Exam 6 - Venous Cannulation and Return Flashcards
1
Q
How much venous return from vena cava
A
- 1/3 from SVC
- 2/3 from IVC
2
Q
Siphon drainage (gravity)
A
- reservoir must be below patient
- lines filled with just fluid
- return depends on: CVP, height of gradient, resistance of cannula/connectors/lines
- gradient of 30-40 mmHg is normal (remember 100 in arterial cannulas)
3
Q
Venous cannulas
A
- made of plastic and either straight or right angled
- single stage or two stage (cave-atrial) (sometimes 3)
- wire reinforced
- want optimal ID to OD ratio
- narrowest point in CBP venous system (limiting factor of drainage)
4
Q
Venous cannulation sites
A
- single in RA (usually just PEDS)
- Bicaval of SVC and IVC (mitral valve repair)
- Dual stage of RA and IVC (most common, CABG, AVR)
- Femoral (Redos and minimally invasives)
5
Q
Two stage
A
- Single cannula into RA through appendage
- tip drains IVC and top part drains RA (coronary sinus, SVC)
- Goods: simple, fast, good right heart decompression, less trauma
- Bads: sensitive to positioning, can lead to poor drainage
6
Q
Two stage process
A
- venous cannula placed AFTER arterial cannula
- purse strings in R auricle
- cut tip of aurical
- insert cannula
- tighten purse strings
- fill cannula w/ fluid
- connect cannula to pump venous line
- clamp tubing to drapes
7
Q
Bicaval venous cannulation
A
- separate cannulation of SVC and IVC
- Incision through RA or directly into vena cava
- caval tapes often used (diverts blood away from right heart)
- caval occlusion is TOTAL BYPASS (only in bicaval)
- Goods: good drainage, best myocardial protection, total bypass
- Bads: slower to cannulate, difficult, less right heart decompression
8
Q
Femoral venous cannulation
A
- emergency bypass, redos, minimally invasives
- want largest cannulation possible (more flow)
- inserted with aid of TEE
- will most like need vacuum or kinetic assist
9
Q
Persistent LSVC
A
- 0.3-0.5% of pop
- 2-10% of patients with congenital heart disease
- two SVC’s
- RSVC usually drains into coronary sinus
10
Q
Problems with persistent LSVC
A
- bad for PA catheter
- bad for retrograde cardioplegia (leaks into RA)
- probs for bicaval cannulation
- surgeon can occlude or cannulate LSVC
11
Q
Complications getting venous return
A
- atrial dysrhythmias
- laceration/bleeding atrium
- laceration of vena cava
- bad position of cannula tips
- displacement of PA catheter
12
Q
Causes of low venous return
A
- decrease in venous press. (drugs, venodilation, hypovolemia)
- bad cannula position
- kinks/clamps in venous line
- air lock
- too small cannula
13
Q
Venous chatter
A
- catheter draining too fast
- drainage holes blocked by RA tissue
- causes sporadic changes in venous flow
- makes it hard to sew…heart is moving
- fix by: decrease height gradient, partially occlude venous line, decrease vacuum
14
Q
Venous cannula performance determined by:
A
- size
- design
- placement
- ability to drain (gravity, vacuum)
15
Q
Pressure generated by height difference
A
- 1 mmHg every 13.6 mm
16
Q
Advantages of VAVD
A
- smaller cannulas and venous lines
- maintains empty heart (myocardial protection)
- longer cannulas for peripheral access
- allows use of femoral cannula
17
Q
When we use VAVD
A
- femoral cannulation
- minimally invaisves
- unprimed venous lines
- small height diff
- small prime circuits
- PEDS
- maybe every case (surgeon/site specific)
18
Q
Methods of augmented venous return
A
- roller pump
- kinetic assist
- vacuum
19
Q
Roller pump assist drainage
A
- shunt is partially clamped to prevent too much negative press.
- pressure monitored 10 cm before roller pump
- pressure should not exceed -60 to -100 (including 30-40)
- rarely used
20
Q
Kinetic assist
A
- shunt is completely clamped
- pressure monitored 10 cm before
- pump speed is 1000-1200 rpm
- pressure should not exceed -60 to -100
21
Q
VAVD
A
- no need for second pump
- vacuum on AFTER initiation of CPB
- set regulator to 20-40 mmHg
- Pressure measured IN hard shell reservoir
- need pressure relief valve
- venous reservoir open to atmosphere when vacuum not in use
