Welcome to PICU Doc On Call, A Podcast Dedicated to Current and Aspiring Intensivists.

I'm Pradip Kama and I'm Rahul Damania, a third-year PICU fellow. I’m Kate Phelps, a second-year PICU fellow and we are all coming to you from Children's Healthcare of Atlanta, Emory University School of Medicine, joining Pradip and Rahul today. Welcome to our episode, where will be discussing rhabdomyolysis and associated acute kidney injury in the ICU.

Rahul: Here's the case, a 7-year-old female presents to the ED with three days of fever, poor PO, and diffuse myalgia. In the ED, her vital signs are T 39.1C, HR 139, BP 82/44, RR 32. She is pale and diaphoretic, complaining weakly about how much her legs hurt. Her parents note that she has not been peeing very well since yesterday, and when she does pee it is “very concentrated, almost brown.” She’s also been spending all her time on the couch and has asked to be carried to the bathroom when she does need to go.

An IV is placed by the emergency room team, and she is given a fluid bolus, acetaminophen, and initial labs are drawn (CMP, CBC, RSV/Flu swab) before she is admitted to the PICU. In the PICU, her fever is better and her vitals have improved to T 37.7, HR 119, BP 115/70, and RR 25. Her respiratory swab has just resulted positive for Influenza A. Further labs are sent, including creatine kinase (CK), coagulation studies, and a urinalysis. Labs are notable for K 3.9, Bicarb 22, BUN 15, Cr 0.8, and CK 5768 IU/L. Her urinalysis is notable for 1 WBC, 2 RBC, +3 blood, negative nitrites, and leukocyte esterase.

Kate: To summarize key elements from this case, this patient has:

Influenza A, as evidenced by her respiratory swab, as well as her clinical prodrome.
She has diffuse myalgias, as well as fevers, diaphoresis, and hypotension.
Labs are most notable for elevated creatinine and elevated creatine kinase, as well as an abnormal urinalysis.
All of which brings up a concern for rhabdomyolysis and myoglobin-induced acute kidney injury.

Before we get into this episode — let's create a mental framework for this episode — we will dissect our case by highlighting key H&P components, visit a differential diagnosis, pivot to speaking about pathophysiology, and finally, speak about management!

Rahul: Let's transition into some history and physical exam components of this case.
The classic presentation of rhabdomyolysis is myalgias, muscle weakness, and tea-colored urine, all of which our patient has. Decreased urinary output can also accompany, a variety of reasons, but most notably if the patient has myoglobin-induced acute kidney injury. In our patient, poor PO is also probably contributing to her decrease in urine output. Red flag signs or symptoms will include anuria, hypotension, and altered mental status (which is rare but may indicate severe acidemia and deterioration)
Pradip: As we think about our case, what other disease processes might be in our differential? As we dive in a bit more, we’ll come up with ways to distinguish between rhabdo and other things!
Viral myositis - inflammation in the muscles in the setting of a viral illness, which can definitely happen with influenza and other common viruses
Some other things which may cause reddish-brown urine, including hematuria, hemoglobinuria, porphyria, some specific foods or drugs (like rifampin, beets, food coloring — even ibuprofen)
We also have to investigate a bit more to convince ourselves that our patient’s AKI is due to rhabdomyolysis, as it could be from dehydration, sepsis, NSAIDS, etc.

Kate: Let’s dive further into rhabdomyolysis!

Rhabdomyolysis affects over 25,000 adults and children every year. While toxins (including prescription drugs, alcohol, and illicit drugs) and trauma are two common causes of...