Cranial vena cava

Technique

Pigs are intelligent and can be trained to accept handling and restraint. They will remember receiving a reward (e.g. food treat) after the procedure, which can make them easier to handle during subsequent procedures.

Sampling from the cranial vena cava is suitable for all breeds commonly used, including the large white and Göttingen minipig, and 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, although minipigs have small ear veins which can collapse if too much vacuum is applied when withdrawing the sample. Sampling from the cranial vena cava is not suitable for taking multiple samples and a catheter (either surgical or percutaneous) should be used for repeated sampling.

The technique should be carried out aseptically. To limit injury and bruising at the sampling site no more than three attempts should be made. 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. 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 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 people is sufficient for minipigs and pigs that are used to the procedure.
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