Hemorrhage initiates a series of compensatory responses. Which of the following statement(s) is/are true concerning the physiologic responses to hemorrhagic shock?

a. An immediate response is an increased sympathetic discharge with resultant reflex tachycardia and vasoconstriction

b. Transcapillary refill is a response serving to restore circulating volume

c. Extracellular fluid becomes increasingly hyperosmolar

Hemorrhage initiates both rapid and slower, more sustained compensatory responses. The body responds to maintain hemostasis almost immediately after the onset of hemorrhage. Decreased activation of the arterial baroreceptors, though a decrease in blood pressure or even more subtly, a decrease in pulse pressure, causes an increased sympathetic discharge, resulting in reflex tachycardia and vasoconstriction. Increased adrenergic output with increased secretion of catecholamines also leads to vasoconstriction, increased heart rate, and increased myocardial contractility. Sustained compensatory responses include the release of vasoactive hormones and fluid shifts from the interstitium and the intracellular space. Adrenergically mediated vasoconstriction affects arterial precapillary and postcapillary sphincters and small veins and venules. The decrease in intravascular hydrostatic pressure distal to the precapillary sphincter leads to reabsorption of interstitial fluid into the vascular space and thereby functions to restore circulating volume. This is known as transcapillary refill. The increased release of stress hormones coupled with relative insulin resistance after shock leads to high extracellular glucose concentrations. In addition, products of anaerobic metabolism from hypoperfused cells accumulate in the extracellular compartment, inducing hyperosmolarity. This extracellular hyperosmolarity draws water from the intracellular space, increasing interstitial osmotic pressure, which in turn drives water, sodium and chloride across the capillary endothelium into the vascular space. If the shock state continues, however, the postcapillary sphincter remains in spasm, but the arteriolar and precapillary sphincters cannot maintain the tension, and they become relaxed. As sphincters relax, the capillary hydrostatic pressure increases and sodium, chloride and water move into the interstitium leading to further depletion of intravascular volume.