7.1 Sepsis, SIRS & Shock States
Key Takeaways
- Sepsis-3 defines sepsis as life-threatening organ dysfunction from a dysregulated host response to infection, not simply infection plus a temperature or white count change.
- qSOFA (altered mentation, systolic BP 100 mmHg or less, respiratory rate 22/min or more) is a bedside screening tool, not a diagnostic criterion for sepsis.
- Septic shock is confirmed when a patient needs vasopressors to keep MAP at 65 mmHg or higher AND has a lactate above 2 mmol/L despite adequate fluid resuscitation.
- The Surviving Sepsis Campaign Hour-1 bundle combines lactate measurement, blood cultures before antibiotics, broad-spectrum antibiotics, 30 mL/kg crystalloid, and vasopressors into simultaneous first-hour actions.
- Norepinephrine is the first-line vasopressor for septic shock; vasopressin is typically added as the second agent rather than escalating norepinephrine indefinitely.
7.1 Sepsis, SIRS & Shock States
Defining Sepsis: From SIRS to Sepsis-3
For decades, sepsis was identified using Systemic Inflammatory Response Syndrome (SIRS) criteria: temperature >38.3°C or <36°C, heart rate >90/min, respiratory rate >20/min or PaCO2 <32 mmHg, and white blood cell count >12,000/mm3, <4,000/mm3, or >10% immature bands. Two or more SIRS criteria plus a suspected infection source once defined sepsis. SIRS terminology may still appear on the exam and in older literature, but the current, AACN-tested framework is Sepsis-3, which redefines sepsis as life-threatening organ dysfunction caused by a dysregulated host response to infection — clinically identified by an acute increase of 2 points or more in the Sequential Organ Failure Assessment (SOFA) score. The shift matters because SIRS criteria are sensitive but not specific — many non-infectious conditions (trauma, pancreatitis, post-op states) trigger SIRS without true sepsis.
qSOFA: A Screen, Not a Diagnosis
The quick SOFA (qSOFA) score was designed as a fast, bedside screening tool to identify patients with suspected infection who are at higher risk of poor outcomes and warrant closer monitoring or escalation of care. It has three components, each worth one point:
- Altered mentation (any acute change in level of consciousness)
- Systolic blood pressure ≤100 mmHg
- Respiratory rate ≥22/min
A qSOFA score of 2 or more flags a patient who should prompt further investigation for organ dysfunction — it does not by itself diagnose sepsis or septic shock, and a low qSOFA does not rule sepsis out. The progressive care nurse's job is to use qSOFA as a trigger for full assessment (full SOFA scoring, lactate, cultures), not as a stand-alone diagnostic endpoint. This distinction is a favorite testing point: qSOFA screens, SOFA (and the Sepsis-3 clinical definition) diagnoses.
Septic Shock: The Clinical Definition
Septic shock is the subset of sepsis in which circulatory, cellular, and metabolic abnormalities are severe enough to substantially raise mortality risk. The Sepsis-3 clinical criteria require both:
- Need for vasopressors to maintain a mean arterial pressure (MAP) ≥65 mmHg, and
- A serum lactate >2 mmol/L, persisting despite adequate fluid resuscitation.
A patient who is simply hypotensive and fluid-responsive is not yet in septic shock; the diagnosis requires the vasopressor requirement plus the persistent lactate elevation after volume has been given.
The Surviving Sepsis Campaign Hour-1 Bundle
The Surviving Sepsis Campaign's Hour-1 bundle compresses the highest-yield interventions into simultaneous, first-hour actions from the moment sepsis or septic shock is recognized (time of triage, not necessarily time of arrival):
| Bundle element | Key detail |
|---|---|
| Measure lactate | Remeasure if the initial level is elevated (>2 mmol/L) to trend clearance |
| Obtain blood cultures | Draw before giving antibiotics whenever this does not meaningfully delay therapy |
| Administer broad-spectrum antibiotics | Give as early as possible — every hour of delay increases mortality |
| Begin rapid 30 mL/kg crystalloid | For hypotension or lactate ≥4 mmol/L |
| Apply vasopressors | If the patient is hypotensive during or after fluid resuscitation, to keep MAP ≥65 mmHg |
Norepinephrine is the first-line vasopressor for septic shock because of its potent alpha-adrenergic vasoconstriction with modest beta-1 inotropic support and a comparatively favorable dysrhythmia profile. When MAP remains inadequate on norepinephrine alone, vasopressin is typically the preferred second agent added (rather than simply escalating norepinephrine indefinitely); epinephrine is an alternative second/third-line option. The progressive care nurse titrates these infusions to a MAP target and monitors for extravasation and end-organ perfusion (urine output, mentation, capillary refill, lactate clearance), watching for the peripheral ischemia risk that comes with high-dose vasopressor therapy.
Untreated or refractory sepsis can progress to Multiple Organ Dysfunction Syndrome (MODS) — progressive, often sequential dysfunction of two or more organ systems (renal, hepatic, pulmonary, cardiovascular, hematologic, neurologic) driven by the same inflammatory cascade. MODS is a leading cause of death in critically ill patients and reinforces why early recognition and Hour-1 bundle compliance are so heavily emphasized on this exam.
The Four Shock Categories
Sepsis produces distributive shock, but the PCCN blueprint expects recognition of all major shock categories and their distinguishing hemodynamic pattern:
| Shock type | Primary problem | Hemodynamic pattern | Examples |
|---|---|---|---|
| Hypovolemic | Inadequate circulating volume | Decreased preload, decreased CO, increased SVR | Hemorrhage, dehydration, third-spacing |
| Cardiogenic | Pump failure | Increased/normal preload, decreased CO, increased SVR | MI, cardiomyopathy, severe dysrhythmia |
| Distributive | Massive vasodilation | Decreased SVR, variable/increased CO | Septic, anaphylactic, neurogenic |
| Obstructive | Physical flow obstruction | Decreased CO, obstruction-dependent findings | Cardiac tamponade, massive PE, tension pneumothorax |
Anaphylactic shock, a distributive subtype, results from a severe IgE-mediated hypersensitivity reaction causing massive vasodilation, capillary leak, and often bronchospasm and laryngeal edema. Intramuscular epinephrine (anterolateral thigh) is the first-line, time-critical treatment — delaying epinephrine in favor of antihistamines or corticosteroids is a recognized error the exam may test. Hypovolemic shock management centers on rapid, adequate fluid (and often blood product) resuscitation to restore preload, while identifying and controlling the source of volume loss.
Recognizing which shock category — or combination, since critically ill patients can have overlapping mechanisms (for example, septic patients who are also volume-depleted) — is present drives the correct hemodynamic and pharmacologic response, making shock differentiation one of the highest-yield clinical judgment skills tested across the Multisystem content area.
Which combination of findings correctly represents the quick Sequential Organ Failure Assessment (qSOFA) screening tool used to identify patients with suspected infection who are at higher risk for poor outcomes?
A patient meets criteria for septic shock and remains hypotensive after receiving 30 mL/kg of crystalloid. Which vasopressor should be initiated first according to Surviving Sepsis Campaign guidance?