IV Acetaminophen Effects on Hyperalgesia After Cardiac Surgery

Coronary artery bypass grafting (CABG) is one of the most commonly performed major surgical
procedures with around 160,000 CABG procedures performed in 2010 in the United States.
Despite the decreasing mortality and morbidity associated with CABG, pain that persists
after the sternotomy remains often unrecognized, but significant clinical problem. The
prevalence of chronic post-sternotomy pain (PSP) ranges from 11 to 56% and approaches limb
amputation and thoracotomy as the surgeries with highest risk of chronic post-surgical pain
(CPSP) development.

Post-operative acute pain and analgesic consumption appear to be associated with the
development of chronic PSP. The amount of secondary hyperalgesia surrounding the surgical
incision also contributes to the amount of post-operative acute pain. Prior studies have
suggested a possible link between post-operative hyperalgesia and the risk of CPSP.
Therefore, there is a need to optimize the treatment of post-operative acute pain and reduce
the amount of secondary hyperalgesia since these interventions could lead to reduced
incidence of CPSP.

The addition of intravenous acetaminophen to analgesic regimen in cardiac surgery patients
represents a new strategy to decrease post-operative acute pain and central sensitization
(i.e., hyperalgesia), which in turn may lead to reduced risk of chronic pain after cardiac
surgery.

The investigators study is designed as a prospective, randomized, double-blind
placebo-controlled trial to evaluate the effects of adding intravenous acetaminophen versus
placebo to standard opioid analgesia regimen on post-operative 24-hour opioid consumption in
cardiac surgery patients. Our secondary aims include the evaluation of intravenous
acetaminophen effectiveness in reducing secondary or dynamic hyperalgesia, acute surgical
and non-surgical pain and development of chronic PSP.