Perioperative Management 1: fluid balance

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PERI-OPERATIVE MANAGEMENT
OF FLUID, ELECTROLYTES AND
KIDNEY FUNCTION
Surgical Student Talk
Brad Bidwell
If you take away one point from today it should be
this:
There is no magic formula for fluid management, it
depends on the patient and the situation, if in doubt
then asks someone more senior
Where is it all going?
Extracellular (1/3)
Sodium rich,
potassium poor
Total body water
Intravascular
(1/3)
Interstitial (2/3)
Intracellular (2/3)
Potassium rich,
sodium poor
Assessing Fluid Balance

Urine output
Peripheral circulation
JVP
Postural blood pressure
Lung sounds
Oedema
Thirst

Heart rate, blood pressure, mucous membranes, tissue turgor, weight

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
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

Assessing Kidney function


Urine output
UECs
 Especially
creatinine and urea
Categories of Fluids

Maintenance fluids
 Daily
requirements
 Ongoing losses
 “Surgical”
losses: bleeding, serous ooze, drain tube losses –
these tend to be sodium rich
 Gastrointestinal losses: vomiting, diarrhoea, nasogastric
losses – these tend to be potassium rich

Resuscitation fluids (replacement of losses)
What is needed each day?

Water
4:2:1 rule: (4ml/kg/hr for the first 10kg body weight PLUS
2ml/kg/hr for 11-20kg of body weight PLUS 1ml/kg/hr for
every kg of body weight after that)
 For a 70kg pt: (40 + 20 + 50 = 110mL/hr = 2640
mL/day)
 Monitor by maintaining urine output in the range of 0.5 1.0mL/kg/hr (i.e. 35 – 70 mL/hr)


Sodium


1 – 2 mmol/kg/day (i.e. 70 – 140 mmol/day)
Potassium

0.5 – 1 mmol/kg/day (i.e. 35 – 70 mmol/day)
Types of Fluids

Crystalloid
 Electrolytes
dissolved in water
 E.g. normal saline, CSL/Hartmann’s, 5% dextrose, 4%
dextrose + 1/5th normal saline (“4 and 1/5th)

Colloid
 Large
molecules dissolved in water
 E.g. gelofusine, albumin

Blood products
 E.g.
PRBCs, FFP, platelets
Crystalloids
Normal
Saline
150mmol
Na+
Hartmann’s
Solution
(CSL)
131mmol Na+
111mmol Cl-
150mmol Cl-

30mmol Na+
50g dextrose
30mmol Cl-
29mmol lactate
5mmol K+
4mmol Ca2+
1L Water
5% Dextrose
1L water
4% dextrose
and 1/5th
normal saline
40g dextrose
1L water
1L water
You can add other electrolytes to these bags!
Rate of fluids

Fluids come in 1 L bags

You write it up as how fast you want to give that bag

Write up 24 hours worth of fluids, and make sure they’re not finishing overnight
Average sized,
middle aged
patient
Small, frail,
elderly patient
Will require
more fluid than
the average
patient
Regular fluid
requirements
Won’t need
much fluid, too
much fluid will
overload their
heart
8/24
10/24
12/24
Big, fit young
patient
The Real World

Check the history:
CCF? Renal failure? Haemorrhage?
 What restriction are they on?
 How much fluid have they had already?


Fluid assess the patient:
Does the patient look well?
 Are they thirsty?
 Check the obs, especially BP and urine output.
 Listen to the lungs, check for sacral oedema.


Check the tests:
Are their electrolytes in normal range and is their kidney function
good
 CXR?

The Autopilot Method

What people usually do:
N.saline 8/24
 N.saline 8/24
 N.saline 8/24


The electrolyte load from this is:
3L of water per day
 450 mmol Na+ per day
 0 mmol K+ per day


The 70kg patient needs:
2.6L of water per day
 70 - 140mmol Na+ per day
 35 - 70mmol Na+ per day

The Autopilot Method

Try this:
+ 1/5th, with 30mmol K+ added
 4% + 1/5th, with 30mmol K+ added
 4% + 1/5th
 4%

This gives:
 3L
water per day
 90mmol Na+ per day
 60mmol K+ per day
8/24
8/24
8/24
Case study 1


HOPC: 28 F presents to ED with 3/7 of poorly localised central
abdominal pain, increasing in intensity and shifting to the RIF over
the last 12/24. Nil fevers, nil changes to bowels/urine, nausea
but no vomiting. Virgin abdomen. No significant PMHx.
O/E: Obs stable, afebrile abdomen soft with focal tenderness in
RIF and voluntary guarding. Pain worse when the right hip is
flexed.

Ix: FBE – mildly elevated WCC, UECs – NAD, LFTs/lipase NAD,
CRP 50, B-HCG negative
Dx: clinically acute appendicitis

Mx: Fasting, for theatre – lap. Appendicectomy
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
The registrar tells you to write up some fluids. What do you
give?
Case study 2

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Hx: 78 M 3/7 cramping abdominal pain with nausea and
vomiting. Hasn’t opened bowels in 2/7. No fevers, no urinary
changes. PMHx – some operation on abdomen 40 years ago,
mild “heart troubles”, AF – on warfarin, high cholesterol.
O/E: Obs: HR 105, BP 110/70, abdomen soft, generalised
tenderness, midline laparotomy scar visible superior to umbilicus
Ix: FBE – NAD, UECs – Na 138 K 3.5
Dx: likely SBO
Mx: CT A/P, trial conservative management – nasogastric and IV
fluids
The registrar tells you to write up some fluids. What do you
give?
Case study 3
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Hx: 52 M presents to ED with a poor thrill in his AV
fistula. PMHx – ESRF due to poorly controlled T2DM,
currently on haemodialysis 3x weekly, 1L fluid
restriction per day, 2 prior AMI’s – stents, on warfarin,
PVD – right BKA, HTN …
O/E: Obs – stable (BP 165/130), afebrile. No thrill
over AVF site, no bruit heard.
Ix: FBE – NAD, UECs – Cr 450, Ur 20.3, K+ 6.2
Dx: blocked fistula
Mx: unblock fistula
The registrar tells you to write up some fluids. What do
you give?
Calcium, Magnesium, Phosphate


Usually we don’t worry about these too much,
especially in patients fasting for a short amount of
time
Treat to target – usually we don’t prescribe regular
CMP supplements, we replace in response to the
test
Supplementation
Electrolyte
Medication
K+ 3.0-3.5
Dose
Route
Frequency
Speed
Chlorvescent 2-4 tabs
oral
STAT
rapid
Slow K
1-2 tabs
oral
Daily/bd
slow
KCl
30mmol
IV
In 1L N.saline over
x/24
rapid
K+ < 3.0
KCl
10mmol
IV
In 100mL N.saline
over 1/24
rapid
Mg < 0.75
Magmin
2 tabs
oral
STAT
slow
Mg < 0.65
MgSO4
10mmol
IV
In 100mL N.saline
over 1/24
rapid
PO4 < 0.8
Phos.
Sandoz
2-3 tabs
oral
STAT
slow
PO4 < 0.6
PO4
13.4mmol IV
In 100mL N.saline
over 4/24
rapid
Resuscitation

Ascertain where the losses are from:
 Blood?
 Dehydration?
 Vomiting

or diarrhoea?
Replace like with like (i.e. if they’ve lost blood, give
them blood).
Haemorrhagic Shock
Class
Blood loss
HR
BP
Urine Out.
RR
I
<15 % (750 mL)
< 100
Normal
> 30mL/hr
14 - 20
15 - 30 mL/hr
21 - 30
II
15-30 % (750 mL -1500
mL)
5-15 mL/hr
31-40
III
30-40 % (1500 mL –
200mL)
None
> 40
IV
>40 %(> 2000 mL)
> 100
> 120
> 140
Decreased
Decreased
Decreased
Replacing Massive Blood Loss



Control the bleeding
1L of normal saline STAT, followed by a second bag
if necessary.
If patient is still unstable, blood products are
necessary at this point
 Group
and screen, crossmatch
 RMH has a “massive exsanguination pack” – O
negative blood products ready to go in a cooler.
Traps



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Beware third spacing conditions – ascites, pleural
effusion, pancreatitis, burns
Pay close attention to old, frail patients
Monitor patients closely when giving large amounts
of N.saline
Ignoring CMP’s in patients who are fasting for a
longer period – treat to target
References
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Fluid Management Student BMJ 2010;18:c5063
http://student.bmj.com/student/viewarticle.html?id=sbmj.c5063
“Maintenance” IV fluids in euvolaemic adults,
Michael Tam
http://vitualis.wordpress.com/2006/05/01/mainte
nance-iv-fluids-in-euvolaemic-adults/
OHCM
Toronto Notes

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