Exam 3 ppt key points Flashcards
What are the Risk Factors for CAD
Age Gender (Male) Family Hx Smoking- 6x greater in women, 3x greater in males HTN High Cholesterol- high LDL & low HDL Diabetes Obesity Physical Inactivity Stress
At the center of the cardiovascular system is ?
the heart.
Myocardial blood supply is derived entirely from ?
the right and left coronary arteries.
The left coronary normally supplies
the LA, interventricular septum, and LV.
The right coronary normally supplies
the RA, most of the RV, and variable amounts of LV.
The most frequently performed cardiac operation is?
Coronary artery bypass grafting
CABG technique involves bypass of a narrowed or occluded epicardial coronary with a small-diameter conduit distal to the narrowed segment. Selected grafts include?
reversed saphenous
internal mammary artery
___________ appears to have superior long-term performance with 90% patency rates at 10 years.
The IMA
The choice of conduit in CABG depends on?
availability and durability
50% of vein grafts will be significantly diseased or occluded at 10 years.
The IMA appears to have superior long-term performance with 90% patency rates at 10 years.
When using a saphenous vein graft in CABG, the proximal arterial inflow source is?
the ascending aorta.
When the LIMA is utilized in CABG, the proximal arterial inflow source is
the left subclavian artery.
_________ is used to replace the function of the heart in CPB
Arterial pump
Arterial pump generally uses one of two primary technologies
A roller pump
A centrifugal pump – thought to be less traumatic
Identify the correct order of steps to CPB
- Priming
- Anticoagulation
- Cannulation
- Initiation
- Maintenance
- Weaning and Termination
The solution used to prime the CPB circuit is generally _______
a balanced electrolyte solution
Hemodilution in CPB is due to?
Prime volume
Standard procedure requires that the patient be ___________ before cannulation for CPB. _______ is still the standard agent used.
fully anticoagulated
Heparin
Heparin administered through a central venous catheter at an initial dose of ________ for CPB
300 U/kg
Heparin Onset is almost immediate, but generally the drug is allowed to circulate for ______________ before it’s effect is measured.
3-5 minutes
The ACT must increase to at least _______ before CPB is initiated.
300 seconds
400 for most institutions
The ACT is not used to monitor heparin levels but to monitor __________
the anticoagulant effects of heparin and other anticoagulants.
Elevated ACT measurements taken, before, during, or after CPB may be influenced by variables other than heparin which include?
Hypothermia
Hemodilution
Aprotinin
Every CPB procedure requires a high-flow cannula in a large vein and another in a large artery for withdrawing blood from and returning blood to the patient. The target for venous cannulation is ?
RA- It’s appendage is conveniently accessible through a sternotomy.
The RA may also be approached through the femoral vein.
For CPB venous cannulation, the right atrium can be accessed through?
appendage is conveniently accessible through a sternotomy.
The RA may also be approached through the femoral vein.
The CPB circuit returns oxygenated blood to the patient through the arterial cannula.
For CABG procedures, the standard target for the arterial cannula is ?
the portion of the ascending aorta below the aortic arch but still 3-4 cm above the aortic valve.
Which patients require direct left ventricular venting in CPB
patients with severely compromised ventricular function undergoing CABG
Patients undergoing any intracardiac procedures
Patients with aortic insufficiency
left ventricular venting in CPB may be necessary for patients with aortic insufficiency because?
The LV vent is separate from the cardioplegia cannula, it can be used to decompress the heart during antegrade cardioplegia administration.
LV vents are typically introduced through ?
the right superior pulmonary vein and advanced through the LA, across the mitral valve, and into the LV
What is the indication that the venous cannula is adequately draining the venous return to the heart?
right sided heart pressure (CVP and PAP) should decrease to O mmHg and become nonpulsatile.
During CPB initiation describe arterial BP and arterial tracing
Arterial blood pressure should reach a normal mean pressure (60-90 mmHg) while also becoming nonpulsatile.
The arterial tracing usually becomes nonpulsatile as the heart is emptied and the pumping force is changed from the ventricle to the nonpulsatile arterial pump of CPB machine.
During CPB initiation, the heart is arrested in diastole by ?
the administration of potassium enriched cardioplegia solution to the heart.
__________ is the single most important step in reducing the heart’s myocardial oxygen consumption by 90%.
Interrupting myocardial electromechanical activity
Reduction in myocardial consumption by cardioplegia during CPB is augmented by?
Hypothermia at 22 degrees C
This is achieved by administering cold cardioplegia solution.
The combined influence of potassium arrest and myocardial temperatures lower than 22 degress C reduces myocardial oxygen consumption by ________% and enables the tissue to withstand complete interruption of blood flow for periods of ________________
97%
20-40 minutes.
For induction of cardioplegic arrest, a “high-K” solution with a potassium concentration of approximately ____________ is used.
20-30 mEq
What are the characteristic of the cardioplegia solution during initiation
Has a potassium concentration of approximately 20-30 mEq.
Designed to be slightly hypertonic to reduce edema.
Include a buffer to counter the heart’s production of acidic metabolites.
Contains a substrate for energy or catalysts to assist the heart’s production of ATP.
Maintenance phase of CPB entails
After isoelectric arrest is induced, the solution is changed to a “low-K” mixture with a potassium concentration of about 10 mEq.
Periodically throughout the procedure, 200-500 mL doses of “low-K” solution are administered to deliver nutrients to the cells and maintain the potassium concentration.
Cardioplegia can be administered antegrade into the coronary arteries via the aortic root, or retrograde into the coronary sinus/veins.
The most complete technique for myocardial protection involves both antegrade and retrograde delivery.
What is the potassium concentration of cardioplegia solution during CPB.
10 mEq
Cardioplegia can be administered antegrade into the coronary arteries via ___________, or retrograde into ________.
the aortic root
coronary sinus
Immediately after termination of CPB, the patient is often hemodynamically supported with?
volume (blood, albumin, crystalloids, hespan)
frequently supplemented with vasopressors or inotropic agents.
During the weaning and termination phase of CPB, when the patient is hemodynamically stable, protamine can be administered to reverse the anticoagulant effect of Heparin. Protamine dose is ?
1mg / 100 units Heparin given.
What is the primary concern during induction of a patient for CABG
Prevention of myocardial ischemia
Two factors associated with myocardial ischemia include
Inadequate oxygen supply (coronary lesions)
Excessive oxygen demand (HR, BP, Adrenergic stimulation)
Patients with _____________ are more susceptible to insult during induction.
disease of the left main coronary
Many cardiac patients require fluid loading or prophylactic treatment with pressors during induction because?
They have low circulating blood volumes because of hypertensive vasoconstriction.
Small doses of phenylephrine or ephedrine may be necessary to avoid excessive hypotension.
The lungs must be deflated to prevent laceration or puncture during sternotomy for how long
for approximately 15-20 seconds
Bolus administration of heparin through the central line may decrease arterial pressure by _________?
10-20%.
ACT should be approximately __________ before it is safe to institute CPB
400 seconds
Anticoagulation is measured _______ after heparin bolus by ACT.
3-5 minutes
Aortic cannulation is associated with hypertensive response, probably because of?
Direct stimulation of sympathetic nerves in the aortic arch.
___________ assists aortic cannulation and prevents laceration of the aorta.
Reduction in MAP
Venous cannulation may lead to?
Fluctuations in arterial pressure and ventricular tachyarrhythmias secondary to manipulation of the heart.
CPB should not commence unless the following have been completed by the anesthesia provider:
Heparin administered
ACT checked and at least 350-400
Adequate muscle relaxation
Inotropic infusions turned off
Pupil symmetry assessed for later comparison
Pulmonary artery catheter pulled back 5 cm
Urinary output emptied before bypass
During CPB initiation, the clamps placed across the cannulas during insertion are removed in what sequence?
venous, then arterial
Multiple events occur simultaneously and can cause a significant drop in blood pressure at the initiation of CPB. They are?
Preload to the heart decreases causing a loss of stoke volume, while hemodilution decreases blood viscosity and dilutes catecholamines in the plasma contributing to the drop in pressure.
During CPB initiation, rapid cooling of the patient occurs to a target temperature of ?
28 degrees C
ACT is checked every __________ by the perfusionist and is maintained at _________ with the addition of heparin.
30-45
> 400 seconds
While most think CPB is break time, it is NOT! Why?
Swan migration Paralysis Amnesia MAP pH Urine output Glucose
What is the checklist for weaning from CPB?
Patient is warm, at least 35 C
Heart rhythm has returned
HR 70-100. < 60 reduced CO; > 120 reduced LV filling
Inflate lungs
Labs: K+, iCa++, Hct, pH, ACT
Drugs: Lidocaine, Calcium, Magnesium
When the patient is weaned from CPB, considerations should include
the ventricular function of the heart before bypass
the length of time the aorta was cross-clamped.
3 Basic Groups Coming Off Bypass
Patients with good ventricular function
Hypovolemic patients
Patients with pump failure
Features of hypovolemic patients (mixed group) coming off CBP
Respond quickly to 100 mL aliquots of pump blood, FFP, or PRBC’s. BP and CO rise with each bolus, sustainable. LVEDP below 10-15 mmHg.
Impairment should be suspected when LVEDP rises with volume infusion without appreciable changes in BP or CO. These patients require LVEDP above 10-15 mmHg
Features of patients with pump failure coming off CBP
Sluggish, poorly contracting heart that progressively distends.
Inotropic therapy is initiated. If SVR is high, afterload reduction can be tried along with inotropic therapy.
Ultimately, CPB may need to be reinstituted.
This drug does not increase filling pressure and may be associated with less tachycardia. CO often increases without significant changes in blood pressure.
Dobutamine
If inotropes and afterload reduction fail during separation from CPB
CPB may be used as a bridge to an intra aortic balloon pump.
This drug improves renal blood flow (low doses) and is often more effective in raising blood pressure than in raising CO.
Dopamine
Clinically is the most potent inotrope and is usually effective in increasing both cardiac output and systemic blood pressure when other agents have failed. In low doses, it predominantly has beta-agonist activity.
Epinephrine
Large doses of this drug compromise renal blood flow.
Norepinephrine
Amrinone and Milrinone
Both are phosphodiesterase inhibitors; inotropes with significant arterial and venodilator properties.
Unlike other inotropes, these two inodilators may not appreciably increase myocardial oxygen consumption because they decrease left ventricular afterload and do not directly increase HR.
Two inotropes that may not appreciably increase myocardial oxygen consumption because they decrease left ventricular afterload and do not directly increase HR.
Amrinone and Milrinone (phosphodiesterase inhibitors)
Chest tube drainage in the first 2 hours of more than ___________ in the absence of a hemostatic defect, is excessive.
250-300 mL/hr (10mL/kg/hr)
Assess pupils after initiation of CPB as unilateral dilation may indicate
arterial inflow into the innominate artery (unilateral carotid perfusion).
Protamine should be administrated slowly over a period of ____________ to reduce the risk for hypotension
5-10 minutes
If the heart fibrillates during rewarming, _________ may be necessary.
defibrillation (5-10 J)
What is given to decrease the likelihood of fibrillation during rewarming
lidocaine 100-200 mg and magnesium sulfate 1-2 g
A-line placement when LIMA is being used for CABG
If the left mammary artery is to be harvested, A-line placement is best suited in the right radial artery because retractors can dampen the waveform of a left radial A-line.
Heparin is always administered before
cannulation
The PA catheter should be pulled back 3-5 cm to
minimize the risk of pulmonary perforation as the pulmonary arteries collapse with the initiation of CPB.
What is desirable SBP during termination of CPB
After termination of CPB, elevated SBP should be avoided to prevent excessive stress on suture lines in the heart and aorta. Usually 90-120 mmHg is a desirable systolic pressure.
___________ is frequently implicated in post-bypass bleeding.
Platelet dysfunction
Amicar dose
10-29 gm load
1-2 gm/hr
Stroke is predominant CNS postop complication of CABG. Indicators are
Visual impairment
Hemiparesis
Aphasia
Sensory impairment
CNS complications after CPB is Usually seen in, pump runs longer than?
90 minutes.
Cause of coagulopathy after CPB
Platelet dysfunction is frequently implicated
Thrombin production and fibrinolysis. Thrombin is produced by the extrinsic and intrinsic pathways and by activated platelets. It is only partially suppressed by heparin therapy.
__________ is the single most important intraoperative monitor of renal system during CABG
Urinary output
Standard is UO of 1 mL/kg/hr.
Renal dysfunction in CPB is related to?
length of time on bypass (longer than 3 hours)
cardiac output
Infection
Type of procedure (valve surgery has higher risk)
Excessive blood loss
Diabetes
Increased use of vasopressors
Perioperative myocardial infarction
Use IABP
Massive transfusions
Hypothermia during CPB depresses renal tubular function; however what interventions will result in adequate urine output?
hemodilution
use of mannitol
maintenance of GFR
Hyperglycemia during CPB can also affect ________
renal tubules
During CPB, as the temp is decreased to 28 C what happens
ACT, PT, and PTT are prolonged
platelets become nonfunctional
Cellular potassium uptake is increased and may result in hypokalemia.
The beneficial aspects of hypothermia include
a reduced basal metabolic rate
improved myocardial protection
tissue and organ preservation
reduced oxygen consumption.
The metabolic requirement for O2 is reduced by _________ for each ________ drop in core body temperature.
50%
7° C
It may not be possible to convert heartbeat to normal sinus rhythm until the rewarming core temperature is _______
34°C.
Normal stroke volume
60-90mL/beath
Normal stroke index
40-60 mL/beat/m2
