17.3A RHABDOMYOLYSIS ( December 2009)
AEROMEDICAL CONCERNS: The physiologic changes that occur in rhabdomyolysis may be precipitated by and severely compounded in the aviation environment and related duties involving flight. Symptoms may include muscular pain, muscular weakness and fatigue. Decreased situational awareness and cockpit distraction are of major concern. Additionally, unrecognized rhabdomyolysis may progress to renal failure, shock, cardiac arrhythmias, and death.
WAIVER: The history of a single episode of uncomplicated rhabdomyolysis is NCD for all aviation classes, including applicants, if the condition fully resolves within three months without sequelae. Any history of prolonged, complicated or recurrent rhabdomyolysis is CD, and a waiver will be considered on a case by case basis in DESIGNATED Aviators only. Waivers are considered under the following conditions:
a. No evidence of a congenital predisposing condition (e.g., myophosphorylase deficiency, sickle cell trait).
b. An identifiable situational stressor led to the occurrence, such as extreme physical exertion, trauma or muscle compression, dehydration, electrolyte abnormality, coexisting infectious disease, toxin exposure, medication effect, or fatigue.
c. No residual organ injury or damage is present.
d. A minimum of three months has passed since the episode of rhabdomyolysis.
INFORMATION REQUIRED:
1. Internal Medicine consultation.
2. Glomerular filtration rate (GFR)
3. Blood urea nitrogen and creatinine
4. Glomerular filtration rate
5. Complete blood count
6. Liver function tests
7. Creatinine kinase
8. Complete metabolic panel Note: Consider thyroid function testing
DISCUSSION: Rhabdomyolysis is a syndrome characterized by muscle necrosis and release of intracellular muscle constituents into the circulation. The disease process can range from mild, asymptomatic enzyme elevations to life-threatening cases involving cardiac arrhythmias, disseminated intravascular coagulation, acute renal failure, and death. The classic presentation of rhabdomyolysis includes myalgias, myoglobinuria causing reddish to brown urine, and elevated serum muscle enzymes. Diagnosis is based upon fractionated serum skeletal muscle creatine kinase levels, which may exceed 100,000 IU/L, and appropriate clinically correlated history. While no specific cutoff for creatine kinase level is used to diagnose rhabdomyolysis, a serum level 5 times greater than baseline is the generally accepted level. Germaine to the aviation environment is the fact that rhabdomyolysis affects patients in a 3:1 male to female preponderance and is exacerbated by extreme heat and load-bearing activity, both of which persist as constant environmental hazards in military aviation. Additional predisposing conditions and causal factors include prolonged unconsciousness resulting in extended dorsal muscle compression, struggling against restraints, episodes of near drowning, burns, sepsis, torture victims, high-voltage electrical injuries, compartment syndrome, hyperthermia, hypothermia, prolonged tourniquet application, seizures, sporadic extreme physical exertion (i.e., ultra-marathoners), dehydration, inappropriate nutritional supplement use, and pre-existing electrolyte abnormalities. Prognosis is generally favorable provided a correctable condition or causative action is identified in those cases that do not progress to acute renal failure. There is concern, however, that multiple sub-clinical episodes of rhabdomyolysis and acute renal insufficiency may predispose patients to early onset chronic renal insufficiency later in life. Additionally, the causal and predisposing factors listed above are synergistic and the chances of developing rhabdomyolysis increase as the number of the risk factors increase.