As already mentioned, hemodynamics are the forces which circulate blood through the body.

Specifically, hemodynamics is the term used to describe the intravascular pressure and flow that occurs when the heart muscle contracts and pumps blood throughout the body. It is important to remember that the vascular system is a closed circuit. Pressure and flow variations in the venous compartment will necessarily affect the arterial compartment and vice versa. Therefore, a hemodynamic measurement is not simply a number in relation to a norm. Rather, it is the minute to minute pressure and flow variations that ocur within and between compartments.

Heart function is the main focus of hemodynamic studies but the heart is not the only factor influencing pressure and flow. There are four factors which influence hemodynamics. They are the three hemodynamic components to the circulation of blood in the body plus chronotropy.

• Intravascular volume: the amount of fluid circulating in the vasculature. This can be affected by dehydration, diuresis, and volume overload due to heart or kidney failure.
• Intropy: the strength of myocardial contractions. Myocytes are the only muscle cells which are able to vary the strength of contraction. Intropy can be affected by exercise, stress and pharmaceutical agents, which increase the strength of myocardial contractions, or by cardiac diseases such as heart failure, which decrease the strength of contractions.
• Vasoactivity: the expanding and contracting of blood vessels to accommodate the variation in blood flow, regulate arterial pressure, and meet the metabolic demands of the organs and body tissues. Certain hormones also affect vasoactivity. They are angiotenson II, epinephrine, norepinephrine, and vasopressin.
• The fourth factor is chronotropy. Chronotropy involves the timing, or rate of heart contraction. This component affects tissue perfusion and is not considered a hemodynamic component. However, a person needs to have all four components functioning normally to remain hemodynamically stable.

RnCeus Homepage | Course catalog | Discount prices | Login | Nursing jobs | Help