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CPC > Equipment > Flashcards

Equipment Flashcards

1
Q

Counterpulsation physics

A
  • Balloon inflation causes volume displacement within the descending thoracic aorta, by creating 2 compartments.
  • Proximal compartment contains aortic root and coronary arteries, distal compartment is the systemic circulation.
  • inflation causes proximal volume displacement and improves distal perfusion via enhancement of intrinsic Windkessel effect
  • Deflation causes sudden volume displacement with lowering of pressure and reduction of LV impedance, lowering afterload component of cardiac work
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2
Q

IABP placement

A

Proximal end should be high enough to maximize augmentation and limit time delay but without impeding great vessels; 1-2 cm distal to the sublcavian above the level of the renal arteries to occlude no more than 90% of the aorta
-Tip should be between 2nd ICS and first lumbar vertebra

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3
Q

IAPB improvement in Cardiac output

A

(Quaal) Usually 0.5-1 LPM increase.

Hensley: maximum 15% decrease in myocardial energy balance

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4
Q

Effects of IABP on myocardial oxygen supply/demand

A

Demand is caused by contraction during systole, supply is caused by diastolic flow to the endocardium during diastole for the LV. AUC for LV pressure vs time graph indicates supply/demand.
-IABP reduces systolic pressure (assisted systole) and increases AUC for diastole (augmented diastolic pressure) improving supply-demand ratio

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5
Q

IABP inflation and coronary artery perfusion

A
  • Effective augmentation of coronary perfusion is dependent on the degree of vasodilation within the coronary bed.
  • MI causes vasodilation from local effects
  • in severe CAD there is no improvement in perfusion to stenosed vessels, but can stimulate collateral vessel perfusion and limit cardiac demand
  • IABC increases coronary blood flow velocity and likely is the effect of ischemic relief in hypotensive patients
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6
Q

IABP afterload reduction mechanism

A

Leplace’s law: stress (LV wall tension) is proportional to aortic pressure x radius. Balloon deflation decreases aortic end diastolic pressure, causing an opening of AoV during static work (work before AoV opening)

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7
Q

IABP afterload reduction and hypotension

A

Systolic unloading only occurs with normal/high blood pressure. In hypotension the aortic compliance increases. Increased Ao compliance causes expansion with balloon inflation and limits work reduction effects

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8
Q

IABP effects on baroreceptor response

A

Baroreceptors are in the aortic arch and carotid sinus bodies and respond to pressure increases by vagal stimulation, decreasing HR.

  • IABP inflation increases diastolic pressure, stretching baroreceptors and decreasing HR with vagal stimulation. This increases diastolic filling time and decreases work.
  • Vagal stimulation also decreases SVR causing improvement in blood flow
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9
Q

IABP and preload

A

Increasing EF with increased ejection efficiency, allowing the heart to empty. This decreases RA wall stretch and decreases preload and the increase in HR form atrial receptors

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10
Q

Decreased urine output following IABP placement

A
  • Assess for aortic dissection
  • Assess for juxtarenal balloon position
  • Assess for persistent low cardiac output, usually the most likely cause
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11
Q

Factors affecting IABP augmentation

A

-Position: closer to AoV the better. Lower balloons decrease volume displacement momentum
-Volume: Aug is maximized when SV=balloon volume.
SVR: High resistance causes decreased system compliance.
-Balloon diameter, shape
-Driving gas: volume and molecular weight
-Timing: inflation, deflation and duration of inflation

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12
Q

Optimum balloon occlusivity (Quaal)

A

Augmentation is greatest at 100% aortic diameter occlusion but this causes RBC destruction and balloon friction.
Estimated optimum occlusivity is 90-95%

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13
Q

Withdrawal of medications with IABP

A

Withdraw all medications prior to removing IABP, other than heparin.
Re-starting drugs is easier than restarting a balloon

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14
Q

IABP and CPR

A

Counterpulasion should be triggered from arterial line so that counter pulsation can be timed with chest compressions

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15
Q

IABP contraindications

A
  • Thoracic or abdominal aortic aneurysm: counter pulsation against diseased aortic wall risks dissection
  • AI: with risk/benefit analysis
  • PVD: inability to pass balloon through atherosclerotic vessels
  • Lack of definitive therapy for underlying condition
  • Sepsis (Hensley) due to bacterial infection of surface
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16
Q

IAPB Complications

A

Quaal: Limb ischemia is the most common.

  • Vascular complications: thromboembolism, compartment syndrome, aortic dissection, local injury like pseudo aneurysm, infection complications, balloon rupture
  • hematologic: hemolysis, thrombocytopenia
  • Hensley: vascular complications most common
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17
Q

Ankle brachial index for IABP assessment

A

ABI: brachial systolic/calf systolic. Normal is 0.8-1.2

Lower calf relative pressure is an indication of poor perfusion

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18
Q

IABP skin incision location

A

1.5 cm below the inguinal ligament

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19
Q

Quaal’s recommendation for heparin administration with IABP

A

5000 units on injection and infusion at 600-1000 u/hr to achieve PT (not APTT) of 50-60. Stop heparin infusion 2-4 hours prior to removal

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20
Q

Contraindications to sheathless IABP insertion

A

Fibrosis and extensive scarring or obesity which causes excessive distance between the skin surface and the femoral artery

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21
Q

IABP balloon volume limitation

A

Ideal balloon volume is equal to the blood volume in the aorta at any given time, with the correct diameter and length.
-Increasing volume only causes aortic distension and not increased blood displacement

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22
Q

Ideal IABP balloon volume

A

CI (in mL) x BSA/(HR x 2)

  • Quaal: Balloon should have at least 50% of the stroke volume
  • Hensley: Set balloon volume to 50-60% of ideal SV
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23
Q

Phlebostatic axis definition

A

External reference point for the level of the right atrium.

The junction of the 4th ICS and the right mid axillary line

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24
Q

Conventional IABP timing

A

Inflation: T wave midpoint as electrical signal of diastole
Deflation: R wave

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25
Q

Ideal pressure wave for IABP timing, invasive pressure monitoring limitations

A
  • Aortic root pressure is the only reliable means, and all other pressure sites are not considered central pressures.
  • Pulse wave velocity is faster than the velocity of blood flow itself and is determined by compliance of arteries.
  • Differing locations, pulse wave, impedance limit timing accuracy. Femoral artery should not be used for timing due to 120 msec delay
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26
Q

IABP pressure timing delay

A

Pulse wave takes 25 msec from AoV closure to reach 1-2 cm distal to subclavian, and the same amount of time for augmented pressure to reach AoV
Therefore, inflation needs to be timed to occur 40-50 msec from midpoint of dicrotic notch to account for delay, when monitoring with IABP tip at optimal position
On standard paper, 0.4 sec= 1 little box

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27
Q

Indications of proper IABP deflation

A
  • Assisted systole is equal to or less than unassisted systole; systole is lowered because of the diastole
  • Assisted diastole is less than unassisted diastole; diastole is lowered because of volume displacement
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28
Q

Indications of improper IABP deflation

A

Early: assisted systole is higher than unassisted systole. The diastolic drop occurs
Late: assisted diastole is higher than unassisted.

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29
Q

IABP Fill pressure definition

A

Balloon pressure baseline pressure, caused by the pressure of helium needed to prime the system itself pneumatically

30
Q

IABP balloon pressure waveform correlation with augmented arterial pressure

A
  • balloon wave should be same width as duration of diastole
  • balloon plateau pressure should reflect peak augmented arterial diastolic pressure, +/- 20-25 mmHg for adults and 10 for children
31
Q

IABP waveforms and MAP

A

High MAP or SVR causes increased resistance to balloon flow and a HIGH pressure.
Low MAP causes low resistance to balloon He flow and causes LOW pressure

32
Q

Causes of abnormally low IABP balloon waveform plateau pressure

A
  • Balloon is too small
  • Balloon doesn’t have enough volume
  • Low SVR, low MAP, hypovolemia.
33
Q

Cause of abnormally high IABP balloon waveform plateau pressure

A
  • Patient is hypertensive, causing more resistance to flow and high pressures
  • if Aug is not increased, then balloon is likely kinked or not inflating correctly
  • Balloon too large for the aorta; decrease the filling volume to resolve the problem
34
Q

IABP and manual blood pressure cuff use

A

Highest pressure generated is augmented diastolic pressure, which is now the first korotkoff sound.

35
Q

Rationale for use of He in IABP inflation

A

Low density, resulting in decreased Reynolds number and slowing for same flow through a physically smaller driveline

36
Q

Turning off an IABP

A

IABP should never be turned off unless the patient is anticoagulated fully
Do not let balloon remain deflated for longer than 30 min
If pump fails, inflate manually with 40 cc air by hand once every 5 min

37
Q

IABP and requirements for anticoagulation

A
  • Heparin not required for first hours following CPB until chest tube drainage is less than 100-150 mL/hr
  • No-heparin protocol has acceptable rates of thrombosis compared to risk of bleeding
  • If prolonged use needed, consider heparin to achieve APTT 1.5-2 normal
38
Q

Determinants of venous drainage flow from siphon-based venous line

A
  • Pressure (volume) within the patient’s central veins
  • difference in height between patient and top of blood level in venous reservoir (pressure gradient is height in cm h20)
  • resistance of venous line, cannulas, connectors
39
Q

Gravlee recommendations for 2 stage venous cannulas

A

BSA 1.8-2.5 is 32/40, greater than BSA 2.5 is 36/46.

32/40 gives a max flow of 6LPM. 36/46 gives max flow 8 LPM

40
Q

Air in Venous line and GME production

A

60% of bubbles transferred from venous reservoir to arterial line despite use of 40 micron filter are transmitted to patient.
98% of GME reduction occurs by removing all visible air from venous cannulas and lines before initiating CPB

41
Q

Bicaval Cannulation and persistent LSVC

A

LSVC drains into the coronary sinus or RA.

  • If right heart is entered there is potential for air to enter retrograde through coronary sinus into LSVC and systemically
  • if bicaval cannulation is used, then using caval tapes (which should be opened during cardioplegia) prevents systemic drainage to venous line
42
Q

Augmented venous drainage pressure monitoring recommendation

A

pressure transducer located 10 cm before the inlet to either the KAVD centrifugal pump or above the inlet to the hard shell reservoir

43
Q

VAVD pressure limit

A

Gravlee: do not exceed -60 to -100 mmHg, with -40 increasing the amount of GME. Usual application is -20 mmHg

44
Q

Table height and siphon pressure

A

40 cm from the table to the top of the blood level of the reservoir causes -32mmHg suction

45
Q

Venous reservoir pressure relief valve recommendations

A

Low pressure valve of -100 mmHg

High pressure valve of +5 mmHg

46
Q

Sources of potential air emboli with augmented venous drainage

A
  • aspiration into venous line across the purse string sutures
  • IV ines or instrumentation with the use of VAVD
  • air lock resulting in transmission of air into reservoir/centrifugal pump
  • charged cardiotomy and retrograde air generation up the venous line
  • imbalance of flow from art and venous flow causing change in patient blood flow
  • all effects worsened with PFO which can lead to systemic embolization
47
Q

Cannula performance index

A

Pressure drop vs outer diameter at any given flow

48
Q

Arterial cannula pressure drop recommendation

A

Less than 100 mmHg; greater than this causes excessive hemolysis and protein denaturation

49
Q

Gravlee assessment of aortic cannula position

A

Test infusion through arterial line is recommended regardless of the location of cannulation. Higher than expected pressures warns of dissection.
Lack of negative flow or flow less than 500 mL/min during RAP suggests misplacement

50
Q

Signs of cannulation of arch vessels or malposition of aortic cannula

A
  • high systemic pressure line readign
  • unilateral facial blanching with clear prime initiation
  • assymetric cooling of neck during cooling
  • unilateral edema, hyperemia, petechai, conjunctival tearing or dilated pupils
  • decreased pulsation prior to CPB on the cannulated side
  • radial artery changes/dampening
51
Q

Coanda effect

A

Jet stream adheres to the boundary wall and produces a lower pressure along the opposite wall. This causes carotid hypoperfusion
Wiki: tendency for fluid to stick to the convex surface

52
Q

Advisable maximum blood velocity in tubing

A

100 cm/sec to avoid hemolysis and trauma

53
Q

Maximum critical blood Reynold’s number

A
  1. Turbulence occurs above this number.

Max flow through 3/8” tubing to achieve this is only 3.7LPM

54
Q

Recommended pressure tolerance of all tubing connections

A

500 mmHg for all connections distal to the pump

55
Q

Roller pump occlusion (Gravlee)

A

Most commonly cited is 30 inches of fluid, drop is less than 1 inch/min, or 30 cm and 1 cm/min
Mike: Pressure drop: 90 mmHg in 120 seconds, which is 2 mmHg in 3 seconds starting at 300 mmHg
Each roller should be checked in 3 positions

56
Q

Spallation generation

A

Particulate emboli form on inner surface of the tubing and at the fold of the edges of the tubing occurs

57
Q

Arterial pump blood handling characteristics

A

Roller pumps are based on setting of occlusion by operator to minimize hemolysis
Roller pump handling is based on operator technique to ensure that high RPM and low flow does not generate unnecessary shear

58
Q

Gravlee pressure monitoring recommendation

A

Pre and post membrane oxygenator to allow for assessment of high pressure gradients

59
Q

Gravlee occlusion discrepancy

A

In the even that the 2 roles in the pump head do not yield the same rate of fluid drop, the occlusion should be set to the roller that is most occlusive

60
Q

Pre-Bypass filter size

A

0.2-5 micron pore size

61
Q

CO2 Flush

A

Advantageous for de airing membrane oxygenators.

Most effective when the CO2 is directed through all blood-contacting components

62
Q

Gravlee recommendation for use of roller pump suction

A

Occlusion of roller pumps used for field suction and venting should be slightly non occlusive to reduce RBC trauma, and requires constant adjustment to minimize tissue and blood damage

63
Q

Recommendations for venous reservoir and deformer to

A

Direct blood injection into defoamer, no inlet turbulence, all blood passes through defoamer, avoid free fall into the reservoir, store the blood in reservoir as long as possible, use microporous filter

64
Q

Screen filters

A
  • woven polymer thread
  • defined pore size
  • filters by interception
  • smallest is the pre bypass filter, which is not woven polymer but is a membrane
  • small screen filters block particles and GME
65
Q

Bubble point pressure

A

Pressure that overcomes inherent surface tension within filters resulting release of trapped bubbles

66
Q

Use of leukocyte depleting filters

A

Only favourable evidence is for use in cardioplegia line just before unclamping, such as with hot shot. Some evidence suggests increased cardiac output, Vfib and cardiac enzymes

67
Q

Purpose of venting the LV

A
  • reduction of LV distension and wall stress
  • reduce myocardial rewarming
  • prevent cardiac ejection of air
  • facilitate surgical view
68
Q

Causes of blood return to LV requiring venting

A
  • Blood that gets around the venous cannula and passes through the lungs
  • bronchial and Thebesian drainage
  • persistant LSVC
  • PDA
  • ASD/VSD
  • Anomolous venous drainage
  • BT and Waterston Shunt
  • Coronary collateral flow
69
Q

Standardized cardioplegia delivery temperatures

A

Cold=4
Tepid is 28-35
Warm is 35-37

70
Q

Gravlee recommendation for cardioplegia pump occlusion

A

Must be fully occlusive to prevent retrograde Flow and possible air entrainment and thus coronary air embolization

71
Q

Recommended antegrade aortic root pressure during cardioplegia delivery

A

60-100 mmHg in the root (Gravlee)

Line pressure= 160-200 (Mike)

72
Q

Ideal cardiac arrest time during induction dose of cardioplegia

A

Arrest within 30 seconds with antegrade cardioplegia

CPC (8 decks)

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