This is a companion article to the feature, “Capillary Blood Sampling.”
The steps illustrated below demonstrate how to take a proper capillary blood sample to ensure accurate point-of-care hemoglobin measurements.
Make sure all items for capillary sampling and performing the test are available and close to hand.
Use the middle or ring finger, ideally of the nondominant hand (a). The patient must not wear a ring on the finger as this may obstruct the blood circulation. Ensure that the patient’s hand is warm and relaxed, and that the patient is comfortably seated.
The puncture should be made slightly off center from the fleshy portion of the finger, near the side of the fingertip (b).
Disinfect and thoroughly dry the puncture site (c).
Gently massage the finger toward the tip to increase blood flow. Avoid going past the first knuckle (d).
Make the incision on the upward-facing side of the fingertip, so that the blood drop sits on top of the finger, to facilitate filling of the hemoglobin cuvette (e). Apply only light pressure on the fingertip until a blood drop appears. Don’t press or milk the finger. It may take a few seconds after the puncture until the blood flow starts.
Wipe away the first two to three drops of blood and make sure there is a free blood flow before filling the cuvette. Release the grip on fingertip when wiping off a drop (f).
Be sure to have a blood drop of sufficient size to fill the cuvette. Fill the cuvette completely in one go. Do not refill, and avoid air bubbles.
