Bone marrow harvesting

Pre-operative preparations

Important to give advanced notice so that theatre time can be booked if necessary and the virological screening results obtained.

Within 30 days before the harvest procedure, arrange the following virological investigations

1. Hepatitis B surface antigen.

2. Hepatitis C antibody.

5. Spare serum stored.

Admit patient day before harvest. Clerk patient and arrange:

• X match 2-3 units blood (CMV -ve). If harvest is on normal donor— offer autologous blood collection to donor. If declined, arrange for genotyped, CMV negative and irradiated X-matched blood to be avail-

304 able for the donor. A CXR and ECG may also be arranged, if felt clinically appropriate.

Harvest procedure

1. Give heparin 50units/kg IV at anaesthetic induction.

2. Prepare harvest bag: adding ACD with a dilution factor of 1:10 for the prospective marrow volume; i.e. 100mL of ACD if expected harvest is ~1L.

3. Heparinise aspirate needles/syringes (0.9% saline containing at least 100U heparin/mL).

4. Begin with posterior superior iliac crests, limiting the number of skin entry points, the aspirate needle should be manoeuvred to collect as much marrow as possible with 5-10mL maximum from each penetration of the bone. Each aspirate should be deposited in a sterile harvest bag and syringe rinsed in the heparinised saline prior to re-use. Gently agitate bag at intervals.

5. Midway through harvest (or 500mL) a bag sample should be sent for FBC to determine the adequacy of the harvest. The final total WBC count should be at least 2 x 108 cells/kg of the recipient for autografts and 3 x 108 cells/kg for allografts.

The volume of marrow required may be calculated as follows:

Total volume required for autograft = 2.0 x recipient weight (kg) * (bag WBC x 10)

e.g. recip. 100kg and bag WBC 20 x109/L then vol. required = (2.0 x100) * (20 x10) = 1.0L

Volume still needed to be harvested = total volume - volume already taken at time of count + ~10%

Notes

1. The extra 10% compensates for reduced harvesting efficiency and the ACD.

2. The formula works at whatever volume you choose to do the first WBC but is a more accurate prediction at ~500mL.

3. If need to harvest >1L, remember to add additional ACD in the same 1 in 10 ratio.

4. For allograft calculations, substitute 3.0 for 2.0 in the formula.

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