Deck 11: Capillary Blood Specimens

Question 1

For the following questions, select the one best answer. Which of the following is a preferred site for a capillary puncture?

A) wrist
B) antecubital area
C) third finger
D) thumb

Answer 1

Skin puncture is done to obtain small amounts of capillary blood for lab testing. In wrist and antecubital area, one can easily find a vein for blood collection, but, finding a capillary is difficult. So, these sites can be used for venipuncture and collection of large amounts of blood. The thumb should never be used for puncturing as it consists of pulse.
Hence , the options a, b and d are incorrect.
The best parts of the body for skin puncture should be fleshier and should not be directly in contact with the bones. In adults, as well as, in older children, fingertip of the fingers is the best site.
Correct finger : One should choose that finger, whose fingertip is fleshier. The best two fingers are the third finger or the fourth finger of the non-dominant hand.
Correct hand : Non-dominant hand is recommended for capillary puncturing as any discomfort that could happen due to skin puncture. The discomforts can be like pain that should not hamper the daily activities of the patient.
Correct site on finger : On third or fourth finger, one should never use nail's edges or the tips of the fingers. Puncture should be made slightly off-centre of the thickest fleshy part of the finger.
Hence, the correct answer is option .

Question 2

For the following questions, select the one best answer. Controlling the depth of puncture during a finger stick prevents which of the following?

A) puncturing a vein
B) bacterial contamination
C) excessive bleeding
D) osteomyelitis

Answer 2

While, puncturing the skin for capillary blood, two of the most important things to be considered are as follows:
1. Puncturing at any site which does not have much of flesh and has bone underneath should be avoided.
2. Using non-sterile syringes or pins for puncturing should be avoided.
Using non-sterile material would not only damage the extracted blood, but, would also spread bacterial infection at the puncture site. This bacterial infection has nothing to do with the depth of the puncture.
Puncturing a vein is also not possible because in a finger, vein is present at a much deeper area and mostly the capillaries are present near to the surface. It is difficult to pinprick a vein in the finger before you can pin prick a capillary.
Excessive bleeding happens only, when the blood pressure at an area is high and blood takes more time to clot. However, in fingers, the blood pressure is low so, excessive bleeding cannot happen with a finger prick.
Hence, the options a, b and c are incorrect.
Repeatedly harming the bone, while skin puncturing, could cause osteomyelitis. Osteomyelitis is the inflammation of bone caused by the bacterial infection. Using lancets is not usually recommended, as there is a greater chance of pricking the bone, while, skin puncturing.
Therefore, it is extremely important to control the depth of puncturing during a fingerstick as to prevent the osteomyelitis.
Hence, the correct answer is option .

Question 3

For the following questions, select the one best answer. A finger puncture should involve which of the following steps?

A) puncturing parallel to fingerprint
B) puncturing along the fingerprint lines
C) puncturing across the fingerprint
D) wiping away the first two drops

Answer 3

A finger puncturing done to isolate the capillary blood should be done at the thickest fleshy site of the third or fourth finger. Also, while picking, the depth of the fingerstick should be controlled as it could harm the bone underneath.
Before puncturing, it is important to ascertain the right site to puncture. Non-dominating hand should be chosen. The finger chosen should not be very cold. In case, the hand is cold, it should be made warm as to increase the blood flow by keeping it inside a warm wet towel for 5-10 minutes.
The site, then, should be cleaned with 70% alcohol pad and allowed to dry as alcohol would interfere in the blood collection. The puncturing should not be parallely to the fingerprint or along the lines of the fingerprint.
It does not involve wiping of the initial two drops of the blood. After blood collection, gentle pressure is applied to the site, so that it stops bleeding. If puncture is made parallel or along to the fingerprint lines, the blood flows down the fingerprint lines and is difficult for its collection.
Hence, the options a, b and d are incorrect.
The hand should be held and the finger should be punctured firmly and the fingerstick should be used such that it cuts across the fingerprints. Cutting across the fingerprint would produce a round drop of blood.
Hence, the correct answer is option .

Question 4

For the following questions, select the one best answer. Skin puncture is not useful for patients who have which of the following conditions?

A) obesity
B) burns
C) fragile veins
D) swollen arms and hands

Question 5

For the following questions, select the one best answer. Which finger(s) are used most often for skin puncture?

A) thumb
B) second (index) finger
C) third or fourth finger
D) fifth (pinky) finger

Question 6

For the following questions, select the one best answer. Blood samples from skin punctures cannot be used for which tests?

A) routine hematology tests
B) glucose testing
C) coagulation studies
D) cholesterol screening tests

Question 7

For the following questions, select the one best answer. Capillary blood is more like arterial blood than venous blood for which of the following reasons?

A) the skin has more arterioles
B) arterial pressure is stronger in capillaries
C) there is more arterial blood than venous blood
D) venous pressure is greater in capillaries

Question 8

For the following questions, select the one best answer. Plastic micro collection tubes should be filled with blood in which of the following ways?

A) using a syringe to fill the tube
B) allowing the tube to fill by itself using capillary action
C) using suction to pull blood into the tube
D) using the tube to scoop droplets off the skin carefully

Question 9

For the following questions, select the one best answer. If alcohol is used to decontaminate the capillary puncture site, which of the following is an essential step?

A) using two alcohol pads for cleansing
B) diluting the strength of the alcohol
C) wiping away the second drop of blood after the puncture
D) allowing the site to air dry prior to the puncture

Question 10

For the following questions, select the one best answer. The best angle for using two glass slides to make a blood smear is approximately

A) 10 degrees
B) 15 degrees
C) 30 degrees
D) 90 degrees