Pain relief after abdominal surgery--a comparison of i.m. morphine, sublingual buprenorphine and self-administered i.v. pethidine

Treating Chronic Pain with Buprenorphine-The Practical Guide

OPINION STATEMENT

Buprenorphine has unique and favorable pharmacological properties that make it useful in a variety of clinical scenarios. It has been recommended to consider buprenorphine first-line opioid for chronic pain, especially in the elderly as it may be associated with less cognitive impairment, falls, sexual dysfunction, and sarcopenia when compared with schedule II opioids. It may be useful in patients with comorbid substance use disorder or non-medical opioid use, as there is less risk of misuse, euphoria and it may improve mood. When used to treat opioid use disorder, the training and waiver was recently waived for licensed practitioners with a DEA and any provider may prescribe buprenorphine. For many reasons outlined in this article, the popularity of using buprenorphine for analgesia continues to grow and a practitioner should consider this as an excellent and safe option for chronic pain.

RETRACTED: Sublingual buprenorphine versus intravenous or intramuscular morphine in acute pain: A systematic review and meta-analysis of randomized control trials

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Authors. The authors have provided a clarification stating that the article does not clearly or fully disclose that it better represents a subset of a previously published manuscript in the British Journal of Anaesthesia (White LD, Hodge A, Vlok R, Hurtado G, Eastern K, Melhuish TM. Efficacy and adverse effects of buprenorphine in acute pain management: systematic review and meta-analysis of randomized controlled trials. (Br J Anaesth. 2018;120:668-678). The papers presented in their meta-analysis are a subset of those in their previous review in the British Journal of Anaesthesia, and do not present additional information beyond their previously published work.

Patient controlled opioid analgesia versus non-patient controlled opioid analgesia for postoperative pain

BACKGROUND

This is an updated version of the original Cochrane review published in Issue 4, 2006. Patients may control postoperative pain by self administration of intravenous opioids using devices designed for this purpose (patient controlled analgesia or PCA). A 1992 meta-analysis by Ballantyne et al found a strong patient preference for PCA over non-patient controlled analgesia, but disclosed no differences in analgesic consumption or length of postoperative hospital stay. Although Ballantyne's meta-analysis found that PCA did have a small but statistically significant benefit upon pain intensity, a 2001 review by Walder et al did not find statistically significant differences in pain intensity or pain relief between PCA and groups treated with non-patient controlled analgesia.

OBJECTIVES

To evaluate the efficacy and safety of patient controlled intravenous opioid analgesia (termed PCA in this review) versus non-patient controlled opioid analgesia of as-needed opioid analgesia for postoperative pain relief.

SEARCH METHODS

We ran the search for the previous review in November 2004. For this update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL 2014, Issue 12), MEDLINE (1966 to 28 January 2015), and EMBASE (1980 to 28 January 2015) for randomized controlled trials (RCTs) in any language, and reference lists of reviews and retrieved articles.

SELECTION CRITERIA

We selected RCTs that assessed pain intensity as a primary or secondary outcome. These studies compared PCA without a continuous background infusion with non-patient controlled opioid analgesic regimens. We excluded studies that explicitly stated they involved patients with chronic pain.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data, which included demographic variables, type of surgery, interventions, efficacy, and adverse events. We graded each included study for methodological quality by assessing risk of bias and employed the GRADE approach to assess the overall quality of the evidence. We performed meta-analysis of outcomes that included pain intensity assessed by a 0 to 100 visual analog scale (VAS), opioid consumption, patient satisfaction, length of stay, and adverse events.

MAIN RESULTS

Forty-nine studies with 1725 participants receiving PCA and 1687 participants assigned to a control group met the inclusion criteria. The original review included 55 studies with 2023 patients receiving PCA and 1838 patients assigned to a control group. There were fewer included studies in our updated review due to the revised exclusion criteria. For the primary outcome, participants receiving PCA had lower VAS pain intensity scores versus non-patient controlled analgesia over most time intervals, e.g., scores over 0 to 24 hours were nine points lower (95% confidence interval (CI) -13 to -5, moderate quality evidence) and over 0 to 48 hours were 10 points lower (95% CI -12 to -7, low quality evidence). Among the secondary outcomes, participants were more satisfied with PCA (81% versus 61%, P value = 0.002) and consumed higher amounts of opioids than controls (0 to 24 hours, 7 mg more of intravenous morphine equivalents, 95% CI 1 mg to 13 mg). Those receiving PCA had a higher incidence of pruritus (15% versus 8%, P value = 0.01) but had a similar incidence of other adverse events. There was no difference in the length of hospital stay.

AUTHORS' CONCLUSIONS

Since the last version of this review, we have found new studies providing additional information. We reanalyzed the data but the results did not substantially alter any of our previously published conclusions. This review provides moderate to low quality evidence that PCA is an efficacious alternative to non-patient controlled systemic analgesia for postoperative pain control.

[Application procedures and dosage recommendations for postoperative analgesia.]

Systemic application of analgesics is still the most frequently used method of postoperative relief of pain. However, neither intermittent intramuscular nor intermittent intravenous application can provide the patient with a continuous level of analgesia. Lipid-soluble analgesics or those with polar binding that are rapidly metabolized demonstrate an rapid effectiveness. If the analgesia must be administered over a long period, it is due to a low level of lipid solubility, high receptor affinity and low elimination rates. Oral as well as sublingual buccal and rectal applications are characterized by uncertain absorption conditions. There are few investigations on the subcutaneous application of analgesics. After intramuscular administration analgesic levels are achieved within 15 to 60 min, but various conditions may alter the absorption criteria. Intradeltoidal application is preferable to intragluteal injection. Analgesics may be administered intravenously as a bolus, as continuous infusion, or as patient-controlled analgesia. The bolus injection is characterized by a short period of action and the necessity to administer several bolus injections by repeated administration. The continuous infusion of analgesics should begin with the administration of an initial bolus injection. Infusion analgesia should be performed under careful monitoring conditions. The most promising method of pain relief is patient-controlled analgesia (PCA). After an initial bolus injection, the continuous infusion of an analgesic is guaranteed and may be completed by the patient with several bolus injections. PCA requires careful monitoring. We suggest that a special analgesia team to take care of the patient in special analgesia units might be appropriate in the future.

Patient controlled opioid analgesia versus conventional opioid analgesia for postoperative pain

BACKGROUND

Patients may control postoperative pain by self-administration of intravenous opioids using devices designed for this purpose (patient controlled analgesia or PCA). A 1992 meta-analysis by Ballantyne found a strong patient preference for PCA over conventional analgesia but disclosed no differences in analgesic consumption or length of postoperative hospital stay. Although Ballantyne's meta-analysis found that PCA did have a small but statistically significant benefit upon pain intensity, Walder's review in 2001 did not find a significant differences in pain intensity and pain relief between PCA and conventionally treated groups.

OBJECTIVES

To evaluate the efficacy of PCA versus conventional analgesia (such as a nurse administering an analgesic upon a patient's request) for postoperative pain control.

SEARCH STRATEGY

Randomized controlled trials (RCTs) were identified from the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2004, Issue 3), MEDLINE (1966 to 2004), and EMBASE (1994 to 2004). Additional reports were identified from the reference lists of retrieved papers.

SELECTION CRITERIA

RCTs of PCA versus conventional analgesia that employed pain intensity as a primary or secondary outcome were selected. These trials included RCTs that compared PCA without a continuous background infusion versus conventional parenteral analgesic regimens. Studies that explicitly stated they involved patients with chronic pain were excluded.

DATA COLLECTION AND ANALYSIS

Trials were scored using the Oxford Quality Scale. Meta-analyses were performed of outcomes that included analgesic efficacy assessed by a Visual Analog Scale (VAS), analgesic consumption, patient satisfaction, length of stay and adverse effects. A sufficient number of the retrieved trials reported these parameters to permit meta-analyses.

MAIN RESULTS

Fifty-five studies with 2023 patients receiving PCA and 1838 patients assigned to a control group met inclusion criteria. PCA provided better pain control and greater patient satisfaction than conventional parenteral 'as-needed' analgesia. Patients using PCA consumed higher amounts of opioids than the controls and had a higher incidence of pruritus (itching) but had a similar incidence of other adverse effects. There was no difference in the length of hospital stay.

AUTHORS' CONCLUSIONS

This review provides evidence that PCA is an efficacious alternative to conventional systemic analgesia for postoperative pain control.

Efficacy and safety of patient-controlled opioid analgesia for acute postoperative pain. A quantitative systematic review

BACKGROUND

The usefulness of intravenous patient-controlled analgesia (PCA) with opioids for postoperative analgesia is not well defined.

METHODS

We systematically searched (MEDLINE, EMBASE, Cochrane Library, bibliographies, any language, to January 2000) for randomised trials comparing opioid-based PCA with the same opioid given intramuscularly, intravenously, or subcutaneously. Weighted mean differences (WMD) for continuous data, relative risks (RR) and numbers-needed-to-treat (NNT) for dichotomous data were calculated with 95% confidence intervals (CI) using fixed and random effects models.

RESULTS

Data from 32 trials were analysed: 22 (1139 patients) were with morphine, five (682) with pethidine, three (184) with piritramide, one (47) with nalbuphine and one (20) with tramadol. In three morphine and one pethidine trial (352 patients), more patients preferred PCA (89.7% vs. 65.8%, RR 1.41 (95%CI 1.11 to 1.80), NNT 4.2). Combined dichotomous data on pain intensity and relief, and the need for rescue analgesics from eight morphine, one pethidine, one piritramide, and one nalbuphine trial (691 patients), were in favour of PCA (RR 1.22 (1.00 to 1.50), NNT 8). In two morphine trials (152), pulmonary complications were more frequently prevented with PCA (100% vs. 93.3%, RR 1.07 (1.01 to 1.14), NNT 15). There was equivalence for cumulative opioid consumption, pain scores, duration of hospital stay, and opioid-related adverse effects.

CONCLUSION

These trials provide some evidence that in the postoperative pain setting, PCA with opioids, compared with conventional opioid treatment, improve analgesia and decrease the risk of pulmonary complications, and that patients prefer them.

[Patient-controlled analgesia. Benefits, risks, methods of monitoring]

Patient-controlled analgesia refers to a relatively new approach to morphine delivery in which patients are allowed to self-administer small doses of an opioid, to achieve adequate relief of postoperative pain. The main benefit is to reduce fluctuations in opioid plasma concentrations. A matter for worry remains the occurrence of side effects, especially ventilatory depression. In order to guarantee the efficacy and safety of this technique, the education of patients and nurses is essential. Protocols are required, specifying the use of this technique (prescription, patient monitoring, treatment of side effects).

Postthyroidectomy analgesia: morphine, buprenorphine, or bupivacaine?

STUDY OBJECTIVE

To compare three analgesic regimens for pain relief after thyroidectomy.

DESIGN

Randomized, double-blind, placebo-controlled study.

SETTING

Inpatient anesthesia in a university department of endocrine surgery.

PATIENTS

342 patients scheduled for elective thyroidectomy with nitrous oxide-oxygen-isoflurane anesthesia in addition to fentanyl.

INTERVENTIONS

Group 1 received preoperative oral controlled release morphine 10 mg, and Group 2 received postoperative sublingual buprenorphine 0.2 mg. Group 3 received 0.25% bupivacaine (10 ml) wound infiltration before skin closure. Eight hours after tracheal extubation, patients received a second dose of the same drug in each group except in Group 3, where medication was changed to sublingual buprenorphine 0.2 mg.

MEASUREMENTS AND MAIN RESULTS

Patients in Group 2 required fewer additional analgesics: 0.54 +/- 0.68 vs. 0.96 +/- 0.84 in Group 1 and 0.79 +/- 0.78 in Group 3. Patients in Group 2 demonstrated a better pain score and this group showed a higher percentage of satisfied patients: 96% vs. 85% in Group 1 and 91% in Group 3. Group 2 also included more patients requiring no analgesics: 56% vs. 32% in Group 1 and 42% in Group 3. The side effects in all three groups did not differ.

CONCLUSION

The administration of sublingual buprenorphine after thyroidectomy provides better analgesia than small doses of oral controlled-release morphine or than 0.25% bupivacaine wound infiltration at the end of surgery.

Buprenorphine blocks diffuse noxious inhibitory controls in the rat

A C-fibre reflex elicited by electrical stimulation within the territory of the sural nerve was recorded from the ipsilateral biceps femoris muscle in anaesthetised rats. Such reflex responses can be inhibited by applying noxious conditioning stimuli to heterotopic areas of the body. These inhibitory processes have been termed diffuse noxious inhibitory controls. The responses were recorded before, during and after the immersion of the tail in a thermoregulated waterbath (at 50 degrees C) for 1 min. The C-fibre reflex responses were depressed by a maximum of 71 +/- 3% at 45 s after the start of such conditioning stimuli. A dose of 3 mu g/kg buprenorphine completely blocked the inhibition and post-stimulus effects triggered by the heterotopic noxious stimuli. In the 0.3-3 mu g/kg range, buprenorphine increased, in a dose-dependent manner, the magnitude of the inhibition. These doses did not produce any changes in the C-fibre reflex itself. The results are discussed in terms of the mechanisms underlying the analgesic properties of buprenorphine.

Premedication with sublingual buprenorphine for out-patient arthroscopy: reduced need for postoperative pethidine but higher incidence of nausea

The effect of preoperative sublingual buprenorphine (B) on postoperative pain (VAS), the need for postoperative opioid injections and on time to discharge, was evaluated in a prospective randomised double-blind study. Forty ASA I-II patients scheduled for arthroscopy of the knee received premedication with 0.4 mg buprenorphine (group B) and 42 patients were given placebo (group P). Postoperatively, pethidine was given to patients with pain. Three of the 40 patients in group B vs 11 of the 42 in group P received pethidine (P < 0.05). In group B, however, 13 of the 40 patients complained of nausea, prolonging median time to discharge from 155 to 255 minutes (P < 0.05). In group P, 3 of the 42 patients were nauseated, P < 0.01, compared with group B. Time to discharge did not differ between the groups in patients without nausea. The median respiratory rate was significantly lower in group B, but no patient required ventilatory support. In conclusion, premedication with sublingual buprenorphine cannot be recommended for this procedure. It reduces the need for postoperative injections of pethidine but increases the incidence of postoperative nausea which prolongs the recovery time. Careful monitoring is also mandatory because of the possibility of respiratory depression.

Self-administered intranasal meperidine for postoperative pain management

Recent studies have demonstrated that intranasal is comparable to intravenous opioid titration in its pain-relieving effect. In these studies, however, the intranasal opioid titration was performed by the investigator, and the treatment period was two hours or less. The purpose of this randomized, prospective study was to investigate whether intranasal opioid administration by the patients themselves for a prolonged postoperative period may be regarded as a therapeutic alternative for postoperative pain management. Forty-four orthopaedic patients were studied over a 12-hr period on the first day after surgery. Twenty-two had free access to intranasal meperidine (nasal group) and were allowed to administer six intranasal puffs (27 mg per dose). The next self-administration was only permitted after a delay of at least ten minutes. Another 22 patients received intermittent subcutaneous meperidine injections (25 or 50 mg) on request (sc group). Pain intensity was recorded at 30-min intervals with the aid of the 101-point numerical rating scale. The pain score was lower in the nasal than in the sc group at the 30, 150 to 330, 420 to 480 and 540 to 600 min measuring points (P = < 0.05). The meperidine requirement was 112.9 +/- 81.3 mg in the nasal and 103.4 +/- 41.5 mg in the sc group (NS). Two patients in each group complained of nausea and vomiting. Thirteen of the 21 nasal and nine of the 15 sc patients who completed the final questionnaire rated the pain management as excellent or good (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Postoperative patient-controlled analgesia: meta-analyses of initial randomized control trials

STUDY OBJECTIVE

To compare outcomes during conventional analgesia (as-needed intramuscular dosing) and patient-controlled analgesia (PCA) in postoperative patients by analyzing data from published comparative trials.

DESIGN

Meta-analyses of 15 randomized control trials.

PATIENTS

Seven hundred eighty-seven adult patients (aged 16 to 65) undergoing various operative procedures.

INTERVENTIONS

Either PCA or conventional analgesia for postoperative pain control.

MEASUREMENTS AND MAIN RESULTS

Data were extracted on analgesic efficacy, analgesic use, patient satisfaction, length of hospital stay, and side effects. Meta-analyses of the data showed the following: (1) greater analgesic efficacy when PCA was used, with a mean additional benefit of 5.6 on a scale of 0 to 100 (SED, 2.2; p = 0.006); (2) a nonsignificant trend toward reduced analgesic use in PCA patients, based on a count of trials finding in one direction or the other (p = 0.092); (3) a 42% difference in the proportion of patients expressing satisfaction over dissatisfaction (SED, 20%; p = 0.02), with PCA being preferred; (4) a nonsignificant trend toward shortening of length of hospital stay with PCA use (mean, 0.15 days, SED, 0.13; p = 0.24); (5) no significant differences in the occurrence of any side effect.

CONCLUSIONS

Patient preference strongly favors PCA over conventional analgesia. Patients using PCA also obtain better pain relief than those using conventional analgesia, without an increase in side effects. Favorable effect of PCA upon analgesic usage and length of hospital stay did not in the initial trials attain statistical significance. Nonetheless, the favorable trends in the mean effect sizes for both outcomes argue that further studies of both outcomes should be performed to determine whether the favorable impact of PCA upon either may become statistically significant if larger numbers of patients are enrolled.

Patient-controlled analgesia for sickle-cell-related pain

To delineate dose ranges, utilization patterns, and the frequency and types of problems encountered, we retrospectively reviewed the medical records of 46 patients with sickle hemoglobinopathies who used patient-controlled analgesia (PCA) a total of 92 times for the management of vasooclusive pain. Patients varied widely in the drug administered, use of basal infusion, individual dose, and total amount of drug received. On the day of heaviest use, the average maximum hourly dose was equivalent to 0.09 mg/kg of morphine. In this study, 11 patients and two families disliked PCA, one patient had respiratory compromise, and one patient tampered with the machine. Patient satisfaction with PCA probably reflects interactions among the psychosocial impact of chronic illness and chronic pain, individual psychological and temperamental factors, environmental contingencies, and the expectations and beliefs of the family and the health-care professionals. Based on this experience, recommendations can be proposed for the use of PCA in this condition.

Transdermal fentanyl

OBJECTIVE

To review the use of transdermal fentanyl for the treatment of moderate to severe chronic pain. The article provides background on the pharmacology and pharmacokinetics of the drug, as well as the properties of the transdermal system. In addition, clinical trials, adverse effects, and therapeutic considerations and recommendations are presented.

DATA SOURCES

Clinical trials, review articles, and reference texts.

STUDY SELECTION

Comparative clinical trials involving the use of transdermal fentanyl on postoperative and chronic pain patients.

DATA EXTRACTION

Data from clinical human trials published in the English language were reviewed. Trials were assessed by sample size, opioid dosage regimen, and therapeutic outcome.

DATA SYNTHESIS

Transdermal fentanyl was found to be effective in the control of chronic and postoperative pain. In one trial the overall patient satisfaction with pain control was 79 percent for the transdermal fentanyl group and 44 percent for the placebo group. In another trial, the amount of additional parenteral morphine was significantly lower for the group receiving transdermal fentanyl than for the placebo group (49.9 +/- 4.9 vs. 77.0 +/- 6.3 mg, respectively, p < 0.01). The most common adverse effects recorded were nausea (45-85 percent), pruritus (14-60 percent), and sedation (40-59 percent). The cost of analgesic therapy with this delivery system is higher than that of parenteral opioid analgesia, but less than patient-controlled analgesia.

CONCLUSIONS

The transdermal fentanyl formulation offers some minor advantages over other forms of conventional pain management. Results of early clinical trials are promising, but more studies are needed to evaluate its long-term effectiveness and adverse effects. Specifically, comparisons with standard parenteral and patient-controlled opioid analgesia in chronic malignant and nonmalignant pain are necessary for adequate evaluation of transdermal fentanyl.

Opioid agonist-antagonist drugs in acute and chronic pain states

The agonist-antagonist opioid analgesics are a heterogeneous group of drugs with moderate to strong analgesic activity comparable to that of the pure agonist opioids such as codeine and morphine but with a limited effective dose range. The group includes drugs which act as an agonist or partial agonist at one receptor and an antagonist at another (pentazocine, butorphanol, nalbuphine, dezocine) and drugs acting as a partial agonist at a single receptor (buprenorphine). These drugs can be classified as nalorphine-like or morphine-like. Meptazinol does not fit into either classification and occupies a separate category. Pentazocine, butorphanol and nalbuphine are weak mu-antagonists and kappa-partial-agonists. All three drugs are strong analgesics when given by injection: pentazocine is one-sixth to one-third as potent as morphine, nalbuphine is slightly less potent than morphine, and butorphanol is 3.5 to 7 times as potent. The duration of analgesia is similar to that of morphine (3 to 4 hours). Oral pentazocine is closer in analgesic efficacy to aspirin and paracetamol (acetaminophen) than the weak opioid analgesics such as codeine. Neither nalbuphine nor butorphanol is available as an oral formulation. At usual therapeutic doses nalbuphine and butorphanol have respiratory depressant effects equivalent to that of morphine (though the duration of such effects with butorphanol may be longer). Unlike morphine there appears to be a ceiling to both the respiratory depression and the analgesic action. All of these 3 drugs have a lower abuse potential than the pure agonist opioid analgesics such as morphine. However, all have been subject to abuse and misuse, and pentazocine (but not the others) is subject to Controlled Drug restrictions. Buprenorphine is a potent partial agonist at the mu-receptor, and by intramuscular injection is 30 times as potent as morphine. A ceiling to the analgesic effect of buprenorphine has been demonstrated in animals and it is also claimed in humans. However, there are no reliable data available to define the maximal dose of buprenorphine in humans. A practical ceiling exists for sublingual use in that the only available formulation is a 2 micrograms tablet and few patients will accept more than 3 or 4 of these in a single dose. The duration of analgesia is longer than that of morphine, at 6 to 9 hours. There have been suggestions that buprenorphine causes less respiratory depression than morphine, but viewed overall it appears that in equianalgesic doses the 2 drugs have similar respiratory depressant effects.(ABSTRACT TRUNCATED AT 400 WORDS)

[Postoperative analgesia after cesarean section: sublingual buprenorphine versus subcutaneous morphine]

This study aimed to compare the efficacy and side-effects of sublingual buprenorphine, a synthetic opioid agonist antagonist, with those of subcutaneous morphine. Fifty ASA class 1 patients were included in the study after having given their informed consent. Caesarean section was carried out under epidural block with 0.5% bupivacaine; no opioids were used during the procedure. The first dose of opioid was given 2 h after the first dose of bupivacaine. Patients were randomly given either 10 mg morphine (n = 25) or 0.4 mg buprenorphine (n = 25), followed by the same dose every 6 h for 36 h. When analgesia was insufficient, tablets containing dextropropoxyphene and paracetamol were given. No attempt was made to blind the study to the patient, but the investigator assessing pain was unaware of the drug given to the patient. Pain intensity was assessed before, and 2 h after each dose of opioid with a 100 mm visual scale, as well as systolic, diastolic and mean arterial blood pressures, heart and breathing rates, and SpO2. Side-effects (pruritus, nausea, vomiting, drowsiness) were also noted. In 2 patients in each group, the protocol was stopped before the 36th h, but after the fourth dose, either because of side-effects, or at the patient's request. Results were similar in both groups of patients, whether for degree of pain relief, or physiological effects. There was no clinically detectable respiratory depression. Duration and intensity of episodes of arterial oxygen desaturation, and the incidence of nausea, were similar in the 2 groups; pruritus was more common in the morphine group.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effects of continuous intrapleural vs epidural administration of 0.5% bupivacaine on pain, metabolic response and pulmonary function following cholecystectomy

Twenty patients undergoing elective cholecystectomy were prospectively randomised to receive either intrapleural (bolus 20 ml followed by 10 ml/h) or thoracic epidural (bolus 9 ml followed by 5 ml/h) bupivacaine 0.5% for 8 h postoperatively to assess the effect of these two techniques on pain, pulmonary function and the surgical stress response. As assessed by the visual analogue scale (VAS), both groups received good but not total pain relief. Both groups had a 50% reduction in forced expiratory volume (FEV1), forced vital capacity (FVC) and peak expiratory flow rate (PEFR) after operation, and there was no observed effect on the stress response as measured by plasma glucose and cortisol. It is concluded that while both techniques provide good analgesia, the degree and extent of nerve blockade are not sufficient to affect the afferent neurogenic stimuli responsible for the observed effects on pulmonary function and the stress response.

Modifiers of patient-controlled analgesia efficacy. I. Locus of control

The effectiveness of patient-controlled analgesia (PCA) depends upon the patient's appropriate response to a strong aversive stimulus (i.e., pain) with subsequent reinforcement (i.e., opiate injection). Each patient may have psychological characteristics that modify this response to aversive stimuli. To test for such characteristics, 76 female patients undergoing abdominal gynecologic procedures were given psychological tests (i.e., the Chance External, Powerful Others External, and Internal subscales of the Multidimensional Health Locus of Control; the Activities of Daily Living scale; and the Hypochondriasis, Depression, and Hysteria scales of the Minnesota Multiphasic Personality Inventory). Patients utilized PCA for postoperative analgesia. At the completion of PCA, patients were given a questionnaire assessing both the level of pain and degree of satisfaction with pain relief. Correlational analysis compared the level of pain and degree of satisfaction with results of psychological testing. Results showed that female patients with an external locus of control had higher levels of pain and greater dissatisfaction with PCA. An internal locus of control was predictive of lower pain scores and increased satisfaction. PCA effectiveness, as measured by the level of pain and degree of patient satisfaction, correlated with results of psychological testing. The delineation of these and other possible modifiers of PCA efficacy may define populations that are optimally responsive to PCA.

Comparison of one technique of patient-controlled postoperative analgesia with intramuscular meperidine

We have compared analgesic requirements, perceived pain, and self-assessment of 'health locus of control' for 72 h in 88 subjects after cholecystectomy, randomized to either a standard technique of self-administration of meperidine (patient-controlled analgesia, PCA) or to intramuscular injections on demand (i.m.). Multivariate analysis revealed no statistical differences between group scores for pain (over any 24 h period) and only minor differences in total meperidine administered. However, the PCA group received significantly less analgesic in the first 24 h (P less than 0.01) and described significantly more pain over the first 4 h (P less than 0.01). Assessment of 'health locus of control' did not show any marked changes. Analysis of patient questionnaires suggests more enthusiasm for patient-controlled analgesia, but in this study, it was difficult to clearly demonstrate any significant advantage for pain management or amount of opiate administered.

Variables of patient-controlled analgesia. 1. Bolus size

The efficacy of a range of demand doses of morphine for patient-controlled analgesia was studied. Patients who self-administered the smallest dose (0.5 mg) were frequently unable to achieve good pain control; patients who received the largest dose (2 mg) had a high incidence of ventilatory depression. A dose of 1 mg was the best increment under the conditions of this study but the relationship between increment and lockout interval requires consideration.

The development and clinical use of patient-controlled analgesia

Patient-controlled analgesia has successfully made the transition from research tool to clinical acceptability. Reliable and sophisticated patient-controlled analgesia systems are commercially available. The technique has been most used for control of postoperative pain but has been successfully used during labour, after burns and other trauma and in terminal care. Virtually every opioid has been administered by patient-controlled analgesia using almost every route of administration. It is more effective than the traditional techniques of pain control after surgery but is not automatically so. Choice of opioid and the settings chosen for demand dose and lockout interval greatly influence effectiveness. Patient-controlled analgesia requires active participation by the patient but the psychology of patient-controlled analgesia has generally been under-estimated. Patient-controlled analgesia has developed empirically and many assumptions have been made; there is a need for fundamental research.

Buprenorphine as premedication and as analgesic during and after light isoflurane-N2O-O2 anaesthesia. A comparison with oxycodone plus fentanyl

Sixty patients undergoing gynaecological laparotomies under isoflurane anaesthesia received 0.4 mg of buprenorphine sublingually or 0.12 mg/kg of oxycodone intramuscularly in random order for preanaesthetic medication. Patients premedicated with buprenorphine were given buprenorphine before, during and after anaesthesia and patients premedicated with oxycodone received fentanyl before and during anaesthesia and oxycodone after anaesthesia. Buprenorphine premedication produced less drowsiness and sedation and alleviated patients' apprehension significantly (P less than 0.05) less than oxycodone. Systolic and diastolic blood pressure and heart rate were significantly (P less than 0.05 to P less than 0.01) higher after intubation in the buprenorphine group when compared with the oxycodone plus fentanyl group. After anaesthesia, spontaneous respiration started rapidly; the return of consciousness and immediate recovery occurred at the same rate in both groups. In the recovery room moderate to severe pain was more common (P less than 0.05) in the oxycodone plus fentanyl group than in the buprenorphine group. The respiratory rate in the recovery room was lower among patients given buprenorphine, and two patients given buprenorphine developed severe respiratory depression. In the ward (2 to 24 h after operation) sublingual buprenorphine provided pain relief as good as intramuscularly administered oxycodone. No differences were noted in the incidence or severity of emetic symptoms between the groups. It is concluded that buprenorphine can provide good postoperative pain relief for gynaecological laparotomies performed under light isoflurane anaesthesia, but patients need to be monitored carefully after operation because of the possibility of respiratory depression.

Patient-controlled analgesia: a controlled trial

Thirty-six patients undergoing lower abdominal surgery were included in a prospective randomized controlled study to compare the effects of patient-controlled analgesia (PCA) and a standard intramuscular/intravenous treatment (conventional analgesia, CA) of postoperative pain. Morphine was used in both groups. There were no significant differences between the two analgesic regimens in respect of linear analogue pain scores, verbal pain-relief scores, amount of morphine used or side-effects. No treatment-induced alterations in vital values were experienced.

Postoperative analgesia with intrapleural administration of bupivacaine-adrenaline

Twenty-one patients who underwent elective cholecystectomy were studied with regard to the effect of intrapleural administration of bupivacaine-adrenaline solution on postoperative pain and ventilatory capacity. Administration of 10 or 20 ml of 2.5 mg/ml or 5 mg/ml bupivacaine solution resulted in complete analgesia in 143 of 159 administrations. Most patients experienced the maximal pain-relieving effect within 1-2 min and analgesia persisted as a rule for 3-5 h. Forced vital capacity and forced expiratory volume in 1 s increased after intrapleural analgesia on average by 56% and 46%, respectively, on the first postoperative day and by 35% and 51%, respectively, on the second day. There was no significant difference in the analgesic effect or in the effect on the ventilatory capacity between the 2.5 mg/ml or the 5 mg/ml solution, in either the 10 ml or the 20 ml dose. Placebo (NaCl) given intrapleurally had no effect on pain or on the ventilatory capacity. The plasma concentration of bupivacaine after intrapleural administration showed a wide interindividual variation, with considerably higher average values when the 5 mg/ml solution had been used than for the 2.5 mg/ml solution. Although no toxic effects were noted, a 2.5 mg/ml solution, which can be given in an initial dose of 20 ml and top-up doses of 10 ml at 3-6 h intervals, is recommended. In four patients minor pneumothorax developed when the catheter was introduced. The pneumothorax was easily evacuated, but underlines the need for great care when introducing the catheter.

An open study of sub-lingual buprenorphine in the treatment of chronic pain in the elderly

Fifty-one patients aged over 65 years with chronic pain entered an open study to assess the efficacy and tolerance of low-dose (0.1 mg) sub-lingual buprenorphine administered 3 to 4-times a day over a 14-day period. There was significant improvement in symptoms during the treatment period and the drug was well tolerated, with good compliance. Patients aged over 80 years responded comparatively better than those aged between 65 and 80 years. The incidence of unwanted effects was low and constipation was only reported by 1 patient.

Newer methods of delivery of opiates for relief of pain

Successful pain management using opiates requires both an analgesic with sufficient intrinsic activity and an effective administration system. Most instances of unsatisfactory pain control, however, are due to failure to achieve and maintain adequate blood concentrations of the chosen drug. Newer techniques of administration aim to overcome this problem. Oral opiate therapy with conventional or sustained-release formulations of morphine provide good control of terminal cancer pain provided that a regular dosing pattern is established and reviewed according to the patient's needs. This represents a significant departure from the traditional 'as required' prescription of this type of drug. In the management of acute severe pain, sublingual and intravenous opiates--self-administered as needed, or given by mandatory dosing schedules--have also been shown to overcome the limitations of intermittent intramuscular injections. A further novel development, stemming from basic neuroscience research, is the selective application of opiates to the spinal cord via the epidural or intrathecal route. This controversial technique has led to major improvements in treatment of some types of acute and chronic pain.

Continuous subcutaneous infusion of morphine for postoperative pain relief

A double-blind randomised study of 48 patients in whom continuous subcutaneous infusion and regular intramuscular injection of morphine were compared as analgesic regimens after upper abdominal surgery, is described. Over a 48-hour period, no difference in pain intensity between the two groups was found by comparing linear analogue scores, assessments on a four-point rank scale, peak expiratory flow rates or requirement for additional analgesia. Nausea and sedation were assessed using a four-point rank scale. These side effects were less frequent with subcutaneous infusion (p less than 0.05). Two patients from each group were judged to have received an overdose. The infusion apparatus was simple and convenient to use. Continuous subcutaneous infusion of morphine is a practical and effective means of achieving post-operative analgesia but, as with other mandatory dosing regimens, relative overdosage may occur.

Effect of premedication with controlled-release oral morphine on postoperative pain. A comparison with intramuscular morphine

Thirty fit patients presenting for elective total hip replacement were randomly allocated to receive a premedication of 60 or 90 mg controlled-release oral morphine or 15 mg intramuscular morphine. Postoperative analgesia was assessed using on-demand intravenous pethidine supplementation requirements. In 15 patients free plasma morphine concentrations were measured. Both 60 and 90 mg controlled-release oral morphine led to a reduced pethidine requirement compared to the intramuscular group but the reduction was not statistically different.

Pharmacokinetics of morphine and its surrogates VI: Bioanalysis, solvolysis kinetics, solubility, pK'a values, and protein binding of buprenorphine

The 10-fold greater sensitivity of buprenorphine to fluorescence compared with morphine provides excellent detection for HPLC assay of buprenorphine in biological fluids with a 5-ng/mL sensitivity. Buprenorphine yields a stoichiometric final acid degradation product, a fluorescent-detectable, rearranged demethoxy analogue of buprenorphine, which serves as an excellent bioassay internal standard. Buprenorphine solvolysis is specific-acid and specific-base catalyzed. Alkaline hydrolysis produces no fluorescent products. Acid hydrolysis also produces a fluorescent-detectable, transient dehydro intermediate that is also completely transformed to the demethoxy analogue. The rate constants and Arrhenius parameters for these transformations have been determined. Estimated buprenorphine pK'a values are 8.24 and 10 for the ammonium and phenol groups, respectively. The intrinsic aqueous solubility of neutral buprenorphine is 12.7 +/- 1.2 micrograms/mL at 23 degrees C. The red blood cell-plasma water partition coefficients of buprenorphine ranged between 6 and 15. Ultracentrifugation and the red blood cell partition methods led to an estimated 95-98% plasma protein binding. Ultrafiltration and equilibrium dialysis methods were inappropriate because of the high membrane binding of neutral buprenorphine.

Administration of ketoprofen suppositories for out-patient post-operative analgesia

A double-blind, randomized, placebo-controlled study was carried out to assess the efficacy of ketoprofen suppositories as a post-operative analgesic in out-patients undergoing extirpation surgery. Thirty patients received 2 X 100 mg ketoprofen suppositories, and 30 patients received placebo suppositories 1-hour pre-operatively. Patients received no premedication and the anaesthetic used was intravenous diazepam and ketamine administered by intravenous drip according to the patient's need. Subjective symptoms of pain were evaluated 15, 30, 60 and 90 minutes post-operatively. None of the patients who received ketoprofen complained of post-operative pain, whereas the patients on placebo showed varying degrees of pain. The only side-effects recorded were nausea and vomiting both in ketoprofen and placebo-treated patients and these were probably related to the anaesthetic.

Mandatory sublingual buprenorphine for postoperative pain

This study examined the analgesic effect, vital signs and side effects when 0.4 mg doses of buprenorphine were given pre-emptively for the treatment of postoperative pain after elective total hip replacement. Pain intensity, pain relief, retrospective peak pain intensity and pain relief, sedation, vital signs and side effects were measured 1 hour after surgery and then in the morning and evening of the first 2 postoperative days. There was a significant improvement in pain measured over the 3 days, with concomitant reduction in side effects and sedation. However, there was a significant increase in the number of patients with a pulse rate greater than 100 beats per minute. No particular benefit for postoperative pain relief was observed in patients receiving buprenorphine premedication in comparison with those who had received morphine or placebo.

Non-parenteral postoperative analgesia. A comparison of sublingual buprenorphine and morphine sulphate (slow release) tablets

Sixty-nine patients undergoing upper and lower abdominal surgery were studied after operation to compare the analgesic effects of sublingual buprenorphine (0.4 mg) and slow release morphine sulphate tablets (MST, 20 mg) given 6 hourly in a double-blind, double-dummy trial. Both MST and buprenorphine produced satisfactory postoperative analgesia but the linear analogue pain scores were significantly lower on the second post operative day with MST.

Nalbuphine versus meperidine for post-operative analgesia: a double-blind comparison using the patient controlled analgesic technique

A double-blind study was undertaken to compare nalbuphine, a synthetic partial agonist opiate, with meperidine in providing analgesia in patients following abdominal surgery, using the patient controlled analgesic technique. Both drugs showed a wide variation in demand requirements, but they were equally effective in relieving pain as assessed by the linear analogue technique. Neither drug caused a reduction of respiratory rate. The patient-controlled analgesic technique gave analgesia of good quality and it aided the comparison of the two drugs. However, some of the patients found the technique difficult to manage, and it is expensive and time-consuming. Until further experience is gained with this device its use should be confined to a constant care unit.