Randomised controlled trial comparing oral and intravenous paracetamol (acetaminophen) plasma levels when given as preoperative analgesia

Elimination of postoperative narcotics in infant robotic pyeloplasty using caudal anesthesia and a non-narcotic pain pathway

INTRODUCTION

Research suggests that narcotic pain medications are dramatically overprescribed. We hypothesize that narcotics are unnecessary for post-operative pain control in most infants undergoing robotic pyeloplasty. In this series, we report our experience combining caudal blocks with a non-narcotic postoperative pathway as a means of eliminating postoperative narcotics following infant robotic pyeloplasty.

METHODS

We reviewed 24 consecutive patients who underwent robotic pyeloplasty by a single surgeon treated with an end-procedure caudal block followed by a non-narcotic postoperative pain pathway treated between May 2017 and May 2021. The standardized postoperative pathway consisted of an end-procedure caudal block followed by alternating intravenous acetaminophen and ketorolac. We reviewed demographics, outcomes and unscheduled healthcare encounters within 30 postoperative days.

RESULTS

63% (15/24) patients were male and average age was 12.1 months (range 4-34 months). 58% (9/15) underwent surgery on the left. 16.7% (4/24) of patients received a single postoperative dose of narcotics in the PACU. No patient required narcotic prescriptions at discharge or anytime thereafter. The average length of stay was 1.13 days. There was no pain-related, unscheduled visits or phone calls after discharge.

CONCLUSIONS

This series shows that a non-narcotic standardized pain management strategy is a viable option for infants undergoing robotic pyeloplasty. Post procedure caudal block is a good addition to a non-narcotic pathway. In the future, we intend to expand these findings to other pediatric urologic procedures in the hope of eliminating unnecessary narcotic use.

Home Recovery After Mastectomy: Review of Literature and Strategies for Implementation American Society of Breast Surgeons Working Group

BACKGROUND

Practices regarding recovery after mastectomy vary significantly, including overnight stay versus discharge same day. Expanded use of Enhanced Recovery After Surgery (ERAS) algorithms and the recent COVID pandemic have led to increased number of patients who undergo home recovery after mastectomy (HRAM).

METHODS

The Patient Safety Quality Committee of the American Society of Breast Surgeons created a multispecialty working group to review the literature evaluating HRAM after mastectomy with and without implant-based reconstruction. A literature review was performed regarding this topic; the group then developed guidance for patient selection and tools for implementation.

RESULTS

Multiple, retrospective series have reported that patients discharged day of mastectomy have similar risk of complications compared with those kept overnight, including risk of hematoma (0-5.1%). Multimodal strategies that improve nausea and analgesia improve likelihood of HRAM. Patients who undergo surgery in ambulatory surgery centers and by high-volume breast surgeons are more likely to be discharged day of surgery. When evaluating unplanned return to care, the only significant factors are African American race and increased comorbidities.

CONCLUSIONS

Review of current literature demonstrates that HRAM is a safe option in appropriate patients. Choice of method of recovery should consider patient factors, such as comorbidities and social situation, and requires input from the multidisciplinary team. Preoperative education regarding pain management, drain care, and after-hour access to medical care are crucial components to a successful program. Additional investigation is needed as these programs become more prevalent to assess quality measures such as unplanned return to care, complications, and patient satisfaction.

Use of Intravenous Paracetamol Preoperatively Favors Lower Risk of Delirium and Functional Recovery in Elderly Patients with Hip Fracture: A Propensity Score-Matched Analysis

We aimed to investigate whether the use of intravenous paracetamol (IVP) preoperatively in intertrochanteric fracture (IF) patients aged 65 years or over receiving intramedullary fixation had significantly benefits on the pain score at discharge, delirium incidence, length of hospital stay (LOS), functional outcomes, and mortality. A retrospective analysis of all surgically treated patients presenting with IF was conducted at a single Level I trauma center in China between Jan. 2016 and Jan. 2020. The data concerning patients' demographics, injury-related data, surgery-related data, operation-related data, in-hospital data, and postoperative outcomes were extracted. To minimize potential confounding and selection bias, the propensity score matching (PSM) method was performed via the caliper matching method by using a 1 : 1 ratio. After PSM, McNemar's chi-square tests were used to examine the association of using IVP with outcome analyses. The Spearman correlations of IVP using, pain scores, and the factors which may influence them were also computed. After screening 2963 consecutive patients, 2166 were included finally, including 1576 in the non-IVP group and 590 in the IVP group. After PSM, 531 remained in each group. The pain scores at discharge were significantly between the two groups before and after matching (all p < 0.001). The differences of delirium rate and functional outcomes became significant after propensity score-based matching (p=0.001 and 0.033, respectively), although they were not significant before matching. No significant difference was observed in other operation-related data, LOS, and crude mortality rates at 30-day, 90-day, and 12-month before and after PSM. In conclusion, this study highlights the need for preoperative IVP use to optimize pain control, postoperative functional recovery, and minimize pain-related comorbidities such as delirium in elderly patients with hip fracture.

Factors Associated With Unplanned Admission in Patients Intended for Same Day Discharge After Minimally Invasive Hysterectomy for Endometrial Cancer

Objectives. To identify factors that lead to successful same-day discharge compared with unplanned and planned admission after minimally invasive hysterectomy for endometrial cancer. Methods. Patients undergoing laparoscopic or robotic hysterectomy for endometrial cancer between 2016 and 2019 were retrospectively reviewed. 3 groups were created: same-day discarge (SDD), unplanned admission (UA), and planned admission(PA). Demographic/perioperative factors and encounters after discharge were compared. A multivariable logistic regression was performed. Results. 262 patients were included. By year, the success of SDD increased from 59.1% to 82.5%. Patients who underwent SDD compared with admission were younger (62.2 vs 66.2, P = .003) and had a lower Charlson Comorbidity Index (4 vs 5, P < .001). BMI was not significant. Comparing SDD and UA, shorter operative time (100.3 min vs 130.6 min, P = .037) was associated with SDD. Postoperative pain scores were not significant (3.8 vs 4.7, P = .086). The rate of unscheduled encounters within 30 days of discharge was not significantly different. On multivariable analysis, the odds of SDD decreased by 4% with each 1-year increase in age (OR .96, P = .017). Each 1-minute increase in operative time decreased the odds of SDD by 2% (OR .98, P < .001). Intraoperative acetaminophen (OR 2.78, P = .003) and ketorolac (OR 2.27, P = .031) were predictive of SDD. Conclusion. SDD can be safely incorporated into clinical practice in gynecologic oncology patients undergoing minimally invasive hysterectomy, even for patients older than previously reported. Shorter operative time was associated with SDD. The role of perioperative acetaminophen and ketorolac should be further investigated.

Pain Management in Breast Surgery: Recommendations of a Multidisciplinary Expert Panel-The American Society of Breast Surgeons

Opioid overdose accounted for more than 47,000 deaths in the United States in 2018. The risk of new persistent opioid use following breast cancer surgery is significant, with up to 10% of patients continuing to fill opioid prescriptions one year after surgery. Over prescription of opioids is far too common. A recent study suggested that up to 80% of patients receiving a prescription for opioids post-operatively do not need them (either do not fill the prescription or do not use the medication). In order to address this important issue, The American Society of Breast Surgeons empaneled an inter-disciplinary committee to develop a consensus statement on pain control for patients undergoing breast surgery. Representatives were nominated by the American College of Surgeons, the Society of Surgical Oncology, The American Society of Plastic Surgeons, and The American Society of Anesthesiologists. A broad literature review followed by a more focused review was performed by the inter-disciplinary panel which was comprised of 14 experts in the fields of breast surgery, anesthesiology, plastic surgery, rehabilitation medicine, and addiction medicine. Through a process of multiple revisions, a consensus was developed, resulting in the outline for decreased opioid use in patients undergoing breast surgery presented in this manuscript. The final document was reviewed and approved by the Board of Directors of the American Society of Breast Surgeons.

Treatment With Oral Versus Intravenous Acetaminophen in Elderly Trauma Patients With Rib Fractures: A Prospective Randomized Trial

BACKGROUND

Rib fractures are common injuries among traumatically injured patients, and elderly patients with rib fractures are at increased risk for adverse events and death. The purpose of this study was to determine if oral Per os (PO) acetaminophen is as effective as intravenous (IV) acetaminophen in treating the pain associated with rib fractures.

METHODS

We performed a single-center, randomized, placebo-controlled, double-blinded study. Trauma patients who were ≥65 years old and had ≥1 rib fracture were included in this study. Patients were randomized into IV acetaminophen and oral placebo (n = 63) or IV placebo and oral solution acetaminophen (n = 75) groups. The primary outcome was a mean reduction in pain score at 24 hours, and secondary outcomes included opioid use, intensive care unit (ICU) length of stay (LOS), hospital LOS, hospital mortality, the difference in incentive spirometry, and development of pneumonia.

RESULTS

Among the 138 patients included, there was no statistically significant difference between the 2 study groups in a mean reduction in pain score at 24 hours after injury (PO: 3.24, IV: 2.49; P = .230). Opioid pain medication use was equivalent between groups (P = .212), and there was no significant difference in hospital mortality rate between groups (P = .827). There was no statistically significant difference in ICU LOS, hospital LOS, or development of pneumonia.

DISCUSSION

In elderly trauma patients (age ≥65 years) with 1 or more rib fractures, PO acetaminophen is equivalent to IV acetaminophen for pain control, with no difference in morbidity or mortality. Oral acetaminophen should be preferentially used over IV acetaminophen when treating the elderly trauma patient with rib fractures.

A systematic review and trial sequential analysis of intravenous vs. oral peri-operative paracetamol

Postoperative pain might be different after intravenous vs. oral paracetamol. We systematically reviewed randomised controlled trials in patients >15 years that compared intravenous with oral paracetamol for postoperative pain. We identified 14 trials with 1695 participants. There was inconclusive evidence for an effect of route of paracetamol administration on postoperative pain at 0–2 h (734 participants), 2–6 h (766 participants), 6–24 h (1115 participants) and >24 h (248 participants), with differences in standardised mean (95%CI) pain scores for intravenous vs. oral of −0.17 (−0.45 to 0.10), −0.09 (−0.24 to 0.06), 0.06 (−0.12 to 0.23) and 0.03 (−0.22 to 0.28), respectively. Trial sequential analyses suggested that a total of 3948 participants would be needed to demonstrate a meaningful difference in pain or its absence at 0–2 h. There were no differences in secondary outcomes. Intravenous paracetamol is more expensive than oral paracetamol. Substitution of oral paracetamol in half the patients given intravenous paracetamol in our hospital would save around £ 38,711 (€ 43,960 or US$ 47,498) per annum.

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.

Delirium Reduced With Intravenous Acetaminophen in Geriatric Hip Fracture Patients

INTRODUCTION

Postoperative delirium is associated with opioid use in the elderly and is a common complication of geriatric hip fractures, with reported incidences from 16% to 70%. Intravenous (IV) acetaminophen is a safe and efficacious medication in elderly patients and has been shown to reduce use of opioids after hip fracture. At our institution, IV acetaminophen was implemented for the first 24 hours postoperatively as part of a multimodal pain control regimen for geriatric hip fracture patients.

METHODS

A retrospective review of 123 hip fragility fracture patients older than 60 years from January 2016 to December 2016 was performed. Delirium was identified using a validated chart-based review tool. The rate of delirium, as well as length of stay, pain scores, opioid administration, need for one-to-one supervision, and readmissions were analyzed.

RESULTS

Sixty-five patients (52.8%) received IV acetaminophen during this period. No notable differences were found in baseline characteristics between groups. Ten of 65 patients receiving IV acetaminophen postoperatively experienced delirium compared with 19 of 58 who did not receive the medication (15.4% versus 32.8%, P = 0.024). The IV acetaminophen group also required fewer doses of IV opioids on postoperative day 1 (0.37 versus 1.19 doses, P = 0.008), were less likely to require one-to-one supervision (9.2% versus 24.1%, P = 0.025), and had shorter lengths of hospital stay (6.37 versus 8.47 days, P = 0.037). Readmission rates and discharge dispositions did not vary with significance between the two groups.

CONCLUSION

The inclusion of IV acetaminophen as part of a multimodal pain regimen led to fewer episodes of delirium in this study. The reduced use of opioids immediately after surgery may have been a large factor in this outcome. Lower delirium rates may reduce the utilization of inpatient resources for direct patient supervision and provide for shorter hospital stays.

Diclofenac Versus Ketorolac for Pain Control After Primary Total Joint Arthroplasty: A Comparative Analysis

Introduction As total hip arthroplasty (THA) and total knee arthroplasty (TKA) transition to outpatient settings, appropriate pain management remains a challenge. Nonsteroidal anti-inflammatory drugs (NSAIDs) may subvert the need for postoperative opioids. This study evaluated: 1) total opioid consumption; 2) postoperative pain intensity; 3) discharge destination; 4) length of stay (LOS); and 5) THA and TKA patients' satisfaction in receiving adjunctive intravenous (IV) diclofenac or ketorolac. Methods In this retrospective cohort study, patients scheduled to undergo primary THA or TKA by a single surgeon between March 2017 and April 2018 were identified. Patients were stratified based on the receipt of IV diclofenac (THA: n = 25; TKA: n = 51) or IV ketorolac (THA: n = 28; TKA: n = 32) in addition to the standard pain management regimen. Student's t-testing and Chi-square were used to analyze continuous and categorical variables, respectively. Results TKA diclofenac patients had lower opioid consumption 12 hours postoperatively (p: 0.037). TKA patients in the diclofenac cohort were discharged to home less often (p: 0.025). Both diclofenac cohorts had greater patient satisfaction than the ketorolac cohorts (p: <0.05). There was no significant difference between groups in postoperative pain intensity at 24 or 48 hours or in the length of stay (p: >0.05 for all). Conclusion This study demonstrated that both TKA and THA patients treated with IV diclofenac had no difference in postoperative pain intensity while THA patients had no difference in opioid consumption relative to those treated with IV ketorolac. Further comparison of IV NSAIDs with other IV pain medications may provide broader insight into the ideal management for postoperative pain for this widening patient population.

Comparison of metamizole and paracetamol effects on colonic anastomosis and fibroblast activities in Wistar rats

BACKGROUND

Leakage following colorectal anastomosis surgery causes various complications associated with high morbidity and mortality, especially in pediatric patients. It might be caused by the use of non-steroidal anti-inflammatory drugs (NSAIDs) as postoperative analgesics. This study aimed to compare the effect of metamizole and paracetamol on colonic anastomosis and fibroblast activities, including proliferation, migration, and collagen synthesis, in Wistar rats.

METHODS

Rats were divided into control, paracetamol and metamizole groups. The colonic anastomosis was evaluated by determining the integrity of the muscle layers, the formation of granulation tissue, and mucosal anastomosis. Fibroblast activities were analyzed by measuring the proliferation, migration, and collagen synthesis.

RESULTS

Metamizole caused more damage to muscle layer integrity, more inhibition of granulation tissue formation in the anastomosis area and lower mucosal anastomosis compared with paracetamol and control groups. Metamizole had a higher cytotoxic effect than paracetamol, which suppressed the proliferation and migration of fibroblasts. Furthermore, both drugs did not affect the synthesis of collagen.

CONCLUSION

Metamizole shows worse effects on the integrity of muscle layers, inhibition of granulation tissue formation, mucosal anastomosis, fibroblast proliferation, and migration, but not collagen synthesis, than paracetamol in Wistar rat intestines following colonic anastomosis. These findings might indicate that paracetamol is safer than metamizole as analgesic following colonic anastomosis.

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.

Opioid Use in the Postoperative Arena: Global Reduction in Opioids After Surgery Through Enhanced Recovery and Gynecologic Surgery

Enhanced recovery programs aim to reduce surgical stress to improve the patient perioperative experience. Through a combination of multimodal analgesia and maintaining a physiological state, postoperative recovery is improved. Many analgesic adjuncts are available that improve postoperative pain control and limit opioid analgesia requirements. Adjuncts are often used in combination, but different interventions may be incorporated for patient-specific and procedure-specific needs. Postoperative pain control can be optimized by continuing nonopioid adjuncts, and prescribing opioid analgesia to address breakthrough pain. Prescribing practices should balance optimizing pain relief, minimizing the risk of chronic pain, while limiting the potential for opioid misuse.

Assessment and Early Management of Pain in Hip Fractures: The Impact of Paracetamol

Introduction

As the number of patients sustaining hip fractures increases, interventions aimed at improving patient comfort and reducing complication burden acquire increased importance. Frailty, cognitive impairment, and difficulty in assessing pain control characterize this population. In order to inform future care, a review of pain assessment and the use of preoperative intravenous paracetamol (IVP) is presented.

Materials and Methods

Systematic review of preoperative IVP administration in patients presenting with a hip fracture.

Results

Intravenous paracetamol is effective in the early management of pain control in the hip fracture population. There is a considerable decrease in use of breakthrough pain medications when compared with other pain relief modalities. Additionally, IVP reduces the incidence of opioid-induced complications, reduces length of stay, and lowers mean pain scores. Another significant finding of this study is the poor administration of all analgesics to patients with hip fracture with up to 72% receiving no prehospital analgesia.

Discussion

The potential benefits of IVP as routine in the early management of hip fracture-related pain are clear. Studies of direct comparison between analgesia regimes to inform optimum bundles of analgesic care are sparse. This study highlights the need for properly constructed pathway-driven comparator studies of contemporary analgesia regimes, with IVP as a central feature to optimize pain control and minimize analgesia-related morbidity in this vulnerable population.

Reduced length of stay and hospitalization costs among inpatient hysterectomy patients with postoperative pain management including IV versus oral acetaminophen

OBJECTIVE

To compare the outcomes of hysterectomy patients who received standard pain management including IV acetaminophen (IV APAP) versus oral APAP.

METHODS

We performed a retrospective analysis of the Premier Database (January 2012 to September 2015) comparing hysterectomy patients who received postoperative pain management including IV APAP to those who received oral APAP starting on the day of surgery and continuing up to the third post-operative day, with no exclusions based on additional pain management. We compared the groups on length of stay (LOS), hospitalization costs, and average daily morphine equivalent dose (MED). The quarterly rate of IV APAP use for all hospitalizations by hospital was used as an instrumental variable in two-stage least squares regressions also adjusting for patient demographics, clinical risk factors, and hospital characteristics.

RESULTS

We identified 22,828 hysterectomy patients including 14,811 (65%) who had received IV APAP. Study subjects averaged 50 and 52 years of age, respectively in the IV APAP and oral APAP cohorts and were predominantly non-Hispanic Caucasians (≥60% in both cohorts). Instrumental variable models found IV APAP associated with 0.8 days shorter hospitalization (95% CI: -0.92 to -0.68, p<0.0001) and $2,449 lower hospitalization costs (95% CI: -$2,902 to -$1,996, p<0.0001). Average daily MED trended lower without statistical significance (-1.41 mg, 95% CI: -3.43 mg to 0.61 mg, p = 0.17).

CONCLUSIONS

Compared to oral APAP, managing post-hysterectomy pain with IV APAP is associated with shorter LOS and lower total hospitalization costs.

A Preliminary Examination of the Comparative Efficacy of Intravenous vs Oral Acetaminophen in the Treatment of Perioperative Pain

Objective

The management of postoperative pain is a major health care issue. While the cost of intravenous acetaminophen (IVA) is significantly greater than its oral acetaminophen (OA) counterpart, less is known regarding comparative effectiveness of these routes. The purpose of this study was to determine whether perioperative IVA is equivalent in reducing postoperative pain compared with perioperative OA for laparoscopic cholecystectomy (LapChole).

Design

Double-blinded, prospective, randomized placebo-controlled trial.

Setting

Womack Army Medical Center, Fort Bragg, North Carolina.

Subjects

Adults (age > 18 years) active duty military, veterans, and beneficiaries receiving a laparoscopic cholecystectomy.

Methods

This study was conducted at Womack Army Medical Center (WAMC), Fort Bragg, North Carolina, between January 2013 and June 2015. Sixty-seven subjects with symptomatic cholelithiasis were randomly assigned to receive two doses (1,000 mg each) of either IVA or OA. A numerical rating scale (NRS) score of pain was obtained preoperatively and every six hours for 24 hours postoperation. The primary objective was to assess whether treatment groups had significantly different 24-hour postoperative sum of pain intensity differences (SPID24) using an analysis of covariance test.

Results

Sixty subjects completed the study and were included in the analysis. Treatment groups did not differ in SPID24, even when controlling for age, gender, and preoperative pain levels (F(1,55) = 0.39, P = 0.54, partial η2 = 0.007), nor did 24-hour opioid consumption when controlling for age, gender, and operation time (F(1, 46) = 0.47, P = 0.50, partial η2 = 0.01). Furthermore, treatment groups were equally as likely to report average postoperative NRS scores of 4 or higher (β = 0.24, Exp(B) = 1.28, P = 0.68).

Conclusions

The results show no evidence of differences between IVA or OA in pain or opioid consumption among a sample of patients undergoing LapChole. Due to low sample size, these descriptive findings warrant larger studies, which may have a significant economic impact.

Perioperative Management of Patients with Addiction to Opioid and Non-opioid Medications

PURPOSE OF REVIEW

With the rise of the opioid epidemic, anesthesiologists will find themselves faced with opioid-addicted patients more frequently. Addiction to opioids may also occur concurrently with abuse of other non-opioid medications. Our review article seeks to outline an armamentarium of pain management strategies in the perioperative period for these patients with addiction to opioid and non-opioid medications.

RECENT FINDINGS

Statistics from the CDC demonstrate a shocking increase in opioid prescription rates and opioid-related deaths. Furthermore, opioid-addicted patients have notoriously undertreated pain in the perioperative period. A multitude of strategies are available in the perioperative period to treat pain in these patients. Formulating treatment plans for opioid and non-opioid-addicted patients undergoing surgery should include considerations in the pre-, intra-, and post-operative period. Our review article outlines several non-opioid modalities which may be employed to treat pain in these patients; however, particularly in the opioid-addicted population, the practitioner must be aware that non-opioids alone may not suffice to treat post-surgical pain. Consultation with pain management may be warranted to optimize opioid and non-opioid treatment for these patients.

Pharmacokinetics of Oral and Intravenous Paracetamol (Acetaminophen) When Co-Administered with Intravenous Morphine in Healthy Adult Subjects

BACKGROUND AND OBJECTIVE

Several features favor paracetamol (acetaminophen) administration by the intravenous rather than the oral route in the postoperative setting. This study compared the pharmacokinetics and bioavailability of oral and intravenous paracetamol when given with or without an opioid, morphine.

METHODS

In this randomized, single-blind, parallel, repeat-dose study in healthy adults, subjects received four repeat doses of oral or intravenous 1000 mg paracetamol at 6-h intervals, and morphine infusions (0.125 mg/kg) at the 2nd and 3rd intervals. Comparisons of plasma pharmacokinetic profiles were conducted before, during, and after opioid co-administrations.

RESULTS

Twenty-two subjects were included in the pharmacokinetic analysis. Observed paracetamol peak concentration (C max) and area under the plasma concentration-time curve over the dosing interval (AUC0-6) were reduced when oral paracetamol was co-administered with morphine (reduced from 11.6 to 7.25 µg/mL and from 31.00 to 25.51 µg·h/mL, respectively), followed by an abruptly increased C max and AUC0-6 upon discontinuation of morphine (to 13.5 µg/mL and 52.38 µg·h/mL, respectively). There was also a significantly prolonged mean time to peak plasma concentration (T max) after the 4th dose of oral paracetamol (2.84 h) compared to the 1st dose (1.48 h). However, pharmacokinetic parameters of paracetamol were not impacted when intravenous paracetamol was co-administered with morphine.

CONCLUSIONS

Morphine co-administration significantly impacted the pharmacokinetics of oral but not intravenous paracetamol. The abrupt release of accumulated paracetamol at the end of morphine-mediated gastrointestinal inhibition following oral but not intravenous administration of paracetamol suggests that intravenous paracetamol provides a better option for the management of postoperative pain. CLINICALTRIALS.

GOV IDENTIFIER

NCT02848729.

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.

Comparative Plasma and Cerebrospinal Fluid Pharmacokinetics of Paracetamol After Intravenous and Oral Administration

BACKGROUND

We compared plasma and cerebrospinal fluid (CSF) pharmacokinetics of paracetamol after intravenous (IV) and oral administration to determine dosing regimens that optimize CSF concentrations.

METHODS

Twenty-one adult patients were assigned randomly to 1 g IV, 1 g oral or 1.5 g oral paracetamol. An IV cannula and lumbar intrathecal catheter were used to sample venous blood and CSF, respectively, over 6 hours. The plasma and CSF maximum concentrations (Cmax), times to maximum concentrations (Tmax), and area under the plasma and CSF concentration-time curves (AUCs) were calculated using noncompartmental techniques. Significance was defined by P < .0167 (Bonferroni correction for 3 comparisons for each parameter). Probability (X < Y) (p″) with Bonferroni corrected 95% confidence intervals (CIs) were calculated (CIs including 0.5 meet the null hypothesis). Results are presented as median (range) or p″ (CI). P values are listed as 1 g IV vs 1 g orally, 1 g IV vs 1.5 g orally and 1 g orally vs 1.5 g orally, respectively.

RESULTS

Wide variation in measured paracetamol concentrations was observed, especially in the oral groups. The median plasma Cmax in the 1 g IV group was significantly greater than the oral groups. In contrast, the median CSF Cmax was not different between groups. The median plasma Tmax in the 1 g IV group was 105 and 75 minutes earlier than in the 1 and 1.5 g oral groups. The median CSF Tmax was not significantly different between groups. The median plasma AUC (total) was not significantly different between groups; however, in the first hour, the median plasma AUC was significantly greater in the IV group than in the oral groups. In the second hour, there was no difference between groups. The median CSF AUC (total) did not significantly differ between groups; however, in the first hour, the median CSF AUC was significantly greater in the IV compared with the orally groups. In the second hour, there was no difference between groups. Our analysis indicated that the median Cmax, Tmax, and AUC values lacked precision because of small sample sizes.

CONCLUSIONS

Peak plasma concentrations were greater and reached earlier after IV than oral dosing. Evidence for differences in CSF Cmax and Tmax was lacking because of the small size of this study.

Hospitalization Costs for Patients Undergoing Orthopedic Surgery Treated With Intravenous Acetaminophen (IV-APAP) Plus Other IV Analgesics or IV Opioid Monotherapy for Postoperative Pain

INTRODUCTION

To assess the impact on hospitalization costs of multimodal analgesia (MMA), including intravenous acetaminophen (IV-APAP), versus IV opioid monotherapy for postoperative pain management in patients undergoing orthopedic surgery.

METHODS

Utilizing the Truven Health MarketScan® Hospital Drug Database (HDD), patients undergoing total knee arthroplasty (TKA), total hip arthroplasty (THA), or surgical repair of hip fracture between 1/1/2011 and 8/31/2014 were separated into postoperative pain management groups: MMA with IV-APAP plus other IV analgesics (IV-APAP group) or an IV opioid monotherapy group. All patients could have received oral analgesics. Baseline characteristics and total hospitalization costs were compared. Additionally, an inverse probability treatment weighting [IPTW] with propensity scores analysis further assessed hospitalization cost differences.

RESULTS

The IV-APAP group (n = 33,954) and IV opioid monotherapy group (n = 110,300) differed significantly (P < 0.0001) across baseline characteristics, though the differences may not have been clinically meaningful. Total hospitalization costs (mean ± standard deviation) were significantly lower for the IV-APAP group than the IV opioid monotherapy group (US$12,540 ± $9564 vs. $13,242 ± $35,825; P < 0.0001). Medical costs accounted for $701 of the $702 between-group difference. Pharmacy costs were similar between groups. Results of the IPTW-adjusted analysis further supported the statistically significant cost difference.

CONCLUSIONS

Patients undergoing orthopedic surgery who received MMA for postoperative pain management, including IV-APAP, had significantly lower total costs than patients who received IV opioid monotherapy. This difference was driven by medical costs; importantly, there was no difference in pharmacy costs. Generalizability of the results may be limited to patients admitted to hospitals similar to those included in HDD. Dosing could not be determined, so it was not possible to quantify utilization of IV-APAP or ascertain differences in opioid consumption between the 2 groups. This study did not account for healthcare utilization post-discharge.

Pharmacokinetics and Bioavailability of a Fixed-Dose Combination of Ibuprofen and Paracetamol after Intravenous and Oral Administration

Background and Objectives

Previously published studies have suggested the lack of a pharmacokinetic interaction between ibuprofen and paracetamol when they are delivered as a fixed-dose oral combination. The aim of this study was to determine the pharmacokinetic profile and safety of a fixed-dose intravenous (IV) combination, containing 3 mg/mL ibuprofen and 10 mg/mL paracetamol, in comparison with its individual components. The study also assessed the relative bioavailability of the same doses of the active ingredients when they were administered as an oral formulation.

Methods

A single-dose, open-label, randomized, five-period cross-over sequence pharmacokinetic study was undertaken in 30 healthy volunteers. Serial plasma samples were assayed for both paracetamol and ibuprofen concentrations, using validated liquid chromatography–tandem mass spectrometry methods. Pharmacokinetic parameters were computed using standard non-compartmental analyses. Adverse events were also assessed. The ratios of the maximum measured plasma concentration (C_max), the area under the plasma concentration–time curve (AUC) from time zero to the time of the last measurable plasma concentration (AUC_t) and AUC from time zero to infinity (AUC_∞) were analysed for bioequivalence as determined by 90 % confidence intervals.

Results

The pharmacokinetic parameters of ibuprofen and paracetamol were very similar for the combination and monotherapy IV preparations; the ratios of the C_max, AUC_t and AUC_∞ values fell within the 80–125 % acceptable bioequivalence range. Precise dose proportionality for both compounds was also determined for the half dose of the IV formulation in comparison with the full dose. The relative bioavailability of paracetamol (93.78 %) and ibuprofen (96.45 %) confirmed the pharmacokinetic equivalence of the oral and IV formulations of the fixed-dose combination.

Conclusion

Concomitant administration of 3 mg/mL ibuprofen and 10 mg/mL paracetamol in a fixed-dose IV combination does not alter the pharmacokinetic profiles of either drug. The IV and oral dose forms of such a combination are pharmacokinetically equivalent.

Acetaminophen, nonsteroidal anti-inflammatory drugs, and cyclooxygenase-2 selective inhibitors: an update

SUMMARY

Plastic and cosmetic surgery is often performed as an ambulatory procedure, and pain is often mild to moderate. Good pain relief is central to patient comfort and satisfaction. Analgesics used should ensure rapid onset and adequate pain relief lasting a sufficiently long duration with minimal or no side effects. Acetaminophen is well tolerated by patients, efficacious, and associated with only minor side effects, when used in the minimal effective doses. Nonsteroidal anti-inflammatory drugs (NSAIDs) are more efficacious, having lower numbers needed to treat compared with acetaminophen, but have several side effects and contraindications. However, when used in the correct doses in healthy patients, NSAIDs are excellent for pain management with one caveat that there is an increased risk for oozing or bleeding. In contrast, cyclooxygenase inhibitors (Coxibs) are equally efficacious as NSAIDs but have the added advantage that they have minimal or no effect on platelet function, and therefore, the risk for bleeding complications is minimal. However, there has been some concern about the risk of vascular events in patients with ischemic heart disease, specifically when using Coxibs, but even some NSAIDs, for example, diclofenac. In conclusion, acetaminophen should be given postoperatively to all patients undergoing plastic surgical procedures. For patients undergoing moderately invasive surgery, the addition of Coxibs to acetaminophen would be an advantage except in the patient with ischemic heart disease where NSAIDs could have a place in management of pain. Side effects and contraindications of NSAIDs, however, restrict their use to the healthy patient with mild comorbidities.

Is Scheduled Intravenous Acetaminophen Effective in the Pain Management Protocol of Geriatric Hip Fractures?

BACKGROUND

Hip fractures have significant effects on the geriatric population and the health care system. Prior studies have demonstrated both the safety of intravenous (IV) acetaminophen and its efficacy in decreasing perioperative narcotic consumption. The purpose of this study is to evaluate the effect of scheduled IV acetaminophen for perioperative pain control on length of hospital stay, pain level, narcotic use, rate of missed physical therapy (PT) sessions, adverse effects, and discharge disposition in geriatric patients with hip fractures.

METHODS

A retrospective review was performed of all patients 65 years and older admitted to a level I trauma center, who received operative treatment for a hip fracture over a 2-year period. Demographic data, in-hospital variables, and outcome measures were analyzed. Three hundred thirty-six consecutive fractures in 332 patients met inclusion criteria. These patients were divided into 2 cohorts. Group 1 (169 fractures) consisted of patients treated before the initiation of a standardized IV acetaminophen perioperative pain control protocol, and group 2 (167 fractures) consisted of those treated after the protocol was initiated.

RESULTS

Group 2 had a statistically significant shorter mean length of hospital stay (4.4 vs 3.8 days), lower mean pain score (4.2 vs 2.8), lower mean narcotic usage (41.3 vs 28.3 mg), lower rate of PT sessions missed (21.8% vs 10.4%), and higher likelihood of discharge home (7% vs 19%; P ≤ .001). Use of IV acetaminophen was also consistently and independently predictive of the same variables (P < .01).

CONCLUSION

The utilization of scheduled IV acetaminophen as part of a standardized pain management protocol for geriatric hip fractures resulted in shortened length of hospital stay, decreased pain levels and narcotic use, fewer missed PT sessions, and higher rate of discharge to home.

LEVEL OF EVIDENCE

Therapeutic level III.

Intravenous versus Oral Acetaminophen for Pain: Systematic Review of Current Evidence to Support Clinical Decision-Making

BACKGROUND

Intravenous (IV) acetaminophen is increasingly used around the world for pain control for a variety of indications. However, it is unclear whether IV administration offers advantages over oral administration.

OBJECTIVE

To identify, summarize, and critically evaluate the literature comparing analgesic efficacy, safety, and pharmacokinetics for IV and oral dosage forms of acetaminophen.

DATA SOURCES

A literature search of the PubMed, Embase, and International Pharmaceutical Abstracts databases was supplemented with keyword searches of Science Direct, Wiley Library Online, and Springer Link databases for the period 1948 to November 2014. The reference lists of identified studies were searched manually.

STUDY SELECTION AND DATA EXTRACTION

Randomized controlled trials comparing IV and oral dosage forms of acetaminophen were included if they assessed an efficacy, safety, or pharmacokinetic outcome. For each study, 2 investigators independently extracted data (study design, population, interventions, follow-up, efficacy outcomes, safety outcomes, pharmacokinetic outcomes, and any other pertinent information) and completed risk-of-bias assessments.

DATA SYNTHESIS

Six randomized clinical trials were included. Three of the studies reported outcomes pertaining to efficacy, 4 to safety, and 4 to pharmacokinetics. No clinically significant differences in efficacy were found between the 2 dosage forms. Safety outcomes were not reported consistently enough to allow adequate assessment. No evidence was found to suggest that increased bioavailability of the IV formulation enhances efficacy outcomes. For studies reporting clinical outcomes, the results of risk-of-bias assessments were largely unclear.

CONCLUSIONS

For patients who can take an oral dosage form, no clear indication exists for preferential prescribing of IV acetaminophen. Decision-making must take into account the known adverse effects of each dosage form and other considerations such as convenience and cost. Future studies should assess multiple-dose regimens over longer periods for patients with common pain indications such as cancer, trauma, and surgery.

OFIRMEV: an old drug becomes new again

This was judged to be the first place winning submission for the American Dental Society of Anesthesiology Student Essay Award. Acetaminophen is an old drug that is now available in an intravenous formulation. Its advantages and disadvantages are reviewed, including its potential role in multimodal postoperative pain therapy.

A retrospective analysis of intravenous acetaminophen use in spinal surgery patients

OBJECTIVE

This study aimed to determine if intravenous acetaminophen [paracetamol] (IV APAP) could decrease visual analog pain scores (VAS), opioid exposure and subsequent opioid related adverse effects (nausea, vomiting, constipation) in spinal surgery patients.

METHODS

Thirty four spinal surgery patients to date have received IV APAP since its addition to the formulary at our institution. The electronic medical record was accessed on all patients who received at least one dose pre or post operatively to collect postoperative opioid consumption (in morphine equivalents), number of antiemetic and laxative doses, use of naloxone, and VAS pain scores from arrival to surgical unit through postop day two. An equivalent number of patients who did not receive any IV APAP were selected and matched on the basis of opioid use prior to admission, surgery type, surgeon, age, and sex to constitute the control group.

RESULTS

The IV APAP group used significantly less opioids than the control group (p=0.015). Frequency of antiemetic and laxative use and VAS pain scores did not differ significantly between the two groups.

CONCLUSIONS

It appears IV APAP can be used effectively as an adjuvant pain management therapy in spinal surgery patients to decrease opioid exposure, but does not necessarily reduce the incidence of opioid related adverse effects or VAS pain scores.

An Audit of the Statistical Validity of Conclusions of Clinical Superiority in Anaesthesia Journals

Making a statistically valid conclusion of the superiority of a clinical intervention in a clinical trial requires not only a statistically significant P value, but also adequate a priori power and an observed effect size larger than the clinically important value specified in the sample size calculation. We scrutinised the five most highly cited clinical trials reporting one or more conclusions of clinical superiority published in Anesthesiology, the British Journal of Anaesthesia, Anaesthesia, Anesthesia and Analgesia and Anaesthesia and Intensive Care in 2011 or 2012 to determine how many met all three requisite criteria. In the 25 articles, there were a total of 36 unconditional conclusions of the superiority of a clinical intervention. All were supported by a statistically significant P value. However, only 15 (41.6%) met all three requisite statistical criteria to support clinical superiority. The remainder included secondary outcomes without specific reference to their observational nature, and primary outcomes whose observed effect size was smaller than the clinically important value specified in the sample size calculation. These findings indicate that clinicians should closely scrutinise conclusions of clinical superiority in anaesthesia journals. Many will be ‘hypothesis-generating observations’ without adequate statistical support for a conclusion of clinical superiority in their own right.

The analgesic efficacy of preoperative oral Ibuprofen and acetaminophen in children undergoing adenotonsillectomy: a randomized clinical trial

Background:

Adenotonsillectomy is one of the most common surgical procedures in children. Several complications and morbidities are common after nasal surgeries and the most common is pain. Several techniques have been employed to reduce the severity of postoperative pain. One of the preoperative techniques is pre-emptive analgesia through preventive central hypersensitization. This technique is performed by applying analgesic methods before the onset of nociceptive stimuli, consequently decreasing postoperative analgesics requirements.

Objectives:

Preoperative oral drug administration for pain analgesia is performed in several methods. The aim of this study was to compare the analgesic effects of preoperatively administration of oral acetaminophen and ibuprofen.

Patients and Methods:

In a double-blinded, randomized placebo-controlled study, sixty 4-12 years old ASA I or II children scheduled for elective adenotonsillectomy, were assigned to receive either acetaminophen 15 mg/kg, ibuprofen 10 mg/kg or placebo 30 minutes before the operation. Postoperative pain was assessed using the Children's Hospital of Eastern Ontario Pain Scale (CHEOPS), upon arrival to the post anesthetic care unit (PACU) and ward. Findings were analyzed by SPSS version 17 using variance analysis and Tukey’s test.

Results:

The average pain intensities were significantly lower in acetaminophen group based on the CHEOPS in both PACU and ward compared to ibuprofen or placebo groups; but there was no difference in pain intensity between the ibuprofen and placebo groups. Pain intensity in PACU in Acetaminophen group was 7.05 ± 0.64 vs. 8.38 ± 1.20 in placebo group and 8.14 ± 0.85 in ibuprofen group, pain intensity in ward in the acetaminophen group was 6.0.87 ± 0.85in the acetaminophen group, vs. 8.04 ± 1.02 in placebo group, and 7.78 ± 0.78 in ibuprofen group.

Conclusions:

This study showed that administration of oral acetaminophen 30 minutes preoperatively, resulted in significantly lower pain intensity in children undergoing adenotonsillectomy in PACU and ward, compared to ibuprofen and placebo.

Efficacy of paracetamol for the treatment of patent ductus arteriosus in preterm neonates

Inhibitors of the cyclo-oxygenase component of prostaglandin-H₂ synthetase, namely indomethacin and ibuprofen, are commonly used in the treatment of hemodynamically significant patent ductus arteriosus. These drugs are associated with serious adverse events, including gastrointestinal perforation, renal failure and bleeding. The role of paracetamol, an inhibitor of the peroxidase component of prostaglandin-H₂ synthetase, has been proposed for the treatment of patent ductus arteriosus. We report a series of 8 neonates (birth weight: 724 ± 173 g; gestational age: 26 ± 2 weeks) treated with paracetamol for a hemodynamically significant patent ductus arteriosus, because of contraindications to ibuprofen or indomethacin. Successful closure was achieved in 6 out of 8 babies (75%). Median ductal diameter was significantly reduced after treatment (from 1.2 mm, range 1.0-2.5 mm to 0.6 mm, range 0.0-2.5 mm, p = 0.038). No adverse or side effects were observed during treatment. On the basis of these results, paracetamol could be considered a promising and safe therapy for the treatment of patent ductus arteriosus in neonates.

The role of intravenous acetaminophen in multimodal pain protocols for perioperative orthopedic patients

Multimodal pain management should be considered for all perioperative orthopedic patients. The goal of reducing the amount of perioperative opioid medication given may be achieved by using nonopioid medications, including intravenous acetaminophen. The site of action of acetaminophen is a variety of receptors in the central nervous system. When given intravenously, acetaminophen produces a much higher plasma concentration, which then leads to higher levels in the cerebrospinal fluid. The safety profile and relative lack of systemic adverse reactions make this an attractive analgesic for a wide variety of orthopedic surgical patients. Clinical studies have demonstrated the efficacy and safety of intravenous acetaminophen in elective total hip and knee arthroplasty, knee arthroscopy, lumbar spine surgery, and for acute traumatic limb pain.

Can intravenous paracetamol reduce opioid use in preoperative hip fracture patients?

Pain due to intra- and extracapsular hip fractures is usually treated with opioid medication. Paracetamol (acetaminophen in North America) has better bioavailability when given intravenously than orally and has been successfully used in the postoperative care of orthopedic patients. However, no study has evaluated its use in the preoperative trauma patient. Our unit conducted a prospective, consecutive cohort study to investigate the opioid-sparing effect of regularly administered intravenous paracetamol compared with oral paracetamol in preoperative hip fracture patients. The total opioid dose given, based on conversion to intravenous morphine, and the reported pain score were evaluated in 75 patients. There were 28 patients in the control group who were give routine oral paracetamol and oral opioids, with morphine for breakthrough pain. There were 47 patients in the study group who received only routine intravenous paracetamol, with opioids reserved for breakthrough pain. The patients in the 2 groups had similar characteristics. The mean preoperative oral paracetamol dose for the control group was 7.2 g compared with 6.3 g in the study group. There was a significant reduction (P<.005) in the mean total intravenous morphine with intravenous paracetamol (6.5 mg) compared with oral paracetamol (21.8 mg). There was no difference in the mean pain score between the groups, 2.1 vs 1.8 (P=.3). Intravenous paracetamol had a significant opioid-sparing effect and satisfactory pain relief in preoperative hip fracture patients.

In vitro clearance of intravenous acetaminophen in extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is a life support system used as a bridge to transplantation in critically ill patients who suffer from acute respiratory or cardiac failure with resultant hypoxemia and tissue hypoxia. This is not amendable to conventional support intervention. Previous studies have shown significant drug losses in the components of an ECMO circuit, leading to decreased plasma drug levels. An in vitro study was conducted to determine: (1) changes in intravenous acetaminophen levels over time and (2) changes in concentration observed between different sites of the ECMO circuit. A single bolus dose of intravenous (IV) acetaminophen was injected into a standard blood-primed ECMO circuit. Plasma drug concentrations in the circuit were then measured at specific time points at three different locations to determine concentrations of the drug at time 0, 15, 30, 60, 240 and 360 minutes. The three samples were drawn pre- and post-membrane oxygenator and the polyvinyl chloride (PVC) tubing. A second bolus dose was administered 24 hours after the first in order to compare "new" and "old" circuits. This entire process was repeated a total of three times. The results show that acetaminophen concentrations do not change significantly over time, with consistent levels seen in both new and old circuits (N=9). Average old circuit concentrations were approximately two times greater than the average new circuit concentrations after the circuit was re-dosed at 24 hours. Drug sequestration in the circuit was not significant in any of the three sites measured. It appears that, while acetaminophen levels remain relatively constant over a six hour period, dosing adjustments may be required for use in a circuit beyond the initial 24 hour period, depending on physiologic clearance of the drug. Assuming a six-hour dosing interval, levels should remain constant.

Postoperative plasma paracetamol levels following oral or intravenous paracetamol administration: a double-blind randomised controlled trial

In day-case surgery paracetamol is commonly given orally preoperatively, or intravenously intraoperatively. In this double-blind randomised controlled trial we investigated which of these methods of administration achieved therapeutic plasma levels most effectively in the early postoperative period. Thirty patients undergoing day case arthroscopy of the knee were randomised to receive either 1.0 g oral paracetamol 30 to 60 minutes preoperatively (20 patients) or 1.0 g intravenous paracetamol intraoperatively (10 patients). Plasma paracetamol levels were measured 30 minutes after arrival in the recovery room. Secondary outcomes included postoperative pain scores, rescue analgesia requirements and duration of stay in the recovery room. All patients receiving the intravenous preparation had plasma levels above the analgesic level compared to less than half (7/20) in the oral group. Mean plasma paracetamol levels were 88.6 µmol/l for the intravenous group and 53.2 µmol/l for the oral group (P=0.0005). There were trends towards reduced rescue analgesia and duration of stay in the recovery room for the intravenous group although not reaching statistical significance. There was no difference in pain scores between groups. Intraoperative administration of 1.0 g of intravenous paracetamol more reliably achieved effective paracetamol levels in the early postoperative period compared to an equal dose given orally preoperatively. Only a minority of patients receiving the 1.0 g oral dose preoperatively had plasma levels in the therapeutic analgesic range.