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Medicine > Fluids & Electrolytes > Flashcards

Fluids & Electrolytes Flashcards

0
Q

What are the normal values of sodium, potassium, creatinine, urea, and eGFR in serum?

A 
Sodium = 135 - 145mmol/L
Potassium = 3.5 - 5mmol/L
Creatinine = 70 - 150umol/L
Urea = 2.5 - 6.7mmol/L
eGFR = >90
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1
Q

What are the physiological limits for pH, PaCO2, PaO2, HCO3, BE and lactate?

A 
pH = 7.35 - 7.45
PaO2 = >10.6kPa
PaCO2 = 4.7 - 6kPa
HCO3 = 22 - 26 mEq/L
BE = +/- 2 mmol
Lactate = <2 mmol
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2
Q

What percentage of body weight is water?

A 
Male = 60%
Female/obese = 50%
Neonate = 8-%
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3
Q

How much of total body water is intracellular and extracellular?

A 
ICF = 2/3
ECF = 1/3
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4
Q

What percentage of total body water is stored in the ECF components of interstitial fluids and plasma?

A

Interstitial fluid = 25%

Plasma = 8%

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5
Q

What is the average output of urine?

A

0.5mls/kg/hour

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6
Q

How much fluid is lost from insensible losses in a hospital pt?

A

Lungs and faeces = ~500ml

Sweat = ~500ml

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7
Q

What is the required fluid intake of an average adult?

A

3L/day

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8
Q

How much potassium and sodium are lost each day?

A 
Potassium = 60mmol
Sodium = 100mmol
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9
Q

How much does fluid requirement rise in patients with fever?

A

Roughly 10% per degree

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10
Q

What are the factors that affect renal control of sodium excretion?

A

1) Reduced effective arterial blood volume
2) Increased Effective Arterial Blood Volume
3) Unloading of High Pressure Baroreceptors
4) Increased ADH release

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11
Q

How does reducing effective arterial blood volume bring about its effect wrt Na control?

A

Reducing effective arterial blood volume –> reduced flow at juxtaglomerular apparatus –> renin release –> angiotensin 2 release

Efferent renal aa constriction –> ^GFR,
Peripheral vasoconstriction,
Aldosterone –> ^reabsorption of Na and water in DCT

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12
Q

How does increased effective arterial blood pressure alter Na control?

A

Increased arterial blood pressure –> stretch of atrial myocardium –> atrial natriuretic peptide [ANP]

Vasodilation of renal arterioules –> ^GFR
Reduced RAA activity
Reduced Na absorbtion in collecting duct
Reduced ADH secretion

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13
Q

Where are high pressure baroreceptors to be found and what does unloading cause?

A

Left atrium, thoracic veins, carotid sinus body, aortic arch (Around heart basically)

Unloading –> SNS activity & RAA activity

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14
Q

What does increased ADH secretion cause?

A

Renal and peripheral vasoconstriction

Increased Na and water reabsorption

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15
Q

What factors affect renal control of water?

A

Mainly by sodium control factors (effective arterial blood volume, ADH, baroreceptor loading)

Increase in plasma osmolality stimulates osmoreceptors (hypothalalmus) –> thirst, ADH secretion (P. pituitary), ^ passive water re-absorption in renal collecting duct

16
Q

What are approximate daily losses of water, Na, and K?

A 
Water = 2500ml
Na = 100mmol/day
K = 80mmol/day
17
Q

What are the symptoms and physical findings of dehydration?

A 
Mild = headache, lethargy, tiredness
Moderate = dry mouth, decreased alertness, sunken eyes, mm cramps
Severe = confusion, disorientation, tachycardia, tachypnoea

Obs = low BP, ^pulse, low CVP, falling weight, -ve fluid balance, anuria

Bloods = ^Na, K, Creatinine, Urea (oft disproportionately raised urea)

18
Q

What is the electrolyte composition of normal saline 0.9%?

A 
Na = 154
Cl = 154
19
Q

What is the electrolyte composition of Hartman’s/Ringers Lactate?

A 
Na = 131
Cl = 111
K = 5
Ca = 2
20
Q

What is the electrolyte composition of 5% dextrose in water?

A

Dextrose 50g

21
Q

What is the electrolyte composition of Dextrose 4%/saline 0.18%?

A 
Na = 31
K = 31
Dextrose = 40g
22
Q

What is the electrolyte composition of albumin solution (4.5%)?

A 
Na = 160
Cl = 136
K = <2
Albumin = 40-50g
23
Q

What electrolyte abnormalities would you see in a patient with excessive gastric losses?

A

Vomiting –> metabolic acidosis
Hyponatraemia
Hypocloraemia
Hypokalaemia

(nb, metabolic acidosis will self correct with restoration of K)

24
Q

What electrolyte and acid-base abnormalities would you see in a patient with diarrhoea?

A 
Acute = hyperchloraemia & metabolic acidosis
Profuse = hypokalaemia & metabolic acidosis

Chronic = metabolic alkalosis

25
Q

Is metabolic acidosis associated with hyper or hypokalaemia and why?

A

USUALLY = hyperkalaemia - approx 50% of buffering of acidosis takes place in cells (i.e. H+ is taken into cells) so K+ is secreted to maintain cellular homeostasis [.: correction acidosis –> eu K+]

BUT if significant gastric losses = normal or hypokalaemia

26
Q

What electrolyte and acid-base abnormalities would you see in a patient with hypovolaemic shock due to blood loss?

A

Eu –> renal retention of water –> hyponatraemia

27
Q

What electrolyte and acid-base abnormalities would you see in a patient with acute tubular necrosis?

A

Hyperkalaemia
Hyponatraemia (if drinking despite oliguria)
Hypocalcaemia (reduced renal production 1,25 dihydroxycholecalciferol
Hyperphophataemia, hypermagnesemia

Metabolic acidosis

28
Q

What electrolyte and acid-base abnormalities would you see in a patient with dehydration?

A

Classified according to Na levels

Isonatraemic = Similar loss in intravascular and extravascular fluid compartments

Hyponatraemic = Shift of fluid from intravascular to extravascular space

Hypernatraemic = Shift of fluid from extravascular to intravascular

29
Q

What electrolyte and acid-base abnormalities would you see in a patient with inappropriate ADH secretion (SIADH)?

A

Reduced water secretion with normal sodium excretion –> hyponatraemia

Also eu/low creatinine & urea, reduced plasma osmolality, raised urine osmolality & Na

30
Q

What electrolyte and acid-base abnormalities would you see in a patient with diabetes insipidus?

A

Reduced secretion ADH –> increased water secretion & normal sodium excretion –> hypernatraemia

Medicine (9 decks)

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