Clinical reasoning notes. Sepsis kills by delay: time to antibiotics and fluids matters more than the perfect diagnosis.
The reasoning chain: recognise sepsis early → find the source → give the first hour's care (the "Sepsis Six") → choose antibiotics for the likely organism and local resistance → source control → watch for organ failure.
1. Definitions (Sepsis-3)
- Sepsis: life-threatening organ dysfunction caused by a dysregulated response to infection. In practice: suspected infection plus an acute rise in SOFA score of 2 or more.
- Septic shock: sepsis with persistent hypotension needing vasopressors to keep the mean arterial pressure at or above 65 mmHg and a lactate above 2 mmol/L despite adequate fluids.
- Bedside screen (qSOFA): two or more of respiratory rate 22 or more, altered mentation, systolic blood pressure 100 or less. It flags patients at risk: it is a warning, not a diagnosis.
2. Find the source
| Source | Clues |
|---|---|
| Lungs | Cough, breathlessness, crackles, consolidation on X-ray |
| Urine | Dysuria, loin pain, catheter, pyuria |
| Abdomen | Peritonism, jaundice (cholangitis), diarrhoea, perforation, abscess |
| Skin and soft tissue | Cellulitis, necrotising fasciitis (pain out of proportion), wounds, injection sites |
| CNS | Headache, neck stiffness, rash (meningococcus) |
| Blood | Endocarditis, line infection, malaria |
| Obstetric and gynaecological | Septic abortion, puerperal sepsis, pelvic inflammatory disease |
Think local: malaria, typhoid, TB, HIV with opportunistic infection, meningitis and puerperal sepsis must be on the list in many settings, and are easily missed when the focus is on bacteria alone.
3. Investigate with purpose
| Test | The question it answers |
|---|---|
| Blood cultures (before antibiotics, two sets) | Which organism, and which antibiotic works? |
| Lactate | How badly is tissue perfusion failing? Above 2 mmol/L is sepsis-range; above 4 is severe |
| Full haemogram | White cells high or very low (a bad sign), platelets low (DIC) |
| Urea, creatinine, electrolytes, liver tests, glucose | Organ dysfunction; hypoglycaemia is common |
| Clotting screen | Disseminated intravascular coagulation |
| Blood gas | Acidosis and oxygenation |
| Urine culture, malaria test, HIV test, chest X-ray | Source |
| Lumbar puncture (if no contraindication) | Meningitis |
| CT or ultrasound | Collection or obstruction needing drainage |
Where results can mislead: a normal white count does not exclude sepsis; elderly, diabetic and immunosuppressed patients may have no fever; lactate may rise from metformin, seizures or liver disease, not only from shock.
4. Management: the first hour (Sepsis Six)
- Give oxygen to keep saturations above 94%.
- Take blood cultures (and other cultures) before antibiotics, but do not delay antibiotics for them.
- Give broad-spectrum IV antibiotics within one hour, chosen for the likely source and local resistance, then narrow when cultures return (de-escalation).
- Give IV fluids: a bolus of balanced crystalloid, then reassess. Stop when the patient is no longer fluid-responsive. Too much fluid causes pulmonary oedema.
- Check lactate and repeat it to see the response.
- Monitor urine output (catheter) and vital signs closely.
If the patient stays hypotensive after fluids: start a vasopressor (noradrenaline first line) to keep the mean arterial pressure at or above 65 mmHg, and move to a high-dependency or intensive care area.
Source control: drain pus, remove an infected line or catheter, debride dead tissue, relieve obstruction (infected obstructed kidney, cholangitis). No antibiotic can clear an undrained abscess.
Other: treat hypoglycaemia, give thromboprophylaxis, and consider hydrocortisone in refractory shock.
5. Antibiotic choice: reason it through
- Match the likely organisms for the source, then local resistance patterns.
- Community-onset sepsis: a third-generation cephalosporin (such as ceftriaxone) is a common start; add cover for atypical organisms, anaerobes (intra-abdominal sepsis) or MRSA when the source suggests it.
- Hospital-acquired sepsis or neutropenia: broader cover (an anti-pseudomonal β-lactam or a carbapenem).
- Malaria endemic area: treat severe malaria with IV artesunate alongside antibiotics until it is excluded.
- Review at 48 to 72 hours with culture results, and stop at the shortest effective course.
6. Complications
Acute kidney injury, ARDS, DIC, liver dysfunction, hypoglycaemia, adrenal insufficiency, ischaemic bowel, and multi-organ failure.
Examiner questions
- Define sepsis and septic shock using Sepsis-3.
- Name the Sepsis Six, and say which parts must happen within an hour.
- Why do we take blood cultures before antibiotics, but not delay antibiotics to do so?
Practice questions
1. A patient has suspected pneumonia, RR 28, BP 85/50 and is confused. The most important next step is: A. CT chest · B. IV antibiotics and fluids within the hour, with blood cultures taken first if quick · C. Wait for culture results · D. Oral antibiotics · E. Discharge Answer: B.
2. Septic shock is defined by sepsis plus: A. Fever above 39 °C · B. A raised white cell count · C. Vasopressors needed to keep MAP at 65 mmHg or above, with lactate above 2 mmol/L despite fluids · D. Positive blood culture · E. Two organ failures Answer: C.
3. After fluids, an infected obstructed kidney is still septic. What will make the biggest difference? A. A third antibiotic · B. Urgent drainage (stent or nephrostomy) · C. Steroids · D. More saline · E. Oral fluids Answer: B. Source control.
4. In sub-Saharan Africa, a febrile, hypotensive patient with a normal-looking chest and urine should also be tested for: A. Gout · B. Malaria · C. Hypothyroidism · D. Osteoporosis · E. Migraine Answer: B.