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Surgery > Fluids and Electrolytes > Flashcards

Fluids and Electrolytes Flashcards

1
Q

T/F: Approx 1/3 of ideal body weight is water.

A

False, 2/3!

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2
Q

Intracellular Fluid is what fraction of Total Body Water?

A

2/3

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3
Q

Extracellular Fluid is what fraction of Total Body Water?

A

1/3

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4
Q

Interstitial Fluid is what fraction of ECF?

A

2/3

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5
Q

Plasma is what fraction of ECF?

A

1/3

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6
Q

What is the average blood volume of a male? Of a female?

A

66 ml/kg

60 ml/kg

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7
Q

What is the Total Blood Volume of a 70 kg patient?

A

4.2-4.6 L

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8
Q

What separates the interstitial fluid and intravascular fluid compartments?

A

Capillary Endothelium - impermeable to proteins (primarily albumin), which determines the plasma/interstitial compartment oncotic pressures.

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9
Q

What separates the intracellular and extracellular compartments?

A

Cell membrane – impermeable to ions (Na) which determine the ICF/ECF osmotic pressure

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10
Q

The infusion of IL of 0.9% NaCl (Isotonic Saline) will expand ______ volume by only 275 ml.

A

Plasma

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11
Q

What types of IV fluids are there?

A
  1. Blood
  2. Lactated Ringers
  3. Normal Saline
  4. Half normal saline
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12
Q

What is the 4:2:1 Rule and what is is used for?

A

4 cc/kg/hr for the 1st 10 kg
2 cc/kg/hr for the 2nd 10 kg
1 cc/kg/hr for each additional kg

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13
Q

For a 70 kg patient, how many ccs should you give per hour (using the 4:2:1 Rule)?

A

40 + 20 + 50 = 110 cc/hr

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14
Q

What is the best indicator of adequate volume replacement?

A

Urine Output greater than or equal to 0.5 cc/kg/hr

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15
Q

What is typical IVF management for a major GI surgery?

A
  1. Use isotonic fluids (LR or NS) for the first 24 hours

2. Switch to D5 1/2 NS + 20 mEq KCl

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16
Q

What does 50 g glucose/L function to do?

A

Stimulates insulin release resulting in amino acid uptake and protein synthesis (prevents protein catabolism)

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17
Q

When you have gastric losses (H+ and Cl-), what IV fluids do you give?
Ex. Diarrhea, Vomiting

A

Normal Saline

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18
Q

When you have pancreatic/bile/small intestine losses (HCO3), what IV fluids do you give?
Ex. biliary drain, ileostomy, fistula

A

Lactated Ringers

May need to give K+ as needed

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19
Q

When you have large intestine losses (HCO3- and K+), what IV fluids do you give?

A

Lactated Ringers +/- Potassium

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20
Q

Clinical signs/symptoms of hypovolemia (dehydration)

A
  1. Dry mucuous membranes
  2. Decreased skin turgor
  3. Extreme Thirst
  4. Low urine output
  5. Climbing BUN +/- Cr (rising BUN:Cr ratio)
  6. Low BP
  7. Low CVP
  8. Tachycardia
  9. FENA < 1%
  10. Altered mental status
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21
Q

How do you assess a hypovolemic patient?

A
  1. ABCs - Airway, Breathing, Circulation
  2. Two large bore IVs
  3. Foley to monitor urine output
  4. MUST RULE OUT BLEEDING! All Sx patients are bleeding until proven otherwise
  5. Give 1-2 L bolus of isotonic fluid and assess response
  6. In no response, check bleeding again.
  7. If not bleeding, may be massively under-resuscitated and just need more fluid.
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22
Q

What is the diagnosis for a patient with a serum Na great than 145 mEq/L

A

Hypernatremia

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23
Q

Signs and Symptoms of Hypernatremia

A
  1. Restlessness
  2. Ataxia
  3. Seizures
  4. Lethargy
  5. Altered Mental Status
24
Q

What is the most common cause of hypernatremia?

A

Loss of hypotonic body fluids.

Especially in the surgical patient

25
Q

What’s another common cause of hypernatremia?

A

Large wounds/burns

26
Q

What is the equation for Free Water Deficit?

A

FWD = TBW x (Serum Na - 140) / 140

27
Q

Can you give more than 10 mEq/day or 0.5 mEq/L/hr? Why or why not/

A

No, risk of cerebral edema.

28
Q

When a patient has a total body sodium deficit in addition to free water deficit, what is this called?

A

Hypovolemic Hypernatremia

29
Q

In a patient with Hypovolemic Hypernatremia, what do you do first?

A

Isotonic Crystalloid (NS/LR)

30
Q

What do you do after correcting with isotonic crystalloids in hypovolemic hypernatremic patients?

A

Calculate and replace their free water deficit

31
Q

Total Body Water of a male is determined by?

A

TBW = 0.6 x Body Weight

32
Q

Total Body Water of a female is determined by?

A

TBW = 0.5 x Body Weight

33
Q

Diabetes Insipidus – Hypernatremia!

A
  1. Often Euvolemic
  2. Excess loss of free water in urine (ADH promotes water reabsorption in the distal tubule)
  3. Central DI: dailure of ADH release from posterior pituitary
  4. Nephrogenic DI: Kidneys unresponsive to ADH (amphotericin, dopamine, lithium, contrast dyes)
34
Q

What is the daily potassium intake?

A

0.5-1 mEq/day

35
Q

What can cause hypokalemia?

A
  1. Diuretics
  2. Diarrhea
  3. Magnesium Depletion (impairs K reabsorption across the renal tubules)
36
Q

Signs/Symptoms of Hypokalemia

A

Muscle Weakness if severe (< 2.5) and can be arhythmogenic when accompanied by other conditions (hypomagnesemia, digitalis, myocardial ischemia)

37
Q

Treating Hypokalemia

A

Replace in increments of 20-60 mEq

For every 10 mEq, expect a 0.1 increase in serum level.

38
Q

A serum level of potassium greater than 5.5 would be diagnostic of what?

A

Hyperkalemia

39
Q

What does hyperkalemia do?

A

Slows the electrical conduction of the heart and can eventually lead to life-threatening dysrrhythmias

40
Q

What can cause hyperkalemia?

A
  1. Iatrogenic
  2. Rhabdomyolysis
  3. Certain Drugs
  4. Renal Insufficiency
  5. Massive Blood Transfusions
41
Q

How do you treat hyperkalemia?

A
  1. Immediately stop K-containing infusions. Check EKG for peaked T wave
  2. If EKG changes are present—give calcium gluconate to stabilize the cardiac membrane
  3. Then give 1 amp of D50 and 10 units of insulin to drive the potassium intracellularly
  4. Kayexalate can be given to enhance K excretion via the GI muscosa, however this will take hours, but will help to lower the total body potassium
  5. Lasix is another option but must check renal function first
  6. In most patients with good kidney function they will not develop hyperkalemia
  7. Dialysis if extremely high K and patient in renal failure
42
Q

Why is Magnesium important?

A

Major intracellular cation, serves as a cofactor for countless enzymatic reactions (ATP). It also regulates the movement of calcium into smooth muscle cells.

43
Q

Causes of Magnesium deficiency?

A
  1. Diuretics
  2. Alcoholics
  3. Chronic malutrition
  4. Diarrhea
  5. Diabetics
44
Q

Diagnostic criteria for hypomagnesemia?

A

< 2 at Shands

<1.5 in general

45
Q

What can happen with hypomagnesemia?

A
  1. Can accompany hypokalemia andhypocalcemia difficult to correct.
  2. Arrhythmias: Replace as needed, typically in increments in 2 mg IV
46
Q

Tell me about hypermagnesemia?

A
  1. Rare, typically renal failure or iatrogenic (OB Wards)
  2. Weakness/Lethargic state, Hyporeflexia.
  3. Give calcium, may require dialysis
47
Q

A serum level of Na less than 135 would be diagnostic of?

A

Hyponatremia

48
Q

What is the most common cause of post-op hyponatremia?

A

SIADH (Syndrome of inappropriate ADH secretion)

Pain or stress of surgery → elevated antidiuretic hormone (ADH) levels postop, Kidneys retain too much free water and the urine is inappropriately concentrated.

49
Q

DDx of post op hyponatremia

A
  1. Loop Diuretics
  2. Iatrogenic
  3. Osmotic Diuresis from hyperglycemia
  4. Adrenal Insufficiency
50
Q

Asymptomatic Treatment of Hyponatremia

A
  1. Hypovolemic = Give volume
  2. Hypervolemic = Na & Water Restriction (loop diuretics if CHF or nephrotic syndrome)
  3. Euvolemic = Water restriction (to counter retention of free water using Hyponatremia) Treat underlying problem, like hypothyroids – give thyroxine
51
Q

In a euvolemic patient, you can use loop diuretics or demclocycine. What can this cause sometimes?

A

The exact opposite problem! Diabetes Insipidus

52
Q

Signs/Symptoms of Hyponatremia

A
  1. Acute - Osmotic Forces cause water movement into brain cells leading to cerebral edema
  2. Mild - Anorexia, nausea, lethargy
  3. Moderate - Disoriented, agitates, neuro deficit
  4. Severe - Sz, Coma, Death
53
Q

What is the treatment for hyponatremia? If this urgent?

A

IT IS URGENT!

If symptomatic and urgent (mental status changes), give hypertonic saline (3% NaCl = 513 mEq/L Na+ and Cl-)

54
Q

How do you calculate a sodium deficit?

A

Na+ Deficit = TBW x (130 - actual Na+ concentration)

55
Q

What is important to remember for Na correction?

A

Do no correct more than 0.5 mEq/L/hr due to the risk of pontine myelinolysis (CPM)

Surgery (12 decks)

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