Venipuncture Techniques Quiz

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Questions and Answers

Which vein is typically the most preferred for venipuncture due to its size and surface proximity?

Cephalic vein

Jugular vein

Median cubital vein (correct)

Basilic vein

What should be avoided when selecting a vein for venipuncture?

Veins in the patient's dominant arm

Veins that feel soft and resilient

Veins that are located deep under the skin

Veins that feel hard and cord-like (correct)

What is the approximate percentage of the population that has H-shaped antecubital veins?

90%

50%

80%

70% (correct)

How long should a tourniquet typically be released after application during vein selection?

2 minutes Signup and view all the answers

What is the recommended antiseptic for cleaning a venipuncture site?

70% isopropyl alcohol Signup and view all the answers

Where in the arm is the antecubital fossa located?

In front of and below the bend of the elbow Signup and view all the answers

Which vein is located in the lateral aspect of the antecubital area and is the second choice for venipuncture?

Cephalic vein Signup and view all the answers

What does palpating a vein help determine?

The state of being freely open, size, depth, and direction of the vein Signup and view all the answers

What is the recommended motion for cleaning the venipuncture site?

Circular motion starting at the point of insertion Signup and view all the answers

What is the recommended drying method for disinfected sites?

Let the site dry naturally Signup and view all the answers

What is the correct angle for needle insertion when performing a venipuncture?

15-30 degrees Signup and view all the answers

How should the skin be pulled during the needle insertion process?

Toward the wrist and slightly to the side Signup and view all the answers

What should be done after the last tube has been removed from the holder?

Hold a clean gauze square against the site Signup and view all the answers

What occurs if the blood flow has been successfully established?

Blood will begin to flow into the collection tube Signup and view all the answers

What should be avoided to prevent contamination while cleaning the venipuncture site?

Using non-sterile gauze to dry the area Signup and view all the answers

When establishing blood flow with an ETS system, what is essential regarding the collection tube?

The stopper must be completely penetrated by the needle Signup and view all the answers

What is the primary purpose of measuring hematocrit?

To evaluate the proportion of red cells to plasma Signup and view all the answers

What is the effect of excessive milking during blood collection?

Causing hemolysis Signup and view all the answers

Which of the following best describes normal hematocrit values in adult females?

36-48% Signup and view all the answers

Which step is crucial to avoid air bubble contamination in a Wintrobe tube?

Use a long stem pipette and ensure no air bubbles are present Signup and view all the answers

Which method for hematocrit determination involves the manual procedure?

Macrohematocrit method Signup and view all the answers

What is the formula used for calculating automated hematocrit?

HCT = (MCV x RBC count) / 10 Signup and view all the answers

What is the consequence of scooping during blood collection?

Activates platelet clumping and hemolysis Signup and view all the answers

What is referred to as packed cell volume (PCV)?

Volume of packed RBCs in whole blood Signup and view all the answers

What is the method indicated for directly counting hematocrit using a tube graduated from 0-10 cm?

Macrohematocrit method Signup and view all the answers

What is the primary disadvantage of the macrohematocrit method?

Time-consuming Signup and view all the answers

How does trapped plasma affect hematocrit readings?

Increases hematocrit by 1-2% or 1-3% Signup and view all the answers

Which component is not necessary for the microhematocrit method?

Blood specimen tube Signup and view all the answers

What is the purpose of sealing the end of the capillary tube in the microhematocrit method?

To prevent leakage of plasma Signup and view all the answers

How full should the capillary tube be filled with blood when performing a manual microhematocrit?

About ⅔ full Signup and view all the answers

What is the required speed and duration for centrifugation in the macrohematocrit method?

11000 to 12000 rpm for 4-5 minutes Signup and view all the answers

During the microhematocrit method, why should the capillary tube be filled from opposite ends if using a colored ring?

To ensure correct capillary action Signup and view all the answers

What anticoagulant should be used for duplicate microhematocrit determinations?

EDTA Signup and view all the answers

At what intervals should centrifuge duplicate specimens for microhematocrit determinations until optimum packing is achieved?

Every 30 seconds Signup and view all the answers

What is the main purpose of hemoglobin in red blood cells?

To transport oxygen and carbon dioxide Signup and view all the answers

Which of the following is a method applicable only to normocytic, normochromic red blood cells?

Rule of Three Signup and view all the answers

What is the formula used to calculate the hematocrit according to the Rule of Three?

Hematocrit = RBC count × 3 Signup and view all the answers

What condition is referred to when free hemoglobin is present in the blood plasma?

Hemoglobinemia Signup and view all the answers

What is the normal hemoglobin concentration range for adult males?

13.5-17.5 g/dL Signup and view all the answers

What occurs when free hemoglobin concentration in plasma reaches between 30 and 300 mg/100mL?

Hemoglobinemia is detected Signup and view all the answers

Study Notes

Selecting the Vein

The antecubital fossa is the most preferred venipuncture site.
The dominant arm typically has the most prominent veins.
Palpate the area to locate veins, determine patency, size, depth, and direction.
Avoid veins that feel hard, cord-like, or lack resilience as they may be sclerosed or thrombosed.
Release and reapply the tourniquet after 2 minutes when selecting veins.

Venipuncture Sites

The antecubital fossa is a shallow depression in the arm, anterior to the bend of the elbow.
The H-shaped antecubital veins are present in about 70% of the population and include the median cubital, cephalic, and basilic veins.
The median cubital vein is the preferred choice as it is large, close to the surface, stationary, and easiest to puncture.
The cephalic vein is located on the lateral aspect of the antecubital area; the second choice.

Clean and Air Dry the Site

The recommended antiseptic for venipuncture site cleaning is 70% isopropyl alcohol.
Clean the site with a circular motion, starting at the intended needle insertion point and moving outward in concentric circles.
Allow the site to dry naturally, do not fan or blow the site.

Anchoring and Needle Insertion

Anchor antecubital veins by supporting the patient's arm with your free hand below the elbow.
Place your thumb 1 to 2 inches below and to the side of the venipuncture site and pull the skin toward the wrist.
Position the needle above the vein, lined up with it and paralleling its path.
The angle of insertion should be 15-30 degrees depending on the vein’s depth.

Establish Blood Flow, Release Tourniquet, Ask Patient to Open Fist

For the ETS system, advance the collection tube into the tube holder until the stopper is penetrated by the needle.
If using a syringe, a flash of blood (about 3.0 mL) in the tube indicates successful vein penetration.
Release the tourniquet after blood flow is established.

Remove Needle and Place Gauze

Place a clean gauze square over the needle insertion site.
Apply pressure to the site for 3 to 5 minutes or until bleeding stops.

Order of Draw for Capillary Specimens

Blood gas specimen (arterial blood)
Slides (unless the specimen is placed in an EDTA tube)
EDTA microcollection tubes
Other additives (Heparin)
Serum microcollection tubes

Pre-Analytical Phase (Hematocrit Determination)

Hematocrit measures the proportion of red cells to plasma in the peripheral blood.
It is reported as PCV (%) or EVF (L/L).
Normal hematocrit values:
- At birth: 45-60%
- Females: 36-48%
- Males: 40-55%

Hematocrit

Packed cell volume (PCV) is the volume of packed red blood cells in a given volume of whole blood.
Hematocrit is used in evaluating and classifying anemia.

Methods for Hematocrit Determination

The Wintrobe tube method is a manual method using a Wintrobe tube, long stem pipette, and centrifuge.
The microhematocrit method is also manual, utilizing a heparinized capillary tube, microhematocrit centrifuge, reader, sealant, and lancet.
The automated method computes hematocrit using the MCV and RBC count.

Macrohematocrit Method

Less commonly used and time-consuming.
Requires a higher blood volume.
Trapped plasma, which increases hematocrit by 1-2 or 1-3%, is not affected by automated tests.

Microhematocrit Method

Requires duplicate microhematocrit determinations using fresh, well-mixed blood anticoagulated with EDTA.

Automated Method

Hematocrit is calculated by (MCV x RBC count).

Pre-Analytical Phase (Hemoglobin Determination)

Hemoglobin is the main content of red blood cells responsible for oxygen transport.
It is a conjugate protein consisting of globin and heme.
Normal hemoglobin concentration for adults:
- Male: 13.5-17.5 g/dL
- Female: 12.0-16.0 g/dL

Hemoglobin Determination Methods

Cyanmethemoglobin method is the most common, using sodium cyanmethemoglobin as a reagent.
Kennedy's and Wong's/Assendelft method is a chemical method that measures iron bound to hemoglobin.
Physical method (Rule of Three) is applicable to patients with normocytic, normochromic RBCs: Hemoglobin = RBC count x 3.
More detailed description is required for the fourth method. The text ends abruptly, and there is no fourth method listed.

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Description

Test your knowledge on venipuncture techniques, including site selection and cleaning protocols. This quiz covers key concepts like the preferred veins and the proper methods for ensuring site sterility. Gain insights into effective practices for successful venipuncture.