INTRODUCTION — Clinicians are often asked to evaluate a patient prior to surgery. The medical consultant may be seeing the patient at the request of the surgeon or may be the primary care clinician assessing the patient prior to consideration of a surgical referral. The goal of the evaluation of the healthy patient is to detect unrecognized disease and risk factors that may increase the risk of surgery above baseline and to propose strategies to reduce this risk.
The evaluation of healthy patients prior to surgery is reviewed here. Preoperative assessments for specific systems issues and surgical procedures are discussed separately:
CLINICAL EVALUATION — In general, the overall risk of surgery is extremely low in healthy adults. Therefore, the ability to stratify risk by commonly performed evaluations is limited.
Screening questionnaire — Screening questions appear on many standard institutional preoperative evaluation forms. The purpose of these instruments is to provide an estimate of perioperative risk and to identify patients who need a preoperative clinician consultation. While many such screening questionnaires exist, we use a questionnaire based upon the American Association of Nurse Anesthesiology (AANA) preanesthesia questionnaire; it is of a suitable length and captures most relevant elements of the preoperative evaluation (table 1) . A more complex instrument, the electronic Personal Assessment Questionnaire [ePAQ], has been validated for use as part of an online preoperative screening process  and may be used if available.
Age — A number of commonly employed and validated indices consider age as a minor component of preoperative coronary risk (see "Evaluation of cardiac risk prior to noncardiac surgery"). However, after adjusting for comorbidities more common with age, the impact of age on perioperative outcomes is modest. Much of the risk associated with older age is due to increasing numbers of comorbidities, which may include cognitive impairment, functional impairment, malnutrition, and frailty . Older patients may benefit from preoperative assessments in those areas, but age should not be used as the sole criterion to guide preoperative testing or to withhold a surgical procedure . Risk assessment in older patients is reviewed elsewhere. (See "Anesthesia for the older adult", section on 'Preanesthesia consultation'.)
Some studies have found a small increased risk of surgery associated with advancing age [5,6]. As examples:
●In a review of 50,000 older adult adults, the risk of mortality with elective surgery increased from 1.3 percent for those under 60 years of age to 11.3 percent in the 80- to 89-year-old age group .
●Among 1.2 million Medicare patients undergoing elective surgery, mortality risk increased linearly with age for most surgical procedures . Operative mortality for patients 80 years and older was more than twice that of patients 65 to 69 years old.
●In a systematic review evaluating mortality among older adults undergoing emergency general surgeries, the overall 30-day mortality among octogenarians was 26 percent, and higher compared with non-octogenarians (odds ratio [OR] 4.07, 95% CI 2.40-6.89) .
By contrast, other studies have found little relation between age and surgical mortality rates. As examples:
●One study reported the outcomes of surgery in 795 patients over 90 years of age . No patients were Class I as classified by the American Society of Anesthesiologists (ASA) physical status classification (table 2); 80 percent were ASA Class III or greater. Despite higher perioperative mortality rates in older adults, survival at two years was no different than the actuarial survival in matched patients not undergoing surgery.
●A larger study of 4315 patients also found a higher perioperative complication and in-hospital mortality rate in individuals ≥80 years old, but the mortality rate was low at 2.6 percent .
●Among 31 patients age 100 years and older undergoing surgery requiring anesthesia, perioperative and one-year mortality rates were similar to matched peers from the general population .
●In another study, age was not a significant predictor of cardiac complications after multivariable analysis in the cohort of patients used to derive a revised cardiac risk index .
In addition to the minor influence of age on perioperative cardiac risk, there is more robust literature supporting age as an independent risk factor for postoperative pulmonary complications. In a systematic review, age was one of the most important patient-related predictors of pulmonary risk, even after adjusting for common age-related comorbidities . This is reviewed elsewhere. (See "Evaluation of perioperative pulmonary risk".)
Exercise capacity — All patients should be asked about their exercise capacity as part of the preoperative evaluation. Exercise capacity is an important determinant of overall perioperative risk; patients with good exercise tolerance generally have low risk. (See "Evaluation of cardiac risk prior to noncardiac surgery", section on 'Assessing functional status or exercise capacity'.)
The American College of Cardiology/American Heart Association guideline on preoperative cardiac evaluation recommends that patients with good exercise capacity (at least 4 metabolic equivalents [METs]) do not require preoperative testing, regardless of the risk of the planned procedure (algorithm 1) . Patients’ ability to expend ≥4 METs can be assessed by estimates from activities of daily living; activities that expend ≥4 METS include the ability to climb up a flight of stairs, walk up a hill, walk at ground level at 4 miles per hour, or perform heavy work around the house.
However, a more formal assessment of functional capacity may more reliably predict surgical risk [15,16], and we favor the use of a standardized assessment and scoring system such as the Duke Activity Status Index (DASI) rather than relying upon subjective self-reported functional capacity (table 3). In the largest trial to formally evaluate the impact of functional capacity on surgical outcomes, investigators in the Measurement of Exercise Tolerance before Surgery (METS) trial compared scores on the standardized DASI questionnaire with subjective self-reported functional capacity . The DASI instrument contains 12 questions related to activities of daily living as well as more vigorous activity (table 3) . In an adjusted analysis, subjectively reported functional capacity did not predict death or myocardial infarction in the first 30 days after surgery, whereas DASI scores were significantly associated with these outcomes. (See "Evaluation of cardiac risk prior to noncardiac surgery".)
In general, healthy patients with moderate (or better) functional capacity have a low risk for major postoperative complications. This was illustrated in a study of 600 consecutive patients undergoing major surgery . The investigators defined poor exercise capacity as the inability to either walk four blocks or climb two flights of stairs. Patients reporting poor exercise capacity had twice as many serious postoperative complications as those who reported good exercise capacity (20 versus 10 percent, respectively). There was also a difference in cardiovascular complications (10 versus 5 percent), but not in total pulmonary complications (9 versus 6 percent).
The importance of functional capacity was confirmed objectively in another report of 847 patients undergoing elective abdominal surgery . In this study, poor exercise capacity, confirmed by cardiopulmonary exercise testing, was a stronger predictor of all-cause mortality than any of the conventional cardiac risk factors of the Revised Cardiac Risk Index.
Medication use — Clinicians should obtain a history of medication use for all patients before surgery and should specifically inquire about over-the-counter, complementary, herbal, and alternative medications. Aspirin, ibuprofen, and other nonsteroidal antiinflammatory drugs (NSAIDs) are associated with an increased risk of perioperative bleeding. A detailed discussion of perioperative medication management is presented separately. (See "Perioperative medication management".)
Obesity — Contrary to popular belief, in noncardiac surgery, obesity is not a risk factor for most major adverse postoperative outcomes, with the exception of pulmonary embolism. None of the published and widely disseminated cardiac risk indices for noncardiac surgery include obesity as a risk factor for postoperative cardiac complications.
Representative studies related to postoperative mortality in noncardiac surgery include:
●In a matched case control study of 1962 patients undergoing noncardiac surgery, obesity was not associated with increased mortality (1.1 percent in obese patients versus 1.2 percent in controls) .
●In a large, multi-institutional prospective cohort of 118,707 patients undergoing non-bariatric general surgery, obesity was inversely associated with postoperative mortality (OR 0.85, 95% CI 0.75-0.99), a phenomenon termed the “obesity paradox” . The authors suggest that the obese state carries a low-grade, chronic inflammatory that may be “primed” to mount an appropriate inflammatory and immune response to the stress of surgery, in addition to supplying more nutritional reserve.
Other studies relating to complications in noncardiac surgery found that obesity increases rates for wound infections but has no effect on other postoperative complications except for postoperative deep venous thrombosis and pulmonary embolism [13,21-26]. (See "Prevention of venous thromboembolic disease in adult nonorthopedic surgical patients".)
However, in cardiac surgery, some studies have shown higher complication rates for patients with obesity, including increased hospital stay , wound infections [27,28], prolonged mechanical ventilation , and atrial arrhythmias [28,29].
Obstructive sleep apnea — Given the increased risks of perioperative morbidity and the potential for altered anesthetic management, it is reasonable to screen patients for obstructive sleep apnea (OSA) before surgery with one of several validated screening instruments, such as the STOP-Bang questionnaire (table 4). OSA increases the risk for postoperative medical complications including hypoxemia, respiratory failure, unplanned reintubation, and intensive care unit (ICU) transfer . Most patients with OSA are undiagnosed. The prevalence of previously undetected OSA is particularly high in patients preparing for bariatric surgery. The ASA recommends screening for OSA before noncardiac surgery . A detailed discussion of the indications and techniques for preoperative screening for OSA is presented elsewhere. (See "Surgical risk and the preoperative evaluation and management of adults with obstructive sleep apnea", section on 'Whom to screen' and "Surgical risk and the preoperative evaluation and management of adults with obstructive sleep apnea", section on 'Screening questionnaires'.)
Alcohol misuse — Patients who misuse alcohol on a regular basis have an increased risk for postoperative complications . Pending further study, it is reasonable to screen all patients for alcohol misuse before elective major surgery. Screening for alcohol misuse before surgery will identify a subset of patients at increased risk for postoperative medical complications. While the benefit of directed alcohol cessation programs before surgery is not well-established in the literature, there is little apparent risk to such a strategy. The preoperative period also serves as an opportunity to identify patients who misuse alcohol and are candidates for intervention as part of primary care follow-up after surgery.
In a study of 9176 male US veterans, a screening questionnaire for alcohol misuse administered at any time within one year before surgery accurately stratified risk of postoperative complications . There was a continuous relationship between postoperative complications and risk scores using the Alcohol Use Disorders Identification Test-Consumption (AUDIT-C) questionnaire (table 5). Surgical site infections, other infections, and cardiopulmonary complications each increased across the strata of risk groups based on alcohol use patterns. A similarly conducted trial of the AUDIT-C questionnaire before total joint arthroplasty revealed comparable results . Patients with high AUDIT-C scores (9 to 12 of 12 possible points) within the year before surgery also have longer lengths of stay, more ICU days, and higher unplanned reoperation rates .
Most trials of alcohol cessation interventions have been conducted in the nonoperative setting; a small study in patients undergoing colorectal surgery reported a beneficial effect of alcohol screening on postoperative complications . The optimal period of cessation is unknown but at least four weeks of abstinence are required to reverse selected physiologic abnormalities .
Illicit drug use — In order to provide appropriate perioperative care, it is helpful to ask patients about illicit drug use . Patients with chronic opioid use may have developed tolerance and require higher than usual doses in the intraoperative and postoperative period. Patients who use opioids, barbiturates, or amphetamines are at risk for drug withdrawal in the postoperative period. (See "Opioid withdrawal in the emergency setting" and "Alcohol withdrawal: Epidemiology, clinical manifestations, course, assessment, and diagnosis" and "Benzodiazepine poisoning" and "Benzodiazepine withdrawal".)
Smoking — Evaluating tobacco use and offering strategies to quit smoking may reduce postoperative morbidity and mortality, as patients who smoke have an increased risk for postoperative complications. Smoking cessation prior to surgery may reduce the risk of postoperative complications, and longer periods of smoking cessation are even more effective . Those who smoke should be encouraged to quit preoperatively. (See "Strategies to reduce postoperative pulmonary complications in adults", section on 'Smoking cessation' and "Overview of prehabilitation for surgical patients", section on 'Smoking cessation' and "Overview of smoking cessation management in adults" and "Behavioral approaches to smoking cessation".)
In cohort and case-control studies, preoperative smoking has been associated with an increased risk of postoperative complications, including general morbidity (relative risk [RR] 1.52, 95% CI 1.33-1.74), wound complications (RR 2.15, 95% CI 1.87-2.49), general infections (RR 1.54, 95% CI 1.32-1.79), pulmonary complications (RR 1.73, 95% CI 1.35-2.23), neurological complications (RR 1.38, 95% CI 1.01-1.88), and admission to an ICU (RR 1.60, 95% CI 1.14-2.25) . (See "Evaluation of perioperative pulmonary risk", section on 'Smoking'.)
Personal or family history of anesthetic complications — Malignant hyperthermia is a rare complication of anesthetic administration that is inherited in an autosomal dominant fashion. Due to the morbidity and potential mortality associated with this condition, the preoperative history should include questioning about either a personal or family history of complications from anesthesia. (See "Susceptibility to malignant hyperthermia: Evaluation and management" and "Malignant hyperthermia: Diagnosis and management of acute crisis".)
LABORATORY EVALUATION — Several review articles in perioperative consultation and most local institutional policies support a selective approach to preoperative laboratory testing [40-47]. A practice advisory from the American Society of Anesthesiologists (ASA) and a safety guideline from the Association of Anaesthetists of Great Britain and Ireland recommend against routine preoperative laboratory testing in the absence of clinical indications [46,48].
Rationale for selective testing — In healthy individuals, the prevalence of unrecognized disease that influences surgical risk is low. Clinicians often perform laboratory tests in this group of patients out of habit and medicolegal concern [49,50]. However, there is little benefit and a high incidence of false-positive results. Representative studies that have addressed this issue include:
●In a trial of 1061 ambulatory surgical patients randomly assigned to preoperative testing or no testing, there was no difference in perioperative adverse events or events within 30 days of ambulatory surgery .
●In a retrospective study of 2000 patients undergoing elective surgery, 60 percent of routinely ordered tests would not have been performed if testing had only been done for recognizable indications; only 0.22 percent of these revealed abnormalities that might influence perioperative management . Further chart review determined that these abnormalities were not acted upon, nor did they have adverse surgical consequences.
●In a prospective study of 1363 patients for whom laboratory testing was performed at the discretion of the perioperative clinician, abnormalities in commonly performed blood tests had no predictive value for surgical complications .
●In a retrospective review using the National Surgical Quality Improvement Program (NSQIP) database and including over 73,000 patients undergoing elective hernia repair, preoperative laboratory tests were performed in 63.8 percent of patients; 61.6 percent of these patients had at least one abnormal test result . Among patients with no accepted medical indication for testing, 54 percent received at least one test. After adjustment for demographics, comorbidities, and procedure characteristics, neither preoperative testing nor the finding of an abnormal test result was associated with adverse postoperative outcomes.
The value of routine preoperative laboratory testing in patients undergoing ambulatory surgery is particularly low among ASA class 1 and 2 patients (table 2). As an example, in a retrospective analysis using the NSQIP database and including over 111,000 patients undergoing low-risk surgeries, 51.6 percent underwent preoperative testing; patients who received testing had higher baseline rates of medical comorbidities . Among those tested, 46.4 percent had at least one abnormal test result. The rates of perioperative mortality, serious morbidity, and unplanned reoperation did not differ between those who received preoperative testing and those who did not. In a multivariable analysis (to adjust for differences in comorbidities), preoperative laboratory testing was associated with a slightly increased risk of surgical complications (odds ratio [OR] 1.28, CI 1.18-1.40) but had no impact on mortality or serious morbidity.
Predictive value — There are several arguments for avoiding routine preoperative tests. Normal test values are usually arbitrarily defined as those occurring within two standard deviations from the mean, thereby ensuring that 5 percent of healthy individuals who have a single screening test will have an abnormal result. As more tests are ordered, the likelihood of a false-positive test increases; a screening panel containing 20 independent tests in a patient with no disease will yield at least one abnormal result 64 percent of the time (table 6).
Thus, the predictive value of abnormal test results is low in healthy patients with a low prevalence of disease (table 7). Aside from possibly causing patient alarm, the additional testing prompted by false-positive screening tests leads to unnecessary costs, risks, and a potential delay of surgery. In addition, clinicians often fail to act upon abnormal test results from routine preoperative testing, thereby creating a medicolegal risk.
A review of studies of routine preoperative testing pooled data and estimated the incidence of abnormalities that affect patient management and the positive and negative likelihood ratios for a postoperative complication (table 8) . For nearly all potential laboratory studies, a normal test did not substantially reduce the likelihood of a postoperative complication (the negative likelihood ratio approached 1.0). Positive likelihood ratios were modest, and they exceeded 3.0 for only three tests (hemoglobin, kidney function, and electrolytes); however, clinical evaluation can predict most patients with an abnormal result. This was illustrated by the low incidence of a change in preoperative management based on an abnormal test result (0 to 3 percent).
Timing of laboratory testing — When preoperative laboratory tests are felt to be necessary, it is reasonable to rely upon test results found to be normal within the prior four months, unless there has been an interim change in a patient's clinical status.
The validity of this approach was illustrated in an observational study of 1109 patients undergoing elective surgery who had 7549 preoperative laboratory tests performed at admission; almost half of these tests had also been performed within the previous year .
●Of previously normal tests (performed a median of two months prior to admission), only 0.4 percent were outside the range considered acceptable for surgery on repeat testing; most of these patients had a change in clinical history that predicted the abnormality.
●Of previously abnormal tests, 17 percent remained outside the range considered acceptable for surgery, suggesting that it is useful to repeat only abnormal tests in the immediate preoperative period.
Other studies have not necessarily supported this approach, but issues with study design limit their applicability. As an example, in a subsequent review of the NSQIP database, 235,010 relatively healthy (ASA physical class status I or II) patients undergoing elective surgery with normal preoperative blood test results in the preceding three months were evaluated for 30-day postoperative morbidity and mortality . Patients were divided into quintiles based on the time elapsed between preoperative blood testing and surgery (<1 week, one to two weeks; two to four weeks; one to two months; two to three months). Patients whose laboratory testing was performed less than two weeks before surgery had better 30-day composite morbidity and mortality outcomes compared with those that had laboratory testing performed two to three months prior to surgery (OR 0.77; 95% CI 0.59-0.99).
However, methodologic flaws (eg, patients were not randomly assigned to quintiles) and other residual confounders may have influenced the results of the study. Thus, we do not feel that these findings change the recommendation that normal tests obtained within four months preoperatively do not need to be repeated unless there is a change in clinical status.
Laboratory studies — While preoperative laboratory testing is not routinely indicated, selective testing is appropriate in specific circumstances, including patients with known underlying diseases or risk factors that would affect operative management or increase risk, and specific high-risk surgical procedures . Specific laboratory studies commonly ordered for preoperative evaluation include a complete blood count, electrolytes, renal function, blood glucose, liver function studies, hemostasis evaluation, and urinalysis. These tests are discussed below with indications for their use in specific populations and surgeries.
Complete blood count
●Hemoglobin/hematocrit – A baseline hemoglobin measurement is suggested for all patients 65 years of age or older who are undergoing major surgery and for any patient undergoing major surgery that is expected to result in significant blood loss. By contrast, hemoglobin measurement is not necessary for those undergoing minor surgery unless the history suggests severe anemia or worsening of chronic, stable anemia.
Preoperative anemia is common; a cohort study of more than 200,000 patients undergoing major non-cardiac surgery found preoperative anemia (defined as a hematocrit of less than 39 percent in men and 36 percent in women) in 30 percent of cases . Postoperative mortality at 30 days was higher in patients with anemia (OR 1.42, 95% CI 1.31-1.54). The risk was similar among those with mild and moderate to severe anemia. Similarly, in a retrospective analysis of almost 86,000 patients, moderate or severe anemia (hemoglobin ≤9 g/dL) was associated with higher 30-day postoperative mortality compared with patients with no or mild anemia (OR 1.51, 95% CI 1.05-2.17) .
The data cannot distinguish whether an abnormal hematocrit serves as a marker for coexistent disease that increases mortality risk, or whether the anemia itself increases physiologic stresses and therefore complication rates.
The observation that outcomes do not differ for patients undergoing hip surgery who were randomly assigned to either liberal or restrictive transfusion policies suggests that anemia is a marker for risk, rather than the cause of morbidity . It remains unclear if the increased risk due to anemia is modifiable by interventions aimed at correcting the hematocrit.
●White blood cell count and platelets – The frequency of significant unsuspected white blood cell or platelet abnormalities is low . It is reasonable to measure platelet count when neuraxial anesthesia (spinal or epidural) is planned. Unlike the hemoglobin concentration, however, there is little rationale to support baseline testing of either. Nevertheless, obtaining a complete blood count, including white count and platelet measurement, can be recommended if the cost is not substantially greater than the cost of a hemoglobin concentration alone. There may be some costs incurred due to follow-up of false-positive results; however, with respect to platelet counts, these costs do not appear to be substantial .
Kidney function — It is appropriate to obtain a serum creatinine concentration in patients over the age of 50 undergoing intermediate- or high-risk surgery, although there is no clear consensus on this point. Creatinine should also be ordered when hypotension is likely, or when nephrotoxic medications will be used.
Mild to moderate kidney impairment is usually asymptomatic. The prevalence of an elevated creatinine among asymptomatic patients with no history of kidney disease is only 0.2 percent [40,60]. However, the prevalence increases with age. In one study, for example, the prevalence among unselected patients aged 46 to 60 was 9.8 percent .
In the revised cardiac risk index (table 9), a serum creatinine >2.0 mg/dL (177 micromol/L) was one of six independent factors that predicted postoperative cardiac complications . Chronic kidney disease is also an independent risk factor for postoperative pulmonary complications  and a major predictor of postoperative mortality . Impaired kidney function necessitates dosage adjustment of some medications that may be used perioperatively (eg, muscle relaxants). (See "Evaluation of cardiac risk prior to noncardiac surgery", section on 'Using risk assessment tools' and "Evaluation of perioperative pulmonary risk".)
Electrolytes — Routine electrolyte determinations are NOT recommended unless the patient has a history that increases the likelihood of an abnormality, such as patients who take diuretics, angiotensin-converting enzyme (ACE) inhibitors, or angiotensin receptor blockers (ARBs). In healthy adults, the frequency of unexpected electrolyte abnormalities is low (0.6 percent in one report) . While preoperative hypernatremia is associated with an increase in perioperative 30-day morbidity and mortality , the relationship between most electrolyte derangements and operative morbidity is not clear. Furthermore, clinicians can predict most abnormalities based on history (for example, current use of a diuretic, ACE inhibitor, or ARB, or known chronic kidney disease).
Blood glucose — Routine measurement of blood glucose is NOT recommended for healthy patients. Unexpected abnormal blood glucose results do not often influence perioperative management. As an example, one study evaluated the benefit of routine laboratory testing in 1010 presumably healthy patients undergoing cholecystectomy . Eight patients had unexpected elevations in preoperative serum glucose; only one of these patients developed significant postoperative hyperglycemia, and this was not recognized until after total parenteral nutrition was started. No patient in this study benefited from routine preoperative measurement of serum glucose.
Also, the frequency of glucose abnormalities increases with age; almost 25 percent of patients over age 60 had an abnormal value in one report . Most controlled studies have not found a relationship between operative risk and diabetes [5,61], except in patients undergoing vascular surgery or coronary artery bypass grafting [64-66]. While the revised cardiac risk index identified diabetes as a risk factor for postoperative cardiac complications, only patients with insulin-treated diabetes were at risk . There is limited evidence that asymptomatic hyperglycemia, in a patient not previously known to have diabetes, increases surgical risk. The rate of asymptomatic hyperglycemia in unselected surgical patients is low; in one report, the incidence was only 1.2 percent . A systematic review examined the relationship between preoperative blood glucose and A1c values in patients without known diabetes and postoperative complications after noncardiac surgery . Among 22 eligible studies, no high-quality tests supported a role for routine preoperative screening in otherwise healthy patients. Exceptions were an increased risk of cardiac complications after vascular surgery and an increased risk for infectious complications after orthopedic surgery, among patients with abnormal preoperative blood glucose or A1c.
Liver function tests — Routine liver enzyme testing is NOT recommended. Unexpected liver enzyme abnormalities are uncommon, occurring in only 0.3 percent of patients in one series . In a pooled data analysis, only 0.1 percent of all routine preoperative liver function tests changed preoperative management (table 8) . In a study of the NSQIP database, among 25,149 patient with no comorbidities, the relative risk for major postoperative complications among patients who received preoperative liver function tests, when compared with those with no testing, approached one (RR 0.94, 95% CI 0.42-2.08) .
Severe liver function test abnormalities among patients with cirrhosis or acute liver disease are associated with increased surgical morbidity and mortality, but no data suggest that mild abnormalities among patients with no known liver disease have a similar impact . Clinically significant liver disease would most likely be suspected on the basis of the history and physical examination.
Tests of hemostasis — Routine preoperative tests of hemostasis are NOT recommended. If the history, physical examination, and family history do not suggest the presence of a bleeding disorder, no additional laboratory testing is required. If the evaluation suggests the presence of a bleeding disorder, appropriate screening tests should be performed, including prothrombin time (PT), activated partial thromboplastin time (aPTT), and platelet count . For some bleeding disorders (eg, inherited platelet disorder, hemophilia carrier), additional tests may be required to establish a diagnosis and identify the degree of abnormality [70,71]. (See "Preoperative assessment of bleeding risk".)
Unexpected significant abnormalities of the PT or PTT are uncommon [40,59]. Inherited coagulation defects are quite rare. For example, the incidence of hemophilia A and B among men is 1:5000 and 1:30,000, respectively . Nearly all of these cases would be evident based on clinical presentation prior to the preoperative medical evaluation. In addition, the relationship between an abnormal result and the risk of perioperative hemorrhage is not well-defined but appears to be quite low, particularly in those who are thought to have a low risk of hemorrhage on the basis of history and physical examination [73,74]. Even among neurosurgical patients, for whom a small amount of unanticipated bleeding could cause substantial morbidity, the medical history is the most useful screening test for bleeding diathesis. In a study of 11,804 patients undergoing spinal or intracranial surgery, a medical history that suggested risk for bleeding complications was substantially more sensitive that PT or PTT values in predicting need for transfusion, unplanned reoperation, and mortality .
In a pooled data analysis, an abnormal PT had a positive likelihood ratio of 0 for predicting a postoperative complication and a negative likelihood ratio of 1.01 (table 8); in no case did the finding of an abnormal PT change patient management or modify the likelihood of a complication . Similarly, the bleeding time is not useful in assessing the risk of perioperative hemorrhage [76,77].
Urinalysis — Routine urinalysis is NOT recommended preoperatively for most surgical procedures. The theoretical reason to obtain a preoperative urinalysis is detection of unsuspected urinary tract infection. Urinary tract infections have the potential to cause bacteremia and postsurgical wound infections, particularly with prosthetic surgery . Patients with positive urinalysis and urine culture are generally treated with antibiotics and proceed with surgery without delay . However, it is unclear whether a positive preoperative urinalysis and culture with subsequent antibiotic treatment prevent postsurgical infection. One study found no difference in wound infection between patients with normal and abnormal urinalysis . Another study found that patients with asymptomatic urinary tract infection detected by urinalysis had an increased risk of wound infection postoperatively, despite treatment .
In a prospective study of 4663 patients undergoing joint replacement surgery at a single institution, the impact of eliminating the requirement for routine preoperative urinalyses was investigated . While 96 percent fewer urinalyses were performed after the policy change, there was no increase in rates of surgical site infection or catheter-associated urinary tract infection.
A cost-effectiveness analysis estimated that 4.58 wound infections in nonprosthetic knee operations may be prevented annually by the use of routine urinalysis, at a cost of USD $1,500,000 per wound infection prevented . In a subsequent analysis evaluating United States insurance claims over a 10-year period, 89 percent of preprocedural urinalyses were considered inappropriate, costing over $48 million, with an additional $4.8 million spent on antibiotic treatment .
Pregnancy testing — Pregnancy substantially changes perioperative management. We suggest pregnancy testing in all females of reproductive potential prior to surgery. In collaboration with treating clinicians, the pregnant patient may choose to cancel elective surgery or elect a different, lower-risk surgery than originally planned. In addition, anesthetic technique differs in pregnancy, and there may be risks to the fetus if a pregnancy goes undetected before surgery and anesthesia.
Guidelines in the United Kingdom recommend always asking about the possibility of pregnancy before surgery and, if pregnancy is possible after history-taking, offering a pregnancy test [85,86]. The ASA recommends that clinicians offer pregnancy testing for females of childbearing age if the results would alter management . While these guidelines provide some discretion in deciding which individuals to test, it is often not possible to reliably exclude pregnancy based on medical history-taking alone . Many institutions require pregnancy testing for all reproductive age females before surgery. There is low risk to this approach; false-positives are rare, testing is inexpensive, and the results return rapidly. (See "Clinical manifestations and diagnosis of early pregnancy", section on 'Detection of human chorionic gonadotropin'.)
COVID-19 screening and testing — Patients scheduled for elective surgery should be screened for exposure to and symptoms of coronavirus disease 2019 (COVID-19). Symptomatic patients should be referred for additional clinical assessment. (See "COVID-19: Evaluation of adults with acute illness in the outpatient setting", section on 'Initial clinical evaluation'.)
Protocols for routine preoperative testing vary by institution and geographic region , although a December 2022 joint statement published by the ASA and the Anesthesia Patient Safety Foundation now recommends against routine screening of asymptomatic patients . (See "COVID-19: Perioperative risk assessment, preoperative screening and testing, and timing of surgery after infection", section on 'Preoperative evaluation' and "COVID-19: Diagnosis", section on 'Selected asymptomatic individuals'.)
ELECTROCARDIOGRAM — We suggest not ordering an electrocardiogram (ECG) for asymptomatic patients undergoing low-risk surgical procedures (see "Preoperative evaluation for anesthesia for noncardiac surgery", section on 'Surgical risk'). ECGs have a low likelihood of changing perioperative management in the absence of known cardiac disease. The prevalence of abnormal ECGs increases with age . Important ECG abnormalities in patients younger than 45 years with no known cardiac disease are very infrequent.
The 2014 American College of Cardiology/American Heart Association (ACC/AHA) Guidelines on Perioperative Cardiovascular Evaluation state that ECGs are not useful in asymptomatic patients undergoing low-risk procedures . Similarly, the European Society of Cardiology 2014 preoperative guidelines do not recommend obtaining ECGs in patients without risk factors .
The 2014 ACC/AHA guidelines recommend a preoperative resting 12-lead ECG for patients with known coronary artery disease, significant arrhythmia, peripheral arterial disease, cerebrovascular disease, or other significant structural heart disease, except for those undergoing low-risk surgery (risk of major adverse cardiac event <1 percent) (table 10) . A preoperative resting ECG can also be considered for asymptomatic patients undergoing surgery with elevated risk (risk of major adverse cardiac event ≥1 percent). Preoperative evaluation of patients with known cardiovascular disease or cardiovascular disease risk factors is discussed in detail elsewhere. (See "Evaluation of cardiac risk prior to noncardiac surgery".)
The 2009 AHA Scientific Advisory on Cardiovascular Evaluation and Management of Severely Obese Patients Undergoing Surgery states that it is reasonable to obtain a 12-lead ECG prior to surgery in patients with class III obesity (body mass index ≥40 kg/m2) with at least one risk factor for coronary heart disease (diabetes, smoking, hypertension, or hyperlipidemia) or poor exercise tolerance . This is discussed separately. (See "Preanesthesia medical evaluation of the patient with obesity", section on 'Cardiovascular disease'.)
CHEST RADIOGRAPHS — We suggest not obtaining routine preoperative chest radiographs in healthy adults, even before high-risk non-cardiothoracic surgery, in the absence of active cardiopulmonary disease (eg, a change in baseline symptoms in patients with established cardiopulmonary disease) or symptoms (algorithm 2) (see 'Exercise capacity' above). This is consistent with the American Society of Anesthesiologists practice advisory . In addition, several systematic reviews and independent advisory organizations in the United States and Europe recommend against routine chest radiography in healthy patients [94-97].
Preoperative chest radiographs add little to the clinical evaluation in identifying patients at risk for perioperative complications . Abnormal findings on chest radiograph occur frequently and are more prevalent in older patients . There is little evidence to support the use of preoperative chest radiographs, regardless of age, unless there is known or suspected cardiopulmonary disease from the history or physical examination. As examples:
●In a meta-analysis including 21 studies of routine chest radiography, among a total of 14,390 routine chest radiographs, there were 1444 abnormal studies . Only 140 abnormal findings were unexpected, and only 14 (0.1 percent) of all routine chest radiographs influenced management.
●In one retrospective study, 905 surgical admissions were evaluated for the presence of clinical factors believed to be risk factors for an abnormal preoperative chest radiograph . The risk factors determined by the investigators included age over 60 years or clinical findings consistent with cardiac or pulmonary disease. No risk factors were identified in 368 patients; of these, only one (0.3 percent) had an abnormal chest radiograph, which did not affect the surgery. Conversely, 504 patients had identifiable risk factors; of these, 114 (22 percent) had significant abnormalities on preoperative chest radiograph. No subgroup analyses are available for review, but the authors note that older age was not associated with increased risk of abnormal chest radiography in the absence of other risk factors.
We do not suggest routine preoperative chest radiography for patients with class III obesity (ie, BMI ≥40 kg/m2), unless additional criteria such as poor exercise tolerance or unexplained dyspnea are present. Although routine preoperative chest radiography is suggested by the American Heart Association for patients with class III obesity , the relationship between chest radiograph findings and perioperative morbidity are not well defined in this population, and studies are not available to indicate that preoperative radiographic abnormalities affect perioperative outcomes.
PULMONARY FUNCTION TESTS — Routine pulmonary function tests are not indicated for healthy patients prior to nonpulmonary surgery. (See "Evaluation of perioperative pulmonary risk".)
These tests generally should be reserved for patients who have dyspnea, poor exercise tolerance, or cough that remains unexplained after careful clinical evaluation, particularly in the presence of risk factors for postoperative pulmonary complications. Clinical findings are more predictive of the risk of postoperative pulmonary complications than are spirometric results . These findings include decreased breath sounds, prolonged expiratory phase, rales, rhonchi, or wheezes. The role of preoperative pulmonary function tests is reviewed in detail elsewhere. (See "Evaluation of perioperative pulmonary risk", section on 'Pulmonary function testing'.)
RECOMMENDATIONS OF OTHERS
●American Society of Anesthesiologists – The American Society of Anesthesiologists (ASA) updated their practice advisory on pre-anesthesia evaluation in 2012 . The ASA does not recommend routine preoperative testing. Selective testing may be indicated based on information from the history and physical examination, or because of the type or invasiveness of the planned procedure and anesthesia. The advisory provides specific recommendations for each potential preoperative test.
●Agency for Healthcare Research and Quality – The Agency for Healthcare Research and Quality (AHRQ) found insufficient evidence for preoperative testing before surgery .
●Health Technology Assessment Program (United Kingdom) – Limited evidence indicated no benefit of complete blood count, electrolyte, and renal function testing . Among apparently healthy patients undergoing surgery, abnormal results were uncommon, and only a small proportion of these results changed perioperative management.
●National Institute for Health and Care Excellence (United Kingdom) – The National Institute for Health and Care Excellence (NICE) guideline makes specific recommendations on the selective use of each commonly performed preoperative test . The recommendations are stratified based on ASA physical status classification and type of surgery (minor, intermediate, major/complex). The guideline does not recommend preoperative chest radiographs, urinalysis, or A1c screening. They recommend selective testing.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Preoperative medical evaluation and risk assessment".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, “The Basics” and “Beyond the Basics.” The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on “patient info” and the keyword(s) of interest.)
SUMMARY AND RECOMMENDATIONS
●Preoperative clinical evaluation – The overall risk of surgery is low in healthy individuals, and the ability to stratify risk with commonly performed evaluations is limited. Screening questionnaires can be helpful in the preoperative evaluation (table 1), particularly to evaluate exercise capacity (table 3). Important potential risk factors to discuss with the patient include functional capacity, alcohol use, smoking, illicit drug use, and medications. Obesity is not a risk factor for most major adverse postoperative outcomes in patients undergoing noncardiac surgery, with the exception of thromboembolic events. Clinicians should also inquire about personal or family history of complications from anesthesia and screen for symptoms of obstructive sleep apnea (OSA). (See 'Clinical evaluation' above.)
●Routine preoperative laboratory testing is not indicated for most patients – Routine preoperative laboratory tests have not been shown to improve patient outcomes among healthy patients undergoing surgery. We do not suggest routinely testing for serum electrolytes, blood glucose, liver function, hemostasis, or urinalysis in the healthy preoperative patient. Routine laboratory testing in healthy patients has poor predictive value, potentially leading to false-positive test results and/or increased medicolegal risk for not following up on abnormal test results. (See 'Rationale for selective testing' above and 'Laboratory studies' above.)
•Preoperative hemoglobin measurement in select patients – We suggest preoperative hemoglobin measurement in the following circumstances (see 'Complete blood count' above):
-All patients ≥65 years of age undergoing major surgery
-Any patient undergoing surgery that is expected to result in significant blood loss
-Any patient undergoing surgery (including minor surgery) if the clinical history suggests severe anemia or worsening of chronic, stable anemia
•Preoperative serum creatinine in select patients – In the revised cardiac risk index (table 9), a serum creatinine >2.0 mg/dL predicted postoperative cardiac complications. We suggest obtaining a serum creatinine concentration in the following circumstances (see 'Kidney function' above):
-Patients >50 years old undergoing intermediate- or high-risk surgery
-Any patient suspected of having kidney disease
-If hypotension is likely during surgery
-If nephrotoxic medications will be used
•Preoperative electrolytes in select patients – We do not routinely check preoperative electrolytes unless there is a clinical history that increases the likelihood of an abnormality, such as patients who take diuretics, angiotensin-converting enzyme (ACE) inhibitors, or angiotensin receptor blockers (ARBs). (See 'Electrolytes' above.)
•Preoperative pregnancy testing – We suggest preoperative pregnancy testing in all females of reproductive potential rather than use of history-taking alone to determine the potential for pregnancy. (See 'Pregnancy testing' above.)
•Preoperative COVID-19 testing – Patients scheduled for elective surgery should be screened for exposure to and symptoms of coronavirus disease 2019 (COVID-19). Symptomatic patients should be referred for additional clinical assessment. (See 'COVID-19 screening and testing' above.)
●ECG is not indicated for asymptomatic patients undergoing low-risk surgery – We suggest not ordering an electrocardiogram (ECG) for asymptomatic patients undergoing low-risk surgical procedures, even for patients with known cardiovascular disease.
According to the 2014 American College of Cardiology/American Heart Association (ACC/AHA) guidelines, a resting 12-lead ECG should be part of the preoperative evaluation in patients with known coronary artery disease, significant arrhythmia, peripheral arterial disease, cerebrovascular disease, or other significant structural heart disease undergoing any other than low-risk surgical procedures.
A preoperative resting ECG can also be considered for asymptomatic patients undergoing surgery with elevated risk (risk of major adverse cardiac event ≥1 percent). This is discussed in detail elsewhere. (See 'Electrocardiogram' above and "Evaluation of cardiac risk prior to noncardiac surgery", section on 'Initial evaluation'.)
●Preoperative chest radiography is not indicated in the absence of active, symptomatic cardiopulmonary disease – We suggest not obtaining routine preoperative chest radiographs in healthy adults, even before high-risk noncardiothoracic surgery, in the absence of active cardiopulmonary disease (eg, a change in baseline symptoms in patients with established cardiopulmonary disease) or symptoms (algorithm 2). There is little evidence to suggest that preoperative chest radiographs alter management or affect surgical outcomes unless there is known or suspected active cardiopulmonary disease. (See 'Chest radiographs' above.)
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