More Heart Crap (CABG, Valve Repair, etc) TEST 2 Flashcards
When was the first open-cardiac procedure performed and by whom?
April 15, 1952 by Dr. R. E. Gross of Children’s Hospital in Boston
_______ ________ ________ 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.
coronary artery disease
The coronary arteries arise from the aorta. Coronary artery perfusion pressure is mainly determined by aortic ______ pressure and ___________ pressure.
The coronary arteries arise from the aorta. Coronary artery perfusion pressure is mainly determined by aortic diastolic pressure and left ventricular end-diastolic pressure.
What are 3 major alterations that CAD causes in regards to the coronaries?
Coronary artery disease alters coronary blood flow, decreases coronary reserve, and increases the incidence of coronary artery vasospasm.
Name some common risk factors of CAD?
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.
Name the 3 layers of an artery.
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.
__________ is a disease process in which fatty lesions are deposited on the intimal layer of the arteries.
atherosclerosis
What is another name for the “fatty deposits” made by atherosclerosis, and which layer of the artery do they adhere to?
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.
Why do the fatty deposits, caused from atherosclerosis, cause so many issues?
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).
Atheromatous plaque and resulting sclerotic lesions lead to loss of arterial ________ and tissue ________ and ________ of the arterial wall.
loss of arterial distensibility (ability to stretch) and tissue degeneration and ulceration of arterial wall.
What is the end result of atheromatous plaque?
thrombi form and embolize… causing blood flow obstruction and distal tissue ischemia
At what % of occlusion do patients with atherosclerotic coronary disease become symptomatic?
75%; results in decreased coronary blood flow.
Depressed myocardial function and pain occur when ischemia develops. What is the pain called?
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
Describe (basics) what cardiopulmonary bypass (CPB) is:
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.
CBP can precipitate changes known as “pump lung”. What are some results of this acute lung injury?
diffuse congestion, edema in alveolar and interstitial regions, and hemorrhagic atelectasis
Discuss some theories behind the cause of pump lung.
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.
Alterations/dysfunction of the _______ nerve can occur from hypothermia and topical cooling during CPB.
phrenic nerve
Gas distribution occurs preferentially to _______ areas of the lung, thereby producing _______ of the ________ lung sections. What does this result in?
Gas distribution occurs preferentially to nondependent areas of the lung, thereby producing hypoventilation of dependent lung sections, which can result in postoperative atelectasis.
What is the predominant post-op neuro complication after open-heart surgeries using CPB?
stroke
Up to _____% of patients demonstrate postoperative neurophysiologic dysfunction in the postoperative period after CPB.
50%
What are some cerebrovascular sequelae indicators that will commonly be seen?
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
What should be done for patients in the intra-op setting with the presence of pre-operative cerebrovascular disease?
maintain higher perfusion pressures during CPB. Recent history of stroke should be considered a contraindication for anticoagulation therapy necessary in CPB-dependent procedures.
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.
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.
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
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.
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
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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)
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
Why propofol (or thiopental) and CCB’s used during CPB?
For cerebral protection; reduces incidence of vasospasm
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
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.
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.
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)
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.
What is the most common catastrophic GI complication post-op CPB?
mesenteric ischemia (often fatal); ischemia may result from atheroembolization, HIT, or hypoperfusion
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
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.
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.
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
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.
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.
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+
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.
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.
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.
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
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
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.
What is ischemic pre-conditioning?
IPC describes the adaptation of the myocardium to ischemic stress preceded by short periods of ischemia and reperfusion.
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
What effect does volatile anesthetics have on MVO2 and CO?
it decreases both
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.
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.
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.
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.
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.
Treatment of ischemia is based on four modes of support: ________, _________, ________, and ________.
oxygen administration, stabilization of hemodynamic parameters, inotropic support, and mechanical support when indicated.
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.
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.
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.
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)
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.
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.
What is the formula for stroke volume?
SV=CO/HR (normal 60-90ml/beat)
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)
