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Biochemical tests Flashcards

1
Q

what are the plasma components usually measured?

A

– Sodium
– Potassium
– Chloride
– Bicarbonate
– Urea
– Creatinine

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2
Q

why is water so important?

A

fundamental to all blood test as patients hydration is important

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3
Q

where is sodium present?

A

it is an extracellular cation- outside

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4
Q

what is the main function of sodium

A

maintain osmolality

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5
Q

what are the major route of sodium excretion?

A

kidneys

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6
Q

what hormones help the kidneys excrete/ maintain sodium balance?

A

– Antidiuretic hormone
– Aldosterone
– Thirst

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7
Q

what are changes in serum sodium concentration usually due to?

A

– Diet (rich or low in sodium)
– The amount of water in the blood
– Kidney function

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8
Q

define hypernatraemia

A

Defined as a plasma sodium concentration of:
– > 145 mmol/L

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9
Q

what causes hypernatraemia?

A

– Water depletion
* Loss of water in excess of sodium
* Decreased fluid intake
– Increased sodium intake or retention in excess of
water
* Mineralocorticoid excess
* Medication
* Renal failure

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10
Q

what are some of the signs and symptoms of hypernatraemia?

A

– Dry skin
– Postural hypotension
– Oliguria
– Thirst
– Confusion
– Drowsiness, lethargy
– Extreme cases – coma (>155 mmol/L)

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11
Q

what are the drugs associated with an increased sodium- hypernatraemia?

A

– Corticosteroids
– NSAIDs
– Laxatives
– Lithium

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12
Q

why must you consider the make up of injectable drugs and soluble preps?

A

as sodium content could be high

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13
Q

how do you manage hypernatraemia?

A
  • Identify and treat underlying cause
  • Replace body water
    – Orally
    – Intravenously
  • Dextrose 5% w/v
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14
Q

define hyponatraemia

A

Low sodium is defined as a serum sodium
concentration below 135mmol/L

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15
Q

generally what does low sodium indicate?

A

– Over hydration in the body
– Too little sodium in the body
– Or a mixture of both

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16
Q

what may result from hyponatraemia?

A

May also include cardiac failure, anorexia and oedema.

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17
Q

what are the potential causes of hyponatraemia?

A

– Medication
– Mineralocorticoid deficiency
– Water/fluid excess
* SIADH
* Certain disease states
– Abnormal losses of sodium
* Diarrhoea, DKA
– Alcohol excess
– Severe burns
– Malnutrition
– Dilution of blood sample by IV fluids

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18
Q

how do you manage hyponatraemia?

A

– Identify and correct the underlying cause
– Depending on cause:
* Increased salt intake
* Fluid restriction
– If needed:
* Mild – moderate:
– Slow – sodium, 4 – 8 tablets (2.4 – 4.8g)
– Demeclocycline 900 – 1200mg daily in divided doses
* Severe:
– I/V NaCl

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19
Q

why do you not increase levels of sodium quick?

A

Remember, do not increase levels too
quickly due to the risk of osmotic
demyelination

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20
Q

where is potassium located in the body?

A

in the cell- intracellular cation

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21
Q

how is k+ regulated?

A
  • Regulated by aldosterone, cortisol, insulin and
    glucose
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22
Q

what do changes in k+ have an effect on?

A
  • Changes in potassium levels have a profound
    effect on the nervous and cardiovascular system
  • → fatal in extreme cases
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23
Q

where is k+ absorbed/ eliminated?

A

– Mainly absorbed in the small intestine
– Eliminated via the kidneys

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24
Q

where is k+ in peoples cells when they are hydrated/dehydrated?

A

– Potassium is lost from cells when people are
dehydrated and returns when hydrated

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25
how are k+ levels influenced?
– Acid-base disturbances * Acidosis (K moves out of cells in exchange for H) * Alkalosis (K moves into cells in exchange for H) – Catabolic states – Anabolic states – Insulin secretion
26
where is the main route of k+ loss?
via kidneys- small amoung in faeces and skin
27
what are some of the causes of hyperkalaemia?
* Medication * Renal * AKI * CKD * Rhabdomyolysis * Hypoaldosteronism * Advanced CCF * Acidosis * DKA
28
how do you exclude pseudohyperkalaemia from hyperkalaemia
Delay in sample reaching the lab * Contamination * Haemolysis of sample * Drip arm
29
what are signs and symptoms of hyperkalaemia?
* Fatigue * Muscle weakness * Abnormal cardiac conduction * Chest pain and palpitations * ECG changes * Cardiac arrest (severe cases)
30
how do you manage hyperkalaemia?
– Assess patient: ABCDE – Identify cause/stop potentially offending drugs immediately – Rule out a pseudohyperkalaemia – Ensure adequate hydration – Consider the severity * Severe/ECG changes: MEDICAL EMERGENCY
31
when do you refer someone with hyperkalaemia to hospital?
– >6.5mmol/L – Acute ECG changes and >5.5 mmol/L – Rapid rise
32
what do you do if there is mild hyperkalaemia?
– Correct underlying cause, repeat blood test – Medication review and dietary changes are often adequate
33
what do you do for moderate hyperkalaemia?
– Carry out an ECG * Assess course of action based on this * No high-risk factors, review patient
34
what is the 5 step hospital approach for the management of hyperkalaemia?
* Step 1: Protect the heart * Step 2: Shift potassium into cells * Step 3: Remove potassium from the body * Step 4: Monitoring * Step 5: Prevention
35
how do you protect the heart in hyperkalaemia?
* If there are ECG changes – 30ml of 10% calcium gluconate IV OR – 10ml of 10% calcium chloride IV
36
how do you shift potassium into cells?
* Insulin-glucose infusion – 10 units of soluble insulin in 250ml dextrose 10% * 10 – 20mg salbutamol nebuliser – IHD * Shifts into the cells temporarily, this is a holding measure only – Does not reduce total body potassium * Will start to leak back into extracellular space (2 – 6 hours)
37
how do you remove potassium?
* Potassium exchange polymers * Anion exchange resin – Calcium resonium: 15g TDS * Potassium binders – Patiromer calcium – Lokelma (sodium zirconium cyclosilicate) dialysis
38
when do you have to do continuous monitoring with hyperkalemia patients?
where ECG features are present k+ every 2-4 hours * Blood glucose levels * Baseline, 15, 30, 60, 90, 120 minutes and up to 6 hours post dose
39
how do you prevent hyperkalemia recurring?
Stop nephrotoxic medications and drugs known to contribute to hyperkalaemia.
40
what are the causes of hypokalaemia?
* Medication * Decreased intake * Abnormal losses * D&V * Ileostomy * Acid-base disturbances
41
what are the signs and symptoms of hypokalaemia?
* Hypotonia * Cardiac arrhythmias * Muscle weakness * Fatigue * Confusion * Paralytic ileus
42
what are some of the drugs causing hypokalaemia?
Salbutamol (especially in high doses) Thiazide diuretics Loop diuretics Insulin Steroids Chronic laxative abuse
43
how do you manage hypokalaemia?
– Depend on the severity – Correct underlying cause or disease process – Use potassium sparing drugs – Oral treatment – Intravenous treatment
44
how do you manage mild and moderate hypokalaemia?
– Oral replacement * Sando K®: 1 – 2 tablets TDS * Kay-Cee-L: 10ml – 20ml TDS * Slow K: avoid where possible
45
how do you manage severe hypokalemia?
– IV replacement (with continuous cardiac monitoring – depending on potassium concentration) – Doses vary across guidelines – Doses and rates may vary in critical care or fluid restricted patients
46
where is there increased risk of digoxin toxicity and why?
– There is an INCREASED risk of digoxin toxicity in the presence of hypokalaemia – Digoxin competes with potassium ions at binding sites, therefore, a low potassium predisposes to toxicity.
47
what is the usual range for chloride?
Usual range is 95 – 105mmol/L
48
what does chloride usually follow?
* Movement follows that of sodium
49
what causes and increase in CL-?
excess ingestion dehydration
50
what causes a decrease in cl?
vomiting diarrhoea diuresis dehydration
51
what does bicarbonate reflect?
* Reflects renal, metabolic and respiratory functions
52
what would be the signs and symptoms of inc/dec bicarbonate?
inc- vomiting dec- headache, drowsiness, coma
53
what are the causes of increased bicarbonate?
excess antacids thiazide and loop diuretcis metabolic alkalosis hypokalaemia vomiting
54
what are the causes of decreased bicarbonate?
diarrhoea renal failure diabetes metabolic acidosis respiratory alkalosis
55
what is the end product of protein metabolism?
urea
56
what causes raised urea?
renal failure sepsis uti CCF dehydrayion GI bleed
57
what causes decreased urea?
pregnancy low protein cld over hydration starvation
58
what is the end product of metabolism
creatine
59
what is the end product of metabolism
creatine
60
what happens if kidney filtration is impaired?
serum creatine will rise
61
what are reduced levels of calcium associated with?
– Renal failure – Raised phosphate levels (as phosphate binds to calcium readily) – Hypoparathyroidism – Low magnesium levels – Deficiency/malabsorption
62
what are reduced levels of calcium associated with?
* Raised levels (>2.65mmol/l):– NB. Can be a medical emergency, if >3.75, at risk of M.I – 90% of cases are due to malignancy or hyperparathyroidism – Hyperthyroidism – Dehydration
63
how do you manage raised levels of calcium?
Manage with fluids initially, if no response IV bisphosphonates
64
how is magnesium eliminated?
via the kidney
65
when is magnesium levels reduced?
– Diuretics – Liver disease – Diarrhoea
66
when are magnesium levels raised?
– Renal impairment
67
what can low levels of mg be assoicated with and why?
low levels of CA and K- as magnesium helps transport calcium and k+ ions in and out of cells
68
what are some factors affecting test results?
* How specimens are collected, transported, stored and processed * When the sample was taken * Patient age * Gender * Nutrition * Sitting/standing
69
what are the two examples of potassium binders?
* Patiromer calcium and Lokelma (SZC)
70
when are potassium binders appropiate?
– Had an acute episode of hyperkalaemia between 6.0- 6.4 mmol/L – There is a clinical case to restart withheld RAASi therapy at a lower dose once resolved – Potassium on repeat testing is between 5.5 – 6.4 mmol/L
71
what do you have to monitor with potassium binders?
– Following initiation/dose changes check potassium 1 – 2 weeks after: * If <4mmol/L: reduce dose of binder * If 4 – 5.3mmol/L: continue * If >5.3mmol/L: increase dose of binder
72
what is HCT?
– Indicates the proportion of RBC that make up the blood pool
73
what is MCV?
– Average size of the RBC
74
what is MCH?
– Average amount of Hb in a RBC
75
what is MCHC?
– Average concentration of Hb inside an average sized cell
76
what do we consider for microcytic anaemia?
A low RBC (red blood count), Haemoglobin (Hb), Haematocrit (HCT) and Mean Cell Volume (MCV) are suggestive of a microcytic anaemia.
77
what are the causes of iron-deficiency anaemia?
– Inadequate diet – Deficient absorption – Blood loss * Menorrhagia * GI bleeding
78
what is the management of microcytic anaemia?
Oral: Iron supplement e.g., ferrous sulphate 200mg OD (65mg elemental iron) * Continue until normal levels are reached and the for 3 months thereafter (NICE) – Parenteral: in presence of malabsorption e.g., Ferinject®, Cosmofer®
79
what would indicate macrocytic anaemia in blood results?
In a macrocytic anaemia the mean cell volume is raised * A raised MCV with a low haemoglobin suggests vitamin B12 or folate deficiency, these should therefore be tested
80
what is the cause of macrocytic anaemia?
This disease affects all the cells of the body and is due to malabsorption of B12 resulting from atrophic gastritis and lack of intrinsic factor secretion
81
what are the causes of macrocytic anaemia?
Common features are tiredness and weakness, dyspnoea, sore red tongue, diarrhoea and mild jaundice
82
how would you treat 1- folate deficiency 2- b12 deficiency?
* Folate deficiency: oral folic acid 5mg daily * B12 deficiency: replenish stores with hydroxocobalamin (B12): – 1mg IM alternate days for 2 weeks. – Maintenance 1mg IM every 3 months FOR LIFE
83
what is the function of neutrophils?
– Ingest and kill bacteria, fungi and damaged cells
84
why would neutrophils rise?
(Neutrophilia) occurs in bacterial infections
85
why would neurophils be low?
(Neutropenia) occur in viral infections, acute leukaemia
86
what is CRP and what does it indicate?
* Protein produced in the acute phase response * Synthesised exclusively in the liver * Rises within 6 hours of an acute event
87
when do platelets rise?
* Rise: (Thrombocytosis) – Malignant disease – Autoimmune disease – Inflammation
88
when are platelets low?
* Low: (Thrombocytopenia) – Drugs – Leukaemia
89
what is ESR?
Erythrocyte Sedimentation Rate (ESR) * Measure of acute phase response

MO1 (50 decks)

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