Patients who are scheduled for a surgical procedure, whether in an outpatient or inpatient setting, are often evaluated by the anesthesiology team to prepare for anesthesia care and may be referred by the surgical team to an internist for medical evaluation prior to surgery. The goal of preoperative medical evaluation is to minimize risk of perioperative complications by identifying medical abnormalities and evaluating the risks posed by known comorbidities. This assessment is used to determine whether additional preoperative preparation and perioperative monitoring and management are needed. In some cases, elective procedures should be delayed so that certain underlying disorders (eg, hypertension, diabetes, hematologic abnormalities) can be optimally controlled. In other cases, if patients are deemed high risk for major surgery, the plan for the surgical approach and anesthesia care may be adjusted preoperatively to reduce risk (eg, using a less invasive intervention).
A thorough preoperative medical evaluation is typically done by a general internist or specialists in areas relevant to a patient's comorbidities (eg, cardiologists, pulmonologists). Such consultants may help manage preexisting disease (eg, diabetes) and help prevent and treat perioperative and postoperative complications (eg, cardiac, pulmonary, infectious). Psychiatric consultation is occasionally needed to assess capacity or help manage underlying psychiatric problems that can interfere with surgery or recovery.
Older adults may benefit from involvement of an interdisciplinary geriatric team , which may include geriatricians, social workers, psychotherapists, physical medicine and rehabilitation specialists, and other health care professionals ( 1 ).
For procedures that are not elective, the acuity and type of proposed operation should be considered as well as the patient's risk with surgery. In addition, if an emergency procedure is required (eg, for intra-abdominal hemorrhage, perforated viscus, necrotizing fasciitis ), there is usually not time for a full preoperative evaluation. However, the patient's history should be reviewed as expeditiously as possible, particularly for allergies and to help identify factors that increase risk of emergency surgery (eg, anticoagulant therapy or a bleeding disorder or prior adverse anesthetic reactions).
A relevant preoperative history includes all of the following:
If an indwelling bladder catheter may be needed, patients should be asked about prior urinary retention and prostate surgery.
Physical examination should address areas involved in the planned surgical procedure and also the cardiopulmonary system, as well as evaluation for any signs of ongoing infection (eg, upper respiratory tract, skin).
If spinal anesthesia is likely to be used, patients should be evaluated for scoliosis and other anatomic abnormalities that may complicate lumbar puncture .
Any cognitive dysfunction, especially in older adults who will be given a general anesthetic, should be noted. Preexisting dysfunction may become more apparent postoperatively and, if undetected beforehand, may be misinterpreted as a surgical complication.
Healthy patients undergoing elective surgery have a low prevalence of undiagnosed disease that would influence perioperative management. Thus, routine preoperative testing should not be done in those without clinical symptoms or significant underlying disease. Such testing is not cost effective and results in false-positive test results, unintended patient anxiety, and delays in surgery.
In symptomatic patients, those with known underlying disease, or those undergoing procedures with a higher risk of significant bleeding or other complications, laboratory evaluation may include the following tests:
Patients with symptomatic CAD need additional tests (eg, stress testing , coronary angiography ) before surgery.
Procedural risk is highest with the following:
Patients undergoing elective surgery, particularly for procedures with a significant risk of hemorrhage, and for patients with reasons to avoid allogeneic transfusion (eg, alloantibodies to red blood cell antigens or religious reasons for refusing blood from other people) may consider banking blood for potential autologous transfusion . The perioperative risk of anemia and possible delay in surgery if time is needed for blood cell counts to normalize should be considered. Autologous donation used to be a more common practice, but its use has decreased with the increasing safety of blood transfusions .
Emergency surgery has a higher risk of morbidity and mortality than the same procedure done electively.
The contribution of a patient's risk factors to perioperative morbidity and mortality is best estimated by validated quantitative risk calculators. For example, the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) has developed a risk calculator to predict perioperative adverse events (see ACS NSQIP Surgical Risk Calculator ). Use of these tools not only allows uniformity in interpreting surgeons' outcomes data but also contributes to better shared decision-making and informed consent for patients and family members ( 1 ).
Cardiac risk factors dramatically increase surgical risk. Perioperative cardiac risk is typically assessed using the American College of Cardiology/American Heart Association's stepwise approach to preoperative cardiac assessment ( 2 ). It considers the following independent predictors of cardiac risk:
Risk of cardiac complications increases with increasing risk factors:
A high-risk surgical procedure (eg, vascular surgery, open intrathoracic or intraperitoneal procedure) also independently predicts a high cardiac perioperative risk.
Patients with active cardiac symptoms (eg, of heart failure or unstable angina ) have a particularly high perioperative risk. Patients with unstable angina have an increased risk of perioperative myocardial infarction ( 3 ). In patients with stable angina, risk is proportional to their degree of exercise tolerance. Patients with active cardiac symptoms thus require thorough evaluation. For example, the cause of heart failure should be determined so that perioperative cardiac monitoring and treatment can be optimized before elective surgery. Other cardiac testing, such as stress echocardiography or even angiography , should be considered if there is evidence of reversible cardiac ischemia on preoperative evaluation.
Preoperative care should aim to control active disorders (eg, heart failure, diabetes) using standard treatments. Also, measures should be taken to minimize perioperative tachycardia, which can worsen heart failure and increase risk of myocardial infarction; for example, pain control should be optimized and beta-blocker therapy should be considered, especially if patients are already taking beta-blockers. Coronary revascularization should be considered for patients with unstable angina. If a heart disorder cannot be corrected before surgery or if a patient is at high risk of cardiac complications, intraoperative and sometimes preoperative monitoring with pulmonary artery catheterization may be advised. Sometimes the cardiac risk outweighs the benefit of surgery. In such cases, a less invasive procedure may provide or serve as a bridge to definitive treatment (eg, tube cholecystostomy for cholecystitis) and decrease morbidity and mortality.
Patients with a history of ischemic stroke are at a higher risk of perioperative stroke, and the ideal timing for surgery after a stroke is uncertain. A study based on Medicare data included almost 6 million patients and found that a history of stroke within 30 days before surgery compared to no prior stroke was associated with an 8-fold risk of postoperative ischemic stroke; between 60 to 90 days after a stroke, the risk of recurrent perioperative stroke decreased, but remained elevated ( 4 ). Therefore, decisions regarding timing of surgery in patients with a history of ischemic stroke should consider both the risk of recurrent stroke and the potential negative consequences of delaying surgery. To minimize risk of recurrence, elective surgery should be deferred for a minimum of 3 months after a stroke, and ideally up to 9 months if possible.
Incidental bacterial infections discovered preoperatively should be treated with antibiotics. However, infections should not delay surgery unless prosthetic material is being implanted; in such cases, surgery should be postponed until the infection is controlled or eliminated.
Patients with respiratory infections should be treated and have evidence that the infection has resolved before receiving inhalational anesthesia.
Viral infections with or without fever should be resolved before elective surgery is done, especially if a general anesthetic is going to be used.
For SARS-CoV-2 , the American Society of Anesthesiologists (ASA) and the Anesthesia Patient Safety Foundation (APSF) recommends against universal preoperative screening in asymptomatic patients; they recommend COVID-19 testing for patients with symptoms and also that each facility implement robust infection control measures and conduct targeted screening based on individual patient exposure, local incidence of COVID‐19, and facility physical layout (see APSF: ASA and APSF Statement on Perioperative Testing for the COVID-19 Virus and ASA and APSF Updated Statement on Perioperative Testing for SARS-CoV-2 in the Asymptomatic Patient ).
Fluid and electrolyte imbalances should be corrected before surgery. Hypokalemia , hyperkalemia , hypocalcemia , and hypomagnesemia must be corrected before general anesthesia to decrease risk of potentially lethal cardiac arrhythmias. Dehydration and hypovolemia should be treated with IV fluids before general anesthesia to prevent severe hypotension on induction—blood pressure tends to fall when general anesthesia is induced.
Undernutrition and obesity increase the risk of postoperative complications in adults. Nutritional status is assessed preoperatively using history, physical examination, and laboratory tests.
Severe nutritional risk factors include the following:
It is important to ask whether weight loss was intentional, because unintentional weight loss may reflect a catabolic state refractory to nutritional repletion, suggesting serious underlying pathology such as cancer.
Severe obesity (body mass index ≥ 40 kg/m 2 ) increases perioperative mortality risk because such patients have increased risk of cardiac and pulmonary disorders (eg, hypertension, pulmonary hypertension, left ventricular hypertrophy, heart failure, coronary artery disease, decreased ventilatory reserve). Obesity is an independent risk factor for deep venous thrombosis and pulmonary embolism ; preoperative venous thromboembolism prophylaxis is indicated in most patients with obesity. Obesity also increases risk of postoperative wound complications (eg, fat necrosis, infection, dehiscence, and abdominal wall hernias).