Preoperative 101 And Fluids & Electrolytes Flashcards
(108 cards)
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
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)
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”)
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
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
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
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
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
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
10
Q
What preoperative medication can decrease postoperative cardiac events and death?
A
Beta blockers
11
Q
What must you always order preoperatively for your patient undergoing a major operation?
A
- NPO/IVF
- Preoperative antibiotics
- Type and cross blood (PRBCs)
12
Q
What electrolyte must you check preoperatively if a patient is on hemodialysis?
A
Potassium
13
Q
Who gets a preoperative ECG?
A
Patients older than 40 years of age
14
Q
What are the two major body fluid compartments?
A
- Intracellular
- Extracellular
15
Q
What are the two subcompartments of extracellular fluid?
A
- Interstitial fluid (in between cells)
- Intravascular fluid (plasma)
16
Q
What percentage of body weight is in fluid?
A
60%
17
Q
What percentage of body fluid is intracellular?
A
66%
18
Q
What percentage of body fluid is extracellular?
A
33%
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)
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
21
Q
On average, what percentage of body weight does blood account for in adults?
A
7%
22
Q
How many liters of blood are in a 70-kg man?
A
0.07 * 70 = 5 liters
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
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
25
What are the levels and sources of normal daily electrolyte loss?
Sodium and potassium - 100 mEq Chloride - 150 mEq
26
What are the levels of sodium and chloride in sweat?
40 mEq/L
27
What is the major electrolyte in colonic feculent fluid?
Potassium—65 mEq/L
28
What is the physiologic response to hypovolemia?
Sodium/H2O retention via renin -> aldosterone, water retention via ADH, vasoconstriction via angiotensin II and sympathetics, low urine output and tachycardia (early), hypotension (late)
29
What is third-spacing
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)
30
When does “third-spacing” occur postoperatively?
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
31
What are the classic signs of third spacing?
Tachycardia
Decreased urine output
32
What is the treatment for third-spacing
IV hydration with isotonic fluids
33
What are the surgical causes of the following conditions:
Metabolic acidosis
Hypochloremic alkalosis
Metabolic alkalosis
Respiratory acidosis
Respiratory alkalosis
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)
34
What is the “classic” acid- base finding with significant vomiting or NGT suctioning?
Hypokalemic hypochloremic metabolic alkalosis
35
Why hypokalemia with NGT suctioning?
Loss in gastric fluid—loss of HCl causes alkalosis, driving K into cells
36
What is the treatment for hypokalemic hypochloremic metabolic alkalosis?
IVF, Cl/K replacement
37
What is paradoxic alkalotic aciduria?
Seen in severe hypokalemic, hypovolemic, hypochloremic metabolic alkalosis with paradoxic metabolic alkalosis of serum and acidic urine
38
How does paradoxic alkalotic aciduria occur?
H is lost in the urine in exchange for Na in an attempt to restore volume
39
With paradoxic alkalotic aciduria, why is H preferentially lost?
H is exchanged preferentially into the urine instead of K because of the low concentration of K
40
What can be followed to assess fluid status?
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
41
With hypovolemia, what changes occur in vital signs?
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
42
What are the insensible fluid losses?
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
43
What are the quantities of daily secretions:
Bile
Gastric
Pancreatic
Small intestine
Saliva
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)
44
How can the estimated levels of daily secretions from bile, gastric, and small-bowel sources be remembered?
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
What comprises normal saline (NS)?
154 mEq of Cl
154 mEq of Na
46
What comprises 1/2 NS?
77 mEq of Cl
77 mEq of Na
47
What comprises 1/4 NS?
39 mEq of Cl
39 mEq of Na
48
What comprises lactated Ringer’s (LR)?
130 mEq Na
109 mEq Cl
28 mEq lactate
4 mEq K
3 mEq Ca
49
What comprises D5W?
5% dextrose (50 g) in H2O
50
What accounts for tonicity?
Mainly electrolytes; thus, NS and LR are both isotonic, whereas 1/2 NS is hypotonic to serum
51
What happens to the lactate in LR in the body?
Converted into bicarbonate; thus, LR cannot be used as a maintenance fluid because patients would become alkalotic
52
IVF replacement by anatomic site:
Gastric (NGT)
Biliary
Pancreatic
Small bowel (ileostomy) Colonic (diarrhea)
D5 1/2 NS + 20 KCl
LR/sodium bicarbonate
LR/sodium bicarbonate
LR
LR/sodium bicarbonate
53
What is the 100/50/20 rule?
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
What is the 4/2/1 rule?
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
What is the maintenance for a 70-kg man?
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
What is the common adult maintenance fluid?
D5 1/2 NS with 20 mEq KCl/L
57
What is the common pediatric maintenance fluid?
D5 1/4 NS with 20 mEq KCl/L (use 1/4 NS because of the decreased ability of children to concentrate urine)
58
Why should sugar (dextrose) be added to maintenance fluid?
To inhibit muscle breakdown
59
What is the best way to assess fluid status?
Urine output (unless the patient has cardiac or renal dysfunction, in which case central venous pressure or wedge pressure is often used)
60
What is the minimal urine output for an adult on maintenance IV?
30 mL/hr (0.5 cc/kg/hr)
61
What is the minimal urine output for an adult trauma patient?
50 mL/hr
62
How many mL are in 12 oz (beer can)?
356 mL
63
How many mL are in 1 oz?
30mL
64
How many mL are in 1 tsp?
5 mL
65
What are common isotonic fluids?
NS, LR
66
What is a bolus?
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
Why not combine bolus fluids with dextrose?
Hyperglycemia may result
68
What is the possible conse- quence of hyperglycemia in the patient with hypovolemia?
Osmotic diuresis
69
Why not combine bolus fluids with a significant amount of potassium?
Hyperkalemia may result (the potassium in LR is very low: 4 mEq/L)
70
Why should isotonic fluids be given for resuscitation (i.e., to restore intravascular volume)?
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
What portion of 1 L NS will stay in the intravascular space after a laparotomy?
In 5 hours, only 200 cc (or 20%) will remain in the intravascular space!
72
What is the most common trauma resuscitation fluid?
LR
73
What is the most common postoperative IV fluid after a laparotomy?
LR or D5LR for 24 to 36 hours, followed by maintenance fluid
74
After a laparotomy, when should a patient’s fluid be “mobilized”?
Classically, POD #3; the patient begins to “mobilize” the third-space fluid back into the intravascular space
75
What IVF is used to replace duodenal or pancreatic fluid loss?
LR (bicarbonate loss)
76
What is a common cause of electrolyte abnormalities?
Lab error!
77
What is a major extracellular cation?
Na
78
What is a major intracellular cation?
K
79
What is the normal range for potassium level?
3.5–5.0 mEq/L
80
What are the surgical causes of hyperkalemia?
Iatrogenic overdose, blood transfusion, renal failure, diuretics, acidosis, tissue destruction (injury/hemolysis)
81
What are the signs/ symptoms of hyperkalemia
Decreased deep tendon reflex (DTR) or areflexia, weakness, paraesthesia, paralysis, respiratory failure
82
What are the ECG findings for hyperkalemia
Peaked T waves, depressed ST segment, prolonged PR, wide QRS, bradycardia, ventricular fibrillation
83
What are the critical values?
K > 6.5
84
What is the urgent treatment for hyperkalemia?
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
What is the nonacute treatment?
Furosemide (Lasix), sodium polystyrene sulfonate (Kayexalate)
86
What is the acronym for the treatment of acute symptomatic hyperkalemia?
“CB DIAL K”:
Calcium
Bicarbonate
Dialysis
Insulin/dextrose
Albuterol
Lasix
Kayexalate
87
What is “pseudohyperkalemia”?
Spurious hyperkalemia as a result of falsely elevated K in sample from sample hemolysis
88
What acid-base change lowers the serum potassium?
Alkalosis (thus, give bicarbonate for hyperkalemia)
89
What nebulizer treatment can help lower K level?
Albuterol
90
What are the surgical causes of hypokalemia?
Diuretics, certain antibiotics, steroids, alkalosis, diarrhea, intestinal fistulae, NG aspiration, vomiting, insulin, insufficient supplementation, amphotericin
91
What are the signs/symptoms of hypokalemia?
Weakness, tetany, nausea, vomiting, ileus, paraesthesia
92
What are the ECG findings for hypokalemia?
Flattening of T waves, U waves,
ST segment depression, PAC, PVC, atrial fibrillation
93
What is the rapid treatment for hyperkalemia?
KCl IV
94
What is the maximum amount that can be given through a peripheral IV?
10 mEq/hour
95
What is the maximum amount that can be given through a central line?
20 mEq/hour
96
What is the chronic treatment in hypokalemia?
KCl PO
97
What is the most common electrolyte-mediated ileus in the surgical patient?
Hypokalemia
98
What electrolyte condition exacerbates digitalis toxicity?
Hypokalemia
99
What electrolyte deficiency can actually cause hypokalemia?
Low magnesium
100
What electrolyte must you replace first before replacing K?
Magnesium
101
Why does hypomagnesemia make replacement of K with hypokalemia nearly impossible?
Hypomagnesemia inhibits K reabsorption from the renal tubules
102
What is the normal range for sodium level?
135–145 mEq/L
103
What are the surgical causes of hypernatremia?
Inadequate hydration, diabetes insipidus, diuresis, vomiting, diarrhea, diaphoresis, tachypnea, iatrogenic (e.g., TPN)
104
What are the signs/ symptoms of hypernatremia?
Seizures, confusion, stupor, pulmonary or peripheral edema, tremors, respiratory paralysis
105
What is the usual treatment supplementation slowly over days for hypernatremia?
D5W, 1/4 NS, or 1/2 NS
106
How fast should you lower the sodium level in hypernatremia?
Guideline is 12 mEq/L per day
107
What is the major complication of lowering the sodium level too fast?
Seizures (not central pontine myelinolysis)
108
What are the surgical causes of the following types of hyponatremia:
Hypovolemic
Euvolemic
Hypervolemic
Diuretic excess, hypoaldosteronism, vomiting, NG suction, burns, pancreatitis, diaphoresis
SIADH, CNS abnormalities, drugs
Renal failure, CHF, liver failure (cirrhosis), iatrogenic fluid overload (dilutional)
