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Clinically, the unknown volume is the patient's blood volume, with the tracer having been injected into the patient's blood stream and tagged to the blood plasma. Once the tracer is injected a technician takes five blood samples which undergo microhematocrit centrifugation to extrapolate true blood volume at time 0. The concentration of the I ...
In a situation of lowered blood volume, secretion of renin by the kidneys results in the production of angiotensin II, which stimulates receptors in the VOLT and subfornical organ to complete a positive feedback loop. [9] [12] [13] These neurons also project to the median preoptic nucleus which is involved in controlling thirst. [11] [9] [12]
Elevated vascular permeability can allow excess fluid to leave blood vessels and collect in tissues resulting in edema; vasodilation prevents blood vessels from constricting to adapt to reduced volume in the vessels, causing low blood pressure and septic shock. [11] In the case of inflammation, vasodilation is caused by cytokines. [7]
Below are several examples of differing types of local blood flow regulation by specific organ type or organ system. In each case, there is a specific type of intrinsic regulation occurring in order to maintain or alter blood flow to that given organ alone, instead of creating a systemic change that would affect the entire body.
where EBV is the estimated blood volume; 70 mL/kg was used in this model and H i (initial hematocrit) is the patient's initial hematocrit. From the equation above it is clear that the volume of blood removed during the ANH to the H m is the same as the BL s. How much blood is to be removed is usually based on the weight, not the volume.
It also serves to regulate blood flow and tissue perfusion, thereby affecting blood pressure and responses to inflammation which can include edema (swelling). Most vessels of the microcirculation are lined by flattened cells of the endothelium and many of them are surrounded by contractile cells called pericytes. The endothelium provides a ...
In hematology, effective circulating volume (ECV) is the volume of arterial blood effectively perfusing tissue. [ 1 ] [ 2 ] ECV is a dynamic quantity and not a measurable, distinct compartment. [ 1 ] This concept is useful for discussion of cardiovascular and renal physiology.
The narrowing of blood vessels leads to an increase in peripheral resistance, thereby elevating blood pressure. While vasoconstriction is a normal and essential regulatory mechanism for maintaining blood pressure and redistributing blood flow during various physiological processes, its dysregulation can contribute to pathological conditions.