Pathophysiology of shock

2. Pathophysiology of shock Dr Mostafavi SN Departement of Pediatric Infectious Disease Isfahan University of Medical Science

3. Shock • Acute dramatic syndrome due to inadequate circulation to vital organs • 2% of hospital admissions • 20-50% mortality, most due to complications • The most common cause in children is hypovolemia then sepsis

4. Factors that influence adequate circulation to organs • Cardiac output • Stroke volume • End diastolic volume: Preload • Contractility: Inotropy • Vascular tone : Afterload • Heart rate: Chronotropy

5. Types of shock • Hypovolemic: ↓ preload • Distributive: ↓ afterload • Cardiogenic: ↓ inotropy, ↓ chronotropy • Obstructive: ↑ afterload • Septic : ↓ preload, ↓ afterload, ↓ inotropy

6. Hypovolemic shock • Causes: • excessive loss • GI: Vomiting, diarrhea • Kidney: DM, DI, renal failure • Vascular: bleeding • Inadequate intake • Course: ↓blood volume→ ↓ preload→ ↓ stroke volume→ shock+ ↓preload

7. Distributive shock • Types • Anaphylactic • Brainstem/ spinal injury • Course: loss of vasomotor tone → ↑venous and arterioles pool → ↓preload & afterload→ ↓↓cardiac output → shock+ ↓preload

8. Cardiogenic shock • Causes: myocardiotis, cardiomyopathy, dysrhythmia, congenital heart disease • Decreased myocardial contractility &/or HR → shock & heart failure+ ↑preload

9. Obstructive shock • Causes: tamponad, pneumothorax, tumor, pulmonary emboli, critical CoA, severe AS • Blood flow obstruction→ ↑afterload → shock & heart failure+ ↑preload

10. Septic shock • Course: exaggerated immune response due to infection & toxic metabolites: • Vasodilatation and increased permeability → ↓afterload → ↓cardiac output • Extravasation of fluids →↓ venous return → ↓preload → ↓cardiac output • Depression of myocardial function → ↓cardiac output

11. Steps of shock • Insufficient delivery of blood, oxygen and nutrients to the cells • Anaerobic metabolism • Lactic acidosis • Sympathoadrenal and respiratory responses( Compensated shock) • ( no intervention) Decompensated shock • Multisystem organ dysfunction • Death

12. Decompensated shock • Progress of insult→ inadequate compensatory mechanisms → ↓BP • ↑HR→ ↓coronary flow & ventricular filling→ ↓ myocardial function → ↓BP • ↑ Vascular resistance+ ↑contractility → ↑ myocardial oxygen need+ ↓ O2→ ↓ myocardial function → ↓BP • Vasoconstriction → tissue ischemia → ↑vasoactive peptides → ↓ myocardial function & ↑ capillary permeability → ↓BP

13. Multisystem organ dysfunction • Brain: cytotoxic edema, ischemia→ decreased level of consciousness, convulsion, focal signs • Kidneys: prerenal renal failure, Acute tubular necrosis • Coagulation: Disseminated intravascular coagulopathy, thrombosis • Lungs: Acute respiratory distress syndrom

14. Multisystem organ dysfunction • Blood: anemia, thrombocytopenia, leukopenia, leukocytosis • Liver: ↑bilirubine, ↑ transaminase, ↓coagulation factors, ↑ amonia • Endocrine: ↑ or ↓insulin, ↑ counter regulatory hormones, ↓ parathyroid→ hypo or hyperglycemia, hypocalcemia

15. Stages of shock

16. ↑HR • < 2 mo → 180 • 2-12 mo → 160 • 1-2 yr → 120 • 2-8 yr → 110

17. ↑RR • < 2 mo → 60 • 2- 12 mo → 50 • 1-5 yr → 40 • 5-8 yr → 30 • >8 yr → 25

18. Normal values • Systolic Blood Pressure: > [70+ 2 age(yr)] or > 80 mmHg • Capilary Refill Time: 2-3 sec • Urine Output: > 1 cc/kg/h • Level Of Counsciousness: Alert, Drowsiness, Confused, Stupor, Light coma, Deep coma

19. Suggestive signs in shock

20. Treatment of shock