Online practical 3- haematology, pluses & pressure

how to obtain a blood sample from finger-tip

lancet

what are finger-tip blood samples for

• glucose levels

• cholesterol testing

• Hb levels

• covid antibody tests

how to obtain larger blood samples

• venepuncture (blood taken from blood in the forearm)

• tourniquet around the upper arm so blood can pool in the vein

• sample is put into a bottle containing EDTA (anti-coagulant) that stop blood clots by binding to Ca

how to measure RBC’s + steps

• haemocytometer

  1. 10ul of blood sample

  2. dilute with 1.99ml of saline fluid

  3. add 10ul of solution to haemocytometer chamber

how to calculate number of RBC’s per ml

how to work out volume factor

number needed to convert units to ml (power of 10)

normal RBC count for men

4.5-6.5 × 10^12 per litre

normal RBC count for women

3.9-5.6 × 10^12 per litre

normal range + threshold for donating Hb for women

• 120-160 g/L

• 125 g/L

normal range + threshold for donating Hb for men

• 135-175 g/L

• 135 g/L

what is haemocrit/packed cell volume

volume of RBC’s as a proportion of total blood volume

how to calculate RBC mean cell volume (MCV)

• packed cell volume/RBC count

• units: fL (10^-15L)

• normal range: 78-100

how to calculate mean cell Hb (MCH)

• Hb concentration/RBC count

• units: pg (10^-12g)

• normal range: 27-32

how to work out mean cell Hb concentration (MCHC)

• Hb concentration/packed cell volume

• units: g/dL

• normal range: 300-350

differential white cell count + 4 steps

• total number of WBC & % of each type

  1. add blood sample to slide

  2. spares blood using another slide

  3. leave to dry & stain with Wright’s stain for 1 min

  4. rinse with water & dry

how to test blood groups

when antigens & corresponding anti-bodies mix agglutination of RBC’s will happen

what colour is anti-a sera

blue

what colour is anti-b sera

yellow

what colour is anti-d sera

clear

how to calculate pulse pressure

systolic BP-diastolic BP

radial pulse point

• determining heart rate

• put fingers around/under wrist

brachial pulse point

• determining blood pressure

• tell person to flex elbow, find bicep tendon, tell person to relax, press heavier to locate pluse

carotid pulse point

put fingers between side of larynx & sternocleidomastoid muscle

how to calculate mean arterial blood pressure

diastolic BP + 1/3 (systolic BP - diastolic BP)