Meeting Uncle Rhabdo
THE PATIENT:
A 28 year old previously healthy male presents to the emergency department with concerns for worsening back pain that is predominantly left sided and along the lumbar spine. Two days prior to the visit he recalls a work out that consisted of many dead lifts. He also played basketball the following day and rode his bike into work, which is more activity than usual for him. He tried NSAIDs for pain control, but his pain is more intense and he noticed his urine looked brown today. He denies any fevers, history of IVDU, weight gain or loss, urinary tract infections or STDs, immunosuppression, recent spinal fracture or procedure, incontinence or retention.
PHYSICAL EXAMINATION:
144/83, 82, 37.1, 18, 98%
Gen: well appearing, no acute distress
HENT: normocephalic, MMM
CV: RRR
Pulm: CTAB
Abd: soft, nontender, nondistended
MSK: muscle spasms along the left lumbar paraspinal muscle, no midline tenderness to palpation, muscle compartments in the upper and lower extremities are soft
Neuro: L1-S5 strength 5/5 and sensation to light touch is intact
Skin: pink, warm, dry
THE COURSE:
As an experienced clinician you are able to quickly arrive at a diagnosis of rhabdomyolysis from the brief history and physical exam, but what else needs to be done? In the emergency department we need to initiate diagnostic studies to evaluate the severity of illness and help plan for an appropriate disposition. Thankfully, your history and exam reveal no red flag findings for more concerning etiologies of back pain, so your evaluation can be quite focused. The patient had lab work sent off and was provided with IVF boluses and given analgesia with marked improvement in his symptoms. He was admitted to the medical floor for continued care for the next couple days.
THE WORK UP:
CK >20,000 IU/L (labs upper limit for reporting without further analysis and quantitative estimates, normal range 20-210, remained >20,000 for 5 consecutive days) finally on day 6 CK 10, 933 IU/L
BMP: Glu 113, BUN 19, Cr 1.0 (on discharge was 0.84), Na 139, K 3.8, Cl 104, CO2 29, Ca 8.9
Urinalysis: Brown, cloudy, trace ketones, specific gravity >1.03, blood 3+, protein >300
Urine microscopic analysis: RBC none seen, WBC 3, amorphous crystals present
Urine myoglobin: >8,750 mcg/ml (normal range < 28mcg/ml)
DISCUSSION:
The key clinical manifestations of rhabdomyolysis include a triad of muscle tenderness and weakness as well as dark urine, so the triage note already had it set up on a silver platter for you. Remember, however, as with any triad in medicine this classic presentation is rare. Some studies revealed that over half of patients do not report muscle pain or weakness. Rhabdomyolysis occurs due to muscle necrosis and the release of intracellular contents into the circulation. Patients may present with a wide range of symptoms and the most concerning complications include hyperkalemia, renal failure and rarely disseminated intravascular coagulation. Patients who present with concomitant acute kidney injury tend to have worse outcomes and the mechanism of injury is primarily related to the nephrotoxic effects of myoglobin. In an acidic environment myoglobin may precipitate and subsequently damage the kidneys by obstruction of the renal tubules, cause oxidative damage and vasoconstriction.
The etiologies of rhabdomyolysis can be broken up into four broad categories: impaired production or use of ATP, dysfunctional oxygen or nutrient delivery, increased metabolic demand exceeding capacity, and direct myocyte damage. Recently, on EM: RAP Dr. DeLaney argued that this can be further simplified into two broad categories, exertional and non-exertional. Classic cases include trauma patients who have crush injuries but can also occur with heat related illnesses such as heat exhaustion or stroke, or in cases of hyper-kinetic states. Medications implicated in this disease process include antipsychotics and statins as well as others such as illegal drugs like cocaine.
CK levels classically rise within two to twelve hours after the onset of injury and peak within three days. The level should return to baseline within ten days. The diagnosis is often considered if the CK level is above five times the upper limit of normal at presentation, roughly 1,000 IU/L. More discrete categories can also be used to differentiate mild to severe cases based on CK levels, however, it is the degree of renal impairment that likely has the greatest role on patient outcome. Emergency department management includes aggressive IVF hydration with a target urine output of approximately 250 ml/hr and attempts to identify and correct the underlying pathology. Some argue for urinary alkalinization; however, the literature is limited with regards to strong recommendations on this topic. Common electrolyte abnormalities include: hyperkalemia, hyperphosphatemia, hyperuricemia, and hypocalcemia. Disseminated intravascular coagulation can rarely be seen as a result of thromboplastin and prothrombotic agents released from damaged myocytes. Acute kidney injury is more common if the presentation includes a CK >5,000 IU/L and in cases with sepsis, acidosis, or dehydration. Ultimately, most patients do well during their hospital courses and rarely require significant interventions, but mortality may be upwards of 20% in those that present with significant kidney injury noted at the time of presentation, therefore, careful evaluation of the patient’s lab studies and admission for close observation remains the mainstay of treatment.
Faculty Reviewer: Dr. Gita Pensa
SOURCES:
DeLaney, M. “Rhabdomyolysis: Part 1 Diagnosis and Treatment.” www.emrap.org March 2018, 18 (3)
DeLaney, M. “Rhabdomyolysis: Part 2 Disposition.” www.emrap.org March 2018, 18 (3)
Majoewsky, M. “Rhabdomyolysis: C3 Project.” www.emrap.org June 2012, 2 (6)
Sauncy, H. (2017). Don’t Get Broken Up About Muscle Breakdown. In Mattu, A. Marcucci, L. et al (Eds.), Avoiding Common Errors in the Emergency Department: Second Edition (pp. 414-16). Philadelphia: Wolters Kluwer.