Chem Path Flashcards
(124 cards)
1
Q
Formula for anion gap
A
(Na + K) - (Cl + HCO3)
2
Q
Normal anion gap
A
14-18
3
Q
Causes of raised anion gap
A
K etoacidosis
U raemia
L actic acidosis
T oxins
4
Q
What is the difference between osmolality and osmolarity?
A
Osmolality - measured (mmol/kg)
Osmolarity - calculated (mmol/L)
5
Q
Osmolarity formula?
A
2(Na+K) + urea + glucose
6
Q
Raised osmolar gap means?
A
Exogenous solutes in plasma ie raised anion gap due to toxins rather than K, U or L
7
Q
In hyponatraemic pts who are hypovolaemic what does it mean if urinary sodium is <20?
A
NON renal cause
- diarrhoea
- vomiting
- sweating
- burns
- 3rd spacing eg ascites
8
Q
In hyponatraemic pts who are hypovolaemic what does it mean if urinary sodium is >20?
A
Renal cause
- diuretics
- salt losing enteropathy
9
Q
When does central pontine myelinolysis present?
A
2-6 days after correcting hyponatraemia too quickly
Increase in Na makes water move out of cells disrupting BBB and allowing entry of cytotoxic cells
- quadriplegia
- dysarthria
- seizures
- coma
10
Q
SIADH diagnosed by:
A
Paired plasma and urine osmolality:
Plasma osmolality LOW
Urine osmolality HIGH
+ raised urinary sodium >20
In absence of heart, thyroid or adrenal disease (diag of exclusion)
11
Q
Treatment for SIADH
A
1 fluid restrict
2 demeclocycline (decreases tubular response to ADH)
3 tolvaptan (V2 antag)
12
Q
Causes of nephrogenic DI
A
Inherited receptor defect
Lithium
Hypokalaemia
Hylercalcaemia
Chronic renal failure
13
Q
Treatment for DI
A
Fluid replacement
5% dextrose
0.9% NaCl
14
Q
Stimuli for aldosterone secretion:
A
1 Ang II
2 raised serum K+
15
Q
Causes of HYPOkalaemia
A
-GI loss (d and v)
- Renal loss
- conn’s (hyperaldosteronism)
- cushing’s (xs cortisol can act of MR)
- increased sodium delivery to DCT
- Bartter syn
- frusemide- type 1 and 2 renal tubular acidosis
- type 1 cannot excrete H so K not exchanged and reabsorbed)
- type 2 leak of HCO3
- type 1 and 2 renal tubular acidosis
- Redistribution into cells
- alkalosis
- insulin
- beta agonists
16
Q
Symptoms of HYPOkalaemia
A
Weakness
Arrhythmias
Polyuria and polydipsia (causes nephrogenic DI)
17
Q
Treatment for HYPOkalaemia
A
Mod 3-3.5 Oral sandoK
Sev. <3
IV potassium chloride
18
Q
Causes of HYPERkalaemia
A
Increased intake
- oral
- blood transfusion
Transcellular
- acidosis
- lack of insulin
- tissue damage (rhabdo)
Decreased excretion
- renal failure (low GFR so not excreted)
- ACEi
- ARBs
- addisons
- spironolactone (MR antag)
19
Q
Treatment of HYPERkalaemia
A
“Small P big T widened QRS”
10ml 10% calcium gluconate
50ml 20% dextrose + insulin
Nebulised salbutamol
*calcium gluconate does NOT reduce potassium but stabilised cardiomyocyte membrane
20
Q
AST:ALT. 2:1
A
Alcoholic hepatitis
21
Q
AST:ALT. 1:1
A
Viral hepatitis
22
Q
AST:ALT. 1:1
+raised gamma GT
A
NAFLD
23
Q
Best marker of liver function?
A
Prothrombin time
24
Q
Isolated raised gamma GT
A
Alcohol binge
25
Raised AST and ALT over 1000
?paracetamol toxicity
26
Half life of albumin?
20 days
If albumin LOW suggests chronic disease
Low in
- liver disease (not produced)
- renal disease (lost across epithelium)
- sepsis (3rd spacing)
27
Aldosterone acts on?
Mineralocorticoid receptor
(Inbits Nedd4 to increase expression of Na channels at apical membrane and Na/K ATPase at basolateral
28
Physiological raised ALP?
Pregnancy (3rd T, produced by placenta)
Childhood (growth spurt)
29
Pathological raised ALP?
>5x ULN
Bone - Pagets, osteomalacia
Liver- cholestasis, cirrhosis
<5xULN
Bone-tumour, fracture, osteomyelitis
Liver- hepatitis
30
Raised amylase
Acute pancreatitis (>10xULN)
Mumps
31
Creatine kinase is a marker of?
Muscle damage
32
CK in skeletal muscle?
In cardiac muscle?
In brain?
MM
MB (1 and 2)
BB
33
CK raised physiologically in?
Afro C
34
Ck raised pathologically in?
Duchenne muscular dystrophy
MI
Statin related myopathy
Rhabdomyolysis
(Excessive exercise)
35
ALP produced by what cells?
Liver
Bone
Gut
Placenta
36
Troponin is?
Not an enzyme - biomarker of cardiac injury
Troponin I better than T
37
When do you measure troponin?
When is it most sensitive?
How long does it stay elevated for?
0 (baseline), 6 and 12 hours
Most sensitive 12
- 24 hours
Elevated for 3-10 days therefore Ck-MB better for re-infarction
38
Diagnostic criteria for acute MI?
Rise in Troponin or Ck-MB and one of:
- ischaemic Sx
- pathological Q waves on ECG
- ST changes on eCG
- coronary artery intervention
- post mortem pathology
39
What is the pattern of ck-MB rise in MI?
Increases 6-12 hours post MI
Peak at 24h
Return to normal by 48 hours
40
What is the calcium status of most patients with renal stones?
NORMOcalcaemic
41
Causes of stones:
1 hyperoxaluria
| 2 hypercalciuria
42
Prevention of stones:
- avoid dehydration
- reduce oxalate intake
- maintain calcium intake
- thiazide diuretics remove calcium from urine
- alkalinise urine (citrate)
43
Most common stone?
Calcium -mixed 45%
| Then calcium oxalate 35%
44
Radiolucent stones?
Uric acid
Cysteine
45
Struvite stones aka Staghorn are associated with?
Klebsiella and proteus infection (urea splitting organisms)
46
Rate limiting step of lipoprotein metabolism in liver?
HMG coA reducatase
| Converts mevalonic acid to cholesterol
Inhibited by statins
47
Main cholesterol carrier?
LDL (70%)
Transports cholesterol from liver to periphery
48
Lipoproteins in order of density?
```
Chylomicron (LEAST)
FFA
VLDL
IDL
LDL
HDL (MOST)
```
49
Cholesterol converted to bile acids by?
7alpha hydroxylase
50
Cholesterol converted to cholesterol ester by?
ACAT
51
HDL converted to VLDL by?
CETP
Cholesterol ester transfer protein
52
BMI classes?
<18 underweight
18-24 normal
25-30 overweight
30+ obese
53
Statins?
HMG coA reductase inhibitors
Can reduce cholesterol 50% by reducing endogenous synthesis in liver
s/e statin related myopathy (raised ck)
+GI disturbance
+rash
+insomnia
54
Ezetimide?
Cholesterol absorption blocker
55
Fibrates?
Increase lipoprotein lipase, apo A1 and apoA5
Decrease VLDL secretion
s/e
Myositis
Gallstones
56
Bile acid sequestrants?
E.g. Colestyramine
Prevent reabsorption via enterohepatic circulation
S/e constipation
Reduced Vit ADEK absorption
57
Anti - PCSK9 mab ?
Lowers LDL levels by preventing degradation of LDL R (so more LDL taken up from blood by liver)
58
Vitamin A?
- name
- deficiency
- excess
Retinol
Colour blindness, dry skin, Bitot's spots (keratin)
Hepatitis
Teratogenic
59
Vitamin D?
- name
- deficiency
- excess
Active - calcitriol
Synth in skin - cholecalciferol (D3)
Plan - ergocalciferol (D2)
Osteomalacia/Ricketts
Hypercalcaemia
60
Vitamin E?
- name
- deficiency
Tocopherol
Neuropathy (ataxia, areflexia)
61
Vitamin K?
- name
- deficiency
- test
Phytomenadione
Defective clotting (low 2,7,9,10 and protein C and S)
Bruising
Haemorrhagic disease of newborn
Test = prothrombin time
62
Vitamin B1?
- name
- deficiency
- excess
- test
Thiamine
```
Beri Beri
Wet - oedema and heart failure
Dry - Neuro Sx
Neuropathy
Wernicke's
1confusion
2ataxia
3 opthalmoplegia
(Progression to korsakoffs if +confabulation and amnesia which would be irreversible)
GIVE PABRINEX
```
Test = RBC transketolase
63
Vitamin B2?
- name
- deficiency
- test
Riboflavin
Glossitis and dry mucous membranes
Test = RBC glutathione reductase
64
Vitamin B3?
- name
- deficiency
Niacin
3 Ds of pellagra
- dementia
- diarrhoea
- dermatitis (casal's necklace)
65
Vitamin B6?
- name
- deficiency
Pyridoxine
Dermatitis, sideroblasric anaemia, neuropathy (isoniazid)
Test = RBC AST activation
66
Vitamin B12?
- name
- deficiency
Cobalamin
Pernicious anaemia
Subacute combined degen of cord
67
Vitamin C?
- name
- deficiency
Ascorbate
Scurvy - bleeding gums, poor wound healing
Excess vit C assoc renal stones
68
Folate deficiency?
Megaloblastic anaemia
And neural tube defect
*folate = vitamin B9
69
Commonest type of thyroid cancer?
Papillary
70
Thyroid cancer that produces calcitonin?
Medullary (assoc Men2)
71
Thyroid cancer assoc chronic hashimotos?
Lymphoma (MALT)
72
Formula for hydrogen ion conc.
H+ = k x CO2/HCO3
Where k = 180
73
Is caeruloplasmin high or low in wilson's?
Low
74
Thyroid cancer with worst prognosis?
Anaplastic
75
What are the purines?
Adenosine, guanine, inosine
76
Purines --> ? --> ? --> ?
Purines --> hypo xanthine --> xanthine --> urate
* catalysed by xanthine oxidase
* in animals urate converted to allantoin (highly soluble) but not in humans
77
Functional excretion of uric acid?
10%
78
Purine synthesis pathway?
Salvage pathway
Rate limiting step = PAT
*HPRT transfers hypoxanthine and guanine back to inosinic acid
79
Enzyme deficiency in Lesch Nyan syndrom?
HPRT
80
Features of Lesch Nyan?
X linked
Normal at birth
Developmental delay at 6mo
Hyperuricaemia --> gout
SELF MUTILATION
81
Features of gout?
Monosodium urate crystals
NEEDLE SHAPED
NEGATIVELY BIREFRINGENT
Acute - podagra
(swollen v painful 1st mtp (big toe))
Chronic - tophaceous
82
Gout management?
Acute:
- NSAIDs
- colchicine
Chronic:
- hydration
- allopurinol
- probenecid (increased renal excretion urate)
83
How does allopurinol work?
Inhibits xanthine oxidase
84
S/e of allopurinol?
Increases toxicity of azathioprine
85
Pseudogout crystals?
BRICK SHAPED
POSITIVELY BIREFRINGENT
86
Where does pseudogout typically affect?
Knee
87
Treatment of pseudogout?
Self limiting 1-3 weeks
88
Why does aspirin worsen gout?
Competes directly with urate for renal excretion
89
Why does ETOH cause gout?
Activates salvage pathway leading to hyperuricaemia and decreases renal urate excretion
90
When does newborn screening programme take place?
Days 5-9
91
Band keratopathy?
In eye secondary to chronic hypercalcaemia
92
HONK?
Hyperglycaemia + hypersomolality but NO ketones
*associated with T2DM where insulin present therefore no ketones
93
Metformin?
Insulin sensitizer
*least weight gain
94
Sulphonylurea?
E.g. Gliclazide
Increased insulin secretion
95
Pioglitazone?
PPARa agonist
Insulin sensitizer
96
GLP-1 analogues?
Incretins eg exenatide
97
Gliptins
DPP4 inhibitors
98
Normal GFR?
120 ml/min
*7.2 L/hr
99
Clearance?
Vol of plasma that can be completely cleared of a marker substance per unit time
* not bound to plasma proteins
* freely filtered
* not secreted or reabsorbed by tubule
100
Gold standard for GFR?
Inulin
101
Clinical measure used rarely eg pre chemo when accuracy needed?
51Cr EDTA
102
Most common clinical measure of GFR?
Creatinine
But actively secreted by tubular cells
103
Equations for eGFR?
Cockcroft Gault
MDRD
cKD Epidemiology Collaboration 2009
104
New alternative marker of
| GFR?
Cystatin C
*but not offered by all labs
105
Top causes of AKI?
1 renal hypoperfusion
2 drugs
3 contrast
4 sepsis
106
Stages of chronic kidney disease?
```
1 GFR 90+
2 60-90
3 30-60
4 15-30
5 <15 or on dialysis (ESKD)
```
107
Top causes of CKD?
1 diabetes
2 atherosclerotic renal disease
3 HTN
108
Complications of CKD?
Metabolic acidosis
Hyperkalaemia
Anaemia of chronic disease (low EPO production when GFR<30)
Uraemia
Vascular calcification (high phosphate beings calcium and deposits)
Renal bone disease
109
How does CKD affect vitamin D?
Osteomalacia (reduced Vit D activation)
*reduced Vit D and high retained phosphate cause secondary hyperparathyroidism
110
What is osteitis fibrosia?
Osteoclastic resorption of bone and replacement by fibrous tissue
111
Cortisol produced from?
Zona fasciculata of adrenal cortex
*hypothalamus (CRH) -> pituitary (ACTH) -> cortisol in circadian rhythm (high am, low Pm)
112
Aldosterone from?
Zona glomerulosa (most peripheral adrenal cortex)
113
Order of hormones lost in panhypopituitarism?
```
LH/FSH
GH
TSH
ACTH
prolactin (last)
```
114
Hyperprolactinaemia treatment?
DA agonists
Bromocriptime, cabergoline
S/e psychotic sx
115
Type 1 crigler najjar?
Complete UDPGT deficiency
*unconjugated BR jaundice from birth -> kernicterus
116
Type 2 crigler Najjar?
Partial UDPGT def
117
Haem is a?
Tetrapyrole with Fe2+ core
118
What cells do porphyrias affect?
Erythroid and liver
119
ALA synthase deficiency
NOT a porphyria
Causes x linked sideroblastic anaemia
120
PBG synthase def
Plumboporphyria
121
HMB synthase (aka PBG deaminase) def.
Acute intermittent porphyria
122
Diagnosing AIP?
Raised urinary ALA and PBG
* PBG oxidised to prophobilin = port wine urine
* neurovisceral sx ONLY as no build up of porphyrinogen
123
"Black liver"
Dubin Johnson
124
Treatment for AIP?
IV dextrose
Haem arginate
*haem is negative feedback to switch off ALA synthesis
