6/10/1999 Mansfield, MA Approximate calculation of needed pump speed (PS) t = Kt/V * V/K * 1000 K = Kt/V *V/t*1000 t = 1.3 *40/300*1000 = 173 min K = 1.3 *40/240 *1000 = 217 K = 1.3 *50/240 *1000 = 270 Pump speed vs. clearance with F-80 dialyz PS = 400; Blood Flow = 360; K = 270
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6/10/1999Mansfield, MA Approximate calculation of needed pump speed (PS) t = Kt/V * V/K * 1000 K = Kt/V *V/t*1000 t = 1.3 *40/300*1000 = 173 min K = 1.3.
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Pump speed vs. clearance with F-80 dialyzerPS = 400; Blood Flow = 360; K = 270
6/10/1999 Mansfield, MA
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
Q p r
4
8L
Poiseuille’s equation
Flow in catheters is directly proportional to the pressure difference and the 4th power of thelumen 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)
6/10/1999 Mansfield, MA
Negative Pressure (mm Hg)
-400 -300 -200 -100 0
Blo
od
Flo
w (
ml/m
in)
0
100
200
300
400
500
600
SNIJ Flush TipSNIJ StaggeredPermCathAccess Cath MedcompSoft Cell Vas Cath
SNIJ - linear regression
Others - linear regression
SNIJ: y = -1.78x + 0.33 r
2 = 0.92
Others: y = -1.15x + 42.2
r2 = 0.95
6/10/1999 Mansfield, MA
6/10/1999 Mansfield, MA
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 rightbrachiocephalic
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 SVCagainst 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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Tip close toinferior vena
cava
Opti-Flow
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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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FibrinSheath
Formation
6/10/1999 Mansfield, MA
FibrinSheath
Formation
Inflow tip occluded
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FibrinSheath
Formation
Inflow tip occluded
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FibrinSheath
Formation
Both tips occluded
6/10/1999 Mansfield, MA
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