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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 = 217K = 1.3 *50/240 *1000 = 270
Pump speed vs. clearance with F-80 dialyzerPS = 400; Blood Flow = 360; K = 270
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 = 1.6 *(40/270)*1000 = 237 min
K = 1.6 *(40/240) *1000 = 267K = 1.6 *(50/240) *1000 = 333
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
6/10/1999 Mansfield, MA
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
6/10/1999 Mansfield, MA
Tip in right brachiocephalic
vein
6/10/1999 Mansfield, MA
Tip in rightbrachiocephalic
vein
6/10/1999 Mansfield, MA
Catheter tip in the mid-SVC
6/10/1999 Mansfield, MA
Tip in right atrium
6/10/1999 Mansfield, MA
Inflow in left brachicephalic vein
Outflow in SVCagainst the wall
6/10/1999 Mansfield, MA
Inflow against wall
Outflow tip
6/10/1999 Mansfield, MA
Tip low in atrium
6/10/1999 Mansfield, MA
Tip in the mid right atrium
6/10/1999 Mansfield, MA
Tip close toinferior vena
cava
Opti-Flow
6/10/1999 Mansfield, MA
Tip in right
ventricle
6/10/1999 Mansfield, MA
Tip in right
ventricle
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
6/10/1999 Mansfield, MA
FibrinSheath
Formation
6/10/1999 Mansfield, MA
FibrinSheath
Formation
Inflow tip occluded
6/10/1999 Mansfield, MA
FibrinSheath
Formation
Inflow tip occluded
6/10/1999 Mansfield, MA
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
6/10/1999 Mansfield, MA
Ball thrombus removed with catheter
6/10/1999 Mansfield, MA
Ball thrombus, closer view