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NC3Rs: National Centre for the Replacement Refinement & Reduction of Animals in Research
Guidance

Blood sampling: Guinea pig

Approaches for sampling blood in the guinea pig, covering non-surgical, surgical and terminal techniques.

General principles

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

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 guinea pig 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. Proper aseptic technique should be used to prevent post operative infection.  Guinea pigs should be allowed to regain their pre-operative body weight before blood samples are taken. See this technique below.

The cannula is exteriorised at the nape of the neck (through a jacket and tether system). The jacket can cause swelling and skin abrasion and guinea pigs require regular and detailed observation to identify any problems. The use of a subcutaneous access port may be more appropriate because they 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 the guinea pigs 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 sand free.

Small cannulas will increase the risk of blood clotting  (large cannulae can abrade the blood vessel wall). To prevent this, the cannula requires regular maintenance, (e.g. Regular flushing with an appropriate lock solution. See our preventing thrombosis section for more information).

Blood should be collected aseptically. Usually, 0.1 - 0.5 ml can be taken per sample. Depending on the sample volume and scientific purpose, 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: 

  • Skin in contact with the jackets should be checked for abrasion.
  • The jacket should be checked for tightness.
  • Wound sites should be checked for infection/bruising/swelling/haemorrhage.
  • The cannula should be checked for patency (without blockage).
  • The weight of the guinea pig (remember weight will include that of the device).

Changes in any of the above may require veterinary advice or treatment, or may indicate that a humane endpoint has been reached and appropriate action should be taken.

Summary

Consideration Recommendation
Number of samples It is recommended up to six samples may be taken in a two hour period, depending on sample volume.
Sample volume 0.1 - 0.5 ml
Equipment 23G - 25G cannula
Staff resource One person is required to take the blood sample. Further staff resource is required for surgery, post-operative care for as long as necessary for the individual animal, and daily animal observations post-surgery.
Adverse effects
  • Infection 1-5%
  • Haemorrhage 1-5%
  • Blocked cannula 1-5%
  • Swelling around the jacket 1-5%
  • Skin sores from the jacket 1-5%

Be sure to use our advice on vascular catheters to reduce the incidence of adverse effects.

Other Guinea pigs should be at their pre-operative weight before blood sampling starts.

Resources and references

  1. Nau R and Schunck O (1993). Cannulation of the lateral saphenous vein-a rapid method to gain access to the venous circulation in anaesthetized guinea pigs. Laboratory Animals 27(1): 23-5. doi: 10.1258/002367793781082449
  2. Birck MM et al. (2014). Non-terminal blood sampling techniques in guinea pigs. Journal of Visualized Experiments: JoVE 92: 51982. doi: 10.3791/51982
  3. Gunaratna PC et al. (2004). An automated blood sampler for simultaneous sampling of systemic blood and brain microdialysates for drug absorption, distribution, metabolism and elimination studies. Journal of Pharmacological and Toxicological Methods 49(1): 57-64. doi: 10.1016/S1056-8719(03)00058-3
  4. Nolan TE and Klein HJ (2002). Methods in vascular infusion biotechnology in research with rodents. Institute for Laboratory Animal Research Journal 43(3): 175-82. doi: 10.1093/ilar.43.3.175

 

Tarsal vein (non-surgical)

Technique

This technique is suitable for all strains of guinea pig but is difficult to perform and, given the high degree of haemorrhage in the subcutaneous tissue, should be avoided unless there is good scientific justification.

The tarsal vein is easily accessible. The guinea pig is held and the foot restrained. Gentle pressure is applied by massaging above the point (proximally to the animal) at which the blood sample is taken to dilate the vessel. A maximum of three samples can be taken from each hind leg and 0.1 - 0.3 ml of blood can be collected per sample. Samples should be rotated between the hind legs and should be removed first distal to the animal (between the toes) and moved proximally to the animal (towards the ankle). No more than six samples, using both the hind legs should be taken in any 24-hour period. If more blood is needed, other forms of blood sampling should be used, such as surgical cannulation. The number of attempts to take a blood sample should be minimised (no more than two needle sticks in any one attempt). 

The technique should be performed aseptically, including removal of hair around the sampling site with a trimmer and sterilising the sampling area. Some haemorrhage in the subcutaneous tissue surrounding the vessel is unavoidable and it can be difficult to stem the blood flow after the blood sample has been taken. Finger pressure on soft tissue for approximately two minutes should be applied to the sampling site and the animal should not be returned to its cage until bleeding stops. Return the animal to a clean cage can reduce the risk of infection.

Summary

Consideration Recommendation
Number of samples No more than six blood samples should be taken in any 24-hour period.
Sample volume 0.1 - 0.3 ml
Equipment 23G needle or lance
Staff resource Two people are required, one to take the blood sample and the other to restrain the guinea pig.
Adverse effects
  • Skin abrasion from the shaving 5%
  • Bruising
  • Infection <1%
  • Haemorrhage 75%
Other Good animal handling is required to restrain the guinea pig for both the shaving and taking the blood sample.

Resources and references

  1. Birck MM et al. (2014). Non-terminal blood sampling techniques in guinea pigs. Journal of Visualized Experiments: JoVE 92: 51982. doi: 10.3791/51982

 

Saphenous vein (non-surgical)

Technique

Sampling from the lateral saphenous vein is a relatively quick method of obtaining blood samples from all strains of guinea pig. It does not require the animal to be warmed.

Slides and videos of restraint, shaving and sampling for this technique with mice are available on the websites of the Norwegian Reference Centre for Laboratory Animal Science.

Blood is collected from the lateral saphenous vein, which runs dorsally and then laterally over the tarsal joint. 

Conscious guinea pigs should be restrained either manually or using a restraint tube. This can cause stress and therefore the duration of restraint should be minimised. Where a restraint tube is used, it should be appropriate for the size of the guinea pig. All forms of restraining equipment should be frequently washed to prevent pheromonally-induced stress or cross-infection.

To collect blood, the hind leg should be immobilised in the extended position by applying gentle downward pressure immediately above the knee joint. This stretches the skin over the ankle, making it easier to clip and immobilise the saphenous vein. Please note that hair removal by shaving with a scalpel blade is no longer recommended as it removes the epidermal layers of the skin. An aseptic technique should be used. Anaesthesia is not necessary but may be used on welfare grounds for animals that are difficult to hold. Where sedatives contain peripheral vasodilators, doses should be low to avoid prolonged bleeding from the puncture site. The number of attempts to take a blood sample should be minimised (no more than three needle sticks in any one attempt). Blood is collected by capillary action into a haematocrit tube or passively into a tube.

Blood flow can be stopped by gentle finger pressure over the puncture site, or simple relaxation of the operator's grip on the animal's leg. Animals should not be returned to their cage before the blood flow has stopped.

No more than four blood samples should be taken within any 24-hour period. If more samples are needed, then temporary or surgical cannulation should be considered. The scab or blood clot is removed for multiple samples.

Guinea pigs may show temporary favouring of the limb following sampling from the saphenous vein.

Summary

Consideration Recommendation
Number of samples No more than four blood samples should be taken within any 24-hour period, depending on sample volumes.
Sample volume A single sample equivalent to 0.5% of the animal's bodyweight may be taken, which can usually be repeated at fortnightly intervals without disturbances to its haematological status. Alternatively, daily samples corresponding to 0.05% bodyweight may be taken.
Equipment 23G needle or lance
Staff resource One person is required if a restraint tube is used. Where manual restraint is used two people may be required: one for handling the guinea pig and one for taking the blood sample.
Adverse effects
  • Bruising
  • Haemorrhage
  • Infection
  • Temporary favouring of the limb

Resources and references

  1. Birck MM et al. (2014). Non-terminal blood sampling techniques in guinea pigs. Journal of Visualized Experiments: JoVE 92: 51982. doi: 10.3791/51982
  2. Hem A et al. (1998). Saphenous vein puncture for blood sampling of the mouse, rat, hamster, gerbil, guinea pig, ferret and mink. Laboratory animals 32(4): 364-8. doi: 10.1258/002367798780599866
  3. Diehl KH et al. (2001). A good practice guide to the administration of substances and removal of blood, including routes and volumes. Journal of Applied Toxicology 21(1): 15-23. doi: 10.1002/jat.727

 

Abdominal/thoracic blood vessel (terminal)

Technique

Appropriate for all strains, this is a suitable technique to obtain a single, large, good quality blood sample from a euthanised guinea pig or a guinea pig under terminal anaesthesia. A sample volume of 10 - 15ml can be collected depending on the size of the guinea pig. As the heart is not punctured, this technique can be used where it is necessary to avoid cardiac damage.

Blood is collected either from the abdominal aorta, caudal or dorsal aorta or vena cava via a laparotomy or thoracotomy. Removal of connective tissue and application of finger pressure may be necessary to dilate the vessel. Blood should be withdrawn slowly to prevent the vessel collapsing. Deep surgical anaesthesia is necessary and correct aseptic technique should be used.

Summary

Consideration Recommendation
Number of samples One
Sample volume Up to 15 ml, depending on the size of the guinea pig.
Equipment 19G - 21G needle
Staff resource One person is required to take the blood sample.

Resources and references

  1. Parasuraman S et al. (2010). Blood sample collection in small laboratory animals. Journal of Pharmacology and Pharmacotherapeutics 1(2): 87-93. doi: 10.4103/0976-500X.72350
  2. Morton DB et al. (2001). Refining procedures for the administration of substances. Laboratory animals 35(1): 1-41. doi: 10.1258/0023677011911345

 

Cardiac puncture (terminal)

Technique

Cardiac puncture should not be used if the peritoneum needs to be lavaged to harvest cells, as this technique can cause blood to escape into the peritoneal cavity.

Cardiac puncture is a suitable technique to obtain a single, large, good quality sample from a euthanised guinea pig or a guinea pig under deep terminal anaesthesia if coagulation parameters, a separate arterial or venous sample or cardiac histology are not required. It is appropriate for all strains of guinea pig.

A sample of 1-25 ml of blood can be obtained depending on the size of the guinea pig and whether the heart is beating. Blood samples are taken from the heart, preferably the ventricle, either via a thoracotomy or the left side of the chest. Blood should be withdrawn slowly to prevent the heart collapsing.

Summary

Consideration Recommendation
Number of samples One
Sample volume 1 - 25 ml, depending on the size of the guinea pig
Equipment 20 - 21G needle
Staff resource One person is required to take the blood sample.

Resources and references

  1. Parasuraman S et al. (2010). Blood sample collection in small laboratory animals. Journal of Pharmacology and Pharmacotherapeutics 1(2): 87-93. doi: 10.4103/0976-500X.72350
  2. Morton DB et al. (2001). Refining procedures for the administration of substances. Laboratory animals 35(1): 1-41. doi: 10.1258/0023677011911345

 

Schedule 1 stunning and decapitation (terminal)

Technique

This is a Schedule 1 method of euthanasia and should be carried out by people competent in this method. Training for stunning and decapitation should be undertaken on dead animals.

The primary reason for carrying out this technique is to obtain a large volume of blood which has not been affected by anaesthetic drugs or carbon dioxide. A large volume of blood can be collected from the trunk if necessary.

Suitable for all strains, this technique should only be used in rare circumstances and with exceptional scientific justification. The ASPA limits its use to rodents of body weight 1 kg or less. The guinea pig must be determined as dead before decapitation can take place (see Section 1(4) of the ASPA).

Summary

Summary Recommendation
Number of samples One
Blood volume 10 - 20 ml
Equipment Suitable sharp instrument to decapitate, (e.g. guillotine or sharp scissors).
Staff resource One person is required to take the blood sample.
Other A high level of expertise is required for this technique.

For more information on this protocol and whether it is appropriate for your scientific purposes, please consult your department's named veterinary surgeon.

 

Decapitation (terminal)

  • Technique
  • Summary
  • Resources and references

Technique

This technique should only be used in rare circumstances with exceptional scientific justification. In the UK this technique is not a Schedule 1 method of euthanasia and therefore personal and project licence authority is required.

Trunk blood is collected from the site where the animal is decapitated, under deep terminal anaesthesia. It should be noted there is a risk of contamination from other body fluids and tissues. Training for decapitation should be undertaken on dead animals.

Summary

Consideration Recommendation
Number of samples One
Blood volume Up to 10 ml
Equipment Suitable sharp instrument to decapitate (e.g. guillotine or sharp scissors).
Staff resource One person is required to take the blood sample.
Other A high level of expertise is required for this technique.

For more information on this protocol and whether it is appropriate for your scientific purposes, please consult your department's named veterinary surgeon.

 

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

Five needles with empty syringes on a pale blue background

Blood sampling resources