Acetaminophen as an adjunct to morphine by patient-controlled analgesia in the management of acute postoperative pain

Assessment of safety and effectiveness of oral morphine on patients attending pain and palliative care: a study on Indian population

Opioid analgesics remain the corner stone of effective management of moderate to severe pain. Morphine in its oral and parenteral form is one of the most affordable options left to treat severe cancer pain in most Palliative centres in India. The main objective of our study was to assess the safety and effectiveness, as well as the prescribing pattern of immediate release oral morphine on the Indian population attending Pain and Palliative Care in a multi-speciality hospital. Within the sample population, 74.8% of all patients achieved a pain score reduction of less than or equal to 3 within the 72nd hour. Although the mean baseline pain score was similar in the cancer (8.23±0.75) and the non-cancer (8.26±0.98) group, the mean pain score at the 24th and 72nd hours were significantly different (5.6±1.29 in cancer and 5.09±1.26 in the non-cancer group within the 24th hour, followed by 3.66±1.479 and 3.12±0.88 after the 72nd hour, respectively). The majority of the patients (58.3%) were prescribed at a frequency of 5 mg every 4th hourly, with double dose at bedtime. A similar prescribing trend was seen in both the cancer and non-cancer groups. Moreover, 14 patients underwent dose escalation – with 12 belonging to the cancer group, while 11 patients falling under the cancer group required a switch to different therapy. The major adverse drug reactions (ADR) observed in both study groups were constipation (89.2%), fatigue (37.4%), dry mouth (36%) and nausea/vomiting (23%). The severity of nausea/vomiting and sleepiness was higher in the cancer group whereas itching was more predominant among the non-cancer group.

Simultaneous Detection of Morphine and Codeine in the Presence of Ascorbic Acid and Uric Acid and in Human Plasma at Nafion Single-Walled Carbon Nanotube Thin-Film Electrode

In clinical settings, the dosing and differential diagnosis of the poisoning of morphine (MO) and codeine (CO) is challenging due to interindividual variations in metabolism. However, direct electrochemical detection of these analytes from biological matrices is inherently challenging due to interference from large concentrations of anions, such as ascorbic acid (AA) and uric acid (UA), as well as fouling of the electrode by proteins. In this work, a disposable Nafion-coated single-walled carbon nanotube network (SWCNT) electrode was developed. We show facile electron transfer and efficient charge separation between the interfering anions and positively charged MO and CO, as well as significantly reduced matrix effect in human plasma. The Nafion coating alters the voltammetric response of MO and CO, enabling simultaneous detection. With this SWCNT/Nafion electrode, two linear ranges of 0.05-1 and 1-10 μM were found for MO and one linear range of 0.1-50 μM for CO. Moreover, the selective and simultaneous detection of MO and CO was achieved in large excess of AA and UA, as well as, for the first time, in unprocessed human plasma. The favorable properties of this electrode enabled measurements in plasma with only mild dilution and without the precipitation of proteins.

Postoperative Pain Management Strategies in Hip Arthroscopy

PURPOSE OF REVIEW

Hip arthroscopy is a rapidly growing field due to its significant diagnostic and therapeutic value in the management of numerous hip disorders. Adequate control of postoperative pain in patients undergoing hip arthroscopy continues to be a challenging and evolving area in orthopedics. In the absence of standardized protocols for pain management in these patients, a variety of different approaches have been utilized in an effort to find a regimen that is effective at reducing postoperative pain, narcotic consumption, and cost to the patient and healthcare system. The purpose of this article, therefore, is to provide a comprehensive review of current literature regarding postoperative pain management techniques in patients undergoing hip arthroscopy.

RECENT FINDINGS

Recent literature demonstrates the importance of a multimodal approach to treat postoperative pain in patients undergoing hip arthroscopy. When a peripheral nerve block or intraoperative anesthetic is used in combination with a pre- and postoperative analgesic medication regimen, patients report less pain and postoperative narcotic consumption. Patient-reported pain scores and postoperative opioid use were similar between the different modalities, however, postoperative complications appear to be less in groups receiving intra-articular (IA) injection or local anesthetic infiltration (LAI) compared to peripheral nerve blocks. In summary, we present evidence that intraoperative techniques, such as IA injection or LAI, in conjunction with pre- and postoperative pain medications, offers an effective multimodal strategy for treating postoperative pain following hip arthroscopy. This topic is of increasing importance due to the need for cost-effective strategies of managing pain and decreasing opioid consumption following hip arthroscopy.

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.

Utilization and effectiveness of multimodal discharge analgesia for postoperative pain management

BACKGROUND

Although evidence-based guidelines recommend a multimodal approach to pain management, limited information exists on adherence to these guidelines and its association with outcomes in a generalized population. We sought to assess the association between discharge multimodal analgesia and postoperative pain outcomes in two diverse health care settings.

METHODS

We evaluated patients undergoing four common surgeries associated with high pain in electronic health records from an academic hospital (AH) and Veterans Health Administration (VHA). Multimodal analgesia at discharge was characterized as opioids in combination with acetaminophen (O + A) and nonsteroidal antiinflammatory (O + A + N) drugs. Hierarchical models estimated associations of analgesia with 45-d follow-up pain scores and 30-d readmissions.

RESULTS

We identified 7893 patients at AH and 34,581 at VHA. In both settings, most patients were discharged with O + A (60.6% and 54.8%, respectively), yet a significant proportion received opioids alone (AH: 24.3% and VHA: 18.8%). Combining acetaminophen with opioids was associated with decreased follow-up pain in VHA (Odds ratio [OR]: 0.86, 95% confidence interval [CI]: 0.79, 0.93) and readmissions (AH OR: 0.74, CI: 0.60, 0.90; VHA OR: 0.89, CI: 0.82, 0.96). Further addition of nonsteroidal antiinflammatory drugs was associated with further decreased follow-up pain (AH OR: 0.71, CI: 0.53, 0.96; VHA OR: 0.77, CI: 0.69, 0.86) and readmissions (AH OR: 0.46, CI: 0.31, 0.69; VHA OR: 0.84, CI: 0.76, 0.93). In both systems, patients receiving multimodal analgesia received 10%-40% less opioids per day compared to opioids only.

CONCLUSIONS

A majority of surgical patients receive a multimodal pain approach at discharge yet many receive only opioids. Multimodal regimen at discharge was associated with better follow-up pain and all-cause readmissions compared to the opioid-only regimen.

Comparative Study of the Effect of Intravenous Paracetamol and Tramadol in Relieving of Postoperative Pain after General Anesthesia in Nephrectomy Patients

Aim:

The aim of this study was to compare the effect of intravenous paracetamol and tramadol in relieving of postoperative pain after general anesthesia for nephrectomy in prospective donor patients for kidney transplantation.

Materials and Methods:

A randomized study was conducted on 100 adult patients scheduled for nephrectomy aged from 35 to 55 years of both sexes and divided into two groups and were administered intravenous paracetamol and tramadol for postoperative pain relief and assessed with visual analog scale score and variations in vital parameters to assess extent of pain relief.

Results:

After statistical interpretation of collected data, the observations were extrapolated. There was a statistically significant difference in the pain intensity scores obtained between the paracetamol and tramadol groups.

Conclusion:

On the basis of the present study, it is concluded that tramadol due to its lesser onset of action time was superior to paracetamol in providing acute postoperative pain relief.

Effect of Intravenous Acetaminophen on Postoperative Opioid Consumption in Adult Orthopedic Surgery Patients

Background: Postoperative pain is managed with opioids, which are associated with adverse effects. The efficacy of intravenous (IV) acetaminophen in reducing opioid consumption has been studied with inconsistent results. The primary outcome of this study was to assess the effect of IV acetaminophen on opioid consumption 24 hours postoperatively. Secondary outcomes included the opiate consumption at 48 hours after the operation, opioid-related side effects 72 hours after the operation, discharge disposition, and length of stay. Methods: This was an IRB-approved, retrospective cohort study including adult patients who underwent an elective total knee arthroplasty (TKA). Patients were stratified into IV and no IV acetaminophen groups; patients who had received at least one dose of IV acetaminophen were included in the IV acetaminophen group. Total opioids were collected, converted to morphine equivalents, and compared between groups. Patients were excluded for alcohol abuse, substance abuse treatment, non-elective TKA, or medication mischarting. Results: Of the 161 patients evaluated, 148 patients were included: 86 in the IV acetaminophen and 62 in the no IV acetaminophen group. There were no differences in mean morphine equivalents between groups postoperatively at 24 hours (54.2 ± 35.9 mg vs 45.4 ± 30.2 mg; p = .12) and 48 hours (99.2 ± 68.7 mg vs 79.5 ± 49.1 mg; p = .06). There were no differences in secondary outcomes (administration of bowel regimen medications, antiemetics, naloxone, discharge disposition, or length of stay) between the groups. Conclusion: The use of IV acetaminophen was not associated with a decrease in opiate use, opiate-related side effects, or any secondary outcomes in patients who underwent TKA.

Intravenous Paracetamol Versus Patient-Controlled Analgesia With Morphine for the Pain Management Following Diagnostic Knee Arthroscopy in Trauma Patients: A Randomized Clinical Trial

Background:

Most patients undergoing outpatient surgeries have the unpleasant experience of high level pain after surgery. Compared with open surgeries, arthroscopic procedures are less painful; however, inadequate pain management could be associated with significant concerns. Opioids alone or in combination with local anesthetics are frequently used for diminishing postoperative pain using intravenous or epidural infusion pumps. Despite morphine various disadvantages, it is commonly used for controlling pain after surgery.

Objectives:

The aim of this study was to compare intravenous paracetamol and patient-controlled analgesia (PCA) with morphine for the pain management following diagnostic knee arthroscopy in trauma patients.

Patients and Methods:

Sixty trauma patients who were scheduled to undergo knee arthroscopy were randomly divided into two groups. Patients immediately received intravenous infusion of 1 g paracetamol within 15 minutes after surgery and every 6 hours to 24 hours in the paracetamol group. The patient-controlled analgesia group received morphine through PCA infusion pump at 2 mL/h base rate and 1mL bolus every 15 minutes. Pain level, nausea and vomiting, and sedation were measured and recorded during entering the recovery, 15 and 30 minutes after entering the recovery, 2, 6, and 24 hours after starting morphine pump infusion in the morphine and paracetamol in the paracetamol groups.

Results:

There was no significant difference regarding the pain level at different times after entering the recovery between the two groups. No one from the paracetamol group developed drug complications. However, 22.3% in the PCA morphine suffered from postoperative nausea; there was a statistically significant difference regarding the sedation level, nausea, and vomiting at various times between the two groups.

Conclusions:

Intravenous administration of paracetamol immediately after knee arthroscopy improved postoperative pain, decreased analgesic administration, maintained stable hemodynamic parameters, had no complications related to opiates, no nausea and vomiting, and increased patient satisfaction and comfort in comparison to PCA with morphine.

The effect of intravenous paracetamol on postoperative pain after lumbar discectomy

Study Design

A randomized, double-blinded controlled trial.

Purpose

Postoperative pain relief especially using analgesic drugs with minimal side effects has considerable clinical importance. This study aimed to examine the effect of intravenous paracetamol on pain relief after lumbar discectomy as a major surgery.

Overview of Literature

Patients undergoing lumbar discectomy experience a high degree of lumbar pain. Some authors emphasize the use of intravenous paracetamol to improve postoperative pain and increase patients' satisfaction following this surgery.

Methods

Fifty-two patients scheduled for lumbar discectomy were randomly allocated into two groups: a group that received intravenous paracetamol (1 g/100 mL normal saline) within the last 20 minutes of surgery as the case group (n=24) and a group that received sodium chloride 0.9% 100 mL as the control group (n=28). Postoperative pain was assessed at 1, 6, 12, 18, and 24 hours after surgery by a visual analogue scale (VAS). The dosage of the administered opioid (morphine), as well as drug-related side effects within the first 24 hours after surgery were also recorded.

Results

The mean VAS score was significantly lower in the paracetamol group than the controls for all of the assessed time points. Although the dose of the administered morphine was numerically lower in the paracetamol group, this difference was not statistically significant (5.53±4.49 mL vs. 7.85±4.17 mL).

Conclusions

Intravenous paracetamol as a non-opioid analgesic can relieve postoperative pain in patients undergoing lumbar discectomy; however, its use alone may not represent the best regimen for reducing the needed dose of opioids after operation.

Attenuation of Hemodynamic Responses to Laryngoscopy and Tracheal Intubation: Propacetamol versus Lidocaine-A Randomized Clinical Trial

The purpose of this study is to assess the effects of propacetamol on attenuating hemodynamic responses subsequent laryngoscopy and tracheal intubation compared to lidocaine. In this randomized clinical trial, 62 patients with the American Anesthesiologists Society (ASA) class I/II who required laryngoscopy and tracheal intubation for elective surgery were assigned to receive propacetamol 2 g/I.V./infusion (group P) or lidocaine 1.5 mg/kg (group L) prior to laryngoscopy. Systolic and diastolic blood pressures (SBP, DBP), mean arterial pressure (MAP), and heart rate (HR) were recorded at baseline, before laryngoscopy and within nine minutes after intubation. In both groups P and L, MAP increased after laryngoscopy and the changes were statistically significant (P < 0.001). There were significant changes of HR in both groups after intubation (P < 0.02), but the trend of changes was different between two groups (P < 0.001). In group L, HR increased after intubation and its change was statistically significant within 9 minutes after intubation (P < 0.001), while in group P, HR remained stable after intubation (P = 0.8). Propacetamol 2 gr one hour prior intubation attenuates heart rate responses after laryngoscopy but is not effective to prevent acute alterations in blood pressure after intubation.

Analgesic effects of paracetamol and morphine after elective laparotomy surgeries

Background:

Opioids have been traditionally used for postoperative pain control, but they have some unpleasant side effects such as respiratory depression or nausea. Some other analgesic drugs like non-steroidal anti-inflammatory drugs (NSAIDs) are also being used for pain management due to their fewer side effects.

Objectives:

The aim of our study was to compare the analgesic effects of paracetamol, an intravenous non-opioid analgesic and morphine infusion after elective laparotomy surgeries.

Patients and Methods:

This randomized clinical study was performed on 157 ASA (American Society of Anesthesiology) I-II patients, who were scheduled for elective laparotomy. These patients were managed by general anesthesia with TIVA technique in both groups and 150 patients were analyzed. Paracetamol (4 g/24 hours) in group 1 and morphine (20 mg/24 hours) in group 2 were administered by infusion pump after surgery. Postoperative pain evaluation was performed by visual analog scale (VAS) during several hours postoperatively. Meperidine was administered for patients complaining of pain with VAS > 3 and repeated if essential. Total doses of infused analgesics, were recorded following the surgery and compared. Analysis was performed on the basis of VAS findings and meperidine consumption.

Results:

There were no differences in demographic data between two groups. Significant difference in pain score was found between the two groups, in the first eight hours following operation (P value = 0.00), but not after 12 hours (P = 0.14) .The total dose of rescue drug (meperidine) and number of doses injected showed a meaningful difference between the two groups (P = 0.00). Also nausea, vomiting and itching showed a significant difference between the two groups and patients in morphine group, experienced higher levels of them.

Conclusions:

Paracetamol is not enough for postoperative pain relief in the first eight hour postoperatively, but it can reduce postoperative opioid need and is efficient enough for pain management as morphine after the first eight hours following surgery.

Postoperative delirium: a 76-year-old woman with delirium following surgery

Delirium (acute confusion) complicates 15% to 50% of major operations in older adults and is associated with other major postoperative complications, prolonged length of stay, poor functional recovery, institutionalization, dementia, and death. Importantly, delirium may be predictable and preventable through proactive intervention. Yet clinicians fail to recognize and address postoperative delirium in up to 80% of cases. Using the case of Ms R, a 76-year-old woman who developed delirium first after colectomy with complications and again after routine surgery, the diagnosis, prevention, and treatment of delirium in the postoperative setting is reviewed. The risk of postoperative delirium can be quantified by the sum of predisposing and precipitating factors. Successful strategies for prevention and treatment of delirium include proactive multifactorial intervention targeted to reversible risk factors, limiting use of sedating medications (especially benzodiazepines), effective management of postoperative pain, and, perhaps, judicious use of antipsychotics.

Prostate cancer pain management: EAU guidelines on pain management

CONTEXT

The first publication of the European Association of Urology (EAU) guidelines on Pain Management in Urology dates back to 2003. Since then, these guidelines have been revised several times with the most recent update achieved in 2010.

OBJECTIVE

Given the scope of the full text guidelines, condensing the entire document was no option in this context. This paper presents a summary of the section of pain management in prostate cancer, a topic considered of direct relevance for the practicing urologist.

EVIDENCE ACQUISITION

A multidisciplinary expert panel (urologists, anaesthesiologists, radio-oncologists) compiled this document based on a comprehensive consultation of the literature. Data were identified through a structured search, covering the time frame 2000 through 2010, using Medline and Embase as well as the Cochrane Library of systematic reviews. The scientific papers were weighed by the expert panel and a level of evidence (LE) assigned. Recommendations have been graded as a means to provide transparency between the underlying evidence and the guidance provided. Pain can occur in each stage of prostate cancer. It could be caused by the cancer itself (77%), be related to the cancer treatment (19%) or be unrelated to either (3%). The incidence of pain rises to 90% as patients enter the terminal phase of their illness. The physician's task is to discover and treat the cause of pain and the pain itself, to determine whether or not the underlying cause is treatable, to provide pain relief and palliative care. These tasks more often than not require a multidisciplinary team. Pain management involves mainly pharmacotherapy, including direct anticancer therapy such as androgen deprivation and chemotherapy, as well as analgetics, for instance non-steroidal anti-inflammatory drugs (NSAIDs) or opioids. In case of local impairment due to the cancer or its metastases, primary treatments like surgery, radiotherapy or radionuclides can provide adequate pain relief. In addition, in palliative care, functional, psychosocial and spiritual support are essential components. The EAU guidelines on Pain Management in Urology are available in a number of different formats through the EAU Central Office and the EAU website ( http://www.uroweb.org/guidelines/online-guidelines/ ).

CONCLUSION

The mainstay of pain management in prostate cancer is involvement of and collaboration between experts from a number of disciplines to be able to achieve a complete pain evaluation and to offer the full range of treatment options. Prostate cancer-related pain can, in most cases, be managed effectively, but it requires careful monitoring where a balance should be found between pain relief and potential side effects of treatment and quality of life (QoL).

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

Gastric absorption of oral paracetamol (acetaminophen) may be unreliable perioperatively in the starved and stressed patient. We compared plasma concentrations of parenteral paracetamol given preoperatively and oral paracetamol when given as premedication. Patients scheduled for elective ear; nose and throat surgery or orthopaedic surgery were randomised to receive either oral or intravenous paracetamol as preoperative medication. The oral dose was given 30 minutes before induction of anaesthesia and the intravenous dose given pre-induction. All patients were given a standardised anaesthetic by the same specialist anaesthetist who took blood for paracetamol concentrations 30 minutes after the first dose and then at 30 minute intervals for 240 minutes. Therapeutic concentrations of paracetamol were reached in 96% of patients who had received the drug parenterally, and 67% of patients who had received it orally. Maximum median plasma concentrations were 19 mg.l(-1) (interquartile range 15 to 23 mg.l(-1)) and 13 mg.l(-1) (interquartile range 0 to 18 mg.l(-1)) for the intravenous and oral group respectively. The difference between intravenous and oral groups was less marked after 150 minutes but the intravenous preparation gave higher plasma concentrations throughout the study period. It can be concluded that paracetamol gives more reliable therapeutic plasma concentrations when given intravenously.

Review articles: postoperative delirium: acute change with long-term implications

Delirium is an acute change in cognition and attention, which may include alterations in consciousness and disorganized thinking. Although delirium may affect any age group, it is most common in older patients, especially those with preexisting cognitive impairment. Patients with delirium after surgery recover more slowly than those without delirium and, as a result, have increased length of stay and hospital costs. The measured incidence of postoperative delirium varies with the type of surgery, the urgency of surgery, and the type and sensitivity of the delirium assessment. Although generally considered a short-term condition, delirium can persist for months and is associated with poor cognitive and functional outcomes beyond the immediate postoperative period. In this article, we provide a guide to assess delirium risk preoperatively and to prevent, diagnose, and treat this common and morbid condition. Care improvements such as identifying delirium risk preoperatively; training surgeons, anesthesiologists, and nurses to screen for delirium; implementing delirium prevention programs; and developing standardized delirium treatment protocols may reduce the risk of delirium and its associated morbidity.

Acetaminophen (paracetamol) improves pain and well-being in people with advanced cancer already receiving a strong opioid regimen: a randomized, double-blind, placebo-controlled cross-over trial

PURPOSE

To determine whether adding regular acetaminophen (paracetamol) could improve pain and well-being in people with advanced cancer and pain despite strong opioids.

PATIENTS AND METHODS

Participants took acetaminophen for 48 hours and placebo for 48 hours. The order (acetaminophen or placebo first) was randomly allocated. Pain was the primary outcome. Preferences, number of opioid breakthrough doses, overall well-being, nausea and vomiting, drowsiness, constipation, and cold sweats were secondary outcomes. Patients rated themselves daily with visual analog scales (VAS) and a verbal numeric scale (VNS) for pain, all scaled from 0 to 10.

RESULTS

Thirty patients completed the trial. The oral opioid was morphine in 23 patients and hydromorphone in seven patients. The median daily opioid dose in oral morphine equivalents was 200 mg (range, 20 to 2,100 mg). Nonsteroidal anti-inflammatory drugs, corticosteroids, or both were used by 16 patients. Pain and overall well-being were better for patients receiving acetaminophen than for those receiving placebo. The mean difference was 0.4 (95% CI, 0.1 to 0.8; P =.03) in VNS for pain, 0.6 (95% CI, -0.1 to 1.3; P =.09) in VAS for pain, and 0.7 (95% CI, 0.0 to 1.4; P =.05) in VAS for overall well-being. More patients preferred the period they took acetaminophen (n = 14) than the period they took placebo (n = 8), but many had no preference (n = 8). There were no differences in the other outcomes.

CONCLUSION

Acetaminophen improved pain and well-being without major side effects in patients with cancer and persistent pain despite a strong opioid regimen. Its addition is worth considering in all such patients.

Paracetamol in osteoarthritis of the knee

BACKGROUND

Paracetamol is a recommended symptomatic treatment of osteoarthritis (OA), but in clinical trials sample sizes have been relatively small and variable daily doses of paracetamol have been used.

OBJECTIVES

To determine the therapeutic efficacy of paracetamol in OA of the knee and identify predictive factors of clinical response to treatment.

METHODS

A double blind, parallel group, placebo controlled trial of analgesic efficacy and safety of paracetamol versus placebo including 779 patients with OA of the knee. Patients were randomly assigned to receive paracetamol 4 g/day (n = 405) or placebo (n = 374) for 6 weeks. Symptomatic OA of the knee was required at inclusion with global pain intensity of the knee during physical activities for the past 24 hours of >or=30 mm on a 100 mm visual analogue scale. The primary end point was a 30% decrease of global pain intensity of the knee. Intention to treat analyses were performed.

RESULTS

The percentage of responders did not differ significantly between groups: 52.6% and 51.9% in paracetamol and placebo groups, respectively (p = 0.840). In a subgroup of patients with chronic mechanical knee pain without signs of inflammation (n = 123), the mean change in pain intensity from baseline was 25.2 mm v 15.2 mm, in the paracetamol (n = 63) and placebo (n = 60) groups, respectively-mean difference 10.0 mm; 95% CI 1.0 to 19.0; p = 0.0294. No serious adverse events were attributable to treatment.

CONCLUSION

A statistically significant symptomatic effect of oral paracetamol 4 g/day over placebo was not found, suggesting that paracetamol use in symptomatic OA of the knee should be further explored. The tolerability and safety of paracetamol, at the recommended maximum dose of 4 g/day, was confirmed over 6 weeks.

The pharmacological basis of contemporary pain management

Pain management has become an increasingly well researched area in medicine over recent years, and there have been advances in a number of areas. While opioids remain an integral part of pain-management strategies, there is now an emphasis on the use of adjuvant drugs, such as paracetamol and anti-inflammatory agents, which through physiological or pharmacological synergism, both enhance pain control and reduce opioid use. The management of neuropathic pain continues to be a challenge. Anti-epileptics and antidepressants, together with clonidine and ketamine, provide the foundations for treatment. Another area of interest has been the widespread use of patient-controlled analgesia and the administration of some drugs, especially opioids, by means other than traditional oral and parenteral routes. The number of new drugs that have reached the stage of clinical trials has been small, yet they offer exciting possibilities. The epibatidine analogue ABT-594 and zinconitide both offer novel approaches to the management of neuropathic pain states, while selective cyclo-oxygenase-2 inhibitors and nitroaspirins may see advances in the management of nociceptive pain states.

The dose-effect relationship for morphine and vomiting after day-stay tonsillectomy in children

A dose-response curve for intravenous morphine and vomiting was investigated in children having day-stay tonsillectomy. A retrospective chart review was performed for the 164 children fulfilling the inclusion criteria. Morphine (mean 0.09 mg/kg SD 0.05) was used in 108 children in the perioperative period and a further 56 children were given no opioid. Fifty-five of these 164 children vomited and 20 children required an overnight stay in hospital because of vomiting. The probability of vomiting or overnight stay in hospital was related to morphine dose (by logistic regression). The overall probability of vomiting after morphine 0.1 mg/kg was 50% and the probability of admission for vomiting with this dose was 10%. Pharmacodynamic parameter estimates for postoperative vomiting were P0 (the baseline probability of vomiting, with no opioid) 0.115, Pmax (the maximal probability of vomiting due to morphine) 0.997, ED50 (morphine dose that induces an effect equivalent to 50% of the logit Pmax) 0.18 mg/kg. Parameter estimates for overnight stay because of vomiting after morphine administration were P0 0.038, Pmax 0.999, ED50 0.369 mg/kg. Satisfactory postoperative analgesia in children has been reported with morphine 0.05 to 0.15 mg/kg. Doses above 0.1 mg/kg are associated with a greater than 50% incidence of vomiting. Our data suggests that lower doses of morphine are associated with a decreased incidence of emesis after tonsillectomy in children.

Pharmacokinetics of paracetamol in adults after cardiac surgery

The pharmacokinetics of paracetamol in adults after cardiac surgery have not been described. Twenty patients were randomized to receive either paracetamol 2 g through a nasogastric tube and as a suppository eight hours later or vice versa. Arterial blood samples were taken at 0.5, one, two, four, six and eight hours after dosing. Each patient was studied for 16 h. There were 16 males and three females. One patient was excluded because of sampling errors. The mean age was 59 (SD 8) years and the mean weight 84 kg (16). The time-concentration profiles for each individual were used to estimate pharmacokinetic parameters using a non-linear mixed effects model (NONMEM). Population parameter estimates with coefficient of variation (CV%), standardized to a 70 kg person, for a one-compartment model with first order input, lag time and first order elimination were volume of distribution 127l (28) and clearance 26.4 l/h (29) Rectal paracetamol had an absorption half-life (Tabs) of 2.02 h (31) with a lag time of 0.28 h. The absorption half-life for the oral preparation was 1.49 h (81) with a lag time of 0.17 h. The relative bioavailability of the rectal compared to the oral formulation was 0.98 (18). Concentrations after either nasogastric or rectal paracetamol 2 g were below a target concentration of 10 mg/l, which is associated with analgesia. Absorption after nasogastric administration was slow compared to healthy adults (Tabs 0.06 to 0.7 h) and the bioavailability was half that expected, due to nasogastric loss. Parameter estimates had large variability. Paracetamol is unlikely to have useful clinical impact in the majority of patients when standard doses (6 g/day) are given on day 1 after cardiac surgery.

Balanced analgesia: what is it and what are its advantages in postoperative pain?

The concept of balanced analgesia was introduced to improve analgesic efficacy and reduce adverse effects. A large amount of clinical data has documented improved analgesia by combining different analgesics, but data on reducing adverse effects are inconclusive. Balanced analgesia should be used whenever possible, and future studies should be directed to define optimal combination regimens in individual surgical procedures.