Learning objectives

• Definition and signs and symptoms of rhabdomyolysis
• Causes of rhabdomyolysis
• Treament and anesthetic management of rhabdomyolysis

Definition and mechanisms

• Rhabdomyolysis occurs when damaged skeletal muscle breaks down rapidly and releases its content in the bloodstream
• Characterized by skeletal muscle disintegration and the release of myoglobin and other intercellular proteins and electrolytes into the circulation
• Hyperkalemia, hyperuricemia, and hyperphosphatemia can all develop rapidly
• This can lead to heart- or kidney failure and can even be fatal
• Rhabdomyolysis ranges from an asymptomatic illness with elevation in the CK level to a life-threatening condition associated with extreme elevations in CK, electrolyte imbalances, acute kidney injury, and disseminated intravascular coagulation
• Most often caused by direct traumatic injury, however, can also result from a wide array of other causes

Signs and symptoms

• Muscle pains or cramps
• Weakness
• Swelling of affected muscles
• Nausea and vomiting
• Confusion 
• Coma
• Tea-colored urine due to the presence of myoglobin
• Abdominal pain
• Fever
• Tachycardia
• Arrhythmias
• Hypotension and shock
• Acute kidney injury

AKI and rhabdomyolysis

• Myoglobin interacts with the Tamm-Horsfall protein in the renal tubules to form brown granular casts which lead to tubular obstruction
• This process is favoured when the urine is acidic
• The heme group of myoglobin could lead to lipid peroxidation
• Myoglobin also scavenges nitrous oxide leading to renal vasoconstriction
• Renal blood flow is furter reduced by hypovolemia, activation of the RAAS system and other vascular mediators

Complications

• Hyperkalemia
• Hypocalcemia
• Acute kidney injury
• Disseminated intravascular coagulation
• Compartment syndrome

Causes

• Strenuous exercise
• Delirium tremens
• Tetanus
• Prolonged seizures
• Crush injuries
• Arterial thrombosis or embolism
• Clamping of an artery during surgery
• Hyperthermia
• Hypothermia
• Drugs and toxins
  • Statins and fibrates
  • Antipsychotic medications may cause the neuroleptic malignant syndrome
  • Neuromuscular blocking agents used in anesthesia may result in malignant hyperthermia, also associated with rhabdomyolysis
  • Medications that cause serotonin syndrome, such as SSRIs
  • Medications that interfere with potassium levels, such as diuretics
  • Heavy metals
  • Venom from insects or snakes
  • Drugs: alcohol, amphetamine, cocaine, heroin, ketamine, and MDMA
• Infection
• Electrical injury
• Immobilization
• Metabolism:
  • Hyperglycemic hyperosmolar state
  • Hyper– and hyponatremiamia
  • Hypokalemia
  • Hypocalcemia
  • Hypophosphatemia
  • Ketoacidosis
  • Hypothyroidism

Risk factors

Diagnosis

• Blood test: creatine kinase (CK) > 5000 U/L
  • Note that myoglobin levels peak before increases in CK
  • However, myoglobin is metabolized rapidly at sites outside of the kidney
  •  This makes CK a more reliable marker of rhabdomyolysis

• A metabolic acidosis with a high anion gap is commonly reported in rhabdomyolysis with associated AKI

Management

Suggested reading

• Floridis, J., Barbour, R., 2022. Postoperative weakness and anesthetic-associated rhabdomyolysis in a pediatric patient: a case report and review of the literature. Journal of Medical Case Reports 16.
• Pollard BJ, Kitchen, G. Handbook of Clinical Anaesthesia. Fourth Edition. CRC Press. 2018. 978-1-4987-6289-2.
• Torres PA, Helmstetter JA, Kaye AM, Kaye AD. Rhabdomyolysis: pathogenesis, diagnosis, and treatment. Ochsner J. 2015;15(1):58-69.
• Williams J, Thrope C. 2014. Rhabdomyolysis. Continuing Education in Anaesthesia Critical Care & Pain. 14;4:163-166.
• Hunter JD, Greggg K, Damani S. 2006. Rhabdomyolysis. Continuing Education in Anaesthesia Critical Care. 6;4:141-143.