Infection L3 (Sepsis)

Question 1

4 Haemodynamic disturbances in Sepsis

Answer 1

1. Vasodilation + Reduced SVR
   Cytokines → vasodilation → ↓ systemic vascular resistance (SVR)

Blood pressure falls = shock risk

Skin may appear warm, but vital organs may be underperfused

BP = (HR × SV) × SVR

2. Compensation mecahnisms
   ↑ HR (tachycardia)

↑ Stroke Volume

↑ SVR via vasoconstriction (to redirect blood to vital organs)

Helps at first → but gets overwhelmed in decompensated shock (low BP, organ failure)

3. Reduced intravascular volume
   - Increased capillary permeability, fluid leaks out of vessels (capillary leak syndrome)
   - Intravascular hypovolemia
   -Worsened by poor fluid intake
   - Reduced venous return, reduxed stroke vol, reduced organ perfusion, tissue ischamiea, hypoxia, lactic acidosis
4. Myocardial dysfunction
   - Early (compensation): ↑ HR, ↑ contractility
   - Later:HR too fast → less coronary filling↓ oxygen to heart → myocardial ischaemiaPro-inflammatory cytokines impair heart functionResult: ↓ cardiac output

Question 2

Clinical findings in Sepsis

Answer 2

• Tachycardia
• Warm or cold peripheries (check capillary refill time) warm hands: early/ septic shock, blood still getting to skin. Cold hands: late/decompensated shock, blood redirected to vital organs
  -BP maintained (compenstaed). Early, blood keeps BP through increasing HR/SVR
  -Low BP (decompensated). Compensatory systems fail. BP drops, dager zone
  -Reduced organ perfusion - leads to tissue hypoxia:Brain (confusion)

Heart (weak pulse, low output)

Lungs (low oxygen)

Kidneys (low urine)

Liver (abnormal LFTs)

Question 3

What happens to the lungs in Sepsis?

Answer 3

↑ Metabolic demand → ↑ oxygen needed
Increased respiratory rate (tachypnoea)
Shortness of breath

Pulmonary oedema (fluid in lungs): because inflammation damages the lungs blood vessels. Inflammtory cytokines make capillaries leaky, causinf fluid to leak into the lungs = pulmonary oedema

Gas exchange blocked. Fluid fills alveoli, oxygen cannot get into blood, hypoxia.

ARDS (Acute Respiratory Distress Syndrome)
(lungs become stiff, inflamed, cant expand well, oxygen drops more, so leads to Respiratory failure)

Sepsis → oxygen demand ↑ → fast breathing → fluid leaks into lungs → oxygen can’t get in → ARDS → respiratory failure

Question 4

What happens in tissues in Sepsis?

Answer 4

Tissue ischaemia + hypoxia (↓ oxygen supply)

Switch to anaerobic respiration → ↓ ATP

Cell and enzyme failure

Leads to organ dysfunction, necrosis

Causes lactic acidosis (↑ lactate = bad perfusion)

Question 5

What happens to the brain in sepsis?

Answer 5

Brain needs oxygen, glucose, CO₂ removal, normal pH

If brain doesn’t get this → confusion, low consciousness, irritability

ACVPU score used for assessment:

Alert, Confused, Voice, Pain, Unresponsive

Good early warning sign

Long-term effects possible (e.g. memory loss)

Question 6

How does sepsis affect kidneys?

Answer 6

↓ Intravascular volume → ↓ renal perfusion

↓ Blood pressure = ↓ filtration

Disrupted fluid/electrolyte balance

Can lead to acute kidney injury (AKI)

Question 7

Describe coagulation in sepsis
What happens when clotting factors run out?

Clinical signs of coagulation being affected by sepsis

Answer 7

1. Bacterial toxins (LPS), and cytokines (TNF, IL-6) damage blood vessel lining (endothelium)
2. This triggers coagulation cascade
3. Intravascular coagulation

Clinical Signs:

Thrombocytopenia (low platelets)

Purpura (purple skin patches due to bleeding under the skin)

Bleeding + clotting happening at the same time

Question 8

Sepsis - Clinical Features
Symptoms

Answer 8

Question 9

What questions do we ask a patient who has presented with Sepsis symptoms

Answer 9

Question 10

Which patients are vulnerable (in terms of sepsis)?

Answer 10

Question 11

Clinical features: Signs of sepsis

Answer 11

Question 12

Fever is a common sign of infection, including sepsis. Why may a patient with sepsis not show a fever?

Answer 12

Patients can have hypothermia
Normal temp etc

Question 13

Investigations in Sepsis

Answer 13

1. Blood gases (pH, PCO2, lactate, glucose)
2. FBC (neutrophils, platelets, WCC)
3. U&Es (renal functtion)
4. LFTs, amylase (liver, pancreas)
5. Clotting screen: DIC risk
6. CRP: inflammation marker
7. Blood cultures (before antibiotics)

Question 14

📊 NEWS2 (National Early Warning Score 2)

Answer 14

Question 15

QSOFA score of sepsis

Answer 15

🧮 qSOFA Score (Quick SOFA)

Used outside ICU (e.g. GP, A&E, wards) to quickly assess for possible sepsis:
Criteria Score
SBP ≤ 100 mmHg (low blood pressure) 1
RR ≥ 22 breaths/min (tachypnoea) 1
GCS ≤ 14 (altered mental status) 1

qSOFA ≥ 2 → suggests higher risk of sepsis-related organ failure

Full SOFA used in ICU to track deterioration

Question 16

SEPSIS RED FLAGS

Answer 16

Question 17

Management of Sepsis

Answer 17

💊 Antibiotics: Do Not Delay!

Start empirical broad-spectrum IV antibiotics as soon as sepsis is suspected

Tailor later based on cultures

Check for allergies

Follow local guidelines (BNF/NICE)

Question 18

🧠 Other Supportive Care (ABCDE Approach)

Answer 18

Question 18

Complications with Sepsis

Answer 18

• Death
  -Organ failure
  -Limb loss
  -Malnutrition

Question 19

Sepsis prevention

Answer 19

Question 20

Sepsis 6
Give 3, Take 3

Answer 20

Do in first hour.

Give
- IV fluids (fluid challenge)
- IV antibioitics
-High flow oxygen

Take:
-Blood cultire
-measure urine output
-measure lactate

Question 21

Key Definition of Sepsis
Sequence of events

Answer 21

• Life threatening
• Organ dysfunction
  -Due to infecting pathogen
  -Dysregulated host response to infection

Sequence of events:

-Bacteria gain entry
-Bacteraemia
-SIRS
-SIRS due to infection = sepsis
-Severe sepsis: Sepsis plus at least one organ failure
Septic shock: Sepsis plus haemodynamic instability

Question 22

Severe sepsis vs septic shock

Answer 22

Severe sepsis: Sepsis + at least one or more organ failing (MODS: multiple organ dysfunction syndrome). More detail: severe sepsis, infection triggers immune response, blood vessels become leaky + dilated. Low blood pressure, less blood flow to vital organs. Organs do not get enough oxygen, organ dysfunction.

Septic Shock: Sepsis + haemodynamic instability (severe sepsis + persistant hypotension even after IV fluids). Body cannot maintain blood circulation, organs do not get enough oxygen, circulatiry failure, metabolic failure.

Question 23

Compensated vs decompensated shock

Answer 23

Compensated: Body still tries to keep BP up (early stage). Heart beats faster (↑ heart rate)

Blood vessels tighten (to push blood to vital organs)

You may look pale, feel cold, dizzy — but blood pressure is still normal or almost normal

Decompensated: body fails to maintain BP, collapse
The body’s compensation fails:

Blood pressure drops dangerously low.

Organs start shutting down.

You may become confused, unconscious, or have very low urine output.

This is a medical emergency — without urgent treatment, it often leads to death.

Question 24

Biggest infectious cause of sepsis

Answer 24

Pneumonia

Question 25

Pathophysiology of Sepsis Immune activation triggers (what does the immune system recognise) The inflammatory response (what actually happens?)

Answer 25

Chain reaction to infection: 1. Pathogen enters, body detects it 2. Immune system activated 3. Coagulation triggered 4. Body tries to compensate Immune activation triggers: Body recognises: 1) PAMPs 2) DAMPs These activate cytokines + inflammatory mediators. causes massive immune response which can get out of control The inflammatory response: - Cytokine storm = blood vessels leak = pressure drops = organs do not get oxygen = organ dysfunction, widespread clorring (DIC) and finally septic shock.

Question 26

Define acute inflammation 5 signs of acute inflammation

Answer 26

Body's rapid protective response 1) Redness 2) Heat 3) Pain 4) Loss of function 5) Swelling

Question 27

Symptoms of acute inflammation

Answer 27

1) Fever 2) Fatigue 3) Swelling 4) Pain 5) Symptoms pointing to the source e.g. cough → lung; painful urination → urinary tract)

Question 28

Blood pressure formula Cardiac output formula

Answer 28

🩸 Blood Pressure in Sepsis – Key Concepts 📏 What Determines Blood Pressure? BP = (Heart Rate × Stroke Volume) × Systemic Vascular Resistance (SVR) Cardiac Output = HR × SV

Question 29

SIRS triggers

Answer 29

SIRS may occur due to other factors than sepsis, including: 1) Trauma 2) Burns 3) Pancreatitis 4) Ichaemia 5) Reperfusion 6) injury

Question 30

Compensatory mechanism to maintain blood pressure (Which systems help with this? Which hormones help?)

Answer 30

To compensate for falling BP: 1) Increase Heart Rate 2) Increase Stroke Volume 3) Increase Systemic Vascular Resistance Systems: - RAAS - Sympathetic Nervous System Hormones: - Cortisol