General Surgery Sheet #3 By Tamara Mousa

Perioperative fluid management
Today we’ll be talking about the perioperative fluid management for surgical patients
The distribution of water in the total body:
0.55% of male’s body weight is water
0.6 % of female’s body weight is water

A patient who weighs 70 kg has 42 liters of water 2/3 this water is within the cells (intracellular) the other 1/3 is in the extracellular fluid

14 liters of water is in the extracellular fluid

Extracellular fluid is divided into two compartments :
1) the interstitial fluid : it is almost 11 liter
2) the intravascular fluid : it is fluid is almost 3 liter
The most important of all is the intravascular volume /fluid because it’s needed for the perfusion of the brain and the main organs of the body (contains blood and plasma and fluids)

Now the electrolyte composition of the intracellular and extracellular components :

We have main anions and main cations that make the osmolarity of the fluid
extracellular fluid = interstitial + intravascular => their components of electrolytes are almost the same



main cation : sodium potassium
main anion : chloride phosphate +organic acids
+organic proteins

**in the extracellular compartment proteins don’t create any major effects on the osmolarity


Intravenous fluid infusion
there are types of intravenous fluids we can give to patients such as :
1) water which has no osmolarity or salts
2) isotonic solutions that contain Na,Cl
3) colloids :fluids containing high molecular weight components like proteins and starch ,albumin

If we give a patient :
1) water without salts or proteins :it’ll distribute freely in the whole body (intravascular, interstitial and intracellular)
2) isotonic solution that contains NaCl : it goes to the extracellular component where the main osmolarity is caused by sodium and does not go to the intracellular component
3) colloids: it remains intravascular
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Water balance
input and output (both are equal 2500 ml)
Input :
• food 1000 ml
• drink 1200 ml
• metabolic oxidation 300 ml (co2+H2o)
Output :
• urine 1500 cc
• feces 100 ml
• the rest is insensible loss (expiration + sweating) 900 ml
Fluid resuscitation
The primary goal is to give the least amount of fluid possible to reach the desired end points of resuscitation
Fluid resuscitation and maintenance help to restore perfusion and hydration and avoiding volume overload, the most important thing is to maintain the intravascular volume
When we give fluid therapy to a patient it should be reassessed at frequent intervals and adjusted to obtain the maximum results (ie, optimal tissue perfusion) because we can’t know for sure the exact need or how much he has or how much Milliliters he lost, so we have other parameters to see if we are giving enough hydration or not.
The fluid therapy plan
1) Resuscitation: which is the correction of perfusion deficit (intravascular volume)
2) Rehydration: to correct the extracellular compartment
3) Maintenance phase(replace ongoing losses, meet metabolic demands, and restore intracellular water balance)
So if the patient is bleeding he’ll lose fluids from the intravascular compartment and the lost fluids will be substituted by with the fluids in the interstitial compartment (all in all he’s dehydrated) so rehydration is to correct the interstitial deficit
How are we going to assess? How are we to know the adequacy of the fluid therapy?
1) Skin turgor: we pinch the patient’s skin and release it , normally what will happen because of the elasticity of the skin it will return to its normal shape but in dehydrated patients it will retain the new shape









2)we look at the tongue if it’s dry or not
3)we measure the cardiovascular system parameters :
*Blood pressure: dehydrated patients have Hypotension
*Heart rate : dehydrated patients have tachycardia (because of decreased fluid in the intravascular volume and as we know the cardiac output =heart rate*stroke volume and in this case the stroke volume is less so to maintain the cardiac output the heart rate increases
4)urine output : the kidney stops producing urine to preserve the fluids within the body we call this (oliguria) which means reduced urine output and in some case it might become anuria which means no urine is produced at all due to severe dehydration,
5) Central venous pressure monitoring : we place a catheter in the central vein superior vena cava by this we measure the pressure in the venous system and measures the PRELOAD of the heart , when this pressure drops it means that the patient is dehydrated
6) Urinary values: we analyze urine, in dehydration urine osmolarity and concentration increase




7) blood tests :analysis of of a blood sample would show an increase in serum urea and an increase in lactate due to metabolic acidosis
Types of dehydration :
Mild dehydration: the patient lost 5% of his total body water because when it’s lost from intravascular and interstitial compartments it’s compensated by from the intracellular fluids
They suffer from dry mouth and thirst
Example : a patient who weighs 70 kg’s has 42 liters of fluid and 5% of 42 =3.5 liter are lost
Moderate dehydration: 5-10% fluid loss
such patients have :
1) decreased skin turgor
2) decreased intraocular pressure (can’t be measured)
3) tachycardia
4) Orthostatic hypotension (meaning just upon standing up he becomes hypotensive but when he’s sitting down he is not ) ,
5)oliguria
6)skeletal muscle weakness
7) drowsiness
Severe dehydration :10-15% fluid loss
They suffer from :
1) severe hypotension
2) tachycardia
3)anuria
4)confusion
5) coma
Causes of dehydration:
1) Bleeding during or before the operation
2) Diarrhea
3) Fasting
Perioperative fluid requirement:
Perioperative period is the time before and during and the following 24 hours after the operation
So this patient has an intake and an output requirement (we call it the maintenance requirement) , and there’s something we need to measure called the preoperative deficit ( to know before we start the operation if the patient is dehydrated or not) , during the operation things can happen like bleeding , and in abdominal surgeries happens what we call third space loss ( the fluid does not go to the interstitial or the intracellular compartments but goes to the peritoneal cavity that’s considered a third space) >>the peritoneal space should normally contain no more than 50 cc fluids but in such operations fluids will accumulate there
After the operation we place the patient on artificial ventilation and this will increase fluid loss through the effects of anesthetic agents and the technique itself so water will be lost
Maintenance:
Any human being needs 40 cc /kg/day roughly (30-50)
In children its calculated this way: the first 10 kg’s he needs 100 cc /kg /day
And the next 10 kg’s he needs 50 cc/kg/day
If he weighs 20 kg’s he’ll need 1500 >>(10*100) +(10*50)=1500
So if he weighs 22 kg’s : he’ll need 1550 >>(10*100)+(10*50) +(2*25)=1550
This is the fluid management for just water, but the patient also needs sodium and potassium:
Sodium given should equal 1-2 mmol/kg/day
Potassium given should equal 1 mmol/kg/day
so if the patient weighs 70 kg he needs :
sodium : 70-140 mmol/day
potassium:70 mmol /day
How to know if the patient has preoperative deficit? By asking the following questions :
The following questions should be asked.
• How long has the patient been starved?
• any reason to expect excessive losses?
• Are they taking diuretics?
• Are they pyrexic?
• Have they been vomiting or do they have a nasogastric tube in situ?
• Have they got diarrhoea or had a bowel preparation?
• Could they have third-space losses or occult bleeding?
• Have they any symptoms of fluid overload
for example the patient spent the 24 hours before operation without eating due to stomach ache so we should keep in mind the 24 hours of fluid deficit
>> that’s how we calculate this deficit: 40 cc/kg/day preoperative deficit, if he is taking diuretics it increases the deficit, if he has fever it will increase the insensible loss, if he is vomiting, NG (nasogastric) tubes for patients undergoing GIT operations to relieve the pressure if the patient has intestinal obstruction so we need to know how much fluids are lost through this tube, if he has diarrhea
So the deficit should be infused during the operation , in the first hour we give half of the deficit and the next hour we give quarter the deficit and the last hour we give the last quarter , so in a major GI operation that requires 3 hours and we the calculated deficit was 4 liter :
1st hour :2 liters
2nd hour : 1 liter
3rd hour :1 liter
So in the normal situations the patient is always reassessed and normally the patient shouldn’t be dehydrated on the table of the operation, but sometimes upon reassessment just before the operation we discover he has a deficit and we have to correct it during the operation ..So if he spent two days in the hospital before the operation and was placed on a NG tube the deficit is known and is corrected simultaneously
Deficits
• NPO deficit = number of hours NPO x maintenance fluid requirement. The deficit may then be replaced with approximately 80 mL/fasting hour.
• Bowel prep may result in up to 1 L fluid loss.
• Measurable fluid losses, e.g. NG suctioning, vomiting, ostomy output.

Replacement of fluids and contents, so if the patient is on NG tube he’ll lose gastric contents, if he has diarrhea he’ll lose fluids
Normally the stomach during 24 hours gives 1500 cc/day of fluids, so NG tube for 24 hours could mean that the patient lost 1500 cc fluids
the ileal fluids = 3 liters/day
diarrhea = 200 cc -2000 cc /day we need to know all these because lots of operations involve the GIT and the ileum and when we open up the ileum ,fluids will be lost (3 liters/24 hours)

Trans cellular component of the body :
CSF
Synovial spaces
GI Tract
Pleural space
Peritoneal space
When the patient has ascites it means his abdomen contains lots of fluids but he is considered dehydrated but the fluids are not lost they are retained inside a place of no importance of no advantage to the patient which is the peritoneal cavity
Fluids can also be retained in the pleural space (pleural effusion)
GIT obstruction leads to edema within the walls so the patient is losing fluids within the GIT coming from the whole body
>> Such fluids come originally from the 42 liters of fluids of the patient<<
Surgical drains are placed in the subcutaneous tissues after surgeries performed in breast, abdomen, subcutaneous tissue removal, this drain takes out fluids of no advantage to the body, if they accumulate they can cause seroma (again the source of such fluids is the body itself so it’s a loss to the inside not to the outside)
• Surgical drains, nasogastric tubes and chest drains produce measurable losses.
• Fluid losses caused by ascites, pleural effusions and bowel obstruction can only be estimated.
• Estimates of fluid loss by evaporation from ‘open abdomens’ are typically 10 ml/kg/hour, whilst ‘open chests’ may lose 5 ml/kg/hour.
• Pyrexia causes a 15% increase in the requirement for water,Na+ and K+ for every °C above normal body temperature..

Terms:
1st spacing and 2nd spacing and 3rd spacing
1st spacing: normal distribution of fluids in the intracellular and extracellular fluid (2/3 in intracellular and 1/3 in extracellular)
2nd spacing: is an abnormal accumulation of fluids in the interstitial fluid
• seen in patients with heart failure >> manifests as lower limb edema
• edema associated with varicose veins
• pulmonary edema
3rd spacing: when fluids accumulate in the 3rd space (peritoneal and pleural cavities and ascites) so it’s Fluid accumulation in part of body where it is not easily exchanged with rest of ECF
• edema due to burns
• ascites [in peritoneal space)

What distinguishes the 2nd spacing from the 3rd spacing is that in the 2nd spacing the patient can still regain those fluids from the interstitium into the intravascular fluids and it takes less time, so if a patient with heart failure comes and we gave him medications and the heart starts to regain its function the fluids would go from the interstitial into the intravascular component
Fluids in the 3rd space even with medications and diuretics need 3 days to go back to the intravascular component >>so in the management of patients with ascites : even if they’re overloaded with fluids they should be given fluids to maintain the intravascular fluid , but after 3 days if there’s improvement and the cause of ascites is gone , the fluids will go to the intravascular compartment so we need to reassess him and reduce the fluids later on
Why do we get 3rd spacing?
1) peritonitis
2) bowl obstruction the patient loses the fluids within the GIT
3) the synovial component is another 3rd space so massive bleeding within the joint upon fracture is considered a 3rd space loss
4) also patients with renal and liver failure s have 3rd spacing through formation of ascites
5) Burns
6) Lowered plasma proteins
7) Increased capillary permeability
8) Lymphatic blockage
phases of 3rd spacing :
loss phase : lasts 48-72 hours , the patient suffers from symptoms of fluid loss or depletion and dehydration
reabsorption phase : take 2-3 days ,after the problem subsides , fluid volume overload is possible , so we have to monitor the vital signs ,input and output , weight and breath sounds , when we have edema or effusion in the lung we might hear crackles ( sometimes we don’t …)
• During operation the patient loses fluids through third spacing and through evaporation depending on the extent of trauma we are dealing with..
• Capillary and Endothelial injury; leak Sequestration of fluid into tissues
• Creation of nonfunctional component of ISF
• The key to adequate replacement lies in careful assessment of the circulating volume both clinically and with the use of invasive monitoring.
• Replacement of fluid sequestered in this way must be with isotonic fluids or colloids.
• Fluid sequestered in this way is usually ‘re-mobilized’ and returns to the circulation around the second or third postoperative day, often inducing a diuresis.
Superficial surgical trauma: 1-2 ml/kg/hr
Minimal surgical operations:
1) the patient doesn’t lose lots of fluids
2) it depends on the duration of surgery and the patient’s weight too ,
Moderate surgical trauma:
Severe surgical trauma:



for a patient who weighs 70 kg ( cc = ml )
Superficial surgical trauma
minimal surgical operations Moderate surgical trauma Severe surgical trauma
example *hernia
*head and neck surgeries
*knee injury *thoracic surgery
*abdominal surgery, *appendectomy
*major orthopaedic
*cholecystectomy
*hysterectomy *Pancreatectomy *nephrectomy
*major bowel resection
*Whipple
fluid loss estimated 1-2 ml/kg/hr 3-4 cc/kg/hour +(200-240 cc are lost due to evaporation) 5-6 ml/kg/hour as evaporation and 3rd space loss 8-10 ml/kg/hour

Estimating blood Loss
• Aspirating blood from the operative fieId into a graduated container
• weighing sponges
• using blood Ioss figures established as average for various operations
• observing the operating field, gowns, floor and sponges;
• watching blood pressure,Pulse rate and respiratory rate;
• blood ceIl count, hemoglobin and blood voIume determinations;
Duration of surgery
Any operation involves blood loss; we see it in the suction tube or the gauzes when they become soaked with blood




• 4*4 gauzes when soaked with blood contain 10-11 cc blood
• Abdominal gauzes when soaked with blood contain 100 cc blood













Fluid lost during surgery
• The insensible perspiration 10 mL/kg/day in normal conditions, and this does not change much during surgery.About two thirds of the volume is lost through the skin and one-third from the airways.
• Insensible losses such as evaporation of water from respiratory tract, sweat, feces, urinary excretion. Occurs continually.
• Extra fluid for fever, tracheotomy, denuded surfaces
The evaporative loss
• in minor incisions with slightly exposed but non-exteriorised viscera it is 2.1 g/hour;
• in moderate incisions with partly exposed but non-exteriorised viscera it is 8.0 g/hour;
• in major incisions with completely exposed and exteriorised viscera it is 32.2 g/hour.
• Note that the loss is given in grams per hour, and is independent of the body weight of the patient.
Fluid Volume Excess (FVE)
• Hypervolemia
• Isotonic expansion of ECF caused by abnormal retention of water and sodium
• Fluid moves out of ECF into cells and cells swell

The patient can also suffer from hypervolemia …
1st important sign is weight gain
2nd distention of veins (especially neck veins)
3rd lower limb edema (pitting edema)
4th lung edema (pulmonary edema) >>we hear Adventitious lung sounds mainly crackles due to the presence of fluids in the lung
5th Periorbital edema
6th th dyspnea
7th Generalized or dependent edema
8th mental status changes
9th when measuring the vital signs we might notice he has hypertension, bradycardia , elevated central venous pressure
10th blood sample (hematocrit) shows dilutional Hb , serum osmolarity will be low , blood urea nitrogen will be less , Low specific gravity.

X ray will show pulmonary edema and congestion of the lung, pericardial effusion, and pleural effusion and ascites
Postoperative fluid therapy
• Check IV regime ordered in op form
• Assess for deficits by checking I/O chart and vital signs
• Calculate maintenance requirements
• Usually K+ not started in first 24 hrs
• Monitor carefully vital signs and urine output
we calculate the loss in blood and fluids during operation and we calculate what was given to the patient too and we give him the maintenance each hour
The ideal fluid :
* Physiochemical properties :
• Cheap and easy to manufacture
• Stable in storage
• Non-reactive with the equipment :
• nonviscous
**2 ideas from nowhere 1: artificial blood is very expensive and requires special conditions for storage but remains the best choice if we want to compensate for blood loss
2: any fluid we use we need it to stay in a compartment for its intended time (the intravascular compartment) but what really happens in the end is that it gets distributed to the whole body : example colloids : they contain high molecular weight compounds like starch , that will make them stay in the intravascular compartment , but after 24 hours it will be metabolized and the 1 liter I gave will go to the whole body , but remains better than crystalloid that go to both extracellular and intracellular

*Pharmacological properties:
• stays in the required body compartment as long as necessary;
• maintains and normalizes electrolyte and acid/base homeostasis;
• facilitates delivery of oxygen to the tissues; : artificial blood has the Hb component which carries oxygen to the tissues
• non-allergenic;
• no interactions with other drugs or fluids;
• physiologically inert, especially with regard to coagulation, immunological or renal function;
• Completely eliminated from the body with no long-term side-effects.
Fluids available are:
• crystalloids
• colloids: last the longest in the intravascular component
• blood products

Isotonic solutions like normal saline distribute in the intravascular and extravascular (interstitial) compartments
If we give 5 % glucose the glucose within half-hour will be metabolized so we it’s like we gave water (meaning 5% dextrose will distribute in the whole body just like water even in the intracellular)
Crystalloid solutions :
contain low molecular weight ions, salts, with or without glucose so it’s just an ionic solution, t1/2 life is 30 minutes

Crystalloid solutions have 3 types :
**Isotonic solutions:
• their osmolarity equals that of extracellular fluid , 1 liter of it goes to the extracellular water >>the osmolarity of extracellular fluid remains the same , the amount that remains in the intravascular equals the 1/3 ( almost 100 cc) ..because 14 liter in extracellular and 3 of the 14 lies in the intravascular (3/14 *100%=20 approximately) so when i give 1 liter 200cc remains in intravascular then excess Na will be excreted in urine and water will distribute all over the body
• Have approximately the same concentration (osmolality) as that of the ECF
• Are given to expand the ECF volume
• Examples:
1) Normal saline (NS or 0.9% NaCL)
2) Lactated Ringer’s (LR)
3) Dextrose 5% in water (D5W)
 note: D5W is considered hypotonic after metabolism of dextrose occurs
If I give 5 % dextrose , glucose will be metabolized within 15 minutes (to 30 minutes) so if I give 2 liters they will first go to the extracellular fluid , then after glucose is gone water will distribute all over the body ….(it’s getting boring really -_-!!!) what will happen here is that the total body fluids will increase therefor the osmolarity will decrease
 0.9 PERCENT SODIUM CHLORIDE / NORMAL SALINE
• Class:
– Isotonic crystalloid solution
• Description:
– Concentration of sodium is near that of blood
– No calories
• Contains:
– Sodium (Na+) 154 mEq/L
– Chloride (Cl-) 154 mEq/L
• Buffered solutions are usually indicated for resuscitating patients in shock because administration of a highly acidic solution may worsen a preexisting metabolic acidosis.
• Used in treatment of hyperkalemia (eg, urinary obstruction and oliguric renal failure), hypercalcemia,and hypochloremic metabolic alkalosis.
• If you infuse NaCl 0.9% 1000ml, all the Na+ will remain in the ECF
• no change in ECF osmolality and no water exchange occurs across the cell membrane
• NaCl expands ECF only
• Intravascular volume will be increased by 250ml
 D5W
• Isotonic
– But becomes hypotonic after dextrose is metabolized b/c only water remains
• A source of “free water
• A source of calories- Prevents ketosis
• Supports edema formation – do not use in clients with cerebral edema!
• If you infuse glucose 5% 1000ml, the glucose will enter the cell and be metabolised
• The water expands both ECF and ICF in proportion to their volumes
• The ECF volume will increase by 333ml
• Intravascular volume will only increase by approximately 100ml

 LACTATED RINGER’S SOLUTION / HARTMANN’S SOLUTION











**Hypotonic solutions :
• the concentration of Na and K is less than that of extracellular component
• Osmolality is lower than that of serum plasma ( fewer solutes than plasma)
• Are given to reverse dehydration
• Cause cells to swell and possibly burst
• Due to fluid shifting effects, it should be administered cautiously -> cerebral edema
• Examples:
½ NS (0.45% NaCL)
Dextrose 2.5% in water (D2.5W)

• **Hypertonic solutions : Osmolality is higher than that of serum plasma (more solutes than plasma)
• Are given to increase the ECF volume and decrease cellular swelling (used for hypovolemia & hyponatremia)
• Cause cells to shrink and contribute to ECF volume overload
• Examples:
1) 5% dextrose in 0.9% NaCl (D5NS)
2) 3% NaCl
3) 10% dextrose in water (D10W)

So if we give 2 liters hypertonic solution IV so they go 1st to the extracellular fluid and the osmolarity will increase in the extracellular fluid and it will drag fluids from the intracellular volume so the extracellular volume will increase more than 2 liters
 Hypertonic saline
It is usually given as a 7.5% solution (2600 mOsm/L).
It is administered in small volumes, at 5 mL/kg, over 5 to 10 minutes.
Due to the osmotic diuresis and rapid redistribution of the sodium cations that ensue following administration of hypertonic saline, the intravascular volume is transient (30 minutes) and additional fluid therapy with a colloid must be used with hypertonic saline.
Potential side effects include hypernatremia, hyperchloremia, hypokalemia,and dehydration. but this effect will be short-lived.
Interstitial hydrators, not intravascular volume expanders.This increase in interstitial fluid can lead to tissue edema (thus decreasing the ability of oxygen to diffuse to the cells).
 5% Dextrose in .9% Sodium Chloride (D5NS
• Class:
– Hypertonic crystalloid
– Cautions:
– May cause venous irritation

Colloids:
• Contain large molecules which do not diffuse freely from intravascular compartment substances like proteins, large glucose polymers, a colloid is a large protein like mass, t1/2 life is 90 minutes , example >>fluids containing albumin ,glucose polymers (dextran), Hetastarch

• Oncotic pressure proportional to number of particles
• Expand vascular volume
• Hypovolemic resuscitation (e.g. head trauma, 3rd spacing)
• Relatively contra-indicated in CHF or oliguric/anuric RF
• May decrease clotting factor activity with synthetic colloids
• Monitor if use synthetic colloids in patients with pre-existing coagulopathy
• Colloids can be considered intravascular volume expanders.
• Colloids are usually isosmolar.
• All synthetic colloids have the potential to cause a dilutional coagulopathy.

 Albumin

• Major plasma protein
• 5% albumin is isotonic
• 25% albumin is hypertonic
• 1 g albumin retains 18 ml of fluid in intravascular space
• May cause febrile reactions (blood product)
• Indications:
1) Volume expander
2) Create diuresis in fluid volume excess
3) Facilitate remobilization of fluid from third-space fluid shifts
4) Burns, trauma, liver failure
5) Contraindicated in:
6) Anemia
7) Dehydration
8) t ½ = 8-9 days in man
 Dextran
• A glucose solution with colloidal activity similar to albumin
• Available as:
o Dextran 40: low molecular weight dextran
o Dextran 70: high molecular weight dextran
o Type and cross-match prior to administration
o Assess for S&S of anaphylaxis
• Dextrans are branched polysaccharides produced by the action of bacteria on a sucrose medium.




 Hetastarch
• Synthetic colloid made from cornstarch
• available in a 6% solution that is diluted in 500 mL of NS (Hespan) and 6% solution that is diluted in 500 and 1000 mL of an electrolyte-lactated solution (Hextend)
• Expands the plasma and is used in shock precipitated by hemorrhage, trauma, burns and sepsis
 HES
• The Hydroxyethyl starches (HES) are modified natural polymers of amylopectin, which are metabolized by amylase.
• contains large molecular-weight particles that effectively increase the COP beyond what can be obtained with blood product infusion alone.
• It expands the volume by about 1.4 times the volume infused.
• half-life of 25 hours
• Synthetic colloids are administered with isotonic crystalloids to reduce interstitial volume depletion.
Differences between crystalloids and colloids:
1) Intravascular persistence colloids are better
2) Haemodynamic stabilisation :colloids cause prolonged stabilisation
3) Required infusion volume crystalloid need to be given in larger volumes
4) Risk of tissue oedema: crystalloids increase the risk more because they go to intravascular and interstitial components unlike colloids which remain intravascular
5) Enhancement of capillary perfusion :colloids provide more enhancement

6) Risk of anaphylaxis: colloids increase such risk (its content of proteins and high molecular weight components )
7) Plasma colloid osmotic pressure: colloids maintain it while crystalloids reduce it
8) Cost: colloids are more expensive
Crystalloids or Colloids, Which Is Better?
The concurrent use of both crystalloids and colloids obviates the need for administration of large volumes of crystalloids, minimizes the risk of interstitial edema, and may restore blood volume rapidly. A 'blending" of crystalloids and colloids should be considered if colloids are not contraindicated….


Done by: Tamara Madhat \m/
I have included all the written slides. But some slides contained complicated figures and useless numbers so refer to them on your own  enshallah kolna nw99il el 100 point 