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