Patient-controlled analgesia in postoperative pain: the relation of psychological factors to pain and analgesic use

Oxycodone: A Current Perspective on Its Pharmacology, Abuse, and Pharmacotherapeutic Developments

Oxycodone, a semisynthetic derivative of naturally occurring thebaine, an opioid alkaloid, has been available for more than 100 years. Although thebaine cannot be used therapeutically due to the occurrence of convulsions at higher doses, it has been converted to a number of other widely used compounds that include naloxone, naltrexone, buprenorphine, and oxycodone. Despite the early identification of oxycodone, it was not until the 1990s that clinical studies began to explore its analgesic efficacy. These studies were followed by the pursuit of several preclinical studies to examine the analgesic effects and abuse liability of oxycodone in laboratory animals and the subjective effects in human volunteers. For a number of years oxycodone was at the forefront of the opioid crisis, playing a significant role in contributing to opioid misuse and abuse, with suggestions that it led to transitioning to other opioids. Several concerns were expressed as early as the 1940s that oxycodone had significant abuse potential similar to heroin and morphine. Both animal and human abuse liability studies have confirmed, and in some cases amplified, these early warnings. Despite sharing a similar structure with morphine and pharmacological actions also mediated by the μ-opioid receptor, there are several differences in the pharmacology and neurobiology of oxycodone. The data that have emerged from the many efforts to analyze the pharmacological and molecular mechanism of oxycodone have generated considerable insight into its many actions, reviewed here, which, in turn, have provided new information on opioid receptor pharmacology. SIGNIFICANCE STATEMENT: Oxycodone, a μ-opioid receptor agonist, was synthesized in 1916 and introduced into clinical use in Germany in 1917. It has been studied extensively as a therapeutic analgesic for acute and chronic neuropathic pain as an alternative to morphine. Oxycodone emerged as a drug with widespread abuse. This article brings together an integrated, detailed review of the pharmacology of oxycodone, preclinical and clinical studies of pain and abuse, and recent advances to identify potential opioid analgesics without abuse liability.

High Frequency, Low Background Rate Extrapleural Programmed Intermittent Bolus Ropivacaine Provides Superior Analgesia Compared with Continuous Infusion for Acute Pain Management Following Thoracic Surgery: A Retrospective Cohort Study

Background

Thoracic surgery often results in severe postoperative pain. Regional analgesia via surgically placed extrapleural local anaesthetic (LA) and continuous infusion (CI) is an effective technique, however usually requires supplemental opioid to achieve satisfactory patient analgesia. We hypothesized that high frequency, low background rate extrapleural programmed intermittent boluses (PIB) of LA by could achieve superior patient analgesia and reduced oral morphine equivalent daily dosage (OMEDD) requirements for up to 3 days after thoracic surgery vs. CI.

Methods

We retrospectively analysed data from 84 adult patients receiving extrapleural analgesia after thoracic surgery in a single tertiary teaching hospital. The primary outcome measure was the effect of PIB vs. CI on maximum daily 11-point numerical rating scale (NRS-11) ratings as determined by multivariate linear regression analysis, corrected for OMEDD use, total daily LA dose, surgery type, age, opioid type, and use of ketamine analgesia. Secondary outcome measures were the effect on OMEDD use, the effect of total ‘rescue’ LA boluses, and univariate analyses of the above outcomes and variables.

Results

PIB on day 0, and a higher proportion of LA given as rescue boluses on day 1 were associated with reduced maximum NRS-11 ratings [standardized/ [unstandardized] beta coefficient -0.34/ [-0.92 NRS-11 if PIB] (P = 0.007); and -0.26/ [-0.029 NRS-11 per mg/kg extrapleural ropivacaine] (P = 0.03)], respectively. Only patient age was associated with reduced OMEDD use [day 0: -0.58/ [-4.4 OMEDDs per year of age] (P ≤ 0.005); day 1: -0.49/ [-3.56 OMEDDs per year of age] (P ≤ 0.005); day 2: -0.32/ [-1.9 OMEDDs per year of age] (P = 0.04)]. OMEDD use on day 2, however, was associated with slightly higher maximum NRS-11 ratings [+0.28/ +0.006 NRS-11 per mg OMEDD (P = 0.036)]. On univariate analysis, PIB patients achieved the largest difference in OMEDD use [-98 mg (95% CI -73 to -123 mg)] and NRS-11 ratings [-1.1 (-0.4 to -1.8)] against CI patients on day 3.

Conclusions

Use of high frequency, low background rate PIB extrapleural LA after thoracic surgery appears to have a modest beneficial effect on acute pain, but not OMEDD use, over CI when adjusted for patient, surgical and other analgesic factors after thoracic surgery. Further work is required to elucidate the potential magnitude of effect that extrapleural LA given by PIB over CI can achieve.

Effects of paclitaxel on mechanical sensitivity and morphine reward in male and female C57Bl6 mice

This study evaluated the hypothesis that a paclitaxel treatment regimen sufficient to produce mechanical allodynia would alter sensitivities of male and female mice to the conditioned rewarding and reinforcing effects of morphine. Saline or paclitaxel were administered on Days 1, 3, 5, and 7 in male and female C57Bl/6 mice to induce morphine-reversible mechanical allodynia as measured by the Von Frey filament test. Paclitaxel treatment did not change sensitivity to morphine conditioned place preference (CPP) relative to saline treatment in either male or female mice. Morphine produced peak self-administration under a fixed ratio-1 (FR1) schedule of reinforcement for 0.03 mg/kg morphine per infusion in female mice and 0.1 mg/kg morphine per infusion in male mice. During the progressive ratio experiments, saline treatment in male mice decreased the number of morphine infusions for 12 days whereas the paclitaxel-treated male mice maintained responding for morphine similar to baseline levels during the same time period. However, paclitaxel did not have an overall effect on the reinforcing efficacy of morphine assessed over a limited dose range during the course of the repeated self-administration. These results suggest that the reward-related behavioral effects of morphine are overall not robustly altered by the presence of paclitaxel treatment under the current dosing regimen, with the exception of maintaining a small yet significant higher baseline than saline treatment during the development of allodynia in male mice. (PsycINFO Database Record

Sex-dependent effects of cannabis-induced analgesia

BACKGROUND

Preclinical studies demonstrate that cannabinoid-mediated antinociceptive effects vary according to sex; it is unknown if these findings extend to humans.

METHODS

This retrospective analysis compared the analgesic, subjective and physiological effects of active cannabis (3.56-5.60% THC) and inactive cannabis (0.00% THC) in male (N=21) and female (N=21) cannabis smokers under double-blind, placebo-controlled conditions. Pain response was measured using the Cold-Pressor Test (CPT). Participants immersed their hand in cold water (4°C); times to report pain (pain sensitivity) and withdraw the hand (pain tolerance) were recorded. Subjective drug ratings were also measured.

RESULTS

Among men, active cannabis significantly decreased pain sensitivity relative to inactive cannabis (p<0.01). In women, active cannabis failed to decrease pain sensitivity relative to inactive. Active cannabis increased pain tolerance in both men women immediately after smoking (p<0.001); a trend was observed for differences between men and women (p<0.10). Active cannabis also increased subjective ratings of cannabis associated with abuse liability ('Take again,' 'Liking,' 'Good drug effect'), drug strength, and 'High' relative to inactive in both men and women (p<0.01).

CONCLUSIONS

These results indicate that in cannabis smokers, men exhibit greater cannabis-induced analgesia relative to women. These sex-dependent differences are independent of cannabis-elicited subjective effects associated with abuse-liability, which were consistent between men and women. As such, sex-dependent differences in cannabis's analgesic effects are an important consideration that warrants further investigation when considering the potential therapeutic effects of cannabinoids for pain relief.

Preanesthetic medication in children: A comparison of intranasal dexmedetomidine versus oral midazolam

Background:

Relieving preoperative anxiety is an important concern for the pediatric anesthesiologist. Midazolam has become the most frequently used premedication in children. However, new drugs such as the α₂ -agonists have emerged as alternatives for premedication in pediatric anesthesia.

Methods:

One hundred and twenty children scheduled for adenotonsillectomy were enrolled in this prospective, double-blind, randomized study. The children were divided into two equal groups to receive either intranasal dexmedetomidine 1 μg/kg (group D), or oral midazolam 0.5 mg/kg (group M) at approximately 60 and 30 mins, respectively, before induction of anesthesia. Preoperative sedative effects, anxiety level changes, and the ease of child-parent separation were assessed. Also, the recovery profile and postoperative analgesic properties were assessed.

Results:

Children premedicated with intranasal dexmedetomidine achieved significantly lower sedation levels (P=0.042), lower anxiety levels (P=0.036), and easier child-parent separation (P=0.029) than children who received oral midazolam at the time of transferring the patients to the operating room. Postoperatively, the time to achieve an Aldrete score of 10 was similar in both the groups (P=0.067). Also, the number of children who required fentanyl as rescue analgesia medication was significantly less (P=0.027) in the dexmedetomidine group.

Conclusion:

Intranasal dexmedetomidine appears to be a better choice for preanesthetic medication than oral midazolam in our study. Dexmedetomidine was associated with lower sedation levels, lower anxiety levels, and easier child-parent separation at the time of transferring patients to the operating room than children who received oral midazolam. Moreover, intranasal dexmedetomidine has better analgesic property than oral midazolam with discharge time from postanesthetic care unit similar to oral midazolam.

Dexmedetomidine use during strabismus surgery in agitated children

OBJECTIVE

We aimed to investigate the effects of dexmedetomidine premedication before intravenous infusion of ketamine in agitated children undergoing strabismus surgery.

SUBJECTS AND METHODS

We enrolled 60 agitated pediatric patients, aged 4.5-11 years. The patients were randomly allocated to one of two anesthesia regimens. Group D patients were premedicated with a single dose of intravenous dexmedetomidine 0.5 μg/kg whereas group P patients received a placebo. Patients in both groups were administered intravenous ketamine 1 mg/kg i.v. over 1 min followed by a continuous infusion of ketamine 1-3 mg/kg/h i.v. (n = 30). Patients were intubated after receiving fentanyl 1 μg/kg and rocuronium bromide 0.5 mg/kg.

RESULTS

21 (70%) patients in group D did not show the oculocardiac reflex (OCR) versus 7 (23%) in group P (p = 0.0006). The preoperative and postoperative agitation scores (p = 0.0001 and p = 0.03, respectively), the score on the Faces Pain Scale during awakening [3.0 (interquartile range, IQR 2.0-4.0) in group D and 0.0 (IQR 1.0-2.25) in group P] (p = 0.001) and at the 60th postoperative minute [IQR 2.0 (1.5-3.0) in group D and 2.0 (IQR 1.5-3.0) in group P] (p = 0.004), sore throat (26.6% in group D and 60% in group P) (p = 0.01) and analgesic requirement (20% in group D and 53% in group P) (p = 0.01) in group P were significantly higher than in group D. The Ramsay Sedation Score (RSS) in group D was significantly higher than in group P during awakening [2.0 (2.0-2.0) in group D and 4.5 (4.0-5.0) in group P] (p = 0.0001).

CONCLUSION

Dexmedetomidine premedication followed by intravenous infusion of ketamine was effective in decreasing OCR, agitation, pain, analgesic requirement in agitated children undergoing strabismus surgery.

Abuse liability of oxycodone as a function of pain and drug use history

The relationship between pain and prescription opioid abuse is poorly understood. Determining whether a patient is seeking additional opioid medications in order to alleviate pain or to abuse the drugs can be difficult. The present study was designed to evaluate two variables that may influence the abuse liability of opioids: drug use history and the presence or absence of experimentally induced pain. Eighteen healthy participants completed this outpatient study. One group was abusing prescription opioids (N=9) and one group had used prescription opioids medically but did not abuse them (N=9). All participants completed twelve sessions during which the effects of orally delivered oxycodone (0, 15, 30mg/70kg, PO) were examined. One dose was tested per day under double-blind conditions and sessions were separated by at least 48h. During the first "sample" session each week, participants were given $10 and the dose that was available later that week. During the second "choice" session, participants could self-administer either money or the previously sampled dose. Six sessions involved repeated hand immersions in cold water (4 degrees C) and six sessions involved immersions in warm water (37 degrees C). Most of the positive subjective effects of oxycodone were similar between the groups, but oxycodone self-administration significantly differed between groups. Non-abusers self-administered active doses of oxycodone only when they were in pain while abusers self-administered oxycodone regardless of the pain condition. These data suggest that an assessment of the reinforcing effects of opioids may be a sensitive method for differentiating opioid abusers from non-abusers.

Clinical factors affecting the pain on injection of propofol

BACKGROUND

Pain on propofol injection is a well-known adverse effect. We evaluated the clinical factors that affect the pain on injection of propofol to develop a strategy to prevent or reduce pain.

METHODS

We conducted a prospective, observational study of 207 adult patients (ASA I-II), and the patients were classified according to gender, age, the body mass index (BMI), the IV site and the side of the IV site. During the 10 seconds after propofol injection, pain intensity was measured on an 11-point numerical rating scale (0 = no pain and 10 = worst possible pain). Pain in excess of 3 on the numerical scale was regarded as moderate to severe pain.

RESULTS

THE SUBGROUPS OF GENDER (FEMALE: 55.6% vs. male: 25.0%; P < 0.01) and the IV site (dorsum of hand: 61.2% vs. wrist: 40.0% vs. antecubital fossa: 22.5%; P < 0.01) had significantly different frequencies for the incidence of pain on injection on the univariate and multivariate analyses. For the subgroup of females, the incidence of pain was statistically different according to the age group (20-40 yr: 71.0% vs. 41-60: 54.8% vs. 61-80: 38.5%; P = 0.014).

CONCLUSIONS

Our results showed that the younger age patients, the patients with a peripheral IV site and female patients are more sensitive to pain on the injection of propofol.

Preoperative psychologic and demographic predictors of pain perception and tramadol consumption using intravenous patient-controlled analgesia

OBJECTIVES

Postoperative pain is characterized by a wide variability of patients' pain perception and analgesic requirement. The study investigated the extent to which demographic and psychologic variables may influence postoperative pain intensity and tramadol consumption using patient-controlled analgesia (PCA) after cholecystectomy.

METHODS

Eighty patients, aged 18 to 70 years, with an American Society of Anesthesiologists physical status I or II and a body mass index between 18.5 and 24.9, undergoing laparoscopic cholecystectomy were enrolled. Self-rating anxiety scale (SAS) and self-rating questionnaire for depression (SRQ-D) were used--1 day before surgery--to assess patients' psychologic status. General anesthesia was standardized. PCA pump with intravenous tramadol was used for a 24-hour postoperative analgesia. Visual analog scale at rest (VASr) and after coughing (VASi) and tramadol consumption were registered. Pearson's and point biserial correlations, analysis of variance, and step-wise regression were used for statistical analysis.

RESULTS

Pearson r showed positive correlations between anxiety, depression, and pain indicators (P<0.05). Moreover, female patients had higher pain indicators (P<0.05). Analysis of variance showed that anxious (P<0.05) and depressed (P<0.001) patients had higher pain indicators, which significantly decreased during the postoperative 24 hours (P<0.00001). Regression analysis revealed that tramadol consumption was predicted by preoperative depression (P<0.001). VASr was predicted by sex and SRQ-D (P<0.05). VASi was predicted by sex and SAS (P<0.05).

DISCUSSION

Pain perception intensity was primarily predicted by sex with an additional role of depression and anxiety in determining VASr and VASi, respectively. Patients with high depression levels required a larger amount of tramadol.

Bodily and verbal expressions of postoperative symptoms in 3- to 6-year-old boys

The aim of this study was to investigate how small boys between 3 and 6 years of age describe bodily and verbal expressions of postoperative symptoms. The data collection was carried out at a large general hospital in Sweden and included both participant observations and semistructured interviews. The results provided a description of how 3- to 6-year-old boys bodily and verbally express postoperative symptoms. The results also showed that small children have difficulties in distinguishing pain, nausea, and anxiety and that postoperative discomfort was experienced in many different ways.

Effects of preanesthetic administration of midazolam, clonidine, or dexmedetomidine on postoperative pain and anxiety in children

BACKGROUND

A growing interest in the possible influences of pre- and postoperative anxiety and pain scores as outcomes of surgical treatment and benefits of anxiety or pain-reducing interventions has emerged. The aim of this study was to evaluate the influence of three different premedication regimens on postoperative pain and anxiety in children.

METHODS

A prospective, randomized, open-label clinical trial enrolled 60 schoolchildren. They were randomized for premedication with oral midazolam 0.5 mgxkg(-1), oral clonidine 4 microgxkg(-1), or transmucosal dexmedetomidine (DEX) 1 mug.kg(-1), submitted to a pre- and postoperative evaluation of anxiety with the State-Trait Anxiety Inventory for Children and asked to report any pain in verbal and visual analog scales. We also evaluated secondary outcomes such as parents' anxiety, sedation, separation from parents, adverse effects and hemodynamic status.

RESULTS

Dexmedetomidine and clonidine were related to lower scores of pain than midazolam. alpha(2)-agonists produced lower scores of peroperative mean arterial pressure and heart rate than midazolam. Both groups had similar levels of postoperative state-anxiety in children. There was no difference in preanesthesia levels of sedation and response to separation from parents between groups.

CONCLUSIONS

These findings indicate that children receiving clonidine or DEX preoperatively have similar levels of anxiety and sedation postoperatively as those receiving midazolam. However, children given alpha(2)-agonists had less perioperative sympathetic stimulation and less postoperative pain than those given midazolam.

Einfluss negativer Stressverarbeitung auf postoperatives Schmerzerleben und -verhalten

OBJECTIVE

The aim of the study is to show whether negative coping style has an impact on post-operative pain reporting and pain-related behaviour.

METHODS

After informed consent 48 gynaecological patients were enrolled in the study. Negative coping style was assessed by using the stress coping questionnaire SVF-78 (Janke and Erdmann). Patients were dichotomised by scores of the negative coping style. Pain reporting concerned pain intensity and pain quality. Pain-related behaviour was assessed by patient-controlled analgesia (PCA). Pain intensity and pain quality were assessed prior to surgery and 24 h after surgery. Patient-controlled analgesia was recorded up to 24 h after surgery. Trait anxiety (STAI-X2) was used as a control variable.

RESULTS

Patients with high scores in negative coping style report increased levels of pain in both affective and sensory pain perception. At the same time patient-controlled analgesia is used less frequently by this group. This result remains significant considering trait anxiety as a covariate.

CONCLUSIONS

High negative coping style may cause a discrepancy between pain reporting and pain-related behaviour. This should be taken into account in the perioperative care of patients.

Preoperative concentration of beta-lipotropin immunoreactive material in cerebrospinal fluid: a predictor of postoperative pain?

Levels of beta-endorphin immunoreactive material (IRM) in cerebrospinal fluid (CSF) have been reported to correlate inversely with postoperative morphine requirement. Considering proopiomelanocortin (POMC) derivatives as predictors for sensitivity to postoperative pain, we determined authentic beta-endorphin (beta-endorphin(1-31)), beta-lipotropin IRM, N-acetyl-beta-endorphin IRM and ACTH in CSF of 17 patients undergoing hip or knee arthroplasty, before surgery (t(A)), immediately after termination of propofol infusion and still under spinal anesthesia (t(B)), under postoperative pain (t(C)) and one day after surgery (t(D)); patients rated their severity of pain on a visual analogue scale (VAS) at those four times. In all patients CSF concentrations of N-acetyl-beta-endorphin IRM and beta-lipotropin IRM were found to be increased after terminating the propofol infusion with spinal anesthesia still effective at t(B). Patients did not feel pain at times t(A), t(B) or t(D); however, they reported moderate to considerable pain at t(C). There were no correlations of postoperative pain severity at t(C) with ACTH, beta-endorphin(1-31) or N-acetyl-beta-endorphin IRM concentrations in CSF. In contrast, we observed significant inverse correlations (Spearman's rank correlation coefficients between -0.83 and -0.85, p<0.01) for postoperative pain severity with beta-lipotropin IRM concentrations in CSF at t(C), and, in addition, at t(A), t(B) and t(D); thus, postoperative pain severity appeared to be dependent on a central system controlling sensitivity to pain, linked to a POMC system releasing beta-lipotropin IRM into CSF and already active at times t(A) and t(B). We conclude that beta-lipotropin IRM in CSF might be considered to serve as a predictor of sensitivity to postoperative pain.

"Anxiebo", placebo, and postoperative pain

Background

Surgical treatment and its consequences expose patients to stress, and here we investigated the importance of the psychological component of postoperative pain based on reports in the clinical literature.

Discussion

Postoperative pain remains a significant clinical problem. Increased pain intensity with increased demand for opioid medication, and/or a relative unresponsiveness to pain treatment was reported both when the analgesia was administered by means of conventional nurse injection regimes and patient-controlled analgesia (PCA). Both the quality of the analgesia, and the sensitivity of postoperative models for assessing analgesic efficacy could be significantly influenced.

The findings could be explained by increased penetration of an algesic anxiety-related nocebo influence (which we chose to call "anxiebo") relative to its analgesic placebo counterpart. To counteract this influence, the importance of psychological effects must be acknowledged, and doctors and attending nurses should focus on maintaining trustful therapist-patient relationships throughout the treatment period. The physical mechanism of anxiebo should be further explored, and those at risk for anxiebo better characterized. In addition, future systemic analgesic therapies should be directed towards being prophylactic and continuous to eliminate surgical pain as it appears in order to prevent the anxiebo effect.

Addressing anxiebo is the key to developing reproducible models for measuring pain in the postoperative setting, and to improving the accuracy of measurements of the minimum effective analgesic concentration.

Summary

Anxiebo and placebo act as counterparts postoperatively. The anxiebo state may impair clinical analgesia and reduce the sensitivity of analgesic trials. Ways to minimize anxiebo are discussed.

Intravenous patient-controlled analgesia: one size does not fit all

Patient-controlled analgesia was introduced as a technique that would allow greater flexibility in opioid delivery for the management of acute pain. However, so far, any benefit compared with conventional methods of pain relief appears to be small. This article reviews some of the factors that could limit the usefulness of intravenous patient-controlled analgesia in the clinical setting and what strategies might allow patient-controlled analgesia to become more effective.

Sex-related psychological predictors of baseline pain perception and analgesic responses to pentazocine

Sex differences in pain perception and analgesic responses have garnered increasing attention in recent years. We examined the association of psychological factors to baseline pain perception and pentazocine analgesia among 49 healthy women and 39 men. Subjects completed psychological questionnaires measuring positive and negative affect as well as catastrophizing. Subsequently, responses to experimental pain were assessed before and after double-blind administration of intravenous pentazocine (0.5mg/kg). In correlational analyses, positive affect predicted lower pain sensitivity among men but not women. Negative affect predicted lower baseline pain tolerances among both sexes but predicted poorer analgesia only among men. Catastrophizing was associated with greater pain sensitivity and less analgesia more consistently in men than women. Regression models revealed that positive affect predicted lower overall pain sensitivity and catastrophizing predicted poorer overall analgesic responses among men, while no significant predictors of overall pain or analgesia emerged for women. Moreover, positive affect and catastrophizing were negatively and positively correlated, respectively, with side effects from the medication, but only among men. These findings indicate sex-dependent associations of psychological factors with baseline pain perception, analgesic responses, and medication side effects.

The effects of a cold-water stimulus on butorphanol effects in males and females

Using a crossover, randomized, double-blind, cumulative-dosing procedure, we examined whether a painful stimulus modulated subjective and psychomotor effects of butorphanol in eight male and eight female volunteers. During each session, volunteers received four intravenous injections of either butorphanol (0, 0.5, 1, and 2 mg/70 kg) or saline (placebo) at hourly intervals. Saline and butorphanol were tested in two conditions, forearm immersion 30 min after each injection into either 2 or 37 degrees C water. During the 180-s immersion, volunteers completed a visual analog scale (VAS), psychomotor test, and pain ratings. VAS ratings of "Coasting ('spaced out')", "heavy or sluggish feeling," and "sleepy" were lower in the 2 degrees C than in the 37 degrees C condition during butorphanol administration, but only in females. Modulation by a painful stimulus of sleepy ratings was confined to the third immersion (i.e., a dose effect). The cold-water stimulus significantly decreased butorphanol-induced impairment during the third immersion for males, and females showed a similar trend. Overall, pain ratings were higher in females, and although not significant, males reported a greater degree of analgesia. The differences in pain ratings and degree of analgesia between the sexes are discussed as a possible mechanism for the sex differences in modulatory effects.

Sex differences in opioid analgesia: clinical and experimental findings

Sex differences in analgesic responses to opioids have received increasing attention in recent years. This article examines the literature on sex differences in opioid analgesia, including the results of studies from the authors' own laboratories. In general, nonhuman animal studies suggest more robust opioid analgesic responses in males relative to females; however, the human studies completed to date seem to indicate greater opioid analgesia among females. The most consistent evidence of sex differences in analgesia comes from studies of kappa-agonist-antagonists administered to patients following oral surgery. These data indicate more robust analgesia in females, and dose-response characteristics suggest that these agents possess both analgesic and antianalgesic properties, and the agonists may produce these effects in different proportions for women versus men. In contrast, the data from laboratory pain models in humans suggest greater analgesic effects in women in response mu-opioid agonists but not kappa-agonist-antagonists. Multiple mechanisms may explain sex differences in opioid analgesia, including gonadal hormonal effects, pharmacokinetics and pharmacodynamics, genetic influences, balance of analgesic/antianalgesic processes, and psychological factors. However, the disparity of results obtained from different pain models--animals versus humans and clinical pain versus experimental pain in humans--suggests that the models themselves are mechanistically different. Additional investigation is warranted in order to further explicate the nature of sex differences in opioid analgesia and to elucidate the underlying mechanisms.

Efficacy of tramadol versus meperidine for pain relief and safe recovery after adenotonsillectomy

BACKGROUND AND OBJECTIVE

Adequate relief of pain after tonsillectomy is a common problem. We compared meperidine and tramadol when given at induction of anaesthesia with respect to their effects on postoperative pain relief and emergence characteristics after adenotonsillectomy in children.

METHODS

Fifty children aged 4-7 yr undergoing tonsillectomy were randomly assigned to receive either tramadol 1 mg kg(-1) (n = 25) or meperidine 1 mg kg(-1) (n = 25) before commencement of the surgical procedure. Anaesthesia was induced with propofol (with cis-atracurium for muscle relaxation) and maintained with sevoflurane in oxygen and nitrous oxide. Postoperative pain was scored by a blinded observer using a facial pain scale in the recovery room at 0 (at arrival of the patient in the postoperative care unit) and at 10, 20 and 45 min thereafter. Agitation scores were also assessed by the same observer at 0 min. Heart rate and mean arterial pressure were recorded at regular intervals. The time to recovery to spontaneous respiration and the incidence of postoperative nausea and vomiting were noted.

RESULTS

Facial pain scale scores were increased in the tramadol group at 0, 10 and 20 min (P < 0.05). No difference was observed in scores at the 45th min postoperation. Agitation scores were higher in the tramadol group than in the meperidine group. No statistical difference was found between the two groups. Heart rates and mean arterial pressures were similar in both groups. The time to recovery to spontaneous respiration was delayed with meperidine compared with tramadol (P < 0.05). The incidence of nausea and vomiting was not statistically different between groups.

CONCLUSIONS

Meperidine was more effective for pain relief and provides better emergence characteristics than tramadol after tonsillectomy in children.

Patient-specific factors affecting patient-controlled analgesia dosing

A study was conducted to evaluate the effect of characteristics patients' gender, age, weight, height, and body surface area, as well as the concurrent or recent use of opioids, ethanol and tobacco, on opioid dose requirements during administration of patient-controlled analgesia (PCA). Data were collected retrospectively from the medical records of 150 patients who underwent open cholecystectomies during an 18 month period at one institution. Demonstrable inter-patient variability in patterns of PCA use was observed. The results of the study demonstrate that during the first 48 hours of PCA therapy, patient age, height, weight, body surface area, gender, smoking, alcohol use, and preoperative opioid use may have significant influence on opioid analgesic use (p < 0.05). The data support the hypothesis that patient-specific factors may contribute to the variability observed in patients' PCA analgesic dose requirements, and these factors should be considered when selecting a proper demand (bolus) dose for PCA therapy.

Are there reliable predictors of postoperative pain?

BACKGROUND

The purpose of this study was to identify the preoperative determinants of severe postoperative pain.

METHODS

Potential predictors were assessed using a questionnaire submitted on the day before surgery. Pain at rest, and pain during coughing/mobilization, were measured using visual analog scales on the day of surgery and on the following 2 days. The type of postoperative pain management was not standardized and was prescribed by the anesthesiologist in charge. Multivariate logistic regression models explaining postoperative pain were developed in Group I, comprising 304 consecutive patients undergoing orthopedic or intraperitoneal surgery, and validated in Group II, comprising 145 independent patients.

RESULTS

Of the 62 variables examined by univariate analysis, only five were found to increase the risk of severe postoperative pain in Group I at rest and six factors during cough/mobilization. In the multivariate model for pain at rest, general anesthesia, expectation of postoperative pain, and chronic sleeping difficulties increased the risk of severe postoperative pain. In Group II, only chronic sleeping difficulties remained (OR: 3.97, 95% Cl: 1.69-9.29). In the multivariate model during cough/mobilization, intraperitoneal surgery, fear of postoperative pain, and having a relative with a history of pain increased the risk of severe postoperative pain in Group I. Intraperitoneal surgery OR 2.45 (95% Cl = 1.01-4.50) and having a relative with a history of pain OR 2.06 (95% Cl = 1.005-4.50) remained in Group II.

CONCLUSION

Of the many factors that may influence postoperative pain, chronic sleeping difficulties emerge in this population of patients as the strongest determinant of pain at rest. Intraperitoneal surgery and having a relative with a history of pain are the strongest determinants of pain during cough/mobilization. These findings make physiological sense and deserve more attention by anesthesiologists.

Sex differences in analgesic responses: evidence from experimental pain models

BACKGROUND AND OBJECTIVE

Sex-related influences on the experience of pain have received considerable empirical attention. Women are at greater risk for several forms of clinical pain and exhibit greater perceptual responses to experimental pain. In recent years, investigators have turned their attention to the influence of sex-related factors on analgesic responses. The purpose of this review is to examine the literature on sex differences in analgesic responses, emphasizing findings from experimental studies.

METHODS

First, important methodological issues in laboratory pain research are presented, and sex differences in responses to experimentally-induced pain are briefly addressed. Next, previous data from non-human animal research and human experimental and clinical research related to sex differences in analgesia are discussed. Also, preliminary results are presented from an ongoing study in our laboratory examining analgesic responses in women and men.

RESULTS AND CONCLUSIONS

Both previous research and preliminary findings from our laboratory suggests that opioids produce greater analgesic responses in women than men. Potential mechanisms underlying sex differences in analgesia are proposed, and important directions for future research are suggested.

Transcutaneous electrical nerve stimulation (TENS) can reduce postoperative analgesic consumption. A meta-analysis with assessment of optimal treatment parameters for postoperative pain

AIM

We investigated the literature of randomised placebo-controlled trials to find out if transcutaneous electrical nerve stimulation (TENS) or acupuncture-like transcutaneous electrical nerve stimulation (ALTENS) can reduce analgesic consumption after surgery.

RESULTS

Subgroup analysis for adequate treatment (pulse frequency: 1-8Hz [ALTENS] or 25-150Hz [TENS], current intensity: "strong, definite, subnoxious, maximal tolerable" or above 15mA, and electrode placement in the incision area) were performed. Twenty-one randomised, placebo-controlled trials with a total of 1350 patients were identified. For all trials, the mean reduction in analgesic consumption after TENS/ALTENS was 26.5% (range -6 to +51%) better than placebo. Eleven of the trials compromising 964 patients, had reports which stated that a strong, subnoxious electrical stimulation with adequate frequency was administered. They reported a mean weighted reduction in analgesic consumption of 35.5% (range 14-51%) better than placebo. In nine trials without explicit confirmation of sufficient current intensity and adequate frequency, the mean weighted analgesic consumption was 4.1% (range -10 to +29%) in favour of active treatment. The difference in analgesic consumption was significantly (p=0.0002) in favour of adequate stimulation. The median frequencies used in trials with optimal treatment was 85Hz for TENS and 2Hz in the only trial that investigated ALTENS.

CONCLUSION

TENS, administered with a strong, subnoxious intensity at an adequate frequency in the wound area, can significantly reduce analgesic consumption for postoperative pain.

Preoperative emotional states in patients with breast cancer and postoperative pain

BACKGROUND

The present study examined the relationship between psychological variables, including anxiety, depression, and patient-controlled analgesia (PCA) use in patients who underwent radical mastectomy.

METHODS

Ninety-nine ASA I-II women with breast cancer between 18 and 60 years scheduled for modified radical mastectomy completed the state scale of the state-trait anxiety inventory and the Beck depression inventory before the day of surgery. Standard general anesthesia, surgery, and IV-PCA therapy was conducted. Postoperative ratings of pain intensity, opioid consumption and satisfaction with PCA were recorded for the first 24 h on the ward. The degree of pain intensity was evaluated by a visual analog scale (VAS, 1-10). Satisfaction with pain control was reported using an five-point scale from 1 (very dissatisfied) to 5 (very satisfied).

RESULTS

The pain intensity, total analgesic consumption and dose/demand ratio were significantly related to preoperative anxiety and depression (P<0.05). Degree of dissatisfaction with PCA was significantly correlated with preoperative anxiety and depression (P<0.01).

CONCLUSION

Patients with higher anxiety and depression levels had higher postoperative pain and analgesic requirements in this study.

Information provision, patient involvement, and emotional support: prospective areas for improving anesthetic care

PURPOSE

To explore patients' perceptions of anesthetic care as measured by a patient-centered care survey. Specifically, the survey examined patient views of multiple diverse dimensions of care that are not typically fully addressed among patients receiving anesthesia services, namely opinions on Information Provision, Involvement in Care, Respect Shown, Physical Comfort, and Emotional Support.

METHOD

A total of 268 patients responded to a patient-centered care survey, a self-report factor analytically derived instrument designed to measure the aforementioned dimensions of care.

RESULTS

Analyses revealed that the highest ratings of care were given to Physical Comfort and Respect. Ratings of Information Provision, Involvement, and Emotional Support were significantly lower. Ratings did not differ as a function of site of service, inpatient vs day surgery, surgical service, type of anesthetic, or anesthesiologist.

DISCUSSION

The findings generated from the study are of value in obtaining a broader understanding of anesthesia services from the patient's perspective, and also in directing quality improvement initiatives. Other departments of anesthesiology interested in quality improvement initiatives may similarly benefit from measurement of patient-centered care.

Postoperative analgesia by combined continuous infusion and patient-controlled epidural analgesia (PCEA) following hip replacement: ropivacaine versus bupivacaine

BACKGROUND

Ropivacaine is a new local anaesthetic, which compared to bupivacaine is less toxic and shows greater sensory and motor block dissociation. We hypothesised that treatment of postoperative pain with a combined regimen of continuous epidural infusion and Patient-Controlled Epidural Analgesia (PCEA) using ropivacaine could have given better results compared with those we had obtained using bupivacaine.

METHODS

Patients undergoing total hip replacement were randomly assigned to two groups. They received epidural analgesia for postoperative pain treatment using ropivacaine, 2 mg x ml(-1) or bupivacaine 2 mg x ml(-1). Both drugs were administered as a constant infusion of 6 ml x h(-1) supplemented by PCEA bolus doses of 2 ml. Patients in both groups received morphine intravenously on demand from a patient-controlled analgesia (PCA) device. An independent observer recorded pain scores, intensity of motor block and morphine consumption at regular intervals during the first 24 h after surgery.

RESULTS

Fifty-one patients were evaluated. Ropivacaine and bupivacaine, in similar amounts, provided similar results assessed as adequate to very good postoperative analgesia, whereas motor block was significantly more intense in patients treated with bupivacaine.

CONCLUSIONS

Despite similar analgesic effects, epidural infusion of ropivacaine combined with PCEA provides higher patient satisfaction than equal doses of bupivacaine due to lack of motor block.

Risk factors for preoperative anxiety in adults

BACKGROUND

Patients who undergo surgery experience acute psychological distress in the preoperative period. The objective of this study was to identify and quantify the effect of risk factors for preoperative anxiety in adults.

METHODS

A cross-sectional study was performed with 592 inpatients scheduled for elective surgery. Age ranged from 18 to 60 years (ASA physical status I-III). Demographic information was collected using a structured questionnaire. The measuring instruments were a visual analog scale, the State-Trait Anxiety Inventory; the Montgomery-Asberg Depression Rating Scale, the WHO Self-Reporting Questionnaire-20, and the future self-perception questionnaire. Multivariate conditional regression modeling was used to control confounding factors and to determine independent predictors of preoperative anxiety, taking into account the hierarchical relationship between risk factors.

RESULTS

High preoperative anxiety was associated with history of cancer (odds ratio (OR)=2.26) and smoking (OR=7.47), psychiatric disorders (OR=5.93), negative future perception (OR= 2.30), moderate to intense depressive symptoms (3.22), high trait-anxiety (3.83), moderate to intense pain (2.12), medium surgery (OR=1.52), female gender (OR=2.0), ASA category III (OR=3.41), up to 12 years of education (OR=1.36), and more than 12 years of education (OR=1.68). Previous surgery (OR= 0.61) was associated with lower risk for preoperative state-anxiety.

CONCLUSIONS

History of cancer and smoking, psychiatric disorders, negative future perception, moderate to intense depressive symptoms, high trait-anxiety, moderate to intense pain, medium surgery, female gender, ASA category III, up to 12 years of education and more than 12 years of education constituted independent risk factors for preoperative state-anxiety. Previous surgery reduced the risk for preoperative anxiety.

Risk factors for postoperative anxiety in children

BACKGROUND

Anxiety is defined as a set of behavioural manifestations that can be divided into state- and trait-anxiety. State-anxiety is a transitory emotional condition that varies in intensity and fluctuates over time. Trait-anxiety is a personality trait which remains relatively stable over time. The objective of this study was to identify and quantify perioperative risk factors for immediate postoperative anxiety in children.

METHODS

A prospective cohort study was performed with 90 schoolchildren, ages ranging from 7 to 13 years old, ASA physical status I-II, submitted to elective surgery. The measuring instruments were verbal scale of pain, visual analogue scale (VAS), Trait-State Anxiety Inventory for Children (STAIC), Trait-State Anxiety Inventory (STAI) for parents, and structured questionnaire.

RESULTS

Patients not submitted to analgesic block and patients with moderate and intense pain presented an estimated risk 5- and 13-fold greater for high levels of postoperative state-anxiety, respectively. High levels of preoperative state-anxiety and administration of doses of midazolam less than 0.056 mg x kg(-1) constituted an estimated risk for postoperative state-anxiety of 3- and 4-fold, respectively. A positive history of previous surgery was associated with lower risk for postoperative anxiety.

CONCLUSIONS

High levels of preoperative state-anxiety, administration of less than 0.056 mg x kg(-1) of midazolam, absence of analgesic block and presence of moderate and intense postoperative pain constituted risk factors for immediate postoperative state-anxiety in children. Previous surgery reduced the risk for postoperative anxiety.

Patient controlled analgesia and intramuscular injections: a comparisons of patient pain experiences and postoperative outcomes

Despite relatively widespread use of various forms of patient controlled analgesia (PCA), there remain conflicting results in the literature as to the efficacy of PCA. This study was conducted to assess the efficacy and postoperative outcomes of intravenous PCA compared to intramuscular (IM) injections in 73 patients who received major abdominal surgery. These patients were randomly selected and randomly assigned preoperatively to receiving IM or PCA modes of analgesia postoperatively. The following factors were compared: amount of pain; amount of analgesia use; degree of patient satisfaction with pain control both while on parenteral analgesia and after switching to oral; length of time to first ambulation; and length of stay in hospital. Results of the study did not demonstrate a statistically significant difference in any of these, using a P-value of 0.01. The PCA patients took an average of 4.5 hours longer than the IM patients to ambulate postoperatively and the IM patients received at least three times as much antiemetic (P = 0.001). Locus of control was not found to be a major factor in satisfaction or pain levels. Subsequent meta-analyses have also failed to yield significant differences between IM and PCA groups except in patient satisfaction. It is recommended that expansion of PCA programmes with abdominal surgery patients be considered only in cases where there is fiscal advantage or where patient satisfaction can be a driving force.

The effects of a cold-water immersion stressor on the reinforcing and subjective effects of fentanyl in healthy volunteers

The reinforcing and subjective effects of fentanyl, an opioid analgesic, were tested in ten healthy volunteers without histories of drug abuse, as a function of the temperature of a water bath in which the volunteers' forearms were immersed. The temperatures were body-temperature (37 degrees C), moderately cold (10 degrees C), and very cold (2 degrees C). A discrete-trial choice procedure was used in which, in each session, volunteers sampled 50 micrograms of fentanyl (delivered as a bolus via an infusion pump) and saline, and then on three successive trials, chose between the two. Volunteers then had to immerse their non-dominant forearm in the water bath 5 min after a drug delivery. Fentanyl was chosen on 77% of choice occasions in the 10 degrees C and 2 degrees C water conditions, which was significantly different from chance levels, and on 60% of choice occasions in the 37 degrees C water condition, which did not differ from chance levels. Several subjective effects of fentanyl were also modulated by the temperature of the water bath. We conclude that in the context of a painful stimulus, 50 micrograms of fentanyl functions as a reinforcer in non-drug abusers.

The influence of lockout intervals and drug selection on patient-controlled analgesia following gynecological surgery

This study systematically compared 2 opioids, morphine (MOR) and fentanyl (FEN), and 2 lockout intervals, long (L) and short (S) in patients utilizing patient-controlled analgesia (PCA). Seventy-eight women undergoing gynecological surgery were randomly assigned to 1 of 4 groups: MOR-S (7 min), MOR-L (11 min), FEN-S (5 min), FEN-L (8 min). PCA measures obtained during the first 24 h after surgery included: number of demands/h, number of completed deliveries/h, dose/h, and demand/delivery ratio. Visual analog scales of pain and anxiety were also obtained. Results indicated that pain relief was equivalent with minimal side effects for both opioids. The selection of opioid, however, influenced the pattern of PCA use, with an improved demand/delivery ratio initially for FEN. The lockout intervals chosen for this study did not influence pain or anxiety levels.

New developments in patient-controlled postoperative analgesia

Patient-controlled analgesia (PCA) is a newer technique for pain management. Patients are allowed to self-administer small analgesic bolus doses into a running intravenous infusion, intramuscularly, subcutaneously or even into the epidural space. Demands are usually controlled by computer-driven infusion pumps, but can also be delivered by disposable devices. Clinical experience demonstrates that individual variability in pain sensitivity and analgesic needs are of utmost importance. In contrast to earlier expectations, opioid consumption is usually higher than with restrictive conventional dosing regimes, but without an increase in serious side effects. Patients' acceptance is generally enthusiastic because of the possibility of self-control. PCA has proved its importance for pain studies, e.g. for algesimetry, to determine predictors of postoperative pain, to describe drug interactions, to evaluate the concept of pre-emptive analgesia or for pharmacokinetic designs. It is concluded that PCA results have been urgently required in order to change the mind of physicians and nursing staff with respect to individual pain management strategies. Once this goal is achieved, PCA concepts should also be used for the improvement of more conventional techniques.

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.

Facilitating the use of noninvasive pain management strategies with the terminally ill

In this paper a number of issues that appear to transcend the range of noninvasive interventions described in this volume are examined. Specifically, we raise the important issue of barriers to treatment. Among those discussed are patients', their significant others', as well as health care providers' conceptualizations of and biases regarding pain and pain control. We emphasize that it is important not only to focus on the details of the specific techniques described but also on how most effectively to present information. We note that it is important to customize any noninvasive intervention to the specific needs of the patient and their significant others. We provide some suggestions as to how this might be accomplished. Finally, we discuss some attitudes and beliefs held by health care providers that may inhibit their use of the full range of noninvasive techniques that are available for managing pain.