Bone marrow examinationis useful in establishing
the diagnosis of a varietyof hematological disorders
and other systemic diseases.
In adult patients, the body of the sternumopposite the second interspace
is the site of choicefor bone marrow aspiration.
Although the ilium and vertebralprocesses may be used,
the patient should be lyingas straight as possible.
The site is first swabbed with a suitable
disinfectant such as Merthiolate.
During this time,the procedure may be explained
and the patient appraised to the factthat there may be some discomfort
or pain and reassured.
The area surrounding the siteis draped with sterile towels.
A local anesthetic such as 1% propane
is administeredto the site of the puncture.
The midline of the sternum
between the second and thirdribs is located,
and the skin and periosteumare infiltrated with one
or two milliliters of the anesthetic.
A small incision is made through the skin
with a sharp pointed knife to facilitate
penetration by the bone marrowneedle while the propane is taking effect,
the external marrow needleis assembled by inserting the stylet.
Also, the syringe is checkedfor adequate suction.
A plain tip syringe is preferable.
The marrow needleis forced through the upper cortex
only by gentle pressure.
In some individuals,penetration is difficult.
In others, elderly women, for instance,the needle penetrates easily.
Great care must be takennot to penetrate both courtesies
since the great vessels lie directlybeneath the sternum at this point.
Note that the fingersof the left hand are held
against the needle collarto restrict the depth of penetration.
When the needle is feltto enter the marrow,
the stylet is withdrawnand the syringe attached.
Two tens or three-tens milliliters
of marrow are withdrawninto the dry syringe.
Smears are quickly preparedbefore clotting occurs.
Slides or coverslips may be usedin the preparation of smears.
To produce smears of proper density,some practice is required.
At least 10 smears are preparedfrom the sample of marrow.
These are stained with right stainand other special stains as indicated.
The remaining marrowis allowed to clot in the syringe
and transferredto a container of 10% formula
or other appropriatefixatives for histologic sections,
H&D, and iron stainsare usually routinely performed.
Peripheral blood smearsare prepared from a finger puncture
for comparative evaluationwith the bone marrow material.