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39 Cards in this Set
- Front
- Back
Anesthetic considerations for a cardiac patient
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-the safest anesthetic approach to an animal with heart disease is to make a diagnosis
-understand the pathophysiology of the specific cardiac disorder -determine the progression of the disease in the patient -understand the normal compensatory responses to the disorder -choose a protocol that will support rather than decompensate the patient |
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Goals in evaluating your patient prior to anesthesia
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-presenting complaint
-determine general health status -discern the progression of heart disease -current medications and response to them |
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Questions asked to owners regarding:
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-exercise intolerance
-activity level -coughing -current meds |
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How to evaluate a patient's status to determine their ability to safely undergo general anesthesia for dentistry
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-CBC and biochem
-radiographs |
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Signs to look for during complete physical exam that are commonly associated with heart disease
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-pallor, cyanosis, slow capillary refill
-weak peripheral pulse -jugular venous pulse -edema, ascites, depression -cough, increased work of breathing |
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Signs to listen for on auscultation
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-murmurs or abnormal heart sounds
-irregular rhythms -pulse deficits -abnormal lung sounds (crackles?---> pulmonary edema) -percussion for fluid accumulation |
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Minimum data base
-for cardiac patient |
-CBC
-Serum biochem -thoracic radiographs |
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Additional data you may want to collect for certain cardiac cases
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-ECG
-urinalysis -BP -SpO2 -arterial blood gas analysis -heartworm test -serum thyroid hormone level |
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Essential tool of the cardiologist
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-ECG
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ECG
-uses |
-diagnosis of specific cardiac or vascular anatomic disorders
-evaluation of chamber enlargement and chamber volume -assessment of heart function |
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Doppler echo
-uses |
-ID of regurgitant flow
-quantification of pressure gradient across valves |
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Establishing patient risk
-use |
-helpful to clarify degree of compromise of patient prior to anesthesia
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ASA classifications of risk
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I) normal healthy patient
II) mild systemic disease III) severe systemic disease limiting activity, but not incapacitating IV) incapacitating systemic disease that is a constant threat to life V) moribund patient not expected to live 24 hrs |
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CBC
-what to look for |
-signs of systemic infection
-hematocrit -total protein -platelets |
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Serum chemistry
-what to look for |
-impaired renal or hepatic function in geriatric animal prior to anesthesia
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If a radiograph is showing left atrial and ventricular enlargement, what is the most likely diagnosis?
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-chronic valvular disease with mitral insufficiency
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Questions to ask when you have a likely diagnosis of the heart condition
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-what is the pathophysiology of the disease?
-how does the animal adapt to the condition? -what is the risk of anesthesia |
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Effects of mitral valve insufficiency on the heart
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-chronic volume overload -----> ventricular dilation
-stroke volume is divided into forward and regurgitant flow -no period of isovolumetric contraction in LV |
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Isovolumetric contraction
-define |
-when the mitral valve and aortic valve should both be closed to build up some pressure in the ventricle
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Effect of volume overload
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-eccentric hypertrophy
-dilation of the ventricle in systole -normal wall thickness -systolic function usually ok -LV wall motion during systole may appear hyperdynamic |
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Why are animals with mitral insufficiency asymptomatic for long periods
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-afterload is low
-oxygen demand is low -LVEDP does not increase (no isovolumetric period ---> no increase in wall pressure) |
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Volume of regurgitant flow in mitral insufficiency
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function of:
-size of mitral valve orifice -time of flow -pressure gradient across the mitral valve |
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Regurgitant orafice size is a function of:
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-left ventricle size
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Mitral insufficiency
-goal of anesthesia |
-promote forward flow
-reduce regurgitation |
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Mitral insufficiency
-dynamic factors that increase regurgitant volume |
Increases in preload
-avoid bradycardia -avoid IV fluid overload Increases in afterload -avoid vasoconstriction Decreases in contractility -avoid decreases in sympathetic tone |
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Drug that are ok for vasodilation in mitral valve insufficiency
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-acepromazine (low dose) with an opioid (analgesia)
-benzodiazepine with opioid -opioids alone as premed |
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Drug contraindicated for mitral valve insufficiency
-why? |
-Alpha-2 agonists
-vasoconstriction----> reflex bradycardia -sympatholytic |
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Drug to consider if bradycardia occurs
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-atropine
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Inhalant anesthetics that are vasodilators
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-isoflurane
-sevoflurane |
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Fluid therapy of patient with cardiac conditions
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-5 mL/kg/hr or less for maintenance during anesthesia
-base on prior chest radiograph evaluation of pulmonary circulation |
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Reason why local nerve blocks may be a good choice in patients with cardiac problems
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-removes pain stimulation ----> lighter anesthetic needed
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Cardiac conditions that constitute major risk
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-decompensated CHF
-high-grade AV block -symptomatic ventricular arrhythmias -supraventricular arrhythmias with uncontrolled rate -severe valvular disease (pulmonic/aortic stenosis) |
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Principles for the higher risk cardiac patient
-hydration status |
-insure effective circulating blood volume
-provide adequate preload -anesthesia usually results in decreased vascular tone, cardiac output -correct hypoproteinemia |
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Principle for higher risk cardiac patient
-optimizing oxygen-carrying capacity |
-insure adequate oxygenation (PaO2 = 100 mmHg, SpO2 > 95%)
-insure adequate hemoglobin (PCV > 20%) -insure adequate cardiac output (SBP > 90 mmHg) |
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Principles for higher risk cardiac patients
-correct arrhythmias |
-stable rhythm to maximize CO
-correct underlying acid-base/electrolyte disorder -choice of antiarrhythmic therapy |
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Principles for higher risk cardiac patients
-treat if there is evidence of: |
-pulmonary edema (diuretics)
-pleural effusion -pericardial effusion -pneumothorax |
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Principles for higher risk cardiac patient
-continue administration of current heart medications up to the point of anesthesia if: |
-the therapy has improved patient condition
-the therapy helps provide hemodynamic or metabolic stability -acute discontinuation of drug could result in adverse effect |
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Drug you may want to discontinue before anesthesia
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-Beta-blocker
-negative ionotrope -hard to deal with accompanied by anesthesia |
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How to choose the correct anesthetic drugs in a cardiac patient
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-CV disease requires careful choice, titration to effect, balanced approach
-choices based on best understanding of physiologic consequences of the state of cardiac dysfunction |