Guidelines for Blood Withdrawal

Guidelines for
Blood Withdrawal

The type of test and amount of blood needed will govern the method and sites of collection. When venipuncture is required, hair should be clipped from the site and the area should be cleaned with alcohol. When collecting blood from the rabbit ear or mouse tail vein, heat (warm water bath) or xylene applied to the area may be helpful. Note: xylene is a dermal inflammatory agent and must be cleaned off with alcohol and water after blood collection is completed.

After occluding the vein manually or by tourniquet, the needle is inserted parallel to the vein and the tip directed into the lumen along the longitudinal axis. When withdrawing blood, slow and gentle aspiration helps prevent collapse of the vein. Gauze held firmly in place at the blood collection site for a few minutes after withdrawal of the needle, will prevent the formation of hematomas.

The following tables list common blood withdrawal sites and recommended needle length and gauge for use in laboratory animals.

Note: Heart puncture and orbital bleeding are acceptable only if the animal is properly anesthetized. Laceration of the marginal ear vein of rabbits is considered to be unnecessarily traumatic and is frequently associated with post-procedural hemorrhage. Heart puncture should be limited to terminal procedures with the exception of the guinea pig.

ANIMAL	SITE	VOLUME OBTAINED*	NEEDLE GAUGES
Cat (5 kg)	Cephalic vein Jugular vein	6 - 12 ml 20 ml	1" 22 ga 1" 18 ga
Cattle	Jugular vein	600 ml	1½" 14-18 ga
Dog (20-25 kg)	Cephalic vein Saphenous vein Heart Jugular vein	6 - 12 ml 6 - 12 ml 80 - 120 ml 20 ml	1" 20-22 ga 1" 20-22 ga 1-1½" 18 ga 1" 18 ga
Domestic Fowl	Brachial Vein	5 - 10 ml	22 ga
Gerbil	Heart**	1.5 - 2.5 ml	5/8" 25 ga 1" 22 ga
Goat	Jugular vein	600 ml	1½" 18-20 ga
Guinea Pig	Heart** Saphenous vein (D)	5 ml 0.5 ml	1-½" 22 ga 5/8" 27 ga
Hamster	Heart**	1.5 - 2.5 ml	5/8" 25 ga
Monkey	Cephalic vein, saphenous vein, femoral vein, jugular vein	5 - 10 ml	1" 22 ga
Mouse	Heart**, tail vein, (D), retro-orbital plexus (least preferred & will required justification)	0.2 - 0.5 ml	5/8" 25 ga 5/8" 27 ga
Pigeon	Heart**, anterior vena cava, wing vein	1 - 3 ml	5/8" 25 ga
Rabbit (SEE NOTE BELOW)	Heart** Marginal ear vein Central artery of ear	50 - 80 ml 1 - 3 ml 30 - 50 ml	1-½" 18 ga 1" 22 ga 1" 23 ga
Rat	Heart** Retro-orbital plexus Tail vein (D) Saphenous vein (D)	5 ml 0.5 - 1 ml 0.5 - 1 ml 0.5 - 1 ml	1" 22 ga Hct tube 5/8" 25 ga 5/8" 25 ga
Sheep	Jugular vein	600 ml	1½" 16 -18 ga
Swine	Anterior vena cava Jugular vein Ear vein	5 - 50 ml 1 - 25 ml 1 - 3 ml	3-4½" 16 ga 1½" 20 ga 1" 20-22 ga

KEY
    D = Difficult

   * Safely take 10% of blood volume followed by a rest of 2-3 wks. Total blood volume for the animal is generally calculated as being 10% of body weight.

    **All heart bleeding techniques are dangerous and must be performed under general anesthesia. This method would only be applied as a terminal event in most species. The guinea pig is generally excepted because of the lack of other bleeding sites, but expect relatively high mortality.

NOTE: Not all blood collection methods are the same in all species, and in some cases will require justification. As example, there are numerous methods of blood collection in mice, each with their own advantages and disadvantage. Retro-orbital bleeding is a good method in some cases, but due to its invasive nature will require justification over other less invasive methods. More more discussion and recommendation, please email a DLAR veterinarian by clicking this link.

RABBITS: To withdraw a large volume of blood, the following parameters are of importance. The estimated total blood volume of a NZW rabbit is approximately 6% (range: 5-8%) of the body weight. Another estimate in the literature is 56 ml blood/kg body weight. Up to 2% of the body weight (25-33% of the blood volume) can safely be removed at one bleeding. A 14 to 21 day recovery period is recommended before repeating this procedure. For repeated smaller samplings, 20 ml of blood can be removed from an average NZW rabbit (3.5-4.0 kg) every 24 hours without causing debilitation. This could be continued until anemia developed, defined as a hematocrit of less than 36%. Since the rate at which anemia develops will vary from rabbit to rabbit it is essential that a hematocrit be run prior to each blood withdrawal. The microhematocrit method is preferred. A 14 to 21 day rest is recommended to restore the hematocrit to normal.