Randomization and blinding Subjects that still meet the inclusion criteria will proceed to the treatment phase. Subjects will be assigned to either the propofol group or placebo group. Sealed envelopes containing a randomized assignment to either propofol or placebo group will be prepared by an individual unconnected with the study using a web-based random number generator, and balanced to ensure equal allocation to each group. The propofol group will receive propofol and a concurrent normal saline bolus. The placebo group will receive intralipid and an identical concurrent normal saline bolus that contains low dose midazolam. There is evidence that low dose midazolam (35 mcg / kg) is sufficient to produce adequate sedation but no evidence to support the use of single dose midazolam as a treatment for CDH; this makes midazolam a suitable choice as an active placebo.50 The use of an active placebo is to minimize treatment recognition and bias by patient and investigator. Identical, sequentially numbered syringes containing either propofol or intralipid will be prepared by the hospital pharmacy and these will be appropriately coupled with identical numbered minibags of saline containing either no drug or midazolam. Subjects will be randomized after inclusion and exclusion criteria have been applied. Investigators will use these syringes / minibags in numeric order. (The named contents of each syringe and minibag will be available to the investigators in a second sealed envelope to be opened only in case of emergency during the infusion). Subject data will be grouped by treatment allocation for analysis into 'Group A' and 'Group B', but the blind will not be fully broken until data analysis is complete. The subject's daily pain diaries will be coded with the corresponding syringe code.