Lecture 15: Body Fluids Flashcards
1
Q
Review slide 4-6 and do what it says
A
Do it.
2
Q
How much daily intake of fluid is recommended daily?
Fluid Loss?
A
- Fluid Intake
- Ingestion (fluids or food): 2100 ml/day
- Metabolism: 200 ml/day
- Fluid Loss:
-Insensible evaporation:
350 ml/day through skin (3-5 liters/day for severe burns)
350 ml/day via lungs - Sweat: 100 ml/day (5000 ml/day during exercise)
- Feces: 100 ml/day
- Urine: 1400 ml/day (500 ml/day during exercise)
Total: 2300 mL/day both in And out
3
Q
Review image on slide 8
What is the water composition in the average person?
A
- Extracellular:
- Interstitial (≈ 11 liters)
- Plasma (≈ 3 liters)
- Transcellular
*Intracellular: 28 liters (40%)
- Total:
- 42 Liters in a 70 kg male
- 50% body weight in females because of more body fat
- 70-75% body weight in premature and newborn
4
Q
Describe the Osmolar Gap
A
Osmolar Gap: (helps to narrow the differential diagnosis)
- Difference between the measured osmolality and the estimated osmolality (Normal ≤ 15)
- ECF Effective osmolality = 2(Na+) mEq/L + (glucose mg%/18) + (urea mg%/2.8)
- Common things that can elevate the osmolar gap:
- Ethanol
- Methanol
- Ethylene glycol
- Acetone
- Mannitol
5
Q
Describe the body fluid compartments
A
- Ionic composition of plasma and interstitial fluid is similar because they are separated by highly permeable capillary membranes.
- Higher concentration of proteins in plasma because capillaries have a low permeability to plasma proteins.
- Intracellular fluid composition:
- Small amounts of sodium and chloride ions
- Almost no calcium ions
- Large amounts of potassium and phosphate ions
- Moderate amounts of magnesium and sulphate ions
6
Q
Describe the indicator dilution principle
A
- Applies to measurement of fluid volumes in body fluid compartments.
- Requirements for an indicator:
- Disperses evenly throughout compartment
- Disperses only in compartment being measured
- Not metabolized or excreted
- Not toxic
Vol B = Vol A x conc. A / conc. B
- See Slide 13
7
Q
Describe Fluid Distribution and Amounts
A
- Relative amounts of extracellular fluids in interstitial spaces and plasma are determined primarily by balance of hydrostatic and colloid forces across capillary membranes.
- Distribution of fluid between intracellular and extracellular compartments is determined mostly by osmotic effects primarily of sodium and chloride ions.
8
Q
What is the difference between Osmolality and Osmolarity?
A
- The total number of particles in a solution is measured in osmoles.
- Osmolal concentration of a solution =
- Osmolality when concentration is expressed as osmoles/Kg of water
- Osmolarity when concentration is expressed as osmoles/liter
9
Q
How does one calculate the potential osmotic pressure of a solution?
A
- About 80% of the total osmolarity of the interstitial fluid and plasma is due to sodium and chloride ions.
- For intracellular fluid, about half the osmolarity is due to potassium ion.
- If the cell membrane is exposed to pure water and the osmolarity of intracellular fluid is 282 mOsm/L:
- The potential osmotic pressure that can develop across the cell membrane is more than 5400 mm Hg.
10
Q
Define the term Isotonic
A
- Note that the terms isotonic, hypotonic, and hypertonic refer to whether or not solutions will change the volume of a cell. Refer to Figures 25-5 and 25-6.
- Addition of isotonic saline to extracellular fluid compartment:
- Extracellular osmolarity does not change
- Extracellular volume increases
- A solution of impermeant solutes having an osmolarity of 282 mOsm/L is isotonic
- Water cannot enter or leave the cell
- Examples: 0.9% NaClor 5% Glucose
11
Q
Define the term Hypertonic
A
- Addition of hypertonic saline to extracellular fluid compartment:
- Intracellular volume decreases
- Extracellular volume increases
- Osmolarity in both compartments increases
- A solution of impermeant solutes having an osmolarity > 282 mOsm/L = hypertonic
- Water will diffuse out of the cell
12
Q
Define the term Hypotonic
A
- Addition of hypotonic saline to extracellular fluid compartment:
- Volume of both compartments increases
- Osmolarity in both compartments decreases
- A solution of impermeant solutes having an osmolarity < 282 mOsm/L = hypotonic
- Water will diffuse into the cell
- See Slides 24-25
13
Q
- Need to figure out:
- What are the causes and consequences of hyponatremia and hypernatremia?
- Compare and contrast intracellular and extracellular edema.
- Name the three conditions especially prone to cause intracellular swelling.
- Review causes of extracellular edema:
- Refer to page 297
A
Have to look this one up on own.
14
Q
Review Slides 27-33
A
Do It
15
Q
Describe the anatomical organization of kidneys
A
- Capsule
- Renal cortex:
- Bowman’s capsule
- Proximal and distal convoluted tubules
- Renal medulla:
- Renal pyramids
- Renal pelvis:
- Major and minor calyces
- See Slides 36
