6-peripheral vascular resistance

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  • Total Peripheral Resistance (TPR)It is the sum of the resistance of all peripheral vasculature in the systemic circulation.

    Total peripheral resistance is used in calculations of blood pressure, blood flow, and cardiac function.

  • Systemic Vascular ResistanceSystemic vascular resistance (SVR) refers to the resistance to blood flow offered by all of the systemic vasculature, excluding the pulmonary vasculature.

    This is sometimes referred as total peripheral resistance (TPR).

  • Blood Pressure and TPRArterial blood pressure due to combination of cardiac output (CO) and total peripheral resistance (TPR).

    CO regulated by heart rate and stroke volume (CO = HR x SV)

  • Calculation TPR is represented mathematically by the formula R = P/Q.R is TPR. P is the change in pressure across the systemic circulation from its beginning to its end. Q is the flow through the vasculature (equal to cardiac output) Total Peripheral Resistance =(MAP MVP) / CO

  • Equation

    SVR = Systemic Vascular Resistance (dyn*s/cm5)MAP = Mean Arterial Pressure (mmHg)CVP = Central Venous Pressure (mmHg)CO = Cardiac Output (L/min)79.92 is a conversion term to equalize units.CVP must be < MAP. (may use Right Atrial Pressure in lieu of CVP).In general, SVR= MAP/CO

  • Equation Parameters(Systemic Vascular Resistance)ParameterAbbrevNormal LowNormal HighLower LimitHigh LimitC UnitsMean arterial pressureMAP701050250mmHgCentral venous pressureCVP170100mmHg

    Cardiac outputCO4.256.12030L/mint

    Systemic vascular resistance SVR700160007500dyn*s/cm5

  • Causes of Change in TPR R = Resistance to blood flowL = Length of the vessel =Viscosityof bloodr = Radius of the blood vessel

  • Major factor affecting resistance is arteriole diameter.

    Vasoconstriction- Increase resistance and decrease blood flow. CausesSympathetic stimulationHormones (Epinephrine, ADH, Angiotensin)

  • Vasodilatation-Decreased resistance and increased flow. CausesBlocked sympathetic stimulation (no direct parasympathetic innervation of arteries)Medications (Nitroglycerin, Lasix)

  • What effects of TPR on the body

  • Effects of TPR on the body

    A decrease in TPR will result in an increased flow to tissues and an increased venous flow back to the heart.

    An increased TPR will decrease flow to tissues and decrease venous flow back to the heart.

  • References and Resources

    (1) Alhashemi JA, Cecconi M, della Rocca G, et al.Minimally invasive monitoring of cardiac output in the cardiac surgery intensive care unit. Curr Heart Fail Rep. 2010 Sep;7(3):116-2