Tail vein

Please read the general principles of blood sampling page before attempting any blood sampling procedure.

Technique

Tail vein sampling is suitable for all strains of rat. With proper training, the procedure is quick and simple to perform. However, this technique requires the rats to be warmed in order to dilate the blood vessel prior to taking the sample. This can be stressful and can cause dehydration due to salivation, in addition to increasing metabolic rate, which may affect the experimental data. As a result, other routes such as saphenous vein sampling should be considered where possible. View the tail vein sampling technique below.

The lateral tail vein is usually used and 0.1 - 2 ml of blood can be obtained per sample depending on the size of the rat, sampling frequency and scientific justification. The tail may need to be washed with diluted Hibiscrub (1%) in order to see the blood vessel. Finger pressure 5 cm from the tail tip can enhance the visibility of the tail vessels.

Rat tail vein fromNC3Rs on Vimeo.

To avoid bruising and damage to the tail, normally no more than eight blood samples should be taken per session and in any one 24-hour period. Where it is necessary and justifiable to take more, the use of temporary cannulation or surgical cannulation should be considered. The number of attempts to take a blood sample should be minimised (no more than three needle sticks in any one attempt) and sufficient time should be given for the tail to recover between blood sampling sessions. Alternate sides of the tail should be used and needle punctures moved towards the tail base.

If it is necessary to warm the animal, a warming cabinet should be used (39oC for up to 10 minutes). Rats should be carefully monitored, including checking for signs of hyperthermia and dehydration. The time the rat is in the warming cabinet should be recorded and the cabinet should be calibrated regularly to avoid hyperthermia; digital displays should not be relied upon. It is important to ensure the temperature in the cabinet is uniform and that there are no 'hot spots'. Alternatively, a warm bath at a maximum of 39oC can be used to warm just the tail of the rat. The temperature of the bath should be monitored to prevent the tail being scalded.

The lateral tail vein is usually accessed approximately one-third along the length of the tail from the tail tip, moving towards the base of the tail for multiple samples. Blood samples should only be taken from the base of the tail if no vein is visible elsewhere. Taking the first sample/s from the proximal end of the tail can result in a perivascular clot and inflammation that significantly reduces blood flow to the distal portion of the vessel.

Proper aseptic technique should be used throughout the procedure. The animal will need to be restrained which can cause stress and therefore the duration of restraint should be minimised.

Blood flow should be stopped by applying finger pressure to the soft tissue. A finger should be placed at the blood sampling site for approximately 30 seconds before the animal is returned to its cage.

Summary

Number of samples No more than eight blood samples should be taken per session and in any 24-hour period, depending on sample volume.
Sample volume 0.1 - 2 ml
Equipment 21G - 23G needle or butterfly needle or lance
Staff resource One person is required to take the blood sample if a tube restrainer is used. Two people are required if the rat is held for sampling.
Adverse effects
  • Infection <1%
  • Haemorrhage <1%
Other Rats may be warmed to dilate the blood vessel. Care should be taken to avoid hyperthermia and dehydration.

Resources and references

Tail vein sampling in other animals

Click here for information on tail vein blood sampling in the mouse

All blood sampling techniques in the rat

Click here for information on blood vessel cannulation in the ratClick here for information on jugular vein blood sampling in the ratClick here for information on saphenous vein blood sampling in the ratClick here for information on retro-orbital blood sampling techniques in the ratClick here for information on using a temporary cannula for blood sampling in the ratClick here for information on abdominal/thoracic blood vessel blood sampling in the ratClick here for information on cardiac puncture blood sampling in the ratClick here for information on schedule 1 stunning followed by decapitation for blood sampling in the ratClick here for information on decapitation blood sampling techniques in the rat