Rhabdomyolysis and subclinical elevation of creatine kinase enzyme (CK), myoglobinemia and myoglobinuria is quite common after physical exertion (1). This is especially applicable when a person is a novice or new to working out after a long hiatus of sedentary life. However, the condition can arise even in a well-trained athlete after extreme events such as a full marathon or triathlons or any other high intensity workouts in hot and humid conditions.
Symptoms of such severe muscle injury includes sore muscle and muscle weakness, little to no urine output with dark “coca cola” colored urine and when tested shows up as positive for blood in urine but without red blood cells visible.
Cause of muscle injury is from insufficient delivery of oxygenated blood to the muscles and depletion of basic energy molecule ATP (2) during exertion. The indirect complication of exercise in electrolyte depletion with or without dehydration from heat and sweating can also cause muscle injury. Once enough muscle injury is sustained, it is followed by release of intracellular CK and myoglobin. This leads invariably to acute kidney injury occasionally to the point of needing hemodialysis. Myoglobin is filtered into the kidneys and is broken down into a heme pigment which is quite toxic to kidney glomerular tissue. The mechanism of harmful kidney injury is manifested by direct toxic effect on cells, via obstruction with urinary cast formation or local vasoconstriction effect.
As you can see, well intentioned exercise for healthy life can easily result in harmful undesired health impacts. There are proven ways to mitigate this. In hospital setting with known laboratory abnormalities, healthcare providers administer aggressive intravenous fluids with occasional mannitol infusion to forcibly diuresis a patient (3). Rationale for this is immediate perfusion of injured muscles by correcting volume depletion, correcting abnormal blood flow and other associated electrolyte abnormalities. It also prevents harmful effects of Heme pigments by “flushing” them out and allowing virtually no time to form urinary casts and hence minimize kidney injury.
Without precise blood test results, prevention of acute kidney injury from heat exhaustion, rhabomyolysis related acute kidney injury can still be safely done in out-patient setting with moderately aggressive IV fluid Lactated ringer solution given in a relatively short period to induce rapid diuresis in a healthy individual. As IV fluids become more widely available to the public, my hope is that such avoidable diseases as I have outlined above can be a relic of the past.
September 13, 2018