# Venous Blood Sampling

## Overview

This module describes how to obtain blood from a vein.

## Indications

## Contraindications

## Patient information and consent

Always verify your patient’s identity and obtain informed consent before proceeding.

### How do I explain this procedure?

“I need to draw blood from a vein to use it for tests. We use a new needle for every patient, and losing this amount of blood does not harm you.”

### What can my patient expect?

“You may feel a sharp scratch when I insert the needle. Test results can sometimes take several days to become available.”

### What is my patient’s role?

“Let me know if you have any allergies or a bleeding tendency, or use blood thinners. Fearing blood or needles is normal, but tell me if you have fainted from it. Keep as still as possible. If you feel strange sensations or pain, tell me immediately. Afterwards, press firmly on the area with cotton wool to prevent bleeding.”

## Preparation

### Documentation

### Equipment

## Site and Positioning

Always position the patient seated, reclining or supine to avoid injury caused by possible fainting.

The most common site for venous blood sampling is from the antecubital fossa where veins are easy to see and palpate. The median cubital vein is the first choice. Avoid inserting the needle where two veins meet as there are often valves.

Other sites include the basilic and cephalic veins, the veins on the hands and wrists, and femoral veins. These sites pose increased risks, and should only be used if the median cubital vein is not an option.

## Procedure

Follow medical asepsis with sterile gloves for collecting samples that include blood culture.

Follow medical asepsis with non-sterile gloves for other samples.

## Troubleshooting

I can’t find a vein.

Check each antecubital fossa. Apply heat to the skin and tap on the site to help raise the vein. Ask the patient to make a fist. If not successful, try the backs of the hands. Inflating a manual sphygmomanometer between systolic and diastolic blood pressure can help to visualise the veins better. Other sites include the feet, the fine veins on the wrists, the femoral veins in the groin, or the neck. Alternatively, switch to arterial blood sampling procedure.

The blood flow stopped during aspiration.

Advance 1 mm and withdraw 1 mm. Attempt rotating the needle 90°.

Don’t poke around any further. Rather withdraw and restart the procedure at another site.

The puncture site continues bleeding.

Use continuous, direct pressure for 5 minutes. If unsuccessful, call your senior and consider investigation for bleeding tendency.

The patient is uncooperative/confused.

Don’t risk a needlestick injury. Call an assistant to hold the limb steady.

I see rapid, pulsatile bleeding at puncture site.

You accidentally entered an artery. Withdraw the needle and apply firm pressure until bleeding stops.

I don’t have a rack to position collection tubes for filling.

It is unsafe to fill tubes while holding them in your hand. To avoid sharps injuries, hold the back end of the tube between index finger and thumb and lay the tube flat on a surface. Pierce the top carefully with your needle at a downward angle, so that if you miss, you will strike the table and not your hand.

## Risks

## References