Haematology. pulses and blood pressure Flashcards
1
Q
What is haematology?
A
The study of normal and pathologic aspects of blood and blood cells
2
Q
What is an erythrocyte?
A
Also known as a red blood cell. These biconcave discs lack a nucleus but contain haemoglobin (Hb) which allows oxygen to be transported to respiring tissues
3
Q
What is a leukocyte?
A
generic name for white blood cell. Mainly function as part of the bodies defence. Examples are granulocytes: neutrophils, basophils and eosinophils and agranulocytes: monocytes and lymphocytes
4
Q
What are the formed elements?
A
The cellular and cell fragment components of blood: cells (erythrocytes and leukocytes), platelets (thrombocytes) which are suspended in the plasma
5
Q
What is plasma?
A
The straw coloured liquid component of blood made up of water, electrolytes and proteins
6
Q
What is an antibody and antigen?
A
A protein produced by the immune system. Also called immunoglobulins. Produced in response to a foreign substance (antigen). Antibodies recognise specific antigens and bind to them so they can be removed from the body
7
Q
What is blood pressure?
A
Pressure of force that moves circulating blood around the body through our circulatory system, specifically measured in our arteries. Blood pressure readings consist of two number: the systolic pressure first and the diastolic pressure second. Readings are given in mmHg
8
Q
What is the systolic phase?
A
The phase of cardiac cycle when the ventricles are contracting. This is the higher of the two numbers
9
Q
What is the diastolic phase?
A
The phase of the cardiac cycle when the ventricles are relaxing. This is the lower of the two numbers
10
Q
What are things to note about health and safety to do with this practical?
A
- PPE should be worn whenever we are handling human tissue or human body fluid (blood)
- Gloves should be worn at all times – blood should never be handled directly
- Individuals who appear healthy may be carriers of infectious hepatitis
- Risk of HIV transmission
- Treat all blood as infected
- Dispose all used or contaminated items the correct way in the correct place
11
Q
What does blood do?
A
- Transports gases
- Carries nutrients, hormones, waste products and heat
- Involved in inflammation and contains antibodies which are responsible for the recognition and destruction of foreign micro-organisms and for triggering the immune response.
12
Q
What does blood consist of?
A
Plasma and formed elements
13
Q
What does plasma play roles in?
A
immunity, transport and osmotic effects
14
Q
What are the formed elements of the blood involved in?
A
gas transport, immunity and the arrest of bleeding (haemostasis)
15
Q
What type of blood sample could be collected for a blood test?
A
venous or capillary
16
Q
What is the procedure for obtaining a sample of capillary blood using a single lancet?
A
- Wipe finger with alcohol wipe and allow to dry (otherwise blood will smudge and it will be hard to obtain the sample)
- Massage bottom of finger gently
- Press the lancet against your finger and then push on the button
- It will always retrieve safely after use
- Dispose of the lancet in the yellow bin
- Squeeze the bottom of the finger until blood comes out
17
Q
give examples of uses of small finger prick samples
A
- Blood glucose levels
- Cholesterol testing
- Haemoglobin levels
- Covid antibody tests (trial June 2020)
- Used in laboratory tests e.g. making a blood smear to view blood cells
18
Q
Is it easier to obtain good sample from a finger tip if the hand is warm of cold?
A
warm
19
Q
What is venepuncture and when is it used?
A
- Where blood is taken directly from a vein in the forearm
- it is used when larger samples of blood are needed
20
Q
How is venepuncture carried out?
A
- A tourniquet is placed around the upper arm to allow blood to pool in the vein making the vein easier to identify and enables the sample to be taken when a small needle is inserted directly into the vein
- A sample obtained by venepuncture is collected directly into a bottle containing an anti-coagulant such as EDTA (ethylene-diaminetetraacetic acid), a chelating agent that binds to calcium
21
Q
What is a haemocytometer?
A
A specially ruled chamber
22
Q
What is the manual method for measurement of blood cells?
A
pipetting a diluted blood sample into haemocytometer (a specially ruled chamber) and then observing it under a microscope
23
Q
What are red blood cell counts and what are they used to do?
A
- they are commonly performed haematology tests that are usually part of the full or complete blood count
- the RBC count approximates the number of circulating red blood cells and is helpful in diagnosing and treating many diseases, especially anaemias
24
Q
What other cells counts is a haemocytometer used for?
A
cell counts in semen and cerebrospinal fluid samples
25
What does a haemocytometer consist of?
• A haemocytometer consists of surface-patterned two enclosed chambers with two ports for sample injection
26
/how is the 10 ul sample of capillary blood diluted for our red blood cell count?
- The diluting fluid for the red blood cell count is 0.9% saline and a preservative. This is an isotonic saline solution which is necessary to prevent haemolysis or destruction of the red blood cells
- 1.99ml of saline is added to the 10ul blood. This will provide a 200 fold dilution (dilution by the factor 200)
- 10ul of the cell/suspension is then taken up using a pipette for adding to the haemocytometer
27
Why can you use one haemocytometer to count independent samples?
Because there are two entirely separate chambers
28
What are the counting areas of the haemocytometer?
* The haemocytometer contains two identical ruled areas composed of etched lines that define squares of specific dimensions. These are in the detection areas A and B
* The detection areas A and B are separate enclosed areas. In each is a chamber which confines the fluid (blood and saline mixture) when the chamber is filled and regulates the depth of the fluid.
* In the detection area there are ruled areas consisting of a large square, 3mmx3mm, divided into nine equal squares, each 1mm square (1mm^2). The total of the large square is 9mm^2
* There are different areas designated for counting white blood cells and red blood cells
* The WBC counting area consists of large squares denoted with ‘W’ and for RBC denoted with ‘R’
* We only use the large centre square for the RBC count. This square is subdivided into 25 smaller squares which in turn are divided into 16 squares. Of the 25 squares only the four corner squares and the centre square are used to perform RBC counts
29
How do you count the cells in a haemocytometer?
• Each of the 5 squares we use to count the red blood cells in turn contains 4 rows of squares. All cells within each of the small squares are counted using the left to right, right to left counting pattern
• When counting RBC using the haemocytometer there are some rules to follow:
- The cells touching either the top or left boundaries of the squares are included in the count
- The cells touching the right boundary and the cells touching the lower boundary of each square are not counted
- Cells lying beyond these boundaries are not counted in the red blood cell count.
- If the number of cells in a square varies from any other square on the same side of the haemocytometer by more than 25 cells the count must be repeated (remixed and reloaded to the haemocytometer) ensuring the most accurate and precise results
30
How do you calculate the number of red blood cells per ml?
- (total cells in 5 squares/5) x 25 x 200(dilution factor) x 10^4 (volume factor)
- Each square has a total volume of 0.1mm^3 (0.1ul) therefore a volume factor of 10 000 (10^4) is needed to obtain the number of red blood cells per ml
- The reading for the red cell count should be multiplied by 10^12 (maybe 10^7 but check) to give the number of red cells per litre. This is the usual format in which these results are expressed
31
What is the normal RBC count values for women?
3.9-5.6 x 10^12 per litre (10^9 per ml or 10^6 per ul) (female)
32
What is the normal RBC count for men?
4.5-6.5 x 10^12 per litre (19^9 per ml or 10^6 per ul)
33
What does haemoglobin (Hb) allow?
the carriage of oxygen from the lungs to the tissues
34
What is the structure of a Hb molecule (simply)?
Each haemoglobin molecule exists as a tetramer, made up of 4 peptide chains (globins) with its associated haem molecule
35
What are the methods that Hb concentration can be estimated based on?
the intensity of colour (or light absorption) of a stable derivative of haemoglobin.
36
In our method what is haemoglobin converted to?
the stable coloured derivative azidemethaemoglobin
37
What is the normal range for haemoglobin concentrations for women?
120-160 g L^-1 (12-16 g/dL)
38
What is the normal range for haemoglobin concentrations for men?
135-175 g L^-1 (13.5-17.5 g/dL)
39
What is the haematocrit/ packed cell volume (PCV)
- This refers to the volume of red blood cells expressed as a proportion of the total volume of a blood sample.
- The remaining volume of the sample consists of the buffy coat (leucocytes and platelets which are usually negligible) and plasma.
- The proportion of RBCs (also described as the ‘haematocrit) may be expressed either as a decimal or percentage
40
How can haemoglobin and haematocrit measurements be obtained?
using a point of care (hand held) device. This is known as ‘point of care testing’ which, in contrast to counting red blood cells using a haemocytometer is an automated method which provides results in approximately 12 seconds
41
How do you use a point of care device?
1. To turn the meter on press the middle button
2. A test strip should be inserted into the strip channel in the same direction as the arrows indicated on the strip, the notched end in first and the hole facing up. Ensure that the test strip is inserted all the way to the end of the strip channel, until the white edge of the test strip above the black line is no longer visible. The notched end should also be no longer visible.
3. The finger or thumb should be prepared to take a sample. The first drop of blood should be wiped away. Light pressure should be applied to obtain the second drop of blood.
4. A sample of 10 µL of capillary blood should be collected using the Gilson pipette.
5. The blood drop symbol will flash on the left hand side of the screen when the meter is ready for the specimen to be applied. The meter will allow 2 minutes for application of the blood sample and will then switch off. To allow you to continue switch the meter back on as quickly as possible.
6. Apply approximately 10 µL of blood to the middle of the specimen application area of the test strip ensuring that the test area is filled with blood:
7. Haemoglobin values will be displayed in g/dL
8. Haematocrit (Hct) values will be displayed at the bottom of the screen as a %
9. Used test strips should be removed and discarded into a yellow clinical waste container
42
Why are Hb levels measured when donating blood?
to check if your Hb levels are adequate for you to give blood at this time
43
Why are the threshold levels for Hb for blood donation set higher than normal blood Hb levels?
so that Hb levels don’t fall to unsafe levels after donation
44
How were Hb level tests traditionally carried out?
- Using a copper sulphate test. This involves taking a small sample of blood from your fingertip and transferring a drop into a vial of copper sulphate solution.
- The time is takes for your blood to sink to the bottom of the vial is monitored. If the blood sinks to the bottom in a set time you can give blood
45
What is the HemoCue test?
- a recent more accurate test to check Hb levels
- involves a machine similar to the carepoint machine and involves taking another small sample of blood from your fingertips
46
When may a slight fall in Hb levels be normal?
- menstruating women
- pregnant women
- following a change in diet
47
What are some more haematological indices which can be used to find out the health of someone's blood?
- Mean corpuscular (cell) volume (MCV)
- Mean cell haemoglobin (MCH)
- Mean cell haemoglobin concentration (MCHC)
48
What are the values we need to calculate the MCV, the MCH and the MCHC?
- Red cell count (x10^12/L)
- Haemoglobin concentration (g/L or g/dL)
- Packed cell volume (PCV) pr haematocrit (Hct %)
49
What should you be aware of when carrying out calculations?
units and decimal places
50
What is the mean cell volume (MCV)?
the mean volume of a single red cell
51
How is the MCV calculated?
PVC (as a decimal)/ red cell count
52
What is the normal MCV range in femtrolitres?
78-100fL (1fL -10^-15 litre)
53
What is the mean cell haemoglobin (MCH)?
the mean quantity of haemoglobin per red cell
54
How is the MCH derived?
Derived from haemoglobin concentration (g/L) or g/dL of whole blood/red cell count
55
What is the normal MCH range?
27-32pg(1pg = 10^-12g)
56
What is the mean cell haemoglobin concentration (MCHC)?
the mean concentration of haemoglobin within the red cells in g/dL
57
How is the MCHC calculated?
haemoglobin concentration of whole blood (g/L)/ PCv (as a decimal)
58
What is the normal MCHC range?
300-350gL (30-35 g/dl)
59
What are the three main types of blood cells?
- Erythrocytes (RBCs)
- Leucocytes (whit blood cells)
- Thrombocytes (platlets)
60
When is a differential white blood cell count (DWCC) carried out?
in hospitals to examine the body’s immune system and it’s ability to fight infection
61
What does a WBC count measure?
The total number of white cells in your blood
62
What does a differential WBC count measure?
determines the percentage of each type of white blood cell
63
What is a differential WBC count used to do?
- examine the body's immune system and ability to fight infection
- detect immature and abnormal WBCs
64
How is a differential white cell count carried out?
* It can be performed manually using a microscope. A blood film is prepared using a small drop of blood from the finger or thumb placed on a clean microscope slide
* The drop is spread along the slide using a spreader and allowed to dry
* When dry the slide can be stained by immersing in Wright’s stain for 1 minute and then rinsing gently with water, ensuring that the cells or stain are not displaced
* We can then look at the cells using the microscope.
* To be able to visualise the internal structures of the blood cells and to be able to count them, the slide will be viewed using x40 magnification
65
What is the ABO blood group classification based upon?
the presence or absence of antigens (agglutinogens) A and B on the surface of red cells
66
What are the four different blood groups in the ABO classification?
A, B, AB and O
67
What does mixing cells carrying an antigen with a serum containing the corresponding antibody (agglutinin) cause?
agglutination or clumping together of the red cells
68
How can the blood group of an individual be determined?
by testing the cells with both anti-A and anti-B sera containing high concentrations of these agglutinins
69
How does the rhesus's blood group work?
Blood can also be classified as Rhesus (Rh) positive (+ve) or negative (-ve) depending on the presence of the Rhesus D antigen on the red cells
70
What is the manual procedure for blood group testing?
1. Approx. 10 drops of isotonic saline should be placed in the plastic petri-dish, using a clean Pastette™.
2. One or two drops of blood should be added to this saline to dilute the sample, and mixed well.
3. Two drops of anti-A, anti-B and anti-D serum should be added to the corresponding well on the white blood grouping tile. One drop of the red cell suspension should be added to each of the samples of sera, taking care not to cross-contaminate them.
4. The sample can be mixed by gently rocking the tile to and fro.
5. After approximately 5 minutes examine for agglutination. Where there is no antibody-antigen reaction, the red cells remain in suspension.
71
what does the heart pulse tell you?
The rate the heart is beating at and it's regularity
72
What is the strength of the pulse determined by?
The pulse pressure - the key difference between the systolic and diastolic blood pressures
73
What is palpation?
Using the fingertips to feel
74
what are the 3 general rules for the examinations of limb pulses by palpation?
1. Limb should be supported and relaxed or you will feel only twitching tendons. Explore with two or three fingertips laid flat side-by-side using only light pressure at first
2. When you have found the pulse accustom yourself to its rhythm before starting to count – this also gives the heart time to settle into a steady rate
3. Feel and compare pulses from the same location on either side of the subject’s body (bilaterally)
75
What are the three common pulses and what are they used to identify?
- Radial: used for determining heart rate
- Brachial: used to the measurement of blood pressure
- Carotid: close to the heart and so is under great pressure
76
How do you measure the radial pulse?
-The subject’s upper arm should be beside the body with the forearm horizontal – it can be either pronated (palm down) or supinated (palm up). Place your fingers around or under the wrist supporting it on the other side with your thumb. The radial artery runs superficially in front of the distal end of the radius – this is where you need to position your fingertips
77
How do you measure the brachial pulse?
The arm should be supinated and extended; place your hand under the elbow to take the weight. Ask subject to flex at the elbow and locate the biceps tendon. Tell the subject to relax again with their arm straight and place fingertips just medial to the tendon (i.e. little finger side) in the cubital fossa. You will need to press more firmly than when locating the radial pulse
78
How do you measure the carotid pulse?
Identify the sternocleidomastoid muscle (from the top of the sternum to behind the ear) and ask the subject to relax with the nick slightly extended. Place your fingertips between the muscle and the side of the larynx. Do not press hard and do not palpitate on both sides simultaneously
79
What is arterial blood pressure?
Measure of the force the blood exerts inside vessels as it presses against the vessel walls
80
What is arterial blood pressure influenced by?
volume and viscosity of the blood and resistance within the vessels?
81
What does blood pressure usually refer to?
the maximum (systolic) and minimum (diastolic) pressure values reached during a cardiac cycle
82
What may a fall in BP (hypotension) lead to?
inadequate perfusion of tissues
83
What may a high BP (hypertension) lead to?
Cardiac and vascular damage
84
How can you calculate blood pressure?
cardiac output x total peripheral resistance
85
What is the CO (cardiac output) dependent on?
heart rate (HR) and stroke volume (SV): CO = SV x HR
86
What's the equation to calculate mean arterial blood pressure (MABP)?
Diastolic blood pressure + 1/3(systolic blood pressure - diastolic blood pressure)
87
What is blood pressure measured indirectly using?
a sphygmomanometer
88
What happens if a vessel is partially occluded?
the flow becomes turbulent. This gives rise to murmurs resulting from blood being rapidly ejected through the compressed region and impacting on the column of blood beyond
89
How can murmurs (Korotkoff sounds) be heard?
through a stethoscope placed downstream from the occlusion site (normally over the brachial artery)
90
How can blood flow within an artery be estimated?
by measuring the external pressure needed to occlude (close) the vessel and stop blood flow
91
How should a sphygmomanometer be fitted?
1. The subject should sit at ease, with their arm resting along a bench or table, close to the height of their heart. The upper arm should be exposed as fully as possible. Thick or tight clothing must be removed, not merely rolled up, since it may cause unwanted compression of the arm.
2. Place the cuff around the arm - make sure it is the correct way round (label outside or indicated on cuff) and that the arrow or Φ symbol is lined up with the brachial artery. The cuff should fit tightly enough that it does not drop down, but not so tight as to constrict the upper arm; the lower border of the cuff should be far enough above the elbow to fit the stethoscope (at least 2-3 cm). N.B. It is not good practice to tuck the head of the stethoscope underneath the cuff as this would reduce the accuracy of measurements by introducing a gap between the cuff and the artery.
3. The cuff should be positioned so that the tubing comes out of the bottom.
4. Ensure that the tubing of the cuff does not make contact with the stethoscope tubing, as this may produce artifactual sounds.
92
Hoe can you measure blood pressure on yourself?
1. Locate the brachial pulse in the cubital fossa of the non-dominant arm (i.e. if you are right-handed, this would be your left arm), which should be clear of the cuff.
2. Fit a stethoscope to your ears; the earpieces should point slightly forward. Make sure that sound is directed through the diaphragm surface of the stethoscope - you can test this by gently tapping on it (if the sound is not amplified then twist the tubing at the head of the stethoscope and try again).
3. The pump consists of a rubber bulb with an inlet valve at the closed end and a pressure-release screw on the outlet. Hold the bulb so that you can open and close the screw with your fingers and thumb. N.B. Make sure that you do not overtighten the screw because this will damage the thread (if in doubt, consult a demonstrator).
4. Place the head of the stethoscope over the brachial pulse. Close the screw and quickly pump up the pressure in the cuff to 180 mmHg* (no higher than this!) - there should be little or no fall in pressure until you open the screw. N.B. At this stage you should hear nothing. DO NOT KEEP THIS PRESSURE FOR MORE THAN A SECOND OR TWO, start reducing immediately.
5. Reduce the pressure at a rate of 2-3 mmHg /sec by opening the screw. Korotkoff sounds should be heard when the pressure in the cuff is equal to the systolic blood pressure (SBP) (make a mental note of this pressure reading).
6. Continue to reduce the pressure until the sounds abruptly become softer or inaudible; if there is a difference between these levels, record both. The pressure when the sounds disappear is taken as the diastolic blood pressure (DBP). Write down your values for SBP and DBP.
7. Deflate completely and then after a pause repeat. Always relieve the pressure completely between the measurements and allow at least a minute between each cuff inflation for circulation in the arm to return to normal
8. three or four quick readings are better than a single slow one
9. from you SBP and DBP values you can determine pulse pressure (PP)
93
How do digital blood pressure monitors measure systolic and diastolic blood pressure?
by detecting oscillations through the skin
94
What are the disadvantages of an automated blood pressure monitor?
that they are not as sensitive as the human ear in detecting the Korotkoff sounds, may give inconsistent readings and need to be calibrated regularly
95
What are the two types of digital blood pressure monitors?
- Fit upper arm and measure pressure in the brachial artery
| - Those that fit the wrist and measure pressure in the radial artery
96
How do you measure blood pressure using an automated wrist monitor?
1. Remove any watches or jewellery from the wrist (of the same arm) and ensure that any clothing is rolled up so that the skin is bare.
2. Fit the cuff around the subject's wrist with the palm facing up - make sure that the edge of the cuff is about 1 cm from the palm. The "box" should be carefully located over the underside of the wrist, not the side or back.
3. Fasten the Velcro strap securely around the wrist so that there is no extra space between the cuff and the wrist.
4. Support the elbow with the other arm, so that the cuff is not touching anything. Alternatively support the arm by holding the hand on the arm to be measured using the other hand, still level with the heart
5. If you have a partner then get them to press the 'on' switch and make sure that the arm is kept still while the cuff automatically inflates and then deflates (if not, you can do this yourself but try to keep the arm as still as possible).
6. The readings for SBP, DBP and pulse will be automatically displayed (and stored in the memory) as soon as the measurement is complete.
97
Why is it important to compare the blood pressure measurements from both arms?
differences could indicate some underlying pathology or an increased risk of cardiovascular disease, chronic renal disease of diabetes
98
What does an increase in stroke volume do?
tends to increase systolic pressure because the aorta has to stretch further to accommodate the blood ejected by the left ventricle
99
What does an increase in heart rate increase?
diastolic pressure because there is less time for blood to lave the aorta (into the peripheral circulation) before the next systole
100
What does increased peripheral resistance do?
slows the flow of blood out of the aorta so that the pressure falls less rapidly during diastole
