Anesthesia for cardiac surgery Flashcards
When is the highest risk of recall during cardiac surgery?
Sternotomy
How many seconds should an ACT be for adequate heparinization for cannulation?
> 400 seconds
How many units of heparin are typically administered for cardiac dosing?
300-400 units/kg
What is a normal ACT?
80-120 seconds
What does Heparin bind to?
Anti-thrombin III and thrombin
How often will you obtain ACTs?
-Baseline
-3-5 mins after heparin administration
-then every 20-30 mins during bypass
What is heparin resistance and when does it happen?
Pts who have been recently exposed to heparin- require higher doses to achieve anticoagulation
-Defined as an ACT <400 seconds despite administration of 400-500 units/kg of heparin
Antithrombin 3 deficiency should be expected if pt does not become anticoagulated after additional hep. administration
How do you treat an antithrombin 3 deficiency?
-2 units of FFP
-AT III concentrate
-Recombinant AT III
Heart is arrested in _______
DIASTOLE
What is cardioplegia?
hyperkalemia crystalloid solution mixed w blood
- typically cold (2-5 degrees C)
How much k+ does the induction dose of cardioplegia contain?
20-30 mEq/L
How much k+ does the maintenance dose of cardioplegia contain?
12-16 mEq/L
How often is cardioplegia administered?
Q 15-20 mins while on bypass
How much does the cerebral metabolic rate decrease for every degrees celsius decrease in brain temp?
6-7%
How much does the cerebral metabolic rate decrease for every degrees celsius decrease in brain temp?
6-7%
Where is antegrade cardioplegia administered?
Delivered down coronary arteries, catheter inserted into the aortic root (just proximal to aortic clamp)
An arrest occurs 1-2 mins
Why is an incompetent AV problematic during antegrade cardioplegia administration?
difficulty achieving diastolic arrest, fluid leaks back into the LV when patient has AR which can cause the ventricle to distend, and increasing risk if ischemia
What is the purpose of the LV vent?
Suction out the fluid from AR that goes into LV during antegrade cardioplegia to prevent the ventricle from distention
LV Vent – Catheter placed in the LV through the right superior pulmonary vein
Small amounts of blood may enter the LV from bronchial arteries or the Thesbian vessels
Aortic Insufficiency - If the patient has AI, blood and cardioplegia can backflow and fill the LV the excess volume can cause the LV to distend, raise LVEDP, and compromise preservation by opposing the cardioplegia flow
What is the Cardiotomy?
Cardiotomy – portion of the venous reservoir that has a separate filter and defoams blood and removes air and debris picked up by suction tip (“pump sucker”)
Pump sucker is used in the surgical field or vents to drain the heart
How is retrograde cardioplegia delivered?
via coronary sinus and cardiac veins
(watch dysrhythmias and hotn )
What do antifibrinolytics (Amicar/TXA) do?
Form a reversible complex w plasmin that then inhibits fibrinolysis
What is the dosing for Amicar?
- 50mg/kg bolus over 20-30 mins followed by infusion of 25 mg/kg
At Hamot – 5 gram bolus over 60 min followed by 5 gram over 5 hours
How is TX administered?
10mg/kg over 209 mins followed by 1-2mg/kg maintenance through procedure
What percent of the nation’s blood supply is used during cardiac surgery?
10-15%
Blood transfusions during cardiac surgery are associated w what?
- worse short-term and long-term survival
What is the approximate hematocrit of cell-savaged blood?
55-70%
When blood is “washed” what is removed?
- Serum
-Coagulation factors
-Platelets
What is retrograde autologous priming (RAP)?
RAP is a technique in which CPB prime is displaced by passive exsanguination (back-bleeding) through the arterial and venous lines back into an empty bag that is out of the main circuit, prior to the start of CPB
RAP significantly reduces allogenic blood transfusions for adult cardiac surgery patients requiring CPB
Have to watch blood pressure during this point (will get hypotensive)
When CPB is initiated what is released d/t to the stress response?
- Cortisol
-Catecholamines
-vasopressin
-Angiotensin
-O2 free radicals
What monitors and lines are needed?
-2 large bore IVs (14-16 g preferred)
-Arterial line
-Central venous access (Rt IJ preferred, Lt IJ be careful to avoid the thoracic duct and lt brachiocephalic vein)
BP, ECG, pulse ox, capnography, temperature, urine output, PAC, CO, mixed venous sat, TEE, cerebral ox
Lead II, V4, or V5 (ST analysis for detection of ischemia) TEE is the most sensitive clinical monitor for detecting wall motion abnormalities caused by myocardial ischemia.
Inhalation agents are considered _______ d/t their _______effects
inhalation agents are considered beneficial d/t their preconditioning effects
What are the inhalation agents that should be used and the ones that shouldn’t?
Use: Sevo & Iso
Avoid: Desflurane (HTN, & Tachycardia
-Nitrous and des increase PVR and PA pressures
How often should beta-lactams be redosed?
Q3-4 hrs while the incision is open
-give within 1 hr of incision
When should vanco and an aminoglycoside be given?
Beta lactam allergy
- redosing not recommended
-give within 2 hrs of incision
LIMA is the gold standard for ?
LAD (excellent patency 90-95% at 15 years)
What should SBP and MAP be during cannulation and de-cannulation?
SBP 90-100 mmgHg MAP <70mmHg (to decrease dissection)
complications of aortic cannulation:
-arterial dissection
-hemorrhage
-plaque
-air embolism
-inadvertent placement of distal tip of the cannula in an aortic arch vessel
What happens after cannulation?
venous cannula is places and RAP happens (need increased BP)
Once there is no longer a pulsatile trace on PA or a-line you know what is or isn’t happening?
Blood is now bypassing lungs- turn off mechanical ventilation
what happens initiation of CPB?
aortic cross-clamp is placed and diastolic cardiac arrest happens w antegrade cardioplegia infused
What is the CPB maintained at?
50-60ml/kg/min to reach a CI of 2-2.5 L/min m2
What should mixed venous o2 be maintained at?
70%
How many joules should you defibrillate at with internal paddles on the myocardium?
10-20 joules
What do you want potassium levels at before bypass?
4-5.5
- Calcium frequently given to counteract potassium and to stabilize membrane
What do you want potassium levels at before bypass?
4-5.5
- Calcium frequently given to counteract potassium and to stabilize membrane
When heart starts to eject again, at what pressure should lung re-inflation be done?
Positive pressure below 30 mmHg
What is the normal dose of protamine?
1mg to reverse every 100 units of heparin
- obtain ACT every 3-5 mins to confirm return to baseline
what are the considerations for protamine?
Basic compound isolated from the sperm of certain fish species
Diabetic patients taking NPH insulin may be allergic to protamine
Systemic hypotension and pulmonary hypertension may occur if administered rapidly
If protamine is administered to a patient who has not received heparin, it can bind to platelets and soluble coagulation factors, producing an anticoagulation effect
Do not administered until the patient is decannulated, clot formation in the in the CPB pump will have devastating consequences
administer over 10-15 mins
What does desmopressin (DDAVP) do?
Increases overall platelet function
Raises Von Willebrand Factor and factor III levels 3-5 fold
0.3 mcg / kg
off-pump considerations?
Must have good LV function
Fluid management on the patient is key –> an on-pump CABG has the fluid deficits corrected by the priming of the pump/dilution of patient’s blood volumes you will give more crystalloid/colloid during an off-pump CABG vs. on pump
Aminocaproic acid is not administered antifibrinolytic
MOA: inhibition of plasminogen binding to fibrin and thus conversion to plasmin
Partial heparinization: 100-200 units/kg –>goal ACT >300
PDA and circumflex require extensive verticalization of the apex
Keep MAP elevated during this time –> volume is given now
what should the MAP be for distal anastomosis?
CPP is maintained by keeping a relatively high MAP (90-100mmHg) during distal anastomosis.
What should the MAP be for proximal anastomosis?
At the point of proximal graft aortic anastomosis, MAP is lowered to 60 mmHg
