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

Lecture 21 11/25/24 Flashcards

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
Q

What is relative hypovolemia?

A

-inappropriate fluid redistribution
-due to pathological vasodilatory state, inhalant anesthesia, or vasodilatory drugs

26
Q

Which parameters are used to assess interstitial fluid space deficits?

A

-decreased skin turgor
-decreased mucus membrane moisture
-increased PCV
-increased TP
-increased BUN
-increased urine osmolality
-increased USG

27
Q

What are the characteristics of dehydration?

A

-typically a loss of interstitial space fluid
-water from intracellular space will also be reduced
-hypovolemia occurs in severe cases

28
Q

What are the clinical signs of the different stages of dehydration?

A

-<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
Q

How are intracellular fluid space deficits assessed?

A

-patient sodium conc.
-solute-free water deficit/free water deficit

30
Q

What are the characteristics of crystalloids?

A

-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
Q

Which fluids most closely resemble extracellular fluid?

A

-isotonic
-high in sodium
-low in potassium

32
Q

What are the characteristics of buffered isotonic crystalloids?

A

-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
Q

Which compounds may be added to form balanced electrolyte solutions?

A

-KCl
-Ca
-MgSO4

34
Q

Which compounds should not be administered in the same port as calcium?

A

-whole blood
-HCO3-

35
Q

What are the characteristics of NaCl 0.9%?

A

-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
Q

What are the characteristics of hypotonic crystalloids?

A

-contain excess water
-administered in slow infusion
-used in hypertonic dehydration or maintenance/daily requirements in patients with inadequate intake

37
Q

What are the characteristics of dextrose solutions?

A

-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
Q

What are the characteristics of hypertonic crystalloids?

A

-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
Q

What are the characteristics of colloids?

A

-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
Q

What are the characteristics of hydroxyethyl starch?

A

-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
Q

Which blood/blood products are natural colloids?

A

-fresh whole blood
-packed red cells
-fresh plasma/fresh frozen plasma
-human serum albumin
-oxyglobin
-cell-free crosslinked bovine hemoglobin
-canine albumin

42
Q

What are the characteristics of IV fluid admin?

A

-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
Q

What are the characteristics of intraosseous fluid therapy?

A

-emergency route when IV access is not possible
-like a large central vein but without the collapse
-risk of infection and fracture

44
Q

What are the characteristics of SQ fluid therapy?

A

-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
Q

What are the characteristics of oral fluid therapy?

A

-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
Q

What are the components of total fluid requirement?

A

-resuscitation rate
-rehydration rate
-maintenance rate

47
Q

What is the resuscitation rate for different species?

A

-given over 15 minutes
-cats: 5-10 ml/kg
-dogs and horses: 10-20 ml/kg

48
Q

What are the characteristics of ongoing fluid loss replacement?

A

-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
Q

What are the daily fluid needs?

A

-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
Q

What are the fluid losses that must be accounted for during anesthesia?

A

-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
Q

What are the characteristics of hypoglycemia?

A

-must be accounted for in hypoglycemic patients and pediatric toy breeds
-corrected with 2.5% dextrose solution

52
Q

What are the characteristics of acute surgical blood loss?

A

-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
Q

What are the characteristics of hypoproteinemia?

A

-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
Q

What are the characteristics of patients with renal disease?

A

-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
Q

What should be monitored when a patient is on fluid therapy?

A

-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
Q

What aspects of the fluids should be considered in monitoring?

A

-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
Q

What are the signs of fluid overload?

A

-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
Q

What should be done if fluid overload occurs?

A

-stop fluid admin.
-use furosemide in patients with pulmonary edema or pleural effusion development

59
Q

What are the consequences of fluid overload?

A

-pulmonary edema
-cerebral edema
-myocardial edema
-increased renal venous pressure
-renal interstitial edema
-gut edema
-tissue edema
-impaired lymphatic drainage
-microcirculatory derangements

60
Q

What are the takeaways of anesthesia fluid therapy?

A

-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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