Fluid and Electrolytes
Zach Gregg
Zachary_Gregg@brown.edu
Total Body Water
60% body weight (50% in women)
ECW- 20% body weight
33% TBW
ICW- 40% body weight
67% TBW
Interstitial – 15% body weight
Intravascular – 5% body weight
8% TBW
25% TBW
ECW
Intravascular
Water supplies the blood
Maintenance essential to survival
Interstitial
Equilibrated rapidly with
intravascular compartment
Increases in size after an
operation, burn, trauma, or
severe illness
(3rd Spacing)
Plasma is separated from interstitium by an endothelial cell layer and
basement membrane
Electrolytes
ECW
Na+
142
K+
4
Cl110
HCO324
Inorg. Phos12
ICW
Na+
K+
ClHCO3Org. Phos-
10
140
3
10
137
Na+/K+ ATPase
• Actively pumps 3 Na+
out of cell and 2K+
inside cell
• Energy from ATP
• Regulated by
– Insulin
– Aldosterone
Daily Requirements
•
•
•
•
Water – 30-35 cc/kg
Sodium – 1mEq/kg
Potassium – 0.5-1mEq/kg
Chloride – 1.5 mEq/kg
Fluid Loss
• Urine Output
– Highest daily water loss
– 0.5cc/kg/hr
• Sufficient UO to excrete the daily solute load
• 70kg pt = 35cc/hr
Fluid Loss
• Insensible
– Skin - 300-400 ml/day
– Breathing – 400 ml/day
– Feces – 100-200 ml/day
• Potential
–
–
–
–
–
Saliva – 1000 ml/day
Bile – 500-1000 ml/day
Gastric – 1000 ml/day
Pacreatic – 1000 ml/day
Small intestine – 3000 ml/day
Maintenance Fluid
• 100/50/20 per 24 hrs for 70kg
– First 10 kg
x 100cc/kg = 1000 cc
– Second 10 kg
x 50cc/kg = 500 cc
– Remaining 50 kg x 20cc/kg = 1000 cc
2500 cc/day
Maintenance Fluid
• 4/2/1 per hr for 70kg
– First 10 kg
x 4cc/kg = 40 cc
– Second 10 kg
x 2cc/kg = 20 cc
– Remaining 50 kg x 1cc/kg = 50 cc
110 cc/hr
Fluid Components per Liter
• Resuscitative Fluids
+
-
– NS (0.9%) 154mEq Na , 154mEq Cl
+
+
– LR 130mEq Na , 110mEq Cl , 4mEq K ,
28mEq HCO3 , 3mEq Ca
• Maintenance Fluids
+
– ½ NS (0.45%) 77mEq Na , 77mEq Cl
• Colloid
-
Fluid Pearls
• Resuscitation – isotonic fluid (LR or NS), no
dextrose, if ongoing losses consider using colloid
• Post-op – LR or NS until pt euvolemic, then
switch to maintenance
• Bolus – Isotonic, no dextrose
• Mobilization – movement of fluid from 3rd space
into intravascular space
Hypovolemia
• Acute volume loss
– Tachycardia
– Hypotension
– Decreased UO
• Gradual volume loss
•
•
•
•
– Loss of skin turgor, dry mucus membranes
– Thirst
– Changes in mental status
Low CVP
Hemoconcentration (Increased HCT)
BUN:Cr > 20:1
Metabolic acidosis due to hypoperfusion
Hypervolemia
•
•
•
•
•
•
Large UO
Pitting edema
JVD
Crackles on lung exam
Hypoxia
CXR – cephalization of vessels, pulm
edema
Hyponatremia
• Serum Na+ < 130mEq/L
• Sx- Nausea, emesis, weakness, MS changes,
seizure
• Hypovolemic
– Causes – Na+ and water are lost and replaced with
hypotonic solutions
•
•
•
•
•
Renal – salt wasting nephropathy
GI – diarrhea, vomiting, fistulas
Excessive sweating
3rd spacing – ascites, peritonitis, pancreatitis, burns
Hypoaldosteronism
– Tx – replete with NS, no faster than 0.5 mEq/L/hr to
avoid central pontine myelinolysis
Hyponatremia
• Euvolemic
– Causes – SIADH, psychogenic polydipsia
– Tx – free water restrict
• Hypervolemic
– Causes - Renal failure, nephrosis, CHF,
cirrhosis
Hypernatremia
• Serum Na+ > 145
• Sx – altered level of consciousness, seizure, coma,
signs of dehydration
• Causes – DI, hyperosmolar diuresis, EtOH
suppresses Vasopressin release
• Tx – Calculate free water deficit =
0.6 x wt(kg) x (measured Na+ - 140)/140
– Replace first ½ in 24hrs, then 2nd ½ in 24 hrs. No faster
then 10mEq/day to avoid cerebral edema
– Use D5W, ½ NS or ¼ NS
Hypokalemia
• K+ < 3.5
• Sx – fatigue, weakness, ileus, N/V, arrhythmia,
rhabdomylosis, flaccid paralysis, resp compromise
– EKG - long QT, depressed ST, low T waves, U waves
• Causes – vomiting, NGT drainage, diarrhea, high
output enteric/pancreatic fistula, hyperaldo, loop
diuretics
• Tx – replete 10 mEq KCl for every 0.1 below 4.0,
if persistent hypoK+, may also need Mg 2+
replacement
Hypokalemia
QuickTime™ and a
decompressor
are needed to see this picture.
EKG - long QT, depressed ST, low T waves, U
waves
Hyperkalemia
• K+ > 5.0
• Sx – weakness, N/V, abdominal cramping,
diarrhea, arrhythmias
– EKG – peaked T waves, prolonged PR, widened QRS,
V-fib, arrest
• Causes – lab error, iatrogenic, renal failure,
acidosis, hemolysis, crush injury, reperfusion after
4hrs ischemia
• Tx – cardiac monitoring
– 1 amp calcium gluconate (stabilizes myocardium)
– 1 amp glucose, 10units IV insulin (shifts K+
intracellular)
– Kayexalate, dialysis
Hyperkalemia
EKG – peaked T waves, prolonged PR, widened QRS, Vfib, arrest
Hypocalcemia
• Ca2+ < 8.5
• Sx – parasthesias, muscle spasms, tetany, seizures,
Chvostek, Trousseau’s
– EKG – prolonged QT, can progress to complete heart
block or V-fib
• Causes – pancreatitis, tumor lysis syndrome, blood
transfusion, renal failure, thyroid or parathyroid
surgery, diet deficient in Vit D or Ca, inability to
absorb fat soluble viatmins
• Tx – For chronic hypoCa give supplemental Ca
and Vit D. For symptomatic give IV Ca
Hypercalcemia
• Ca2+ > 10.5
• Sx – stones, moans, groans, psychologic
overtones
• Causes – CHIMPANZEES
• Tx – Identify cause and treat,
severe/symptomatic hyperCa tx with IVF,
bisphosphonates if due to release of Ca
from bone