Rhabdomyolysis
Introduction
Rhabdomyolysis, a term derived from the Greek words for “striated muscle” (rhabdo), “muscle” (myo), and “dissolution” (lysis), represents a complex medical syndrome characterised by the breakdown of skeletal muscle tissue that can be released into the circulation. While relatively uncommon, rhabdomyolysis can have severe consequences, ranging from acute kidney injury (AKI) to life-threatening electrolyte imbalances and compartment syndrome.
Rhabdomyolysis Pathophysiology
The pathophysiology of rhabdomyolysis involves a cascade of events initiated by skeletal muscle injury (by any means), leading to the release of intracellular contents into the bloodstream and subsequent systemic effects occur:
- Muscle Injury
Rhabdomyolysis typically begins with an insult to skeletal muscle tissue, which can result from various causes such as trauma, prolonged pressure, ischemia, extreme exercise, medications, toxins, infections, metabolic disorders, or genetic abnormalities. This insult can lead to direct muscle damage and disruption of cellular integrity.
- Release of Intracellular Contents
Following muscle injury, there is a rapid release of intracellular components into the extracellular space and circulation. The most significant of these components is myoglobin, a protein found in muscle cells that stores oxygen.
- Myoglobin Toxicity
Once in the bloodstream, myoglobin can cause toxicity to various organs, particularly the kidneys. Myoglobin is filtered by the glomeruli in the kidneys however the heme pigment can obstruct renal tubules, leading to acute tubular necrosis (ATN) and/or acute kidney injury (AKI). Additionally, myoglobin can induce oxidative stress and inflammation, further contributing to renal damage.
- Electrolyte Imbalances & Inflammatory Response
Alongside myoglobin, other intracellular contents released during muscle breakdown include potassium, phosphate, and creatine kinase which can all cause electrolyte imbalances. Additionally, the release of intracellular contents triggers an inflammatory response which can contribute to tissue damage and exacerbate the systemic effects of rhabdomyolysis.
Aetiology
Rhabdomyolysis, the breakdown of skeletal muscle tissue, can be attributed to various factors, including:
Trauma
Direct physical injury, such as crush injuries, falls, or blunt trauma, can cause muscle damage leading to rhabdomyolysis.
Extreme Physical Exertion
Strenuous exercise or overexertion, particularly in untrained individuals or during endurance events, can overwhelm muscle tissue and trigger rhabdomyolysis.
Medications
Certain medications, including statins (cholesterol-lowering drugs), antipsychotics, antiretrovirals, and illicit substances like cocaine or amphetamines, can induce muscle breakdown and rhabdomyolysis.
Toxins
Exposure to toxins such as alcohol, snake or insect venom, heavy metals, or certain industrial chemicals can damage muscle cells and lead to rhabdomyolysis.
Ischemia
Prolonged lack of blood supply to muscles, as seen in compartment syndrome, vascular occlusion, or prolonged immobilization, can result in muscle ischemia and subsequent breakdown.
Metabolic Disorders
Underlying metabolic conditions, including electrolyte imbalances (e.g., hyperkalaemia, hypokalaemia), mitochondrial disorders, glycogen storage diseases, or inherited muscle disorders like muscular dystrophies, can predispose individuals to rhabdomyolysis.
Infections
Severe infections such as sepsis, influenza, or viral myositis can lead to systemic inflammation and muscle damage, contributing to rhabdomyolysis.
Clinical Features & Investigations
Features of rhabdomyolysis can vary between individuals and tend to be non-specific. Asking for potential causes of muscle trauma can be useful in considering rhabdomyolysis such as long lie falls and intense exercise.
Muscle Pain and Weakness: Patients typically present with muscle pain, tenderness, and weakness, often involving the affected muscle groups. This can range from mild discomfort to severe, incapacitating pain.
Dark Urine: One of the hallmark signs of rhabdomyolysis is the presence of dark, tea-coloured urine, known as myoglobinuria, due to the release of myoglobin from damaged muscle cells.
Swelling and Tenderness: Affected muscles may appear swollen and tender to touch, particularly in cases of trauma or exertion-related rhabdomyolysis.
Fatigue and Malaise: Patients may experience generalized fatigue, malaise, and a sense of weakness, reflecting the systemic effects of muscle breakdown.
Nausea and Vomiting: Some individuals may experience nausea, vomiting, or abdominal pain, which can accompany the systemic inflammatory response associated with rhabdomyolysis.
Decreased Urine Output: In severe cases, rhabdomyolysis can lead to acute kidney injury (AKI), resulting in decreased urine output and signs of renal dysfunction.
Urinalysis: Presence of myoglobin in urine can lead to a false positive indication of haematuria on dipstick testing. However, upon microscopic examination by the laboratory, no red blood cells will be observed in the urine sample.
ECG: An ECG in severe cases can show electrolyte imbalances or other cardiac arrhythmias.
Bloods: Will show creatine kinases and electrolyte levels in addition to renal function.
Management
The management in prehospital is limited although the initial management involves rehydration with intravenous fluids to prevent/limit the acute kidney injury. Although, guidance from JRCALC advocates fluid administration in patients with BP < 90mmHg.
In hospital, management of electrolyte disturbances will be corrected using further intravenous fluids such as calcium or insulin-glucose infusion.
Complications
As mentioned, rhabdomyolysis can lead to several serious complications, including:
Acute Kidney Injury (AKI): Myoglobin released from damaged muscles can cause kidney damage, leading to AKI and potential long-term kidney dysfunction.
Electrolyte Imbalances: Muscle breakdown can result in abnormal levels of potassium, calcium, phosphate, and other electrolytes, which can lead to cardiac arrhythmias, muscle weakness, and other complications.
Disseminated Intravascular Coagulation (DIC): Severe rhabdomyolysis can trigger a cascade of clotting factors, leading to abnormal blood clotting, and bleeding throughout the body.
Conclusion
Rhabdomyolysis represents a complex and potentially life-threatening condition characterized by the breakdown of skeletal muscle tissue. From trauma and extreme physical exertion to medication reactions and metabolic disorders, various factors can precipitate muscle damage and trigger this syndrome.
Timely recognition and management of rhabdomyolysis are crucial to prevent serious complications like kidney injury, electrolyte imbalances, and systemic inflammation.
Key Points
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Rhabdomyolysis is characterised by the breakdown of striated muscle tissue, leading to the release of harmful substances such as myoglobin into the bloodstream.
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Common causes of rhabdomyolysis include trauma, extreme physical exertion, medication reactions, metabolic disorders, and infections.
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Clinical features of rhabdomyolysis include muscle pain, weakness, dark-coloured urine (myoglobinuria) with potential complications including acute kidney injury, electrolyte imbalances and systemic inflammation.
Bibliography
Stanley, M., & Adigun, R. (2020). Rhabdomyolysis. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK448168/
Torres, P. A., Helmstetter, J. A., Kaye, A. M., & Kaye, A. D. (2015). Rhabdomyolysis: pathogenesis, diagnosis, and treatment. The Ochsner Journal, 15(1), 58–69. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4365849/
What is rhabdomyolysis and what are the causes? | The Faculty of Intensive Care Medicine. (n.d.). Www.ficm.ac.uk. https://www.ficm.ac.uk/documents/what-is-rhabdomyolysis-and-what-are-the-causes
