Important CV Equations Flashcards
Flow
Q = Δ P / R
MAP/SVR
Cardiac Output
CO = HR x SV
Blood volume that ejects from the heart each minute
Dependent on preload, afterload, & contractility
Reference adult value = 4-8 L/min
Cardiac Index
CI = CO / BSA
= (HR x SV) / BSA
Reference adult value = 2.8-4.2 L/min/m^2
Stroke Volume
SV = (CO x 1000) / HR
OR
= EDV - ESV
Blood volume ejected from the ventricle in one heart beat
Reference adult value = 50-110 mL/beat
Systemic Vascular Resistance
SVR = [(MAP - CVP) / CO] x 80
Resistance blood meets across the entire circulation
1° determinant LV afterload
Reference adult value = 800-1500 dynes/sec/cm
Ejection Fraction
EF = [(EDV - ESV) / EDV] x 100%
= (SV / EDV) x 100
Blood amount that exits the ventricle after one systolic contraction
Reference adult value = 60-70%
Blood Pressure
BP = CO x SVR
= HR x SV x SVR
Mean Arterial Blood Pressure
MAP = [SBP + (DBP x 2)] / 3
OR
MAP = [(CO x SVR) / 80] + CVP
Average arterial pressure throughout the cardiac cycle, used to estimate perfusion pressure throughout the body
Cardiac cycle 1/3 systole & 2/3 diastole
Reference adult value = 70-105 mmHg
Pulse Pressure
PP = SBP - DBP
= SV output / arterial compliance
L ventricle SV, blood flow velocity, & arterial compliance
↑pulse pressure d/t aging ↓arterial compliance, aortic regurgitation, & along the arterial tree (lowest in the aortic & higher in dorsalis pedis)
Reference adult value = 40-60 mmHg
Afterload
= Wall tension / thickness
(LVP x chamber radius) / cardiomyocyte wall thickness
CorrPP
= ADBP - LVEDP (or PAOP)
Driving CBF pressure
CBF autoregulates MAP 60-140 mmHg
Coronary Blood Flow
= CorrPP / coronary artery resistance
What impacts demand?
Preload
Afterload
Contractility
Heart rate
Cardiac Workload α
Cardiac output
LVP
Preload (volume)
Frank-Starling
What factors impact LVEDP?
L ventricle end diastolic pressure
- LV volume
- LV compliance
- External pressure
What factors impact LVP?
= LVSP
Systolic ejection α afterload
1. ADBP
2. Chamber radius
3. Outflow tract diameter
4. Wall thickness (inversely proportional)
Impacts coronary artery demand
What factors impact ADBP?
- SVR
- Volume (SV/CO)
- Peripheral run-off
O2 Supply
= CaO2 x CO = O2 delivery
O2 Carrying Capacity
CaO2 = (Hgb x SaO2 x 1.34) + (PaO2 x 0.003)
How much oxygen contained in arterial blood (O2 bound to Hgb + O2 dissolved in the plasma)
Reference adult value = 20 mL O2/dL
Venous Oxygen Content
CvO2 = (Hgb x SvO2 x 1.34) + (PvO2 x 0.003)
Reference adult value = 15 mL O2/dL
O2 Delivery
DO2 = [(Hgb x SaO2 x 1.34) + (PaO2 x 0.003)] x CO x 10
= CaO2 x CO x 10 (conversion factor dL→L)
How much O2 in the blood & how fast O2 delivered to the tissues (based on CO)
Reference adult value = 1,000 mL O2/min
Oxygen Consumption
VO2 = CO x (CaO2 - CvO2) x 10
250 mL/min or 3.5 mL/kg/min
Oxygen Extraction Ratio
EO2 = (CaO2 - CvO2) / CaO2
25%
Maximum Allowable Blood Loss
ABL = EBV x [(starting Hgb - allowable Hgb) / starting Hgb]
Estimates how much blood patient able to lose before considering a transfusion
Cerebral Perfusion Pressure
CPP = MAP - ICP (or CVP)
Pressure gradient b/w systemic circulation & cranium
Brain autoregulates CBF to maintain pressures 50-150 mmHg
*Range varies based on patient-to-patient
Anion Gap
= Na+ - Cl¯ + HCO3¯
Gap acidosis → acid accumulation
Non-gap acidosis → loss bicarbonate or ECF dilution
Reference adult value = 8-12 mEq/L
Plasma Osmolarity
= 2[Na+] + (glucose / 18) + (BUN / 2.8)
Measures hydration status
Reference adult value = 280-290 mOsm/L
Normal Hgb
Male 15 g/dL
Female 13 g /dL
Normal Hct
Male
Female
Ohm’s Law
Flow = Pressure gradient / Resistance
Q = ΔP / R
Q = CO
ΔP = MAP - CVP
R = SVR
Poiseuille’s Law
Q = (π ⋅ r^4 ⋅ ΔP) / (8 ⋅ η ⋅ l)
Q = blood flow
r = radius
ΔP = pressure gradient
η = viscosity
l = length
