Test 1 Flashcards
Major branches of left coronary artery
LAD
- diagonal
- septal perforator
- intermediate
Circumflex
- obtuse marginal
Major branches of RCA
Acute marginal
PDA (in most)
3 most effective monitors to detect myocardial ischemia
ECG (detects ischemia 80% of the time)
PAC
TEE
2 factors which decrease myocardial oxygen supply and increase demand
Heart rate
Filling pressures (PCWP)
2 factors affecting coronary perfusion pressure
DBP (diastolic blood pressure)
LVEDP (Left ventricle end diastolic pressure)
Formula for coronary perfusion pressure
CPP = DBP - LVEDP
Role of HR management in optimizing myocardial oxygen supply and demand
LV fills during diastole
Total time in diastole key in perfusion
Modest increase in demand (HR) has major effect on supply
as heart rate foes up, filling time goes down
Hemodynamic variable most commonly associated with myocardial ischemia
Heart rate
Four factors that may adversely affect ventricular wall tension
Systolic BP
Afterload
LV filling volumes
Myocardial ischemia
Myocardial ischemia effect on wall tension
Changes compliance and will have higher pressures for same volume
Effect of IABP on myocardial oxygen supply
Augmentation of diastolic pressure resulting in increased coronary perfusion
Effect of IABP on myocardial oxygen demand
Reduction in afterload
- decreased cardiac work, oxygen consumption
- increased cardiac output
- decreased hemodynamic abnormalities associated with mechanical defects
Most commonly associated complication associated with CABG
A-Fib or rhythm disturbances
MI
Post op bleeding
Stroke
ARF
Post-perfusion syndrome (pump head)
Respiratory failure
Sternal wound infection
Predictors of morbidity/mortality with CABG
Age Prior MI MI location Coagulopathies CHF Dysrhythmia HTN DM PVD cerebrovascular disease Valvular heart disease Smoking Lung disease ECG abnormalities
Time period most associated with morbidity mortality after MI
Within 1 month 35% have repeat MI
2 test measuring ventricular function in pt presenting for CABG
TEE
PAC
3 commonly used home meds in pt with CAD presenting for CABG
Beta blockers
Calcium channel blockers/ ACE inhibitors
Diuretics/thiazides
6 indications for placement of PAC
- LV dysfx
- angina w/i 48 hours
- symptomatic valve disease
- severe HTN w/ hx of angina
- large operation with anticipated intravascular volume changes
- vascular surgery with clamp of major arter
4 uses of PAC data during CABG
Measure CO
Detect, to, and trend myocardial ischemia
Measure and optimize ventricular preload and volume
Detect, treat, and trend valve dysfx
Clinical uses of intraoperative TEE during CABD
Ventricular function (EF, wall motion)
Wall motion abnormalities
Valve dysfunction
Stenosis or regurgitation
Chamber size may be indicative of dysrhythmia and dysfunction
Phenylephrine dose for CABG
30-60 mcg/min vs bolus
Dose for sedative hypnotics for CABG
Midazolam
Propofol
Etomidate
Midazolam 3-5 mg
Propofol 20-200mg
Etomidate. 10-20 mg
Opiod induction sequence dosage
Fentanyl
Sufentanil
Fentanyl 3-25 mcg/kg
Sufentanil 0.5-1.5 mcg/kg
Effect of fentanyl on volatile agent requirement
Dose of 25 mcg/kg, 50 mcg/kg, 75 mcg/kg, 100 mcg/kg
Increasing dosage of fentanyl results in decrease in MAC of volatile
25 mcg/GI = 40% decrease MAC
50 mcg/kg = 55% decrease MAC
75 mcg/kg = 65% decrease MAC
100 mcg/kg = 70% decrease MAC
With high dose fentanyl anesthesia resulting changes in hemodynamics
Vs inhalation anesthetic
Increase in HR, MAP, CI, MVO2
Inhalation results in decreased HR, CI, MVO2, MAP
Dose of epinephrine associated with extrasystoles when using Isoflurane
7 mcg/kg
6 causes of Myocardial ischemia during anesthesia
- coronary artery occlusion
- tachycardia
- high PCWP/CVP (>12-15)
- hypotension
- severe hypertension
- increased workload or high CO (sepsis)
6 signs of myocardial ischemia
- ST segment abnormality
- dysrhythmia
- conduction abnormality
- PA waveform abnormality
- decreased myocardial performance (low CI or BP)
- wall motion abnormality( echo, visual)
Intervention of Nitrates for myocardial ischemia
Decreases wall tension better than anything else
Intervention of beta blockers for myocardial ischemia
Decreased contractility and HR
use esmolol not metoprolol
Intervention of calcium channel blocker drugs for myocardial ischemia
Just drop BP
Not helpful with anything else
5 patient subgroups requiring higher perfusion pressures
- Acute MI/ongoing ischemia
- renal/cerebral insufficiency
- Left main/left main equivalent
- aortic stenosis
- chronic hypertension
4 potential sources of conduit for bypass grafts for CABG
- LIMA
- RIMA
- radial
- saphenous veins
- gastroepiploic
Blood pressure maintenance during arterial cannulation
Maintain SBP <100
if higher can dissect aorta
6 sources of rhythm disturbances associated with surgical manipulation CPB
- atrial cannulation/vent stitch
- RFG catheter (retrograde cardioplegia)
- pericardiotomy
- lap under heart to explore distal
- myocardial ischemia
- dissecting out heart for redo/pericarditis
Heparin dose in prep for CPB
Goal ACT after periocardiotomy and prior to aortic cannulation
300 units/kg
Goal ACT >400 second
Hemodynamic consequences of “mixing” or “RAPing”
Decreases viscosity and circulating norepinephrine levels
decreases SVR
4 goals of cardiopulmonary bypass
- oxygenation of blood and elimination of carbon dioxide (ventilation)
- circulation of the blood
- systemic cooling and rewarding
- diversion of blood from heart to provide bloodless surgical field
Cross clamp strategies for distal anastomoses
Distals done with cross clamp on
Mammary done last to avoid twisting IMA
Cross clamp strategy for proximal anastomoses
Cross clamp removed, partial clamp of aorta for proximal
At risk for ischemia until proximal completed
Protamine dosing after separation of CPB
10mg test dose after satisfied with heart performance
Then 25 mg every minute
Typical dose 250 mg
remove aortic cannula with 1/2 protamine dose is in*
On CPB blood pressure is
Flow X SVR
To reduce flow and separate from CPB (hemodynamics)
SVR is increased
Prior to CPB what should you do with PAC
Pull PAC back 2 cm bc easier to perf RA when volume lost to go on CPB
Law relating to wall tension
LaPlace’s Law
Difference in collateral flow and natural flow r/t perfusion of heart
Collateral flow doesn’t reach subendocardial as well as epicardial
5 advantages of OPCAB
Less neuropsychological impairments
Fewer inotrope, dysrhythmia postop
Improved hemostasis
Less need for transfusion and fluids
Less postop renal insufficiency
6 pt subgroups most likely to benefit from OPCAB
>70 yrs old Low EF Redo CABG Significant comorbidities Calcified aorta Pt refusing blood products
Role of intracoronary shunts for distal anastomoses
Placed after arteriotomy
Decreased bleeding
CBF maintained though reduced
4 methods of display ante of heart for distal anastamosis
Laps
Towel
Deep pericardial sutures
Suction stabilizer devices
Effects of displacement on
CO/SV and BP
Decreased RV filling but elevated filling pressures rt RA compression
Decreased RV output = underfilled LV = lower SV/CO
Decreased CO = decreased BP
Effects of displacement on valve function
Vertical position = distortion of MV and TV
Significant regurgitation
Myocardial ischemia manifestations during OPCAB
Elevated PA **
Deterioration in heart performance
ST elevation
New RWMA
Target vessel positioning associated with biggest decrease in SV and increase in CVP
Circumflex positioning
4 strategies to manage Herat rhythm disturbances during OPCAB
Lidocaine (esp RCA) Magnesium 2gm (keep K4.0) Nitro during distal anastamosis for spasm
Heaprin dose
ACT goal
1.5-2mg/kg (usually 10,000-15,000 units)
—1/2 full CBP dose)
3000 units if vein taken prior to bolus for revascularization
Keep ACT >250
Usefulness of TEE monitoring
RWMA
CI superior to TEE with displacement
Order of grafting
Colalteralized LAD w. LIMA Proximal before distal Diagonals RCA PDA Circ 2nd and 3rd OM PLA OM Ramus intermediate
Inferior wall exposure surgical maneuver fo limit hemodynamic compromise
Table flat and retraction sutures relaxed
Decreases compression of RA/RV
Surgical maneuvers to manage hemodynamic changes
- Order of grafts based on hemodynamic consequences
- OR graft most diseased first
-close communication with anesth - DPS to bring great vessels and chambers into same plane
- open R pleura for lat grafts to avoid compression
- lift R sternum to make more space
(Towel under R side of retractor) - remove pleurocardial fat
