Chapter 11 – Cardiovascular Physiology and Anesthesia DIRECTIONS (Questions 915 through 994): Each of the questions or incomplete statements in this section is followed by answers or by completions of the statement, respectively Select the ONE BEST answer or completion for each item 915 A 67-year-old man is to undergo a radical retropubic prostatectomy He has aortic stenosis with a gradient of 37 mm Hg at rest He has an allergy to penicillin Which of the following is the best regimen for subacute bacterial endocarditis (SBE) prophylaxis in this patient? A Ampicillin and gentamicin B Vancomycin and gentamicin C Clindamycin and gentamicin D Clindamycin alone E None of the above 916 A 68-year-old patient is undergoing elective coronary revascularization Just before cardiopulmonary bypass, the hemoglobin concentration is 8.3 g/dL and platelet count is 253,000/mm3 After cardiopulmonary bypass is initiated, the patient is cooled to 20° C and units of packed red blood cells (RBCs) are transfused because of bleeding During bypass, the anesthesiologist notices that the platelet count is 10,000/mm3 and the hemoglobin concentration is g/dL The most likely cause of thrombocytopenia is A Sequestration B Hemolytic transfusion reaction C Dilutional thrombocytopenia D Disseminated intravascular coagulation E Heparin-induced thrombocytopenia 917 Which of the following is the most sensitive indicator of left ventricular myocardial ischemia? A Wall-motion abnormalities on the echocardiogram B ST-segment changes in lead V5 of the electrocardiogram (ECG) C Appearance of V waves on the pulmonary capillary wedge pressure tracing D Elevation of the pulmonary capillary wedge pressure E Decrease in cardiac output as measured by the thermodilution technique 918 Oxygen consumption (VO2) is measured in a 70-kg subject on a treadmill at 2500 mL per minute This corresponds to: A metabolic equivalent (MET) B METs C 10 METs D 15 METs E 20 METs 919 Accidental injection of air into a peripheral vein would be LEAST likely to result in arterial air embolism in a patient with which of the following anatomic cardiac defects? A Patent ductus arteriosus B Eisenmenger’s syndrome C Teratology of Fallot D Pulmonary atresia with ventricular septal defect E Tricuspid atresia 920 Each of the following could be placed on the x-axis of the curve shown in the figure EXCEPT A Stroke volume B Left ventricular end-diastolic pressure C Left ventricular end-diastolic volume D Left atrial pressure E Pulmonary artery occlusion pressure 921 The ECG rhythm strip below represents A Atrial flutter B Third-degree heart block C Sinus tachycardia second-degree heart block D Malfunctioning DDD pacemaker E Junctional rhythm 922 A 71-year-old man is undergoing revascularization of three coronary vessels on cardiopulmonary bypass at 28° C After the first gr aft is sewn into the aorta, the arterial pressure measured from a left radial artery is 47 mm Hg and the pulmonary artery pressure is mm Hg Thirty minutes later, the arterial pressure is 52 mm Hg and pulmonary artery pressure is 31 mm Hg The most likely explanation for this is A Malposition of the aortic cannula B Malposition of the venous cannula C Faulty ventricular venting D Bypass associated sympathetic nervous system stimulation E Pulmonary artery catheter migration 923 A78-year-old patient is anesthetized for right hemicolectomy with isoflurane and nitrous oxide Vecuronium is administered to facilitate muscle relaxation At the end of the operation, the neuromuscular blockade is reversed with neostigmine mg and glycopyrrolate 0.8 mg The rhythm below is noted shortly after administration of these drugs The patient’s blood pressure is 90/60 The most appropriate course of action at this point is A DC cardioversion B Isoproterenol drip C Atropine D Transcutaneous pacemaker E Begin chest compressions 924 While on cardiopulmonary bypass during elective coronary artery revascularization, the patient is noted to have bulging sclerae Mean arterial pressure is 50 mm Hg, temperature is 28° C, and there is no ECG activity The most ap propriate action to take at this time is to A Administer mannitol, 50 gm IV B Administer furosemide, 20 mg IV C Decrease the cardiac index D Check the position of the aortic cannula E Check the position of the venous return cannula 925 Which of the following correctly describes the effect of transposition of the great vessels on the rate of induction of anesthesia? A Inhalation induction is faster than normal; intravenous induction is slower than normal B Inhalation induction is slower than normal; intravenous induction is faster than normal C Both inhalation and intravenous induction are faster than normal D Both inhalation and intravenous induction are slower than normal E Inhalation induction is normal; intravenous induction is faster than normal 926 Anastomosis of the right atrium to the pulmonary artery (Fontan procedure) is a useful surgical treatment for each of the following congenital cardiac defects EXCEPT A Tricuspid atresia B Hypoplastic left heart syndrome C Pulmonary valve stenosis D Truncus arteriosus E Pulmonary artery atresia 927 By what percentage is tissue metabolic rate reduced during cardiopulmonary bypass at 30° C? A 10% B 25% C 50% D 75% E 90% 928 Effective inflation of an intra-aortic balloon catheter should occur at which of the following times? A Immediately after P wave on ECG B Immediately after closure of aortic valve C During opening of the aortic valve D During systolic upstroke on arterial tracing E At midpoint of QRS complex 929 Afterload reduction is beneficial during anesthesia for noncardiac surgery in patients with each of the following conditions EXCEPT A Aortic insufficiency B Mitral regurgitation C Tetralogy of Fallot D Congestive heart failure E Patent ductus arteriosus 930 Administration of protamine to a patient who has not received heparin can result in A Anticoagulation B Hypercoagulation C Profound bradycardia D Seizure E Hypertension 931 The primary determinants of myocardial O2 consumption, from most to least important, are A Preload > afterload > heart rate B Heart rate > preload > afterload C Afterload > preload > heart rate D Heart rate > afterload > preload E Afterload > heart rate > preload 932 Cardiac tamponade is associated with A Pulsus alternans B Pulsus tardus C Pulsus parvus D Pulsus paradoxus E Bisferiens pulse 933 Which of the following drugs should NOT be administered via an endotracheal tube? A Lidocaine B NaHCO3 C Atropine D Naloxone E Epinephrine 934 The mean arterial pressure in a patient with a blood pressure of 180/60 mm Hg is A 90 mm Hg B 100 mm Hg C 110 mm Hg D 120 mm Hg E 130 mm Hg 935 Hypothyroidism and hyperthyroidism could develop in patients receiving which of the following antidysrhythmic drugs? A Amiodarone B Verapamil C Phenytoin D Lidocaine E Procainamide 936 Calculate the systemic vascular resistance (in dynes/sec/cm–5) from the following data: cardiac output 5.0 L/min, central venous pressure mm Hg, mean arterial blood pressure 86 mm Hg, mean pulmonary arterial blood pressure 20 mm Hg, pulmonary capillary wedge pressure mm Hg, heart rate 85 beats/min, patient weight 100 kg A 750 B 1000 C 1250 D 1500 E Cannot be calculated 937 Which of the following is NOT included in tetralogy of Fallot? A Patent ductus arteriosus temporarily abolished with a left stellate ganglion block, which shortens the QT intervals If this is successful, surgical ganglionectomy may be performed as permanent treatment (Kaplan: Cardiac Anesthesia, ed 4, pp 186-187) 943 The use of mechanical circulatory support is becoming more frequent because of (A) advances in technology and a relative scarcity of organs available for transplant Mechanical circulatory support can be used as bridge therapy for patients awaiting cardiac transplantation, or a bridge to recovery for those recovering from a viral cardiomyopathy or patients recovering from cardiogenic shock after myocardial infarction In other patients, it can be destination therapy Currently, the HeartMate VE is the only mechanical device approved for destination therapy in the United States Various versions of these devices can be used to support the right (not approved for destination therapy), the left, or both ventricles Axial (continuous) flow is non-pulsatile and non-physiologic These pumps are connected in parallel to the heart Specifically, on the left side, blood is taken from the apex of the heart and returned to circulation via the aorta In this configuration, little or no blood exits the aortic valve during systole Measuring blood pressure with a cuff is not accurate in most patients and may be impossible Pulse oximeters work with some patients, but this, too, requires pulsatile flow Measurement of blood pressure with an arterial line is easily done, just as it is in patients on cardiopulmonary bypass undergoing open heart operations (Miller: Anesthesia, ed 7, p 1941) 944 In a normal heart, approximately 20% to 30% of the cardiac output is produced by the (A) “atrial kick.” In pathologic conditions, such as aortic stenosis, the “atrial kick” may contribute more substantially to cardiac output (Morgan: Clinical Anesthesiology, ed 4, p 423) 945 The figure in this case shows a bisferiens pulse, recognized by its two systolic peaks A (A) bisferiens pulse can be seen in patients with significant aortic regurgitation In aortic regurgitation, the left ventricle ejects a large volume of blood in systole with a rapid diastolic runoff as blood flows both to the periphery and back into the left ventricle The first systolic peak of the bisferiens pulse represents the wave of blood ejected from the left ventricle The second systolic peak represents a reflected pressure wave from the periphery In contrast, patients with aortic stenosis display a delayed pulse wave with a diminished upstroke (pulses tardus and pulses parvus), whereas patients with cardiac tamponade show an exaggerated inspiratory decline in systolic blood pressure (pulsus paradoxus) Patients with hypovolemia may demonstrate systolic blood pressure variation, particularly during mechanical ventilation (Miller: Anesthesia, ed 6, p 1285) 946 In patients with tetralogy of Fallot, it is important to maintain systemic vascular resistance (E) to reduce the magnitude of the right-to-left intracardiac shunt Therefore, induction of anesthesia in these patients is best accomplished with ketamine to mg/kg IM or to mg/kg IV Remember that with right to left shunts, IV medications work more rapidly Induction of anesthesia with a volatile anesthetic such as sevoflurane may be used, but careful monitoring of systemic oxygenation is needed because any decrease in systemic blood pressure would increase the right to left shunt (and would decrease the oxygen saturation) Ketamine will usually improve arterial oxygenation, which reflects increased pulmonary blood flow due to ketamine-induced increases in systemic vascular resistance (Hines: Stoelting’s Anesthesia & Co-Existing Disease, ed 5, pp 50-53; Morgan: Clinical Anesthesiology, ed 4, p 482) 947 Mitral stenosis in adults occurs almost exclusively in individuals who had rheumatic fever (A) during childhood Mitral stenosis causes pathophysiologic changes both proximal and distal to the abnormal valve In general, the left ventricle is “protected” or unloaded, that is, it is not exposed to excessive volume or pressure loads and therefore rarely associated with abnormalities in left-sided myocardial contractility In contrast, proximal to the valve, a diastolic pressure gradient develops between the left atrium and left ventricle in order to force blood across the stenotic valve orifice, which results in elevated left atrial pressures and decreased left atrial compliance and function The elevated left atrial pressures are reflected back into the pulmonary vascular system, causing an increase in pulmonary vascular resistance and eventually poor right ventricular function The left ventricular pressure-volume loop in patients with mitral stenosis demonstrates low-to-normal left ventricular end-diastolic volumes and pressures and a corresponding reduction in stroke volume (Morgan: Clinical Anesthesiology, ed 4, p 467) 948 Ischemia of the posterior wall of the left ventricle and posterior leaflet of the mitral valve (A) can cause prolapse of the posterior leaflet and retrograde blood flow into the left atrium during systole This can be manifested as V (ventricular) waves on the pulmonary capillary wedge pressure tracing even before ST-segment depression can be seen on the ECG (Miller: Anesthesia, ed 6, pp 1312-1313; Morgan: Clinical Anesthesiology, ed 4, pp 469471) 949 The patient described in this question has a wide complex tachycardia of undetermined (B) origin As this patient appears to be hemodynamically stable and has an uncertain rhythm, amiodarone 150 mg IV over 10 minutes, repeated as needed to a maximum dose of 2.2 g IV over 24 hours is recommended (2005 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care Circulation 112: IV69IV76, 2005; Miller: Anesthesia, ed 6, p 1404; Hensley: Cardiac Anesthesia, ed 4, p 92) 950 The daily production of cortisol under normal circumstances is approximately 15 to 20 mg (B) Under maximum stress, daily cortisol production can increase to 75 to 150 mg/day yielding a plasma cortisol level of 30 to 50 µg/dL (Hines: Stoelting’s Anesthesia & Co-Existing Disease, ed 5, p 396) 951 The anesthetic management of patients with artificial cardiac pacemakers should include (D) ECG monitoring to confirm continued function of the pulse generators as well as emergency equipment (e.g., electrical defibrillator, external converter magnet) and drugs (atropine, isoproterenol) to maintain an acceptable intrinsic heart rate if the artificial pacemaker malfunctions Inadvertent displacement of the endocardial electrodes by catheters has not been reported when the electrodes have been in place for weeks or more In general, anesthetic drugs will not alter the function of artificial cardiac pacemakers However, the stimulation thresholds for ventricular capture are not static values and can be altered by a number of physiologic events For example, acute hypokalemia and respiratory alkalosis will increase the threshold for ventricular capture, which could result in a loss of pacing In contrast, acute hyperkalemia and acidosis will decrease the threshold for ventricular capture, which may make the patient vulnerable to ventricular fibrillation (VF) A decrease in the programmed rate of the pacemaker greater than 10% is a sign of battery failure Should this occur, elective surgery should be canceled and a thorough evaluation of the pacemaker should be undertaken (Hensley: Cardiac Anesthesia, ed 4, p 482; Miller: Anesthesia, ed 6, pp 1416-1427) 952 (E) The Fick equation can be used to calculate cardiac output ( ) if the patient’s O2 consumption (˙VO2), arterial O2 content (CaO2), and mixed venous O2 content ( determined The downfalls of this type of and analysis errors in accurate determination of Fick equation is as follows: ) are measurement are threefold: (1) sampling , (2) changes in Q while samples are being taken, and (3) may be difficult because of cumbersome equipment The ∗The factor 10 converts O2 content to mL O2/L of blood (instead of mL O2/dL of blood) (Hensley: Cardiac Anesthesia, ed 4, pp 128-130; Miller: Anesthesia, ed 6, p 1331) 953 Myocardial preservation is achieved during cardiopulmonary bypass primarily by infusing (C) cold (4° C) cardioplegia solutions containing potas sium chloride 20 mEq/L This rapidly produces hypothermia of the cardiac muscle and a flaccid myocardium In the normal contracting muscle at 37° C, myocardial O consumption is approximately to 10 mL/100 g/min This is reduced in the fibrillating heart at 22° C to approximately mL/100 g/min Myocardial O2 consumption of the electromechanically quiescent heart at 22° C is less than 0.3 mL/100 g/min (Miller: Anesthesia, ed 6, pp 1976-1978; Stoelting: Basics of Anesthesia, ed 5, p 388) 954 All of the drugs listed in this question except phenylephrine will increase the inotropic state (D) of the myocardium, which can increase left ventricular outflow obstruction and decrease cardiac output Phenylephrine, because it is a pure α-adrenergic receptor agonist, has minimal direct effects on myocardial contractility (Hines: Stoelting’s Anesthesia and CoExisting Disease, ed 5, p 119) 955 The classic signs and symptoms of critical aortic stenosis (angina, syncope, and (A) congestive heart failure) are related primarily to an increase in left ventricular systolic pressure, which is necessary to maintain forward stroke volume These elevated pressures cause concentric left ventricular hypertrophy With severe disease, the left ventricular chamber becomes dilated and myocardial contractility diminishes The primary goals in the anesthetic management of such patients undergoing noncardiac surgery are to maintain normal sinus rhythm and avoid prolonged alterations in heart rate (especially tachycardia), systemic vascular resistance, and intravascular fluid volume Supraventricular tachycardia (especially new onset atrial fibrillation) should be terminated promptly by electrical cardioversion in this patient because of concomitant hypotension and myocardial ischemia (Hines: Stoelting’s Anesthesia and Co-Existing Disease, ed 5, pp 36-38, 68) 956 Positive end-expiratory pressure (PEEP) is produced by the application of positive (C) pressure to the exhalation valve of the mechanical ventilator at the conclusion of the expiratory phase It is often used to increase arterial oxygenation when FIO2 exceeds 0.50 to reduce the hazard of O2 toxicity Positive end-expiratory pressure (PEEP) increases lung compliance and functional residual capacity by expanding previously collapsed but perfused alveoli, thus improving ventilation/perfusion matching and reducing the magnitude of the right to left transpulmonary shunt There are, however, a number of potential hazards associated with the use of PEEP These include decreased cardiac output, pulmonary barotrauma (i.e., tension pneumothorax), increased extravascular lung water, and redistribution of pulmonary blood flow Barotrauma, such as pneumothorax, pneumomediastinum, and subcutaneous emphysema, occurs as a result of overdistention of alveoli by PEEP Pulmonary barotrauma should be suspected when there is abrupt deterioration of arterial oxygenation and cardiovascular function during mechanical ventilation with PEEP If barotrauma is suspected, a chest x-ray film should be obtained and if a tension pneumothorax is present, a chest tube should be placed in the involved chest cavity (Morgan: Clinical Anesthesiology, ed 4, pp 1038-1039) 957 Resting coronary artery blood flow is approximately 225 to 250 mL/min or about 75 (C) mL/100 g/min, or approximately 4% to 5% of the cardiac output Resting myocardial O2 consumption is to 10 mL/100 g/min, or approximately 10% of the total body consumption of O2 (Barash: Clinical Anesthesia, ed 5, p 868; Stoelting: Pharmacology and Physiology in Anesthetic Practice, ed 4, pp 752-753) 958 Pulmonary artery rupture is a disastrous but fortunately rare complication associated with (B) the use of pulmonary artery catheters The hallmark of pulmonary artery rupture is hemoptysis, which may be minimal or copious Efforts should be made to separate the lungs This can be achieved by endobronchial intubation with a double-lumen endotracheal tube The presence of atheromas in the pulmonary artery is not associated with an increased risk of pulmonary artery rupture Atheromatous changes are usually minimal or absent in the middle and distal portions of the pulmonary artery (i.e., in the segments where the tip of the pulmonary artery catheter typically resides) (Miller: Anesthesia, ed 6, pp 1306-1307) 959 Anaphylactic and anaphylactoid reactions to protamine occur in less than 5% of all allergic (B) reactions during anesthesia and when they occur, usually so within to 10 minutes of exposure These reactions can occur in patients who have been exposed to protamine (e.g., diabetics taking NPH or PZI insulin, both of which contain protamine as a protein modifier; regular insulin does not contain protamine) Since protamine in derived from salmon sperm, patients with seafood allergies as well as men who have had a vasectomy (who may develop circulating antibodies to spermatozoa) may also develop a reaction The likelihood of reactions may be reduced with prior administration of H1 blockers, H2 blockers and corticosteroids Protamine should be avoided in patients who have a history of previous anaphylactic reactions to protamine (Hines: Stoelting’s Anesthesia and CoExisting Disease, ed 5, pp 527-529; Stoelting: Basics of Anesthesia, ed 5, p 390) 960 Twenty thousand units of heparin is equal to 200 mg Heparin is commonly neutralized by (B) administration of 1.3 mg of protamine for each milligram of heparin Protamine is a basic protein that combines to the acidic heparin molecule to produce an inactive complex that has no anticoagulant properties The half-life of heparin is 1.5 hours at 37° C At 25° C, metabolism of heparin is minimal (Hensley: Cardiac Anesthesia, ed 4, p 504; Miller: Anesthesia, ed 6, p 1982) 961 Unlike most organs of the body where perfusion is continuous, coronary perfusion is (E) somewhat intermittent It is determined by the difference between aortic diastolic pressure and left and right ventricular end diastolic pressures During systole, left ventricular pressure increases to or above systemic arterial pressure, resulting in almost complete occlusion of the intramyocardial portions of the coronary arteries Thus, perfusion of the left ventricular myocardium occurs almost entirely during diastole, resulting in a decrease in left ventricular coronary perfusion as heart rate increases In contrast, the right ventricle is perfused during both systole and diastole, because right ventricular pressures remain less than that of the aorta An increase in heart rate results in a relatively shorter diastolic period (Morgan: Clinical Anesthesiology, ed 4, p 432) 962 The thromboelastograph is a viscoelastometer that measures the viscoelastic properties of (A) blood during clot formation The coagulation variables measured from a thromboelastogram are: (1) the R value (reaction time; normal value 7.5 to 15 minutes) and K value (normal to minutes), which reflects clot formation time; (2) MA (maximum amplitude; normal value 50 to 60 mm), which represents maximum clot strength; and (3) A60 (amplitude 60 minutes after the MA; normal value MA – mm), which represents the rate of clot destruction (i.e., fibrinolysis) The MA is determined by fibrinogen concentration, platelet count, and platelet function The thromboelastogram depicted in the figure of this question is consistent with fibrinolysis (Barash: Clinical Anesthesia, ed 5, pp 229-230; Miller: Anesthesiology, ed 6, pp 1341-1342) 963 At the time of collection, an anticoagulant is added to donor blood Nonetheless, small (E) clots will occasionally form in the units, requiring filtration at the time of transfusion A 170µm filter is present in standard blood administration sets for this purpose Those filters permit rapid transfusion and should be used for infusions of platelets, fresh frozen plasma, cryoprecipitate, red blood cells, and granulocyte concentrates Albumin does not need to be administered through a 170-mm filter because it does not contain blood clots (Miller: Anesthesiology, ed 6, p 1815) 964 Adenosine in doses of mg IV (repeated if needed 1-2 minutes later with 12 mg) can be (B) very effective in the treatment of supraventricular tachycardias, including those associated with Wolff-Parkinson-White (WPW) syndrome (unless atrial fibrillation [AF] with a wide complex WPW occurs, where adenosine may increase the heart rate [HR]) The drug is rapidly metabolized such that it is not influenced by liver or renal dysfunction Its effects, however, can be markedly enhanced by drugs that interfere with nucleotide metabolism such as dipyridamole Administration of the usual dose of adenosine to a patient receiving dipyridamole may result in asystole If adenosine is used in patients receiving dipyridamole, or the patient has a central line, the initial dose is mg Methylxanthines, such as caffeine, theophylline, and amrinone, are competitive antagonists of this drug, and doses may need to be adjusted accordingly (2005 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care Circulation; 112:IV70-IV73, 2005; Barash: Clinical Anesthesia, ed 5, pp 316-317; Fleisher: Anesthesia and Uncommon Diseases, ed 5, p 69; Morgan: Clinical Anesthesiology, ed 4, p 260) 965 Temperature of the thermal compartment can be measured accurately in the pulmonary (D) artery, distal esophagus, tympanic membrane, or nasopharynx These temperature monitoring sites are reliable, even during rapid thermal perturbations such as cardiopulmonary bypass Other temperature sites, such as oral, axillary, rectal, and urinary bladder, will estimate core temperature reasonably accurately except during extreme thermal perturbations During cardiac surgery, the temperature of the urinary bladder is usually equal to the pulmonary artery when urine flow is high However, it may be difficult to interpret urinary bladder temperature because it is strongly influenced by urine flow The adequacy of rewarming after coronary artery bypass is thus best evaluated by considering both the core and urinary bladder temperatures (Stoelting: Pharmacology and Physiology in Anesthetic Practice, ed 4, p 694; Morgan: Clinical Anesthesiology, ed 4, p 499; Stoelting: Basics of Anesthesia, ed 5, pp 387-388) 966 The transgastric mid-papillary short axis view images myocardium supplied by all three (B) major coronary arteries: left anterior descending (LAD), left circumflex (CX), and right coronary (RCA) arteries Thus, this view is preferred for the purpose of ischemia monitoring The mid-esophageal chamber view displays the anterolateral (LAD or CX) and inferoseptal (LAD or RCA) walls only, while the long axis view displays the anterior septal (LAD) and inferolateral (CX or RCA) walls Two chamber views display the anterior (LAD) and inferior (RCA) walls (Kahn RA, Shernan SK, Konstadt SN, et al: Intraoperative Echocardiography In: Essentials of Cardiac Anesthesia, Kaplan, ed, Philadelphia, W.B Saunders, 2008, p 206) 967 The most frequent initial rhythm in a witnessed sudden cardiac arrest (SCA) is ventricular (D) fibrillation (VF) Delays in either starting CPR or defibrillation reduce survival from SCA Current recommendations for health care providers in any facility with an automated external defibrillator (AED) readily available is AED use within moments of the cardiac arrest If an AED is not readily available then CPR is started until the AED arrives at the scene Recall cycle of CPR is 30 compressions and breaths It is no longer recommended to a shock sequence with biphasic defibrillators, because it is unlikely for the second or third shock to work after a failed first shock, and the second and third shocks may be harmful After the shock continue CPR for cycles, check for a pulse Then if VF persists, repeat shock and add epinephrine or vasopressin before or after a shock when an IV or IO line is available With monophasic defibrillators it may be OK to shock sequences, but all adult shocks should be 360 joules With out-of-hospital unwitnessed cardiac arrest by EMS personnel, cycles of CPR (about minutes) should be performed before checking the ECG and attempting defibrillation, especially when the response interval is greater than minutes because shock effectiveness appears more successful after CPR (2005 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care Circulation, 112:IV35-41, IV58-61, 2005) 968 The renin-angiotensin-aldosterone system is important in controlling blood pressure and (A) blood volume Renin helps to convert angiotensinogen to Angiotensin I Angiotensin converting enzyme (ACE) helps to convert Angiotensin I to Angiotensin II Angiotensin II has many pharmacologic actions including potent vasoconstriction action as well as stimulating aldosterone release from the adrenal gland Losartan is an angiotensin receptor blocker (ARB) and is commonly used to treat hypertension Patients taking ARBs, as well as patients who are on ACE inhibitors, are more prone to develop hypotension during anesthesia In addition, the hypotension that develops may be more difficult to treat That is why ARBs are commonly discontinued the day before surgery Terazosin is an α1 blocker, lisinopril is an ACE inhibitor, spironolactone is a competitive antagonist to aldosterone and amlodipine is a calcium channel blocker Note: If you look at the endings of many generic drug names you can know the drug class, ARBs end in -sartan, α1 blockers end in -osin, ACE inhibitors end in - pril, and calcium channel blockers end in dipine (Hines: Stoelting’s Anesthesia and Co-Existing Diseases, ed 5, pp 92-97) 969 Hemodynamically unstable cardiac dysrhythmias can result in hypoperfusion and (E) metabolic acidosis If severe metabolic acidosis is confirmed on arterial blood gases, intravenous sodium bicarbonate should be administered Adverse effects associated with administration of sodium bicarbonate are well documented and include severe plasma hyperosmolality, paradoxic cerebral spinal fluid acidosis, hypernatremia, and hypercarbia, particularly in patients who are not adequately ventilated Bicarbonate lowers potassium by lowering the extracellular hydrogen ion concentration, which results in lowering, not raising the potassium concentration (Miller: Anesthesia, ed 6, pp 1770, 1781, 2938) 970 Hypercyanotic attacks primarily occur in infants to months of age and are frequently absent after to years of age These attacks usually occur without provocation but can (D) be associated with episodes of excitement, such as crying or exercise The mechanism for these attacks is not known It is believed, however, that hypercyanotic attacks occur as a result of spasm of the infundibular cardiac muscle or a decrease in systemic vascular resistance; both will exacerbate the right-to-left intracardiac shunt Phenylephrine, an αadrenergic receptor agonist, is the drug of choice for treatment of hypercyanotic attacks, because presumably phenylephrine increases systemic vascular resistance, which reduces the intracardiac right-to-left shunt and improves arterial oxygenation Esmolol is also effective, presumably because it reduces spasm of the infundibular cardiac muscle Isoproterenol with its betamimetic effects reduces afterload and therefore increases right to left shunting and may exacerbate infundibular spasm Because hypovolemia may increase sympathetic stimulation, adequate hydration with IV fluids may be helpful (Fleisher: Anesthesia and Uncommon Diseases, ed 5, pp 108-110; Hines: Stoelting’s Anesthesia and Co-Existing Disease, ed 5, p 51) 971 Sildenafil (Viagra) is used for erectile dysfunction Erection of the penis involves the local (D) release of nitric oxide (NO) which increases cyclic guanine monophosphate or cGMP in the corpus cavernosum Sildenafil has no direct effects but inhibits phosphodiesterase type (PDE5) which breaks down cGMP The net effect is increasing cGMP Yohimbine is an α-adrenergic blocker Nitroglycerin and hydralazine are both direct acting smooth muscle relaxants Enalapril is an ACE inhibitor Milrinone is an inhibitor of phosphodiesterase type (PDE3) (Barash: Clinical Anesthesia, ed 5, pp 320, 329-330; Physicians Desk Reference-2008, ed 62, pp 2562, 2986) 972 After a drug eluting stent (DES) is placed, dual antiplatelet therapy (ASA + clopidogrel) is (C) started to decrease the chance of stent thrombosis Because stent thrombosis may develop months after a DES is placed, a minimum of year of dual antiplatelet therapy is recommended before stopping the drugs prior to elective surgery If surgery is planned within one year of angioplasty and stent placement, consideration for using a bare metal stent is recommended (where a minimum of month of antiplatelet therapy is recommended) (AHA/ACC/SCAI/ACS/ADA Science advisory: Prevention of premature discontinuation of dual antiplatelet therapy in patients with coronary artery stents J Am Coll Cardiol, 49:734-739, 2007) 973 Heparin induced thrombocytopenia (HIT) can be either nonimmune (type I) or immune (D) (type II) HIT type I is a transient and clinically insignificant condition where heparin binds to platelets causing a shortening of the platelet’s left span and a modest decrease in the platelet count However, HIT type II can be a serious condition where antibodies are formed (in 6% to 15% of patients who are receiving unfractionated heparin for >5 days) to a complex of heparin and a platelet protein factor This heparin-platelet factor antibody complex binds to endothelial cells, which then stimulates thrombin production with a net result of both thrombocytopenia (>50% reduction in the platelet count) and venous and/or arterial thrombosis (7 mEq/L) produce widening of the QRS complex that can merge with the T wave producing a sine wave pattern, decrease in P wave amplitude, and an increase in the PR interval The terminal event would be VF or asystole The earliest changes with hypokalemia include T wave flattening or inversion, appearance of U waves and ST segment depression With severe hypokalemia the PR interval may become prolonged and the QRS complex may widen, then arrhythmias develop Hypocalcemia prolongs the QT interval (ST portion) while hypercalcemia shortens the QT interval Hypernatremia and hyponatremia not produce characteristic changes in the ECG (Barash: Clinical Anesthesia, ed 5, p 1542; Kasper: Harrison’s Principle of Internal Medicine, ed 16, pp 260, 262, 1318-1319; Miller: Anesthesia, ed 6, pp 1049-1050, 11061107) ... Methemoglobinemia 957 Normal resting coronary artery blood flow is A 10 mL /10 0 g/min B 40 mL /10 0 g/min C 75 mL /10 0 g/min D 12 0 mL /10 0 g/min E 16 0 mL /10 0 g/min 958 Each of the following is associated with an... L/min 953 Normal resting myocardial O2 consumption is A 2.0 mL /10 0 g/min B 3.5 mL /10 0 g/min C 10 mL /10 0 g/min D 15 mL /10 0 g/min E 25 mL /10 0 g/min 954 A 22-year-old man with hypertrophic cardiomyopathy... The mean arterial pressure in a patient with a blood pressure of 18 0/60 mm Hg is A 90 mm Hg B 10 0 mm Hg C 11 0 mm Hg D 12 0 mm Hg E 13 0 mm Hg 935 Hypothyroidism and hyperthyroidism could develop