Indian Society of Extracorporeal Technology

Indian Perfusionists

  Login

Perfusion Tools

BSA Calculations formulae

  • Boyd: 0.0003207 (cm) 0.3 x (gm) 0.7285-0.0188log10 (gm)

  • Dubois: 0.20247 x Height (m) 0.725 x Weight (kg) 0.425

  • Mosteller: ([Height (cm) x Weight (kg)]/ 3600)1/2 Or v (Height (cm) x weight (kg)/3600)
    New (weight) BSA = (4xW+7) / (90+W)

  • Simple estimate: (H + W - 60) /100

  • Even more simple: (adults): W / 40

BSA Calculations formulae

  • EBF in adults: 1.8 - 2.8 x BSA (L/min/m2)

  • EBF in pediatrics: 2.4 - 3.2 x BSA

EBF from weight alone:

< 3 kg

200 cc/kg/min

3-10 kg

150 cc/kg/min

10-15 kg

125 cc/kg/min

15-30 kg

100 cc/kg/min

30-50 kg

75 cc/kg/min

50-75 kg

65 cc/kg/min

75-100 kg

60 cc/kg/min

>100 kg

50 cc/kg/min

Heat exchanger performance

Heat exchanger specifications are qualified by a "performance factor" defined as the difference of inlet (venous) and outlet (arterial) blood temps divided by the difference of inlet (venous) blood and inlet water temperatures.

The performance factor is frequently in the range of 0.4-0.7 at a device's maximum rated flow.

formula

Correction of Metabolic acidosis:

Sodium bicarbonate to be added = (kg wt) (0.3) (BE)/2

Correction of Potassium:

Potassium to be added = (kg wt) (0.3) (K diff)/2

K diff = desired K+ - actual K+

Lean Body Mass Calculations

Sometimes it is more accurate to perform calculations by using Lean Body Mass (LBM) rather than height, weight or BSA. The simplest way to calculate LBM using height and weight is the following set of equations developed by Hume:

  • Male LBM = ((0.32810 * (weight in kg)) + (0.33929 * (height in cm)) - 29.5336

  • Female LBM = 0.29569 *(weight in kg)) + (0.41813 * (height in cm)) - 43.2933

  • Example, the LBM for a male patient, weight: 85, Height: 175 is LBM = ((0.3281 x 85) + (0.33929 x 175)) - 29.5336 = 57.73 kg

Oxygen Dynamics

Formulae used in estimating the oxidative needs of the patient and adequacy of perfusion

  • 1 gm hemoglobin, fully saturated, carries 1.34 ml O2

  • The coefficient of solubility for O2 in blood is 0.003

Oxygen content

Oxygen content can be calculated for both venous blood and arterial blood. The difference between the two is important to understand oxygen consumption and extraction. Oxygen content is the sum of two means of oxygen transport in the blood i.e. oxygen that is carried on the hemoglobin and oxygen that is carried in the blood. The former accounts for the majority of oxygen transport. The calculation, using the values listed above in the chart is as follows

O2 content = (gm Hbg)(1.34 ml O2/gm Hbg)(% sat) + 0.003(pO2) = ml O2/dL

Note

The pO2 contributes very little to the oxygen content of blood, having little impact on arterial blood oxygenation. The PaO2 should be used more for assessing pulmonary (or oxygenator) gas exchange.

NOTE: The unit " ml O2/dL" is equivalent to "ml O2 %"

ABG data:

A/V

Q Bld

Sweep

FiO2

Temp

pH

pCO2

pO2

Sat

Hgb

HCO3

BE

Na+

Ca++

K+

Glu

A

4.8

2.9

70

36.4

7.41

42

293

100

8.5

26

1

144

1.0

4.6

110

V

4.8

2.9

70

36.4

7.34

48

45

76

8.5

26

1

143

1.0

4.6

111

Patient weight - 83 kgs

height - 177 cms

BSA -2.0 m2

For example, consider the above blood gas results. Calculate both the arterial and venous O2 contents and find the arterial-venous O2 difference (A-V O2 diff). Note that the saturation percentage gets converted to decimal format and, for convenience, we ill round off to two decimal points.

Art O2 content = CaO2 = 8.5(1.34)1 + 0.003(293)
= 11.39 + 0.88= 12.27 ml O2%

Venous O2 content = CvO2 = 8.5(1.34)(.76) + 0.003(45)
= 8.66 + 0.14= 8.67 ml O2%

Venous O2 content = CvO2 = 8.5(1.34)(.76) + 0.003(45)
= 8.66 + 0.14= 8.67 ml O2%

A-V O2 difference = CaO2 - CvO2 = 12.27 - 8.67 = 3.6 ml O2%

Formula to calculate A-V O2 diff in single equation is as follows:
A-V O2 diff = (gm Hgb)(1.34)(AO2sat - VO2 sat) + 0.003(ApO2 - VpO2)

Oxygen Delivery

Oxygen delivery (DO2) is the amount of O2 delivered per unit time.
DO2 = CaO2 x Q,

Where Q is blood flow (either cardiac output or arterial pump flow)

NOTE: If L/min is the unit of measure for flow, a factor of 10 will be used to convert everything to "mls".

For example using the above ABG data, the DO2 is calculated as:
DO2 = CaO2 x Q x 10= 12.27 ml O2% x 4.8 L/min x 10= 588.9 ml O2/min

Oxygen Consumption

Oxygen consumption (VO2) is the difference between what is delivered to the tissues and what is "left over" on the venous side per unit time. The equation is as follows:

VO2 = Q (CaO2 - CvO2)10
= Q (A-V O2 diff)10

example considering above ABG
VO2 = 4.8 x (12.27 - 8.86)10= 163.7 ml O2/min

Oxygen Extraction

Oxygen extraction ration (ER) is the ratio (percentage) of what is delivered to the tissues and what is utilised. ER is the ratio of oxygen consumption to oxygen delivery, both of which have already been calculated. Therefore, using above sample,

ER = VO2/DO2= 81.12/292= 0.28= 28%

NOTE: With the exception for coronary and diaphragm circulation, the rate of oxygen extraction will vary according to the needs of the tissues. For example, if blood flow drops off, extraction rate should increase in a compensatory mechanism. Likewise, if metabolic demand increases, extraction will likely increase especially if blood flow is unable to increase.

Normal ranges

Normal ranges for various components of oxygen dynamics. The normal ranges are for non-CPB patients but can be very useful in accessing the status of a patient on CPB.

Category

Normal range

Content (CaO2)

16-19 ml O2%

Delivery (DO2)

520-720 ml O2/min/m2

Consumption (VO2)

110-160 ml O2/min/m2

Extraction (ER)

22-32 %

Mixed venous pO2

33-53 mmHg

Mixed venous saturation

68-77 %


Normal oxygen requirements and flow requirements with reference to kg weight.

 

Required O2 Requirement

Required Flow

Adults

4 ml O2/min/kg

80 ml O2/min/kg

Pediatrics

9 ml O2/min/kg

100-180 ml O2/min/kg

How to estimate the adequacy of perfusion - Is it mean arterial pressure or Flows

Consider a Patient on CPB with MAP of 45 mm Hg, CVP of 4 is at a pump flow of 6 Lpm. Prepare the following information to assess whether flows are adequate.

Systemic vascular resistance (SVR) is important in accessing vascular tone, formula for calculating SVR is

SVR = (MAP-MRAP) 80/CO

where MAP = mean arterial pressure, MRAP = mean right atrial pressure and CO = cardiac output (L/min)
SVR = (45-4)80/6 = 547 dynes/sec.cm-5

Example shows that SVR is low meaning CPB flows are adequate inspite of low MAP.

Pulmonary vascular resistance (PVR) the resistance across the lungs can be calculated as:

PVR = (MPA - MPCWP) 80/CO
PVR = (13-9)80/6= 53 dynes/sec.cm-5

Normal levels

Index

Normal range

SVR

770-1500 dynes/sec.cm-5

PVR

20-120 dynes/sec.cm-5

Referernce Charts

Common index flows during cardiopulmonary bypass

Patient temperature (°C)

Bypass flow rate (L/min/m2)

≥35

2.4–3.5

32

2.2

30

2

28

1.8

26

1.6

24

1.4

22

1.2

20

1

<20

0.7

Typical tubing sizes with flow maximums

Tubing size

Max flow boot line in standard race way (mL/min)

Max flow arterial line (mL/min)

Max flow in venous line with gravity siphon drainage (ml/min)

Max flow venous line with assisted drainage (mL/min)

3/16″

1200

1500

600

800

1/4″

2100

3150

1800

2500

3/8″

4400

>3150

3750

>3750

1/2″

>4400

NA

>3750

>6000

Arterial cannulae for central aortic cannulation

Weight (kg)

Size (Fr)

Brand

Water chart flow (LPM)

<2.5

6

Medtronic DLP

0.4

2.5–4.5

8

Biomedicus

0.7

4.5–10

10

Biomedicus

1.3

10–14

12

Biomedicus

2.1

14–28

14

Biomedicus

2.8

25–35

16

Medtronic One-Piece

3.8

28–35

18

Medtronic EOPA CAP

2.6

35–50

18

Medtronic EOPA

4.8

50–75

20

Medtronic EOPA CAP

4.1

75–100

20

Medtronic EOPA

5.7

75–90

22

Medtronic EOPA CAP

5.4

>90

22

Medtronic EOPA

>6

>90

24

Medtronic EOPA

>6

Arterial cannulae for femoral cannulation

Weight (kg)

Size (Fr)

    Brand

Water chart flow (LPM)

 

 

 

 

<4.5

8

Edwards Lifesciences Fem-Flex

0.8

4.5–10

10

Edwards Lifesciences Fem-Flex

1.3

10–14

12

Edwards Lifesciences Fem-Flex

2

14–28

14

Edwards Lifesciences Fem-Flex

2.4

28–40

15

Biomedicus

3

40–55

17

Biomedicus

4

55–75

19

Biomedicus

5.3

>75

21

Biomedicus

6.5

Venous cannulae for bicaval cannulation

Weight (kg)

SVC (Fr.)

IVC (Fr.)

<3

12

12

3–6

12

14

6–8

12

16

8–12

14

16

12–16

14

18

16–22

16

18

22–30

16

20

30–34

18

20

34–46

18

20 or 22

46–58

20

22

58–75

20

24

75–100

22

24

>100

22 or 24

24 or 28

Water chart flow rates for select femoral venous cannulae

Weight (kg)

Size (Fr.)

Brand

Water chart flow (LPM)

<4.5

10

Edwards Lifesciences Fem-Flex

0.8

 

10

Biomedicus, 7.5″

0.7

4.5–10

12

Edwards Lifesciences Fem-Flex

1.25

 

12

Biomedicus, 7.5″

1.25

10–14

14

Edwards Lifesciences Fem-Flex

1.8

 

14

Biomedicus, 7.5″

1.75

14–28

15

Biomedicus, 30″

1.2

28–40

17

Biomedicus, 30″

1.7

40–55

19

Biomedicus, 30″

2.5

55–75

21

Biomedicus, 30″

3

75–90

23

Biomedicus, 30″

3.8

>90

25

Biomedicus, 30″

4.7

 

27

Biomedicus, 30″

5.5

 

29

Biomedicus, 30″

>6.0

Water chart flow rates for select venous cannulae

Venous Cannula

Size (Fr.)

Manufacturer

Water chart

flow (LPM)

12

 

 

 

Medtronic DLP angled metal

0.8

Medtronic DLP angled PVC

0.6

Medtronic DLP straight PVC

0.6

Terumo angled tenderflow

0.7

14

 

 

 

Medtronic DLP angled metal

1.6

Medtronic DLP angled PVC

0.8

Medtronic DLP straight PVC

0.8

Terumo angled tenderflow

1.1

16

 

 

 

Medtronic DLP angled metal

1.9

Medtronic DLP angled PVC

1.4

Medtronic DLP straight PVC

1.4

Terumo angled tenderflow

1.5

18

 

 

 

Medtronic DLP angled metal

2.6

Medtronic DLP angled PVC

1.8

Medtronic DLP straight PVC

1.8

Terumo angled tenderflow

2

20

 

 

Medtronic DLP angled metal

3

Medtronic DLP angled PVC

2.4

Medtronic DLP straight PVC

2.4

Terumo angled tenderflow

2.4

22

 

 

Medtronic DLP angled metal

3.7

Medtronic DLP angled PVC

3.1

Medtronic DLP straight PVC

3.1

 

24

 

Terumo angled tenderflow

2.7

Medtronic DLP angled metal

4.2

Medtronic DLP angled PVC

3.5

External arterial line filters

Manufacturer

Model

Maximum flow (LPM)

Prime volume (mL)

Pore size (µm)

Sorin

KiDS D130

0.7

16

40

Sorin

KiDS D131

2.5

28

40

Terumo

Capiox AF02

2.5

40

32

Sorin

D736

2.5

47

40

Sorin

D735

2.5

47

27

Pall

AL3

3

28

40

Medtronic

Affinity Pixie

3.2

39

30

Sorin

D731

6

100

27

Sorin

D733

6

100

40

Terumo

Capiox AF125X

7

125

37

Maquet

QUART

7

180

40

Terumo

Capiox AF200X

7

200

37

Medtronic

Affinity

7

212

20

Medtronic

Affinity

7

212

38

Pall

AL6

8

100

40

Pall

AL8

8

170

40

Sorin

D732

8

195

27

Sorin

D734

8

195

40

Pall

AV6SV

8

220

40

Example of equipment selection based on anticipated maximum pump flow rate.

Maximum Pump flows

Total circuit prime (mL)

Oxygenator with integrated 32 µm ALF

Primary tubing pack components

Milliliters of prime for oxygenator (O), reservoir (R), arterial limb (A), boot (B), venous limb (V), centrifugal venous head and tubing (CH)

Up to 1.2

 

 

215

 

 

Terumo Capiox FX05 rated

3/16 arterial

(O) 43, (R) 75, (A) 30, (B) 15, (V) 52

to 1.5 LPM

3/16 boot

 

 

1/4 venous

 

1.2–1.5

 

 

230

 

 

 

3/16 arterial

(O) 43, (R) 75, (A) 30, (B) 30, (V) 52

 

1/4 boot

 

 

1/4 venous

 

1.5–1.8

 

 

460

 

 

Terumo Capiox FX15-30

1/4 arterial

(O) 144, (R) 150, (A) 75, (B) 30, (V) 61

rated to 5 LPM (with

1/4 boot

 

assisted drainage)

1/4 venous

 

1.8–2.1

 

 

535

 

 

 

1/4 arterial

(O) 144, (R) 150, (A) 75, (B) 30, (V) 136

 

1/4 boot

 

 

3/8 venous

 

2.1–3.15

 

 

570

 

 

 

1/4 arterial

(O) 144, (R) 150, (A) 75, (B) 65, (V) 136

 

3/8 boot

 

 

3/8 venous

 

3.15–3.6

 

 

675

 

 

 

3/8 arterial

(O) 144, (R) 150, (A) 175, (B) 65, (V) 141

 

3/8 boot

 

 

3/8 venous

 

3.6–4.4

 

 

750

 

 

 

3/8 arterial

(O) 144, (R) 150, (A) 175, (B) 65, (V) 141, (CH) 75

 

3/8 boot

 

 

1/2 venous

 

4.4–5

 

 

775

 

 

 

3/8 arterial

(O) 144, (R) 150, (A) 175, (B) 90, (V) 141, (CH) 75

 

1/2 boot step up

 

 

1/2 venous

 

5.0–7.0

 

 

980

 

 

Terumo Capiox FX25 rated

3/8 arterial

(O) 250, (R.) 250, (A) 175, (B) 90, (V) 140, (CH) 75

to 7 LPM

1/2 boot step up

 

 

1/2 venous

 

Crystalloid solution properties

 

Plasma-Lyte A 7.4

Isolyte S 7.4

Normosol-R

Lactated Ringer’s

Hartmann’s solution

Sodium (mEq/L)

140

141

140

130

131

Potassium (mEq/L)

5

5

5

4

5

Magnesium (mEq/L)

3

3

3

0

0

Chloride (mEq/L)

98

98

98

109

111

Acetate (mEq/L)

27

27

27

0

0

Gluconate (mEq/L)

23

23

23

0

0

Phosphate (mEq/L)

0

1

0

0

0

Lactate (mEq/L)

0

0

0

28

29

Calcium (mEq/L)

0

0

0

1.5–3.0

2

Calculated osmolarity (mOsm/L)

294

295

295

273

279

pH range

 

6.5–8.0

7.0–7.8

6.5–7.6

6.0–7.5(though lactate metabolized by the liver can be alkalinizing)

5.0–7.0 (though lactatemetabolized by the liver can be alkalinizing)

Medications administered during bypass

table