From a very high level, you're probably going to need to create a recordset in VBA that contains just the one record you want to export. You can then use that recordset as your source for your mailmerge.
I've never done mailmerges, but this should get you started:
Dim db as Database
Dim rec as Recordset
Set db = CurrentDB
Set rec = db.OpenRecordset("SELECT Initials, HospNo, [date], comment FROM MyTableName WHERE SomeFilterCriteria")
'Mailmerge based on "rec"
Obviously you need to change MyTableName and MyFilterCriteria based on your specific info, you didn't give us the table name or how you want to determine which record of data to mailmerge.
Either that or you can build a query, set up the mailmerge from the query, and then put filters in the query that point to your form. In the Criteria line in a query (if you open it in Design View), you would put something like
[Forms]![MyFormName].[MyFieldName]
Also, if you have the ability to do so, change your date field name. The word "date" is a reserved word, which means you have to enclose it in brackets so Access doesn't think it's a built-in command. Change the field name to scandate or something to avoid future problems.