Ah Sue - trying to tame the untameable beast.
Decision to hold is sometimes made by the medic, sometimes by the nurse. Sometimes a reason is documented, sometimes not. In our opinion omission is only indicated pre biopsy/ ERCP/ surgery if it is imminent, as in within the next 6 hours (unless poor renal function). Like you, and no doubt many others, there is indecision around surgery, doses omitted the evening before, surgery postponed until the following day...... and repeat.
We are moving our default giving time for once-daily prophylactic LMWH to 2pm; I hope this will support appropriate administration pre-op, though will no doubt cause problems in other areas?