Fluid balance for surgical patients. Dr. Ahmed khashaba, MD

Fluid Balance For Surgical Patients
1
Dr. Ahmed Sayed Khashaba, MBBS. MD. Ph.D.
Associate Professor of Medical Physiology
College of Applied Medical Sciences
Basic Sciences Department
Riyadh Elm University
Kingdom of Saudi Arabia, P.O. Box: 84891 Riyadh
11681
Tel: 0112481222, ext. 324
email: ahmedkhashaba@riyadh.edu.sa

Intended Learning Outcomes
• Describe the physiology of human fluid dynamics.
• Define Intravenous therapy.
• List the aims of adult perioperative fluid therapy.
• Recognize the commonly used fluid preparations.
• Describe the properties and indications of commonly used IV solutions.
• Describe the side effects and precautions of commonly used IV solutions.
• Explain the (NICE) principles and protocols for intravenous fluid therapy.
• Discuss the assessment and management of hydration and volume status of surgical patients.
• Describe the type, rate and volume of fluid administered to surgical patients.
• Recognize the different types of venous access.
• Explain the potential local complications of peripheral IV therapy.
• Identify the universal equations used by nurses to calculate the IV flow rate and medication dosage.

I. Physiology-Body Fluid Compartments
■Total body water (TBW) is approximately
60% of body weight.
■A. Distribution of water
1. Intracellular fluid (ICF)
■is two-thirds of TBW.
■The major cations of ICF are K+ and Mg2+.
■The major anions of ICF are protein and organic
phosphates.
2. Extracellular fluid (ECF)
■is one-third of TBW.
■is composed of interstitial fluid and
plasma. The major cation of ECF is
Na+.
■The major anions of ECF are Cl- and HCO3-.
a. Plasma is one-fourth of the ECF.
■The major plasma proteins are albumin and
globulins.
b. Interstitial fluid is three-fourths of the ECF.
■The composition of interstitial fluid is the same
as that of Plasma except that it has little protein.
Thus, interstitial fluid is an ultrafiltrate of plasma.
3. 60-40-20 rule
■TBW is 60% of body weight.
■ICF is 40% of body weight.
■ECF is 20% of body weight.

4- Normal Fluid Balance
N.B. Water requirements increase by 100 to 150 mL/day for each ○C of body temperature elevation.

5. Examples of shifts of water between compartments
a. Sweating in a desert—loss of water
■is also called hyperosmotic volume contraction.
(1)The osmolarity of ECF increases because sweat is hyposmotic
(relatively more water than salt is lost).
(2)ECF volume decreases because of the loss of volume in the sweat.
(3)Water shifts out of ICF; as a result of the shift, ICF osmolarity
increases until it is equal to ECF osmolarity, and ICF volume decreases.
b. Excessive NaCl intake—addition of NaCl
■is also called hyperosmotic volume expansion.
(1)The osmolarity of ECF increases because osmoles (NaCl) have been
added to the ECF.
(2)Water shifts from ICF to ECF. As a result of this shift, ICF osmolarity
increases until it equals that of ECF.
(3)As a result of the shift of water out of the cells, ECF volume
increases (volume expansion) and ICF volume decreases.

II- Distribution of Electrolytes

III. Concentration and dilution of urine

• Produced by
HYPOTHALAMUS.
• Stored by
POSTERIOR
PITUITARY
• Decrease amount of
water loss
• Vasoconstriction.
• Made by cells of Adrenal
cortex (Zona Glomerulosa)
• Controls levels of Na+
& K+ in ECF.
• Simultaneous
reabsorption of Na+ &
excretion of K+.
• Water follows Na+
• Atrialnatriureticpeptide(ANP)made
by cells of Right Atrium when
blood volume increases
(atria stretched).
• Brain natriuretic peptide (BNP)
produced from stretched
ventricles.
• Promote loss of water
& Na+,(-) Renin, (-)ADH
& Aldosterone
27
IV- Hormonal effects on fluid homeostasis

V- Starling's forces
• Represent the movement of fluids at the vascular
endothelium. Starling's forces describe the movement of
fluids at the vascular endothelium. Starling described 4
forces: (a) the capillary hydrostatic pressure, (b) the capillary
oncotic pressure, (c) the interstitial hydrostatic pressure, and
(d) the interstitial oncotic pressure. The sum of the four
forces results in the net movement of small amounts of fluid
across the vascular endothelium into the interstitial space.
Normally, the lymphatic system returns this fluid to the
circulation to prevent interstitial edema (Saraghi, M., 2015.
Intraoperative fluids and fluid management for ambulatory
dental sedation and general anesthesia).
• In patients who are septic, the tight junctions between the
capillary endothelial cells break down and vascular
permeability increases. As a result, increasing hydrostatic
pressures and reducing oncotic pressure lead to fluid leaving
the vasculature and entering the tissue. It is often therefore
necessary to give relatively large volumes of intravenous fluid
to maintain the intra-vascular volume. Close monitoring of
the fluid balance will be required.

Definition:
Intravenous therapy, also referred to as ‘IV therapy’, constitutes the
administration of liquid substances directly into a vein and the general circulation
through venepuncture (Mosby, 1998).
INTRAVENOUS THERAPY

11
AIMS OF IV FLUID THERAPY
The intravenous route is a fast and efficient method to administer fluids and medication,
which can be given continuously or intermittently.
Intravenous fluid therapy may be used to:
• Replace fluids and replace imbalances.
• Maintain fluid, electrolyte and acid-base balance.
• Administer blood and blood products.
• Administer medication.
• Provide parenteral nutrition.
• Monitor cardiac function.

IV Fluids can be broadly categorized into two groups:
1- Crystalloids: are more widely used than colloids, with research supporting the
idea that neither is superior in replenishing intravascular volume for
resuscitation purposes (with crystalloids also significantly cheaper). Therefore,
crystalloids are used very commonly in the acute setting, in theatres, and for
maintenance fluids.
2- Colloids: One advantage of colloids is that they remain in the intravascular
space for longer periods of time with less risk of peripheral and pulmonary
edema. Commonly used colloids include albumin, hydroxyethyl starch, and
dextran. Disadvantages include increased cost and risks for hypersensitivity
reactions, coagulopathy, and renal failure. Colloids expand the volume of the
intravascular space, resulting in dilution of blood cells, platelets, and coagulation
can inhibit coagulation. Dextran, in particular, affect coagulation. Serious allergic
or anaphylactoid reactions are another disadvantage associated with colloid
administration. The crystalloid versus colloid debate continues and is one of the
unresolved questions in perioperative fluid management.

Compositions of Commonly Prescribed Crystalloids

Properties and Indications of Commonly Used IV Fluids
Different types of crystalloids have different properties and will, therefore, be appropriate in
different situations according to the cause of fluid loss and the patient’s condition.
1- Isotonic crystalloids have a sodium and a chloride concentration of 154mmol/L and a similar
electrolyte concentration to plasma. With isotonic infusions, there is no significant fluid shift
across cellular or vascular membrane for a normally hydrated patient. These fluids are usually
used to treat low extracellular fluid loss (for example, in a dehydrated patient), in fluid challenge
or during fluid resuscitation.
2- Balanced crystalloid solutions (e.g., lactated Ringer’s). They are called ‘balanced’ because
their ionic composition is closer to the human body’s plasma levels than other crystalloids. A
post-operative patient at risk of fluid loss leading to electrolyte imbalance, for example, will
benefit from balanced crystalloids.
3- Hypotonic crystalloids have a lower osmolarity than plasma, which means they cause fluids
to shift from the intravascular space to the intracellular or interstitial space. They also help the
kidneys excrete fluids and electrolytes, and are often used in patients with diabetic
ketoacidosis.
4- Hypertonic crystalloids have a higher electrolyte concentration than plasma and, therefore,
draw fluid from the intracellular and interstitial space into the intravascular space. They may be
used to treat patients with cerebral oedema.

IV FLUID CHOICE FOR DENTAL, ORAL, AND MAXILLOFACIAL PROCEDURES
• For outpatient treatments involving sedation/general anesthesia and just modest blood loss,
such as most dentistry and oral surgery, isotonic balanced crystalloids are the preferred fluid.
• The majority of patients who come in for surgery have not just an intravascular fluid deficit
but also an interstitial space deficit. Thankfully, crystalloid will compensate for the losses in
both compartments. Insensible and urine losses are minimal in most office-based dental and
oral surgery procedures.
• Colloids have no place in office-based dental and minor oral treatments, and their use is
limited to prolonged and/or invasive maxillofacial surgical operations involving significant
blood loss and advanced monitoring of blood pressure and/or urinary output (Saraghi, M.,
2015. Intraoperative fluids and fluid management for ambulatory dental sedation and general
anesthesia).

Side-effects and Precautions of Commonly Used IV Fluids
1- Isotonic crystalloids should be used with caution in patients with cardiac or renal disease,
as there is a risk of fluid overload. Patients’ sodium and chloride levels need to be monitored
regularly to avoid hypernatraemia and hyperchloraemia. All isotonic crystalloids can cause
peripheral and pulmonary oedema.
2- The lactate contained in balanced isotonics is metabolized by the liver into bicarbonate, so
these fluids should not be used in patients who cannot metabolize lactate due to liver
disease; nor should they be administered to patients with pH >7.5. They should be used with
caution in patients with renal failure because of the kidneys’ inability to filter potassium.
3- Hypotonic crystalloids should not be administered to patients at risk of increased
intracranial pressure, those with liver disease or trauma or burns patients, mainly because
these patients need to maintain a good intravascular volume.
4- Hypertonic crystalloids main risks are hypernatraemia and hyperchloraemia, so these fluids
need to be given slowly and cautiously to avoid intravascular fluid overload and pulmonary
oedema. It is also worth noting that 20% dextrose is an osmotic diuretic. Hypertonic solutions
should not be given to patients with cardiac conditions, as there is a risk of fluid overload.

IV Fluid Replacement Precautions in Specific Patients
• Patients with hypernatremia who receive fluid replacement with quick correction of
hypernatremia are more likely to develop cerebral edema due to increased intracellular and
extracellular fluid loads, as well as increased pressure inside the brain region. This results in
neurological damage and, eventually, death. This situation can be averted by slowly infusing
fluids to lower sodium levels at a rate of 2 to 3 mEq/L per hour for a total change of 12
mEq/L per day until sodium levels return to normal.
• Rapid correction of hyponatremic patients, on the other hand, may result in central pontine
myelinolysis syndrome. When hyponatremia is quickly treated, brain cells shrink and the
blood-brain barrier's tight connections are broken, resulting in cell injury and neuron
demyelination. This can result in a condition known as "locked-in syndrome’’ which is
characterized by paralysis, dysphagia, and dysarthria. The serum sodium should be increased
by approximately 1 to 2 mEq/L per hour until the neurologic symptoms of hyponatremia
subside or until plasma sodium concentration is over 120 mEq/L.
• Diabetic ketoacidosis is a diabetic condition that occurs when the body is unable to use
glucose for energy production. Glucose is an osmotically active molecule excreted at high
amounts in the urine (osmotic diuresis). Dehydration arises as a result of the excessive fluid
loss through urine. This demands a large volume resuscitation of approximately 6 to 9 liters
of normal saline (Brinkman, J.E., Dorius, B. and Sharma, S., 2018. Physiology, Body Fluids).

National Institute for Health and Care Excellence (NICE) Principles and
protocols for intravenous fluid therapy
• The assessment and management of patients’ fluid and electrolyte needs are fundamental to
good patient care. Fluid balance is an important area of perioperative medicine. If managed
incorrectly it is a significant cause of morbidity.
• Provide intravenous (IV) fluid therapy only for patients whose needs cannot be met by oral or
enteral routes, and stop as soon as possible.
• When prescribing IV fluids, remember the five Rs after the initial assessment:
resuscitation, routine maintenance, replacement, redistribution, and reassessment.
• Offer IV fluid therapy as part of the following protocol:
– Assess patients’ fluid and electrolyte needs following algorithm 1 (assessment)
– If patients need IV fluids for resuscitation, follow algorithm 2 (fluid resuscitation)
– If patients need IV fluids for routine maintenance, follow algorithm 3 (routine maintenance)
– If patients need IV fluids to address existing deficits or excesses, ongoing abnormal losses, or
abnormal fluid distribution, follow algorithm 4 (replacement and redistribution).
• Include the following information in IV fluid prescriptions:
– The type of fluid to be administered
– The rate and volume of fluid to be administered.
– The fluid and electrolyte prescription over the next 24 hours.

I- Assessment of Fluid Status
• It is essential to utilize various clinical parameters to continually assess the patient’s
fluid status. A doctor’s first assessment is the patient’s clinical status.
• Assess the patient using the ABCDE approach (airway, breathing, circulation, disability,
exposure).
A- In the fluid depleted patients (HYPOVOLEMIA), one should be looking for:
• Dry mucous membranes and reduced skin turgor
• Decreasing urine output (should target >0.5 ml/kg/hr)
• Orthostatic hypotension
• In worsening stages:
• Systolic blood pressure <100mmHg;
• Heart rate >90 beats per minute;
• Capillary refill time >2 seconds or peripheries cold to touch;
• Respiratory rate >20 breaths per minute;
• NEWS ≥ 5.
• Passive leg raising suggesting fluid responsiveness.
B- In patients who may be fluid overloaded (HYPERVOLEMIA), one should be looking for:
• Raised Jugular Venous Pressure (JVP)
• Peripheral or sacral oedema
• Pulmonary oedema
C- Ensure that the patient has a fluid input-output chart and daily weight chart commenced
via nursing staff. Also ensure to monitor the patient’s urea and electrolytes (U&Es) regularly,
for any evidence of dehydration, renal hypoperfusion, or electrolyte abnormalities.

N.B. NEWS should be used as an aid to clinical assessment, and is not a substitute for sound clinical judgement. Therefore
a low score is not necessarily reassuring but the higher the NEWS, the greater the clinical risk.
A *RED score refers to an extreme variation in a single physiological parameter and warrants clinical evaluation.

N.B. Hypervolemia can be managed by fluid restriction, diuretics, and dialysis in severe cases.

II. RESUSCITATION
Resuscitation is correction of existing abnormalities in volume status or serum
electrolytes (as in hypovolemic shock).
• Regardless of the etiology of volume depletion, the mainstay of treatment
strategy is a goal-directed resuscitation to restore intravascular volume. This will
contribute to improved cardiovascular function and tissue perfusion.
• As the extracellular space is restored, focus can begin to shift towards
maintaining the current extracellular volume state and restoring intracellular
volume. Electrolyte correction can occur during and after the maintenance
phase is established.
• Correction may be anticipated from the clinical context and verified using
diagnostic tests.
• With adequate tissue perfusion, most pH abnormalities should correct.
• The inverted pyramid below illustrates the focus of acute management in
descending order of priority:

II- RESUSCITATION (Continued)
• Any reduced urine output (<0.5ml/kg/hr.) should be managed aggressively, the fluid
challenge should be urgently administered according to the clinical parameters, including
the urine output.
• The fluid challenge should be either 250ml or 500ml over 15-30mins, depending on the
patient’s size and co-morbidities.
• Fluids can be given in a variety of ways. A large observational research revealed significant
differences in practice. Crystalloids made up 74.3 percent of the fluids utilized in the
challenge, with 0.9 percent saline accounting for 45.9 percent and 53.5 percent balanced
solutions, with colloids accounting for the remaining 25.6 percent (Cecconi, Maurizio, et al.
2015. Fluid challenges in intensive care: the FENICE study).
• Ongoing Monitoring of Fluid Challenge
Frank Starlings Law and SV maximization:
• The relationship between preload and stroke volume is best described by the Frank-Starling
curve. An increased venous return, or increased preload increases ventricular filling and the
end-diastolic volume. This increases the stretch of the cardiac myocyte, which increases
sarcomere length with the resultant increased force of contraction, leading to an increase in
the volume of blood ejected from the heart. For a fluid challenge to be effective, it, therefore,
needs to be of sufficient volume to cause stretch of the cardiac myocytes and test the Frank-
Starling principle. If the heart can accommodate the increased volume, then stroke volume
will increase; otherwise, the volume will remain within the venous system (Bennett, V.A. and
Cecconi, M., 2017. Perioperative fluid management: From physiology to improving clinical
outcomes).

Frank Starlings Law and SV maximization
N.B. When giving the fluid challenge, the following are the signs of fluid responsiveness:
• ≥ 10–15% increase in cardiac output (CO) or stroke volume (SV)
• Increase in systolic blood pressure
• Normalization of heart rate and respiratory rate
• Increase in urine output ≥ 0.5 mL/kg/hour

A number of minimally invasive and noninvasive diagnostic tools are currently available that
allow clinicians to assess volume responsiveness using dynamic procedures that challenge the
patients' Frank-Starling curve. These technologies complement one another; each has a useful
place in the continuum of the resuscitation process.
N.B.
Esophageal Doppler monitoring (EDM) was recently endorsed by the National Health Service as a rational
alternative to central venous pressure monitoring in patients undergoing major surgery.

III- Routine Maintenance (Daily Requirements)
• Providing the patient’s renal function is adequate
and is Clinically Euvolemic, maintenance therapy is
usually undertaken when the individual is not
expected to eat or drink normally for a longer time
(e.g., perioperatively or patient on a ventilator).
• Patients do not just require water, they also need
Na+, K+, and glucose replacing too, particularly if
they are nil by mouth (NPO). There are numerous
ways of calculating the daily requirements of the
following four components and they are invariably
based on the patient’s weight.
• Current National Institute for Health and Care
Excellence (NICE) guidelines suggest the following:
• 1- Water: 25 mL/kg/day
• 2- Na+: 1.0 mmol/kg/day
• 3- K+: 1.0 mmol/kg/day
• 4- Glucose: 50g/day
Based on these required, it is necessary to consider
the fluids that are available for prescription and what
exactly they contain, to be able to prescribe
appropriately.

A Practical Example on Routine Maintenance:
- Let us say that our patient is a 70kg healthy male.
• From the daily requirements mentioned in the previous slide, we need to prescribe fluids
over 24 hours that provide 1750mL of water (70kg x 25mL/kg/day), 70mmol of Na+ (70kg x
1.0mmol/kg/day), 70mmol of K+ (70kg x 1.0mmol/kg/day), and 50g (50g/day) of glucose.
• Consequently, a typical fluid maintenance regimen is as follows:
• First bag: 500mL of 0.9% saline with 20mmol/L K+ to be run over 8 hours
• This provides all of their Na+, ~1/3rd of their K+, and a quarter of their water.
• Second bag: 1L of 5% dextrose with 20mmol/L K+ to run over 8 hours
• This provides a further 1/3rd of their K+, and half of their water, as well as glucose.
• Third bag: 500mL of 5% dextrose with 20mmol/L K+ to run over 8 hours
• This provides the remaining 1/3rd of their K+, and a quarter of their water, as well as
glucose.

IV- Replacement and Redistribution
Aspects to be replaced may include:
• Are there any third-space losses?
• Third-space losses refer to fluid losses into spaces that are not visible,
such as the bowel lumen (in bowel obstruction) or the retroperitoneum (as
in pancreatitis).
• Is the patient losing electrolyte-rich fluid?
Common scenarios of electrolyte imbalances through fluid losses that
may be encountered include dehydration (high urea: creatinine ratio
and high PCV), vomiting (low K+, low Cl–, and alkalosis), or diarrhea
(low K+ and acidosis).

A. Dehydration
Dehydration is largely due to inadequate water intake to meet the body’s metabolic needs. The average
adult has an obligatory intake requirement of 1500 mL per day. This value increases depending on activity
and metabolism. Primary sources of normal fluid loss include urine, sweat, respiration, and stool.
• Dehydration manifests clinically as decreased urine output, dizziness, fatigue, tachycardia, increased skin
turgidity, and fatigue or confusion in severe cases.
• Whenever possible, oral fluid replacement should be attempted. In more urgent situations, IV fluid
replenishment should be based on bolus supplementation of the deficit of fluids and a maintenance
replenishment of obligatory intake requirements.
The fluid deficit can be calculated when the pre-dehydration weight and post-dehydration weight are
known.
• The equation in males is:
Deficit = 0.6 X weight in kilograms X [1-(140/measured Na+)]
• The equation in females is:
Deficit = 0.5 X weight in kilograms X [1-(140/measured Na+)]
• IV fluid replacement options include normal saline (0.9% NaCl), one-half normal saline (0.45% NaCl),
Dextrose 5% in either normal saline or one-half normal saline, and lactated Ringer's solution.
• The choice of replacement fluids is patient scenario-specific and dependent on the electrolyte status of
laboratory evaluation.

B. Vomiting
A man is admitted to the hospital for evaluation of severe
epigastric pain. He has had persistent nausea and vomiting
for 4 days. Upper gastrointestinal (GI) endoscopy shows a
pyloric ulcer with partial gastric outlet obstruction. He has
orthostatic hypotension, decreased serum [K+], decreased
serum [Cl−], arterial blood gases consistent with
metabolic alkalosis, and decreased ventilation rate.
a. Loss of H+ from the stomach by vomiting causes
increased blood [HCO3-] and metabolic alkalosis. Because
Cl− is lost from the stomach along with H+,
hypochloremia and ECF volume contraction occur.
b. The decreased ventilation rate is the respiratory
compensation for metabolic alkalosis.
c. ECF volume contraction is associated with production of
angiotensin II is increased. Thus, the ECF volume
contraction worsens the metabolic alkalosis because
angiotensin II increases HCO3− reabsorption in the
proximal tubule (contraction alkalosis).
d. The increased levels of aldosterone causes increased
distal H+ secretion, further worsening the metabolic
alkalosis.
e. The choice of the IV fluid replacement fluid is
dependent on the electrolyte status of laboratory evaluation
to correct ECF volume contraction.

C. Diarrhea
A man returns from a trip abroad with “traveler’s diarrhea.” He has weakness, weight loss, orthostatic
hypotension, increased pulse rate, increased breathing rate, pale skin, a serum [Na+] of 132 mEq/L, a serum
[Cl−] of 111 mEq/L, and a serum [K+] of 2.3 mEq/L. His arterial blood gases are pH, 7.25; Pco2, 24 mm Hg;
HCO3-, 10.2 mEq/L.
a. Loss of HCO3- from the GI tract causes a decrease in the blood [HCO3−] and, according to the
Henderson-Hasselbalch equation, a decrease in blood pH. Thus, this man has metabolic acidosis.
b. The increased breathing rate (hyperventilation) is the respiratory compensation for metabolic acidosis.
c. As a result of his diarrhea, this man has ECF volume contraction, which leads to decreases in blood
volume and arterial pressure. The decrease in arterial pressure activates the baroreceptor reflex, resulting
in increased sympathetic outflow to the heart and blood vessels. The increased pulse rate is a consequence
of increased sympathetic activity in the sinoatrial (SA) node, and the pale skin is the result of cutaneous
vasoconstriction.
d. ECF volume contraction also activates the renin–angiotensin–aldosterone system. Increased levels of
aldosterone lead to increased distal K+ secretion and hypokalemia. Loss of K+ in diarrhea fluid also
contributes to hypokalemia.
e. Treatment consists of replacing all fluid and electrolytes lost in diarrhea fluid and urine, including Na+,
HCO3−, and K+ by administrating isotonic balanced IV fluid.
e- If more Potassium IV infusion is indicated, it should not be administered exceeding 10 mmol/hour, and
maximum dose in 24 hours should not exceed 200 mmol.

V. Reassessment
• If the patient is receiving IV fluids for resuscitation, reassess the patient using the ABCDE;
monitor respiratory rate, pulse, blood pressure, and perfusion continuously; and measure
venous lactate level or arterial pH and base excess according to the Resuscitation Council’s
guidance on advanced life support.
• All patients continuing to receive IV fluids need regular monitoring. This should initially
include at least daily reassessments of clinical fluid status, laboratory values (urea, creatinine,
and electrolytes), and fluid balance charts, along with weight measurement twice weekly.
• Additional monitoring of urinary sodium may be helpful in patients with high volume
gastrointestinal losses: reduced urinary sodium excretion (<30 mmol/L) may indicate total
body sodium depletion even if plasma sodium levels are normal; however, urinary sodium
values may be misleading in the presence of renal impairment or diuretic therapy.
• If patients have received IV fluids containing chloride concentrations >120 mmol/L (such as
saline 0.9%), monitor their serum chloride concentration daily. If patients develop
hyperchloraemic acidosis, reassess their IV fluid prescription and assess their acid-base
status. Using balanced electrolyte solutions that contain base or base-equivalents and
chloride concentrations that are more physiologic may not only prevent the development of
hyperchloremic acidosis, but may avoid some of the possible harmful effects of associated
with hyperchloremic solutions such as normal saline.

Hourly maintenance is determined by the 4-2-1 rule. This is as follows:
- Maintenance fluid alone:
• 4 ml/kg for the first 10 kg of the patient’s weight
• 2 ml/kg for the second 10 kg of the patient’s weight
• 1 ml/kg for all the rest.
Practical Example on a 42 kg Patient undergoing surgery:
• 40 ml for the first 10kg (4 ml x 10 kg)
• 20 ml for the second 10kg (2 ml x 10 kg)
• 22 ml for the rest (1 ml x 22 kg)
• Total = 82 ml. This would be the hourly needs of the patient.
- NPO extra fluid calculation:
If the same patient had been NPO for 12 hours, he would need 984 ml of fluid to get
caught up (82 ml x 12 hours). This would typically be replaced over 3 hours. The first
hour would be half the volume, while the second and third hours would replace the
remaining volume in quarters. For example:
1st Hour 2nd Hour 3rd Hour
NPO 492 246 246

- Replacing Third Space Losses
• These surgical losses account for fluids that have moved out of the vascular
space. So, depending on the surgery, the losses here range far and wide. It ranges
between 0-10 ml/kg. So, let’s suppose it’s 4 ml/kg. This would mean that you
need to replace about 168 ml for every hour for the above patient (42 kg x 4 ml).
Let’s add it in:
NPO 492 246 246
Hourly 82 82 82
Surgical 168 168 168
Total 742 496 496
- Surgical blood losses can be difficult to estimate but is based on blood volume in
suction canisters, soaked gauzes and laparotomy pads. Surgical blood loss is
replaced in a 3 : 1 ratio of crystalloid to blood loss, and a 1 : 1 ratio if colloid is
administered.

TYPES OF VENOUS ACCESS
There are a variety of options available, and a venous access device must be selected based on
the duration of IV therapy, type of solution to be infused, and the needs of the patient. There
are two types of venous access: peripheral IV access and central venous catheters.
1- Peripheral IV is a common, preferred method for short-term IV therapy in the hospital
setting. A peripheral IV (PIV) is a short intravenous catheter inserted by percutaneous
venipuncture into a peripheral vein, held in place with a sterile transparent dressing to keep
the site sterile and prevent accidental dislodgement. Upper extremities (hands and arms) are
the preferred sites for insertion by a specially trained health care provider.
PIVs are used for infusions under six days and for solutions that are iso-osmotic. They are easy
to monitor and can be inserted at the bedside.
PIVs should be replaced every 72 to 96 hours to prevent infection and phlebitis in adults.

2- Central venous catheter (CVC), also known as a central line or central venous access
device, is an intravenous catheter that is inserted into a large vein in the central
circulation system, where the tip of the catheter terminates in the superior vena cava
(SVC) that leads to an area just above the right atrium. CVCs have become common in
health care settings for patients who require IV medication administration and other IV
treatment requirements. CVCs can remain in place for more than one year. Some CVC
devices may be inserted at the bedside, while other central lines are inserted surgically.
Ultrasound guided placement is recommended to reduce time of insertion and
complications.
A CVC has many advantages over a peripheral IV line, including the ability to deliver fluids
or medications that would be overly irritating to peripheral veins, and the ability to access
multiple lumens to deliver multiple medications at the same time. Central venous
catheters can be inserted percutaneously or surgically through the internal jugular,
subclavian, or via the chest or upper arm peripheral veins. Femoral veins are not
recommended, as the rate of infection is increased in adults. Site selection for a CVC may
be based on numerous factors, such as the condition of the patient, patient’s age, and
type and duration of IV therapy.

POTENTIAL LOCAL COMPLICATIONS OF PERIPHERAL IV THERAPY
Phlebitis is the inflammation of the vein’s inner lining, the tunica intima. Clinical indications are
localized redness, pain, heat, and swelling, which can track up the vein leading to a palpable
venous cord. Mechanical causes: Inflammation of the vein’s inner lining can be caused by the
cannula rubbing and irritating the vein. Chemical causes: Inflammation of the vein’s inner lining
can be caused by medications with a high alkaline, acidic, or hypertonic solutions.
Infiltration occurs when an IV solution is accidentally administered into surrounding tissue.
Signs and symptoms include pain, swelling, redness, skin surrounding insertion site is cool to
touch, change in quality or flow of IV, tight skin around IV site, IV fluid leaking from IV site, and
frequent alarms on the IV pump.
Extravasation is characterized by the same signs and symptoms as infiltration but also includes
burning, stinging, redness, blistering, or necrosis of the tissue.
Hemorrhage is defined as bleeding from the puncture site.
Local infection is indicated by purulent drainage from site, usually two to three days after an IV
site is started.

Theformulaforworkingoutflowratesis:
volume(ml) Xdrop factor (gtts /ml)
=gtts / min (flow rate)
Example:
1500mlIV.Salineisorderedover12hours.Usingadrop factor of 15drops/ ml,how manydropsper
minute needto bedelivered?
=31drops/minute
1500(ml) X15(drop /ml)
---------------------------------------------------------
12x 60 (givesustotalminutes)
---------------------------------------------
time (min)
How nurses calculate IV flow rates ?
Drop factor is the number of drops in one milliliter used in IV fluid administration
(also called drip factor).
Universal equations of IV flow rate and medication dosage calculation
With the advent of smart technology infusion pumps, unit dose preparations and standardized
concentrations by drug manufacturers and pharmacists; medication errors have been greatly reduced.
Even when the technology works well, and pharmacy support is optimal, nurses remain responsible for
safe administration of IV medications directly to patients. To fulfill this responsibility, nurses must
maintain competency in basic medication calculations.

How nurses calculate drug dosage?
Example:
• The ordered dose is Ceftriaxone 750 mg IV. the container contain 1g in a 10 ml vial.
• Youshould convert first g to mg , then :
(D) 750 mg X (V) 10 ml = 7.5 ml
(H) 1000 mg
D
H
x V=Amount to Give
D = dose ordered or desired dose
H = dose on container label or dose on hand
V = form and amount in which drug comes (tablet, capsule, liquid)

41
• Understanding the physiology of human fluid dynamics and the types of intravenous fluid
options available allows the clinician to optimize his/her treatment of surgical patients.
• The most important goal is to maintain hemodynamic stability and protect vital organs
(heart, liver, brain, and kidneys).

A twenty y/o euvolemic female patient, 50 kg,
admitted for Knee surgery.
•NPO after 0300, surgery at 0800.
•Estimated Fluid loss from surgical trauma 4ml/kg.
•3 hr. procedure, 200 cc blood loss.
•Crystalloid fluid will be administered.
Practical Quiz to calculate the estimated intraoperative fluid requirements

Answer
• 40 ml for the first 10kg (4 ml x 10 kg)
• 20 ml for the second 10kg (2 ml x 10 kg)
• 30 ml for the rest (1 ml x 30 kg)
• Total = 90 ml. This would be the hourly needs of the patient.
- NPO extra fluid calculation:
The same patient had been NPO for 5 hours, she would need 450 ml of fluid to get caught up
(90 ml x 5 hours). This would typically be replaced over 3 hours. The first hour would be half the volume,
while the second and third hours would replace the remaining volume in quarters.
NPO 225 112.5 112.5
• Surgical fluids lost out of the vascular space (50 kg x 4 ml)=200ml/hr.
• NPO 225 112.5 112.5
• Hourly 90 90 90
• Surgical 200 200 200
• Total 515 402.5 402.5
Surgical blood loss is replaced in a 3 : 1 ratio of crystalloid to blood loss= 200x3= 600ml.
Total estimated intraoperative fluid requirements= 515+402.5+402.5+600= 1,920 ml.

Fluid balance for surgical patients. Dr. Ahmed khashaba, MD

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