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Principles III > off pump cardiac anesthesia > Flashcards

off pump cardiac anesthesia Flashcards

1
Q

what are the advantages of off pump coronary artery bypass?

A
  • eliminates aortic cannulation, cross-clamping
  • decrease the systemic inflammatory response
  • decrease coagulopathies, decreased transfusion
  • reduce multi-organ dysfunction
  • decrease inotropic requirements
  • decrease morbidity
  • reduce cost, length of intubation, time in ICU
  • decreased atrial fib
  • feasible in most patients
  • neurologic advantages are inconclusive
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2
Q

what are the major differences with off pump coronary artery bypass?

A

bypass grafting done on

  • a warm, beating heart (may slow w/ beta blockers or CCB and/or adenosine )
  • w/o CPB pump (dry CPB and perfusionist MUST be on standby; conversion rate less than 1 and up to 25%)
  • w/ only moderate anticoagulation (heprainization 100-200 U/kg to ACT 250-300 seconds)
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3
Q

why is heparinization required w/ off pump coronary artery bypass?

A

surgeon is occluding coronaries and interfering w/ flow

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4
Q

what are disadvantages of off pump bypass?

A
  • challenge of adequate exposure vs. cardiac motion
  • severe hemodynamic instability
  • poor cardiac pump function
  • challenge of myocardial protection w/ coronary artery flow interruption
  • myocardial ischemia intra-op
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5
Q

what is different w/ heart positioning w/ off pump bypass?

A

heart position may require extreme alteration to allow anastomosis to posterior or lateral wall

  • vertical position w/ apex up
  • ventricles above the attire
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6
Q

what are the effects of the extreme positioning alterations of the heart during off pump bypass?

A
  • ventricles above atria
  • increased atria pressures must be maintained to ventricular filling which requires flow upward
  • leg elevation, trendelenburg, fluid administration
  • decreased CO
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7
Q

what are side effects of the stabilizer device?

A

used to immobilize the area of the myocardium for anastomosis

  • causes decreased CO
  • most detrimental effect on the anterior and lateral walls (circumflex)
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8
Q

what are side effects of folding valves?

A
  • regurgitation increases

* mitral and tricuspid are effected the most d/t the fold occurring at the AV fold

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9
Q

what are goals of off pump bypass?

A
  • same goals of avoiding HTN, hypotension, and tachycardia like w/ pre CPB phase
  • harder to achieve
  • myocardial protection: inhalation agents
  • maintain perfusion pressure, cardiac output, and normothermia
  • avoid myocardial ischemia
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10
Q

what causes intra-op ischemia?

A

coronary arteries must be clamped to allow anastomosis

  • worse w/ 50-80% stenosis w/ poor collateralization
  • RCA clamping may cause ischemia to AV node causing arrhythmias (complete AV block), which may necessitate temporary pacing
  • protect w/ sevo or iso- 2 MAC at least 30 min prior to insult (but causes vasodilation so hypotension)
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11
Q

what are techniques to decrease ischemia?

A
  • surgeon may place stent during clamping
  • maintain O2 balance- HR, contractility decrease w/ beta blockers
  • decrease wall tension- vertical position takes care of that
  • BP- maintain MAP greater 70, use vasopressors (less than 65 and CPP less than 50 associated w/ ischemia)
  • “Buffington ratio”: pts. w/ CAD are at increased risk of ischemia when MAP is less than heart rate
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12
Q

what are pharmacologic preventions of ischemia?

A
  • beta blockers (may increase PAP)
  • calcium channel blocker- diltiazem: slow HR, lowers PAP, vasodilation
  • may provide protection from reperfusion injury by antagonizing free calcium intracellularly
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13
Q

how are dysrhythmias (commonly seen) treated?

A
  • increasing perfusion pressure

- antiarrhythmics: lidocaine, amiodarone, magnesium

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14
Q

what is the concern w/ clamping and release of partial aortic clamp for proximal anastomoses?

A
  • increased SVR w/ clamp

- release after completion may cause reperfusion dysrhythmias and/or air through coronary grafts

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15
Q

describe monitoring for off pump bypass

A
  • ECG: positioning of heart changes the tracing in shape and magnitude
  • first 30 min. after revascularization, T wave inversion is seen (reperfusion injury)
  • art line
  • PA catheter: vertical heart; careful w/ surgeon manipulations (accidental wedging; monitor PA waveforms)
  • TEE: limited at time; watch for ischemia or injury on EKG if none
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16
Q

what are indications for conversion to CPB?

A
  • persistence for more than 15 min despite aggressive treatment:
  • CI less than 1.5
  • SvO2 less 60%
  • MAP less 50 mmHg
  • ST segment elevation more than 2 mV
  • new large wall motion abnormalities, decreased LV function
  • sustained ventricular arrhythmias
  • *communication is key, must chart and get MDA on board
17
Q

what are AIs for off pump bypass?

A
  • maintain normothermia: hyperthermia predictor of morbid cardiac events (fluid warmer, warming mattress, warmed inhaled gases, room temp 24 degrees C)
  • early extubation (in OR): individualized based on pt.’s temp, need for vasopressors, mechanical assistance, comorbidities, and bleeding
18
Q

how does results of off pump compare w/ CPB?

A
  • no decrease in incidence of post-op neurologic complication
  • off pump pts. received fewer transfusions
19
Q

what are specifics of robotic cardiac cases?

A
  • venous drainage via 17 fr RIJ venous cannula
  • possible endoaortic occlusion device w/ bilateral radial artery catheters
  • defibrillator pads, external in place
  • one lung ventilation (can pt. tolerate? clamp lung to be deflated and ensure tolerates prior to start)
  • total endoscopic CABG w/ CO2 insufflation
  • bypass: femoral arterial and venous cannulation (severe PVD limiting?)
20
Q

describe clamping in robotic cardiac cases

A
  • transthoracic aortic cross-clamp

- endoaortic balloon occlusion w/ TEE (danger of aortic dissection)

21
Q

describe proper positioning w/ robotic cardiac cases

A

30 degrees right lateral decubitus

22
Q

what advantages do early results of the emergence of robotic cardiac cases show?

A
  • shorter hospital stay
  • fewer blood transfusions
  • faster return to function
  • improved quality of life

Principles III (6 decks)

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