Ischemia Monitoring & Cardiac SX Flashcards
What diagnostic test is indicated for all with history, suspicion or risk factors of ischemia
12 lead EKG
Can an EKG be normal despite significant CAD?
Yes
What is a stress test?
Response to exercise
What indicates a stress test?
Unstable angina
Suspicious CP
Risk factors
High risk surgery
Can a stress test be normal despite CAD?
Yes, but it does suggest that severe disease is unlikely
What is angiography?
Invasive cardiac catheterization
What information is obtained with angiography?
Coronary circulation
Ventricular muscle movement
EF
What indications call for an angiography?
Accelerating angina
Postive stress test
Questionable stress test in patient with risk factors
What EF is acceptable?
50% or greater
What EF indicates moderate LV function?
Under 50%
What EF indicates poor LV function?
Under 30%
What is the primary goal during anesthesia for a patient that has ischemic heart disease?
Balance myocardial oxygen supply and demand
What BP meds should be continued through prep?
Beta blockers
Continuation of which BP meds are more debated?
ACE inhibitors and ARBs
- BP in better control
- vs intraop hypotension
What other common mediation can be continued through prep?
Statins
-other benefits besides lowering cholesterol
Can anxiety reduction meds be given to these patients?
Yes, Benzos.
-help maintain O2 balance of supply and demand due to anxiety
What is the number one thing anesthetist can do to maintain O2 balance?
Avoid tachycardia
Why is tachycardia so bad for patients with known/risk factors of ischemic heart disease?
Tachycardia increases O2 demand and decreases supply
What are the goals to maintain O2 balance in these patients?
Avoid tachycardia
Try and avoid increased SBP
Avoid decreased DBP
Tolerate increased SBP if it’s necessary to maintain DBP
What induction drugs can be used in these patients?
Any except for Ketamine
Why is ketamine such a bad choice for patients with ischemic heart disease?
Ketamine increases HR
What else should be decreased during induction in order to avoid an increase in HR?
Excessive SNS stimulation
What can you do to decrease sympathetic response associated with induction?
Quick laryngoscopy Lidocaine Narcotics BB (can give extra dose) - or Nipride
What should be considered when choosing maintenance of anesthesia?
LV function
What anesthetic maintenance can be used with strong LV function?
Inhalation agents
What benefit can come from using inhalation agent?
All inhalation agents cause myocardial depression, this decreases O2 demand
What is a common option for maintenance with LV dysfunction?
Low inhalation use with more opioids to supplement
-opioid with less myocardial depression
Postop ventilation may be needed due to higher opioid use to avoid myocardial depression
Amnesia is more likely without adequate inhalation agent
What are 2 risks with using more opioids for maintenance?
Longer emergence
-takes longer to extubate
Amnesia is more likely without adequate inhalation agent
Which agent is most associated with coronary steal?
Isoflurane
Why is isoflurane most closely associated with coronary steal?
It is the strongest vasodilator
When is coronary steal clinically a significant problem?
Only with certain steal prone anatomies
Should isoflurane be avoided in patients with ischemic heart disease?
No
What is coronary steal?
A reduction in the perfusion of ischemic myocardium with simultaneous improvement of blood flow to non-ischemic tissues
What is a risk in using regionals in patients with ischemic heart disease?
Need to maintain BP
- hypotension risk ischemia
- especially DBP hypotension
What are the NMB of choice in patients with ischemic heart disease?
Vecuronium or Rocuronium
What is the risk in using pancuronium in patients with ischemic heart disease?
It causes an increase in HR
-this can be used to offset the bradycardia that occurs with narcotics
Is there a concern with NMB reversal and tachycardia?
No. Addition of anticholinergic does not cause tachycardia at these usually used doses
What two diagnostics are used intraoperatively to detect ischemia?
EKG
TEE
What is the only practical way to monitor myocardial oxygen supply versus demand in unconscious patients?
EKG
Is an EKG or a TEE more sensitive to detecting ischemia?
TEE is more sensitive
What information can be obtained from a PA catheter?
CO
Filling pressures
When are PA catheters more useful?
With LV dysfunction
Is ischemia an indication for use of a PA catheter?
No
Why is hypothermia a concern in the postoperative period?
Shivering increases metabolism and O2 demand
Vasoconstriction occurs to preserve heat, but it increases SVR > heart works harder and uses more O2
What can be done for patients who are cold to help prevent ischemia?
Provide warming measures and apply supplemental O2
What is the concern about pain in these patients?
Pain activates SNS
-Increases myocardial demand
Where is the J point and what is its significance?
The J point can be used to decipher ischemia and it is at the junction of the QRS and ST
How is the J point used to determine if ischemia is present?
It is compared to the PR interval
- if the J point is the same everything is fine
- if the J point is lower there is ST depression
- If the J point is higher there is ST elevation
What is the threshold value?
How much change is clinically significant
-common recommendation is 1mm or greater
What is up sloping?
When the ST segment goes from the J point upward?
What is the significant of up sloping?
It has more false positives
What is the automatic ischemia detection result indicating ST depression?
A negative number
What is ST depression more likely associated with?
Transient ischemia
- O2 balance is out of balance but does not indicate MI
ST depression is more likely indicating transient ischemia, except for what instance?
Subendocardial infarct
What is ST elevation more associated with?
Infarction
What do the leads of an EKG correspond with?
Vectors
-current with direction
How many limb leads are there?
6
What is the common factor with limb leads?
They are all in frontal plane
-superior to inferior
What is the best lead for rhythm detection?
II
What is Einthoven’s triangle
The triangle formed by the RA, LA and LL lead
Where is Lead I?
RA to LA
Where is Lead II
RA to LL
Where is Lead III?
LA to LL
What are the other limb leads called?
Augmented
-direction from the heart out to leads I, II, or III
What are the names of the other limb leads?
aVF, aVR, aVL
What plane are the precordial leads in?
Transverse plane
What leads are the precordial leads?
V1 - V6
Traditionally what 2 leads should be monitored during anesthesia?
II and V5
What 2 leads according to Nagelhout should be monitored?
III and V3
How many leads (patch system) allows you to get a true transverse plane? (anterior wall of LV)
5 lead system
What plane does the 3 lead EKG monitor?
Frontal plane
What is a modified chest lead? In Nagelhout
In a 3 lead EKG you can move the LA black to V1 (MAC1L)
- monitor setting to aVL
- actually monitors V1
What is a modified chest lead? Traditionally
In a 3 lead EKG move the LL red to V1 (MACL1)
- monitor setting to III
- actually monitors V1
What is ST elevation associated with?
MI
-STEMI
What blood test is used to confirm ST elevation?
Troponin
When will Troponin increase?
Within 3 hours of event
What interprets infarct on a 12 lead?
Changes in leads of involved area Changes in reciprocal leads T wave changes -last longer than ST changes Pathological Q wave -develops last
What leads indicate inferior ischemia?
II
III
aVF
What leads indicate lateral ischemia?
I
aVL
V5
V6
What leads indicate anterior ischemia?
V3-V4
Co-existing: V3-V5
What leads indicate septal ischemia?
V1 - V2
Which coronary artery is associated with the lateral wall?
Circumflex
Which coronary artery is associated with the inferior wall?
Right coronary artery
Which coronary artery is associated with the septum?
Left anterior descending artery
Which coronary artery is associated with the anterior wall?
Left anterior descending artery
What makes detection of ischemia impossible?
LBBB
What does BBB do to the QRS complex
BBB makes QRS wider
What is R wave progression?
On the precordial leads the R wave height increases to about V4, and then decreases
What is indicated with poor R wave progression?
LV dysfunction
LVH
COPD
Old anterior MI
Overall what does poor R wave progression tell you?
Patient is at risk of failure
With ischemia, an increased HR and normal BP what can be used to improve O2 balance?
BB
With ischemia what can be used to decrease preload and therefore demand?
NTG
With ischemia, an increased HR and low BP cause can be used to improve O2 balance?
Fluids
Phenylephrine
-Increases CPP and lowers HR
When should a BB be avoided?
If no tachycardia
BP is low
Evidence of failure
What is coronary angioplasty?
Fluroscopically guided coronary stenting/ballooning
What are the big risks of angioplasty?
Re-stenosis and artery rupture
How long should elective surgery be delayed after placement of drug eluding stent?
12 months
Why should elective surgery be delayed after placement of drug eluding stent?
Surgery induces a prothrombotic state and increases risk
Should anti-platelet therapy be continued in patients who have drug eluding stents who present for surgery?
Most commonly ASA is continued but other therapy is stopped
-Include cardiologist
What is the main goal during CABG?
Balance of O2 supply and demand
What technique can be used for CABG in those with LV dysfunction?
High opioid technique
What technique can be used for CABG in those with perserved LV function?
Inhalation anesthetic
CPB flow can be related to what measurement?
The patient’s cardiac output
What does the perfusionist manage?
Flow
Temperature
acid/base balance
What type of flow does a roller pump do?
Continuous flow regardless of resistance
- some have pulsatile, so systolic and diastolic
What is a downside of a roller pump?
It can allow air to circulate if reservoir is low
What kind of flow occurs with a centrifugal pump?
Flow varies
Not pulsatile
What is an advatange of centrifugal pump?
It will not allow air to circulate
What kind of pressure does patient have with centrifugal pump?
Just a mean pressure
Where is the venous cannula for CPB inserted?
Venous cannula into the vena cava
Where is blood returned to the patient with CPB?
Arterial cannula into the aorta
What is said about a pateint’s blood once it enters the CPB pump?
It is hemodiluted
What is a patient on CPB have hemodiluted blood?
Volume increases due to the inclusion of the pump
What happens to viscosity with CPB?
It is decreased
Why would some of the patient’s autologous blood be removed before CPB?
To protect some of it from the deterimental effects of the pump
What does the CPB machine do to the blood cells?
Mechanical trauma
What stress response does the body have to CPB?
The body is stressed and releases:
- catecholamines
- cortisol
- vasopressin
- angiotensin
What inflammatory effects does the CPB have?
Systemic inflammation from artificial surfaces:
- complement
- coagulants
- platelet dysfunction
What occurs due to the high oxygen use during CPB?
Oxygen derived free radicals > oxygen toxicity
What anticoagulant is used during CPB?
Heparin
What test is used to evaluate heparinization?
ACT
What is the minimum ACT value for safe CPB?
400
What additional monitoring is needed during CPB?
A-line (Sx may also put in a femoral line)
PA catheter
Foley - UOP
Temperature in multiple sites - at least 2
What purpose does CPB serve while surgeon is operating on coronaries?
To preserve myocardium, avoid ischemia and maintain balance of O2 supply and demand
Why is hypothermia initiated with CPB?
Hypothermia decreases oxygen requirements by half for every 10 degree reduction
What is cardioplegia?
Solution delivered by perfusionist that is used to decrease O2 demand of the heart
Why does cardioplegia contain potassium?
To stop electrical activity which decreases O2 demand
What rhythm can occur due to this cardioplegia postop?
Heart block
-temporary pacemaker
What happens to anesthetic need during CPB?
Hemodilution > diluted doses, but hypothermia reduces requirement
How are IV drugs given during CPB?
Via CPB pump
How is inhalation anesthetic given during CPB?
Via CPB pump
What may be required when rewarming?
Additional medications due to increased metabolism
How does weaning from CPB occur?
Slowly to monitor how heart responded to returning volume
When can the CPB be discontinued?
Patient is fully warmed
Heart is handling volume
Hemodynamics are stable
What may be needed if heart is not contracting well?
Inotropes
What are somethings that may cause you to go back on pump?
Hemodynamic instability
Ischemia
What is an intraortic balloon pump?
Balloon located in aorta
- Inflates during diastole
- deflates during systole
- “counter pulsation”
During IABP inflation, what is occurring?
Balloon inflates during diastole
-puts back pressure on blood flow to push it into coronaries
During IABP deflation, what is occurring?
Balloon deflates during systole
-creates vacuum effect pulling blood forward, decreasing afterload and increases SV
Where will you see inflation pressure of there balloon on the monitor?
At the dicrotic notch
What is given to reverse heparin?
Protamine
What besides protamine can be given to help return clotting ability?
Autologous blood
Blood products
What can occur with rapid administration of protamine?
Vasodilation
What occurs with a protamine reaction?
Pulmonary HTN
What patient’s are at greater risk for protamine reaction?
Fish allergy
Insulin managed diabetics
-there is an insulin that contained a small amount of protamine in it
Vasectomy
What does increased chest tube bleeding possibly mean?
Return to OR for re-exploration
- possible suture loose
- cardiac tamponade possible from bleeding
If a postop CABG has cardiac tamponade is Ketamine THE choice for induction?
No, due to easy/quick surgical opening of chest ketamine does not have to be used to preserve HR
What are the risks of CPB?
Inflammatory response
Complement reaction
Coagulation abnormalities
Neurological injury
What is MIDCAB?
Minimally invasive direct coronary artery bypass
- smaller incision
- normothermia
- +/- sternotomy
- +/- pump
What medication WAS used to slow HR for MIDCAB that may not be needed anymore?
Beta blockers
What kind of technique can be used by anesthesia to give surgeon better view and more access during MIDCAB?
One lung ventilation
If pacing is needed after MIDCAB what kind is used?
Transcutaneous pacing
What is an off pump CABG?
CABG performed with:
- sternotomy
- normothermia
- beating heart (tool used by surgeon quiets only surgical area)
What occurs in the quieted area of the heart during an off pump CABG?
Temporary occlusion and ischemia
Is heparinization required with off pump CABG?
Yes, full or partial
What “back up” equipment should be readily available with an off pump CABG?
CPB pump
What is used to maintain BP during off pump CABG?
Volume and pressors
What possible benefit does using inhalation agents have with off pump CABG?
Preconditioning
What has been shown to be reduced with off pump CABG?
Neuro complications and transfusions
What causes hemodilution in CPB?
M&M
The CPB pump is primed with a balanced salt solution (LR) Other added components may include: -collides -mannitol -heparin -bicarb
What is the driving force for flow into the CBP pump?
It is directly proportional to the difference in height of the patient and the reservoir, and inversely proportional to the resistance of the cannulas and tubing
Where is anesthetic gas added on a CPB pump?
In the oxygenator
How does the heat exchanger warm or cool the blood?
Via conduction
-temp of the water flowing through the exchanger
Which pump delivers continuous non-pulsation flow?
Roller pump
Which pump can can continue to pump regardless of resistance encountered?
Roller pump
Which pump is non-occlusive and therefore less traumatic to the blood?
Centrifugal pump
Which type of CBP can have pulsatile flow?
Roller pump
Which CPB does not have the possibility of entraining air?
Centrifugal pump
What are the perceived benefits of pulsatile flow with CPB?
Improved tissue perfusion
Enhances oxygen extraction
Attenuated the release of stress hormones
Results in lower SVR during CPB
How much is metabolic oxygen requirements reduced with hypothermia?
Requirements are generally halved with each reduction of 10 degrees Celsius
What core body temperature is usually used?
Tepid bypass?
Profound hypothermia?
20 to 32 C
30 to 35 C
15 to 18 C
What are some of the adverse effects of hypothermia?
Platelet dysfunction
Coagulopathy
Depression of myocardial contractility
What is circulatory arrest?
Profound hypothermia for complex repairs of 15 to 18 C
Duration of as long as 60 minutes
Both heart and CPB machine are stopped
What may be produced with reperfusion following a period of ischemia?
Excessive oxygen-derived free radicals
Intracellular calcium overload
Abnormal endothelial-leukocyte interactions
Myocardial cellular edema
How does cardioplegia work?
By increasing extracellular potassium concentration transmembrane potential is reduced
What affect does CPB have on pharmacokinetics?
Plasma and serum concentrations of most water soluble drugs acutely decreases (ND-NMB); minimal and inconsequential change for most lipid soluble drugs (fentanyl)
Why may a radial arterial catheter give a falsely low reading following sternal retraction?
Compression of the subclavian artery between the clavicle and the first rib
Why is the right internal jugular preferred for CVC?
Placement on the left are more likely to kink following sternal retraction and are less likely to pass into the superior vena cava
What can happen to the PAC during CPB?
It can migrate distally and spontaneously wedge without balloon inflation
- routinely retract 2-3 cm during CPB
- inflate balloon slowly, if catheter wedges with less than 1.5 mL of air, withdrawal further
What laboratory testing during cardiac surgery should be available?
Blood gases Hgb K+ iCa GLU ACT
What can TEE provide during cardiac surgery?
Cardiac anatomy and function
Regional and global ventricular abnormalities
Chamber dimensions
Valvular anatomy
Intracardiac air
Confirm cannulation of coronary sinus for cardioplegia
What is a normal ACT?
< 130 s
What are disadvantages or high-dose opioid anesthesia?
Prolonged postop respiratory depression
High incidence of recall
Failure to control hypertensive response to stimulation in those with preserved LV fx
Skeletal muscle rigidity
Prolonged postop ileus
If given with benzos: hypotension and myocardial depression
Why is N2O generally not used, especially during the time interval between cannulation and decannulation?
Because of its tendency to expand an intravascular air bubbles
Which NMB is associated with markedly enhanced bradycardia with large doses of opioids (especially sufentanil)?
Vecuronium
What NMB has vagolytic effects and is often used in patient with marked bradycardia who are taking BB?
Pancuronium
What NMB have almost no effect on hemodynamics on their own?
Rocuronium
Vecuronium
Cisatracurium
When can accentuated vagal responses occur in the prebypass period? (Marked bradycardia and hypotension)
Sternal retraction and opening of the pericardium
What ACT result is considered adequate to in a CPB case?
ACT longer than 400 to 480 s
What patients can show a resistance to heparin?
What can be given in order to combat this for adequate heparinization?
Those with antithrombin III deficiency (acquired or congenital)
Infusion of antithrombin III or FFP
What drug class is given either before or shortly after anticoagulation for bleeding prophylaxis?
Antifibrinolytics
Do the antifibrinolytics e-amniocaproic acid and tranexamic acid affect the ACT?
No
On CPB what is the equation for MAP?
MAP = pump flow x SVR
What serial blood tests are performed on CPB?
ACT (every 20-30 min)
Hct
K+
GLU
When is ventilation discontinued during CPB?
When adequate pump flows are reached and the heart stops pumping blood
What can occur if ventilation is discontinued prematurely when there is an remaining pulmonary blood?
It acts as a right-to-left shunt and promotes hypoxemia
When is an intraaortic ballon pump used?
When drug therapies fail to improve contractility
When should the balloon on IABP inflate?
Just after the dicrotic notch to augment DBP and coronary flow after closure of the aortic valve
When should the balloon on the IABP deflate?
Just prior to LV ejection to decrease afterload
What inotrope is the most potent?
Epinephrine
What inotrope does not increase filling pressures and may be associated with less tachycardia?
Dobutamine
What class drug is milrinone?
Selective phosphodiesterase inhibitor and inotrope with arterial and venous dilator properties
After bypass, where is SBP maintained, and why?
< 140mmHg to minimize bleeding
On a computerized ST segment analysis, which depressed ST segment has greater specificity?
Horizontal or downsloping depressed ST segment
-fewer false positives
Nagelhout
Is it more challenging to identify the affect regions of the myocardium based on ST segment depression or elevation?
ST segment depression
In patient without a preop 12 lead ECG or those who have a baseline 12 lead that is unremarkable what leads in what order are recommended for continuous monitoring?
V3, V4, V5, III, aVF
What lead was found to detect ischemia earliest and most frequently?
V3
What is the purpose of drug eluding stents?
Co-existing
Reduce neointimal hyperplasia by preventing cell division
What makes a coronary artery prone to thrombosis after angioplasty?
Angioplasty causes vessel injury, especially destruction of the endothelium?
Why is a coronary prone to thrombosis for so long after angioplasty and placement of a drug eluding stent?
It takes 2-3 weeks for a vessel to reendothelialize after angioplasty
Up to 12 weeks after bare metal stent placement
Even up to more than 1 year after drug eluding stent placement
What are the categories of stent thrombosis occurrence? Acute Subacute Late Very late
It is by time interval:
- acute within 24 hours
- subacute between 2 and 30 days
- late between 30 days and 1 year
- very late after a year
What antiplatelet therapy is best at preventing stent thrombosis?
Dual antiplatelet therapy:
Aspirin and a P2Y12 inhibitor
What is the most significant independent predictor of stent thrombosis?
Discontinuation of P2Y12 inhibitor
How long should dual antiplatelet therapy be maintained?
Angioplasty: at least 2 weeks
Bare-metal stent: at least 6 weeks
Drug eluding stent: at least 1 year
Recommended time intervals to wait for elective non cardiac surgery after coronary revascularization?
Angioplasty w/o stent: 2-4 weeks
Bare metal stent: at least 30 days; 12 weeks preferable
Coronary artery bypass grafting: at least 6 weeks; 12 weeks preferable
Drug eluting stent: at least 12 months
Why should hyperventilation be avoided?
Hypocapnia may cause coronary artery vasoconstriction
What drugs have been shown to blunt the increase in HR associated with tracheal intubation?
Laryngotracheal lidocaine IV lidocaine Esmolol Fentanyl Remifentanil Dexmedetomidine
What NMB is associated with histamine release and resulting decrease in BP?
Atracurium
-not a desirable drug in these patients
In NMB reversal which anticholinergic is preferred with cardiac patients due to it having less chronotropic effect and central effect?
Glycopyrrolate
What is the simplest and most cost effective method for detecting peri operative myocardial ischemia?
ECG
What events other than myocardial ischemia can cause ST-segment abnormalities?
Dysrhythmias Conduction disturbances Digitalis Electrolyte abnormalities Hypothermia
If a PAC is being used intraoperatively, how can myocardial ischemia be detected?
Acute increase in pulmonary artery occlusion pressure due to changes in left ventricular compliance and LV systolic performance
When should treatment of myocardial ischemia (noted on ECG) be instituted?
When there are 1 MM ST-segment changes on ECG
Depolarization toward a positive electrode results in what type of deflection?
Positive deflection
Depolarization direct away from a positive electrode produces what type of deflection?
Negative deflection
When a depolarization wave is perpendicular to the lead what type of deflection is seen?
Biphasic
Lead I consists of what 2 leads?
Left shoulder +
Right shoulder -
Lead II consists of what 2 leads?
Left leg +
Right shoulder -
Lead III consists of what 2 leads?
Left leg +
Left arm -
What is the normal range of the axis of the heart?
-30 to 90 degrees
Hypertrophy of the LV shifts the axis in what direction?
Left
Hypertrophy of the RV shifts the axis in what direction?
Right
Left axis deviation is defined as what degree?
Less than -30
Right axis deviation is defined as what degree?
Greater than 90 degrees
What is standard calibration for ECG?
1 cm / 1 mV and 25 mm per second
How much voltage does each 1 mm vertical line represent on ECG paper?
0.1 mV
How much times does each 1 mm horizontal line represent on ECG paper?
0.04 seconds
The distance between 2 darker lines on ECG represents how much time?
- 2 seconds
0. 5 mV
HR is beats per minute can be calculated by using 2 consecutive beats on ECG paper how?
Divide 300 by the number of large boxes between 2 beats
- because 1 minute is 300 big boxes
- or 1,500 small boxes
