Shock: Clinical features and pathophysiology

1. Shock: Clinical features and pathophysiology Mahesh Nirmalan Critical Care Unit, Manchester Royal Infirmary

2. Objectives • Life-threatening condition • Immediate or delayed mortality • Multiple aetiology • Recognition and Assessment • Physiological consequences of shock • clinical features • Document and report on progression

3. Definition of Shock • Inadequate tissue perfusion • Decreased oxygen supply • Anaerobic metabolism • Accumulation metabolic waste

4. Causes of Shock • Severe or sudden blood loss • Large drop in body fluids • Myocardial infarction • Major infections • High spinal injuries • Anaphylaxis • Extreme heat or cold

5. Types of Shock • Hypovolemic Shock: • haemorrhagic • or non haemorrhagic • Other causes of shock • Cardiogenic Shock • Septic Shock • Neurogenic Shock • Anaphylactic Shock

6. Harvest of Death: T H O’Sullivan

7. Hypovolaemic Shock • Haemorrhage: Overt or occult • Reduction in circulating volume • Reduction in venous return and CO • O2 supply-demand imbalance • Lactic acidosis • Reduction in venous oxygen saturation • Non haemorrhagic hypovolaemia • Severe burns, vomiting and diarrhoea

8. CO, MAP and SvO2

9. Effect of EDV and contractility on SV

10. Changes in CO and MAP in haemorrhage

11. % Blood loss Clinical Signs < 15 Slightly increased heart rate, local swelling, bleeding 15-30 Increased heart rate, increased diastolic blood pressure, prolonged capillary refill 30-50 Above findings plus: hypotension, confusion, acidosis, decreased urine output > 50 Refractory hypotension, refractory acidosis, death Clinical Signs of Acute Hemorrhagic Shock

12. Signs of Shock • Cold, clammy and pale skin • Rapid, weak, thready pulse • Shallow, rapid breathing • Oliguria • Reduction in MAP • Cyanosis • Loss of consciousness

13. Non-Haemorrhagic Shock • Cardiogenic Shock • Septic Shock • Neurogenic Shock • Anaphylactic Shock

14. Cardiogenic Shock • Primary myocardial failure • Arrhythmia • Tamponade • Contusion • Pump failure • Reduction in cardiac output: • Decreased blood supply • Decreased oxygen delivery

15. Cardiogenic Shock • Assess for: • Signs of heart failure • Signs of tamponade • Cardiac dysrrhythmia • Myocardial infarction • Tachycardia • Muffled heart sounds or third heart sound • Engorged neck veins with hypotension • Dyspnoea • Oedema in feet and ankles

16. Septic Shock • Bacterial, viral, fungal infection • Gram negative and gram positive bacteria • High output failure: “warm shock” • Fever, tachycardia, tachypnoea, leucocytosis • Inadequate oxygen extraction • High SvO2, Metabolic acidosis • “Cold shock” • Atypical presentation in immuno-compromised patients • Diabetes, Cirrhosis, immunosuppression

17. Septic Shock in trauma patients • Develops 2 - 5 days after injury occurs • Carries a poor prognosis • Assess for: • Penetrating abdominal injuries • Signs of infection • Warm pink skin and dry elevated body temperature • Tachycardia • Wide pulse pressures

18. Neurogenic Shock • Caused by: • Spinal cord injury • Certain drugs • Brain stem, spinal or torso trauma • Venous pooling and arteriolar dilatation • Signs and Symptoms: • Hypotension without tachycardia • Warm pink skin • Low blood pressure & minimal response to fluids

19. Anaphylactic shock

20. Anaphylactic Shock • Rapid onset • Primary systems: • Cardiovascular, Respiratory • Skin, Gastrointestinal, coagulation • Face, pharynx and laryngeal oedema • Adrenaline is life saving

21. Anaphylactic Shock • Diffuse vasodilatation • Increase size of vascular bed • Blood is trapped in small vessels and viscera • Temporary loss in total circulatory volume • Sudden severe allergic reaction to: • Drugs, Toxins, Foods, Plants

22. Symptoms • Apprehension and flushing • Wheezing or shortness of breath & cough • Rapid, weak pulse • Cyanosis • Generalized itching or burning • Watering and itching of the eyes • Hypotension • Coma

23. Stages of shock • Compensated shock • Autotransfusion • Decompensated shock • Blood moves to more vital organs • Irreversible shock • Multiple system / organ damage • Even with treatment, death is the result

24. Plasma [Lactate] A priori groups Post hoc groups

25. Evaluation of Shock • Internal or external hemorrhage • Underlying cardiac problems • Sepsis • Trauma to spine cord • Contact with known allergic substance • Determine amount of blood loss • How long has casualty been bleeding?

26. Level of Consciousness Report and record • Alert • Verbal response to stimuli • Pain response to stimuli • Unresponsive to any stimuli

27. Early Signs of Shock in Non Complicated Patients • High index of suspicion • Minimum tachycardia • No measurable changes occur in blood pressure • Pulse pressure is potentially very useful

28. Definitive management Where? By whom?

29. Invasive monitoring • Essential in the definitive treatment • Direct arterial pressure • Central venous pressure • Cardiac output

30. Direct arterial pressure

31. CVP AND CIRCULATING VOLUME?

32. Treatment of Shock • Maintain airway • Control bleeding • Baseline vital signs • Level of consciousness Increase tissue perfusion and oxygenation status

33. Treatment of Shock • Positioning • ABCD approach • Fluid therapy • Drug therapy • Keep patient at normal temperature • Prevent hypothermia • Minimize effect of shock • On-going assessment - every 10-15 minutes

34. Specific measures • Hypovolaemia: Blood transfusion • Electrolyte/acid base imbalance • Sepsis: Antibiotics, ?steroids • Neurogenic: Steroids • Anaphylactic: Adrenalin

35. Summary • Life threatening: Early goal directed therapy and regular monitoring by trained staff will change outcome. • Early detection : DON’T RELY ON BP • High index of suspicion • Monitor casualties susceptible to shock