pharmacologic considerations in the cardiac patient wayne e. ellis, ph.d., crna
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Pharmacologic Considerations in the
Cardiac Patient
Wayne E. Ellis, Ph.D., CRNA
04/10/23
Treatment of Ischemia(primary)
• ASA 325 mg immediately
• Thrombolytics (Retevase) – > flow rate than TPA– 2 doses @ 30 min intervals– lyse clots through the activation of
plasminogen
04/10/23
Primary Treatment
• Antiplatelet agents(abciximab, eptifibatide, tirofiban, integullin)
• GPIIb-IIIa antagonists
• inhibit platelet function by blocking the GPIIb-IIIa receptor, the final pathway of platelet aggregation
• thereby decreasing thrombi development and prevents arterial vessel occlusion
04/10/23
Percutaneous Coronary Intervention
• Advantages include: higher recanulazation rates
• improved blood flow through the infarct-related vessel
• improved LV function
• lower in-hospital mortality rates
Anesthetic Technique
Goals of Anesthesialoss of consciousness
amnesia
analgesia
suppression of reflexes (endocrine and autonomic)
muscle relaxation
Preoperative Preparation
AnginaMedications to control it
Blood pressure controlledDiastolic < 95 torr
Congestive heart failure treatedDiuretics
Afterload reduction
Bed rest if indicated
Control diabetes
Preoperative Medications
Sedation
Prevent tachycardia
Hypertension
Prepared for hypoxia
Supplemental oxygen
Calcium channel blockers not protective of perioperative ischemia
Antihypertensives continue on day of surgery
Stop Diuretics
04/10/23
Low Molecular Weight Heparin
• Enoxaparin, Dalteparin
• Anticoagulant activity by binding to antithrombin III, which further binds and inactivates the coagulation factors IIa (thrombin) and Xa
• Advantages include dosed per body wt.
• Given q12 sub q.
• Less trombocytopenia and bleeding
04/10/23
Opioids
• Advantage relates to the relative lack of myocardial depression – Exception Sufenta, Carfentanil, and high dose fentanyl
• They maintain stable hemodynamics and reduce heart rate
• A primary opioid technique may be of value in the patient with severe myocardial dysfunction
Opioids
AdvantagesExcellent analgesia
Hemodynamic stability
Blunt reflexes
Can use 100% oxygen
Opioids
DisadvantagesMay not block hemodynamic and hormonal
responses in patients with good LV function
Do not ensure amnesia
Chest wall rigidity
Respiratory depression
04/10/23
Vasoconstrictors
• are useful in the prevention and treatment of ischemia r/t the ability to increase systemic BP
• Phenylephrine improves coronary perfusion pressure, at the expense of increasing afterload and Mv02
04/10/23
Vasoconstrictors
• At the same time, phenylephrine causes venoconstriction, increasing venous return and left ventricular preload.
• The increase in CPP more than offsets the increase in wall tension
Inhalation Agents
AdvantagesMyocardial oxygen balance altered favorably
by reductions in contractility and afterload
Easily titratable
Can be administered via CPB machine
Rapidly eliminated
04/10/23
Inhalational Agents
• Disadvantages include myocardial depression
• systemic hypotension with possible tachycardia
• lack of postoperative analgesia
Inhalation Agents
DisadvantagesSignificant hemodynamic variability
May cause tachycardia or alter sinus node function
Possibility of “coronary steal syndrome”
Inhalation Agents
Potential for coronary steal
Alters coronary autoregulation
Alters regional blood flow
Little influence on outcome
Coronary Steal
Arteriolar dilation of normal vessels diverts blood away from stenotic areas
Commonly associated with adenosine, dipyridamole, and SNP
Forane causes steal and new ST-T segment depression
May not be important since Forane reduces SVR, depresses the myocardium yet maintains CO
04/10/23 WE Ellis 20
Antianginal medications
Beta-blockers
Calcium Channel Blockers
Nitrates
Nitropaste morning of surgery
04/10/23
Nitrates
• Nitroglycerin = venodialator, reduces venous return, decreases wall tension(Mv02) also a coronary arterial dialator.
• Drug of choice for coronary vasospasm• Although primarily is a systemic
venodialator, at high doses causes arterial dilatation and systemic hypotension
Cardioactive drugs
NitroglycerinLower LVEDP
Vasodilator
Poor ventricular function
04/10/23
Beta Blockers
• Beta blockers reduce myocardial workload(Mv02), and oxygen consumption(V02) by reducing HR,BP, and contractility, and they increase the threshold for ventricular fibrillation.
• Indications for beta blockers include: sinus tachycardia, supraventricular dysrhythmias and hyperdynamic states
Beta Blockers
Negative inotropic effects
Withdrawal following stoppage of beta blockerUnstable angina
Myocardial infarction
04/10/23
Beta Blockers
• Propranolol (non-selective) t1/2 = 4-6 hours
• Metoprolol (B1 selective) t 1/2 = 4-6 hours
• Labatelol (1:7 ratio) t 1/2 = 2-4hours
• Esmolol (Beta1 selective) t1/2 = 9.5 minutes
Esmolol
Control heart rate and blood pressure
Induction
Emergence
Labetalol
Mixed alpha and beta
Control hypertension
Heart rate management
04/10/23
Ca Channel Blockers
• Evidence for beneficial effects post mi is less compelling
• Nifedipine treatment is associated with a trend towards increased mortality and reinfarction
• Verapamil does not reduce mortality or reinfarction
• Verapamil - useful for slowing the ventricular response in atrial fibrillation/flutter
04/10/23
Ca Channel Blockers
• Cardizem- in pt’s with non-Q wave infarction seems to reduce the reinfarction rate during the 1st 6 months after the infarction, but incidence of late infarction was similar to a placebo.
• Cardizem increases cardiac events in pt’s with LVEF<40% , but decreases their incidence in pt’s with preserved LV function
04/10/23
Ca Channel Blockers
• All Ca blockers depress contractility, reduce coronary and systemic tone, decrease sino-atrial node firing, and impede atrioventricular conduction.
• The negative inatropic effect is greatest with verapamil
• Nifedipine + Cardizem are used in the prevention of coronary vasospasm
Nifedipine
Controlling hypertension
Manage coronary artery spasm
04/10/23
ACE Inhibitors
• Are effective in reducing ischemic effects after MI
• Treatment should be instituted within the 1st 24 hours of all pt’s with acute mi complicated by symptomatic or asymptomatic left ventricular dysfunction
04/10/23
ACE Inhibitors
• Contraindicated in pt’s with hypotension, bilateral renal artery stenosis, history of a cough or angio-edema with ace inhibitors
04/10/23
Aspirin
• ASA benefit well established as a secondary prevention
• Antiplatelet therapeutic dose (75-325mg/day)
• other antiplatelet agents such as dipyridamole are not supported in the literature except in pt’s with allergies to ASA who are poor candidates to oral anticoagulants
04/10/23
Anticoagulants
• Studies of anticoagulant treatment after mi show reduction in death, recurrent MI, and thromboembolitic complications
• However, trials comparing warafin to ASA for secondary prevention show no difference in recurrent infarction or death
04/10/23
Anticoagulants
• Are indicated for pt’s with ASA intolerance and for those at risk of embolisation from left ventricular or atrial clot(i.e. persistent atrial fib)
04/10/23
Lipid Lowering Agents
• meta analysis of clinical trials show that lipid lowering agents produce a reduction in fatal and non-fatal MI’s and cardiovascular deaths
• Should be given to pt’s with LDL concentration >3.37 mmol/1
Clonidine
Less hypertension
Decreased anesthesia requirements
Anesthetic Management
Regional vs. general
Anesthetic management skills more important than technique
Safest technique is the one the practitioner does best
Regional Anesthesia
Monitor patient more accurately
Control sympathetic responsesFluids
Esmolol
General anesthesia
Avoids sympathectomy
Risks with intubationSympathetic stimulation
Hypoxia
Increased catecholamines
Loss of subjective monitorChest pain
Ischemia
General Anesthesia required
NarcoticsEffective control of catecholamines
Respiratory depression
Prolonged ventilation
Lidocaine
Blunt effects of intubation
1.5 mg/kg 4-6 minutes prior to intubation
Nitrous Oxide
Rarely used due to:increased PVR
depression of myocardial contractility
mild increase in SVR
air expansion
Induction Drugs
Barbiturates
Benzodiazepines
Ketamine
Etomidate
Avoid Ketamine
Hypertension
Tachycardia
Use in trauma
Etomidate
Painful to inject
More CV stability
Barbiturate
Direct depressant
Extended duration of activity
Smaller doses1-2 mg/kg
Add benzodiazepines and narcotic
Benzodiazepines
Quell anxiety
Hemodynamic stability
Extended duration of action
Potential for hypoxia
Lidocaine
Esmolol
Muscle Relaxants
Used to:facilitate intubation
prevent shivering
attenuate skeletal muscle contraction during defibrillation
Muscle Relaxants
Avoid pancuroniumTachycardia
ST segment changes consistent with ischemia
Doxacurium Duration similar to pancuronium
No cardiovascular effects
Avoid Histamine releasing drugs
Curare
Atracurium
Mivacurium <15 mcg/kg
Hypotension
Tachycardia
Nitrous Oxide
Constricts coronary arteries
Aggravates myocardial ischemia
High FiO2 recommendedMaintain saturation at 95-100%
Intraoperative predictors
Choice of anesthetic
Site of surgery
Duration of Anesthesia
Emergency Surgery
Intraoperative predictors
Choice of AnestheticNo difference in infarction rate GETA vs. Regional
No significant hypotension
No significant tachycardia
TURPRegional decreased risk post MI
Reinfarction rateSAB < 1%
GETA 2-8%
Intraoperative predictors
Choice of AnestheticPatient with CHF will benefit from regional
techniqueSympathectomy
Decreased preload
Coronary StealPotent inhalation agents vs. narcotics
Intraoperative predictors
Site of SurgeryThoracic and upper abdominal
2-3 X’s risk of extremity procedures
Duration of Anesthetic> 3 hours > risk of morbidity & mortality
Emergency Surgery2 - 5 X’s greater risk than nonemergent surgery
Postoperative Management
Maintain analgesia
Balance supply and demand
Supplemental oxygen
Continue monitoring into postoperative period
Early transfusion
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