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MedEd Chem 2 Flashcards

1
Q

what is osmolality vs osmolarity

A

osmollity = mass of solvent
osmolarity = volume of solvent

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2
Q

how do you calculate osmolality

A

2 (Na + K) + glucose + urea

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3
Q

what is a normal osmolality

A

275 - 295

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4
Q

causes of a raised osmolality

A

(ions that aren’t in the equation)
alcohol
sugars
lipid
proteins

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5
Q

what is the main contributor to osmolality

A

sodium

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6
Q

rank the following in order of highest to osmolality to lowest
DI
DKA
HHS
pneumonia
SIADH

A

HHS
DKA
DI
pneumonia
SIADH

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7
Q

what is HHS

A

hyperosmolar hperglycaemia state (T2DM DKA)

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8
Q

why does HHS / DKA have higher osmolality

A

high glucose

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9
Q

why does pneumonia have a lower osmolality

A

can lead to SIADH

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10
Q

why does SIADH have a very low osmolality

A

lots of water resorption so decreases ion conc (osmolality)

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11
Q

describe the mechanism of sodium regulation when the blood volume increases inc receptors, what they are detecting and hormones released

A

increased blood volume –> atrial stretch –> baroreceptors –> ANP release –> decreased aldosterone / ADH / renin release –> decreased Na conc

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12
Q

where is renin released from

A

kidney

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13
Q

high osmolality –> ___ (body’s physiological response) + ADH _____ –> _____ Na conc

A

thirst
released
decreased

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14
Q

low osmolality –> ADH ______ –> _____ Na conc

A

suppression
increased

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15
Q

which is more important for ADH, the control of blood volume or osmolality

A

blood volume –> ADH increases the blood volume which decreases the osmolality

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16
Q

what is the commonest electrolyte imbalance

A

hyponatraemia

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17
Q

what is the first thing to check if someones blood show low Na & why

A

plasma osmolality
- to exclude pseudohyponatraemia (low Na with normal / high osmolality)

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18
Q

what are causes of pseudohyponatraemia and how can you distinguish them

A

high lipids / proteins - normal osmolality
high sugars / alcohol - high osmolality
(in hyponatraemia, the osmolality should be LOW tho, so even normal is abnormal !)

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19
Q

after excluding pseudohyponatraemia, what is the next thing to check in someone with hyponatraemia

A

check fluid status - hypo/eu/hypervolaemic

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20
Q

what is the ADH level in hypovolaemic hyponatraemia

A

appropriately high

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21
Q

what Ix is useful in someone with hypovolaemic hyponatraemia

A

urinary sodium osmolality

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22
Q

what cause for hypovolaemic hyponatraemia is suggested by a urinary Na conc of <20

A

extra renal losses (kidneys working) eg D&V, burns

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23
Q

what cause for hypovolaemic hyponatraemia is suggested by a urinary Na conc of >20

A

renal losses (kidneys not working) eg renal disease, diuretics, cerebral salt wasting

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24
Q

mx of hypovolaemic hyponatraemia

A

treat underlying cause eg loperamide
IV 0.9% NaCl
or slow IV hypertonic 3% NaCl (ITU for Sx pts)

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25
if someone is hypervolaemic hyponatraemia, where/what is the problem
low effective arterial blood volume ie the blood volume is not sufficient to supply cells
26
what can cause hypervolaemic hyponatraemia
reduced cardiac output - CCF increased peripheral arterial vasodilation - cirrhosis
27
what does a urinary sodium of <20 suggest in hypervolaemic hyponatraemia
CCF, cirrhois, nephrotic syndrome
28
what does a urinary sodium of >20 suggest in hypervolaemic hyponatraemia
CKD
29
tx of hypervolaemic hyponatraemia
treat underlying cause fluid restriction
30
what is the umbrella cause of euvolaemic hyponatraemia
endocrinological
31
what does a urinary sodium of <20 suggest in euvolaemic hyponatraemia
psychogenic polydipsia, tea and toast diet
32
what does a urinary sodium >20 suggest in euvolaemic hyponatraemia
hypothyroidism adrenal insufficiency SIADH
33
mx of euvolaemic hyponatraemia - inc resistant SIADH
treat underlying cause fluid restrict demeclocycline / tolvaptan for resistant SIADH
34
causes of SIADH
brain - craniopharyngoma / tumours lung - pneumonia, small cell lung ca drugs - SSRIs, PPIs, DA antagonists
35
how do you diagnose SIADH
diagnosis of exclusion !! check TFTs and cortisol first urinary / plasma Na
36
diagnostic criteria of SIADH
low plasma sodium (<135) / osmolality (<270) high urinary sodium (>20) / osmolality (>100) no adrenal / thyroid / renal dysfunction
37
causes of hypovolaemic hypernatraemia
osmotic diuresis diarrhoea burns
38
causes of hypervolaemic hypernatraemia
hypertonic 3% NaCl use hyperaldosteronism
39
causes of euvolaemic hypernatraemia
DI
40
Mx of hypernatraemia
oral intake of water slow IV 5% dextrose (1L/6hr) - guided by urine utput / plasma sodium
41
2 types of DI and what the defect is in each
central = lack of production of ADH nephrogenic = ADH resistance in kidneys
42
causes of central DI
pituitary surgery irradiation tumour trauma
43
mx of central DI
desmopressin
44
causes of nephrogenic DI
electrolyte disturbances (low K, high Ca) drugs - lithium, demeclocycline
45
mx of nephrogenic DI
thiazides
46
primary Ix for ?DI
excluding other causes - serum glucose (DM) - serum K (hypoK) - serum Ca (hyperCa)
47
diagnostic tests for DI
plasma / urine osmolality *** water deprivation test ***
48
post water deprivation test... urine concentrates after fluid restriction Dx?
normal or primary polydipsia
49
post water deprivation test... urine concentrates after desmopressin Dx?
central DI
50
post water deprivation test... urine remains dilute after desmopressin Dx?
nephrogenic DI
51
diagnostic criteria for DI
despite raised plasma osmolality, urine is dilute with urine:plasma osmolality of <2:1
52
best Ix for SIADH
paired urinary:plasma osmolality
53
PC of low K
muscle weaknes cramps hypotonia
54
ECG of low K
flattened / inverted T wave prominent U waves prolonged PR ST depresion
55
3 groups of causes of low K
increased K loss increased cellular influx decreased intake
56
causes of increased loss causing low K
GI losses - D&V, high output stoma renal losses - Conn's, diuretics, congenital defects eg Bartter / Gitelman syndrome
57
causes of increased cellular influx leading to low K
insulin beta agonits refeeding syndrome metabolic alkalosis
58
what acid base picture does hypokalaemia cause
metabolic alkalosis
59
what causes a metabolic acidosis in low K
renal tubular acidosis partially treated DKA
60
key Ix for hypokalaemia
serum Mg aldosterone:renin ratio (if HTN)
61
if low K and low Mg what needs to be done
correct them together - correcting low k alone won't work
62
mx of mild to mod low K (2.5-3.5)
oral sando K (replacement)
63
mx of severe low K (<2.5)
10mmol/hour IV KCl with continuous ECG monitoring
64
what Ix needs to be done with any mx of low K
daily U&Es
65
ecg features of hyperK
tall tented T waves small p wave widened QRS prolonged PR interval sine wave
66
groups of causes of hyperK
artefact iatrogenic reduced excretion increased cellular release
67
what does artefact causing hyperK mean
haemolysis - release of intracellular K causing high K
68
what iatrogenic causes can lead to high K
massive blood transfuion xs K+ mx
69
causes of high K due to reduced excretion
renal disease aldosterone deficiecny drugs - K-sparing diuretics, ACEi, ARBs
70
causes of low K due to increased cellular release
metabolic acidosis tissue breakdown eg rhabo
71
ixs for hyperK
U&Es eGFR CK - rhabdo cortisol / short synthACTHen test
72
mx of hyper K
IV calcium gluconate IV insulin with dextrose consider: nebulised salbutamol, K binders, dialysis
73
when would you tx hyperK
ECH changes or K >6.5
74
where is ca found in the body
99% in bone 1% serum
75
how is calcium found in the serum (%s)
50% free, ionised (biologically active) bound to albumin 40% complexed with citrate / phosphate 10%
76
what are the 2 main functions of PTH
increase serum Ca decrease serum PO43
77
which hormone decreases serum Ca and increases serum PO43
calcitonin
78
3 actions of PTH
bone resorption by osteoclasts increased Ca resorption at DCT / increased PO43 excretion at PCT increased ca reabsorption in gut
79
3 actions of calcitonin
less bone resorption by osteoclasts decreased ca reabsoprtion at DCT decreased ca reabsoprtion in gut
80
which hormone aids the actions of PTH
calcitriol
81
sx of hypocalcaemia
paraesthesia (peri oral) arrythmia convulsions tetany / spasms
82
2 signs associated with hypocalcaemia & what each is
trousseau's sign - tetany Chvostek's sign - spasms
83
causes of hypocalcaemia
hypoparathyroidism - digeorge (primary) or post-thyroidectomy (secondary), low Mg vitamin D deficiency
84
fatal result of hypocalcaemia with sx
laryngospasm - hoarse voice, inability to swallow
85
who gets laryngospasm
post thyroidectomy surgery
86
ix of low ca
ECG bloods - Mg, PO43, PTH level, LP imaging - DEXA
87
mx of mild hypoCa (>1.9, no sx)
oral calcium vit D
88
mx of severe hypoCa (<1.9, sx)
IV calcium gluconate
89
sx of hypercalcaemia
stones, bones, moans, groans
90
when you see high ca, what else do you need to look at to start thinking of cause
PTH
91
causes of high ca with low PTH
malignancy - PTHrP, bony mets, MM hyperthyroidism hypodrenalism sarcoidosis thiazides vitamin d excess
92
causes of high ca with high PTH
primary / tertiary hyperparathyroidism
93
ix for hyperca
myeloma screen TFTs cortisol
94
mx of hypercalcaemia
IV 0.9% NaCl +/- diuretics biphosphonates if cancer parathyroidectomy is PTH adenoma
95
biochem of pagets
isolated high ALP
96
biochem of osteoporosis
normal ca, PTH, PO43 --> just density of bone is abnormal
97
what is the defect in primary hyperPTH
increase in PTH eg parathyroid adenoma
98
what is the defect in secondary hyperPTH
renal osteodystrophy
99
what is the defect in tertiary hyperPTH
autonomous PTH secretion post renal transplant
100
rank the plasma Ca conc highest to lowest primary hyperPTH secondary hyperPTH osteoporosis osteomalacia parathyroid carcinoma
parathyroid carcinoma primary hyperPTH osteoporosis secondary hyperPTH osteomalacia
101
which enzyme is raised in pagets and osteomalacia and is caused by osteoblast activation
ALP (alkaline phosphatase)
102
commonest cause of high Ca in community
parathyroid adenoma
103
commonest cancers that met to bone
prostate breast lung
104
4 steps of interpreting a blood gas acid base status
what is the pH is CO2 high / low ? is this causing the change? is bicarb driving the change? is there compensation? - pH in normal range or not
105
when can anion gap be useful when interpreting blood gases
when you're not sure what type of acid base status it is
106
how do you calculate anion gap
(Na + K) - (HCO3 + Cl)
107
what is a normal anion gap
14 to 18
108
what can cause a raised anion gap
alcohol uraemia DKA iron lactic acid salicylates / isoniazid
109
which LFTs are markers of liver function
clotting - PT / INR albumin BR
110
which LFTs are markers of liver damage
BR ALT, AST GGT ALP
111
when are the following LFTs raised in liver damage - ALT - AST - GGT - ALP
- viral hep - viral hep - alcoholic hep - obstructive
112
prehepatic causes of jaundice
HA ineffective erythropoesis
113
hepatic concepts causing jaundice
hepatocellular dysfunction impaired conjugation impaired BR uptake
114
post hepatic causes of jaundice
obstruction - stones / pancreatic cancer
115
2 key features of prehepatic jaundice **buzzwords
absent conjugated BR absent urinobilinogen
116
2 key features of post hepatic jaundice **buzzwords
dark urine - raised urobilinogen pale stools - low stercobilinogen
117
raised ALT > AST dx?
viral hep
118
raised AST > ALT dx?
alcoholic hep
119
causes of ALT/AST in 1000s
ischemia viral hep toxins
120
causes of raised unconjugated BR
increased haemolysis drugs that impair hepatic uptake eg rifampacin impaired conjugation - Gilberts, crigler-najjar
121
what is crigler-najjar
severe gilberts (gilberts is deficiency of an enzyme but CN is complete lack of it)
122
causes of raised conjugated BR
hepatocellular dysfunction decreased hepatic excretion
123
what other organs make ALP
bone, placenta, GIT, kidney, prostate
124
causes of isolated raised ALP
pregnancy childhood growth spurts pathological - mets
125
causes of raised ALP and GGT
obstructive cholestasis - gallstones, drugs (OCP, co-amox) alcoholic hepatitis
126
best marker of liver func in acute liver injury
PTT

MedEd Path (10 decks)

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