Fluid and Electrolyte Disturbances

Fluid and Electrolyte Disturbances

• Fluid and electrolyte disturbances is a topic within the Department of Pathology at Rīga Stradiņš University for the academic year 2022/2023.

Key Contributors

• The topic is taught by Prof. Ilze Štrumfa and Katrīne Vecvagare.

Content Overview

• The contents include composition of body fluids, sodium and water balance, osmosis, osmolarity, osmolality, tonicity, sodium disorders, hypovolemia, edema, potassium disorders, and magnesium disorders

Abbreviations Used

• ICF refers to intracellular fluid
• ECF refers to extracellular fluid
• ADH refers to antidiuretic hormone (also called vasopressin)
• ACTH refers to adrenocorticotropic hormone
• RAAS refers to the renin-angiotensin-aldosterone system

Composition of Body Fluids

• Total body water as a percentage of lean body weight varies with age and fat amount, approximating 60% in adults
• Body fluid is divided into two compartments: 55–75% intracellular fluid (ICF) and 25–45% extracellular fluid (ECF)
• Intravascular space consists of plasma water, which is 1/4 of ECF
• Extravascular space consists of interstitium, which is 3/4 of ECF
• Osmotic equilibrium depends on water that flows freely through a membrane barrier permeable to water but impermeable to solutes
• Cell membranes are not permeable to electrolytes in order to keep the solute composition different between the two compartments.
• Starling force regulates fluid movement between intravascular and interstitial spaces across the capillary wall, influenced by capillary hydraulic pressure and colloid osmotic pressure
• When the transcapillary hydraulic pressure gradient exceeds the oncotic pressure gradient, plasma ultrafiltrate shifts into the extravascular space.
• Fluid return to the intravascular compartment happens via lymphatic flow.

Electrochemical Equilibrium

• Intracellular fluid (ICF) and extracellular fluid (ECF) have differing solute concentrations because of sodium-potassium-ATPase, which is an enzyme that maintains high sodium in the ECF and high potassium in the ICF;
• Electrochemical equilibrium controls the environment, since ion flow responds to electrical charge and solute gradient
• The number of positive and negative charges are equal, and in overall balance within each bodily compartment
• Primary cation in extracellular fluid (ECF) is Sodium (Na+)
• Primary cation in intracellular fluid (ICF) is Potassium (K+).

Osmosis

• Osmosis occurs when water spontaneously diffuses across cell membranes between ECF and ICF to achieve osmotic equilibrium and maintain balance
• Cell membranes are freely permeable to water, resulting in equivalent ECF and ICF osmolality
• Major ECF osmoles are sodium, chloride, and bicarbonate
• Major ICF osmoles are potassium, organic phosphate esters (ATP, creatine phosphate, phospholipids)
• Ineffective osmoles include solutes (e.g., urea) that move freely from ECF to ICF without affecting osmotic pressure gradients.

Osmotic Pressure

• Osmotic pressure happens when osmosis is in motion
• The Hydrostatic pressure needed to prevent fluid movement across a semipermeable membrane
• In U-shaped tube with different solute concentrations, fluid moves to the part with higher concentration until equilibrium
• In the blood vessels, hydrostatic pressure comes from gravity and heart with oncotic pressure is the counter force
• The Oncotic pressure (π) is osmotic pressure from impermeable proteins, primary factor effecting capillary vessel (effective osmotic pressure)

Osmolality

• Osmolality is a measure of dissolved particles per kilogram of solvent, primarily water which is the solvent in clinical settings
• Plasma solutes primarily consist of sodium salts with smaller contributions from ions like potassium, calcium, glucose, and urea
• Normal Posm is 275 to 290 mosmol/kg
• It can be calculated using the formula: P[osm] = 2 x [Na] + [Glucose] + [Urea]

Osmolarity

• Osmolarity is defined as the measure of number of number of dissolved particles in each liter of solution

Osmolality versus Osmolarity

• Practically Interchangeable terms for clinical use-cases
• Measurements of Osmolality are performed directly
• Osmolarity is Calculated

Tonicity

• Serum tonicity is also known as affective plasma or serum osmolality
• Serum tonicity is also the physical property that osmoreceptors can sense
• The transcellular distribution of water depends on it
• Reflection of concentration of solutes
• Solutes do not easily cross cell membranes

Classes based on Tonicity

• Hypotonic means the ECF has a lower osmolarity than the cell interior, thus water flows into the cell
• Isotonic means ECF and the cell share identical osmolarity
• No net movement of tonicity happens
• Hypertonic means the ECF has a higher osmolarity than the cell interior, water moves out of the cell

Estimating Tonicity

• The formula is P[tonicity] = 2 x [Na] + [Glucose]

Dehydration and Hypovolemia

• Dehydration and hypovolemia are distinct conditions impacting water and sodium balance;
• Dehydration reduces total body water below normal without proportionate sodium/potassium reduction, elevating plasma sodium
• It is induced by water losses such as diabetes insipidus, osmotic diarrhea, or osmotic diuresis
• Hypovolemia reduces the ECF (water and sodium), caused by unreplaced losses from vomiting, diarrhea, diuretic therapy, bleeding, or third-space sequestration.

Regulation of water and sodim balance

• Alterations in overall water balance help maintain steady plasma tonicity
• The hypothalamus and cardiovascular system are crucial for keeping water correct blood levels by detecting changes in osmolality and blood pressure
• Production of ADH in hypothalamus is regulated by these receptors, is main factor in free water excretion

Osmoregulation vs Volume regulation

• Osmoregulation volume regulation regulate water and volume, respectively
• Plasma volume versus effective Circulating volume

Osmoregulation

• Osmoreceptors versus carotid sinus
• Hypothalamus osmoreceptors versus Afferent glomerular ateriole
• ADH effector versus Atria, Sympathetic nervous system, and Renin
• Water versus Sodium

Regulation Mechanisms Related to Water and Sodium Balance

• ADH (antidiuretic hormone) is produced by the hypothalamus' supraoptic as well as paraventricular nuclei but is kept, and then released, in the posterior pituitary
• The primary role is encouraging reabsorption of the water through permeability on membranes water the medullary collecting tubule, the principle cells

Types of receptors

• V1: -Systemic higher: Smooth muscle, blood vessels, in V1a -ACTH Secretion: anterior pituitary, in V1b
• V2:
  • water absorption enhanced - Renal distal tubules

Osmolality changes relation to waterbalance

• Volume status impacts ADH reaction
• Is slightly lower, steep the response curve - Hypovolemia, with osmolality, influences
• Decreases circulation - Hypervolemia

Regulation in Volume

• Blood Volume in effective levels are affected sodium changes, which change volume
• Carotid Sinus Receptors, sympathetic stimulation of the aortic baroreceptors
• Glomerular arteriole receptors - if BP is decreased, then renin-angiotensin-aldosterone goes up
• Cardiac, ventricle and atrial receptors - atrial and brain natriuretic peptide which lowers blood pressure

Classic Renin Angiotension

• Kidney independently can lower sodium and water so body can maintain correct levels of both
• Increase of water and salt reobsorbption via vasocontriction, lowering body fluids and sodium excretion
• In effective situations is not the isolated events, when body is restored with sodium from outside sources it excreted that
• Kidney regulates how much excretion is what volume, if we take it it, because independent

Homeostatic and Imbalance States

• Body, excrete if excess and restores in other situations
• In isotonic saline : increase sodium activity (and water), excretion would be high if it comes for the high
• Suppressed secretion if water (ADH)
• In ADH, plasma water is low, body is not restoring from diet
• Increase of [sodium] -> volume low excretion urine (high rate water) -> decrease in urine

Combined Plasma Regulation

• Conditions with systemic vascular resistance + cardiac output - Neurohumoral: water, sodium, kidneys and arterial underfilling
• Exemplified 0.9 to 77 milimol - ADH secretion is reduced
• RAAS, and sodium levels lower then excretion Kidney handles regulation for sodium, body excretes it, and salt on its own

Water and Sodium Levels

• Hyponatremia levels increases - plasma ADH, water cells
• Hyper - Plasma decreases: sodium excretion with aldosterone, angiotensis

Sodium Balance

• There are some primary disorders: Too low = hypo, or too high = hyper
• Water balance: too high or hypo, water or hyper
• Then there's some secondary: volume to low = sodium too low, to high=volume to high= edema

Hyponatremia

• Serum sodium < 135 mmol/l
• Hyponatremia is classified by tonicity, volume status, time, and osmolality
• tonicity: hypertonic, isotonic, o hypotonic
• volume: euvolemic, hypervolemic, or hypovolemic
• subacute = short
• osmolality; hyper- or hypoosmolar
• Hyponatremia is hypoosmolar for diagnostic

Types of losses in Hyponatremia: Hypovolemic Causes

• Depletion (water loss is a issue)
• Inappropriate the + CL in urine: renal issues

• 20 mmol is the amount

• High levels is due : the increase of saline, due to kidney can't use it
• GI and fluid problems can increase ADE, insensible too
• <20 mmol and diuretic
• NaCl, Circulating amount of ADE decreased

Low Aldosterone

• With low pressure and levels of Na, deficiency happens
• Na+ increases which highly suggest the problem

Salt Losses

• Intake is reduced: Impaired in function
• Reflux of kidney disease Post issues

Diuretic causes

• Thiazide: polydipsia
• AVP still has full effect since concetration mechansism of kidney is not affected
• TALH loop diuretics Na -Cl issues

Glycosuria/ ketonuri

• Where associated lead : Na
• Execretion
• Increase volume -> sodium is

High Cerebal

• With clinical NA increase in disease, rate is high

Hypervolemic Hyponatremia

• High CL- and water are more than proportional
• So concentration is low: High NA or Low concentration urine can differ disorders

Euvolemic Hyponatremia

• ADE syndrome is frequently seen as problem
• Suspected with 100 osmolality, normal potassium levels- sodium increases over 40
• Cause increase ADE
• Certain drugs affect

Hypernatremia

• Is > 144 milimoles increase on the body
• Combined water +lyte is problem is what causes , it less deadly
• Contrast- In cells are are full in hypernatremia so increase water

Causes of Hypernatremia

• It is either body is not taking in water , or increased sodium from certain medical issue
• Unplaced , increased Skin - low Gi losses
• Diarrhea or
• Urine with Diabetes
• Polydipsia with dibetes

Causes 3 Categories

• Common : No water
• Loss cells water , exersixe
• 3 sodium overload

Unreplaced Water Loss - skin

• Sensible sensible, 500 to 700 for water, ECF glands so hypertonic
• Sodium goes in, skin

Unreplaced Losses - GI issues

• Is low intake
• Osymiotic diarrhea -> volume or hypernatremia
• iso, it has hypo , no

Urine

• Insulin

DI

• AVP degradation is high volume

Hypothlamic

• Congential issue

Water losses

• Caused, eltectrolyte induced. So cells shifts

Sodium Increase

• Unaccitable salt
• Hypo, in brain the. It is not

Features of of sodium, in water leaving

• Neurological. With no clear levels that leads to bad issues
• Weight loss with

Sodium diagnostic

• By measuring of urine/ ADH is that or

Water regulation

• ADH -> Central Nephrogininc and are of the

Hypovolemia (low blood volume)

• Combined water and loss
• Could be rental or nonrenal

Causes of volume Loss Renal

• Endogenous
• osmotic,
• Na/CL excreation is
• hereditary
• Mindo
• Aldosterone sensitive nephron
• Obstructuve distale NaCL

Causes nonrenal volumes

• Gastro
• Ph increase, alksdois or acid if decrease
• Tissue comprtmets

Clinicl Features

• Nispefici
• Hypo

Diagnotixc of clinical

• . 453

Edmea and formation

Causes off Edma

• Kidney
• Preaminstral

Potassium

• 3/4 the body
• 90 in

Regulation

• By kidney
• Potassium levels
• Sodium levels

High Potassium - hperkatema

5.5mmol

Hyopo levels or lower

• Low adostorne or lower
• Acuet or kidneuy

Acute/Chronic

• Chronic in diayslus
• Distal issues

Potassium Clinical

• medical, and is
• nause /
• Muscle is intact,

Clinical features potassium

• Ecg high, of intervals
• And in
• NH is

What Causes

• Basic lab
• Urine for

Definition

• It and blood cells
• And causes

Potassium - metabolic

• potasiousm in cell
• Organic acids-
• Cell via. N

Insulin hyergolcmeu

• Potassium is

The reason for hypo

• Osmolar

Hyper tension

• Kidney
• Primary

Acute and dkhdney

Kddney

• In

Features high of potatisoum

• Medical
• Symtopns

Potassium

• Incease of -poter
• And then

The reason in body

• Urine, to acid

Test

• Gaps can be

Low Mg test

Mg,

• Kidneys -> balance it in .07-. 1.1
• Reabodrbsion-> in leine
• Funxtion is the -> storage cell

Mag test Hyper

1.1 is , the

Main Reason

• Impariment

Caused

• Commo

Tests for this

• Enmeads

Test Low

• Apathy, high test is heart

What can the

• Kidney test show electrolyte