• Turn up the rheostat to the medium setting .
• Slowly move the stage downwards using the coarse focus , then use the fine focus to sharpen the image [ 3 ] .
• Thoroughly scan the slide using a methodical approach , such as the battlement technique .
• Lower the stage and use the next objective lens (× 10 and then × 40 ). Rack up the stage and follow the same procedure as mentioned earlier .
• For the × 100 objective lens , immersion oil is used . Place one drop of oil on to the microscope slide and rack up the stage until the oil is just touching the objective lens .
When the specific blood cell or crystal is found , take a vernier scale reading to allow others to locate it on the slide without the need to search each time .
How to read a vernier scale
• With the specific point under the microscope , lower the stage so the vernier scale can be read .
• There are two scales to read and record : the main stage scale and the vernier scale next to the main stage . There is also a horizontal and a vertical scale on the microscope .
• Read the main scale first , recording the number on the main scale closest to 0 on the vernier scale . Always round down . For example , if the 0 on the vernier scale is between 24 and 25 , the main scale reading is 24 .
• The vernier scale is read where the line on the vernier scale matches the main scale . For example , you may read the vernier scale as 7 , therefore , the first reading will be 24.7 .
• Repeat this process on the other axis . To report the readings , write the vertical scale reading , then the horizontal scale reading , to avoid confusion when someone else tries to find that spot .
After use , remove the slide from the microscope and dispose of it in the sharps bin , or package it appropriately if it is being sent for external laboratory testing . Wipe the microscope with alcohol-free wipes and dry it with dust-free wipes . Protect the microscope from damage by placing the microscope cover over it after use . Report the findings to the VS so they can check and diagnose .
Ideally , VNs should be able to identify types of blood cells under the microscope . ( Read the guide to interpreting blood panels from p . 44 of this issue of VNJ for further information on identifying different types of blood cells .)
The following are the common red and white blood cells and their function [ 4 ] .
• Erythrocytes are red blood cells that carry oxygen to the tissues and transport carbon dioxide to the lungs .
• Neutrophils ( also known as neutrocytes ) are white blood cells and are essential to the innate immune system . They are phagocytes , meaning they can engulf other cells or particles that are perceived as a threat to the body , a process known as phagocytosis . Immature and mature neutrophils differ in their characteristics .
• Eosinophils are white blood cells that combat parasites and other infectious diseases .
• Basophils are white blood cells associated with parasitic , neoplastic and allergic conditions .
• Lymphocytes are white blood cells associated with the immune response . They include T cells , which regulate adaptive immunity and are responsible for cell-mediated immune responses , and B cells , which are responsible for producing antibodies .
• Monocytes are white blood cells and are phagocytes . They help to produce antigens and cytokines . Cytokines are proteins that act as intercellular communication signals in a variety of processes including the immune response .
• Thrombocytes are also known as platelets and are involved in the clotting process .
Packed cell volume
When a blood sample is taken , the VS may also request a manual packed cell volume ( PCV ), if levels are abnormal .
How to prepare a PCV
• Put on gloves before handling the blood sample . Invert the EDTA tube gently a few times to mix the sample .
• Place a capillary tube into the sample and fill until three-quarters of the tube is filled . Place a gloved finger over the top of the capillary tube , remove it from the EDTA sample and wipe the base of the tube with tissue to remove any excess .
• Place the sample in sealant to form a plug at the end of the tube to stop the blood from escaping .
• Place the capillary tube in the centrifuge , ensuring the seal is facing out . Balance the centrifuge by using two capillary tubes . Apply the safety lid and close the centrifuge . Set to fast setting or 10,000 rpm for 5 minutes .
54 Veterinary Nursing Journal