Medical School · Year 3 · Internal Medicine · includes a discussion video

Seminar 20: Perioperative Medicine

Internal Medicine Clerkship

Learning Objectives

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

1. Assess preoperative cardiovascular risk using the Revised Cardiac Risk Index and functional capacity evaluation to guide further testing and optimization
2. Optimize pulmonary, glycemic, and medication management in the preoperative period to reduce perioperative complications
3. Apply evidence-based protocols for perioperative anticoagulation and antiplatelet therapy management including bridging decisions and DOAC timing
4. Recognize and manage common postoperative complications including fever, delirium, acute kidney injury, and cardiac events
5. Implement appropriate venous thromboembolism prophylaxis for medical and surgical patients based on validated risk assessment tools
6. Describe perioperative management considerations for special populations including elderly patients, patients with cirrhosis, chronic kidney disease, and obstructive sleep apnea

Seminar Outline

Section 1: Preoperative Cardiovascular Risk Assessment

The Revised Cardiac Risk Index is the most widely used clinical tool for estimating the risk of major adverse cardiac events in patients undergoing non-cardiac surgery. The index comprises six independent predictors of perioperative cardiac complications: high-risk surgery including intraperitoneal, intrathoracic, and suprainguinal vascular procedures; history of ischemic heart disease defined by prior myocardial infarction, positive stress test, current angina, nitrate use, or pathologic Q waves on ECG; history of congestive heart failure including prior or current CHF, pulmonary edema, paroxysmal nocturnal dyspnea, bilateral rales, S3 gallop, or radiographic evidence of pulmonary congestion; history of cerebrovascular disease including prior transient ischemic attack or stroke; insulin-requiring diabetes mellitus; and preoperative serum creatinine exceeding 2.0 mg/dL. Each risk factor receives one point, and the score is summed to provide a composite risk estimate that guides the need for further evaluation and the intensity of perioperative monitoring.

The interpretation of the RCRI score translates directly into estimated major adverse cardiac event rates that inform clinical decision-making. A score of 0 corresponds to an estimated MACE rate of 0.4%, indicating very low risk that generally permits proceeding to surgery without further cardiac evaluation. A score of 1 corresponds to a MACE rate of approximately 0.9%, still considered low risk. A score of 2 corresponds to a MACE rate of approximately 6.6%, representing a significant step up in risk that warrants careful consideration of the need for additional evaluation. A score of 3 or greater corresponds to a MACE rate of approximately 11%, indicating high risk and potentially triggering further cardiac testing or optimization depending on the urgency of the surgery and the patient's functional capacity. The RCRI has been validated in multiple large cohorts and serves as the foundation of the stepwise approach to preoperative cardiac evaluation recommended by the American College of Cardiology and American Heart Association guidelines.

Non-cardiac surgical procedures are stratified by the intrinsic cardiovascular risk they carry, which interacts with the patient's baseline cardiac risk to determine the overall probability of perioperative cardiac events. Low-risk procedures carrying less than 1% cardiac event risk include endoscopic procedures, superficial surgeries, cataract surgery, and breast surgery, and these procedures generally require no further cardiac evaluation regardless of patient risk factors. Intermediate-risk procedures carrying 1 to 5% cardiac event risk include orthopedic surgery, abdominal surgery, carotid endarterectomy, and head and neck surgery. High-risk procedures carrying greater than 5% cardiac event risk include aortic and major vascular surgery, prolonged procedures with large fluid shifts, and emergency surgery. The risk of the procedure is an important consideration in the stepwise approach because it determines whether further cardiac testing is warranted in patients with elevated RCRI scores.

The stepwise approach to preoperative cardiac evaluation follows a structured algorithm that efficiently allocates testing resources to patients most likely to benefit. Step one asks whether the surgery is emergent, in which case the patient proceeds to the operating room with appropriate intraoperative and postoperative monitoring. Step two evaluates for active cardiac conditions including unstable coronary syndromes, decompensated heart failure, significant arrhythmias, and severe valvular disease, any of which require evaluation and treatment before elective surgery. Step three considers the risk of the surgical procedure itself, and if it is low risk, no further evaluation is needed. Step four assesses functional capacity, which is the patient's ability to perform activities of daily living measured in metabolic equivalents. Step five integrates the RCRI score and functional capacity to determine whether the patient should proceed to surgery or undergo additional cardiac stress testing. This approach prevents unnecessary testing in low-risk patients while identifying those who may benefit from preoperative optimization.

<image>Panel A: RCRI scoring chart showing the six independent risk factors with their definitions and point assignments, and the composite score with corresponding MACE rates of 0.4%, 0.9%, 6.6%, and 11% for scores of 0, 1, 2, and 3 or greater. Panel B: Surgical risk classification showing low-risk procedures below 1%, intermediate-risk between 1-5%, and high-risk above 5% with representative examples for each category. Panel C: Five-step preoperative cardiac evaluation algorithm showing emergency surgery assessment, active cardiac conditions, surgery risk, functional capacity, and RCRI-guided testing decisions. Panel D: Integration diagram showing how patient risk factors (RCRI) interact with surgical risk category to determine the overall perioperative cardiac risk and the need for further testing.</image>

Section 2: Cardiac Testing and Optimization

Functional capacity, measured in metabolic equivalents, is a critical determinant in the preoperative cardiac evaluation because it reflects the cardiovascular system's ability to meet the hemodynamic demands of surgery. Poor functional capacity, defined as less than 4 METs, includes the ability to walk indoors, dress oneself, and perform basic activities of daily living. Moderate functional capacity of 4 to 7 METs includes climbing a flight of stairs, walking uphill, and performing moderate household activities. Good functional capacity exceeding 7 METs includes participation in strenuous sports such as running, swimming, or playing singles tennis. A functional capacity of 4 METs or greater generally indicates that the cardiovascular system can tolerate the hemodynamic stress of most surgical procedures, and patients who can achieve this level typically do not require further cardiac testing regardless of their RCRI score. The assessment of functional capacity is most commonly performed through clinical history, using the Duke Activity Status Index or similar validated instruments, rather than through formal exercise testing.

Preoperative stress testing should be considered only when the result will change perioperative management, avoiding the common pitfall of reflexively ordering testing that generates information without clinical actionability. The indication for stress testing is the combination of poor functional capacity, defined as less than 4 METs, elevated cardiac risk with an RCRI score of 1 or greater, and a planned elevated-risk surgical procedure. If the stress test result would not change the decision to proceed with surgery, such as in emergency or urgent procedures, testing should not be performed. Pharmacologic stress testing with nuclear imaging or dobutamine echocardiography is preferred over exercise stress testing in patients who cannot achieve adequate exercise levels due to orthopedic limitations, peripheral vascular disease, or other conditions. A normal stress test provides substantial reassurance about perioperative cardiac safety, while an abnormal result may lead to further evaluation with coronary angiography, preoperative revascularization in select cases, or intensification of perioperative medical therapy.

Perioperative beta-blocker management requires adherence to well-established principles supported by randomized trial evidence. Patients already receiving beta-blockers for established cardiac indications should continue them throughout the perioperative period because abrupt discontinuation has been associated with rebound tachycardia, hypertension, and myocardial ischemia. The POISE trial demonstrated that while perioperative beta-blocker initiation reduced myocardial infarction, it increased the risk of stroke and all-cause mortality when started immediately before surgery without adequate dose titration, leading to the current recommendation against initiating beta-blockers on the day of or day before surgery. Starting a beta-blocker may be considered in patients with an RCRI score of 3 or greater when there is sufficient time, ideally more than one week, to titrate the dose to a target heart rate of 60 to 80 beats per minute before surgery. The principle of avoiding abrupt discontinuation also applies to the postoperative period, as the hemodynamic stress of surgery and recovery makes the rebound phenomenon particularly dangerous.

Statin therapy has demonstrated perioperative cardioprotective effects through both lipid-lowering and pleiotropic anti-inflammatory mechanisms, and their management in the perioperative period follows straightforward principles. Patients already receiving statin therapy should continue their medication throughout the perioperative period, as discontinuation has been associated with increased perioperative cardiac events in observational studies. For patients undergoing vascular surgery, initiating a statin preoperatively should be considered regardless of baseline lipid levels, based on randomized trial evidence demonstrating reductions in perioperative myocardial infarction and mortality. The anti-inflammatory and plaque-stabilizing properties of statins are thought to be the primary mechanisms of perioperative benefit, as they reduce endothelial inflammation, improve nitric oxide bioavailability, and stabilize vulnerable coronary plaques that may rupture under the hemodynamic stress of surgery. Unlike beta-blockers, which require careful dose titration before initiation, statins can be safely started immediately before surgery without the risk of adverse hemodynamic effects.

<image>Panel A: Functional capacity assessment showing MET levels from 1 to greater than 7 with corresponding daily activities, the threshold of 4 METs as adequate for surgery, and the Duke Activity Status Index as the clinical assessment tool. Panel B: Preoperative stress testing indications flowchart showing the three required criteria of poor functional capacity, elevated RCRI, and elevated-risk surgery with the decision to test only when results will change management. Panel C: Perioperative beta-blocker management algorithm showing continuation for current users, avoidance of initiation immediately before surgery per POISE trial, and consideration for high-risk patients with adequate titration time. Panel D: Statin perioperative management showing continuation for current users, initiation consideration for vascular surgery patients, and the pleiotropic anti-inflammatory mechanisms including endothelial protection and plaque stabilization.</image>

Section 3: Pulmonary Risk Assessment

Risk factors for postoperative pulmonary complications span both patient-related and procedure-related variables and must be systematically assessed during the preoperative evaluation. Patient-related risk factors include age greater than 60 years, chronic obstructive pulmonary disease, American Society of Anesthesiologists physical status classification greater than 2, obesity with body mass index exceeding 30, and active smoking, which impairs mucociliary clearance and increases airway reactivity. Procedure-related risk factors include thoracic and upper abdominal surgery, which disrupt diaphragmatic function and reduce functional residual capacity; prolonged surgical duration exceeding 3 hours; and emergency surgery, which precludes the opportunity for preoperative optimization. General anesthesia carries higher pulmonary risk compared to regional anesthesia because endotracheal intubation and positive pressure ventilation predispose to atelectasis, aspiration, and ventilator-associated lung injury. The cumulative effect of multiple risk factors substantially increases the probability of complications, making comprehensive risk assessment essential for informed surgical consent and perioperative planning.

Preoperative pulmonary testing is significantly less evidence-based than preoperative cardiac evaluation, and routine pulmonary function testing is not recommended for most patients. Chest radiography should not be obtained routinely and is indicated only when acute pulmonary symptoms are present or when clinical findings suggest an undiagnosed condition that might alter surgical management. Pulmonary function tests are not routine preoperative studies and do not predict postoperative pulmonary complications better than clinical assessment alone; their primary indication is for patients being evaluated for lung resection surgery, where they guide the assessment of residual lung function after resection. Arterial blood gas analysis is not routinely indicated and does not add predictive value beyond clinical assessment. Spirometry may be useful in patients with known COPD or asthma to assess the degree of airflow obstruction and ensure that bronchodilator therapy is optimized, but an abnormal spirometric result alone should not be used to deny a patient surgery, as no pulmonary function value is an absolute contraindication to non-thoracic surgery.

Preoperative risk reduction strategies for pulmonary complications are evidence-based and should be implemented whenever feasible before elective surgery. Smoking cessation is the single most effective intervention, with the greatest benefit achieved when cessation occurs at least 4 to 8 weeks before surgery to allow recovery of mucociliary function and reduction of airway inflammation. Even cessation within 24 hours of surgery reduces carboxyhemoglobin levels and improves oxygen delivery. Optimization of existing COPD and asthma through appropriate bronchodilator therapy, and a short course of systemic corticosteroids if the patient is experiencing an exacerbation, can improve airflow and reduce bronchospasm risk during anesthesia. Inspiratory muscle training, consisting of daily breathing exercises against resistance for several weeks before surgery, has been shown to reduce postoperative pulmonary complications in patients undergoing abdominal and thoracic surgery. Postoperative lung expansion strategies including incentive spirometry, deep breathing exercises, and early CPAP application should be planned preoperatively and initiated immediately after surgery.

Postoperative pulmonary complications encompass a spectrum of conditions that collectively represent the most common serious complications of surgery. Atelectasis is the most frequent postoperative pulmonary complication, resulting from alveolar collapse due to reduced tidal volume, diaphragmatic splinting from surgical pain, and the effects of general anesthesia on surfactant production and mucociliary function. Early ambulation and incentive spirometry are the primary prevention strategies. Postoperative pneumonia develops in approximately 1 to 5% of surgical patients and carries significant mortality, with aspiration of oropharyngeal contents being a major risk factor. Prevention includes aspiration precautions, oral hygiene, and head of bed elevation. Respiratory failure requiring prolonged mechanical ventilation may occur in patients with marginal preoperative pulmonary reserve or those experiencing significant postoperative complications. COPD exacerbation can be triggered by the stress of surgery, anesthetic agents, and inadequate postoperative bronchodilator therapy, emphasizing the importance of preoperative optimization and uninterrupted maintenance therapy.

<image>Panel A: Pulmonary risk factor assessment showing patient-related factors of age, COPD, ASA class, obesity, and smoking alongside procedure-related factors of surgery type, duration, emergency status, and anesthesia type with their relative contributions to risk. Panel B: Preoperative pulmonary testing algorithm showing chest radiography only for acute symptoms, PFTs only for lung resection planning, ABG not routinely indicated, and spirometry for COPD/asthma optimization. Panel C: Risk reduction strategies timeline showing smoking cessation at 4-8 weeks, COPD/asthma optimization, inspiratory muscle training, and postoperative lung expansion planning with evidence levels for each intervention. Panel D: Postoperative pulmonary complications showing atelectasis, pneumonia, respiratory failure, and COPD exacerbation with their risk factors, prevention strategies, and management approaches.</image>

Section 4: Anticoagulation Management

The decision to bridge anticoagulation during the perioperative period in patients on warfarin requires assessment of the patient's thromboembolic risk, which determines whether the temporary interruption of anticoagulation necessitates substitution with a short-acting parenteral agent. High thromboembolic risk, warranting bridging with therapeutic-dose low-molecular-weight heparin, includes patients with mechanical heart valves in the mitral position, atrial fibrillation with a CHA2DS2-VASc score of 6 or greater or recent stroke within 3 months, and recent venous thromboembolism within 3 months. Low thromboembolic risk, in which bridging is not recommended, includes patients with a bioprosthetic valve, atrial fibrillation with a CHA2DS2-VASc score of 4 or less without recent stroke, and VTE that occurred more than 12 months ago. Moderate thromboembolic risk requires individualized decision-making, weighing the specific circumstances of the patient and the bleeding risk of the planned procedure. The BRIDGE trial demonstrated that forgoing bridging in patients with atrial fibrillation at moderate risk was noninferior to bridging with regard to arterial thromboembolism and was associated with significantly less major bleeding.

The timing of warfarin discontinuation and resumption follows a standardized protocol based on the pharmacokinetics of warfarin and the time required for clotting factor levels to normalize and then return to therapeutic range. Warfarin should be stopped 5 days before surgery, allowing sufficient time for the INR to decline to a safe range as vitamin K-dependent clotting factors are resynthesized. For patients requiring bridging, therapeutic-dose LMWH is initiated 3 days before surgery and the last dose is given the evening before surgery, approximately 24 hours preoperatively, to allow adequate clearance before the procedure. On the day of surgery, the INR is checked to confirm that it has fallen to 1.5 or below, which is generally considered safe for most surgical procedures. Postoperatively, warfarin is resumed on the evening of surgery or the following day once adequate hemostasis is confirmed, and bridging LMWH is restarted 24 to 48 hours postoperatively depending on the bleeding risk of the procedure, with bridge therapy continued until the INR has been at or above 2.0 for at least 24 hours.

Direct oral anticoagulant management in the perioperative period is simpler than warfarin management because DOACs have predictable pharmacokinetics, short half-lives, and do not require bridging anticoagulation. The timing of DOAC discontinuation is determined by the specific drug, the patient's renal function, and the bleeding risk of the planned procedure. For standard bleeding risk procedures, apixaban and rivaroxaban should be stopped 24 to 48 hours before surgery, as their half-lives of approximately 12 and 7 to 11 hours respectively allow adequate clearance within this timeframe. Dabigatran requires longer discontinuation intervals because it is predominantly renally cleared: 48 to 72 hours in patients with normal renal function and 72 to 96 hours in patients with renal impairment, defined as creatinine clearance 30 to 50 mL/min. For high bleeding risk procedures, all DOACs should be discontinued at the longer end of their respective windows, typically 48 to 72 hours before surgery. DOACs are resumed postoperatively once adequate hemostasis is confirmed, typically 24 to 48 hours after surgery for standard procedures and 48 to 72 hours for high bleeding risk procedures.

Reversal agents are available for situations requiring emergency surgery or managing life-threatening bleeding in patients on anticoagulation therapy. Vitamin K reverses warfarin anticoagulation but requires 6 to 24 hours for effect, while four-factor prothrombin complex concentrate provides immediate reversal by supplying the depleted clotting factors directly. Idarucizumab is a specific reversal agent for dabigatran, a humanized monoclonal antibody fragment that binds dabigatran with high affinity and provides immediate and complete reversal within minutes. Andexanet alfa reverses the factor Xa inhibitors apixaban and rivaroxaban by serving as a decoy receptor that binds the drug and prevents it from inhibiting factor Xa. Knowledge of these reversal agents is essential for perioperative management because the need for emergent or urgent surgery in an anticoagulated patient is a common clinical scenario that requires rapid decision-making about anticoagulation management.

<image>Panel A: Bridging decision algorithm showing high, moderate, and low thromboembolic risk categories with specific conditions in each category and corresponding bridging recommendations. Panel B: Warfarin perioperative timeline showing day minus 5 stop warfarin, day minus 3 start bridging if indicated, day minus 1 last bridge dose, day of surgery INR check, and postoperative warfarin and bridge resumption schedule. Panel C: DOAC discontinuation timing chart showing apixaban and rivaroxaban at 24-48 hours, dabigatran at 48-72 hours with normal renal function and 72-96 hours with impairment, and adjustments for high bleeding risk procedures. Panel D: Anticoagulation reversal agents showing vitamin K and PCC for warfarin, idarucizumab for dabigatran, and andexanet alfa for factor Xa inhibitors with onset of action and clinical indications.</image>

Section 5: Antiplatelet Management

Aspirin management in the perioperative period requires balancing the cardiovascular protective benefits of continued therapy against the bleeding risk imposed by the planned procedure. For patients taking aspirin for primary prevention without established cardiovascular disease, aspirin should be stopped 7 days before surgery to allow complete recovery of platelet cyclooxygenase function, as the antiplatelet effect of aspirin persists for the lifespan of affected platelets. For patients taking aspirin for secondary prevention after a cardiovascular event, the decision is more nuanced and should involve discussion between the internist, surgeon, and cardiologist. In general, aspirin is often continued through non-cardiac surgery in patients with established coronary artery disease, prior stent placement, or recent acute coronary syndrome because the cardiovascular risk of discontinuation may outweigh the surgical bleeding risk. For procedures with very high bleeding risk, including intracranial surgery and certain spinal procedures, aspirin may need to be held even in secondary prevention patients, with the decision made on a case-by-case basis.

Dual antiplatelet therapy management in patients with coronary stents represents one of the most consequential perioperative decisions because premature discontinuation of a P2Y12 inhibitor can trigger catastrophic stent thrombosis. Bare metal stents require a minimum of 4 to 6 weeks of DAPT before elective surgery can be safely performed, while drug-eluting stents require 6 to 12 months of uninterrupted DAPT, reflecting the longer time required for endothelialization of the drug-coated stent surface. After the minimum DAPT duration has been met, aspirin should be continued perioperatively while the P2Y12 inhibitor is discontinued for the appropriate washout period before surgery. If elective surgery is needed before the minimum DAPT duration is complete, the surgery should be delayed whenever possible, and the decision to proceed requires multidisciplinary input from cardiology, surgery, and anesthesia. The morbidity and mortality of perioperative stent thrombosis are extremely high, making this one of the most important perioperative risk assessments.

The timing of P2Y12 inhibitor discontinuation before surgery varies by specific agent based on their pharmacokinetic properties and duration of antiplatelet effect. Clopidogrel and ticagrelor should both be stopped 5 days before surgery, reflecting their respective mechanisms of platelet inhibition and recovery of platelet function. Prasugrel, which produces more potent and less variable platelet inhibition, requires 7 days of discontinuation before surgery. These timing recommendations balance the need for adequate platelet recovery to minimize surgical bleeding against the ongoing cardiovascular risk during the drug-free interval. For patients requiring urgent surgery who cannot wait for complete P2Y12 washout, platelet function testing may be considered to assess residual antiplatelet effect, though the clinical utility of point-of-care platelet function assays in guiding surgical timing remains an area of active investigation. Resumption of P2Y12 inhibitors after surgery should occur as soon as the surgeon deems the bleeding risk acceptable, typically within 24 to 72 hours postoperatively.

Special considerations in antiplatelet management apply to several common perioperative scenarios that require individualized approaches. Patients with recent percutaneous coronary intervention within the past 12 months should have elective surgery delayed until the minimum DAPT duration has been completed, with the specific duration determined by the type of stent, the clinical indication for PCI, and whether any high-risk features are present. When urgent surgery cannot be delayed in a patient on DAPT, aspirin should be continued and the P2Y12 inhibitor stopped, with platelet transfusion available in the event of clinically significant bleeding. Emergent surgery in patients on DAPT proceeds without delay with platelet transfusion support available, as the risk of surgical delay exceeds the bleeding risk. Patients undergoing cardiac surgery should have clopidogrel stopped 5 days before the procedure to reduce mediastinal bleeding and transfusion requirements, though urgent cases may proceed with appropriate blood bank preparation. The key principle across all scenarios is that multidisciplinary communication between the cardiologist, surgeon, and anesthesiologist is essential for optimal perioperative antiplatelet management.

<image>Panel A: Aspirin perioperative management algorithm showing primary prevention patients stopping 7 days before surgery versus secondary prevention patients where continuation is often recommended with exceptions for very high bleeding risk procedures. Panel B: DAPT and stent timeline showing bare metal stent minimum of 4-6 weeks and drug-eluting stent minimum of 6-12 months before elective surgery, with the recommendation to delay surgery when possible until minimum DAPT is complete. Panel C: P2Y12 inhibitor discontinuation timing showing clopidogrel at 5 days, ticagrelor at 5 days, and prasugrel at 7 days with pharmacologic rationale and resumption recommendations. Panel D: Special scenarios decision matrix showing recent PCI, urgent surgery on DAPT, emergent surgery on DAPT, and cardiac surgery with the recommended approach and multidisciplinary communication requirements for each.</image>

Section 6: Diabetes Management

Preoperative glycemic management aims to ensure adequate glucose control during the perioperative period while preventing the potentially devastating consequences of hypoglycemia in patients who are unable to recognize or report symptoms due to anesthesia. There is no specific hemoglobin A1c threshold above which elective surgery must be canceled, but markedly elevated HbA1c values should prompt optimization of glycemic control when the surgical timeline permits. The perioperative glucose target is 140 to 180 mg/dL, a range supported by randomized trial evidence demonstrating that this moderate target achieves equivalent or superior outcomes compared to tighter glucose control while substantially reducing the risk of hypoglycemia. Avoidance of hypoglycemia, defined as blood glucose below 70 mg/dL, is paramount because perioperative hypoglycemia is associated with increased mortality, cardiac events, and neurologic injury, and the anesthetized patient cannot exhibit the adrenergic warning symptoms that normally alert conscious individuals to falling glucose levels.

Oral antidiabetic medication management follows agent-specific protocols based on the pharmacologic properties and risks of each drug class during the perioperative fasting state. Metformin should be taken the day before surgery but held on the morning of surgery to reduce the risk of lactic acidosis, particularly in procedures involving contrast dye administration or hemodynamic instability. Sulfonylureas should be taken the day before surgery but held on the day of surgery due to the risk of hypoglycemia in the fasting patient. SGLT2 inhibitors require special attention because they must be held 3 to 4 days before surgery to eliminate the risk of euglycemic diabetic ketoacidosis, a dangerous and often unrecognized complication in which ketoacidosis develops without significant hyperglycemia. DPP-4 inhibitors may be taken the day before surgery but are held on the morning of surgery. Thiazolidinediones follow the same pattern of taking the day before and holding on the day of surgery. All oral agents are resumed postoperatively once the patient is eating a regular diet and has stable hemodynamics.

Insulin management in the perioperative period requires thoughtful dose adjustments to prevent both hyperglycemia and hypoglycemia in fasting patients. Basal insulin, whether administered as insulin glargine, detemir, or degludec, should be given at full dose the night before surgery, with most protocols recommending a 20 to 50% dose reduction on the morning of surgery to account for the reduced caloric intake during the fasting period. NPH insulin, which has both basal and prandial properties, is typically reduced to 50% of the morning dose on the day of surgery. Bolus or mealtime insulin is held entirely on the day of surgery because the patient will be NPO and does not require prandial coverage. Patients on insulin pump therapy should continue their basal rate through surgery, with consideration of a 10 to 20% basal rate reduction, and the pump should be managed in consultation with the patient's endocrinologist or a diabetes management team. The principle underlying all insulin adjustments is to maintain sufficient basal insulin coverage to prevent ketosis and severe hyperglycemia while eliminating prandial insulin that would cause hypoglycemia in the fasting state.

Intraoperative and postoperative glucose management continues the same target range of 140 to 180 mg/dL and employs monitoring protocols calibrated to the complexity of the procedure and the patient's baseline glycemic control. Glucose monitoring should occur every 2 to 4 hours during and after surgery, with more frequent monitoring in patients receiving intravenous insulin. A continuous insulin infusion is indicated for major surgery, patients with type 1 diabetes, and patients with persistent hyperglycemia exceeding 180 mg/dL despite subcutaneous insulin, with the infusion rate adjusted based on a validated protocol. The transition from intravenous to subcutaneous insulin should occur once the patient is eating and hemodynamically stable, with the first subcutaneous basal insulin dose administered at least 2 hours before the infusion is discontinued to prevent a gap in insulin coverage. The home insulin and oral medication regimen is resumed once the patient is tolerating a regular diet. Patients previously taking SGLT2 inhibitors should be monitored for euglycemic DKA in the early postoperative period, particularly in the setting of dehydration, fasting, or acute illness.

<image>Panel A: Perioperative glucose management principles showing the target range of 140-180 mg/dL, the paramount importance of hypoglycemia avoidance, and the inability of anesthetized patients to manifest hypoglycemic symptoms. Panel B: Oral antidiabetic medication management timeline showing each drug class with instructions for the day before surgery, day of surgery, and resumption criteria with special emphasis on SGLT2 inhibitor 3-4 day hold for euglycemic DKA prevention. Panel C: Insulin adjustment protocol showing basal insulin at full dose night before with 50-80% on morning of surgery, NPH at 50% of AM dose, bolus insulin held, and insulin pump continuation with reduced basal rate. Panel D: Intraoperative and postoperative glucose monitoring schedule showing every 2-4 hour monitoring, insulin drip indications and transition protocol, and SGLT2 inhibitor DKA surveillance in the postoperative period.</image>

Section 7: Other Medication Management

Medications that should be continued through the perioperative period share the common characteristic that their discontinuation poses a greater risk than their continuation. Beta-blockers must be continued to prevent rebound tachycardia and hypertension that can precipitate myocardial ischemia. Statins should be continued for their cardioprotective pleiotropic effects. Most antihypertensive medications should be continued to prevent rebound hypertension, though specific exceptions exist. Anticonvulsant medications must be continued without interruption because perioperative seizures can be catastrophic, and many anticonvulsants have complex pharmacokinetics that make re-attainment of therapeutic levels difficult. Chronic corticosteroid therapy at a dose equivalent to 5 mg or more of prednisone daily for 3 weeks or longer suppresses the hypothalamic-pituitary-adrenal axis, necessitating stress-dose supplementation to prevent adrenal crisis during the physiologic stress of surgery. Thyroid medications should be continued perioperatively, and levothyroxine has a long half-life that makes a single missed dose inconsequential.

Medications that should be held on the morning of surgery or in the days preceding surgery are those whose continuation poses unnecessary perioperative risk. Nonsteroidal anti-inflammatory drugs should be stopped 3 days before surgery because they inhibit platelet function and increase surgical bleeding risk. Diuretics are held on the morning of surgery to prevent intravascular volume depletion and intraoperative hypotension, particularly in patients who will be NPO and unable to replace urinary fluid losses. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are held on the morning of surgery based on evidence that their continuation is associated with refractory intraoperative hypotension requiring vasopressor support, though this recommendation is debated and some clinicians continue these agents in patients with heart failure. Monoamine oxidase inhibitors require careful discussion with the anesthesia team because of their interactions with sympathomimetic agents and meperidine, though the traditional recommendation to discontinue them 2 weeks before surgery has been replaced by more nuanced approaches. Oral hypoglycemic agents are held as discussed in the diabetes management section.

Stress-dose steroid coverage is required for patients with anticipated hypothalamic-pituitary-adrenal axis suppression from chronic glucocorticoid therapy to prevent perioperative adrenal crisis, which manifests as refractory hypotension, tachycardia, and cardiovascular collapse. The threshold for HPA axis suppression is generally considered to be a prednisone-equivalent dose of 5 mg or more daily for 3 or more consecutive weeks within the past year. The dose of supplemental hydrocortisone is scaled to the magnitude of surgical stress: minor procedures such as inguinal hernia repair under local anesthesia require only the patient's usual daily dose plus 25 mg of hydrocortisone; moderate procedures such as open cholecystectomy or joint replacement require the usual dose plus 50 to 75 mg of hydrocortisone on the day of surgery; and major procedures such as cardiothoracic or complex abdominal surgery require the usual dose plus 100 mg of hydrocortisone on the day of surgery, tapered over 1 to 2 days back to the baseline dose. The stress dose is administered intravenously at the time of anesthesia induction.

Herbal supplements and complementary medications present unique perioperative challenges because many of these substances have pharmacologic effects that can increase surgical bleeding, interact with anesthetic agents, or produce cardiovascular instability. Garlic and ginkgo biloba have antiplatelet properties that can increase intraoperative and postoperative bleeding. St. John's wort induces cytochrome P450 enzymes and can alter the metabolism of anesthetic agents, warfarin, cyclosporine, and numerous other medications, potentially causing subtherapeutic drug levels. Ephedra, though banned from dietary supplements due to cardiovascular toxicity, may still be encountered and can cause intraoperative hypertension, tachycardia, and arrhythmias through its sympathomimetic effects. Kava and valerian have sedative properties that may potentiate the effects of anesthetic agents. The general recommendation is to discontinue all herbal supplements 1 to 2 weeks before elective surgery, and all patients should be specifically asked about supplement use during the preoperative assessment because many patients do not volunteer this information unless directly questioned.

<image>Panel A: Medications to continue perioperatively showing beta-blockers, statins, antihypertensives, anticonvulsants, chronic steroids requiring stress dosing, and thyroid medications with the rationale for continuation of each. Panel B: Medications to hold showing NSAIDs at 3 days before, diuretics on morning of surgery, ACE inhibitors/ARBs on morning of surgery, and oral hypoglycemics with specific timing and clinical rationale. Panel C: Stress-dose steroid protocol showing the HPA suppression threshold, surgical stress categories of minor, moderate, and major with corresponding hydrocortisone doses of 25 mg, 50-75 mg, and 100 mg with taper schedule. Panel D: Herbal supplement perioperative concerns showing garlic and ginkgo bleeding risk, St. John's wort drug interactions, ephedra cardiovascular effects, and kava/valerian sedation potentiation with the recommendation to stop all supplements 1-2 weeks before surgery.</image>

Section 8: VTE Prophylaxis

Perioperative VTE risk assessment determines which patients require pharmacologic prophylaxis, mechanical prophylaxis, or both, and guides the duration and intensity of the prophylactic regimen. Surgical risk factors for VTE include the type of procedure, with major orthopedic surgery and cancer surgery carrying the highest risk, patient factors including prior VTE, active malignancy, immobility, and advanced age, and the duration of surgery, with prolonged procedures increasing VTE risk through sustained immobility and tissue injury. The Caprini score is a widely validated risk assessment tool that assigns points for patient-specific and procedure-specific risk factors, yielding a composite score that categorizes patients into very low, low, moderate, and high VTE risk groups. Higher Caprini scores correlate with increasing VTE rates and guide the intensity of prophylaxis, from early ambulation alone for very low-risk patients to combination pharmacologic and mechanical prophylaxis for high-risk patients. The risk assessment should be performed and documented for every surgical patient as part of the preoperative evaluation.

Pharmacologic prophylaxis options for surgical patients include low-molecular-weight heparin, unfractionated heparin, fondaparinux, and direct oral anticoagulants, with the choice of agent guided by the type of surgery, renal function, and specific contraindications. LMWH is the preferred pharmacologic agent for most surgical patients, offering more predictable pharmacokinetics, once-daily subcutaneous dosing, and superior efficacy compared to unfractionated heparin in several large trials. UFH administered as 5,000 units subcutaneously every 8 to 12 hours is an alternative when LMWH is contraindicated, such as in patients with severe renal failure or when the reversibility of UFH is desired in patients at high bleeding risk. Fondaparinux is an option for patients with a history of heparin-induced thrombocytopenia because it does not cross-react with HIT antibodies. Mechanical prophylaxis using intermittent pneumatic compression devices should be applied to all surgical patients unless contraindicated by lower extremity peripheral vascular disease and is the sole prophylactic modality in patients with active bleeding or very high bleeding risk in whom pharmacologic agents are contraindicated.

Extended VTE prophylaxis beyond the hospital stay is an evidence-based practice for specific high-risk surgical populations. Major orthopedic surgery, including total hip arthroplasty, total knee arthroplasty, and hip fracture repair, warrants extended pharmacologic prophylaxis for 28 to 35 days postoperatively based on multiple randomized trials demonstrating significant reductions in symptomatic VTE compared to in-hospital prophylaxis alone. Cancer surgery, particularly abdominal and pelvic procedures, warrants extended prophylaxis for 28 days because the prothrombotic state of malignancy persists well beyond the operative period. General surgical procedures without additional risk factors typically require prophylaxis only for the duration of the hospital stay. DOACs, specifically rivaroxaban and apixaban, have been approved for extended VTE prophylaxis after hip and knee replacement, offering the convenience of oral administration without the need for injections during the outpatient phase of extended prophylaxis.

The timing of prophylaxis initiation relative to the surgical procedure and the type of anesthesia requires careful attention to prevent both VTE and bleeding complications. For LMWH administered preoperatively, the dose should be given 12 hours before surgery, ensuring adequate anticoagulant levels at the time of the procedure while allowing sufficient clearance to minimize surgical bleeding. For LMWH administered postoperatively, the first dose is given 12 to 24 hours after surgery depending on the bleeding risk assessment. In patients receiving neuraxial anesthesia, including epidural and spinal techniques, specific timing intervals must be observed to prevent the catastrophic complication of epidural hematoma. LMWH should not be given within 12 hours before neuraxial catheter placement and should be withheld for at least 12 hours after catheter removal. For UFH, the interval is 4 to 6 hours before and 1 hour after neuraxial procedures. These timing guidelines are critical safety measures that must be communicated clearly between the surgical, anesthesia, and medical teams.

<image>Panel A: VTE risk assessment showing the Caprini score components with surgical and patient risk factors and the resulting risk categories from very low to high with corresponding prophylaxis intensity recommendations. Panel B: Pharmacologic prophylaxis comparison showing LMWH as preferred with advantages, UFH for renal failure, fondaparinux for HIT history, and mechanical IPC for all patients with high bleeding risk considerations. Panel C: Extended prophylaxis duration chart showing hip arthroplasty at 28-35 days, knee arthroplasty at 10-14 days extendable to 35, cancer surgery at 28 days, and general surgery for hospital stay only with DOAC oral options for orthopedic patients. Panel D: Prophylaxis timing relative to surgery and neuraxial anesthesia showing LMWH preoperative 12 hours before, postoperative 12-24 hours after, and neuraxial catheter interval requirements for LMWH and UFH.</image>

Section 9: Postoperative Complications

Postoperative fever is one of the most common reasons for medical consultation after surgery and follows a temporal pattern that guides the differential diagnosis. Fever in the first 48 hours after surgery is most commonly due to the inflammatory response to surgical tissue injury or atelectasis and is typically self-limited. The classic mnemonic "Wind, Water, Wound, Walking, and Wonder drugs" provides a temporal framework: wind refers to pulmonary causes including atelectasis and pneumonia occurring in the first days; water refers to urinary tract infection developing around postoperative days 3 to 5; wound refers to surgical site infection typically presenting around postoperative days 5 to 7; walking refers to deep vein thrombosis occurring around postoperative days 5 to 7; and wonder drugs refers to drug fever, which can occur at any time but is often considered when other causes have been excluded, typically after postoperative day 7. Abscess formation may present with persistent fever beyond the first postoperative week. The evaluation should be guided by the timing and associated symptoms rather than a reflexive ordering of a comprehensive infectious workup for all postoperative fevers.

Postoperative delirium is a common, serious, and potentially preventable complication that is characterized by acute onset of fluctuating inattention and altered level of consciousness, and it is associated with increased mortality, prolonged hospitalization, cognitive decline, and institutional placement. Age greater than 65 years is the strongest risk factor, followed by pre-existing cognitive impairment, which may be subclinical and unrecognized before the surgical stressor unmasks it. Medications are a major modifiable risk factor, with opioids, benzodiazepines, and anticholinergic drugs being the most commonly implicated agents. Prevention using multicomponent non-pharmacologic strategies has been shown to reduce delirium incidence by 30 to 40% and includes early and frequent reorientation, maintaining the sleep-wake cycle with adequate daytime light and nighttime quiet, ensuring availability of sensory aids including eyeglasses and hearing aids, encouraging early mobilization, maintaining adequate hydration and nutrition, and minimizing the use of delirium-provoking medications. When pharmacologic treatment is required for severe agitation threatening patient safety, low-dose haloperidol or quetiapine may be used for the shortest duration possible.

Acute kidney injury is a frequent postoperative complication that increases mortality, length of hospital stay, and the risk of progression to chronic kidney disease. The most common cause in the immediate postoperative period is prerenal azotemia resulting from intravascular volume depletion due to surgical blood loss, third-space fluid shifts, inadequate intravenous fluid replacement, and the NPO state. Treatment involves prompt fluid resuscitation with isotonic crystalloid and assessment of hemodynamic adequacy. Nephrotoxic insults should be minimized by avoiding or using alternatives to iodinated contrast, holding NSAIDs, reviewing antibiotic dosing, and discontinuing any unnecessary nephrotoxic agents. Obstructive uropathy should be considered in patients with new-onset oliguria or anuria, particularly after pelvic surgery, and can be diagnosed by bladder scan or ultrasound and treated with Foley catheter placement. Monitoring of daily serum creatinine and urine output is essential in all postoperative patients at risk for AKI, with prompt consultation of nephrology for patients with severe or worsening renal function despite appropriate initial management.

Perioperative cardiac complications represent a leading cause of postoperative morbidity and mortality and include myocardial infarction, heart failure, and arrhythmias. Perioperative myocardial infarction is frequently silent, presenting without classic chest pain symptoms in the anesthetized or recently sedated patient, and may manifest only as unexplained hypotension, tachycardia, new heart failure symptoms, or isolated troponin elevation. The mechanism often involves oxygen supply-demand mismatch in the setting of fixed coronary stenosis exacerbated by surgical stress, tachycardia, anemia, and hypotension, rather than the plaque rupture mechanism of spontaneous MI. Postoperative heart failure may result from excessive fluid administration, unmasking of subclinical cardiac dysfunction by surgical stress, or perioperative myocardial infarction. Atrial fibrillation is the most common postoperative arrhythmia, particularly after thoracic and cardiac surgery, and may be precipitated by pain, electrolyte disturbances, volume shifts, or sympathetic activation. Management of perioperative cardiac complications follows the same principles as their management in the non-surgical setting, with attention to the unique constraints imposed by the recent surgical procedure.

<image>Panel A: Postoperative fever timeline showing the Wind, Water, Wound, Walking, Wonder drugs mnemonic with corresponding postoperative days, likely diagnoses at each timepoint, and the guided evaluation approach. Panel B: Delirium prevention and management showing risk factors of age, cognitive impairment, and medications, the multicomponent prevention strategy reducing incidence by 30-40%, and pharmacologic treatment with low-dose antipsychotics as last resort. Panel C: Acute kidney injury workup showing prerenal causes with fluid resuscitation, nephrotoxin avoidance, obstructive uropathy evaluation, and daily creatinine and urine output monitoring with nephrology consultation criteria. Panel D: Perioperative cardiac complications showing silent MI with troponin monitoring, heart failure from volume overload, and atrial fibrillation as the most common arrhythmia with management principles adapted to the surgical context.</image>

Section 10: Special Populations

Elderly patients present unique perioperative challenges that extend beyond the standard cardiovascular and pulmonary risk assessments and require attention to frailty, cognition, and goals of care. Frailty assessment, using validated tools such as the Modified Frailty Index or the Clinical Frailty Scale, has been shown to predict postoperative complications, prolonged hospitalization, discharge to skilled nursing facilities, and 30-day mortality independently of age and comorbidities. Preoperative cognitive assessment establishes a baseline against which postoperative delirium can be detected and is particularly important because delirium is frequently the first manifestation of underlying dementia in elderly surgical patients. Functional status, assessed by activities of daily living and instrumental activities of daily living, is one of the strongest predictors of surgical outcomes in the elderly and should be documented as part of the preoperative evaluation. Polypharmacy is common in elderly patients and necessitates thorough medication reconciliation to identify high-risk medications, unnecessary agents, and potential interactions. Goals of care discussions should occur preoperatively, particularly for high-risk procedures, to ensure that the surgical plan aligns with the patient's values and preferences regarding outcomes, recovery expectations, and acceptable levels of functional decline.

Patients with cirrhosis have substantially elevated surgical risk that is proportional to the severity of their liver disease, and perioperative management requires careful attention to the multisystem complications of hepatic dysfunction. The Child-Pugh score and MELD score provide quantitative risk assessment, with Child-Pugh Class C cirrhosis carrying an operative mortality approaching 80% and generally precluding elective surgery. Elective surgery should be avoided in patients with decompensated cirrhosis, defined by the presence of ascites, encephalopathy, variceal bleeding, or jaundice. Coagulopathy in cirrhosis is complex, reflecting simultaneous deficiencies in both procoagulant and anticoagulant factors, and the INR does not reliably predict bleeding risk as it does in patients on warfarin. Fresh frozen plasma and platelet transfusion may be required before invasive procedures, though the rebalanced hemostasis of cirrhosis means that routine correction of laboratory abnormalities is often unnecessary. Nutritional optimization before elective surgery is essential because protein-calorie malnutrition is present in the majority of patients with advanced cirrhosis and is associated with impaired wound healing and immune function.

Chronic kidney disease introduces perioperative considerations related to medication dosing, fluid and electrolyte management, and the avoidance of nephrotoxic exposures. All medications that are renally cleared must be dose-adjusted based on the estimated glomerular filtration rate, including antibiotics, analgesics, and anticoagulants. Nephrotoxic agents including iodinated contrast media, NSAIDs, aminoglycoside antibiotics, and angiotensin-converting enzyme inhibitors should be avoided or used with extreme caution. If iodinated contrast is required, prehydration with isotonic saline and use of iso-osmolar or low-osmolar contrast agents at the lowest effective volume can reduce the risk of contrast-induced nephropathy. Patients on maintenance hemodialysis should undergo dialysis on the day before surgery to optimize fluid and electrolyte status, with careful attention to potassium management because hyperkalemia is a common and potentially lethal perioperative complication in patients with end-stage renal disease. Electrolyte monitoring, particularly potassium, should be performed frequently in the immediate postoperative period.

Obstructive sleep apnea is an underrecognized condition that significantly increases the risk of postoperative respiratory complications, particularly in the context of opioid analgesic administration and sedation. The STOP-BANG questionnaire provides a validated screening tool using eight yes-or-no questions addressing snoring, tiredness, observed apnea, blood pressure, BMI greater than 35, age greater than 50, neck circumference greater than 40 centimeters, and male gender, with a score of 3 or higher indicating high risk for OSA. Patients with known OSA should bring their CPAP device to the hospital and use it throughout the perioperative period, including immediately after extubation. Opioid analgesics should be used at the lowest effective dose, as patients with OSA have heightened sensitivity to the respiratory depressant effects of opioids, and multimodal analgesia with non-opioid adjuncts such as acetaminophen, NSAIDs, regional blocks, and gabapentinoids should be employed whenever possible. Continuous pulse oximetry monitoring in the postoperative period is recommended for all patients with known or suspected OSA, particularly during the first 24 to 48 hours when residual anesthetic effects compound the underlying respiratory vulnerability. These measures can dramatically reduce the incidence of postoperative respiratory failure and death in this high-risk population.

<image>Panel A: Elderly perioperative assessment showing frailty screening tools, cognitive baseline assessment, functional status evaluation, polypharmacy medication reconciliation, and goals of care discussion with their prognostic significance. Panel B: Cirrhosis surgical risk assessment showing Child-Pugh and MELD scoring with operative mortality by class, avoidance of elective surgery in decompensated disease, coagulopathy management, and nutritional optimization. Panel C: CKD perioperative management showing medication dose adjustment by GFR, nephrotoxin avoidance, contrast nephropathy prevention protocol, dialysis timing, and potassium monitoring schedule. Panel D: OSA perioperative management showing STOP-BANG screening questionnaire, CPAP continuation requirements, opioid minimization with multimodal analgesia alternatives, and continuous pulse oximetry monitoring recommendations.</image>

Summary

• RCRI assesses cardiac risk using 6 factors: ischemic heart disease, heart failure, cerebrovascular disease, insulin-dependent diabetes, creatinine above 2.0, and high-risk surgery
• Functional capacity of 4 METs or greater generally indicates safety for surgery without further cardiac testing
• Beta-blockers: continue if already prescribed; do not initiate immediately before surgery; titrate if starting in high-risk patients
• Warfarin: stop 5 days before surgery; bridge with LMWH only for high thromboembolic risk
• DOACs: stop 24 to 72 hours before surgery based on specific agent and renal function; no bridging required
• DAPT: delay elective surgery until minimum duration is complete; continue aspirin perioperatively when possible
• Diabetes: hold oral agents on day of surgery; reduce basal insulin to 50 to 80% of dose; target glucose 140 to 180 mg/dL
• Continue beta-blockers, statins, and anticonvulsants; hold ACE inhibitors/ARBs and diuretics on morning of surgery
• VTE prophylaxis: mechanical plus pharmacologic based on risk; extended prophylaxis for 28 to 35 days after orthopedic and cancer surgery
• Postoperative fever: Wind, Water, Wound, Walking, Wonder drugs guides temporal differential diagnosis
• Special populations: assess frailty in elderly; avoid elective surgery in decompensated cirrhosis; screen for OSA with STOP-BANG

Key Terms

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