Collecting Blood from Lab Animals
- Overview
- Restraint
- Blood Collection Volumes
- Single Blood Draw
- Multiple Blood Draws
- Monitoring
- Terminal Blood Withdrawal
- Rabbit Bleeding
- Common Sites for Blood Collection
Overview
Guidelines for safe blood withdrawal for laboratory mammals takes into account the fact that each species has a different blood volume to body weight ratio measured in milliliters of blood to kilogram of body weight. These guidelines are for normal, healthy adult animals. Animals that are young, aged, stressed, have undergone experimental manipulations, or are suffering from cardiac or respiratory disease may not tolerate this amount of blood loss.
Blood Collection techniques must be described in the Animal Care and Use Application.
Restraint
Appropriate instruction for all species can be obtained from Veterinary Services, 824-5079.
- Dogs, Cats, and Sheep: usually require only physical restraint to collect blood.
- Swine: may require only physical restraint if they have been trained to the procedure. Otherwise, chemical restraint or sedation is recommended.
- Rabbits, Mice and Rats: may be placed in appropriate restraining devices or chemically restrained with anesthetics or sedatives.
- Birds: usually require only physical restraint to collect blood.
Anesthesia is required to perform blood collection from the rodent orbital sinus or by cardiac puncture because of the pain involved in the procedure and the potential for complications (including cardiac tamponade and death, or injury to the eye). In rare instances, if the IACUC is satisfied an individual is extremely proficient in orbital sinus bleeding of rodents, permission may be granted for an individual to collect blood without anesthesia.
Blood Collection Volumes
Approximate blood volumes:
- 1 percent of body weight = maximum volume per collection every two weeks.
- 3 percent of body weight = amount expected of exsanguination.
- 5-10 percent of body weight = total blood volume.
Single Blood Draw
A maximum of 1% of the animal's body weight may be removed as a single blood draw. For example:
- 0.15 ml from a 15 gram mouse
- 50 ml from a 5 kg cat
- 400 ml from a 40 kg dog.
Approximately 14 days are needed for the average healthy adult animal to completely recover from this blood loss. Although the blood volume is restored within 24 hours, two weeks are needed for all blood constituents to return to normal. As a rule, an animal will replace blood constituents at a rate of 1 ml/kg/day.
Multiple Blood Draws
If blood must be drawn more frequently than once every two weeks, 0.05% of the animal's body weight may be removed each week. This volume may be divided into several draws.
Collecting blood by lacerating ear or tail vessels is prohibited. These procedures are more painful than needle puncture and there is greater risk of lacerating an artery with subsequent hemorrhage. However, for rodents, laceration of the saphenous vein is preferable to orbital sinus bleeding. (See http://www.uib.no/dyreavd/Vivarium-blood-sampling.pdf)
Regardless of the method of collection used, an animal may not be returned to its cage until complete hemostasis at the collection site has been achieved. Hemostasis may be achieved using gauze and direct pressure. Up to several minutes of pressure may be required following arterial puncture.
Monitoring
By monitoring the hematocrit (Hct or packed cell volume-PCV) and/or hemoglobin of the animal, it is possible to evaluate whether the animal has sufficiently recovered from a single or multiple blood draws. After a sudden or acute blood loss, it takes up to 24 hours for the hematocrit and hemoglobin to reflect this loss. In general, if the animal's hematocrit is less than 35 percent or hemoglobin concentration is less than 10 g/dl it is not safe to remove the volume of blood listed above.
Terminal Blood Withdrawal
Terminal bleeds are only allowed on animals under general anesthesia, and the animal's death must be verified at the end of the bleed. An alternative euthanasia method is recommended after the blood withdrawal.
A general rule: An animal's blood volume is 10 percent of its body weight, and only about half of that can be recovered when the animal is bled out. Therefore, as a terminal bleed, 5-6 percent of an animal's body weight is a reasonable amount of blood (ml) that may be collected at exsanguination.
Rabbit Bleeding for Polyclonal Service and Investigators
Blood volume limits need to be considered in blood collection because overbleeding can leave the animal hypovolemeic, anemic, weak and susceptible to disease and death. Total blood volume is approximatly 6% of body weight. As a guideline up to 20% of blood volume can be taken from a rabbit every two weeks HWEVER this is not recommended by ULAR and necessitates fluid replacement. A safer 10% blood volume taken within two weeks is recommended.
A guideline is 200 mls blood volume of an average adult reabbit—20 mls in two weeks is 10%&emdash;40 mls in two weeks is 20%.
ULAR may decide to run blood tests on a Polyclonal Antibody Service rabbit and even this conservative schedule may have to be limited on an individual rabbit.
Common sites for Blood Collection
| Species | Site of Collection and Permitted Conditions |
|---|---|
| Mouse(2) | cardiac,(1) orbital sinus (anesthetized only), tail vein, saphenous vein |
| Rat(2) | as with mouse, plus subclavian veins Guinea Pig cardiac,(1) anterior vena cava/subclavian vein |
| Rabbit | cardiac,(1) marginal ear vein. It is often helpful to apply a vasodilator on the ears of rabbits prior to collecting blood, such as oil of wintergreen (methyl salicylate). |
| Dog & Cat | cephalic, saphenous veins, femoral and jugular veins |
| Ruminants | jugular vein |
| Swine | jugular vein, anterior vena cava, ear veins |
| Chicken | brachial vein, right jugular vein, cardiac(1) |
1 Cardiac puncture for blood collection must be performed as a terminal event, and the animal must be under general anesthesia.
2 Tail cutting in rodents: Lancing blood vessels in the tail and cutting the distal tip of the tail are not acceptable methods of blood collection in rodents. IACUC approval is required prior to performing these procedures in rodents.
