Time of Intravenous Acetaminophen Administration

Phase 4

Completed

Brief Summary: The purpose of the study is to examine the effects of timing of administration of intravenous (IV) acetaminophen and how timing relates to analgesic efficacy as measured by postoperative pain scores. A maximum of 138 patients meeting inclusion criteria who present for a scheduled total hip replacement under general anesthesia will be randomized into one of two arms: 1) the pre-closure group will receive the first dose administered upon onset of skin closure, 2) the preemptive group will receive the first dose administered within 60 minutes prior to incision. Both groups will receive subsequent doses every 6 hours x 24 hours.

Detailed Description: The purpose of the study is to examine the effects of timing of administration of intravenous (IV) acetaminophen and how timing relates to analgesic efficacy as measured by postoperative pain scores. A maximum of 138 patients meeting inclusion criteria who present for a scheduled total hip replacement under general anesthesia will be randomized into one of two arms: 1) the closure group will receive the first dose of one gram of intravenous acetaminophen administered upon onset of skin closure, 2) the preemptive group will receive the first dose of one gram of intravenous acetaminophen administered within 60 minutes prior to incision. Both groups will receive subsequent doses of one gram of intravenous acetaminophen every 6 hours x 24 hours. The maximum dose in a 24 hour period will not exceed 4 grams according to FDA recommendations.

Recruitment & Eligibility

Inclusion Criteria

Patients 30-75 years of age weighing ≥55 kg scheduled for elective total hip arthroplasty performed under general anesthesia will be included. As determined by the anesthesia team assigned to the case, eligible patients will also be assigned ASA physical status of I, II, or III and deemed capable of reporting their perceived pain using numeric pain scales and capable of operating a patient controlled anesthesia (PCA) device.

Exclusion Criteria

Exclusion criteria include known allergy, hypersensitivity, or contraindication to acetaminophen, history of alcohol or drug abuse, prisoners, emergency THAs, patients with chronic malnutrition or a body mass index (BMI) < 18 kg/m2 and non-English speaking patients. Additional exclusion criteria include impaired liver function defined as AST and ALT each ≥ twice normal limits and renal dysfunction (creatinine >2.0 mg/dl).

Arm && Interventions

Group	Intervention	Description
Preemptive group	Acetaminophen	The preemptive group will receive one dose of 1 gram of IV acetaminophen every 6 hours x 24 hours with the first dose administered within 60 minutes prior to incision. Each infusion will be administered over 15 minutes as recommended by manufacturer package insert.
Closure group	Acetaminophen	The closure group will receive one dose of 1 gram of IV acetaminophen every 6 hours x 24 hours with the first dose administered upon onset of skin closure.

Primary Outcome Measures

Name	Time	Method
Changes in Postoperative Pain Scores	preoperatively (baseline), post-anesthesia care unit (PACU or recovery room) arrival (2-3 hour), and 6,12, 18, and 24 hours following the initial administration of the study drug	To compare analgesic efficacy as measured by changes in postoperative pain scores assessed preoperatively, at 6, 12, 18, and 24 hours following the initial administration of the study drug. Pain scores are assessed on a scale of 0 - 10. 0 = No Pain; 10 = Worst Possible Pain

Secondary Outcome Measures

Name	Time	Method
Pain Medication Consumption Rates	Arrival to post-anesthesia care unit (PACU or recovery room) (2-3 hours post baseline) to 24 hours post administration of study drug	Number of participants who required rescue pain medication. Rescue pain medications is defined as administration of pain medication in excess of standard postoperative pain medication orders.