Fluid and Electrolyte Balance IN SURGICAL PATIENTS. By; Col. Abrar Hussain Zaidi. INTRODUCTION. One of the most critical aspects of patient care is management of the composition of body fluids and electrolytes.
Fluid and Electrolyte Balance
Col. Abrar Hussain Zaidi
to understand the fluid and
electrolyte management is;
the extent and composition of the various body fluid compartments.
The main fluid in the body is water
separated from each other by cell membranes.
a. The intracellular compartment - area within the cell.
b. Extra-cellular compartments
1. The interstitial compartment
(between and around cells)
2. The intravascular compartment
Distribution of Water
[in health or disease]
Shifting between the three major fluid compartments of the body and in addition being continuously lost from, and taken into, the person.
WATER INPUT = WATER OUTPUT.
is of prime importance in maintaining health.
water loss from the body (healthy adult)
The mechanisms for the regulation of body fluids:
1- center in the hypothalamus.
2- Hypothalamic-pituitary axis
3- Anti Diuretic Hormone (ADH)
Main regulator of fluid volume and
This is manifest if the body is short of fluid intake (such as during sleep) and results in a concentrated, darker coloured urine of reduced volume.
Absence of ADH occurs when the individual is over-hydrated such as at a party if a lot of beer, cider, alcopops etc. are being drunk Here the urine is dilute, pale or colourless and of high volume.
located in the atria of the heart and the
pulmonary artery and vein
Relay their messages to the hypothalamus
via the vagus nerve
Changes in osmolality
Chemoreceptors in hypothalamus
Chemoreceptors in carotids
Overall, there is near equilibrium
fluid forced out of the capillaries and the fluid absorbed back .
[This is because the lymphatic system collects the excess fluid forced out at the artery end and eventually drains it back into the veins at the base of the neck.]
More complicated by the presence of ion pumps and carriers.
Extra cellular Intracellular Function
acid- base balance
Extra cellular Intracellular Function
Role of hypothalamus and ADH
Other hormones [aldosteron,steroids]
CLASSIFICATION OF BODY FLUID CHANGES
three general categories:
(1) Disorders of volume
(2) Disorders of concentration
(3) Disorders of composition.
Although these disturbances are separate entities –they are interrelated.
For instance, a rise of the serum potassium concentration from 4 to 8 mEq/L would have a significant effect on the myocardium, but it would not significantly change the effective osmotic pressure of the extracellular fluid compartment.
Distributional change An internal loss of extracellular fluid into a nonfunctional space, such as the sequestration of isotonic fluid in a burn, peritonitis, ascites, or muscle trauma
This transfer or functional loss of extracellular fluid internally may be extracellular (e.g., peritonitis), or intracellular (e.g., hemorrhagic shock), or both (e.g., major burns).
In any event, all distributional shifts or losses result in a contraction of the functional extracellular fluid space.
a low level of potassium is called hypokalemia,
a high level of sodium is called hypernatremia.
[the poor kidneys function ].
Measuring electrolyte levels in blood or urine.
Determine the cause of the abnormalities.
Treat the disorder causing the abnormality
Assess the extent of disorder
The extent of volume deficit/ecxcess
The extent of electrolyte def./excess
Assess the normal need for age /weight
Define the mode of correction
A. Volume deficit/hypovolemia/Dehydration—
B Volume excess/hypervolemia/Overhydration—
(for example, giving excessive amounts of intravenous fluids or giving them too rapidly )
Overproduction of ADH caused by ;
pneumonia and stroke and by drugs such as carbamazepine
Intravenous fluids or blood transfusions too rapidly.
Clinical Features / Diagnosis
D/D -chronic venous insufficiency
fluid backs up in the lungs.
worse when a person lies down
The person may wake up shortly after lying
Clinical Features / Diagnosis
a- Restrict the fluids
b-Help the body excrete the excess water.
Diuretics - kidneys to excrete the excess
can be taken by mouth or I/V.
Thiazides- often used first- mild and tend
tohave few side effects.
Frurosemide more potent.
not having enough water in the body.
-olig urea / an-urea]
Older people and Children
More prone to dehydration
Moderate [ 20-30%]
Severe [ 40% or above]
involves replacing lost fluids.
How rapidly -?
Mild dehydration - 2 to 3 liters of water to drink over a
period of a few hours.
Moderate dehydration - Add some salt (sodium) and other electrolytes.
Rehydration formulas (available without a prescription)
Severe Dehydration -INTRAVENOUS REPLACEMENT.
I/V also for those who cannot swallow, and those who are in a coma. If electrolytes must also be replaced, they are given intravenously with the fluids.
when a person drinks a lot of water without consuming enough salt (sodium chloride), typically during hot weather when a person also sweats more.
The sodium level may decrease when large amounts of fluids that do not contain enough sodium are given intravenously.
Diuretics help the kidneys excrete excess sodium and excess water. However, diuretics may cause the kidneys to excrete more sodium than water, resulting in a low sodium level.
caused by :
drugs -anticonvulsants -carbamazepine)
antidepressant -selective serotonin
reuptake inhibitors (SSRIs—such as
muscle weakness, and seizures.
A rapid fall in the sodium level often causes more severe symptoms than a slow fall.
A low sodium level - restored to a normal
gradually and steadily giving sodium and water
caused by ;
Typically--- thirst is the first symptom.
Hypernatremia - Treatment
Oral plain fluids - If the sodium level is
Intravenous fluids - If the sodium level is very high.
Once the body's fluids are replaced, the high level of sodium returns to a normal level.
Mild decrease -- no symptoms.
The body tends to produce less insulin. As a result, the level of
sugar in the blood may increase.
Moderate -- fatigue, confusion, and muscle weakness cramps .
Severe -- paralysis and abnormal heart rhythms (arrhythmias).
[ people who take digoxin [for heart failure), abnormal rhythms develop when the potassium level is even moderately low.
Potassium supplements by mouth as a tablet or liquid or eating foods rich in potassium.
Potassium-sparing diuretic –In People on diuretics - reduces the amount of potassium excreted .
IV-supplement in surgical cases
Drugs that reduce the amount of potassium excreted by
diuretic spironolactone and angiotensin-converting
enzyme (ACE) inhibitors (used to lower blood pressure).
When a person who takes one of these drugs also eats potassium-rich foods or takes a potassium supplement, the kidneys cannot always excrete the potassium.
If the potassium level is very high or is increasing, treatment
must be started immediately.
Then diuretics – Frusemide prevents potassium from being re-absorbed are given to reduce the amount of potassium in the body. These drugs may be given intravenously, taken by mouth, or given as enemas.
Hypocalcemia:result when a disorder such as;
Hypocalcaemia -Clinical Features
weak ness , numbness in the hands or feet.
confusion or seizures
Muscle twitching / tetany +latent tetany
involves taking calcium supplements by
mouth. Or I/V
Treat the Cause.
a-Excessive intake – milk alkali syndrome
b-Exessive brake down of bone and release
of calcium into the bloodstream.
Hyperparathyroidism- the cause is production of an excessive amount of hormone by a tumor in the parathyroid gland.
lung cancers, can also produce “Ectopic parathyroid hormone”.
A slight increase in the calcium level may not cause any symptoms.
A very high level can result in dehydrationbecause it causes the kidneys to excrete more water.
A very high level can also cause loss of appetite, nausea, vomiting, and confusion. A person may even go into a coma and die.
calcitonin and bisphosphonates - given intravenously for short periods of time. [ decrease the amount of bone being broken down /decrease calcium released into the bloodstream.
Paget's disease, bisphosphonates are often taken by mouth
Tumor of parathyroid gland,-surgery
Compositional abnormalities of importance include:
Maintenance fluids should be administered at a rate that is sufficient to maintain a urine output of 0.5–1.0 mL/kg per hour.
Maintenance fluid requirements can be approximated on the basis of body weight as follows:
100 mL/kg per day for the first 10 kg, 50 mL/kg per day for the second 10 kg, and 20 mL/kg per day for each subsequent 10 kg.
Maintenance fluids in general should contain Na+ (1–2 mmol/kg per day) and K+ [0.5–1.0 mmol/kg per day (e.g., D5/0.45% NaCl + 20–30 mmol K+/L)].
Correct the deficits Preexisting volume and electrolyte .
Consideration - duration and route of loss -for extent and
type of fluid and electrolyte abnormalities.
Intr-aoperative fluid management
Replacement of preoperative deficit
maintenance fluids for the duration of the case,
hemorrhage, and “third-space losses.”
Maintenance fluid requirement is calculated .
Acute blood loss replaced with ;
a volume of crystalloid that is three to four times the
blood loss or
with an equal volume of colloid or blood.
Intra-operative insensible and third-space fluid losses
dependent on :
Replaced with an appropriate volume of lactated Ringer's solution.
Small incisions with minor tissue trauma (e.g., inguinal hernia repair) result in third-space losses of approximately 1–3 mL/kg per hour.
Medium-sized incisions with moderate tissue trauma (e.g., uncomplicated sigmoidectomy) result in third-space losses of approximately 3–7 mL/kg per hour.
Larger incisions and operations with extensive tissue trauma and dissection (e.g., pancreaticoduodenectomy) can result in third-space losses of approximately 9–11 mL/kg per hour or greater.
Postoperative fluid management