Fluids Pathophys Flashcards
IV Fluids & Management
what makes up intracellular fluid
- all fluid enclosed in cells by plasma membranes
- makes up ~2/3 of body water
- fluid volume is stable
IV Fluids & Management
what makes up extracellular fluid
- fluid outside of the cells
- Intravascular fluid (plasma): fluid component of blood
- interstitial fluid: fluid surrounding cells
IV Fluids & Management
what is the term that describes the distribution of water present in the body?
fluid spacing
IV Fluids & Management
what is first spacing?
- normal distribution of fluid in the intracellular and extracellular compartments
- extracellular fluids are distributed between the interstitial (tissue) and intravascular (plasma) compartments 75-25%
IV Fluids & Management
describe second spacing
- abnormal accumulation of interstitial fluid in the body (edema)
- can move back to first spacing
IV Fluids & Management
describe third spacing
- mobilization of body fluid to a non-contributory space rendering it unavailable to the circulatory system (ascites)
IV Fluids & Management
define osmosis
- spontaneous movement of water across semi-permeable membrane
- water moves from region of high solute concentration to a region of low solute concentration
- tries to equalize concentrations
IV Fluids & Management
define osmotic pressure
- hydrostatic pressure necessary to counteract the process of osmosis
- depends on the solut concentration (increases osmotic pressure with high solute concentration)
- NOT dependent on mass/size of molecules
IV Fluids & Management
describe tonicity
the capability of a solution to modify the volume of cells by altering their water content
IV Fluids & Management
define isotonic, hypertonic, and hypotonic
- isotonic: IV fluid concentration = plasma concentration
- hypertonic: IV fluid concentration > plasma concentration
- hypotonic: IV fluid concentration < plasma concentration
IV Fluids & Management
what would happen if a patient received IV water instead of normal saline?
RBCs would swell and burst
IV Fluids & Management
what is osmolar concentration
how much of a solute is present
IV Fluids & Management
osmolarity vs osmolality
- osmolarity: solute in solution based on 1L
- osmolality: solute in solution based on kilogram
IV Fluids & Management
major intracellular vs extracellular ions?
- intracellular: potassium
- extracellular: sodium
IV Fluids & Management
describe water balance in the body
- our body wants intake and excretion to be equal
- majority of intake: GI tract
- majority of output: urine
IV Fluids & Management
what center helps regulate water intake/output?
- hypothalmic thirst center
IV Fluids & Management
describe activation of hypothalamic thirst center
- stimulated when osmoreceptors detect an increase in plasma osmolality or a decrease in blood volume/pressure
- body releases ADH and aldosterone
IV Fluids & Management
describe feedback loop of hypothalamic thirst center
- drinking water inhibits thirst center
- inhibitory feedback: relief of dry mouth, activation of stomach/intestinal stretch receptors
IV Fluids & Management
role of anti-diuretic hormone (ADH) in thirst response
- hypothalamus stimulates release of ADH from posterior pituitary gland when dehydrated
- ADH works on the kidneys to recover water from urine
IV Fluids & Management
describe role of aldosterone with thirst
- kidneys increase production of angiotensin II which stimulates thirst and stimulates the release of aldosterone from the adrenal galnds
- aldosterone tells the kidneys to increase resorption of sodium in distal tubules (water will follow sodium)
IV Fluids & Management
common indications of IV fluid administration
4
- fluid resuscitation
- correction of electrolyte imbalances
- maintenance of fluids for patients that cannot take fluids enterally
- IV med delivery
IV Fluids & Management
2 categories of fluid administration
- crystalloid solutions
- colloid solutions
IV Fluids & Management
two components of:
* crystalloid
* colloid
- crystalloid: small molecular weight solutes (minerals, dextrose) and sterile water (more commonly used)
- colloid: large molecular weight solutes (albumin, blood products) and sterile water
IV Fluids & Management
describe what crystalloid solutions do in the body
3 components
- consist of aqueous electrolyte solutions w/ varying concentrations
- do not readily cross plasma membranes, but will cross capillary membranes
- can be isotonic, hypotonic, hypertonic, mixed, and concentrated
IV Fluids & Management
what are 2 isotonic crystalloid solutions?
- Normal saline (0.9% NaCl)
- Lactated Ringer’s (LR)
IV Fluids & Management
what are 2 hypotonic crystalloid solutions?
- Dextrose solutions (D5W or D10W)
- Saline Solutions (0.45% NaCl, .22% NaCl)
IV Fluids & Management
what are two types of hypertonic crystalloid solutions?
- 3% NaCl
- 5% NaCl
IV Fluids & Management
what are mixed crystalloid solutions?
2
- dextrose in saline solutions
- Isotonic bicarbonate
IV Fluids & Management
2 concentrated crystalloid solutions?
- 8.4% sodium bicarbonate
- 50% dextrose in water (D50W)
IV Fluids & Management
describe normal saline
- 0.9% NaCl
- contains equal mEg/L of Na+ and Cl-
- increase extracellular volume w/ no change in intracellular volume
- indicated: fluid resuscitation, maintenance of fluid therapy, IV drug admin
- risks: hyperchloremic non-anion gap metablic acidosis, fluid overload
IV Fluids & Management
describe lactated ringers
- contains Na+, Cl-. K+, Ca2+, lactate
- increases extracellular volume, minimally increases intracellular volume
- mild buffering action which prevents acidosis
- indicated: fluid resuscitation, maintenance fluid therapy
- risks: hyperkalemia, fluid overload, accumulation of lactate (only in liver failure)
IV Fluids & Management
describe use of dextrose solution
- can be 5% or 10% dextrose (D5W, D10W)
- increases extracellular and intracellular volume
- indications: correction of free water deficit (hypernatremia), maintenance fluid therapy (hypoglycemia, ketosis)
- risks: hyponatremia, hypokalemia, hyperglycemia, cerebral/pulm edema
IV Fluids & Management
describe use of 1/2 or 1/4 normal saline solutions
- 0.45% NaCl (1/2 NS) or 0.22% NaCl (1/4 NS)
- increases both extracellular and intracellular volume
- indications: correction of hypernatremia, maintenance fluid therapy
- Risks: hyponatremia, cerebral/pulm edema
IV Fluids & Management
describe use to hypertonic crystalloid solutions
- infuse very slowly
- contains high Na+ and Cl-
- decreases intracellular volume and increases extracellular volume
- indications: severe hyponatremia, tx of cerebral edema
- risks: osmotic demyelination syndrome
IV Fluids & Management
describe use of dextrose in saline (mixed crystalloid)
- 5% dextrose iin 0.9% NaCl (isotonic) or 5% dextrose in 0.45% NaCl (hypotonic)
- indications: fluid resuscitation, maintenance therapy
IV Fluids & Management
describe use of isotonic bicarb (1.3% NaHCO3)
- mixed crystalloid
- indications: corrects severe metabolic acidosis, urinary alkalinization (decreases toxicity of drugs), correction of bicarb deficit (severe diarrhea, renal tubular acidosis)
- Risks: metabolic alkalosis, hypernatremia, hyperglycemia
IV Fluids & Management
describe use of 8.4% sodium bicarb
- indications: antidote for sodium channel blocker toxicity, severe metabolic acidosis
- Risks: metabolic alkalosis, hypernatremia
IV Fluids & Management
describe use of 50% dextrose in water (D50W)
- available in ampules of 25 mL or 50 mL
- indications: rapid reversal of hypoglycemia, adjunctive treatment of hyperkalemia when combined with insulin (enhances uptake of K+)
- Risks: hyperglycemia
IV Fluids & Management
describe use of colloidal solutions
- solutions that contain large proteins or cells
- do not readily cross capillary membranes and therefore remain in the intravascular space
IV Fluids & Management
describe use of albumin as a colloidal solution
- naturally occuring colloid and most abundant protein in plasma
- increases extracellular volume
- indications: cirrhosis, critically ill pts
- risks: fluid overlaod, allergic rxns
Volume Depletion & Dehydration
what are cell membranes composed of?
lipids and proteins (phospholipid bilayer)
Volume Depletion & Dehydration
functions of cell membrane?
- separates the interior of the cell from the outside environment
- provides protection to the cell
- allows for selective transport of molecules
Volume Depletion & Dehydration
active vs passive transport
- lipid soluble molecules pass thru the membrane (passive transport)
- water soluble molecules require a channel for pass through (active transport)
Volume Depletion & Dehydration
describe passive diffusion
- no ATP required
- movement of molecules from high to low conentration along electrochemical gradient
- involves simple diffusion (movement of small or lipophilic molecules), osmosis (simple diffusion of water), facilitated diffusion (movement of large/charged molecules via chanell/carrier protein)
Volume Depletion & Dehydration
describe active transport
- requires ATP
- movement against gradient (low concentration to high concentration)
- Primary Active: direct, use to ATP to mediate transport
- Secondary Active: indirect, coupling the molecule w/ another moving along gradient
Volume Depletion & Dehydration
differentiate endo and exo cytosis
- endocytosis: into the cell
- exocytosis: out of the cell
Volume Depletion & Dehydration
define volume status
balance between water and solutes
Volume Depletion & Dehydration
define volume depletion (hypovolemia)
- refers to extracellular fluid loss (loss of water and Na)
- decreased circulating volume
- caused by decreased oral Na intake and/or increased volume losses
Volume Depletion & Dehydration
define dehydration
- refers to total body water loss across all compartments
- decreased circulating volume, decreased intracellular volume
- caused by decreased oral water intake
Volume Depletion & Dehydration
causes of dehydration?
- dehydration: decreased oral intake, acute/critical illness, altered thirst mechanisms, dementia
Volume Depletion & Dehydration
causes of volume depletion due to:
* decreased oral Na intake
* increased volume loss
- decreased Na: acute/critical illness, eating disorders, dementia
- Increased volume loss: bleeding, GI (diarrhea, vomiting, drains), renal (diabetic ketoacidosis, diuretics, diabetes insipidus), third space losses (burns, severe pancreatitis), insensible lossses (skin/mucous membranes)
Volume Depletion & Dehydration
define total body water
- ~55% of body weight for women, ~60% of body weight for men
- varies with muscle mass (more H2O) and fat mass (less H2O)
- decreases in elderly and obesity
Volume Depletion & Dehydration
pathophys for dehydration
- fluid shifts with illness/disease
- occurs due to diffusion across semipermeable membrane
- regulated by difference in plasma osmolality between ECF and ICF
Volume Depletion & Dehydration
“flow chart” for dehydration pathophys?
- H2O is lost, Na+ is retained
- H2O lost from ECF which increases ECF osmolality
- H2O diffuses from ICF to ECF
- Net effect: ECF hypertonicity and cellular hypernatremia
Volume Depletion & Dehydration
pathophys for hypotonic volume depletion
- water loss > Na+ loss
- hypotonic fluid is lost from ECF
- ECF osmolality increases
- H2O diffuses from ICF to ECF
Volume Depletion & Dehydration
pathophys of isotonic volume depletion
- Na+ loss = H2O loss
- isotonic fluid is lost from ECF
- ECF osmolality does not change because there is no gradient for diffusion with ICF
- caused by diarrhea, loss of whole blood
Volume Depletion & Dehydration
pathophys of hypertonic volume depletion
- Na+ loss > H2O loss
- fluid is lost from ECF
- ECF contracts and ECF osmolality decreases
- H2O shifts from ECF to ICF via diffusions
- Example: loop diuretics, primary adrenal insufficiency
Acid Base
what is normal pH for body
7.35 to 7.45
Acid Base
define acidemia
- more hydrogen ions (H+) in blood
- pH < 7.35
Acid Base
define alkalemia
- more hydroxide ions (OH-) in blood
- pH > 7.45
Acid Base
differentiate strong and weak acids
- strong: fully ionize in water, greater effect on pH
- weak: partially ionize in water, smaller effect on pH
Acid Base
differentiate volatile and nonvolatile acids
- volatile: can change phase into a gas, produced via aerobic metabolism, removable via lungs (CO2)
- non-volatile: cannot change phase into a gas, removed by the kidneys, produced via anaerobic metabolism or the GI tract
Acid Base
differentiate strong and weak bases
- strong: fully ionize in water, more OH- released into water, greater effect on pH
- weak: partially ionize in water, less OH- released into water, smaller effect on pH (HCO3)
Acid Base
eqn for most physiologically important buffer
HCO3- + H+ –> H2CO3 –> CO2 + H2O
can go either way.
Acid Base
what are buffers
substances that consume or release hydrogen ions to stabilize pH
Acid Base
what is acid base balance maintained by?
3
- chemical buffering
- pulmonary activity (acid- CO2)
- renal activity (base- HCO3)
Acid Base
causes of left shift (alkalosis) on oxygen-hemoglobin dissociation curve
- decreased pCO2/H+
- decreased temp
- increased affinity for O2
Acid Base
causes of right shift (acidosis) on oxygen-hemoglobin dissociation curve
- increased pCO2, H+
- increased temp
- decreased affinity for O2
Acid Base
what can pH changes impact in the body?
protein configuration/function
Acid Base
ABG test purposes?
6 components
Vital
* pH
* PaCO2 (partial pressure CO2)
* Bicarb (HCO3)
Supplemental
* O2CT (oxygen content)
* PaO2 (partial pressure O2)
* O2Sat (oxygen saturation)
Acid Base
normal values for ABG?
- pH: 7.35 to 7.45
- PaCO2: 35-45 mmHg
- HCO3: 22-26 mEq/L
- pO2: 75-100 mmHg
- SaO2: 95-100%
Acid Base
Allen’s test before ABG?
used to assess collateral blood flow to the hands
Acid Base
what is VBG?
venous blood gas
Acid Base
normal values VBG
- pH: 0.03-0.04 lower
- pCO2: 7-8 mmHg higher
- HCO3: 2 mEq/L higher
Acid Base
ultimate acid base regulator
kidneys!
Acid Base
how to determine respiratory disturbance to balance?
- change in CO2
- elevated: acidic
- decreased: alkalotic
Acid Base
how to determine metabolic disturbance to balance?
- change in HCO3
- elevated: alkalotic
- decreased: acidic
Acid Base
What formula is used to determine the degree of compensation?
Winter’s formula
Acid Base
Describe use of anion gap
calculated for primary metabolic disturbances
Acid Base
anion gap for metabolic alkalosis? for metabolic acidosis?
- alkalosis: low
- acidosis: high
Acid Base
how to calculate anion gap?
Na + K - (Cl + HCO3)
