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Peri-operative Medicine > Anaemia > Flashcards

Anaemia Flashcards

1
Q

What is the percentage of pre-op anaemia in non cardiac patients?

A

NSQIP database has approximately 30% (20-40)

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2
Q

Patient blood management - PBM has 3 pillars what are they?

A
  1. Detection and treatment of preop anaemia
  2. Reduction of periop blood loss
  3. optimising patient specific physiological reserve (tolerance of anaemia)

SHOT scheme/PBM retrospectively analysed in 1996 and in WA lead to 41% reduction (saved >18million)

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3
Q

What are some strategies of the three Patient Blood Management scheme?

A
  1. Optimise erythropoesis
    - preop - detect, manage disorders causing anaemia, treat iron
    - intraop - timing surg with haem optimisation
    - post op - stimulate erythropoiesis
  2. Minimise blood loss
    - preop - manage bleeding risk
    - intraop haemostasis in surgery, blood sparing techniques, haemostatic agents
    - post op - monitoring, prophylaxis of upper GI haemorrhage
  3. Optimise physiological reserve
    - Preop - assess physiological reserve
    - intraop - optimsie CO
    - postop - maximise oxygen, optimise anaemia reserve, minimise O2 consumption
    - restrictive transfusion thresholds
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4
Q

What are some of the physiological effects of anaemia?

A

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

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5
Q

What are some of the downsides to blood transfusions?

A

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

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6
Q

What is the cause of poor outcomes from anaemia?

A
  • impaired oxygenation
  • underlying cause (iron def, untreated B12/folate, chronic inflammation, renal dysfunction, old age)
  • effects of transfusion
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7
Q

What are some causations of anaemia? What is the physiology?

A
  • 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)

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8
Q

How do you measure iron in the body?

A

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

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9
Q

What investigations are used to diagnose iron deficiency?

A

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

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10
Q

What are the main things to look for in B12 deficiency? how is it treated?

A 
- FBE - 
high MCV (but less common than myelodysplasia and alcohol abuse)

treated with IM hydoxocobalamin

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11
Q

In what conditions will there be folate deficiency?

A
  • bread is now supplemented

Groups:
- small bowel absorption (coeliacs) or - weird diets

often a waste of money to test

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12
Q

When would you do thalassemia testing?

A

Only rarely required

  • major (early in life)
  • intermedia - microcytosis on presentation

Hb >100, will not respond to iron replacement

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13
Q

When to investigate causes of blood loss prior to surgery?

A

pre-menopausal women
- rarely require endoscopy

men and postmenopausal should have cause investigated
- cancers of 10%

timing depends on situation

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14
Q

What is a restrictive transfusion threshold and how has it been shown to aide patient care?

A
  • 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

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15
Q

What are the different categories of iron deficiency?

A

Absolute - lack of stored iron

Functional - iron-restricted erythropoiesis in presence of normal stored body iron

  • impaired iron transport
  • chronic inflammation
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16
Q

What are some treatment strategies for iron deficiency?

A

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)
17
Q

What is the indication to transfuse someone pre-surgery?

A

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
18
Q

In patients with anaemia of chronic disease what iron supplementation should be used?

A

IV only
functional iron deficiency (true with GI blood loss, reduced intake)
and high hepcidin from chronic disease

  • IV Iron leads to mortality reduction
19
Q

What approach should be used for iron replacement?

A

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
20
Q

What are some predictors of response to oral iron?

A
  • 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
21
Q

What are the indications for IV iron?

A

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…)

22
Q

What time should you have iron infusion?

A

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

23
Q

What are the IV iron infusions available? What is the physiology? What dose?

A

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

24
Q

What are some adverse effects of IV iron? What are some long term harms?

A

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
25
Q

When can you use ESAs (erythropoietin stimulating agents)?

A
  • renal patients on HDx
  • works within 5 days
  • preop Cochrane review of colorectal patient showed nil significant change and did not change need for blood while ortho/cardio showed improvement

Guidelines - NATA
- potential harmful effects of HTN, thrombotic/ischaemic events (higher Hb conc) and secondary effects of ESA on other cells (stimulate tumour growth)

26
Q

How can you avoid blood loss intraoperatively?

A
  • haemostatic management intraop
  • anticoag therapy cessation/planning
  • choice of surgical technique (minimally invasive, positioning of patient)
  • neuroaxial anaesthesia (systemic hypotension/decreased venous tone)
  • autotransfusion - risk of other substances aspirated (e.g. bacteria, cancer cells) but 2013 study showed now increased risk.
  • avoid hypothermia, acidosis and hypocalcemia (below 35 degrees platelet function is reduced and enzymatic clotting factors impaired)
    1degree decrease increases blood loss by 16% and increases the risk ratio of transfusion by 22%

Acute normovolemic haemodilute
- whole blood donation prior to surgery and replacement with crystalloid - reduce risk of loss with bleeding, and provide fresh blood post op

27
Q

What are some agents to prevent blood loss?

A

antifibrinolytic drugs
- TXA and aminocaproic acid (lysine agents that reversibly inhibit fibrinolysis)
improved mortality if given for major ortho/liver/CVD/urological surg

  • aprotinin inhibits plasmin - withdrawn as increased mortality

topical haemostatic agents
- fibrin sealants and thrombin - spray or liquid form.

Peri-operative Medicine (11 decks)

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