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Brandon’s AFN Health Assessment > Unit 2 Fluids > Flashcards

Unit 2 Fluids Flashcards

1
Q

Surgical cardiovascular insufficiency

A

Caused by either induced loss of vasomotor tone and baroreceptor responsiveness from anesthesia

Or

Mechanical obstruction to blood flow

Surgical stress also causes a cytokine storm, combined with immune modulation alters micro circulation causing sub clinical injury

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2
Q

Absolute minimum blood delivery to tissues required during surgery to avoid tissue dysoxia

A

600ml/min/m^2

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3
Q

TBW Formula

A

0.6 X body weight (kg)

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4
Q

Interstitial fluid is how much of ECF?

A

3/4

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5
Q

Plasma is how much of ECF?

A

1/4

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6
Q

How much trans cellular fluid?

A

0.5L
Fluid contained within epithelial lined spaces

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7
Q

What determines Osmolarity? And what is normal level?

A

Determined by Na, K, Bun, Glucose
Normal 290 MOSM/Kg

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8
Q

Osmotic pressure

A

Pressure across a semipermeable membrane exerted by a solute containing solution
Plasma osmotic pressure: 28mmHg (19mmHg protein)

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9
Q

Plasma oncotic pressure

A

Proteins - only dissolved substance that doesn’t readily diffuse through capillary membranes

If they do diffuse for some reason, usually removed by lymphatic system under normal circumstances

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10
Q

TBW Dynamics

A

60% of body weight, approx 40L
Men have more than women
It decereases with increasing age for everyone
It decreases in obesity (proportional to lean body mass) (inversely proportional to obesity)

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11
Q

Total Body Weight by age/gender

A

Adult Male: 75ml/kg
Adult Female: 70ml/Kg
School age child: 75ml/Kg
Infant (1-12months): 80ml/Kg
Neonate: 85ml/Kg

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12
Q

Pressures

A

Interstitial fluid pressure: 0mmHg
Arterial Inter capillary pressure: 35mmHg
Venous Inter capillary pressure: 15mmHg

Capillary Osmotic pressure: 25mmHg
Interstitial osmotic pressure: 4mmHg

Some movement out of capillary at arterial end and movement into capillary at venue end

Normally slight predominance of water efflux into tissues

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13
Q

Preoperative considerations

A

Patients at risk of Hypovolemia
NPO and/or bowel prep
Chronic diuretic therapy
Chronic renal failure with or without dialysis
Chronic HTN (constant vasoconstriction > less intravascular volume > relative Hypovolemia with administration of anesthesia)
Trauma from blood loss
Burns from tissue loss > loss of protein and fluid
Sepsis from vasodilation
Liver failure from decreased plasma protein > intravascular hypovolemia from decreased intracapillary oncotic pressure > fluid leak out of vasculature

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14
Q

Chronic gastric loss

A

Hypochloremic metabolic alkalosis

Consider 0.9% NS

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15
Q

Chronic diarrhea (loosing bicarbonate)

A

Hyperchloremic metabolic acidosis
Consider LR (a bicarbonate substrate)

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16
Q

Effects of anesthesia on fluid regulation

A

Anesthesia causes decreased vasomotor tone and baroreceptor responsiveness

Surgical stress > ADH release > fluid retention

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17
Q

Other surgical considerations

A

Evaporative fluid loss with mechanical ventilation

Decreased atrial naturetic factor which produces Na to help retain fluids

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18
Q

Clinical evaluation for preoperative hypvolemia

A

Positive tilt test:
HR ^ >20bpm and decrease of SBP >20mmHg

Oliguria
Weak peripheral pulses

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19
Q

Laboratory evaluation for preoperative hypovolemia

A

BUN:CR ration > 20 indicates prerenal azotemia (hypovolemia)

Low urinary Na on UA

Minor hypovolemia: metabolic alkalosis
Major hypovolemia: metabolic acidosis

Increased hematocrit (after fluid replacement) it says the same during the acute blood loss.

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20
Q

Main goal of fluid therapy??

A

provide adequate delivery of oxygen to tissues

Maintain environment necessary for proper function of cells and organ systems

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21
Q

One way to reduce PNV?

A

Adequate fluid replacement

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22
Q

Complications of too much fluid replacement on bowel and lungs?

A

If bowel is edematus will have slow return of bowel function
Pulmonary edema

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23
Q

If you fail to give enough fluids during surgery?

A

Can have Increased release of stress hormones

24
Q

LR

A

Most commonly used in OR

Caution in metabolic/resp alkalosis
already have increased levels of bicarbonate/lactate

Caution in severe hepatic failure
impaired utilization of lactate may lead to accumulation

Caution with severe renal failure
risk of Hyperkalemia

Na content is too high and K too low for normal maintained fluid???

25
Q

Balanced salt solutions

A

LR (don’t use with blood products because it has calcium)
Plasmalyte (more expensive) (does not have Ca, so it can be given with blood products)
Normal Saline

26
Q

“Normal Saline”

A

When compared to plasma:
lower pH, higher osmolarity, higher chloride content

With excessive administration:
can cause hyperchloremic metabolic acidosis
can take days to resolve in pts with renal failure/insufficiency

27
Q

Hypertonic Solutions

A

Usually used to treat deficit
I.e. dextrose for glucose deficiency or hypertonic saline for Na deficiency

28
Q

Hypertonic Saline Contents and Considerations

A

NaCl 513 mEq/L
Osmolarity of 1025 mosm/L

Risk of hypernatremia, hyperchloremia, & cellular dehydration
Consider giving through a central line
Gradual admin to achieve Na of 145-155
Increase no more than 10-20mEq/L in 24hrs (risk of cerebellar pontine demyelination)

Uses:
severe symptomatic hyponatremia
fluid resuscitation
increased ICP; neurosurgery

29
Q

D5W

A

Hypertonic in the bag
Hypotonic in patient as glucose is rapidly metabolized, essentially resulting in free water

30
Q

Look at Nagelhout chart with fluid compositions

A

D5W
0.9% NS
LR
Plasmalyte
D5W 1/4 NS

31
Q

Albumin

A

Human albumin that is plamapheresed, and pasteurized to decrease risk of anaphylaxis, infection, or coagulopathy (aside from hemodilution)

25% (salt poor) albumin
pulls H20 intravascular lay
unpredictable effects

5% albumin Used in OR
hypothetically stays intravascular longer than crystaloid (16hrs)
isotonic to plasma

Will have opposite effect with capillary leak as it will mostly go interstitial and then pull fluid interstitial as well.

32
Q

Hetastartch

A

Dilutional effect on coagulation factors
Direct inhibition of clot formation (reduced platelet aggregation)
Binds Factor VIII, VWF, fibrinogen
FDA black box warning, rarely used anymore
Increased risk of mortality and renal failure

33
Q

Crystalloid vs colloid

A

Contraversial research

In general:
Start with crystalloid, hetastarch, then protein colloid

34
Q

When to use colloids?

A

Only specific patient populations

35
Q

4-2-1 Rule

A

Not evidence based, but need to know it. Based on patient weight.

For the first 10Kg 4ml/Kg/hr
Second 10Kg add 2ml/Kg/hr
For the remainder add 1ml/Kg/hr

Also account for bowel prep and NG loss
bowel prep: add 1000ml to fluid plan. Typically replace upfront first 1-2 or 1-3 hrs depending on length of case

36
Q

NPO replacement

A

Number of hours NPO x hourly maintince requirement (4-2-1 rule)
Replace over the first 2-3 hours of the surgery

37
Q

Types Surgical loss

A

Evaporative or third space losses (based on potential tissue trauma)
minimal 0-2ml/kg/hr
moderate 2-4 ml/kg/hr
severe 4-8 ml/kg/hr

True surgical loss
replace with crystalloid on a 3:1 basis
replace with colloid on a 1:1 basis

38
Q

Calculating blood loss

A

Not an exact science
Saturated lap pad holds 100ml
Raytek 10-20ml

During the case keep track of the blood loss in canisters as well as the # of saturated sponges

39
Q

Allowable blood loss formula

A

[EBV X (HCT initial - HCT final)] / HCT initial

When you hit the allowable blood loss you need to draw a hgb to evaluate blood loss/status

40
Q

Do fluid loss calculation

A

Do it and check the results

41
Q

Physiologic variable affected by fluid administration

A

Temperature: can exacerbate hypothermia and acidosis. Typically warm fluids, but especially if giving more than 2L.
pH: especially NS, but LR can also lead to acidosis with large volumes
RBCs: hemodilution, temp, and pH all affect RBC concentration and function.
WBCs: artificial colloids and LR activate neutrophils - may be related to resuscitation injury
Platlets/coagulation: hypothermia and acidosis = decreased plt function and coagulopathy

42
Q

Variables affecting decisions for fluid replacement

A

Patient
Anesthetic technique
Type of surgery
Intraoperative course

43
Q

Special neurosurgical patient considerations

A

Never give glucose containing fluids, it will make intercranial ischemia worse

44
Q

ARDS patient special considerations

A

Fluid restriction shown to decrease morbidity
complication is we still need to maintain euvolemia in order to perfuse kidneys etc.

45
Q

CHF special considerations

A

Judicious fluid management
Risk of post-op third space redistribution causing increased cardiac work (diastolic HF)

46
Q

Lung resection special considerations

A

Postpneumonectomy pulmonary edema (excess fluids make this worse)
Minimize fluids, use pressors if necessary
Avoid blood products (inflammatory response)

47
Q

Liver failure/transplant special considerations

A

Multiple co-morbid conditions confound fluid management
cerebral edema, hepatorenal syndrome, electrolyte disturbances
Consider use of colloids replacement early
Replace paracentesis >4L with albumin

48
Q

Burn special considerations

A

Initial replacement is formula guided. E.G parkland formula

Consider albumin after the first 24 hrs

49
Q

Parkland formula

A

BSA% X WT X4 = total volume in first 24hrs
Give 1/2 in the first 8 hours

50
Q

Laparoscopy special considerations

A

Transient intraoperative oliguria
The gastric insufflation puts pressure on kidneys so blood flow goes down and they are not perfused, kidneys think there is not enough blood volume so they retain fluid (RAAS activation) these patients may not make urine a lot of the time,

DONT USE URINE OUTPUT AS A GUIDE FOR FLUID REPLACEMENT IN LAPAROSCOPIC CASES

Be careful with too much volume - post pneumoperitoneum redistribution

51
Q

Sepsis special considerations

A

Early and aggressive fluid replacement is important

52
Q

Massive trauma special considerations

A

Lethal triad of acidosis, hypothermia, and coagulopathy

53
Q

Plasmapheresis special considerations

A

Replace volume with albumin

54
Q

Liposuction

A

Tumescent technique (most common) can have large fluid shifts with > 5L of liposuction resulting in cardiopulmonary complications.

Most keep track of how much is removed during these procedures.

55
Q

Renal patient special considerations

A

Tendency to have hyperchloremic metabolic acidosis
can be made worse with NS admin
dilution of bicarb by large volumes of buffer free solution

Acidosis can contribute to decreased splanchnic blood flow

Hyperchloremia may contribute to renal vascular constriction

Anuric: judicious fluid management
Nephrotic syndrome: albumin for fluid resucitation

56
Q

How do we know we achieved our goal?

A

Normal cardiac indicies
Adequate hemoglobin
Normothermia
Prevention of fluid loss/excess
Met unique needs of the patient
Normal lab values: pH, lactate, anion gap, coagulation profile, electrolyte levels, glucose

Brandon’s AFN Health Assessment (17 decks)

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