Efficacy of IV Acetaminophen for Pain Management

The investigators' goal in this planned prospective, randomized, patient blinded study is to compare our standard of care as the control group to an experimental group in which patients receive preemptive IV acetaminophen dosing that is continued every 6 hours for a total of 8 doses in patients who have undergone major gynecologic surgery. The outcomes analyzed will include amount of rescue opioids required, time to return of bowel function, length of hospital stay, and patient satisfaction. The hypothesis is that the addition of IV acetaminophen will decrease the need for opioid rescue and thereby decrease the incidence of associated gastrointestinal side effects including nausea, vomiting, bloating, and constipation. The hope is that it will affect the final outcome of quicker return of bowel function, increased patient satisfaction, shortened hospital stay and prove to be an overall more effective postoperative pain management approach.

This is a patient-blinded prospective study in which patients that undergo major gynecologic surgery via an open abdominal approach will be randomized into two arms:

1. Control Group: Morphine patient-controlled-anesthesia (PCA) for the initial 24 hours post-operation with a low-dose basal rate (0.5mg/hr) and patient administered boluses prn. Oral oxycodone from 24-48 hours post-operation will be used prn for pain and then patients will be transitioned to oral combined oxycodone/acetaminophen for the remainder of their hospital stay. Normal saline 100cc IV will be infused as placebo every 6 hours for a total of eight doses with the first dose being given at time of anesthesia induction.
2. Experimental Group: Morphine PCA for the initial 24 hours post-operation with low-dose basal rate (0.5mg/hr) with patient administered boluses prn. IV acetaminophen 1,000mg will be given every six hours for a total of eight doses with the first dose being given at time of anesthesia induction. Oral oxycodone from 24-48 hours post-operation will be used prn and then patients will be transitioned to oral combined oxycodone/acetaminophen for the remainder of their hospital stay.

Outcomes that will be analyzed include the amount of opioids used; time to return of bowel function designated as passage of flatus; time to first bowel movement if it occurs while inpatient; duration of hospital stay; and patient symptoms and satisfaction at the 24 and 48 hour marks as well as at time of discharge.

Eligibility Criteria:
Inclusion Criteria:

-Female patients undergoing major gynecologic surgery via an open abdominal approach. The included surgeries would be exploratory laparotomy with or without removal of uterus, fallopian tubes, or ovaries.

Exclusion Criteria:

* Patients with baseline preoperative liver function enzymes (AST and ALT) that are greater than twice the upper limit of normal would be excluded.
* Patients with baseline CrCl \<30.
* Patients that require intensive postoperative care and delayed extubation will typically require additional sedation which would impede adequate evaluation of the two study pain regimens as they are designed to be patient controlled.
* Patients with complications unrelated to the pain regimens that prolong their stay would be excluded from the evaluation of hospital stay and cost effectiveness analyses. Examples would include but are not limited to pre-renal azotemia and acute renal failure; pneumonia; venous thromboembolism; or need for re-exploration laparotomy.
* Allergy to acetaminophen would exclude those patients set to enter the experimental IV acetaminophen study arm. One exception would be if the allergy were trivial and related to route of administration such as mild nausea with oral acetaminophen.
* Patients that undergo a bowel resection during surgery as it may adversely effect return of bowel function
* Patients that have required regular opioid intake for the 7 days preceding surgery.
* NSAIDs within 8 hours of surgery.
* Chronic steroid use with the exception of low-dose inhaled steroid formulations.
* Chronic alcohol or drug abuse.
* Patients currently pregnant.
* Patients unable to provide informed consent.
* Age \>85
* Any physical, medical, and mental condition that would make participation in the study inadvisable.