Lec 5: Fluid/Electrolyte Balance

Fluid and Electrolyte Balance – Definition

process of regulating the extracellular fluid volume, body fluid osmolality, and plasma concentrations of electrolytes

• dependent on communication and interaction between several body systems

how much fluid is in the adult body

60% of body

• varies with age, gender and body fat

• intracellular fluid

• extracellular fluid

what are the diff types of extracellular fluid

• intravascular

• interstitial

• transcellular

third spacing def

loss of ECF into a space that does not contribute to equilibrium

electrolytes def

active chemicals that carry positive (cations) and negative (anions) electrical charges

what are the major cations and their location

• sodium = extra

• potassium = intra

• calcium

• magnesium = intra

• hydrogen ions

what are the major anions and their location

• chloride = extra

• bicarbonate = extra

• phosphate = intra

• sulfate = intra

• proteinate ions

what is the optimal and outer ranges of Na osmolality

optimal= 135-145 mEq/L

• osm = 280-300

what is the optimal and outer ranges of potassium [ ]

• hypokalemia= <3.5 mEq/L

• optimal= 3.5-5 mEq/L

• hyperkalemia = >5 mEq/L

what does Movement of fluid through capillary walls depends on:

• hydrostatic pressure=pressure exerted on the walls of blood vessels

• osmotic pressure=pressure exerted by the protein in the plasma

what does the direction of fluid movement depend on

the differences of hydrostatic and osmotic pressures

diffusion def and what it relies on

movement of substances from high to low [ ]

• relies on pressure gradient

what does active transport use as energy source

adenosine triphosphate (ATP)

what does osmosis use

• solutes, colloids, crystalloids create pressure

• osmotic pressures = pulls fluid in

• hydrostatic pressure = pushes fluid out

what are the elements of Fluid and Electrolyte Balance

• intake and absorption

• distribution (compartmental distribution of body fluids and electrolytes)

• output (elimination)

osmolarity def

concentration of all solutes (particles) in a given weight of water

what is the human osmolarity level

275–300 mosm/kg

what does low osmolality indicate

dilution

• Na+ concentration relatively low

• RBCs = relatively decreased due to hemodilution, low hematocrit

what does high osmolality indicate

dehydration

• Na+ concentration relatively high

• RBCs = relative increased due to hemo-concentration, high hematocrit

sensible vs insensible water loss

• sensible = losses you can see ex urine

• insensible= cant see ex evaporation

what hormones along with the kidney’s help with water retention

• arginine vasopressin (AVP)

• renin-angiotensin-aldosterone system (RAAS)

• atrial natriuretic peptide (ANP) = excretes water if excess

• brain natriuretic peptide (BNP) = release excess from ventricles

• aldosterone

• antidiuretic hormone (ADH)

• creatinine and BUN lab values are useful

aldosterone fx

regulates renal excretion of Na+ and water through renin-angiotensin-aldosterone system

antidiuretic hormone (ADH) fx

regulates excretion of water (but not Na+) in kidneys

electrolytes pic

Phosphate characteristics/fx (PO4)

0.8-1.45 mmol/L

• major intracellular anion

• plays role in muscle contraction, acid base balance, RBC functioning, formation of ATP

• low levels=decreased energy levels

Hyperphosphatemia cause (high phosphate)

• causes=increased intake, renal failure

• signs=tetany/hyperreflexia, N/V

• may need phosphate binders/Ca supplementation if excessively high and symptomatic

Hypophosphatemia (low phosphate) causes

lack of intake and refeeding syndrome (depleted intracellular stores = glucose load = insulin shifting phosphorus intracellular)

• signs=muscle weakness, paresthesia, overall low energy

• supplementation IV/PO required

calcium characteristics

2.2-2.6 mmol/L

• 99% of Ca in body contained in bone

• remaining Ca is either bound to albumin or ionized

• ionized form is also important to measure (1.1-1.3 mmol/L) because it plays a role in muscle contraction (including cardiac) and coagulation

Hypercalcemia (high Ca) causes and signs

increased intake and thyroid malignancy (increased PTH), signs:

• flaccidity or lack of tone in muscle tissues (including cardiac, leading to dysrhythmias and/or cardiac arrest if significant)

• N/V

• CNS changes

what is the tx for hypercalcemia

• acute IV dilution with NS and excretion with IV lasix

• long term=treat malignancy

Hypocalcemia causes and signs

lack of intake, lack of weight bearing activity, hypothyroid dysfunction, signs:

• seizures

• tetany

• spasms

• cognitive dysfunction

• dysrhythmias/hypotension if profound

what is the tx for hypocalcemia

• IV calcium if severe

• PO if asymptomatic

magnesium characteristics

0.72-0.93 mmol/L

• 2nd most abundant intracellular cation next to potassium

• big role in regulating neuromuscular activity and cardiac contractility

• exerts its effect on the CVS through peripheral vasodilation=decreased BP/CO

Hypermagnesemia causes and signs

increased intake and renal failure, signs:

• muscles too relaxed

• weakness

• hypotension

• decreased deep tendon reflexes (DTRs)

• may require dialysis if excessively high/symptomatic

Hypomagnesemia causes and signs

lack of intake as in chronic alcoholism, GI/renal losses and changes in Mg distribution (ex burns)

• tachycardia

• neuromuscular irritability

• tremors

• increased DTRs

• seizures

hypomagnesemia tx

IV or PO supplementation

• can exacerbate or predispose arrhythmias such as atrial fibrillation

sodium characteristics

135-145 mmol/L

• most abundant electrolyte in the ECF, primary regulator of ECF volume

• helps establish electrochemical state necessary for muscle contraction and the transmission of nerve impulses

what happens when you increase or decrease Na

• increase = increase in ECF volume

• decrease = decreased ECF volume

Hypernatremia causes

• lack of fluids or excessive Na intake

• ex dehydration, DI, diarrhea, heatstroke, salt and water consumption

hypernatremia signs and tx

• restlessness

• hallucinations

• seizures

• muscle twitching

• thirst

• dry mucous membranes

• tx=administering D5W to dilute serum

Hyponatremia causes

anything that causes Na loss or dilution

• ex water intoxication, SIADH, diuretics, renal disease

hyponatremia signs and tx

• confusion

• seizures

• muscle twitching

• N/V

• fatigue

• if severe, tx is more complex and requires tight monitoring

critical hyponatremia level and tx

<120 mmol/L, needs to be corrected slowly and Na levels checked at least q4h

• 3% hypertonic saline infusion or bolus

• salt pills (less commonly used and harder to predict effect)

• increase level no faster than 12 mmol/L in 24 hrs

• fluid restriction or restricting diuretics

Why is it so important to correct critically low sodium slowly?

may cause osmotic demyelination=permanent brain damage

• for severe hyponatremia, seizure precautions may be needed

potassium characteristics/fx

3.5-5 mmol/L

• 95% of K in the body is intracellular

• most abundant (+) electrolyte inside cells with a normal [ ] of approx 150 mEQ/L

• promotes skeletal muscle fx

• maintains nerve impulse conduction in the heart

Hyperkalemia: causes

decreased excretion, high K intake, extracellular shifts

• the more severe condition that requires immediate attention

hyperkalemia signs

• tall peaked T waves

• muscle twitching/cramps (early)

• weakness/paralysis (late)

Hypokalemia causes and signs

GI/renal loss, intracellular shifts and poor intake

• muscle weakness/spasm

• numbness/tingling

• fatigue

• bradycardia

• lightheadedness

• flat T wave

what is the tx focus for hyperkalemia

• correct serious cardiac conduction abnormalities=calcium chloride

• drive K into cell=insulin IV followed by dextrose IV

• eliminate K from the body=lasix and kayexalate, dialysis

what is the tx focus for hypokalemia

• bananas, melons, raw spinach

• switch to K sparing diuretics

• oral supplements (K-Dur)

• IV supplements delivered with IV pump

• be aware of safety and scope of practice especially if giving potassium IV via secondary line (IV piggyback)

what are the 2 products that are signs of liver failure

• ammonia

• albumin 35-50 g/L

ammonia levels and characteristics

0-35 umol/L

• converted by liver into urea to be excreted by the kidneys

• liver failure=increase in toxic levels of ammonia, decrease in blood urea nitrogen (BUN) = hepatic encephalopathy

• neurological changes can be subtle to more apparent cognitive changes

what are the other liver lab tests that can be done

• GGT (gamma glutamyl transpeptidase)

• ALP (alkaline phosphatase)

• both may elevate in a person with liver disease

what are some alterations in fluid balance

• hypovolemia = not enough circulating fluids

• dehydration

• third spacing

• hypervolemia

Causes of Fluid/Electrolyte Imbalance.

N&V, dehydration, surgery/trauma, burns, bleeding, liver/kidney problems

• regulated by GI, endocrine, vascular, renal

what populations are at risk of fluid/electrolyte imbalance

• infants = dehydrate fast

• children

• some people with mental health issues ex eating disorders

• older adults

edema scale pic

Fluid Volume Deficit: Nursing Management/what we can do

• take I&O and daily weights

• assess for breath sounds, edema, and other symptoms

• monitor responses to meds such as diuretics

• promote adherence to fluid restrictions and pt teaching related to sodium/fluid restrictions

• monitor and avoid sources of excessive Na, include meds

• promote rest

• oral hygiene

• provide skin care and positioning or turning

interrelated concepts pic

0.9% NaCl characteristics/uses

expands intravascular volume

• hypovolemia

• dehydration

• fluid replacement

• hypotension

• compatible with blood product

lactated ringers characteristics/uses

replaces fluid and electrolytes

• fluid resuscitation

• dehydration

• GI losses

• perioperative fluid replacement

0.45% Nacl characteristics/uses

provides free water and some Na

• hypernatremia

• cellular dehydration when appropriate

D5W charateristics/uses

provides free water + 170 kcal/L

• free water replacement

• prevention/tx of some hypernatremia situations

D5 ½ NS charateristics/uses

provides water, glucose, nacl

• maintenance fluid

3% NaCl charateristics/uses

pulls water into intravascular space

• severe symptomatic hyponatremia

• cerebral edema in specific situations

what are Signs and symptoms of a fluid volume deficit

• thirst, dry mouth, dry mucous membranes

• poor skin turgor

• decreased urine output, concentrated urine

• dark urine

• tachycardia

• hypotension or orthostatic hypotension

• weakness, dizziness, fatigue

• increased hematocrit

• increased BUN

• weight loss

what are Signs and symptoms of a fluid volume excess

• peripheral or dependent edema

• rapid weight gain

• increased BP

• bounding pulse

• JVD

• crackles

• dyspnea/orthopnea

• increased work of breathing

• decreased o2 sat

• possible pulmonary edema