Introduction
Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. It kills approximately 48,000 people in the UK each year and is one of the most common causes of avoidable hospital death. Sepsis recognition and management is a near-universal OSCE station — you will be expected to know the diagnostic criteria, complete the Sepsis Six bundle within one hour, and demonstrate safe escalation.
Defining Sepsis
Current Definitions (Sepsis-3, 2016)
- Sepsis: life-threatening organ dysfunction caused by a dysregulated host response to infection, defined by an acute change in SOFA score ≥2 in the context of suspected infection
- Septic shock: sepsis with persisting hypotension requiring vasopressors to maintain MAP ≥65 mmHg AND serum lactate >2 mmol/L despite adequate fluid resuscitation
The qSOFA score is used as a quick bedside screening tool:
| qSOFA Criterion | Threshold |
|---|---|
| Altered mentation (GCS <15) | 1 point |
| Respiratory rate ≥22/min | 1 point |
| Systolic BP ≤100 mmHg | 1 point |
qSOFA ≥2 in a patient with suspected infection warrants urgent sepsis assessment and escalation.
SIRS Criteria (Historical — Still Examined)
| SIRS Criterion | Value |
|---|---|
| Temperature | >38.0°C or <36.0°C |
| Heart rate | >90 bpm |
| Respiratory rate | >20/min OR PaCO₂ <4.3 kPa |
| White cell count | >12 × 10⁹/L or <4 × 10⁹/L or >10% bands |
Two or more SIRS criteria with a suspected source of infection = SIRS. SIRS + organ dysfunction = sepsis (historical Sepsis-2 definition).
NEWS2 Scoring
The National Early Warning Score 2 (NEWS2) is the standardised physiological scoring system used across NHS England and Wales.
| Parameter | Score 3 | Score 2 | Score 1 | Score 0 | Score 1 | Score 2 | Score 3 |
|---|---|---|---|---|---|---|---|
| Resp rate (breaths/min) | ≤8 | — | 9–11 | 12–20 | — | 21–24 | ≥25 |
| SpO₂ Scale 1 (%) | ≤91 | 92–93 | 94–95 | ≥96 | — | — | — |
| Systolic BP (mmHg) | ≤90 | 91–100 | 101–110 | 111–219 | — | — | ≥220 |
| Heart rate (bpm) | ≤40 | — | 41–50 | 51–90 | 91–110 | 111–130 | ≥131 |
| Temperature (°C) | ≤35.0 | — | 35.1–36.0 | 36.1–38.0 | 38.1–39.0 | ≥39.1 | — |
| Consciousness | — | — | — | Alert | — | — | CVPU |
SpO₂ Scale 2 is used for patients with confirmed hypercapnic respiratory failure (target 88–92%).
NEWS2 Escalation Thresholds
| Total Score | Risk Level | Response Required |
|---|---|---|
| 0 | Low | Minimum 12-hourly observations |
| 1–4 | Low | Minimum 4–6 hourly observations |
| 3 in single parameter | Medium | Urgent review by ward nurse and doctor within 1 hour |
| 5–6 | Medium | Urgent review by clinician with critical care competencies within 1 hour |
| ≥7 | High | Emergency review by critical care team; consider HDU/ICU |
💎 Clinical Pearl
In patients with sepsis, a rising NEWS2 score is more prognostically significant than any single threshold. A score of 5–6 that was 2–3 an hour ago demands the same urgency as a score of 7. Trends matter as much as absolute values.
The Sepsis Six Bundle
The Sepsis Six should be initiated within one hour of sepsis recognition. Remember: Give 3, Take 3.
🧠 Mnemonic
Sepsis Six — Give 3, Take 3
Give:
- 1High-flow oxygen — target SpO₂ 94–98% (88–92% in hypercapnic COPD)
- 2IV fluids — 500 mL crystalloid bolus over 15 minutes; reassess
- 3IV antibiotics — broad-spectrum empirical therapy within 1 hour (as per local guidelines)
Take:
- 1Blood cultures — before antibiotics if this does not delay them by more than 45 minutes
- 2Lactate — venous or arterial; lactate ≥2 mmol/L indicates anaerobic metabolism
- 3Urine output — insert urinary catheter and monitor; target >0.5 mL/kg/hr
⚠️ Red Flag
Do not delay antibiotics to obtain blood cultures. The UK Sepsis Trust guidance states blood cultures should be obtained within 45 minutes, but if there is any delay, commence antibiotics immediately. Every hour's delay in appropriate antibiotic therapy increases mortality by approximately 7%.
Lactate Interpretation
| Lactate (mmol/L) | Interpretation | Action |
|---|---|---|
| <2 | Normal | Reassess clinically; continue monitoring |
| 2–4 | Elevated — tissue hypoperfusion likely | Sepsis confirmed; aggressive Sepsis Six; senior review |
| >4 | Critically elevated — severe sepsis/shock | ICU review urgently; vasopressors may be required |
A lactate >4 mmol/L with hypotension despite fluid resuscitation meets criteria for septic shock — this carries >40% mortality and requires immediate critical care involvement.
Identifying the Source
| Source | Clues |
|---|---|
| Urinary | Dysuria, frequency, loin pain; leucocytes/nitrites on dipstick |
| Respiratory | Productive cough, pleuritic pain, consolidation on CXR |
| Abdominal | Peritonism, right iliac fossa tenderness, jaundice |
| Skin/soft tissue | Cellulitis, wounds, rash (purpura = meningococcal) |
| Line-related | Indwelling catheter, IV cannula, CVC — redness or exudate |
| Endocarditis | New murmur, splinter haemorrhages, Janeway lesions |
⚠️ Red Flag
A non-blanching purpuric rash in a febrile patient is meningococcal septicaemia until proven otherwise. Administer IV ceftriaxone 2 g immediately — this takes clinical priority over everything else. Do not wait for results or senior review.
FAQs
"What is the difference between sepsis and septic shock?"
Sepsis is organ dysfunction from a dysregulated response to infection (SOFA ≥2). Septic shock is a subset where persistent hypotension requires vasopressors to maintain MAP ≥65 mmHg AND lactate remains >2 mmol/L despite adequate fluid resuscitation. Septic shock carries significantly higher mortality (>40%).
"Should I always give the full 500 mL fluid bolus in sepsis?"
Give an initial 500 mL crystalloid bolus over 15 minutes and reassess. In patients with known heart failure, severe aortic stenosis, or signs of fluid overload, be cautious and reassess after each 250 mL. Document your reassessment and monitor for worsening SpO₂ or basal crepitations.
"When should I escalate to critical care?"
Escalate if: NEWS2 ≥7, lactate >4 mmol/L, systolic BP <90 mmHg despite two fluid boluses, urine output <0.5 mL/kg/hr after catheterisation and fluids, new confusion or reduced GCS, or any clinical concern. Do not wait for all criteria — escalate early.
"What NEWS2 score triggers an emergency response?"
A NEWS2 score of ≥7 triggers an emergency response — call the critical care outreach team immediately. A score of 5–6 requires urgent response within 1 hour by a clinician with critical care competencies. A single parameter scoring 3 (red score) requires urgent ward doctor review regardless of total score.
"Can blood cultures be taken after antibiotics have been given?"
Blood cultures taken after antibiotics have significantly reduced sensitivity. Always attempt cultures before antibiotics. However, if cultures will cause a delay of more than 45 minutes, commence antibiotics immediately and accept a negative culture result rather than delay treatment.
Related Posts
- A–E Assessment OSCE — systematic approach to the acutely unwell patient, including sepsis recognition
- Blood Results Interpretation OSCE — interpreting FBC, CRP, lactate, and cultures in the context of sepsis
- Venepuncture & Cannulation OSCE — blood culture technique and cannulation for IV antibiotics and fluids