Rat: Blood vessel cannulation (surgical)

Technique

Blood vessel cannulation should be considered when repeated samples are required, as it avoids multiple needle entries at any one site. It is suitable for use in all strains of rat and can be used to take blood from the femoral artery and vein, carotid artery, jugular vein, vena cava and dorsal aorta. Surgery is required and appropriate anaesthesia and analgesia should be used to minimise any pain caused. Rats should be allowed to regain their pre-operative body weight before blood samples are taken. See this technique below.

Rat surgical cannulation blood vessel trimmed 2 copyright NC3Rs from NC3Rs on Vimeo.

The cannula is exteriorised at the nape of the neck (through a jacket and tether system) or the base of the tail (via a tail cuff and tether system). The use of a tail cuff is preferable to a jacket as the percentage of adverse effects has been found to be 1% of animals with the tail cuff compared to 5-10% for jacketed models. The tail cuff model also has minimal weight loss after surgery, whilst in the jacketed model the rat takes at least 24 hours to regain pre-operative weight. The use of a subcutaneous access port should be explored as it can eliminate the need for tethering systems during periods when animals are not being sampled from.

The jacket and tether system can restrict free movement and rats may need to be housed singly after surgery. The caging, bedding and environmental enrichment need to be appropriate to prevent the tether becoming entangled and the wound contaminated. In addition, the bedding needs to be sange free.

The cannula is small, which can promote blood clotting (larger cannulae can abrade the blood vessel wall). To prevent this, the cannula requires regular maintenance, (e.g. flushing with an anticoagulant).

Blood should be collected aseptically. Usually 0.1 - 0.2 ml can be taken per sample, and depending on the sample volume and scientific justification, up to six samples over a two hour period or up to 20 samples over a 24-hour period may be taken. Sterile saline with anticoagulant should be flushed into the cannula after blood sampling to prevent the blood from clotting. A pin is then inserted into the exteriorised end of the cannula, which stops the blood from flowing. A sterile locking solution can be used to lock the cannula after a series of samples have been taken, allowing flushing to be avoided for a number of days.

The following should be checked daily

  • The skin in contact with the jackets should be checked for abrasion.
  • The jacket should be checked for tightness.
  • The tail cuff should be checked for tightness and the tail for swelling.
  • Wound sites should be checked for infection/bruising/swelling/haemorrhage.
  • The cannula should be checked for patency.
  • The weight of the rat (for recovery work).

Summary

Number of samples Depending on sample volume, up to six samples may be taken in a two hour period or up to 20 samples over a 24-hour period. 
Sample volume 0.1 - 0.2 ml
Equipment 23G - 25G cannula
Staff resource One person is required to take the blood sample. However, further staff resource is required for surgery, post-operative care for up to five days after surgery, and daily animal observations post-surgery.
Adverse effects
  • Infection: 5-10% with jacketed rats, 1% with tail cuffs.
  • Haemorrhage: 5-10% with jacketed rats, 1% with tail cuffs.
  • Blocked cannula: 5-10% with jacketed rats, 1% with tail cuffs.
  • Swelling around the jacket: 5-10% with jacketed rats, 1% with tail cuffs.
  • Skin sores from the jacket: 5-10% with jacketed rats, 1% with tail cuffs.

Resources and references

Blood vessel cannulation in other animals

Click here for information on blood vessel cannulation in the mouseClick here for information on blood vessel cannulation in the guinea pigClick here for information on blood vessel cannulation in the ferret

All blood sampling techniques in the rat

Click here for information on tail vein blood sampling 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