Hypovolemia, or low blood volume, in burn patients is a critical consequence of severe burns, primarily due to significant fluid loss from the damaged tissue. This fluid loss isn't simply water; it's plasma leaking from blood vessels into surrounding tissues.
The Mechanism of Hypovolemia in Burns
Large burns (e.g., exceeding 20% of total body surface area or TBSA) cause widespread damage to blood vessels. This damage increases capillary permeability, meaning the vessels become "leaky." As a result, plasma (the liquid component of blood) seeps out of the capillaries and into the surrounding injured and even uninjured tissues, leading to a decrease in circulating blood volume. This process is further compounded by the release of inflammatory mediators like histamines and prostaglandins, which exacerbate fluid leakage. https://www.physio-pedia.com/Burn_Shock
This fluid shift causes a reduction in intravascular volume, triggering a cascade of events:
- Decreased venous return: Less blood returns to the heart.
- Inadequate preload: The heart receives less blood to pump out.
- Fall in cardiac output: The heart pumps less blood per minute.
- Decreased myocardial activity: The heart's contractility is compromised.
This combination of factors leads to burn shock, a severe form of hypovolemic shock. https://www.ncbi.nlm.nih.gov/books/NBK430795/ https://www.sciencedirect.com/topics/medicine-and-dentistry/burn-shock It's important to note that burn shock is a complex interplay of hypovolemic and distributive shock, sometimes even accompanied by cardiogenic shock. https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/burn-shock https://www.urmc.rochester.edu/MediaLibraries/URMCMedia/flrtc/documents/BurnShock_HANDOUTS-2023.pdf
Consequences of Burn-Induced Hypovolemia
Burn-induced hypovolemia is life-threatening. The decreased blood volume reduces oxygen delivery to vital organs, potentially leading to multi-organ failure and death. Aggressive fluid resuscitation is crucial to combat this dangerous condition. https://pubmed.ncbi.nlm.nih.gov/27600122/ https://www.criticalcare.theclinics.com/article/S0749-0704(16)30049-5/pdf The goal of fluid resuscitation is to maintain vital organ function while minimizing both immediate and long-term physiological costs. https://pubmed.ncbi.nlm.nih.gov/1290260/
