Clinical Case Scenario

A 35-year-old male is brought to the emergency department after being found unconscious in his apartment. His roommate reports that the patient had been complaining of severe muscle pain and dark urine for the past two days, as shown below. His roommate also described the patient having run a marathon the day prior to becoming unconscious. Upon examination, the patient's legs are swollen and tender. Laboratory results reveal a markedly elevated creatinine kinase (CK) level of 15,000 U/L, elevated creatinine, and myoglobinuria. Although the first line of treatment for this condition is hydration with IV fluids,

Wrong Answer: a. Alkaline diuresis is preferred over saline diuresis

Wrong Answer: b. Aggressive IV fluid administration is continued till the patient develops signs of fluid overload

Wrong Answer: c. Diuretics and dialysis can help to avoid acute kidney injury (AKI) in rhabdomyolysis.

Wrong Answer: d. CK levels are a poor guide to titrate fluid resuscitation.

Right Answer: e. Careful monitoring of volume status and urine output can help guide therapy

Explaination:
The classical triad of muscle pain, weakness, and dark urine is seen in only less than 10% of cases of rhabdomyolysis. Brown or tea-colored urine is one of the features of rhabdomyolysis.

The first line for the treatment of rhabdomyolysis includes fluid resuscitation and prevention of end-organ complications (e.g., acute kidney injury). Although the optimal type of fluid has not been established, initial volume administration is done with isotonic saline rather than other IV fluids. An initial rate of 1 to 2 liters per hour is appropriate.

Fluid titration should be based on the patient's volume status and urine output. These can be categorized into 3:
1. Volume replete and producing urine: IV fluids are titrated to a goal urine output of 200-300 ml/hr while avoiding fluid overload. IV fluids are continued until serial CK levels are below 5000 units/L and are not increasing.
2. Volume replete with oligoanuria: Decrease IV fluids to a rate that can maintain stable circulatory status with avoidance of fluid overload. This category of patients is considered to have established acute kidney injury (AKI). Close follow-up for the need for dialysis should be done in these patients.
3. Volume overload: IV fluids should be stopped and loop diuretics should be considered.

Interestingly, serial CK level monitoring can help to guide hydration dose. If CK levels shoot up or remain high, fluid resuscitation should be escalated to improve renal perfusion. Effective hydration leads to improved renal clearance of myoglobin and other toxic byproducts of muscle breakdown.
Other supportive measures to manage rhabdomyolysis-AKI include the correction of electrolyte imbalances (hypocalcemia and hyperkalemia).
Urinary alkalinization with bicarbonate therapy with appropriate monitoring may be beneficial. After an adequate diuresis has been established with isotonic saline, a bicarbonate infusion is given to patients who have severe rhabdomyolysis, such as those with a serum CK level above 5000 units/L or clinical evidence of severe muscle injury (e.g., crush injury) and a rising serum CK level, regardless of the initial value. However, no clear evidence is available to prove whether alkaline diuresis is more beneficial than saline diuresis.
Diuretics and dialysis have no role in the removal of pigments to prevent pigment-nephropathy and avoidance of AKI.