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FA2 Anesthesiology > Lecture 21 11/25/24 > Flashcards

Lecture 21 11/25/24 Flashcards

(60 cards)

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1
Q

How does body water relate to body weight?

A

-total body water equals 60-70% of body weight
-intracellular fluid volume equals approx. 40% body weight
-extracellular fluid volume equals approx. 20% body weight

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2
Q

What is the principle extracellular cation?

A

sodium

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3
Q

What is the principle intracellular cation?

A

potassium

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4
Q

What are the characteristics of plasma proteins?

A

-net negative charge
-important role in vascular volume

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5
Q

What are the characteristics of osmosis?

A

-process by which water is drawn across a semi-permeable membrane in response to presence of osmotically active particles
-impacted by sodium, potassium, chloride, and glucose

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6
Q

What is osmotic pressure?

A

theoretical pressure that would have to be applied against the semipermeable membrane to prevent movement of water by osmosis

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7
Q

What is osmolality?

A

number of osmoles of solute per KG of solvent

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8
Q

What is osmolarity?

A

number of osmoles of solute per L of solution

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9
Q

What is the normal ECF osmolality?

A

300 mOsm/kg

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10
Q

Which molecules contribute 95% of total osmolality of plasma?

A

-sodium
-potassium
-chloride
-bicarb.
-urea
-glucose

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11
Q

What are the characteristics of tonicity?

A

-measure of osmotic pressure gradient between two solutions
-influenced only by solutes unable to cross semipermeable membrane
-used to categorize fluids as hypotonic, isotonic or hypertonic based on how they compare with plasma tonicity

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12
Q

What are effective osmoles?

A

molecules unable to cross the semipermeable membrane

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13
Q

What are the characteristics of transcapillary fluid movement?

A

-fluid shifts between interstitial and intravascular compartments maintain the intravascular fluid volume
-balance between hydrostatic pressure and oncotic pressure favors or opposes fluid movement between compartments

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14
Q

What are the characteristics of hydrostatic pressure?

A

-independent of osmotic and oncotic pressures within blood vessels
-hydrostatic pressure is higher than that of the ISF compartment at the arterial end of a capillary; fluid is forced from intravascular to interstitium
-hydrostatic pressure is lower at the venous end of the capillary; fluid is not forced out of the vessel

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15
Q

What are the characteristics of osmotic pressure?

A

-exerted by proteins in plasma, namely albumin
-pulls/maintains fluid into intravascular space
-opposing force to hydrostatic pressure
-important for the maintenance of intravascular volume

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16
Q

What is the consequence of hypoproteinemia?

A

fluid can be shifted into the interstitium, resulting in edema

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17
Q

What is normal for the vascular endothelium?

A

selective permeability to larger molecules such as proteins

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18
Q

What are the characteristics of the endothelial glycocalyx layer?

A

-intraluminal hydrated gel in the vascular endothelium layer consists of glycoproteins, polysaccharides, and proteoglycans
-protective barrier between vessel wall and moving blood
-has a main role in transvascular fluid exchanges
-permeable to electrolytes and fluids but not larger molecules like albumin

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19
Q

What can perturb the endothelial glycocalyx layer?

A

-trauma
-sepsis
-diabetes/hyperglycemia
-electrolyte imbalance
-surgery
-overzealous fluid management

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20
Q

Why is fluid therapy an important component of anesthesia?

A

-optimize and maintain cardiac output and tissue perfusion
-maintain electrolyte conc. and acid-base balance
-replace fluids not being gained due to reduced intake
-replace ongoing fluid losses
-replace fluids lost to surgical bleeding/hemorrhage
-expand intravascular volume to offset vasodilation caused by anesthetic agents
-maintain intravenous catheter patency
-improve blood pressure
-maintain caloric balance
-address fluid resuscitation
-correct dehydration

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21
Q

What are the steps of goal-directed fluid therapy?

A

-recognize which fluid compartment deficit/s exist
-understand which fluid type and admin. route will best replace each deficit
-calculate fluid dose and admin. rate
-monitor patients for response to therapy and signs of complications

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22
Q

What is the order for addressing patient fluid deficits?

A

-treat hypovolemia/intravascular fluid space
-treat dehydration/interstitial fluid space
-treat free-water deficit/intracellular fluid space

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23
Q

How are intravascular fluid space deficits assessed?

A

*patient history: trauma, V+, D+, decreased water intake, fever
*perfusion parameters: mentation, HR, CRT, MM color, extremity temp., pulse quality
*BP: hypotension
*ECG: arrhythmias
*labs: hyperlactatemia, metabolic acidosis, decreased PCV/TS
*imaging: microcardia, small/collapsable vena cava

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24
Q

What is absolute hypovolemia?

A

-decreased fluid volume within the vascular space
-often due to hemorrhage

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25
What is relative hypovolemia?
-inappropriate fluid redistribution -due to pathological vasodilatory state, inhalant anesthesia, or vasodilatory drugs
26
Which parameters are used to assess interstitial fluid space deficits?
-decreased skin turgor -decreased mucus membrane moisture -increased PCV -increased TP -increased BUN -increased urine osmolality -increased USG
27
What are the characteristics of dehydration?
-typically a loss of interstitial space fluid -water from intracellular space will also be reduced -hypovolemia occurs in severe cases
28
What are the clinical signs of the different stages of dehydration?
-<5%: not detectable -5-6%: some change in skin turgor -6-8%: mild decreased skin turgor, dry mucous membranes -8-10%: obvious decreased skin turgor, retracted globes within orbits -10-12%: persistent skin tent due to complete loss of skin elasticity, dull corneas, evidence of hypovolemia ->12%: hypovolemic shock, death
29
How are intracellular fluid space deficits assessed?
-patient sodium conc. -solute-free water deficit/free water deficit
30
What are the characteristics of crystalloids?
-long term correction of dehydration -used most frequently -water based solutions w/ small molecules permeable to capillary membrane -interstitial compartment replacement solutions -treat dehydration, electrolyte imbalances, hypovolemic shock, and free water deficits -only 10-25% of crystalloids volume persists in vasculature 30-60 mins after admin
31
Which fluids most closely resemble extracellular fluid?
-isotonic -high in sodium -low in potassium
32
What are the characteristics of buffered isotonic crystalloids?
-commonly used -composition resembles that of extracellular fluid -ideal to replace ongoing losses, isotonic dehydration, treat hypovolemic shock, and correct electrolyte imbalances -alkalinizing solutions
33
Which compounds may be added to form balanced electrolyte solutions?
-KCl -Ca -MgSO4
34
Which compounds should not be administered in the same port as calcium?
-whole blood -HCO3-
35
What are the characteristics of NaCl 0.9%?
-isotonic but unbalanced -compatible with many drugs, blood products, and anticoags -large IV volumes can produce hyperchloremic metabolic acidosis and predispose to post-op vomiting -indicated in metabolic alkalosis
36
What are the characteristics of hypotonic crystalloids?
-contain excess water -administered in slow infusion -used in hypertonic dehydration or maintenance/daily requirements in patients with inadequate intake
37
What are the characteristics of dextrose solutions?
-isotonic only as administered -dextrose is metabolized to provide energy, leaving behind "free water" and a hypotonic solution -hypertonic when administered with other balanced electrolyte solutions and approaches isotonicity as dextrose is metabolized
38
What are the characteristics of hypertonic crystalloids?
-used in emergencies such as hypovolemia/shock -given in 4-6 ml/kg IV bolus to rapidly restore circulating volume -draws extravascular fluids into intravascular space -followed by isotonic solutions to maintain circulating volume and replenish interstitial and intracellular volumes -avoid in severely dehydrated/hypernatremic patients
39
What are the characteristics of colloids?
-water based solutions with both small/permeable and large/impermeable molecules -intravascular volume replacement solutions -natural colloids include plasma, blood, albumin, and oxyhemoglobin -synthetic colloids include large molecules in NaCl 0.9%
40
What are the characteristics of hydroxyethyl starch?
-immediate/sustained increase in hemodynamics with comparatively lower risk of fluid overload -100% of infused volume still in vessels one hours post-admin -followed by crystalloid therapy -cons include interference with cross-matching, interfering with hemostasis, expensive
41
Which blood/blood products are natural colloids?
-fresh whole blood -packed red cells -fresh plasma/fresh frozen plasma -human serum albumin -oxyglobin -cell-free crosslinked bovine hemoglobin -canine albumin
42
What are the characteristics of IV fluid admin?
-patients under anesthesia -patients with severe fluids/perfusion deficits or acute fluid losses -patients NPO -safe delivery of large fluid volumes/hypertonic fluids -risk of infection and phlebitis
43
What are the characteristics of intraosseous fluid therapy?
-emergency route when IV access is not possible -like a large central vein but without the collapse -risk of infection and fracture
44
What are the characteristics of SQ fluid therapy?
-no evidence-based info for volume, frequency. or adverse side effects -not effective in edematous and hypo-perfused patients -should be avoided in euhydrated patients -good for outpatient fluid therapy -avoid excessive tissue distention
45
What are the characteristics of oral fluid therapy?
-should be used whenever possible -can use feeding tubes if animal is anorexic -can be used to correct mild dehydration or to supplement parenteral routes -useful in dehydrated patients that cannot tolerate IV fluids
46
What are the components of total fluid requirement?
-resuscitation rate -rehydration rate -maintenance rate
47
What is the resuscitation rate for different species?
-given over 15 minutes -cats: 5-10 ml/kg -dogs and horses: 10-20 ml/kg
48
What are the characteristics of ongoing fluid loss replacement?
-done over 24 hours -calculate dehydration vol. in L by taking dehydration % x BW in kg -replaces losses due to GI loss, wounds, kidney disease, and inadequate intake
49
What are the daily fluid needs?
-total of 50-65 ml/kg/day -approx. 20 ml/kg/day lost in urine -approx. 10 ml/kg/day lost in feces -approx. 20 ml/kg/day lost to skin/respiration -40-60 ml/kg/24h is the maintenance rate
50
What are the fluid losses that must be accounted for during anesthesia?
-insensible water loss: 0.5 ml/kg/h -extravasation due to surgical trauma: 1 ml/kg/h -sensible loss: 0.5-1 ml/kg/h
51
What are the characteristics of hypoglycemia?
-must be accounted for in hypoglycemic patients and pediatric toy breeds -corrected with 2.5% dextrose solution
52
What are the characteristics of acute surgical blood loss?
-fluid rate up to 10 ml/kg/hr while surgically correcting tissue -3X crystalloid volume to replace 1X volume of blood lost -colloid can aid perfusion if blood products are unavailable and patient's perfusion is compromised
53
What are the characteristics of hypoproteinemia?
-canine albumin used when TS = 2.0 g/dL -colloid followed by crystalloid used when TS = 4.0 g/dL -fresh frozen/frozen plasma should be used when available
54
What are the characteristics of patients with renal disease?
-correct dehydration prior to anesthesia -optimize cardiac output with appropriate anesthetic protocol -closely monitor and manage blood pressure -avoid rectifying hypotension with excessive fluid infusion rates
55
What should be monitored when a patient is on fluid therapy?
-pulse rate/quality, BP, pulse ox -CRT, MM, skin turgor -resp rate/effort, lung sounds -body weight -urine output, USG -mental status -extremities temp. -venous and arterial blood gases -PCV/TS/lactate/creatinine/electrolytes
56
What aspects of the fluids should be considered in monitoring?
-duration of anesthesia -total vol. of IV fluids -max of 20 ml/kg per single anesthetic episode -do not exceed rate of 5 ml/kg/h for extended periods unless significant blood loss occurs -calc. daily maintenance rate volume to determine total fluid admin. per anesthetic event
57
What are the signs of fluid overload?
-weight greater than 10% from baseline admission -gallop sound/new murmur -tachypnea -pulmonary crackles -low SpO2 -peripheral tissue swelling or chemosis -clear nasal discharge -pleural effusion/ascites -electrolyte or acid-base disturbance -hemorrhage exacerbation -hemodilution
58
What should be done if fluid overload occurs?
-stop fluid admin. -use furosemide in patients with pulmonary edema or pleural effusion development
59
What are the consequences of fluid overload?
-pulmonary edema -cerebral edema -myocardial edema -increased renal venous pressure -renal interstitial edema -gut edema -tissue edema -impaired lymphatic drainage -microcirculatory derangements
60
What are the takeaways of anesthesia fluid therapy?
-do not withhold water pre-op -most animals do not require fluids post-op -return patients to normal eating and drinking asap -anorexic patients may need post-op fluids and SQ fluids at home -all patients need IV catheter -administer balanced isotonic crystalloid fluids -assess fluid deficits -maintain MAP > 60 mmHg to maintain perfusion

FA2 Anesthesiology (23 decks)

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