From the Guidelines
A 2-liter blood loss causes a base deficit of approximately -6 due to significant hemorrhage leading to tissue hypoperfusion and anaerobic metabolism, as supported by the most recent evidence from the European guideline on management of major bleeding and coagulopathy following trauma: sixth edition 1.
Mechanism of Base Deficit
When a person loses a significant amount of blood, such as 2 liters, which is approximately 40% of the total blood volume in an average adult, the decreased oxygen delivery to tissues forces cells to switch from aerobic to anaerobic metabolism. This shift to anaerobic metabolism results in the production of lactic acid, leading to metabolic acidosis, which is measured as a base deficit.
Relationship Between Blood Loss and Base Deficit
The relationship between blood loss volume and base deficit is relatively linear, with each liter of acute blood loss typically corresponding to a base deficit of about -3, as inferred from the principles of tissue hypoperfusion and anaerobic metabolism discussed in the context of hemorrhagic shock 1. Therefore, a 2-liter hemorrhage would produce a base deficit around -6.
Clinical Value of Base Deficit Measurement
This measurement is clinically valuable as it helps quantify the severity of shock and guides resuscitation efforts. The base deficit serves as an important marker of tissue perfusion and can help predict mortality risk in trauma patients, as highlighted in the guidelines for the management of bleeding following major trauma 1.
Treatment and Resuscitation
Treatment focuses on stopping the bleeding source and restoring circulating volume with crystalloids, blood products, or both, while monitoring base deficit improvement to assess the adequacy of resuscitation. The use of base deficit as a marker for the severity of hemorrhagic shock and the effectiveness of resuscitation efforts is supported by recent clinical guidelines 1.
Key Points
- A 2-liter blood loss leads to a base deficit of approximately -6.
- The base deficit is a marker of tissue hypoperfusion and metabolic acidosis.
- It is used to quantify the severity of shock and guide resuscitation efforts.
- Monitoring base deficit improvement is crucial for assessing the adequacy of resuscitation in trauma patients.
From the Research
Metabolic Acidosis and Base Deficit
- A base deficit of -6 indicates metabolic acidosis, which can occur due to various causes, including lactic acidosis, ketoacidosis, and hyperchloremic acidosis 2, 3, 4.
- Metabolic acidosis can result from inadequate oxygen delivery to tissues, leading to cellular and organ dysfunction, increased morbidity, mortality, and hospital stay 5.
- A 2-liter blood loss can lead to significant metabolic acidosis due to poor tissue perfusion and anaerobic glycolysis, resulting in hyperlactataemia 6.
Causes of Metabolic Acidosis
- High anion gap metabolic acidosis can occur due to the accumulation of endogenous acids, such as lactic acidosis, ketoacidosis, and renal failure 4.
- Hyperchloremic metabolic acidosis can result from gastrointestinal bicarbonate loss, renal tubular acidosis, and administration of acids 4.
- Resuscitation with lactated Ringer's solution can also lead to hyperchloremic acidosis, which is associated with lower mortality than base deficit secondary to other causes 2.
Treatment of Metabolic Acidosis
- The appropriate treatment of acute metabolic acidosis is controversial, and the only effective treatment for organic acidosis is cessation of acid production via improvement of tissue oxygenation 3, 4.
- Treatment with sodium bicarbonate has not been shown to reduce morbidity and mortality in patients with lactic acidosis and ketoacidosis, despite improvement in acid-base parameters 3, 4.