Study guide
18.3 Perioperative Anticoagulation, Bridging & Postoperative Complications
ABIM Internal Medicine Exam
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1 Chapter 0: The ABIM Exam, Blueprint & Study Strategy
0.1 Exam Format, Question Types & the 2026 Blueprint 0.2 Eligibility, Registration, Fees & Exam-Day Logistics 0.3 Scoring, the Passing Standard & Score Reports 0.4 Building a Blueprint-Weighted Study Plan
2 Chapter 1: Cardiovascular Disease (14% of Exam)
1.1 Ischemic Heart Disease & Acute Coronary Syndromes 1.2 Antithrombotic Therapy, Secondary Prevention & Mechanical Complications of MI 1.3 Atrial Fibrillation, Atrial Flutter & Stroke Prevention 1.4 Supraventricular Tachycardias, Ventricular Arrhythmias & Bradycardias 1.5 Heart Failure: Classification, Staging & Guideline-Directed Medical Therapy 1.6 Device Therapy, HFpEF & the Cardiomyopathies 1.7 Valvular Heart Disease & Endocarditis Prophylaxis 1.8 Pericardial Disease & Acute Aortic Syndromes 1.9 Hypertension: Classification, Diagnosis & Secondary Causes 1.10 Hypertensive Crises & Dyslipidemia 1.11 Adult Congenital Heart Disease & Coarctation of the Aorta 1.12 Syncope: Reflex, Orthostatic & Cardiac Causes 1.13 Cardiac Physical Examination, Murmurs & Antithrombotic Selection
3 Chapter 2: Endocrinology, Diabetes & Metabolism (9% of Exam)
2.1 Diabetes Mellitus: Diagnosis, Glycemic Targets & Pharmacotherapy 2.2 Insulin Therapy, Hyperglycemic Emergencies & Chronic Complications 2.3 Thyroid Function Testing & Hypothyroidism 2.4 Thyrotoxicosis, Thyroid Storm & Thyroid Nodules 2.5 Adrenal & Pituitary Disorders 2.6 Hypercalcemia, Hypocalcemia & Disorders of Mineral Metabolism 2.7 Osteoporosis & Paget Disease of Bone 2.8 Ovarian, Testicular & Reproductive Endocrine Disorders 2.9 Hypoglycemia, Endocrine Tumors, Polyglandular Syndromes & Severe Hypertriglyceridemia
4 Chapter 3: Gastroenterology & Hepatology (9% of Exam)
3.1 Esophageal Disease 3.2 Stomach & Duodenal Disease and Gastrointestinal Hemorrhage 3.3 Inflammatory Bowel Disease 3.4 Celiac Disease & Irritable Bowel Syndrome 3.5 Diverticular Disease & Colorectal Cancer Screening 3.6 Viral Hepatitis, Steatotic & Alcohol-Associated Liver Disease 3.7 Cirrhosis & the Complications of Portal Hypertension 3.8 Acute Pancreatitis 3.9 Chronic Pancreatitis & Biliary Tract Disease 3.10 Inherited, Autoimmune & Drug-Induced Liver Disease 3.11 Small Intestinal Disease, Ischemia & Gastrointestinal Complications of HIV
5 Chapter 4: Infectious Disease (9% of Exam)
4.1 Lower Respiratory Tract Infections & Sepsis Syndromes 4.2 Viral Respiratory Pathogens & Tuberculosis 4.3 Central Nervous System Infections 4.4 Skin, Soft Tissue, Bone & Joint Infections 4.5 Infective Endocarditis & Cardiovascular Infection 4.6 Clostridioides difficile & Catheter-Related Bloodstream Infection 4.7 HIV Diagnosis, Antiretroviral Therapy & Prevention 4.8 Opportunistic Infections & Sexually Transmitted Infections 4.9 Fever of Unknown Origin, Neutropenic Fever & Toxic Shock 4.10 Travel-Related Illness, Vector-Borne Disease & Outbreaks 4.11 Infection Prevention, Nosocomial Infection & Postexposure Prophylaxis 4.12 Rheumatic Fever, Poststreptococcal Disease, Enteric & Hepatic Infections
6 Chapter 5: Pulmonary Disease (9% of Exam)
5.1 COPD: Diagnosis, GOLD Classification & Initial Pharmacotherapy 5.2 Interventions That Reduce COPD Mortality & Exacerbation Management 5.3 Asthma: Diagnosis, Stepwise Therapy & Status Asthmaticus 5.4 Interstitial Lung Disease & Idiopathic Pulmonary Fibrosis 5.5 Sarcoidosis, Hypersensitivity Pneumonitis & Occupational Lung Disease 5.6 Pulmonary Embolism: Diagnosis, Risk Stratification & Anticoagulation 5.7 Pulmonary Hypertension & Sleep-Disordered Breathing 5.8 Acute Respiratory Distress Syndrome & Mechanical Ventilation 5.9 Pleural Disease, Empyema & Pneumothorax 5.10 Bronchiectasis, Cystic Fibrosis & Restrictive Lung Disease 5.11 Evaluation of Cough, Dyspnea, Hemoptysis & the Solitary Pulmonary Nodule
7 Chapter 6: Rheumatology & Orthopedics (9% of Exam)
6.1 Rheumatoid Arthritis: Diagnosis & Systemic Manifestations 6.2 Antirheumatic Pharmacotherapy & the Spondyloarthropathies 6.3 Gout: Pathophysiology & Acute Management 6.4 Urate-Lowering Therapy & Calcium Pyrophosphate Deposition Disease 6.5 Osteoarthritis 6.6 Systemic Lupus Erythematosus 6.7 Systemic Sclerosis, Sjogren Syndrome & Inflammatory Myopathies 6.8 The Vasculitides 6.9 Regional Musculoskeletal Syndromes, Back Pain & Sports Injuries 6.10 Other Primary Rheumatic Disorders & Mixed Connective Tissue Disease 6.11 Osteonecrosis & Metabolic Bone Disease
8 Chapter 7: Hematology (6% of Exam)
7.1 Approach to Anemia & the Microcytic Anemias 7.2 Macrocytic, Normocytic & Hemolytic Anemias 7.3 Hemoglobinopathies, Thalassemias & Paroxysmal Nocturnal Hemoglobinuria 7.4 Platelet Disorders, Thrombocytopenia & the Bleeding Patient 7.5 Coagulation Factor Disorders, Thrombophilia & Anticoagulant Reversal 7.6 Acute Leukemias, Chronic Leukemias & Myeloproliferative Neoplasms 7.7 Lymphomas & Plasma Cell Disorders 7.8 Myelodysplastic Syndrome, Myeloproliferative Neoplasms & Porphyria 7.9 Transfusion Medicine & Late Complications of Transplantation
9 Chapter 8: Medical Oncology (6% of Exam)
8.1 Breast, Lung, Colorectal & Prostate Cancer 8.2 Oncologic Emergencies 8.3 Genitourinary & Gynecologic Malignancies 8.4 Head and Neck, Bone & Soft Tissue Cancer and Cancer of Unknown Primary 8.5 Complications of Cancer & Its Treatment 8.6 Cancer Prevention, Survivorship & Psychosocial Care
10 Chapter 9: Nephrology & Urology (6% of Exam)
9.1 Acute Kidney Injury: Staging, Etiology & Urine Microscopy 9.2 Glomerular Disorders & Nephrotic Syndrome 9.3 Nephritic Syndromes, RPGN & Indications for Renal Replacement Therapy 9.4 Chronic Kidney Disease: Staging & Progression Retardation 9.5 Complications of Chronic Kidney Disease: Anemia, CKD-MBD & Acidosis 9.6 Hyponatremia, Hypernatremia & Water Balance 9.7 Potassium Disorders & Systematic Acid-Base Analysis 9.8 Renal Tubular Acidosis & Nephrolithiasis 9.9 Prostate Disorders, Urinary Incontinence & Other Urologic Conditions 9.10 Cystic Kidney Disease, Obstructive Uropathy, Tubulointerstitial Disease & Hematuria
11 Chapter 10: Neurology (4% of Exam)
10.1 Acute Ischemic Stroke: Syndromes & Reperfusion 10.2 Transient Ischemic Attack, Secondary Prevention & Hemorrhagic Stroke 10.3 Headache & Facial Pain 10.4 Seizures, Epilepsy & Movement Disorders 10.5 Multiple Sclerosis & Neuromuscular Junction Disorders 10.6 Motor Neuron Disease & Acute Peripheral Neuropathy 10.7 Cranial Neuropathies & Neuro-Ophthalmology 10.8 Peripheral Neuropathies, CNS Tumors & Other Neurologic Disorders
12 Chapter 11: Psychiatry & Behavioral Health (4% of Exam)
11.1 Major Depressive Disorder & Medical Mimics 11.2 Antidepressant Pharmacotherapy & Treatment-Resistant Depression 11.3 Bipolar Disorder, Mood Stabilizers & Lithium Toxicity 11.4 Anxiety, Stress-Related & Obsessive-Compulsive Disorders 11.5 Alcohol Use Disorder & Withdrawal 11.6 Pharmacotherapy for Alcohol & Opioid Use Disorder 11.7 Toxidromes, Psychiatric Emergencies & Suicide Risk Assessment 11.8 Psychotic, Somatic Symptom, Factitious & Personality Disorders 11.9 Eating Disorders, Sleep Disorders & Sexual Health
13 Chapter 12: Dermatology (3% of Exam)
12.1 Dermatitis, Papulosquamous & Inflammatory Dermatoses 12.2 Acne, Rosacea & Cutaneous Infections 12.3 Herpes Zoster & Autoimmune Blistering Diseases 12.4 Nodules, Tumors & Cutaneous Oncology 12.5 Dermatologic Emergencies & Severe Cutaneous Adverse Reactions 12.6 Pigment Disorders, Alopecia, Nail Disease & Photosensitivity 12.7 Vascular Dermatoses, Environmental Injury & Cutaneous Signs of Systemic Disease
14 Chapter 13: Obstetrics & Gynecology / Women's Health (3% of Exam)
13.1 Contraception, Preconception Care & Teratogenicity 13.2 Hypertensive Disorders of Pregnancy & Gestational Diabetes 13.3 Thyroid Disease & Venous Thromboembolism in Pregnancy 13.4 Menopause & Menopausal Hormone Therapy 13.5 Abnormal Uterine Bleeding, Endometrial Disease & Gynecologic Cancer Screening 13.6 Breast Disorders & Diseases of the Vulva and Vagina 13.7 Menstrual Disorders, Fibroids, Endometriosis & Early Pregnancy Complications
15 Chapter 14: Geriatric Syndromes (3% of Exam)
14.1 Comprehensive Geriatric Assessment & Frailty 14.2 Falls, Gait Assessment & Polypharmacy 14.3 Urinary Incontinence & Pressure Injuries in Older Adults 14.4 Mild Cognitive Impairment, Dementia & Its Subtypes 14.5 Delirium & the Pharmacotherapy of Cognitive Disorders 14.6 Palliative Care, Hospice & Advance Care Planning 14.7 Chronic Wounds, Nutrition, Swallowing, Constipation & Hip Fracture 14.8 Sensory Impairment, Dizziness, Elder Mistreatment & Care Settings
16 Chapter 15: Allergy & Immunology (2% of Exam)
15.1 Anaphylaxis: Recognition & Emergency Management 15.2 Urticaria & Angioedema 15.3 Drug Allergy, Desensitization & Adult Immunodeficiency 15.4 Food Allergy, Insect Venom Hypersensitivity, Serum Sickness & Contrast Reactions 15.5 Rhinitis, Conjunctivitis, Eosinophilic & Mast Cell Disorders
17 Chapter 16: Preventive Medicine, Immunization & Clinical Epidemiology
16.1 The USPSTF Framework & Evidence-Based Cancer Screening 16.2 Cardiovascular & Metabolic Screening and Primary Prevention 16.3 Adult Immunization & Vaccines in Special Populations 16.4 Clinical Epidemiology, Biostatistics & Study Design
18 Chapter 17: Miscellaneous - Ethics, Patient Safety & Quality Improvement (2% of Exam)
17.1 Principles of Bioethics & Decisional Capacity 17.2 Informed Consent, Treatment Refusal & Special Scenarios 17.3 Surrogate Decision-Making, Advance Directives & Confidentiality 17.4 Patient Safety Science, Medical Error & Diagnostic Reasoning 17.5 Quality Improvement Methods, Health Disparities & Health Equity
19 Chapter 18: Perioperative Medicine & Medical Consultation
18.1 Preoperative Cardiovascular Risk Assessment 18.2 Preoperative Pulmonary Risk & Perioperative Medication Management 18.3 Perioperative Anticoagulation, Bridging & Postoperative Complications
20 Chapter 19: Ophthalmology (1% of Exam)
19.1 The Acute Red Eye & Ophthalmic Emergencies 19.2 Painless Vision Loss & Chronic Ophthalmic Disease 19.3 Uveitis, Scleritis & Orbital Disease
21 Chapter 20: Otolaryngology & Dental Medicine (1% of Exam)
20.1 Dizziness, Vertigo & Epistaxis 20.2 Ear Disorders, Hearing Loss & Upper Respiratory Infections 20.3 Oral Cavity, Salivary Gland, Laryngeal & Taste and Smell Disorders
18.3 Perioperative Anticoagulation, Bridging & Postoperative Complications
Key Takeaways Explain This Topic AI
Direct oral anticoagulants are held for an interval determined by renal function and procedural bleeding risk and do not require bridging.
Bridging with heparin is reserved for the highest thromboembolic risk groups such as mechanical mitral valves and recent thromboembolism.
Early postoperative fever in the first 48 hours is most often inflammatory rather than infectious.
Malignant hyperthermia after volatile anesthetic or succinylcholine exposure is treated with dantrolene alongside cooling and supportive care.
Postoperative delirium is reduced by multicomponent prevention, adequate analgesia and avoidance of high-risk medications.
Last updated: August 2026
- Anticoagulation & Heparin Bridging Protocols
- Direct Oral Anticoagulants (DOACs: Apixaban, Rivaroxaban, Dabigatran, Edoxaban)
Rapid Onset & Offset: DOACs have predictable half-lives (8–14 hours). Routine heparin bridging is NOT indicated for DOACs (bridging provides no thrombotic protection and dramatically increases major bleeding complications).
Discontinuation Timing:
Low/Moderate Bleeding Risk & Normal Renal Function: Hold 24 hours prior to surgery (skip 2 doses of Apixaban/Dabigatran, skip 1 dose of Rivaroxaban).
High Bleeding Risk OR Renal Impairment (CrCl 30–50 mL/min, particularly Dabigatran): Hold 48 to 72 hours prior to surgery (skip 4–6 doses).
Severe Renal Impairment (CrCl < 30 mL/min on Dabigatran): Hold >= 72 to 96 hours.
Postoperative Resumption: Resume DOAC at full dose 24 hours postoperatively for low bleeding-risk procedures, or 48 to 72 hours postoperatively for high bleeding-risk surgeries once definitive surgical hemostasis is established.
Warfarin Management & Heparin Bridging Guidelines
Preoperative Warfarin Management: Discontinue Warfarin 5 days prior to surgery to allow the INR to normalize to < 1.5 on the day of surgery. If the INR remains >= 1.5 on the day prior to surgery, administer low-dose oral Vitamin K (1 to 2.5 mg).
Thrombotic Risk Category Clinical Indication / Patient Criteria Bridging Strategy with Therapeutic LMWH?
HIGH Thrombotic Risk • Mechanical Mitral Valve prosthesis; • Older caged-ball or tilting-disc Mechanical Aortic Valve ; • Bileaflet mechanical AVR with additional stroke risk factors (AFib, prior stroke/TIA, HTN, DM, CHF); • Recent TIA or Ischemic Stroke (< 3 months) ; • Recent Venous Thromboembolism (< 3 months) ; • Severe Antiphospholipid Syndrome (high-titer triple positive) YES — BRIDGING IS INDICATED .; Start Therapeutic LMWH ( Enoxaparin 1 mg/kg SC q12h or 1.5 mg/kg SC daily) when INR falls < 2.0 (usually POD -3).; Stop LMWH 24 hours prior to surgery (12 hours for prophylactic dose).
MODERATE Thrombotic Risk • Bileaflet Mechanical AVR with 1 stroke risk factor; • Atrial Fibrillation with CHA2DS2-VASc score 5–6; • VTE within 3 to 12 months INDIVIDUALIZED DECISION (Generally NO bridging unless procedure is delayed or patient has multiple compounding risks).
LOW Thrombotic Risk • Atrial Fibrillation with CHA2DS2-VASc <= 4 (no prior TIA/stroke); • Bileaflet Mechanical AVR without stroke risk factors; • Remote VTE (> 12 months ago) NO — BRIDGING IS CONTRAINDICATED .; The landmark BRIDGE Trial demonstrated that bridging low/moderate risk AFib patients produced NO reduction in arterial thromboembolism but caused a three-fold increase in major bleeding .
- 1. Postoperative Complications
- The 5 Ws of Postoperative Fever
Postoperative fever is a common clinical challenge. Systematic evaluation follows the classic "5 Ws" chronologic framework:
Wind (Postoperative Days 1–2):
Etiology: Atelectasis is the most common cause of fever in the first 48 hours, caused by shallow breathing, diaphragmatic splinting, and alveolar collapse. Early aspiration pneumonia can also manifest in this window.
Management: Aggressive pulmonary toilet, incentive spirometry, early ambulation, and effective pain control. (Routine antibiotics are NOT indicated for uncomplicated atelectasis).
Water (Postoperative Day 3):
Etiology: Urinary Tract Infection (UTI) , strongly associated with prolonged indwelling urethral (Foley) catheterization.
Management: Prompt catheter removal, urinalysis, urine culture, and targeted antimicrobial therapy.
Wound (Postoperative Days 5–7):
Etiology: Surgical Site Infection (SSI) , ranging from superficial incisional cellulitis to deep fascial necrosis or intra-abdominal/organ-space abscesses.
Clinical Signs: Erythema, warmth, localized induration, purulent wound drainage, wound dehiscence, fluctuance, and focal tenderness.
Management: Open surgical incision, evacuate purulence, debride necrotic tissue, pack wound with moist sterile gauze, obtain wound cultures, and initiate systemic antibiotics if surrounding cellulitis or systemic toxicity is present.
Walking (Postoperative Days 7–10+):
Etiology: Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE) resulting from perioperative immobilization, endothelial injury, and surgical hypercoagulability.
Clinical Signs: Unilateral lower extremity swelling, calf tenderness; acute pleuritic chest pain, tachypnea, tachycardia, and hypoxemia.
Management: Diagnostic lower extremity venous duplex ultrasound or CT Pulmonary Angiography (CTPA); immediate therapeutic anticoagulation (LMWH, DOAC, or IV heparin).
Wonder Drugs (Anytime / POD > 7):
Etiology: Drug-induced fever (antibiotics [beta-lactams, sulfonamides], Heparin-Induced Thrombocytopenia [HIT], anticonvulsants), blood product transfusion reactions, or Malignant Hyperthermia (immediate intraoperative).
Malignant Hyperthermia (MH)
Pathophysiology: A life-threatening, autosomal dominant pharmacogenetic disorder of skeletal muscle excitation-contraction coupling. Most commonly caused by gain-of-function mutations in the ryanodine receptor 1 gene ( RYR1 ) on chromosome 19q13.1 (or the voltage-gated calcium channel alpha-1S subunit gene [ CACNA1S ]).
Triggering Agents:
Volatile Halogenated Inhalational Anesthetics: Sevoflurane, Desflurane, Isoflurane, Halothane .
Depolarizing Neuromuscular Blocker: Succinylcholine .
(Safe Anesthetics: Propofol, etomidate, ketamine, barbiturates, opioids, local anesthetics, and non-depolarizing neuromuscular blockers like rocuronium and vecuronium are completely safe).
Pathogenesis: Exposure to triggers leads to uncontrolled, massive efflux of calcium from the sarcoplasmic reticulum into the myoplasm via dysfunctional RYR1 channels. This triggers sustained, hyperactive actin-myosin cross-bridging, causing intense muscle contraction, massive ATP consumption, aerobic/anaerobic hypermetabolism, extreme heat production, metabolic acidosis, rhabdomyolysis, and myocyte lysis.
Clinical Presentation:
Earliest & Most Sensitive Sign: Unexplained, rapid, progressive elevation in End-Tidal CO2 (ETCO2 / hypercarbia) that is refractory to substantial increases in minute ventilation.
Muscle Rigidity: Masseter muscle spasm (trismus) following succinylcholine administration; generalized skeletal muscle rigidity ("wooden-chest").
Autonomic Instability: Sinus tachycardia, tachypnea, labile blood pressure, and ventricular arrhythmias.
Hyperthermia: Rapidly rising core body temperature (frequently exceeding 40.0°C to 42.0°C [104.0°F to 107.6°F] , rising up to 1°C every 5 minutes); hyperthermia is a late sign but confirms catastrophic hypermetabolism.
Laboratory Findings: Severe mixed respiratory and lactic acidosis , profound hyperkalemia (from myocyte necrosis; can trigger fatal ventricular fibrillation), markedly elevated serum creatine kinase ( CK > 10,000 to 100,000 U/L ), hyperphosphatemia, and myoglobinuria (cola-colored urine leading to acute tubular necrosis).
Emergency Resuscitation Protocol:
Immediately Discontinue Triggering Agents: Stop all volatile anesthetics and succinylcholine; shut off vaporizers. Maintain anesthesia with IV propofol/opioids.
Hyperventilate with 100% Oxygen: Deliver 100% high-flow O2 at >= 10 L/min using clean circuit to blow off excess CO2.
Administer IV Dantrolene Sodium (Definitive Antidote): Initial bolus dose of 2.5 mg/kg IV rapidly , repeated every 5 to 10 minutes until hypercarbia, rigidity, and tachycardia resolve (cumulative doses up to 10 to 30 mg/kg may be required). Mechanism: Dantrolene directly binds to the RYR1 channel, inhibiting sarcoplasmic calcium release and halting uncontrolled muscle hypermetabolism.
Active Aggressive Cooling: Infuse cold (4°C) IV normal saline (500–1000 mL); apply ice packs to axillae, groin, and neck; perform cold gastric/bladder lavage. Stop cooling when core temperature reaches < 38.5°C to avoid rebound hypothermia.
Treat Life-Threatening Hyperkalemia: IV Calcium chloride (10 mL of 10% solution) or Calcium gluconate, IV Regular Insulin (10 units) + 50% Dextrose (50 mL), IV Sodium bicarbonate (50 mEq), and nebulized Albuterol.
Maintain Renal Perfusion: Administer IV fluids and IV Furosemide/Mannitol to achieve target urine output > 1 to 2 mL/kg/hour , preventing obstructive myoglobinuric acute renal failure.