Cranial vena cava

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

Technique

Sampling from the cranial vena cava is suitable for all breeds commonly used, including the large white and minipig. It is the best technique for taking a single blood sample from a pig at any one time. It can be used to obtain a relatively large volume of blood (e.g. >20 ml). For smaller volumes, the peripheral ear veins of the pig can be used, or saphenous cannulation when repeat sampling is required. Sampling from the cranial vena cava is not suitable for taking multiple samples as repeated sampling from this area will result in hematoma or blood clot formation in the thoracic inlet. Multiple samples can be collected via the jugular vein or use of a catheter (either surgical or percutaneous).

The pig needs to be restrained for sampling and this can be stressful. Stress can be minimised by training the animal to cooperate with the procedure and by conducting it in a quiet environment. Pigs are intelligent animals and will remember receiving a reward (e.g. food treat) after the procedure, which can make them easier to handle on subsequent occasions. Positive reinforcement training should be used where possible for all procedures from weighing to procedural work to minimise stress to technician and pig.

The technique should be carried out aseptically. To limit injury and bruising at the sampling site no more than three attempts should be made. Small pigs should be held in a supine position; head and neck straightened out and front limbs drawn backwards. An adjustable V-shaped cushioned restrainer, or sling, can help hold the animal in position. Large pigs (>15kg) can be bled whilst standing (a snout rope is positioned behind the canine teeth and the neck lifted upwards). If it is necessary to place the animal in dorsal recumbency, this should be for the minimum length of time possible; five minutes should be sufficient time to collect a sample. Inhaled anaesthesia may be used if the animal needs to be restrained for longer (up to 20 minutes).

The needle is inserted at a 45o angle into the vena cava approximately 1" (0.5 1" for minipigs) cranial to the sternum a little lateral and to the right of the midline. Blood flow should be stopped by applying finger pressure on a gauze pad or other absorbent material placed on the blood sampling site for between 30 seconds and two minutes. The pig should not be returned to its pen until the blood has stopped flowing.

Summary

Number of samples

Usually one in seven days.

Sample volume

5 - 30 ml, depending on the size of pig. A vacutainer system can be used to collect small samples (e.g. down to 3 ml of blood).

Equipment

19G - 21G needles for pigs and 20 - 21G needles for minipigs (1" long for minipigs/young pigs and 2" long for larger/older pigs).

Staff resource

Four people are required, three to hold the pig in position (head, stifle and front legs) and one person to take the blood sample. Two to three people are sufficient for minipigs, pigs that are used to the procedure or pigs in slings.

Adverse effects

  • Bruising
  • Infection <1%
  • Haemorrhage <1%

Other

Pigs should be trained to cooperate with blood sampling in order to minimise stress. A reward (e.g. food treat) should be given, where possible, after the procedure.

When sampling from large pigs, correct positioning of the snout rope is important to reduce the potential for injury to the mouth and undue pressure on sensitive nasal tissues.

 

Resources and references

Cranial vena cava sampling in other animals 

This technique is only appropriate for use in the pig.

All blood sampling techniques in the pig

Click here for information on ear vein sampling in the pig