Smoking increases Perioperative risk, and quitting reduces risk - the facts
A meta-analysis of 107 studies found that smoking more than doubled the risk of developing a wound-related complication such as surgical site infection (relative risk = 2.2), increased the risk of pulmonary complications such as pneumonia (relative risk = 1.7), and increased the risk of ICU admission (relative risk = 1.6).
A Cochrane review found that tobacco treatment to help surgical patients quit smoking was effective in reducing the rate of perioperative complications
The longer the duration of preoperative abstinence the better, but there is good evidence that even just not smoking on the morning of surgery reduces the risk of surgical site infection. There is NO evidence that quitting shortly before surgery increases the risk of pulmonary complications.
Bottom line - smoking increases perioperative risk, but we can reduce these risks if we help our patients quit smoking
Read more about the evidence here.