A 30-year-old man loses 1 liter of whole blood acutely. Within the next hour, which compensatory fluid movement maintains his plasma volume?

• A Shift of intracellular fluid into the vascular compartment
• B Movement of lymph into the venous circulation
• C Shift of transcellular fluid from the CSF into plasma
• D Transcapillary refill of interstitial fluid into the plasma ✓

Explanation

Acute hemorrhage lowers capillary hydrostatic pressure below plasma oncotic pressure, so interstitial fluid moves across the capillary wall into the vascular compartment, called transcapillary refill. Because interstitial fluid is large (about 11 to 12 liters versus 3 liters of plasma), this replaces much of the lost volume within hours. Intracellular fluid cannot cross capillary endothelium directly, and lymph flow is far too small to matter acutely.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.