Hwmo

Maryam AL-Qahtani.

G:3

Clinical vignette 2

Shock

Objectives:

What would be the central venous and/or

pulmonary capillary occlusion pressure

(Low, normal, high )?

Hemorrhagic shock is a condition of reduced tissue perfusion,

resulting in the inadequate delivery of oxygen

and nutrients that are necessary for cellular

function.

Venous pressure:is a term that represents the average blood pressure within the venous compartment.

Central venous pressure:considered a direct measurement of the blood pressure in the right atrium and vena cava.

Central venous

pressure

Normal

value :CVP is 2-6 mm Hg.

ΔCVP = ΔV / Cv

change in volume (ΔV)The compliance (Cv)

Equation:

Factors influencing the Central Venous Pressure:

Cardiac output.

Blood volume.

Venous constriction.

Changing from standing

to supine body posture.

Arterial dilation.

CVP is elevated by :Heart failure or PA stenosis which limit venous

outflow and lead to venous congestion.

CVP decreases with:Hypovolemic shock from hemorrhage, fluid shift,

dehydration.

Pulmonary capillary occlusion pressure:

intravascular pressure as measured by a catheter

wedged into the small pulmonary artery ; used to

measure indirectly the mean left atrial pressure.

Normally about 8-10 mmHg.

In our case :What would be the central venous and/or pulmonary capillary occlusion

pressure (Low, normal, high )?

Early stage of shock .Compensate stage

The central venous pressure

and pulmonary capillary

occlusion pressure ……

Due to the compensatory

mechanism

Systemic arterial blood pressure

Blood volume venous return volume

the central venous pressurepulmonary arteries blood flow

Initial stage: CVP slightly decrease

Compensatory stage:

1/ increasing stroke volume.

2/ increasing the heart rate.

3/raising blood pressure.

4/increasing the rate of return of venous

blood to the heart.

Vasoconstriction blood

vessels + increase blood

volume …..>increase

arterial pressure.

CVP Normal

•Hemorrhage decreases blood volume and decreases CVP (A→B)

•By compensatory mechanism (B→C),which increases CVP andshifts blood volume toward heart…..> increase pulmonary capillary occlusion pressure

In Short:

The CVP & PCWP in hypovolemic shock differs

depend on the stage of the shock.

Initial stage decrease

Compensatory stage normal

Uncompensatory stage decrease

Guyton & Hall. Text book of Medical physiology .

.Merck Manual.

.Up to data. Website

http://www.rnceus.com/hemo/cvp.htm

http://www.medscape.com/viewarticle/749208_7

http://cvphysiology.com/Blood%20Pressure/BP020.htm