Blood Products in Critically ill Children

Shamiel Salie Paediatric Intensive Care Unit Red Cross Children’s Hospital, University of Cape Town

1818 -

Extracted 4 ounces of blood from the arm of the patient’s husband with a syringe and successfully transfused it

•

Anaemia in critically ill children

• Causes – Chronic anaemia – Overt and occult blood loss – Bone marrow suppression from diseases/treatment – Inadequate erythropoietin response to anaemia

Red Blood Cell Transfusions

• For decades considered to be a low risk with obvious benefits • 10/30 rule • Restrictive use of blood since the 1980’s

What actually happens in PICU?

• 50% of children in PICU’s transfused Bateman: Am J Resp Crit Care Med 2008 • Large variability in clinical practise • Bedside observational studies Gauvin 2000 & Armano 2005 – transfusion threshold ranges from 7 - 11 g/dl • 30 North American PICU’s – Pretransfusion Hb 9.7 g/dl Bateman: Am J Resp Crit Care Med 2008

Physiological benefits of RBC transfusions

• Tissue hypoxia may be due to low Hb concentration, cardiac output or SaO 2 • Oxygen delivery exceeds requirements • Adaptive processes as oxygen delivery decreases with anaemia – Increased oxygen extraction – Increased heart rate and stroke volume – Preferential perfusion of head and heart at the expense of splanchnic perfusion

• Altered physiological adaptation to low Hb in critically ill children – Increased metabolic rate in SIRS increases oxygen consumption and lowers reserves – Impaired LV function and vascular tone restricts oxygen delivery and blood redistribution – Infants have high resting heart rates, which limits the ability to increase cardiac output

Microcirculatory effects of transfused RBC

• Global increase in oxygen delivery with potentially decreased microcirculatory flow – Increased blood viscousity – Cytokines my cause vasoconstriction – Low levels of 2,3 DPG shifts curve left, impeding oxygen availability – Decreased RBC membrane deformability – Free Hb may bind NO causing vasoconstriction

Immunologic effects of RBC transfusion

• Some evidence that it may cause – Immune suppression by altering lymphocyte reactivity – Pro inflammatory : cytokines in unfiltered rbc’s might trigger SIRS or multi organ failure

When should critically ill children be transfused?

• 637 critically ill children • Equivalence of restrictive strategy (Hb<7) and liberal strategy (Hb <9.5) • No difference in MODS, death, icu stay and sepsis • 44% reduction in blood transfusions • 50% of study children transfused

• 838 critically ill adults • Restrictive strategy (Hb<7) and liberal strategy (Hb <9) • Restrictive group had 54% fewer rbc units • Decrease mortality in adults who were less sick • Possible exceptions: unstable angina and MI’s

• 1269 Kenyan children hospitalized for malaria English, Lancet 2002 – RBC transfusion decreased mortality in severe anaemia, <4g/dl or if Hb < 5g/dl and dyspnoeic - some benefits to keep Hb > 5 in hospitalized children

• Haemodynamically unstable children: Hb > 10 • De Oliveira et al (Intens. Care Med. 2008) – children with severe sepsis – significant reduction in 28 day mortality (11% vs 39%, p=0.002) and new organ failure – targeting SVC sats > 70% using fluids, inotropes and blood transfusions keeping Hb > 10g/dl • Similar outcomes in adults using goal directed therapy Rivers et al, NEJM 2001 • Children with severe congenital heart disease and traumatic brain injuries might need higher Hb’s

Transfusion related acute lung injury (TRALI)

• Aetiology poorly understood • Diagnostic criteria – Acute lung injury occurring within 6 hours of a transfusion – No signs of fluid overload – Bilateral lung infiltrates on cxr • Usually resolves within 48 hours

Leukocyte reduced RBC’s

• Reduces leukocytes by up to 99% • reduces the number of cell associated viruses: cmv, herpes and ebv • May reduce transmission of prions and parasites and incidence of TRALI

Fresh Frozen Plasma

• Treatment of DIC and replacement of clotting factor • Effectiveness judged by cessation of bleeding. • aPTT and INR poor predictor of bleeding Gajic: Crit Care Med 206 • Not recommended as a volume expander

Platelets

• Thrombocytopenia and qualitative platelet defects impairs ability to form platelet plugs • Risk of massive bleeding when platelet count < 10 and IVH when platelets <1 • No scientific basis for keeping platelets > 20

Cryoprecipitate

• Rapid increase in fibrinogen levels in patients with DIC and active bleeding

• Meta-analyses of 24 studies, 1419 patients • 6% increase in mortality or ‘1 death for every 17 patients given albumen’

• Meta-analysis of 55 trials, 3504 patients

• No difference in mortality

• Nearly 7000 patients • No significant difference in mortality • Similar rates of secondary outcomes – Survival time, organ dysfunction, duration of mechanical ventilation, length of icu and hospital stay • Albumin to saline ratio 1: 1.4

Conclusions

• Stable critically ill children can support an Hb > 7 • Maintain Hb > 10 in haemodynamically unstable children, those with significant cardiovascular disease and traumatic brain injuries

Conclusions

• Advantages to using leukocyte reduced blood • Platelet transfusion thresholds not evidence based • Prophylactic use of FFP is controversial

Questions