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Sunday June 20 2004 |
From the Department of Anesthesia and Critical Care, SUNY Upstate Medical University, Syracuse, New York, USA.
Address correspondence to: Dr. Michael F. Roizen, Department of Anesthesia and Critical Care, SUNY Upstate Medical University, Institute of Human Performance, 750 East Adams Avenue, Syracuse, New York 13210, USA. Phone: 315-464-9858; Fax: 315-464-9850; E-mail: roizenm{at}upstate.edu
ALTHOUGH the goals of preoperative medical assessment have not changed, the volume and choice of preoperative tests has changed progressively in the last four decades. The goals of preoperative medical assessment are to reduce the morbidity of surgery and to return a patient to normal functioning as quickly as possible. Traditionally these goals have been facilitated by a pre-operative meeting of patient and anesthesiologist. The meeting has six objectives:
Reduction of anxiety and informed consent should not be overlooked at the time of preoperative evaluation. Recovery occurs more quickly when the anesthesiologist allays the patient’s concerns, informs the patient about what is to come, and plans postoperative pain therapy with the patient.1–4
Because we now no longer enjoy the luxury of seeing patients leisurely in the hospital the night before surgery, the methods of preoperative evaluation are changing. In response to these changes, the American Society of Anesthesiologists (ASA) has developed a practice advisory for preanesthetic evaluation.5 Most concepts of that document will be discussed here. These changes in patterns also mean that we must ensure that perioperative care is predictable for both patient and surgeon; comprehensive, so that no facet of care is overlooked to create problems later; and efficient and cost-effective, to save resources and time. To attempt effective preoperative evaluation without the consensus of your group, the surgeons, gynecologists, and radiologists you serve, and your administration will be futile and frustrating. But efficient choice of laboratory tests, effective patient education, and consensus building yield a satisfying practice and expand the role of the anesthesiologist.
The two initial steps of preoperative evaluation are closely related. A pertinent medical history and information about physical and medical conditions affect all the decisions about testing, consultation, and discussion of care plans with the patient. Optimizing patient health before surgery and planning the most appropriate perioperative management improve outcome and reduce costs. Data supporting these claims are substantial but indirect: studies over four decades repeatedly show that preoperative patient conditions predict postoperative morbidity.5–11 The data imply (but do not prove) that preoperative treatment of conditions such as congestive heart failure and diabetes can reduce the severity of disease and thus perioperative morbidity and mortality. To reduce morbidity, preoperative assessment must be made far enough in advance to provide the primary care physician with a "second opinion" to guide optimization of preoperative health of the patient. This step obliges the preoperative evaluator to take a thorough history to find alterable factors that influence perioperative risk and to order laboratory tests that will be beneficial in planning perioperative care. The list of indications in the Table can be considered, as well as whether or not the patient has had laboratory tests recently. Tests within one year need not be repeated. Patients of ASA physical status I or patients who will undergo a minimally invasive procedure may not need laboratory tests to alter their risk.5,12–14
Can this process be accomplished in isolation by a primary care physician? Although much of the process probably could be, a condition considered optimal for daily life (such as some degree of prerenal azotemia in the patient with congestive heart failure) may not be optimal preoperative status (at which time vasodilation may cause hypotension and/or permanent renal impairment). Thus, attention to the effects of planned perioperative maneuvers on patient physiology would be desirable, maybe even necessary, if the benefit of such preplanning is deemed worth the cost. While a nurse practitioner can substitute for a physician in primary care screening in a cost and quality efficient fashion, such has not been shown quantitatively in the preoperative setting.15,16 Preoperative evaluation by a specialty trained physician (or even a specialty trained nurse) is not inexpensive. However, preoperative planning can be much less expensive if tests are ordered selectively and information tools are used to increase efficiency. Thorough preoperative assessment can uncover hidden conditions that may affect outcome. In this way, an anesthesiologist can anticipate problems and plan therapies to minimize their effects.
At the University of Florida, pre-anesthetic evaluations altered care plans for more than 15% of all healthy patients (i.e., ASA class I or II patients) and for 20% of all patients.17 The most common conditions causing changes were gastric reflux, insulin-dependent diabetes mellitus, asthma, and suspected difficult intubation. However, no data indicated that the changes initiated improved patient outcome. Nevertheless, practitioners think that the discovery of these conditions calls for a change in plans, which usually delays operating room (OR) schedules and increases costs. Examples of last-minute changes would be administration of an H2 blocker one to two hours before surgery and an oral antacid before OR entry; obtaining equipment to measure blood glucose levels; obtaining a history of a patient’s diabetic course from his primary care physician; and requesting a fibreoptic laryngoscope or additional skilled help. Thus, even if preoperative evaluation was not to alter outcome substantially, its ability to reduce costs by reducing laboratory tests and delays in obtaining equipment or treatments perceived to be beneficial (and medicolegally required) would be substantial. In addition, preoperative evaluation gives practitioners confidence that unexpected patient conditions will not surprise them and gives patients confidence that the health care system is responding to their needs. Preoperative evaluation can take place in various settings: for relatively well patients, in the surgeon’s office or via telephone; for sicker patients or for those in whom more invasive surgical procedures are planned, in a preoperative evaluation clinic.
History, physical examination, and chart review vs laboratory tests
Discussing testing theory might lead to boredom were it not so economically relevant. More than 75% of patients now receiving anesthesia are either outpatients or "come-and-stay" patients. I believe that use of a written, telephonic, or automated questionnaire to ask the screening questions, coupled with a personal interview to pursue positive answers, does not decrease the accuracy or perceived personalization of the care given.18–20 My own practice gradually adopted this combination for inpatients as well, so that my task is to explore areas of positive history in depth and to discuss issues important to the patient. There are ways of putting the classic pattern together (chart review; history-taking; physical examination; and discussion of risks, alternative anesthetic plans, and postoperative pain therapies) so that all of the elements are part of a compassionate flow of thought that facilitates patient recall and care.
Laboratory tests as screening devices
It has been suggested that we forget the history and use laboratory screening for disease. Review of the literature forces me to disagree strongly: the history and the investigation of positive answers by an in-person interview is many times more effective in screening for disease than use of laboratory tests alone. The primary problem with ordering batteries of laboratory tests for all patients is that laboratory tests are not very good screening devices for disease; their results are costly to pursue; and they add new risk for the patient, increase medicolegal risk to the physician, and render ORs inefficient. Many studies have compared the yield from indicated (warranted from history or risk group) vs unindicated (unwarranted) preoperative testing.12,21–27 Few unindicated tests yield beneficial changes in perioperative care: at most, only 16 patients of more than 16,000 who had unindicated preoperative tests benefited from such testing. Furthermore, this figure
represents the most optimistic interpretation, as four patients in a study by Kaplan et al.23 received no benefit, and for at least another seven patients in a study by O’Connor and Drasner,25 the benefit of treating asymptomatic anemia before surgery with expected minor blood loss was not clear.
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Human immunodeficiency virus (HIV) testing provides another example. More than 92% of the population at low risk for HIV infection who have positive (abnormal) results on two enzyme-linked immunosorbent assays and one Western blot test in reality are not infected with HIV.28 Similar false-positive results have been found for mammography.29 Do not mistake these data: mammography saves lives, but still has many false positives.30 Therefore, it is not surprising that the benefit from non-selective testing is so low, or that so few abnormal results arising from unwarranted tests are acted upon.
Patient risk
Unnecessary testing may lead physicians to pursue and treat borderline and false-positive laboratory abnormalities. In one study addressing this issue, Roizen et al.31 retrospectively examined the adverse effects of chest radiographs on patients. For 606 patients, 386 extra chest radiographs were ordered without indication of need. Among those 386 patients, the discovery of only one abnormality (an elevated hemidiaphragm probably caused by phrenic nerve palsy) may have resulted in improved care for that patient. On the other hand, the existence of three lung shadows on chest radiographs led to three sets of invasive tests, including one thoracotomy, but no discovery of disease. Tape and Mushlin32 found a similar result when examining the benefits and risks of chest radiographs obtained preoperatively.
Development of testing guidelines: benefit-risk strategies
From a review of the literature and benefit-risk analysis, one can derive a practice policy to help clinicians select tests that are likely to be more beneficial than risky for their patients. Let us assume the chest x-ray in the under-40 population has a sensitivity of 75% and a specificity of 95%. (These values are better than the best in the literature for readings reviewed by a single radiologist). Let us also assume that the prevalence of disease detectable by the test is 0.5%, that the benefit from true positives is 20/100 (higher than the greatest benefit reported in the literature),12,14,21–28,33 and that harm from false positives is 6/100,31,32 and Apfelbaum JL et al., unpublished data. For the asymptomatic under-40 population, the result would be harm to three individuals and benefit to only 0.8 individuals per 1,000 chest x-rays. Similar analyses are possible for other tests and situations. The table below was formulated after such calculations.
Patients undergoing minimally invasive surgery after a careful medical history was obtained have little potential to benefit from more testing.5,11,12,14,33,34 The 30-day morbidity of these patients was little different from that which could be expected simply from living 30 days. Guidelines for preoperative tests could be modified when more invasive procedures are anticipated. In the state of Maine guidelines, no laboratory tests are required for surgery isolated to one limb where peripheral nerve block or monitored care with hypnotics only is administered. One might question such a guideline in the event that an anticipated "little anesthetic" turns into a "big general anesthetic." The experience in Maine suggests otherwise: few anesthetic plans had to be altered because of failed block; inadequate sedations; or change in surgical plans. Perhaps most important in determining patient perioperative risk (and therefore need for testing) are invasiveness of procedure and patient ability to walk two or five flights of stairs.35,36
Lead- and length-time biases
Two important concepts related to the reported benefits and risks of screening tests deserve consideration: lead-time and length-time biases. These two factors can indicate an apparent benefit of testing when there is none. This subject has been reviewed in detail.37
Implementing accuracy and efficiency in preoperative evaluation
The ability of preoperative evaluation even of healthy patients (ASA class I or II) to detect important symptoms from medical history makes its benefit greater than its risk. An informed patient will know what to expect, and planned pain therapy can decrease resource utilization.37 Specific issues regarding pregnancy and genetic testing can be included in the evaluation protocol. The ASA membership is clearly divided as to need for pregnancy testing prior to elective surgery in females of child bearing age.5,38 The protocol places the burden of accuracy on the history-taker. Use of the protocol requires that a system be in place to communicate the readiness of the patient for surgery to the primary care physician, surgeon, and scheduling system. This step places an additional burden on the preoperative assessor: he or she must determine what degree of consultation with the primary care physician and surgeon is necessary to judge optimal health for perioperative care.38 Ultimately, preoperative evaluation is cost effective for the institution, the health care payers, and the patients. It would be justifiable to compensate the anesthesiologist for pre-operative assessment at the rate for OR time.39 The preoperative meeting of anesthesiologist and patient should also serve other important functions: to educate about anxiety treatment options and pain therapy. Neither function can be performed adequately by most primary care physicians, and no one is better trained to do so than anesthesiologists.
Our primary goal must be efficient delivery of quality care. Patients undergoing surgery move through a continuum of medical care to which a primary care physician, an internist, an anesthesiologist, and a surgeon contribute to ensure the best outcome possible. No aspect of medicine requires greater cooperation than performance of surgery and perioperative care for a patient. The importance of integrating practice is even greater because of the increasing life span of our population and the popularity of alternative therapies that may interfere with the drugs we administer perioperatively.40–42 At a time when medical information is encyclopedic, it is difficult for even the most conscientious anesthesiologist to keep abreast of medical issues relevant to perioperative patient management. Thus, the proposed preoperative assessment clinic facilitates those most sought-after goals, increased quality and reduced costs.43
References
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17 Gibby GL, Gravenstein JS, Layon AJ, Jackson KI. How often does the preoperative interview change anesthetic management? Anesthesiology 1992; 77: A1134 (abstract).
18 Lutner RE, Roizen MF, Stocking CB, et al. The automated interview versus the personal interview. Do patient responses to preoperative health questions differ? Anesthesiology 1991; 75: 394.[Medline]
19 Roizen MF, Coalson D, Hayward RS, et al. Can patients use an automated questionnaire to define their current health status? Med Care 1992; 30(Suppl): S574.
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28 Burke DS, Brundage JF, Redfield RR, et al. Measurement of the false positive rate in a screening program for human immunodeficiency virus infections. N Engl J Med 1988; 319: 961.[Abstract]
29 Elmore JG, Barton MB, Moceri VM, et al. Ten-year risk of false positive screening mammograms and clinical breast examinations. N Engl J Med 1998; 338: 1089–96.
30 Tabar L, Yen MF, Vitak B, Chen HH, Smith RA, Duffy SW. Mammography service screening and mortality in breast cancer patients: 20-year follow-up before and after introduction of screening. Lancet 2003; 361: 1405–10.[Medline]
31 Roizen MF, Kaplan EB, Schreider BD, et al. The relative roles of the history and physical examination, and laboratory testing in preoperative evaluation for outpatient surgery: the "Starling" curve in preoperative laboratory testing. Anesthesiol Clin North Am 1987; 5: 15.
32 Tape TG, Mushlin AI. How useful are routine chest x-rays of preoperative patients at risk for postoperative chest disease? J Gen Intern Med 1988; 3: 15.[Medline]
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35 Reilly DF, McNeely MJ, Doerner D, et al. Self reported exercise tolerance and the risk of serious perioperative complications. Arch Intern Med 1999; 159: 285–92.
36 Brunelli A, Refai MA, Monteverde Borri A, Salati M, Fiachini A. Stair climbing test predicts cardiopulmonary complications after lung resection. Chest 2002; 121: 1106–10.
37 Roizen MF, Foss JF, Fischer SP. Preoperative evaluation. In: Miller RD (Ed.). Anesthesia, 5th ed. vol 1. Philadelphia: Churchill Livingstone; 2000: 824–83.
38 Eagle KA, Brundage BH, Chaitman BR, et al. Guidelines for perioperative cardiovascular evaluation for noncardiac surgery: report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Am Coll Cardiol 1996; 27: 910–48.[Medline]
39 Fischer SP. Development and effectiveness of an anesthesia preoperative evaluation clinic in a teaching hospital. Anesthesiology 1996; 85: 196–206.[Medline]
40 Roizen MF. Is a patient’s history of food supplement use simply supplementary? (Editorial). J Clin Anesth 1998; 10: 89–90.[Medline]
41 Ang-Lee MK, Moss J, Yuan CS. Herbal medicines and perioperative care. JAMA 2001; 11: 208–16.
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43 van Klei WA, Moons KG, et al. Effect of outpatient preoperative evaluation on cancellation of surgery and length of hospital stay. Anesth Analg 2002; 94: 644–9.
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