test 7 Flashcards
Normal right ventricle blood return
- systemic venous return
- coronary sinus drainage
- +/- small cardiac vein(s)
- cardioplegia
- thebesian veins
Normal left ventricle blood return
- bronchial circulation
- cardioplegia
- thebesian veins
Abnormal right ventricle blood return
-persistent left superior vena
cava (LSVC)
-atrial / ventricular septal
defects
Abnormal left ventricle blood return
-patent ductus arteriosus (PDA)
-systemic-to-pulmonary artery shunt
-anomalous systemic venous drainage to left heart
-aortic insufficiency
-atrial / ventricular septal
defects
bronchial circulation
- provides nutritional flow to lungs
- 1-3% of CO
- can go as high as 10% CO with lung problems
- bronchial veins empty into pulmonary veins
small cardiac veins
- usually empty into coronary sinus
- might empty into RA, middle cardiac vein, or never develop
Cardioplegia antegrade
- left coronary drains into coronary sinus and the right atrium
- right coronary drains into RA by small cardiac veins
- some flow return to all chambers by thebesian veins
cardioplegia retrograde
- most empties into artic root via left coronary ostia
- really bad job of protecting the heart
Persistent left superior vena cava
- normally drains into right coronary sinus
- occurence: 0.3% to 0.5% of general population and 2-10% of patients with congenital heart disease
problems associated with LSVC
- procedures requiring opening of right heart and use of bicaval cannulation with tapes
- delivery of retrograde cardioplegia: proper position of balloon in coronary sinus, delivery of solution up LSVC rather than coronary sinus, and dilution of solution by LSVC return
LSVC results from
1) Failure of the L. brachiocephalic vein to fully develop
2) Failure of the left common cardinal vein to disappear during development
systemic to pulmonary artery shunts
- Blalock-Taussig shunt= transected right subclavian artery connected to right pulmonary artery
- Waterston= posterior ascending aorta connected to anterior right pulmonary artery
aortic insufficiency
-Not a problem as long as heart beating
-Placement of cross-clamp stops regurgitation
from arterial cannula
-Can occur during cardioplegia delivery: indicated by low delivery pressure into aortic root
-Can result in significant left ventricular
distension in fibrillating or arrested heart
Ventricular venting: purpose
-Prevent ventricular distension (and all the “bad” that goes with it!) -Improve surgical exposure -Aid in myocardial protection -Remove air -Prevent pulmonary venous hypertension
myocardial protection by decompression
-Accounts for approximately 40% of myocardial protection
-Reduces wall tension and myocardial stretch – reduces RESTING oxygen
consumption
myocardial protection by increased subendocardial perfusion
-Normal coronary perfusion pressure (CPP) = mean arterial (MAP) minus left
ventricular end diastolic (LVEDP)
-With cross-clamp applied and antegrade delivery of cardioplegia CPP = aortic root pressure – LVEDP
-with left ventricle empty LV coronary perfusion is optimal
myocardial protection by preventing myocardial rewarming
- Hypothermia accounts for approximately 10% of myocardial protection
- By removing systemic return to heart, heart stays cool
air removal
-Large quantities may arise during intracardiac
operations
-Venting aids de-airing upon closure of incision
into heart but before cross-clamp removal
-Small amounts may be introduced during
coronary bypass procedures
concerns with venous cannulation and blood return
- Venous cannulation must collect all return from: superior vena cava, inferior vena cava, coronary sinus
- Bicaval cannulation with snares/tapes- cannot collect coronary sinus return
- Improper placement of cannula
- Inadequate cannula size
- Inadequate height (siphon) gradient (∆P)
vent locations
- aortic root
- right superior pulmonary vein
- main pulmonary artery
- apex of left ventricle: very dangerous (not used much to at all anymore)
venting aortic root description
-Small bore catheter direct into the aorta
-May be wyed into catheter along with antegrade cardioplegia
delivery line
venting Right superior pulmonary vena cava description
-Can be Advanced across mitral valve into LV or left in LA
venting Main pulmonary artery description
-Tends to interfere with the pulmonary artery monitoring catheter
venting Apex of left ventricle description
-Problems associated with direct cannulation of the left ventricle
-Surgeon may insert a 27 gauge needle into apex for temporary
use to remove air stuck in the apical area
Root vent with antegrade cardioplegia needle
- Vent must be off during cardioplegia delivery
- Able to remove some air in the ascending aorta prior to cross-clamp removal or even as air is ejected from the left ventricle (remember, air rises and the aorta’s a tube…)
Left ventricular vent
Pliable with multiple fenestrations (openings) to aid blood removal and limit risk of sucking tissue into catheter
mechanical drainage
-Via roller pump
-Always best to include one-way valve in return line to
minimize chance of pump air into heart
Can use higher pump RPMs if:
-Use a vacuum relief valve – opens if too much vacuum applied – prevents pulling ventricular tissue into catheter tip = “Endocardial hickies” (can be part of one-way valve or separate)
-Must use low pump RPMs if no relief value used
-Best to monitor LA pressure
-Always a good idea to “run
your CP to your vent”
ahead of time because you don’t want to send bubbles to aorta
gravity drainage: “Y’ vent line into venous return line
Venous return blood passing opening of wye connector creates Venturi Effect
- Usually done at the table – shorter line with less resistance to flow
- Vent line needs to be primed to reduce chance of venous air lock
- Surgeon controls vent (on versus off) at field)
gravity drainage: normal vent line
-Procedure: fill vent line with couple turns of roller pump and remove line from pump to allow gravity pressure gradient to move fluid from
heart to the reservoir
-May not adequately drain heart if large amounts of return
-May need to use larger bore tubing for vent line
cardiotomy/ pump suction
-Blood from the field that is returned to the CPB circuit during bypass, or an autotransfusion reservoir pre- and post-CPB
-Large amount of air-blood interface can will
lead to hemolysis and potential micro air
emboli: Use of separate cardiotomy filter has been shown to reduce # of air emboli.
blood collected in chest
- typically has elevated
concentrations of activated humoral elements
including”: Coagulation factors (tissue factor), Endotoxin, Complement, Interleukins
-Profound drop in arterial blood pressure often seen
when cardiotomy suction blood is directly infused into
patient
cardiotomy suction using cell saver
- Reduction in post-operative bleeding when stagnant chest blood is washed and filtered prior to reinfusion
- Reduction in cerebral fat emboli and stroke rate by eliminating chest blood return via pump suckers
cell saver guidlines
-Use collection reservoir with a built-in 40 to 150 micron filter
-Vacuum attached to collection reservoir should not exceed -120 mmHg
-An anticoagulant drip must be used
-Washed product should be returned to the patient through a
transfusion filter
-Collected cells should be washed with AT LEAST 1,000 mLs of normal saline – wash effluent should be clear
-Washed product must be transferred to a separate
reinfusion bag (reduce chance of air emoli)
-don’t use pressure bag to speed reinfusion time
Reinfusion bag should be properly labeled with four
things:
1) Patient name and ID#;
2) Expiration time (6 hours from collection time at room temperature);
3) Volume in bag;
4) Note stating “Autologous Use Only”
quarterly testing should check
- Product hematocrit greater than 40%
- Product potassium less than 3.0 mEq/L
- Product free hemoglobin concentration less than 100 mg/dL
- Product heparin concentration less than 0.5 units per ml
summary
- Use of vent and pump suction should be minimal amount needed to expose operative field and protect the myocardium
- Use of cell saver device in lieu of pump suction for pooled and/or stagnant blood
