Acid-Base Imbalances

intracellular fluids (ICF)

inside the cells

extracellular fluids (ECF)

outside the cells

interstitial

intravascular (plasma)

transcellular

electrolyte composition in ICF & ECF

electrolyte composition varies between ICF & ECF, but concentration is nearly the same

fluid compartments of the body

plasma - 3 L

interstitial fluid - 10 L

intracellular fluid - 28 L

1 L of water weighs…

2.2 pounds (1kg)

body weight change is an excellent indicator of

overall fluid volume loss or gain

cations vs anions

cations - positively charged

anions - negatively charged

ICF prevalent cation and anion

cation - K+

anion - PO43-

ECF prevalent cation and anion

cation - Na+

anion - Cl-

diffusion

movement of molecules across a permeable membrane from high to low concentration

facilitated diffusion

uses carrier to help move molecules

active transport

process in which molecules move against concentration gradient

external energy is needed for this process

osmosis

movement of water “down” concentration gradient from region of low solute concentration to one of high solute concentration

across semipermeable membrane

requires no outside energy sources

osmotic pressure

amount of pull required to stop osmotic flow of water

osmolarity vs osmolality

osmolarity → measures the total mOsm/L of solution

osmolality → measures the number of mOsm/kg of water

how to calculate the plasma osmolality

plasma osmolality = (2 x Na) + (BUN / 2.8) + (glucose / 18)

normal plasma osmolality

between 280 and 295 mOsm/kg

greater than 295 mOsm/kg =

water deficit

less than 275 mOsm/kg =

water excess

isotonic

same as cell interior → same osmolarity

hypotonic

solutes less concentrated than in cells/hypoosmolar → lower osmolarity

hypertonic

solutes more concentrated than in cells/hyperosmolar → increased osmolarity

effects of water status on RBC

hypotonic → RBC swell

isotonic → normal

hypertonic → RBC shrink

hydrostatic pressure

force of a fluid in a compartment

blood pressure generated by hearts contraction

oncotic pressure

pressures exerted by colloids (ex. proteins such as albumin)

fluid movement in capillaries amount and direction is determined by

capillary hydrostatic pressure

plasma oncotic pressure

interstitial hydrostatic pressure

interstitial oncotic pressure

edema is caused by

shifts of plasma to interstitial fluid

elevation of venous hydrostatic pressure

decreased in plasma oncotic pressure

elevation of interstitial oncotic pressure

first spacing

normal distribution

second spacing

abnormal accumulation of interstitial fluid (edema)

third spacing

fluid is trapped where it is difficult or impossible for it to move back into cells or blood vessels (burns, blisters)

hypothalamic-pituitary regulation

osmoreceptors in hypothalamus sense fluid deficit or increase

deficit stimulates thirst and antidiuretic hormone (ADH) releases

decreased plasma osmolality (water excess) suppresses ADH release

increase in plasma osmolarity or decreased in circulating blood volume =

stimulation of ADH

what is renal regulation

when the kidneys regulate fluid and electrolyte balance

adjusts urine volume

selective reabsorption of water and electrolytes

what are renal tubules sites of

sites of action of ADH and aldosterone

adrenal cortical regulation

releases hormones to regulate water and electrolytes

hormones include ….

• glucocorticoids (cortisol)

• mineralocorticoids (aldosterone)

cardiac regulation of water balance

natriuretic peptide are antagonists to the RAAS

hormones made by cardiomyocytes in response to increased atrial pressure

they suppress secretion of aldosterone, renin, and ADH to decrease blood volume and pressure

GI regulation of water balance

oral intake accounts for most water

small amounts of water are eliminated by GI tract in feces

diarrhea and vomiting can lead to significant fluid and electrolyte loss

for geriatric pts, structural changes in kidneys decrease ability…

to conserve water

for geriatric pts, hormonal changes include a

decrease in renin and aldosterone and increase in ADH and ANP

for geriatric pts subcutaneous tissue loss leads to..

increased moisture loss

fluid and electrolyte imbalances are directly caused by

illness or disease (burns or heart failure)

result of therapeutic measures (colonoscopy preparation, diuretics)

what is hypovolemia

ECF volume deficit

abnormal loss of body fluids

inadequate fluid intake

plasma to interstitial fluid shift

dehydration

loss of pure water without corresponding loss of sodium

hypervolemia

fluid volume excess

excess intake of fluids

abnormal attention of fluids

interstitial-to-plasma fluid shift

what is the most common clinical manifestation of fluid volume excess (hypervolemia)

weight gain

interprofessional care for hypovolemia

correct underlying cause and replace water and electrolytes

• orally

• blood products

• balanced IV solutions

interprofessional care for hypervolemia

remove fluid without changing electrolyte composition or osmolality of ECF

• diuretics

• fluid restriction

• restriction of sodium intake

• removal of fluid to treat ascites or pleural effusion

nursing diagnoses for ECF volume deficit

fluid imbalance

impaired cardiac output

acute confusion

potential complication of ECF volume deficit

hypovolemic shock

nursing diagnoses for ECF volume excess

fluid imbalance

impaired gas exchange

impaired tissue integrity

activity intolerance

disturbed body image

potential complications of ECF volume excess

pulmonary edema

ascites

what are sodium imbalances typically associated with

parallel changes in osmolality

sodium plays a major role in..

ECF volume and concentration

generating and transmitting nerve impulses

muscle contractility

regulating acid-base

hypernatremia

high serum sodium may occur with inadequate water intake, excess water loss, or sodium gain

what does hypernatremia cause

hyperosmolality leading to cellular dehydration

what is the primary protection against hypernatremia

thirst

symptoms of hypernatremia

dehydration

postural hypotension

weakness

tachycardia

thirst

why is hypernatremia manifested in the central nervous system

dehydration of brain cells

shrinkage of cells

what changes in mental status can hypernatremia cause

drowsiness

restlessness

confusion

lethargy

seizures

coma

nursing diagnoses for hypernatremia

electrolyte imbalances

fluid imbalances

risk for injury

potential complications: seizures and coma

treatment for hypernatremia

primary water deficit → replace fluid orally or IV with isotonic or hypotonic fluids

excess sodium → dilute with sodium-free IV fluids and promote sodium excretion with diuretics

hyponatremia

results from loss of sodium-containing fluids and/or from water excess

clinical manifestations of hyponatremia

mild → headache, irritability, difficulty concentrating

more severe → confusion, vomiting, seizures, coma

nursing diagnoses for hyponatremia

electrolyte imbalance

risk for injury

acute confusion

potential complications: seizures and coma

treatments for hyponatremia if the cause is water excess →

fluid restriction may be only the only treatment

loop diuretics

demeclocyline

severe symptoms (seizures) → give small amounts of IV hypertonic saline solution (3% NaCl)

treatments for hyponatremia if the cause is abnormal fluid loss

fluid replacement with isotonic sodium-containing solution

encouraging oral intake

witholding diuretics

drugs that block vasopression (ADG)

• Convaptan (Vaprisol)

• Tolvaptan (Samsca)

potassium is necessary for.. (MAJOR ICF CATION)

resting membrane potential of nerve and muscle cells

cellular growth

maintenance of cardiac rhythms

acid-base balance

sources of potassium

protein-rich food

fruits and vegetables

salt substitutes

potassium medications (PO, IV)

stored blood

what is potassium regulated by

the kidneys

what is hyperkalemia caused by

impaired renal excretion

shift from ICF to ECF
massive intake of potassium

some drugs

hyperkalemia is most common in what disease?

renal failure

manifestations of hyperkalemia

dysrhythmias

fatigue, confusion

tetany, muscle cramps

weakened or paralyzed skeletal muscles

abdominal cramping/diarrhea

nursing diagnoses for hyperkalemia

electrolyte imbalance

activity intolerance

impaired cardiac output

potential complication: dysrhythmias

how do you stabilize cardiac cell membranes in hyperkalemic pts

IV calcium gluconate

how do you force K+ from ECF to ICF

by IV insulin with dextrose and an alpha agonist or sodium bicarbonate

hypokalemia causes

increased loss of K+ via the kidneys or gastrointestinal tract

increased shift of K+ from ECF to ICF

Dietary K+ deficiency (rare)

renal losses from diuresis

manifestations of hypokalemia

cardiac most serious

skeletal muscle weakness (legs)

paralysis

weakness of respiratory muscles

respiratory arrest

decreased GI motility

hyperglycemia

what increases digoxin toxicity

low K+ level

nursing diagnoses for hypokalemia

electrolyte imbalance

activity intolerance

impaired cardiac output

potential complication: dysrhythmias

how to give IV KCl

always dilute

never push K+ or bolus

do not exceed 10 mEq/hr

must use an infusion pump

what is the function of calcium

formation of teeth and bone

blood clotting

transmission of nerve impulses

myocardial contractions

muscle contraction

what are the most common causes of hypercalcemia

hyperparathyroidism causes 2/3 cases

rest is caused by malignancy

how is calcium obtained

dietary intake

needs vitamin D to absorb

what affects calcium levels

changes in pH and serum albumin affect levels

what is calcium balance controlled by and what do they do

parathyroid hormone - increases bone resorption, GI absorption, and renal reabsorption of calcium

calcitonin - increases calcium deposition into bone, increases renal calcium excretion, and decreases GI absorption

manifestations of hypercalcemia

fatigue, lethargy, weakness, confusion

hallucinations, seizures, coma

dysrhythmias

bone pain, fractures, nephrolithiasis

polyuria, dehydration

nursing diagnoses of hypercalcemia

electrolyte imbalance

acute confusion

impaired physical mobility

potential complication → dysrhythmias

nursing interventions for hypercalcemia

low calcium diet

increased weight-bearing activity

increased fluid intake

hydration with isotonic saline infusion

biphosphonates

calcitonin

hypocalcemia is caused by

decreased production of PTH

multiple blood transfusion

alkalosis

increased calcium loss

manifestations of hypocalcemia

positive trousseau’s or chvostek’s signs

laryngeal stridor

dysphagia

numbness and tingling around the mouth or in the extremities

dysrhythmias

paresthesia, circumoral numbness

monitor pts with thyroidectomy for…

hypocalcemia

chovstek’s sign

Trousseau sign

nursing diagnoses for hypocalcemia

electrolyte imbalance

impaired breathing

activity intolerance

potential complication : fracture, respiratory arrest

treatment for hypocalcemia

treat cause

calcium and vitamin D supplements

IV calcium gluconate

rebreathe into paper bag

treat pain and anxiety to prevent hyperventilation → induced respiratory alkalosis

what does phosphate do

primary anion in ICF

essential to function of muscle, red blood cells, and nervous system

involved in acid-base buffering system, ATP production, cellular uptake of glucose, metabolism of carbohydrates, proteins and facts

serum levels of phosphate is controlled by…

parathyroid hormone

maintenance of phosphate requires….

adequate renal functioning

phosphate has a reciprocal relationship with…

calcium

What causes hyperphosphatemia

acute kidney injury or chronic kidney disease

excess intake of phosphate or vitamin D

hypoparathyroidism