Fluid Imbalance Disorder

Patho--(Exam II)

Total Body Water

is the sum of all the fluids in the body, including intracellular and extracellular compartments. 60% of body is water.

1 liter of body water

2.2 ibs or 1 kg

Intracellular Fluid (ICF)

Fluid within cells

Makes up 2/3 of TBW

Extracellular Fluid (ECF)

All fluids outside the cell

Interstitial Fluid

fluid between cells but not in blood vessel

Intravascular Fluid

fluid found within blood vessels

Transcellular fluids

fluids contained in epithelial lined cavities of the body

The movement of body fluids between intracellular and extracellular fluid depends on….

extracellular fluid levels of water and sodium

The major regulators of sodium and water balance is….

the amount circulating blood volume

Our bodies continuously strive to maintain adequate vascular volume to effectively perfuse tissues

supplies them with nutrients and removes waste

Excess

too much

Deficit

too little

Hyperosmolar

increased of solutes for little amount of water

hypoosmolar

decreased of solutes for a large amount of water

Fluid Homeostasis

the body maintains a balance of water and electrolytes to support physiological functions and overall health

Fluid Intake and Absorption

entry of fluid into the body by any route

Primary route

• Drinking (thirst): regulated by the hypothalamus

• Triggers ↑ in extracellular fluid osmolarity (osmoreceptors)

• ↓Blood volume (baroreceptors, angiotensin II)

• Older Adults: reduces thirst response risk of insufficient intake

Other Routes

• Intravenous (IV)

• GI Tubes and Body cavity infusions

• Subcutaneous or bone marrow infusion

• Rectal intake (enema)

The movement between the vascular and interstitial compartments

fluid distributions

The movement of fluid between the interstitial and intral cellular compartments

fluid distributions

What pushes fluid out of capillaries?

Capillary Hydrostatic Pressure

What pulls fluid into capillaries?

Capillary Oncotic Pressure

What pushes fluid into capillaries?

Interstitial Hydrostatic Pressure

What pulls fluid out of capillaries?

Interstitial Oncotic Pressure

Vascular side (the capillaries)

• Hydrostatic pressure

• Oncotic pressure

Hydrostatic pressure

• the pressure water exerts against the vessel walls

• Pushes fluid out of the blood vessels (vascular space) and into the tissues (interstitial space)

Oncotic Pressure (colloid osmotic pressure)

• Suction forces created by proteins (especially albumin) in the blood

• Pulls fluid back into the blood vessels from the tissues

Interstitial Side (the tissues)

• Hydrostatic pressure

• Oncotic pressure

Hydrostatic Pressure

pushes fluid back into the blood vessels

Oncotic Pressure

sucks fluid into the tissues

• usually very weak because albumin is mainly in the vascular space

Water in capillaries push out into where?

tissues

Tissues in water go into where?

Capillaries

If albumin is low in concentration then…

there is a leakage in fluid into tissue

• Low oncotic pressure

If albumin is high in concentration then…

concertation is held in

• high oncotic pressure

Does electrolytes move across the cell membrane freely?

No, only water does

Water shifting to areas with more particles is

high osmolarity

balancing concentration and the movement of water is

osmosis

What do particles like electrolytes use to cross the membrane?

• diffusion

• facilitated diffusion

• active transport

Tonicity

Concentration of solutes in a solution relative to the inside of a cell

• Not net water movement

• cell remains same size and shape

Hypertonic

• cell shrinks

• ISF is greater inside the cell

Hypotonic

• ISF is less in the cell

• cell swells

Isotonic IV fluids

• fluid and electrolytes replacement

• 0.9% NaCI, Lactated Ringers, DW5

Hypotonic IV Fluids

• Water replacements

• 0.45% NaCI

Hypertonic IV Fluids

• Eloectrolytes replacement

• D10W, 3% NaCI

• 25% Albumin

Serum Osmolarity

275-295 mOsm/kg

What are the two ways to measure fluid excretion?

• Sensible Fluid Loss (measurable)

• Insensible Fluid Loss (not measurable)

Sensible Fluid Loss (measurable)

• Urinary tract: largest volume excreted (0.5L/day obligatory)

Depends on:

• adequate blood pressure to perfuse kidneys (RAAS)

Glomerular Filtration Rate 1mL/kg/hour in adults bowels normal bowel function increases with diarrhea 

Insensible Fluid loss (not measured)

Lungs: exhalation

Skin

• Insensible perspiration 

• Visible sweat (*may count as sensible loss) 

What is the amount of fluid excreted in the urine and controlled primarily by hormones

Hormonal fluid

Antidiuretic hormone (ADH)

• holds water

• not peeing

Aldosterone

• regulates blood pressure and electrolyte balance

• signals kidneys to reabsorb Na and excrete K+

Natriuretic peptides (ANP and BNP)

• cardiac derived hormones

• regulate blood pressure

• fluid volume

• cardiovascular homeostasis

What are significant factors in altering fluid states?

• Emesis (vomiting)

• Tubes in GI tract or other body cavities

• Hemorrhage (bleeding)

• Drainage from fistulas, wounds, or open skin

- Paracentesis (uses needle to remove abnormal excess fluid)

Antidiuretic Hormone (ADH) 

• helps kidneys retain water by increasing the permeability of the renal collecting ducts—which reduces urine output 

• Synthesized by cells in the hypothalamus

• released from the posterior pituitary gland

Factors that increase the release of ADH

• ↑ osmolality of the extracellular fluid 

• ↓ circulating fluid volume

•  Pain, nausea 

• Physiologic/psychological stressors 

High ADH 

• Water reabsorption increases. 

• Produces small, concentrated urine therefore, decreases urine volume and fluid loss.

Low ADH

• Water excretion increases

•  Produces large, dilute urine. 

• Ethanol inhibits ADH (why alcohol increases urination).

Aldosterone

• Produced by adrenal cortex 

• Causes renal tubules to reabsorb sodium and water (saline) and excrete potassium 

• Decreases fluid excretion, but by a different mechanism than ADH 

What is aldosterone major stimuli for its release 

• Angiotensin II 

→ From the renin-angiotensin-aldosterone system (RAAS) 

→ Activated by:

• decreased circulating blood volume

• low blood flow to kidneys

• low BP

• low sodium levels

ADH is the tap water hormone 

• Dilutes body fluids through water retention

Aldosterone is the salt water hormone 

Aldosterone is the salt water hormone 

• Expands extracellular fluid volume through sodium retention in kidneys

Natriuretic Peptides 

• Hormones produced mainly by myocardium 

• Released in response to increased atrial pressure (increased blood volume)

• Oppose RAAS system

• Cause vasodilation and increases sodium AND water excretion, therefore, reducing BP 

What is the Atrial Natriuretic Peptide (ANP) produced by?

atria 

B-type Natriuretic Peptide (BNP) produced by?

ventricles

Albumin

• Plasma protein synthesized by the liver from dietary protein 

• Maintains Blood Volume: By keeping fluid in the vasculature, albumin helps sustain normal blood pressure and tissue perfusion 

• Enhances Oncotic (Colloid Osmotic) Pressure: High concentration of albumin in blood pulls water from the interstitial space back into capillaries, preventing edema

Hypoalbuminemia 

• Low oncotic pressure: fluid may leak into tissues 

• Poor wound healing 

What is Imbalances of Extracellular Fluid Volume for Albumin?

the amount or volume of saline

• Volume deficit/excess 

• Saline deficit/excess 

Imbalances of Extracellular Fluid for Albumin are

Concentration (sodium) of extracellular fluid is the problem   

• Hyponatremia/Hypernatremia 

• Water intoxication/Water deficit

• Hypoosmolality/Hyperosmolality 

ECF Volume Deficits

• Caused by the removal of sodium-containing fluid from the body

• Condition sometimes termed saline deficit 

What causes ECF Volume Deficits?

Removal of a sodium-containing fluid from the extracellular compartment via:

• Fluid Loss: Significant loss of body fluids through vomiting, diarrhea, excessive sweating, or excessive urination (as in diabetes mellitus). 

• Third spacing: In some instances, its not a true fluid loss but rather fluid is sequestered in a “third space” in the body (ex. ascites) 

• Inadequate Intake: Insufficient fluid intake, which may occur due to conditions like anorexia or impaired ability to drink. 

Some ECF Volume Deficit Clinical Manifestation 

• Sudden weight loss 

• Postural (taking blood pressure in different positions) blood pressure decrease with increased heart rate

•  Flat neck veins 

• Lightheadedness 

• Dizziness 

• Syncope 

• Hard stools

• Oliguria or small volume of concentrated urine 

• Decreased skin turgor 

• Dryness of oral mucous membranes 

• Soft sunken eyeballs 

• Longitudinal furrows in the tongue

ECF Volume Deficit Clinical Manifestation (In infants )

• Fontanel may be sunken

• Neck veins are not reliably assessed in infants

ECF Volume Excess 

• Amount of extracellular fluid is abnormally increased 

• Vascular and interstitial areas have too much fluid

What causes ECF Volume Excess?

• addition or retention of isotonic saline; sometimes termed saline excess 

• excessive secretion of hormone aldosterone—-—causes kidneys to retain saline, which may lead to ECV excess

•  compensatory mechanism that happen along a chronic heart failure

• excessive intravenous infusion of sodium-containing isotonic solutions

• renal retention of sodium and water

ECF Volume Excess Clinical Manifestations 

• Manifestations of fluid volume overload

→  Bounding pulse 

→Neck vein distention (JVD)

→Crackles in dependent lung fields 

→Dyspnea 

→Orthopnea 

→Pink frothy sputum of pulmonary edema

ECF Volume Excess Clinical Manifestations 

• Sudden weight gain 

→ Sensitive measure of ECF volume 

→1L = 1 Kg (2.2 lbs) 

• Edema

ECF Volume Excess Clinical Manifestations (In infant )

• Bulging fontanels 

• Assessment of neck veins is not effective in infants

What is Interstitial Fluid Volume Excess: Edema 

• Accumulation of fluid within the interstitial spaces (tissue) 

What causes Interstitial Fluid Volume Excess: Edema

•  Increase in capillary hydrostatic pressure 

• Losses or diminished production of plasma albumin 

• Increases in capillary permeability 

• Lymph obstruction (lymphedema) 

Sodium (Na+)

• Normal: 135-145 mEq/L

Function 

→Aids in balancing fluid volume 

• More prevalent in ECF 

• Regulating ECF volume 

• Water follows sodium 

 → Plays a role in normal nerve and muscle function

Hyponatremia

• A serum sodium concentration below the lower limit of normal <135 mEq/L

• Extracellular fluid is more dilute than normal (hypoosmotic) 

What causes hyponatremia?

• Factors that produce a relative excess of water in proportion to salt in the extracellular fluid 

• Cells swell due to osmosis 

Two primary causes of hyponatremia?

→  gaining more water than sodium 

• Prolonged or excess release of ADH 

• Water intake that exceeds normal limit 

→ loosing more sodium than water

• Diuretics 

What are mild CNS dysfunction? (hyponatremia)

• Malaise 

• Anorexia 

• Nausea 

• Vomiting 

• Headache

What are severe central nervous system dysfunction? (hyponatremia)

• Confusion 

• Lethargy 

• Seizures 

• Coma 

• Fatal cerebral herniation

Hypernatremia

• Serum sodium concentration above upper limit of normal (> 145 mEq/L)

• Extracellular fluid is too concentrated (hyperosmotic) 

What causes hypernatremia?

• Factors that produce a relative excess of salt in proportion to water in the extracellular fluid 

• Cells shrivel due to osmosis 

What are two causes hypernatremia?

-A gain of relatively more salt than water

•  Enteral feeding 

• No access to water 

 - A loss of relatively more water than salt 

     → Deficient release of ADH 

              -Osmotic diuresis 

Mild central nervous system dysfunction (hypernatremia)?

• Thirst 

• Oliguria 

• Confusion 

• Lethargy

Severe central nervous system dysfunction (hypernatremia)?

• Seizures 

• Coma 

• Death 

Clinical Dehydration

• Fluid out put is more than ECF volume (which decreases)

• There is a low volume of ECF returning to the heart

• There us a decrease in stroke volume and BP

• poor perfusion

What causes clinical dehydration?

• Vomiting

• Diarrhea

• Decreased Fluid Intake

• Third-spacing

• Polyuria

• Burns

What are the Dehydration Clinical Manifestation EVC deficit?

• Postural hypotension 

• Rapid, thready pulse 

• Sudden weight loss 

• Lightheaded, dizzy, or syncopal on standing 

• Flat neck veins 

• Decreased skin turgor 

• Dry mucous membranes, furrows 

• Hard stools 

• Soft, sunken eyeballs 

• Decreased skin turgor

What are Dehydration Clinical Manifestation CNS dysfunction? 

• Thirst 

• Oliguria 

• Confusion 

• Lethargy 

• Seizures 

• Coma

•  Death

Wat happens during Syndrome of Inappropriate ADH   (SIADH)?

the brain is drowning

• Excess ADH → increased water reabsorption in kidneys → fluid retention and dilutional hyponatremia 

• ECF volume excess 

• Hyponatremia 

What cause Syndrome of Inappropriate ADH (SIADH)?

• Malignant tumors (lung) 

• Pulmonary tuberculosis

•  Drug induced

What happens to the brain during Diabetes Insipidus (DI)?

The brain is salty

• There is an insufficient (central DI) ADH or kidney’s inability to respond to ADK (nephrogenic DI) excess water loss

• ECF volume deficits

• Hypernatremia

What causes Diabetes Insipidus (DI)?

• Idiopathic

• Surgical/nonsurgical brain trauma

• Hypophysectomy (surgical removal of the pituitary gland)

What are some clinical manifestations of Diabetes Insipidus (DI)?

Excessive urination

Excessive drinking

Same as clinical dehydration

• Central DI: desmopressin (synthetic)

• DI: address underlying cause, low-salt diet, possible thiazide diuretic