Capillary puncture is the collection of blood through the capillaries; hence, through the capillaries of the skin. The most common sites are the pads of the fingers.

Alternate sites include:

Ear lobes

Big toes

Heel of infants

These are alternate sites of puncture that you can take advantage of. Remember to wipe the first drop of blood before collection as this is contaminated with tissue juices. Knowing the correct procedure in collecting from these alternate sites will ensure the reliability of your laboratory results.

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There are different ways to draw blood from a patient and capillary puncture is one of them.  If you compare it with venipuncture and arterial puncture, it is the easiest way to obtain a blood specimen. Usually doctors request the procedure when there is minimal volume of blood needed. If you have a blood request stating capillary puncture in the laboratory request form, here are some basic information about the procedure.

Capillaries

Also known as the “finger stick”, the capillary puncture involves the smallest blood vessels in the body. Since the capillaries are found all throughout the body and in a more superficial location, it only involves poking the skin with a sharp object called a lancet.  The most common sites for specimen collection are the palmar surfaces of the fingers, ear lobe and big toe or heel for the infants. Once the blood starts to ooze from the punctured site, the medical worker will collect the specimen in a capillary tube or in an appropriate specimen container.

Preparation

There are no special patient preparations indicated for capillary puncture. In fact, it only requires minimal training to correctly perform the blood collection. Even non- health workers can obtain the blood provided that they have the necessary equipment and basic knowledge on the proper collection technique. Oftentimes, diabetic patients are the most common lay persons who perform the capillary puncture at home for their daily blood sugar monitoring.

Procedure

The principle in obtaining blood through capillary puncture is the same with venipuncture and arterial puncture. Of course, the health worker needs to correctly identify the patient and choose the most appropriate site. Highly calloused fingers or those with skin injuries like hematoma and bruises and edematous areas are not recommended. Once the health provider has settled with the site, he/she has to clean the site of puncture with a cotton and alcohol starting from the center moving outwards. Using a swift and deliberate motion, he/she will then puncture the skin with a lancet, wipe the first drop of blood and collect the blood using a capillary tube.

Precautions

During the collection, squeezing of the punctured must be avoided. It leads to dilution of blood with tissue juices, thereby leading to erroneous results. Since young children are the common patients indicated for capillary puncture, assistance from adults and use of restraining devices may be necessary. If your kids are the patients, you must help the health worker explain the procedure to your child. Be truthful about what to expect. Tell them about the minimal but tolerable pain that they will feel. Do not tell them it does not hurt, because it does. Reassure them though that the pain is tolerable.

Aftercare

Since capillary puncture involves a minor puncture, there are no known health risks for it, if performed by knowledgeable personnel. However, you must apply pressure to the site for 3 to 5 minutes to stop the bleeding. The whole procedure only takes up to 5 minutes to complete. After the capillary puncture, you can always go back to your regular activities.

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Materials needed

Sterile dry cotton

Sterile wet cotton

Lancet or penlet

Capillary tube of capillette or an appropriate collection vessel

Steps

Step 1

Prepare your materials and place it within your reach.

Step 2

Identify your patient properly b y asking his/her name.

Step 3

Select a suitable site, usually the ring finger of the left hand for adults and the big heel or big toe for infants.

Step 4

Sterilize the site of puncture from the center going outwards in a circular manner.

Step 5

With a smooth and deliberate manner, puncture the site.

Step 6

Wipe the first blood and collect your specimen making use of your capillary tubes or other appropriate container.

Step 7

Press the wound for 3-5 minutes and apply sterile dry cotton and a micropore.

Tips

* Smile and introduce yourself before asking the name of the patient.

* Give a brief description of the test to be done.

* Children 5 years old and below, most likely would need a restraining blanket or device.

* Older children would understand if you explain why you need to perform the procedure.  You have to make them an active participant by making them understand that you need their cooperation for the success of the blood collection.

* The other pads of the fingers and the earlobes are other alternative capillary puncture sites.  Determine which is best for your patient by examining the site.

* Say thank you after the procedure.

Precautions

* Do not state his name but let him state it.  The patient may not hear correctly and still say yes or no.  Let him spell it out if you cannot hear clearly, or best if he can write it down; and then patient identification would be done properly.

* Your material should not be near the patient, especially if the patient is a child. Children can pull your material.

* Do not underestimate children, they become stronger when intimidated and afraid.  Restrain them properly.

* Do not puncture sites, which have hematoma or bruises.

* Wipe the first drop of blood, as it contains mainly tissue juices and may yield inaccurate results.

* If the test is bleeding time (BT) or clotting time (CT) then do not wipe the first drop of blood. Refer to the protocol with these two tests.

* All materials should be sterile and dry to prevent infecting the patient and contaminating your blood samples.

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