A guide to performing a bone marrow aspiration

1. Decide on the most appropriate site for aspiration;

• The usual site for puncture in adults is the posterior superior iliac spine (PSIS).
• This may be technically difficult in obese or immobile subjects.
• The main advantage of this site is that a trephine biopsy can also be performed. Alternatively the sternum ( manubrium or 1^st or 2^nd parts of the body) can be used with care as there is a danger of  perforating the inner cortical layer and damaging the underlying large blood vessels and right atrium with serious consequences.

2. Obtain informed written consent;

• The procedure (in brief) and its main adverse effects (although rare) should be explained to the patient prior to obtaining consent.
• Pain, bleeding/haematoma formation and infection at aspiration site are the most commonly seen adverse effects, however, very rarely cause major concern.

3. Positioning the patient;

• Either left or right lateral decubitous on a bed/couch, with the dorsal surface of the patient facing the operator.
• Hold the hips and knees flexed to a comfortable maximum – knees drawn up and tucked into chest.

4. Operator;

• Should always wear sterile gloves after washing hands thoroughly with soap and water.
• Added precautions should be taken if it is a “high risk” patient (a pack containing a face mask and goggles should be available).
• Should be positioned comfortably (either standing or seated) with the height of the bed adjusted appropriately.

5. Procedure;

• Clean the skin over and around the area of the PSIS adequately with 70% alcohol or 0.5% chlorhexidine.
• Use sterile towels to cover the area surrounding the PSIS
• Palpate the PIS, usually in the region of the “posterior skin dimple”.
• Infiltrate the skin, subcutaneous tissue and periosteum overlying the selected site with a local anaesthetic. (About 5ml of 2% lignocaine via a 23G needle). Check the label and expiry date on the bottle prior to procedure. Give a few minutes for the anaesthetic to act.
• For patients who are very apprehensive towards needles, mentally unstable and children a general anaesthetic may be required. A topical anaesthetic like an anaesthetic cream (Emla) or lignocaine patches may be used prior to piercing of the skin with the needle for the local anaesthetic.
• Confirm that the skin is well anaesthetized and make a small (just enough to permit entry of the bone marrow needle) skin incision over the selected site with a No. 11 scalpel blade. *This step may not be necessary if a sharp tipped disposable marrow aspiration needle is used. The most common re-usable needles are Salah’s and Klima’s.
• The aspiration needle with the stilette in place is introduced through the skin incision and gently pushed through the subcutaneous tissue until the bone is felt.With a boring movement, pass the needle perpendicularly into the cavity of the ileum at the centre of the oval PIS. When the cortical bone has been penetrated (decreased resistance -usually! indicates penetration of cortex and entry into the marrow cavity) advance needle about 1 cm into the marrow cavity.Unlock and slowly remove the stilette. Some patients may notice pain if the stilette is not removed carefully.
• Attach a 2 or 5ml syringe to the needle and suck up marrow contents into the syringe. Patient may feel pain at this point and will need reassurance.  

6. Samples;

• Aspirate about 0.3ml of marrow for morphological examination. More than this increases dilution of the marrow with peripheral blood.
• If large amounts of marrow are required for several tests like immunophenotyping, cytogenetics and molecular studies – the syringe can be detached from the aspiration needle, and the stilette replaced, leaving the needle in the bone. After the smears are made the syringe can be re-attached to the needle and the required volume of marrow aspirated.
• It is imperative that the appropriate anticoagulants/culture media into which samples for special tests (immunophenotyping, cytogenetics, molecular studies and mycobacterium culture etc) are required to be collected are discussed with the respective laboratories prior to starting the procedure.    

7. Remove aspiration needle and apply pressure with sterile gauze until bleeding ceases.

• Perform a trephine biopsy or place a folded piece of gauze over the site, apply a pressure bandage, and have the patient lie supine for at least 30 minutes.  

8. The area that the procedure was performed in must be cleaned up and the sharps (needles/ scalpel blade etc.) should be accounted for and properly disposed of in a sharps container.

9. Preparing films;

•  Place a drop of the aspirate on a glass slide. Make a film 3-5cm in length using a smooth –edged glass spreader of not more than 2 cm in width.

References:

1. Bates I. Collecion and handling of blood. In: Lewis SM, Bain BJ, Bates I, eds. Practical haematology. 9^th ed. London: Churchill Livingstone; 2001.101-114.
2. Riley RS, Ben-Ezra JM, Pavot DR, Forysthe R, et al. An Illustrated Guide to Performing the Bone Marrow Aspiration and Biopsy.Medical College of Virginia,Virginia Commonwealth University Richmond, VA.