Anesthesia for Cardiothoracic Surgery Flashcards
According to the cardiac risk assessment, which gender is at higher risk for complications?
females >70 yo because tend to be diagnosed later and more difficult to do CPB because of smaller vasculature
What is the goal standing for determining cardiac risk?
cardiac cath, tells you where blockages are in coronary arteries, EF, and state of valves
How is cardiac oxygen utilization decreased for cardiac surgery?
- anesthesia
- hypothermia
- electrical silence, using cardioplegia
- empty cardiac chambers, specifically, the LV
How can you maintain oxygen supply during cardiac surgery?
hemodilution and acceptable perfusion pressure and flow
What should you ensure before going on pump?
that heparin has been given
What is the only cardiac drug you would want the patient to stop before surgery?
ACE-I
What should be included in your preop evaluation for someone undergoing cardiac surgery?
- cardiac history
- past surgical history
- medications
- angina presentation
- past medical history
- renal disease
- hepatic disease
- comorbid disease
- HIT+
- heparin resistance
WHat is involved with patient preparation for cardiac surgery?
- O2 via nasal cannula
- mild sedation with versed
- line placement: 2 PIVs, aline, cordis, PAC
- baseline ABG and baseline ACT
- blood type and cross matched
- place external defibrillation pads prior to induction
- make sure OR is ready before you move in
- move in asap if patient becomes unstable
What monitors should be used for cardiac surgery?
- EKG
- pulse ox
- aline
- TEE echo
- aortic pressure (surgeon places needle in aorta to measure pressure, peripheral aline can be dampened post CPB)
- temperature (measure in more than 1 spot)
- BIS
Where is ABP monitoring usually located?
radial, good for collateral circulation, perform Allen’s test
If have to use axillary arterial line, which side is preferred?
left because catheter tip will lie distal to the aortic arch and great vessels
What is the importance of CVP monitoring?
provide estimate of adequacy of circulating blood volume and right ventricular preload
Can CVP estimate LV if there is lung disease or valve pathophysiology?
No
What does it mean with LV compliance and volume if your transduced PAWP is 20 and your transmural PAWP is 25?
LV compliance can be normal or stiff
LV volume increased or normal
* important to write down pressure to monitor trends
What does it mean with LV compliance and volume if you transduced PAWP is 20 and your transmural PAWP is 10?
LV compliance normal
LV volume normal (or reduced)
What are complications of the PAC?
- ventricular arrhythmias
- heart block
- pneumothorax
- blood stream infection
- unintended arterial puncture
- hematoma
- vascular injuries
- cardiac tamponade
What is a TEE helpful in assessing?
- evaluation of ventricular filling
- estimated of cardiac output
- assessment of ventricular systolic function
- assessment of ventricular diastolic function
- calcified aorta
- cardiac tamponade
- arterial thrombus
What is a contraindication to TEE?
esophageal pathology (always empty stomach before placing probe)
What is involved with induction for cardiac surgery?
- high dose narcotic or propofol with low dose narcotic technique
- don’t be hesitant to do awake intubation for difficult airway
- central line, OG, esophageal stethoscope, TEE placement
- tuck arms carefully
Which induction agent is preferred if going on pump and doing circ, arrest?
pentothal because neuroprotective, but does cause hypotension and cardiac depression
What drug should you avoid during induction and on CPB?
N2O
Why are anti-fibrinolytics important with cardiac surgery?
- during CPB, large amounts of circulating tPA are found and increase post-op bleeding due to inappropriate fibrinolysis
- fibrinolysis diagnosed by TEG
- drugs exist that inhibit the binding of plasminogen to fibrin
- to be effective, must be started before going on CPB
- ACA (aminocaproic acid), TXA
Why and when should steroids be given for cardiac surgery?
decreases systemic inflammatory response, should be given before CPB
Why is DDAVP given and when should it be given?
- increases vWf release from endothelial cells which increases platelet aggregation
- has little effects on platelet defects due to ASA and CPB trauma
- given after CPB
Should you use a fluid warmer for cardiac surgery?
definitely not preoperatively, want temp. to drift down
Why would you want to use a BIS for cardiac surgery?
used as another means of assessing sedation, beta blockade will mask true anesthetic depth specifically during prepping and draping
Where is the first incision for CABG surgery?
vein/radial artery graft harvesting
Which direction does the sternal saw open the chest and what should you keep in mind regarding opening the chest?
from inferior to superior aspects of sternum, very stimulating, must turn off vent and deflate lungs because can lacerate lung tissue, observe for RV/aortic laceration
What is the heparin dosing for CPB?
300 IU/kg
What ACT is desired for CPB?
> 400 secs
Should you give heparin centrally or peripherally?
centrally always
What is used to evaluate the amount of supplemental heparin needed to maintain the ACT at a safe level on CPB?
heparin dose-response curve
What is needed for heparin to be effective?
anti-thrombin III
Does an ACT measure the actual amount of heparin in the blood?
no, measures the inhibiting effect that heparin and other antithrombotic meds have on the body’s clotting system
When should Protamine be given?
at conclusion of operation if ACT>150 secs
Which cannula is placed first for CPB?
aortic, surgeon may ask you to look for calcium with TEE
What should you do while the aortic cannula is being placed for CPB?
drop BP (90/60), look for signs of dissection after cannulation, if BP goes to 200 blood gets between the layers and the arch has to be reconstruted with circ. arrest, we are the guardian of the aorta
What should you do during right atrial cannulation?
will see lots of PACs and decreased BP, can ask perfusionist to give 100 mL fluid increments via aortic line
What happens during cardioplegia induced asystole?
- electrical and mechanical activity ceases
- potassium given continuously during cross clamping
- must be able to cross clamp aorta
- blood versus clear prime
- hyperkalemia is an issue with renal patients
Where does antegrade cardioplegia start?
coronary arteries
Where does retrograde cardioplegia start?
coronary sinuses
What is the CPB machine primed with and why?
primed with 1500-2000 mL of asanguinous fluid consisting primarily of a balanced salt solution, albumin often added to increase osmolality, causes significant hemodilution with decreased viscosity and promotes microvascular blood flow (even though O2 carrying capacity is reduced, studies show that CBF increases in response to anemia and is sufficient to maintain adequate O2 delivery)
What Hct is typically acceptable for CPB?
20%
When should you do when the surgeon says he’s ready to go on pump?
- ensure heparin given
- perfusionist opens venous clamp, blood drains passively into venous reservoir, immediately begins cooling pt
- arterial trace goes flat but ECG still present
- pull back PAC into RV, assess head for swelling
- check pupils and BIS
- do nto stop vent until heart is empty
- make sure mixed venous saturation is adequate
What are the most frequently encountered problems pre-CPB?
- arrhythmias (usually related to cardiac manipulation and cannulation, may be the first sign of myocardial ischemia)
- HTN (esp. during aortic cannulation)
- HoTN (volume can be given through aortic line via pump)
- heart failure
- bleeding (sternotomy lacerates RV or aorta)
How do you know when to ventilate the pt from the arterial waveform?
if an arterial waveform is present, then need to ventilate pt, when flat indicates that pt is on pump and don’t need to ventilate
Where is the aortic clamp usually placed and what happens next?
clamp placed above the AV and cardioplegia takes the path of least resistance through the coronary ostia
Where should you keep the temp. and MAP while on CPB?
temp 30-32 degrees Celsius
MAP 50-70 mmHg
What happens if your aortic valve is incompetent during aortic clamping?
cardioplegia will go forward into coronary arteries but also retrograde in the LV which increases LVEDP and decreases CPP
What is a venting cannula and why is it used?
placed into the LV via the aorta to remove filling that occurs via cardioplegia and coronary venous blood returning to the LV
What are the components of the cardioplegia solution?
KCl 26 mEq/L Glucose 43.9 gm/L Mannitol 12.5 gm/L Sodium bicarb 2.67 mEq/L Solu-Medrol 1 gm/L Vehicle - Normosol-R pH 7.60 Osmolality 480 mOsm/kg H2O
What can happen from prolonged cross-clamp time?
correlates with major post-operative morbidity
When can occur during reperfusion after cross-clamping?
may paradoxically cause myocardial damage and limit the extent of recovery, can cause: acidosis increased myocardial O2 consumption dec. high energy phosphate production inc. catecholamines inc. intracellular calcium inc. free radical activity myocardial edema platelet deposition vascular endothelial injury vascular compression increased automaticity impaired systolic and diastolic function
How can you prevent reperfusion injuries?
- take time reperfusing empty heart at adequate perfusion pressure (20-30 mins)
- correct metabolic abnormalities
- if exceptionally long clamp time, consider IABP
- mechanical recovery parallels biochemical recovery
How many joules should you defibrillate with during cardiac surgery with open chest and direct contact defibrillation?
10-13 joules
What should you do if a patient already has an existing pacemaker?
convert to asynchronous (using magnet) to ensure capture during chest entry, particulary during reoperations, don’t reprogram
What should you do if a patient has an AICD preop?
call cardiology for deprogramming
What should you do if your patient has complete heart block after weaning from CPB?
- can exist initially due to hypothermia
- pace at 85-90 bpm
- make sure mA is acceptable
- as the patient’s temperature and potassium increase, reliance on pacemaker decreases
- Test before using!!
What is everything you have to consider/do when coming off CPB?
- turn the vent on
- bureaucracy: K, acid-base, Hct, reperfusion
- rhythm, a-paced or v-paced, need rate ~90
- contractility, make sure oxygenation ok before starting epi
- best monitor: eye, look at the heart and see how vigorously it beats
- inspect for bleeding
- look at TEE for volume, wall motion and valve function
- systemic pressure in relation to PA pressure
- epi usually first choice inotrope
- give protamine slowly
- assess for s/s of cardiac tamponade when chest closing
Where should you keep Protamine until you are ready to use it?
in the cart!
What is involved with transporting the patient to the ICU?
- ambu bag and O2 tank
- ECG, aline monitoring
- emergency drugs
- keep surgical table sterile until out of room
- after move to bed, recheck breath sounds
- once in ICU, attach to vent, recheck breath sounds, make sure patient is being ventilated
- transport assistance is needed in the form of a surgeon, anesthesiologist or another CRNA
What are common post CPB challenges?
- recall
- bleeding
- organ hypo-perfusion
- systemic inflammation response
- residual hypothermia
- reperfusion issues
What are post-op issues?
- respiratory - ARDS, PE, etc., pulm. edema from cardiac dysfunction, atelectasis
- renal dysfunction - treat with volume and vasodilators, inotropes, diuretics
- hypothermia - SVR higher when pt’s cold then drops when they warm up
- shivering - increases O2 demand 200-400% and interferes with ventilation
- potassium - replace prn, hypokalemia common post CPB diuresis
- acid-base issues - typically due to low CO or elevated citrate levels
- platelet function altered by drugs and CPB
- RV dysfunction or failure can occur from adequate myocardial protection during CPB
What should you keep in mind post-heart transplant surgery
- denervated heart will not rapidly respond to vasodilation with tachycardia and increased CO
- will not feel chest pain
- volume dependent due to F/S mechanisms and preload dependent
- have direct acting vasoactive agents, both inotropes and vasoconstrictors available for HR, BP, and CO control
What is involved with the anesthetic management for a heart transplant?
- induction: modified RSI; high dose fentanyl; ketamine; etomidate
- sterile or “very clean” induction and intubation
- do not cannulate RIJ, reserve for post-transport biopsies
- PAC may or may not be used for infection risk
- tachycardia and high filling pressures may be needed to generate BP
- go on CPB as fast as possible
- adhere to immunosuppression protocol
- right heart failure most common rason for inability to wean from CPB and the donor heart is not accustomed to facing such elevated PVR
