Anaemia Flashcards
What is the percentage of pre-op anaemia in non cardiac patients?
NSQIP database has approximately 30% (20-40)
Patient blood management - PBM has 3 pillars what are they?
- Detection and treatment of preop anaemia
- Reduction of periop blood loss
- optimising patient specific physiological reserve (tolerance of anaemia)
SHOT scheme/PBM retrospectively analysed in 1996 and in WA lead to 41% reduction (saved >18million)
What are some strategies of the three Patient Blood Management scheme?
- Optimise erythropoesis
- preop - detect, manage disorders causing anaemia, treat iron
- intraop - timing surg with haem optimisation
- post op - stimulate erythropoiesis - Minimise blood loss
- preop - manage bleeding risk
- intraop haemostasis in surgery, blood sparing techniques, haemostatic agents
- post op - monitoring, prophylaxis of upper GI haemorrhage - Optimise physiological reserve
- Preop - assess physiological reserve
- intraop - optimsie CO
- postop - maximise oxygen, optimise anaemia reserve, minimise O2 consumption
- restrictive transfusion thresholds
What are some of the physiological effects of anaemia?
Multiorgan adaptive mechanisms:
Resp: increased RR,
CVD: increased CO, reduced systemic vasc resistance
increased O2 extraction
release of hypoxia inducible factor and EPO
tissue injury and ischaemia
What are some of the downsides to blood transfusions?
dose dependent increase in morbidity and mortality
immunomodulatory effects
- increased cancer recurrence/metastasis (colorectal cancer review), post op infection
risk of circulatory overload
transfusion reactions
infective complications
UK SHOT report (2600 adverse events from 2 million units)
cost - NHS cost 300million pounds
What is the cause of poor outcomes from anaemia?
- impaired oxygenation
- underlying cause (iron def, untreated B12/folate, chronic inflammation, renal dysfunction, old age)
- effects of transfusion
What are some causations of anaemia? What is the physiology?
- unexplained anaemia of the elderly
- true B12/folate (rare)
- inflammation/CKD
- iron deficiency most accesible reversible cause
Hepcidin - protein produced by liver which controls iron balance, inhibiting absorption across duodenum and release from liver and reticular endothelial system.
Deficiency iron - hepcidin inhibited (increased absorption and increased in blood)
Anaemia of chronic disease
- high hepcidin (reduced absorption)
Iron deficient erythropoeisis
high cytokines - lead to low iron (inhibited erythropoeisis and reduced take up in bone marrow)
- stores of iron normal, plasma iron low (trans ferrin sats low)
How do you measure iron in the body?
Tissue iron supply
- serum iron (initial test) level varies hour to hour (low in chronic disease, post surg). Not used alone
- transferrin (increased, transport protein, not up in early)
- transferrin sat (measured iron and transferin, reduced in iron deficiency/chronic disease/post surg)
Iron supply to bone marrow
- serum transferrin receptor
Iron stores
- ferritin serum (reduced always means iron deficiency, acute phase, alcoholic liver disease mask it)
Tissue iron
- bone marrow
What investigations are used to diagnose iron deficiency?
Iron deficiency
- transferrin normal
- low transferrin sats 10%
- <10 ferritin
Anaemia of chronic disease
- normal transferrin
- low transferrin sats (10%)
- ferritin 1000 (high)
Ferritin in normal range - ?iron deficiency or of chronic disease
- CRP doesn’t exclude anaemia of inflammation
- serum transferrin receptor (proportional to serum upregulated in iron deficiency)
trial of iron replacement
What are the main things to look for in B12 deficiency? how is it treated?
- FBE - high MCV (but less common than myelodysplasia and alcohol abuse)
treated with IM hydoxocobalamin
In what conditions will there be folate deficiency?
- bread is now supplemented
Groups:
- small bowel absorption (coeliacs) or - weird diets
often a waste of money to test
When would you do thalassemia testing?
Only rarely required
- major (early in life)
- intermedia - microcytosis on presentation
Hb >100, will not respond to iron replacement
When to investigate causes of blood loss prior to surgery?
pre-menopausal women
- rarely require endoscopy
men and postmenopausal should have cause investigated
- cancers of 10%
timing depends on situation
What is a restrictive transfusion threshold and how has it been shown to aide patient care?
- TRICC study - only transfusing if it fell below 70 was as effective in critically ill patients (not those with MI or angina)
- did not differ in mortality in the FOCUS study
cochrane review concluded transfusing between 70-80 decreased the proportion exposed to RBC transfusion 43%
transfusing 1x unit if between 70-100 for patients post MI or ischaemic cerebrovascular insult and reassessing
What are the different categories of iron deficiency?
Absolute - lack of stored iron
Functional - iron-restricted erythropoiesis in presence of normal stored body iron
- impaired iron transport
- chronic inflammation
What are some treatment strategies for iron deficiency?
Oral Iron
- cheap, readily available, effective if no underlying disease
- 3-4g total iron stores
- bioavailability of ferrous iron is 10-15%
- inflammation/infection (downregulation of duodenal absorption)
- eneteral 2-16mg/day
- 3-6mths of treatment can provide 1000-2000mg to replenish reserve
- Common Cx - 1/3 abdo pain, diarrhoea, constipation
- when administered: (empty stomach, with vitamin C, 1-2x a day)
- response within 72hrs and Hb rise 20 every 3weeks
- multivitamin supplements are inadequate (1-5mg elemental)
- reduced dose reduces side effects
IV iron
- 15mins
- polymaltose, dextrans, ferumoxytol, iron sucrose, ferric gluconate
- high rates of adverse events (anaphylaxis) historically were associated with dextran containing preparations (exposure to dextrans with dental carries)
What is the indication to transfuse someone pre-surgery?
Absolute Iron deficiency
- should be treated
Loss of iron from 1 unit blood (250mls) minimal pre-op ferritin 46 microg/L
Anaemia of chronic disease
- difficult to decide - no diagnostic algorithm
- if concomitant functional iron deficiency and absolute iron deficiency
In patients with anaemia of chronic disease what iron supplementation should be used?
IV only
functional iron deficiency (true with GI blood loss, reduced intake)
and high hepcidin from chronic disease
- IV Iron leads to mortality reduction
What approach should be used for iron replacement?
Systematic approach
- early testing
- protocol
- referral patterns where causation uncertain
- repeat testing prior to operation
1)
Hb <130 in males
Hb <120 females
2) Ferritin low
- GI Ix
- determine cause
- commence therapy
Ferritin normal - CRP raised (possible iron deficiency)
- ?Renal
- ?Haem
- commence iron therapy
high ferritin
- check B12/folate
- LFT/TFT
- ?Renal
- ?Haem
What are some predictors of response to oral iron?
- compliance
- ongoing blood loss
- serum hepcidin (high hepcidin unlikely to respond) - not available
- response to iron therapy (Day 14 >1g increase in Hb, reticulocytosis, increase in iron/transferrin)
2nd daily dosing
- increased fractional absorption with 2nd daily (hepcidin release)
- if not complying trial spacing of dosing
What are the indications for IV iron?
Failure of response to oral iron
Rapid response required (>4-6wks)
Chronic disease suspected
Failure to respond (except co-existing condition - B12/folate, bone marrow disease etc…)
What time should you have iron infusion?
2.2g/L Hb increase - normal marrow function/EPO lvl
Pre-op Hb cannot be improved in <7 days
Rapid dose combination therapy in Lancet 2019 (Spahn)
Study
- anaemia/ferritin <100
- given carboxymaltose, EPO and vitamin B12/folic acid
response not enough to initiate prior to treatment
What are the IV iron infusions available? What is the physiology? What dose?
Iron Sucrose - 100mg with Hdx
Iron polymaltose - 2hrs up to 2000mg
Ferrinject (carboxymaltose) 15mins up to 1000mg
Monofer (derisomaltose) up to 1500mg
carbohydrate shell allows the iron to last longer in the blood
size/Hb <100 20mg/kg (<50kg) if low body weight
What are some adverse effects of IV iron? What are some long term harms?
Acute
- n/v, pruritis, flushing, headaches
- myalgia, arthralgia, back/chest pain
- history of atopy
Hypophosphataemia
- transient, asymptomatic
Hypersensitivity
Anaphylaxis <1:200,000
- pre-medication with antihistamines not advised
Most serous!
- skin staining post extravasation (permanent) rate unknown
- predicted by pain and swelling at site
