Fluids Flashcards
(83 cards)
1
Q
Body weight at birth is comprised of what % of total body water? Then at adult?
A
75-80% then it decreases with age
60%
2
Q
What is the fluid compartment 60:40:20 rule?
A
60% is total water in body
Intracellular space is 40% bw
Extracellular is 20% bw
- Interstitial is 15% bw
- Intravascualr/plasma water is 5% bw
3
Q
What is osmolality?
A
number of particles in a solution (osmoles of
solute) per kg of solvent.
The plasma contains unbound particles, positively and
negatively charged for an overall charge of roughly zero (electrically quasi-neutral medium).
Those particles dissolved in the plasma are chemicals like electrolytes, proteins, glucose.
4
Q
What is the osmolality of the plasma?
A
Typically, the osmolality of the plasma is about 280-310 mOsm/kg in most healthy animals
5
Q
What is the plasma osmality of some birds>
A
▸ African Grey: 288-324 mOsm/kg
▸ Hispaniolan Amazon: 308-345 mOsm/kg
▸ Red-fronted macaws: 223-369 mOsm/kg
6
Q
What are the principle electrolytes in plasma?
A
Anions - and Cations +
▸ mmol/L or mEq/L
Principal extracellular Cation
▸ Sodium
Principal extracellular Anions
▸ Chloride and Bicarbonate
Plasma proteins
- Net negative charge
- Important role in vascular volume
7
Q
What is oncotic pressure and what plasma protein contributes to this?
A
Form of osmotic pressure exerted by proteins, notably albumin, in the plasma that
usually tends to pull water into the circulatory system
▸ It is the opposing force to hydrostatic pressure
8
Q
What is the endothelial glycocalyx layer and how does this contribute to fluid therapy?
A
- Sugar protein coating (proteoglycan, glycoproteins
and glycosaminoglycans (GAGs)) at the luminal
surface of the vascular endothelium - Contributes to 2% of the plasma volume
- Essential role in maintaining the normal fluid homeostasis of the body
a. Protective barrier between blood and vessel wall - Permeable to electrolytes and fluids but not larger molecules like albumin if intact!
9
Q
How can the glycocalyx become damaged?
A
Trauma, sepsis, diabetes, electrolyte imbalance, surgery and overzealous fluid management
10
Q
Fluid therapy should be individualized and is considered a what?
A
Prescription
11
Q
When should fluid therapy be instituted?
A
- Anesthesia period (pre/per/post) lasting longer than 30 minutes
- Hydration / volemia / perfusion status
- Electrolytes &/OR Acid-base balance
- Renal function
- Cardiac function/cardiovascular status
- Caloric balance
12
Q
How does dehydration present in a patient and what might be important history?
A
- Vomiting/diarrhea, frequency/duration
- Urination frequency, urine color, thirst
- Unable to access water/food: level of ambulation/consciousness EX: cervical disk pain/tetraparesis
- Unable to eat or to drink: trauma to mouth/head, swallowing issue
13
Q
What would you find on your PE in a dehydrated patient?
A
- loss of Skin elasticity
- Eyes: sunken
- Bladder : small
14
Q
What are some causes of hypovolemia?
A
- Hemorrhage secondary to trauma
- Coagulopathy
- Neoplasia
- Gastroenteritis, Pancreatitis, Peritonitis
15
Q
How does dehydration present in a patient and what might be important history?
A
- MM dry, pale or dark, CRT >2 sec
- Heart Rate: Tachycardia
- Blood Pressure: PA Systolic <90 mmHg
- Perfusion and BP issues
16
Q
What are some lab values you should analyze in fluid therapy and should you reevaluate any throughout TX?
A
o PCV, TS
o Urine specific gravity
o Chemistry
▪ Electrolytes panel, acid-base status, BUN, Albumin (>1.5 g/dl), creatinine
o CBC (Hb >5-7 g/dl)
o Blood lactate
Reevaluate all of them
17
Q
What are the 2 major types of fluid?
A
A. Crystalloids
B. Colloids
18
Q
What type of fluid is used most often?
A
Crystalloids
19
Q
What are crystalloid fluids?
A
- Water based solutions with small molecules like electrolytes, glucose and buffer, permeable to
capillary membrane. - Interstitial volume replacement solutions
20
Q
Crystalloids are used for treating what?
A
dehydration and electrolyte derangements and correcting free water deficits.
▸ Only 10-25% of crystalloid volume administered IV persists in the vasculature 1 hour after administration
21
Q
What are the tonicities of crystalloids?
A
- Isotonic, hypotonic, hypertonic
22
Q
Fluids that most closely resemble the ECF are
A
- Isotonic
- High in sodium and low in potassium
23
Q
What are some isotonic fluids?
A
Normosol R, LRS, Plasmalyte 148, NaCl 0.9%
24
Q
When would you use isotonic fluids?
A
Ideal to replace ongoing losses, isotonic dehydration, treat hypovolemic shock, correct electrolytes imbalances
▸ Select a solution according to patient’s need
25
What are some alkalizing solutions? and what does this mean?
LRS, PLASMALYTE 148, Normosol-R
- Metabolism of substrates like lactate, acetate, gluconate to alkalinizing equivalents to reduce acidemia
26
What isotonic solution is unbalanced?
NACL 0.9%
26
You should avoid administering balanced solutions containing what?? to the same port as whole blood or what will happen?
Balanced solution containing calcium (LRS) should not be administered in same port as whole blood or HCO3- to avoid calcium precipitation
27
Balanced electrolyte solutions may need what added to them?
May necessitate the addition of KCl, Ca, MgSO4, etc
28
NaCl 0.9% is compatible with?
Compatible w/ +++drugs, blood products, anticoagulants
28
When should you use NasCl 0.9%?
Usually appropriate only as replacement (not maintenance)
▸ Large volumes IV (> 30 ml/kg): produces metabolic acidosis, can impair renal blood flow,
predisposes to postoperative vomiting
29
What are some indications that you should give unbalanced isotonic solution instead of balanced like LRS?
Metabolic Alkalosis: High in chloride, promotes bicarbonates renal excretion
▸ Hyperkalemia?, hypercalcemia?
30
What are some hypotonic crystalloid solutions?
NaCl 0,45%, D5W, ½LRS or ½ NaCl +2,5% Dextrose, Plasmalyte 56, Normosol-M
31
Hypotonic solutions contain? and should be administered how?
Contain excess water
▸ **Administered in slow infusion
32
When should you use hypotonic solutions?
For hypertonic dehydration (hypernatremia)
33
What is dextrose solution that is available and how is it used? ?
- 5% dextrose in water (D5W) is isotonic only as administered
- When Dextrose is metabolized, providing energy, it leaves “free water”
a. can result in a hypotonic solution
- May be added to other balanced electrolytes solutions (2.5% or 5% dextrose)
a. Hypertonic when administered, but approaches isotonicity as dextrose is metabolized
34
What are some hypertonic crystalloid solutions?
NACL 5-7.5% in water
35
When should you use hypertonic NaCl 5-7.5%?
For emergency, hypovolemia/shock transient therapy
▸ Small doses (4-6ml/kg, IV bolus) rapidly restores circulating volume to hypovolemic patients:
osmotically draws extravascular fluids into the intravenous space
- Only temporary and fluid will rediffuse back into extravascular space later
36
You must follow hypertonic solutions with:
Must be followed by isotonic solutions, crystalloids or colloids, to maintain circulating volume
37
You should avoid hypertonic solutions in:
severely dehydrated/hypernatremic patients
38
What are colloids?
Water based solutions with both small (permeable) and large (impermeable) molecules
39
Colloids provide volume replacement into what space?
▸ Intravascular volume replacement solutions
- Draws fluid into vessels from interstitial and intracellular space for up to 24 hrs
40
What are the natural colloids?
plasma, blood, albumin, oxyhemoglobin
41
What are some sythetic colloids?
large molecules in NaCl 0.9%
42
Colloids are indicated for:
Hypovolaemia:
- shock
- hemorrhage
- circulatory support
Hypoalbuminemia:
- provides oncotic support
43
What is hydroxyethyl starch (HES)?
Hetastarch, a synthetic colloid
- Heterogeneous mix with molecular weights ranging from 10,000 to 1 million
- Each gram of HES has the capacity to retain 30 ml of fluid in the intravascular space
- HETASTARCH, PENTASTARCH, TETRASTARCH
44
Why should you use synthetic colloids like HES?
- Immediate/sustained increase in hemodynamics w/comparatively lower risk of fluid overload
- 100 % of volume infused still in intravascular compartment 1 hour post administration
45
You should follow sythetic colloid fluid with:
Followed with crystalloid fluid therapy
46
What can sythetic colloids interfere with?
May complicate cross-matching for blood transfusions, interfere w/ hemostasis, $$$
47
What are the total daily doses in animals?
Total daily doses should not exceed 20 ml/kg/day for most animals, Cats: 10 ml/kg/day
48
Warning! You should be cautious using sythetic colloids in what patients?
- Current shift away from colloids (or large volumes) in critical care and sepsis
- Caution w/dehydrated animals, animals with coagulopathy, head trauma, impaired renal
function (elevated BUN or creatinine concentrations)
- Adverse effects and toxicities caused by colloidal solutions are dose-dependent
- Strictly follow guidelines for dosing
49
What are some natural colloid products that can be used for fluid therapy?
- BLOOD AND BLOOD PRODUCTS
- Fresh whole blood: if Hb < 7 g/dl
- Packed red cells
- Fresh frozen plasma, fresh plasma: Coagulation factors, AB
- Human serum albumin ($$)
- Oxyglobin
- Cell-free (stroma-free) crosslinked bovine hemoglobin
- Canine albumin
50
What are the three goals of fluids when determining how much should be given?
- Replace existing deficits
* Maintain daily needs
* Take care of ongoing losses
51
How do you calculate replacement volume in a patient that is dehydrated?
- Replacement volume (L) = Body weight (kg) x % dehydration
- Replacement volume (ml) = Body weight (kg) x % dehydration (in decimals) x 1000 (1 kg water =
1000 ml)
- Ex: 400 kg Mare, 8% dehydrated: 32 L.
- Ex: 25 kg Dog, 8 % dehydrated (0.08) : 2 000 ml.
52
What are some ongoing losses that indicate fluid therapy?
- Diarrhea, gastric reflux, wound bleeding or oozing
- Ex: 400 kg Mare, 8% dehydrated, colic: proximal enteritis: reflux 2 L/hour = 48 L/day
53
What are the daily needs (Maintenance) of fluid?
- Patient does not eat or drink but normal losses still occur through urine (≈ 20 ml/kg), feces (≈ 10 ml/kg), skin & respiration (≈ 20 ml/kg) (total ≈ 50 ml/kg/day)
- Equine: 40-60 ml/kg/24h
- Dog: 132ml/kg/24h
- Cat: 80ml/kg/24h
54
How much fluid should be given with existing deficit, daily maintenance, and ongoing losses?
Ex: Mare 400 kg: Existing deficit: 32L + Daily maintenance: 16-24L + Ongoing losses: 48 L = 96-104
L/24h for 1st 24 h
55
What should you constantly reevaluate when determining fluid needs?
▸ Ongoing losses may vary through the day
▸ Measure PCV/TS frequently (q4-6 hours)
▸ Replace 75-80% of the original deficit over 24 h and reassess needs/dehydration
56
Insensible water loss under anesthesia is:
low, rarely exceeding 0.5 ml/kg/h
57
Surgical trauma will cause how much extravasation of fluid on average?
The extravasation of fluid due to “average” surgical trauma is less than 1 ml/kg/h
58
Is the administration of fluids to counteract the affects of anesthetic vasodilation inidicated?
The administration of a crystalloid or colloid to counteract the effects of anesthetic induced
vasodilatation (i.e. relative hypovolemia) is frequently ineffective and cannot be guaranteed
59
When we give IV fluids under GA we should aim for how much given and whats our goal?
- Aim at a total of 20-30 ml/kg/procedure
- Adjust fluid amount/type based on assessment/monitoring: GOAL directed therapy
60
How rapidly should the solution be given?
depends do we need shock therapy or maintenance therapy?
61
What is maintenance fluid therapy?
Cats: 80 * BW (rule of thumb: 2-3 mL/kg/hr)
Dogs: 132 * BW (rule of thumb: 2-6 mL/kg/hr)
Excessively rapid administration of maintenance fluid can result in fluid overload or
electrolyte imbalance
62
What is the shock fluid therapy protocol?
Large bore IV catheters
▸ Dogs: 80-90 ml/kg/h, Cats: 50-55 ml/kg/h
▸ Give 25% of calculated dose and reassess
63
The main points of fluid rates during anesthesia are?
- Rule of thumb for cats for initial rate: 3 ml/kg/hr
- Rule of thumb for dogs for initial rate: 5 ml/kg/hr
- Lower rates with cardiovascular diseases
- Fluid pre-op and post in patients with chronic renal disease
- Reduce fluid rates if procedure lasts > 1 hour
64
What are the differences of continuous and intermittent IV fluid therapy?
Continuous rate IV therapy
* Often best, may be unnecessary, impractical or problematic
* Delivered via drip sets/various fluid infusion pumps
Intermittent IV fluid therapy
* Often a practical/effective alternative to continuous IV
The risks of infection at catheter sites, phlebitis, and the dynamic volume requirements in the critically ill
65
When should you do intraosseous fluid therapy?
- Very useful for emergency vascular access
- Functionally analogous to a large central vein without the collapse!
- Neonates, exotic species, selected critically ill patients
66
What are the significant risk of IO therapy?
▸ Infection
▸ Periostitis
▸ Severe pain
▸ Rarely - loss of limb
67
When should give SQ fluid therapy?
▸ Patient must already be reasonably well perfused in order to mobilize SC fluids
▸ Not effective if the patient is edematous
68
You can give these fluids SQ but not what?
appropriate only for isotonic fluids without dextrose!
69
What are the risks/complications associated with SQ fluid therapy?
Avoid excessive tissue distention: Excessive volume administered in one site increases the risk of
tissue sloughs, infection, and pain
70
How will the success of the therapy be evaluated?
GOAL DIRECTED FLUID THERAPY
Pulse rate and quality, Blood pressure
Capillary refill time/Mucous membrane color, Skin turgor
Respiratory rate and effort/Lung sounds
Body weight
Urine output, urine sg
Mental status
Extremity temperature
venous/arterial blood gases
PCV/Total solids/serum lactate/bun/creatinine/electrolytes
71
What is PVI?
- Plethysmographic Variability Index (PVI)
- Respiratory variations in the amplitude of the pulse oximeter-derived plethysmography pulse
pressure waveform have been shown to predict fluid responsiveness.
- Dynamic variables (indices evaluating the response to cyclical changes in venous return, or
preload) are more predictive of fluid responsiveness.
- Arterial pulse pressure variation induced by manual or mechanical ventilation has been
demonstrated to be a specific and sensitive guide to fluid therapy.
- Respiratory variations in the amplitude of the noninvasively recorded pulse oximeter-derived
plethysmography (change in volume) pulse pressure waveform have been shown to predict fluid
responsiveness.
72
When does fluid overload occur?
Increase >10% from baseline admission weight
73
what are the clinical signs of fluid overload?
- Pulmonary edema, ascites, peripheral edema
- Tachypnea, clear nasal discharge, crackles at pulmonary auscultation
- Chemosis
- Electrolyte/acid base imbalance, hemorrhage exacerbation, hemodilution, coagulopathy
74
T/F: In general, the choice of fluid is less important than the fact that it is isotonic.
True
75
T/F: Volume benefits the patient much more than exact fluid composition
true
76
Isotonic fluids wont have a severe negative impact on most:
electrolyte imbalances, and their
use will begin to bring the body’s fluid composition closer toward normal pending laboratory
results that will inform the clinician of more specific fluid therapy.
77
When flushing an IVC normal saline is just as good as
heparinized saline
78
What solutions may be used in liver disease?
LRS or acetated Ringer’s solution may be used in liver disease. LRS contains both D- and Llactate and is unlikely to increase blood lactate levels
79
T/F: Use of K-containing balanced electrolytes solution does not increase blood K in cats w/urethral
obstruction
True
80
Can you use fluids in HCM patients?
Patients with subclinical HCM may be able to tolerate cautious fluid boluses for hypotension if
their volume status is questionable, but they should be closely monitored for fluid overload &
congestive heart failure
81
