Fluid Therapy Flashcards
Indications for fluid therapy
Decreased intake dehydration decreased circulating volume (shock) need for overhydration correct electrolyte abnormalities
What clinical indicators are used to indicate need for fluid therapy
skin turgor (changes at 8-10%) - neck in adults, eyelid in foals or geriatric
MM - moisture level and CRT
urine production - decreased unless renal disease
sunken eyes - rare in horse
depression, muscle weakness
heart rate - tachycardia = one of first things you’ll see
decreased jugular distensibility
What lab indicators are used to indicate need for fluid therapy?
PCV - splenocontraction can over or underestimate degree dehydration
TP - increase
BUN/Cr
Albumin - need to keep above 1.5g/dL, only cause of hyperalbuminemia is dehydration
lactate
urinalysis - typically USG of >1.030
PCV increase iwith dehydration
for every 2-3% increase in % dehydration over 5%, PCV increases 5%
5% dehydration
skin tent: 1-3s MM - moist to slightly tacky CRT - normal, <2s HR - normal Other: decreased urinary output
8% dehydration
skin tent: 3-5s MM - tacky CRT - variable (2-3s) HR - 40-60bpm other: decreased arterial blood pressure
10-12% dehydration
skin tent: 5 or more s MM - dry CRT - variable, often >4s HR - >60bpm other: reduced jugular fill, barely detectable peripheral pulse, sunken eyes
15% dehydration
death imminent
oral fluids
animals drink at own will
- never place electrolyte solution alone, always with access to free water
nasogastrically intubated - can leave in for short time to avoid repeated trauma, can give 6-8L = 12-16L/h (30m transit to stomach)
A: most physiologic, non-invasive, not expensive, can loosen impactions in LI
D: DON’T GIVE IF ILEUS, GASTRIC DISTENTION OR REFLUX
IV fluids
place catheter so fluids flow towards the heart
typically 14G 5.5” Angiocath
A: easy access, allows easy change in fluid plan, almost unlimited available amount of fluids and rate
D: danger of compromise to vein, sepsis risk, sterility, cost, requires monitoring
jugular vein
easy access, well tolerated, catheter inserted downwards
Lateral thoracic vein
second choice, esp if dysfunction of one jugular v
catheter placed horizontal to gravity, towards head
poor choice for recumbent animal
Cephalic vein
first choice for limb catheters, placed tip towards heart,
disadvantages: easily clots due to placement against gravity, advised to always have fluids running through, not used for medication administration alone
Saphenous vein
easily bent due to limb motion, placement MUCH less tolerated, typically only used if “running out’ of veins
Subcutaneous fluid administration
helpful in foal but rarely used, not used in skin
no clinical indications for use
Intraperitoneal fluid administration
A: can get large volumes in at rapid rate, easy access, could be alternative if limited venous access
D: vigilant monitoring needed, sepsis is risk, except to get large volumes but practically cannot because fluid tracks down within abdomen
Rectal fluid administration
use gravity flow or pump, have horse standing on an incline with head lower than hind limbs
A: no sterility required, absorption across gastric mucosa, potentially large fluid volumes, helpful if limited venous access
D: can’t help in moderate to severe ileus, cannot be used in severe colitis
Intraosseus fluid administration
used in severe dehydration to increase circulatory volume if no jug filling, esp foals
D: difficult, strict sterility, limited rate of administration due to needle size
Intracecal fluid administration
A: large volumes directly into intestinal segment with greatest absorption
D: more invasive, strict sepsis
Rate of flow through system dependent on:
radius/diameter of catheter
pressure differences (change in fluid height - rate can increase if you raise fluid higher)
length of system components - longer = slower rate
viscosity of fluid
STAT IV flow rates
14G - 5.25” - 13.1L/hr
12G - 26.9L/hr
10G - 36.5L/hr
Typical STAT IV equine set up
8’ above horse head, 28L/hr gravity flow capacity
12 drops/ml
Long term vs short term catheters
Long term: up to 14d, soft material, over wire placement, expensive, polyurethane or silicone
Short term: up to 72h, teflon and polyethylene
catheter complications
thrombosis, cracking, breakage, air embolism, extravasation
Rate of thrombosis dependent on
systemic state (coagulation status) of animal
stiffness of catheter - more stiff more thrombogenic
size of catheter - larger more thrombogenic
length of catheter - more thrombogenic
material - polypropylene = most thrombogenic, polyurethane (mila) = least thrombogenic
vessel trauma
air embolisms in IV catheters
death due to cardiac arrest if 3-8ml/kg of air in circulation
typical acid-base disturbance in horse
metabolic acidosis
2 electrolytes horses tend to lose
K and Ca
Crystalloid fluids
most commonly used
composition based on electrolytes and non-electrolyte solutes only
replacement crystalloids: composition similar to ECF
maintenance crystalloids: composition with less sodium and more potassium
-LRS, Saline, Normosol, Plasmalyte, Dextrose, bicarbonate solution
- hypertonic saline most commonly used in resuscitation, 7.2%HS
Colloid fluids
if hypoproteinemia
less commonly used
recommended when need to increase oncotic force within IV space to retain fluid within that space
- hetastarch, dextran, plasma, serum
Fluid tonicity always named in reference to
plasma tonicity
Isotonic fluids
includes most commonly used solutions
hypotonic solutions
decreased tonicity compared to plasma
used in cases of plasma hyperosmolality
hypertonic solutions
tonicity above plasma
Hypertonic saline
resuscitation and emergency use
hypovolemia
MOA: fluid shift from intracellular space to ECF space associated with increased tonicity
Effect: temporarily improves CO, MABP, urine production, decreases SVR
- increases preload while decreases afterload
Major disadvantages/contraindications:
- rapid decay of effect, may combine with 6% dextran 70
- uncontrolled hemorrhage
- renal failure, CV alterations, hypokalemia
Calculate dehydration deficit
Deficit (L) = BW (kg) x % dehydration
Calculate maintenance
Maintenance (ml) = BW(kg) x 60ml/kg/d
divide by 1000 to get L
5% dextrose infusion is like infusing
free water
Typical equine fluid rate
10-20ml/kg/hr
shock dose for horse
30-40L/hr
degree dehydration and catheter size
if severe, recommend 10-12G or possibly 2 12-14G
if moderate, 12-14G
miniature horses and weanlings with moderate dehydration
goal of replacing estimated deficits (time)
1-2h
can safely give 1 blood volume per hour
24 hour fluid plan
incorporate maintenance, continued dehydration (if it exists, and estimated ongoing losses)
dehydration (L) = % dehydration x BW
maintenance = 50-60ml/kg/day
ongoing losses - vomit, diarrhea, anything quantifiable
Potassium
plasma level not good indicator of total body K, intracellular concentration better
large amount ingested in diet so large amount excreted daily
see large total body depletion in anorexia and colic
hypokalemia
caused by decreased intake, sequestration loss, associated with alkalosis
clinical effect: arrhythmias, myocardial dysfunction, weakness, decreased intestinal motility
hyperkalemia
lab error - RBC rupture in sample
associated with HYPP, acidosis, uroabdomen, acute oliguric renal failure
clinical effect: cardiac arrhythmias, standstill (KCl can be used as euthanasia solution)
Potassium supplementation
Max IV dose: 0.5mEq/kg/hr
Calcium
highly protein bound to albumin
most interested in maintaining ionized fraction to maintain normal physiologic functions
ionized Ca most accurately reflects Ca status
large amount in diet so large amount excreted
in anorexia, see total body depletion of Ca
Hypocalcemia
synchronous diaphragmatic flutter - Thumps
functional abnormality of no clinical significance
appears as hiccoughs
hyper responsiveness of phrenic nerve
Effects: muscle paresis, tremors, excitability, cramping, aggression, excitation, hypersensitivity, decreased myocardial contractility, hypotension
3 things that can cause synchronous diaphragmatic flutter (thumps)
hypocalcemia
hypokalemia
metabolic alkalosis
Hypercalcemia
seen in renal failure
effects: toxic to cells, effects heart, kidneys, CNS, GIT
cardiac arrhythmias, seizues, twitching
Ca supplementation
recall decreased intake –> total body Ca deficit
general 100-150ml Ca gluconate in fluids without bicarbonate SLOWLY
recheck after giving half desired dose
incompatible with tetracycline, IV lipids, bicarbonate
give slo because cardiotoxicity if too rapid, bradycardia
Magnesium
hypomagnesemia often associated to conditions leading to hypoK and hypoCa, may blunt response to Ca therapy
can potentiate cardiac arrhythmias
IV administration: Mg sulfate
- vasodilator properties, dont give if hypotensive
- IV slow as 10% solution if severe hypomagnesemia
Sodium
typically reflect water balance, water follows Na
changes often concomitant with changes in Cl
Determining type of fluid loss
hypertonic loss - loss of electrolytes in excess of water
hypotonic loss - loss of water in excess of electrolytes
isotonic loss - loss of electrolytes in same ratio as found in serum
HORSE - typically has isotonic losses especially as it relates to GIT disease, horses exercising lose isotonic then as become more dehydrated losses become hypertonic
Sodium disturbances
both hypo- and hyper-natremia cause CNS signs
CS dependent on severity of Na alteration and speed of development
Compensatory mechanism: within brain cells, adjust intracellular osmolality to equal to that of extracellular environment - only occurs if CHRONIC changes
neurons create idiogenic osmoles to maintain osmolality and can destroy them
Acute: recommended rapid restoration to normal Na status
Chronic: rapid restoration can be detrimental due to compensatory mechanisms in play - can increase CNS intracellular volume = brain edema
- outside compensated range, chronic still appears as if it were acute showing clinical signs
Most common acid-base disturbance in horse
metabolic acidosis
Quantitative analysis of acid base
for every 10mmHg increase in PCO2, there is corresponding 0.05 decrease in pH
Metabolic acidosis
most common in horses
caused by loss of bicarbonate or increase in acid
- hyperchloremia - loss of base
- increased anion gap - gain of acid (lactic acidosis, toxins, renal failure)
Treatment of metabolic acidosis
use alkalinizing solution: buffer base in solution (LRS, normosol)
typically lactate
bicarbonate as Tx for metabolic acidosis
not used unless bicarb <17-18 or pH <7.2
never treat empirically to correct, need to measure actual level
calculate deficit: deficit X distribution X bwt kg = ____mEq
Distribution factor: 0.3 conservative 0.4 typical 0.5 young animals Give 1/2 of dose over first hour then re-evaluate to avoid putting them into metabolic alkalosis
Metabolic alkalosis
only occasionally, endurance racing (swear losses)
also high GIT disease
contributes to development of synchronous diaphragmatic flutter
Treatment: acidifying solution (NaCl)
Patterns of specific disturbances
Endurance - losses of Na, Cl especially, hypocalcemia and hypokalemia also seen
- loss of Cl results in retention of bicarbonate and metabolic alkalosis (high pH)
Choke - losses of Cl
- results in retention of bicarbonate and metabolic alkalosis (high pH)
General - most common alteration = metabolic acidosis
