A common practice used to control autonomic responses during surgery is to administer beta-blockers intraoperatively. This practice has been shown to effectively blunt autonomic responses to intraoperative events. Several studies have shown that administration of beta-blockers can decrease intraoperative anesthetic requirements. Additionally, it has been demonstrated in several studies that intraoperative beta-blocker administration may actually decrease postoperative pain scores and opioid requirements, although these results are not entirely consistent. The mechanism by which the decrease in postoperative pain and narcotic requirements occurs is unclear. It has been postulated that esmolol may itself possess some analgesic-like properties, as was suggested by studies performed in rodent models. It has also been postulated that perioperative beta-blockade may attenuate the neuroendocrine stress response to surgery, thereby decreasing inflammatory responses in tissues; however, this theory was not supported by a study in which stress hormone levels were measured in patients who received beta-blockers and compared to a control group. Several studies which investigated the effects of beta-blockade on postoperative pain and opioid requirements compared the beta-blocker treatment group to an opioid treatment group, and did not include a true control group in which no treatment was given. Therefore, it is unclear whether the decrease in postoperative pain and opioid requirements in these studies was due to a true effect of the beta-blockers or whether it was due to an effect of the opioids.