02/07/13 Wayne E. Ellis Anesthesia for Noncardiac Surgery
Ischemia and Heart Disease 02/07/13 WE Ellis
Anaesthesia for cardiac patient undergoing non cardiac surgery
Dr.Kanchan ChauhanAssociate Professor in Anaesthesiology
INTRODUCTION Stress due to surgery leads to an increase in cardiac output which can be achieved easily by normal patients, but which results in substantial morbidity and mortality in those with cardiac disease. Most suitable anaesthetic can be given by understanding different cardiac disease. The skill with which the anaesthetic is selected and delivered is more important than the drugs used. No. of patients with cardiac disease are increasing. due to the fact that the surgery is being performed on older patients in whom the incidence of coronary artery disease (CAD) is higher, and secondly, recent advances in diagnostic technology have allowed us to detect CAD in asymptomatic or mildly symptomatic patients. With increased awareness and improved cardiac surgical results, patients who have undergone corrective cardiac surgery are also presenting for noncardiac surgery.
What Should be our Approach ? Preoperative – Pre anaesthetic evaluation, Risk stratification and preparation Intraoperative – Smooth induction , Smooth recovery , Smooth monitoring Postoperatively – Cont. monitoring and vigilance
Pre anaesthetic evaluation ASSESSMENT OF PERIOPERATIVE RISK Goldman Cardiac Risk Index. Lee’s risk stratification criterion Detsky’smodified approach to Goldman index NYHA Classification Canadian Cardiovascular Society Classification Follow AHA ( American Heart Association) guidelines for perioperative cardiovascular evaluation
Medications : Keep in Mind Continue all antianginals, anti hypertensives Continue anti arrythmics Continue Beta blockers and Statins Continue Aspirin (not in some institue) Discontinue Diuretics, Digitalis, Oral hypoglycemics, ACE inhibitors
O T Preparation Ready Emergency cardiovascular drugs (iv beta blockers, NTG, SNP, Inotropes, Ephedrine, Phenylephrine, CCB, anti arrythmics etc. Cardiac equipments :Defibrillator, Pacemakers, Syringe pump
Monitoring ECG Blood Pressure Temperature Pulse oximetry End tidal CO2
Arterial Catheter Beat to beat blood pressure monitoring ABGs Early detection of hypotension
PA catheterAssessment of LV FunctionEarly detection of ischemia “v” waves Increased PCWPMore accuracy than CVP Intravascular volume problems Especially in patients with severe lung disease
TransesophagealEchocardiography Demonstrates regional wall motion abnormalities Suggestive of ischemia Most accurate measure of left ventricular volume
Non-invasive ContinuousCardiac Output Monitors Transesophageal Doppler Thoracic impedance Limited Accuracy is controversial No information about systemic vascular resistance Measure CVP Invasive Monitoring
TemperatureKeep warmDecreasing temperature Shift Oxygen dissociation curve to left Hemoglobin retains oxygen at tissue levelPrevent alkalosis02/07/13 WE Ellis 13
Preoperative PreparationAngina Medications to control itBlood pressure controlled Diastolic < 95 mm hgCongestive heart failure treated Diuretics Afterload reduction Bedrest if indicatedControl diabetes
Our Approach 2012 for beta blockers Continue beta blockers for those already receiving Initiate beta blockers prior to surgery (cautiously) for patients who would otherwise need them - Begin low dose as early as possible- >1 week - not day of surgery Titrate to heart rate (60-70) and BP Carefully follow those on beta blockers in the postoperative period Hypotension Bradycardia Postoperative tachycardia: look first for a treatable cause (hypovolemia, anemia) rather than just increasing beta blocker dose.
Anesthesia Goal Does technique make a difference? Laryngoscopy Maintenance Regional anesthesia02/07/13 WE Ellis 16
Anesthetic TechniqueGoals of Anesthesia loss of conciousness amnesia analgesia suppression of reflexes (endocrine and autonomic) muscle relaxation
Anesthetic ManagementAnaesthetic techniques –Local anaesthesiaRegional anaesthesiaCombined Regional – General anaesthesiaGeneral anaesthesiaAnesthetic management skills more important than technique.Safest technique is the one the practitioner does best.Anaesthetic technique must be based on the type of surgery and the desired haemodynamic goals during anaesthesia.
Role of LocalAnaesthesia LA should be with appropriate IV sedation Large doses of anaesthetic should be avoided - cardiac toxicity - dysrrhythmias and myocardial depression. Epinephrine with LA - tachycardia, which is undesirable and should be avoided. Monitored with an ECG, BP and a pulse oxymeter. Supplemental oxygen therapy Regular verbal contact with patient are important.
Regional Anaesthesia Intraoperative adverse cardiac events do not differ when general or regional anaesthesia is used.(study shows) Certain procedures have shown better outcome under RA. E.g.- McLaren et al found no mortality under spinal anaesthesia for fracture neck femur, versus 25%mortality after GA. Patients with prior MI undergoing transurethral resection of prostate had <1% reinfarction rate after spinal versus 2-8% after GA.
Regional Anaesthesia RA - loss of sympathetic efferent tone - rapid haemodynamic deterioration contraindicated in severe aortic stenosis or hypertrophic obstructive cardiomyopathy. In a patient with a failing heart who is dependent on sympathetic tone – central neural blockade can precipitate cardiac arrest.Monitor patient more accuratelyControl sympathetic responses
Combined Regional-General Anaesthesia Requires a lot of experience on the part of anaesthesiologist. E.g. - For lower abdominal surgery, a combination of lumbar epidural analgesia and GA can be considered when long surgical procedure, large blood loss or marked hypothermia is anticipated. The combination of thoracic epidural and GA can be used for upper abdominal, thoracic and major vascular surgery. The main advantages of epidural blockade are superior postoperative analgesia and less diminution of vital capacity. Epidural analgesia by suppressing pain improves transmural distribution of regional myocardial blood flow and thus minimizing myocardial ischaemia.
Generalanesthesia Most common anaesthetic technique used for cardiac patients undergoing noncardiac surgery. Avoids sympathectomyRisks with intubation Sympathetic stimulation Hypoxia Increased catecholaminesLoss of subjective monitor Chest pain Ischemia
General Anesthesia required I. Pre-anaesthetic medication Integral part of anaesthetic practice ( particularly in patients with CAD and hypertension.) Benzodiazepines – Quell anxiety Hemodynamic stability Extended duration of action Potential for hypoxia Intravenous narcotics (e.g. Fentanyl) Effective control of catecholamines Respiratory depression Prolonged ventilation
OpioidsAdvantages Excellent analgesia Hemodynamic stability Blunt reflexesDisadvantages May not block hemodynamic and hormonal responses in patients with good LV function Do not ensure amnesia Chest wall rigidity Respiratory depression
Inductions AgentsAvoid Ketamine Hypertension Tachycardia Use in traumaEtomidate Painful to inject More Cardiovascular stabilityBarbiturate Direct depressant Extended duration of activity Smaller doses 1-2 mg/kg Add benzodiazepines and narcotic Propofol Outpatient anaesthesia (quick recovery) Benzodiazepines
Laryngoscopy and intubation Adequate depth of anaesthesia should be ensured prior to intubation. Fentanyl 5-8 mgm/kg can be given to blunt the sympathetic responses to laryngoscopy and intubation. Lidocaine Blunt effects of intubation 1.5 - 2 mg/kg 4-6 minutes prior to intubation Esmolol i.v. – 0.5 to 1mg/kg 90 sec before intubation
Muscle Relaxants Succinylcholine is notorious - producing arrhythmias. Avoid pancuronium Tachycardia ST segment changes consistent with ischemia (Pancuronium may be used in patients with CAD who have a slow heart rate) Vecuronium provides minimal haemodynamic alterations. Doxacurium -cardiovascular stable. Rocuronium should be considered during rapid sequence induction technique.Avoid Histamine releasing drugs Curare Atracurium Mivacurium <15 mcg/kg - Hypotension ,Tachycardia
Nitrous Oxide increased PVR depression of myocardial contractility mild increase in SVR air expansion Constricts coronary arteries Aggravates myocardial ischemia High FiO2 recommended Maintain saturation at 95-100% N2O - Detrimental effects in patients with CHF, pulmonary hypertension and regional myocardial ischaemia
Inhalation AgentsAdvantages Myocardial oxygen balance altered favorably by reductions in contractility and afterload Easily titratable Can be administered via CPB machine Rapidly eliminatedDisadvantages Significant hemodynamic variability May cause tachycardia or alter sinus node function Possibility of “coronary steal syndrome”
Inhalation Agents Depress myocardium, Cause arterial and venous dilation and decrease sympathetic nervous activity. decrease in BP and CO, and thus decrease in myocardial oxygen consumption. (advantageous in patients with CAD, may produce cardiovascular collapse in patients with poor myocardial reserve.) Potential for coronary steal - isoflurane Alters coronary autoregulation Alters regional blood flow Little influence on outcome
Coronary StealArteriolar dilation of normal vessels diverts blood away from stenotic areasCommonly associated with adenosine, dipyridamole, and SNPIsoflurane causes steal and new ST-T segment depressionMay not be important since Isoflurane reduces SVR, depresses the myocardium yet maintains CO
Intraoperative predictorsChoice of Anesthetic No significant hypotension No significant tachycardiaSite of Surgery Thoracic and upper abdominal 2-3 X’s risk of extremity proceduresDuration of Anesthetic > 3 hours > risk of morbidity & mortalityEmergency Surgery 2 - 5 X’s greater risk than nonemergent surgery
Cardioactive drugsNitroglycerin Lower LVEDP , VasodilatorEsmolol Control heart rate and blood pressure Labetalol Control hypertension , Heart rate managementClonidine Less hypertension , Decreased anesthesia requirementsNifedipine Controlling hypertension Manage coronary artery spasm
Coronary Artery DiseaseMajor Goal Balance Supply and DemandPrimary Determinants of Myocardial Oxygen DemandWall tension and ContractilityFactors modifying coronary blood flow diastolic time perfusion pressure coronary vascular tone intraluminal obstruction
Hemodynamic Goals forthe Patient with CADPreload - keep the heart small, decrease wall tension, increase perfusion pressureAfterload - maintain, hypertension better than hypotensionContractility - depression is beneficial when LV function is adequateH R - slowRhythm - usually sinusMVO2 - control of demand frequently not enough, monitor for and treat ischemia
Monitored Anaesthesia Care Employed in CAD patients Patients carrying the highest risk are selected Minimum anaesthetic interference Adequate analgesia is mandatory Failure to suppress the stress response Highest incidence of 30 day mortality (isacon 2008)
HEART FAILURE Inability of the heart to pump enough blood to match tissue requirements. Commonest cause ischaemic heart disease. Other causes include hypertension, valvular heart disease and cardiomyopathies. Note that with an increase in contractility there is a greater cardiac output for the same ventricular end- diastolic volume. . Drug treatments may include ACE (angiotensin converting enzyme) inhibitors, diuretics and nitrates. Echocardiogram to assess ejection fraction - values of less than 30% equate to severe heart failure.
Anaesthesiaconsideration Preload can be reduced with diuretics and nitrates, and both central venous and pulmonary artery pressures can be monitored. Trans-oesophageal echocardiography, if available, is a useful tool to visualize overall cardiac performance. Maintenance of myocardial contractility - in particular inotropes may be needed to oppose the cardiodepressant action of anaesthetic agents. Reduction of afterload by vasodilation, for example as a secondary effect of spinal or epidural anaesthesia. This not only reduces myocardial work, but helps maintain cardiac output. However, the benefit of such actions may be limited by falls in blood pressure which can compromise blood flow to vital organs such as the brain and kidneys. So balance should be there
Mitral StenosisCharacterized by: Normal ventricular function Obstruction to left atrial emptying decreases cardiac output Pulmonary congestion from elevations in LA and pulmonary venous pressure Pulmonary hypertension and RVH over time
Hemodynamic Goals for thePatient with MSPreload - Enough to maintain flow across stenotic valve so to maintain ventricular feeling, excess fluid may cause pulmonary edemaAfterload – SVR should be maintained,avoid decrease in SVR Avoid increased RV afterload (PVR)Contractility - LV usually ok until after CPB, with longstanding PHTN, RV may be impairedHR -keep slow to allow time for ventricular filling, AVOID SINUS TACHYCARDIA
Hemodynamic Goals forthe Patient with MSRhythm - Often atrial fibrillation, control ventricular responseMVO2 - Not a problemCPB - Vasodilators may help post-CPB RV failure, control of ventricular response may be difficultepidural preffered over spinalphenylephrine preffered over ephedrine
Mitral RegurgitationCharacterized by: Chronic volume overload similar to AI Increased ventricular compliance without change in LVEDP May mask signs of impaired ventricular function
Hemodynamic Goals forthe Patient with MIPreload – maintain or slightly increase ;an elevated preload may cause increase in regurgitant flow and low preload may cause inadequate cardiac output Usually pretty full, may need to keep that wayAfterload - Decreases are beneficial, increases augment regurgitant flow, avoid sudden increase in SVRContractility - Unrecognized myocardial depression possible, titrate myocardial depressants carefully, maintain or increase to decrease left ventricular volumeHR – maintain or increase , avoid bradycardia which worsens regurgitant flow
Hemodynamic Goals forthe Patient with MIRhythm - Atrial fibrillation is occasionally a problemMVO2 - only if associated with CAD, then caution!CPB - New valve will increase afterload, unmasking impaired ventricleSpinal and epidural well tolerated but avoid bradychardia
Mitral valve prolapse-anaesthesia consideration Aboid decrease in preload Continue antiarrhythmic drugs Same consideration as for MI
Aortic StenosisCharacterized by: Obstruction to LV outflow Intraventricular systolic pressure and wall tension increase Concentric hypertrophy Decreased LV compliance Reliance on atrial contribution
Hemodynamic Goals forthe Patient with ASPreload - full, adequate intravascular volume to fill noncompliant ventricle and to maintain BPAfterload - already elevated but relatively fixed, coronary perfusion pressure must be maintained,Contractility - usually not a problem, inotropes may be helpful preinduction in end-stage AS with hypotensionWatch out for vasodilationTreat hypotension with phenylephrine
Hemodynamic Goals forthe Patient with ASRate - not too slow (decrease CO), not too fast (ischemia)Rhythm - Sinus!! Cardioversion if hemodynamic instability from SV dysrhythmiasMVO2 - Ischemia is an ever present risk, Avoid tachycardia and hypotensionMild to moderate may tolerate spinal and epidural (epidual preferred)spinal and epidural contraindicated in severe ASHigh risk of myocardial ischaemia
Aortic InsufficiencyCharacterized by: Chronic volume overload Ventricular dilatation Eccentric hypertrophy Forward stroke volume higher than normal causing increased systolic pressure Regurgitation across the valve causes diastolic pressure to be lower than normal
Hemodynamic Goals forthe Patient with AIPreload - normal to slightly increased to maximize forward cardiac output and maintain BPAfterload - Reduction beneficial with anesthetics or vasodilators,increases augment regurgitant flow, avoid sudden increase in afterloadContractility - usually adequateRate - Modest tachycardia shortens diastolic phase decreases regurgitant fraction and increases cardiac outputMost patient tolerate spinal or epidural provided intravascular volume is maintained
Aortic Insufficiency Once asymptomatic death can occur with in 5 yrs unless lesion is surgically repaired Digitalis , Diuretics and afterload reduction (ACE inhibitors) for chronic cond. (eventual surgical repair) Inotropes (dopamine,dobutamine) and vasodilators for severe,chronic aortic regurgitation (requires surgery)
Hemodynamic Goals forthe Patient with AIRhythm - usually sinus, not a problemMVO2 - Not usually a problemCPB - observe for ventricular distention (decreased HR, increased ventricular filling pressure) when going onto bypass
Hypertension – Anaesthesiaconsideration HTN (defined as a diastolic BP>90mmHg or a systolic BP>140mmHg in adults) is the most common of all the cardiovascular diseases. Most patients are under adequate control preoperatively and their medication should be continued till the day of surgery. Poorly controlled or uncontrolled hypertensives are at increased risk of perioperative complications such as ischaemia, MI, arrhythmias and cerebrovascular accidents (CVA). In mild hypertensive patients a single dose of long acting beta-blocker may reduce the risk of myocardial ischaemia during stressful periods. However, in patients with moderate to severe HTN, cardiology consultation should be obtained and BP brought under control prior to elective surgery.
Coronary Artery RevascularizationProphylaxis Trial (CARP) Coronary revascularization prior to vascular surgery is not of benefit in the patient with stable CAD if treated with beta blockers, aspirin, statins in the absence of: unstable coronary disease left main coronary disease aortic stenosis severe left ventricular dysfunction
Elective vascular surgery in high risk patients.101 patients3 or more cardiac risk factorsAll with extensive inducible ischemia by stress test43% with LVEF < 35%75% with Left main or 3-vdAll received beta blocker titrated to HR 60-65Antiplatelet agents continued in perioperative periodNo benefit of prophylactic coronary revascularization
How about the patient who has already received a stent and requires noncardiac surgery ?
Drug eluting stent related issues Stent thrombosis ASA + clopidogrel Hemorrhage ASA + clopidogrel
Joint Advisory Recommendationsand Noncardiac Surgery Consider bare metal stent if patient requires PCI and is likely to require invasive or surgical procedure within next 12 months. Educate patient prior to discharge re: risk of premature antiplatelet discontinuation Instruct patient to contact treating cardiologist before antiplatelet discontinuation Healthcare providers who perform surgical or invasive procedures must be made aware of catastrophic risks of premature antiplatelet discontinuation and should contact the treating cardiologist to discuss optimal management strategy
Joint Advisory Recommendations and Noncardiac Surgery Defer elective procedures for which there is bleeding risk until completion of antiplatelet course 1 month bare metal stent 12 months drug eluting stent For patient with drug eluting stent who are to undergo procedures that mandate discontinuation of thienopyridine (eg, clopidogrel), continue aspirin if at all possible and restart thienopyridine as soon as possible No evidence for “bridging therapy” with antithrombins, warfarin, or glycoprotein IIb/IIIa agents
Postoperative predictorsIschemia does occur most commonly in the postoperative periodPersists for 48 hours or longer following non-cardiac surgeryPredictor value is unknownGoldman, L., (1983) Cardiac Risk and Complications of noncardiac surgery, Annals of Internal Medicine. 98:504-513
PostoperativeManagement Maintain analgesia Balance supply and demand Supplemental oxygen Continue monitoring into postoperative period Early transfusion
Key Points Clearance. Perform evaluation and make recommendations that will relate to perioperative and long – term issues. Tests only if likely to influence treatment. Preoperative coronary revascularization if independently indicated. Selective use of beta blockers. (beware bradycardia) Statins Beware of premature antiplatelet discontinuation in the patient post PTCA stent. Continue beta blocker, aspirin, statins,
Summary Patients with cardiac disease present for anaesthesia every day. Since their perioperative courses are associated with greater morbidity and mortality, it is important to provide a haemodynamically stable anaesthetic This requires knowledge of the pathophysiology of the disease, and of the drugs and procedures and their effects on the patient.