Urea and Electrolytes Flashcards

1
Q

What does a reddish serum indicate in a separated blood sample?

A

Haemolysis

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2
Q

What are some physiological compensatory mechanisms for fluid loss?

A
  • Thirst
  • ADH
  • RAAS system
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3
Q

What are some therapeutic compensatory mechanisms for fluid loss?

A
  • IV therapy
  • Diuretics
  • Dialysis
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4
Q

What is ADH stimulated in response to?

A

Rise in concentration of osmotically active particles (osmolality)

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5
Q

Since ADH analysis is not readily available how can it be measured?

A
  • Measuring plasma and urine osmolality

- Urine > plasma suggests ADH is active

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6
Q

What levels suggest the RAAS is active?

A

If urine Na+ is < 10 mmol/l

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7
Q

What do plasma and urine levels of creatinine usually reflect?

A

Muscle mass

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8
Q

What is elevated urea found in?

A
  • CCF
  • Shock
  • MI
  • Severe burns
  • Gastric bleed
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9
Q

How much urea enters the tubular lumen each day?

A

800 mmol (48g)

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10
Q

What is the normal range of GFR?

A

90 - 150 ml/min

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11
Q

What is GFR influenced by?

A
  • Renal perfusion pressure
  • Renal vascular resistance
  • Glomerular damage
  • Post-glomerular resistance
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12
Q

What is the best overall measure of kidney function?

A

GFR

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13
Q

What is eGFR used for?

A

Used to aid ‘staging’ of kidney disease

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14
Q

What is an AKI flag used for/

A

Highlights subtle changes in renal function

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15
Q

eGFR and AKI flag values are calculated based on what substance?

A

Creatinine

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16
Q

What is hyponatraemia caused by?

A
  • Too little Na in ECF (alcoholics usually)
  • Excess water in ECF
  • Pseudo hyponatraemia due to increased protein or lipid
17
Q

What is hypernatraemia caused by?

A
  • Too little water in ECF

- Too much in ECF

18
Q

What is dehydration caused by?

A
  • Water deficiency

- Fluid (Na and water) depletion

19
Q

What can hypovolaemia plus decreased urine sodium be due to?

A
  • Vomitting
  • Diarrhoea
  • Skin loss
20
Q

What can hypovolaemia plus increased urine sodium be due to?

A
  • Diuretics
  • Addisons
  • Na losing nephritis
21
Q

What can euvolemia plus normal plasma osmolarity be due to?

A

Pseudohyponatraemia

22
Q

What can euvolemia plus low plasma osmolarity plus increased urine Na+ be due to?

A
  • SIADH
  • Drugs
  • CRF
23
Q

What can euvolemia plus low plasma osmolarity plus decreased urine Na+ be due to?

A
  • Stress
  • Post surgery
  • Endocrine: Hypothyroid
24
Q

What can high plasma osmolarity and euvolemia be due to?

A

HYpertonic hyponatraemia

25
What factors can affect plasma potassium?
- Acid-base status - Insulin / glucose therapy - Adrenaline - Rapid cellular incorporation - TPN, leukaemia
26
What is the effect of an acidosis oh K+?
Potassium moves out of cells (hyperkalaemia)
27
What is the effect of an alkalosis on K+?
Potassium moves into cells (hypokalaemia)
28
What can the causes of hyperkalaemia be?
``` Artefactual - Delay in sample analysis - Haemolysis - Drug therapy - excess intake Renal - Acute + Chronic renal failure Acidosis (intracellular exchange) Mineralocorticoid dysfunction - Adrenocortical failure - Mineralocorticoid resistance - e.g spironalactone Cell death - Cytotoxic therapy ```
29
What are the causes of potassium depletion?
- Low intake - Increased urine loss (diuretics, tubular dysfunction, mineralocorticoid excess) - GI losses - Hypokalaemia without depletion (alkalosis, insulin therapy)
30
What can potassium depletion cause in the kidney?
- Polyuria | - Alkalosis - increase renal HCO3 production
31
What could you possibly see in a history of someone with potassium depletion?
- Diarrhoea, vomitting, drugs (diuretics, digoxin) - Symptoms of lethargy / weakness - Cardiac arrythmias