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POSTOPERATIVE FLUID MANAGEMENT
Postoperative management, especially in emergency cases, poses
a complex problem in finding the right fluid balance. Not
all the volumes that have been lost and replaced will be known.
In terms of input and output, consider:
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Replacement
of the preoperative deficit:
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The
patient may have been dehydrated for several
days |
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The
longer the history of illness before operation,
the more fluids you should give postoperatively |
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This
may result in a 5–10 litre positive fluid
balance in the first 24 hours postoperatively |
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Replacement
of losses during the operation plus other fluids given
in the course of anaesthesia; again, input will greatly
exceed output, resulting in a positive fluid balance |
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Expected
further losses: e.g. from nasogastric drainage, other
drains, bleeding |
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Hypothermic
patient warming up: as the peripheries become warm, more
circulating volume is needed |
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Normal
maintenance requirement. |
Your decision on how to give the fluid will be determined by three factors:
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The need to correct a residual deficit from the preoperative state – as
estimated above: this should ideally be given fast as a fluid bolus, under
your direct supervision
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A maintenance schedule |
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The patient’s response, including:
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Slowing
of tachycardia |
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Urine
output |
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Increased
blood pressure |
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Rising
jugular venous pressure |
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Return
of skin turgor to normal |
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Sunken
eyes returning to normal. |
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Maintenance fluids
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Give
3 litres a day to an adult (125 ml/hour); rotate 1
litre bags over 8 hours
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With
normal body electrolytes, give normal saline followed
by 5% dextrose (glucose) followed by Ringer’s
lactate; 5% glucose is suitable only as replacement
for water in patients who cannot drink |
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Replace
other fluid losses with solutions containing sodium:
normal saline or Hartmann’s solution, with
added potassium 20 mmol/litre, if necessary.
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When deciding on your fluid regime, use all the variables above to enable you
to write down what must be given. If you are unsure how much to give, write up
a regime for the next hour only, and then come back and check the patient’s response.
It is useful to have laboratory estimations of sodium and potassium after a few
days of fluid therapy to adjust the input accordingly. Normal values are:
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Sodium: 125–145 mmol/litre
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Potassium:
3.5–5.5 mmol/litre
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Additional
potassium supplements may be required if hypokalaemia
is demonstrated (K+ less than 3.5 mmol/litre) |
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Potassium
must be diluted and given slowly at not more
than 20 mmol/hour |
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The
average adult will need about 100 mmol to increase
plasma levels by 1 mmol/litre. |
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See also The Clinical Use of Blood (WHO, 2000) for further information on fluid
regimens.
Blood
Only give blood if absolutely necessary because of the risk of acute or delayed reactions
and of transfusion-transmissible infection.
Fluid balance chart
The fluid balance chart measures the patient’s hourly fluid intake and
output over a 24 hour period. At the end of 24 hours, the total measured output
(urine, drains, nasogastric drainage) is subtracted from the total measured
intake (intravenous infusion, oral intake). The result is called the fluid
balance.
A “positive” fluid balance means that there is more intake than output:
that is, the patient is accumulating water. In fact, a positive fluid balance
is not really positive because there are certain outputs that are not measured
very accurately (e.g. faeces) and others that are not possible to measure at
all (in sweat and respiration – so called “insensible” losses).
Thus a normal healthy adult will appear to have a positive fluid balance of about
1–1.5 litres
a day.
For these reasons, in the first 24 hours, the fluid balance chart will usually
show a big positive balance, perhaps as high as 10 litres. In succeeding days,
fluid balance should revert to the normal 1–1.5 litre positive per day.
In general, if a
severely ill patient, such as a septic surgical case, shows a persistent positive
fluid balance each day, it means an ongoing illness that is not resolving.
Care of the infusion site
Postoperative infusions are life saving. Loss of the drip and failure to correct
hypotension is the commonest cause of death during the first postoperative night
after major surgery.
All patients having major surgery will need a postoperative infusion to correct
any deficit and for maintenance. Secure placement of the intravenous cannula is
very important:
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Use
a vein in a position that will last a long time in
the wards
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Secure
the cannula and giving set carefully; you should be
able to lift the arm with the giving set |
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Use
tape that sticks to the skin and use the wings or
other large part of the IV cannula for attachment.
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