Fluid & Electrolyte Physiology, Part 2

Front 1

What is the effective circulating volume?

Back 1

is that portion of the ECF that is contained in the vascular space and is effectively perfusing the tissues

Front 2

Is effective circulating volume a measurable entity? it refers to?

Back 2

no, but rather refers to the rate of perfusion of the capillaries
-ie, the sites of exchange between blood and tissue cells

Front 3

In general, the effective circulating volume varies directly with?

Back 3

the ECF volume in normal subjects

Front 4

Is some disease states, the effective circulating volume and ECF may be?

Back 4

dissociated

Front 5

In congestive heart failure patients, the effective circulating volume is?

Back 5

reduced, due to a primary decrease in CO

Front 6

What compensatory mechanisms occur in CHF patients with a decreased effective circulating volume?

Back 6

sodium and water retention by the kidney leads to an increase in ECF (and plasma) volume

Front 7

Maintenance of effective circulating volume is essential for?

Back 7

delivery of adequate oxygen and energy substrates to tissues, and for removal of C02 and metabolic end-products

Front 8

Maintenance of effective circulating volume is closely linked to regulation of?

Back 8

sodium balance

Front 9

Sodium loading (retention) leads to?

Back 9

volume expansion

Front 10

Sodium loss leads to?

Back 10

volume depletion

Front 11

What are the two steps in response to variations in effective circulating volume?

Back 11

1. Volume change is sensed by multiple receptors
2. Activation of effector mechanisms that act together to restore normovolemia

Front 12

What is the location of the primary receptors? 3

Back 12

1. carotid sinus and aortic arch (baroreceptors)
2. atria of the heart
3. afferent arterioles in the kidney (JG cells)

Front 13

What variable are the volume receptors actually sensing?

Back 13

pressure (stretch)

Front 14

Pressure and volume are usually ________ related.

Back 14

directly

Front 15

The rate of discharge of the stretch-sensitive nerve endings in the carotid sinuses and aortic arch are proportional to?

Back 15

the degree of stretch

Front 16

Afferent activity from the receptors in the carotid sinuses and aortic arch is directed to?

Back 16

the vasomotor centers in the medulla and to the paraventricular nuclei (ADH secretion) in the hypothalamus

Front 17

What does volume depletion do to activity of the stretch receptors in the carotid sinuses and aortic arch?

Back 17

tends to decrease stretch and afferent activity directed to the brain which causes a reflex increase in both vasomotor center output and ADH secretion

Front 18

What does volume expansion cause?

Back 18

increased pressure, increased afferent activity and reflex decrease in vasomotor output and ADH secretion

Front 19

Atrial stretch receptors detect?

Back 19

the degree of atrial filling

Front 20

Volume expansion has what effect on atrial stretch receptors?

Back 20

increases filling and stretch, reflex decrease in ADH secretion and release of ANP into the circulation

Front 21

Volume depletion has what effect on the atrial stretch receptors?

Back 21

decrease filling and stretch, reflex increase in ADH secretion and decreased release of ANP into the circulation

Front 22

Renin secretion from JG cells of afferent arteriole is _______ related to?

Back 22

inversely, the degree of stretch of the arteriolar wall

Front 23

What does volume depletion do to afferent arteriole stretch?

Back 23

reduces stretch which increases renin secretion and increases angiotensin II production and aldosterone release

Front 24

What does volume expansion do to renin secretion?

Back 24

suppresses it

Front 25

What 3 effector mechanisms are involved in volume regulation?

Back 25

1. SNS
2. RAS
3. Renal sodium excretion

Front 26

SNS outflow from the medulla vasomotor centers is regulated, in part, by?

Back 26

input from peripheral baroreceptors (inverse relationship)

Front 27

What is the response of the SNS to decreased effective circulating volume?

Back 27

Decreased venous return, CO, BP, baroreceptor stimulation, increased sympathetic tone

Front 28

Pharmacologic blockade of SNS in hypovolemic patients can cause?

Back 28

marked hypotension

Front 29

Volume expansion reduces?

Back 29

sympathetic output from vasomotor centers to minimize changes in CO and BP, and to facilitate sodium excretion

Front 30

Secretion of renin from JG cells of afferent arteriole is influenced by?

Back 30

sympathetic nervous system activity - direct relationship (beta-1 adrenergic receptors)

Front 31

Degree of stretch of afferent arteriole is?

Back 31

independent of SNS input, inverse relationship
-myogenic response

Front 32

What converts angiotensin I to II?

Back 32

ACE

Front 33

Angiotensin II is a potent?

Back 33

vasoconstrictor

Front 34

Angiotensin II stimulates secretion of? which promotes?

Back 34

aldosterone from the adrenal cortex which promotes sodium reabsorption in principal cells of the CCT AND stimulates sodium reabsorption in PCT

Front 35

When are renin secretion and angiotensin II formation enhanced?

Back 35

in hypovolemic states such as sodium restriction/loss, hemorrhage, or decompensated heart failure

Front 36

If you were to administer a pharmacologic blockade of the renin-angiotensin system in hypovolemic states would would happen?

Back 36

marked hypotension

Front 37

Renal sodium excretion varies directly with?

Back 37

effective circulating volume

Front 38

Volume expansion causes?

Back 38

increased sodium excretion

Front 39

Volume depletion causes?

Back 39

decreased sodium excretion (urine can be virtually sodium free)

Front 40

Adjustments in sodium excretion are due primarily to?

Back 40

adjustments in sodium reabsorption by the tubules

Front 41

What are factors that affect sodium reabsorption? 3

Back 41

1. aldosterone
2. atrial natriuretic peptide
3. filtration fraction (FF)

Front 42

Aldosterone promotes?

Back 42

sodium reabsorption in CCT

Front 43

ANP inhibits?

Back 43

sodium reabsorption in MCT

Front 44

Increased FF does what?

Back 44

enhances proximal tubular sodium reabsorption; decreased FF has opposite effect

Front 45

ECF volume determined by?

Back 45

absolute amounts of sodium and water present

Front 46

ECF osmolality determined by the ratio of?

Back 46

solutes (primarily sodium salts) to water

Front 47

Sweating leads to loss of hypoosmotic fluid which causes a?

Back 47

rise in Posm and fall in ECF volume

Front 48

Infusion of isotonic saline causes a?

Back 48

rise in ECF volume but no change in Posm

Front 49

So ECF volume and ECF osmolality can?

Back 49

vary independently

Front 50

Osmoregulation is achieved by?

Back 50

regulation of water balance; sodium is not directly affected unless there are concurrent changes in ECF volume

Front 51

Volume regulation is achieved primarily by?

Back 51

regulation of sodium excretion; the hypovolemic stimulus for ADH secretion, however, also promotes water retention to help restore normovolemia

Front 52

Crystalloid solutions contain?

Back 52

water and electrolytes; no colloids

Front 53

What is the replacement of blood loss ratio?

Back 53

3:1 to 4:1, 3-4mL of crystalloid solution per mL of blood loss

Front 54

what is the intravascular "half-life" of crystalloid solutions?

Back 54

20-30 min

Front 55

Balanced solutions have an?

Back 55

electrolyte composition similiar to that of ECF

Front 56

Lactated ringers solution

Back 56

most physiological replacement fluid, though slightly hypotonic (273mosm/kg H20)

Front 57

LR contains?

Back 57

lactate, which is converted to bicarbonate

Front 58

What are other examples of balanced solutions?

Back 58

PlasmaLyte and Normosol-R

Front 59

Normal saline is what type of solution?

Back 59

isotonic and isosmotic solution

Front 60

Normal saline has a?

Back 60

chloride concentration that is higher than that of ECF

Front 61

NS administered in large amounts can cause?

Back 61

hyperchloremic (non-anion gap) metabolic acidosis

Front 62

NS is the preferred replacement fluid (over LR) in patients with?

Back 62

brain injury, hyperkalemia, or hypochloremic metabolic alkalosis

Front 63

What is the preferred solution for dilution of packed RBCs prior to transfusion?

Back 63

NS

Front 64

Hypertonic saline solutions

Back 64

3% may be used for treatment of severe, symptomatic hyponatremia

Front 65

What solutions have been used for treatment of hypovolemic shock?

Back 65

3%-7.5% saline

Front 66

5% dextrose in water (D5W) is a?

Back 66

hypotonic solution (253 mosm/kg H20)

Front 67

D5W is used to provide?

Back 67

free water, as the dextrose (glucose) is metabolized, but does not cause hemolysis

Front 68

Why is D5W most commonly used?

Back 68

used to provide glucose and prevent hypoglycemia in diabetic patients who have been administered insulin

Front 69

D5W may also be used to treat?

Back 69

hypernatremia

Front 70

What is the replacement ratio for colloid solutions?

Back 70

1:1

Front 71

What is the intravascular "half-time" of colloid solutions?

Back 71

much longer than that of crystalloids

Front 72

What is Plasmanate composition?

Back 72

5% albumin, 5% plasma protein fraction

Front 73

What is the colloid osmotic pressure of Plasmanate?

Back 73

20 mmHg

Front 74

The preparation of Plasmanate involves?

Back 74

heating to destroy infectious agents

Front 75

Plasmanate is appropriate for treating?

Back 75

conditions with large protein losses eg, peritonitis, burns

Front 76

Dextran solutions are?

Back 76

water-soluble glucose polymers

Front 77

Dextran 70 (Macrodex) has an average polymer MW of?

Back 77

70,000

Front 78

6% dextran 70 expands the vascular volume the same as?

Back 78

5% albumin

Front 79

Dextran 40 (Rheomacrodex) has an average MW of?

Back 79

40,000

Front 80

Dextran 40 is not used to?

Back 80

expand plasma volume; used in vascular surgery to reduce blood viscosity, improve microcirculatory blood flow, and prevent thrombosis

Front 81

Dextrans have?

Back 81

antiplatelet activity and can increase bleeding time

Front 82

Dextrans may cause?

Back 82

anaphylactic or anaphylactoid reactions

Front 83

Dextran polymers are enzymatically degraded to?

Back 83

glucose

Front 84

Hydroxyethyl starch is a?

Back 84

synthetic colloid- very effective plasma volume expander; less expensive than albumin and nonantigenic

Front 85

Hespan is 6% hydroxyethyl starch in?

Back 85

NS

Front 86

Hextend is 6% hydroxyethyl starch in?

Back 86

solution that contains electrolytes, glucose, and lactate; the polymer molecules are smaller than those of Hespan

Front 87

Hetastarch preparations may interfere with?

Back 87

clotting and raise PTT - more likely with Hespan

Front 88

Pentastarch contains?

Back 88

smaller hydroxyethyl starch molecules