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6902 test 2 > Bypass > Flashcards

Bypass Flashcards

1
Q

When you hear the testing of the saw

A
  1. Re-dose analgesic
  2. Re-dose paralytics
  3. Get ready to hold lungs when actually begin sawing
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2
Q

order of clamping/cannulation

A

aortic side clamped first, then venous.

venous unclamped to fill reservoir

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3
Q

Highest incidence of MI

A

pre-op and post-op due to anxiety and pain, so treat

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4
Q

Pre-bypass stimulation

A

variable

Blunting sympathetic responses very important

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5
Q

Pre-bypass sequence

A
  1. Room set up
  2. Pre-op evaluation and patient prep (lines)
  3. Transport to OR, monitors connected
  4. Induction
  5. Foley, TEE, antifibrinolytic, labs, abx
  6. Saphenous vein harvest
  7. Sternotomy (lungs down, pain meds)
  8. LIMA harvesting & repositioning
  9. Pericardial sutures
  10. Heparinize & ACT 3 min later
  11. Cannulation
  12. Venting the heart
  13. Partial bypass
  14. Aortic cross clamping
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6
Q

Bypass sequence

A
  1. Full bypass & cardioplegia
  2. Surgeons connect grafts
  3. Aortic cross clamp released, re-expand lungs and ventilate
  4. Give protamine & inotropic support
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7
Q

Post bypass sequence

A
  1. Fluid mgmt. after
  2. Epicardial pacing wire insertion by surgeon
  3. Chest tube placed by surgeon
  4. Give cell saver
  5. Chest closure (hypotension)
  6. Transfer pt (and hypotension)
  7. hand of in SICU
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8
Q

Common positioning injury

A

Brachial plexus - hyperextended arms of chest wall retraction
Brachial and radial artery and nerve compression from screen or chest wall retractor

Heels, sacrum, scalp prone to ischemia from long surgical times

Alopecia

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9
Q

Glucose checks?

A

Important even in nondiabetic pt as a massive stress response

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10
Q

Baseline ACT and ABGs

A

obtained while starting antifibrinolytics

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11
Q

When is the highest risk of recall?

A

Pre-bypass during initial incisions, sternotomy, sternal spread, vessel harvesting

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12
Q

LIMA

A

Left Internal Mammary Artery has better long term patency

Reduce lung volumes and give faster RR so surgeon can access the vessels

If vessel spasms, may ask to give CCB or NTG low dose

Hypotension managed via Trendelenburg

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13
Q

When the pericardial sac is opened . . .

A

Retraction sutures are placed
Hypotension
Bradycardia

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14
Q

Heparin dose

A

300-400 units/kg body weight

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15
Q

Prior to blood being sent into the circuit . . .

A

THE PATIENT MUST BE ANTICOAGULATED

Confirm ACT 3 minutes after anticoagulation

ACT must be > 400 (450)

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16
Q

HAD2SUE

A 
Heparin
ACT
Drugs (NMB, amnestic)
Drips (turned off)
Swan pulled back
Urine accounted for 
Emboli check
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17
Q

SBP before cannulation

A

btwn 90-100 mmHg or MAP < 70 mmHg

worry about aortic dissection

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18
Q

When is bypass initiated?

A

When the perfusionist releases the venous clamp to fill the venous reservoir

Hypotension common from hemodilution decreasing SVR

If MAP cannot be raised above 30 mmHg, aortic dissection considered

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19
Q

When reach full flow what will happen to tracings?

A

Lose PAC and art line

Lungs now being bypassed

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20
Q

Passive lung inflation

A

200 mL/min is continued

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21
Q

Once on flow - NMB? Anesthetics?

A

Very important to maintain appropriate anesthetic depth

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22
Q

Infusions on bypass?

A

All stopped except insulin and antifibrinolytics

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23
Q

Left ventricle is vented . . .

A

through a left superior pulmonary vein with tip in LV - allows blood to enter the LV
aortic cross-clamp is applied - note the time as this correlates to the start of cardiac arrest
Cardioplegia is given and arrests the heart in diastole

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24
Q

CPB flow

A

50-60mL/kg/min with a pressure of 50-70mm Hg

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25
Q

Mixed SvO2

A

is maintained at 70%

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26
Q

Hypertension means?

A

anesthetic is needed

Deep NMB to prevent shivering is also required

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27
Q

ABGs and ACTs are checked . . .

A

Q 30 minutes or more

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28
Q

Urine output

A

goal is 1 mL/kg/hr

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29
Q

Patient’s head and face are monitored for signs of

A

cannula malposition as indicated by edema and JVD

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30
Q

Rewarming

A

to 36 degrees

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31
Q

Cardioplegia can induce what?

A

Hyperkalemia. K levels are monitored

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32
Q

Magnesium is given. Why?

A

Reduced post-op atrial fib

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33
Q

Coming off bypass - lungs

A

Gently re-inflated to max 30 cm H2O.

Look over the drape and see them expand

Too aggressive can rupture grafts

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34
Q

Coming off bypass - reperfusion cardioplegia

A

arrhythmias
ACLS
TEE to assess the heart
Pressors and positive inotropes

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35
Q

Coming off bypass - filling the heart

A

perfusionist will occlude venous return line to fill the right heart.

CPB is gradually decreased and preload can be added until appropriate status is reached

PAC is re-advanced

CPB can be initiated if emergently needed

IABP can be placed if pharmacologically unable to support the heart

36
Q

Coming off Pump

Wide Receiver Most Valuable Player

A 
Warm - is the pt and heart warm?
Rhythm - NSR?  pace?
Monitors - turn them back on
Ventilation - turn on the ventilator
Perfusion - what is the pump flow
37
Q

Post bypass

A

heparin reversed

BP is lowered to MAP of 70 or systolic of 90

Venous cannula removed first, arterial cannula second.

Blood left in the reservoir is washed and given back to pt

38
Q

When can you fast track a pt?

A

Without low CO syndrome (EFs > 35%)

39
Q

Bypass machine - flow of blood

A

Blood is removed from RA via tubing
Drained into a reservoir
Pumped into an oxygenator (adds O2 and removes CO2). Volatile gases can be added here. heat exchanger in conjunction with oxygenator
Filtered back into the aorta to perfuse the body

40
Q

Electrical arrest

A

Heart is held in arrest by use of cardioplegia

CI is kept at 2-2.4 L/min and is typically non-pulsatile

The machine can change flow to create a MAP btwn 50-80

41
Q

Non-endothealized circuit causes

A

a massive inflammatory response

42
Q

The Prime

A

Circuit is primed with electrolyte solution
Air is removed
Meds can be added
Colloids can be added - heparin, mannitol, etc.

Causes dilution anemia that lowers HCT to 22-25%

43
Q

Cardioplegia mix

A

Hyperkalemic crystalloid mixed with blood 4:1 blood to crystalloid

First dose (induction dose) is cold with 30 mEq of K, with subsequent doses having 1/2 this K level and are given every 15-20 minutes

The K arrests the heart in diastole

44
Q

Myocardial protective strategy

A

Systemic hypothermia
Cardia hypothermia

also provides some cerebral protection

45
Q

Bypass physiologic effects

Systemic inflammatory response

A

Large spike in cortisol, catecholamines, vasopressin, angiotensin levels, oxygen free radicals

46
Q

Bypass physiologic effects

Heart

A

Myocardial stunning

SIRS can cause injury as well

47
Q

Bypass physiologic effects

Brain

A

Type 1 outcomes - death, stroke, coma, TIA
Type 2 outcomes - cognitive defects

*only hypothermia demonstrates efficacy in reducing these complications

48
Q

Bypass physiologic effects

Lungs

A

Mild atelectasis Pleural effusions
Hemo/pneumo thorax
Pulmonary emboli

49
Q

Bypass physiologic effects

Kidneys

A

AKI

50
Q

Bypass physiologic effects

GI

A

splenic hypo-perfusion

51
Q

Bypass physiologic effects

Coagulation

A

Platelets and clotting factors are diluted and denatured by mechanical trauma

Protamine too can cause anti-coag effect

52
Q

Risk factors for CNS injury

A 
poor baseline cognition
lower years of education
advanced age
diabetes
CPB time
IABP
Excessive alcohol intake
Hx of CABG
Arrhythmia on day of surgery
Hx of unstable angina
Atheroma of the aorta
Presence of carotid disease (repair prior to surgery)
53
Q

Hypotension and CNS injury

A

Not risk factor for cognitive decline

Risk of CVA higher - higher pressures perfuse pneumunbric areas better

54
Q

Hyperthermia post op

A

common in first 24 hrs

55
Q

Neuroprotection strategies

A
  1. Emboli reduction
  2. Pulsatile flow
  3. Hypothermia
  4. Acid base mgmt
56
Q

Temp hypothermia of 10 degrees C

A 
Lowers CMRO2 6-7%
Blocks metabolism
Blocks glutamate
Reduces Ca influx
Hastens recovery of protein synthesis
57
Q

Temp over 37 associated with

A

increased risk of stroke

58
Q

How does CPB keep CBF autoregulated?

A

CBF remains autoregulated in non-pulsatile hypothermic pt using alpha stat blood gas mgmt. w/in the range of 50-100 mmHg.

HTN shifts this to 60 mmHg.

Diabetics may require a higher minimum MAP

59
Q

Glucose mgmt. and CNS

A

essential
<180
>180 bad for brain
glucose is converted to lactate that increases intracellular acidosis and impairs intracellular homeostasis and metabolism

60
Q

hemodilution and serum cr

A

falsely lowers creatinine

61
Q

Risk factors for AKI

A 
emergent
re-do procedures
valvular procedures
prolonged CPB
old age
obesity
AA
HTN
anemia
atherosclerosis
DBM
62
Q

Renal protection

A

precedex

glycemic control

63
Q

Pharmacologic interventions and AKI?

A

not good for protection or treatment

64
Q

Anesthesia for Bypass

Pre-meds

A

Reduce apprehension and provide relief

  1. benzos - versed
  2. Alpha agonists (precedex) (note: brady, MAP reduction, CO reduction make these less attractive)
  3. Continue BB, statins, ASA
  4. ABX (Cafazolin, Vanco which is re-dosed at end of procedure if 50% of BV is replaced)
65
Q

Monitoring for Bypass

A
  1. ECG leads II and V5
  2. artline
  3. Central venous line to monitor RAP and provide pressors
  4. PAC ? (current guidelines for Cardio shock or NYHA III or IV)
  5. TEE
  6. Cerebral oximetry
66
Q

TEE in bypass

A

Earliest recognition of ischemia
Allows for aorta assessment where the CPB cannula enters to assess for atheromatous plaques and ensure appropriate cannulation

*Should be used in all cardiac or thoracic aortic surgeries

67
Q

Anesthesia for Bypass

Induction drugs

A
  1. Etomidate is typically preferred
  2. Propofol in hemodynamically stable pts
  3. Newer studies show preference for volatile agents over TIVA bc of anesthetic preconditioning - continuous providing greatest benefit
  4. Ketamine rarely used bc of sympathomimetic effect
  5. Versed is used bc has minimal hemo effects
68
Q

Why etomidate?

A

Lack of inotropic or sympathomimetic effects

Can cause pain on injection

Combine with opioids

69
Q

Morphine in CABG?

A

no bc of vasodilation from histamine

did not allow for appropriate amnesia

70
Q

Fentanyl in CABG

A

yes but in combo with other anesthetics

max of 20 mcg/kg

71
Q

Sufena in CABG

A

More expensive with no benefit over fentanyl

3 mcg/kg

72
Q

Remifentanil

A

Good thought, but extreme care must be given to ensure pt control at the end of surgery to prevent an abrupt catecholamine surge

73
Q

NMB and CABG

A

Avoid histamine release
Avoid vagolytic effects that cause tachycardia

Vec is hemodynamically stable but repeat doses can accumulate an active metabolite

Roc is hemodynamically stable UNLESS using high doses which can produce mild vagolytic effects

74
Q

Alpha 2 agonists and CABG

A

rarely used preoperatively but perhaps in ICU and postop care

Reduce catecholamine levels and provide analgesia

75
Q

Why is pt ALWAYS heparinized prior to cannulation?

A

W/o it massive clot formation will occur300-400 units/kg for CPB and given through a central line

ACT is used to measure

76
Q

ACT values - normal and Bypass

A

Normal is 80-120 secs

Bypass > 400

77
Q

Neuraxial anesthesia

A

Profound sympathectomy
Thoracic epidurals dilate the coronary arteries

Cases can be canceled due to a blood tap during the epidural placement and these pts are on antiplatelet meds

Benefits? reduction in delirium, pneumonia, ARF, myocardial dysfunction, cost savings

78
Q

Ischemia mgmt

A
  1. NTG has blunted response while pt is on CPB due to PVC absorption of the drug, alterations in blood flow and hemodilution
  2. When coming off pump, NTG is useful to treat residual ischemia, spasm, reduce preload and afterload and is combined with a vasopressor to maintain CA PP. Performs more favorably then using CCB or SNP
  3. Can use nicardipine or Clevidipine
  4. BB - esmolol
  5. Propofol - no benefit/harm
79
Q

Blood use and Conservation

A 
Antibrinoytics reduce bleeding and chances of needing transfusion
Aminocaproic acid and TXA inhibit plasmin
Cell saver (lacs coag factors, so dilation coagulopathy can occur)
Retrograde autologous priming - reduce the prime solution.  arterial system allowed to backprime the CPB machine
Ultrafiltration - leaving coag factors and RBCs, raises HCT.  Useful in hypervolume pt
80
Q

Amicar and TXA doses

A

Amicar - 50 mg/kg bolus over 30 min and then 25 mg/kg/ hr infusion

TXA is given as a 10 mg/kg bolus and a 1-2 mg/kg/ hr

*TXA is 5-10x more potent

81
Q

Off pump CABG

A

Involves changing heart geometry which has marked hemodynamic effects

1/3 CABG off pump

Suciton devices are used to pull and suspend the heart during off pump grafting. The heart is lifted to work on posterior vessels.

SV can be reduced by 44%, CO by 32% and MAP by 26% and HR by 26%. Corrected with Trend.

Starfish apical sucion has less hemo effects

Anesthesia technique isn’t different.

BP preferred mgmt. with pressors vs. fluid to avoid aortic cross clamping which reduces embolization risk

Lose temp - no active re-warming

82
Q

Off pump distal anastomosis

A

MAP > 80 mmHg

83
Q

Off pump proximal anastomosis

A

MAP down to 60 mm Hg

84
Q

Off pump anticoag

A

controversial

Some use 100-200 units/kg with target ACTS of 250-300. Others use full dose

85
Q

MIDCAB

A

Minimally invasive direct coronary artery bypass

LIMA takedown and anastomosis to the LAD through a small anterior thoracotomy

86
Q

TECAB

A

Totally endoscopic coronary revascularization utilizes mall chest wall incisions and thoracospic instruments with robot to perform the surgery

87
Q

Port Access CABG

A

uses video assistance for left internal thoracic artery harvesting - CPB is used and anastomoses are sewn

6902 test 2 (8 decks)

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