ANAESTHESIA FOR THE HIGH RISK PATIENT - PART 2 potx

Exercise stress testing Exercise is most commonly employed in exercise ECGs under the Bruce Protocol. Although not validated for improving outcome, it is extremely useful as a pre- dictor of pre-operative risk as it identifies patients with both poor functional capacity and associated ischaemia. 19 It is effective at stratifying coronary risk according to: • degree of functional incapacity, • ischaemic symptoms, • ischaemic severity (stage of onset, depth and duration of ST segment depression), • haemodynamic instability, • electrical instability. The degree of positivity of test correlates with extent and severity of disease. The risk of peri-operative cardiac events and long-term risk is significantly increased in patients with an abnormal exercise ECG at low workloads. The sensitivity gradient for detecting obstructive coronary disease is depend- ent on: • severity of stenosis, • criteria used for a positive test, • extent of disease, i.e. the presence of a prior clinical history. For example, in patients with no cardiac history and a normal resting ECG, only 20–25% of patients will have an abnormal exercise ECG, whereas in patients with a prior history of MI or an abnormal rest ECG 35–50% of patients will have an abnormal exercise ECG. However, it should be borne in mind that: • As many as 50% of patients with significant CAD and adequate levels of exercise can still produce a normal exercise ECG. 35 • There is no evidence to support its use in low-risk groups. Pharmacological stressors Inotropes • Commonly used inotropes include dobutamine and the newer agent arbutamine. These drugs increase myocardial oxygen demand through inotropic stimulation. ANAESTHESIA FOR THE HIGH RISK PATIENT 20 Chap-01.qxd 2/1/02 12:03 PM Page 20 • They can often achieve coronary blood flows greater than with exercise but not as great as with adenosine or dipyridamole. • They tend to be used in patients with asthma who cannot tolerate vasodilators. • Dobutamine is best avoided in patients with serious arrhythmias and severe hypertension or hypotension. Coronary vasodilators These agents produce non-physiological and sometimes supra-physiological increases in coronary flow without altering the metabolic demands of the heart. • Adenosine is a breakdown product of ATP metabolism and is a potent coronary vasodilator. In conditions of oxygen starvation rising adeno- sine levels result in coronary vasodilation linking coronary blood flow to myocardial oxygen demand. • Dipyridamole inhibits the breakdown of free adenosine causing levels to rise and thereby produces coronary vasodilatation as described above. • Methylxanthines (e.g. caffeine) are competitive inhibitors of adeno- sine at purinergic receptors and patients are advised to avoid these for at least 6–8 h prior to testing achieve maximal coronary vasodilator effect. All these agents can induce or exacerbate bronchospasm, and their use is relatively contraindicated in asthmatics. Unexpected severe bronchospasm can be readily antagonised with intravenous aminophylline. Dipyridamole should also be avoided in patients with critical carotid disease. Other adverse effects include headaches, flushing and hypotension. Examples of some non-invasive tests that employ pharmacological stressors include: Dobutamine stress echocardiography • Provides an opportunity to assess both LV and valvular function. • Can be performed safely and with acceptable patient tolerance. • Very accurate in identifying patients with significant angiographic coronary disease. • The published experience of dobutamine stress echocardiography to assess peri-operative risk before vascular and non-vascular surgery is rela- tively small compared with the published literature on exercise testing or intravenous dipyridamole myocardial perfusion imaging. EPIDEMIOLOGY AND IDENTIFICATION OF THE HIGH-RISK SURGICAL PATIENT 21 Chap-01.qxd 2/1/02 12:03 PM Page 21 • Adding atropine to those patients who fail to meet the target heart rate improves sensitivity. • Several studies suggest that the degree of wall motion abnormalities and/or wall motion change at low infusion rates of dobutamine is espe- cially important. Myocardial perfusion stress imaging • Myocardial uptake of perfusion agents is dependent on blood flow rather than oxygen demand or metabolic activity. • Resting images alone can be done but sensitivity is very low and is significantly increased if stress images are taken. • Any of the agents described above can be used to increase coronary blood flow with the most data available for dipyridamole. • The tests have high sensitivity and specificity for peri-operative coron- ary events. The technique involves the injection of a radionuclide during peak blood flow. The main isotopes in use are: • Thallium-201 is a monovalent cation and like potassium is taken into myocardial cells by Na–K ATPase. It emits both X-rays and gamma radi- ation and has a relatively long half-life of 73.1 h. It readily and rapidly redistributes with myocardial blood flow so that a 2nd dose is not required to obtain rest images. The main disadvantage with thallium is the low energy of its emitted radiation resulting in significant soft tissue attenu- ation, which can affect image quality and hinder image interpretation. • Technetium-99m is an isotope with many advantages over thallium for producing better quality myocardial images; it emits radiation at a higher energy resulting in less attenuation, and its shorter half-life of 6 h allows larger doses. Technetium-99m does not redistribute and, there- fore, requires separate stress and rest injections. The main compound incorporating this isotope is known as Sestamibi. Unfortunately the superior image quality of images produced with Technetium-99m has yet to be shown to improve diagnostic accuracy. Images of the myocardium are then compared at peak or stress coronary flow and after a delay, at rest. Exercise-induced ischaemia results in a perfusion defect on the stress images that fills in or redistributes on the rest images. MI manifests as fixed perfusion defects on both the stress and rest images. Severe myocardial disease causing exercise-induced pump failure can also be detected using this technique. The LV decompensates with a fall in stroke volume ANAESTHESIA FOR THE HIGH RISK PATIENT 22 Chap-01.qxd 2/1/02 12:03 PM Page 22 and ejection fraction with a resultant increase in LV end diastolic pressure and diameter; on the stress images the ventricular cavity is larger and the ventricle wall is thinner. As a further consequence of the rise in LV end diastolic pressure, raised levels of isotope will often accumulate in the lungs. Subendocardial ischaemia results in reduced endocardial uptake of isotope and may also appear as LV dilatation. In increasing grade of risk, possible scan results are: Normal scan Ͻ fixed defects Ͻ redistribution defects Furthermore, as the size of the defect increases, risk significantly increases. Digital quantitation of scan abnormalities improves positive predictive value and is improving alongside advances in technology. The need for caution in routine screening with a dipyridamole–thallium stress test of all patients before vascular surgery was raised by Baron et al. 36 In this review of 457 patients undergoing elective abdominal aortic surgery, the presence of definite CAD on clinical assessment and age Ͼ 65 years were better predictors of cardiac complications than perfusion imaging. LV ejection fraction Resting ventricular function (including LV ejection fraction) is usually deter- mined by echocardiography but may also be determined by radionuclide angio- graphy, gated radionuclide imaging or contrast ventriculography. Ejection fraction determined by echo is limited in accuracy as the formula used in its calculation assumes the ventricle to be a sphere and the diameters of the ‘full sphere’ and ‘empty sphere’ are only measured in one plane. Increased risks of complications are associated with: • LV ejection fraction Ͻ 35%, 19 • diastolic and systolic dysfunction are markers for post-operative con- gestive cardiac failure, and in critically ill patients, death. It is important to note that resting LV function is not a consistent predictor of peri- operative ischaemic events. Recommendations for non-invasive testing 19 In most ambulatory patients, the test of choice is exercise ECG testing, which can both provide an estimate of functional capacity and detect myocardial ischaemia through changes in the ECG and haemodynamic response. EPIDEMIOLOGY AND IDENTIFICATION OF THE HIGH-RISK SURGICAL PATIENT 23 Chap-01.qxd 2/1/02 12:03 PM Page 23 In patients with contraindications to exercise ECG testing, e.g. left bundle branch block or LV hypertrophy, other techniques may be preferable such as: • exercise echocardiography, • exercise myocardial perfusion imaging. In those patients unable to perform adequate exercise the following may be more useful: • dipyridamole–thallium scanning; • dobutamine echocardiography; • finally if there is an additional question about valvular dysfunction, the echocardiographic stress test is favoured; • in many instances, either myocardial stress perfusion imaging or stress echocardiography are appropriate. In a recent meta-analysis assessing the use of, ambulatory ECG, dobutamine stress echocardiography, radionuclide ventriculography and dipyridamole–thallium scanning, for predicting adverse cardiac outcome after vascular surgery, all tests had a similar predictive value, with overlapping confidence intervals. Other important points to note include: • Local expertise and experience of a test is probably more important than the particular type of test. • Selective rather than routine testing improves cost effectiveness. • Non-selective blanket tests are not cost effective and are an inefficient use of resources because at the extremes of risk these tests add very little predictive value. Invasive testing (coronary angiography) For very high-risk patients it may be sometimes more appropriate to proceed with coronary angiography rather than perform a non-invasive test. These might include: • patients with major clinical predictors, • advanced ischaemic risk such as unstable angina or residual ischaemia following a recent MI. In addition it may be reasonable to consider coronary angiography and percu- taneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG) before non-cardiac surgery when the stress of elective non-cardiac surgery is likely to exceed the stress of daily life. ANAESTHESIA FOR THE HIGH RISK PATIENT 24 Chap-01.qxd 2/1/02 12:03 PM Page 24 However, before proceeding to coronary angiography one needs to ascertain that the patient is fit enough for either PTCA or CABG. If not angiography only adds to the cost and will not improve outcome. • As far as the new treatment modality of PTCA is concerned, there is little evidence available at present concerning its pre-operative use to optimise patients for non-cardiac surgery. • Indeed there are no controlled trials comparing peri-operative cardiac outcome after PTCA versus medical therapy. • A number of small observational series have suggested that cardiac death is infrequent in patients who have coronary angioplasty before non-cardiac surgery. • Observational studies have shown a risk reduction for non-cardiac sur- gery after coronary bypass. PRE-OPERATIVE ASSESSMENT AND RISK The aim of pre-operative assessment is to minimise morbidity and mortality. Three questions should be asked when assessing surgical patients with the aim of minimising operative risk: 1. Is the patient’s medical and physiological status optimum? 2. If not, can the patient’s status be improved (time permitting)? 3. If not, should the operation still proceed? In other words do the risks of not operating outweigh the risks of operating. For example, medical status is almost irrelevant if the operation is clearly life saving. Thus, no patient is ‘not fit’ for surgery – it just depends on the urgency of the situation. Pre-operative assessment should identify those patients who are at high risk of pre- or post-operative organ failures. Such patients may need additional moni- toring and may warrant admission to ICU or an HDU post-operatively for organ function monitoring or support. Once the risk has been established and attempts have been made to optimise the patient’s condition (i.e. reduce the risk), patients and their families may need to decide whether to proceed with surgery. One of the responsibilities of the anaesthetist is be able to give the patient relevant and accurate information on risk in order to help them decide. Unfortunately few patients will have read the chapter in this text on the meaning of risk! EPIDEMIOLOGY AND IDENTIFICATION OF THE HIGH-RISK SURGICAL PATIENT 25 Chap-01.qxd 2/1/02 12:03 PM Page 25 Further reading Adams AM, Smith AF. Risk perception and communication: recent developments and implications for anaesthesia. Anaesthesia 2001; 56: 745–55. References 1. Rogers FB, Simons R, Hoyt DB et al. In-house board-certified surgeons improve outcome for severely injured patients: a comparison of two university centers. J Trauma 1993; 34: 871–5. 2. Reynolds HN, Haupt MT, Thill-Baharozian MC et al. Impact of critical care physician staffing on patients with septic shock in a university hospital medical intensive care unit. JAMA 1988; 260: 3446–50. 3. Harmon JW, Tang DG, Gordon TA et al. Hospital volume can serve as a sur- rogate for surgeon volume for achieving excellent outcomes in colorectal resection. Ann Surg 1999; 230: 404–11. 4. Merry AF,Ramage MC,Whitlock RM et al. First-time coronary artery bypass grafting: the anaesthetist as a risk factor. Br J Anaesth 1992; 68: 6–12. 5. Campling EA, Devlin HB, Hoile RW et al. Who operates when. The report of the National Confidential Enquiry into Perioperative Deaths 1996/1997. NCEPOD, London, 1997. 6. Stidham KR, Johnson JL, Seigler HF. Survival superiority of females with melanoma. A multivariate analysis of 6383 patients exploring the significance of gender in prognostic outcome. Arch Surg 1994; 129: 316–24. 7. Wichmann MW, Inthorn D, Andress HJ et al. Incidence and mortality of severe sepsis in surgical intensive care patients: the influence of patient gender on disease process and outcome. Int Care Med 2000; 26: 167–72. 8. Offner PJ, Moore EE, Biffl WL. Male gender is a risk factor for major infec- tions after surgery. Arch Surg 1999; 134: 935–8. 9. Kollef MH, O’Brien JD, Silver P. The impact of gender on outcome from mechanical ventilation. Chest 1997; 111: 434–41. 10. Norman PE, Semmens JB, Lawrence-Brown M et al. The influence of gender on outcome following peripheral vascular surgery: a review. Cardiovasc Surg 2000; 8: 111–15. 11. Moul JW, Douglas TH, McCarthy WF et al. Black race is an adverse prognos- tic factor for prostate cancer recurrence following radical prostatectomy in an equal access health care setting. J Urol 1996; 155: 1667–73. ANAESTHESIA FOR THE HIGH RISK PATIENT 26 Chap-01.qxd 2/1/02 12:03 PM Page 26 12. Connell PP, Rotmensch J, Waggoner SE et al. Race and clinical outcome in endometrial carcinoma. Obstet Gynecol 1999; 94: 713–20. 13. Andersson B, Sylven C. The DD genotype of the angiotensin-converting enzyme gene is associated with increased mortality in idiopathic heart failure. J Am Coll Cardiol 1996; 28: 162–7. 14. Poeze M,Takala J,Greve JWM, Ramsay G. Pre-operative tonometry is predict- ive for mortality and morbidity in high-risk surgical patients. Int Care Med 2000; 26: 1272–81. 15. Kelion AD, Banning AP. Is simple clinical assessment adequate for cardiac risk stratification before elective non-cardiac surgery. Lancet 1999; 354: 1838. 16. Castelli WP. Epidemiology of coronary heart disease: the Framingham study. Am J Med 1984; 76: 4–12. 17. Becker RC, Terrin M, Ross R et al. and the Thrombolysis in Myocardial Infarction Investigators. Comparison of clinical outcomes for women and men after acute myocardial infarction. Ann Intern Med 1994; 120: 638–45. 18. Shah KB, Kleinman BS, Rao TLK et al. Angina and other risk factors in patients with cardiac diseases undergoing non-cardiac operations. Anesth Analg 1990; 70: 240–7. 19. Eagle KA, Brundage BH, Chaitman BR et al. Guidelines for perioperative cardiovascular evaluation for non-cardiac surgery: an abridged version of the report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol 1996; 27: 910–48. 20. Goldman L, Caldera DL. Risks of general anesthesia and elective operation in the hypertensive patient. Anesthesiology 1979; 50: 285–92. 21. Goldman L, Caldera DL, Nussbaum SR et al. Multifactorial index of cardiac risk in non-cardiac surgical procedures. N Engl J Med 1977; 297: 845–50. 22. Reyes VP, Raju BS, Wynne J, Stephenson et al. Percutaneous balloon valvulo- plasty compared with open surgical commissurotomy for mitral stenosis. N Engl J Med 1994; 331: 961–96. 23. Alpert JS, Chipkin SR, Aronin N. Diabetes mellitus and silent myocardial ischemia. Adv Cardiol 1990; 37: 279–303. 24. ASA. New classification of physical status. Anaesthesiology 1963; 24: 111. 25. Detsky AS, Abrams HB, Forbath N, Scott JG, Hillard JR. Cardiac assessment for patients undergoing non-cardiac surgery. A multifactorial clinical risk index. Arch Int Med 1986; 146: 2131–4. EPIDEMIOLOGY AND IDENTIFICATION OF THE HIGH-RISK SURGICAL PATIENT 27 Chap-01.qxd 2/1/02 12:03 PM Page 27 26. Lee TH, Marcantonio ER, Mangione CM et al. Derivation and prospective validation of a simple index for prediction of cardiac risk of major non-cardiac surgery. Circulation 1999; 100: 1043–9. 27. Wolters U, Wolf T, Stutzer H, Schroder T. ASA classification and peri- operative variables as predictors of postoperative outcome. Br J Anaes 1996; 77: 217–22. 28. Copeland GP, Jones D, Waiters M. POSSUM: a scoring system for surgical audit. Br J Surg 1991; 78: 355–60. 29. Lazarides MK,Arvanitis DP, Drista H et al. POSSUM and APACHE II scores do not predict the outcome of ruptured infrarenal aortic aneurysms. Ann Vasc Surg 1997; 11: 155–8. 30. Jones DR, Copeland GP, de Cossart L. Comparison of POSSUM with APACHE II for prediction of outcome from a surgical high-dependency unit. Br J Surg 1992; 79: 1293–6. 31. Sagar PM, Hartley MN, Mancey-Jones B et al. Comparative audit of colorec- tal resection with the POSSUM scoring system. Br J Surg 1994; 81: 1492–4. 32. Hlatky MA, Boineau RE, Higginbotham MB, Lee KL, Mark DB, Califf RM, Cobb FR, Pryor DB. A brief self-administered questionnaire to determine functional capacity (the Duke Activity Status Index). Am J Cardiol 1989; 64: 651–4. 33. Mangano DT. Perioperative cardiac morbidity. Anesthesiology 1990; 72: 153–84. 34. Taylor LM Jr, Porter JM. Basic data related to clinical decision-making in abdominal aortic aneurysms. Ann Vasc Surg 1987; 1: 502–4. 35. Chaitman BR. The changing role of the exercise electrocardiogram as a diag- nostic and prognostic test for chronic ischemic heart disease. J Am Coll Cardiol 1986; 8: 1195–210. 36. Baron JF, Mundler O, Bertrand M, Vicaut E, Barre E, Godet G, Samama CM et al. Dipyridamole–thallium scintigraphy and gated radionuclide angiography to assess cardiac risk before abdominal aortic surgery. N Engl J Med 1994; 330: 663–9. ANAESTHESIA FOR THE HIGH RISK PATIENT 28 Chap-01.qxd 2/1/02 12:03 PM Page 28 29 2 RESPIRATORY RISK AND COMPLICATIONS There is now an increasing volume of literature regarding the identification of the patient at risk of respiratory complications: • Respiratory complications are at least as, and sometimes more common than cardiac complications. 1 However, reaching a consensus on what constitutes a postoperative respiratory complication has proved difficult in recent years and has significantly hindered research in this area. Improvements in the health of the population, advances in anaesthesia and surgery and reduction in prevalence of smoking amongst the popu- lation have all combined to cause problems interpreting the significance of some of the early studies on respiratory risk and complications. It is now increasingly gaining acceptance that significant respiratory complications are those that affect outcome. These are problems that prolong hospital or inten- sive care unit (ICU) stay, or alternatively contribute to morbidity or mortality. 2–4 They include: • pneumonia, • respiratory failure requiring mechanical ventilation, • bronchospasm, • atelectasis, • exacerbation of chronic underlying disease. Factors that have been shown to be predictive of postoperative pulmonary respiratory complications can be subdivided into patient- and surgery-related risk factors. Chap-02.qxd 2/2/02 12:54 PM Page 29 [...].. .ANAESTHESIA FOR THE HIGH RISK PATIENT PATIENT-RELATED FACTORS The relative increases in risk associated with the presence of patient- related factors is given in table 2. 1 Smoking Smoking has long been recognised as a respiratory risk factor for patients both with and without chronic lung disease, and causes a 3–4-fold increase in the incidence of pulmonary complications... physical status and have a coexisting cardiovascular or neurological disorder 45 ANAESTHESIA FOR THE HIGH RISK PATIENT Adequate pre-operative assessment and preparation for theatre is vital in the management of the high risk surgical patient The management of the patient at this time will greatly influence the subsequent outcome of the operation and it is crucial that appropriate care is given and appropriate... or crackles Table 2. 3 – Other surgical factors affecting pulmonary risk Risk factor Site of surgery Unadjusted relative risk associated with factor Surgery Ͼ 3 h duration Unselected Thoracic or abdominal 1.6–5 .2 3.6 General anaesthesia Unselected Thoracic or abdominal or vascular 1 .2 ϳ 2. 2–3.0 Use of muscle relaxants Unselected 3 .2 Adapted from Ref 9 33 ANAESTHESIA FOR THE HIGH RISK PATIENT PULMONARY... trigger for alerting inexperienced doctors to a high risk patient NCEPOD suggested that the use of the P-POSSUM score should be more widespread.10 • The importance of avoiding rushing patients to theatre before adequate resuscitation is a recurring theme of NCEPOD .2, 8 Emergency patients invariably require appropriate fluid resuscitation prior to theatre In some patients this can safely be undertaken on the. .. pulmonary risk True volume Percentage of predicted volume achieved FVC% FEV1% FEV1/FVC% Predicted postoperative volume ppoFEV1 High risk Ͻ 800 ml High risk if Ͻ 70%8 High risk if Ͻ 70%8 High risk if Ͻ 65 %25 Percentage of predicted postoperative volume ppoFEV1% High risk Ͻ 40%19 Percentage predicted volumes achieved based on population normals for age, sex and height Adapted from Refs 9, 19, 26 35 ANAESTHESIA. .. Since the introduction of clinical governance in April 1999, participation in the confidential enquiries has become a mandatory requirement for clinicians in the NHS • The data collection runs from 1st April to 31st March • Each year a sample is selected for more detailed review • Questionnaires were returned by 83% surgeons and 85% of anaesthetists for the 1998/99 report.3 41 ANAESTHESIA FOR THE HIGH RISK. .. been one of the cornerstones of the NCEPOD reports over the years:7–10 • In the most recent NCEPOD report1 of the cases sampled 59% of anaesthetics were given by a consultant and 52% of operations were performed by a consultant surgeon • • Consultant presence in these cases has changed little since the first report .2 Comparing NCEPOD 20 001 to NCEPOD 199 02 fewer of the sampled patients are anaesthetised... intractable bronchospasm SURGERY-RELATED FACTORS Anatomical site of surgery Even with the patient- related factors described above taken into account, the anatomical site of surgery remains the most important predictor of respiratory risk: 9 • The risk of pulmonary complications is directly related to the proximity of the incision to the diaphragm (table 2. 2) Table 2. 2 – Effect of surgical site on postoperative... leading to increased risk of perioperative gastric aspiration 31 ANAESTHESIA FOR THE HIGH RISK PATIENT Chronic obstructive pulmonary disease • Patients with chronic obstructive pulmonary disease (COPD) are at increased risk of postoperative respiratory complications, the level of increased risk related to the severity of the lung disease.9 Hypercapnia is particulary ominous • Patients with COPD should... DEATHS The National Confidential Enquiry into Perioperative Deaths (NCEPOD) has produced its 10th report.1 They take the opportunity to reflect on their own contribution to improving the quality of patient care since publication of their first report in June 1990 .2 It is also a convenient time to reflect on the issues highlighted by NCEPOD and the lessons to be learnt in the management of the high risk . cardiac risk before abdominal aortic surgery. N Engl J Med 1994; 330: 663–9. ANAESTHESIA FOR THE HIGH RISK PATIENT 28 Chap-01.qxd 2/ 1/ 02 12: 03 PM Page 28 29 2 RESPIRATORY RISK AND COMPLICATIONS There. subdivided into patient- and surgery-related risk factors. Chap- 02. qxd 2/ 2/ 02 12: 54 PM Page 29 PATIENT- RELATED FACTORS The relative increases in risk associated with the presence of patient- related. (CABG) before non-cardiac surgery when the stress of elective non-cardiac surgery is likely to exceed the stress of daily life. ANAESTHESIA FOR THE HIGH RISK PATIENT 24 Chap-01.qxd 2/ 1/ 02 12: 03 PM