Fluid Balance 216A (copy G. Audenart)

0.5-1ml/kg/h

how much urine per hour

220lbs

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

what % of body fluid is water

60%

where is water in the body and %

ICF (40% in cells, intracellular fluid)

ECF (plasma 20%)

Where is ECF distributed

1. 16% interstitial - aka fluid between cells

2. 20% in plasma

Edema

High interstitial fluid can cause edema, which can cause crackles and create difficulties breathing.

continuous movement of water

need good lymph circulation

5L blood

plasma 3L only part of volume

hypotension

low blood volume

CNS injury can impact

(dis)ability to regulate vitals

fluid regulation

homeostasis

baroreceptors

mechanoreceptors in walls of BV and heart, detect BP

• jutxaglomerulator in nephron of kidney, detects BP changes, and responds

• doesn’t fx w/out inflammation

• triggers vasomotor center in medulla

vasomotor center in medulla

triggered by baroreceptors

• low perfusion activates SNS which releases norepinephrine

norepinephrine

triggers vasoconstriction

• this is released from the adrenal glands

• response to low BP to help raise it
  -also lungs dilate

kidneys

detect the drop in perfusion pressure and release renin. Adjusts how much water/electrolytes are kept/excreted.

renin

converts angiotensinogen to angiotensin I

angiotensin I

converted to angiotensin II by ACE in the lungs

angiotensin II

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

aldosterone

• tells kidneys to reabsorb sodium and water and excrete potassium.

• Water follows retained sodium and 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.

From hypothalamus to kidneys

I&O

intake should be greater than or equal to output

oliguria

• low output of urine

• <o.2ml/kg/h

creatinine clearance

check kidney function by checking this bloodwork

electrolytes in body

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 (+aquaporin channels)

-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

severe changes in sodium and water balance

can cause confusion, seizures, other neuro problems.

Blood tests

can measure substances of liquid portion of blood to assess fluid balance, electrolyte levels and organ function.

Bicarbonate

alkaline substance, balanced via kidneys. helps maintain body’s acid-base balance

Process of protein breakdown

1. dietary proteins

2. digestion → amino acids

3. Amino acids are used to build proteins and other substances

4. excess nitrogen turned in urea (produced in liver)

5. Kidneys filter urea into urine.

Urea and kidneys

urea build up causes changes in kidney function

Electrolytes and extracellular fluid

high in sodium, chloride and calcium

Electrolytes and Intracellular fluid

High in potassium, phosphate, magnesium

Abnormal Potassium levels

can affect electrical activity of heart and cause arrythmias

Magnesium and nerves

magnesium supports normal neuromuscular function and cellular reactions

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’

fluid and tonicity

tonicity dictates fluid movement btw compartments

sodium and dextrose

iv fluids tonicity’s main solutes

isotonic fluid

same as plasma (same osmolality)

isotonic fluid effect

no major net water shift. ex NS.

hypertonic fluid

higher than plasma

-plasma expanders, draws water from other compartments into plasma

-increased osmolality in plasma

hypertonic fluid effect

higher effective solute concentration than plasma, so water moves out causing shrinking.

hypotonic fluid

lower than plasma

-diluting plasma, water moves to cells and interstitial fluid

-rehydrating cells

-smaller plasma volume

hypotonic fluid effects

lower effective solute concentration than plasma, water moves into cells causing swelling

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 - risk of fluid overload and high strain)

• EX: plasbumin, alburex

what is hypovolemic shock

loss of significant blood or fluid.

iv fluid colloids

albumin

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 ‘hypertonic’ 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

- 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 (often pre/post surgery, GI issues, intubated)

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)

If NPO for >3 days

consider additional nutrition, at risk for malnutrition

dextrose adult fluid calc

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

-need minimum

dextrose calories

1L of dextrose has 170 cal

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 148

• D5W

• D5.2NS

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

• dextran 70

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

NS 0.9% contents

Contents per L:

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)

• hyperchloremia, low other electrolytes

• no dextrose

hypochloremia

low levels of chloride

LR contents

per L:

-Na 130 mEq

-Potassium 4 mEq

-Calcium 2.7 mEq

-Chloride 109 mEq

-Sodium Lactate 28mEq (metabolized into bicarbonate)

LR

• isotonic tonicity

• side effects: hyperkalemia, no dextrose

• pediatric contraindication: high electrolytes

Plasma-Lyte 148 contents

Per L:

• Na 140 mEq

• Potassium 5 mEq

• Mg 3 mEq

• Chloride 98 mEq (normo-chloremic)

• Aklalizing agents: 27 mEq and 23 mEq gluconate - (not for metabolic acidosis tx)

Plasma Lyte 148

21 calories

• common choice for post OR

• Caution: hypersensitivty reactions

Dextran 40 contents

large polysaccharide

contains some 0.9% NS

Dextran 40

Stays in circulation - volume expander.

Binds RBC and platelets, reduces aggregation: antiplatelet fluid, reduces blood viscosity, risk of bleeding.

common hypertonic fluids characteristics

-fluid out of cells, tonicity high plasma

-high glucose &/or high sodium

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

-D5LR

Common Hypertonic Fluids: names

1. D5NS

2. D5LR

3. D5Plasma-Lyte

4. D10W (dextrose 10% in water)

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

6. 3% NaCl

7. 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

-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)

Good if dextrose required

-s/e hyponatremia

Hyponatremia

Low blood sodium

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 15 minutes (infuzed volume, 100 ml → acts like 350ml)

common hypotonic fluids

• Fluid into cells, low NaCl or low dextrose

1. 0.45% ns (1/2 ns)

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

3. D5 0.2% NS (good dextrose, less na)

hypotonic application

dehydrated patient with high serum solute “hypernatremic dehydration'‘ → water loss to ECF > fluid and 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 potential causes

• PUD

• esophageal varices (barrets esophagus)

• esophagitis

• Mallory-Weiss tears

lower gi bleed

• tumors,

• inflammatory bowel disease

• Diverticular disease

• Colon polyps

• Hemmorrhoids

• Anal Fissures

• Proctitis (inflammation of rectum)

gi bleed tx

1. stop taking: NSAIDs and drugs that decrease clotting (antiplatelets, anticoagulants, thrombolytics). Analayze Blood Work, determine infectious agents

2. IV fluid resuscitation/maintenance

3. Blood products

4. Abx if pathogen

5. Adjunct tx: PPI’s (symptom relief)

assess for gi bleed

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