Shock

1. Shock Sarah A. Murphy, MD Pediatric Critical Care Fellow MassGeneral Hospital for Children Boston, MA

2. What is shock??

3. Shock • State of acute energy failure, in which there is not enough ATP production to support cellular function • To make ATP (body’s energy source) you need: • Oxygen • Glucose

4. Krebs Cycle: in mitochondria, leads to ATP production

5. Shock: three mechanisms • Lack of oxygen delivery • Anemia • Need RBC to carry O2) • Hypoxia • Not enough O2 in blood • Ischemia • Blood not getting to tissues

6. Shock: three mechanisms 2. Lack of glucose delivery • Hypoglycemia • DKA • Unable to use glucose in blood

7. Shock: three mechanisms 3. Mitochondrial dysfunction • After cellular damage from hypoxia or ischemia mitochondria may not work and cannot produce ATP • “cytopathic hypoxia” • Cyanide poisoning

8. Shock • Final common effect: inadequate tissue perfusion/ oxygenation

9. Shock • Initially, effects are reversible • But prolonged tissue deprivation leads to cellular hypoxia and secondary injury from derangement of biochemical processes • Abnormalities become irreversible with time, resulting in cell death, end-organ dysfunction, multi-system organ failure and death

10. Shock • Aggressive treatment to restore perfusion within the first few hours may prevent the invariable progression that is the natural course of untreated shock: • end-organ damage • failure of multiple organ systems • death

11. How to Recognize Shock?

12. Physical Signs of Shock • Tachycardia • Early indicator, non-specific • Poor perfusion/cool extremities • Cap refill > 2 seconds, mottled skin • Or, flushed, hyperemic extremities • Weak pulses

13. Physical Signs of Shock • Signs of impaired organ perfusion: • Poor mentation, lethargy • Poor urine output • Lactic Acidosis

14. Physical Signs of Shock • Autonomic response to poor perfusion: • Tachycardia (most important early sign) • Tachypnea • Blood pressure – normal initially as body vasoconstricts to maintain perfusion

15. Physical Signs of Shock • Signs of decreased tissue perfusion • Color: Pale, ashen grey • Capillary refilling time (>2-3sec) • Decreased skin surface temperature • Increased difference between core and peripheral temperature >2o C

16. Physical Signs of Shock • Signs of major organ dysfunction • Brain:Agitation, stupor-coma, ischemic brain injury • Kidneys: Acute renal failure, Oliguria • GI: Erosive gastritis, ischemic pancreatitis • Liver:Ischemic hepatitis-elevation of transminases and biliurbin • Hematologic:Coagulation abnormality, elevated PT, PTTK in all forms of shock, also can see severe DIC and thrombocytopenia

17. Shock

18. Understanding Shock: Pathophysiology • What factors determine oxygen delivery? • Blood flow (cardiac output) • Oxygen content of blood (oxygen carrying capacity) • Balance between oxygen supply and metabolic demand

19. Shock Physiology • Cardiac Output = Stroke Volume x Heart Rate • Stroke Volume = function of (Preload, Cardiac Contractility, Afterload)

20. Shock Physiology • Body’s Compensatory Mechanisms: Autonomic Response • Increase Systemic Vascular Resistance (SVR) • to shunt blood to heart and CNS and maintain perfusion pressure • Increased venous tone to increase preload and improve CO • Increased cardiac contractility also improves CO

21. Shock Physiology • As a result of these compensatory mechanisms, children may initially have normal blood pressure! • Hypotension is a late finding in the development of shock in children

22. Shock: Stages • Shock is often classified in stages: • Compensated • Decompensated • Irreversible

23. Stages of Shock • Compensated Shock • Autonomic mechanisms compensate for impaired perfusion • Blood pressure is maintained within normal range • Tachycardia, often evidence of vasoconstriction • Decompensated/Hypotensive Shock • Compensatory mechanisms are overwhelmed and BP drops • Signs of organ dysfunction (UOP, MS changes, etc) • Irreversible Shock • Progressive end-organ dysfunction

24. Laboratory Findings • Bicarbonate Level • low with lactic acidosis may indicate shock/ and body using anaerobic metabolism • May also have: • Coagulopathy • Hypoglycemia • Hypocalcemia • Anemia • Hypoxia

25. Shock • Three basic kinds of shock: • Hypovolemic : not enough blood • Dehydration • Hemorrhage • Distributive : blood doesn’t stay in vessels • Sepsis • Anaphylaxis • Cardiogenic: heart not able to pump enough blood to body • Cardiac disease • Can be seen in Sepsis

26. Hypovolemic Shock • Most common form of shock • See from either: • Extravascular fluid loss (ex: diarrhea, vomiting, diuresis) • Intravascular fluid loss (capillary leak or hemorrhage)

27. Causes of Hypovolemic Shock • Fluid and electrolyte loss: • Diarrhea, vomiting, excessive sweating, pathologic renal loss, diuretics, heart stroke Blood loss: External-Laceration, Internal-Ruptured visceras, GI bleed, Intracranial bleed (esp. Neonates), Post­surgery

28. Distributive Shock • Vasodilation results in abnormal distribution of blood flow • Causes: • Sepsis : capillary leak syndrome • Anaphylaxis • Neurogenic shock: spinal cord injury results in loss of sympathetic tone

29. Sepsis and Septic Shock • Sepsis: clinical syndrome characterized by systemic inflammation and tissue injury in the setting of known or suspected infection • Septic Shock: Sepsis with persistent cardiovascular dysfunction after 40cc/kg of fluid resuscitation

30. Sepsis • Capillary leak from infection and inflammatory mediators • may see “flash” capillary refill • hyperemia • warm skin • edema

31. Sepsis • Sepsis can present as “warm shock” • Toxins and inflammatory mediators cause vasodilation and capillary leak • Causes “flash capillary refill”, hyperemia, warm, flushed skin

32. Cardiogenic Shock • Decreased systolic function and depressed cardiac output • Cardiomyopathy (including myocardial depression from late sepsis) • Arrhythmia (ventricular or atrial arrhythmias, SVT, bradycardia) • Obstructed output (tension pneumothorax, cardiac tamponade, massive pulmonary embolism)

33. Causes of Cardiogenic Shock • Myocardial insufficiency: • Congestive heart failure (Congenital, or acquired heart disease), Cardiomyopathies, myocarditis, Arrhythmias: Supraventricular tachycardia. • Metabolic: • Hypothermia, drugs, toxins, myocardial depressant effect of hypoglycemia, acidosis, hypoxia, poor myocardial perfusion - Kawasaki disease, congenital coronary abnormalities • Outflow obstruction: • Cardiac tamponade, Pneumopericardium, Tension pneumothorax, Pulmonary embolism

34. Causes of Cardiogenic Shock * Congenital heart disease = an important cause of shock in the neonate! Commonly, from left-sided obstructive lesions (ex: hypoplastic left heart and coarctation of aorta) These may present up to two weeks of age, when ductus arteriosis closes

35. Causes of Cardiogenic Shock In neonate presentating with shock, check: • Femoral pulses • 4 extremity blood pressures • Murmur • EKG with extreme right axis (150) for HLHS

36. Causes of Cardiogenic Shock • SVT (supraventricular tachycardia) • Why does SVT cause cardiogenic shock?

37. Causes of Cardiogenic Shock • How to diagnose SVT? • Rate > 210 (>180 in teen) • P wave usually absent or flipped • Rate extremely constant • How to treat SVT? • Valsalva, ice pack to face • Or, adenosine: 0.1mg/kg IV • Or, synchronized cardioversion, 0.5-1 joule/kg

38. Causes of Cardiogenic Shock • Tamponade, pericardial effusion, tension pneumothorax • Check for pulsus paradoxicus, narrowed pulse pressure, liver enlarged, muffled heart sounds, JVD on inspiration (Kussmaul’s sign)

39. Pulsus Paradoxus • A drop in greater than 15-20mm Hg in SBP with inspiration • Auscultate for pulse with BP cuff inflated • Note pressure at which you can hear SOME beats • Then release until you here ALL beats • Difference >10-15 mm hg = abnormal • If greater than 20mmHg, difference can be appreciated by palpation of pulse as well • Signifies cardiac impairment with tamponade or asthma • May need more fluids to help heart fill

40. Shock States

41. Treatment of child presenting with shock • Goal is to maintain/improve cardiac output to restore perfusion to tissues • Remember, CO = HR X SV

42. Maintaining cardiac output • Children with sepsis/shock need volume! • Quickly! • Most children with shock will respond to volume resuscitation • Re-evaluate frequently for effect of volume, if worsening, consider cardiogenic origin of shock • Goal with treatment is to maintain perfusion pressure above point at which flow to vital organs is compromised

43. Treatment of Sepsis/Shock • “Goal-directed Therapy” • Principle of early aggressive treatment of shock state with goal of restoring BP and perfusion to vital organs within 6 hours of presentation • Has been shown to improve survival and decrease morbidity in adults (Rivers, et al. “Early goal-directed therapy in the treatment of severe sepsis and septic shock” NEJM 2001) • No studies looking at goal-directed therapy in non-septic shock, but data extrapolated • No studies looking at children, but consensus guidelines for children agreed upon by expert committee

44. Treatment of Sepsis/Shock • IV access • Begin Fluid resuscitation • Central Line and Arterial Line if not fluid responsive and if possible • Initiate antibiotics ASAP if suspecting sepsis/infection

45. Treatment of Sepsis/Shock • Fluid resuscitation: • 20/kg boluses NS or 5% albumin • Repeat, q 5-10 mins until: • Normal pulse • Cap refill <2 sec • Mental status • Urine output >1cc/kg/hr • Normal BP • MAP – CVP : • 55-60 for Newborn • 60 for >1yr • 65 for >2 yrs

46. Treatment of Sepsis/Shock • Fluid resuscitation: • Note: large fluid boluses do NOT increase risk of cerebral edema, ARDS • Monitor for signs of fluid overload or poor cardiac function: • Rales • Gallop • Hepatomegaly • Increased WOB

47. Treatment of Sepsis/Shock • Start Dopamine for refractory shock after 60-80cc/kg of fluid resuscitation • Add Epinephrine (warm shock) or Norepinephrine (cold shock) • Consider hydrocortisone if BP still inadequate

48. Fluid refractory shock • Vasopressors • Dopamine • Norepinephrine • Epinephrine

49. Alpha receptors • arterioles

50. Beta 1 receptors • heart