Chapter 178 - Hemodialysis access - failing and thrombosed

Question 1

Urea clearance with dialysis normal value

Answer 1

1.2 Kt/V

K = urea clearance
t = duration of dialysis
V = urea distribution volume

Question 2

Typical high flow dialysis pump speed

Answer 2

350 ml/min

up to 500 ml/min

Question 3

AV access flow in relation to pump speed

Answer 3

must be several folds higher

usually 1000-1200 ml/min

Question 4

Causes of recirculation

Answer 4

1) venous outflow stenosis
2) Arterial inflow stenosis
3) poor cardiac output (with reduced preload after volume removed)
4) cannulation too close or inside pseudoaneurysms

Question 5

Areas of stenosis and intimal hyperplasia along a dialysis fistula

Answer 5

1) venous outflow anast: mismatch in size and compliance
2) puncture site
3) central under TOS

Question 6

Clinical signs of access failure

Answer 6

1) pick normal sized AVF - thrill good, pulse bad, nothing really bad
2) Collateral veins or edema
3) prolonged access bleeding

Question 7

Venous pressure measurements during dialysis steps

Answer 7

1) Dialysis pump turned off
2) circuit equilibrates
3) efferent (venous) needle used as static pressure
4) Pressure > 50% of MAP is abnormal
5) trend of increase over time is also important

Question 8

Flow measurement during dialysis steps

Answer 8

1) Transonic hemodialysis monitoron dialysis circuit
2) bolus of isotonic saline into blood stream to dilute blood and ultrasound velocity
3) sensor calculates flow rate
4) needles are reversed for flow
5) needles normal orientation for recirculation

Question 9

What flow rate will predict thrombosis in prosthetic access

Answer 9

600-800 ml/min

Question 10

KDOQI rule of 6

Answer 10

1) 6 mm from skin
2) vein diameter 6 mm
3) flow rate 600 ml/min

Question 11

Balloon inflation times for treating stenotic AVF

Answer 11

2-3 min

allow remodeling of the lesion to occur

Question 12

Benefit of cutting balloon

Answer 12

Utilize lower pressures to treat lesions - theoretically reduce amount of trauma to vein

Question 13

Causes of AV access thrombosis

Answer 13

1) inadequate inflow
2) inadequate outflow
3) pseudoaneurysm thrombosis

Question 14

Fogarty size for 6 mm graft

Answer 14

4F

Question 15

Percutaneous thrombectomy first described by

Answer 15

1984 Glanz

Question 16

Steps of percutaneous thrombectomy/thrombolysis

Answer 16

1) crossed sheath access around clot
2) balloon inflation to encompass whole clot
3) 2-4 mg tpa infusion
4) clot balloon plastied into pulmonary circulation or removed
5) mechanical thrombectomy
6) treat underlying disease
7) covered stent in outflow stenosis

Question 17

Mechanical thrombectomy devices

Answer 17

1) Angiojet
2) Arrow-Trerotola device
3) Hydrolyser