Management of paediatric shock – fluids and inotropes

1. Management of paediatric shock – fluids and inotropes Allan Wardhaugh Paediatric Intensivist UHW Cardiff

3. Management of shock • Physiology • Basic clinical assessment • Laboratory and invasive clinical assessment • Management • Fluid choice • Inotropes and vasopressors

4. Definition of Shock

5. Definition of Shock Inadequate oxygen delivery to tissues to meet demand because of circulatory failure

6. Cause of shock • Not enough fluid in circuit • Sepsis • Haemorrhage • Dehydration • Maldistribution – ‘third spacing’ – many causes • Pump failure • Sepsis • Cardiomyopathy/ myocarditis • Arrythmia • Inadequate oxygen carrying capacity • Anaemia • CO poisoning • Very low circuit resistance • AVM • Sepsis

7. Physiological aims of treatment • Get oxygen into the fluid • Get fluid in the circuit • Make sure the fluid can carry oxygen • Maintain adequate perfusion pressure • Maintain pump pressure • Optimise circuit resistance

8. Physiology – oxygen delivery O2 delivery =[(1.34  Hb  O2 sats) + (PO2  0.023)]  CO CO = HR  SV

9. Oxygen supply – dependence in critically ill

10. Critical point Physiology – fluid filled circuit and Ohm’s Law • I = V/R • Flow = Perfusion pressure/ Resistance • Cardiac Output = MAP-CVP/ SVR Perfusion pressure = CO  SVR Aim of treatment – prevent perfusion pressure dropping below critical point

11. Clinical assessment

12. Recognition - clinical • Tachycardia • Tachypnoea • Energy conservation • Relative inactivity • Vasoconstriction • CRT • Core–peripheral temperature gap • Organ hypoperfusion • Oliguria • Irritability, diminished consciousness • Hypotension

13. Distribution of cardiac output • Kidneys receive high proportion CO – if urine is flowing >0.5 – 1ml/kg/hr, cardiac output is probably adequate

14. Has enough fluid been given?

15. Distribution of blood in circulation • Heart 5% • Systemic 80% • Arteries 10% • Veins 65% • Pulmonary 15%

16. Venous reservoir • ‘Window’ on venous reservoir • Liver in neonates/ infants • Jugular venous pulse in older children • Response to hepatic pressure – simulates venoconstriction and fluid bolus • beware cardiogenic shock

17. Recognition - bloods • Base deficit > -4 • Hyperchloraemia confounds after volume resuscitation • Lactate >2.5 mmol/l • May signify poor tissue oxygen delivery • Beware other causes (metabolic, liver failure) • Mixed venous oxygen saturations • Venous PO2 reflects tissue oxygenation • Low values probably more reliable than high • Mixed venous sats > 70% imply adequate tissue oxygenation

18. More invasive monitoring? • Once in ICU, clinical parameters correlate less well to cardiac output • Cardiac output estimation • TOE • PiCCO • Li dilution • et al Tibby et al. Clinicians’ abilities to estimate cardiac index in ventilated children and infants. Archives of Disease in Childhood1997;77:516–518

19. Management • Get oxygen into the fluid • Get fluid in the circuit • Make sure the fluid can carry oxygen • Maintain adequate perfusion pressure • Maintain pump pressure • Optimise circuit resistance

20. ABC • Oxygen • A also stands for antibiotics • Ceftriaxone 80mg/kg

21. Management • Get oxygen into the fluid • Get fluid in the circuit • Make sure the fluid can carry oxygen • Maintain adequate perfusion pressure • Maintain pump pressure • Optimise circuit resistance

22. Volume Volume Volume • Sepsis - >40ml/kg fluid volume in first hour – should almost certainly be ventilated • Early intubation and ventilation easier and safer • Prevents hypoxia • Facilitates line placement for adequate monitoring, inotrope delivery

24. Restoring circulating volume • Blood volume 65ml/kg adult, 80-90ml/kg infant • 40ml/kg corrects volume in most cases if ongoing losses have stopped • Ongoing losses hidden in • Intra-abdominal/ intra-thoracic haemorrhage • IVH in neonates • Sepsis • Gut obstruction

25. Which fluid?

26. 0.9% Saline or 4.5% Albumin • Meta-analysis 1998 flawed • Units reporting improving outcomes in sepsis use 4.5% albumin routinely • More recent meta-analyses show no increased mortality with albumin • 0.9% saline cheaper • Albumin produces greater expansion in ECF and plasma volume • Individual responses to this vary

27. SAFE study • MCRCT of 4% human albumin vs 0.9% saline 16 ICUs Australia/ New Zealand. • Patients aged >18years and needed fluid resuscitation. • Randomised to have saline or albumin for duration of stay in ICU, or 28/7. • Burns, liver transplant and cardiac surgery excluded. • Death at 28 days primary outcome. • 3499 HAS, 3501 Saline. • Baseline characteristics of both groups similar.

28. SAFE – fluid volume given

31. Which crystalloid? • Normal saline • Hartmann’s solution

32. Crystalloid electrolyte composition

33. Which colloid? • Albumin • Gelatins • Starches • Dextrans  hypertonic saline

34. Colloids

35. Management • Get oxygen into the fluid • Get fluid in the circuit • Make sure the fluid can carry oxygen • Maintain adequate perfusion pressure • Maintain pump pressure • Optimise circuit resistance

36. Haemodilution • Keep Hb > 10g/dL in resuscitation phase • Clotting factors – FFP • Platelets • X Match at presentation

38. Haemorrhagic shock - lose blood  give blood? • Less O2 carrying capacity, but better than clear fluid • 3 for 1 rule using crystalloid to correct ECF fluid shifts • Animal models suggest aggressive volume resuscitation may be harmful • One RCT in adults promoted delayed fluid resuscitation (Houston 1994)

39. Houston penetrating trauma study • 8% in DR violated protocol (received volume) • Severity of shock varied from pulse barely palpable to systolic bp 90mmHg • Arrival bp higher in DR group • Deaths before theatre removed ( destined to die) – no difference in outcome • Times from injury to theatre short • NNT 12.5 ( 6.4 – 230) – very wide confidence intervals Bickell et al.Immediate versus Delayed Fluid Resuscitation for Hypotensive Patients with Penetrating Torso Injuries. N Engl J Med 1994; 331:1105-1109

40. Hypotensive resuscitation cannot presently be recommended in paediatric trauma

42. How much fluid?

43. Aggressive volume resuscitation associated with improved survival in septic children • Only study to show a beneficial intervention in paediatric septic shock – observational study • Recruited all paediatric sepsis patients to ER in Washington DC Childrens Hospital – PA catheter in situ by 6 hours • 34 patients – mean age 13.5 months • Divided into 3 groups by volume received in first hour (post hoc) • Group 1 <20ml/kg • Group 2 20 – 40ml/kg • Group 3 >40ml/kg Carcillo et al. Carcillo et al. Role of early fluid resuscitation in pediatric septic shock. JAMA. 1991;266:1242-1245

44. Totals in each group 14 11 9 Mortality

45. ARDS

46. Hypovolaemia at 6 hours

47. Management • Get oxygen into the fluid • Get fluid in the circuit • Make sure the fluid can carry oxygen • Maintain adequate perfusion pressure • Maintain pump pressure • Optimise circuit resistance

48. Inotropes (and pressors)

49. Advantages Improve pump function Increase SVR improving perfusion pressure Increase diastolic BP improving coronary artery perfusion Disadvantages May increase afterload Increase myocardial oxygen demand Arrythmia Extravasation danger – should go centrally Inotropes and pressors

50. When to start inotropes • Sepsis – failure to respond to 40ml/kg fluid in first hour • Mortality in paediatric septic shock strongly associated with low cardiac output • Will need adequate monitoring • Invasive BP if possible