Retro-orbital

Technique

Also referred to as peri-orbital, posterior-orbital and orbital plexus bleeding. Retro-orbital bleeding should typically be performed as a terminal procedure. It should only be used with recovery in rare circumstances with exceptional scientific justification (e.g. where a large blood volume is necessary or where peripheral veins are used for dosing), because of its potential impact on animal welfare.

Where its use is unavoidable, retro-orbital bleeding should only be used under general anaesthesia. Because of the severity of the adverse effects that can occur with this technique, even in skilled hands, it is essential that it is conducted only by staff members competent (practiced) in the technique.

Blood is collected from the venous plexus. The hamster is restrained, the neck gently scruffed and the eye made to bulge. A capillary tube/pipette is inserted medially, laterally or dorsally. Blood is allowed to flow by capillary action into the capillary tube/pipette. The sample obtained is a mixture of venous blood and tissue fluid, and is not representative of venous blood.

Blood flow can be stopped by applying gentle finger pressure to the soft tissue. A finger should be placed over the closed eyelid for approx. 30 seconds. The hamster should be checked for post-operative peri-orbital lesions approximately 30 minutes after blood sampling and on at least one more occasion within two hours of the sampling.

Sequential sampling is not recommended as histological changes, abnormal clinical signs and evidence of discomfort have been reported. Ideally, no more than one bleed per eye should be taken - where a second retro-orbital bleed is required this should be performed as a terminal procedure. In rare circumstances where there is exceptional scientific justification sequential sampling may be used. In such instances only one orbit should be sampled from at any one sampling time. Adequate time should elapse between sampling to allow peri-orbital tissue repair to take place. An interval of two weeks between bleeds should allow damaged tissue to repair in most cases.

Summary

Number of samples It is recommended that only one sample be taken.
Sample volume 0.1-0.5 ml
Equipment A glass capillary tube or Pasteur pipette.
Staff resource One person is required to take the blood sample.
Adverse effects
  • Tissue damage
  • Histological changes, abnormal clinical signs and evidence of discomfort have been reported for repeated bleeds.
Other Careful monitoring for adverse effects is necessary peri-operatively.

Resources and references

Retro-orbital sampling in other animals

Click here for information on retro-orbital blood sampling techniques in the mouseClick here for information on retro-orbital blood sampling techniques in the rat

All blood sampling techniques in the hamster

Click here for information on saphenous vein blood sampling in the hamster Click here for information on cardiac puncture blood sampling with recovery in the hamsterClick here for information on cardiac puncture blood sampling in the hamster