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Shock

Shock. Scott G. Sagraves, MD, FACS Assistant Professor Trauma & Surgical Critical Care Associate Director of Trauma UHS of Eastern Carolina. Objectives. Define & classify shock Outline management principles Discuss goals of fluid resuscitation

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Shock

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  1. Shock Scott G. Sagraves, MD, FACS Assistant Professor Trauma & Surgical Critical Care Associate Director of Trauma UHS of Eastern Carolina

  2. Objectives • Define & classify shock • Outline management principles • Discuss goals of fluid resuscitation • Understand the concepts of oxygen supply and demand in managing shock. • Describe the physiologic effects of vasopressors and inotropic agents

  3. Goals • Review hemodynamic techniques in the ICU • Introduce the concept of the cardiac cycle • Review of the pulmonary artery catheter parameters • Utilize the presentation to analyze clinical cases and to feel comfortable with pa-c parameters.

  4. Shock: “A momentary pause in the act of death.” -John Collins Warren, 1800s

  5. Hypotension • In Adults: • systolic BP  90 mm Hg • mean arterial pressure  60 mm Hg •  systolic BP > 40 mm Hg from the patient’s baseline pressure

  6. Definition SHOCK: inadequate organ perfusion to meet the tissue’s oxygenation demand.

  7. “Hypoperfusion can be present in the absence of significant hypotension.” -fccs course

  8. Pathophysiology ATP + H2O  ADP + Pi + H+ + Energy Acidosis results from the accumulation of acid when during anaerobic metabolism the creation of ATP from ADP is slowed. H+ shift extracellularly and a metabolic acidosis develops

  9. Pathophysiology • ATP production fails, the Na+/K+ pump fails resulting in the inability to correct the cell electronic potential. • Cell swelling occurs leading to rupture and death. • Oxidative Phosphorylation stops & anaerobic metabolism begins leading to lactic acid production.

  10. Why Monitor? • Essential to understanding their disease • Describe the patient’s physiologic status • Facilitates diagnosis and treatment of shock

  11. History • 1960’s • low BP = shock; MSOF resulted after BP restored • 1970’s • Swan & Ganz - flow-directed catheter • thermistor  cardiac output • 1980’s • resuscitation based on oxygen delivery, consumption & oxygen transport balance.

  12. Pulmonary Artery Catheter

  13. Pulmonary Artery Catheter • INDICATIONS • volume status • cardiac status • COMPLICATIONS • technical • anatomic • physiologic

  14. PLACEMENT

  15. West’s Lung Zones • Zone I - PA > Pa > Pv • Zone II - Pa > PA > Pv • Zone III - Pa > Pv > PA • PA = alveolar • Pa = pulmonary artery • Pv = pulmonary vein

  16. Correct PA-C Position

  17. Measured Blood pressure Pulmonary A. pressure Heart rate Cardiac Output Stroke volume Wedge pressure CVP Calculated Mean BP Mean PAP Cardiac Index Stroke volume index SVRI LVSWI BSA Standard Parameters

  18. Why Index? • Body habitus and size is individual • Inter-patient variability does not allow “normal” ranges • “Indexing” to patient with BSA allows for reproducible standard

  19. PATIENT A 60 yo male 50 kg CO = 4.0 L/min BSA = 1.86 CI = 2.4 L/min/m2 PATIENT B 60 yo male 150 kg CO = 4.0 L/min BSA = 2.64 CI = 1.5 L/min/m2 Index Example

  20. PA Insertion 20 15 10 5 PA 19/10 PAOP = 9 RA = 5 RV = 22/4 0

  21. CVP • CVP of SVC at level of right atrium • pre-load “assessment” • normal 4 - 10 mm Hg • limited value

  22. PAOP • End expiration • Reflection changes with positive pressure • Waveforms change  every 20 cm

  23. Waveform Analysis • A wave - atrial systole • C wave - tricuspid valve closure @ ventricular systole • V wave - venous filling of right atrium

  24. Cardiac Cycle PVRI MPAP pulmonary PCWP Right ventricle Left ventricle RVSWI LVSWI MAP CVP systemic SVRI

  25. Hemodynamic Calculations ParameterNormal Cardiac Index (CI) 2.8 - 4.2 Stroke Volume Index (SVI) 30 - 65 Sys Vasc Resistance Index (SVRI) 1600 - 2400 Left Vent Stroke Work Index (LVSWI) 43 - 62

  26. Cardiac Index C.I. = HR x SVI SVI measures the amount of blood ejected by the ventricle with each cardiac contraction. Total blood flow = beats per minute x blood volume ejected per beat

  27. SYSTEMIC (SVRI) MAP - CVP CI  SVR = vasoconstriction  SVR = vasodilation PULMONARY (PVRI) MPAP - PAOP CI PVR = constriction PE, hypoxia Vascular Resistance Index x 80 x 80 Vascular resistance = change in pressure/blood flow

  28. Stroke Work LVSWI = (MAP-PAOP) x SVI x 0.0136 normal = 43 - 62 VSWI describe how well the ventricles are contracting and can be used to identify patients who have poor cardiac function. ventricular stroke work =  pressure x vol. ejected

  29. Too Many Numbers

  30. Definitions • O2 Delivery - volume of gaseous O2 delivered to the LV/min. • O2 Consumption - volume of gaseous O2 which is actually used by the tissue/min. • O2 Demand - volume of O2 actually needed by the tissues to function in an aerobic manner Demand > consumption = anaerobic metabolism

  31. Rationale for Improving O2 Delivery Insult Tissue Hypoxia Demands are met Increased Delivery Increased Consumption

  32. Critical O2 Delivery VO2I The critical value is variable & is dependent upon the patient, disease, and the metabolic demands of the patient. DO2I

  33. Arterial Oxygen Content (CaO2) Venous Oxygen Content (CvO2) Arteriovenous Oxygen Difference (avDO2) Delivery (O2AVI) Consumption (VO2I) Efficiency of the oxygenation of blood and the rates of oxygen delivery and consumption Oxygen Calculations

  34. Arterial Oxygen Content CaO2 = (1.34 x Hgb x SaO2) + (PaO2 x 0.0031) If low, check hemoglobin or pulmonary gas exchange

  35. Arteriovenous Oxygen Difference avDO2 = CaO2 - CvO2 Values > 5.6 suggests more complete tissue oxygen extraction, typically seen in shock

  36. Oxygen Delivery (DO2I) O2AVI = CI x CaO2 x 10 Normal values suggests that the heart & lungs are working efficiently to provide oxygen to the tissues. < 400 is bad sign

  37. Oxygen Consumption VO2I = CI x (CaO2 - CvO2) If VO2I < 100 suggest tissues are not getting enough oxygen

  38. SvO2 VO2 SvO2 = 1- DO2

  39. Oxycalculations

  40. Resuscitation Goals • CI = 4.5 L/min/m2 • DO2I = 600 mL/min/m2 • VO2I = 170 mL/min/m2 NOT ALL PATIENTS CAN ACHIEVE THESE GOALS Critically ill patients who can respond to their disease states by spontaneously or artificially meeting these goals do show a better survival.

  41. Break Time…

  42. “Shock is a symptom of its cause.” -fccs course

  43. Signs of Organ Hypoperfusion • Mental Status Changes • Oliguria • Lactic Acidosis

  44. Components

  45. Categories of Shock • HYPOVOLEMIC • CARDIOGENIC • DISTRIBUTIVE • OBSTRUCTIVE

  46. Goals of Shock Resuscitation • Restore blood pressure • Normalize systemic perfusion • Preserve organ function

  47. In general, treat the cause...

  48. Causes hemorrhage vomiting diarrhea dehydration third-space loss burns Signs  cardiac output  PAOP  SVR Hypovolemic Shock

  49. Classes of Hypovolemic Shock

  50. Treatment - Hypovolemic • Reverse hypovolemia vs. hemorrhage control • Crystalloid vs. Colloid • PASG role? • Pressors?

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