Collection of Blood

Venous blood is most readily obtained from the left or right jugular vein, although cephalic, saphenous and lateral thoracic venipuncture may also be used on occasion.

The horse should be restrained by head stall and lead rope for the safety of operators. Occasionally brief application of a nose twitch may be required to facilitate collection.

Blood may be collected by aspiration into appropriate size syringes, or collected directly into Vacutainer(s) with appropriate anticoagulants, or plain tubes for serum.

Needles should be 21G, 20G, 19G or 18G, 1 to 1.5 inches. Smaller needles are likely to cause excessive haemolysis.

Collection of large volumes of blood (for example, for transfusion) has been described previously. Larger needles or intravenous catheterisation, which may be required for collection of large volumes, may require subcutaneous administration of local anaesthetic and are not covered in this SOP.

Generally blood collection should be ≤ 8L every 30 days. Donors should have a PCV of 35 to 40% if large volumes of blood (>1L) are to be collected.

Skin Preparation

Routine blood collection requires a clean (not ‘sterile’) access site: the hair over the vein should be cleared of gross contamination such as excessive dust or mud. Alcohol alone is insufficient for disinfecting skin, but may make the vein more visible. If a sterile sample is required, full surgical preparation (clip, scrub three times alternatively with chlorhexidine or iodine scrub, wipe with ethanol/methanol) should be performed immediately
prior to collection.

After collection transient pressure should be applied to the skin (until no evidence of cutaneous bleeding) to reduce haematoma formation.

Drugs, chemicals or biological agents

None.

Impact of procedure on well being of animal or animals

Minimal – transient restraint and minimal discomfort.

Reuse and repeated use

Repeated sampling (as a guide, greater than every 30 minutes or more than five samples in a 24 hour period) is best achieved by use of an indwelling catheter. Care should be taken to ensure that catheter and tubing deadspace is purged of saline (discard volume equivalent to deadspace) prior to sampling, and the catheter should be flushed with heparinised saline (1-5 IU/mL) after each collection. Strict aseptic care of the catheter and extension tubing should be maintained if sampling from an indwelling catheter.

Care of animals during / after procedure(s)

Distress to animals is best reduced by efficient sampling by an experienced operator. Needle penetration of the skin has the potential to cause discomfort: repeated ‘stabs’ should be avoided – if the vein is not accessed immediately the needle should be redirected without
withdrawal if possible.>

Pain relief measures

None.