Anesthesia in the Cardiac Patient. Monitoring Routine Pulse Oximetry PNS Capnography Temperature Core and peripheral ECG Leads V5 and II

Anesthesia in the Cardiac Patient

Monitoring

RoutinePulse OximetryPNSCapnographyTemperature

Core and peripheral

ECGLeads V5 and II

Monitors of Cardiac Performance

Arterial LineStandard of CareSite selection

Pulmonary Artery CatheterProvides means for assessing filling pressuresReliable site for drug administration

Transesophageal Echocardiography

Anesthetic Technique

Goals of Anesthesialoss of conciousnessamnesiaanalgesiasuppression of reflexes (endocrine and autonomic)muscle relaxation

Inhalation Agents

AdvantagesMyocardial oxygen balance altered favorably by

reductions in contractility and afterloadEasily titratableCan be administered via CPB machineRapidly eliminated

Inhalation Agents

DisadvantagesSignificant hemodynamic variabilityMay cause tachycardia or alter sinus node functionPossibility of “coronary steal syndrome”

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 depressionMay not be important since Forane reduces SVR,

depresses the myocardium yet maintains CO

Opioids

AdvantagesExcellent analgesiaHemodynamic stabilityBlunt reflexesCan use 100% oxygen

Opioids

DisadvantagesMay not block hemodynamic and hormonal

responses in patients with good LV functionDo not ensure amnesiaChest wall rigidityRespiratory depression

Induction Drugs

BarbituratesBenzodiazepinesKetamineEtomidate

Nitrous Oxide

Rarely used due to:increased PVRdepression of myocardial contractilitymild increase in SVRair expansion

Muscle Relaxants

Used to:Facilitate intubationPrevent shiveringAttenuate skeletal muscle contraction during

defibrillation

Cardiopulmonary Bypass

Basic ComponentsArterial and venous cannulaReservoirPumpOxygenatorHeat exchanger


OxygenatorsBubble - most common

Direct contact between blood and fresh gasThe smaller the bubbles the greater the rate of transferPerfusate must be de-foamedAssociated with platelet destruction, microemboli, and

decreased leukocyte counts


OxygenatorsMembrane

Blood gas interface separated by semipermeable membrane

No direct mixing of gas and bloodLess trauma to blood


CannulationVenous cannula placed into RA, IVC, or SVCArterial cannula into proximal aorta or femoral

arteryAorta cannulated firstSystolic BP reduced to 100 - 110 mm Hg.


Complications of CannulationArterial

Hypertension

VenousSupraventricular dysrhythmiasAtrial fibrillation


PumpsRoller

positive displacement pump that maintains constant flow when increased resistance is encountered

Impellerwith increased resistance forward flow is reduced


Heat ExchangerAdjusts temperature of perfusate to provide

hypothermiaMetabolic requirements are decreased about 8%

per degree of decrease in body temperatureProvides protection during periods of

hypoperfusion and potential tissue ischemia


Heparinization300 u/kgACT determines adequacy of anticoagulationACT value greater than 400 sec.


Preparation of MachineCrystalloid solution used to “prime pump”Causes a dilution of plasma drug concentrationHgb and HCT are reducedBlood viscosity decreasesMAP drops to 30 -40 mm Hg.


Management of Gas ExchangepH statAlpha-Stat


Adequacy of PerfusionMAPHematocritMixed venous oxygen saturationBlood lactate levelsCentral and peripheral temperatureUrine output


Central Nervous System ProtectionInjury thought to be a consequence of emboliContributing factors

inadequate cerebral perfusionduration of bypassage


Rewarming10 degree gradient maintained to reduce gas

bubble formationAwareness may be a problem

Separation from Bypass

Accomplished in three stagesPreparationPartial BypassOff Bypass


PreparationRelease of aortic cross clamp

reestablishes myocardial perfusion and cardiac rhythmOften requires electrical defibrillation


Problems encountered during preparation phaseRecurrent or resistant ventricular fibrillationPersistent left ventricular distentionPersistent asystole


Partial BypassVenous return partially restrictedVenous blood enters the right ventricleLungs inflated and right ventricle ejects blood into

pulmonary arteryModest PA pressure and good systemic pressure

indicate successful separation


Factors contributing to problems during partial bypassunusually low hematocritexcessive vasodilationmarked respiratory or metabolic acidosis


Off BypassComplete occlusion of venous return to machineContinuous assessment of filling pressures

importantvenous blood remaining in reservoir used to

transfuse as necessary

Reversal of Anticoagulation

Protamine administrationMost common method to use standard dose

calculated on original dose of Heparin1 mg Protamine per 100 u Heparin

Protamine Reactions

Three TypesHypotensive (Type I) - Transient hypotension

occuring with rapid administration of ProtamineAnaphylactic/ Anaphylactoid (Type II) - True

allergic reaction or response to release of vasoactive mediators

Catastrophic Pulmonary Vasoconstriction (Type III) - systemic hypotension and elevated PAP

Hemodynamic Goals Post-Bypass

Heart RateMust provide adequate cardiac output70 -90 bpmRhythm should be sinusVentricular dysrhythmiasSupraventricular dysrhythmias

Ventricular Dysrhythmias

Cause must be identified rapidly and treatment instituted

V tach and V fib treated with internal defibrillation

V tachydysrhythmias treated with:Lidocaine ProcainamideBretylium EsmololMagnesium

Supraventricular Dysrhythmias

Atrial fib and tachycardia treated with synchronized internal cardioversion

Need to look at blood gases, acid-base status, and electrolytes

Assume ischemia - use NTGOther treatments;

Digoxin Esmolol Verapamil AdenosineEdrophonium Procainamide


PreloadEnough to support CO but avoid distentionVolume may be administered from CPB machineExcessive preload may be relieved with NTG or

diuretic


AfterloadReduction advantageous to the post-bypass patientDecreased wall stress lowers MVO2Favors forward flow


ContractilityOptimize to maintain COMay be augmented with inotropic supportChoice of agent depends on:

severity of ventricular dysfunctionheart rateafterloadpersonal preference

Inotropic Drugs

Dopamine 2-20 ug/kg/min

Increased RBF Mild vasocanstriction

Tachycardia, dysrhythmias

Dobutamine 2-20 ug/kg/min

Vasodilation Tachycardia, dysrhythmias

Epinephrine Bolus 5-10mcg

Common Problems Post-Bypass

Left Ventricular FailureCauses

IschemiaValve failureHypoxemiaInadequate PreloadVolume OverloadDecreased contractility


Left Ventricular FailureTreatment

NitroglycerineInotropesTransfusionTreat any acid-base/electrolyte abnormalities


Right Ventricular FailureCauses

Same as LV failureRV ischemia or infarctionPulmonary HTNCOPDMechanical ventilationProtamine reactionPulmonary embolus


Right Ventricular FailureTreatment

Ischemia treated with NTG to decrease preload and improve coronary flow

Control Preload Pulmonary vascular resistance

Mechanical Assist Devices

Intraaortic Balloon Pump (IABP)Indications for use

Intractable cardiac failurePreop stabilization of angina or LV failureComplications of MI refractory to pharmacologic

support


IABPPlaced percutaneously or via cutdown through

femoral arteryBalloon inflates at beginning of diastole augmenting

coronary blood flowBalloon deflates at beginning of systole reducing

afterloadTriggered by ECG or arterial pressure waveform


Ventricular Assist DevicesDesigned to augment either R or L ventricular

functionGoal is to decrease MVO2Three types available

Roller pumpsCentrifugal pumpsPneumatic pulsatile pumps


CoagulopathyPulmonary Complications

Pump lungBroncho spasm

Postoperative predictors

Ischemia does occur most commonly in the postoperative period

Persists for 48 hours or longer following non-cardiac surgery

Predictor value is unknown

Goldman, L., (1983) Cardiac Risk and Complications of noncardiac surgery, Annals of Internal Medicine. 98:504-513

Nonadrenergic Cardiovascular Drugs

Nonadrenergic CV drugsNonadrenergic CV drugs

• Direct-Acting VasodilatorsDirect-Acting Vasodilators– Hydralazine (Apresoline)Hydralazine (Apresoline)• Arterial dilatorArterial dilator

– Diazoxide (Hyperstat)Diazoxide (Hyperstat)• Arterial dilator (can cause hyperglycemic coma)Arterial dilator (can cause hyperglycemic coma)

– NitroglycerinNitroglycerin• VenodilatorVenodilator

– Nitroprusside (Nipride)Nitroprusside (Nipride)• Arterial and venous dilatorArterial and venous dilator


• Calcium Channel BlockersCalcium Channel Blockers– VerapamilVerapamil• Arterial dilator and decreases heart rateArterial dilator and decreases heart rate

– DiltiazemDiltiazem• Arterial dilator and decreases heart rateArterial dilator and decreases heart rate

– Nifedipine (Procardia)Nifedipine (Procardia)• Arterial dilator (causes reflex increase in heart rate)Arterial dilator (causes reflex increase in heart rate)


• Angiotensin Converting Enzyme InhibitorAngiotensin Converting Enzyme Inhibitor– Captopril (Capoten)Captopril (Capoten)• Arterial dilatorArterial dilator

– Enalapril (Vasotec)Enalapril (Vasotec)• Arterial dilatorArterial dilator


• Phosphodiesterase (PDE) Inhibitors Phosphodiesterase (PDE) Inhibitors (Positive Inotropes)(Positive Inotropes)– Inamrinone (Inocor)Inamrinone (Inocor)– Milrinone (Primacor)Milrinone (Primacor)• Block breakdown of cAMPBlock breakdown of cAMP• Increase myocardial contractilityIncrease myocardial contractility• Decrease SVR (relaxes smooth muscle)Decrease SVR (relaxes smooth muscle)

Documents

Anesthesia in the Cardiac Patient. Monitoring Routine Pulse Oximetry PNS Capnography Temperature Core and peripheral ECG Leads V5 and II