Myoglobin, Spot Urine

Myoglobin is a small protein that binds to oxygen and is found in heart and skeletal muscle. It is released into the blood, when heart or skeletal muscle is injured. A myoglobin blood test may be used to detect muscle damage, as the levels rise very quickly and can be measured within the first few hours. Urine myoglobin test is done to evaluate myoglobin levels, when there is extensive damage to skeletal muscles (rhabdomyolysis), as myoglobin is filtered by the kidneys and released in to the urine. Urine myoglobin levels reflect the degree of muscle injury and the risk of kidney damage. Myoglobin blood test may be used as a cardiac biomarker along with a troponin test for early detection of heart attack. In a heart attack or muscle injury, the levels of myoglobin in the blood start to rise within 2-3 hour, peak within 8-12 hours and returns to normal within a day. Myoglobin levels are detected earlier than troponin, but it is non specific for heart damage and the levels do not stay elevated as long as troponin. A negative myoglobin result effectively rules out a heart attack but a positive result needs further confirmation by testing for troponin.

1. What is rhabdomyolysis?

Rhabdomyolysis is the rapid breakdown of muscle tissue due to a serious injury to the muscle. It occurs due to trauma, crushing injuries, electrical shock, burns, Blood clot (thrombosis), toxins such as heavy metals, snake venom, or carbon monoxide, Infections such as HIV, influenza, Streptococcus, muscular dystrophy, uncontrolled diabetes, hypothyroidism, or hyperthyroidism.

2. What are the complications of rhabdomyolysis?

Rhabdomyolysis results in the release of cell contents into the blood. This can cause damage to kidneys and/or disseminated intravascular coagulation (DIC).

3. What is the treatment for rhabdomyolysis?

Rhabdomyolysis can be treated with intravenous fluids and other supportive care. Other procedures like dialysis may be done to prevent or limit damage to the kidneys.

4. Which drugs cause rhabdomyolysis?

Drugs like Antibiotics (amphotericin B, ampicillin), Anaesthesia drugs, Antidepressants, Antihistamines, Salicylates, Corticosteroids, Lithium, Statins (used to treat high cholesterol) and substances of abuse such as alcohol, heroin, cocaine, etc.

5. Is a myoglobin test required in all cases of muscle pain and weakness?

Myoglobin test is not done routinely. Muscle pain and weakness are common symptoms of many medical conditions that require no specific treatment. However myoglobin test is done if a person who is at risk for rhabdomyolysis.

6. Does a chest pain, always mean a heart attack?

Chest pain can be caused due to many other problems such as heartburn, other problems involving the stomach and esophagus, emotional stress and lung problems. Rarely chest pain may be due to temporary heart spasms and is called variant angina. Variant angina usually occur at night when a person is at rest. It can cause severe but temporary pain. If the chest pain lasts longer, even at rest , immediate medical attention is required.