Effect of Intravenous Acetaminophen on Postoperative Opioid-related Complications

Effect of Intravenous Acetaminophen on Postoperative Opioid-related Complications

Some patients have respiratory depression (decreased breaths per minute) after surgery. Acetaminophen, an FDA approved pain medication, may prevent this problem. The purpose of this study is to determine if acetaminophen decreases respiratory depression after surgery. The investigators will also evaluate the cost effectiveness of acetaminophen.

Patients having elective major abdominal surgery are being asked to participate in this research study. If eligible, a patient will have their baseline tidal volume (amount of air moved into or out of the lungs) and vital capacity (how much air the lungs are capable of holding) measured using a spirometer (apparatus for measuring the volume of air inspired and expired by the lungs) measured before surgery. Three questionnaires will also need to be completed before surgery.

The patient will then be randomized, like flipping a coin, to receive either Acetaminophen or placebo (inactive substance) as an infusion throughout surgery and for the first two days thereafter. Neither the patient nor his or her physician will know if the patient is assigned to study drug or placebo. Regardless of study assignment, both groups will receive standard pain management medications and sedation.

After surgery, the patient's blood pressure, activity, posture, respiratory rate, the electrical activity of the heart, oxygen saturation, tidal volume, minute ventilation and respiratory rate will be continuously monitored and recorded for 48 hours using a wireless pulse-oximeter and a respiratory volume monitor.

48 hours after surgery the patient will be asked to complete a patient satisfaction questionnaire, which will allow the patient to rate the satisfaction with the treatment received for pain. The patient will also be asked to complete a questionnaire about recovery.

At discharge, the patient will be given two questionnaires about pain and quality of life.

Inclusion Criteria:

• Written informed consent
• 18-85 years old
• above 50 kg
• American Society of Anaesthesiologists Physical Status 1-3
• Scheduled for elective open or laparoscopic abdominal surgery, including colorectal, prostate, and hysterectomy surgeries
• Patients with anticipated hospitalization of two nights
• Expected to require parenteral opioids for at least 48 hours for postoperative pain
• Able to use IV Patient-Controlled Analgesia systems

Exclusion Criteria:

• Hepatic disease, e.g. twice the normal levels of liver enzymes
• Kidney disease, e.g. twice the normal level of serum creatinine
• Epidural analgesia or regional blocks (including Transverse abdominis plane block)
• Acetaminophen sensitivity or known allergy
• Female patients who are pregnant or breastfeeding
• Patients taking warfarin