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| ARTICLES |
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| Year : 2007 | Volume
: 51
| Issue : 4 | Page : 280 |
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Anaesthetic considerations in cardiac patients undergoing non cardiac surgery
Tej K Kaul1, Geeta Tayal2
1 Professor & Head, Department of Anaesthesiology and Resuscitation, Dayanand Medical College & Hospital, Ludhiana, India
2 Assistant Professor, Department of Anaesthesiology and Resuscitation, Dayanand Medical College & Hospital, Ludhiana, India
| Date of Web Publication | 20-Mar-2010 |
Correspondence Address:
Geeta Tayal
1841, Street No. 6, Maharaj Nagar, Ludhiana. 141001
India
 Source of Support: None, Conflict of Interest: None  | Check |
Keywords: Peri-operative anaesthesia care, Cardiac diseases, Non cardiac surgery
How to cite this article:
Kaul TK, Tayal G. Anaesthetic considerations in cardiac patients undergoing non cardiac surgery. Indian J Anaesth 2007;51:280 |
 Introduction | |  |
Administering anaesthesia to patients with preexisting cardiac disease is an interesting challenge. Most common cause of peri-operative morbidity and mortality in cardiac patients is ischaemic heart disease (IHD). IHD is number one cause of morbidity and mortality all over the world [1] . Among the estimated 25 million patients in the United States who undergo surgery each year, approximately 7 million are considered to be at high risk of IHD. Indian figures are not available. Goldman et al reported that 500,000 to 900,000 MIs occur annually worldwide with subsequent mortality of 10-25%.Care of these patients require identification of risk factors, pre-operative evaluation & optimization, medical therapy, monitoring and the choice of appropriate anaesthetic technique and drugs.
Risk factors Influencing peri-operative cardiac morbidity are:
i. Recent myocardial infarction ii. Congestive cardiac failure iii. Peripheral vascular disease iv. Angina pectoris v. Diabetes mellitus vi.Hypertension vii. Hypercholesterolemia viii. Dysrrhythmias ix. Age x. Renal dysfunction xi. Obesity xii. Life style and smoking
| Risk stratification | | |
In 1977, Goldman and colleagues proposed the landmark Cardiac Risk Index [2] . Although not validated prospectively, this index was used extensively for preoperative cardiac risk assessment for the next two decades. Subsequently, other cardiac risk indices were proposed and adopted. In 1996, a 12-member task force of the American College of Cardiology and the American Heart Association (ACC/AHA) published guidelines regarding the perioperative cardiovascular evaluation of patients undergoing noncardiac surgery [3] . In March 2002, these guidelines were updated based on new data. The overriding theme remains that "preoperative intervention is rarely necessary, simply to lower the risk of surgery, unless such intervention is indicated irrespective of the perioperative context". No test should be performed unless it is likely to influence patient treatment.
| Evaluation | | |
Patients having any sort of cardiac ailment need to be evaluated properly preoperatively [6] .
| History | | |
History elicits the severity, progression and functional limitation introduced by cardiac disease. History should include:-.
- Exercise tolerance :- It depicts the cardiac reserve. It can be Excellent -history of participation in sports like swimming, football, tennis, basket-ball, skating etc. Adequate-patient able to climb stairs, run a short distance. Poor- able to do leisure activities only e.g. slow ballroom dancing or can walk around in the house only.
- Angina pectoris:-It is the symptomatic manifestation of myocardial ischaemia characterized by typical substernal pain which is evoked by physical exertion and relieved by rest or sublingual nitroglycerine.
- Myocardial infarction:- The incidence of myocardial infarction during the peri-operative period is related to time period since the previous myocardial infarction. According to Tarhan et al - incidence of perioperative re-infarction is 37% if the time elapsed is less than 3 months,16% when time elapsed is 4-6 months and 5% when time elapsed is more than 6 months. This is the basis for recommendation to wait for 6 months after MI for elective major surgery.
- Co-existing noncardiac diseases
i. Peripheral vascular disease ii. Cerebro vascular disease iii. Chronic obstructive pulmonary disease in patients with history of cigarette smoking iv. Renal dysfunction may be associated with chronic hypertension v. Diabetes- May be the cause of silent MI[Additional file 1] vi. Anaemia, polycythemia, thrombocytosis when present will need careful management.
- Current medications-Awareness about the medications that patient is taking is important during anaesthesia. All cardiac medications like beta blockers, calcium channel blockers, nitrates should be continued until the morning of surgery. Patient may be on oral anticoagulants or aspirin which should be stopped 5-7 days prior to surgery.
- Congestive cardiac failure:-The stress of anaesthesia, surgery and fluid replacement may result in overt failure in patients bordering on congestive heart failure.
- Dysrrhythmias.
| Examination | | |
A careful general physical examination should be done. It should include assessment of vital signs like blood pressure, pulse rate and rhythm, jugular venous pulse, oedema, pallor, cyanosis, clubbing , jaundice, lymphadenopathy. In systemic examination, cardiovascular system should be examined for heart sounds & any murmur. Further evaluation is needed as per the findings. Respiratory system also needs to be assessed in details.
| Laboratory investigations | | |
Cardiac specific tests like ECG, echocardiography to know ejection fraction, any valvular lesion , wall motion abnormalities, LV function and pressure gradients, Holter monitoring, Treadmill test, thallium scintigraphy to detect myocardium at risk, radionuclide ventriculography, dobutamine stress test(DST) for evaluating inducible ischemia in patients who have poor functional capacity, coronary angiography in patients where DST is positive should be done.
| Anaesthetic management | | |
Anaesthesia goals remain
i. Stable haemodynamics ii. Prevent MI by optimizing myocardial oxygen supply and reducing oxygen demand iii. Monitor for ischaemia iv. Treat ischemia or infarction if it develops v. Normothermia vi. Avoidance of significant anaemia
Management depends upon the type of surgery whether emergency or elective. For emergency surgery proceed for the surgery with medical management of cardiac ailment. For elective surgery perioperative management depends upon various clinical risk factors and surgery specific risk factors [3] .
| Clinical risk factors | | |
Obtained by history, physical examination & review of ECG, the clinical risk factors are grouped into 3 categories
- Major clinical predictors are unstable coronary syndrome, decompensated heart failure, significant dysrrhythmia and severe valvular disease. They mandate intensive management even if that leads to delay or cancellation except emergency surgery.
- Intermediate clinical predictors are mild angina pectoris, previous MI by history or pathological Q waves, compensated or prior heart failure, insulin dependent diabetes mellitus, and renal insufficiency. These are markers of enhanced risk of peri-operative cardiac complications. It appears reasonable to wait for 4-6 weeks after MI for elective surgery.
- Minor clinical predictors are hypertension, LBBB, nonspecific ST-T wave changes and history of stroke. They have not proved to increase risk independently.
| Surgery specific risk factors | | |
- High risk surgeries-
(emergent major operations particularly in the elderly, aortic and other major vascular surgery, anticipated prolonged surgical procedures associated with large fluid shifts or anticipated blood loss) are often reported to have a cardiac risk of greater than 5%. Intermediate risk surgeries- (carotid endarterectomy, head and neck surgery, intraperitoneal and intrathoracic surgery, prostate surgery) are reported generally to have cardiac risk of less than 5%. Low risk procedures:- (endoscopic procedures, superficial procedures, cataract surgeries, breast surgery) are reported to have less than 1% risk of cardiac events.
| Preoperative management | | |
At risk patients need to be managed with pharmacologic and other perioperative interventions that can ameliorate perioperative cardiac events. Three therapeutic options are available before elective noncardiac surgery.
- Optimisation of medical management
- Revascularization by PCI, revascularization by surgery ( CABG)
However it may not be necessary to intervene preoperatively (except for beta blocker therapy or c 2 agonists) to improve perioperative outcome. Beta blockers have been shown to be useful in reducing perioperative morbidity and mortality in high risk cardiac patients and preferably titrated to a heart rate of 50 to 60 bpm [7] . α2 agonists by virtue of their sympatholytic effects can be useful in patients where beta blockers are contraindicated. Nitroglycerine lowers LVEDP by reducing preload . It improves collateral coronary flow and reduce systemic B.P. Other agents like calcium channel blockers, ACE inhibitors, aspirin, insulin, statins prove to be beneficial perioperatively.
Coronary intervention should be guided by patient's cardiac condition (unstable angina, left main or equivalent CAD, three vessel disease, decreased LV function) and by the potential consequences of delaying the noncardiac surgery for recovery after coronary revascularization [3] .Patients who underwent PCI had better outcome after noncardiac surgery. However the need for dual anti-platelet therapy for several months to one year can significantly impact the perioperative course. Acute postoperative stent thrombosis has been reported when anti-platelet agents were temporarily held preoperatively to reduce chance of bleeding. Continuing the therapy can lead to significant postoperative bleeding. Discontinuing or modifying anti-platelet therapy should involve a multidisciplinary team of cardiologist, surgeon, anaesthesiologist [8] .
| Preanaesthetic considerations | | |
Preoperative visit to the patient is very important. A good rapport should be made with the patient and written consent obtained. Patient should be explained about the risk of surgery and anaesthesia. It is important to continue the medications till the day of surgery like beta blockers, calcium channel blocker, digitalis. Potassium level should be normal as hypokalemia can cause digitalis toxicity. Anticoagulants should be stopped.
| Premedication | | |
Significance of premedication in allaying anxiety in cardiac patients is of paramount importance. This is to prevent increase in B.P. and HR which can disturb the myocardial oxygen supply and demand and can induce ischaemia. Any combination of benzodiazepine like lorazepam and opioid like morphine should be given one hour prior to arrival in operation theatre.
The following algorithm helps in easy reference for planning perioperative management of cardiac patients undergoing noncardiac surgery.
[Additional file 2]
| Intraoperative management | | |
Monitoring
Incidence of ischaemia in the intraoperative period is low (as compared with pre and postoperative period)
i. ECG is the most commonly used monitoring tool . If ECG is to be used effectively as an ischaemic monitor, the monitor should be set on diagnostic mode. Monitoring three ECG leads (II,V4,V5 or V3,V4,V5) improves recognition of ischaemia. The ST segment trending system also helps in the detection of ischaemia ii. Blood pressure iii. Pulse oximetry iv. Capnography v. Temperature monitoring vi. Urine output monitoring vii. Central venous pressure viii. Pulmonary artery pressure and cardiac output- can be measured with pulmonary artery catheter as required. In a haemodynamically unstable patient, the requirement of volume or inotropes can be judiciously calculated and response monitored closely ix. TEE (transesophageal echocardiography) is a sensitive monitor for ischaemia. However TEE is not advocated for routine use [9] .
Choice of anaesthetics
The anaesthesiologist should select the drugs with the objective of minimizing demand and optimum supply of oxygen. Along with the anaesthetic agent some cardiac drugs should be readily available to maintain haemodynamics, to prevent & treat ischaemia, if it occurs.
General anesthesia
1. Intravenous anaesthetics
Thiopentone -It reduces myocardial contractility, preload and blood pressure and there is slight increase in heart rate. It should be administered slowly and with caution.
Propofol - It reduces arterial blood pressure and heart rate significantly. There is dose dependent reduction in myocardial contractility. It can be used in with good ventricular function but is not good induction agent for patients with CAD.
Ketamine - It is not good in IHD and valvular heart disease patients. It is however a useful agent in situations like cardiac tamponade and cyanotic heart disease.
Midazolam - It produces decrease in mean arterial pressure and increase in heart rate. It provides excellent amnesia and is widely used for patient with CAD
Etomidate - It causes minimum haemodynamic changes. It is excellent for induction in patients with poor cardiac reserve.
2. Narcotics - Morphine is the preferred drug for its relative cardiac stability and very good analgesic effect. It produces arterial and venous dilatation ,resulting in reduction of after load and preload. Newer narcotic analgesic agents like fentanyl, alfentanyl and sufentanil also provide adequate cardiac stability and pain relief.
3. Inhalational agents - Isoflurane is recommended in patients with good myocardial contractility. Halothane has the disadvantage of myocardial depression and potential of dysrrhythmias.
4. Nitrous oxide -It provides stable haemodynamics in cardiac patients.
5. Muscle relaxants -Vecuronium produces minimum haemodynamic alterations and is short acting, therefore suitable for use in cardiac patients. Pipecuronium, mivacurium, doxacurium are newer non depolarizing muscle relaxants without any significant cardiovascular side effects.
6. Glycopyrrolate -It is preferred over atropine since it produces less tachycardia & should be used only if specifically required.
Regional anesthesia
The potential and well known advantage of regional anesthesia over G.A should be an asset in cardiac patients if the surgery can be performed under regional block. Patient should be nicely premedicated without any apprehension. Disadvantages of regional anesthesia include hypotension from uncontrolled sympathetic blockade and need for volume loading can result in ischemia. Care should be taken while giving local anaesthetic because larger doses can cause myocardial toxicity and myocardial depression. Use of epinephrine with local anaesthetic is not recommended [10].
| Managing intraoperative complications | | |
1) Intraoperative ischaemia
1 If patient is haemodynamically stable-
1- Beta blockers ( I/V metoprolol upto 15mg)
I/V Nitroglycerine
Heparin after consultation with surgeon
2 If patient is haemodynamically unstable
Support with inotropes
Use of intraoperative ballon pump may be necessary
Urgent consultation with cardiologist to plan for earliest possible cardiac catheterization
2) Other complications like dysrrhythmias, pacemaker dysfunction should be managed accordingly
| Post operative management | | |
Goals are same as intraoperative
i. Prevent ischaemia ii. Monitor for MI iii. Treatment for MI
Although most cardiac events occur within first 48 hours, delayed cardiac events (within first 30 days ) still happen and could be the result of secondary stress. Post operative stress of extubation, pain, sepsis, haemorrhage, anaemia, respiratory problems can increase the demand on the heart and should be minimized and treated.
| Valvular heart diseases | | |
Patients with valvular heart diseases coming for surgery present many challenges to the anaesthesiologist. Now it is no longer necessary or even advisable to delay surgery until advanced symptoms are present. Valvular surgery is advised in such patients before elective noncardiac surgery. The perioperative physician has to be aware of the varying effects of haemodynamic variables on this sub population of patients. The five variables in dealing with the valvular heart diseases are important. They are:- i. Preload ii. After load iii. Myocardial contractility iv. Heart rate v. Rhythm.
Keeping in mind these variables , the anaesthetic technique can be chosen with a view to maintain optimal cardiac performance. In general ,the goal in stenotic lesions is to enhance forward flow , where as in regurgitant lesions is to decrease regurgitant flow . All the patients with valvular heart disease undergoing non-cardiac surgery should get antibiotic prophylaxis to prevent infective endocarditis. AHA recommends ampicillin, 2 g I.M or I.V plus gentamicin 1.5 mg.kg -1 I.M or I.V 30 min. before procedure and 6 hrs later ampicillin 1 gm I.M or I.V. For patients allergic to penicillin, vancomycin 1 gm I.V is recommended. For dental and endoscopic procedures, oral amoxicillin 2gm or cephalexin 2 gm or azithromycin 500 mg ,1 hr. before the procedure is given. Use of oral anticoagulants in patients with mitral stenosis who have atrial fibrillation should be kept in mind. Tachycardia is detrimental in both aortic and mitral stenosis. In MR and AR , it is advisable to maintain normal to high heart rate and mild vasodilatation to decrease the amount of regurgitant flow. In AS consideration should be given to the possibility of CAD [11]
| Hypertension | | |
Hypertension is the commonest cardiac disease all over the world. These patients are documented to have associated CAD, left ventricular dysfunction, renal failure which increase the perioperative risk. Hence it is advisable to control BP preoperatively. But this does not need surgery to be deferred for weeks, to achieve ideal blood pressure control, in patients with mild to moderate hypertension. It is also important to evaluate for target organ damage. It is advisable to continue antihypertensives till the day of surgery. For patients with marked elevations of BP intra or post operatively should be managed by either nitroglycerine or sodiumnitroprusside by I.V. infusion. Intraarterial B.P. monitoring is recommended for such patients. Any factors of sympathetic stimulus should be avoided.
| Dysrrhythmias | | |
Dysrrhythmias may be a marker of severity of underlying CAD or left ventricular dysfunction. A symptomatic ventricular ectopics with stable haemodynamic parameters do not need any treatment preoperatively. Similarly prophylactic treatment is not required in supraventricular tachycardia. In atrial fibrillation rate needs to be controlled. Perioperatively if they occur can be treated by calcium channel blockers ,beta blockers, adenosine.
Patients with conduction delay, LBBB do not require pacing unless there is history of syncope. But in complete heart block, patients need to be paced. In patients on permanent pace makers ,electro cautery should be used with caution and for minimum period of time. The cautery plate should be as far as possible from the heart .Use of bipolar cautery decreases the risk of pacemaker dysfunction. Use of magnet will turn pace maker into asynchronous mode , preventing unwanted inhibition.
The material submitted remains only an overview of the guidelines, which will continue changing from time to time, depending upon the evidence procured over a period of time. Also the techniques need to be tailored varying from patient to patient, surgical needs and the facilities available.
| References | | |
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