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[Causes of myoglobinemia in surgery with artificial circulation]
Abstract:
Release of myoglobin (Mg) into the plasma and increase of its concentration during perfusion are a result of muscle cell injury during artificial circulation. High values of oxygen tension and hypothermia during cardiosurgery are sources of active oxygen forms damaging the biomembranes. We investigated release of Mg into the blood and relationship of this parameter with oxygen tension and depth of cooling. 95 patients were tested during open-heart surgery and operations on the main vessels: 25 perfusions at 30-32 degrees C, 41 at 26-29 degrees C, and 20 at 12-14 degrees C. The patients were divided into subgroups depending on arterial blood oxygen pressure. Myoglobin release into the blood was minimum under mild hypothermia and moderate PaO2. The degree of myoglobinemia increased with elevation in PaO2. As body temperature decreased, the concentration of Mg increased and differences between the groups with different PaO2 leveled. Critical myoglobinemia (30-fold vs. the initial value) was observed in the group with the deepest hypothermia (14 degrees C). Since the myocardium contains high amounts of Mg, it is clear that loss of this heme-containing protein impairs the feeding of the myocardium and, hence, decreases its contractility.
Insights
Muscle cell injury during artificial circulation releases myoglobin into the blood. Deep hypothermia and high oxygen levels during heart surgery significantly increase myoglobin levels, potentially harming heart function.
Area of Science:
- Cardiovascular Surgery
- Biochemistry
- Physiology
Background:
- Artificial circulation during cardiosurgery can cause muscle cell injury, leading to myoglobin release.
- High oxygen tension and hypothermia generate active oxygen species that damage cell membranes.
Purpose of the Study:
- To investigate myoglobin (Mg) release into the blood during open-heart surgery.
- To determine the relationship between myoglobinemia, oxygen tension, and hypothermia depth.
Main Methods:
- Studied 95 patients undergoing open-heart surgery or major vessel operations.
- Assessed myoglobin levels across different hypothermia groups (30-32°C, 26-29°C, 12-14°C) and oxygen tension levels.
Main Results:
- Myoglobin release was lowest with mild hypothermia and moderate oxygen tension.
- Increased oxygen tension elevated myoglobin levels.
- Deeper hypothermia led to higher myoglobin concentrations, with critical levels observed at 14°C.
Conclusions:
- Myoglobin release is influenced by both temperature and oxygen tension during cardiopulmonary bypass.
- Significant myoglobinemia, particularly under deep hypothermia, may impair myocardial function due to myoglobin loss from cardiac muscle.