Septic Shock

1) SIRS/Sepsis definitions
SIRS (Systemic Inflammatory Response Syndrome): 2 or more criteria.  Note that these criteria are purposefly nonspecific, but highly sensitive.  SIRS can be caused by infections (obviously), but lots of other things - trauma, burns, pancreatitis, DVT/PE, etc.

• Temp > 38 or < 36
• HR > 90
• RR > 20, pCO2 < 32, or need for mechanical ventilation
• WBC > 12, < 4, or > 10% bands

Sepsis = SIRS plus documented or suspected infection

• Infection can be "documented" by positive cultures (blood cultures, UA/urine cultures), or by visual inspection (cellulitis, wound infection, or infiltrate on CXR); even if you only have a strong suspicion of infection, that counts as sepsis!
• It is a common misconception that sepsis = bacteremia.  You do NOT need bacteremia to have sepsis (although the incidence of bacteremia increases along the sepsis severity continuum).

Severe Sepsis = Sepsis + Organ hypoperfusion or dysfunction. 
Useful to think of organ dysfunction by systems:

• Cardiovascular: Hypotension that responds to fluids (vs septic shock - refractory to fluids), lactic acidosis (> 2), mottled skin or impaired capillary refill, or new cardiac dysfunction by echo or cardiac index (due to cytokines causing myocardial depression)
• Neuro - significantly altered mental status
• Renal - decreased urine output <0.5 cc/kg/hr
• Pulm - acute lung injury or ARDS
• Heme - DIC or thrombocytopenia (plts <100)
• GI - elevated bilirubin (>4) - due to poor perfusion of liver and cytokines

Septic Shock = Sepsis + Hypotension refractory to fluids

 

 

2) Pathogenesis of Sepsis and Septic shock, and overview of categories of Shock
Think of cardiovascular system as a pump with pipes and tank.  Malfunction can occur in 4 ways:

• Cardiogenic Shock - malfunction of pump - e.g. massive MI, severe CHF
• Hypovolemic Shock - not enough fluid in the tank  - e.g. hemorrhage, GI bleed, severe dehydration
• Distributive Shock - pipes are dilated - e.g. Sepsis, Anaphylaxis, Neurogenic shock, Adrenal crisis
• Obstructive Shock - obstruction to pump or to flow through pipes - e.g. Tamponade, massive PE, tension pneumothorax

- Sepsis -is mainly distributive shock - due to extreme vasodilation, but also has hypovolemic component (fluid leaks into intersitium) and cardiogenic component (myocardial depression due to cytokines)

 

 

Differentiating Shock states based on PA catheter #s:

Here is a basic table and some normal values to help you think about the numbers from a PA catheter (ie. RHC).

 

Shock	CVP	PCWP	CO	SVR
Distributive (ie. Sepsis)	↓	↓	↑	↓
Cardiogenic	↑	↑	↓	↑
Hypovolemic	↓	↓	↓	↑

 

Normal Cardiovascular Pressures :

RA - 0-7 mmHg

RV - 15-30 / 0-7 mmHg ( systolic / diastolic )

PA - 15-30 / 8-15 / 10-17 mmHg ( systolic / diastolic / mean )

PCWP mean - 6-12 mmHg

 

Normal Hemodynamic Parameters :

MAP - 70-110 mmHg

SVR - 900-1200 dynes/cm square

PVR - 80-120 dynes/cm square

CO - 4-7 L/min

 

 

3) Overview of management of sepsis and septic shock
Keys:

• IV fluids - be aggressive! 2 large bore IVs, often require several liters of crystalloid - give as rapid boluses, not maintenance
• Early appropriate antibiotics - this is key! Time to appropriate abxs is strongest predictor of mortality.  Start broad.  Get cultures before starting antibiotics!
• Monitoring - place foley catheter, consider central line (for CVP monitoring), a-line for close BP monitoring
• Source control - must identify source and control; all else is supportive.  Examples: DC infected central line, drain infected abscess, surgically debride necrotizing fasciitis

Early Goal Directed Therapy - from Rivers paper in NEJM 2001.  Protocol for severe sepsis/septic shock, decreased mortality from 47% to 31%.

• CVP 8-12 - achieve with fluids
• MAP > 65 - achieve with vasopressors
• Central venous O2 sat > 70% - if < 70% and Hct < 30, transfuse to goal Hct 30.  If still < 70% ScvO2, use inotropes (dobutamine)

 

(Victoria Kelly MD, 12/17/10)

(Chanu Rhee MD, 7/22/10)