PHRM 844 E1; fluids & electrolyte (Walroth)

adjusting wts - when to use nutrition body wt (NBW)

actual wt / IBW ≥ 130%

adjusting wts - when to use actual body wt (ABW)

actual wt / IBW < 130%

what is the body water composition (%) of an adult man

50-60% of body weight

what is the body water composition (%) of an adult woman

45-55% of body weight

what is the body water composition (%) of an adult neonates/infants

75-90% of body weight

why is fluid balance important

maintains body temp, cell shape, transport nutritients, gases, wastes

organs that affect fluid balance (fluid intake = fluid losses)

skin, lungs, kidneys

examples of fluid intake

liquids, solid food, meds

what are almost completely reabsorbed and not counted in the daily fluid balance

gastric, intestinal, pancreatic, and biliary sxns

examples of sensible (measurable) fluid losses

- urination (400-1500 mL)

- defecation (100-200 mL)

- wounds (varies)

what is the average amount of sensible fluid losses per day

1 - 1.5 L/day

examples of insensible (immeasurable) fluid losses

- skin (350 - 400 mL)

- lungs (350 - 400 mL)

what is the average amount of insensible fluid losses per day

1 L/day

what are additional fluid losses that may or may not be measurable but will affect fluid balance

- NG output

- vomit

- diarrhea

- burns

- fistualas

- drains

- bleeding

- large wounds

what are the 3 things that help regulate fluid volume

1. kidneys (nephrons, glomerular filtration)

2. thirst

3. hormonal changes

what are the 3 hormones responsible for regulating fluid volume

1. antidiuretic hormone (ADH)

2. renin-angiotensin aldosterone system (RAAS)

3. atrial natriuretic peptide (ANP)

what are the roles of the antidiuretic hormone (ADH)

- reduces diuresis

- inc water retention

what are the roles of the renin-angiotensin aldosterone system (RAAS)

- renin sxn

- sodium/water regulation (aldosterone)

what are the roles of the atrial natriuretic peptide (ANP)

- dec ADH release

- counteracts effects of RAAS

what are the monitoring parameters for fluid status

1. daily wt

2. daily ins/outs (I/O)

3. volume status: volume overload, euvolemic, dehydration

4. urine output (UOP) in mL/kg/hr

5. vitals: HR/BP, central venous pressure (CVP), invasive hemodynamic parameters (Swan-Ganz PA Catheter)

what are the signs of dehydration

- PE: dec skin turgor, dry mucus membranes, delayed capillary refill

- tachycardia & hypotension may = "dry"

- peripheral pulses weak, not palpable

- dec urine output (< 0.5 mL/kg/hr) = dark urine

- BUN/SCr ratio > 20

- May vary based on age, concomitant disease states, meds, cause of fluid depletion, etc.

definition of tonicity (osmolarity)

measure of solute concentration

osmolarity is dependent on ___ & ____

pH & temperature

why are osmolarities important?

IV infusions of hypotonic or hypertonic solutions can result in hemolysis of RBCs, renal failure, and death

what is the value of hypotonic fluid

< 275 mOsm/L

what is the value of isotonic fluid

275 - 290 mOsm/L

what is the value of hypertonic fluid

> 290 mOsm/L

hypotonic solutions < ____ should not be dispensed

< 154 mOsm/L

hypotonic fluid: __(more/less)__ concentration than extracellular fluid = fluid moves __(into/out of)___ cell = __(inc/dec)___ cellular volume

less concentrated

moves into cell

inc cellular volume

definition of isotonic fluid

SAME concentration of active solutes as extracellular fluid = prevents fluid shift b/w compartments

hypertonic fluid: __(more/less)__ concentration than extracellular fluid = fluid moves __(into/out of)___ cell = __(inc/dec)___ cellular volume

more concentrated

moves out of cell (pulled into bloodstream)

dec cellular volume

hypertonic solution > ___ mOsm/L = admit in small volumes (≤ 500 mL) via a central line

> 600 mOsm/L

calculating osmolarity of IVs: total osmolarity equation

total osmolarity = osmolarity of IV soln + osmolarity of added electrolytes

calculating maintenance IV fluids (MIVF; normal art needed over 24 hrs) requirements - what is the clinical estimate range for adults

30 - 40 mL/kg/day

what are the characteristics of the ideal fluid

· Predictable effects

· Sustained inc in intravacular volume

· No accumulation in tissues

· No SE's

· Cost-effective

· Sufficiently stable when stored

· Readily available

Easy to administer

what is the most common MIVF? what is it used for? it's composition is similar to what?

D5W + ½ NS + 20 mEq KCl/L

· Used to inc plasma oncotic pressure

· Similar composition to urine

what are the two types of fluids?

crystalloids and colloids

what type of tonicity can crystalloids have?

Hypotonic, isotonic, hypertonic

what type of tonicity can colloids have?

Hypertonic

what are examples of crystalloid fluids?

· NS

· ½ NS

· D5W

· LR

Balanced salt solutions

what are examples of colloid fluids?

· Albumin (5% or 25%)

· Synthetic colloids: Hetastarch (Hespan), Tetrastarch (Voluven)

· Blood

Plasmanate

what are characteristics of crystalloid fluids?

· Provide water and/or sodium

Maintain osmotic gradient b/w intravascular and extravascular compartments

what are the characteristics of colloid fluids?

· Inc plasma oncotic pressure

Move fluid from the interstitial compartment to the intravascular (plasma) compartment

when would you use NS (normal saline; 0.9% NaCl)

- intravascular (extracellular) fluid replacement (resuscitation)

- hydration needs: hemorrhage, vomit, diarrhea, drainage from GI suction, metabolic acidosis, or shock

- sodium and/or chloride replacement

when would you use 1/2 NS (0.45%)?

maintenance fluids (combo products)

when would you use lactated ringers (LR)?

** most similar to blood plasma concentration

- replacement of blood loss

- resuscitation (trauma, burn, etc.)

when to use D5W (Dextrose 5%)

· Free water replacement (no Na+ or Cl- in the soln)

· NOT a resuscitative fluid

- NOT a MIVF by itself (given in combo)

what are balanced salt solutions?

· Crystalloid solns containing physiologic levels of Chloride and Buffer solns

· NS contains 10% higher Na+ and 50% higher Cl- than normal plasma (NOT "normal")

Ex: LR, Normosol-R, Plasma-lyte

outcomes (NS vs. BSS complications)

· inc mortality

· inc hypercholremic metaolic acidosis

· inc blood transfusions

· inc renal inury (AKI/HD/RRT)

· inc hyperkalemia

· inc postoperative infecction

colloids are only hypertonic fluids, and therefore are used selectivity for volume expansion, intravascular repletion in __(asymptomatic/symptomatic)___ patients

symptomatic

colloids are also considered "plasma expander" because they

- inc MW = inc intravascular retention time (half-life) compared to cystalloids

a colloid =

blood

colloids are second-line therapy for _____ _____

hypovolemic shock (first-line = a crystalloid)

when would you use a colloid?

in hemorrhagic shock

what colloid is a supportive/symptomatic tx, unless hypoproteinemia?

albumin

common indications of albumin

· Volume expansion

· Shock

· Burn

· ARDS (acute respiratory distress syndrome)

· Cardiopulmonary bypass

· Intraoperative fluid repletion

adverse effects of albumin

· Hypervolemia

· Azotemia

Infusion related rxn/anaphylaxis

what are examples of synthetic colloids

- Hetastarch (Hespan)

- Tetrastarch (Voluven)

what are the 2 components in synthetic colloids?

- substation ratio (SR)

- molecular weight (MW)

what is the definition SR for synthetic colloids

# of hydroxyethyl groups per glucose molecule

high SR in synthetic colloids = ____ intravascular expansion

prolonged

what is the value of a high SR for synthetic colloids

> 0.5

what is the value of a high MW for synthetic colloids

> 200 kDa

high MW synthetic colloid = ___ coagulation

altered

what agents should you use with caution?

synthetic colloids

synthetic colloids have a safety concern in severe ____

sepsis

synthetic colloids safety concerns in severe sepsis

- inc risk of death at day 90

- inc risk of requiring renal replacement therapy

- inc association w bleeding

1 unit of RBCs = ___ - ____ mL

230 - 350 mL

1 unit of RBCs increases hemoglobin by ___ g/dL

1 g/dL

when should you use blood (packed red blood cells, RBC) colloid

- acute blood loss (30-40% of blood volume)

- inadequate resuscitation from fluids alone

- preoperatively

- low hemoglobin

what is the value of low hemoglobin in a patient

≤ 7-8 g/dL

overall fluid and electrolyte goals of therapy

· Prevent & tx complication

· Normalize serum concentration

· Identify and correct underlying cause(s)

Avoid overcorrection

normal lab value of Na+

135-145 mEq/L

normal lab value of K+

3.5-5 mEq/L

normal lab value of Cl-

98 - 110 mEq/L

normal lab value of CO2

22 -28 mEq/L

normal lab value of BUN

8 - 20 mg/dL

normal lab value of SCr

0.6 - 1.2 mg/dL

normal lab value of Glu

70 - 100 mg/dL

normal lab value of AST (aspartate aminotransferase; enzyme in liver, used to diagnose liver damage or disease)

0 - 35 units/L

normal lab value of ALT (alanine transaminase; enzyme in liver)

0 - 35 units/L

normal lab value of Alb (albumin)

3.5 - 5.5 g/dL

normal lab value of Ca+2

8.5 - 10.5 mg/dL

osmolality equation

·= (2 x Na+) + (BUN/2.8) + (BG/18)

corrected Na+ equation

= · Naserum + 1.6[(BG-100)/100]

corrected Ca+2 equation

= Cameasured + [0.8(4-albumin)]

what is the primary extracellular cation

Na+

what are the two roles of Na+

1. maintains cellular integrity

2. maintains osmolar gradient: regulate fluid homeostasis through the different compartments

what is the term for Na+ deficiency

hyponatremia

what is the value of hyponatremia

Na+ < 135 mEq/L

what is the most common electrolyte disturbance in hospitalized pts

hyponatremia

what is the main effect of hyponatremia

brain injury -> death

brain injury effects of hyponatremia

1. too rapid correction of Na+

2. acute effects of hypo-osmolality

what electrolyte disturbance has significant morbidity and mortality

hyponatremia

what is the serum osmolality range of hyponatremia

275 - 290 mOsm/L

what is the definition of osmolality

# of particles per liter of water (mOsm/L)

how is osmolality measured

in lab or calculated (should predict the measured serum ism within 5-10 mOsm/L)

low serum osmolality = ____ hyponatremia

hypotonic

what is the osmolality value for hypotonic hyponatremia

< 275 mOsm

normal serum osmolality = ____ hyponatremia

isotonic = "pseudo"