Venous Cannula Flashcards
picking cannulas
you pick cannula size based on the FLOW you need, while standing under maximum pressure drop
Durometer
difference between the inner diameter and the outer diameter of the cannula/tubing
Durometer increases –> pressure increases –> volume decreases –> less compliance –> less flow
wired cannulas increase thickness of the wall
ribbon technology is flat –> decreases thickness of wall –> increases compliance –> increases flow
Aortic cannula
selection is based on calculated flow
if flow is < 5 –> use 7.0 mm (21 french)
if flow is > 5 –> use 8.0 mm (24 french)
the smaller the french, the higher the pressure drop.
cannula sometimes goes inside a graft
EX: axillary –> graft size will be in mm
can be curved or straight
Hemoglobin x 3 = HEMATOCRIT
Calculating French cannula size
mm x 3 = french cannula size
arterial cannulas
a) pressure drop maximum = 100 mmHg
1. Remember, arterial pressure is POSITIVE (pushing)
2. Pressure drops are tested with water; blood is more viscous –> more resistance –> slightly decreased flow
3. main sources of resistance are size of cannula (radius), length of tubing and systemic vascular resistance of the patient
b) side ports comming off arterial cannula can be used for different things
–> cerebral antegrade perfusion
–> direct arterial line pressure - closest pressure to the pressure in the aorta
anatomy of aorta
- aortic annulus around the valve
- Ascending aorta is composed of
I. sinus of Valsalva - where the coronary arteries branch from
ii. sinotubular junction - where aortic root aneurysm would be
iii. tubular ascending aorta - aortic arch consists of the 3 branches:
I. Innominate artery –> right common carotid and right subclavian artery
ii. Left common carotid artery
iii. Left subclavian artery - ligamentum arteriosum - small fibrous remnant of the fetal ductus arteriosum
- Descending aorta
I. Thoracic aorta - from the aortic arch to the diaphragm
ii. Abdominal aorta - from the diaphragm to the bifurcation of the common iliac arteries
Ascending aorta
is used in most procedures for arterial cannula placement
must be healthy meaning –> needs a competent aortic valve
contraindications for ascending aorta cannulation:
1. Porcelain aorta - excessive calcification of the aorta; can be seen on TEE or palpated by surgeon
2. anatomically short ascending aorta that doesn’t have enough length for cannulation and the cross calmp
cannulating the aorta steps:
- Purse string sutures are placed on the ascending aorta
–> I. two separate sutures placed in a circle, going opposite directions –> DRAWSTRING EFFECT
–> ii. purse string sutures are used for arterial cannula, venous cannula, CPG cannula and vents - Tourniquets(bumper) hold the sutures
I. don’t lose the sutures
ii. keeps tight tension on the sutures
iii. rubber stopper on top or suture is knotted to prevent loosening - systolic pressure is dropped below 100 mmHg
- stab incision is made inside of the purse string sutures
- aortic cannula inserted
- tourniquets snared down
- pressure goes back up
reasons to use Femoral artery cannulation
- if there is an aortic dissection or aneurysm
- porcelain aorta or any reason that makes aorta cannulation undesirable
- sometimes used prophylactically as defense/preventing - achieve arterial flow prior to sternotomy
- reentry sternotomy/re-op –> significant scar tissue, heart is stuck to sternum –> femoral artery us used to go on by pass –> it decompresses the heart and moves away from the sternum –> surgeon can perform a sternotomy
risks of femoral cannulation
- Dissection of the arterial wall extending to the entire aorta after blood is perfused through the cannula
- Limb ischemia
–> a) oxygenated blood is flowing RETROGRADE (from lower body to the head)
–> b) Distal limb perfusion is used during ECMO (long periods of time)
Different methods of doing femoral cannulation (artery or vein)
–> femoral cannulation (artery or vein) must be a straight cannula
Femoral cannulation must be BELOW inguinal ligament
–> above the inguinal ligament is the retroperitoneal space
–> if the artery dissects above the inguinal ligament then the pt will bleed into their abdomen (retroperitoneal bleed)
- Open femoral artery cannulation - purse string sutures hold cannula in place
- Percutaneous (closed) - through the skin, using seldinger technique
i. “ Temponaded off” - leaking blood fills compartment and “tomponades itself” meaning the accumulated blood in the space clsed the hole where it was leaking from –> if you open this space then it will start bleeding again
Fem-fem VV ECMO
- bullet tip cannula goes into right femoral vein and sits in the RA
- Multistage cannula goes in the left femoral vein –> crosses over –> IVC –> sits at the junction of the IVC and RA
- there needs to be good spatial relationship between the two cannulas to avoid sucking back oxygenated blood to the ECMO circuit
axillary artery
i. must be done open (purse string) and w/ a side graft - CANNOT be done via Seldinger technique
1. graft allows for dispersion of flow
2. cannula goes inside the graft
ii. must be a straight cannula
Advantages of cannulating axillary artery
- arterial return can be established prior to the sternotomy
- antegrade flow (forward natural flow) –> less likely to cause cerebral atheroembolization
- Perfusion of the right common carotid artery can be continued with the aortic arch open when the arch repair is complex and time consuming
–> allows antegrade cerebral perfusion
Reasons to use axillary artery over femoral artery
if the transverse (aortic arch) and descending aorta has atheroma (fatty material that forms plaques in the arteries) that may embolize into the brain with retrograde flow from the femoral cannula
risks of cannulating axillary artery
High risk bleeding: small artery, small cannula, high flow, high pressure –> if you’re losing blood then ask surgeon how the axillary site is
Venous cannulas
a) Pressure drop maximum = 50 - 80 mmHg
I. REMEMBER venous pressure is NEGATIVE (vacuum/suction)
ii. if you go above 80 mmHg for venous cannula in addition to using vacuum assisted venous drainage, you are risking collapsing the cannula and stopping venous return to the circuit
b) better drainage out of metal tip than plastic tip because they have LESS COMPLIANCE
I. Adding positive pressure to something w/ compliance makes it expand/ open
ii. adding negative pressure to something w/ compliance makes it collapse
c) purse strings
I. if purse strings are not tight enough then air can be entrained (sucked in) - this is an example of VENTURI EFFECT (we do NOT purposefully use venturi on our circuit)
1. you can only get a venturi effect on the NEGATIVE pressure side
2. if enough air gets in the venous line and you’re not using assisted vacuum drainage –> you can get an airlock in the venous tubing and will need to walk the air out
Single Dual-stage (cavoatrial) Venous Cannulation
i. Purse string + tourniquet
ii. cannulated through right atrial appendage
iii. Upper basket (holes) sits in RA and lower basket sits in IVC
iv. Wider portion sits in the RA
v. narrower tip sits in IVC
vi. used for operations in which you do NOT open the right side of the heart (prevent air entrainment); these operations include
1. CABG - coronary artery bypass graft
2. AVR - aortic valve replacement
3. Left atrium approach for a mitral valve replacement
4. Aortic root replacement
5. LVAD
advantages and disadvantages of using dual stage
Advantages:
faster, less traumatic due to single incision in the RA Appendage
Disadvantages:
adequacy of drainage is interfered during manipulation of the hear (I.e. “circumflex position” when lifting the heart to make an anstomosis to the posterior branches of the circumflex coronary artery) –> decreased venous return
Bicaval (2 single stage) venous cannulation
i. Purse string sutures + tourniquette + snaring off the SVC and IVC from the RA
- why? –> we need to snare the cannulas off so we DONT entrain air
- surgeon should always tell you when they’re snaring and you need to be watching your venous return volume
- improper snaring –> possible air entrainment
- improper placement of cannula –> decreased venous return
- cerebral oximetry is used to determine if decreased venous drainage is from the SVC (decreased cerebral oximetry) or IVC (no change in cerebral saturation)
ii. Typically straight cannula in the IVC and a right angle cannula in teh SVC; depends on surgeon preference
–> can be 2 right-angle cannulas
–> can be 2 malleable cannulas, etc.
- The LARGER cannula always goes in teh IVC (drains 2/3 of the body)
what surgeries are single dual-stage cannulas used for?
vi. used for operations in which you do NOT open the right side of the heart (prevent air entrainment); these operations include
1. CABG - coronary artery bypass graft
2. AVR - aortic valve replacement
3. Left atrium approach for a mitral valve replacement
4. Aortic root replacement
5. LVAD
What surgeries are bicaval (two single-stage) cannulation used for?
used for ANY surgery that requires the RIGHT side of the heart to be opened:
- ASD
- VSD
- right atrium approach for a mitral valve replacement (transeptal approach)
- TVR - tricuspid valve replacement
- PVR - pulmonary valve replacement
- OHTX - open heart transplant
- PTE - pulmonary embolism
- RVAD/BIVAD - right ventricular assist device/biventricular assist device
reasons we would use femoral venous cannulation
- quick access into the patient and heart for decompression of the heart (re-op)
–> EX: femoral venous cannulation to drain IVC and central cannulation of SVC - Emergencies
- Surgeries where access to normal cannulation is impaired
–> structural issue on the right side of the heart - minimally invasive surgeries
- Thoracoabdominal aortic aneurysms
Femoral venous cannulation (peripheral cannulation)
adequate flow rates using peripheral cannulation require a cannula as large as possible and advancing the catheter into the RA guided by TEE (transesophageal echocardiography); TEE can see the junction of the IVC into the RA
1. Percutaneous method –> look for guide wire
2. open method –> look for cannula
Seldinger technique
a) Done percutaneously
b) seldinger technique is used for either femoral arterial or venous cannulation
c) steps:
i. vessel is found on ultrasound or palpated - longest part of process
ii. Attach needle to syringe –> stick vessel –> flash of blood –> take syringe off
- traditional seldinger technique is when the needle goes into the vessel (no syringe), you get a flash of blood and then you push the needle through the other side of the vessel and then pull it back to the lumen of the vessel
- now that we use a syringe, when the needle is in the lumen of the vesssel and you have a flash of blood then you ca pull back with the syringe to make sure youre patent in the vessel
iii. take syringe off –> venous blood will drip out of needle, arterial blood will squirt out of needle
iv. wire goes thorugh needle
v. when the wire is in the appropriate vessel then the needle comes out
vi. now you have a wire through the skin → you may need to cut the skin with the scalpel slightly to get the first dilator over the wire and into the vessel
vii. you keep increasing the size of the dilator until oyu reach the size you need
viii. cannula goes in, wire comes out, blood comes out with the wire and you clamp the cannula to stop the bleeding
ix. the cannula is sewed to the skin (no purse string)
Cut-down (open technique)
a) artery or ein is exposed
b) direct cannulation
c) must use purse strings to hold cannula in place
insertion kits
a) sledinger technique
b) typically arterial cannulas do not come pre-packaged in an insertion kit, so you’ll need a separate insertion kit
c) insertion kits usually contain similar items:
I. Needle
ii. Syringe
iii. wire
iv. scalpel
v. dilators - must be close in size to your cannula
–> EX: arterial cannula is 20 F then dilator should at least 18 F
cardioplegia cannulas and coronary arteries
- antegrade cardioplegia delivery - *you can only give CPG antegrade when a cross-clamp is on
a) CPG cannula (needle) in the aortic root - requires competent aortic valve; requires an aortic root pressure (coronary artery perfusion occurs at diastolic pressure –> 70-80 mmHg
c) flow path (natural forward flow): coronary ostia in the aortic root –> coronary arteries –> coronary veins –> thebesian veins and coronary sinus drain into the RA
preferred technique when aortic valve is competent
- if there is aortic INSUFFICIENCY (incompetant aortic valve) then there wont be enough pressure generated in the aortic root for CPG to enter the coronary ostia
- you can give antegrade CPB with mild aortic valve stenosis
III. During procedures on the ascending aorta, you may start with a ntegrade CPG and then switch to retrograde CPG for the subsequent doses
using Antegrade CPG w. bicaval cannulation
if antegrade CPB is used w. bicaval venous cannulation then you need a way to drain the CPG from the RA in order to prevent RV from distending/strething –> the surgeon will open the RA and use a sucker to drain the remaining CPG
i. the bicaval venous cannulas must be completely snared
ii. frank-starling law: when actin and myosin filaments are no longer in contact and stretched beyond tehir limits then they cant come back together and no longer are able to contract
- this is especially important in pts with right sided heart failure
using antegrade CPG with single dual-stage venous cannulation
Cardioplegia that drains into the RA will be returned to the venous reservoir
Coronary ostial perfusion cannula (“hand held” device)
does NOT require competent aortic valve, can be used when there is AI; does NOT require an aortic root pressure
I. another method of delivering antegrade cardioplegia
ii. surgeon holds the canula directly in the coronary ostia
ii. if diastolic pressure of coronary artery perfusion is 80 mmHg then each coronary artery (L&R) gets 40 mmHg –> if CPG Vanguard is a doctor of 3 then your system (back) pressure is 120 mmHg for each coronary artery (3 x 40 mmHg =120 mmHg)
iii. surgeon may want to increase pressure (flow) if there is coronary artery stenosis
retrograde cardioplegia delivery
“deliver low and slow so you dont burst the CS”
a) preferred when there is coronary artery disease (CAD) with high grade stenosis, aortic valve or aortic root disease, mitral valve disease or during operations on the ascending aorta (including aortic root or sinus of valsalva)
b)Retrograde CPG cannula has a BALLOON/ cuff tip to occlude the opening of the coronary sinus –> forces CPG flow into the coronary sinus and coronary vessel be of the heart
I. the cannula sits in the RA w/ the balloon tip sitting in the opening of the coronary sinus. the tip of the cannula is pointed into the coronary sinus OSTIA to allow CPG flow into the coronary sinus
ii. Self inflating balloon - activated by blood flow, such that pts blood fills the balloon
iii. Saline filled ballon (manual) - surgeon introduces saline into the ballon to inflate it
1. ***ballon is NEVER filled with air
Flow path (backward flow) of retrograde CPG
Coronary sinus ostia (in the RA) and thebesian veins –> coronary sinus –> coronary arteries –> coronary ostia into the aortic root –> drains into LA and LV bc the heart is arrested/ floppy valves/ no pressure in aortic root
LV vent
you need an LV vent when using retrograde cardioplegia –> b/c the CG will drain from the aortic root into the LV since the heart is arrested
I. LV vent enters the Right Superior pulmonary vein –> left atrium –> left ventricle
ii. LV vent is placed before CPG is given while the heart is beating
iii. Heart must be full when lv vent is placed or else you’ll have a venturi effect (sucking air)
a. Purposes: prevention of LV distention and de-airing the ventricle when closing the heart
i. Air that goes into LV vent will go to cardiotomy
ii. During de-airing of the heart they fill the heart and put the pt in Trendelenburg
b. Looks similar to a basket venous cannula
c. LV vent is placed in superior pulmonary vein
d. Heart must be filled w/ blood to avoid entraining air when LV vent is inserted and removed
e. Connected to a sucker
f. You cannot turn the LV vent too high → negative pressure inside the ventricle will cause
air to be entrained through the purse strings into the LV (Venturi effect) → when the heart ejects it will pump the air to the patient
i. You get venturi before you get cavitation (excessive negative pressure causes ventricle to collapse on cannula → release of gas bubble from solution)
Coronary sinus pressure
should be < 40 or 30 mmHg
I. if you want coronary sinus pressure to be 30 mmHg, what should your system (back) pressure be?
ANS: 90 mmHg
1. 30 mmHg x 3 = 90 mmHg
clear crystalloid CPG
If “clear” crystalloid CPG is given in large amounts you have to think about where it’s returning to
based on you’re CPG delivery and sucker/vent system
a. Large amounts of clear CPG will cause hemodilution if returned to the venous reservoir
i. You can add a Y-connector in your circuit to divert the clear CPG return to a bag or cell saver
b. Small/normal amounts of clear CPG can be diverted to the hemoconcentrator, which will remove the CPG and then enter the cardiotomy
back pressure or system pressue vs direct pressure
a) Back (system) pressure includes the pressure in the tubing circuit, oxygenator, cannula,
CPG delivery system, etc. → in Joe’s circuit the direct patient pressure (aortic root or
coronary sinus) is a
factor of 3
of the system pressure, ex: aortic root pressure is 80
mmHg and system pressure is 240 mmHg
b) In a centrifugal pump when pressure drops and RPM stays constant → flow increases i. When pressure increases and RPM stays constant → flow decreases
c. If your circuit doesn’t change (Vanguard, length of tubing and size of tubing) and your system pressure increases then the main source of new resistance would be a change in blood viscosity
i. Vanguard - CPG delivery device
d. You need to figure out what your system pressure needs to be in order to deliver the
correct pressure to the aortic root and coronary sinus
i. System pressure depends on your oxygenator, circuit tubing length and radius, CPG delivery device, cannula, etc.
weighted sump suckers
sits behind the pericardium and suck blood back to the pump
Weighted suckers - sits in the pericardium behind the heart; blood from weighted suckers can
go back to our circuit because the blood was not stagnant
○ Stagnant blood (sitting for 20-30 min) needs to go to the cell saver
multi-perfusion/multi-plegia devices/ “cardioplegia octopus”
a. Blue → retrograde
b. Red → antegrade
c. CPG can be delivered in the vein graft during a CABG
d. The cardioplegia octopus gives the surgeon the ability to deliver CPG through different
routes throughout the surgery
i. If they switch the delivery route of CPG they have to communicate that w/ the
perfusionist because your pressure readings will be different based on the route
1. antegrade CPG - 80 mmHg
2. retrograde CPG - 30 mmHg
CPG protects the heart, cold blood pretects the brain …What protects the lungs?
High oncotic pressure / edema management
○ Lungs are like a sponge and will collect all the water - we don’t want this
■ When the lungs get wet this is now a barrier for gas exchange
■ “Pump lung” - difficulty coming off ventilator due to wet lungs
○ High oncotic pressure (i.e. give albumin) will cause water to stay in the vasculature
