fluids & electrolytes imbalances
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Fluids & Electrolytes Imbalances
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Body Fluid Compartments• 2/3 (65%) of TBW is intracellular fluid (ICF)• 1/3 extracellular fluid (ECF)
– 25 % interstitial fluid (ISF)– 5-8 % in plasma [(IVF) intravascular fluid]– 1-2 % in trans-cellular fluids: CSF, intraocular
fluids, serous membranes, and in GI, respiratory and urinary tracts (third space)
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• Fluid compartments are separated by membranes that are freely permeable to water.
• Movement of fluids due to:– Diffusion– Osmotic pressure– Active transport– Hydrostatic pressure– Reabsorption
Movement of Fluids
DIFFUSION
• Solutes shift from an area of greater concentration to an area of higher concentration
• Passive process
OSMOSIS
• Movement of fluid across membrane from a lower solute concentration to a higher solute concentration
• Passive process
ACTIVE TRANSPORT• Solutes move from an area of lower concentration to an area of higher concentration
• Process requires energy
Hydrostatic Pressure•Capillary filtration
•Movement of fluid through capillaries results from blood pushing against walls of the capillary. It forces fluids and solutes through the capillary wall
REABSORPTION
• Prevents too much fluid from leaving capillaries no matter how much hydrostatic static pressure is inside them
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Homeostasis
Maintained by:– Ion transport– Water movement – Kidney function
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TONICITY:Isotonic – A solution that
has the same solute concentration as another solution to which it’s being compared • i.e. sodium in blood vs.
0.9% NSS
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• Hypertonic - A solution that has a higher solute concentration than another solution to which it’s being compared• Dextrose 5% in
NSS
TONICITY:
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• Hypotonic - A solution that has a lower solute concentration than another solution to which it’s being compared• 0.45%NSS
TONICITY:
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BalanceFluid and electrolyte homeostasis is maintained in the body• Neutral balance: input = output• Positive balance: input > output• Negative balance: input < output
Fluid Gain & LossRoutes of Gain and Loss:
Kidneys (urine)
Skin (perspiration)
Lungs (respiration)
GI Tract (feces)
Fluid Gain & LossAverage Intake of Body H2O
= 2600 ml/day
Liquid = 1500 mlSolid Foods = 800 mlOxidation = 300 ml
Fluid Gain & LossSensible Loss• Fluid loss that can be measured
– Urination– Defecation– Bleeding– Wound drainage– Gastric drainage– Vomiting
Fluid Gain & LossInsensible Loss• Fluid loss that cannot be measured
– Perspiration– Respiration– Changes in humidity levels, respiratory rate
and depth, and fever affect insensible loss
Fluid Gain & LossAverage Output of Body H2O
= 2600 ml/day
Urine = 1500 mlFeces = 100 mlLungs = 400 mlSkin = 600 ml
Balancing SystemsRenal System (kidneys)
–RF = difficulty maintaining fluid balance–Na+ & K+ are either filtered or
reabsorbed via the renal system
Balancing SystemsAntidiuretic Hormone (ADH)
–Water-retaining hormone–Hypothalamus senses low blood volume
& increased serum osmolality; triggers its release from the pituitary gland
–Prompts kidneys to retain H2O– Increases concentration of urine
Balancing SystemsRenin-Angiotensin-Aldoseterone
System (RAAS)–Release of renin triggered by low
pressures–Angiotensin II potent vasoconstrictor
and triggers the release of aldosterone from the adrenal cortex
–Aldosterone = fluid retention and secretion of K+; triggers the thirst center
Balancing SystemsAtrial Natriuretic Peptide (ANP)
– Released when atrial pressures increase– Opposes the RAAS (shuts it off)– Key Functions of ANP:
• Suppresses serum renin levels• Decreases aldosterone release• Increases glomerular filtration rate (excretion of
Na+ and H2O)• Decreases ADH release• Decreases vascular resistance by causing
vasodilation
Balancing SystemsThirst Mechanism
– Simplest mechanism in maintaining fluid balance
– Increases after even small fluid loss– Increase in salty foods dries mucous
membranes, which stimulates the thirst center in the hypothalamus
Hypovolemia blood volume caused by internal/external bleeding,
fluid losses, or inadequate fluid intake.
(AKA: Fluid Volume Deficit (FVD) or Extracellular Fluid Volume Deficit (ECFVD))
HypovolemiaFVD occurs when loss of ECF exceeds intake of fluid.
Hypovolemia or FVD ≠ dehydration
Dehydration is loss of H2O only!!
FVD → Fluid Loss = Electrolyte LossRatio Remains the Same (usually)
HypovolemiaSigns & Symptoms
Weight Loss Skin TurgorOliguriaConcentrated UrinePostural HypotensionWeak, rapid pulseFlattened Neck Veins
TempCool, clammy skinThirstAnorexiaNauseaMuscle WeaknessMuscle Cramps
HypovolemiaTreatment:
Infusion of Isotonic IV solutions: Hypotensive patients
Infusion of Hypotonic IV solutions: Normotensive patients
Hypovolemia d/t blood loss: Blood transfusion
HypervolemiaECF → H2O gain is balanced retention of sodium.
• Usually 2 retention of Na+
• Concentration of sodium to H2O is balanced. • serum sodium levels WNL (usually)
(A.K.A. Extracellular Fluid Volume Excess (ECFVE))
HypervolemiaHormonal Imbalances - ADH
• Can occur 2 heart failure, renal failure, or cirrhosis.
• Fluid overload r/t administration of excessive IV fluids
• Dietary: Excessive sodium intake
HypervolemiaSigns & Symptoms
JVDEdemaCracklesTachycardia B/PWeight Gain Urine OutputSOB/Wheezing
HypervolemiaTreatment: Treat the underlying
cause!!!
• Renal Failure: dialysis• Heart Failure: diuretics, etc.• Dietary: low-salt diet and/or fluid
restriction• Discontinuation of IV infusions
Sodium
Reference Range:135 – 145 mEq/L
Sodium• Accounts for 90% of ECF cations.
• Almost all Na+ is found in ECF; 10% in ICF.
• Na+ attracts fluid + helps preserve ECF volume/fluid distribution.
• Na+ helps transmit impulses in nerve/muscle fibers, & combines w/ Cl- & HCO3 to regulate acid-base balance
Sodium• Excreted mainly via the kidneys (GU)
– Also via the GI tract and perspiration
• Increased Na+ levels trigger thirst & ADH
• Sodium-Potassium pump helps maintain normal Na+ levels– Pump also creates an electrical charge for both cardiac &
neuromuscular function
Sodium
Hyponatremia is Na+ < 135
Hypernatremia is Na+ > 145
Hyponatremia
Causes an osmotic fluid shift from plasma into brain cells
HyponatremiaSigns & Symptoms:
Nausea/VomitingHeadacheMalaiseConfusionDiminished ReflexesConfusionConvulsionsStupor or Coma
HyponatremiaCauses:
• ↑ Vasopressin/ADH• SIADH• Adrenal Insufficiency• Diuretics• Hypervolemia• Liver Failure• Heart Failure
HyponatremiaTreatment:• Administration of oral or IV Na+ (3%) Supplements• Encourage foods high in Na+
• Fluid restriction• Monitor Neuro Status• Monitor for Arrhythmias• Normovolemic hyponatremia
– Vaprisol (conivaptan) – IV infusion– Samsca (tolvaptan) - PO
HypernatremiaCauses:• Dehydration/Hypovolemia• Diabetes Insipidus• Ingestion of Hypertonic Solutions• IV Infusion of Hypertonic Solutions• Cushing’s Syndrome• Hyperaldosteronism• Loss of pure water (excessive sweating or respiratory infections)
HypernatremiaSigns & symptoms
• Thirst• Lethargy • Neurologic Dysfunction (d/t dehydration of brain cells)
– Irritability– Weakness– Seizures– Coma
• Edema• Decreased vascular volume
HypernatremiaTreatment:• Administration of IV Fluids
– (Isotonic Salt-Free)• Encourage foods low in Na+
• Push P.O. Fluids• Monitor Neuro Status• Monitor for Arrhythmias
Potassium
Reference Range:3.5 – 5.0 mEq/L
Potassium
Potassium is gained by intake and lost by excretion.
If either is altered, hyperkalemia or hypokalemia may result!
Regulated by aldosterone and insulin
PotassiumPotassium levels directly affect cell, nerve, &
muscle function:– Maintains electrical neutrality and osmolality of cells– Aids in neuromuscular transmission of nerve impulses– Assists skeletal & cardiac muscle contraction and electrical
conductivity– Affects acid-base balance in relationship to H+ (another
cation)
Potassium
Hypokalemia is K+ < 3.5
Hyperkalemia is K+ > 5.o
HypokalemiaLevels < 3.5
Mildly Low Levels usually asymptomatic
If level < 3.2, usually accompanied by symptoms
HypokalemiaCauses of Hypokalemia:
Increased Urine Output Malnutrition
Vomiting and/or DiarrheaHypomagnesemia
DKA
Hypokalemia
May be a result of acid-base imbalances = alkalosis
• In alkalosis, K+ moves into cell to maintain balance, -may lead to hypokalemia
Treatment• Oral or IV Potassium Chloride
Replacement• D/C or adjust medications that
may cause hypokalemia• Reverse alkalosis, if cause• Monitor closely for arrhythmias• Monitor Respiratory Status• Monitor LOC• Monitor GI symptoms
HyperkalemiaLevels > 5.0
Mildly elevated levels usually asymptomatic
Levels > 8.0Disturbances in cardiac conduction occur
HyperkalemiaCauses:
• Renal Failure• Meds (ACEIs, ARBs, K+ sparing diuretics, NSAIDs)• Addison’s Disease• Aldosterone Insufficiencies• Dig Overdose• Beta-Blocker Therapy
HyperkalemiaMay be a result of acid-base imbalances =
acidosis
In acidosis, excess [H+] move into cells & push K+ into ECF, - may lead to hyperkalemia as K+ moves out of cell to maintain
balance.
HyperkalemiaTreatment:Medications:
– Cation-exchange resins (bind with K+ and excreted via feces)– IVP insulin & glucose (K+ binds to insulin)– IV Ca++ (protect the heart from the effects of hyperkalemia)– Sodium bicarbonate (to reverse acidosis)– Diuretics (non-K+ sparing)– Beta2 Adrenergic agonists (epinephrine, albuterol)
D/C meds that may cause hyperkalemiaRestrict foods with K+
Dialysis for renal failure Monitor closely for arrhythmiasMonitor Blood PressureMonitor GI symptoms
Calcium
Reference Range:8.5 – 10.5 mg/dl
Calcium• 99% Ca++ in bones; 1% in serum/soft tissue (measured in
blood serum levels)• Found in both ECF & ICF• Can be measured in 2 ways:
– Total serum calcium (total Ca++in blood)– Ionized calcium level (various forms of Ca++ in ECF)
• 41% ECF Ca++ is bound to protein; 9% bound to citrate or other organic ions
Calcium• Ca++ functions in the following ways:
– Responsible for formation of teeth & bones– Helps maintain cell structure & function– Plays a role in cell membrane permeability & impulse
transmission– Affects contraction of cardiac, smooth, and skeletal muscle– Participates in blood-clotting process
CalciumCa++ helps K+ & Na+ move into and out
of cells in the sodium-potassium pump mechanism
HypocalcemiaCauses:• Vitamin D Deficiency
– Vitamin D promotes Ca++ absorption in intestines, resorption from bones, and kidney resorption all of which raise Ca++ levels
• Deficiency of parathyroid hormone– Calcitonin, secreted by PTH, helps regulate Ca++– s absorption of Ca++/enhances excretion by kidneys
• Inefficient parathyroid hormone
HypocalcemiaManifestations• Tetany• Laryngospasm• Cardiac Arrhythmias• EKG Δ’s → prolonged QT interval
HypocalcemiaManagement…• PO or IV calcium replacement(depends on severity of symptoms or deficiency)• Vitamin D supplement• Encourage foods high in calcium
HypercalcemiaCauses:• Excessive calcium release• Increased intestinal calcium absorption
** Decreased renal calcium excretion **
HypercalcemiaManifestations:• Cardiac Arrhythmias• EKG Δ’s → shortened QT interval
HypercalcemiaSevere Hypercalcemia (> 15mg/dl)
is a…
Medical Emergency
May result in
Coma or Cardiac Arrest
HypercalcemiaSigns & Symptoms
FatigueDepressionConfusionAnorexiaN/VConstipationPancreatitisIncreased Urination
HypercalcemiaTreatment…• Hydration• Increased Salt Intake• Diuretics• Dialysis (renal failure)• Glucocorticoids
Magnesium
Reference Range:1.3 – 2.3 mEq/L
Magnesium• 2nd most abundant ICF cation (K+ #1)• 60% Mg+ found in bones, < 1% ECF• Mg+ performs the following functions:
– Promotes enzyme reactions in carbohydrate metabolism– Helps produce ADP (adenosine triphosphate)– Helps with protein synthesis– Influences vasodilation (normal CV function)– Helps Na+ and K+ ions cross cell membranes
Magnesium• Mg+ performs the following
functions:– Regulates muscle contractions– Affects irritability and contractility of
cardiac and skeletal muscle– Influences Ca++ levels
• maintain Ca++ levels in ECF
Magnesium
Hypomagnesemia is Mg+ < 1.8
Hypermagnesemia is Mg+ > 2.4
HypomagnesemiaResults in cardiac dysrhythmias and
irritates the nervous system (tetany)
HypomagnesemiaCauses:• ETOH Abuse (#1)• Malnutrition• Chronic Diarrhea• Malabsorption• Diuretics• AMI• Pancreatitis
Hypomagnesemia• Does not produce specific EKG changes• May contribute to arrhythmias caused by digoxin toxicity,
ischemia, or K+ imbalances
• Monitor:– EKG for Arrhythmias– Muscle cramps
HypomagnesemiaReplacement of Mg: PO or IV• PO = Mg Oxide 400mg tabs• MgSo4 IV administration is usually given at a rate of 1 gram/hr
(1 gram/100 ml)• Encourage foods high in magnesium
HypermagnesemiaSevere hypermagnesemia is associated with:
– AV blocks– Intraventricular conduction disturbances