Medicine JC094: High Fever, Low BP: Septic Shock Flashcards
Sepsis
膿毒症
Definition:
- **Systemic activation of **Innate immune response to injury ***regardless of cause
- New concept: Sepsis = Infection + Response of body to infection
- Old concept: Sepsis = Infection + SIRS
Complicated innate immune response (everybody can mount same response to the infection)
—> when Innate immune response is **dysregulated
—> Sepsis
—> Induce cytokine response
—> Both **Pro-inflammatory + ***Anti-inflammatory cytokines are activated
Infection:
- Microbial phenomenon
- Defined as invasion of pathogens
—> Survival of pathogen in sterile space (i.e. pathogen in unusual space e.g. CNS, lung, pericardium)
—> Survival to **anomaly space (i.e. unusual organism in space e.g. TB, influenza virus)
—> Clinical / Pathological infection characterisation (e.g. abscess, endocarditis)
- No commonly accepted serum marker of sepsis (*Procalcitonin promising but still not gold standard)
SEPSIS-3 guideline 2016
Definition of sepsis:
- Life-threatening organ dysfunction caused by a ***dysregulated host response to infection
Full-blown sepsis:
- ***Multi-organ dysfunction syndrome (MODS)
Septic shock:
- Subset of Sepsis with **circulatory + **cellular / ***metabolic dysfunction associated with higher risk of mortality
- Characterised by ***Distributive shock in circulatory system
Clinically identified by:
- Vasopressor requirement (NOT ionotrope) to maintain a mean arterial pressure of >=65 mmHg
- ***Lactate level >2 mmol/L (>18 mg/dL) in absence of hypovolaemia (i.e. presence of anaerobic respiration even without hypovolaemia)
Multi-organ dysfunction syndrome (MODS) due to sepsis
- Full blown sepsis
- Manifestation of septic shock is normally ***stereotypic (∵ Innate immune response)
- Multiple organ involved (記: 心, 肝, 肺, 腎, 血, 腸, 神經)
- CVS
- **Septic shock —> **Vasodilatation + ***High CO - Respiratory
- **ARDS —> **Type 1 failure - Renal
- ***ATN (Acute tubular necrosis) —> Oliguric renal failure - Blood
- ***DIC —> Thrombocytopenia, High D-dimer, Deranged clotting - GI
- Multifactorial —> ***Stress ulcer bleeding, Ileus - Liver
- Multifactorial —> ***Jaundice - CNS
- ***Septic encephalopathy —> Encephalopathy - Peripheral NS
- ***Critical illness polyneuropathy —> Weakness, Weaning failure
qSOFA score
- Quick Sequential Organ Failure Assessment score
- In **out-of-ICU setting for **quick recognition of sepsis with worse outcome
3 criteria:
- ***RR >=22
- ***SBP <=100
- ***Altered mentation
SOFA score (6 criteria, not useful in clinical setting):
- CVS
- CNS
- Respiratory
- Renal
- Coagulation
- Liver
Sepsis: CVS system: ***Types of shock
- Distributive (Septic (most common), Anaphylactic, Neurogenic) (characterised by **vasodilation + **high CO —> systemic hypoperfusion)
- BP: ↓
- CO: **↑ (i.e. not problem of CO but maldistribution in microcirculation)
- Preload: ↑ then ↓
- Systemic vascular resistance: **↓ (vasodilation) - Cardiogenic
- BP: ↓
- CO: ↓
- Preload: ↑
- Systemic vascular resistance: ↑ - Hypovolaemic
- BP: ↓
- CO: ↓
- Preload: ↓
- Systemic vascular resistance: ↑ - Obstructive
- BP: ↓
- CO: ↓
- Preload: ↑
- Systemic vascular resistance: ↑
Sepsis: Systemic inflammatory response involving Respiratory system
Acute respiratory distress syndrome (ARDS)
- aka Non-cardiogenic pulmonary edema
- ***Type 1 failure
- ***Low lung compliance
- Acute onset with known insult
Euro-American consensus definition:
All 3 criteria need to be met:
1. CXR: bilateral airspace shadows compatible with ***pulmonary edema
2. No evidence of LA hypertension / PAWP (pulmonary arterial wedge pressure) <18 (i.e. LH failure)
3. PaO2 / FiO2 <200 (acute lung injury if <300)
Berlin definition 2012:
- Acute: within ***1 week of known insult / new respiratory symptoms
- Chest imaging: ***bilateral opacities not fully explained by effusions, collapse, nodules
- Origin of edema: ***not fully explained by heart failure / fluid overload, need objective assessment if no risk factors (e.g. sepsis, septic shock, pancreatitis)
- Oxygenation
- Mild: 200 < PaO2 / FiO2 <= **300 (with PEEP / CPAP >=5)
- Moderate: 100 < PaO2 / FiO2 <= **200 (with PEEP >=5)
- Severe: PaO2 / FiO2 <= ***100 (with PEEP >=5)
Sepsis: Renal failure
RIFLE criteria:
- Risk / Injury / Failure / Loss / ESRD
2 criteria:
- ***GFR
- ***Urine output
***Treatment of Sepsis
Still very difficult, try a lot of theoretical sounding methods but studies have shown -ve results / more harm
—> still NO magic bullet
Surviving Sepsis Campaign 2016 guideline
- Infection source control
- Eradication of source if possible
- Prompt initiation of appropriate ***antibiotics (within hours) - Appropriate fluid resuscitation
- Favouring ***crystalloid > colloids
- Recognise early —> Give some treatment in right direction - Appropriate vasopressor use
- ***NE: preferred vasopressor
- Aim MAP: 65-70 mmHg (higher BP no extra help, only marginal benefit in patient with chronic HT but more harm of AF) - Adjunctive therapy
- **Ventilatory strategy
- **Renal replacement therapy
- Nutritional protocol
Is Early resuscitation effective in saving patients?
**Early Goal Directed Therapy (EGDT)
- Early resuscitation to achieve pre-defined haemodynamic targets of perfusion within **6 hours
—> CVP: 8-12 mmHg
—> MAP: >65 mmHg
—> Urine output: >0.5 ml/kg/hour
—> Mixed central venous saturation: >70% (or mixed venous saturation >65% if pulmonary artery catheter is used)
Recent studies have shown no superior benefits to Protocol-based standard therapy / Usual care
Fluid to give
Crystalloid:
- Normal saline
- much higher Na and Cl than physiological —> hyperchloraemic metabolic acidosis —> harmful to kidney (e.g. renal failure) - Ringer’s lactate
- Other solutions
Colloid:
- Natural: Albumin, Plasma fractions
- Synthetic: Gelatin-based (Gelofusine), Starch-based (Voluven / 6% HES)
Studies have shown:
- Starch-based colloids: No survival benefits, **More renal failure
—> **Crystalloid is superior
Balanced solution:
- Better than 0.9% NaCl (Na + Cl both too high for physiological)
- Close to physiological electrolyte composition (e.g. Ringer’s lactate, Plasmalyte)
- Theorectical pH neutral on massive infusion
—> Volume expansion ↓ plasma pH
—> Solution with high strong ion difference ↑ plasma pH
—> Balanced out
BP vs CO in sepsis
NOT necessary targeting Supranormal CO (class 1B)
Choice of drugs:
- **Vasopressors:
- vasoconstrictor to ↑ BP
- Catecholamines: ***NE (minimal β activity), Dopamine (in high dose) (minimal β activity), Phenylephrine (α1 agonist)
- ***Vasopressin
Dopamine vs NE:
- Dopamine has more patients discontinued for ***arrhythmia
- Dopamine associated with higher mortality in cardiogenic shock
DO NOT give Inotropes:
- Inotrope: ↑ CO but in septic shock CO already ↑
- ***Dobutamine (β1 agonist)
- peripheral vasodilation —> may ↓ BP
Dopamine vs Dobutamine vs E vs NE
α1: Vasoconstriction
β1: ↑ CO
Dopamine:
- α1: +++ (high dose)
- β1: ++ (low dose)
—> “Renal dose / Low dose” Dopamine to preserve kidney is out of fashion now
Dobutamine:
- α1: 0
- β1: +++
E:
- α1: +++
- β1: +++
- **NE:
- α1: ++++
- β1: ++
Blood glucose control
Blood glucose ↑ during sepsis
Management:
- NOT necessary to maintain normal blood glucose —> risk of severe hypoglycaemia if on tight glucose control
- Aim at preventing hyperglycaemia of ***>10 mmol/L
Lactate clearance
- **Prognostic
- Lactate clearance associated with ***better prognosis in sepsis
Revision: Shock
Definition:
- State of generalised hypoperfusion of all cells + tissues
- due to:
1. ↓ Blood volume (Hypovolaemic shock)
2. ↓ CO (Cardiogenic shock, Obstructive shock)
3. Redistribution of blood (Distributive shock)
—> ALL leads to inadequate ***effective circulating volume
