A search of Joanna Briggs Institute EBP retrieved this evidence summary:
Surgical Site Infection: Post-anesthesia and Post Operative Management. 2015.

It references a systematic review: Blondet JJ, Beilman GJ. Glycemic control and prevention of perioperative infection. Curr Opin Crit Care. 2007;13(4):421-427.
This review references studies documenting effect of perioperative hyperglycemia on post-surgical infection and mortality.

Additional references
PubMed: hyperglycemi* AND (postoperative OR post-operative OR perioperative) AND (complications OR mortality OR morbidity
Retrieves many references.  It is more efficient to begin with the systematic reviews from this search:
hyperglycemi* AND (postoperative OR post-operative OR perioperative) AND (complications OR mortality OR morbidity))systematic[sb]
Some of these reviews will evaluate effect of controling blood glucose in the postoperative period, but they should also address the literature documenting the problem.