Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Integrative > Fluid Balance > Flashcards

Fluid Balance Flashcards

1
Q

What body compartments do different infusions of fluid move into?

A

5% dextrose (isotonic)

  • 1/3 in ECF (1/4 in plasma, 3/4 in interstitial fluid)
  • 2/3 in intracellular compartment

0.9% NaCl saline
- plasma
- interstitial fluid
(not intracellular compartment - capillary walls impermeable to NaCl)

Colloid (proteins, starch)
- plasma
(not interstitial fluid - cell membrane usually impermeable to large molecules)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Compare the concentration of electrolytes in the ECF and ICF.

A

ECF

  • high Na+
  • low K+
  • high Cl-

ICF

  • low Na+
  • high K+
  • low Cl-
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Outline the thirst response.

A

Increased plasma osmolality:

  • –> reduced saliva —> dry mouth —> hypothalamic thirst centre
  • –> osmoreceptors in hypothalamus —> hypothalamic thirst centre

Reduced plasma volume —> reduced BP —> stimulates juxtaglomerular cells —> activates RAAS —> increases angiotensin II —> hypothalamic thirst centre

Hypothalamic thirst centre —> stimulates sensation of thirst

Drink taken:

  • –> moistens mouth & throat —> reduces sensation of thirst
  • –> stretches stomach & intestine —> reduces sensation of thirst
  • –> water absorbed from GI tract —> reduces plasma osmolality —–> reduces sensation of thirst

note: sensation of thirst diminishes with age (confusion due to dehydration occurs quickly)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Outline the actions of ADH.

A

Increased plasma osmolality OR increased [Na+]plasma
—> stimulates osmoreceptors in hypothalamus —> pos. pituitary gland

Reduction in plasma volume OR reduction in BP (10-15%)
—> reduced stimulation of baroreceptors in atrium & large vessels —-> pos. pituitary gland

+ sensation of water in stomach stimulates increase in ADH secretion

Pos. pituitary gland —> release of ADH —> increases water reabsorption in collecting ducts & kidneys

  • –> concentrated urine
  • –> reduced osmolality & increased plasma volume —> inhibits osmoreceptors in hypothalamus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Outline the effect of aldosterone on the kidneys.

A

Reduction in [Na+] OR increase in [K+] in plasma OR RAAS activation —> stimulate adrenal cortex to release aldosterone

  • –> increase [Na+] reabsorption
  • –> increase [K+] secretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Contrast some of the causes of hypotension.

A

Hypovolaemic shock

Haemorrhagic shock

Cardiogenic shock (IV fluid will make things worse - increases preload)

Septic shock (IV fluid will not work - fluid will leak into interstitial spaces, causing peripheral oedema and reducing BP)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What needs to be considered when prescribing resuscitation fluid?

A
  1. Do they need IV fluids?
    - oral intake?
    - nil by mouth?
  2. Composition of fluid prescribed?
  3. Goals of therapy?
  4. Possible complications?
    - review other drugs e.g. BP drugs, lithium
  5. Causes of ongoing losses?
    - e.g. bleeding, vomiting
    - able to stop?
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What needs to be considered when prescribing replacement fluid?

A
  1. Consider input & output of fluids
    - note: cannulation difficulties may prevent IV fluids being delivered (central line may be required)
  2. Review electrolytes & serum bicarbonate
  3. Consider insensible losses
    - pure water loss (fever, dehydration, hyperventilation)
    - vomiting & nasogastric tube loss
    - biliary drainage loss
    - pancreatic drain/fistula
    - jejunal loss via stoma/fistula
    - diarrhoea or excess colostomy loss
    - ileal loss
    - ongoing blood loss e.g. melaena
    - inappropriate urinary loss e.g. polyuria
  4. What are you replacing?
    - ongoing losses hypotonic or hypertonic?
    - note: ensure to correct hypokalaemia (activates RAAS, impairs ADH response, and effects muscle contractility and cardiac function)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What needs to be considered when prescribing maintenance fluid?

A

Meet nutritional requirements & caloric expenditure

  1. Consider oral intake
    - need to be nil by mouth?
  2. Review other drugs e.g. diuretics
  3. Consider causes of ongoing losses
    - can you stop them?
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why do hospitalised patients (esp. the elderly) often require maintenance fluid?

A
  • ADH affected by drugs (e.g. morphine), pain, nausea, and hypothyroidism
  • do not sweat excessively
  • RAAS activated by stress (peri-operative)
  • catecholamine release
  • reduced caloric expenditure
  • reduced free water excretion —> hyponatraemia
  • increased water & salt retention —> fluid overload
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Estimate the volumes of fluid in the different compartments of the body.

A

TOTAL BODY WATER = 40l (60% of body weight)

  • INTRACELLULAR FLUID = 25l (40% of body weight)
  • EXTRACELLULAR FLUID = 15l (20% of body weight)

—> INTERSTITIAL FLUID = 12l (80% of ECF)

—> PLASMA = 3l (20% of ECF) (+ cells = 5l of blood)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What fluid compartment is tested in dehydration?

A

Intravascular (all compartments affected but the intravascular compartment is easiest to test)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the indications for prescribing resuscitation fluids? When are they not indicated?

A

Indications:

  • Hypovolaemic shock
  • Haemorrhagic shock

Contraindicated:

  • Septic shock (fluid will leak out of capillaries and cause peripheral oedema)
  • Cardiogenic shock (increased fluid will make things worse)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the consequences of hypokalaemia on fluid balance? What complications can arise from hypokalaemia?

A

Activates RAAS —> increases Na+ and water retention

Impairs ADH response

  • –> cannot produce concentrated urine
  • –> cannot prevent interstitial oedema

S&S:

  • weakness/fatigue
  • increased muscle contractility —> muscle cramps/pain
  • worsening diabetes/polyuria
  • palpitations/arrhythmias
  • psychosis, delirium, hallucinations, depression
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does the total body water vary in babies and the elderly compared to adults?

A

Adults = total body water is 60% of body weight

Babies = total body water is 75% of body weight

Elderly = total body water is 56% of body weight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Contrast the mechanism of the formation of oedema in different disorders.

A

Decreased oncotic pressure of plasma
e.g. cirrhosis, Kwashiorkor, nephrotic syndrome

Increased hydrostatic pressure of capillary
e.g. heart failure, venous thrombosis (before occlusion)

Lymph node drainage compromised
e.g. cancer, radiation poisoning

Increased permeability of capillaries
e.g. burns, inflammation, anaphylaxis

16
Q

What are the consequences of hyperkalaemia?

A
  • muscle paralysis
  • dyspnoea
  • palpitations
  • chest pain
  • N&V
  • paraesthesia
17
Q

What physiological mechanisms and hormones stimulate the sensation of thirst?

A

ADH

Angiotensin II via stimulation of:

  • subfornical organ (ventral surface of fornix)
  • osmoreceptors of OVLT

Osmoreceptors of organum vasculosum of lamina terminalis (OVLT - located in the median preoptic nucleus of the hypothalamus)

Arterial baroreceptors and cardiopulmonary receptors stimulate the area postrema and nucleus tractus solitarius

18
Q

Outline the components and therapeutic actions of 5% dextrose solution.

A

Isotonic saline

50g/l of glucose

  • glucose quickly taken up by cells
  • water reduces osmolality of all compartments (treats dehydration, not hypotension)
  • can enter the plasma, interstitial fluid, and intracellular compartments
  • only ~1/12 stays in intravascular space (hence not good for replacing blood loss)

Indications:

  • hypoglycaemia
  • hypernatraemia
  • dehydration

Cautions:

  • if infusion rate exceeds the rate of glucose uptake and metabolism —> hyperglycaemia
  • hypokalaemia may result
  • peripheral/pulmonary oedema may result
19
Q

Outline the components and therapeutic actions of 0.9% NaCL saline.

A

1l 0.9% saline = 155mmol Na+ & 155mmol Cl- (isotonic)

  • Na+ remains in ECF —> fluid remains in ECF
  • no change in osmolarity
  • can enter the plasma and interstitial fluid, but not the intracellular compartments (unless via transporters)
  • only ~1/4 stays in intravascular space

Indications:

  • hypovolaemic shock
  • metabolic acidosis
  • hypercalcaemia

Cautions:
- may cause fluid overload in cardiac/renal disease

20
Q

Outline the components and therapeutic actions of crystalloid.

A

Crystalloid = aqueous solution of mineral salts
e.g. Hartmann’s solution (Na+, lactate, etc.) (known as Ringer’s lactate in U.S.)

Indications:
- replace fluid lost via burns/trauma/fistulae/GI losses

Cautions:

  • risk of interstitial oedema
  • may cause lactic acidosis
  • may cause liver disease (via increased lactate)
21
Q

Outline the components and therapeutic actions of colloid.

A

Colloid = larger insoluble molecules
e.g. blood

  • high in NaCl —> high oncotic pressure —> rapid intravascular expansion —> risk of volume overload
  • can only enter the plasma (proteins too large to leave vasculature - usually

Not recommended at present due to:

  • risk of fluid overload
  • anaphylactic reaction to proteins in colloid
22
Q

Outline the components and therapeutic actions of 4% dextrose/0.18% saline.

A

Glucose = 40g/l
30mmol/l of NaCl

Indications:
- maintenance fluid

Cautions:

  • risk of hyponatraemia if too much given too quickly
  • use with caution in children
23
Q

What are the signs and symptoms of hypovolaemia?

A

Dehydration

  • –> dry mucous membranes
  • –> reduced urine output

Hypotension

  • –> light-headedness/feeling faint
  • –> syncope
  • –> flattened neck veins
  • –> tachycardia
  • –> increased resp. rate
  • –> peripheral cyanosis
  • –> confusion
24
Q

What is the normal osmolarity of the blood? How does this change immediately after haemorrhage?

A

~ 280mOsm

Osmolarity will stay the same, as isotonic fluid (blood) has been lost

Compensatory mechanisms will take place eventually which will alter the osmolarity

25
Q

What is haematocrit? What might cause a reduction in haematocrit? How does it differ from the erythrocyte sedimentation rate?

A

Packed cell volume (% volume of blood composed of RBCs)
(NOT CHANGED WHEN RBC SIZE IS ALTERED!)

Therefore haematocrit can fall if:

  • there is a loss of RBCs
  • there is an increase in water in the intravascular compartment

ESR = “stickiness” of RBCs

26
Q

What is the osmolarity of sweat compared to plasma? How does the production and composition of sweat vary according to the external temperature?

A

Isotonic when initially secreted, then modified by removal of electrolytes (becomes hypotonic compared to plasma)

Hot day: increased production but less modified —> less hypotonic

Cool day: reduced production but more modified —> more hypotonic

27
Q

Why are athletes at risk of dilutional hyponatraemia? How can this be avoided?

A

Drinking water or isotonic sports drinks (containing glucose) whilst exercising

Replaces water lost in sweat, but not electrolytes

Increased water:Na+ —> diltutional hyponatraemia

(+ glucose —> Na+ follows glucose into cells)

This can be avoiding by using rehydration fluid or salt supplements (replace electrolytes and water)

28
Q

Why is urine output a more sensitive indicator of fluid balance than thirst?

A

Thirst is a late response to hypovolaemia, urine concentration changes earlier

Urine output is a direct measure of fluid balance

29
Q

Why are children more prone to dehydration than adults?

A

A higher % of total body weight is water in children

Increased s.a —> more water lost by sweating

Immature renal system (connection between kidney and brain not formed)

Reduced awareness of water intake?

Reduced control over water intake

30
Q

What is the initial daily fluid and electrolyte requirement of a patient who is nil by mouth and euvolaemic?

A

1500ml fluid (25-30ml/kg/day) + 750ml from food

[Na+] = 1mmol/kg/day

[K+] = 1mmol/kg/day

31
Q

What hormonal changes occur in hospitalised patients that influence IV fluid prescribing?

A

Increased cortisol and adrenaline secretion (stress response)

Increased ADH (stress response)

32
Q

How would the composition of IV fluid prescribed for vomiting differ from that prescribed following an ileostomy?

A

Vomiting: NaCl solution prescribed

Ileostomy: HCO3- and Cl-

33
Q

How do signs and symptoms of dehydration manifest in the elderly? How are the control mechanisms affected?

A

S&S:

  • constipation
  • postural hypotension
  • confusion (delirium)

Reduced sensation of thirst (due to degeneration of osmoreceptors in hypothalamus)

Confusion (delirium) occurs rapidly with dehydration

Lower % of total body weight is water

Appearance of skin is less useful (reduced collagen means skin turgor is difficult to assess)

Integrative (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions