Capillary

• Capillary sampling refers to the sampling of blood from a puncture on the finger, heel or earlobe.
• Also known as fingerstick sampling, it enjoys several advantages over

  venous blood sampling: it is less invasive, requires smaller amounts of blood volume and it can be performed quickly and easily.
• However, it is commonly used in pediatric patients.
• Capillary blood sampling has now become increasingly being used

  worldwide due to the growing availability of point-of-care (POC) testing.
• the third or fourth finger is preferred in adults and children.
• The thumb has a pulse and is likely to bleed excessively.
• The index finger can be calloused or sensitive and the little finger does not have enough tissue to prevent hitting the bone with the lancet.
• The puncture is done to the left or right of the midline of the palmar surface of the fingertip, staying away from the fingernail.
• the fingers of infants less than one year old are too tiny to prick that is why the heel is used.
• The puncture is done on the farthest lateral or medial aspect of the plantar surface of the heel, not on the bottom.
• Punctures done on the plantar surface can damage cartilage or bone.
• The big toe can be used if necessary in infants who are not yet walking.
• Callous formation after a child starts walking can interfere with blood collection and is a contraindication.
• The site should be lateral to the midline of the plantar surface of the toe.
• Only the great toe has the amount of tissue necessary to protect the bone from injury.
• Other collection sites include the ear lobe, but is no longer recommended.
• Studies have shown that the blood flow in the ear lobe is less than that in either the fingertip or the heel.
• The other alternative site are the palms.
• Especially in diabetics who test their own blood sugars frequently, alternate sites give some relief from reusing the same sites over and over. The thenar and hypothenar eminences have capillary circulation equivalent to the fingertip.