Scheduled intravenous acetaminophen reduces postoperative narcotic analgesic demand and requirement after laparoscopic Roux-en-Y gastric bypass

Pediatric obesity and anesthetic challenges of metabolic surgery

Obesity in the pediatric population is considered a growing problem. It is likely that there will be a significant impact related to obesity on the health of future generations. Obesity has increased the incidence of a spectrum of diseases ranging from microvascular complications over the retina and peripheral nerves to an increased incidence of cancer. We have conducted an electronic search in MEDLINE, PubMed, ISI Web of Science, and Scopus scientific databases targeting studies published between 2000 till 2019. Several modalities have shown a wide spectrum of the effectiveness of weight control among adolescents. Despite achieving short-term success among obese adolescents, maintaining such change is challenging. The emergence of metabolic or bariatric surgeries has opened the door for long-term control over weight gain with considerable remission of unfavorable metabolic mediated or modulated effects associated with obesity such as diabetes mellitus and hypertension. The most commonly practiced metabolic surgery among adolescents is sleeve gastrectomy which is associated with comparable weight and metabolic control and a lesser risk of complication. Anesthesia is considered a major challenge among the pediatric population, especially those with significant obesity. Preoperative evaluation is always warranted to exclude and manage different associated comorbidities. The anesthetic challenges associated with pediatric obesity begin with intubation. Maintenance and emergence from anesthesia along with postoperative antiemetics and analgesia can pose additional challenges. Managing the postoperative period is considered a cornerstone in the early detection and management of any postoperative complication. Especially those complications related to the metabolic and nutritional aspects of the bariatric surgery. Finally, despite being a valuable option in managing obesity, bariatric surgery in adolescents comes with significant anesthetic challenges that need to be consistently evaluated and managed.

National Intravenous Acetaminophen Use in Pediatric Inpatients From 2011–2016

OBJECTIVE

To 1) determine current intravenous (IV) acetaminophen use in pediatric inpatients; and 2) determine the association between opioid medication duration when used with or without IV acetaminophen.

METHODS

A retrospective analysis of pediatric inpatients exposed to IV acetaminophen from January 2011 to June 2016, using the national database Health Facts.

RESULTS

Eighteen thousand one hundred ninety-seven (2.0%) of 893,293 pediatric inpatients received IV acetaminophen for a median of 14 doses per patient (IQR, 8–56). A greater proportion of IV acetaminophen patients were admitted to the intensive care unit (ICU) (14.8% vs 5.1%, p < 0.0001), received positive pressure ventilation (2.0% vs 1.5%, p < 0.0001), had a higher hospital mortality rate (0.9% vs 0.3%, p < 0.0001), and were operative (35.5% vs 12.8%, p < 0.001) than those not receiving IV acetaminophen. The most common operations associated with IV acetaminophen use were musculoskeletal and digestive system operations. Prescription of IV acetaminophen increased over time, both in prescription rates and number of per patient doses. Of the 18,197 patients prescribed IV acetaminophen, 16,241 (89.2%) also were prescribed opioids during their hospitalization. A multivariate analysis revealed patients prescribed both IV acetaminophen and opioids had a 54.8% increase in opioid duration as compared with patients who received opioids alone.

CONCLUSIONS

This is the first study to assess IV acetaminophen prescription practices for pediatric inpatients. Intravenous acetaminophen prescription was greater in the non-operative pediatric inpatient population than operative patients. Intravenous acetaminophen prescription was associated with an increase in opioid duration as compared with patients who received opioids alone, suggesting that it is commonly used to supplement opioids for pain relief.

Association of Intravenous Acetaminophen Administration With the Duration of Intravenous Opioid Use Among Hospitalized Pediatric Patients

Importance

Adoption of multimodal pain regimens that incorporate nonopioid analgesic medications to reduce inpatient opioid administration can prevent serious opioid-related adverse effects in children, including tolerance, withdrawal, delirium, and respiratory depression. Intravenous (IV) acetaminophen is in widespread pediatric use; however, its effectiveness as an opioid-sparing agent has not been evaluated in general pediatric inpatients.

Objective

To determine if IV acetaminophen administered prior to IV opioids is associated with a reduction in the total duration of IV opioids administered compared with IV opioids administered without IV acetaminophen in general pediatric inpatients.

Design, Setting, and Participants

This comparative effectiveness research study included data on pediatric inpatients from 274 US hospitals between January 2011 and June 2016 collected from a national database. Outcomes were compared with a propensity score-matched analysis of pediatric inpatients administered IV opioids without IV acetaminophen (control) and those administered IV acetaminophen prior to IV opioids (intervention). Data were analyzed from January 2020 through October 2021.

Exposures

Patients in the intervention group received IV acetaminophen prior to IV opioids. Patients in the control group received IV opioids without IV acetaminophen.

Main Outcomes and Measures

Total duration of all IV opioids administered during a patient's hospitalization.

Results

Of 893 293 pediatric inpatients, a total of 104 579 were included in analysis (median [IQR] age, 1.3 [0-14.7] years; 59 806 [57.2%] female; 21 485 [21.5%] African American, 56 309 [53.8%] White), of whom 18 197 (2.0%) received IV acetaminophen, and 287 504 (34.0%) received IV opioids. After applying exclusion criteria, among patients who received IV acetaminophen, 1739 (10.8%) received IV acetaminophen prior to IV opioids within a median (IQR) treatment time of 1.5 (0.02-7.3) hours. After propensity score matching produced comparable groups in the control and intervention groups (with 839 patients in each group), the multivariable model estimated a 15.5% shorter duration of IV opioid use in the intervention group, with an absolute IV opioid reduction of 7.5 hours (95% CI, 0.7-15.8 hours).

Conclusions and Relevance

In this comparative effectiveness study, IV acetaminophen administered prior to IV opioids was associated with a reduction in IV opioid duration by 15.5%. Multimodal pain regimens that use IV acetaminophen prior to IV opioids could reduce IV opioid duration.

The Effect of Scheduled Intravenous Acetaminophen in an Enhanced Recovery Protocol Pathway in Patients Undergoing Major Abdominal Procedures: A Prospective, Randomized, and Placebo-Controlled Clinical Trial

OBJECTIVE

Enhanced recovery protocols (ERPs) utilize multi-modal analgesia regimens. Individual regimen components should be evaluated for their analgesic efficacy. We evaluated the effect of scheduled intravenous (IV) acetaminophen within an ERP on analgesia and recovery after a major abdominal surgery.

DESIGN

This study is a prospective, randomized, double-blinded clinical trial.

SETTING

The study setting was a tertiary care, academic medical center.

SUBJECTS

Adult patients scheduled for elective major abdominal surgical procedures.

METHODS

Patients in group A received 1g IV acetaminophen, while patients in group P received IV placebo every six hours for 48 hours postoperatively within an ERP. Pain scores, opioid requirements, nausea and vomiting, time to oral intake and mobilization, length of stay, and patient satisfaction scores were measured and compared.

RESULTS

From 412 patients screened, 154 patients completed the study (Group A: 76, Group P: 78). Primary outcome was the number of patients with unsatisfactory pain relief, defined as a composite of average Numeric Rating Scale (NRS) scores above 5 and requirement of IV patient-controlled analgesia for pain relief during the first 48 hours postoperatively, and was not significantly different between the two groups (33 (43.4%) in group A versus 42 (53.8%) patients in group P, p=0.20). Opioid consumption was comparable between two groups. Group A utilized significantly less postoperative rescue antiemetics compared to group P (41% vs. 58%, p= 0.02).

CONCLUSIONS

Scheduled administration of IV acetaminophen did not improve postoperative analgesia or characteristics of postoperative recovery in patients undergoing major abdominal surgery within an ERP pathway.

An Opioid-Sparing Protocol Improves Recovery Time and Reduces Opioid Use After Laparoscopic Sleeve Gastrectomy

PURPOSE

The current literature is sparse on post discharge pain management for bariatric surgical patients. This study aimed to determine if an opioid-sparing protocol could decrease opioid use during the postoperative period (hospital to home).

MATERIALS AND METHODS

In this retrospective cohort study, we implemented an opioid-sparing protocol in January 2018, for patients undergoing laparoscopic sleeve gastrectomy (LSG) at our institution. We compared recovery time, pain scores (in hospital and at home), and perioperative opioid use between the historic control group (February 2017 to December 2017) and the opioid-sparing group (January 2018 to December 2018). A p value of < .05 was considered statistically significant.

RESULTS

The study included 400 patients (200 in each group), and 165 participated in the phone survey. Baseline characteristics were similar, except the control group had a higher body mass index and body weight. The average recovery time was significantly shorter in the opioid-sparing group (18.9 versus 35.3 days, P = .043). There was no significant difference in mean postoperative pain scores in the hospital or at home. The opioid-sparing group required significantly fewer opioids postoperatively (10.4 versus 16.1 morphine milligram equivalents, P < .001). Only 1 out of the 200 patients in the opioid-sparing arm requested an opioid prescription after discharge.

CONCLUSION

Implementation of an opioid-sparing protocol improved recovery time and reduced postoperative opioid use in the hospital and after discharge without changing perceived pain in patients undergoing LSG.

Community hospital decreases narcotic usage in postoperative bariatric patients

BACKGROUND

Opioids have long been used as an effective form of analgesia for pain in the postoperative setting; however, their addictive potential and associated complications have become a detriment. There has been an increasing movement to decrease opioid prescribing.

OBJECTIVE

The aim of this study was to look at common bariatric surgery procedures at a single institution and compare opioid usage before and after the implementation of a multimodal pain regimen.

SETTING

Community program, hospital-employed, and private practice, United States.

METHODS

Six hundred twelve laparoscopic gastric bypass and laparoscopic sleeve gastrectomy patients were included in this single-institution retrospective cohort study. Data were obtained from chart review. Comparison was made between patients from 2016 and patients from a 3-month period in 2017 when the new pain management protocol had been instituted.

RESULTS

The postoperative opioid usage of 516 patients from 2016 was compared with that of 96 patients from a 3-month period in 2017 after initiating the new pain management protocol. The mean intravenous hydromorphone usage of the control group, 16.0 ± 14.6 morphine milligram equivalent (or 4.0 mg ± .2), over the postoperative inpatient stay decreased to 7.3 ± 6.7 morphine milligram equivalent (or 1.8 mg ± .2) in the study group. This represents a 55% decrease. The study group did show less 30-day postoperative complications compared with the control, 1.04% and 2.13%, respectively, although this was not statistically significant.

CONCLUSION

A multimodal pain regimen is an effective way to cut opioid usage with no statistical difference in overall 30-day complications.

Effect of scheduled intravenous acetaminophen on postoperative nausea and vomiting in patients undergoing laparoscopic gynecologic surgery

PURPOSE

The aim of this study was to assess the effect of scheduled intravenous acetaminophen (SIVA) on the incidence of postoperative nausea and vomiting (PONV) in patients undergoing laparoscopic gynecologic surgery (LGS).

METHODS

This retrospective observational study identified consecutive patients who underwent LGS at our institution from January to November of 2017 and were managed with either our hospital's old protocol (Group H) or a new protocol using SIVA (Group S). Primary outcomes included the incidences of PONV and the amount of additional antiemetic required in the postoperative period. The secondary outcomes included the pain score on postoperative day 1, the requirement for additional analgesic medications, and the length of hospitalization (LOH).

RESULTS

Patients in Group S had significantly lower incidences of PONV from postoperative days 0 to 1 and required significantly less antiemetics or tramadol than those in Group H (P = 0.0085). Patients at a low risk for PONV in Group S had significantly lower incidences of PONV than those in Group H (P = 0.0129). Further, the amount of additional tramadol required was lower in Group S than in Group H (P = 0.0021).

CONCLUSION

Introduction of SIVA into the postoperative pain management protocol of LGS may reduce the incidence of PONV and the amount of adjunctive antiemetic medication required from postoperative days 0 to 1. In patients undergoing LGS, PONV prophylaxis using antiemetics should be prescribed depending on PONV risk profile; however, SIVA prophylaxis can be used in all patients regardless of PONV risk profile.

Evolving the management of acute perioperative pain towards opioid free protocols: a narrative review

Objective: Identification of pain as the fifth vital sign has resulted in over-prescription and overuse of opioids in the US, with addiction reaching epidemic proportions. In Europe, and more recently in the US, a shift has occurred with the global adoption of multimodal analgesia (MMA), which seeks to minimize perioperative opioid use. Improved functional outcomes and reduced healthcare utilization costs have been demonstrated with MMA, but wide scale use of opioids in pain management protocols continues. As a next step in the pain management evolution, opioid-free analgesia (OFA) MMA strategies have emerged as feasible in many surgical settings.Methods: Articles were limited to clinical studies and meta-analyses focusing on comparisons between opioid-intensive and opioid-free/opioid-sparing strategies published in English.Results: In this review, elimination or substantial reduction in opioid use with OFA strategies for perioperative acute pain are discussed, with an emphasis on improved pain control and patient satisfaction. Improved functional outcomes and patient recovery, as well as reduced healthcare utilization costs, are also discussed, along with challenges facing the implementation of such strategies.Conclusions: Effective MMA strategies have paved the way for OFA approaches to postoperative pain management, with goals to reduce opioid prescriptions, improve patient recovery, and reduce overall healthcare resource utilization and costs. However, institution-wide deployment and adoption of OFA is still in early stages and will require personalization and better management of patient expectations.

Intravenous Acetaminophen Reduces Length of Stay Via Mediation of Postoperative Opioid Consumption After Posterior Spinal Fusion in a Pediatric Cohort

OBJECTIVES

Since approval of intravenous acetaminophen (IV APAP), its use has become quite common without strong positive evidence. Our goal was to determine the effect of IV APAP on length of hospital stay (LOS) via mediation of opioid-related side effects in pediatric patients.

MATERIALS AND METHODS

After Institutional Review Board approval, 114 adolescents undergoing posterior spinal fusion were prospectively recruited and managed postoperatively with patient-controlled analgesia and adjuvant therapy. Patients were divided into 2 groups based on the use of IV APAP: control (n=70) and treatment (n=44). Association of IV APAP use with opioid outcomes was analyzed using inverse probability of treatment weighting (IPTW)-adjusted propensity scores to balance the 2 groups for all significant covariates except postoperative opioid consumption. Mediation analysis was carried out for LOS with IV APAP as the independent variable and morphine consumption as the mediator.

RESULTS

Oral intake was delayed by ∼1 day (P<0.001) and LOS was 0.6 days longer in the control group (P=0.044). After IPTW, time to oral intake remained significantly longer in the control group (P=0.014). The mediation model with IPTW revealed a significant negative association between IV APAP and morphine consumption (P<0.001), which significantly increased LOS (P<0.003). IV APAP had a significant opioid-sparing effect associated with shorter LOS.

DISCUSSION

IV APAP hastens oral intake and is associated with decreased LOS in an adolescent surgery population likely through decreased opioid consumption. Through addition of IV APAP in this population, LOS may be decreased, an important implication in the setting of escalating health care costs.

Efficacy of intravenous acetaminophen in multimodal management for pain relief following total knee arthroplasty: a meta-analysis

Background

The efficacy of intravenous acetaminophen in multimodal pain management in patients undergoing total knee arthroplasty (TKA) is controversial. The purpose of this meta-analysis was to compare the efficacy of intravenous acetaminophen versus placebo in TKA.

Methods

Randomized controlled trials (RCTs) or retrospective cohort studies (RCSs) concerning related topics were retrieved from PubMed (1996–June 2018), Embase (1980–June 2018), and the Cochrane Library (CENTRAL June 2018). Any studies comparing intravenous acetaminophen with a placebo were included in this meta-analysis. Meta-analysis results were collected and analyzed by Stata 12.0. Subgroup analysis was performed according to the general characteristics of the patients.

Results

In total, the patients from six studies met the inclusion criteria. Our meta-analysis results indicated that compared with a control group, intravenous acetaminophen was associated with reductions in total morphine consumption and visual analogue scale (VAS) score at postoperative day (POD) 3. However, there was no significant difference in morphine consumption at POD 1 or in VAS at POD 1 or POD 2. Moreover, there was no significant difference in the length of hospital stay.

Conclusions

Based on our results, intravenous acetaminophen in multimodal management has shown better efficacy in pain relief at POD 3 and has morphine-sparing effects. High-quality studies with more patients are needed in the future.

Electronic supplementary material

The online version of this article (10.1186/s13018-018-0950-7) contains supplementary material, which is available to authorized users.

Efficacy of Intravenous Acetaminophen in Length of Stay and Postoperative Pain Control in Laparoscopic Roux-en-Y Gastric Bypass Surgery Patients

Background: Opiate-based pain medications may incur adverse effects following bariatric surgery. The aim of this study was to evaluate the efficacy of intravenous Acetaminophen (IVAPAP) on length of stay (LOS) after laparoscopic Roux-en-Y gastric bypass (LRYGB) surgery.

Methods: This was a prospective, double-blind, randomized controlled trial conducted from October 2011 to March 2014 at a 416-bed teaching hospital. Eighty-nine total patients were included (control group, n = 45; treatment group, n = 44). Patients were administered either 1000 mg of IVAPAP or placebo every 6 h beginning preoperatively and continuing for four doses. LOS, total narcotic consumption, pain and nausea scores, time to return of flatus (ROF), and postoperative rescue pain medication used were measured during the first 24 h after surgery.

Results: LOS was significantly decreased in the treatment group compared with control (2.72 days vs. 3.18 days; p = 0.03). There was significant reduction in time to ROF (1.87 days vs. 2.24 days; p = 0.04). Pain was significantly decreased in the first 2 postoperative hours in the treatment group (p = 0.02). Total opioid consumption, postoperative nausea scores, and use of rescue pain medications were not affected.

Conclusions: The use of IVAPAP significantly decreases LOS following LRYGB, improves acute postoperative pain control, and mediates quicker return of bowel function.

The rising tide of opioid use and abuse: the role of the anesthesiologist

Opioid use has risen dramatically in the past three decades. In the USA, opioid overdose has become a leading cause of unintentional death, surpassing motor vehicle accidents. A patient's first exposure to opioids may be during the perioperative period, a time where anesthesiologists have a significant role in pain management. Almost all patients in the USA receive opioids during a surgical encounter. Opioids have many undesirable side effects, including potential for misuse, or opioid use disorder. Anesthesiologists and surgeons employ several methods to decrease unnecessary opioid use, opioid-related adverse events, and side effects in the perioperative period. Multimodal analgesia, enhanced recovery pathways, and regional anesthesia are key tools as we work towards optimal opioid stewardship and the ideal of effective analgesia without undesirable sequelae.

A Multimodal Analgesic Protocol Reduces Opioid-Related Adverse Events and Improves Patient Outcomes in Laparoscopic Sleeve Gastrectomy

BACKGROUND

Laparoscopic sleeve gastrectomy (LSG) is one of the most commonly performed procedures for the treatment of obesity. Patients with obesity are more prone to experience opioid-related adverse events (ORAE).

OBJECTIVES

The objective of this study is to determine if a multimodal analgesia protocol (MAP) reduces ORAE and provides effective pain relief for patients after LSG.

SETTING

This study was conducted at University Hospital, Singapore.

METHODS

The MAP consists of mandatory pre-operative etoricoxib, intra-operative acetaminophen, and post-operative acetaminophen with optional post-operative tramadol. We identified and collected data for patients who underwent LSG between May 2010 and November 2015 and compared patients before and after the implementation of the MAP.

RESULTS

One hundred fifty-eight patients were included and 68 patients were treated with the MAP. There were no differences in age, gender, body mass index, ethnicity, or comorbidities between the two groups except for the incidence of hypertension (p = 0.015). There was a significant reduction in the incidence of ORAE from 33.3 to 8.8% (p < 0.001) after the implementation of the MAP. There was also a significant reduction in the use of opioids intra-operatively from 58.2 to 43.6 mg (p < 0.001) and post-operatively from 23.7 to 0.7 mg (p < 0.001). Pain scores were similar at 1, 6, and 48 post-operatively, while pain scores were significantly reduced at 12 (p = 0.033) and 24 h (p = 0.02) post-operatively. Multivariate analysis showed that these results remained significant.

CONCLUSION

Our study suggests that a MAP reduces ORAE and provides effective pain relief for patients undergoing LSG.

Cost-effectiveness of intravenous acetaminophen and ketorolac in adolescents undergoing idiopathic scoliosis surgery

BACKGROUND

Enhanced recovery after surgery protocols increasingly use multimodal analgesia after major surgeries with intravenous acetaminophen and ketorolac, despite no documented cost-effectiveness of these strategies.

AIMS

The goal of this prospective cohort study was to model cost-effectiveness of adding acetaminophen or acetaminophen + ketorolac to opioids for postoperative outcomes in children having scoliosis surgery.

METHODS

Of 106 postsurgical children, 36 received only opioids, 26 received intravenous acetaminophen, and 44 received acetaminophen + ketorolac as analgesia adjuncts. Costs were calculated in 2015 US $. Decision analytic model was constructed with Decision Maker^® software. Base-case and sensitivity analyses were performed with effectiveness defined as avoidance of opioid adverse effects.

RESULTS

The groups were comparable demographically. Compared with opioids-only strategy, subjects in the intravenous acetaminophen + ketorolac strategy consumed less opioids (P = .002; difference in mean morphine consumption on postoperative days 1 and 2 was -0.44 mg/kg (95% CI -0.72 to -0.16); tolerated meals earlier (P < .001; RR 0.250 (0.112-0.556)) and had less constipation (P < .001; RR 0.226 (0.094-0.546)). Base-case analysis showed that of the 3 strategies, use of opioids alone is both most costly and least effective, opioids + intravenous acetaminophen is intermediate in both cost and effectiveness; and opioids + intravenous acetaminophen and ketorolac is the least expensive and most effective strategy. The addition of intravenous acetaminophen with or without ketorolac to an opioid-only strategy saves $510-$947 per patient undergoing spine surgery and decreases opioid side effects.

CONCLUSION

Intravenous acetaminophen with or without ketorolac reduced opioid consumption, opioid-related adverse effects, length of stay, and thereby cost of care following idiopathic scoliosis in adolescents compared with opioids-alone postoperative analgesia strategy.

Controlling postoperative use of i.v. acetaminophen at an academic medical center

PURPOSE

Results of an interprofessional formulary initiative to decrease postoperative prescribing of i.v. acetaminophen are reported.

SUMMARY

After a medical center added i.v. acetaminophen to its formulary, increased prescribing of the i.v. formulation and a 3-fold price increase resulted in monthly spending of more than $40,000, prompting an organizationwide effort to curtail that cost while maintaining effective pain management. The surgery, anesthesia, and pharmacy departments applied the Institute for Healthcare Improvement's Model for Improvement to implement (1) pharmacist-led enforcement of prescribing restrictions, (2) retrospective evaluation of i.v. acetaminophen's impact on rates of opioid-related adverse effects, (3) restriction of prescribing of the drug to 1 postoperative dose on select patient care services, and (4) guideline-driven pain management according to an enhanced recovery after surgery (ERAS) protocol. Monitored metrics included the monthly i.v. acetaminophen prescribing rate, the proportion of i.v. acetaminophen orders requiring pharmacist intervention to enforce prescribing restrictions, and prescribing rates for select adjunctive analgesics. Within a year of project implementation, the mean monthly i.v. acetaminophen prescribing rate decreased by 83% from baseline to about 6 doses per 100 patient-days, with a decline in the monthly drug cost to about $4,000. Documented pharmacist interventions increased 2.7-fold, and use of oral acetaminophen, ketorolac, and gabapentin in ERAS areas increased by 18% overall.

CONCLUSION

An interprofessional initiative at a large medical center reduced postoperative use of i.v. acetaminophen by more than 80% and yielded over $400,000 in annual cost savings.

Morbidly Obese Patients Exhibit Increased CYP2E1-Mediated Oxidation of Acetaminophen

Introduction

Acetaminophen (paracetamol) is mainly metabolized via glucuronidation and sulphation, while the minor pathway through cytochrome P450 (CYP) 2E1 is held responsible for hepatotoxicity. In obese patients, CYP2E1 activity is reported to be induced, thereby potentially worsening the safety profile of acetaminophen. The aim of this study was to determine the pharmacokinetics of acetaminophen and its metabolites (glucuronide, sulphate, cysteine and mercapturate) in morbidly obese and non-obese patients.

Methods

Twenty morbidly obese patients (with a median total body weight [TBW] of 140.1 kg [range 106–193.1 kg] and body mass index [BMI] of 45.1 kg/m² [40–55.2 kg/m²]) and eight non-obese patients (with a TBW of 69.4 kg [53.4–91.7] and BMI of 21.8 kg/m² [19.4–27.4]) received 2 g of intravenous acetaminophen. Fifteen blood samples were collected per patient. Population pharmacokinetic modelling was performed using NONMEM.

Results

In morbidly obese patients, the median area under the plasma concentration–time curve from 0 to 8 h (AUC_0–8h) of acetaminophen was significantly smaller (P = 0.009), while the AUC_0–8h ratios of the glucuronide, sulphate and cysteine metabolites to acetaminophen were significantly higher (P = 0.043, 0.004 and 0.010, respectively). In the model, acetaminophen CYP2E1-mediated clearance (cysteine and mercapturate) increased with lean body weight [LBW] (population mean [relative standard error] 0.0185 L/min [15 %], P < 0.01). Moreover, accelerated formation of the cysteine and mercapturate metabolites was found with increasing LBW (P < 0.001). Glucuronidation clearance (0.219 L/min [5 %]) and sulphation clearance (0.0646 L/min [6 %]) also increased with LBW (P < 0.001).

Conclusion

Obesity leads to lower acetaminophen concentrations and earlier and higher peak concentrations of acetaminophen cysteine and mercapturate. While a higher dose may be anticipated to achieve adequate acetaminophen concentrations, the increased CYP2E1-mediated pathway may preclude this dose adjustment.

Electronic supplementary material

The online version of this article (doi:10.1007/s40262-015-0357-0) contains supplementary material, which is available to authorized users.

Randomized Prospective Trial Comparing the Use of Intravenous versus Oral Acetaminophen in Total Joint Arthroplasty

BACKGROUND

Multimodal pain management has had a significant effect on improving total joint arthroplasty recovery and patient satisfaction. There is literature supporting that intravenous (IV) acetaminophen reduces postoperative pain and narcotic use in the total joint population. However, there are no studies comparing the effectiveness of IV vs oral (PO) acetaminophen as part of a standard multimodal perioperative pain regimen.

METHODS

One hundred twenty patients undergoing hip and knee arthroplasty surgeries performed by one joint arthroplasty surgeon were prospectively randomized into 2 groups. Group 1 (63 patients) received IV and group 2 (57 patients) received PO acetaminophen in addition to a standard multimodal perioperative pain regimen. Each group received 1 gram of acetaminophen preoperatively and then every 6 hours for 24 hours. Total narcotic use and visual analog scale (VAS) scores were collected every 4 hours postoperatively.

RESULTS

The 24-hour average hydromorphone equivalents given were not different between groups (3.71 vs 3.48) at 24 hours (P = .76), or at any of the individual 4-hour intervals. The 24-hour average visual analog scale scores in group 1 (IV) was 3.00 and in group 2 (PO) was 3.40 (P = .06). None of the 4-hour intervals were significantly different except the first interval (0-4 hour postoperatively), which favored the IV group (P = .03).

CONCLUSION

The use of IV acetaminophen may have a role when given intraoperatively to reduce the immediate pain after surgery. Following that, it does not provide a significant benefit in reducing pain or narcotic use when compared with the much less expensive PO form.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.