Study guide
4.1 Lower Respiratory Tract Infections & Sepsis Syndromes
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
4.1 Lower Respiratory Tract Infections & Sepsis Syndromes
Key Takeaways Explain This Topic AI
Bronchitis, pneumonia, lung abscess, tuberculosis and pleural space infection are enumerated under lower respiratory tract infections.
Bacteremia and sepsis syndrome is a separate subsection listing fever and neutropenia, systemic inflammatory response syndrome, septic shock and toxic shock syndrome.
Blood cultures should be drawn before antibiotics whenever this does not delay administration in suspected sepsis.
Vasopressors are started when hypotension persists after initial crystalloid resuscitation, with norepinephrine as the first-line agent.
The healthcare-associated pneumonia category has been retired; empiric coverage for resistant organisms is driven by local antibiogram data and individual risk factors.
Last updated: August 2026
Infectious pulmonary and systemic diseases constitute a major percentage of inpatient admissions and critical care consultations. Mastery of clinical prediction rules (CURB-65, PSI), empiric antimicrobial selection, sepsis resuscitation bundles, antiviral pharmacology, and antimycobacterial therapy is vital for the ABIM Internal Medicine Board Examination.
1. Community-Acquired Pneumonia (CAP)
Community-Acquired Pneumonia (CAP) is defined as an acute infection of the pulmonary parenchyma acquired outside of a healthcare facility or diagnosed within <48 hours of hospital admission.
Microbiology
Typical Bacterial Pathogens: Streptococcus pneumoniae (most common bacterial cause across all age groups; classically causes lobar consolidation, rusty sputum, lancet-shaped Gram-positive diplococci), Haemophilus influenzae (frequent in COPD and smokers), Moraxella catarrhalis , Staphylococcus aureus (post-viral influenza, cavitary/necrotizing pneumonia), and Klebsiella pneumoniae (alcohol use disorder, currant-jelly sputum, upper lobe cavitation).
Atypical Pathogens: Mycoplasma pneumoniae (young adults, cold agglutinins, autoimmune hemolytic anemia, erythema multiforme), Chlamydia pneumoniae (subacute presentation, pharyngitis, hoarseness), and Legionella pneumophila (contaminated water aerosols, air conditioning cooling towers, presents with high fever, relative bradycardia [Faget sign], gastrointestinal symptoms/diarrhea, hyponatremia, and elevated transaminases; diagnosed via urine antigen test for serogroup 1).
Respiratory Viruses: Influenza A and B, Respiratory Syncytial Virus (RSV), SARS-CoV-2, Metapneumovirus, and Adenovirus.
Clinical Risk Stratification & Site-of-Care Triage
Determining outpatient versus inpatient versus intensive care unit (ICU) admission is the critical initial decision in CAP management.
Scoring Tool Components & Criteria Clinical Thresholds & Action
CURB-65 Score • C onfusion (new mental disorientation); • U rea >20 mg/dL (BUN >19 mg/dL / >7 mmol/L); • R espiratory Rate >=30 breaths/min; • B lood Pressure (SBP <90 mmHg or DBP <=60 mmHg); • Age >= 65 years • Score 0–1: Low risk (mortality <1.5%); safe for Outpatient management.; • Score 2: Intermediate risk (mortality ~9%); consider Inpatient Ward admission or close outpatient observation.; • Score >=3: High risk (mortality 15–40%); mandates Inpatient Admission , evaluate for ICU if score 4–5.
Pneumonia Severity Index (PSI / PORT) 20 clinical, demographic, laboratory, and radiographic variables (calculates point score) • Class I–II (<70 pts): Outpatient treatment.; • Class III (71–90 pts): Outpatient vs. Short-stay observation unit.; • Class IV (91–130 pts): Inpatient medical ward admission.; • Class V (>130 pts): Inpatient / ICU admission (mortality up to 28%).
IDSA/ATS Severe CAP Criteria (ICU Triage) • Major Criteria (1 required for ICU): ; 1. Septic shock requiring vasopressor support; 2. Acute respiratory failure requiring invasive mechanical ventilation; • Minor Criteria (>=3 required for ICU): ; 1. RR >=30/min | 2. PaO2/FiO2 ratio <=250; 3. Multilobar infiltrates | 4. Confusion/disorientation; 5. BUN >=20 mg/dL | 6. Leukopenia (WBC <4,000/mcL); 7. Thrombocytopenia (Plt <100,000/mcL) | 8. Hypothermia (core temp <36.0°C); 9. Hypotension requiring aggressive fluid resuscitation Direct admission to the Intensive Care Unit (ICU) is mandated if 1 Major criterion OR >=3 Minor criteria are met.
- Empiric Antimicrobial Regimens for CAP (IDSA/ATS Guidelines)
- A. Outpatient Regimens
Healthy Adults Without Comorbidities or Risk Factors for Resistant Pathogens:
- Amoxicillin 1 g PO TID (preferred high-dose beta-lactam) OR
- Doxycycline 100 mg PO BID OR
Macrolide (Azithromycin 500 mg day 1, then 250 mg daily; or Clarithromycin 500 mg BID) ONLY IF local pneumococcal macrolide resistance is documented to be <25% .
Adults with Chronic Comorbidities (COPD, HF, DM, Chronic Kidney/Liver Disease, Alcoholism, Asplenia, Malignancy):
Combination Therapy (Beta-lactam + Atypical Coverage):
Amoxicillin-clavulanate (Augmentin) 875/125 mg PO BID or 2000/125 mg PO BID, OR Cefuroxime 500 mg PO BID, OR Cefpodoxime 200 mg PO BID PLUS
Azithromycin 500 mg daily (or Clarithromycin 500 mg BID) OR Doxycycline 100 mg PO BID.
Monotherapy with Respiratory Fluoroquinolone:
Levofloxacin 750 mg PO daily OR Moxifloxacin 400 mg PO daily.
B. Inpatient Regimens (Non-ICU Medical Ward)
Standard Dual Therapy (Class I Recommendation):
IV Beta-lactam ( Ceftriaxone 1–2 g IV daily, Ampicillin-sulbactam 1.5–3 g IV q6h, or Cefotaxime 1–2 g IV q8h) PLUS
IV/PO Macrolide ( Azithromycin 500 mg IV/PO daily).
Monotherapy Alternative:
Respiratory Fluoroquinolone ( Levofloxacin 750 mg IV/PO daily or Moxifloxacin 400 mg IV/PO daily).
C. Inpatient Regimens (ICU / Severe CAP)
Core Backbone: IV Beta-lactam ( Ceftriaxone 2 g IV daily or Ampicillin-sulbactam 3 g IV q6h) PLUS IV Azithromycin 500 mg daily OR IV Levofloxacin 750 mg daily.
Risk Factors for MRSA (Prior isolation, post-influenza necrotizing infiltrates, cavitary lesions, end-stage renal disease):
Add Vancomycin (15–20 mg/kg IV q8–12h targeting AUC/MIC 400–600 or trough 15–20 mcg/mL) OR Linezolid 600 mg IV/PO q12h.
Clinical Pearl: Nasal MRSA PCR screening has a Negative Predictive Value (NPV) >96–98% ; a negative nasal PCR allows rapid discontinuation/de-escalation of anti-MRSA therapy.
Risk Factors for Pseudomonas aeruginosa (Prior isolation, bronchiectasis, severe structural lung disease, frequent systemic corticosteroid/antibiotic courses):
Replace Ceftriaxone with an Antipseudomonal Beta-lactam ( Piperacillin-tazobactam 4.5 g IV q6h, Cefepime 2 g IV q8h, Ceftazidime 2 g IV q8h, or Meropenem 1 g IV q8h) PLUS Levofloxacin 750 mg IV daily or Ciprofloxacin 400 mg IV q8h.
Loading diagram... Community-Acquired Pneumonia (CAP) Triage and Empiric Treatment Algorithm
2. Hospital-Acquired Pneumonia (HAP) & Ventilator-Associated Pneumonia (VAP)
Hospital-Acquired Pneumonia (HAP): Pneumonia occurring >=48 hours after hospital admission that was not incubating at the time of admission.
Ventilator-Associated Pneumonia (VAP): Pneumonia arising >48–72 hours following endotracheal intubation .
Microbiology: Gram-negative bacilli ( Pseudomonas aeruginosa , Klebsiella pneumoniae , Escherichia coli , Enterobacter cloacae , Acinetobacter baumannii , Stenotrophomonas maltophilia ) and Staphylococcus aureus (MRSA and MSSA).
Empiric Treatment Strategy
Single Antipseudomonal Beta-Lactam (Cefepime 2 g IV q8h, Piperacillin-tazobactam 4.5 g IV q6h, or Meropenem 1 g IV q8h).
Add MRSA Coverage (Vancomycin 15–20 mg/kg IV q8–12h or Linezolid 600 mg IV q12h) if patient has prior IV antibiotic exposure within 90 days, hospitalization in a unit where MRSA prevalence is >20% or unknown, or high risk of mortality.
Add Second Antipseudomonal Agent (Aminoglycoside: Amikacin/Tobramycin, or Fluoroquinolone: Ciprofloxacin/Levofloxacin) if high mortality risk, septic shock, or prior IV antibiotics within 90 days.
Duration: Standard course is 7 days for responding patients with clinical improvement and resolving procalcitonin.
- 3. Sepsis & Septic Shock (Surviving Sepsis Campaign 2021 Guidelines)
- Definitions (Sepsis-3 Criteria)
Sepsis: Life-threatening organ dysfunction caused by a dysregulated host immune response to infection. Organ dysfunction is clinically identified by an acute increase in the Sequential Organ Failure Assessment (SOFA) score >= 2 points .
Septic Shock: A subset of sepsis in which underlying circulatory and cellular/metabolic abnormalities are profound enough to substantially increase mortality. Defined clinically as: Persisting hypotension requiring vasopressors to maintain Mean Arterial Pressure (MAP) >= 65 mmHg AND serum lactate > 2.0 mmol/L (18 mg/dL) despite adequate volume resuscitation .
The Surviving Sepsis Hour-1 Bundle
All 5 elements should be initiated immediately within the first 60 minutes of triage or recognition:
Measure Serum Lactate Level: Remeasure within 2–4 hours if initial lactate is elevated (>2.0 mmol/L) to guide resuscitation and clearance kinetics.
Obtain Blood Cultures Prior to Antibiotics: Obtain at least 2 sets of blood cultures (aerobic and anaerobic bottles from distinct venipuncture sites). Do not delay antibiotic administration by >45 minutes if blood cultures are difficult to draw.
Administer Broad-Spectrum IV Antimicrobials: Initiate full-dose empiric IV antimicrobials within 1 hour of recognition.
Administer Rapid IV Crystalloid Resuscitation: Administer 30 mL/kg of IV balanced crystalloid (Lactated Ringer's or Plasma-Lyte preferred over 0.9% Normal Saline to reduce hyperchloremic metabolic acidosis and acute kidney injury) within 3 hours for hypotension (MAP <65 mmHg) or initial serum lactate >= 4.0 mmol/L.
Apply Vasopressors for Refractory Hypotension:
First-Line Vasopressor: Norepinephrine (potent alpha-1 and modest beta-1 agonist) titrated to maintain MAP >= 65 mmHg .
Second-Line Vasopressor: Vasopressin (fixed continuous infusion of 0.03 units/min ) added to norepinephrine when high-dose norepinephrine is required, allowing norepinephrine dosage reduction.
Third-Line Inotrope/Vasopressor: Epinephrine (if MAP remains inadequate) or Dobutamine (added if myocardial dysfunction or persistent hypoperfusion despite adequate volume and MAP).
Avoid Dopamine: Associated with significantly higher incidence of tachyarrhythmias compared to norepinephrine.
Refractory Septic Shock Corticosteroids: Initiate IV Hydrocortisone 200 mg/day (given as 50 mg IV q6h or continuous infusion) ONLY IF blood pressure remains refractory to fluid resuscitation and moderate-to-high dose vasopressor therapy (e.g., Norepinephrine >=0.25 mcg/kg/min).