From the Guidelines
Bicarbonate therapy is recommended to treat myoglobinuria in rhabdomyolysis by alkalinizing the urine, as it increases myoglobin's solubility and reduces precipitation in the renal tubules, as suggested by the 2021 guideline from the Association of Anaesthetists 1. The mechanism of myoglobinuria in rhabdomyolysis involves the release of myoglobin into the bloodstream due to muscle breakdown, which is then filtered by the kidneys. This large protein molecule can precipitate in the renal tubules, causing obstruction and direct tubular toxicity. Additionally, myoglobin contains heme pigments that release free iron in acidic environments, generating harmful free radicals that damage kidney cells.
- Key points to consider in the management of myoglobinuria include:
- Maintaining a high urine output of > 2 ml.kg1.h1 to prevent precipitation of myoglobin in the renal tubules
- Using sodium bicarbonate to alkalinize the urine, as it reduces the likelihood of myoglobin precipitation
- Carefully monitoring fluid status, electrolytes, and acid-base balance to prevent complications
- The use of bicarbonate therapy is supported by the 2021 guideline, which recommends its use in the absence of convincing evidence for harm 1.
- A common approach to bicarbonate therapy involves adding sodium bicarbonate to intravenous fluids, such as D5W or normal saline, and adjusting the infusion rate based on urine pH monitoring.
- It is essential to balance the benefits of bicarbonate therapy with the potential risks, such as volume overload or metabolic alkalosis, and to closely monitor patients receiving this treatment.
From the Research
Mechanism of Myoglobinuria in Rhabdomyolysis
- Myoglobinuria occurs due to the breakdown of skeletal muscle cells, releasing myoglobin and other intracellular contents into the blood [ 2 , 3 ].
- The primary mechanism of renal damage in rhabdomyolysis is the toxicity of myoglobin, which causes vasoconstriction, intraluminal casts, tubular obstruction, and direct myoglobin toxicity [ 3 ].
Use of Bicarbonate in Rhabdomyolysis
- Bicarbonate is used to aid in the excretion of myoglobin and to alkalize the urine, which may help reduce the toxicity of myoglobin [ 4 , 5 ].
- However, there is limited evidence to support the routine use of bicarbonate-containing fluids, and its effectiveness is still a topic of debate [ 2 ].
- In some cases, sodium bicarbonate infusion has been used to aid in the excretion of myoglobin and to manage high anion gap metabolic acidosis [ 5 ].