Disturbance of Circulation Series - Shock

1. Disturbance of Circulation Series -Shock Jianzhong Sheng, MD PhD

2. Outline • Definition • Epidemiology • Physiology • Classes of Shock • Clinical Presentation • Management • Controversies

3. Definition • A physiologic state characterized by • Inadequate tissue perfusion • Clinically manifested by • Hemodynamic disturbances • Organ dysfunction

4. Epidemiology • Mortality • Septic shock – 35-40% (1 month mortality) • Cardiogenic shock – 60-90% • Hypovolemic shock – variable/mechanism

5. Pathophysiology • Imbalance in oxygen supply and demand • Conversion from aerobic to anaerobic metabolism • Appropriate and inappropriate metabolic and physiologic responses

6. Pathophysiology • Cellular physiology • Cell membrane ion pump dysfunction • Leakage of intracellular contents into the extracellular space • Intracellular pH dysregulation • Resultant systemic physiology • Cell death and end organ dysfunction • MSOF and death

7. Physiology • Characterized by three stages • Preshock (warm shock, compensated shock) • Shock • End organ dysfunction

8. Physiology • Compensated shock • Low preload shock – tachycardia, vasoconstriction, mildly decreased BP • Low afterload (distributive) shock – peripheral vasodilation, hyperdynamic state

9. Pathophysiology • Shock • Initial signs of end organ dysfunction • Tachycardia • Tachypnea • Metabolic acidosis • Oliguria • Cool and clammy skin

10. Physiology • End Organ Dysfunction • Progressive irreversible dysfunction • Oliguria or anuria • Progressive acidosis and decreased CO • Agitation, obtundation, and coma • Patient death

11. Classification • Schemes are designed to simplify complex physiology • Major classes of shock • Hypovolemic • Cardiogenic • Distributive

12. Hypovolemic Shock • Results from decreased preload • Etiologic classes • Hemorrhage - e.g. trauma, GI bleed, ruptured aneurysm • Fluid loss - e.g. diarrhea, vomiting, burns, third spacing, iatrogenic

13. Hypovolemic Shock • Hemorrhagic Shock Crit Care. 2004; 8(5): 373–381.

14. Cardiogenic Shock • Results from pump failure • Decreased systolic function • Resultant decreased cardiac output • Etiologic categories • Myopathic • Arrhythmic • Mechanical • Extracardiac (obstructive)

15. Distributive Shock • Results from a severe decrease in SVR • Vasodilation reduces afterload • May be associated with increased CO • Etiologic categories • Sepsis • Neurogenic / spinal • Other (next page)

16. Distributive Shock • Other causes • Systemic inflammation – pancreatitis, burns • Toxic shock syndrome • Anaphylaxis and anaphylactoid reactions • Toxin reactions – drugs, transfusions • Addisonian crisis • Myxedema coma

17. Distributive Shock • Septic Shock

18. Clinical Presentation • Clinical presentation varies with type and cause, but there are features in common • Hypotension (SBP<90 or Delta>40) • Cool, clammy skin (exceptions – early distributive, terminal shock) • Oliguria • Change in mental status • Metabolic acidosis

19. Evaluation • Done in parallel with treatment! • H&P – helpful to distinguish type of shock • Full laboratory evaluation (including H&H, cardiac enzymes, ABG) • Basic studies – CxR, EKG, UA • Basic monitoring – VS, UOP, CVP, A-line • Imaging if appropriate – FAST, CT • Echo vs. PA catheterization • CO, PAS/PAD/PAW, SVR, SvO2

20. Treatment • Manage the emergency • Determine the underlying cause • Definitive management or support

21. Manage the Emergency • Your patient is in extremis – tachycardic, hypotensive, obtunded • How long do you have to manage this? • Suggests that many things must be done at once • Draw in ancillary staff for support! • What must be done?

22. Manage the Emergency • One person runs the code! • Control airway and breathing • Maximize oxygen delivery • Place lines, tubes, and monitors • Get and run IVF on a pressure bag • Get and run blood (if appropriate) • Get and hang pressors • Call your senior/fellow/attending

23. Determine the Cause • Often obvious based on history • Trauma most often hypovolemic (hemorrhagic) • Postoperative most often hypovolemic (hemorrhagic or third spacing) • Debilitated hospitalized pts most often septic • Must evaluate all pts for risk factors for MI and consider cardiogenic • Consider distributive (spinal) shock in trauma

24. Determine the Cause • What if you’re wrong? • 85 y/o M 4 hours postop S/P sigmoid resection for perforated diverticulitis is hypotensive on a monitored bed at 70/40 • Likely causes • Best actions for the first 5 minutes?

25. Definitive Management • Hypovolemic – Fluid resuscitate (blood or crystalloid) and control ongoing loss • Cardiogenic - Restore blood pressure (chemical and mechanical) and prevent ongoing cardiac death • Distributive – Fluid resuscitate, pressors for maintenance, immediate abx/surgical control for infection, steroids for adrenocortical insufficiency

26. Controversies • IVF Resuscitation • Limited resuscitation in penetrating trauma • Use of hypertonic saline resuscitation in trauma • Endpoints for prolonged resuscitation • Pressors • Best pressors for distributive shock • Monitoring • Most appropriate timing and use for PA catheterization or intermittent echocardiogram

27. Thanks!