1
Q
Body water distribution
A
TBW
(60% / 42 L)
ICF ECF (40% / 28 L) (20% / 14 L)
Interstitial fluid Plasma
(15% / 11 L) (5% / 3 L)
2
Q
Major ECF ions
A
- Na
- Ca
- Cl
- HCO3
3
Q
Major ICF ions
A
- K
- Mg
4
Q
Neonates TBW%
A
higher
5
Q
Females, obese, elderly TBW%
A
lower
6
Q
Starling forces
A
dictate passive exchange of H2O b/t capillaries & interstitial fluid
7
Q
Forces that move fluid from capillary to interstitial space
A
- Pc = capillary hydrostatic pressure (push)
- Interstitial oncotic pressure (pull)
8
Q
Forces that move fluid from interstitial space into capillary
A
- Pif = interstitial hydrostatic pressure (push)
- capillary oncotic pressure (pull)
9
Q
endothelial glycolayx
A
- protective layer on interior wall of vessel
- gatekeeps what can pass from vessel to interstitial space
- disruption contributes to capillary leark
10
Q
What factors disrupt glyocalyx?
A
- sepsis
- ischemia
- DM
- vascular surgery
11
Q
Hematocrit
A
fraction of BV occupied by erythrocytes
12
Q
Hct is increased by:
A
- increased # RBCs (polycythemia)
- decreased plasma volume (hypovolemia)
13
Q
Hct is decreased by:
A
- decreased # RBCs (anemia)
- increased plasma volume (hemodilution)
14
Q
Lymphatic system
A
- removes fluid protein, bacteria, & debris in interstitium
- propels lymph through vessel network via one way valves
- creates negative pressure
15
Q
Return of lymph for systemic circulation
A
- returned via thoracic duct at juncture of IVC & subclavian vein
16
Q
osmosis
A
net movement of H2O across semipermeable membrane
17
Q
diffusion
A
net movement of substance from area of high concentration to area of lower concentration across fully permeable membrane
18
Q
osmotic pressure
A
pressure of a solution against a semipermeable membrane that prevents H2O from diffusion across
19
Q
osmolarity
A
- measures concentration of particles in a solution
- unit of measurement = osmoles per L of solution (mOsm/L)
20
Q
osmolality
A
- measures concentration of particles in a solution
- unit of measurement = osmoles per kg of solvent (mOsm/kg of H2O)
21
Q
plasma osmolarity formula
A
2 [Na+] + Glucose/18 + BUN/2.8
22
Q
normal plasma osmolarity
A
280-290 mOsm/L
23
Q
most important determinant plasma osmolarity
A
Na+
24
Q
What 2 things can increase plasma osmolarity?
A
- hyperglycemia
- uremia
25
Hypotonic solutions
- solution hypotonic to cell
- H2O enters & cell swells
- lower osmolarity than plasma
- increases ECF & ICF volume
- decreases plasma osmolarity
26
isotonic solutions
- solution isotonic to cell
- no H2O transfer & cell remains same size
- osmolarity approximates plasma
- expand plasma volume & ECF
- increases ECF
- ICF & plasma osmolarity stay same
27
hypertonic solutions
- solution hypertonic to cell
- H2O exits cell & cell shrinks
- osmolarity exceeds plasma
- expands IV volume
- ECF & plasma osmolarity increase
- ICF decreases
28
Hypotonic solution examples
Crystalloids
- NaCl 0.45%
- D5W
29
Isotonic solution examples
Crystalloids
- NaCl 0.9%
- LR
- Plasmalyte A
Colloids
- albumin 5%
- volvuven 6%
- hespan 6%
30
Hypertonic solution examples
Crystalloids
- NaCl 3%
- D5 NaCl 0.9%
- D5 NaCl 0.45%
- D5 LR
Colloids
- Dextran 10%
31
What complication can result from large amounts of NaCl?
hyperchloremic metabolic acidosis
32
How long do crystalloids remain in the IV space?
~ 30 minutes
33
What complication can result when hypertonic saline is administered too quickly?
central pontine myelinolysis
34
Crystalloid advantages
- 3:1 replacement
- expands ECF
- restores 3rd space loss
35
Colloid advantages
- 1:1 replacement
- increases plasma vol (3-6 hr)
- smaller vol needed
- less peripheral edema
- albumin has anti-inflammatory properties
- dextran 40 reduces blood viscosity
35
Crystalloid disadvantages
- limited ability to expand plasma volume
~ increases for ~ 20-30 min
~ higher potential for peripheral edema
- large vol NaCl --> hyperchloremic met acidosis
- dilutional effect on albumin
- dilutional effect on coagulation factors
36
Colloid disadvantages
- albumin binds Ca+ --> hypocalcemia
- black box warning on synthetic colloids- renal injury
- coagulopathy
Dextran > Hetastarch > Hextend (no >20 ml/kg)
- anaphylactic potential- highest = dextran
37
What is the black box warning on synthetic colloids?
risk of renal injury
38
Which colloid has highest incidence of coagulopathy?
dextran > hetastarch
39
How does albumin affect serum calcium?
hypocalcemia
40
Fluid Calculation (Historical)
1: Fluid Hourly Maintenance (4:2:1)
- 4 ml/kg/hr = 1st 10 kg
- 2 ml/kg/hr = 2nd 10 kg
- 1 lm/kg/hr remaining kg
2. Calculate fluid deficit
- # fasting hours x hourly maintenance
3. Calculate "third space" loss
- very minimal surgical trauma = 1-2 ml/kg/hr
ex: orofacial surgery
- minimal surgical trauma = 2-4 ml/kg/hr
ex: inguinal hernia repair
- moderate surgical trauma = 4-6 ml/kg/hr
ex: major nonabdominal surgery
- severe surgical trauma: 6-8 ml/kg/hr
ex: major abdominal surgery
4. Calculate blood loss replacement
- crystalloid = 3:1 (3 ml for q 1 ml blood loss)
- colloid or blood = 1:1
41
Goal-directed fluid therapy
- attempts to optimize pt's position on Starling curve
- administration of small quantities of fluid (200-250 ml) to determine difference b/t preload dependence & preload independence
42
Enhanced Recovery After Surgery
43
5 objectives to enhance postsurgical outcomes w/ ERAS
1. Attenuate physiologic changes that accompany surgical trauma
2. Minimize impact of fluid shifts
3. Maximize nutritional impact of healing
4. Improve postop pain
5. Improve patient education & compliance
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