Medical School · Year 3 · General Surgery · includes a quiz and discussion video

Seminar 01: Preoperative Evaluation

Year 3: General Surgery Clerkship

Learning Objectives

By the end of this seminar, students will be able to:

1. Describe the components of a comprehensive preoperative evaluation
2. Assess surgical risk using validated tools
3. Identify patients requiring additional cardiac workup
4. Optimize medical conditions before surgery
5. Apply informed consent principles
6. Describe preoperative testing guidelines

Seminar Outline

I. Goals of Preoperative Evaluation

The primary objectives of preoperative evaluation encompass a systematic approach to estimating surgical risk and identifying opportunities for patient optimization before the planned procedure. Risk assessment involves a comprehensive evaluation of the patient's baseline health status, comorbidities, and the specific demands of the proposed surgery to estimate the likelihood of perioperative complications including cardiac events, pulmonary complications, and mortality. This process enables the surgical team to anticipate potential problems and implement preventive strategies that may significantly reduce morbidity and mortality. The preoperative evaluation serves as the foundation for informed surgical decision-making and allows the healthcare team to determine whether the benefits of surgery outweigh the risks for each individual patient.

Patient optimization represents a critical component where modifiable risk factors are identified and addressed before proceeding with elective surgery. This may include improving glycemic control in diabetic patients, treating anemia, optimizing cardiac medications, addressing nutritional deficiencies, or implementing smoking cessation programs. The timing of optimization efforts depends on the urgency of the procedure and the specific conditions being addressed, with some interventions requiring weeks of preparation while others can be accomplished in days. Optimization strategies are tailored to individual patient needs and the specific physiologic demands of the planned surgical procedure.

Preoperative planning involves preparing for potential complications by ensuring appropriate resources, personnel, and contingency plans are in place before the day of surgery. This includes decisions about the surgical approach, anesthetic technique, level of postoperative monitoring required, and need for intensive care unit admission. Effective planning requires clear communication between all members of the perioperative team including surgeons, anesthesiologists, internists, and nursing staff. Documentation of the preoperative evaluation must be thorough and accessible to all team members involved in the patient's care.

Informed consent represents both an ethical and legal requirement ensuring patients understand their diagnosis, the proposed procedure, expected benefits, potential risks and complications, and alternative treatment options including non-surgical management. The consent process should include adequate time for patients to ask questions and should verify that patients have decision-making capacity. Special considerations apply in emergency situations, for minors, and for patients who lack capacity to make their own medical decisions. Proper documentation of the informed consent discussion protects both patients and healthcare providers.

<image>Panel A: A flowchart diagram showing the sequential steps of preoperative evaluation including history, physical examination, risk stratification, and optimization pathways with decision nodes. Panel B: A surgeon and patient seated in consultation room with informed consent documents visible, demonstrating the shared decision-making process. Panel C: A multidisciplinary team meeting with surgeon, anesthesiologist, internist, and nursing staff reviewing a patient's preoperative assessment on a display screen. Panel D: A timeline graphic showing optimal preoperative evaluation timing for different surgery types including elective major surgery at one to two weeks before, elective minor surgery on day of surgery, and emergency surgery with abbreviated evaluation.</image>

II. History and Physical Examination

The medical history component of preoperative evaluation requires systematic inquiry into all organ systems with particular attention to conditions that increase perioperative risk. Cardiac history must document prior myocardial infarction, congestive heart failure, angina patterns, arrhythmias, valvular disease, and prior cardiac interventions including stents or bypass surgery. Pulmonary conditions including chronic obstructive pulmonary disease, asthma, sleep apnea, and history of pulmonary embolism significantly impact anesthetic management and postoperative care. Hepatic and renal dysfunction alter drug metabolism and clearance, affect coagulation, and increase the complexity of perioperative fluid management.

Surgical history provides crucial information about previous anesthetic experiences, including any history of difficult intubation, adverse reactions to anesthesia, or personal or family history of malignant hyperthermia. Prior surgical procedures inform the surgeon about potential adhesions, altered anatomy, and previous complications that may affect the current surgical plan. Documentation of complications from prior surgeries such as wound infections, venous thromboembolism, or prolonged ileus helps identify patients at increased risk for similar problems. A complete surgical history also reveals any prosthetic devices, implants, or grafts that may require antibiotic prophylaxis or special considerations.

Medication review must include all prescription medications, over-the-counter drugs, and herbal supplements with attention to those requiring perioperative adjustment. Anticoagulants and antiplatelet agents require careful management with timing of discontinuation based on the specific agent, indication for therapy, and bleeding risk of the procedure. Antihypertensive medications including beta-blockers and statins should generally be continued while ACE inhibitors and diuretics are often held on the morning of surgery. Herbal supplements including garlic, ginkgo, ginseng, and St. John's wort may affect bleeding, sedation, or drug metabolism and should be discontinued one to two weeks before surgery.

Physical examination focuses on systems most relevant to perioperative risk with particular attention to airway assessment, cardiovascular status, and pulmonary function. Airway evaluation using Mallampati classification, assessment of neck mobility, thyromental distance, and dentition helps predict difficult intubation and guides anesthetic planning. Cardiovascular examination should document murmurs that may indicate valvular disease, signs of heart failure including jugular venous distension and peripheral edema, and evidence of vascular disease. Functional status assessment provides one of the most valuable prognostic indicators with patients unable to climb two flights of stairs or walk two blocks being at significantly increased cardiac risk.

<image>Panel A: A systematic diagram showing key elements of preoperative history taking organized by organ system with cardiac, pulmonary, hepatic, renal, hematologic, endocrine, and neurologic categories displayed. Panel B: An anatomical illustration demonstrating Mallampati airway classification grades one through four with progressively obscured visualization of oropharyngeal structures. Panel C: A physical examination scene showing auscultation of cardiac sounds with labels indicating assessment for murmurs, S3 gallop, and irregular rhythms. Panel D: A functional capacity assessment scale showing metabolic equivalent levels from one MET representing self-care activities to greater than ten METs representing strenuous athletic activity.</image>

III. Cardiovascular Risk Assessment

Active cardiac conditions represent circumstances requiring evaluation and treatment before proceeding with elective noncardiac surgery due to the significantly elevated perioperative risk they confer. Unstable coronary syndromes including unstable angina and recent myocardial infarction within sixty days require cardiology consultation and may necessitate delay of elective procedures until stabilization. Decompensated heart failure manifested by new onset or worsening symptoms must be optimized before surgery as these patients face substantially increased perioperative mortality. Significant arrhythmias including high-grade atrioventricular block, symptomatic ventricular arrhythmias, and supraventricular arrhythmias with uncontrolled rate require treatment before proceeding with surgery.

The Revised Cardiac Risk Index represents the most widely validated tool for predicting major adverse cardiac events following noncardiac surgery and assigns one point each for six independent risk factors. These factors include high-risk surgery such as intrathoracic, intraabdominal, or suprainguinal vascular procedures, history of ischemic heart disease, history of congestive heart failure, history of cerebrovascular disease, insulin-dependent diabetes mellitus, and preoperative serum creatinine greater than two milligrams per deciliter. Patients with zero risk factors have an estimated major cardiac event rate of approximately 0.4 percent while those with three or more factors face risks exceeding five percent. The RCRI helps guide decisions about the need for additional cardiac testing and perioperative monitoring level.

Functional capacity assessment using metabolic equivalents provides crucial information about a patient's ability to meet the physiologic demands of surgery. One to four METs represents the ability to perform basic self-care activities such as eating, dressing, and walking indoors, indicating limited functional capacity. Four to seven METs corresponds to climbing one to two flights of stairs, walking up a hill, or performing light housework and generally indicates adequate capacity for most surgical procedures. Patients able to achieve greater than seven METs through activities such as strenuous sports or heavy labor have excellent functional capacity and generally require no additional cardiac testing regardless of other risk factors.

The stepwise approach to cardiac evaluation begins with determining surgical urgency since emergency procedures proceed with risk reduction strategies rather than delayed evaluation. For elective surgery, the presence of active cardiac conditions triggers evaluation and treatment before proceeding. Low-risk procedures such as superficial surgery and ophthalmologic procedures may proceed without additional testing in most patients. For intermediate and high-risk surgery in patients with poor functional capacity and clinical risk factors, the decision to pursue additional cardiac testing depends on whether the results will change management and should involve shared decision-making between the surgical and medical teams.

<image>Panel A: A table display of the Revised Cardiac Risk Index showing the six independent predictors with checkboxes and corresponding risk percentages for zero, one, two, and three or more risk factors. Panel B: A graphic representation of metabolic equivalent activities ranging from resting at one MET through walking at three METs, climbing stairs at four to five METs, to vigorous exercise at greater than seven METs. Panel C: A clinical decision algorithm flowchart for perioperative cardiac evaluation starting with emergency surgery determination and proceeding through active cardiac conditions, surgery risk level, and functional capacity assessment. Panel D: An echocardiogram image panel demonstrating evaluation of left ventricular function and valvular assessment relevant to preoperative cardiac risk stratification.</image>

IV. Pulmonary Risk Assessment

Patient-related risk factors for postoperative pulmonary complications include advanced age greater than sixty years, chronic obstructive pulmonary disease, current smoking status, and American Society of Anesthesiologists physical status classification of two or higher. Congestive heart failure represents one of the strongest predictors of pulmonary complications even exceeding chronic lung disease in some studies. Functional dependence, defined as requiring assistance with activities of daily living, significantly increases pulmonary complication risk independent of specific diagnoses. Obesity alone confers modest increased risk primarily related to restrictive physiology and increased work of breathing, while the presence of obesity hypoventilation syndrome substantially elevates risk.

Surgery-related factors substantially influence pulmonary risk with upper abdominal and intrathoracic procedures carrying the highest rates of postoperative pulmonary complications. Prolonged surgery exceeding three hours, emergency procedures, and general anesthesia compared to regional anesthesia all increase pulmonary complication rates. The proximity of the surgical site to the diaphragm correlates with the degree of postoperative pulmonary dysfunction, explaining why upper abdominal procedures carry higher risk than pelvic or extremity surgery. Laparoscopic approaches may reduce pulmonary complications compared to open surgery for equivalent procedures though the benefit varies by specific operation.

Optimization of patients with chronic obstructive pulmonary disease or asthma involves ensuring that maintenance inhaler therapy is continued through the day of surgery and that acute exacerbations are treated before elective procedures. Patients with active respiratory infections should have elective surgery postponed until resolution of symptoms. Smoking cessation provides benefit at any time before surgery though eight weeks of abstinence allows for recovery of mucociliary function and reduces perioperative complication rates by approximately thirty percent. Preoperative pulmonary rehabilitation programs may benefit patients with severe COPD undergoing major thoracic or abdominal procedures.

Obstructive sleep apnea screening using tools such as the STOP-BANG questionnaire identifies patients at increased risk for perioperative airway and opioid-related complications. Patients with known or suspected sleep apnea should be instructed to bring their continuous positive airway pressure device to the hospital and have it available in the recovery area. Postoperative management of sleep apnea patients requires heightened vigilance for airway obstruction and may require continuous pulse oximetry, judicious use of opioids, and preference for regional anesthesia or multimodal analgesia when feasible. Routine preoperative pulmonary function testing is not indicated for most patients and should be reserved for those undergoing lung resection or those with unexplained dyspnea.

<image>Panel A: A risk factor diagram showing patient and procedure-related factors contributing to postoperative pulmonary complications with relative risk magnitudes indicated by arrow thickness. Panel B: An anatomical illustration showing the relationship between surgical site location and postoperative pulmonary dysfunction with upper abdominal incisions highlighted. Panel C: The STOP-BANG questionnaire screening tool displayed with scoring criteria for identifying patients at risk for obstructive sleep apnea. Panel D: A preoperative chest radiograph demonstrating COPD findings with hyperinflation and flattened diaphragms alongside a normal comparison image.</image>

V. Preoperative Laboratory Testing

The evidence-based approach to preoperative testing has shifted away from routine comprehensive panels toward selective testing based on individual patient factors, medication use, and procedure-specific requirements. Multiple studies have demonstrated that routine testing in healthy patients undergoing low-risk procedures rarely yields clinically significant abnormalities and may lead to unnecessary delays, additional testing, and patient anxiety. Testing should be ordered when results will influence perioperative management or when there is clinical suspicion of an undiagnosed condition based on history and physical examination. Recent laboratory results from within the past three to six months may be utilized if the patient's clinical status has been stable.

Complete blood count is indicated for patients undergoing procedures with expected significant blood loss, those with symptoms or signs suggestive of anemia, patients with hematologic disorders, and those receiving chemotherapy or other myelosuppressive medications. Basic metabolic panel is appropriate for patients with renal disease, diabetes, those taking diuretics, ACE inhibitors, angiotensin receptor blockers, or other medications affecting electrolytes. Coagulation studies including prothrombin time and partial thromboplastin time are indicated for patients on anticoagulation therapy, those with liver disease, known bleeding disorders, or personal or family history of abnormal bleeding. Liver function tests should be obtained for patients with known hepatic disease or those taking hepatotoxic medications.

Electrocardiogram recommendations have evolved with current guidelines suggesting ECG for patients with known cardiovascular disease, significant arrhythmia, or structural heart disease undergoing intermediate or high-risk surgery. Patients with multiple cardiac risk factors and limited functional capacity undergoing elevated risk procedures may benefit from preoperative ECG for baseline comparison should perioperative events occur. Routine ECG based solely on age without other indications is no longer recommended by most guidelines. The presence of significant new findings on preoperative ECG should prompt further evaluation before elective surgery.

Blood typing and screening or crossmatching should be performed when significant blood loss is anticipated or when the patient has had previous transfusion or pregnancy. Institutional protocols often dictate type and screen versus crossmatch requirements for specific procedures based on historical transfusion rates. Pregnancy testing should be performed for all women of childbearing potential due to the implications for anesthetic management, medication choices, and surgical timing. Urinalysis is not routinely indicated but may be appropriate before urologic procedures or when urinary tract infection is suspected.

<image>Panel A: A decision matrix showing which preoperative laboratory tests are indicated based on patient conditions and procedure risk categories with check marks indicating appropriate testing. Panel B: An electrocardiogram strip demonstrating significant preoperative findings requiring further evaluation including ST segment changes and arrhythmias. Panel C: A flowchart for pregnancy testing protocol in preoperative patients with decision points for patient age, contraceptive status, and surgical urgency. Panel D: A comparative display contrasting evidence-based selective testing approach with traditional routine testing panels showing reduction in unnecessary tests.</image>

VI. Special Populations

Elderly patients require particular attention to frailty assessment, cognitive screening, and careful medication reconciliation given the strong association between frailty and adverse surgical outcomes. Frailty represents a state of decreased physiologic reserve and increased vulnerability to stressors that can be assessed using validated tools such as the Clinical Frailty Scale or the Fried frailty phenotype. Preoperative cognitive screening establishes baseline function for comparison in detecting postoperative delirium, which occurs in fifteen to fifty percent of elderly surgical patients. Goals of care discussions should occur preoperatively in elderly patients undergoing major surgery to clarify treatment preferences and establish advance directives.

Obese patients present challenges including difficult airway management, altered drug pharmacokinetics, and increased risk for wound complications and venous thromboembolism. Preoperative evaluation should include screening for obesity hypoventilation syndrome and obstructive sleep apnea, both of which significantly impact perioperative management. Enhanced venous thromboembolism prophylaxis is required with weight-based dosing of pharmacologic agents and extended duration prophylaxis for major procedures. Operating room planning must account for specialized equipment including appropriately rated operating tables, longer instruments, and specialized positioning devices.

Cirrhotic patients face substantially elevated perioperative risk with mortality stratified by Child-Pugh classification, ranging from approximately two percent for Class A to over fifty percent for Class C patients. The Model for End-Stage Liver Disease score provides additional prognostic information and helps identify patients at prohibitively high surgical risk. Coagulopathy in cirrhotic patients is complex and may not be accurately reflected by standard laboratory values, requiring individualized management often with guidance from hepatology consultation. Ascites management, portal hypertensive bleeding risk, and hepatorenal syndrome represent additional considerations in surgical planning for these patients.

Pregnant patients require careful coordination between surgical, anesthesia, and obstetric teams with attention to fetal well-being while ensuring maternal safety remains the primary priority. The second trimester represents the optimal timing for elective surgery when organogenesis is complete and the risk of preterm labor is lower than in the third trimester. Positioning considerations including left lateral tilt to prevent inferior vena cava compression are essential after twenty weeks of gestation. Fetal monitoring before and after surgery should be performed when fetal viability has been reached, typically around twenty-four weeks, with immediate obstetric support available.

<image>Panel A: The Clinical Frailty Scale displayed as a visual gradient from one representing very fit to nine representing terminally ill with descriptions and corresponding perioperative risk levels for each category. Panel B: An operating room setup for bariatric surgery showing specialized equipment including reinforced table, longer instruments, and appropriate positioning devices. Panel C: The Child-Pugh classification system displayed as a scoring table with parameters including bilirubin, albumin, INR, ascites, and encephalopathy grade. Panel D: A pregnant patient positioned for surgery with left lateral tilt demonstrated and fetal monitoring equipment visible.</image>

VII. Informed Consent

The elements of informed consent establish the legal and ethical framework for patient authorization of surgical procedures and include diagnosis, proposed procedure, risks, benefits, alternatives, and opportunity for questions. The diagnosis or condition requiring treatment should be explained in terms the patient can understand, establishing the medical necessity for the proposed intervention. The procedure description should include what will be done, the surgical approach, expected duration, and type of anesthesia without requiring the patient to comprehend technical surgical details. Both common complications and rare but serious risks should be disclosed, with the standard generally requiring disclosure of information that a reasonable patient would want to know.

Capacity assessment evaluates a patient's ability to make informed medical decisions through four components including understanding, appreciation, reasoning, and expression of choice. Understanding requires that the patient can comprehend the information being provided about their condition and the proposed treatment. Appreciation involves the ability to apply this information to their own situation and recognize the consequences of their decision. Reasoning ability means the patient can weigh the options and consider how the decision aligns with their values and goals, while expression of choice simply requires the ability to communicate a decision.

Special circumstances modify the standard informed consent process and include emergency situations, minors, and patients lacking decision-making capacity. In emergencies when the patient cannot provide consent and no surrogate is immediately available, implied consent allows treatment necessary to prevent death or serious harm. For minors, consent is generally provided by parents or legal guardians, though emancipated minors and mature minor doctrines may allow self-consent in certain jurisdictions. When patients lack capacity, consent must be obtained from a legally authorized surrogate such as a healthcare proxy, durable power of attorney for healthcare, or next of kin according to jurisdictional hierarchy.

Documentation of informed consent includes a signed consent form that specifies the procedure, the operating surgeon, and acknowledgment that risks, benefits, and alternatives were discussed. The consent form itself does not constitute informed consent but rather documents that the process occurred. A progress note should detail the specific discussion including patient questions and the information provided in response. For high-risk procedures or complex situations, having a witness present during the consent discussion provides additional documentation and may be institutionally required.

<image>Panel A: A visual representation of the six essential elements of informed consent displayed as interconnected components forming a complete consent process. Panel B: A physician and patient interaction demonstrating the consent discussion with the patient asking questions and the physician providing explanations with visual aids. Panel C: A flowchart showing surrogate decision-maker hierarchy when patient lacks capacity including healthcare proxy, spouse, adult children, parents, and siblings in descending order of priority. Panel D: A sample consent form document with key sections highlighted including procedure description, surgeon identification, risk acknowledgment, and signature areas.</image>

VIII. Medication Management

Medications that should be continued perioperatively include beta-blockers, which if stopped abruptly may cause rebound tachycardia and hypertension increasing cardiac risk, particularly in patients taking these medications for coronary artery disease or heart failure. Statins provide cardioprotective effects beyond lipid lowering and should be continued, with evidence suggesting that perioperative statin therapy reduces cardiac complications in vascular surgery patients. Anticonvulsant medications must be continued to prevent seizures, with parenteral formulations available for patients who cannot take oral medications. Thyroid hormone replacement should continue without interruption, and most antihypertensive medications including calcium channel blockers should be maintained.

Medications requiring discontinuation or modification include warfarin, which typically should be stopped five days before surgery to allow INR to normalize, with bridging anticoagulation using heparin products considered for patients at high thrombotic risk. Direct oral anticoagulants should be held for twenty-four to seventy-two hours depending on the specific agent and patient renal function. Antiplatelet therapy management requires balancing bleeding risk against thrombotic risk, with aspirin often continued for patients with coronary stents while P2Y12 inhibitors such as clopidogrel are typically held for five to seven days. ACE inhibitors and angiotensin receptor blockers are usually held on the morning of surgery due to increased risk of intraoperative hypotension.

Patients on chronic corticosteroid therapy may require supplemental perioperative steroid coverage due to hypothalamic-pituitary-adrenal axis suppression, which can occur with prednisone doses as low as five milligrams daily for three or more weeks. Stress-dose steroid requirements are based on the magnitude of surgical stress, with minor procedures typically requiring only the usual daily dose while major surgery may require hydrocortisone one hundred milligrams intravenously followed by tapered dosing over twenty-four to seventy-two hours. The traditional practice of empiric stress-dose steroids for all patients on chronic steroids has been questioned, with some advocating for continuation of usual doses unless signs of adrenal insufficiency develop.

Herbal supplements and over-the-counter medications pose often-underappreciated perioperative risks including bleeding, cardiovascular effects, and drug interactions. Garlic, ginkgo biloba, and vitamin E may increase bleeding risk and should be discontinued at least one week before surgery. Ginseng can cause hypoglycemia and may potentiate the effects of antiplatelet agents. Kava and valerian have sedative properties that may interact with anesthetic agents. St. John's wort induces cytochrome P450 enzymes and can affect metabolism of numerous medications including some anesthetics. Patients should be specifically asked about supplement use as they may not volunteer this information.

<image>Panel A: A medication management chart showing perioperative recommendations for major drug classes divided into continue, hold, and modify categories with specific timing guidelines. Panel B: A warfarin bridging protocol diagram showing the timeline for discontinuation, initiation of bridging anticoagulation, and resumption after surgery. Panel C: A table displaying stress-dose steroid regimens stratified by surgical magnitude from minor to major procedures with specific hydrocortisone dosing. Panel D: Common herbal supplements displayed with their associated perioperative concerns including garlic, ginkgo, ginseng, kava, and St. John's wort with recommended discontinuation timing.</image>

IX. VTE Prevention Planning

Venous thromboembolism risk assessment should occur for all surgical patients using validated tools such as the Caprini score, which incorporates patient-related factors, procedure-related factors, and additional risk factors to stratify patients into risk categories. Patient factors conferring increased risk include prior VTE, active malignancy, known thrombophilia, advanced age, obesity, and immobility. Procedure factors include prolonged surgery greater than forty-five minutes, pelvic or lower extremity surgery, and procedures requiring postoperative immobilization. The Caprini score assigns weighted points to each factor, with total scores guiding prophylaxis intensity from early ambulation alone for very low-risk patients to combination pharmacologic and mechanical prophylaxis for high-risk patients.

Prophylaxis options include mechanical methods such as graduated compression stockings and intermittent pneumatic compression devices, which are indicated for essentially all surgical patients unless contraindicated by lower extremity conditions. Mechanical prophylaxis is particularly important in patients with contraindications to pharmacologic therapy and should be initiated before induction of anesthesia and continued until the patient is fully ambulatory. Early and frequent ambulation represents the simplest and most physiologic form of thromboprophylaxis and should be encouraged for all surgical patients. Mechanical methods may be used as sole prophylaxis in very low-risk patients or in combination with pharmacologic agents for higher-risk patients.

Pharmacologic prophylaxis with low-molecular-weight heparin, unfractionated heparin, or fondaparinux is indicated for patients at moderate to high VTE risk when bleeding risk permits. Low-molecular-weight heparin such as enoxaparin is preferred for most patients due to more predictable pharmacokinetics and lower rates of heparin-induced thrombocytopenia compared to unfractionated heparin. Unfractionated heparin may be preferred in patients with renal insufficiency or when rapid reversibility is desired. Timing of initiation varies with some protocols starting twelve hours before surgery and others beginning postoperatively once adequate hemostasis is achieved. Direct oral anticoagulants are approved for thromboprophylaxis after hip and knee arthroplasty.

Extended prophylaxis beyond hospital discharge is recommended for selected high-risk patients including those undergoing major abdominal or pelvic surgery for malignancy, where four weeks of post-discharge thromboprophylaxis has been shown to reduce VTE events. Hip replacement patients should receive twenty-eight to thirty-five days of prophylaxis, while knee replacement patients benefit from ten to fourteen days of extended prophylaxis. The decision to extend prophylaxis should consider patient-specific risk factors, bleeding risk, and patient preference. Patients should be educated about VTE symptoms and the importance of medication compliance during the extended prophylaxis period.

<image>Panel A: The Caprini risk assessment model displayed as a scoring form with risk factors, assigned points, and risk category determinations based on total score. Panel B: Proper application of intermittent pneumatic compression devices shown on a patient's lower extremities with the sequential compression mechanism illustrated. Panel C: A comparison of pharmacologic prophylaxis agents including LMWH, UFH, and fondaparinux with dosing, advantages, and specific considerations for each. Panel D: Extended prophylaxis recommendations displayed by procedure type showing duration recommendations for major cancer surgery, hip replacement, and knee replacement.</image>

X. Day of Surgery Preparation

Nil per os guidelines have evolved from traditional nothing by mouth after midnight rules to more physiologically based recommendations that reduce patient discomfort and metabolic stress while maintaining safety. Clear liquids including water, pulp-free juices, clear tea, and black coffee may be consumed up to two hours before anesthesia in most patients. Breast milk may be given to infants up to four hours before the procedure. Infant formula, nonhuman milk, and light meals require six hours of fasting, while full meals containing fried or fatty foods require at least eight hours. These guidelines apply to healthy patients undergoing elective procedures and may be modified for patients with conditions affecting gastric emptying.

Mechanical bowel preparation for colorectal surgery has been the subject of considerable debate with evidence supporting several approaches depending on the specific procedure. Combined mechanical and oral antibiotic bowel preparation has demonstrated reduction in surgical site infection rates for elective colorectal resection and represents current standard practice at many institutions. The typical regimen includes polyethylene glycol solution for mechanical cleansing combined with oral neomycin and metronidazole or erythromycin the day before surgery. Some studies support mechanical preparation alone or oral antibiotics alone, and the optimal approach continues to evolve. Enhanced recovery protocols generally include bowel preparation as part of a multimodal approach to reducing complications.

Hair removal, when necessary at the operative site, should be performed using clippers immediately before surgery rather than razors, which cause microscopic skin injuries that can harbor bacteria and increase surgical site infection risk. Many procedures do not require hair removal at all, and this should be performed only when hair will interfere with the surgical procedure or wound closure. Shaving the night before surgery is associated with higher infection rates than clipping immediately before the procedure. The operative site should be cleansed with antiseptic solution in the preoperative area, with chlorhexidine-based preparations preferred for most procedures.

Antibiotic prophylaxis timing requires administration within sixty minutes before surgical incision to achieve adequate tissue concentrations at the time of potential contamination. For antibiotics with longer infusion times such as vancomycin and fluoroquinolones, infusion should begin within one hundred twenty minutes of incision. The most commonly used prophylactic antibiotic is cefazolin, which provides coverage for skin flora including staphylococci and streptococci. Procedure-specific guidelines dictate when additional coverage for gram-negative or anaerobic organisms is required. Redosing during prolonged procedures is based on the antibiotic's half-life, and prophylaxis is typically discontinued within twenty-four hours postoperatively.

<image>Panel A: A timeline graphic showing current ASA fasting guidelines with icons representing clear liquids at two hours, breast milk at four hours, light meal at six hours, and full meal at eight hours before anesthesia. Panel B: A comparison of bowel preparation regimens including mechanical only, antibiotics only, and combined preparation with associated surgical site infection rates. Panel C: Proper surgical site clipping technique demonstrated with electric clippers compared to razor shaving showing microscopic skin trauma. Panel D: An antibiotic prophylaxis timing diagram showing the sixty-minute window before incision with infusion duration considerations for various agents.</image>

Summary

• Preoperative evaluation encompasses history, physical examination, risk assessment, and optimization of modifiable conditions to reduce perioperative complications
• The Revised Cardiac Risk Index assigns one point each for six factors and predicts major adverse cardiac events with scores of three or more indicating significant risk
• Functional capacity of at least four metabolic equivalents, demonstrated by climbing two flights of stairs, generally indicates adequate physiologic reserve for surgery
• Active cardiac conditions requiring evaluation before elective surgery include unstable angina, decompensated heart failure, significant arrhythmias, and severe valvular disease
• Preoperative testing should be based on clinical indications from history and examination rather than routine panels
• Medication management requires continuing beta-blockers and statins while holding ACE inhibitors, ARBs, and diuretics on the morning of surgery
• Anticoagulation management involves holding warfarin five days before surgery and DOACs twenty-four to seventy-two hours before with bridging based on thrombotic risk
• Informed consent requires disclosure of diagnosis, procedure, risks, benefits, and alternatives with documentation of the discussion
• VTE prophylaxis should be risk-stratified with mechanical measures for most patients and pharmacologic prophylaxis for moderate to high-risk patients
• NPO guidelines allow clear liquids up to two hours and solid food up to eight hours before elective surgery

Key Terms

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