Perioperative Management — Risk Assessment

• Surgical stress response and sympathetic activation: Surgery triggers a profound neuroendocrine stress response involving catecholamine release (epinephrine and norepinephrine), cortisol elevation, and inflammatory cytokine production (IL-6, TNF-α, IL-1β). This hyperadrenergic state increases myocardial oxygen demand, heart rate, and systemic vascular resistance, precipitating myocardial ischemia in patients with coronary artery disease. Patients with left ventricular dysfunction, prior myocardial infarction, or significant coronary stenosis are at highest risk, as their myocardium cannot meet the increased oxygen requirements. The inflammatory cascade simultaneously increases prothrombotic activity through tissue factor activation and platelet aggregation, explaining the increased risk of perioperative thromboembolism. This stress response persists for 48-72 hours postoperatively, creating a vulnerable window for acute cardiovascular events.

• Airway and respiratory compromise mechanisms: Perioperative respiratory complications stem from multiple pathophysiologic mechanisms. General anesthesia causes loss of airway protective reflexes, hypoventilation with resulting hypercarbia and hypoxemia, and atelectasis formation (particularly in dependent lung zones due to mechanical compression and loss of negative pressure ventilation). Patients with obstructive sleep apnea (OSA), obesity, chronic obstructive pulmonary disease (COPD), and restrictive lung disease have baseline ventilation-perfusion mismatch and reduced respiratory reserve that is further compromised. Postoperatively, residual anesthetic agents, opioid analgesics, and pain-related splinting of the chest wall perpetuate hypoventilation. In patients with significant COPD or pulmonary hypertension, the loss of hypoxic pulmonary vasoconstriction compensation can cause acute right heart decompensation. Additionally, aspiration risk is elevated due to delayed gastric emptying from perioperative stress hormones, mechanical bowel obstruction, and reduced mental status.

• Thromboembolism pathophysiology: The perioperative period creates a prothrombotic state through Virchow's triad mechanisms. Endothelial injury from surgical trauma activates tissue factor and von Willebrand factor release. Stasis results from immobilization during and after surgery, reduced cardiac output from anesthesia, and mechanical compression of venous return. Hypercoagulability develops through increased thrombin generation (prothrombin fragment 1+2 elevation), elevated Factor VIII and fibrinogen, increased platelet count and reactivity, and suppression of natural anticoagulants (protein C and S). Tissue trauma releases microparticles expressing tissue factor, directly activating the extrinsic pathway. This prothrombotic milieu persists for 2-4 weeks postoperatively, explaining why venous thromboembolism (VTE) risk extends beyond the immediate perioperative period. Patients with active malignancy, prior VTE, thrombophilia, and immobility have amplified baseline prothrombotic tendency that compounds surgical risk.

• Renal dysfunction and metabolic derangement mechanisms: Surgery-induced renal injury occurs through decreased renal perfusion (from anesthesia-induced hypotension and fluid shifts), increased renal vasoconstriction (from catecholamine and angiotensin II activation), and direct tubular injury from myoglobinuria (in extensive trauma), hemoglobinuria, or contrast exposure. Acute kidney injury (AKI) develops in 1-5% of general surgical patients and >10% of cardiac surgery patients, substantially increasing morbidity and mortality. Baseline chronic kidney disease (CKD) reduces functional reserve and impairs medication clearance. Additionally, the perioperative stress response causes insulin resistance through increased counterregulatory hormones and decreased insulin secretion, leading to hyperglycemia that impairs wound healing and increases infection risk. Fluid overload from perioperative administration of crystalloids can precipitate pulmonary edema in patients with heart failure or renal dysfunction.

• Functional status as a surrogate for cardiopulmonary reserve: Metabolic equivalent (MET) capacity represents the oxygen consumption during activity relative to resting baseline (1 MET = 3.5 mL O₂/kg/min). Patients unable to achieve 4 METs (inability to climb stairs, walk 2 blocks, or perform light housework) have severely impaired cardiopulmonary reserve and are at substantially elevated risk for perioperative cardiac and pulmonary complications. This functional impairment reflects underlying cardiac, pulmonary, or deconditioning pathology that will be unmasked by surgical stress. The inability to manifest a normal heart rate or blood pressure response to exercise indicates autonomic dysfunction or cardiac limitation (chronotropic incompetence is particularly predictive of coronary artery disease).

• Cardiovascular risk factors: Established coronary artery disease (prior MI, angina, positive stress test) carries 2-5% risk of perioperative MI or death, with risk stratified by symptom severity and functional limitation. Uncontrolled hypertension (SBP >180 mmHg or DBP >110 mmHg) increases risk of myocardial ischemia, arrhythmias, and stroke; however, acute preoperative treatment paradoxically increases risk and should be avoided unless truly severe. Congestive heart failure significantly increases risk, particularly if ejection fraction <35% or symptoms at rest (New York Heart Association class III-IV). Valvular heart disease (particularly aortic stenosis with a valve area <1 cm² or severe mitral stenosis) impairs the heart's ability to increase cardiac output in response to stress. Arrhythmias, especially uncontrolled atrial fibrillation, increase thromboembolism and hemodynamic compromise risk. Peripheral vascular disease is a powerful surrogate for coronary artery disease burden and independently increases cardiac risk.

• Pulmonary risk factors: Chronic obstructive pulmonary disease with baseline FEV₁ <50% predicted, obstructive sleep apnea (particularly if untreated or severe with apnea-hypopnea index >30), obesity (BMI >30, with very high risk if BMI >40), and restrictive lung disease (interstitial pulmonary fibrosis, kyphoscoliosis) all substantially impair perioperative respiratory function. Active smoking within 8 weeks of surgery impairs mucociliary clearance and increases secretions, substantially elevating pneumonia risk; smoking cessation for even 24 hours reduces carboxyhemoglobin and improves oxygen delivery. Obstructive sleep apnea predisposes to difficult intubation, postoperative airway obstruction, and opioid-induced respiratory depression.

• Metabolic and endocrine risk factors: Poorly controlled diabetes mellitus (HbA₁c >8%) substantially increases surgical site infections through multiple mechanisms including impaired neutrophil function, reduced complement activity, and microvascular complications impairing tissue perfusion. Renal dysfunction (baseline creatinine >1.5 mg/dL or estimated GFR <60 mL/min/1.73m²) impairs fluid and electrolyte homeostasis, medication clearance, and hemostasis (uremia-induced platelet dysfunction). Advanced liver disease with cirrhosis increases operative mortality 3-4 fold due to coagulopathy, encephalopathy risk, and reduced synthetic function. Hypoalbuminemia (<3.0 g/dL) reflects malnutrition or chronic illness and is associated with impaired wound healing and increased infections.

• Age and functional status: Advanced age (>70 years) is an independent risk factor, though chronologic age matters less than physiologic status and comorbidities. Inability to perform activities of daily living (ADL) or achieve 4 METs functional capacity represents profound cardiopulmonary limitation and dramatically increases perioperative risk. Frailty (characterized by weakness, slowness, low activity, exhaustion, and unintentional weight loss) identifies elderly patients at extreme perioperative risk even if comorbidities seem mild.

• Anemia and hematologic factors: Preoperative anemia (Hgb <10 g/dL) impairs oxygen delivery and increases myocardial ischemia risk, particularly when combined with coronary artery disease. Thrombophilia (inherited or acquired), active malignancy, prior VTE, and immobility create markedly elevated VTE risk in the perioperative period.

• Medication-related factors: Anticoagulation (warfarin, DOACs) must be managed carefully; perioperative bridging decisions depend on thromboembolism risk versus bleeding risk. Antiplatelet therapy (aspirin, P2Y₁₂ inhibitors) impacts bleeding risk but is often continued for patients with coronary stents. Beta-blockers provide protection in high-risk cardiac patients but should not be initiated acutely. Statins provide perioperative cardioprotection through pleiotropic effects beyond lipid lowering.

• Surgery-specific risk factors: The magnitude of surgical insult is critical—major vascular surgery, cardiac surgery, and high-risk urgent/emergent procedures carry substantially higher complication rates than minor superficial procedures. Duration >2-3 hours, extensive blood loss, and emergency status dramatically increase risk.

• History of prior perioperative complications: A history of prior myocardial infarction (particularly if within 30 days, when risk of reinfarction is maximal), prior stroke or transient ischemic attack, prior perioperative arrhythmia requiring intervention, or prior difficult intubation substantially elevates recurrent risk. Documentation of the timing and circumstances of prior events provides prognostic information—recent MI indicates active coronary instability, whereas remote MI reflects healed infarction with residual dysfunction but lower acute ischemia risk.

• Symptom assessment and functional capacity: Patient-reported chest pain or angina with exertion, particularly if occurring with <4 METs activity (such as climbing one flight of stairs or walking less than two blocks), indicates significant coronary limitation and requires further cardiac workup. Dyspnea on exertion reflects cardiopulmonary limitation; the METs threshold at which dyspnea appears correlates directly with surgical risk. Orthopnea and paroxysmal nocturnal dyspnea indicate heart failure decompensation. Syncope or presyncope suggests arrhythmia or hemodynamic compromise and requires evaluation. Leg swelling or pain raises concern for DVT and requires assessment.

• Vital sign abnormalities: Uncontrolled hypertension (SBP >180 mmHg or DBP >110 mmHg) should prompt discussion with anesthesia but not acute treatment. Hypoxemia (SpO₂ <90% on room air) indicates underlying pulmonary disease or cardiac-pulmonary compromise. Tachycardia at rest (HR >100) suggests pain, anxiety, decompensated heart failure, or hyperthyroidism. Bradycardia in a non-athlete raises concern for conduction abnormality.

• Physical examination findings: Distant heart sounds or new murmur (especially diastolic murmur of aortic regurgitation or harsh systolic murmur of aortic stenosis) raises concern for hemodynamically significant valvular disease. Elevated jugular venous pressure or hepatojugular reflux indicates right heart dysfunction or volume overload. Bilateral lower extremity edema suggests heart failure, venous disease, or cirrhosis. Cachexia and temporal wasting indicate significant malnutrition or malignancy. Asterixis or confusion suggests hepatic encephalopathy. Wheezing or crackles on lung examination indicate reactive airway disease or pulmonary edema. Severely limited range of motion or inability to stand from sitting confirms functional impairment.

• Medication list review: The presence of beta-blockers, ACE inhibitors, diuretics, antiarrhythmics, insulin, and anticoagulants reveals chronic disease burden and medication dependencies that require perioperative management. Patients on multiple cardiac medications (particularly those on beta-blockers, ACE inhibitors, and aldosterone antagonists) likely have significant cardiac dysfunction.

• Clinical variants and special considerations: Patients with diabetes mellitus may have silent myocardial ischemia due to autonomic neuropathy, making symptom absence unreliable for risk assessment. Elderly patients often minimize or underreport symptoms, necessitating more aggressive objective testing. Patients with renal failure have atypical anginal presentations and warrant ECG assessment even with atypical symptoms.

• Revised Cardiac Risk Index (RCRI): This widely-used tool stratifies preoperative cardiac risk based on six clinical predictors: (1) high-risk surgery type, (2) history of ischemic heart disease, (3) history of heart failure, (4) history of cerebrovascular disease, (5) preoperative treatment with insulin, and (6) preoperative creatinine >2 mg/dL. The RCRI score predicts the risk of major cardiac complications (MI, cardiac death, pulmonary edema, complete heart block): 0 points = 0.4% risk, 1 point = 0.9%, 2 points = 7%, and ≥3 points = >11% risk. While useful for general stratification, RCRI has been superseded by more refined models in some settings and does not adequately capture functional capacity limitations.

• Metabolic Equivalent (MET) assessment: Functional capacity quantification is among the most powerful perioperative predictors. Ask patients directly: "Can you climb a flight of stairs?" (≈4 METs), "Can you walk two blocks on level ground at normal pace?" (≈4 METs), or "Can you perform light housework?" (≈4 METs). Patients unable to achieve 4 METs due to cardiac or pulmonary limitation are at substantially increased cardiac risk (approximately 10-15% incidence of major cardiac complications). This single subjective assessment often surpasses objective test results in predicting perioperative complications.

• 12-lead electrocardiogram (ECG): Obtain preoperatively in all patients age >65, those with cardiovascular disease history, those with cardiac risk factors, and any patient with exercise-induced symptoms. Interpret for: prior MI pattern (pathologic Q waves, persistent ST elevation), active ischemia (ST depression, T-wave inversions), left ventricular hypertrophy (increased voltage suggesting chronic hypertension and LV dysfunction risk), complete heart block or high-degree AV block (contraindications to elective surgery), uncontrolled atrial fibrillation with rapid ventricular response (hemodynamically significant arrhythmia), and prolonged QT interval (predisposition to torsades de pointes). Absence of ECG abnormalities does NOT exclude significant coronary disease; sensitivity is only 60-70% for hemodynamically significant stenosis.

• Transthoracic echocardiography: Obtain when clinical suspicion of structural cardiac disease exists (murmur, known history of cardiomyopathy, dyspnea without clear pulmonary cause). This objectively quantifies: ejection fraction (EF <35% is high-risk; EF 35-50% is intermediate-risk), **

Medical optimization (ACC/AHA, ADA Standards of Care, CHEST antithrombotic guidance)

• Beta blockers (e.g., metoprolol): continue in chronic users — abrupt withdrawal precipitates rebound ischemia. Do not start a beta blocker on the day of surgery — POISE showed fewer MIs but more strokes and higher total mortality.
• Statins (e.g., atorvastatin): continue perioperatively; continuation is guideline-supported for patients already on therapy and for vascular surgery.
• Aspirin: continue in patients with coronary stents; POISE-2 showed no benefit from initiating aspirin de novo.
• Antithrombotics: warfarin held ~5 days; per BRIDGE, most atrial fibrillation patients need no heparin bridge (reserve bridging for mechanical mitral valves, recent VTE/stroke). DOACs held 1–2 days based on renal function and bleeding risk.
• Diabetes agents: hold metformin the day of surgery; hold SGLT2 inhibitors several days preoperatively (FDA labeling) to avoid euglycemic DKA.
• Chronic glucocorticoids: give stress-dose hydrocortisone for major surgery.
• VTE prophylaxis (ACCP/CHEST): risk-stratify (Caprini) and use LMWH such as enoxaparin plus mechanical prophylaxis.
• Antibiotic prophylaxis: cefazolin within 60 minutes of incision (IDSA/ASHP/SIS).

Cardiovascular

• Myocardial injury after noncardiac surgery (MINS) / perioperative MI: demand–supply mismatch (type 2 MI) from tachycardia, hypotension, anemia, and the catecholamine surge. Most episodes are silent because opioids and residual anesthesia mask chest pain — the signal is an asymptomatic troponin rise in the first 48–72 hours. Independently predicts 30-day mortality. Emergency.
• Coronary stent thrombosis: premature interruption of dual antiplatelet therapy in an incompletely endothelialized stent, worsened by the prothrombotic surgical state. Presents as abrupt ST-elevation MI with cardiogenic shock. Emergency — cath lab.
• Decompensated heart failure / flash pulmonary edema: perioperative crystalloid load plus diastolic dysfunction; signals are rising oxygen requirement, JVD, and bilateral crackles on postoperative day 1–3.
• Atrial fibrillation with RVR from inflammatory and adrenergic stimulation; loss of atrial kick is poorly tolerated in aortic stenosis or HFpEF.

Pulmonary

• Atelectasis → pneumonia → respiratory failure: loss of functional residual capacity, splinting, and impaired mucociliary clearance. Fever and hypoxemia in the first 48 hours suggest atelectasis; new infiltrate with purulent secretions suggests pneumonia.
• Opioid-induced respiratory depression in OSA: blunted arousal plus upper-airway collapse; unexplained hypercapnia or a naloxone-responsive somnolent patient. Emergency.
• Pulmonary embolism: Virchow triad as described above; sudden dyspnea, tachycardia, hypoxemia, sometimes with right-heart strain on ECG or echo. Emergency.

Other

• Acute kidney injury: intraoperative hypotension plus nephrotoxins; oliguria with a creatinine rise. Avoid NSAIDs and ACE inhibitor/ARB dosing in the hypotensive patient.
• Postoperative delirium: high-yield in the elderly and frail; prevention favors nonpharmacologic measures, and antipsychotics are not recommended for routine prophylaxis.
• Surgical site infection: potentiated by hyperglycemia, hypothermia, and mistimed prophylaxis.
• Adrenal crisis in steroid-dependent patients: refractory hypotension unresponsive to fluids/pressors. Emergency.
• Malignant hyperthermia after succinylcholine/volatile agents: rising end-tidal CO₂, rigidity, hyperthermia — stop the trigger and give dantrolene. Emergency.
• Treatment-induced harms: bleeding from bridging heparin, stroke and hypotension from newly initiated beta blockade, and euglycemic DKA from continued SGLT2 inhibitors.

• The 4-MET rule is the pivot of the whole algorithm: a patient who can climb a flight of stairs or walk two level blocks proceeds to surgery without further cardiac testing, regardless of an elevated RCRI. "Order a stress test" is the classic wrong answer in a stem that already tells you the patient walks up two flights without symptoms.
• Emergency surgery = proceed, with perioperative surveillance. No test, consult, or optimization outweighs a ruptured aneurysm or perforated viscus.
• Never start a beta blocker on the day of surgery (POISE: fewer MIs but more strokes and deaths). But never stop a chronic beta blocker either — withdrawal causes rebound tachycardia and ischemia. Examiners test both halves.
• Memorize the six RCRI variables: high-risk surgery, ischemic heart disease, heart failure, cerebrovascular disease, insulin-treated diabetes, and creatinine >2 mg/dL. Note that age is not an RCRI variable — a common distractor.
• Stent timing: elective noncardiac surgery is deferred after coronary stenting until the mandated duration of dual antiplatelet therapy has elapsed — shortest after balloon angioplasty/bare-metal stent, longest after drug-eluting stent. Stopping P2Y₁₂ inhibitors early risks catastrophic stent thrombosis; when urgent surgery cannot wait, continue aspirin if at all possible.
• Symptomatic severe aortic stenosis is the valvular lesion examiners love: fixed cardiac output, poor tolerance of vasodilation and tachycardia. Elective surgery is postponed for valve intervention.
• Prophylactic coronary revascularization before noncardiac surgery does not reduce mortality (CARP) — the correct answer is medical optimization, not preoperative PCI/CABG.
• Silent perioperative MI: a postoperative day-2 troponin rise without chest pain in a diabetic patient is MINS, not a lab error — think demand ischemia and hypotension, not plaque rupture.