Table of contents
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UNDER CONSTRUCTION
Introduction
- State of decreased tissue perfusion, resulting in poor oxygen delivery causing tissue ischemia.
- Can cause organ dysfunction.
- Shock develops when one or more of key hemodynamic parameters contribute to perfusion.
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Common Clinical Features of Shock
Hypotension
SBP <90 mm Hg
MAP <60 mm Hg
Acute decrease in SBP of >40 mm Hg
Lack of MAP response to initial fluid challenge
End-Organ Dysfunction Due to Hypoperfusion
Decreased urine output
Change in mental status
Increased serum lactic acid level
- Three main types of shock:
- Cardiogenic
- Decreased cardiac output (i.e heart failure, massive PE, etc..)
- Distributive
- Deceased SVR (i.e. sepsis, anaphylaxis)
- Hypovolemic
- Decreased preload (i.e. hemorrhage, dehydration)
- Cardiogenic
General Management Principles
- 1. Restore perfusion!!!
- Often fluids can help perfusion.
- Vasopressors
- Inotropes
- 2. Reverse the cause. (i.e. lysis of PE, treatment of infection).
- Often requires understanding which hemodynamic parameter is affected.
- Swan Ganz Catheter has been used to differentiate shock states, but outcomes shown to be same (use vs. no use).
- No longer recommended.
- Swan Ganz Catheter has been used to differentiate shock states, but outcomes shown to be same (use vs. no use).
Fluids
- No conclusive evidence exist favour colloid vs. crystalloids (crystalloids b/c cheaper).
- Aggressive volume expansion = good outcomes in hypovolemic and septic shock.
- NOTE: Low albumin states: initially use crystalloid, but can third space, and often providers start using colloids (albumin). Text book answer: no evidence to support colloids.
- NOTE: Concern about precipitating heart failure should not stop large bolus of fluids.
Vasopressors
- Contract smooth muscles at arterial walls, increase SVR, some also improve cardiac contractility.
- Nearly all have side-effects:
- Cardiac arrhythmias, extremities or mesentery ischemia. (response to pressors can vary).
- See Vasopressor Section
Septic Shock
Cardiogenic Shock
- Systemic hypotension and evidence of end-organ hypoperfusion (poor cardiac output).
- Examples:
- AKI
- Aminotransferases
- Hyperbilirubinemia
- Cool extremities
- Decreased mental status
- Examples:
- Definition of cardiogenic shock
- Cardiogenic shock is defined by persistent hypotension (sBP <80-90 mm Hg or MAP 30 mm Hg lower than baseline) with severe reduction in cardiac index (<1.8 L/min/m2 without hemodynamic support or <2.0-2.2 L/min/m2 with support) and adequate or elevated filling pressure (for example, left ventricular end-diastolic pressure >18 mm Hg or right ventricular end-diastolic pressure >10-15 mm Hg).
- Use IV vasoactive medications and device-based hemodynamic support.
- Identify treatable causes
- MI (reperfusion) - free wall rupture, papillary muscle rupture (require urgery surgery).
- Medications:
- Main idea: many vasodilatory to reduce afterload in cardiogenic shock or increase cardiac output/index (inotropic).
- Dopamine and vasopressin for BP support rather than inotropy.
- If systemic BP is acceptable, can add IV vasodilator (i.e. nitroprusside) to help decrease cardiac output (drop afterload)
- But careful because: Dobutamine and Milirinone associated with higher risk of arrhythmias.
- IF vasoactive medications are not helpful, can use mechanical support:
- Intra-aortic balloon pump
- During diastole improves coronary and systemic perfusion
- During systole deflates, reducing LV afterload.
- Ventricular Assist Devices
- Intra-aortic balloon pump
Notes
- EARLY treatment of shock always has a survival benefit.
- Studies showing pre-hospital initiation of shock treatment or pre-ICU treatment by ward personnel improve outcomes.
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