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Equations Flashcards

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1
Q

Arterial O2 Content

A

CaO2 = [Hg x 1.34 x SPO2] + [PaO2 x 0.003] = ml/dL

Normal = 19 - 21 mL/dL

Hg = 1/3 PCV

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2
Q

Cardiac Output (CO)

A

CO = SV x HR

100 - 200 mL/kg/min

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3
Q

Stroke Volume (SV)

A

SV = CI/HR (mL/beat/kg)

CI = CO/BSA

1.5 - 2.5 mL/beat/kg

or

EDV-ESV

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4
Q

Oxygen Delivery (DO2)

A

DO2 = CaO2 x CO

20-35 ml/kg/min

Critical DO2 = 9-10 mL/kg/min

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5
Q

O2 Consumption (VO2)

A

VO2 = CO x (CaO2 - CvO2)

4-11 ml/kg/min

CvO2 = [Hg x 1.34 x SvO2] + [PvO2 x 0.003]

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6
Q

Oxygen Extraction Rate (OER)

A

OER = VO2/DO2 x100

CO x (CaO2-CvO2)/ CO x CaO2 x 100

Cancel both CO

(CaO2-CvO2)/CaO2 x 100

Can also use SO2

(SaO2-SvO2)/SaO2 x 100

Normal = 25% (20-30)

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7
Q

Systemic Vascular Resistance (SVR)

A

(MAP-CVP)/CO (mmHg/mL/Kg/min)

0.5-0.8 mmHg/ml/kg/min

or - 1600-2500 dynes/sec/cm-5

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8
Q

Pulmonary Vascular Resistance (PVR)

A

(PAP - PAOP)/CO

mmHg/mL/kg/min

0.04-0.06 mm Hg/ml/kg/min

or - 125-250 dynes/sec/cm-5

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9
Q

Mean Arterial Pressure (MAP)

A

MAP = ((SAB-DAP)/3) + DAP

Dogs = 80-120 mm Hg

Cats = 100-150 mm Hg

or

BP = CO x SVR

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10
Q

Ejection Fraction (EF)

Fractional Shortening (FS)

A

EF = EDV-ESV / EDV (normal 70%)

FS = LVDd - LVDs / LVDd

Dog - 25-45

Cat- 30-55%

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11
Q

ECG

Instantaneous Heart rate

A

@ 50mm/sec = 3000/x

@ 25 mm/sec = 1500/x or use Square trick (image)

x = small boxes between R-R interval

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12
Q

Alveolar O2 content (PAO2)

A

PAO2 = [FiO2 x (BaroPressure - H2O pressure)] - [PaCO2/RQ]

PAO2 = [FiO2 x (760 - 47)] - [PaCO2/0.8-1]

(room air) PAO2 = [0.21 x (760 - 47)] - [PaCO2/0.8-1]
150 - [PaCO2/0.8]

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13
Q

A-a Gradient

A

PAO2 - PaO2
PAO2 (calculated) PaO2 (measured)

FiO2 x [760-47] - [PaCO2/0.8] - PaO2

< 15 is normal

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14
Q

P:F ratio (S:F)

A

PaO2:FiO2 = 500

or

SaO2:FiO2

P:F < 300 = ALI
P:F < 200 = ARDS

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15
Q

Respiratory Shunt Equation

A

Qs/Qt = [CcO2-CaO2/CcO2-CvO2] = < 5%

CcO2 (capillary O2 content) = [Hg x 1.34] + [PAO2 x 0.003]
CaO2 (arterial O2 content) = [Hg x 1.34 x SaO2] + [PaO2 x 0.003]
CvO2 (venous O2 content) = [Hg x 1.34 x SvO2] + [PvO2 x 0.003]
PAO2 - FiO2 x (760-47) - (PaCO2/0.8)

Normal is < 5%
10-20% minimaly affected
20-30% pulmonary disease
> 30% life threatning disease

or 1 - SaO2 / 1 - SvO2

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16
Q

Physiologic Dead Space

(Bohr’s Equation)

A

Vd/Vt = (PaCO2-PeCO2) / PaCO2

Can also use PetCO2 (end-tidal)

< 24%

Also PAO2-PEO2/PAO2 (alveolar)

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17
Q

Alveolar Ventilation (VA)

A

VA = TV - Vd

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18
Q

Fick Equation for CO

In a measurement of cardiac output using the Fick Principle, the oxygen concentration of mixed venous and arterial blood are 16 and 20 mL/100mL, respectively, and the O2 consumption is 300mL/min. The cardiac output in L/min is:

A

Fick Eq CO = Oxygen consumption/arteriovenous difference

CO = VO2/(CaO2-CvO2)

answer: 7.5.

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19
Q

Haldane effect and Bohr Effect

A

Haldane - offload of O2 allows more CO2 to be carried (Shift curve to the left)

Bohr effect - hemoglobin has decreased affinity for CO2 when O2 is bound (enhancement of CO2 dissociation and elimination in the lungs). A decrease in pH and increase CO2 will decrease affinity for O2 (shift curve to the right)

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20
Q

Henderson Hasselbalch Equation

A

pH = 6.1 + Log ([HCO3)]/[PaCO2 x 0.03]

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21
Q

Laplace Law

A

Pressure (P) = 2 x t / r

Wall tension (T) = P x r / 2h

P = pressure
t = surface tension
r = radius
T = tension
h = wall thickeness
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22
Q

Modified Bernoulli Equation

A

P = 4 x V(2) (power)

Used to estimate pulmonary artery pressure on echocardiography

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23
Q

Ohm’s Law

and

Poiseuille Equation

A

Q = P / R

or

P = Q x R

Q = Flow
R = Resistance
P = Pressure

Resistance comes from Poiseuille Equation
R = 8 x L x n / 2x(pi) x r(4)

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24
Q

Reynolds Number

A

Re = ( D x p x V ) / n

D = diameter
p = Density
V = velocity
n = viscosity

< 2000 laminar
> 3000 turbulent

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25
Ventilation Equation of Motion
Pressure = (TV/compliance) + (Resistence x Flow)
26
Lung compliance Static and Dynamic
Compliance = DV/DP Static compliance (remove interference of airway resistance, measure during vent. inspiratory hold. Cstat = TV / (Pplat - PEEP) Dynamic compliance (measured during airflow, might be less than static) Cdyn = TV / (PIP - PEEP)
27
Daily Maintenance Fluid Dehydration correction
Maintenance (BW (kg) x 30) + 70 2-4 ml/kg/hr Dehydration BW(kg) x %(dehydration) / 1000 = mL/L
28
Calculated and Effective Osmolality
Calculated 2(Na + K) + GLU/18 + BUN/2.8 Effective 2(Na) + GLU/18 Normals (mOsm/L) DOG - 290-310 CATS - 290 - 330
29
Osmol Gap
Difference between the calculated and measured Osmolality OsmGap = Measured Osm - CalcOsm DOG - 0 to 1 CAT = 2
30
Anion Gap
(Na + K) - (CL + HCO3) ``` DOG = 8-21 CAT = 12-16 ``` Gen. \< 25
31
Anion Gap with correction for Low Alb
AG = (Na + K) - (CL + HCO3) If low ALB then; DOG = AG + 0.42 (3.77 - ALB) CAT = AG + 0.41 (3.3 - ALB)
32
Anion Gap corrected for Hyperphosphatemia
AG = (Na + K) - (CL + HCO3) If high Phosphorus, then; AG + [(2.52 - (0.58 x Pi)]
33
Total Body Water
TBW = Kg x 0.6 | (60% of Body weight)
34
Free Water Deficit
FWD = TBW x (Nam / Nan -1) TBW = kg x 0.6 so; Kg x 0.6 x (Nam/Nan - 1) Nam = Na measured Nan = Na normal (145)
35
Traditional Acid-Base components Non-traditional Acid-Base components
Traditional - PCO2, HCO3, pH, AG, BE Non-Traditional - SID, Atot, SIG, pH, PCO2
36
Strong Ion GAP
``` DOG = (ALB x 4.9) - AG CAT = (ALB x 7.4) - AG ``` Correct AG for Phosphorus if needed; AG + [2.52 - (0.58 x Pi)] Normal SIG dog = −0.09 mEq/L (−0.82–0.65 mEq/L) Normal SIG cat = ?
37
Corrected Na
Nac = Nam + [1.6 x (GLUm - GLUn)/100] An Increase of 1.6 Na / 100 mg/dL GLU above normal or An increase of 1.0 Na / 62 mg/dL GLU above normal
38
Corrected CL
CLc = CLm x (Nan/Nam) Note, Na is the inverse of Free water deficit. Incr. CLc in renal CL retention, RTA, Chronic resp. alkalosis Decr. CLc in GI diseaes (v/d), Loop diuretics, Hypoadre/steroids, chronic resp. acidosis
39
Corrected Calcium
Cac = Ca - ALB + 3.5
40
Na deficit
Nad = 0.6 x Kg (Nan - Nam) Note, here you subtract and not divide Na.
41
Starling Law for fluids Revised formula
Jv = KF x [(Pc - Pi) -o [(Oc - Oi) - Qlymph Revised for Glycocalyx Jv = KF x [(Pc - Pi) -o [(Oc - Osg) Osg = sub-glycocalyx
42
Colloidal Osmotic pressure normals
DOG = 15 - 26 CATS = 17 -33 Target therapeutic ~ 16 mmHg
43
Cerebral Perfusion Pressure (CPP)
CPP - MAP - ICP
44
Coronary Perfusion Pressure (CoPP)
CoPP = DiastAorticP - RAp ## Footnote Diastolic aortic pressure Right atrial pressure
45
Normal circulating pressures
LA - 5-10 mmHg LV - 125-10 mmHg AO - 120-80 mmHg RA - 0-5 mmHg RV - 25-5 mmHG PA - 25-10 mmHg
46
Albumin Deficit
ALBd = 0.3 x 10 x Kg x (desiredALB - pALB) or 3 x Kg x (desALB - pALB) Products FFP - 3g/100mL Whole Blood - 1.4g/100mL HSA 25% - 25g/100mL CSA - 5g/100mL
47
Blood transfusion Calculations
Rule - 1ml/kg of pRBC raise 1% - 10mL/kg raise 10% 2ml/kg of Whole Blood raise 1% - 20ml/kg raise 10% Kg x 90 x (Desired PCV - Patient PCV) / Donor PCV Example - 20kg dog with PCV 15% pRBC PCV-80% Want to increase to 28% 20 x 90 x (28 - 15)/80 20 x 90 x 0.162 20 x 14.62 = 292.4
48
Bicarbonate deficit
BD = 0.3 x kg x (HCO3n - HCO3m) Give 1/4/-1/3
49
Simplified quantitative approach to acid-base analysis proposed by Hopper and Haskins (list contribution to Acid-Base + formula) Free water effect
FWE = (Nam - Nan) / 4 or dog = 0.25 x (Nam - Nan) cat = 0.22 x (Nam - Nan) Decreased free water = increased sodium = leads to alkalosis Increased free water = decreased sodium = leads to acidosis
50
Simplified quantitative approach to acid-base analysis proposed by Hopper and Haskins (list contribution to Acid-Base + formula) Chloride effect
CLe = CLn - CLc CLc = corrected CL CLm x (Nan/Nam) Low chloride promotes an alkalosis High Chloride promotes Acidosis
51
Simplified quantitative approach to acid-base analysis proposed by Hopper and Haskins (list contribution to Acid-Base + formula) Phosphate effect
Phe = (Phn - Phm) / 2 or 0.58 x (Phn - Phm) Increased phos promotes an acidosis Decreased Ph promotes alkalosis
52
Simplified quantitative approach to acid-base analysis proposed by Hopper and Haskins (list contribution to Acid-Base + formula) Albumin effect
ALBe = (ALBn - ALBm) x 4 or 3.7 (ALBn - ALBm) Low albumin promotes an alkalosis High albumin promotes acidosis
53
Simplified quantitative approach to acid-base analysis proposed by Hopper and Haskins (list contribution to Acid-Base + formula) Lactate effect
Le = -1 x lactate Hyperlactatemia promotes acidosis
54
Fractional Na Excretion
FNaE = (UNa x Pcr) / (PNa x Ucr) x 100 (UX x Pcr) / (PX x Ucr) x 100
55
Renal Clearance ## Footnote A non-steroidal anti-inflammatory drug (X) given to a 50kg animal has a concentration of 0.05mg/mL in the plasma and 1.8mg/ml in the urine. Assuming this animal is producing 100ml of urine/hr, the renal clearance of the drug X per minute is... (pay attention to the UNITS)
100mL/hr = 1.66 mL/min Renal Clearance = Urine Flow x Urine [] / plasma [] 1.66 x 1.8 / 0.05 = 60 mL/min
56
Renal Blood flow
RBF / (1 -HCT)
57
Renal Filtration Fraction
GFR / RBF normal about 20%
58
Renal filtered load
GFR x [plasma]
59
Renal excretion rate
Urine flow rate x [Urine]
60
Renal reabsorption rate
Filtered load - excretion rate
61
Secretion rate
Excretion rate - filtered rate
62
Resting Energy Requirement
RER = (30 x kg) + 70
63
Total Parenteral Nutrition calculations
Dog protein required: 4-5g/100 Kcal Cat protein requirement: 6-8g/100 Kcal Dextrose for 30-50% remaining calories (50% dex has 1.7 Kcal/mL) Lipid for 50-70% remaining calories (20% lipid has 2.0 Kcal/mL)
64
Acid-Base compensation for Metabolic Acidosis and Alkalosis
``` Metabolic Alkalosis (icr. HCO3) - expect resp. acidosis (icr. CO2) incr. CO2 by 0.7 mmHg for each icr. HCO3 of 1 mEq/L ``` ``` Metabolic Acidosis (decr. HCO3) - expect resp. alkalosis (decr. CO2) decr. CO2 by 0.7 mmHg for each decr. in HCO3 of 1 mEq/L ```
65
Acid-Base compensation for Respiratory Acidosis and Alkalosis
Respiratory Acidosis (incr. CO2) - expect Metabolic Alkalosis (incr. HCO3) Acute - incr of 0.15 mEq/L HCO3 for each incr CO2 of 1 mmHg Chronic - incr. of 0.35 mEq/L HCO3 for each incr. CO2 by 1 mmHg Respiratory Alkalosis (decr. CO2) - expect Metabolic acidosis (dedr. HCO3) Acute - decr of 0.25 mEq/L of HCO3 for each decr. CO2 of 1 mmHg Chronic - decr. 0.55 mEq/L og HCO3 for each decr. CO2 of 1 mmHg
66
Normal values for CO SV DO2 VO2 CaO2 OER SVR PVR MAP (dog/cat) A-a P:F Qs/Qt
CO = 100-200 mL/Kg/min SV = 9 mL/bet/min DO2 = 20-35 mL/kg/min VO2 = 4-11 mL/kg/min CaO2 = 19-21 mL/dL OER = 25% SVR = 0.5-0.8 mmHg/mL/kg/min PVR = 0.04 0.06 mmHg/mL/kg/min MAP dog = 80-120 mmHg cat = 100-150 mmHg A-a = \< 15 P:F - Normal 500 ALI \< 300 ARDS \< 200 Qs/Qt = \<5%

ECC Equations (1 decks)

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