From a reprocessing perspective, the most consistent challenge I see to proper cleaning is organic soils, most commonly blood, are allowed to dry on instruments before cleaning begins. Once dry, blood and other proteins become highly insolvent and are orders of magnitude much more difficult to remove.
Ideally, cleaning would begin the moment surgical use of the instruments ends. Most device manufacturers recommend cleaning begin within 30 minutes. Of course, in most real world settings, this is simply not possible. Equipment resources, physical work space, distance for transportation and manpower are all limiting factors.
This does not mean, however, that allowing soils to dry on instruments is inevitable or acceptable. It absolutely is not. Steps can and should be taken to insure that this does not happen, no matter however long instruments wait for cleaning to begin. First off, staff in the O.R. can help by reducing gross contaminants as much as possible (by wiping off instruments during the procedure). Second, instruments should be placed into containers with measures to keep them moist.
Depending upon the expected delay time these measures (from shortest wait time to longest) could be:
1) moist towel on top of the instruments;
2) using suitable spray-on enzymatic solution;
3) placing inside a humidity preserving pack. Once delivered to Sterile Processing, cleaning should begin as soon as possible, beginning with rinsing off gross contaminants prior to placing into automated cleaning equipment.