Capillary Fluid Exchange: Water Movement Explained

• The document discusses fluid, electrolyte, and acid-base imbalances, focusing on the roles of water, electrolytes, and associated regulatory mechanisms within the human body
• These notes are a review of concepts and processes surrounding these elements

Water in the Body

• Water is crucial for homeostasis as it stabilizes the internal environment, balances fluids, and supports normal body functions
• Metabolic Reactions rely on water as their medium, allowing for digestion and energy production
• Nutrients, oxygen, and waste are efficiently transported via water in the blood and lymph
• Water in joints and other body parts facilitates smooth body movement

Fluid Compartments

• Intracellular Compartment (ICF) holds fluid inside cells and makes up a large portion of the body’s total water
• Extracellular Compartment (ECF) is fluid outside cells, including intravascular fluid (IVF) in blood vessels, interstitial fluid (ISF) between cells, cerebrospinal fluid (CSF) around the brain and spinal cord, and transcellular fluids
• Transcellular fluids include digestive secretions, joint fluid, and eye fluid
• In elderly women, water content is reduced to ~45% of body weight

Movement of Water

• Balance is key; the amount of water entering the body should equal the amount leaving, and is achieved through fluid intake and loss
• Eating solid food and drinking fluids account for water intake
• Water is lost though urine, feces, perspiration (sweating), exhaled air

Balance of Water and Electrolytes

• Thirst is triggered by osmoreceptors in the hypothalamus detecting the body needing more water
• Antidiuretic Hormone (ADH) helps the kidneys conserve water by increasing reabsorption and preventing dehydration
• Aldosterone increases kidney reabsorption of as sodium and water, increasing blood volume and maintaining electrolyte balance
• Heart cells (myocardial cells) produce atrial Natriuretic Peptide (ANP) and T-type Natriuretic Peptide, regulating fluid, sodium, and potassium balance

Circulation via Filtration and Osmosis

• Water moves through filtration and osmosis
• Filtration refers to fluid movement due to pressure
• Osmosis involves water movement from areas of lower to higher solute concentration

Membrane Permeability

• Water movement relies on cell membrane permeability, enabling easier transfer between areas

Water Movement Between Compartments

• Hydrostatic Pressure, created by fluid volume, pushes water out of capillaries into tissues
• Osmotic Pressure pulls water back into blood vessels, influenced by solutes like salt or proteins

Movement of Water and Solutes

• "Filtration" indicates movement of water and solutes out of the capillary and into the ISF
• "Osmosis" indicates water movement back into the capillary from the ISF, driven by solute concentration differences

Clinical Takeaways

• Filtration pushes/reabsorption pulls, with each effect being driven by hydrostatic pressure
• The balance between hydrostatic and osmotic pressures determines overall fluid direction/magnitude
• Imbalances in the Starling forces are clinically significant, especially with edema, dehydration, and kidney function

Capillary Exchange

• Nutrients, oxygen, and carbon dioxide are exchanged between the blood and tissues through capillary exchange, across the smallest blood vessels, aka capillaries
• Microcirculation governs exchange through hydrostatic pressure and osmotic pressure interplay

Capillary Exchange: Mechanisms

• Filtration: driven by hydrostatic pressure at the arterial end pushing water, glucose, amino acids, and ions, out of capillaries into interstitial fluid
• Diffusion: driven by concentration gradients through the capillary, transferring oxygen from blood to tissues and carbon dioxide from tissues to blood along with lipophilic molecules
• Osmosis: protein concentration (albumin) drives osmotic pressure at the venous end, bringing ISG water back into capillaries
• Active Transport: cellular energy (ATP) moves ions, glucose, and amino acids throughout the capillary, against concentration gradients to maintain electrolyte balance etc

Other Capillary Exchange Elements

• Blood flows out through the venule
• Substances can move between the ISF and ICF
• Metabolic waste products from cells enter the capillary for transport to excretory organs
• Filtration and osmosis balance blood and tissue water levels, diffusion exchanges gases/solutes, and active transport moves specific gradient substances via exchange imbalances
• Fluid and edemas result from exchange exchange processes
• Nutrient delivery, waste removal can be hindered or inflammation is affected by capillary exchange disruptions

Edema

• Too much interstitial fluid leads to tissue swelling
• This fluid buildup causes localized/generalized tissue swelling
• Excess fluid can reduce blood flow to tissues, affecting their function, trapping medications

Edema: Causes

• Increased capillary hydrostatic pressure is caused by too much fluid being pushed out of the capillaries, higher blood pressure, venous obstruction, or heart failure
• Low plasma protein levels reduce osmotic pressure, making it difficult to pull fluid back into the bloodstream.
• Blockage of lymphatic vessels prevents fluid from draining away, and inflammation increases capillary leaks, leading to fluid accumulation

Edema: Visual Summaries

• Normal capillary filtration demonstrates a normal hydrostatic/osmotic pressure balance
• Hydrostatic pressure - 30mmHg (arterial) / 10mmHg (venous)
• Osmotic pressure - 25mmHg
• Filtrate removed via Lymphatic Vessel - increased arterial pressure, venous system backups, and reduced heart ability cause increased pressure
• Increased protein in the ISF, due to inflammation or burns, draws more fluid from the capillary
• Tumors, surgery, infection, or parasitic filariasis block drainage Low albumin or reduced synthesis affect the capillary by impairing reabsorption

Edema: Other Info

Decreased albumin production or increasing albumin loss reduces or limits fluid being redrawn into the capillary Local edema is swelling in one spot/area, from the tissues, usually due to lymphatic vessels failing to return lost fluid and protein Increased capillary permeability due to inflammatory or infections Swelling in a local area (pale/red) or throughout the body (pitting with fluid/no fluid moving to the side) Functional impairment (restricted join, reduced breathing, and/or heart relaxation) Pain or Pressure on nerves cause headaches from cerebral movements or stretching in kidneys/liver Ischemia (lack 02) leading to tissue breakdown Accurate impressions become difficult due to swelling with ill fitting dentures Skin is more vulnerable to pressure, causing tissue breakdown

Fluid Deficit - Dehydration

Insufficient body Fluid through lack of intake or excessive volume exits. This volume changes are measured as a change in body mass, with a quick BM reduction being indicative of dehydration. Infants/Older Adults are have an reduced ability to handle fluid imbalances Water is lost with electrolytes or proteins, which are used for body functioning Both vomiting and diarrhea cause loses of Water Excessive sweating causes depletion of Na/Water Diabetic Ketoacidosis causes high excretion of fluids/electrolytes/glucose in urine

• Insufficient water Intakes affect Older adults (or impaired ability to hydrate) Use of concentrates dehydrates infants Dryness inside the mouth feel due to insufficient saliva and decreased skin Turgor (wont spring back to normal due to lowered elasticity) Lower blood pressure/weakened pulse leading to fatigue Hematocrit (of Red blood cells) become concentrated with lessened fluid count Confusion is an effect on the brain, leading to lowered mental functioning in severe cases. Attempts through through signaling of thirst, or increasing the BM pressure to combat fluid depletion using high heart rate and constricting blood vessels.

Fluid Shifts out of Body/ Cavities and Tissues

These shifts CAN'T Return to Blood Vessels if located in a cavity like the abdomen Too little blood volume, and the fluids pulls more 02 to the site Infection, Bacteria, or Permeability of capillaries affect the water levels

Electrolytic Imbalances

In adults, water content is 48-52%. Intracellular fluid makes more than 55% Extracellular is a combo of fluids which comprise of 45% body mass Loss of water (with diarrhea, etc) can also lower proteins Potassium and sodium maintains the balance of nerve and electrolyte regulation, and can cause confusion of unconsciousness if depletion takes hold

Sodium + Electrolytic Activity

Sodium is the primary Cation for Extracellular Fluid, moving to maintain hydration. Moves via the Na/K+ pump Sodium can deplete through Sweating, throwing up Diuretics cause increased urine output/loss of hydration Aldosterone helps retain low water through Hormonal processes ADH causes the kidneys to keep water, while excessive ADH dilution causes Na in the water. Diuresis by Increased urination/ excessive water intakes Low Na + fatigues, causing fluid loss in compartments. Low Electrolytic pressure = fluid is shifted into cells, and is usually because of loss of water

Hyponatremia

Causes the loss of the thirst mechanism where it is unable to replace lost water that is needed Diarrhea Breathing rapidly, which cases loss of fluids Ingestions of Na through food are not able to retain balance though elevated BM pressure Sodium is in high concentration outside of cell so it allows K concentration to be high inside

Hypernatremia

High BM pressure (38%) due to excess of electrolyte use There has to be more P+ cells inside than outside Electrolytes move through the fluid for various physiological purposes Deficit causes electrolyte increase through capillary failure Edema can also lead to imbalances

Potassium Overview

Key roles through Positive Ion usage inside and outside, usually regulated in urine or with the kidneys Acid base balance and pH levels are connected to electrolytes (acidic environments often lead to excessive H+ increase outside, requiring H+ and K to work together to regulate the influx. This process usually lowers the levels of hydration

Sodium and Potassium's Function

Negative charge on the outside while Positive charge is inside to move. Na influx inside the ell K efflux outside of cell

Hypokalemia vs. Hyperkalemia Overview

• Hypokalemia occurs when serum potassium (K+) levels are below 3.5 mEq/L and can be caused by excessive losses through diarrhea and diuretics and in state where electrolyte increased through diuretics etc.
• Hyperkalemia occurs when serum potassium (K+) is greater than 5 mEq/L from excessive or impaired kidney processes, and is is a seriously potent effect on BM function

Calcium Imbalance

Helps with nerve + BM function Regulated through parathyroids and released via food Deficient Levels: More permeability and muscle stimulation is at the area Heart + BM contractions Excess Levels: Increased loss of function or loss of muscle tone at those areas (lack of appetite or nausea)

Phosphate, Chloride, and Magnesium Imbalances

• Phosphate assists with metabolism for energy usage
• Chloride usually accompanies excess sodium (Hypocholremia)
• Magnesium balances out for all cells where needed.

The Chloride Shift Cycle of Bicarbonate and CO2:

Vomiting decreases fluid. Which decreases Cl levels. Which increases HCO levels to be Alkaline instead due to increase in red blood cells. This keeps the Electrolytes at equilibrium by moving chloride inside the blood.

Acid-Base Balance

• Acid-base balance is essential to staying at a blood pH that is between 7.35 to 7.45 (death occurs if the pH falls far outside this range)

Acidosis vs. Alkalosis

• Acidosis has a higher H, while Alkalonisis has decreased H.
• The body regulates this at certain levels and also balances with electrolytes through the use kidney and BM system

• This is accomplished through several processes like :Increased production of acids/Impaired kidney/Respiratory functioning.

• Bicarbonate helps reuptake. Alkalosis + H/Electolye regulation balances through hyperventation due to excessive CO2

Alkalosis Types

There is insufficient ADH if at all through the usage for diabetes A lack of water leads to loss of electrolytes, which need to get balanced with enough water intakes

Respiration Overview

• Acid base levels and pH affect respiration, O2 and CO2 levels. Hyperventilation causes decreased CO2 levels Rapid short time increase of acidity which limits CO2 Kidneys reabsorb then excrete

Edemic Problems

Hyponatremia can also be a problem that has problems in Fluid Imbalances due to BM in the bloods stream due to low volumes, shifting too much H2 inside the cells Hyperatremia is a problem with the cells being swelled up, affecting their various functions due to high H volume inside vs outside

HypoKalemia Problems (Low levels)

Decreased aldosterone due to the BM balance Diarrhea or drugs cause an increase of loss Cardiac + BM and fatigue issues begin to occur from nerve disfunction due to H/K imbalance

HyperKalemia

BM damage and or cell damage causes a leak from cells that can be dangerous though paralysis. So it works with H/K concentration balance Decreased BM pressure needs to increase hydration to combat the reduced volume and also regulate nerve processes Hyper + Hypo = loss of N/BM functioning

Distribution Electrolytes

Increased H2 in the flood + increased K from cells. Causes high K concentration BM level, which leads to high BM concentrations to get excreted Imbalance can cause disruption of the startlight (BM disruption), which affect hydration. BM must increase K absorption to regulate everything back to homeostasis

Hypo/Hyper Calcimia

Hyoparathyroidim increases risk, where dietary factors impair and Renal failures effect absorption Neuromusclar disfunciton and weak contractions begin because of this problem This is caused by overactive thyroid and stress

Nephron and BM review

Intercalated cells inside (Kidneys) secreate BM to balance Collecting Duct regulates fluid and its balances in both Na and K

Gi disorders

dysphasia = issues with ability to swallow Can be an issue through: Neuromuscular problems of food fluidity from upper digestive tract. Also the loss of functionality between both stomach and or esophagus structure, muscle use The Esophagus has nerve pain due to acid levels, which are caused by powerful contractions and infections due to lack of nutrients. Caused by poor bowel problems resulting in an improper usage in BM/Nutrients

Intestines

The small section, when inflamed by infection, causes BM contractions Gas issues are from Swallows, and Bacterial Digestive actions of stomach acid (ant-acids) usually. High Flatus and excessive wind are Bacterial breakdown foods

Gall Bladder

Functions as structure to be the path to BM and more important function. These processes must be properly completed (or can cause severe medical problems) Dysphagia is a result of high inflammation. Bowel restrictions can cause high BM problems that need special care and may lead tissue damage Lipids and B salts that all come together for proper function.

Gallstones:

Three Stages through Saturation of too high Cholesterol + Nucleation of BSalt in the lymph nodes This leads to sludge build up + then causes more saturation BM becomes disrupted with a lack of good bacteria and may or may not show for a large period of time. But the stones will cause blockage. Too much choleserol leads to problems with the blood stream as well In summary:

Gi/Hormonal levels often lead to increase/decrease electrolyte levels Various hormones and bodily signals or reactions can have effects

High BM pressure issues increase H2O levels to compensate to maintain proper heatlh Increased fluid/high potassium increases cell function to the brain (seizures, headaches) In extreme situations or if not reated, extreme dehydration or health problems occur

Various medical procedures must undergo or balance to restore everything to proper function