Fluid Balance 216A

0.5-1ml/kg/h

how much urine per hour

220lbs

if the patient weighs 100 kg how many pounds does the patient weigh

body fluid

60% is h2o

where is water in the body?

ICF (40%) in cells, intracellular fluid

ECF (plasma 20%):

• interstitial 16% plasma 4%

• travelling cells, in circulation (stay there = edema)

continuous movement of water

need good lymph circulation

5L blood

plasma 3L only part of volume

hypotension

low blood volume

CNS injury

disability to regulate vitals

fluid regulation

homeostasis

baroreceptors

senses BP in hypothalamus -in glomerulus of kidney, knows to keep water or not and doesn’t fx w/out inflammation

-triggers vasomotor center in medulla

vasomotor center in medulla

baroreceptors trigger this (low perfusion activates SNS which releases norepinephrine)

norepinephrine

triggers vasoconstriction -this is released from the adrenal glands -in response to low BP to help raise it
-also lungs dilate

kidneys

these detect the drop in perfusion pressure and they release renin

renin

converts angiotensinogen to angiotensin I

angiotensin I

converted to angiotensin II by ACE in the lungs

angiotensin II

causes vasoconstriction which raises bp and stimulates adrenal cortex to release aldosterone

aldosterone

tells kidneys to reabsorb sodium and water and excrete potassium which raises blood volume and pressure

hypothalamus

detects low bp and signals posterior pituitary to release ADH

ADH

causes water reabsorption and less urine output = increasing blood volume and BP

I&O

intake should be greater than or equal to output

oliguria

<o.2ml/kg/h -low output of urine

creatinine clearance

check kidney function by checking this bloodwork

electrolytes to fx

sodium, potassium, calcium, chloride

patients that experience fluid balance issues or losses

GI patients, and any crucial organ dysfunction

osmolality

dependent on number of dissolved solutes in a fluid

-like sodium, glucose, urea

measured osmolality

275-295 mOsm/kgH20

changes in osmolality

can cause water to move to different compartments via osmosis

-cells, interstitial fluids, plasma

dehydration

increases osmolality

-high electrolytes compared to water

overhydration

decreases osmolality

-low electrolytes compared to water

• can lead to cell swelling (edema)

• occurs when replacing water but not electrolytes

IV fluid admin

aims to maintain homeostasis and correct fluid imbalance

osmosis

mov’t of H2O from low solute to high solute (dilutes)

-how IV fluid works

-the correct iv fluid will achieve the desired shift

tonicity

clinical application of osmolality

-a relative (to blood) measurement of IV fluid’s osmolality

-relates osmolality of the fluid to that of plasma

all iv fluids

are dispensed according to their ‘tonicity’

dictates movement of fluid

tonicity dictates fluid movement btw compartments

sodium and dextrose

iv fluids tonicity’s main solutes

isotonic fluid

same as plasma (same osmolality)

hypertonic fluid

higher than plasma

-plasma expanders, draws water from other compartments into plasma

-increased osmolality in plasma

hypotonic fluid

lower than plasma

-diluting plasma, water moves to cells and interstitial fluid

-rehydrating cells

-smaller plasma volume

iv fluid categories

colloids and crystalloids

colloids

-protein based iv fluid

-stay in circulation (can’t cross membranes)

-aka plasma expanders: bring water to plasma

tx of hypovolemic shock

-colloids

-contra. in most other cases (not first line)

• due to no pass via capillaries and high renal workload (need high kidney fx and high strain)

-plasbumin, alburex

iv fluid colloids

plasbumin and alburex

crystalloids

most common iv fluids

-H2O + electrolytes + other solutes (ex. glucose)

-easily move btw ECF & ICF

-tonicity directs fluid movement

isotonic in the ‘bag’

although it is this in the bag, it will be hypertonic in the body  due to protein content 

-water moves towards, protein can’t move -eg Albumin 5%

hypertonic in bag

if dextrose is the solute making it ‘this’ in the bag, once in the body dextrose is quickly utilized = the remainder fluid will become more isotonic or even hypotonic

-D5 ½ NS (mildy hypertonic in bag d/t dextrose)

fluid maintenance

meeting body requirements

-oral intake (eating/feeding tube); IV infusion; SC infusion

-or intake may not work for GI due to SNS stimulation, can be switched to IV

fluid resuscitation

replacing deficits

-PO if minor; IV if concerning

-goal: adequate perfusion → rescue intravascular volume

fluid restriction

restricted fluid intake

NPO

nothing by mouth, all fluids given IV

skin is big hint

organ not vital to life, lack perfusion when SNS stimulated

adult fluid calculation

35ml/kg/day of water

-electrolytes (potassium, sodium, chloride)

dextrose adult fluid calc

50-100 g/day of glucose to limit ‘starvation’ ketosis

-need minimum

if NPO adult

> 3 days, consider IV fluid content and additional nutrition

paediatric fluid calc

4/2/1 rule

-4ml/kg/hr for 1st 10kg of body weight

-2ml/kg/hr for 2nd 10kg of body weight

-1ml/kg/hr for the remaining kgs

common isotonic crystalloids

-normal saline 0.9%

-lactated ringer’s (LR or RL)

-plasma-lyte A 

-D5W (5g of dextrose in water)

plasma lyte a

has components turn into bicarb

-alkylizes

-normal blood ph = 7.35-7.45, need to consider, shouldn’t use when in homeostasis

common isotonic colloids

-isotonic in bag, hypertonic in body

-5% albumin

-dextran 40

-hydroxyethyl starch 6% (higher in hypertonic) (tetrastarch, heptastarch - rescue not first choice)

NS 0.9% contents

154 mEq Na

154 mEq Cl

NS tonicity

isotonic

-#1 resuscitation fluid

adults ns

500 ml bolus, reassess, keep adding and reassess

paediatrics ns

15ml/kg, reassess, switch to D5 ½ NS (77mEq)

ns s/e

if prolonged use (>2days)

-hypokalemia (no potassium)

-no dextrose

LR contents

per L:

-Na 130 mEq

-Potassium 4 mEq

-Calcium 2.7 mEq

-Chloride 109 mEq

-Lactate 28mEq (alkyline, not an issue for acidosis patients)

LR

isotonic tonicity

-side effects: hyperkalemia, no dextrose -pediatric contraindication: high electrolytes

common hypertonic fluids

-fluid out of cells, tonicity high plasma

-high glucose &/or high sodium

-D5NS (may be isotonic in body bc demand is high)

-D5LR

-D10W (dextrose 10% in water)

-D5 0.45%NS (D5 ½ NaCl; D5.45 NS) (hypertonic in bag = becomes isotonic quickly)

-3% NaCl

-25% Albumin (colloid)

3% NaCl

high sodium, give small dose and reassess

-tx for head injury to lower ICP (cerebral edema) (shrink cells - water into plasma)

-hypertonic fluid

-crystalloid

25% albumin

colloid

-5% = isotonic

-tx: resuscitation fluid option, watch fluid shift

-common hypertonic fluid

D5.45 NS content per L

50g dextrose

77 mEq Na

77 mEq Cl

D5.45 ns

hypertonic (mildly)

1st choice paediatric maintenance fluid (+consider adding KCl); during interventions; if dextrose req’d

-s/e hyponatremia (low Na in blood)

25% Albumin contents

per L:

250g albumin

130-160 mEq Na

25% albumin

hypertonic tonicity

colloid

biologic - from donors (heat treated to eliminate pathogens)

-plasma volume expander extreme!

• 3.5 times it volume of additional fluid into circulation in minutes (infuzed volume, 100 ml → acts like 350ml)

common hypotonic fluids

fluid into cells, low nacl or low dextrose

-0.45% ns (1/2 ns)

-3.3% dextrose 0.3% sodium (2/3 1/3) short term not maintenance

-D5 0.2% NS (good dextrose, less na)

hypotonic application

dehydrated patient with high serum solute “hypernatremic dehydration'‘ → water loss > solute loss, high na in blood

-h20 shifting into ECF (circulation) need fluid back into cells

-administer hypotonic fluids to shift some fluid back into cells

GI bleed upper

PUD, esophageal varices (barrets esophagus), esophagitis

lower gi bleed

tumors, inflammatory bowel disease

gi bleed need to stop

stop taking

NSAIDs

drugs which decrease clotting (antiplatelets, anticoagulants, thrombolytics)

tx for gi bleed

iv fluids resuscitation &/or maintenance

-blood products (electrolytes, RBC (CBC))

-abx if caused by pathogen

adjunct: PPIs (symptom relief)

assess for gi bleed

VS (map), peripheral pulses, dx to tx cause, endoscopt or colonoscopy, bw, pathogen specific

blood results

rbc count (need to replenish?)

differential

c-reactive protein (chrons, after tx, level drops, general inflammation marker)

pathogen specific PRN (c diff, h. pylori)

maturation of rbcs

erythropoietin produced in kidney, triggered by low O2 to speed maturation

erythropoietin

stimulates red bone marrow to enhanced erythropoiesis increases rbc count

isotonic iv fluids and hemorrhaging

complication if administering only isotonic IV fluids to a hemorrhaging patient is possible diluting of clotting factors leading to worsened bleeding. -replacing fluid and not electrolytes

PRBCs

packed red blood cells, improve o2 carrying capacity

whole blood

need to find blood type, o neg universal

platelets

not in prbc but in whole blood

FFP

fresh frozen plasma

-proteins, clotting factors, immunoglobulins

-when considering clotting and proteins

cryoprecipitate

cryo - for serious hemmorhage

-portion of plasma made from FFP

-fibrinogen (F8+10 in clotting), clotting factors

electrolytes

positively or negatively charged inorganic molecules

-essential for cellular fx, nerve conduction, water balance

hyponatremia

<135mEq/L

-common cause: loss of Na via GI, diaphoresis, diuretic drugs

-tx: D5NS

hypernatermia

>145mEq/L

-common cause: renal disease, high Na intake

-tx: restrict salt intake, diuretic meds to remove Na, if IV fluid → low in Na

hypokalemia

<3.5 mEq/L

-common cause: loss of K via GI, potassium wasting diuretic drugs

-tx: KCL (IV or PO)

hyperkalemia

>5 mEq/L

-common cause: potassium sparing diuretics, renal disease

-tx: Kayexalate (PO, NG) binds K for excretion