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Master Deck > Fluids, Electrolytes, and Acid-Base Disorders > Flashcards

Fluids, Electrolytes, and Acid-Base Disorders Flashcards

1
Q

What factors affect the percentage of total body water (TBW)?

A

Weight, age, sex, and relative amount of body fat

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2
Q

Equation for calculating Free Water Deficit

A

Free Water Deficit = TBW x [1 - (140/Serum Sodium in mEq/L)]

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3
Q

Which body tissue is the least hydrated?

A

Adipose tissue

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4
Q

What are the 3 compartments of TBW distribution?

A

Intracellular fluid, extracellular fluid, and transcellular fluid

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5
Q

Which fluid compartment is the most clinically important?

A

Extracellular fluid because it contains the intravascular and interstitial spaces

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6
Q

What is osmotic pressure and why is it of clinical importance?

A

The pressure required to maintain equilibrium with no net movement of solvent. Prime importance in determining the distribution of water between the extracellular and intracellular spaces

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7
Q

Equation for calculating lean body weight (LBW) for males and females

A

LBW (women) = 1.07 x weight (kg) - 148 x [weigh (kg)/height (cm)]^2
LBW (men) = 1.1 x weight (kg) - 128 x [weight (kg)/height (cm)]^2

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8
Q

Describe the composition of D5W (5% dextrose) including its tonicity

A

Provides 50 g dextrose per liter
Hypotonic
No electrolytes
1000 ml/L free water

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9
Q

Describe the composition of 0.225% NaCl (1/4 normal saline) including its tonicity

A

Hypotonic
Provides 38.5 mEq/L Na, 38.5 mEq/L Chloride

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10
Q

Describe the composition of 0.45% NaCl (1/2 normal saline) including its tonicity

A

Hypotonic
Provides 77 mEq/L Na, 77 mEq/L Chloride
500 ml/L free water

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11
Q

Describe the composition of 0.9% NaCl (normal saline) including its tonicity

A

Isotonic
Provides 154 mEq/L Na, 154 mEq/L Chloride
0 ml/L free water

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12
Q

Describe the composition of 3% NaCl (hypertonic saline) including its tonicity

A

Hypertonic
Provides 513 mEq/L Na, 513 mEq/L Chloride
-2331 ml/L free water

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13
Q

Describe the composition of Lactated Ringers (LR) including its tonicity

A

Isotonic
Provides 130 mEq/L Na, 109 mEq/L Chloride, 4 mEq/L K+, 3 mEq/L Calcium
0 ml/L free water

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14
Q

Describe the composition in 0.9% NaCl including its tonicity

A

Isotonic
Provides 154 mEq/L Na and 154 mEq/L Chloride

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15
Q

Describe the water distribution of 1 L IV Dextrose in water to extracellular fluid and intracellular fluid

A

333 mL ECF (250 mL interstitial fluid + 83 mL intravascular fluid)
667 mL ICF

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16
Q

Describe the water distribution of 1 L IV 0.9% NaCl (normal saline) to extracellular fluid and intracellular fluid

A

1000 mL ECF (750 mL interstitial fluid + 250 mL intravascular fluid)
0 mL intracellular fluid

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17
Q

What fluid requirement calculations are recommended in individuals age 65 years or older to prevent dehydration?

A
  1. An adjusted Holliday-Segar formula (1500 mL for the first 20 kg body weight + 15 mL/kg for remaining body weight)
  2. 30 mL/kg with a minimum of 1500 mL
  3. 1500-2000 mL/day
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18
Q

List some clinical conditions which would require the addition of fluid

A

Patients with severe diarrhea or emesis; large draining wounds; excessive diaphoresis; constant drooling; paracentesis losses; drains; high gastric fistula and ostomy outputs; persistent fevers; lactation

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19
Q

Explain the 2 equations some clinicians have success using for fluid requirements when the average between the 2 formulas is used

A

Equation 1 (based on body weight and age):
Age 18-55: 35 mL x body weight (kg)
Age 56-75: 30 mL x body weight (kg)
Age >75: 25 mL x body weight (kg)
Fluid-restricted adults (kidney/cardia disease or fluid overload states) </= 25 mL x body weight (kg)

Equation 2 (Holliday-Segar formula adjusted for age)
Age </=50 years: 1500 mL for first 20 kg body weight + [20 mL x remaining body weight (kg)]
Age >50 years: 1500 mL for first 20 kg body weight + [15 mL x remaining body weight (kg)]

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20
Q

What is the calculation for obesity-adjusted weight?

A

Obesity-Adjusted Body Weight (lb) = [(Actual Weight - IBW) x 0.25] + IBW

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21
Q

When is an obesity-adjusted weight often used?

A

When an individual’s weight is equal to or greater than 125% IBW unless the excess weight is due to muscle mass

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22
Q

Calculate the fluid requirements for a 61 year old woman who is 5’4” tall and weighs 160 lb

A

BMI is 27.5, patient is 133% IBW
1. Calculate IBW: 100 lb + (5x4 lb) = 120 lb
2. Calculate obesity-adjusted weight: [(160-120)] x 0.25] + 120 = 130 lb (59 kg)
3. Calculate fluid requirements using Equation 1: 30 mL x 59 kg = 1770 mL/day
4. Calculate fluid requirements using Equation 2: 1500 mL + [15 x (59kg - 20kg)] = 2085 mL/day
5. Calculate the mean of the results from steps 3 and 4: (1770 + 2085)/2 = ~1900 mL/day

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23
Q

How would you manage maintenance fluids for a patient with heart failure?
Patient info: 65 y/o male, current weight 75 kg (IBW 66 kg), admit w/ 3+ pitting edema BLE receiving 8L/min O2, given 0.9% NaCl at 125 ml/hr, O2 requirements subsequently increased

A

Heart failure pt with evidence of fluid overload should be treated with loop diuretics and sodium and fluid restrictions. Start this patient on IV furosemide and change IV fluids to 0.45% NaCl at 10 mL/hr to maintain IV access. For pt with heart failure, fluid intake should be approximately 20-25 mL per kg estimated dry weight and clinical symptoms of fluid overload should be taken into account. Sodium intake restricted to <2000 mg/day (87 mEq). This patient received 3 L maintenance IV fluids which contributed to further respiratory decompensation requiring aggressive diuresis

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24
Q

List the volume and average electrolyte composition of saliva

A

1.5 L/day, 10 mEq/L Na, 26 mEq/L K+, 10 mEq/L Chloride, 30 mEq/L bicarbonate (HCO3-)

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25
Q

List the volume and average electrolyte composition of the stomach

A

1.5 L/day, 60 mEq/L Na, 10 mEq/L K+, 130 mEq/L Chloride, 0 bicarbonate

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26
Q

List the volume and average electrolyte composition of the duodenum

A

Variable volume, 140 mEq/L Na, 10 mEq/L K+, 80 mEq/L Chloride, 0 bicarbonate

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27
Q

List the volume and average electrolyte composition of the ileum

A

3 L/day, 140 mEq/L Na, 5 mEq/L K+, 104 mEq/L Chloride, 30 mEq/L bicarbonate

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28
Q

List the volume and average electrolyte composition of the colon

A

Variable volume, 60 mEq/L Na, 30 mEq/L K+, 40 mEq/L Chloride, 0 bicarbonate

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29
Q

List the volume and average electrolyte composition of the pancreas

A

Variable volume, 140 mEq/L Na, 5 mEq/L K+, 75 mEq/L Chloride, 115 mEq/L bicarbonate

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30
Q

List the volume and average electrolyte composition of bile

A

Variable volume, 145 mEq/L Na, 5 mEq/L K+, 100 mEq/L Chloride, 35 mEq/L bicarbonate

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31
Q

What are the treatment considerations in general if the electrolyte level is below normal range?

A

Consider available administration routes (IV access peripheral vs central), GI tract function, renal function, fluid status, concurrent electrolyte abnormalities, product availability

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32
Q

What are general potential treatments if an electrolyte level is above normal range?

A

Remove exogenous sources, discontinue offending agents or medications, facilitate elimination of electrolyte, treat other conditions that may be contributing to disorder

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33
Q

Normal sodium level?
Mild hyponatremia:
Moderate hyponatremia:
Severe hyponatremia:

A

Normal range 135-145 mEq/L
Mild: 130-135 mEq/L
Moderate: 125-129 mEq/L
Severe: <125 mEq/L

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34
Q

Difference between osmolality and osmolarity?

A

Osmolality is a measurement of concentration per weight (mOsm/kg H2O)
Osmolarity is a measurement of concentration per volume (mOsm/L)
Serum osmolality and osmolarity are used interchangeably since 1 L of H2O weighs 1 kg

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35
Q

Clinical manifestations of hyponatremia related to central nervous system dysfunction are more likely when the serum sodium concentration drops below ___, gradually or rapidly?

A

Below 120 mEq/L, rapidly

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36
Q

How does the rate of correction differ between acute vs chronic hyponatremia?

A

Acute hyponatremia correction can occur at the same rate of onset of hyponatremia (patients are often symptomatic)
Chronic hyponatremia requires slow correction because these patients have adapted to lower serum sodium levels

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37
Q

What is the recommended rate of correction for acute and chronic hyponatremia?

A

10-12 mEq/L per day for acute
6-8 mEq/L per day for chronic or unknown duration

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38
Q

Explain hypertonic hyponatremia

A

Caused by the presence of osmotically active substances other than sodium in the ECF (hyperglycemia and hypertonic infusions such as dextrose and mannitol)

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39
Q

What are the 3 main types of hypotonic hyponatremia?

A

Hypovolemic, euvolemic, and hypervolemic

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40
Q

What are the treatment goals for hypovolemic hyponatremia? Euvolemic? Hypervolemic?

A

Hypovolemic: volume expansion (for both urine Na < or > 20 mEq/L) with isotonic fluids to expand the ECF volume
Euvolemic: water restriction (500-1000 ml/day)
Hypervolemic: sodium and water restriction

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41
Q

Explain hypovolemic, euvolemic, and hypervolemic hyponatremia

A

Hypovolemic: losing more sodium than water
Euvolemic: urine osmolality is always greater than serum osmolality and urine sodium is >20 mEq/L, stable sodium intake/output but retain additional amounts of water, kidneys are inappropriately concentrating urine and volume status is adequate
Hypervolemic: have some element of end-organ damage (renal failure, liver failure with ascites, heart failure), resulting in fluid retention or third spacing; retain more water than sodium

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42
Q

What are the extrarenal loss causes of hypovolemic hypotonic hyponatremia?

A

Fluid losses from excessive sweating, GI loss (vomiting, diarrhea, fistula drainage, NG suction, ostomy drainage), open wounds, fluid drains or third spacing/sequestration (burns, effusions, peritonitis, ascites, pancreatitis, intestinal obstruction)

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43
Q

What are the renal loss causes of hypovolemic hypotonic hyponatremia?

A

Fluid loss from the use of diuretics, osmosis diuresis, salt-wasting nephropathy, mineralocorticoid deficiency, pseudohypoaldosteronism, bicarbonaturia

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44
Q

What are the causes of euvolemic hypotonic hyponatremia?

A

SIAD (syndrome of inappropriate antidiuresis), hypothyroidism, drug induced, reset osmostat, hypopituitarism, psychogenic polydipsia

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45
Q

What are the edema-forming state causes of hypervolemic hypotonic hyponatremia? What is the other cause?

A

Disorders associated with edema: heart failure/CHF, nephrotic syndrome, hepatic cirrhosis
Acute and chronic renal failure

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46
Q

Describe hypovolemic hypernatremia and the treatment

A

Deficit of both sodium and water but water losses exceed sodium losses; need to determine source of fluid loss; treatment involves volume expansion by replacing hypotonic fluids (isotonic saline) via enteral or parenteral route

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47
Q

What are the extrarenal and renal fluid loss causes of hypovolemic hypernatremia?

A

Extrarenal: profuse sweating, severe diarrhea, respiratory losses
Renal: diuretics, glycosuria, obstructive uropathy, acute/chronic renal failure

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48
Q

Describe euvolemic hypernatremia, common causes, and treatment

A

Decrease in total body water, but total body sodium remains normal; commonly caused by diabetes insipidus (central or nephrogenic); treated by replacing water deficit and removing and/or treating the underlying cause; desmopressin challenge to determine if central or nephrogenic

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49
Q

What is the difference between central and nephrogenic diabetes insipidus?

A

Central is an impairment of ADH secretion; nephrogenic occurs when kidneys cannot respons to ADH circulating in the serum

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50
Q

Describe hypervolemic hypernatremia, common causes, and treatment

A

An increase in total body sodium and total body water may be normal or increased. Common causes are iatrogenic (overadministration of sodium-containing IV fluids) and mineralocorticoid excess (Cushing’s syndrome, adrenal hyperplasia). Treated by correcting underlying disorder, administering diuretics (furosemide), and replacing water deficit

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51
Q

How do you calculate free water deficit for the initial replacement volume?

A

Free water deficit = TBW (total body water in L) x [1 - (140/serum Na)]

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52
Q

Correction rate for chronic and acute hypernatremia

A

Due to risk of cerebral edema. Should not exceed 10 mEq/L/day in chronic or unknown duration; may correct at a rate of 2 mEq sodium per L per hour until serum sodium reaches 145 mEq/L

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53
Q

Calculate free water deficit for a 78 year old woman (60 kg) with serum sodium level 165 mEq/L

A

TBW for women = LBW x 0.5
LBW for women = 1.07 x weight in kg - 148 x (weight in kg/height in cm)^2
Free water deficit = TBW x [1 - (140/serum sodium)]

4.5 l

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54
Q

Mainstay treatment for SIAD?

A

Restrict fluids to 500-1000 ml/d. If symptomatic, administer exogenous salt. If refractory to conventional treatment, may require pharmacologic therapy with loop diuretics and/or vasopressin-2 receptor antagonists (conivaptan, tolvaptan)

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55
Q

Normal potassium concentration?

A

3.5-5 mEq/L

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56
Q

Where is most of the body’s potassium located?

A

Inside the cells

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57
Q

What are normal daily potassium requirements?

A

0.5-2 mEq/kg
1 gm of potassium = 25 mEq of potassium
adequate potassium intake is 40-50 mEq (1600-2000 mg/day)

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58
Q

Which factors are the most important in the influence of the regulation of the internal distribution of potassium?

A

The Na-K-ATPase pump and the plasma potassium concentration

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59
Q

Range for mild, moderate, and severe hypokalemia

A

Mild: 3-3.5 mEq/L
Moderate: 2.5-2.9 mEq/L
Severe: <2.5 mEq/L

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60
Q

Drug-induced causes of hypokalemia occur in what 3 ways?

A

Increased renal potassium loss/excretion, excess/increased loss in stool, and transcellular shift (potassium shift from ECF to ICF)

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61
Q

When are patients with hypokalemia more likely to be symptomatic?

A

Commonly asymptomatic in mild disorders, symptoms occur with more severe cases

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62
Q

Symptoms of moderate and severe hypokalemia?

A

Nausea, vomiting, lassitude, constipation, generalized weakness, cardiac arrhythmias, rhabdomyolysis, paralysis leading to respiratory compromise, death

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63
Q

Nonmedication causes of hypokalemia from loss in stool?

A

Infectious diarrhea, tumors, jejunoileal bypass, enteric fistula, malaborption, intestinal ion-transport defects, cancer therapy, geophagia

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64
Q

Nonmedication causes of hypokalemia from loss in urine?

A

Mineralocorticoid excess, primary hyperaldosteronism, congenital adrenal hyperplasia, renin-secreting tumors, extopic corticotrophin syndrome, Cushing’s syndome, glucocorticoid-responsive aldosteronism, renovascular hypertension, malignant hypertension, vasculitis, apparent mineralocorticoid excess, Liddle’s syndome, 11beta-hydroxysteroid hydrogenase deficiency, impaired chloride-associated sodium transport, Bartter’s syndrome, Gitelman’s syndrome

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65
Q

Describe the treatment options for the following scenario: 78 year old woman (60 kg) w/ h/o uncontrolled hypertension presents with 5 day history of N/V, fever, fatigue. BP low, unable to keep food down, decreased skin turgor and dry mucous membranes. Na level 165 mEq/L, BUN 26, creatinine 0.86, urine sodium <5 mEq/L, all other labs WNL

A

Vital signs reflect hypovolemia, urine sodium level is consistent with sodium conservation and hypovolemia, differential diagnosis includes extrarenal losses from history of vomiting and high fevers. Treatment options include correction of water deficit slowly over a period of at least several days bc hypernatremia is likely chronic based on the onset of vomiting. Calculate water deficit (= 5.3 L). Administer hypotonic fluids IV to correct half of the water deficit (2.65 L) in the first 24 hours.
0.45% NaCl (1/2 normal saline): 1L only contributes 500 mL toward the water deficit so approximately 5.3L will be needed in the first 24 hours.
Dextrose 5% in water: 1L contributes 1000mL toward the water deficit so approximately 2.65L will be needed in the first 24 hours

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66
Q

Potential causes of transcellular shifts of potassium into the cells?

A

Metbolic alkalosis and increases in insulin and catecholamiones (epinephrine or norepinephrine)

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67
Q

Hypokalemia is often refractory to treatment in the setting of what other electrolyte deficiency?

A

Hypomagnesemia

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68
Q

What are the goals of therapy for hypokalemia?

A

Avoidance or resolution of symptoms, restoring the serum potassium concentration to normal, and preventing hyperkalemia

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69
Q

IV replacement dosing guidelines for hypokalemia in patients with normal renal function

A

Serum potassium 3-3.5 mEq/L: IV not recommended 20-40 mEq
Serum potassium 2.5-2.9 mEq/L: IV potassium 40-80 mEq
Serum potassium <2.5 mEq/L: IV potassium 80-120 mE

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70
Q

What are the available variations of IV potassium supplements?

A

Available as chloride, acetate, and phosphate salts

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71
Q

When is potassium acetate use as an alternative to potassium chloride?

A

In the presense of a metabolic acidosis because acetate is converted to bicarbonate by a normally functioning liver

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72
Q

Why is oral correction of hypokalemia generally safer than IV correction?

A

Reduces the risk of overcorrection and rebound hyperkalemia

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73
Q

What dosage of oral potassium is generally sufficient to prevent hypokalemia? What dosage may be required to treat hypokalemia?

A

10-30 mEq/day for prevention, 40-100 mEq/day for treatment

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74
Q

How are potassium supplements best administered orally?

A

In a moderate dosage over a period of several fays to 1 week to achieve complete potassium repletion

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75
Q

When is IV potassium supplementation reserved for?

A

For the treatment of severe hypokalemia or when the condition of the GI tract precludes the use of oral agents

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76
Q

What precaution should be taken if potassium infusion exceeds 10 mEq/hour?

A

Continuous cardiac monitoring to detect any signs of hyperkalemia

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77
Q

Total daily potassium supplementation in most cases should not exceed:

A

40-100 mEq/day (or 0.5 to 1.2 mEq/kg/day)

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78
Q

Potential complications of peripheral potassium infusion?

A

Phlebitis and burning

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79
Q

Caveats to consider when replacing a potassium deficit

A

Consider the dilutant (dextrose versus saline) and the presense of hypomagnesemia

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80
Q

Why should dextrose solutions be avoided when replacing a potassium deficit?

A

May worsen the hypokalemia by stimulating insulin release that promotes an intracellular shift of potassium

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81
Q

How would hypomagnesemia result in refractory hypokalemia?

A

Related to accelerated renal potassium loss or the impairment of Na-K-ATPase pump activity

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82
Q

Patients with hyperkalemia are often asymptomatic until levels exceed what value?

A

> 5.5 mEq/L

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83
Q

Signs and symptoms of hyperkalemia

A

Muscle twitching, cramping, weakness, ascending paralysis, electrocardiogram changes, and arrhythmias

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84
Q

How does metabolic acidosis result in an extracellular potassium shift?

A

Some of the excess hydrogen ions are buffered intracellulary

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85
Q

In general, for every 0.1 decrease in pH, potassium will increase by an average of:

A

0.6 mEq/L (but the increase can range from 0.3-1.3 mEq/L)

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86
Q

What are the various mechanisms for drug-induced hyperkalemia?

A

Impaired renal potassium excretion, increased potassium input, potassium shift from ICF to ECF

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87
Q

Goals of therapy for treating hyperkalemia

A

Antagonizing the cardiac effects of potassium, reversing symptoms (if present), and returning the serum potassium concentration to normal. All sources of exogenous potassium and other medications that can cause hyperkalemia should be discontinued if feasible.

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88
Q

When should IV Calcium gluconate be given to treat hyperkalemia?

A

When patient is symptomatic and those with electrocardiogram changes to restore membrane excitability to normal.

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89
Q

Which medication treatments for hyperkalemia cause potassium to move intracellularly?

A

Insulin and dextrose, sodium bicarbonate, and beta2-adrenergin agonists

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90
Q

Which treatments for hyperkalemia facilitate potassium removal?

A

Loop and thiazide diuretics, cation-exchange resins (sodium polystyrene sulfonate), and dialysis

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91
Q

Normal magnesium concentration

A

Normal serum concentration = 1.5-2 mEq/L (or 1.8-2.4 mg/dL)

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92
Q

Total body magnesium content and distribution throughout the body

A

Total body magnesium content is 25 gm (2000 mEq). 50-60% is in bone, the rest is located in cardiac muscle, skeletal muscle, and the liver. 2% in the ECF

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93
Q

Mg absorptive capacity may be as low as __% on a high Mg diet, and as high as __% on a low Mg diet

A

25%
75%

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94
Q

What factors may impair intestinal absorption of Mg?

A

High phosphate diets and high fiber foods containing phytate

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95
Q

Concomitant electrolyte abnormalities in the setting of Mg deficiency that are refractory to treatment until Mg deficit is corrected?

A

Hypokalemia and hypocalcemia

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96
Q

General etiologies of hypomagnesemia?

A

Decreased intake or absorption, excessive losses, or redistribution into the ICF

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97
Q

What are common causes of reduced Mg intake or absorption?

A

Protein-energy malnutrition, prolonged administration of Mg-free IV fluids or PN, alcoholism, presence of an ileostomy or colostomy, malabsorption syndromes, short bowel syndrome, and intestinal bypass operations

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98
Q

Non-medication related renal loss causes of hypomagnesemia?

A

Acute tubular necrosis, renal tubular acidosis, Barter syndrome, hyperaldosteronism, hypercalcemic states including malignancy, post-obstructive diuresis, renal transplant, glucosuria-induced osmotic diuresis in DM

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99
Q

Drug-induced renal loss causes of hypomagnesemia?

A

Thiazide and loop diuretics, cisplatin, cyclosporine, amphotericin B, aminoglycosides, foscarnet, PPIs, digoxin, alcohol

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100
Q

When might intracellular shifts of Mg be seen?

A

During refeeding, DKA, hyperthyroidism, acute MI

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101
Q

Why might serum Mg levels not correlate with intracellular concentrations or total body Mg levels?

A

Because only 1-2% of total body Mg is located in the ECF

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102
Q

Why is IV administration of Mg preferred over oral?

A

Issues with oral administration, slow onset of action, GI intolerance

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103
Q

What is the maximum infusion rate of magnesium sulfate and why?

A

Should not exceed 1gm/hr (8 mEq/hr) in asymptomatic patients because more than 50% of the dose may be lost in the urine as renal magnesium reabsorption is exceeded

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104
Q

Expected serum Mg changes with IV treatment of hypomagnesemia?

A

Serum Mg change of 0.1 mg/dL for each gram (8 mEq) administered, although the plasma concentration typically takes up to 48 hours after the bolus to equilibrate

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105
Q

Guidelines for treatment in the first 24 hours of hypomagnesemia according to severity:
Mild (1.3-1.5 mEq/L [1.5-1.8 mg/dL])
Moderate (0.8-1.2 mEq/L [1-1.4 mg/dL])
Severe (<0.8 mEq/L [<1 mg/dL])

A

Mild = 0.5 mEq/kg
Moderate = 1 mEq/kg
Severe = 2 mEq/kg

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106
Q

Clinical presentation/manifestation of hypomagnesemia?

A

Primarily associated with other electrolyte abnormalities. Neuromuscular symptoms (muscle fasciculations, tremors, hyperreflexia, paresthesias, positive Chvostek’s and Trousseau’s signs, myalgias, tetany, myoclonic jerk); Cardiac (V.fib, ventricular tachycardia, PR prolongation, QT prolongation, torsades de pointes); Metabolic (hypokalemia, hypocalemia); CNS (nystagmus, seizures, depression, agitation, psychosis, disorientation, confusion, hallucinations, irritability, restlessness)

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107
Q

Define hypermagnesemia

A

Serum Mg level >2.8 mg/dL

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108
Q

Etiology and symptoms of hypermagnesemia?

A

Occurs in the setting of CKD in combination with Mg intake. Generally well tolerated but can affect neurological, neuromuscular, and cardiac function when levels exceed 4.8 mg/dL. Symptoms include nausea, vomiting, diaphoresis, flushing sensation of heat, depressed mental functioning, drowsiness, muscular weakness, loss of deep tendon reflexes, hypotension, bradycardia

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109
Q

Treatment for symptomatic and asymptomatic hypermagnesemia?

A

Symptomatic: IV calcium (chloride or gluconate) administered to reverse cardiac and neuromuscular effects
Asymptomatic: removal of exogenous sources of Mg (PN and IV fluids), Mg restriction, loop diuretics

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110
Q

Normal serum calcium (Ca2+) level?

A

8.6-10.2 mg/dL

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111
Q

Low serum calcium concentrations stimulate which functions?

A

Release of PTH which increases bone resorption, augments renal conservation of calcium, and activate vitamin D, which in turn increases intestinal calcium absorption

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112
Q

What is the purpose of calcitonin and when is it released?

A

Released by the thyroid gland in response to elevated serum calcium concentrations and acts to inhibit bone resorption and increase urinary calcium excretion

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113
Q

What 3 forms does serum calcium exist in and which is the metabolically active form that is of greatest physiological importance?

A

Complexed, protein bound, and ionized. Ionized

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114
Q

Normal range of ionized calcium?

A

1.12-1.3 mmol/L

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115
Q

What is the equation for adjusting total calcium with hypoalbuminemia?

A

Corrected Total Serum Calcium = Measured Total Serum Calcium + [0.8 x (4 - serum albumin)]

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116
Q

True or False: Hypoalbuminemia decreases total serum calcium and ionized calcium levels

A

False. Does not affect ionized calcium levels

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117
Q

Range for hypocalcemia and its most frequent cause?

A

Total serum calcium <8.6 mg/dL or ionized calcium less than 1.12 mmol/L
Hypoalbuminemia

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118
Q

Causes of hypocalcemia?

A

Decreased vitamin D activity (vitamin D deficiency, hyperphosphatemia, pseudohypoparathyroidism), decreased PTH activity (acute pancreatitis, hypomagnesemia, hypoparathyroidism), citrate anticoagulation during CRRT, hungry bone syndrome (can occur after total parathyroidectomy or thyroidectomy)

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119
Q

Conditions in critical illness that are associated with hypocalcemia?

A

Sepsis, rhabdomyolysis, massive blood transfusion (secondary to citrate preservative in the blood bank binding with serum calcium)

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120
Q

What are some drugs implicated in the etiology of hypocalcemia?

A

Biphosphonates, calcitonin, furosemide, foscarnet, and long-term therapy with phenobarbital and phenytoin

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121
Q

Clinical manifestations of hypocalcemia?

A

Cardiovascular: hypotension, decreased myocardial contractility, or prolonged QT interval
Neuromuscular: distal extremity paresthesias, Chvostek sign, Trousseau sign, muscle cramps, tetany, seizures

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122
Q

What is the empirical treatment for acute hypocalcemia?

A

Serum ionized calcium 1-1.2 mmol/L = 1-2 gm (4.65-9.3 mEq) calcium gluconate over 1-2 hours
Serum ionized calcium <1 mmol/L = 2-4 gm (9.3-18.6 mEq) calcium gluconate over 2-4 hours

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123
Q

What is the limiting factor for using calcium chloride to correct acute symptomatic hypocalcemia even though it contains 3 times more elemental calcium than an equivalent amount of calcium gluconate?

A

It may cause tissue necrosis if extravasation occurs

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124
Q

How can chronic or asymptomatic hypocalcemia be treated?

A

With oral calcium supplements and vitamin D

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125
Q

Range for hypercalcemia and its most frequent causes?

A

Total serum calcium >10.2 mg/dL or ionized calcium >1.3 mmol/L
Most often occurs with hyperparathyroidism and cancer with bone metastases (primarily breast cancer, lung cancer, and multiple myeloma)

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126
Q

Name some causes for hypercalcemia?

A

Hyperparathyroidism, cancer with bone metastases, toxic levels of vitamin A or D, chronic ingestion of milk and/or calcium carbonate-containing antacids in the setting of renal insufficiency (milk-alkali syndrome), adrenal insufficiency, immobilization, TB, and use of various medications (thiazide diuretics and lithium)

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127
Q

Describe some early clinical manifestations of hypercalcemia?

A

Fatigue, nausea, vomiting, constipation, anorexia, and confusion. Cardiac arrhythmia (bradycardia) in more severe cases

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128
Q

Treatment of mild hypercalcemia (total serum calcium 10.3-11.9 mg/dL)?

A

Usually responds well to hydration and ambulation

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129
Q

Range for severe hypercalcemia and potential consequences if not treated immediately?

A

Total serum calcium greater than or equal to 14 mg/dL. Can lead to acute renal failure, obtundation, ventricular arrhythmias, coma, death

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130
Q

What is the treatment for severe hypercalcemia?

A

IV hydration using 0.9% NaCl should be started promptly at 200-300 ml/hr to reverse the volume depletion caused by hypercalcemia. After adequate hydration is achieved, 40-80mg IV furosemide may be used to enhance renal calcium excretion if the patient is vigilantly monitored to avoid further volume depletion. Calcitonin can be used but tachyphylaxis often limits its usefulness after 48 hours. Hemodialysis may be necessary in life-threatening hypercalcemia or in patients with CKD

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131
Q

Normal serum phosphorus concentration?

A

2.7-4.5 mg/dL
Reflects <1% of total body phosphorus, most found in bones and soft tissue

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132
Q

What functions is adequate total body phosphorus needed for?

A

Necessary for carbohydrate use, glycolysis, maintenance of normal pH, 2,3-diphosphoglycerate synthesis and function (necessary for oxygen release from hemoglobin and ultimately tissue oxygenation), neurologic function, and muscular function

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133
Q

What determines serum phosphorus concentration?

A

Intake, intestinal absorption, renal excretion, hormonal regulation of bone resorption and deposition, and distribution between intracellular shifts of phosphorus

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134
Q

What can result in the release of phosphorus from the cell to the ECF?

A

Cellular destruction and acidosis

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135
Q

Define hypophosphatemia and manifestations of it?

A

Serum phosphorus concentration <2.7 mg/dL
Neurologic: ataxia, confusion, paresthesias
Neuromuscular: weakness, myalgia, rhabdomyolysis
Cardiopulmonary: cardiac and ventilatory failure
Hematologic: reduced 2,3-diphosphoglycerate concentration, hemolysis

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136
Q

Conditions in which hypophosphatemia is common

A

Chronic alcoholism, critical illness, respiratory and metabolic alkalosis, following the treatment of DKA, patients receiving phosphate binders

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137
Q

What are limitations of oral phosphate supplementation?

A

Diarrhea and unreliable absorption

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138
Q

Empirical treatment (intravenous) for mild, moderate, and severe hypophosphatemia?

A

Mild (2.3-2.7 mg/dL) = 0.08-0.16 mmol/kg
Moderate (1.5-2.2 mg/dL) = 0/16-0.32 mmol/kg
Severe (<1.5 mg/dL) = 0.32-1 mmol/kg

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139
Q

When should patients receive IV potassium phosphate or sodium phosphate to correct phosphorus levels?

A

Patients with symptomatic, moderate or severe hypophosphatemia as well as those that cannot tolerate oral phosphate formulations

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140
Q

Where is phosphorus actively absorbed and what enhances its absorption? Diminishes it?

A

2/3 of phosphate is actively absorbed from the proximal small intestine (predominately jejunum). Absorption increased by the presence of vitamin D- and moderate amounts of calcium. Absorption diminished in the presence of a large amount of calcium or aluminum in the intestine (antacids) due to formation of soluble phosphate compounds

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141
Q

IV potassium phosphate is preferred for phosphorus replacement except when:

A

Unless the potassium concentration is >4 mEq/L or renal insufficiency exists
3 mmol potassium phosphate = 4.4 mEq potassium

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142
Q

Why should infusion rates of phosphorus not exceed 7 mmol/hour?

A

Because faster infusion rates can often cause thrombophlebitis and soft tissue calcium-phosphate deposition

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143
Q

Hypophosphatemia secondary to intracellular shifts is more likely to occur under what circumstances?

A

Respiratory alkalosis, after a carbohydrate load, with PN containing inadequate phosphorus, in nutrition recovery, and during androgen therapy

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144
Q

General treatment for mild hypophosphatemia?

A

Can usually be treated by increasing dietary intake or giving an oral supplement

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145
Q

Treatment for moderate hypophosphatemia?

A

Usually can be treated with dietary/oral supplement but may require IV replacement. IV replacement indicated when symptomatic, according to severity of illness, and underlying cause of depletion

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146
Q

Scenario: How can complications be prevented when providing nutrition support therapy to a malnourished esophageal cancer patient?
Patient info: 37 y/o M 68 kg, 6’, esophageal cancer s/p chemoradiation and esophagectomy admit with progressive wt loss (-10 kg in 2 months) and FTT. J-tube placed hospital day 2, on day 4 pt falls getting out of bed with weakness and pain. EN support was advanced to goal within 24 hours. From hospital day 1 to 4, Na increased, K+ decreased, Mg decreased, Phos decreased

A

Nutrition support therapy should be advanced cautiously for patients at risk for refeeding. Goal EN rate for scenario patient was 70 ml/hr of a 1.5 kcal/ml formula. Rate was decreased to 20 ml/hr and IV electrolyte replacement ordered, serum chemistry ordered q 12 hours, daily administration of 100mg thiamin added. Scenario patient started on aggressive feeding regimen with no titration which resulted in massive intracellular shift of K+, Mg, Phos that caused symptomatic hypokalemia, hypomagnesemia, hypophosphatemia. Decrease nutrition support therapy to safe rate of 500 kcal/day before further advanced

147
Q

Range for hyperphosphatemia and 3 primary mechanisms for its occurrence?

A

Serum phosphorus concentration >4.5 mg/dL
Increased phosphorus load, primary increase in renal phosphate reabsorption, and decrease in renal excretion

148
Q

What is the most serious complication of hyperphosphatemia?

A

Soft tissue and vascular calcification

149
Q

Name some causes of endogenous release of phosphorus into the ECF:

A

Cellular destruction from massive trauma, cytotoxic agents, neoplastic disease (leukemia and lymphoma), chemo, hypercatabolism, hemolysis, rhabdomyolysis, malignant hyperthermia

150
Q

What causes transcellular shifts of phosphorus from the ICF to the ECF?

A

Respiratory or metabolic acidosis

151
Q

Recommended dietary phosphorus restriction with hyperphosphatemia?

A

800-1000 mg/day

152
Q

Describe clinical manifestations of hyperphosphatemia

A

Anorexia, nausea, vomiting, muscle weakness, hyperreflexia, tetany, tachycardia

153
Q

When does calcification occur in the setting of hyperphosphatemia?

A

When the calcium-phosphorus product exceeds 55 mg^2/dL

154
Q

Describe consequences of hyperphosphatemia?

A

Secondary hyperparathyroidism, renal osteodystrophy

155
Q

How can hyperphosphatemia be treated?

A

Removing or limiting exogenous sources of phosphorus (dietary sources, PN, phosphate-containing enemas or laxatives), Aluminum- and calcium-based phosphate binders, dialysis, volume repletion with normal saline IV, loop diuretic

156
Q

Name potential disadvantages of using an aluminum-based phosphate binder

A

Risk of bone, hematological and neurological toxicity, constipation

157
Q

Definition of an acid? A base?

A

A substance that can donate hydrogen ions (H+); A substance that can accept or combine with hydrogen ions

158
Q

Normal range for pH of arterial blood?

A

7.35-7.45

159
Q

pH below 7.35 is called ___ and a pH greater than 7.45 is called ___

A

Acidemia; alkalemia

160
Q

Processes that tend to raise or lower the H+ concentration are called ___ and ___ respectively

A

Acidosis; alkalosis

161
Q

Metabolism of carbohydrates and fats alone results in the daily production of approximately how many mmols of CO2

A

15,000 mmol

162
Q

Protein metabolism accounts for how many mEqs of daily acid production?

A

50-100 mEq

163
Q

Name the 3 sequential steps required in the process of H+ regulation

A
  1. Chemical buffering by extracellular and intracellular mechanisms
  2. Control of the partial pressure of CO2 in the blood by alterations in the rate of alveolar ventilation
  3. Control of the plasma bicarbonate concentration by change in renal H+ excretion
164
Q

What is the principle buffer system? Name other buffer systems

A

The carbonic acid/bicarbonate system (H2CO3/HCO3-)
Proteins, phosphate, and hemoglobin

165
Q

What is the principle role of the lungs in maintaining acid-base balance?

A

To regulate the pressure exerted by dissolved CO2 gas in the blood (PCO2)

166
Q

Which chemical is the most powerful respiratory stimulant?

A

CO2

167
Q

What are the 2 processes that alter renal H+ excretion?

A
  1. Reabsorption of filtered HCO3-
  2. Excretion of the H+ produced daily as a result of protein metabolism
168
Q

What is the only organ that is able to regulate levels of alkaline substances in the blood and eliminate acids from the body?

A

Kidneys

169
Q

Difference between ABG and VBG

A

ABG (arterial blood gas) reflects the ability of the lungs to oxygenate blood
VBG (venous blood gas) reflects tissue oxygenation

170
Q

Increases in PCO2 represent ___ and decreases in PCO2 represent ___

A

Acidosis
Alkalosis

171
Q

Increases in HCO3- represent ___ and decreases is HCO3- represent ___

A

Alkalosis
Acidosis

172
Q

Define the stepwise approach to evaluating acid-base disorders

A
  1. Assess pH of blood to determine whether pt is acidemic (pH <7.4) or alkalemic (pH >7.4). If pH is 7.4, an acid-base disorder cannot be ruled out; a mixed acid-base disorder or compensation may be present
  2. Assess PCO2 to determine whether a respiratory process may be contributing. If PCO2 is elevated, patient has respiratory acidosis; if low, patient has respiratory alkalosis
  3. Assess serum HCO3- to determine whether metabolic process may be contributing. If HCO3- is elevated, patient has metabolic alkalosis; if low, patient has metabolic acidosis
  4. Calculate anion gap to determine whether metabolic acidosis is present. Calculation is critical to determine the etiology of the acid-base disorder and select the appropriate treatment
  5. Determine whether acid-base disorder is acute or chronic; determine whether they are appropriately compensated and if not, then patient has mixed acid-base disorder
173
Q

Define PCO2

A

Provides information on the lungs’ ability to excrete CO2

174
Q

Name the blood gas measurements

A

pH, PCO2, PO2 (partial pressure of oxygen in the blood), SaO2 (oxygen saturation), calculated HCO3-, base excess

175
Q

Define respiratory acidosis

A

Clinical disorder characterized by a reduced pH, an elevation in the PCO2, and a variable increase in the serum HCO3- concentration. Almost always results from decreased effective alveolar ventilation, not an increase in CO2 production

176
Q

Define respiratory alkalosis

A

Clinical disturbance characterized by an elevated pH, a decrease in PCO2, and a variable reduction in serum HCO3-. Occurs when effective alveolar ventilation is increased beyond the level necessary to eliminate metabolically produced CO2 (hyperventilation)

177
Q

List common causes of respiratory acidosis

A

Medications: opioids, anesthetics, sedatives, neuromuscular blockers
Neuromuscular: Guillain-Barre, Myasthenia gravis, MS, ALS, central respiratory depression, head/spinal cord/brainstem/cervical cord injury, stroke, hypophosphatemia
Metabolic: PN or EN overfeeding
Pulmonary/Thoracic disease/complications: massive PE, ARDS, interstitial lung disease, flail chest, pleural disease, pneumothorax, severe pulmonary edema, severe pneumonia, smoke inhalation, COPD, emphysema, bronchitis, asthma, sleep apnea, obesity hypoventilation, hypoxemia, mechanical ventilator hypoventilation
Airway obstruction: foreign body, severe asthma attack/bronchospasm, aspiration, malignancy
Perfusion abnormalities
Cardiac arrest

178
Q

List common causes of respiratory alkalosis

A

Medications (stimulate CNS respiration): xanthine derivatives, nicotine, catecholamines (epinephrine, norepinephrine, dopamine), salicylate overdose
CNS stimulation of respiration: brain tumors, encephalitis/meningitis, head trauma, vascular accidents, anxiety, pain, fever, pregnancy
Hypoxia: high altitudes, hyperventilation, hypoxemia, pneumonia, pulmonary edema, severe anemia
Peripheral stimulation of respiration: pulmonary embolus, asthma
Other: thyrotoxicosis, cirrhosis, hepatic encephalopathy, mechanical ventilator hyperventilation

179
Q

Define metabolic acidosis

A

Clinical disturbance characterized by a reduced pH, reduced serum HCO3- concentration, and compensatory hyperventilation resulting in a decrease in PCO2

180
Q

What are the 2 fundamental mechanisms that can induce metabolic acidosis?

A
  1. An inability of the kidneys to excrete the dietary H+ load
  2. An increase in the generation of H+ either by the addition of H+ or the loss of HCO3-
181
Q

What is the anion gap?

A

Represents unmeasured serum anions (proteins, phosphate, sulfate, and organic ions) and unmeasured serum cations (potassium, calcium, magnesium). Useful in the diagnosis of metabolic acidosis. It is equal to the difference between the serum concentrations of the major measured cation and the major measured anions

182
Q

What is the equation for calculating the anion gap?

A

Anion Gap = (Serum Na) - ([Serum Cl] + [Serum HCO3-])
All values measured in mEq/L

183
Q

What is a normal anion gap?

A

9 mEq/L (range from 3-11 mEq/L)

184
Q

List common causes of normal (non-) anion gap metabolic acidosis

A

GI loss of HCO3-: obstructed ileal loop conduit, ketoacidosis, ureterosigmoidostomy, anion-exchange resins, cholestyramine, diarrhea, high output (>1L/day) ostomy, pancreatic/biliary/small bowel fistula
Excessive ingestion of acidic/chloride-based substances: ammonium chloride, overuse of chloride salts in PN
Renal loss of HCO3-: carbonic anhydrase inhibitors, hyperparathyroidism, hypoaldosteronism, type 2 renal tubular acidosis (spironolactone, amiloride)

185
Q

List common causes of increased anion gap metabolic acidosis

A

Failure to excrete acids: acute and chronic renal failure
Increased production of endogenous acid: ketoacidosis (diabetic, alcohol, starvation), inborn errors of metabolism, lactic acidosis: tissue hypoxia (shock/sepsis), Propofol (doses >80 mcg/kg/min for >48 hr), Metformin use in renal failure, Nitroprusside use, Nucleoside-analog reverse transcriptase inhibitors, carbon monoxide poisoning, liver disease, rhabdomyolysis, seizures, thiamine deficiency
Toxins/overdoses: salicylate, propylene glycol, propyl alcohol, methanol, ethylene glycol

186
Q

Scenario: How would you alter the electrolyte composition of a PN formulation for a patient with an elevated end ileostomy output?
Patient info: 54 y/o F with 30 yr h/o Crohns, multiple small bowel resections with creation of end ileostomy. Admit w/ progressive wt loss and fatigue, elevated ostomy OP (3-4.5 L/day), ARF 2/2 volume depletion. Albumin/Prealbumin 2.1g/dL and 18.6 mg/dL. IV NaCl (0.9%) started @ 125 ml/hr + oral diet. Developed severe metabolic acidosis on day 3 with continued ostomy OP >3L/day. Primarily consuming high fat foods. Na increase, K+ increase, Cl increase, HCO3- decrease, BUN decrease, Creatinine decrease.

A

PN formulation for high-output ileostomy should contain maximum amounts of acetate salts to prevent and/or correct a hyperchloremic metabolic acidosis. PN started at 50% of estimated energy needs to reduce risk of refeeding and acetate salts maximized. Acetate additives include sodium and potassium and should be tailored for individual needs/tolerance. Sodium concentration of PN should be equal to that of 0.9% NaCl (normal saline) to approximate the sodium concentration of ileostomy fluid. Pt with high OP ileostomies are at risk for acid-base disturbances 2/2 anatomical changes. Management should include fluid replacement that approximates the electrolyte composition of ileal fluid

187
Q

Define metabolic alkalosis

A

An elevation in the pH, an increase in serum HCO3- concentration, and compensatory hypoventilation resulting in a rise in the PCO2

188
Q

Most commonly observed acid-base disorder in hospitalized patients (33-55% of hospitalized patients with acid-base disturbances)?

A

Metabolic alkalosis

189
Q

What is saline-responsive metabolic alkalosis?

A

Urine chloride <20 mEq/L
The increase in HCO3- reabsorption that maintains the alkalosis can be reversed by the administration of half-isotonic or isotonic saline

190
Q

What is saline-resistant metabolic alkalosis?

A

Urine chloride >20 mEq/L
Characterized by high urinary chloride concentration

191
Q

List causes of saline-responsive metabolic alkalosis

A

Cystic fibrosis (loss of Cl- in sweat)
Diuretic therapy: loop and thiazide
Excessive HCO3- administration: sodium bicarbonate, citrate, antacids, overuse of acetate salts in PN
GI losses: vomiting, NG suction, gastric fistula, villous adenoma
Rapid correction of hypocapnia
Renal loss

192
Q

List causes of saline-resistant metabolic alkalosis

A

Cushing’s syndrome
Excess mineralocorticoids
Hyperaldosteronism
Profound hypokalemia (serum potassium <2 mEq/L)
Excessive licorice ingestion (chewing tobacco)
Renal artery stenosis
Laxative abuse
Clay ingestion

193
Q

Simple review of the characteristics of the primary acid-base disorders (name the disorder, pH, primary disturbance, and compensatory response)

A

Metabolic acidosis: pH ↓ , HCOs- ↓ , PCO2 ↓
Metabolic alkalosis: pH ↑, HCO3- ↑, PCO2 ↑
Respiratory acidosis: pH ↓ , PCO2 ↑, HCO3- ↑
Respiratory alkalosis: pH ↑ , PCO2 ↓ , HCO3- ↓

194
Q

With metabolic alkalosis induced by moderate/severe hypokalemia, what is the only way to reverse the metabolic alkalosis?

A

Administration of potassium chloride. Although adequate NaCl repletion with usually normalize the plasma HCO3- concentration, it will not reverse the metabolic alkalosis

195
Q

major extracellular electrolytes

A

Sodium (142 mEq/L), Chloride (103 mEq/L), Calcium (2.4 mEq/L)
Bicarb (28 mEq/L)

196
Q

major intracellular electrolytes

A

Potassium (140mEq/L), Magnesium (58 mEq/L), Phosphate (74 mEq/L)

197
Q

% extracellular body water

A

1/3 (33%)

198
Q

% intracellular body water

A

2/3 (67%)

199
Q

% body water for an adult male

A

60%

200
Q

% body water for an adult female

A

50%

201
Q

% body water for an elderly male

A

50%

202
Q

% body water for an elderly female

A

45%

203
Q

what weight should be used to estimate total body water in obesity

A

ideal body weight

204
Q

insensible water gains

A

water oxidation of metabolism (250mL)

205
Q

total water gain in healthy adult

A

1.5-2.5 Liters

206
Q

sensible water gains

A

oral fluid intake (800 mL to 1.5 L) and water from solid foods (500-700mL)

207
Q

total water loss in healthy adult

A

1.5-2.5 liters

208
Q

sensible water loss

A

urine output (800-1.5 L) and GI output (0-250mL)

209
Q

insensible water loss

A

skin (600-900mL) and lungs

210
Q

Where does fluid gain occur during digestion

A

saliva, food/drink, bile, pancreatic fluid, small bowel fluid, gastric fluid

211
Q

how much water is reabsorbed total from digestion

A

6.5 Liters

212
Q

how much fluid is created daily from saliva

A

1.5 Liters

213
Q

how much water is gained total from digestion

A

8.5 liters

214
Q

the stomach typically produces _____ L of fluid

A

2 liters

215
Q

how much fluid is reabsorbed in the colon

A

1.9 liters (out of 2)

216
Q

a patient has tented/dry skin, with dry mucous membranes, has increased heart beat (tachycardia), decreased blood pressure and urinary sodium above 20 they are likely

A

dehydrated

217
Q

how to calculate fluid maintenance (adults and children over 5 years old)

A

4,2,1 or 100,50,20 method

218
Q

calculate fluid maintenance for a 60 kg male (4,2,1 method)

A

4mL x 10 kg = 40mL/hr
2mL x10 kg = 20mL/hr
1mL x 40kg = 40mL/hr
Total 100mL/hr x 24 hours = 2.4 Liters

219
Q

calculate fluid maintenance for a 60 kg male (100,50,20 method)

A

100mL x 10 kg = 1000mL
50mL x 10kg = 500 mL
20mL x 40 kg= 800 mL
Total = 2300mL/day

220
Q

Fever, excessive sweating , hyperventilation and hyperthyroid _____ fluid needs

A

increase

221
Q

abnormal shifts of fluid from the intravascular space (blood vessels) into the interstitial fluids (the tissues)

A

Edema

222
Q

common causes of edema

A

decreased cardiac output, hypotension, decreased urine output

223
Q

when you have edema, you are considered in a state of water

A

loss

224
Q

conditions that can cause 3rd spacing

A

bowel obstruction, peritonitis, acute pancreatitis, ascites in liver/renal function, trauma

225
Q

isotonic IV fluids

A

Normal Saline with Dextrose or balanced crystalloids (LR, plasmalyte)

226
Q

should post op major abdominal surgical patients have liberal or restricted fluids in the 1st 24 hours post op

A

liberal fluids to prevent AKI

227
Q

water deficit calculation

A

(Current Na - Desired Na / Desired Na) x %body water x body weight (kg)

228
Q

Causes of primary hypervolemia

A

poor renal function leading to sodium retention and extracellular fluid expansion to preserve blood pressure

229
Q

causes of secondary hypervolemia

A

CHF, cirrhosis, excessive IV administration

230
Q

symptoms of hypervolemia

A

weight gain, edema, ascites, pulmonary effusion, rales, distended jugular veins

231
Q

the primary extracellular cation is

A

sodium

232
Q

the primary anion of the ECF is

A

chloride

233
Q

the primary cation of the ICF is

A

potassium

234
Q

the primary anion of the ECF is

A

phosphate

235
Q

non-electrolyte components of body fluids that do not dissociate in solution are

A

glucose, urea and creatinine

236
Q

when levels of cations and anions are in equal amounts is called

A

electroneutrality

237
Q

electroneutrality is maintained by

A

buffering systems

238
Q

a patient that has high loses via NG suction of about 2L a day would likely benefit from the replacement of ___ to maintain homeostasis

A

chloride

239
Q

if a patient has high losses from diarrhea they would likely benefit from the replacement of ____ to maintain homeostasis

A

bicarb, alkaline solutions

240
Q

the most common cause of hypernatremia

A

inappropriate/inadequate provision of fluids

241
Q

increased blood glucose of hypertonic sodium free IV fluids can cause

A

hypertonic hyponatremia

242
Q

when glucose is high, sodium will be artificially low because

A

hyperglycemia is a hypertonic state intracellular water shifts out from inside the cell into the vascular space causing dilutional hyponatremia

243
Q

for ever 100mg/dL increase in serum glucose from normal, serum Na decreases by

A

1.6 mEq/L

244
Q

the most common cause of hyponatremia is

A

excess water provision

245
Q

sodium is largely regulated by this organ _____ and this hormone_____

A

kidney, aldosterone (vasopressin)

246
Q

aldosterone hormone causes ____ to be reabsorbed in the distal renal tubule in response to a change in sodium/volume status

A

sodium

247
Q

serum ____ is essential to assess the cause and treatment of low sodium

A

osmolality

248
Q

fatigue, weakness and muscle twitching are signs of symptomatic

A

hyponatremia

249
Q

Normal Saline (IV) provides ____ sodium per liter

A

154 mEq/L

250
Q

Hypernatremia is always associated with a __ state. Free water moves from the ICF to the ECF causing dehydration

A

hypertonic

251
Q

dry mucous membranes, hypotension, oliguria, tachycardia and decreased skin turgor are symptoms of

A

dehydration

252
Q

calculate the free water deficit of a 70 kg man with a serum sodium of 158

A

5.4 L (to 140mEq/L) 1.6 L (to 152 mEq/L)

253
Q

Phosphorous is the primary ____ anion

A

intracellular

254
Q

Phosphorous maintains the _____ cellular fluid, normal muscle/nervous function and important in metabolic pathways

A

intracellular

255
Q

nervous system dysfunction, respiratory failure, decreased levels of 2,3-diphosphoglycerate and muscle weakness can be caused by

A

hypophosphatemia

256
Q

reasons for elevated phosphorous

A

renal failure, metastatic calcification of soft tissue/blood vessels cellular destruction from trauma, cytotoxic medications, severe rhabdomyolysis

257
Q

Optimal total serum phos and calcium should be a

A

55

258
Q

the most common clinical manifestation of hyperphosphatemia is ___ caused by hypocalcemia d/t calcium phosphate precipitation

A

tetany

259
Q

a patient with hypokalemia should also be assessed for what electrolyte

A

hypomagnesemia (magnesium regulates intracellular potassium)

260
Q

when hypokalemia co-exists with hypokalemia and hypomagnesemia replete which first

A

magnesium

261
Q

the following electrolyte disturbance can cause a deficit of hydrogen ions in the ECF precipitating in alkalosis

A

hypokalemia (potassium is on the inside of the cell normally, if low, protons will pump in potassium to correct causing a deficit of hydrogen ions into the ECF)

262
Q

this electrolyte is integrating maintaining cell volume , hydrogen ion concertation, enzyme function, neuromuscular /cardiac function and cell growth

A

potassium

263
Q

clinical manifestations of hypokalemia

A

cardiac arrhythmia, muscle weakness, ileus, EKG changes and paralysis

264
Q

renal failure, rhabdomyolysis and acidosis can all cause

A

hyperkalemia

265
Q

common causes of hypomagnesemia (3)

A

inadequate GI absorption, refeeding syndrome and DKA

266
Q

DKA lowers serum hypomagnesemia because

A
  1. increased renal excretion during diuresis from high blood glucose
  2. shifting of magnesium into the cells by insulin
267
Q

when maintained slightly above normal serum concentrations, which of the following electrolytes reduces the amount of potassium required in critically ill patients

A

magnesium

268
Q

a patient getting a standard enteral feeding constantly has a magnesium level of 3.0 mEq/L. A prudent first step would to be

A

ensure that medications with supplemental magnesium have been held

269
Q

causes of hypermagnesemia

A

renal failure ,excessive use of laxatives’ as they contain large amounts of magnesium (milk of magnesia)

270
Q

low levels of serum calcium stimulates the release of this hormone which increases bone resorption, stimulates renal conservation of calcium and activates vitamin D (in turn increasing the absorption of calcium in the GIT)

A

parathyroid hormone

271
Q

in response to elevated levels of serum calcium, the ____ releases ___ hormone which inhibits bone resorption

A

thyroid, calcitonin

272
Q

Adjust the calcium for a patient with an albumin of 2.4 and calcium of 6.9

A

8.2

273
Q

in the absence of excessive exogenous provision of calcium in a patient with normal renal function, the most common cause (s) of hypercalcemia are

A

hyperparathyroidism and bone cancer

274
Q

decreased vitamin D, decreased PTH activity after thyroidectomy/parathyroidectomy, massive soft tissue damage 2/2 trauma ,infection , or multiple blood transfusions 2/2 citrate binding of this element causes _____

A

calcium, hypocalcemia

275
Q

in the setting of critical illness or injury, a patient has decreased UOP, hypotension, tachycardia, high urinary specific gravity, high osmolality, elevated Cr, poor skin turgor with minimal if any changes in body wt. The clinician should consider this change in body fluid

A

third spacing

276
Q

Third spacing and critical illness/trauma

A

traumatic injury results in redistribution of intravascular fluid into the area of injury, therefore decreasing intravascular fluid volume, Sepsis produces generalized capillary leak, causing larger molecules such as proteins to readily pass through membranes, precipitating a disruption of oncotic pressure allowing the ICF to leak out of the cells

277
Q

what are therapies used for standard care to treat third spacing

A

IV LR/normal saline, blood transfusion, correction of underlying cause

278
Q

the most appropriate enteral formula for a patient with SIADH is

A

a concentrated formula (low in water)

279
Q

the syndrome of inappropriate antidiuretics hormone (SIADH) is likely to present as

A

hyponatremia

280
Q

hallmark signs of SIADH

A

low sodium, increased urine sodium and increased osmolarity

281
Q

Euvolemic body with total body water overload d/t inappropriate concentration of the urine

A

SIADH

282
Q

elevated serum sodium, flat neck veins, dry mucous membranes are signs of

A

dehydration

283
Q

the preferred oral rehydration solution should be/contain

A

isotonic, with sodium and glucose/carbohydrate

284
Q

oral rehydration solutions decrease _____ in short bowel syndrome

A

dehydration

285
Q

this type of fluid is readily absorbed from the jejunum

A

sodium chloride

286
Q

saline water is not absorbed well from commercially available rehydration solutions because they are hypotonic true or false

A

true

287
Q

optimal sodium level (in mmol/L) of sodium in oral rehydration solutions

A

90mmol/L

288
Q

____ in oral rehydration solutions is an important component because it promotes sodium/water absorption by acting as a transporter

A

glucose

289
Q

this disorder is represented by hypernatremia with high urine output from 4-12L /day

A

Diabetes Insipidus

290
Q

electrolyte abnormalities after feeding after starvation is called

A

refeeding syndrome

291
Q

in the early phase of refeeding syndrome excessive sodium and fluid intake causing

A

fluid overload, pulmonary edema, cardiac decompensation

292
Q

the three labs depleted in refeeding syndrome

A

hypomagnesemia, hypophosphatemia, hypokalemia

293
Q

chronic starvation/alcoholism, anorexia/malabsorption, morbid obesity with weight loss and AIDS/Cancer patients are all at risk for

A

refeeding syndrome

294
Q

A cachectic 42 year old F is re admitted 2 weeks s/p ex lap with post op SBO. She has lost an additional 8% of her body weight since her first admit to the hospital. She undergoes surgical repair of the obstruction and has a naso-enteric feeding tube placed in the OR. Upon initiation of nutrition support which of the following would be a major concern

A

refeeding syndrome

295
Q

a patient getting normal saline at 75mL/hr with 20mEq KCl/L provides how many mE1 of sodium and _ mEq potassium chloride

A

154 mEq sodium (154 x 1.8)

36 mEq potassium (20 X 1.8 )

296
Q

Lactated Ringers fluid is most similar to ____ fluid

A

jejunal fluid

297
Q

Electrolytes of the GI tract Jejunum (Na, K, Cl, Bicarb)

A

Sodium: 95-120 mEq/L
Potassium: 5-15 mEq/L
Chloride: 80-130 mEq/L
Bicarb 10-20 mEq/L

298
Q

Electrolytes of the GI tract Ileum (Na, K, Cl, Bicarb)

A

Sodium: 110-130 mEq/L
Potassium: 5-15 mEq/L
Chloride: 90-110 mEq/L
Bicarb: 20-30 mEq/L

299
Q

Electrolyte Composition of Lactated Ringers

A 
Na: 130 mEq/L
Potassium: 4 mEq/L 
Chloride: 109 mEq/L
Lactate: 28 mEq/L
Calcium 2.7-7.7 mEq/L
300
Q

1/2 Normal Saline (0.45%) provides ___ mEq of sodium and ___ mEq of chloride

A

77 mEq sodium

77 mEq chloride

301
Q

Normal Saline (0.9%) provides __ mEq/L of sodium and __ mEq/L of chloride

A

154 mEq sdoium

154 mEq chlroide

302
Q

D5W + 1/2 Normal Saline (0.45%) provides ___g/L dextrose, ___ mEq/L Sodium, and ___ mEq/L chloride

A

50 g/L dextrose
77mEq/L sodium
77mEq/L chloride

303
Q

Compensation for a metabolic disorder occurs via the __ and takes approximately __ hours

A

Lung: 12-24 hours

304
Q

During acidosis, serum potassium

A

increases

305
Q

During alkalosis, serum potassium

A

decreases

306
Q

a patient with nasogastric suctioning output exceeding 2L a day is likely to manifest

A

metabolic alkalosis

307
Q

acidemia

A

pH <7.35

308
Q

alkalemia

A

pH >7.45

309
Q

normal blood pH range

A

7.35-7.45

310
Q

pCO2 normal range

A

35-45

311
Q

normal bicarbonate range

A

23-25

312
Q

how to correct metabolic acidosis with parenteral nutrition ?

A

increase acetate

313
Q

PN metabolites that are acidic

A

arginine, lyseine, histidine, methionine, cysteine

314
Q

Metabolic acidosis is associated with _____kalemia

A

hyperkalemia ; correction of metabolic acidosis re distributes potassium into the intracellular space to correct hyperkalemia

315
Q

when a patient is hyperkalemic, what can be given to correct it?

A

bicarbonate as the body is in a state of acidosis

316
Q

Decrease pH, Increased PCO2, Normal Bicarb indicates which acid base disorder

A

respiratory acidosis

317
Q

How to correct respiratory acidosis in PN

A

avoid overfeeding to prevent excessive CO2 production , less carbohydrate

318
Q

Causes of respiratory acidosis

A

HYPOventilation, sleep apnea, pneumothorax, COPD, ARDS, hypophosphatemia

319
Q

Causes of respiratory alkalosis

A

HYPERventilation (lost all your CO2), anxiety, pneumonia, high altitude, catecholamines (compromised lung function)

320
Q

Normal Anion Gap

A

10-12

321
Q

Causes of normal anion gap metabolic acidosis

A

providing high amounts of chloride in blood (ie IVF)
Bicarbonate loss from high output fistula or ileostomy or excessive diarrhea
Impaired renal function
D-Lactic acidosis

322
Q

What metabolites are used to calculate Anion Gap?

A

Sodium - Chloride + Bicarb

323
Q

what are causes of high anion gap metabolic acidosis

A

renal failure, thiamine deficiency (build up of lactate), ketoacidosis, SIBO, diuretic use

324
Q

If HCO3 and pH move in the same direction it is a _____ disorder

A

metabolic disorder

325
Q

If PCO2 and pH move in opposite directions it is a ____ disorder

A

respiratory disorder

326
Q

First line of defense in acid base imbalance

A

Buffers

327
Q

Second line of defense in acid base imbalance

A

Lungs

328
Q

Primary buffer in the body

A

bicarbonate

329
Q

a mixed acid base disorder occurs when pCO2 and HCO3 move in the ____ direction (s)

A

Opposite

330
Q

a simple acid base disorder occurs when pCO2 and HCO3 move in the ______direction (s)

A

Same

331
Q

How to alter PN in the setting of respiratory alkalosis

A

None

332
Q

In respiratory acidosis, pCO2 _____ and pH ____

A

increases, decreases

333
Q

pH and hydrogen ions move in ___ direction (s)

A

Opposite

334
Q

In respiratory alkalosis, pCO2 ___ and pH ___

A

decreases, increases

335
Q

In metabolic acidosis HCO3 ___ and pH ___

A

decreases, decreases

336
Q

What can you alter in PN in the setting of metabolic acidosis

A

Increase acetate

337
Q

acidic IVF solutions

A

D5W and D5w 1/2 NS

338
Q

In metabolic alkalosis HCO3 ___ and pH ___

A

increases, increases

339
Q

IVF treatment of metabolic alkalosis

A

Isotonic saline + KCl

340
Q

During acidosis, hydrogen ions are prominent in the serum. In order to correct the acidosis, Hydrogen ions are pumped _____ the cell, in exchange for ____ which exits the cell. Therefore the patient becomes hyper______

A

into the cell, potassium, hyperkalemic

341
Q

During alkalosis potassium moves _______ the cell while hydrogen ions move ____ of the cell. Therefore the patient becomes hypo_____

A

into the cell, out of the cell, hypokalemic

342
Q

Case: a 42 year old male is admitted with dizziness and weakness. He has a normal blood pressure of 120/80 mmHg while sitting but a low blood pressure while standing (100/64 mmHg) . This suggests orthostatic hypotension. He has had a history of vomiting. Sodium is 129, Potassium is 2.5, chloride is low, bicarbonate is 58, Creatinine is 1.9, BUN is 32, pH is 7.52, pCO2 is 63, pO2 is 68. What disorder is this? What is the cause? What is the expected compensation? What is the proposed treatment?

A

Metabolic Alkalosis caused by loss of hydrochloric acid from the stomach due to vomiting, it is expected that he will decrease his respiratory rate to increase is concentration of PCO2 (hypo ventilate). He can be treated with Normal saline with KCl as potassium is also low, Normal saline is an acidic IVF solution.

343
Q

Case: a 31 year old male is admitted with abdominal pain and weakness. He has a respiratory rate of 24 breaths per minute (normal is 13-16) and has a history of chronic IV drug use. His sodium is 136, potassium of 5.1, chloride of 100, HCO3 of 14, creatinine of 10, BUN of 120, pH of 7.28, pCO2 of 30 , pO2 of 100 and HCO3 13. What disorder is this? What is the cause? What is the expected compensation? What is the proposed treatment?

A

Metabolic acidosis caused by kidney failure. It is expected that his respiratory rate will increase to get rid of acidic CO2 in order to compensate (hyperventilation). Treatment would be dialysis, NaHCO3

344
Q

total body water for an adult male is __%

A

60%

345
Q

total body water for females is __%

A

50%

346
Q

which conditions would increase a person’s fluid requirements

A

ileostomy, high output fistula, fever

347
Q

the older you are the ____ muscle mass you have there fore less% body water

A

lower

348
Q

functions of water in the body

A

metabolic functions
maintains temperature
circulatory function

349
Q

if the abnormal accumulation of fluid occurs in the ICF compartment or body cavities, the following is most likely to occur

A

edema

350
Q

the component of plasma that is the principal determinant of colloid oncotic pressure

A

albumin

351
Q

the number of osmotically active particles per KG of solvent is known as

A

osmolality

352
Q

the body’s normal osmolality range

A

290-310 mOsm/L

353
Q

the direction and extent of water movement between fluid compartments is determined by the

A

osmolality

354
Q

during osmosis, fluids will shift from an area of lower concentration to an area of higher concentration until the water by

A

osmosis

355
Q

in addition to osmosis the regulation of body fluid compartments also occurs via (3 items)

A

diffusion, filtration and sodium potassium pumps

356
Q

which organs maintain the composition and volume of body fluid (6)

A

heart, lungs, kidneys, pituitary glands, adrenal gland, parathyroid gland

357
Q

As ADH increases, water retention _____

A

increases

358
Q

the majority of sensible water losses occur via

A

urine

359
Q

the majority of insensible losses of fluid come from the _____ and _____

A

skin and lungs

360
Q

third spacing, polyuria, and excessive GI losses are potential losses of

A

fluid

361
Q

3 potential causes of fluid overload include

A

heart failure, cirrhosis, steroid therapy

362
Q

estimated fluid needs for patients in critical illness and sepsis

A

30-40mL/kg/day

363
Q

a patient getting PN that provides NaCl 50mEq/L, KCl 20mEq/L, K Phos 30mEq/L with lab values Na 140, K 4.0, Cl 119, CO211, what is an appropriate adjustment for this PN

A

Change NaCL to Na acetate, add acetate

364
Q

in providing PN to a patient with metabolic alkalosis, the clinician should pay careful attention to the provision of salts as

A

acetate

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