Infectious Disease · Sepsis and Septic Shock
The facts most likely to be tested
Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, identified by an increase in the SOFA score of 2 or more points.
Septic shock is a subset of sepsis in which underlying circulatory and cellular/metabolic abnormalities are profound enough to substantially increase mortality, requiring vasopressors to maintain a mean arterial pressure (MAP) ≥ 65 mmHg despite adequate fluid resuscitation.
Lactate levels > 2 mmol/L in the presence of adequate fluid resuscitation are diagnostic of septic shock due to tissue hypoperfusion.
Early goal-directed therapy mandates the administration of broad-spectrum intravenous antibiotics within one hour of recognition.
Intravenous crystalloid fluid resuscitation at a dose of 30 mL/kg is the initial standard of care for patients with sepsis-induced hypoperfusion or septic shock.
Norepinephrine is the first-line vasopressor of choice for patients who remain hypotensive despite adequate fluid resuscitation.
Blood cultures must be obtained prior to the administration of antibiotics to ensure accurate pathogen identification without delaying the initiation of therapy.
Vignette unlocked
A 68-year-old male is brought to the emergency department with fever, chills, and confusion. Physical examination reveals a temperature of 39.2°C (102.6°F), blood pressure of 88/50 mmHg, and a heart rate of 124/min. Laboratory studies show a leukocytosis with a left shift and a serum lactate of 4.2 mmol/L. Despite the administration of 2 liters of normal saline, his blood pressure remains 85/48 mmHg.
What is the most appropriate next step in the management of this patient?
Initiation of norepinephrine
The patient meets criteria for septic shock (persistent hypotension despite adequate fluid resuscitation and elevated lactate), necessitating the initiation of a first-line vasopressor like norepinephrine.
Full handout
High yield triage
Etiology / Epidemiology
Life-threatening organ dysfunction caused by a dysregulated host response to infection. Immunocompromise, advanced age, and indwelling devices are primary risk factors.
Clinical Manifestations
Suspect in patients with SIRS criteria plus suspected infection. Hypotension, altered mental status, and tachypnea are classic signs.
Diagnosis
Diagnosis requires qSOFA score ≥ 2 or SOFA score increase ≥ 2. Serum lactate > 2 mmol/L is the critical threshold for tissue hypoperfusion.
Treatment
Initiate IV fluid resuscitation (30 mL/kg) and broad-spectrum antibiotics within 1 hour. Do not delay antibiotics for imaging.
Prognosis
Septic shock carries a >40% mortality rate. Multi-organ failure is the leading cause of death.
Full handout
Epidemiology & Etiology
Sepsis is most commonly triggered by Gram-negative bacteria, Staphylococcus aureus, and Streptococcus pneumoniae. High-risk populations include the elderly, neonates, and patients with asplenia or diabetes mellitus. Source control is mandatory for success.
Pertinent Anatomy
Systemic involvement affects the microvasculature leading to diffuse endothelial damage. Pulmonary involvement often manifests as ARDS, while renal involvement presents as acute tubular necrosis.
Pathophysiology
The host response involves a massive release of pro-inflammatory cytokines, leading to vasodilation and increased capillary permeability. This results in third-spacing of fluids and profound distributive shock. Impaired oxygen utilization at the cellular level leads to a shift toward anaerobic metabolism.
Clinical Manifestations
Patients present with tachycardia, tachypnea, and fever or hypothermia. Altered mental status is a critical sign of end-organ hypoperfusion. Look for mottled skin and delayed capillary refill as signs of impending cardiovascular collapse.
Diagnosis
The SOFA score is the gold standard for quantifying organ dysfunction. Serum lactate levels must be trended to assess resuscitation efficacy. Obtain blood cultures prior to antibiotic administration if it does not delay treatment.
Treatment
Administer 30 mL/kg of balanced crystalloids within the first 3 hours. Start broad-spectrum antibiotics (e.g., vancomycin + piperacillin-tazobactam) immediately. If hypotension persists despite fluids, initiate norepinephrine as the first-line vasopressor. Avoid hydroxyethyl starches due to increased risk of renal failure.
Prognosis
Monitor urine output (>0.5 mL/kg/hr) and mean arterial pressure (MAP ≥ 65 mmHg) as markers of successful resuscitation. Disseminated intravascular coagulation (DIC) is a frequent and lethal complication.
Differential Diagnosis
Cardiogenic shock: elevated JVP and pulmonary edema
Hypovolemic shock: history of hemorrhage or severe dehydration
Anaphylactic shock: presence of urticaria and wheezing
Adrenal crisis: refractory hypotension despite vasopressors
Neurogenic shock: bradycardia and warm, dry skin