part 1 of fluid and electrolyte balance. i hope it's helpful.

1. Mays Yousuf – Alquds university; Palestine. Sep 2015
Fluid and electrolyte balance
 Water makes 60% of lean body mass in males, and 50% of lean body mass in females.
 It’s divided into intra and extracellular components as follows:
a. 40% intracellular.
b. 15% interstitial fluid.
c. 5% plasma.
 Osmotic pressure across cell membrane determines the extracellular volume through [Na].
 Urea and Mg don’t contribute to the water balance.
 Oncotic and hydrostatic pressures maintains water balance across the endothelium.
 Application of that:
IV Fluid added Effect
Water (D5W) ↑ volume in all compartments
NS or renal NaCl retention due to  EABV ↑ volume in interstitium
Colloid ↑ volume intravascularly
 [Na] is related to volume regulation NOT Na excretion.
 Osmoregulation vs. volume regulation:
Item regulated Factors Water added NS added Salt added
Osmolarity ADH, thirst -- -- ↑
Volume Aldosterone, ANP --  Aldosterone  Aldosterone
Urine -- Watery Isotonic Salty
 What happens in edematous conditions?
In case of heart failure, liver cirrhosis, or hypoalbuminemia, EABV decreases due to water
shiftingintothe interstitium.Thisleadstopersistentsympatheticstimulation and increased
renal absorption of sodium and water to compensate.
 What causes ADH release?
1. Osmotic: increase plasma osmolarity due to salt intake.
2. Non osmotic: increase sympathetic innervation in stress, CNS or psychic diseases.

2.  What types of ADH receptos are there?
1. 1a : vasoconstriction.
2. 1b: increase ACTH.
3. 2: renal effect.
 What drugs have aldosterone-like effect?
1. Estrogen.
2. Mineralocorticoid and liquorice.
3. NSAIDs.
 What other medications might cause sodium retention and edema?
1. Initiation of insulin.
2. Refeeding syndrome.
3. Dihydroperidines.
 How does TZD cause sodium retention?
It works by activationof PPAR-gamma;anuclear receptor in the collecting ducts that cause salt
and water retention. It’s contraindicated in patients with heart failure.
 What is the duiretic of choice for TZD-induced edema?
Aldosterone-antagonists:spironolactome, amlioride, and triamterene. Because these work on
ENaC receptors.
 What factors contribute to edema formation?
1. Venous hydrostatic pressure.
2. Plasma oncotic pressure.
3. Capillary permiability.
4. Lymphatic drainage.
 IV fluid management in patients:
 We use IV fluids when we can’t use GIT for any reason.
 Our daily need of fluid is divided into:
1. Maintenance:basal needof fluiddaily. it’s calculated by Holliday-Segard equation.
2. Deficit: lost volume daily either to the outside or to third spacing. This includes
ongoing loss into NGT, drains, ostomies,..

3.  Holliday-Segard equation for fluid maintainance:- 100:50:20
First 10 kg of weight 100 ml/kg/day
Second 10 kg of weight 50 ml/kg/day
> 20 kg of weight 20 ml/kg/day
** rememberthat1 bag of fluid= 500 ml.if maintenance is 2000 ml/24 hr for example. It’s the same as
4 bags/24 hr, or 1 bag/6 hr.
 What is the common adult maintaince fluid? D5W 1/2 NS + 20 KCL.
 What is the common pediatrics maintaince fluid? D5W 1/4 NS + 20 KCL.
Why ¼ instead of ½ in pediatrics? Because of decreased ability of children to concentrate urine.
Why sugar must be added to the maintaince solution? To inhibit muscle breakdown.
 Deficit calculation depends on:
a. If the patienthasan NGT, drain of serosangious,ostomy:addvolume drained fromeach
b. If the patient has fever: add 10% maintenance for each +1 celcius.
c. If the patient is hyperventilating: add 1 L /day
d. If the patient has lost or is losing blood: 3 cc crystaliod or 1 cc blood for each 1 cc blood
e. If this isthe firstpresentationof the patient and the deficit is unknown: rely on weight
loss as a measure of degree of dehydration. E.g. 10% of TBF.
** deficit is given 1:1 as 16 hr:8 hr. E.g. if the deficit is 1000 cc/day, it’s given as 500cc in the first 8 hrs,
then 500 in next 16 hr.
 This table clarifies the daily secretions of different organs:
Organ Secretion/day Fluid to substitute
Stomach 2000 cc/day D5W ½ NS + 20 KCL
Small intestine 3000 cc/day LR
Biliary 1000 cc/day LR ± NaHCO3
Pancreatic 600 cc/day LR ± NaHCO3
Colonic In diarrhea LR ± NaHCO3

4.  What is the best way to assess fluid volume? Urine output. If the patient has cardiac or renal
dysfunction use CVP or wedge pressure.
 Minimumurine outputinanadulton IV maintenance? 30 ml/hr
 Minimum urine output in an adult in trauma? 50 ml/hr
 Why not mix combine bolus fluid with dextrose or potassium? To avoid hyperglycemia or
hyperkalemia.
 What is the first line fluid in trauma rescucitation? LR because it’s physiological.
 Case:an elderlyhasgone intoCHFon POD #3, why?Because mobilization of 3rd
space fluid into
intravascular space occurs on POD #3.