10.2 Preoperative Anaemia

Question 1

A 58-year-old female is listed for elective hemicolectomy for colon carcinoma.

Her blood results are shown below.

Hb 8.4 g/dL (13–16)
PCV 0.35 (0.38–0.56)
MCV 71 fL (80–100)
MCH 20 pg (26–34)
Platelets 218 (140–400)
U’s & E’s normal

comment on these blood results and suggest possible causes of her anaemia.

Answer 1

Her FBC shows a microcytic, hypochromic anaemia.

Possible causes include:

1. • Chronic blood loss
     (e.g. from GI tract in association with her colon cancer)
2. • ‘Anaemia of chronic disease’
     (resulting in reduced production and lifespan of red cells)
3. • Bone marrow failure
     (due to recent chemotherapy, metastatic infiltration,
     or a concurrent haematological malignancy)
4. • Dietary iron deficiency
5. • Chronic kidney disease is unlikely given her normal U’s & E’s

Question 2

what are the general principles of managing preoperative anaemia?

Answer 2

In general, management should involve

balancing the benefits of correcting the anaemia
against
the risks of delaying surgery.

This is an elective case,
but the cancer diagnosis lends it a degree of urgency.

However, anaemia increases her risk of postoperative morbidity
(particularly ‘MACE’—major adverse cardiovascular events—
such as MI or stroke)
and overall mortality.

Question 3

What could you do about the anaemia

Answer 3

In this case, the options are:

• Do nothing and proceed with surgery
  (not advisable as it increases her perioperative risk).
• Correct the cause
  (will require further investigation and may take weeks,
  or even months; most likely cause is her cancer).
• Red cell transfusion causes rapid correction of Hb,
  but concerns exist regarding allogeneic blood transfusion
  and long-term survival/cancer recurrence rates.

The current evidence on this is inconclusive, however.

Cautious transfusion should also be practised in patients at risk of fluid overload.

• Initiate oral iron therapy
  (may take several weeks to correct Hb, depending on degree of deficiency).
• Deliver intravenous iron therapy
  (emerging evidence that this is a cost-effective means
  of reducing perioperative transfusion requirements).

The urgency of correcting the Hb depends not only on the urgency of
surgery but also whether she has evidence of cardiovascular compromise
(shortness of breath/chest pain/heart failure), in which case urgent
transfusion would be warranted.

Question 4

What role does 2,3 DPG (diphosphoglycerate) play in oxygen delivery to tissues?

Answer 4

Oxygen delivery is determined by

cardiac output (Co) and arterial o2 content (Cao2).

Do2 = Co × Cao2

• Arterial O2 content depends on
  Hb +O2 saturation
  (plus a tiny contribution from dissolved o2,
  unless you are in a hyperbaric chamber).
• In chronic anaemia,
  a low Hb is partly compensated by increasing CO.
• Increased levels of 2,3 DPG in RBCs improves oxygen delivery to tissues
  by shifting the HbO2 dissociation curve to the right.

Question 5

Would you transfuse this patient, and if so, when?

Answer 5

This would depend on urgency of surgery and
whether the anaemia is symptomatic.

In general, I would try to avoid transfusing unless I felt she
was sufficiently anaemic to place her at risk of an adverse cardiac event—

in which case I would transfuse her urgently—
or if surgery was deemed urgent.

Question 6

TRICC Trial bottom line

Answer 6

The transfusion threshold in critically ill patients can be between 7-9g/dl without adverse effects. Compared with the previously higher (>9g/dl) threshold, this results in less blood transfusion and its associated costs and potential complications. Caution has been advised in patients with evidence of active cardiac ischaemia

Question 7

Are there concerns regarding transfusion in cancer patients [already mentioned above]?

Answer 7

Concerns exist that blood transfusion may increase
the risk of disease recurrence
and/or decrease long-term survival.

• A 1993 study of 475 patients with colorectal cancer found no difference
  in survival between patients who received allogenic transfusions and
  those who had an autologous transfusion. .

Furthermore, a 20-year follow-up of these patients showed significantly better survival in those who received allogenic transfusions.

• A retrospective American study from 2013 of 27,000 patients with
  colorectal cancer found a significantly higher 30-day mortality and rate of
  postoperative complications in those who received blood transfusions.

Question 8

What do you know about fast-track surgery?

Answer 8

Fast-track surgery, also known as enhanced recovery, means a targeted
approach to perioperative care of minimising disruption to the patient’s usual
activities and returning them to normal function as soon as possible after
surgery.

The theoretical advantages include quicker patient discharge and
reducing the per-patient cost of treatment.

The overall aim is to improve surgical outcomes by reducing avoidable
postoperative complications (e.g. DVT/PE, chest infections, ileus).

Question 9

What are the pre intra and post op elements of ERAS

Answer 9

• Preoperative preparation aims to
  minimise fasting times,
  avoid bowel preparation,
  optimise nutrition/hydration.
• Intraoperative management, in particular the anaesthetic management,
  involves
  goal-directed fluid therapy guided by cardiac output monitoring
  to maximise oxygen delivery,
  and multimodal analgesia to minimise postoperative pain.
• Postoperative management aims to
  restore oral intake and
  mobility as soon as possible and
  to minimise invasive lines/catheters.

Question 10

The patient is also a smoker and reports shortness of breath on exertion.

How else might you investigate her?

Answer 10

Her exertional shortness of breath may be due to

anaemia or an underlying respiratory or cardiac disease.

• History and examination:
  Is she known to have COPD?
  If so, how severe?
  How much exertion precipitates shortness of breath?
  Does she have signs of respiratory/cardiac failure?
• CXR and ABG on air would be mandatory in this instance.

Lung function tests may also be indicated.

• Formal testing of functional capacity would be useful.

n exercise test or stress echo would be good;
best would be cardiopulmonary exercise testing (CPET).

CPET involves the patient performing ramped exercise on an exercise bike,
while recording ECG, HR, BP, and expired gases.

It correlates well with risk of postoperative adverse events,
because it reflects the patient’s degree of cardiorespiratory reserve,
and thus their ability to increase oxygen delivery
in the face of the postoperative stress response to surgery.

The most useful measurements obtained are
Vo2 max (the patient’s maximum oxygen delivery)
anaerobic threshold (AT is the point at which the demands of
cellular metabolism exceed the oxygen supply to tissues).

A Vo2max < 15, and AT < 11
strong predictors of postoperative complications
following major surgery.