VPHY 4200E Case 6: Hypovolemic Shock and Cardiovascular Regulation

central venous pressure (CVP) (mean venous pressure (MVP))

the pressure of blood near the right atrium; often a good approximation of right atrial pressure; reflects the volume of venous return

venous return

CVP reflects the volume of ? because pressure can allow you to estimate volume

hypervolemia (increased total blood volume), heart failure (congestion, hard to pump), pulmonary hypertension (harder for RV to pump), pulmonary embolism (blood clot in pulmonary circulation)

factors that increase CVP

crystalloid

substance whose particles are smaller than those of a colloid, form a true solution, and are therefore capable of passing through a semi-permeable membrane

crystalloid solution

immediate treatment given for hypovolemic shock; a type of IV solution that contains compounds that quickly disassociate in solution and can cross membranes

0.9

a saline solution is ?% NaCl, pH 5.7, and isotonic

electrolyte

an example of a crystalloid solution

dextrose

DSW is a crystalloid solution that is 5% ? in water, isotonic, pH 5.0

total blood volume

the patient's CVP increased after treatment because the crystalloid solution increased the patient's ?

capillary refill time

the time it takes for the vessels in the mucous membranes to return to normal after being pressed; normal is <2 seconds; indicates that there is sufficient blood volume

lactated saline (lactated Ringer's solution)

a sterile crystalloid isotonic IV solution of 273mOsm/L (Na+, Cl-, lactate, K+, Ca2+); the *lactate* (base) can help correct *metabolic acidosis* by removing H+ from the body fluid

pressure (P)

the amount of force exerted on a given area

P = F/A

formula for pressure

increased, low, decreased

vasodilation causes (increased/decreased) area, (low/high) resistance, and (increased/decreased) BP

decreased, high, increased

vasoconstriction causes (increased/decreased) area, (low/high) resistance, and (increased/decreased) BP

cardiac output (C.O.; Q)

regards the pumping ability of the heart; the blood volume (mL or L) pumped per min. by each ventricle

cardiac output (mL/min) = cardiac rate (beat/min) x stroke volume (mL/beat, mL/systole, or mL/ventricular contraction)

formula for cardiac output

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SA node (sinoatrial node)

without neuronal influences, ? will drive heart rate at its spontaneous activity (autorhythmic, or pacemaker cells)

chronotropic (time, frequency) effect

the effect on the rate of contraction of the heart (heart rate); autonomic activity on SA node is the main controller of cardiac rate

spontaneous depolarization, conduction

sympathetic and parasympathetic nerve fibers modify the rate of ? and of ? rate on autorhythmic cells

stimulatory

sympathetic nerve fibers are (stimulatory/inhibitory) on autorhythmic cells

inhibitory

parasympathetic nerve fibers are (stimulatory/inhibitory) on autorhythmic cells

net effect

the actual pace set by the SA node depends on the ? of antagonistic influences of sympathetic nervous system and parasympathetic nervous system

medulla oblongata (vital center)

vasomotor and cardiac control centers are located here; where the activity of autonomic innervation of the heart is coordinated

norepinephrine, epinephrine, Na+

sympathetic stimulation (using neurotransmitters ? and ?), causes ? channels to open -> increased rate of depolarization in autorhythmic cells of SA node -> increased cardiac rate -> + chronotropic effect

acetylcholine, K+, hyperpolarizes

parasympathetic stimulation (using neurotransmitter ?), allows ? channels to open longer -> ? autorhythmic cells of SA node -> - chronotropic effect

contractility (strength of ventricular contraction), EDV (end diastolic volume), TPR (total peripheral resistance)

factors affecting stroke volume

increase

an increase of EDV will (increase/decrease) stroke volume

end diastolic volume (EDV)

volume of blood in ventricles at the end of diastole

ejection fraction

measurement of the volume percentage of left ventricular contents ejected with each contraction; SV/EDV; normally 60-70%

total peripheral resistance (TPR)

frictional resistance of impedance to blood flow in arteries

decrease

an increase of TPR will (increase/decrease) stroke volume

Frank-Starling Law of the Heart (intrinsic regulation of contractility)

the more the heart fills with blood during diastole, the greater the force of contraction during systole; varying degree of stretching of myocardium by EDV

increased, increased

increased EDV -> (increased/decreased) cardiac contractility -> (increased/decreased) cardiac output

positive inotropic, Ca2+

extrinsic regulation of contractility

rate, contractility

summary of sympathetic NS effects on cardiac output

chronotropic

summary of parasympathetic NS effects on cardiac output

venous return (VR)

the volume of blood to the heart via veins, driven by venous pressure

capacitance vessels

the term for veins because they have the ability to stretch; they have thinner walls and hold about 60-70% of the blood in the body

total blood volume, venous pressure

the venous return is affected by ? and ?

increase, increase

increase in venous return -> (increase/decrease) EDV -> (increase/decrease) Q

sympathetic, increases

increasing ? activity -> increases venous constriction -> (increases/decreases)

venous return

Q, R

P is proportional to ? x ?

cardiac rate, SV, TPR

3 most important variables that will increase blood pressure

kidneys, sympathoadrenal

BP can be regulated by the ? and the ? system

afferent, thick ascending

the juxtaglomerular apparatus is the region in each nephron where the ?

arteriole comes in contact with the ? limb of the LOH

juxtaglomerular apparatus

region of a nephron that helps regulate blood pressure by secreting renin in response to blood pressure changes in the kidney; located near the glomerulus; contains granular cells, macula densa cells, and mesangial cells

granular cells (juxtaglomerular cells), afferent

? are modified smooth muscle cells in the wall of ?arterioles in the juxtaglomerular apparatus that secrete renin

sympathetic (beta-1 adrenergic)

? stimulation increases renin secretion from granular cells