Video: Blood collection in ferrets
Video created and narrated by Dr. M. Scott Echols.
All but the weakest ferrets (Mustela putorius furo) can be challenging to restrain for blood collection. Consider sedation with midazolam (midazolam 0.25- 1.0 mg/kg IM) or general anesthesia, using isoflurane or sevoflurane, particularly if the handler or phlebotomist is relatively inexperienced.
Remember that anesthesia can affect ferret hematology. Ferrets anesthetized with isoflurane exhibit a rapid decrease in hematocrit, hemoglobin, and red blood cell count. These values do not return to pre-anesthetic levels for approximately 45 minutes.
Syringe and needle size will vary with the vessel selected (Fig 1).
- Depending on the vessel used, select a 22- to 30-gauge needle.
- Use a small syringe (0.5 to 1.0 ml) to reduce the risk of collapsing smaller veins.
- A 3-ml syringe can be used for the jugular vein and cranial vena cava in larger ferrets.
Ferret skin is relatively thick, especially over the neck, so if you are not able to collect a sample on your first try be prepared to use a fresh needle each time.
Place blood samples into microtainers (BD Microtainer Blood Collection Tubes; Becton Dickinson and Company, Franklin Lakes, NJ) (Fig 2).
The total volume of blood that can be safely collected typically ranges from 0.5% to 1.0% of body weight.
Example: A maximum of 10 ml can be collected from a 1000-gram healthy ferret.
Collect smaller volumes (0.5% BW) from geriatric and anemic, hypoproteinemic or otherwise
Recommended venipuncture sites
The jugular vein is the most common venipuncture site in the ferret.
- Restrain patients in dorsal or lateral recumbency with the head extended and the legs pulled down toward the body.Ferrets can also be held in sternal recumbency at the edge of the exam table like a cat (Fig 3). Take care not to overextend the neck as this will flatten out the vessel.
- When compared to the cat, the ferret jugular vein tends to lie in a more lateral position. Clipping the fur can help to identify the vein.
- Insert the needle bevel up; be prepared to encounter tough ferret skin.
- Collect the blood sample as usual (Fig 4).
- Afterwards gently remove the needle, and apply firm, steady pressure
A third option for jugular venipuncture is described as follows:
- Restrain the ferret in a scruffed position with the feet dangling (Fig 5). The handler also holds the forearms back, by the ferret’s side.
- A second handler restrains holds the hips.
- The phlebotomist then palpates the same landmarks as described for the cranial vena cava described below (point of the shoulder, point of the manubrium and the first rib) (Fig 6-8).
- Preferably select a 1 cc tuberculin syringe to minimize the risk of excessive negative pressure.
- Insert the needle parallel to the ground and perpendicular to the ferret. Aim the needle toward the cervical spine.
- Slowly move the needle caudally, while applying gentle negative pressure, until blood begins to flow (Fig 9).
The “hanging” jugular stick is a much more ‘forgiving’ position when compared to venepuncture of the cranial vena cava as you are truly hitting the jugular vein so there is far less risk involved.
Cranial vena cava
Venipuncture of the cranial vena cava is generally the quickest way to collect the largest amount of blood from the ferret. The ferret heart sits caudally within the long thoracic cavity and the risk of cardiac puncture is negligible (Fig 10). Nevertheless the cava can be lacerated if the ferret moves; therefore all but the most severely debilitated individuals should be sedated or anesthetized for “caval sticks”.
Caval venipuncture is a blind technique, which relies on the identification of anatomic landmarks
- Place the ferret in dorsal recumbency with the forelegs pulled back along the sides of the chest.
- Position the animal squarely on the table in perfectly straight alignment. (If the ferret is not sedated, this technique requires 2 handlers).
- Identify the thoracic notch, the angle created by the manubrium and the first rib.
- Insert a 25 -gauge needle on a 1.0-3.0 ml syringe into the thoracic notch (Fig 11).
- While maintaining slight negative pressure, direct the needle towards the opposite hip at an approximately 30-degree angle (Fig 12).
- Once blood starts to fill the syringe, do not move the needle.
- If blood is not aspirated, slowly pull the needle out until it is just beneath the skin, then slightly redirect the needle towards midline. Alternatively, simply pull the needle out completely, and start over using a fresh needle.
Lateral saphenous vein
The lateral saphenous vein is generally used to collect small volumes of blood for blood glucose testing, packed cell volume measurement, or complete blood count.
- Two or three people are required for saphenous venepuncture. One or two people to restrain the ferret, and one person to collect the blood sample.
- Grasp the rear leg just above the stifle to engorge the vessel and prevent the limb from moving (Fig 13). Alternatively apply a tourniquet, such as a Penrose drain clamped with a hemostat.
Simply hold the vessel rather than rolling it.
- Clipping the fur can help with identification of the vessel. It is generally easiest to cannulate the straight segment of the saphenous vein as it passes along the back of the leg as opposed to the segment of vein that crosses the hock (Fig 14).
- Securely tucking a small towel around the bottom foot will prevent kicking at a crucial moment.
- Select a 22- to 30-gauge needle on a 0.5- to 1.0-mL syringe. Use of a small syringe and slow, gentle aspiration will prevent the vein from collapsing (Fig 15).
The cephalic vein is usually quite prominent in the ferret, and it is relatively easy to cannulate, however consider reserving this vessel for intravenous catheter placement whenever possible (Fig 16).