09 Starling

• preload can be either pressure or volume
• the more you load the ventricle with fluid, the more it'll pump
• allows heart to pump with higher venous return, otherwise blood would pool in venous system

• shifting to left: at same preload, more stroke volume

• TPR = SVR = peripheral resistance

Venous Return

• venous return = CO: blood returned to heart = blood pumped out of heart
• X axis could be either venous return or CO
• as CO increases, RAP falls

• RAP equal to venous pressure from SVC/IVC
• Increased CO: pulls more blood out of RV/RA, lowers RA pressure

• how actually drawn

• MSFP defined by volume in venous system and tone of veins in body
• MSFP = pressure when CO is 0

• green: right shift

• increased TPR: same CO leads to lower venous pressure and lower RAP

Combined Curves

HF

• lower contractility: shift to right of starling curve
• fluid retention: increased fluid volume, shift venous return curve right
• increased TPR: changes slope of venous return curve

• lower CO and higher RAP

Hemorrhage

• blood loss: shift venous return left
• TPR up: slope left
• contractility: starling curve up

• lower CO, lower RAP

Exercise

• venous contraction from sympathetic activation
• venous contraction: move to right
• decreased TPR: slope right
• higher CO in exercise

Fistula

• same as exercise
• high output heart failure

• nl: arteriole connectes arteries and veins. Arteries have high resistance
• AV: bypass from A to V with low resistance
• result: TPR down

Vasopressors