Cardiac Anesthesia Flashcards
(35 cards)
1
Q
What should be included in the preop evaluation of a cardiac patient?
A
- Severity of disease/hemodynamic status
- degree of impairment of contractility
- development of compensatory mechanisms
- exercise tolerance
- Hx of CHF or MI-ST segment changes
- Angina
- dysrhythmias
- compensatory increase in sympathetic nervous outflow
- HR, anxiety, diaphoresis
- Hx of previous surgery
2
Q
Which labs should be included in the pre-op of a cardiac patient?
A
- CBC
- electrolytes
- cardiac enzymes
- serum creatinine
- coagulation profile
- type and cross
- MUST have PRBCs available
3
Q
What changes will you see in lab values after an acute MI?
(graph)
A
- Peak A- early realease of myglobin or CK-MB (Creatinine Kinase with myocardial band) isoforms after AMI
- Peak B- cardiac troponin after AMI
- can be used to determine how much cardiac cell death occured from the MI
- Peak C- CK-MB after AMI
- Peak D- cardiac troponin after unstable angina
4
Q
What is the preferred biomarker for myocardial damage?
Why?
A
- Cardiac troponin
- absolute myocardial tissue specificity (CK can be elevated for other reasons like diet, etc.)
- high sensitivity
5
Q
What other cardiac tests can be done?
A
- Catheterization can tell you:
- LVEDP
- EF
- CI
- Echo can show you:
- EF
- wall motion abnormalities
- CXR can show:
- Cardiomegaly
- pulmonary vascular congestion, edema, effusion
- Angiography
- EKG can show:
- ischemia/infarct
6
Q
What daily medications should be taken up until the operative day?
A
- antiarrhythmics
- Ca+ channel blockers
- B blockers
- nitrates
7
Q
What monitors would you use during a cardiac surgery?
A
- Pulse Ox
- TEE
- EKG- leads V and II
- Temp
- ABG- usually radial, sometimes femoral
- CVP- mandatory for infusion of drugs
- PA catheter
- pts with severe LV dysfunction
- pts with profound pulmonary HTN
8
Q
TEE:
Frequency?
What can it determine?
A
- Intermittent pulses with a frequency of 2.5-7.5 MHz
- Can determine:
- preload
- hypotension
- CO
- LV filling pressures
- LV contractility
- LV afterload
- ischemia, emboli, valvular pathology
- assessment of surgical repairs
9
Q
How do you set up the OR for a cardiac case?
A
- Pacemaker
- Drips (most common):
- NTG/ NTP
- epinephrine/Norepi
- phenylephrine/ephedrine
- dopamine/dobutamine
- antiarrhythmics (esmolol, lidocaine, mag, amiodarone)
- Heparin and coagulation monitoring capability (ACT, TEG)
- emergency drugs
- PRBC available in OR
10
Q
What are the doses for an opioid anesthetic?
What muscle relaxant would be chosen and why?
A
- Fentanyl 50-100mcg/kg
- Sufentanyl 10-20 mcg/kg
- Pancuronium- b/c opioids decrease HR and pancuronium brings it back up
- *today pts are still given large opioid doses, but are induced with etomidate
- **Will get chest rigidity with these large narcotic doses, pre-treat with vecuronium
11
Q
What are the risks associated with administration of vasoconstrictors?
A
- can cause further vasospasm in vasospastic-prone areas of the heart
12
Q
What happens during the incision to bypass period of the surgery?
A
- Intense surgical simuli
- Hypertension
- deepen anesthetic, NTG/NTP
- handling of the heart by the surgeon
- can cause hyper or hypotension and arrhythmias
- communication is very important
- bleeding can be significant
- identifying and localizing inschemia
- drop the lungs for sternotomy
- arterial and saphenous veins are harvested
13
Q
What happens immediately before bypass?
A
- heparinization
- binds to antithrombin III and potentiates its natural anticoagulant properties
- 200-300 units/kg- peaks in 2 minutes
- Check ACT (nml is <130 (70-110)
- ACT of 350-500 is accteptable
- Administer heparin through CVP or directly into RA
- Effects of Heparin:
- SVR and BP decreasy by 10-20%
14
Q
What are some “special circumstances” to keep in mind regarding the heparin administration.
A
- Pt may have antithrombin deficiency
- pt may be on long term heparin therapy
- excessive hemodilution
- heparin-induced thrombocytopenia, antibdy mediated
- NTG- heparin doesnt work properly if pt takes NTG frequently
- **check the ACT 3-5 min after administration. If it is not increased, either give more heparin, or give FFP or thrombate III so the heparin has something to bind to.
15
Q
What happens immediately before bypass?
A
- **Cannulation of the aorta (arterial) and RA (venous)
- Must drop the pts BP for aortic cannulation (to avoid rupture of the aorta)
- BP might drop and /or arrhythmias can occur while placing venous cannula
- the perfusionist can give fluids via the arterial line
- *cannulation of the coronary sinus for retrograde cardioplegia
- can have similar effects (decrease in BP)
- ,medicate pt with muscle relaxant, midaz and fentanyl because VD is increased d/t the increased amt of fluids that prime the pump
- this is cause of recall with cardiac survery
- make sure perfusionist has anesthetic gas turned on
16
Q
What happens right as pt is put on bypass?
A
- pt cooling starts
- cease ventilation- disconnect the pt from vent?
- IV fluids shut off
- VA turned off
- make sure perfusionist has instituted anesthetic
- pull back swan catheter
- give NMB to prevent shivering
- Significant drop in BP
- hemodilution causes decreased viscosity
- rapid dilution of catecholamines
- aortic cross-clamp to prevent systemic extravasation of antegrade cardioplegic solution
17
Q
What is cardioplegia solution?
A
- Cold, K+ containing solution that reduces metabolism of the heart.
- 4 degrees C
- V-fib occurs at 25-30 degrees C
- depolarization of the heart- stops heart
- don’t want the cardioplegia solution to become systemic.
- check labs after coming off pump
18
Q
Once heart has been arrested and surgeon begins revascularization or valve replacement procedure, what happens to the pts BP?
Where is it maintained?
What is the CVP?
A
- Flow is no longer pulsatile
- flow rate is usally 50-60 ml/kg
- BP is maintained at 50-60 mmHg
- lower BP is beneficial for hematology
- not as good at perfusing kidney and brain
- empty foley before going on bypass and check throughout time on bypass
- higher BP is beneficial for stroke pts
- lower BP is beneficial for hematology
- CVP is 0 mmHG, if higher there might be a kink
19
Q
What are the hematological effects of CPB?
A
- Effects both extrinsic and intrinsic coagulation pathways
- Factor XII conversion to factor XIIa on various surfaces of CPB circuit
- Directly impairs platelet function
- rapid adhesion and conformational alteration of plasma proteins, ie von Willebrand factor (vWF) and fibrinogen
- platelet aggregation and detatchment due to shear forces
- Shear damage sets off intrinsic pathway of coagulation
- impaired coagulation + heparinization leads to bleeding problems
20
Q
How can bleeding be prevented?
A
- Prophylactic use of antifibrinolytic drugs before CPB reduces bleeding and transfusion
- aminocaproid acid (EACA) and TXA
- serine protease inhibitor aprotinin
- taken off the market, being researched again in canada
21
Q
What are the risks to the CNS system during bypass?
A
- embolization
- hypoperfusion
- inflammation-
- influencing factors
- aortic athermatous plaque- dislodged while surgeon is cannulating
- cerebrovascular disease
- altered cerebral autoregulation
- hypotension
- intracardiac debris- dislodging plaques in heart
- air
- cerebral venous obstruction- keep head centered
- cerebral hypothermia
- hypoxia
22
Q
What can we do to promote cerebral protection?
A
- Emboli are the biggest culprits
- hypothermia- wrap brain in ice if pt has history of stroke or TIA
- barbiturate therapy?
- Ca+ channel blockers to vasodilate in brain
- blood gas management
- adequate BP
- cerebral oximetry
23
Q
How should fluids be managed?
A
- Keep fluids to a minimum
- replace blood loss with colloids, cell saver or PRBCs
- generally 1-1.5 L is acceptable for crystalloids
24
Q
When is rewarming started?
A
- begins prior to aortic cross-clamp removal
- OR begins with the last distal anastomosis in angioplasty procedure
- OR begins when all the valve sutures are in and knots are being tied down
25
How is rewarming done?
* 1° C per 3-5 min
* turn on heating blanket
* temp gradient between arterial and venous blood should remain below 10°C
* too large of gradient can cause lots of air emboli
* usually takes 30-40 minutes
* amnestic and NMB agents should be given
* SVR drops d/t vasodilation
26
What must be done prior to discontinueing bypass?
* Pt must be warmed
* surgical field should be dry
* lab values checked- correct any electrolyte abnormalities
* pulmonary compliance evaluated- reconnect circuit, re-expand lungs and start ventilating again
* begin ventilating lungs
* regulate cardiac rhythm by pacing, defibrillating or pharmacologically
* transfuse pt with pump volume (about 50-100 ml)
* Look at PA diastolic BP, now with TEE we can look at the heart.
27
What should you think about as you prepare to wean off bypass?
(table)
28
What is the ratio of systemic BP to pulm BP used for in discontinueing bypass?
* If pulmonary pressure is high but BP is low then there is ventricular failure???
* If CO is low, but BP is adequate, then vasodilation is necessary
* If BP is low, use inotropes, give volume (cell saver, PRBC)
* \*\*Once pt is stable, bypass is completely d/c'd
29
What can we do if LV function is decreased?
* Inotropes
* PRBC
* preload
* afterload
30
What can we do if RV function is decreased?
* decrease pulm vasoconstriction
* beta2 agonists, prostaglandind E1, nitric oxide based vasodilators
* If unrealated to pulmonary vasoconstriction, cyclic adenosine monophosphate-specific phosphodiesterase inhibitors may be beneficial
* ventricular assist devices
31
What is the checklist for coming off bypass?
Step 1?
Step 2?
(chart)
32
Describe the pressure volume loops of the LV.
(diagram)
33
Protamine:
Who is at risk for anaphylaxis?
where is it derived from?
dose?
* Anaphylaxis:
* pts with previous exposure
* pts having a vasectomy
* pts of NPH insulin
* Derived from salmon sperm
* 2-4 mg/kg or 1-1.3 mg per 100u of heparin given
* Check ACT and give more accordingly
* Can cause vasodilation, vige slowly over \>5 min
34
What should be done if pt has a history of reaction to protamine?
* do not rechallenge the pt
* option to not reverse the heparin
* surgeon may do less invasive procedure off pump with an alternative to heparin
* if heparin is used, non-protamine heparin reversal drugs such as PF4 or heparinase or waiting for the heparins effects to dissipate
35
What are some goals for minimally invasive cardiac surgery?
* reduce HR, increase preload
* avoid and treat arrhythmias
* adjust ventilator settings
* have heparin ready in case pt goes on bypass
* reversal of heparin depends on the institution
