More Heart Crap (CABG, Valve Repair, etc) TEST 2 Flashcards
1
Q
When was the first open-cardiac procedure performed and by whom?
A
April 15, 1952 by Dr. R. E. Gross of Children’s Hospital in Boston
2
Q
_______ ________ ________ is the predominant cause of death in patients in the fourth and fifth decades and the most common cause of premature death in men aged 35-45.
A
coronary artery disease
3
Q
The coronary arteries arise from the aorta. Coronary artery perfusion pressure is mainly determined by aortic ______ pressure and ___________ pressure.
A
The coronary arteries arise from the aorta. Coronary artery perfusion pressure is mainly determined by aortic diastolic pressure and left ventricular end-diastolic pressure.
4
Q
What are 3 major alterations that CAD causes in regards to the coronaries?
A
Coronary artery disease alters coronary blood flow, decreases coronary reserve, and increases the incidence of coronary artery vasospasm.
5
Q
Name some common risk factors of CAD?
A
age, gender, genetic predisposition, obesity, hyperlipidemia, hypertension, stress, diabetes mellitus, and smoking. Exacerbating effects of CAD are combo’s of peripheral vascular disease, carotid disease, and a compromised pulmonary system.
6
Q
Name the 3 layers of an artery.
A
The outermost layer is known as the tunica externa also known as tunica adventitia and is composed of connective tissue made up of collagen fibres. Inside this layer is the tunica media, or media, which is made up of smooth muscle cells and elastic tissue. The innermost layer, which is in direct contact with the flow of blood is the tunica intima, commonly called the intima. This layer is made up of mainly endothelial cells. The hollow internal cavity in which the blood flows is called the lumen.
7
Q
__________ is a disease process in which fatty lesions are deposited on the intimal layer of the arteries.
A
atherosclerosis
8
Q
What is another name for the “fatty deposits” made by atherosclerosis, and which layer of the artery do they adhere to?
A
Fatty deposits are also called atheromatous plaques that adhere to the intima and smooth muscle layer of the arteries. They begin as crystals of cholesterol.
9
Q
Why do the fatty deposits, caused from atherosclerosis, cause so many issues?
A
the cholesterol crystals develop and form a larger matrix that stimulates fibrous tissue and smooth muscle growth to create additional layers on which larger plaques grow. eventually the plaques mature and develop into obstructive lesions or contribute to the development of fibroblasts, which eventually deposit dense connective tissue, resulting in sclerosis (fibrosis).
10
Q
Atheromatous plaque and resulting sclerotic lesions lead to loss of arterial ________ and tissue ________ and ________ of the arterial wall.
A
loss of arterial distensibility (ability to stretch) and tissue degeneration and ulceration of arterial wall.
11
Q
What is the end result of atheromatous plaque?
A
thrombi form and embolize… causing blood flow obstruction and distal tissue ischemia
12
Q
At what % of occlusion do patients with atherosclerotic coronary disease become symptomatic?
A
75%; results in decreased coronary blood flow.
13
Q
Depressed myocardial function and pain occur when ischemia develops. What is the pain called?
A
angina pectoris; in addition to pain, cells are subject to increased irritability and become increasingly vulnerable to fibrillation, alterations in conduction pathways, and thrombus formation
14
Q
Describe (basics) what cardiopulmonary bypass (CPB) is:
A
Cardiopulmonary bypass (CPB) is a technique that temporarily takes over the function of the heart and lungs during surgery, maintaining the circulation of blood and the oxygen content of the body. The CPB pump itself is often referred to as a heart–lung machine or “the pump”. Cardiopulmonary bypass pumps are operated by perfusionists. CPB is a form of extracorporeal (meaning outside of the body) circulation.
15
Q
CBP can precipitate changes known as “pump lung”. What are some results of this acute lung injury?
A
diffuse congestion, edema in alveolar and interstitial regions, and hemorrhagic atelectasis
16
Q
Discuss some theories behind the cause of pump lung.
A
one theory is that microemboli of protein aggregates, disintegrated platelets, damaged fibrin, and fat particles contribute to the development of pump lung; acute lung injury can also be caused by complement activation, inflammatory response, hemodilution, lung hypoxia, and elevated pulmonary artery pressure.
17
Q
Alterations/dysfunction of the _______ nerve can occur from hypothermia and topical cooling during CPB.
A
phrenic nerve
18
Q
Gas distribution occurs preferentially to _______ areas of the lung, thereby producing _______ of the ________ lung sections. What does this result in?
A
Gas distribution occurs preferentially to nondependent areas of the lung, thereby producing hypoventilation of dependent lung sections, which can result in postoperative atelectasis.
19
Q
What is the predominant post-op neuro complication after open-heart surgeries using CPB?
A
stroke
20
Q
Up to _____% of patients demonstrate postoperative neurophysiologic dysfunction in the postoperative period after CPB.
A
50%
21
Q
What are some cerebrovascular sequelae indicators that will commonly be seen?
A
visual impairment, hemiparesis (one-sided weakness), aphasia, and sensory impairment; other neurologic deficits include abnormal reflexes, loss of sensation of vibration, impaired locomotion, and impaired visual acuity associated with retinal lesions or infarction
22
Q
What should be done for patients in the intra-op setting with the presence of pre-operative cerebrovascular disease?
A
maintain higher perfusion pressures during CPB. Recent history of stroke should be considered a contraindication for anticoagulation therapy necessary in CPB-dependent procedures.
23
Q
CNS is sensitive to hypoxia and is at risk if cerebral hypoperfusion occurs. At a mean arterial pressure between ____ and ____ mmHg (autoregulatory plateau), cerebral blood flow is maintained at approximately 50ml/100g/min because of changes in cerebrovascular tone.
A
The CNS is sensitive to hypoxemia and is at risk when cerebral hypoperfusion occurs. At a mean arterial pressure (MAP) between 50 and 150 mm Hg (autoregulatory plateau), cerebral blood flow (CBF) is maintained at approximately 50 mL/100 g/min because of changes in cerebrovascular tone. ; maintenance of adequate CBF may decrease the incidence of arterial hypoperfusion, which could result in stroke.
24
Q
Cerebral autoregulation is dependent on _____ and _____ and is established at a lower plateau with hypothermia.
A
Cerebral autoregulation is dependent on CBF and MAP and is established at a lower plateau with hypothermia. Global ischemia is possible with rapid hypoperfusion of collaterals, lost autoregulation in profound hypothermia, or circulatory arrest of longer than 1 minute.
25
What are some sources that may precipitate changes in arterial blood pressure?
hypothermic response, hypocarbia, venous congestion arising from superior vena caval obstruction, or emboli
26
During bypass, what are some potential sources of emboli?
aortic atheroma from the aortic clamp, intraventricular thrombi, valve calcification, air during open-chamber procedures, aortic cannulation, bubble oxygenators, nitrous oxide administered before bypass, or factors associated with a long-pump run.
27
If a CPB pump runs longer than ____ minutes, it is considered an independent risk factor in which the risk of cognitive dysfunction is greatly increased.
>90 minutes
28
What gas should you avoid using during open-heart surgeries?
Avoidance of nitrous oxide decreases the possibility of remobilization. The use of nitrous oxide can increase the size of gaseous emboli.
29
CNS is sensitive to hypoxia and is at risk if cerebral hypoperfusion occurs. At a mean arterial pressure between ____ and ____ mmHg (autoregulatory plateau), cerebral blood flow is maintained at approximately 50ml/100g/min because of changes in cerebrovascular tone.
The CNS is sensitive to hypoxemia and is at risk when cerebral hypoperfusion occurs. At a mean arterial pressure (MAP) between 50 and 150 mm Hg (autoregulatory plateau), cerebral blood flow (CBF) is maintained at approximately 50 mL/100 g/min because of changes in cerebrovascular tone. ; maintenance of adequate CBF may decrease the incidence of arterial hypoperfusion, which could result in stroke.
30
Cerebral autoregulation is dependent on _____ and _____ and is established at a lower plateau with hypothermia.
Cerebral autoregulation is dependent on CBF and MAP and is established at a lower plateau with hypothermia. Global ischemia is possible with rapid hypoperfusion of collaterals, lost autoregulation in profound hypothermia, or circulatory arrest of longer than 1 minute.
31
What are some sources that may precipitate changes in arterial blood pressure?
hypothermic response, hypocarbia, venous congestion arising from superior vena caval obstruction, or emboli
32
During bypass, what are some potential sources of emboli?
aortic atheroma from the aortic clamp, intraventricular thrombi, valve calcification, air during open-chamber procedures, aortic cannulation, bubble oxygenators, nitrous oxide administered before bypass, or factors associated with a long-pump run.
33
Name the techniques used during CPB for cerebral protection.
maintain MAP >50mmHg, maintain euglycemia, maintain mild hypothermia (nasopharyngeal temp <37C at rewarming), perform pharmacologic metabolic suppression (B-blockers, lidocaine, thiopental, propofol, CCB, volatile anesthetics, ketamine), emboli reduction, acid-base management; the propofol/thiopental and use of CCB reduce incidence of vasospasm.
34
What gas should you avoid using during open-heart surgeries?
Avoidance of nitrous oxide decreases the possibility of remobilization. The use of nitrous oxide can increase the size of gaseous emboli.
35
What effect does blood glucose control have on the CNS during CPB?
hyperglycemia may intensify global and focal insults to the CNS; strict control is essential b\c evidence suggests that hyperglycemic states increase the magnitude and extent of neurologic injury that ensues during ischemia.; avoid solutions containing glucose.
36
Why does insulin resistance develop during CPB for diabetic patients?
In part b\c of increased endogenous catecholamines which increase the incidence of refractory hyperglycemia.
37
What mechanisms (although not fully understood) may be responsible for brain pre-conditioning?
complex and may involve changes in murine thymoma viral oncogene homolog (Akt gene) expression, adenosine triphosphate (ATP)-sensitive potassium channels, and nitric oxide.
38
There are many disagreements that exist in regards to the extent (if any) neurocognitive function declines post-bypass. What are some of the origins that are suspected to attribute to the decline?
use of the CPB, cerebral microemboli and hypoperfusion, inflammation, cerebral hyperthermia and edema, BBB dysfunction, and genetic influences (recent data shows that NONE of these are the case)
39
Name the techniques used during CPB for cerebral protection.
maintain MAP >50mmHg, maintain euglycemia, maintain mild hypothermia (nasopharyngeal temp <37C at rewarming), perform pharmacologic metabolic suppression (B-blockers, lidocaine, thiopental, propofol, CCB, volatile anesthetics, ketamine), emboli reduction, acid-base management
40
Why propofol (or thiopental) and CCB's used during CPB?
For cerebral protection; reduces incidence of vasospasm
41
Deep hypothermic circulatory arrest can be used for arch reconstruction and for treatment of giant aneurysms. What is the technique/parameters used during this procedure?
Necessitates core and external cooling to temperatures of 15deg to 20deg C, selective cerebral perfusion, pH management, and intermittent or low-flow perfusion
42
What creatinine levels are considered normal, abnormal, and as indicating renal failure?
Normal creatinine is 1.8 mg/100 mL or less; values ranging from 1.9 to 5 mg/100 mL are considered abnormal. A creatinine level in excess of 5 mg/100 mL indicates renal failure, and the patient requires dialysis.
43
What mechanisms (although not fully understood) may be responsible for brain pre-conditioning?
complex and may involve changes in murine thymoma viral oncogene homolog (Akt gene) expression, adenosine triphosphate (ATP)-sensitive potassium channels, and nitric oxide.
44
There are many disagreements that exist in regards to the extent (if any) neurocognitive function declines post-bypass. What are some of the origins that are suspected to attribute to the decline?
use of the CPB, cerebral microemboli and hypoperfusion, inflammation, cerebral hyperthermia and edema, BBB dysfunction, and genetic influences (recent data shows that NONE of these are the case)
45
GI tract morbidity in the post-op CPB patient is a significant complication of bypass procedures. What are some predictive factors?
Previous CVA, COPD, Type II heparin induced thrombocytopenia (HIT-II), a-fib, prior MI, renal insufficiency, HTN, and use of intraaortic balloon counterpulsation. Valve surgery, concomitant valve and CABG, deep sternal infection, prolonged ventilation, and low ejection fraction (<30%) also contributed to post-op GI complications.
46
What is the most common catastrophic GI complication post-op CPB?
mesenteric ischemia (often fatal); ischemia may result from atheroembolization, HIT, or hypoperfusion
47
Impairment of renal function of varying degrees is related to what factors during bypass surgery?
length of time on bypass (longer than 3 hours), CO, infection, type of procedure (valve surgery has higher incidence of renal dysfunction), excessive blood loss, diabetes, increased use of vasopressors, perioperative myocardial infarction, use of intraaortic balloon pump (IABP), deep hypothermic circulatory arrest, low CO syndrome, advanced age, and low urinary output during the pump run
48
What is hemodilution?
Hemodilution can be normovolemia which implies the dilution of normal blood constituents by the use of expanders. During acute normovolemic hemodilution (ANH) blood subsequently lost during surgery contains proportionally fewer red blood cells per millimetre, thus minimizing intraoperative loss of the whole blood. Therefore, blood lost by the patient during surgery is not actually lost by the patient, for this volume is purified and redirected into the patient.
49
Hypothermia during CPB depresses renal tubular function; What 3 things result in adequate urinary output?
hemodilution, administration of mannitol (CPB prime), and maintenance of glomerular filtration rate result in adequate urinary output.
50
What is the standard for measurement of renal perfusion during CPB?
at least 1ml/kg/hr; studies show hypothermia have no effect on urinary output during CPB
51
What is the cause of non-diabetic hyperglycemia during CPB?
increased glucose re-absorption by the kidneys; even small amounts introduced during CPB have shown to precipitate hyperglycemia; which is detrimental to the brain as well as the renal tubules.
52
Catecholamines rise progressively during CPB. The release and circulation of which catecholamine, is thought to occur in response to low atrial pressures, hypotension, and non-pulsatile flow... that may cause renal vasoconstriction?
The release and circulation of vasopressin (antidiuretic hormone; ADH) are thought to occur in response to low atrial pressures, hypotension, and nonpulsatile flow. Reduction in urinary output may be the result of renal vasoconstriction stimulated by high levels of vasopressin.
53
What are the effects of hemodilution on the release of vasopressin?
increases perfusion to the outer cortex of the kidney, thereby stimulating renal plasma flow and the clearance of free water and K+
54
What is hemodilution?
Hemodilution can be normovolemia which, as we said, implies the dilution of normal blood constituents by the use of expanders. During acute normovolemic hemodilution (ANH) blood subsequently lost during surgery contains proportionally fewer red blood cells per millimetre, thus minimizing intraoperative loss of the whole blood. Therefore, blood lost by the patient during surgery is not actually lost by the patient, for this volume is purified and redirected into the patient.
55
What is the single most important intraoperative monitor of the renal system during CABG procedures using CPB?
urinary output; anuria is not uncommon and can occur in 1/3 of patients during CPB; it is thought that the non-pulsatile flow of the extracorporeal circuit interferes with autoregulation of renal blood flow.
56
What negative effect does hypothermia, used during CPB, have on the body?
profound effect on enzyme systems and the coagulation cascade; activated clotting time (ACT), prothrombin time (PT), and partial thromboplastin time (PTT) are prolonged, and platelets become non-functional as the body temperature is lowered approximately to 28C; K+ uptake is increased and may result in hypokalemia.
57
What are the benefits of hypothermia during CPB?
reduced basal metabolic rate, improved myocardial protection, tissue and organ preservation, and reduced oxygen consumption; metabolic requirement for O2 is reduced by 50% for each 7C drop in core body temp; core temp needs to be rewarmed to around 34C before convert to NSR
58
What are the 4 main goals of anesthetic management for coronary revascularization (restoration of perfusion to an ischemic area: the heart)?
The goals of anesthetic management for coronary revascularization are directed toward (1) producing analgesia, amnesia, and muscle relaxation; (2) abolishing autonomic reflexes; (3) maintaining physiologic homeostasis; and (4) providing myocardial and cerebral protection. **** So in summary: anesthesia triad, abolish reflex, maintain, and protect
59
Discuss some anesthetic considerations in the peri-op setting with patients undergoing CPB surgeries?
an effective preoperative evaluation, administration of modest doses of sedation and pain medication before any attempt at line placement is made, and use of O2 in the preoperative setting. Administration of a balanced anesthetic with opioid, inhalation agents, sedative-hypnotics, and muscle relaxant provides a stable hemodynamic state for the difficult cardiovascular patient. The inhalation agents offer the additional advantage of anesthetic preconditioning that is cardioprotective.
60
What is ischemic pre-conditioning?
IPC describes the adaptation of the myocardium to ischemic stress preceded by short periods of ischemia and reperfusion.
61
What effect does volatile anesthetics have on ischemic pre-conditioning?
volatile anesthetics inhibit Ca+ influx through voltage and receptor operated Ca+ channels in coronary vascular smooth muscle; also reduce Ca+ accumulation and release by the coronary vascular smooth muscle sarcoplasmic reticulum, inhibit G proteins linked to phospholipase C, and decrease formation of the second messenger inositol triphosphate
62
What effect does volatile anesthetics have on MVO2 and CO?
it decreases both
63
Ischemia (IPC) may be protective for the heart if it is _____ and ______.
mild and reversible; inhalation agents may precondition the heart and reduce post-op ischemia; SIDE NOTE: A study by Kalenka and colleagues on the proteome of the left ventricle (LV) using 2D gel electrophoresis and mass spectrometry demonstrated that volatile agents alter cardiac gene and protein expression. They showed a two-fold change in 106 different proteins predominantly associated with glycolysis, mitochondrial respiration, and stress. This distinct change in myocardial protein expression was the same for desflurane, isoflurane, and sevoflurane, suggesting a class action of these agents lasting for 72 h.
64
What are the basic components to a thorough pre-op assessment of a cardiac surgery patient?
A thorough preoperative assessment of the patient who will undergo cardiac surgery should include comprehensive review of systems, airway status, and laboratory data; physical examination; review of surgical history; and review of current medications Actual reports of diagnostic procedures such as cardiac catheterization, echocardiogram, and Doppler studies should be reviewed by the anesthesia care provider.
65
Why is airway assessment so important for cardiac surgery patients?
such patients are unable to compensate for a reduced oxygen supply. Often patients who undergo cardiac revascularization procedures are oxygen compromised because of body habitus, pulmonary disease, age, and general physical condition. These patients cannot tolerate decreases in oxygen supply. Careful evaluation and preparation for airway management is very important.
66
A patient subjected to peri-operative ischemia is ___ times for likely to suffer an MI.
3 times; Alterations such as tachycardia, hypertension, hypotension, and ventricular distention can cause myocardial ischemia. Treatment of ischemia is directed at stabilizing hemodynamic parameters.
67
What are some peri-operative events that may elicit ischemia?
coronary spasm, ET intubation, sympathetic stimulation, sternal split, light anesthesia, cannulation, initiation of bypass, incomplete revascularization, tachycardia, atherosclerotic plaque, HTN, air or particulate thrombus formation, manipulation of the heart, fibrillation; goal of anesthesia management is to reduce or obtund responses to these stimuli to reduce ischemia.
68
Treatment of ischemia is based on four modes of support: ________, _________, ________, and ________.
oxygen administration, stabilization of hemodynamic parameters, inotropic support, and mechanical support when indicated.
69
What are some pre-operative risk factors (co-existing disease states) that are associated with ischemia in CPB?
age, cigarette smoking (which contributes to development of atherosclerosis), peripheral vascular and cerebral vascular disease, hypertension, angina, congestive heart failure (CHF), previous MI, and diabetes mellitus.
70
What is the difference in stable and unstable angina?
Angina is defined as stable if there has been no change in frequency, precipitating event, or duration for the previous 2 months. Unstable angina (crescendo angina) is defined as angina of new onset that lasts longer than 30 minutes and is associated with ST- or T-segment changes. Unstable angina often does not respond to rest or medication.
71
Why is a history of previous cardiac surgery of significant concern prior to CPB surgery?
Previous cardiac surgery results in an increase in blood loss because of reoperation through adhesions from a previous sternotomy. Anticipation of excessive blood loss may indicate the use of antihyperfibrinolytic agents and implementation of a cell-saver device. The sternotomy is a cause for significant concern because scar tissue formation may have led to anatomic distortion or superficial attachment of the pericardium to the anterior chest wall, which presents a potential hazard for laceration of the myocardium or great vessels. It may become necessary for the anesthesia care provider to heparinize the patient earlier than anticipated to allow for percutaneous femoral artery cannulation for bypass. Blood products and heparin bolus must be immediately available should this extremely emergent situation occur.
72
State the normal intracardiac pressures for the following: CVP, RAP, RVESP, RVEDP, PAP systolic, PAP diastolic, PAP mean, PAOP/PCWP
CVP (0-8), RAP (0-8), RVESP (15-25), RVEDP (0-8), PAP systolic (15-25), PAP diastolic (8-15), PAP mean (10-20), PAOP/PCWP (6-12)
73
How does functional status of a patient relate to anesthesia? (especially before cardiac surgery)
Assess what activities of daily living the patient can perform. If a patient is unable to climb one flight of stairs without difficulty, then the anesthesia care provider can plan for a patient with reduced ability to handle the hemodynamic changes inherent to induction and maintenance of anesthesia.
74
What information does a cardiac catheterization provide?
The catheterization report provides significant information regarding patient cardiac performance. The catheterization evaluation provides information about pressures and oxygen saturations of the four chambers of the heart, PA pressure, systemic pressure, body surface area, CI (liters per minute per square meter), stroke index (milliliters per beat per square meter), left ventricular ejection fraction (EF), degree of stenosis in coronary vessels, and coronary dominance.
75
What is the formula for stroke volume?
SV=CO/HR (normal 60-90ml/beat)
76
What is the difference in stroke volume and stroke index?
stroke index takes in consideration the patients body surface area; SI=SV/BSA (normal 40-60ml/beat)
77
What is the formula for CO?
CO= SVxHR (normal is 5-6 L/min)
78
What is cardiac index?
It is the CO divided by the BSA?
79
What is the formula for MAP?
SBP + (2 x DBP) divided by 3 (normal is 80-120)
80
What is the formula for SVR?
SVR= (MAP-CVP) divided by (CO x 80) (subtracting the pressures from both sides of the body... arterial and venous) normal is 700-1400 dyne/sec/cm5
81
What is the formula for PVR (pulmonary vascular resistance)?
PVR= (PAP-PCWP) divided by (CO x 80) normal is 50-300 dyne/sec/cm5 (this is subtracting the pressure on both sides of the lung)
82
What is the formula for CPP?
CPP= diastolic BP-LVEDP (normal is 50mmHg)
83
What is the formula for EF?
EF= (EDV-ESV) divided by EDV (normal is 55-70%)
84
What is the primary indication for use of phenylephrine?
The primary indication for use is hypotension induced by a reduction in systemic vascular resistance (SVR) as opposed to compromised CO. Advantage is the increased CPP with minimal changes to chronotropy.
85
What are some risks for diabetic patients during CPB surgery?
increased risk intra-op and post-op of silent ischemia and MI; these patients have both peripheral and autonomic neuropathies; with autonomic neuropathy they are at risk for aspiration and sudden death
86
How many risk factors should be present for absolute inclusion of laboratory examination?
2 or more associated risk factors for ischemic heart disease (diabetes, obesity, family history, smoking); include CBC, electrolytes, CE, serum creatinine, cholesterol, and coags
87
What information can be obtained from a pre-op EKG?
Leads II and V5 help in diagnosis of dysrhythmias, ischemia, conduction defects, and electrolyte disturbances; none of the standard leads can detect posterior wall ischemia. EKG will not assess the degree of coronary artery occlusion
88
When using an arterial line, what arm should the BP cuff be placed?
The noninvasive blood pressure cuff must be placed on the same side as the arterial line to allow for correlation of blood pressure. This is a backup monitor.
89
Does it matter which radial artery is used during a CABG?
Sternal retraction may play a role in distorting the radial artery waveform. The right radial artery is usually selected in cases in which the left internal mammary artery is dissected for anastomosis and because radial arterial line monitoring may show a false low number because of compression of the subclavian artery at the retractor.
90
While once a staple for all CABG surgeries, due to its associated complications, PA catheters are only recommended for high risk patients with an EF of less than _____%.
40%
91
What pressures are represented by the PA cath when deflated and inflated?
During systole with the balloon deflated, the catheter transduces right ventricular systolic pressure. During diastole with the balloon deflated, the catheter transduces PA diastolic pressure, which also represents left atrial pressure. During ventricular diastole with the balloon inflated, the pulmonary catheter is said to be wedged and reflects left ventricular filling pressure. During ventricular systole with the balloon wedged, the catheter reflects left atrial filling pressure.
92
What is the most accurate indicator of core temperature during CPB surgery?
the thermistor of the PA catheter; if using nasopharyngeal the probe should be inserted 7-10cm through the nares (a lag time occurs on rewarming but normally reflects brain temperature)
93
Brain temperature should not drop below _____ degrees C. Profound hypothermia (____ to ____ degrees C) appears to cause a loss of cerebral autoregulation.
20; 15-20
94
What is the distance from skin to the vena-cava right atrium junction from the following sites? IJ and Fem Vein
IJ= 15-20cm; Fem Vein= 30cm
95
Is BIS a decent substitute for EEG during CPB?
No: EEG is not an effective method for monitoring subtle changes, but any asymmetric EEG activity is considered a problem. Bispectral analysis (BIS) monitoring may correlate with the depth of anesthesia, but it is actually a derived parameter to assess the degree of wakefulness. BIS does not measure brain function or the adequacy of oxygenation of the brain.
96
What is the effect of hyperglycemia on adenosine?
Monitoring glucose is important in cerebral preservation because hyperglycemia increases the extent and degree of any ischemia that may occur. Glucose is considered an independent risk factor for aggravation of ischemia. Hyperglycemia prevents the increase of adenosine (responsible for cerebrovasodilatation), thereby preventing the brain from protecting itself from ischemic damage.
97
Maintaining normal glucose levels, induce mild hypothermia, once rewarming has begun, maintaining a mean arterial pressure > 50
mm Hg, administer drugs that cause metabolic suppression, correct acid-base disturbances, and providing embolism reduction measures are ways of offering ______ _______ during CPB.
cerebral protection
98
What are the two major determinants of coronary artery perfusion pressure?
left ventricular end-diastolic pressure and aortic diastolic pressure
99
Angina is classified as _____ if the duration, frequency, or precipitating event has not changed for the last 2 months.
stable
100
What patient populations should receive PA catheters during CABG?
High risk patients with an EF < 40%, unstable angina, severe CAD or valvular disorders, active CHF, hx of recent MI, advanced renal disease, and severe pulmonary disease.
101
What cross allergy is of concern with a DM patient on NPH insulin presenting for cardiac surgery?
Protamine
102
Why are patients with DM at an increased risk for adverse outcomes during and after cardiac surgery?
The possibility of silent ischemia and MI places patients with DM at increased risk.
103
What is normal EF?
55-70%
104
What is an indicator of POOR cardiac function?
EF <30%
105
When the balloon of a PA cath is not inflated, what pressures are reflected during systole and diastole?
RV systolic pressure is transduced during systole and PA diastolic pressure is transduced during diastole (also represents LA pressure).
106
What are some characteristics of unstable angina?
lasts longer than 30min in duration, exhibits ST or T segment changes, and is new onset. Typically refractory (difficult to treat) to medication or rest.
107
For every 7 degree C decline in core temperature, how much is the metabolic requirement for O2 reduced?
50%
108
What are the benefits of hypothermia during CPB?
reduced O2 consumption, BMR reduced, preservation of tissues and organs, and increased myocardial protection
109
Is a patient who has recently had a stroke a candidate for open heart surgery?
No. anticoagulation is necessary in procedures using CPB. This is contraindicated in patients who recently had a stroke.
110
Are patients with a previous history of cardiac surgery at higher risk for increased blood loss during reoperation?
Yes. d\t adhesions as a result of previous sternotomy that predispose the patient to increased blood loss with reoperation. Or pericardium could be superficially attached to anterior chest wall resulting in laceration of the great vessels or myocardium.
111
How does nitroglycerin treat myocardial ischemia?
relieves myocardial ischemia primarily through coronary vasodilation and reduction of pre-load reduction from venodilation.
112
What hemodynamic alteration has the highest likelihood to cause myocardial ischemia?
tachycardia decreases the myocardial oxygen supply (the quicker you beat, the less you fill, the less the coronaries are perfused) while increasing the demand.... high chance of MI
113
When a potassium solution is administered into the coronary circulation, it is called?
cardioplegia
114
What are the benefits associated with the use of beta blockers during open heart surgery?
they reduce use of oxygen through reduction in contractility, blood pressure, and heart rate. by slowing HR, the left ventricle has more time to be oxygenated d\t increased diastolic time. they can also reduce incidence of ventricular arrhythmias induced by catecholamines.
115
What are some disadvantages to the use of beta-blockers during open heart surgery?
bronchospasm, as well as heart block and bradyarrhythmias
116
Describe the CPB pump.
The CPB pump acts as the patient's heart and lungs in order to provide a surgeon a bloodless field and a non-beating heart.
Blood is removed from the venous circulation via cannulas usually in the right atrium, or superior and/or inferior vena cava, oxygenated and CO2 elimintated, then returned to the body through an arterial cannula located in the ascending aorta.
117
What test is used to monitor the use of heparin during CPB?
ACT (activated clotting time)
118
What is the expected ACT in patients PRIOR to the use of heparin during CPB?
90-120 seconds
119
What is the desired ACT value during CPB?
> 400 seconds (~6.6 minutes!!)
120
What factors influence venous drainage to the venous reservoir of the CPB pump?
gravity, table height, the position of the venous cannula, resistance from the venous cannula, and the intravascular volume of the patient
121
What are the two different types of oxygenators used on a CPB pump?
membrane oxygenators (post-pump d\t higher resistance to flow) and bubble oxygenators (pre-pump)
122
Is inotropic support needed in ALL patients following revascularization?
No. The aortic cross-clamp time and the pre-bypass function of the ventricle are important factors to consider. Patients with good
ventricular function and short cross-clamp times usually do not require inotropic support after successful revascularization of the coronaries. Also, the patient's perfusion status, as well as body termperature and heart rhythm should be assessed.
123
What is the initial dose of heparin given prior to the initiation of CPB?
200-400 units/kg; maintenance doses are given based on ACT values during surgery.
124
What are the risk factors that pose the MOST significant risk for increased mortality following CABG?
renal failure, emergency surgery, history of cardiac surgery, > 80 years of age.
125
Following a CABG, a patient develops an increased PA pressure and low arterial blood pressure. What might this be indicative of?
left ventricular dysfunction
126
Why is BP lowered prior to cannulation of the aorta?
to reduce aortic wall tension and reduce risk of aortic dissection.
127
What is the single most prudent action for an anesthetist to take immediately prior to a sternotomy?
ventilation is interrupted (typically 15-20 seconds) to allow lungs to deflate. This decreases the likelihood that the lung parenchyma will be cut by the sternal saw
128
JUST IN CASE IT HASN'T BEEN ASKED ENOUGH...... What is the importance of glucose control during cardiac surgery?
Hyperglycermia exacerbates all forms of ischemia and can have detrimental effects on cerebral preservation. Hyperglycemia
interferes with the brain's intrinsic ability to protect itself from ischemia by inhibiting the increase of adenosine, which is responsible for cerebrovasodilation.
129
What device can be considered in a patient that fails to wean from CPB despite optimal drug therapies and placement of IABP?
A ventricular assist device (VAD); just FYI: A ventricular assist device (VAD) is a mechanical circulatory device that is used to partially or completely replace the function of a failing heart. Some VADs are intended for short term use, typically for patients recovering from heart attacks or heart surgery, while others are intended for long-term use (months to years and in some cases for life), typically for patients suffering from advanced congestive heart failure. IT PUMPS BLOOD FROM THE LEFT VENTRICLE TO THE AORTA.
130
What is the purpose of an intra-aortic balloon pump?
It increases the supply of oxygen to the myocardium (diastolic augmentation) and decreases the myocardial oxygen demand (by decreasing afterload); FYI: mechanical device that increases myocardial oxygen perfusion while at the same time increasing cardiac output. Increasing cardiac output increases coronary blood flow and therefore myocardial oxygen delivery. It consists of a cylindrical polyethylene balloon that sits in the aorta, approximately 2 centimeters (0.79 in) from the left subclavian artery and counterpulsates. That is, it actively deflates in systole, increasing forward blood flow by reducing afterload through a vacuum effect. It actively inflates in diastole, increasing blood flow to the coronary arteries via retrograde flow. These actions combine to decrease myocardial oxygen demand and increase myocardial oxygen supply.
131
When does inflation of the balloon of an IABP occur?
during diastole. allows blood to be pushed into the coronary arteries
132
What is the most appropriate surgical technique for a patient with an aortic arch lesion?
hypothermic circulatory arrest
133
What is the most probable cause of a cardiac tamponade in a cardiac surgical patient?
leakage from the anastomosis
134
What type of gas is used in the balloon of an IABP and WHY?
A computer-controlled mechanism inflates the balloon with helium from a cylinder during diastole, usually linked to either an electrocardiogram (ECG) or a pressure transducer at the distal tip of the catheter; some IABPs, such as the Datascope System 98XT, allow asynchronous counterpulsation at a set rate, though this setting is rarely used. Helium is used because its low viscosity allows it to travel quickly through the long connecting tubes, and has a lower risk than air of causing an embolism should the balloon rupture.
135
What is the purpose of the MAZE procedure?
to eliminate atrial fibrillation; patients who have undergone unsuccessful pharmacologic treatment and are at high risk for stroke are candidates. The open heart procedures name is derived from the serial maze like incisions made in the atria to eliminate abnormal electrical pathways.
136
What two valves most commonly necessitate surgical involvement?
aortic and mitral (left sided heart valves)
137
Using the RIJ for placement of CVP line is recommended because cannulation of the left IJ vein increases risk of laceration of the left _______ ______?
brachiocephalic vein
138
What are some relative contraindications to right IJ cannulation?
carotid disease, recent cannulation (increases thrombosis risk), contralateral diaphragmatic dysfunction, thyromegaly, and prior major neck surgery
139
What effect does CPB have on plasma and cellular constituents of blood?
clinical and experimental evidence indicates significant alteration of plasma and cellular constituents of blood that affects platelet count and function; as a result of hemodilution the platelet count decreases rapidly to 50% of initial pre-op level, but usually remains above 100,000 per microliter.; bleeding time is greatly prolonged, and platelet aggregation and function are impaired (II, V, VII, IX, X, and XII)
140
How many milliliters of solution (normosol, plasma-lyte A, isolyte, which pH and electrolytes closely matching the composition of whole blood) do most circuits require to prime?
2000mL; also added to this base solution are heparin, sodium bicarb, mannitol, hetastarch, albumin, and possibly corticosteroids or antihyperfibrinolytic agents. ; this can cause a hemodilutional bolus from priming volumeof 30% to 50% of patient's circulating volume.
141
Aortic cannulation is distal to the sinus of ______ and proximal to the ________ artery.
valsalva; brachiocephalic (innominate) artery
142
What are the 3 main techniques used to ensure myocardial protection during CPB?
rapid cardioplegia-induced cardiac arrest, decompression of the ventricles, and hypothermia
143
Name some benefits of intermittent doses of cold crystalloid cardioplegia.
Intermittent doses of cold crystalloid cardioplegia help maintain cardiac arrest, hypothermia, and pH; counteract edema; wash out metabolite; and provide oxygen and substrate for aerobic metabolism.
144
The phenomenon known as "anesthetic induced pre-conditioning" derives from positive effects on......
mitochondria, K+ ATP channels, reactive oxygen species, calcium overload, and inflammation; reduces myocardial necrosis and improves post-op cardiac performance
145
What is cardioplegia composed of and what purpose does each component serve?
Cardioplegia is a potassium solution administered into the coronary circulation to provide diastolic arrest. It is composed of potassium (15 to 30 mEq/L), calcium to prevent ischemic contracture (stone heart), albumin or mannitol for osmolarity correction, and glucose or simple amino acids as a metabolic substrate. The cardioplegia delivers oxygen and nutrients, removes waste products, and cools or rewarms the heart. It is administered in an anterograde manner into the aortic root, from which it distributes to the coronaries and into the myocardium. It may also be administered in a retrograde fashion into the coronary sinus, from which it distributes through veins, venules, and capillaries of the myocardium.
146
Heparin is a catalyst and binds with circulating __________ and potentiates its natural anticoagulant properties.
antithrombin III
147
How long does it take for the peak effect of heparin, and when should an ACT be established?
2 min peak, check ACT 5-10 min after adinistration
148
What is the indicator that a patient has developed HIT?
HIT is evident after exposure to heparin, because the platelet count suddenly falls; onset can be as soon as 2 days or as long as 5 days following heparin
149
These drugs increase the duration of diastole to allow for a more complete oxygenation of the left ventricle. Who am I?
beta-blockers; they also act synergistically with nitroglycerin and blunt tachycardia and decrease ischemia of the myocardium
150
What are two methods of reversing the effects of beta-blockers?
b-agonists, such as isoproterenol; and cardiac pacing
151
Name 3 common direct vasodilators.
hydralazine, nitroglycerin, or nitroprusside
152
Name a common alpha and beta adrenergic blocker.
labetolol
153
Name some common CCB's.
nicardipine, verapamil, diltiazem
154
Two direct acting vasopressors are phenylephrine and vasopressin. What are there effects?
phenylephrine is alpha 1 agonist causing vasoconstriction; vassopressin provides direct acting peripheral vasoconstriction with no beta-adrenergic effects
155
What are 3 common drugs used to provide positive inotropy?
dobutamine, dopamine, and milrinone
156
What is the function of calcium in the presence of hypotension?
Calcium reverses hypotension associated with the use of halogenated agents, calcium channel blockers, hypocalcemia, β-blockers, and CPB. It can also reverse the negative cardiac effects of hyperkalemia.
157
During induction myocardial ischemia can be detected by the use of what 3 monitors?
ECG, TEE, or PA wedge pressure readings
158
What are some methods for diminishing the incidence of ischemia during induction of CPB surgeries?
Methods for diminishing the incidence of ischemia include therapeutic interventions such as preoxygenation before induction, reduction of wall tension with nitroglycerin, control of heart rate with β-adrenergic blocking agents, reduction of the work of the myocardium through control of myocardial depression with increased anesthetic levels, and maintenance of coronary perfusion pressure through the use of a non-chronotropic agent such as phenylephrine.
159
What are the two most stimulating steps in the process of preparation for CPB?
skin incision and sternal split
160
What is a possible effect of heparin administration on arterial blood pressure?
may decrease arterial pressure by 10-20%.
161
What are the steps that are listed in the pre-bypass checklist?
anticoagulation, arterial cannulation, venous cannulation, pulmonary artery catheter pulled back, are all monitoring/access catheters functional, TEE in freeze mode and scope in neutral unlocked position, supplemental meds (NMB, anesthetics, analgesics, amnestics), inspection of head and neck
162
As core temperature is lowered, the pH _____.
rises; placing the patient in an alkalotic state
163
What is included in the checklist for bypass procedure?
assess arterial inflow, assess venous outflow, is bypass complete, discontinue drug and fluid administration, discontinue ventilation and inhalation drugs to patients lungs
164
What is included in the checklist for preparation for separation from bypass?
air clearance maneuvers completed, rewarming completed, address issue of adequacy of anesthesia and muscle relaxation, obtain stable cardiac rate and rhythm, pump flow and systemic arterial pressure, metabolic parameters, are all monitoring/access catheters functional, respiratory management
165
What are the guidelines for protamine reversal of heparin?
10 mg of protamine reverses 1000 units of heparin
166
How does protamine work?
inactivates heparin by binding with it to form an inert salt
167
What are ways to manage impaired diastolic function?
treating HTN and decreasing ventricular load with vasodilator therapy; Nitroglycerin and Sodium Nitroprusside are commonly used agents that promote vasodilation, counteracting the vasoconstrictive effects of circulating catecholamines, and reduce ventricular distention by relieving myocardial wall tension; in combo with adequate inotropic support, the vasodilators provide adequate CO while minimizing demand on revascularized myocardium
168
What are characteristics of milrinone?
phosphodiasterase inhibitor; helpful in providing prophylactic support in anticipation of ventricular failure. In combo with decreased left ventricular wall tension, milrinone promotes cardiac function without increasing myocardial oxygen demand. FYI: Milrinone is similar to dobutamine in its effects on myocardial contractility, myocardial oxygen consumption rate, SVR, and pulmonary vascular resistance; however, patients are less susceptible to biochemical changes in neurohumoral regulation that may reduce the efficacy of β-agonists.
169
Fibrillation of myocardium typically occurs on rewarming. If spontaneous defibrillation does not occur post- bypass, what should be your initial action?
anti-arrhythmic therapy, electrical cardioversion, or both
170
What is MIDCAB?
minimally invasive direct coronary artery bypass; does not require CPB, cardioplegia, or a large incision. Through a small incision (10-12cm), the graft is anastomosed while the heart is beating.
171
What are disadvantages of MIDCAB?
limited to use for only one or two arteries and that one lung ventilation if often requested. Due to beating heart, anastomoses are difficult to suture and significant ischemia can occur, precipitating hemodynamic compromise of the patient.
172
What are the advantages of MIDCAB?
smaller incision, absence of CPB and its complications, and reduced need for blood transfusions
173
What positioning technique can be used to promote recovery of BP when retraction is used?
trendelenburg position with a right rotation
174
What are some complications of SIRS?
leucocytosis, histamine release, increased capillary permeability, accumulation of interstitial fluid, organ dysfunction, late depression of inflammatory response (day 5+); CPB CAUSES SIRS
175
What are the MAJOR clinical predictors of increased peri-op cardiovascular risk?
unstable coronary syndromes, acute or recent MI with evidence of important ischemic risk by clinical symptoms or non-invasive studies, unstable or severe angina, decompensated HF, significant arrhythmias, high grade atrioventricular block, symptomatic ventricular arrhythmias in presence of underlying heart disease, supraventricular arrhythmias with uncontrolled ventricular rate, severe valvular disease
176
What are the INTERMEDIATE clinical predictors of increased peri-op cardiovascular risk?
mild angina pectoris, previous MI by history of pathological Q waves, compensated or prior HF. DM, renal insufficiency
177
What are the MINOR clinical predictors of increased peri-op cardiovascular risk?
advanced age, abnormal ECG (LV hypertrophy, LBBB, ST-T abnormalities), rhythm other than sinus (a-fib), low functional capacity (inability to climb one flight of stairs with a bag of groceries), history of stroke, uncontrolled systemic HTN
178
How long does it take for the chance of reinfarction after a post-op MI to decease to 5%?
6 mos.
179
What is the single biggest risk for a peri-op MI?
MI w\in past 30 days
180
What is the most common reason for failure to wean from CPB?
Poor left ventricular function
181
What is thought to be the primary cause of AAAs in more than 90% of patients?
Atherosclerosis; HTN and cigarette smoking increase the potential for development of aneurysms.
182
Data suggest that risk of rupture is very low for AAAs less than ____cm in diameter, but the risk dramatically increases for AAAs with a diamater _____cm or greater.
4cm; 5cm
183
What law corresponds to aneurysmal vessel dimensions?
Law of LaPlace: T=Pxr; as radius of a vessel increases, the wall tension increases; the larger the aneurysm, the more likely the risk of spontaneous rupture
184
What is the most common site for cross-clamping the aorta for AAA repair?
infra-renal; because most aneurysms appear below the level of the renal arteries
185
What are some changes seen in hempdynamics with the aortic clamping during AAA repair?
hypertension above the clamp, hypotension below the clamp; increases in afterload cause myocardial wall tension to increase; MAP and SVR also increase; CO may decrease or remain unchanged
186
After the application of the aortic cross-clamp, what metabolic alterations occur distal to the clamp?
lack of blood flow to distal structures make these tissues prone to hypoxia--> metabolites such as lactate accumulate-->anaerobic metabolism-->induce vasodilation and vasomotor paralysis
187
What happens when the cross clamp is released after AAA repair?
SVR decreases, blood is sequestered into previously dilated veins-->decreased venous return--> decreased preload and afterload--> this hemodynamic instability that may ensue is called "declamping shock syndrome"
188
What is the effect of inhalation agents on the myocardium?
ALL inhalation agents may depress the myocardium and cause hemodynamic instability; high concentrations of IAs should in patients with moderate to severe decreased EF should not be used; dose dependent, so it is acceptable to administer dose of less than or equal to 1 MAC
189
What is the difference in true vs. false aneurysms?
aneurysms involving all three layers of the arterial wall—tunica adventitia, tunica media, and tunica intima—are considered to be true aneurysms. In comparison, aneurysms that solely involve the adventitia are termed false aneurysms.
190
What are factors that affect "heart" supply and demand?
Supply: reduced content, reduced coronary flow, increased left ventricular pressure, fixed vascular obstruction; Demand: positive chronotropism, positive inotropism, increase LV volume, increased wall tension, increased afterload
191
How does Sodium Nitroprusside work?
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Sodium nitroprusside (Abbreviated SNP, brand name: Nitropress) has potent vasodilating effects in arterioles and venules (venules more than arterioles, but this selectivity is much less marked than that of nitroglycerin). It is administered intravenously in cases of acute hypertensive emergency. SNP breaks down in circulation to release nitric oxide (NO). NO activates guanylate cyclase in vascular smooth muscle and increases intracellular production of cGMP. cGMP activates Protein Kinase G which activates phosphatases which inactivate Myosin light chains. Myosin light chains are involved in muscle contraction. The end result is vascular smooth muscle relaxation, which allow vessels to dilate.
In the human heart, nitric oxide reduces both total peripheral resistance as well as venous return, thus decreasing both preload and afterload. For this reason, it can be used in severe cardiogenic heart failure where this combination of effects can act to increase cardiac output. In situations where cardiac output is normal, the effect is to reduce blood pressure.
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