Risk Preparedness in Sperm Banks

Abstract

Risk preparedness is a vital component of sperm bank operation and management. The primary requirement in minimising risk is to have standard operating procedures (SOPs) which stipulate that one person processes one sample at a time at each workstation, followed by strict double-checking of all patient details and labelling by a second person before the straws or vials are frozen. An equally important requirement is for ongoing training to the SOPs and effective communication between laboratory staff and between staff and management to ensure that the SOPs are “live” documents which are continually undergoing critical evaluation.

Appendix 1: Dewar and Dry Shipper Maintenance

All new dewars and dry shippers should have holding-time checks before being used routinely. Regular dewars should be filled with liquid nitrogen to the level that they will be operating at under routine usage conditions and the liquid nitrogen depth and/or weight checked daily for at least one week prior to addition of any storage samples. If the evaporation rate is outside the manufacturer’s specifications, the dewar may need to be replaced.

Dry Shipper Procedure

New Dry Shipper

• Determine the “as received” tare weight by weighing the empty shipper with the empty canister and lid in place (=E).

• Record this weight and the shipper serial number on an appropriate worksheet.

• Determine the “complete fill” weight and the “90% charged weight” of the shipper as follows:

• 1. Fill the dry shipper with liquid to the bottom of the neck tube.

• 2. Allow the unit to stand undisturbed while the refrigerant is being absorbed.

• 3. Approximately every 5 min, add liquid to maintain the refrigerant level as the liquid is absorbed by the filler. The procedure can take ten to fifteen cycles.

• 4. When the liquid level remains at the bottom of the neck tube for at least 30 min, the shipper is full.

• 5. Pour off any free liquid nitrogen and replace the lid.

  Record the complete fill weight (=F) on the worksheet mentioned above. You now have your baseline “empty” (E) and “full” (F) weights for this shipper. Calculate the 90% charged weight as per the formula below and record it on the worksheet:

  90%CW = E + 0.9(F-E)

Holding-Time Check

Check the holding time of the shipper by weighing it daily and checking for liquid nitrogen vapour visually. Record the holding time as the number of days required for the shipper to get down to 10% charged weight with nitrogen vapour still visible.

Acceptable Holding Times

Defined in our laboratory as 3 days less than the manufacturer’s static holding time for MVE shippers, or 3 days less than the manufacturer’s working time for Taylor-Wharton shippers, however this is up to the laboratory concerned to decide what margin of safety they are comfortable with.

Routine Use of Dry Shippers

• Charge the dry shipper with liquid nitrogen as described above and record the weight on the worksheet used for this particular shipper.

• Do NOT send the dry shipper out unless it is at least 90% charged.

• When the shipper is subsequently returned to the laboratory, re-weigh it (after removing any remaining straws or vials) and record the weight on the worksheet.

• Every 2 years or if the shipper appears to be losing nitrogen more rapidly than on its initial commissioning test run, then allow it to come up to room temperature for re-evaluation of holding time. After the shipper has come up to room temperature, remove the lid and leave the shipper to equilibrate at room temperature for 2–3 days before weighing it again. The shipper is acceptably dry when the tare weight is within 5% of the “as received from the manufacturers” tare weight.

If the shipper does not meet this requirement, then invert it (with lid off) and allow it to stand for 2 weeks before re-weighing it. If necessary, leave it a further 2 weeks. If it is still non-compliant, then it should be de-commissioned and replaced with a new shipper.