Chapter 4: Basic Practical Medical Procedures

VENEPUNCTURE AND INTRAVENOUS CANNULATION

Basic venepuncture

Purpose

Collection of blood, including large volume collection for transfusion. The ideal site is the basilic vein or median cubital vein, otherwise the dorsum of the hand or others according to availability (Fig. 4.1). Use local anaesthetic for large volume blood collection.

Method

1. Explain the method to the patient. Ensure the patient is warm and comfortable.

2. Dilate the vein by means of a tourniquet applied to occlude venous return.

3. Place a padded block under the arm to keep it straight.

4. After using a sterile swab to prepare the site, place the needle with attached syringe on the skin. Using downwards oblique pressure, puncture the vein firmly, ensuring the needle lies well within the vein. Remove the tourniquet.

Venepuncture in children

The same process for adults applies to adolescents and older children, but in infants and small children a 23-gauge butterfly needle provides more stability. A palpable vein is more likely to be successful than a visible but non-palpable vein. An assistant is necessary to support the limb and provide a tourniquet in small children.

For analgesia consider topical anaesthesia (amethocaine or EMLA^®), sucrose in infants < 3 months or consider sedation with midazolam (oral, intranasal or buccal) or nitrous oxide in children > 2 years.

Tips to aid dilation of veins

There are several ways in which peripheral veins can be dilated to facilitate venepuncture. The following are some of the methods used.

Vasodilation methods

• Apply a warm flannel for 60 seconds, or

• Rub glyceryl trinitrate ointment over the vein, or

• Give the patient half a glyceryl trinitrate tablet (if no contraindications).¹

Sphygmomanometer methods²

• Dilate the vein by means of the sphygmomanometer to keep BP at about 80–90 mmHg (veins will stand out).

        or

• Using the sphygmomanometer, inflate it to a pressure around 30 mmHg above systolic arterial pressure for 1 to 2 minutes while the patient opens and closes their hand. Thereafter it is deflated to around 80 mmHg and the resulting reactive hyperaemia is effective in filling even the shyest of veins. According to Wishaw this is the method par excellence.

Venesection tourniquet method³

Apply the tourniquet tightly and then release. After a reactive hyperaemia occurs reapply it and the veins should stand out well.

Intravenous cannulation

Use sterile gloves for this procedure.

Best site

• Choose a suitable prominent vein in the non-dominant forearm (not over a joint), e.g. ...