How Much Blood can you draw on Dogs
IACUC Policy for Blood Collection in Laboratory Animals
Approximate Blood Volume
5-10% of body weight= total blood volume
- The circulating blood volume can generally be estimated as 55-70 ml/kg of total body weight. However, care should be taken in these calculations as the % of total blood volume will be lower (-15%) in obese and older animals.
Blood Collection Volumes
1% of body weight = maximum volume withdrawn over 14 days, without requiring supplemental fluids. This applies for total blood collections as well as repeated collections. For irregular sampling schedules, calculate the total amount needed over a 14 day span.
0.07% of body weight = amount that can be taken daily without requiring supplemental
fluids.
4-5% of body weight = amount expected at exsanguination.
Single Blood Draw
Maximum of 1% of body weight can be removed as a single blood draw every 14 days,
without requiring administration of supplemental replacement fluids. Withdrawing the minimum amount of blood necessary is strongly recommended. Examples:
0.15 ml from a 15 g mouse
3 ml from a 300 g rat
30 ml form a 3 kg rabbit
Multiple Blood Draws
If the total volume withdrawn over a 14 day period is less than 1% BW, than no additional action needs to be taken.
If the total volume withdrawn over a 14 day period is up to 2% BW, fluid volume replacement must be considered. Withdrawing the minimum amount of blood necessary is strongly recommended. Examples:
o Up to 0.15 ml withdrawn from a 15 g mouse over 2 weeks is OK
o Up to 0.3 ml withdrawn from a 15 g mouse over 2 weeks, replace volume with
0.3 ml saline SC
o Up to 3 ml from a 300 g rat over 2 weeks is OK
o Up to 6 ml from a 300 g rat over 2 weeks, replace volume with 6ml saline SC
o Up to 30 ml from a 3 kg rabbit over 2 weeks is OK
o Up to 60 ml from a 3 kg rabbit over 2 weeks, replace volume with 60 ml saline SC or IV
o As a helpful guideline, daily blood draws under 0.07% BW will keep the total 2-week withdrawal under 1% BW.
Monitoring
If too much blood is withdrawn too rapidly or too frequently without replacement (approximately 2% of the animal’s body weight at one time), the animal may experience hypovolemic shock. If signs of shock are observed, contact LAR veterinary staff immediately. Signs of shock include:
Fast and thready pulse
Pale dry mucous membranes
Cold skin and extremities
Restlessness
Hyperventilation
Sub-normal body temperature
If 15-20% of total blood volume is removed, cardiac output and blood pressure will be reduced.
If 30-40% of total blood volume is removed, death will result in at least 50% of animals.
If >40% of total blood volume is removed, death of the animal is expected.
Stressed, sick, or otherwise compromised animals may not tolerate the blood collection criteria noted above, which is for healthy animals. By monitoring hematocrit (HCT or PCV) and/or hemoglobin (Hb) it is possible to evaluate if the animal has sufficiently recovered from single or multiple blood draws. Remember it may take up to 24 hours for hematocrit or hemoglobin to reflect a sudden or acute blood loss. In general, if the animal is anemic (below the normal PCV range for the species), or if the hemoglobin concentration is less than 10 g/dL, it is not safe to remove the volumes of blood listed above.
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