Approximate calculation of needed pump speed (PS)

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Approximate calculation of needed pump speed (PS)
t Kt/V V/K 1000
t 1.3 40/3001000 173 min
K Kt/V V/t1000
K 1.3 40/240 1000 217 K 1.3 50/240 1000
270
Pump speed vs. clearance with F-80 dialyzer
PS 400 Blood Flow 360 K 270
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Approximate calculation of needed pump speed (PS)
t (Kt/V) (V/K) 1000
t 1.6 (40/270)1000 237 min
K (Kt/V) (V/t)1000
K 1.6 (40/240) 1000 267 K 1.6 (50/240)
1000 333
Pump speed vs. clearance with F-80 dialyzer
PS 400 Blood Flow 360 K 270
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Blood flow through the catheter

• Design
• Length
• Diameter
• Cross section
• Tip location
• Tip occlusion
• Fibrin sheath
• Ball thrombus
• Mural thrombus

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Catheter design
Poiseuilles equation
Flow in catheters is directly proportional to
the pressure difference and the 4th power of
the lumen radius, and inversely proportional to
the lumen length and the viscosity of fluid
(blood)
In lumens deviating from circular, resistance is
higher (flow is lower at the same length and
cross section)
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Tip location

• The best tip location is at the superior vena
  cava/right atrium junction
• Flows are usually worse with other locations

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Tip in right brachiocephalic vein
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Tip in right brachiocephalic vein
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Catheter tip in the mid-SVC
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Tip in right atrium
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Inflow in left brachicephalic vein
Outflow in SVC against the wall
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Inflow against wall
Outflow tip
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Tip low in atrium
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Tip in the mid right atrium
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Opti-Flow
Tip close to inferior vena cava
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Tip in right ventricle
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Tip in right ventricle
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Tip occlusion

• Fibrin sheath (sleeve) - probably on all
  catheters
• Asymptomatic
• Poor or no inflow when involving catheter tip
• Ball thrombus
• A large clot adherent to the catheter tip but not
  to the vessel wall.
• Difficult to dissolve, can be stripped
• Mural thrombus
• A large clot adherent to both catheter and vessel
  wall and causing partial or complete occlusion of
  the vessel

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Inflow tip occluded
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Inflow tip occluded
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Both tips occluded
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Tip occlusion

• Fibrin sheath (sleeve) - probably on all
  catheters
• Asymptomatic
• Poor or no inflow when involving catheter tip
• Ball thrombus
• A large clot adherent to the catheter tip but not
  to the vessel wall.
• Difficult to dissolve, can be stripped
• Mural thrombus
• A large clot adherent to both catheter and vessel
  wall and causing partial or complete occlusion of
  the vessel

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Ball thrombus removed with catheter
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Ball thrombus, closer view