· Definitions
· Metabolic effects
· Organ system effects
Systemic inflammatory response syndrome (SIRS) |
≥2 of 1. Temp > 38°C or <36°C 2. HR > 90 3. RR >20 or PaCO2 <32mmHg 4. WCC >12 or <4 or >10% immature cells |
Septicaemia |
Systemic infection |
Sepsis |
Systemic infection + SIRS |
Severe sepsis |
Systemic infection + SIRS + hypotension |
Septic shock |
Systemic infection + SIRS + hypotension + end-organ dysfunction |
Sepsis |
Life-threatening organ dysfunction caused by a dysregulated host response to suspected or confirmed infection |
Septic shock |
Sepsis mAP <65 Lactate >2 Despite adequate volume resuscitation |
Causes |
· Pathogen -> WBC activation -> cytokine release (TNF-α, IL1, IL6, IFN) |
Overall |
· ↑Metabolic rate · ↑Insulin resistance · ↑Catabolism |
Autonomics |
· Cytokines and baroreceptor reflex -> ↑medullary SNS output |
Hormones |
· ↑Cortisol · ↑Insulin (resistance) · ↑ADH · ↑Catecholamines · ↓Thyroid hormones |
Acid-base |
· Hypoperfusion -> ↓tissue pO2 -> ↑anaerobic metabolism, lactic acidosis · ↑Metabolic rate -> further ↑ anaerobic metabolism |
Fluid |
· Vasodilation, capillary leak -> ↓plasma volume, ↑interstitial volume (e.g. APO) |
Substrate |
· ↑[Glucose] · ↑[Lipids] · ↑[Ketones] |
Liver |
· ↓Glucose uptake, ↑gluconeogenesis · ↑Proteolysis · ↑Lipolysis · ↑Ketogenesis |
Skeletal muscle |
· ↓Glucose uptake, ↑gluconeogenesis · ↑Proteolysis · ↑Lipolysis |
Adipose |
· ↑Lipolysis |
Brain |
· Blood-brain-barrier disruption -> cytokine and pathogen effects -> delirium · mAP <50mmHg -> CNS ischaemic response -> ↑↑SNS -> ↑HR/contractility/SVR |
Heart |
· Cytokines -> ↓inotropy +/- septic cardiomyopathy · SNS -> ↑contractility (predominates if pH >7.2), ↑HR · Acidosis: ↓inotropy (predominates if pH <7.2) · Risk of myocardial ischaemia: ↑demand, ↓supply |
Vasculature |
· -Cytokines: vasodilatation, capillary leak, microvascular thrombosis -> ↓SVR · Acidosis: vasodilatation · SNS: vasoconstriction (partly offsets dilation) |
Respiratory |
· ↑metabolic rate -> ↑VCO2 -> ↑VA · Capillary leak -> +/- pulmonary oedema, ARDS |
Renal |
Effects of hypotension · ↑renin, angiotensin, aldosterone · +/- Failure of autoregulation (if mAP <70mmHg) · +/- ATN (if severe, prolonged) |
Haem |
· Cytokines -> ± platelet dysfunction / microvascular thrombosis / DIC |
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