Pathophysiology CV*

Question Answer Vessels that are maximally dilated are completely dependent on coronary perfusion pressure. Coronary blood flow is autoregulated between a MAP of 60-120 mmHg. When MAP falls below the range of autoregulation, coronary perfusion becomes entirely dependent on coronary perfusion pressure. Autoregulation is the net effect of what three things local metabolism, the myogenic response, and the autonomic nervous system Coronary blood flow equation coronary perfusion pressure / coronary vascular resistance Coronary Perfusion pressure equation Aortic DBP – LVEDP which ventricle has compromised blood flow during systole? Left. Left epicardium is fine, but the deeper tissues are squeezed. Right pressures are not high enough to have the same effect Coronary blood flow comprises about _____ of blood which is 4-7% of cardiac output 225-250ml/min when oxygen demand increases, ______ must increase to be able to satisfy the demand. coronary blood flow and Ca02 The left ventricular subendocardium is best perfused during diastole The subendocardium of the right ventricle is well perfused ____ (when) throughout the cardiac cycle primary components of CO are preload, afterload, contractility, LV compliance, and HR. is the ventricular wall tension at the end of diastole Preload is the force that the ventricle must overcome to eject its stroke volume. Afterload normal systemic vascular resistance 800-1500 dynes normal pulmonary vascular resistance 150-250 dynes couple things that would influence myocardial supply and demand HR and BP Factors that Reduce Myocardial Oxygen Delivery/Supply (8) v Coronary Flow (Tachycardia, v aortic pressure, v vessel diameter (spasm or hypocapnia), Increased end diastolic pressure), v Ca02 (Hypoxemia, Anemia), v Oxygen Extraction (Left shift of Hgb dissociation curve (vP50), v capillary density) Factors that Increase Oxygen Demand (7) Tachycardia, Hypertension, SNS stimulation, Increased wall tension, Increased end diastolic volume, Increased afterload, Increased contractility The ability of the myocardial sarcomeres to perform work (shorten and produce force) contractility normal BP SYS/DIA: <120/<80 Prehypertension SYS/DIA: 120-139/80-89 Stage 1 htn SYS/DIA: 140-159/90-99 Stage 2 htn SYS/DIA: >=160/>=100 hypertensive crisis SYS/DIA: >180/>120 This classification of hypertension means that your doctor or health care team is not able to locate a single cause that explains the elevated blood pressure primary/essential hypertension (or idiopathic) A modest number of high blood pressure diagnoses are classified as ______ This classification differs from a diagnosis of primary hypertension by a clearly identifiable cause of the high blood pressure. secondary/non-essential hypertension Htn effects other organs in what ways? accelerates athrosclerotic changes in both arteries and organs (brain, kidney, heart): primary risk factor for development of coronary artery disease, significant cause of cardiomyopathy, CAD, renal failure, and stroke the best leads to monitor for intraoperative ST changes: Normal EKG V3 > V4 > V5 > Ill > aVF Lead______ is best for monitoring for dysthymias with anarrow QRS where Pwave analysis is critical for diagnosis Uunctional, a-ftutte~ or a-fib) II In patients with CAD, Nagelhout suggests the following lead combinations provide the best assessment of intraoperative ST changes: 5 cable EKG: V3, aVF, and MCLS or Ill; 3 cable EKG: aVF and MCL5 CAD: clinical manifestations Chest pain, fatigue (women), shortness of breath with exercise (men), orthopnea, paroxymal nocternal dyspnea, dizziness, fainting T/F – No increased morbidity and mortality associate with stable angina in patients presenting for non-cardiac surgery true This form of angina is associated with MI unstable Infarction occurs in the ____ and extends to the ____ subendocardium, myocardium myocardial Ischemia: <20 min EKG changes Peaked T waves, Inverted T waves, ST segment depression myocardial Ischemia: (20-40 minutes) ST segment elevation myocardial Ischemia: >1-2 hours Abnormal Q waves: >=% height of R wave in that lead, >=2 mm wide Treatment of Myocardial ischemia: increased O2 demand Beta-blocker to a HR < 80 bpm, increased Depth of anesthesia, vasodilator, Nitroglycerin Treatement of MI ischemia: Decreased 02 Supply Anticholinergic, pacing, Vasoconstrictor, reduce depth of anesthesia, Nitroglycerin, inotrope how would the EKG look in a STEMI ST elevation (>1mm) in 2 or more leads how would the EKG look in a NSTEMI or High risk Unstable Angina (UA) ST depression (0.5mm or greater) OR T-wave inversion (2mm or greater) how would the EKG look in low/intermediate Unstable Angina (UA) No EKG changes Infarcted myocardium releases 3 key biomarkers: what are they? creatine kinase-MB, troponin I, and troponin T _____ are more sensitive than _____ for the diagnosis of myocardial infarction. Cardiac troponins, CK-MB Creatine Kinase-MB (CK-MB): inital elevation, peak elevation, return to baseline 3-12hrs, 24hrs, 2-3days Troponin I: inital elevation, peak elevation, return to baseline 3-12hrs, 24hrs, 5-10days Troponin T: inital elevation, peak elevation, return to baseline 3-12hrs, 12-48hrs, 5-14days Incidence of Intraoperative MI: general population, 1 month, 3 months, 3-6 months, >6months %: 0.3, >50, 30, 15, 6 occurs when coronary artery occlusion approximates 50-70% stable angina Anesthesia management for anyone at risk of MI avoid anything that would get them upset or stimulate SNS like getting cold, uncontrolled emergence, etc. Stabalize the blood pressure, ***avoid muscle relaxants that release histamine (***atracurium/mivacurium) unstable angina – what are the criteria angina at rest, new onset < 2mths, increasing symptoms, duration exceeds 30 min, not responsive to medical therapy greatest risk of perioperative MI unstable angina Six independent predictors of cardiac complications during surgery High risk surgery, History of ischemic heart diseas, Hx of CHF, Hx of Cerebrovascular disease, DM (pretreatment with insulin), Serum Creatinine >2 mg/dl High risk surgeries for the possibility of an MI: Emergency surgery (especially in the elderly), Open aortic surgery, Peripheral vascular surgery, Long surgical procedures with significant volume shifts and/or blood loss Incidence of intraoperative MI in patients with a Hx of CABG 1-2%

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