestive heart failure (CHF), chronic liver disease (CLD), obesity using the International Classification of Diseases, Ninth Revision, Clinical Modification and Procedure Coding System (ICD-9-CM, PCS). The identified admissions were stratified into two cohorts based on the requirement of RRT. We compared the baseline demographic characteristics and comorbidities. We used multivariable survey regression models to evaluate the outcomes, including in-hospital mortality, length of stay (LOS), costs. Secondary outcomes include invasive mechanical ventilation rate and fasciotomy rate. P-value <0.001 was used as the significance threshold.

Results: There was an estimation of 246315 adult admissions with a discharge diagnosis of rhabdomyolysis for the year 2014. Among them, 116050(47.1%) patients developed AKI. 10365(8.9%) required RRT. Compare with the non-RRT group, more male (69.4% vs. 64.0%) and younger (mean age 55.4 vs. 62.3) patients underwent RRT. Higher prevalence of CHF (23.9% vs. 18.9%), chronic liver disease (7.0% vs. 3.8%), obesity (20.1% vs. 14.0%) was also noticed in the RRT group. Among all hospitalizations with rhabdomyolysis developed AKI, the mortality rate was 11665(10.1%). After adjusting for patient and hospital-level confounders, the RRT group was associated with higher mortality [21.8% vs. 8.9% adjusted odds ratio (aOR) 2.86, 95% confidence interval (CI) 2.53- 3.25]. Compare with the non-RRT group, patients in the RRT group were more likely requiring invasive mechanical ventilation (42.5% vs. 16.3%, aOR 3.29, 95% CI 2.96- 3.67). More patients underwent fasciotomy (4.0% vs 1.2%, aOR 2.68, 95% CI 2.01- 3.58). RRT group experienced significantly longer mean LOS of (16.5 days vs. 7.9 days), higher total cost adjusted for inflation ($51580.7 vs. $20153.8).

Conclusions: Our study is the first population-based retrospective study about rhabdomyolysis with AKI in a national hospital database in the U.S. Hospitalizations with rhabdomyolysis and AKI requiring RRT had significantly higher inpatient mortality than those not requiring RRT. Hospitalizations requiring RRT were also associated with a more frequent requirement for invasive mechanical ventilation and fasciotomy, a vast increase in hospital resource use as measured by both LOS and costs.