JC94 (Microbiology) - Septic shock

Question 1

Define Infection

Answer 1

Invasion of pathogen with

• Survival of pathogen in sterile space (e.g. CNS, Lungs)
• Survival to anomaly space (e.g. TB, influenze)
• Clinical or pathological infection characterization

Question 2

Define sepsis and septic shock

Answer 2

□ Sepsis: life-threatening organ dysfunction caused by dysregulated host response to infection

□ Septic shock: subset of sepsis with circulatory and cellular/metabolic dysfunction a/w higher risk of mortality
Clinically identified by:
→ Vasopressor requirement to maintain MABP ≥65mmHg
→ Serum lactate >2mmol/L
→ No hypovolaemia

Question 3

List all organ dysfunctions a/w septic shock

Answer 3

□ CVS: septic shock with high CO** and vasodilatation

□ Lungs: ARDS with non-cardiogenic pulmonary oedema → T1RF and decrease lung compliance

□ Kidneys: acute renal injury

□ Blood: DIC with thrombocytopenia

□ GI (GI bleeding, ileus), liver (jaundice)

□ brain (septic encephalopathy), PNS (critical illness polyneuropathy)

Question 4

Clinical screening criteria for septic shock

Answer 4

qSOFA score

Sequential sepsis-related organ failure assessment score

Respiratory rate ≥ 22/min
Altered mentation
Systolic BP ≤100mmHg

Question 5

Describe the effects of septic shock on cardiovascular system

Answer 5

Hypotension (similar to all other types of shock)

Increase cardiac output/ CO only type of shock with higher CO, due to microvascular dysfunction

Variable preload (c.f. increase preload in cardiogenic and obstructive shock, low preload in hypovolemic shock)

Lower Systemic Vascular Resistance (Afterload) only type of shock with systemic hypoperfusion

Question 6

Describe the effect of septic shock on respiratory system

Diagnostic criteria for ARDS

Answer 6

ARDS with Non-cardiogenic pulmonary edema
- type I failure with low lung compliance

ARDS criteria: all 3 must be present:
- CXR: Bilateral airspace shadows compatible with Pulmonary edema (not due to effusion, lobar or lung collapse or nodules)

• No evidence of left atrial hypertension or Pulmonary Arterial Wedge Pressure <18 mmHg (not due to cardiac failure or fluid overload)
• PaO2/ FiO2 <200mmHg; Acute lung injury if ratio is <300mmHg (i.e. inadequate oxygenation) despite PPV

Question 7

Diagnostic criteria for acute renal failure

Answer 7

RIFLE criteria

accounts Risk, Injury, Failure, Loss and ESKD
Measures GFR and Urine output

Question 8

Approach to anti-microbial treatment of sepsis

Answer 8

1. Must give higher-grade/ aggressive antimicrobials as first-line
   - De-escalating treatment after starting = better survival
   - Escalating treatment after starting = worse prognosis
2. Must choose correct group of antimicrobials
3. Must give antimicrobials as soon as possible
   - Each hour delay = 7.6% increase mortality

Question 9

Haemodynamic targets for resuscitation from septic shock

Answer 9

Achieve these targets in 6 hours:

• Central venous pressure: 8-12mmHg
• Mean arterial pressure >65 mmHg
• Urine output >0.5ml/kg/hour
• Mixed central venous saturation >70%
  (or >65% if pulmonary artery catheter is used)

Question 10

List all management options for septic shock

Answer 10

1. Infection control: IV broad spectrum antibiotics ASAP
2. Fluid resuscitation: IV Crystalloids ± albumin
3. Vasopressors: Norepinephrine as 1st choice ± vasopressin or epinephrine
4. Adjunctive:
   - ventilatory strategy: PEEP or BiPAP
   - renal replacement therapy (NOT to be used in sepsis-related AKI unless
   otherwise indicated)
   - Nutrition: Early enteral feeding
   - Serum lactate as marker of tissue hypoperfusion
   - Glucose control: prevent hyperGly of >10mmol/L

Question 11

Fluid resuscitation for septic shock

Which fluids?
Why?

Answer 11

Crystalloids***
- ≥ 30mL/kg IV crystalloids within first 3h of hypoperfusion
- prefer balanced solution e.g. Ringer’s lactate
(High volume Normal saline > hypochloremia and hypokalemic acidosis is harmful for kidneys)

Do NOT use starch-based colloids
- Increase renal failure w/o no survival benefit or worse prognosis

Question 12

Dobutamine can be used to correct cardiac dysfunction in septic shock

True or False?

Answer 12

False

No inotropes for septic shock: already high CO
Dobutamine and other B1 agonists cannot be used as it increases CO and does not treat systemic hypoperfusion

Question 13

Therapy options for cardiovascular dysfunction in septic shock
Which option is preferred?
Target for resuscitation therapy

Answer 13

Initial target MABP at 65mmHg
- Higher BP targets (eg. 80-85mmHg) w/ similar mortality but ↑AF risk, only beneficial if chronic HTN (↓RRT)

Norepinephrine as 1st choice ± vasopressin or epinephrine

• a1 agonist causes vasoconstriction to treat systemic hypoperfusion
• a1 agonists: Norepinephrine, Dopamine HIGH DOSE, Phenylephrine

Dopamine = more arrhythmia, mortality rate than Norepinephrine

Question 14

Glucose control in septic shock

• Treatment target
• Purpose of glucose control

Answer 14

Aim: to prevent hyperGly of >10mmol/L

Maintaining normoGly a/w higher mortality rate

Question 15

Septic shock related renal failure

Which type of renal failure

Answer 15

Acute tubular necrosis causing acute oliguric renal failure