Download Fluid Management For Dental Anesthetist

Dr. Jeffrey Elliot Field
HBSc,DDS, Diplomat of the National Dental Board
of Anesthesia,Fellow of the American Dental
Society of Anesthesia
 To
understand and manage fluid balance for
office based anesthesia.
 Accurate
replacement of fluid deficits is
based on an understanding of the distribution
of water, sodium , and potassium.
 60%
of the total body weight is water. Based
on a 70 kg adult this is 42 kg


28 kg is intracellular(2/3)
14 kg is extracellular(1/3)
 Intravascular
volume is 5 liters and made up
of plasma and red blood cell volume.


3 liters is plasma volume
2 liters is red blood cell volume
 Total
body water
 70 kg man has ~42 L (%60) body fluids.
Distribution of fluid in the body is:
 1/3 in extracellular fluid (14 L)



Interstitial fluid 10L
Plasma 3L
Transcellular fluid 1L

Transcellular fluids include cerebrospinal fluid,
synovial fluid, pleural fluid, ocular fluid, etc
 2/3


in intracellular fluid
Red blood cells 2L
Other body cells outside the vasculature 26 L
 Fluid
movement between these
compartments is governed by osmotic and
Starling forces
 Osmotic
equilibrium at the cell membrane
regulates the water balance between ECF
and ICF. Osmotic forces depend on osmolality
(Osmoles of solute per kilogram of solvent).
Main solutes include charged (Na+, K+, Cl-,
HCO3‐) and uncharged (urea, glucose)
molecules.
 Starling
equation illustrates movement of
fluid across capillaries depending on three
factors:
 Hydrostatic forces that push fluid across
membranes.
 Oncotic pressure exerted by proteins in fluid
that pulls water across membranes
 Permeability of endothelium between plasma
and interstitial fluid
 On
the arterial side of capillary bed,
intravascular fluid moves into interstitial
space (higher intravascular hydrostatic
force). On the venous side, fluid is
reabsorbed into plasma (lower intravascular
hydrostatic force).
 When fluid is infused into plasma,
hydrostatic forces increase and oncotic
pressure decrease (dilution effect) until fluid
is evenly distributed in ECF and Starling
forces are in equilibrium.
 Aldosterone
enhances sodium re-absorbption
 ADH ( antidiuretic hormone) enhances water
resorbption( a lack of ADH  diabetes
insipidus see later module on diabetes).
 Atrial natriuretic peptide enhances both
sodium and water excretion (and increased
levels are an indicator of poor left
ventricular function ( leading to congestive
heart failure) and an indicator of inability to
get successful or sustained cardioversion
when needed).
 Sodium
is 140mEq/L and mostly in the
extracellular fluid
 Potassium is 150mEq/L and mostly in the
intracellular fluid
 Daily



Requirements
Water: 40 ml/kg/day (rough estimation, see 4,2
and 1 rule below for exact calculation)
Sodium ~ 100 mmol/day
Potassium ~60 mmol/day

Intake: ~2500 ml




1500 ml – liquid intake
750 ml – food
250 ml – oxidative phosphorylation (The process by
which ATP is produce in cells and of which H2O is a
byproduct)
Output: ~ 2500 ml
1500 ml – urine*
100 ml – feces
 900 ml – insensible loss (skin, lungs)



* Minimal volume of urine a healthy person needs
to produce is 0.5 – 1 ml/kg/hr or else you have
renal failure.
 In
looking at fluid requirements one must
make up for:




GI losses of 100 ml/day or 4.17 ml/hr.
Insensible losses ( respiratory and cutaneous) of
900 ml/day or 37.5 ml/hr.
Urine losses of 1500ml/day
Therefore total daily fluid requirements are
around 2500ml/day.




Sodium losses of 100 mEq/day.
Potassium of 60 mEq/day.
Note in the short term potassium, chloride
,calcium and ,magnesium do not need
replacement.
Similarly in the short term glucose does not need
replacement. Therefore glucose solutions are
only indicated in infants( which we don’t do) and
diabetics( to be discussed in a later module).
 There
are several ways to calculate this.
 1) For an average adult ( 70 kg) figure on
2500 ml/day or approximately 104 ml/hr.
 A more sophisticated approach is to use the
4-2-1 rule which takes into account body
weight:



Give 4 ml/kg/hr for the 1st 10kg (e.g. 40 ml/hr).
Give 2 ml/kg/hr for the next 10kg (e.g. 20
ml/hr).
Give 1 ml/kg/hr for the remaining kgs( 50
ml/hr).
 For
surgical patients you must consider these
additional factors in your fluid replacement
calculations:

Blood loss



for which you need to give 3 and some authors say 4
liters of normal saline for each liter of blood lost
or 1 liter of colloid for each liter of blood loss.
Third space space losses ( water loss from intra
and extracellular spaces secondary to tissue
manipulation or damage).
 Calculating


Blood Loss
Suction contents less irrigation fluid=blood loss
Blood contained in the gauze.


Take the weight of a bloody gauze –the weight of the
dry gauze
or use a stock calculation for the blood contained on
a saturated gauze swab if using scales to weigh gauzes
are not practical.
 Calculating





Blood Loss
Each swab ( 10X10 Cm gauze) weighs 2.0 gms
Each lap sponge weighs 36 gms
Each gm of blood equals 1 ml of blood
Weigh the bloody gauzes or lap sponges
If no scale available then an approximate
estimate is as follows:


Soaked lap sponge =30ml of blood loss
Soaked 10X10 cm gauze = 10ml of blood loss









So we have 16 saturated 10X 10 gauzes for a total blood loss on the gauzes of
160 ml ( 10 ml per saturated 10X 10 cm gauze)
 These
are replaced based on the degree of
tissue trauma/damage.



Minimal tissue damage ( dental surgery, surgeries
of the extremities etc) are replaced at 4ml/kg/hr
Moderate tissue damage ( abdominal surgery) are
replaced at 6ml/kg/hr
Severe tissue damage ( 3rd degree burns) are
replaced at 8 ml/kg/hr
 Remember
all are patients are fasting. So
you calculate their fluid requirements from
the time they started fasting.
 Usually midnight for all morning
patients)(i.e. NPO midnight)
 Replace ½ the NPO deficit in the first hr and
rest in the second hr
Solution
mmol/L
Na+
Normal
saline
154
Hartmans
/Ringers
131
K+
HC03-
Cl154
5
111
5%
Dextrose
4%
dextrose
and
0.18%
saline
30
Ca+
30
2

The choices are:
1)Crystalloids like normal saline, Hartman's/called Ringers
lactate in the US) and glucose or a combination of glucose and
normal saline.
 2)Colloids like albumin, starches and Gelatins like gelofusin.
 blood or blood products( RBC/packed cells ,fresh frozen
plasma, factor specific blood ).





The jury is still out as to how helpful colloids or hypertonic
saline are in long term survival rates.
Blood or blood products have the real potential for cross
infection and allergic reactions.
Crystalloids alone are used unless over 3.0 L of
replacement fluid is needed acutely . At this point colloids
are introduced.
In the office environment the only choices are
crystalloids.
 So
from the above we can see that for 90% of
our patients normal saline is the fluid of
choice.
 Hartmans/Ringers could be considered if you
believe there might be some minor
electrolyte deficit in your patient.


Examples might be that the patient is on
diuretics which can lead to low K+
The patient was not taking much orally for a day
or 2 secondary to pain. As a result they may be
electrolyte depleted and would benefit from the
small amount of electrolytes in
Hatrmans/Ringers.
first look at blood loss based on a
classification system from class I to class IV
This classification system considers the
volume of blood lost as a percentage each
individual patients estimated blood volume.
 next look at hemoglobin and platelet levels
that the patient needs to be maintained at or
above.( outside the scope of this
presentation)
 We will look at the classification system only
so that you know when to transport to
hospital based on blood loss.

 First
thing to know is what your patients
blood volume ( based on age) is.
 Premature
neonates 95 ml/kg
 Full term neonates 85 ml/kg
 Infants-8yr olds 80 ml/kg
 Adult males 75 ml/kg ( over the age of 8 yrs)
 Adult Females 65 ml/kg ( over the age of 8
yrs)
 So for Australian in office sedation the last 2
( adult male and female) is all you have to
know because that’s the only age groups we
see.

class one blood loss is when less than 15%
of circulating blood volume is lost



resuscitate with crystalloids and colloids only
only transfuse if there was a pre-existing anemia
such that the patient’s hemoglobin carrying
capacity is reduced to the point that clinical
signs and symptoms are evident. [e.g., dizziness,
shortness of breath, new worsening angina]
class II use is when less than 30% of the
circulating blood volume is lost.

resuscitate with crystalloids and colloids only

class III is when less than 30-40% of the
circulating blood volume is lost



rapid value replacement with both crystaloid
and colloids is indicated.
these patients will also require transfusion in
order to maintain an appropriate hemoglobin.
class IV is when of over 40% of circulating
blood volume is lost


rapid fluid replacement with both crystaloid and
colloids
these patients will also require transfusion in
order to maintain an appropriate hemoglobin
level.
 Prior
to the start of case calculate the EBV
and what volumes of blood loss represent
class I-IV blood loss. From this you will know
when you are reaching the threshold values
for the use of colloid and the need for
transfusion and transfer.
clear fluids may be taken up till two hours
preop.
 Breast milk may be taken up until four hours
preop
 a light meal( toast and clear fluids), infant
formula and other milk or milk products
require a fasting period of six hours preop.


Milk is considered a solid because when mixed
with gastric juices if thickens and congeals into
a solid.
 Solids
require 8 or more hours of fasting
 Note
in certain patients these times must be
increased As certain metabolic diseases,
medications will cause delayed gastric
emptying.
 it should be noted that the delayed gastric
emptying refers to solids and does not apply
to clear liquids.

the conditions, and medications associated
with delayed gastric emptying are as follows:





Diabetics secondary to gastroparesis
Patients with GER
Obesity secondary to both gastroparesis and GER
opioid use
in all these cases it is possible that greater
than eight hours of fasting is required.

conditions which will decrease gastric motility
and therefore gastric emtying are as follows:
head injury
 pyloric stenosis


patients at risk of regurgitation are as follows:
pregnant patients
 obese patients


in all these cases it is possible that greater than
eight hours of fasting is required and all of these
patients should have rapid sequence inductions
performed.( see discussion on airway
management later)
 Take





into account all of the following
GI + insensible losses ( 50 ml/day for 70 kg adult)
Maintenance requirements ( 4-2-1 rule)
NPO deficit
Acute Blood loss
Third space losses
 76
kg male having wisdom teeth removed
 Fasting from midnight
 Appoint at 10 am
 HOW MUCH FLUID dose he need by 1100 am
 76




kg
4=40ml
2=20ml
1=56 ml
Total maintenance=116ml/hr
 NPO
deficit = 1200am till 1100 am or 11 hrs
at 116/hr=1276 ml
 Third space loss 304/hr
 Total fluid required by 11 am is 2130 ml of NS
 At
1030 am he looses 200 ml of blood
 How much and what type of fluid does he
need by 1100 am?

76 kg
4=40ml
 2=20ml
 1=56 ml
 Total maintenance=116ml/hr






NPO deficit = 1200am till 1100 am or 11 hrs at 116/hr=1276 ml
3rd space loss of 304/hr
Replace blood loss 3 to one so 600.00 ml
Total fluid required by 1100 am is 2730.00 ml
Options are:
Give NS( ½ of required fluid) in the first hour and 1/2of normal saline
in the second hour
 Give NS( ½ of required fluid) in the first hour and 1/2 of hartmans in
the second hour
 Give hartmans( ½ of required fluid) in the first hour and hartmans ( ½
of required fluid) in the second hour


Since he is under the three liters no colloid will be required
 Thank
you for your commitment to
continuing education.