Transcript O 2 CONTENT OF BLOOD

ANAEMIA-ITS IMPORTANCE IN GENERAL
SURGICAL PRACTICE
Dr.R.Selvakumar
ANAEMIAIs it that important to discuss
for an hour..?
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How much importance we give to anaemia?
How do we diagnose anaemia?
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When we see 3G and 4G% Hb
in the general population…
Why do we have to worry?
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To answer these questions…
…knowing some basics is necessary
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O2 is carried in blood in 2 forms:
1. Combined with Hb
2. Dissolved in plasma
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HOW MUCH O2 IS DISSOLVED IN PLASMA?
• Quantity
• Importance
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What do we achieve in
giving O2 by mask?
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IMPORTANCE OF Hb
• Amount of O2 carried by Hb
• Reserve O2
• Amount of O2 needed for metabolism
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O2 CONTENT OF BLOOD
{Hb X 1.32 X SaO2 } +{ 0.003 X paO2 }
O2 FLUX:
O2 content X cardiac output
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O2 CASCADE:
150mm
100mm
50mm
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In nutshell….
What we need is just 2mm of Hg of O2
at mitochondrial level……
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What will happen if that is not provided?
•Anaerobic metabolism
•Scarcity of ATP
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If some stupid ATP is not provided
why the cell has to die…?
Importance of ATP pump
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COMPENSATORY MECHANISMS IN ANAEMIA:
Can u increase the O2 content of blood by
manipulating the factors involved in the formula?
{Hb X 1.32 X SaO2 } +{ 0.003 X paO2 }
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COMPENSATORY MECHANISM IN ANAEMIA;
•Tachycardia
•Cardiac strain
•Vascular tone
•Increased cardiac output
•Associated hypoproteinaemia
EASY TENDENCY FOR PULMONARY EDEMA
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HOW DO WE CORRECT ANAEMIA?
•Oral and parentral preparations
•Blood transfusion
Is there any other way to tackle anemia?
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Can we manage without Hb?
O2 content of 100ml of arterial blood= 20ml
O2 content of 100 ml venous blood = 15 ml
Tissues need just 5ml of O2
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Impact of increasing atmospheric pressure
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Atm.
press
FiO2
1atm
0.3ml
1
0.21 150m 87mm 18.7ml
m
1
713
673
21.2
2
1
1473 1218
23.1
3.7
3
1
2233 1864
25.1
5.6
pIO2
paO2
Dissolv
O2
content ed O2
1.7
Is there any alternate to Hb?
SYNTHETIC O2 CARRIERS:
1.Perfluoro carbon-Fluosol-DA
paO2 has to be above 300 mm of Hg
2. Perflurooctyl bromide:
longer half life
3-4 times more O2
on the trials
3. Hb based O2 carriers
outdated human RBCs, or bovine RBC
increased affinity to O2
renal toxicity
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SYNTHETIC O2 CARRIERS:
4. Recombinant Hb from E.Coli
5. Recombinant erythropoietin
6. Haemopure:
ultrapurified bovine RBC –
gluteraldehyde polymerised
no croosmatching or typing
no transmission of infection
increased BP and decreased CI
approved in south africa
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ROLE OF ERYTHROPOIETIN IN
TREATING ANEMIA
•Recombinant erythropoietin ( rHuEPO)
•300 units/kg S/C daily for 5 days
•Every other day for a minimum of 2 weeks
•Improves the haematocrit
•36% compared to 31% in placebo
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BLOOD TRANSFUSION
•Role of pre-op transfusion
•How many bottles of blood to be given?
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PREOP BLOOD TRANSFUSION..
•Packed red cells
•Risk of infection,circulatory overload.
•1 unit increases Hb by 1G%
•? Quality of the donated blood
•? Quality of storage
•? Simultaneous frusemide administration
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Is there a magic figure of Hb level before
submitting the patient for an elective surgery?
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If oxygen saturation is good, can you take a
patient for surgery with anaemia?
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If an ectopic rupture can be taken with a Hb
of 3 or 4 g%, Why not a patient with 7 G%?
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DANGERS OF ANEMIA-INTRA OP PERIOD
•May be masked
•Increased O2 supply during GA compensates
•Spinal- mild hypotension and vasodilatation
compensate
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DANGERS OF ANAEMIA – INTRAOP PERIOD
Impact of anemia depends on
existing organ function
vascular status
level of atherosclerosis
cardiac status…etc
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DANGERS OF ANAEMIA – INTRAOP PERIOD
Even during a normal course of a well
conducted anesthesia and an uneventful
Surgery, there may be brief periods of
hypotension and hypoperfusion….
The impact of this is aggravated
by anemia
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Word of caution:
We measure the success of surgery only by
looking at the absence of mortality not morbidity.
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DANGERS OF ANAEMIA- POSTOP PERIOD
•Most dangerous period
•All the supports are withdrawn
•Persistent impact of anesthetic drugs and techniques
•Surgical incision,pain all increase O2 requirement
•Even shivering increases it by 200%
All these factors resulting in a subtle hypoxaemia
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DANGERS OF ANEMIA- LATE POST OP PERIOD
•Wound healing requires good O2 supply
•Burst abdomen, wound dehescence, bowel anastamotic
leak,skin graft failure- all due to reduced O2supply
•Associated hypoproteinaemia aggravates..
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Summarising…
1.The tissues need just 2mm of Hg Oxygen
2. The O2 content of the blood can only be
increased by maximising Hb.
3. Body tries to compensate for chronic anemia
4. Immediate preop blood transfusion may not help
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Summarising…
5. One unit of preop transfusion improves Hb
by 1 g%
6. There is no fixed,magic figure of Hb
before any surgery
7. Anaemia may not kill a patient intra operatively.
8. The most dangerous period is the post op period
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CONCLUSION:
DON’T TAKE ANEMIA LIGHTLY
IT IS A SILENT KILLER.
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Dr.R.Selvakumar
Assistant professor,
Madurai Medical College,Madurai
THANK YOU
THANK YOU