Nurse Faith should recognize that fluid shift in a client with burn injury results from an increase in the:
A. Total volume of circulating whole blood
B. Total volume of intravascular plasma
C. Permeability of capillary walls
D. Permeability of kidney tubules
Correct Answer: C. Permeability of capillary walls
In burn, the capillaries and small vessels dilate, and cell damage causes the release of a histamine-like substance. The substance causes the capillary walls to become more permeable and significant quantities of fluid are lost.
Option A: The steady intravascular fluid loss due to these sequences of events requires sustained replacement of intravascular volume in order to prevent end-organ hypoperfusion and ischemia. Reduced cardiac output is a hallmark in this early post-injury phase.
Option B: Increase in transcapillary permeability results in a rapid transfer of water, inorganic solutes, and plasma proteins between the intravascular and interstitial spaces. Subsequently, intravascular hypovolemia and haemoconcentration develop and maximum levels are reached within 12 hours after injury.
Option D: Disruption of sodium-ATPase activity presumably causes an intracellular sodium shift which contributes to hypovolemia and cellular edema. Heat injury also initiates the release of inflammatory and vasoactive mediators. These mediators are responsible for local vasoconstriction, systemic vasodilation, and increased transcapillary permeability.
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