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Surgical Recall > Preoperative 101 And Fluids & Electrolytes > Flashcards

Preoperative 101 And Fluids & Electrolytes Flashcards

1
Q

When can a patient eat prior to major surgery?

A

Patient should be NPO after midnight the night before or for at least 8 hours before surgery

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2
Q

What risks should be discussed with all patients and documented on the consent form for a surgical procedure?

A

Bleeding, infection, anesthesia, scar; other risks are specific to the individual procedure (also MI, CVA, and death if cardiovascular disease is present)

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3
Q

If a patient is on antihypertensive medications, should the patient take them on the day of the procedure?

A

Yes, (remember clonidine “rebound”)

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4
Q

If a patient is on an oral hypoglycemic agent (OHA), should the patient take the OHA on the day of surgery?

A

Not if the patient is to be NPO on the
day of surgery

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5
Q

If a patient is taking insulin, should the patient take it on the day of surgery?

A

No, only half of a long-acting insulin (e.g., lente) and start D5 NS IV; check glucose levels often preoperatively, operatively, and postoperatively

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6
Q

Should a patient who smokes cigarettes stop before an operation?

A

Yes, improvement is seen in just 2 to 4 weeks after smoking cessation

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7
Q

What laboratory test must all women of childbearing age have before entering the O.R.?

A

HCG and CBC because of the possibility of pregnancy and anemia from menses

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8
Q

What is a preop colon surgery “bowel prep”?

A

Bowel prep with colon cathartic (e.g., GoLYTELY), oral antibiotics (neomycin and erythromycin base), and IV antibiotic before incision

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9
Q

Has a preop bowel prep been shown conclusively to decrease postop infections in colon surgery?

A

No, there is no data to support its use

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10
Q

What preoperative medication can decrease postoperative cardiac events and death?

A

Beta blockers

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11
Q

What must you always order preoperatively for your patient undergoing a major operation?

A
  1. NPO/IVF
  2. Preoperative antibiotics
  3. Type and cross blood (PRBCs)
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12
Q

What electrolyte must you check preoperatively if a patient is on hemodialysis?

A

Potassium

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13
Q

Who gets a preoperative ECG?

A

Patients older than 40 years of age

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14
Q

What are the two major body fluid compartments?

A
  1. Intracellular
  2. Extracellular
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15
Q

What are the two subcompartments of extracellular fluid?

A
  1. Interstitial fluid (in between cells)
  2. Intravascular fluid (plasma)
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16
Q

What percentage of body weight is in fluid?

A

60%

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17
Q

What percentage of body fluid is intracellular?

A

66%

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18
Q

What percentage of body fluid is extracellular?

A

33%

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19
Q

What is the composition of body fluid?

A

Fluids 60% total body weight: Intracellular 40% total body weight Extracellular 20% total body weight
(Think: 60, 40, 20)

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20
Q

How can body fluid distribution by weight be remembered?

A

TIE”:
T Total body fluid 60% of body
weight
I Intracellular 40% of body weight
E Extracellular 20% of body
weight

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21
Q

On average, what percentage of body weight does blood account for in adults?

A

7%

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22
Q

How many liters of blood are in a 70-kg man?

A

0.07 * 70 = 5 liters

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23
Q

What are the fluid requirements every 24 hours for each of the following substances:
Water
Potassium
Chloride
Sodium

A

30 to 35 mL/kg
1 mEq/kg
1.5 mEq/kg
1–2 mEq/kg

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24
Q

What are the levels and sources of normal daily water loss?

A

Urine—1200 to 1500 mL (25–30 mL/kg)
Sweat—200 to 400 mL
Respiratory losses—500 to 700 mL Feces—100 to 200 mL

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25
Q

What are the levels and sources of normal daily electrolyte loss?

A

Sodium and potassium - 100 mEq Chloride - 150 mEq

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26
Q

What are the levels of sodium and chloride in sweat?

A

40 mEq/L

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27
Q

What is the major electrolyte in colonic feculent fluid?

A

Potassium—65 mEq/L

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28
Q

What is the physiologic response to hypovolemia?

A

Sodium/H2O retention via renin -> aldosterone, water retention via ADH, vasoconstriction via angiotensin II and sympathetics, low urine output and tachycardia (early), hypotension (late)

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29
Q

What is third-spacing

A

Fluid accumulation in the interstitium of tissues, as in edema, e.g., loss of fluid into the interstitium and lumen of a paralytic bowel following surgery (think of the intravascular and intracellular spaces as the first two spaces)

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30
Q

When does “third-spacing” occur postoperatively?

A

Third-spaced fluid tends to mobilize back into the intravascular space around POD
#3 (Note: Beware of fluid overload once the fluid begins to return to the intravascular space); switch to hypotonic fluid and decrease IV rate

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31
Q

What are the classic signs of third spacing?

A

Tachycardia
Decreased urine output

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32
Q

What is the treatment for third-spacing

A

IV hydration with isotonic fluids

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33
Q

What are the surgical causes of the following conditions:
Metabolic acidosis
Hypochloremic alkalosis
Metabolic alkalosis
Respiratory acidosis
Respiratory alkalosis

A

Loss of bicarbonate: diarrhea, ileus, fistula, high-output ileostomy, carbonic anhydrase inhibitors
Increase in acids: lactic acidosis (ischemia), ketoacidosis, renal failure, necrotic tissue

NGT suction, loss of gastric HCl through vomiting/NGT

Vomiting, NG suction, diuretics, alkali ingestion, mineralocorticoid excess

Hypoventilation (e.g., CNS depression), drugs (e.g., morphine), PTX, pleural effusion, parenchymal lung disease, acute airway obstruction

Hyperventilation (e.g., anxiety, pain, fever, wrong ventilator settings)

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34
Q

What is the “classic” acid- base finding with significant vomiting or NGT suctioning?

A

Hypokalemic hypochloremic metabolic alkalosis

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35
Q

Why hypokalemia with NGT suctioning?

A

Loss in gastric fluid—loss of HCl causes alkalosis, driving K into cells

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36
Q

What is the treatment for hypokalemic hypochloremic metabolic alkalosis?

A

IVF, Cl/K replacement

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37
Q

What is paradoxic alkalotic aciduria?

A

Seen in severe hypokalemic, hypovolemic, hypochloremic metabolic alkalosis with paradoxic metabolic alkalosis of serum and acidic urine

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38
Q

How does paradoxic alkalotic aciduria occur?

A

H is lost in the urine in exchange for Na in an attempt to restore volume

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39
Q

With paradoxic alkalotic aciduria, why is H preferentially lost?

A

H is exchanged preferentially into the urine instead of K because of the low concentration of K

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40
Q

What can be followed to assess fluid status?

A

Urine output, base deficit, lactic acid, vital signs, weight changes, skin turgor, jugular venous distention (JVD), mucosal membranes, rales (crackles), central venous pressure, PCWP, chest x-ray findings

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41
Q

With hypovolemia, what changes occur in vital signs?

A

Tachycardia, tachypnea, initial rise in diastolic blood pressure because of clamping down (peripheral vasoconstric- tion) with subsequent decrease in both systolic and diastolic blood pressures

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42
Q

What are the insensible fluid losses?

A

Loss of fluid not measured:
Feces—100 to 200 mL/24 hours
Breathing—500 to 700 mL/24 hours
(Note: increases with fever and
tachypnea)
Skin—300 mL/24 hours, increased
with fever; thus, insensible fluid loss is not directly measured

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43
Q

What are the quantities of daily secretions:
Bile
Gastric
Pancreatic
Small intestine
Saliva

A

1000 mL/24 hours
2000 mL/ 24 hours
600 mL/ 24 hours
3000 mL/day
1500 mL/24 hours
(Note: almost all secretions are reabsorbed)

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44
Q

How can the estimated levels of daily secretions from bile, gastric, and small-bowel sources be remembered?

A

Alphabetically and numerically: BGS and 123 or B1, G2, S3, because Bile, Gastric, and Small bowel produce roughly 1 L,
2 L, and 3 L, respectively!

45
Q

What comprises normal saline (NS)?

A

154 mEq of Cl
154 mEq of Na

46
Q

What comprises 1/2 NS?

A

77 mEq of Cl
77 mEq of Na

47
Q

What comprises 1/4 NS?

A

39 mEq of Cl
39 mEq of Na

48
Q

What comprises lactated Ringer’s (LR)?

A

130 mEq Na
109 mEq Cl
28 mEq lactate
4 mEq K
3 mEq Ca

49
Q

What comprises D5W?

A

5% dextrose (50 g) in H2O

50
Q

What accounts for tonicity?

A

Mainly electrolytes; thus, NS and LR are both isotonic, whereas 1/2 NS is hypotonic to serum

51
Q

What happens to the lactate in LR in the body?

A

Converted into bicarbonate; thus, LR cannot be used as a maintenance fluid because patients would become alkalotic

52
Q

IVF replacement by anatomic site:
Gastric (NGT)
Biliary
Pancreatic
Small bowel (ileostomy) Colonic (diarrhea)

A

D5 1/2 NS + 20 KCl
LR/sodium bicarbonate
LR/sodium bicarbonate
LR
LR/sodium bicarbonate

53
Q

What is the 100/50/20 rule?

A

Maintenance IV fluids for a 24-hour period:
100 mL/kg for the first 10 kg
50 mL/kg for the next 10 kg
20 mL/kg for every kg over 20 (divide
by 24 for hourly rate)

54
Q

What is the 4/2/1 rule?

A

Maintenance IV fluids for hourly rate: 4 mL/kg for the first 10 kg
2 mL/kg for the next 10 kg
1 mL/kg for every kg over 20

55
Q

What is the maintenance for a 70-kg man?

A

Using 100/50/20:
100 x 10 kg = 1000
50 x 10 kg = 500
20 x 50 kg = 1000
Total = 2500
Divided by 24 hours = 104 mL/hr
maintenance rate
Using 4/2/1:
4 x 10 kg = 40
2 x 10 kg = 20
1 x 50 kg = 50
Total = 110 mL/hr maintenance rate

56
Q

What is the common adult maintenance fluid?

A

D5 1/2 NS with 20 mEq KCl/L

57
Q

What is the common pediatric maintenance fluid?

A

D5 1/4 NS with 20 mEq KCl/L (use 1/4 NS because of the decreased ability of children to concentrate urine)

58
Q

Why should sugar (dextrose) be added to maintenance fluid?

A

To inhibit muscle breakdown

59
Q

What is the best way to assess fluid status?

A

Urine output (unless the patient has cardiac or renal dysfunction, in which case central venous pressure or wedge pressure is often used)

60
Q

What is the minimal urine output for an adult on maintenance IV?

A

30 mL/hr (0.5 cc/kg/hr)

61
Q

What is the minimal urine output for an adult trauma patient?

A

50 mL/hr

62
Q

How many mL are in 12 oz (beer can)?

A

356 mL

63
Q

How many mL are in 1 oz?

A

30mL

64
Q

How many mL are in 1 tsp?

A

5 mL

65
Q

What are common isotonic fluids?

A

NS, LR

66
Q

What is a bolus?

A

Volume of fluid given IV rapidly (e.g., 1 L over 1 hour); used for increasing intravas- cular volume, and isotonic fluids should be used (i.e., NS or LR)

67
Q

Why not combine bolus fluids with dextrose?

A

Hyperglycemia may result

68
Q

What is the possible conse- quence of hyperglycemia in the patient with hypovolemia?

A

Osmotic diuresis

69
Q

Why not combine bolus fluids with a significant amount of potassium?

A

Hyperkalemia may result (the potassium in LR is very low: 4 mEq/L)

70
Q

Why should isotonic fluids be given for resuscitation (i.e., to restore intravascular volume)?

A

If hypotonic fluid is given, the tonicity of the intravascular space will be decreased and H2O will freely diffuse into the interstitial and intracellular spaces; thus, use isotonic fluids to expand the intra- vascular space

71
Q

What portion of 1 L NS will stay in the intravascular space after a laparotomy?

A

In 5 hours, only 200 cc (or 20%) will remain in the intravascular space!

72
Q

What is the most common trauma resuscitation fluid?

A

LR

73
Q

What is the most common postoperative IV fluid after a laparotomy?

A

LR or D5LR for 24 to 36 hours, followed by maintenance fluid

74
Q

After a laparotomy, when should a patient’s fluid be “mobilized”?

A

Classically, POD #3; the patient begins to “mobilize” the third-space fluid back into the intravascular space

75
Q

What IVF is used to replace duodenal or pancreatic fluid loss?

A

LR (bicarbonate loss)

76
Q

What is a common cause of electrolyte abnormalities?

A

Lab error!

77
Q

What is a major extracellular cation?

A

Na

78
Q

What is a major intracellular cation?

A

K

79
Q

What is the normal range for potassium level?

A

3.5–5.0 mEq/L

80
Q

What are the surgical causes of hyperkalemia?

A

Iatrogenic overdose, blood transfusion, renal failure, diuretics, acidosis, tissue destruction (injury/hemolysis)

81
Q

What are the signs/ symptoms of hyperkalemia

A

Decreased deep tendon reflex (DTR) or areflexia, weakness, paraesthesia, paralysis, respiratory failure

82
Q

What are the ECG findings for hyperkalemia

A

Peaked T waves, depressed ST segment, prolonged PR, wide QRS, bradycardia, ventricular fibrillation

83
Q

What are the critical values?

A

K > 6.5

84
Q

What is the urgent treatment for hyperkalemia?

A

IV calcium (cardioprotective), ECG monitoring
Sodium bicarbonate IV (alkalosis drives K intracellularly)
Glucose and insulin Albuterol
Sodium polystyrene sulfonate
(Kayexalate) and furosemide (Lasix) Dialysis

85
Q

What is the nonacute treatment?

A

Furosemide (Lasix), sodium polystyrene sulfonate (Kayexalate)

86
Q

What is the acronym for the treatment of acute symptomatic hyperkalemia?

A

“CB DIAL K”:
Calcium
Bicarbonate
Dialysis
Insulin/dextrose
Albuterol
Lasix
Kayexalate

87
Q

What is “pseudohyperkalemia”?

A

Spurious hyperkalemia as a result of falsely elevated K in sample from sample hemolysis

88
Q

What acid-base change lowers the serum potassium?

A

Alkalosis (thus, give bicarbonate for hyperkalemia)

89
Q

What nebulizer treatment can help lower K level?

A

Albuterol

90
Q

What are the surgical causes of hypokalemia?

A

Diuretics, certain antibiotics, steroids, alkalosis, diarrhea, intestinal fistulae, NG aspiration, vomiting, insulin, insufficient supplementation, amphotericin

91
Q

What are the signs/symptoms of hypokalemia?

A

Weakness, tetany, nausea, vomiting, ileus, paraesthesia

92
Q

What are the ECG findings for hypokalemia?

A

Flattening of T waves, U waves,
ST segment depression, PAC, PVC, atrial fibrillation

93
Q

What is the rapid treatment for hyperkalemia?

A

KCl IV

94
Q

What is the maximum amount that can be given through a peripheral IV?

A

10 mEq/hour

95
Q

What is the maximum amount that can be given through a central line?

A

20 mEq/hour

96
Q

What is the chronic treatment in hypokalemia?

A

KCl PO

97
Q

What is the most common electrolyte-mediated ileus in the surgical patient?

A

Hypokalemia

98
Q

What electrolyte condition exacerbates digitalis toxicity?

A

Hypokalemia

99
Q

What electrolyte deficiency can actually cause hypokalemia?

A

Low magnesium

100
Q

What electrolyte must you replace first before replacing K?

A

Magnesium

101
Q

Why does hypomagnesemia make replacement of K with hypokalemia nearly impossible?

A

Hypomagnesemia inhibits K reabsorption from the renal tubules

102
Q

What is the normal range for sodium level?

A

135–145 mEq/L

103
Q

What are the surgical causes of hypernatremia?

A

Inadequate hydration, diabetes insipidus, diuresis, vomiting, diarrhea, diaphoresis, tachypnea, iatrogenic (e.g., TPN)

104
Q

What are the signs/ symptoms of hypernatremia?

A

Seizures, confusion, stupor, pulmonary or peripheral edema, tremors, respiratory paralysis

105
Q

What is the usual treatment supplementation slowly over days for hypernatremia?

A

D5W, 1/4 NS, or 1/2 NS

106
Q

How fast should you lower the sodium level in hypernatremia?

A

Guideline is 12 mEq/L per day

107
Q

What is the major complication of lowering the sodium level too fast?

A

Seizures (not central pontine myelinolysis)

108
Q

What are the surgical causes of the following types of hyponatremia:
Hypovolemic
Euvolemic
Hypervolemic

A

Diuretic excess, hypoaldosteronism, vomiting, NG suction, burns, pancreatitis, diaphoresis

SIADH, CNS abnormalities, drugs

Renal failure, CHF, liver failure (cirrhosis), iatrogenic fluid overload (dilutional)

Surgical Recall (1 decks)

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