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Preanesthetic assessment (also called preanesthesia evaluation or pre-op evaluation) is a final medical evaluation conducted by an anesthesia provider before a surgery or medical procedure to ensure anesthesia can be administered safely.[1] The anesthesia team (Anesthesiologists, Certified Registered Nurse Anesthetists or Certified Anesthesia Assistants) reviews the patient’s medical history, medications, past anesthesia experiences and obtains consent.[2] A personal interview is usually conducted with the patient by the anesthesia provider to verify medical history details and address any questions or concerns. The anesthetic plan is then tailored to maximize the patient's safety.[3] Finally, the patient must sign an informed consent form acknowledging they were informed of risks of anesthesia.[4]
A face-to-face discussion with the anesthesia provider helps ensure all necessary precautions are taken.
Addressing Anxiety: Providing information about the procedure can help ease concerns.[8]
Discussing Anesthesia Options: Determining whether general or regional anesthesia is most appropriate with the patient's preferences in mind.
Jewelry or Piercings: Removal is often required to prevent complications. A metal piercing could cause a severe burn if electrocautery is used during surgery.
Uncontrolled Medical Conditions: Uncontrolled blood sugar or blood pressure may need management before the surgical case.
Religious Considerations: Some patients, such as Jehovah’s Witnesses, may decline blood transfusions, and this should be clarified with the anesthesia provider.[9] Those of the Muslim faith may have specific requests in terms of physical contact.[10]
Eating or Drinking Before Surgery: Failure to follow NPO (nothing by mouth) guidelines may postpone surgery for safety reasons.[11] Anesthesia medications can temporarily impair the muscles responsible for keeping food and liquids in the stomach. Consuming food or liquids beyond the instructed time can significantly increase the risk of aspiration (stomach contents entering the lungs), which can lead to serious complications, including the need for intensive care. Normal muscle function returns once anesthesia has worn off, and the patient is transferred to the post-anesthesia recovery unit.
Confirming the Surgical Plan: An extra safety measure to verify all necessary details.
Medications:
Diabetes: Adjustments to insulin or other medications may be necessary. Certain drugs, such as GLP-1[12] and SGLT2 inhibitors, may require special instructions. These medications can prevent the stomach from emptying out normally, seriously increasing the risk of choking on stomach contents when a breathing tube is inserted and removed.
Airway AssessmentAirway Evaluation: The anesthesia provider may use the Mallampati score or other tools to predict potential intubation difficulties. This occurs when the anesthesia provider asks patients to open their mouths widely for inspection. They may also ask the patient to turn their head side to side or to look up at the ceiling.
Lung Health: Conditions such as asthma, sleep apnea, or smoking history can impact breathing under anesthesia. Frequently, a preoperative chest x-ray is performed to ensure readiness for possible ventilatory support during surgery.[1]
Heart Health: Surgery can be considered to be as stressful as walking up 1-2 flights of stairs. The inability to tolerate such exertion may require modifications to the anesthetic plan. Sometimes, a 12-lead EKG may be necessary to ensure a patient's heart is ready.[1] In select cases a more in-depth test called a transthoracic echocardiogram (ultrasound of the heart) is also performed.[1]
Physical Limitations and Frailty: Issues with mobility, stiff joints, or other conditions may affect positioning during surgery. These challenges tend to be more common for the elderly who require up to four times the number of surgical procedures.[14]
Before a patient is taken to the operating room, an anesthesia provider verifies the number and size of intravenous (IV) catheters required for the procedure. IV access is essential for administering fluids, medications, and life-saving blood products.[15] In many cases, two IV catheters are placed as a precaution in case one fails during the procedure. Larger-bore IVs may be necessary to accommodate high-volume fluid administration.[15] For patients with allergies to inhaled anesthetics, anesthesia can sometimes be administered exclusively through an IV.[16] In cases where IV access is challenging due to patient-specific factors, ultrasound guidance may be used to facilitate catheter placement.[17]
There are many details to be covered before anesthesia is provided.[4] The information covered and how depends on the needs of the patient.[18] If available, the anesthetist may offer different options for pain control during and after surgery. Adverse effects of anesthesia and need for possible admission to the intensive care unit (ICU) are discussed.[19] Patients have the opportunity to ask questions and make decisions to guide their care.
^ abcdApfelbaum JL, Connis RT, Nickinovich DG, Pasternak LR, Arens JF, Caplan RA, et al. (March 2012). "Practice advisory for preanesthesia evaluation: an updated report by the American Society of Anesthesiologists Task Force on Preanesthesia Evaluation". Anesthesiology. 116 (3): 522–538. doi:10.1097/ALN.0b013e31823c1067. PMID22273990.
^American Society of Anesthesiologists Task Force on Preanesthesia Evaluation (February 2002). "Practice advisory for preanesthesia evaluation: a report by the American Society of Anesthesiologists Task Force on Preanesthesia Evaluation". Anesthesiology. 96 (2): 485–496. doi:10.1097/00000542-200202000-00037. PMID11818784.
Preanesthetic assessment is the systematic clinical evaluation conducted by an anesthesiologist or qualified physician prior to anesthesia administration for surgical or nonsurgical procedures, encompassing a review of the patient's medical history, physical examination, and relevant diagnostic data to identify risks, optimize health, and formulate a tailored anesthetic plan.[1]The primary goals of this assessment are to verify the medical necessity of the procedure, mitigate perioperative morbidity and mortality, select the safest anesthesia technique, and obtain informed consent while addressing patient anxieties.[2][3]Key components include a detailed patient interview covering current and past medical conditions, prior anesthetic experiences, medication use, allergies, and familyhistory of anesthesia complications; a targeted physical examination focusing on the airway, cardiovascular, respiratory, and neurological systems; assignment of the American Society of Anesthesiologists (ASA) Physical Status classification to gauge risk levels; and selective preoperative testing such as electrocardiography for cardiovascular concerns or laboratory analyses only when they may influence management, avoiding routine screens.[1][4][5]The timing of the assessment depends on procedural invasiveness and patientcomorbidity severity: for highly invasive surgeries or patients with significant disease, an initial evaluation including record review, interview, and examination should occur before the day of surgery to enable optimization and specialist consultations, whereas lower-risk cases may be assessed on the day of the procedure.[1]These practices are outlined in standards from authoritative bodies like the American Society of Anesthesiologists (ASA), emphasizing individualized care to enhance safety, efficiency, and outcomes in perioperative settings.[6]
Overview
Definition and Purpose
Preanesthetic assessment is defined as the process of clinical assessment that precedes the delivery of anesthesia care for surgery and nonsurgical procedures, conducted by an anesthesiologist or qualified anesthesia provider.[7] This comprehensive evaluation involves reviewing medical records, interviewing the patient, and performing a focused physical examination to identify potential risks, optimize the patient's condition, and develop an individualized plan for anesthesia, which may include general, regional, or local techniques.[6] The assessment ensures that anesthesia is tailored to the patient's physiological status, comorbidities, and the requirements of the planned procedure.The primary purposes of preanesthetic assessment are to minimize perioperative complications, promote informed patient decision-making, determine the suitability of specific anesthesia modalities, and support planning for postoperative recovery.[5] By systematically evaluating factors such as cardiovascular stability, respiratory function, and medication interactions, the process enables proactive interventions that enhance safety and reduce the likelihood of adverse events during and after surgery.[8] This evaluation also facilitates communication among the perioperative team, ensuring coordinated care that aligns with the patient's overall health goals.Preanesthetic assessment has evolved from rudimentary practices in the early 20th century, coinciding with the professionalization of anesthesiology following the founding of the American Society of Anesthesiologists in 1905, to modern standardized protocols such as the ASA Basic Standards for Preanesthesia Care, last amended October 15, 2025 and remaining a cornerstone of practice in 2025.[6] Key benefits include significant reductions in perioperative mortality and morbidity, with systematic reviews demonstrating associations between thorough preanesthetic clinics and lower rates of postoperative complications, including mortality following high-risk surgeries.[9] These outcomes underscore the assessment's role in improving patient safety through evidence-based risk mitigation.
Timing and Setting
The preanesthetic assessment for elective surgery is ideally conducted 1 to 30 days preoperatively to allow sufficient time for optimization of patient conditions and coordination of care, with an update or re-evaluation by an anesthesiologist required within 48 hours before the day of surgery and an immediate review just prior to induction.[8][7] For urgent or emergent cases, the assessment may be compressed to the same day, focusing on essential elements to minimize delays while ensuring safety.[10][11]This evaluation typically occurs in diverse settings tailored to patient needs and institutional resources, including dedicated preoperative clinics, hospital preadmission units for outpatient procedures, or bedside assessments for inpatients.[12]Telehealth platforms have become increasingly utilized in 2025, particularly for low-risk patients, enabling remote consultations that maintain assessment quality while enhancing accessibility.[13][14] The process involves multidisciplinary input, such as coordination with surgeons and other specialists, to integrate findings into the overall perioperative plan.[7][15]The duration of the assessment generally ranges from 15 to 60 minutes, varying with patient complexity, comorbidities, and procedure type; simpler cases may conclude in under 20 minutes, while high-risk evaluations require more extensive discussion.[16][17] Modern protocols incorporate electronic health records (EHR) for seamless remote data access, which supports virtual assessments and can significantly reduce the need for in-person visits without increasing complications.[18][19]
History Taking
Medical History Review
The medical history review in preanesthetic assessment involves a systematic examination of a patient's documented records to identify chronic conditions, prior surgical and anesthetic events, and ongoing therapies that may influence perioperative risks. This process draws from multiple sources, including electronic medical records (EMRs), pharmacy databases, and reports from consulting specialists, to compile a comprehensive profile of the patient's health status. Emphasis is placed on recent changes in health, such as acute illnesses or medication adjustments, as well as compliance with preoperative fasting (NPO) guidelines to mitigate aspiration risks.[7][20][21]Key elements reviewed include comorbidities such as diabetes and hypertension, which can affect hemodynamic stability and wound healing under anesthesia. Surgical history is scrutinized for patterns of complications, while previous anesthesia experiences are evaluated for adverse events, notably malignant hyperthermia—a rare but life-threatening genetic disorder triggered by certain anesthetics. Allergies to drugs or latex are documented to prevent anaphylactic reactions, and current medications, including anticoagulants or beta-blockers, are assessed for potential interactions with anesthetic agents. Family history of anesthetic complications, such as prolonged apnea or susceptibility to malignant hyperthermia, is also noted to guide genetic screening if indicated.[5][22][6]Additional specific facts from records encompass documentation of tobacco and alcohol use, which correlate with increased postoperative pulmonary and cardiovascular risks, as well as bleeding disorders like hemophilia that may necessitate transfusion planning. Immunization status, particularly for infections like influenza or COVID-19, is reviewed to evaluate infection risks in the perioperative period. In 2025, per the American Society of PeriAnesthesia Nurses (ASPAN) standards, the review incorporates social determinants of health (SDOH), such as housing stability, to identify barriers like medication storage issues or transportation challenges that could impact surgical readiness and outcomes.[5][6][23]The process concludes with cross-verification against patient-reported information to detect discrepancies, such as unreported medication changes, thereby forming the foundational basis for perioperative risk identification and mitigation strategies. This record-based review complements subsequent clinical examinations by highlighting areas warranting focused physical evaluation.[7][24]
Patient Interview
The patient interview forms the interactive core of preanesthetic assessment, enabling anesthesiologists to elicit subjective insights from the patient or guardian that complement medical records. This dialogue focuses on gathering details about recent symptoms, daily functioning, emotional state, and perioperative expectations to tailor anesthesia planning and identify potential risks.Key elements include open-ended questions probing current symptoms, such as chest pain that may signal cardiac concerns or dyspnea indicating respiratory compromise, allowing patients to describe experiences in their own words.[25] Functional status is evaluated through queries on exercise tolerance, briefly introducing metabolic equivalents (METs) where 1 MET equates to the oxygen consumption at rest (approximately 3.5 mL/kg/min), helping gauge cardiovascular reserve—for instance, inability to climb one flight of stairs suggests <4 METs.[4] Psychological readiness is addressed by exploring anxiety, fears, or prior anesthesia experiences, alongside clarifying expectations for the procedure and recovery to build trust and reduce uncertainty.[26]Validated tools enhance the process, such as the Amsterdam Preoperative Anxiety and Information Scale (APAIS), a six-item questionnaire assessing anxiety and information needs with high reliability (Cronbach's alpha >0.8), often administered during the interview.[27] Cultural and language barriers are proactively managed through interpreters or culturally sensitive phrasing to ensure accurate responses and informed consent.[6]This interview uniquely uncovers unreported information, including over-the-counter supplements like herbal remedies that could interact with anesthetics, or recent infections such as upper respiratory tract illnesses that might increase postoperative complications.[5] In pediatric settings, guardians provide essential developmental history, detailing the child's age-appropriate behaviors, allergies, and previous separations to anticipate cooperation challenges.[28]Patients may briefly mention airway-related symptoms, such as snoring or choking episodes, during symptom discussions. Typically lasting 10-20 minutes, the interview flows efficiently when integrated with record review, prioritizing high-yield topics to respect patient time while maximizing informational value.[29]
The physical examination in preanesthetic assessment is a targeted, hands-on evaluation designed to identify acute or subclinical abnormalities in key organ systems that could influence anesthesia administration and perioperative outcomes. It prioritizes anesthesia-relevant domains such as cardiovascular stability, respiratory function, and overall physiological reserve, rather than a complete head-to-toe survey. This focused approach allows anesthesiologists to establish baseline parameters for intraoperative monitoring and to detect conditions like dehydration or undiagnosed heart failure that may require intervention before surgery.[6][7]Vital signs form the cornerstone of the examination, providing objective data on hemodynamic and respiratory status. Blood pressure, heart rate, respiratory rate, oxygen saturation via pulse oximetry, and temperature are routinely measured and recorded to establish baselines for comparison during and after anesthesia. Abnormalities, such as hypertension or tachycardia, may signal underlying issues like anxiety, pain, or autonomic dysfunction that could exacerbate intraoperative risks. In high-volume or resource-limited settings, these measurements are often automated but must be corroborated with manual checks if discrepancies arise.[6][30]General appearance is assessed through inspection to gauge nutritional status, mobility, and signs of systemic illness. Indicators such as obesity (e.g., body mass index >30 kg/m²), cachexia, or frailty can predict challenges in positioning, drug dosing, or recovery, while pallor or diaphoresis might suggest anemia or instability. For frailty evaluation, point-of-care ultrasound (POCUS) of the quadriceps muscle has emerged as a quantitative tool in 2025 practices, correlating muscle thickness with postoperative complications in older adults.[7][31]The cardiovascular examination employs palpation, auscultation, and inspection to evaluate cardiac and vascular integrity. Palpation of peripheral pulses assesses for regularity and strength, while auscultation over the precordium detects murmurs, gallops, or rubs indicative of valvular disease or heart failure. Signs like jugular venous distension or peripheral edema signal volume overload, potentially altering fluid management plans. In contemporary assessments, POCUS transthoracic echocardiography provides rapid visualization of ejection fraction or pericardial effusion, guiding decisions in patients with known cardiac history.[6][31][30]Respiratory evaluation focuses on lung function through inspection for chest wall deformities, palpation for symmetry, and auscultation for breath sounds, wheezes, or crackles that may indicate infection, obstruction, or chronic disease. Cyanosis or clubbing suggests chronic hypoxemia, prompting further optimization. POCUS lung ultrasound, increasingly integrated by 2025, quantifies aeration via B-lines or consolidations to predict postoperative pulmonary risks, such as atelectasis.[7][31]Neurological status is briefly reviewed for alertness, orientation, motor strength, and focal deficits, ensuring no acute changes like stroke that could contraindicate anesthesia. Techniques include simple tests of gait, grip strength, and cranial nerve function, with documentation of baseline cognition to monitor for postoperative delirium. While routine in all patients, this is expanded in those with neurological comorbidities.[6][30]Throughout the examination, techniques such as inspection for visible abnormalities, palpation for tenderness or masses, and auscultation for adventitious sounds are applied selectively to high-yield areas. All findings are documented meticulously to facilitate intraoperative comparisons and multidisciplinary communication, emphasizing the exam's role in personalized anesthesia planning.[7]
Airway Assessment
Airway assessment is a critical component of preanesthetic evaluation, aimed at identifying anatomical and functional features that may predict difficult intubation or ventilation, thereby allowing for tailored airway management strategies to minimize perioperative risks. This evaluation focuses on the upper airway's structure and mobility, using non-invasive bedside tests to gauge the likelihood of challenges during laryngoscopy or bag-mask ventilation. Early detection of potential difficulties enables anesthesiologists to prepare alternative techniques, reducing the incidence of adverse events such as hypoxia or failed intubation.One of the foundational methods is the modified Mallampati classification, which categorizes airway visibility into four classes based on the oropharyngeal structures observed when the patient sits upright with the mouth maximally open and tongue protruded: class I shows full visibility of the soft palate, fauces, uvula, and tonsillar pillars; class II partially obscures the uvula; class III reveals only the base of the uvula; and class IV displays only the hard palate. Classes III and IV are associated with increased risk of difficult laryngoscopy, with sensitivity around 50-70% in predictive studies.[32]Additional key assessments include measuring thyromental distance—the straight-line distance from the thyroid notch to the mental prominence—with a value less than 6 cm indicating potential difficulty due to limited submandibular space for laryngoscope maneuverability. Neck mobility is evaluated by assessing the range of extension and flexion; restricted movement, such as inability to achieve the sniffing position (neck flexion with head extension), heightens risk, particularly in patients with cervical spine limitations. The jaw protrusion test, also known as the mandible protrusion or upper lip bite test, examines the ability to advance the lower incisors beyond the upper incisors (class A: lower incisors protrude past uppers; class B: align with uppers; class C: cannot align); class C correlates with higher intubation difficulty by revealing temporomandibular joint dysfunction or retrognathia.[33][34][35]Common risk predictors encompass anatomical factors such as a short neck, receding mandible, or prominent overbite, which compromise glottic exposure during direct laryngoscopy. Obesity, defined by a body mass index greater than 30 kg/m², contributes to difficult airways through excess pharyngeal soft tissue and reduced functional residual capacity, increasing the odds of intubation challenges by up to 2-3 times in severe cases. Conditions like rheumatoid arthritis further elevate risk via synovial inflammation leading to temporomandibular joint erosion and reduced neck extension, with studies showing an incidence of difficult intubation around 13% in affected patients.[36][37][38]Advanced tools enhance predictive accuracy; for instance, point-of-care ultrasound evaluates anterior neck soft tissue thickness and hyomental distance, offering superior sensitivity (up to 90%) for difficult laryngoscopy compared to traditional exams; for example, skin-to-epiglottis membrane distance greater than 1.6 cm at the thyrohyoid level is a high-risk indicator. As of 2025, artificial intelligence-assisted models are emerging for high-risk cases, integrating clinical data and imaging to predict difficult airways with areas under the receiver operating characteristic curve exceeding 0.85, outperforming single bedside tests in validation studies.[39][40]These assessments directly inform perioperative planning; identification of high-risk features prompts selection of specialized intubation aids, such as video laryngoscopes for improved glottic visualization in obese patients, or awake fiberoptic intubation techniques for those with limited neck mobility, as recommended in major society guidelines to ensure safe airway securing.[41]
Diagnostic Testing
Laboratory Tests
Laboratory tests in preanesthetic assessment involve targeted blood and fluid analyses to detect physiological abnormalities that could compromise anesthesia safety or surgical outcomes. These tests are selected based on patient history, comorbidities, and procedural risks rather than performed routinely, as unnecessary testing increases costs without improving care. The American Society of Anesthesiologists (ASA) recommends against baseline laboratory evaluations for low-risk patients (ASA physical status I or II) undergoing minor procedures, emphasizing individualized approaches to minimize interventions.[42][43]Common routine tests include a complete blood count (CBC) to assess for anemia or infection, electrolyte panels and renal function markers such as blood urea nitrogen (BUN) and creatinine to evaluate hydration and kidney status, coagulation profiles including prothrombin time (PT), partial thromboplastin time (PTT), and international normalized ratio (INR) to identify bleeding risks, and blood glucose levels to manage perioperative hyperglycemia, particularly in diabetic patients. For females of childbearing age, pregnancy testing is offered when pregnancy status could influence anesthetic choices or procedural planning, though it is not mandatory and requires informed consent. Indications for these tests often include advanced age greater than 50 years, known comorbidities like renal or cardiac disease, or medications such as warfarin that necessitate INR monitoring to guide reversal strategies.[43][44][45]In patients with cardiac comorbidities, additional biomarkers such as high-sensitivity troponin are prompted to stratify perioperative myocardial injury risk, with elevated levels predicting adverse events like myocardial infarction. Similarly, N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels are assessed in individuals aged 65 or older or with cardiovascular disease to gauge heart failure risk and inform optimization. Hemoglobin levels from the CBC are critical, as preoperative anemia (often defined as <13 g/dL in men or <12 g/dL in non-pregnant women) is associated with increased risks and typically prompts optimization before elective surgery to reduce transfusion needs.[46][47][48]As of 2025, point-of-care testing has become integral, enabling rapid results for electrolytes, glucose, coagulation via viscoelastic assays like thromboelastography, and even biomarkers, thereby reducing preoperative wait times and facilitating same-day decisions without compromising accuracy. Adhering to ASA and similar guidelines by avoiding indiscriminate testing can achieve cost reductions of up to 30%, with broader U.S. estimates suggesting annual savings exceeding $373 million from eliminating low-value labs in low-risk cases.[49][43][50]
Imaging and Functional Tests
Imaging and functional tests in preanesthetic assessment are selectively ordered based on patient history, physical examination findings, and surgical risk to evaluate potential organ dysfunction that could impact perioperative care. These tests provide visual or physiological insights into cardiac, pulmonary, and vascular systems, but are not recommended routinely due to limited evidence of benefit in asymptomatic patients. Guidelines emphasize individualized indications to avoid unnecessary procedures that may lead to delays or incidental findings without clinical relevance.[51]Electrocardiography (ECG) is a common initial functional test for detecting arrhythmias, ischemia, or conduction abnormalities, particularly in patients with cardiovascular risk factors such as hypertension, diabetes, or prior myocardial infarction; if arrhythmia is detected on preoperative ECG, additional tests may include 24-hour Holter monitoring, echocardiography, or cardiologist consultation. Indications include recent myocardial infarction (within 30 days), known coronary heart disease, or intermediate- to high-risk surgery in patients aged over 65 years or with poor functional capacity. According to the 2024 AHA/ACC guidelines, preoperative ECG is reasonable (Class IIa) for patients with known cardiovascular disease undergoing elevated-risk procedures, but not for low-risk surgery in asymptomatic individuals. Abnormal ECG findings occur in 11-79% of indicated cases, though they alter management in only 0.5-20% of patients.[52][51]Chest X-ray is utilized to assess pulmonary conditions like infiltrates, effusions, or cardiomegaly in patients with symptoms or risk factors such as smoking history, recent upper respiratory infection, or chronic obstructive pulmonary disease (COPD). The American Society of Anesthesiologists (ASA) recommends it selectively for those with acute cardiopulmonary symptoms or unstable chronic lung disease, rather than routinely, as abnormalities are found in 8-86% of indicated patients but lead to management changes in under 20%. It is not indicated for stable, asymptomatic patients, where yield is low (0.3-60%).Echocardiography evaluates cardiac structure and function, including ejection fraction and valvular disease, in cases of unexplained dyspnea, heart failure symptoms, or suspected cardiomyopathy identified during history or exam. Preoperative transthoracic echocardiography is indicated for patients with recent heart failure exacerbation or moderate-to-severe valvular disease, per AHA/ACC guidelines, with abnormalities detected in 8-25% of such cases and occasional surgery postponement (0.8%). It is not routine for asymptomatic patients without cardiovascular risk factors. For assessing cardiac reserve in high-risk scenarios, stress echocardiography—such as dobutamine stress echo—is considered in patients with poor functional capacity (<4 METs) and elevated perioperative risk, though only if results would alter management (Class 2b recommendation).[51][52][53]Pulmonary function tests (PFTs), including spirometry and diffusion capacity, quantify lung capacity and airflow obstruction in patients with known or suspected respiratory disease like COPD or asthma, especially prior to thoracic or upper abdominal surgery. Indications include symptomatic COPD, recent exacerbations, or scoliosis, where abnormalities appear in 27-66% of cases, though evidence of management impact remains limited. PFTs are rarely justified for elective non-thoracic surgery in stable patients, as they poorly predict postoperative complications.[54][55]In vascular surgery cases, carotid duplex ultrasound screens for stenosis in patients with neurological symptoms, age over 70, or multivessel disease, as significant carotid artery stenosis (>50%) occurs in approximately 22% of cardiac surgery candidates and increases stroke risk. For detailed cardiac assessment without radiation, non-invasive options like cardiac MRI are increasingly used for complex cases such as suspected infiltrative cardiomyopathy or viability evaluation, offering superior tissue characterization over traditional methods.[56][57]These tests are not performed routinely, as meta-analyses indicate overuse in up to 50-70% of low-risk preoperative evaluations, leading to delays in surgery, increased costs, and false positives that prompt unnecessary further testing without improving outcomes. Management changes occur in only 5-10% of cases across studies, underscoring the need for targeted application based on clinical suspicion from history or physical exam.[58][59]
Risk Stratification
ASA Physical Status Classification
The American Society of Anesthesiologists (ASA) Physical Status (PS) Classification System is a standardized framework used to evaluate a patient's overall health and physiological fitness prior to anesthesia and surgery, focusing solely on the impact of comorbidities rather than the procedure itself.[60] Developed in 1941 by Myer Saklad and colleagues to facilitate statistical data collection on perioperative outcomes, it was revised in 1963 by Robert D. Dripps to simplify the categories into five main classes with an added "E" suffix for emergencies, based on an analysis of over 33,000 patients that demonstrated its utility in predicting mortality.[61] Further refinements occurred in 2014, reintroducing disease-specific examples to enhance consistency, with the most recent approval in 2020 maintaining its core structure.[60] As of 2025, the system remains the global standard for preoperative assessment, billing, and research, though it is not intended as a comprehensive risk predictor on its own.[62]The classification comprises six ordinal categories, denoted ASA I through VI, each reflecting the severity of systemic disease and its functional limitations:
ASA Class
Description
Examples
I
Normal healthy patient without any clinical disease.
A fit 25-year-old undergoing elective hernia repair.[60]
II
Patient with mild systemic disease that is well-controlled and does not limit activity.
Controlled hypertension or mild asthma in a patient with no functional impairment.[60][62]
III
Patient with severe systemic disease that significantly limits physical activity but is not incapacitating.
Uncontrolled diabetes or stable angina with exertional limitations.[60][62]
IV
Patient with severe systemic disease that is a constant threat to life.
Recent myocardial infarction or end-stage renal disease requiring dialysis.[60]
V
Moribund patient who is not expected to survive 24 hours with or without the operation.
Ruptured abdominal aortic aneurysm with hemodynamic instability.[60]
VI
Brain-dead patient whose only purpose is organ donation.
Declared brain-dead donor for transplantation.[60]
The "E" modifier is appended to classes I-V to indicate emergency procedures where delay would threaten life or bodily function.[60] Assignment relies on clinical judgment of disease severity and impact, independent of age, smoking status, or pregnancy unless they contribute to systemic effects.[62]In practice, the ASA PS system guides clinical decision-making by informing resource allocation, such as prioritizing intensive care unit monitoring for higher classes, and serves as a prognostic tool in research and quality improvement initiatives.[60] It correlates with postoperative outcomes, with meta-analyses showing perioperative mortality rates increasing progressively: 0-0.3% for ASA I, approximately 0.3-1.4% for ASA II, 1.8-4.5% for ASA III, 7.8-23% for ASA IV, and 9.4-50% for ASA V.[63]Inter-rater reliability is moderate, with exact agreement rates of 70-80% across studies involving anesthesiologists, though variability arises from subjective interpretation of disease impact.[64] The system may integrate briefly with specialized assessments, such as airway evaluation, to refine overall risk communication.[62]
Perioperative Risk Factors
Perioperative risk factors encompass patient-specific and procedure-related elements that elevate the likelihood of adverse events during the surgical period, including cardiac, pulmonary, and other complications. These factors are evaluated using validated tools to guide risk stratification beyond broad patient fitness assessments, enabling targeted interventions to mitigate potential harm. Key considerations include historical comorbidities, physiological metrics, and surgical characteristics that independently predict outcomes such as myocardial infarction (MI), respiratory failure, or renal dysfunction. As of 2024, the American Heart Association/American College of Cardiology (AHA/ACC) Guideline reaffirms established tools like the Revised Cardiac Risk Index (RCRI) while recommending integration with preoperative biomarkers such as high-sensitivity troponin for enhanced accuracy.[52]The Revised Cardiac Risk Index (RCRI) is a widely adopted tool for estimating the risk of major cardiac complications, such as MI, pulmonary edema, ventricular fibrillation, or primary cardiac arrest, following noncardiac surgery.[65] It incorporates six independent predictors, each scored as 1 point for a total ranging from 0 to 6: (1) high-risk surgery (intraperitoneal, intrathoracic, or suprainguinal vascular procedures); (2) history of ischemic heart disease (prior MI, positive exercise test, current angina, use of nitrate therapy, or pathologic Q waves); (3) history of congestive heart failure (e.g., history of heart failure, pulmonary edema, or paroxysmal nocturnal dyspnea); (4) history of cerebrovascular disease (prior stroke or transient ischemic attack); (5) preoperative insulin use for diabetes mellitus; and (6) preoperative serum creatinine greater than 2 mg/dL.[65] The risk of major cardiac events escalates with higher scores: approximately 0.4% for a score of 0, 0.9% for 1, 7% for 2, and 11% for 3 or more.[65] This index has been externally validated across diverse populations and remains a cornerstone for preoperative cardiac risk prediction due to its simplicity and prognostic accuracy.[66]Functional capacity, quantified in metabolic equivalents (METs), provides an additional layer of cardiac risk assessment by reflecting a patient's ability to perform daily activities, which correlates with perioperative outcomes. One MET represents the resting oxygen consumption of a 70-kg adult (approximately 3.5 mL O2/kg/min). Patients achieving ≥4 METs—equivalent to climbing one flight of stairs or walking briskly—are considered to have adequate capacity and low perioperative cardiac risk, whereas those with <4 METs (e.g., unable to perform light housework) face elevated risks of events like MI or heart failure exacerbation.[52] This metric is particularly useful when formal testing is unavailable, as it can be elicited from patient history.For pulmonary complications, the ARISCAT score serves as a targeted index to predict postoperative pulmonary risks, including respiratory failure, pneumonia, or the need for mechanical ventilation. Developed from a large surgical cohort, it assigns points based on seven factors: age ≥50 years (3 points), preoperative SpO2 <96% (24 points), recent respiratory infection (17 points), anemia (preoperative hemoglobin ≤10 g/dL; 11 points), surgical site (thoracic: 24 points, upper abdominal: 15 points, neurosurgery or other: 0 points), duration of surgery ≥2 hours (16 points), and emergency procedure (8 points). Total scores categorize risk as low (0-25 points; 1.6% complication rate), intermediate (26-44 points; 13.3%), or high (≥45 points; 42.1%), facilitating decisions on preoperative optimization like incentive spirometry or smoking cessation.Cardiac risk factors prominently include a history of recent MI, which approximately 5-fold increases the odds of perioperative reinfarction compared to patients without prior events.[67] Pulmonary risks are heightened by chronic smoking, with exposure exceeding 20 pack-years associated with a significant dose-dependent rise in postoperative complications such as atelectasis or pneumonia. Renal impairment, indicated by preoperative creatinine >2 mg/dL, not only contributes to the RCRI but also independently elevates risks of acute kidney injury and cardiovascular events due to underlying vascular disease. Aspiration risk factors, such as gastroesophageal reflux disease, obesity, or delayed gastric emptying, further compound perioperative hazards by predisposing to chemical pneumonitis, particularly in emergency settings.Procedure-specific elements amplify these patient factors; high-risk surgeries like vascular or thoracic procedures elevate the odds of cardiac and pulmonary complications by 2- to 4-fold compared to low-risk operations, as reflected in tools like the RCRI.[65] Emerging biomarkers, including preoperative high-sensitivity troponin elevations >0.04 ng/mL, signal subclinical myocardial ischemia and are associated with up to a 2-fold increase in major adverse cardiac events, prompting closer monitoring in at-risk patients; the 2024 AHA/ACC Guideline recommends their use to refine RCRI predictions.[52]Mitigation strategies focus on optimization rather than routine prophylaxis. For instance, continuing beta-blockers in patients already prescribed them reduces cardiac event rates without increasing overall harm, whereas initiating them de novo is not universally recommended due to potential risks like bradycardia. Smoking cessation at least 4-8 weeks preoperatively can attenuate pulmonary risks, and renal protective measures, such as avoiding nephrotoxic agents, are tailored to individual creatinine levels. These approaches, informed by risk indices, aim to balance surgical urgency with evidence-based preparation.
Preoperative Optimization and Preparation
Medication Management
Medication management in preanesthetic assessment involves evaluating and adjusting a patient's current medications to minimize perioperative risks such as bleeding, thrombosis, hypotension, or metabolic disturbances while maintaining therapeutic benefits. Core principles emphasize continuing most chronic medications, particularly those for cardiovascular conditions, unless specific risks outweigh benefits; for instance, antihypertensives, beta-blockers, and statins should generally be continued to avoid rebound effects or cardiovascular events.[52][68] Anticoagulants like warfarin are typically held 5 days preoperatively to allow normalization of INR, with bridging therapy using unfractionated heparin considered for patients at high risk of thrombosis, such as those with mechanical heart valves.[52]Specific adjustments are tailored to medication type and patient factors. Antiplatelet agents, such as aspirin, should be continued in patients with recent cardiac stents or high ischemic risk when bleeding risk is low, but P2Y12 inhibitors like clopidogrel may be discontinued 5-7 days prior for procedures with significant bleeding potential.[52] Herbal supplements pose unique risks and should be discontinued 7-14 days preoperatively; for example, ginseng increases bleeding risk through antiplatelet effects and potential interactions with anticoagulants.[69] For diabetic patients on insulin, the long-acting basal dose is reduced by 20-25% (to 75-80% of usual) the evening before and morning of surgery to prevent hypoglycemia, with frequent glucose monitoring and short-acting insulin adjustments as needed intraoperatively.[70]Guidelines from the American College of Cardiology/American Heart Association (ACC/AHA 2024) provide patient-specific recommendations, advocating continuation of guideline-directed medical therapy for cardiovascular drugs while individualizing holds for renin-angiotensin-aldosterone system inhibitors (e.g., ACE inhibitors or ARBs) on the day of surgery to mitigate intraoperative hypotension, particularly in high-risk cases.[52] The Society for Perioperative Assessment and Quality Improvement (SPAQI) consensus similarly supports holding ACE inhibitors and ARBs 24 hours preoperatively but continuing beta-blockers and statins perioperatively.[68] Antibiotic prophylaxis for the prevention of infective endocarditis is recommended only for high-risk patients undergoing specific dental procedures involving manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa, per current American Heart Association/American College of Cardiology (AHA/ACC) guidelines. For surgical procedures, antibiotic prophylaxis is selectively administered to prevent surgical site infections based on procedure-specific guidelines from organizations such as the Centers for Disease Control and Prevention (CDC) or the Surgical Care Improvement Project (SCIP).[71][72]Potential risks include intraoperative hypotension from unadjusted beta-blockers or ACE inhibitors/ARBs, which can exacerbate hemodynamic instability, and hyperglycemia in patients on chronic steroids due to surgical stress impairing glycemic control.[52][68] In patients with a history of drug allergies, medication reconciliation must prioritize avoidance of cross-reactive agents to prevent anaphylaxis under anesthesia.
Fasting and NPO Guidelines
Preoperative fasting, also known as being nil per os (NPO), is a standard protocol designed to reduce the risk of pulmonary aspiration of gastric contents during anesthesia induction by ensuring adequate gastric emptying. The primary rationale stems from the variable times required for different food and liquid types to empty from the stomach: clear liquids typically empty within 1-2 hours, breast milk in about 4 hours, nonhuman milk or light meals in 6 hours, and heavy or fatty meals in 8 hours or more. Compliance with these guidelines has been associated with a very low incidence of aspiration, estimated at less than 0.01% in elective procedures among adults and children. However, factors such as obesity and diabetes can delay gastric emptying, potentially prolonging the residual risk even with adherence.[73]The American Society of Anesthesiologists (ASA) provides evidence-based recommendations, originally published in 2017 and affirmed with modular updates in 2023, which form the cornerstone of these protocols in most healthcare settings. Patients may consume clear liquids (e.g., water, black coffee, or clear fruit juices without pulp) up to 2 hours before elective surgery; breast milk up to 4 hours; infant formula, nonhuman milk, or a light meal (e.g., toast and clear liquids) up to 6 hours; and fried, fatty foods, or a heavy meal up to 8 hours. These durations apply to healthy patients undergoing elective procedures, with the goal of balancing aspiration prevention against the risks of dehydration, hypoglycemia, and patient discomfort from prolonged fasting.Exceptions to standard NPO guidelines are necessary in certain populations to tailor care while maintaining safety. For patients with diabetes, modified schedules may be required due to potential gastroparesis, which delays gastric emptying; however, recent evidence suggests that standard fasting times are generally sufficient for most, with individualized assessment recommended. In emergency cases, where fasting history is unavailable or inadequate, rapid-sequence induction with cricoid pressure is employed to mitigate aspiration risk without enforcing strict NPO.Within enhanced recovery after surgery (ERAS) protocols, which have gained widespread adoption by 2025, preoperative carbohydrate-rich clear drinks (e.g., 400 mL containing 50 g of complex carbohydrates) are permitted up to 2 hours before surgery in select elective cases. This practice attenuates the catabolic response to fasting, reducing postoperative insulin resistance and improving outcomes such as earlier mobilization and shorter hospital stays, without increasing aspiration risk in low-risk patients. ERAS guidelines emphasize this approach particularly for major abdominal or orthopedic procedures to optimize metabolic status.[74]
Intravenous Access
Intravenous access is a critical preparatory step in preanesthetic assessment to facilitate the safe administration of anesthetic agents, fluids, and medications during the perioperative period.[75] Site selection typically prioritizes peripheral veins in the forearm or antecubital fossa, such as the cephalic, basilic, or median cubital veins, due to their accessibility, lower risk of complications, and preservation of veins for potential surgical needs.[76][77] For adults, catheter gauges of 18-20 are commonly selected to balance flow rates sufficient for rapid fluidresuscitation—up to 100-200 mL/min—with patient comfort and vein patency, particularly in elective procedures where high-volume needs are anticipated.[78][79][75]Establishment of intravenous access often occurs in the preoperative holding area following the initial assessment, allowing time for vein evaluation integrated with the physical examination.[80] Patency is verified by aspirating blood and flushing with 5-10 mL of saline to ensure unobstructed flow before induction.[75] In cases of difficult intravenous access (DIVA), which affects approximately 20-30% of adult patients due to factors like obesity or chronic illness, ultrasound guidance is employed to visualize superficial veins and improve first-attempt success rates from under 50% to over 80%.[81][82] By 2025, near-infrared vein finders have become standard in many anesthesia centers for enhancing vein visualization in DIVA scenarios, projecting subsurface vascular patterns to reduce insertion attempts and procedural time.[83][84]For obese patients, where subcutaneous fat obscures peripheral veins and increases DIVA risk, initial attempts favor longer catheters (1.1-1.9 inches) at alternative sites like the cephalic vein in the deltopectoral groove; if multiple failures occur, escalation to larger-bore peripheral lines or central venous access may be necessary to ensure reliable delivery.[85][86] This approach supports rapid response to intraoperative hypotension by enabling swift volume and vasopressor administration.[75] Common complications include infiltration, occurring in up to 18% of peripheral insertions due to dislodgement or veinperforation, and phlebitis in about 10% of cases from mechanical irritation or infusate properties, both of which can delay care if not monitored.[87][88] Prophylactic measures, such as securement devices and site rotation every 72-96 hours, mitigate these risks in the perioperative setting.[89]
Informed Consent
Elements of Consent
Informed consent for anesthesia requires disclosure of essential information to enable patients to make autonomous decisions about their care. This process encompasses the nature and purpose of the anesthesia, its anticipated benefits such as pain relief and facilitation of surgery, potential risks, and available alternatives. The American Society of Anesthesiologists emphasizes that anesthesiologists should participate in this informed decision-making to ensure patients understand the proposed plan.[90][91]Key disclosures include common risks, which occur in a substantial proportion of cases, such as postoperative nausea and vomiting affecting 20-30% of patients undergoing general anesthesia. Serious but rarer complications must also be addressed, including intraoperative awareness in less than 0.2% of cases and anesthesia-related mortality at approximately 1 per 100,000 procedures. Alternatives, such as regional anesthesia versus general anesthesia, are discussed to highlight differences in risks and benefits, tailored to the patient's specific profile—for instance, emphasizing potential airway challenges for those with a Mallampati class III airway identified during assessment. Benefits are framed to include not only procedural safety but also enhanced recovery and pain management options.[92][93][94][91]The consent process typically involves a verbal discussion by the anesthesiologist, supplemented by a written form that the patient signs after questions about recovery expectations and postoperative pain control are addressed. This interactive dialogue promotes comprehension, often using techniques like teach-back to confirm understanding. In recent years, digital tools incorporating videos and multimedia have enhanced patient comprehension, particularly for complex information on risks and alternatives. As of 2025, systematic reviews highlight that AI-assisted and multimedia digital tools consistently improve comprehension and documentation quality, especially in diverse settings.[91][95]Legal standards mandate assessing the patient's decision-making capacity, defined as the ability to understand the information, appreciate its consequences, reason through options, and communicate a choice. If capacity is impaired, consent is obtained from a surrogate decision-maker, such as a legally authorized representative, following established ethical guidelines.[91][96]
Documentation and Legal Aspects
The preanesthetic assessment must be thoroughly documented in the patient's medical record to ensure continuity of care, facilitate communication among providers, and support quality improvement initiatives. Essential components of the preoperative note include a detailed medical history, physical examination findings, review of pertinent test results, formulation of an anesthetic risk plan, and confirmation of informed consent with the patient's signature. These elements align with the American Society of Anesthesiologists (ASA) Basic Standards for Preanesthesia Care, which emphasize discussing prior anesthetic experiences, current medical therapy, and relevant physical conditions to guide perioperative management. Standardized forms, such as ASA-recommended checklists, promote consistency and completeness in recording these details, reducing variability in practice.[6][6][1]Legal considerations in preanesthetic documentation center on protecting patient privacy and mitigating liability risks. Compliance with the Health Insurance Portability and Accountability Act (HIPAA) is mandatory, requiring safeguards for protected health information (PHI) in anesthesia records, including secure storage, limited access, and regular security risk analyses to prevent unauthorized disclosures. Omissions in documentation, such as failure to record a known drug allergy, can lead to adverse events like allergic reactions and expose providers to malpractice liability if harm results from inadequate preoperative evaluation. The ASA Statement on Documentation of Anesthesia Care underscores that records must meet all regulatory and legal requirements to defend against claims, particularly in cases involving preoperative decision-making.[97][98][99][100]In contemporary practice as of 2025, electronic signatures are valid for preanesthetic records and consent forms under HIPAA, provided systems ensure signer authenticity through mechanisms like audit trails and encryption. Medical records from preanesthetic assessments, including anesthesia care documentation, should be retained for 7 to 10 years post-discharge to comply with federal and state regulations, such as those from the Centers for Medicare & Medicaid Services (CMS), which mandate 10 years for Medicare-related records. A re-evaluation note, confirming the patient's status and any interval changes, must be documented immediately before anesthetic induction to address evolving risks.[101][102][103][6]Best practices for preanesthetic documentation include incorporating timestamps on all entries to track the sequence of events and enable accurate reconstruction during reviews or audits. Multidisciplinary sign-offs, involving anesthesiologists, surgeons, and other relevant specialists, enhance accountability and integration of input into the risk plan. Clinical audits of documentation compliance have demonstrated that standardized processes and regular reviews significantly reduce documentation errors and improve patient safety outcomes.[104][105][106][107]
Special Considerations
High-Risk Populations
Preanesthetic assessment for high-risk populations requires tailored approaches to account for physiological vulnerabilities and optimize outcomes. In pediatrics, the evaluation emphasizes age-specific considerations to mitigate anxiety and anatomical challenges, while in geriatrics, it focuses on frailty and cognitive risks. Patients with multiple comorbidities demand targeted screenings for conditions like obesity, end-stage renal disease, and pregnancy, with emerging integrations of social determinants of health (SDOH) and telehealth enhancing accessibility as of 2025.For pediatric patients, the preanesthetic assessment prioritizes developmental stage, parental involvement in history-taking, and airway evaluation due to anatomical features such as a relatively larger tongue and smaller mouth, which increase the risk of obstruction. Dosing adjustments are calculated based on weight and age to avoid overdose, with developmental history informing risk stratification. Fasting guidelines are modified for safety: clear liquids are permitted up to 2 hours preoperatively, breast milk up to 4 hours, and solids up to 6 hours, reducing dehydration risks in infants compared to adults.[28][108]In geriatric patients, frailty assessment using the Fried criteria—encompassing unintentional weight loss, self-reported exhaustion, weakness (grip strength), slow walking speed, and low physical activity—is integral to identify vulnerability, with scores of 3 or more indicating frailty and higher postoperative complication risks. Polypharmacy review is essential, as older adults often take multiple medications that interact with anesthetics, necessitating adjustments or holds. Cognitive screening, such as the Mini-Mental State Examination, evaluates baseline function to predict postoperative delirium, which occurs in 20-50% of elderly surgical patients due to factors like inflammation and medication effects. These elements align with ASA physical status adjustments for age-related declines.[109]Assessments for patients with comorbidities are customized to address organ-specific challenges. In obesity, screening for obstructive sleep apnea (OSA) using the STOP-Bang questionnaire (scoring ≥3 indicates high risk) guides preoperative continuous positive airway pressure (CPAP) initiation to prevent desaturation. For end-stage renal disease, dialysis timing is critical: elective procedures should follow dialysis within 24 hours to minimize fluid overload and electrolyte imbalances, with intervals longer than 48 hours associated with elevated 90-day mortality. In pregnancy, particularly beyond 20 weeks, fetal monitoring via non-stress tests or biophysical profiles assesses viability and uteroplacental perfusion, with intraoperative electronic fetal heart rate monitoring recommended if feasible to detect hypoxia early.[110][111][112]As of 2025, preanesthetic evaluations increasingly incorporate SDOH, such as assessing frailty exacerbated by low income and limited social support in elderly patients, which correlates with higher perioperative disparities and requires advocacy for equitable resource allocation. Telehealth platforms enable remote assessments for homebound individuals, facilitating history review and virtual examinations with high patient satisfaction (over 90% in select cohorts) while maintaining safety through follow-up protocols.[24][113]
Role of Anesthesia Trainees
In the hierarchy of anesthesia training, medical students typically observe or assist with patient interviews during preanesthetic assessments, gaining foundational exposure under direct faculty oversight, while residents perform the core components of history-taking and physical examinations with graded supervision that progresses from direct to indirect as competency develops.[114] Fellows, as advanced trainees, manage more complex cases involving multifaceted risk profiles, such as those with comorbidities, but all levels of trainees operate under the ultimate oversight of an attending anesthesiologist who ensures patient safety and finalizes the assessment.[114] This structured progression aligns with Accreditation Council for Graduate Medical Education (ACGME) requirements, emphasizing competence in preoperative evaluation through rotations dedicated to preanesthetic medicine.[114]Trainees contribute significantly to the preanesthetic process by conducting histories, performing targeted examinations, and identifying potential risks, yet final decisions on optimization, anesthetic planning, and informed consent remain the responsibility of the attending faculty, who review and approve all findings.[115] For consent, attending involvement is mandatory to discuss risks, benefits, and alternatives, with trainees supporting but not independently obtaining it, ensuring ethical and legal compliance.[91]The educational value of trainee participation in preanesthetic assessments lies in developing critical skills in risk stratification, patient communication, and interdisciplinary coordination, fostering future independence as anesthesiologists.[116] Studies indicate that supervised trainee involvement does not elevate perioperative complications, with error rates in anesthesia care remaining below 1%, such as medication errors at 0.49% under oversight, comparable to outcomes achieved by fully trained providers.[117][118]As of 2025, training incorporates virtual reality simulations to enhance preanesthetic skills, allowing safe practice of assessment scenarios without patient risk, as evidenced by improved technical proficiency in airway and procedural evaluations.[119] Ethically, disclosure of the trainee's role to patients during consent is emphasized, with guidelines requiring transparency about supervision levels; surveys suggest this practice is mandated in a majority of U.S. programs to uphold informed consent principles.[90][91]
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