Analgesic and respiratory effects of epidural sufentanil in patients following thoracotomy

Assessment of chest wall movement following thoracotomy: a systematic review

Thoracotomy is a major cause of respiratory impairment, increasing the risk of postoperative pulmonary complications (PPC). Systems assessing ribcage kinematics may detect changes in chest expansion following thoracotomy and may thus aid in the development of patient-tailored chest physiotherapy. Hence, we aimed to identify studies assessing changes in chest wall movement following thoracotomy using objective measures. The Cochrane library, MEDLINE, EMBASE, Scopus and Web of Science databases were searched to find relevant articles providing an objective assessment of chest wall movement following thoracotomy. Methodological quality of included studies concerning chest wall movement following thoracotomy was assessed by use of QUADAS-2 tool. A total of 12 articles were included for the assessment of chest wall changes following thoracotomy using objective measures. Four studies measured changes in the cross-sectional area of the ribcage and abdomen using the respiratory inductive plethysmography (RIP), 1 study computed the chest wall compliance by monitoring the intra-pleural pressure, 3 studies measured changes in chest circumference with a simple tape measure and 4 articles performed a compartmental analysis of the chest wall volume by means of an optoelectronic plethysmography (OEP). There was no delay in the collection of data of the index test and reference standard, resulting in a low risk of bias for the flow and timing domain. Across all studies, participants underwent the same reference standard, resulting in a low risk of verification bias. Several objective measures were able to detect changes in chest wall displacement following thoracotomy and differed in the practical use and invasive nature. OEP allows a compartmental analysis of the chest wall volume. Hence, this system allows to assess chest wall movement changes following thoracotomy and the impact of different types of surgical approach. Furthermore, it could aid in the development of tailored physiotherapy.

Management of Pain in the Critically Ill

Analgesia for critically ill patients can be provided most effectively by the use of modern techniques. Under standing of the anatomical pathways for nociceptive sig nal transmission allows the use of techniques that mod ulate or block nociceptive information at several levels (periphery, spinal cord, and systemic). A comprehen sive discussion of analgesic techniques at each level is presented. Formulation of a treatment plan is discussed. Several examples are presented to show the decision- making process for the use of modern analgesic tech niques in critically ill patients.

Postthoracotomy paravertebral analgesia: will it replace epidural analgesia?

Thoracotomy is associated with significant acute postoperative pain and a high incidence of development of chronic pain. Thoracic epidural analgesia has long been standard treatment for postthoracotomy pain, but recently there has been increased interest in alternative regional techniques, particularly paravertebral analgesia. This article compares the analgesic efficacy, side effects, complications of, and contraindications for thoracic epidural and paravertebral analgesia techniques and discusses their effects on the development of chronic postthoracotomy pain. This information will allow a more considered choice of analgesic technique after thoracotomy.

Epidural and spinal agents for postoperative analgesia

The discovery of opioid receptors and the subsequent development of the technique of epidural and intrathecal opioid administration are undoubtedly two of the most significant advances in pain management in recent decades. The use of spinal opioids is widespread and increasing. The technique is used widely to treat intraoperative, postoperative, traumatic, obstetric, chronic, and cancer pain. Newer developments include the increasing use of combined local anesthetics and opioids or nonopioids and also PCEA, particularly in the obstetric population. Meta-analysis of controlled trials has demonstrated improved pulmonary outcome in patients receiving epidural postoperative analgesia. Although rare, respiratory depression continues to be a major problem of the technique. None of the currently available opioids is completely safe; however, extensive international experience has shown that patients receiving spinal opioids for postoperative analgesia can be safely nursed on regular wards, provided that trained personnel and appropriate guidelines are available. The importance of a good acute pain service to provide the safe and effective use of spinal opioids cannot be overemphasized.

Pain management in cardiothoracic practice

All analgesia regimens have benefits and side effects, and personal expertise can greatly influence the efficacy of regional techniques. A multimodal approach to analgesic management allows physicians to achieve maximum analgesic efficacy while limiting side effects. An appropriate analgesic plan takes into account the extent of pain associated with the type of incision and adjusts this according to each patient's individual needs. As we enter the new millennium, thoracic and cardiac surgery is becoming more innovative, and the life expectancy of people in the first world is constantly increasing. Older people with less physiologic reserve and more multisystem dysfunction are undergoing more major surgical procedures, and adequate pain control in the postoperative period is becoming increasingly important.

[Postoperative locoregional analgesia in the adult: epidural and peripheral techniques. Indications, adverse effects and monitoring]

Regional analgesia is a very effective way to treat postoperative pain. Lumbar and thoracic epidural analgesia are well adapted to major abdominal and thoracic surgery. Nevertheless, respiratory side effects induced by opioids are potentially severe and an adequate monitoring is essential. In orthopaedic surgery, perineural blocks are the best technique to manage postoperative pain and perineural catheters may be used. The importance of intra-articular analgesia, simple and safe, is not fully understood. The association of a local anaesthetic inducing a minor motor block and a strong sensitive block (bupivacaine, ropivacaine), with an opioid seems to be the best pharmacologic choice regarding quality of analgesia and safety. Benefits of postoperative regional analgesia on mortality and morbidity are not demonstrated. Medical and nursing staff and specialized units should improve quality of postoperative regional analgesia as well. General guidelines for the practice of regional anaesthesia must be closely followed.

Patient-controlled analgesia with sufentanil: a comparison of two different methods of administration

STUDY OBJECTIVE

To examine the safety and analgesic efficacy of sufentanil administered via either epidural or intravenous (i.v.) patient-controlled analgesia (PCA) in patients recovering from gynecologic surgery.

DESIGN

Randomized, double-blind comparison.

SETTING

Patient care unit at a university medical center.

PATIENTS

29 healthy women presenting for major intraabdominal gynecologic surgery with epidural anesthesia who requested postoperative PCA.

INTERVENTIONS

Following completion of surgery performed using epidural anesthesia with 2% lidocaine and i.v sedation, patients were assigned to one of three treatment groups: Group 1-epidural PCA (EPCA) with sufentanil: 0.3 microgram/kg bolus followed by 8 micrograms/hr infusion plus epidural PCA boluses of 4 micrograms every 6 min as needed; Group 2-i.v. PCA with sufentanil: 0.3 microgram/kg bolus followed by 8 micrograms/hr infusion plus IV PCA boluses of 4 micrograms every 6 min as needed; or Group 3-i.v. PCA with morphine: 0.1 mg/kg bolus followed by 0.5 mg/hr infusion plus i.v. PCA boluses of 1 mg every 6 min as needed.

MEASUREMENTS AND MAIN RESULTS

Patients were observed at regular intervals during a 24-hour evaluation period. Visual analog scale (VAS) scores were used to assess analgesia and satisfaction with therapy. Pulmonary function was assessed by monitoring respiratory rate, oxygen (O2) saturation, and forced expiratory flow. Total opioid dose delivered and the presence/severity of side effects was also collected. Sufentanil plasma levels were measured in a subset of eight patients. Patients receiving either EPCA or i.v. PCA sufentanil experienced equivalent analgesia that was more rapid in onset than i.v. PCA morphine. Total dose administered and plasma concentration of drug were similar in both sufentanil groups; however, a greater number of patients in the i.v. delivery group experienced clinically significant O2 desaturation.

CONCLUSIONS

The main advantage of EPCA sufentanil in this postsurgical setting was its ability to provide a more rapid onset of analgesia than traditional i.v. PCA with morphine while offering greater safety than i.v. sufentanil.

Pharmacotherapy of opioids: present and future developments

The clinically available opioids have different physicochemical properties, resulting in differences in clinical profile with regard to potency, onset, and duration of activity. However, they all have comparable side-effects after acute systemic application. Several approaches can be used to overcome these side-effects. The following approaches, with special emphasis on the perioperative use of the opioids, are discussed: (1) the use of alternative routes of administration, such as via the spine (epidurally and intrathecally); (2) optimization of opioid delivery by means of slow-release preparations, chronic infusions with indwelling catheters, and transdermal delivery systems; (3) use of additional agents to potentiate the analgesic properties of the opioids so that the dose of opioid can be reduced; and (4) searching for new analgesics on the basis of knowledge of the pain-transmission system and the different opioid receptors with their functional interactions.

Does epidural sufentanil provide effective analgesia per- and postoperatively for abdominal aortic surgery?

To assess the efficacy of epidural sufentanil in providing per- and postoperative analgesia, 40 patients undergoing elective abdominal aortic surgery received either 50 mu g sufentanil in 10 ml normal saline solution (n = 20, ES group) or 10 ml normal saline (n = 20, control group) via a thoracic epidural catheter. The study solution was given (double-blind and at random) after the patients had been anaesthetized with i.v. midazolam, sufentanil and vecuronium. Anaesthesia was maintained with 60% nitrous oxide in oxygen and halothane at a 1% inspiratory concentration. When patients showed signs of inadequate analgesia, supplementary doses of 25 mu g sufentanil were given i.v. The number of patients requiring additional i.v. sufentanil differed significantly between the two groups: 5 out of 20 patients in the ES group vs 13 out of 20 patients in the control group required additional sufentanil (P<0.05). The mean dose administered i.v. did not differ significantly between the two groups: 105 +/- 109.5 mu g vs 138.5 +/- 126.9 mu g (mean +/- SD) in 5 and 13 patients, respectively. No cardiovascular changes were observed after the epidural bolus dose. Postoperative analgesia, consisting of a continuous epidural infusion of 50 mu g sufentanil in 50 ml bupivacaine 0.125% at a rate of 6-10 ml/h after a bolus dose of 10 ml of this solution, was adequate in the majority of patients, as determined by VAS-scores assessed during the epidural treatment (4.3 +/- 1.5 days).

Epidural clonidine or sufentanil for intraoperative and postoperative analgesia

This study contrasts the efficacy and side effects of epidural clonidine and sufentanil in the perioperative period. Using a randomized, prospective, double-blind study design, 40 patients undergoing abdominal surgery under propofol/nitrous oxide anesthesia were enrolled. Before anesthesia, an epidural catheter was inserted at the L1-L2 interspace. At induction of anesthesia, the patients received epidurally either clonidine (4 micrograms/kg in 10 mL) infused in 20 min followed by a 2-micrograms.kg-1.h-1 infusion (5 mL/h) during 12 h (Group 1) or sufentanil (0.5 microgram/kg in 10 mL) in 20 min followed by a 0.25-microgram.kg-1.h-1 infusion (5 mL/h) during 12 h (Group 2). Intraoperatively, increases in arterial blood pressure and heart rate not responding to propofol bolus (0.5 mg/kg) were treated with a bolus of intravenous (IV) sufentanil 0.035 microgram/kg. Postoperatively, IV sufentanil boluses (5 micrograms) were given through a patient-controlled analgesia (PCA) device. Postoperative analgesia was assessed by recording the IV PCA sufentanil requirements and the patients' visual analog scale (VAS) at 3, 6, 12, 18, 24, 36, and 48 h. Sedation analog scales and side effects were also recorded. Plasma clonidine and sufentanil concentrations were measured after 20 min and 6, 12, and 24 h. The number of reinjections of propofol (n = 1.6 +/- 1.6 in Group 1 vs 6.5 +/- 4.0 in Group 2) and of IV sufentanil (n = 0.6 +/- 0.8 in Group 1 vs 3.8 +/- 3.7 in Group 2) was significantly reduced (P < 0.001) in the epidural clonidine group. In the early postoperative period, pain scores and rescue analgesic requirements were very low in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term intraspinal infusions of opioids in the treatment of neuropathic pain

Long-term intraspinal infusions of opioid drugs are being increasingly utilized in patients with noncancer pain. Despite this, there is a lack of long-term information, including success and failure rates for pain relief and technical problems. During a 5-year period, 18 noncancer patients underwent implantation of programmable infusion pumps for long-term intrathecal opioid infusion. Patients had (a) neuropathic pain, (b) had failed or been ineligible for noninvasive treatments, and (c) obtained greater than 50% pain relief with intrathecal trial infusions of morphine sulfate or sufentanil citrate. A disinterested third-party reviewer evaluated patients at the most recent follow-up. Sixty-one percent (11/18) of patients had good or fair pain relief with mean follow-up 2.4 +/- 0.3 years (0.8-4.7 years). Average numeric pain scores decreased by 39% +/- 4.3%. Five of the 11 responders required lower opioid doses (12-24 mg/day morphine) and the remaining six patients required higher opioid doses (> 34 mg/day morphine). Failure of long-term pain relief occurred in 39% (7/18) despite good pain relief in trial infusions and the use of both morphine and sufentanil. Technical problems developed in 6/18 patients but appeared to be preventable with further experience. Long-term intrathecal opioid infusions can be effective in treatment of neuropathic pain but might require higher infusion doses.

Side effects of intrathecal and epidural opioids

The purpose of this article is to review the literature on the side effects of intrathecal and epidural opioids. English-language articles were identified through a MEDLINE search and through review of the bibliographies of identified articles. With the increasing utilization of intrathecal and epidural opioids in humans during the 1980s, a wide variety of clinically relevant side effects have been reported. The four classic side effects are pruritus, nausea and vomiting, urinary retention, and respiratory depression. Numerous other side effects have also been described. Most side effects are dose-dependent and may be more common if the opioid is administered intrathecally. Side effects are less common in patients chronically exposed to either intrathecal, epidural, or systemic opioids. Some side effects are mediated via interaction with specific opioid receptors while others are not. It is concluded that the introduction of intrathecal and epidural opioids marks one of the most important breakthroughs in pain management in the last two decades. However, a wide variety of clinically relevant non-nociceptive side effects may occur. All physicians utilizing intrathecal and epidural opioids must be aware of these side effects, for while most are minor, others are potentially lethal.

Oxygenation and ventilation characteristics of thoracic surgical patients the night before surgery

Studies of the respiratory effects of perioperative analgesic and anesthetic agents are complicated by evidence that healthy subjects and those with COPD may have abnormalities of oxygenation and ventilation during sleep. This report thus characterizes respiration during sleep preoperatively in a population frequently examined in postoperative analgesia studies. Sixty-two thoracic surgical patients were monitored by continuous respiratory inductive plethysmography, 49 of whom also had continuous pulse oximetry and bi-hourly blood gas measurements. The mean respiratory rate (RR) at each hour during sleep was similar to the awake RR (P > 0.06). The minimum RR during sleep was 7.6 +/- 2.1 (2.6-9.8; median 7.9). At least 1 apnea (tidal volume < 100 mL for > or = 15 sec) occurred in 77% of subjects, and 32% had > or = 1 slow respiratory rate (SRR; 5-min RR < 10 beats/min) episode. The mean SpO2 for hours 2 to 4 was significantly less than while awake (P < 0.0015), but the differences were < or = 1.1%. The minimum SpO2 was 88 +/- 7% (62-97; 89) and 40% of subjects had > or = 1 desaturation (DESAT90; SpO2 < 90% for > or = 15 sec) episode. The pH at hours 2 and 4 was significantly (P < 0.0009) less than while awake, but the differences were only 0.02. Other bi-hourly pH, PaCO2, and PaO2 values were similar to the awake values (P > 0.02). Interpatient variability was high, especially for episodic abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Postoperative pain treatment after cholecystectomy with epidural sufentanil at lumbar or thoracic level

The difference in analgesic activity following lumbar (group I) or thoracic (group II) epidural administration of 50 micrograms sufentanil was studied after cholecystectomy. Fifteen patients in each group were evaluated for pain relief using a linear analog scale (LAS), heart rate (HR), mean arterial pressure (MAP), respiratory rate (RR), peak expiratory flow (PEF), forced vital capacity (FVC), forced expiratory volume (FEV1) and arterial CO2 tension (PaCO2). In five additional patients in each group 75 micrograms sufentanil was injected for determination of serum levels. Pain scores were lower than three in both groups after 10 min, while mean pain scores remained below one from 20 min until 2 h following injection in both groups. Satisfactory pain relief lasted for 4 h. RR was significantly decreased from two until 360 min. in the lumbar group and from five until 120 min in the thoracic group. PaCO2 was raised in both groups only during the first hour. PEF and FVC were significantly improved compared to control 1, 2 and 4 h following injection. Serum sufentanil levels reached a maximum of 0.299 +/- 0.052 ng.ml-1 in the lumbar group and 0.377 +/- 0.076 ng.ml-1 in the thoracic group after 5 min. There were no significant differences between the two groups in the variables studied.

An intra-operative comparison of lumbar with thoracic epidural sufentanil for thoracotomy

The efficacy of thoracic epidural sufentanil 50 micrograms was compared with lumbar epidural sufentanil 50 micrograms in 30 patients (n = 15 in each group) undergoing lateral thoracotomy. Sufentanil was administered epidurally after induction of anaesthesia with sufentanil 1 microgram.kg-1 and thiopentone 2-5 mg.kg-1 intravenously. Anaesthesia, nitrous oxide 66%, halothane 0.3% and sufentanil 25 micrograms intravenously were given whenever the systolic arterial blood pressure increased more than 15 mmHg above the preoperative value and heart rate exceeded 90 beat.min-1 in the absence of hypovolaemia, or when other autonomic or somatic signs were seen. Four patients in the thoracic epidural group and five in the lumbar epidural group needed supplementary sufentanil. Six patients in the thoracic epidural group and three in the lumbar epidural group each had a single hypotensive episode. Lumbar and thoracic epidural sufentanil are equally effective in contributing to intra-operative analgesia for lateral thoracotomy.

Intrathecal morphine during thoracotomy, Part II: Effect on postoperative meperidine requirements and pulmonary function tests

The ability of intrathecal morphine (ITM) to reduce post-thoracotomy pain and meperidine requirements was investigated. Thirty adult patients scheduled for thoracic surgery were studied. Following induction with thiamylal sodium and succinylcholine, anesthesia was maintained with 100 micrograms of fentanyl, vecuronium, and enflurane. Prior to skin incision, 16 patients received intrathecal morphine, 12 micrograms/kg, injected at the L3-4 or L4-5 level. The other 14 patients were controls. Postoperatively, patients were evaluated for pain scores and the total doses of meperidine required over 24 hours. The patients in the ITM group required significantly less meperidine compared to the control group (59 +/- 68 v 167 +/- 97 mg, respectively) and had lower pain scores (1.4 +/- 1.1 v 2.4 +/- 0.9 mg, respectively). There were no serious side effects attributable to ITM. It is concluded that ITM is an effective adjunctive treatment for control of post-thoracotomy pain.

Sufentanil: clinical use as postoperative analgesic--epidural/intrathecal route

Although morphine and fentanyl remain the predominant epidural opioids, sufentanil offers some unique advantages. Because of its greater lipophilicity and mu-receptor binding capacity, sufentanil has a faster onset of action and longer duration than epidural fentanyl. Compared with morphine, sufentanil has been associated with a lower incidence of side effects, particularly delayed respiratory depression. The effective doses and adverse effects profile of epidural sufentanil are relatively well understood. Ventilatory depression is minimal with both bolus and continuous administration. Rapid vascular uptake after large epidural bolus, however, has been associated with acute-onset respiratory depression and even respiratory arrest. Sufentanil is more ideally suited than morphine to continuous epidural administration. The faster onset in comparison with fentanyl may make sufentanil the ideal agent for patient-controlled epidural analgesia. The synergistic effect of combined sufentanil and low-concentration bupivacaine offers advantages over sufentanil alone. High doses of epidural sufentanil have been uniquely associated with cessation of shivering and hypothermia. As with fentanyl, the intrathecal administration of sufentanil for postoperative analgesia is limited by its short duration of action.

Epidural lidocaine with sufentanil and epinephrine for abdominal hysterectomy under general anaesthesia: respiratory depression and postoperative analgesia

The purpose of this investigation was to compare the analgesic actions and side-effects of a 50 micrograms epidural bolus of sufentanil and 50 micrograms epinephrine, with a control group receiving saline and epinephrine. The method employed was a prospective, randomised, double-blind trial involving 40 ASA I or II patients for total abdominal hysterectomy. All received 1.5% lidocaine with 1/200,000 epinephrine epidurally before operation, until a block to T4 was established. Patients were anaesthetised, their tracheas were intubated, and they were allowed to breathe spontaneously before administration of the test drug. Results showed that sufentanil prolonged the duration of local anaesthesia (198 +/- 35 min vs 174 +/- 29 min; P less than 0.05), and of analgesia (288 +/- 85 min vs 188 +/- 42 min; P less than 0.01). There was an increase in somnolence in the sufentanil group (9/20 vs 2/20; P less than 0.05). Glycopyrollate was given to 11/20 patients in the sufentanil group vs 1/20 in the control group (P less than 0.01) following bradycardia and hypotension. Clinical respiratory depression occurred in the sufentanil group; 5/20 patients required controlled ventilation following apnoea greater than 20 sec. It is concluded that epidural sufentanil causes considerable cardiorespiratory depression in the setting of general anaesthesia, and should be used with caution in the spontaneously breathing, anaesthetised patient.

Postoperative pain management and respiratory depression after thoracotomy: a comparison of intramuscular piritramide and intravenous patient-controlled analgesia using fentanyl or buprenorphine

STUDY OBJECTIVE

To compare the analgesic efficacy of fentanyl, buprenorphine, and piritramide and to define the respiratory risk during conventional postoperative pain management and patient-controlled analgesia (PCA).

DESIGN

Randomized, single-blind study.

SETTING

Department of anesthesiology of an urban hospital.

PATIENTS

Sixty patients (ASA) physical status II and III) recovering from unilateral thoracotomy performed under standardized general anesthesia including intercostal blockade.

INTERVENTIONS

Patients were treated with intramuscular (IM) piritramide (7.5 to 15 mg as needed) or intravenous (IV) PCA with fentanyl (demand dose 34 micrograms) or buprenorphine (demand dose 80 micrograms) during the early postoperative period, using the On-Demand Analgesia Computer (ODAC, Janssen Scientific Instruments, Beerse, Belgium).

MEASUREMENTS AND MAIN RESULTS

The mean postoperative observation period was 24 to 25 hours. During this time, patients requested 55.8 +/- 23.2 mg of piritramide, 1.04 +/- 0.54 mg of fentanyl, or 1.81 +/- 0.78 mg of buprenorphine. Analgesia in all groups was judged mostly good to excellent, with a preference for PCA. Side effects were only of minor intensity in all groups; euphoria or dysphoria occurred only with buprenorphine. Two patients using PCA and five patients having IM analgesia developed short periods of respiratory depression (respiratory rate less than or equal to 8 breaths/minute and/or oxygen (O2) desaturation less than or equal to 90%), which promptly responded to commands to breathe deeply. Respiration rates did not differ, and frequent arterial blood sampling showed normal mean partial pressures of oxygen (PO2) and carbon dioxide (PCO2) and arterial oxygen saturation (SaO2) in all subgroups.

CONCLUSIONS

Opioid-induced respiratory depression occurred infrequently during postoperative pain management whether by conventional means or using PCA, even though high doses of opioid analgesics were required intermittently for adequate postoperative pain relief by either technique.

Continuous epidural hydromorphone for postthoracotomy pain relief

Forty-four patients were treated with a continuous infusion of lumbar epidural hydromorphone (0.05%) after thoracic operations. Postoperatively, visual analog pain scores were obtained. On postoperative day 1 and 2, more than 90% of the patients experienced either no pain (visual analog pain scale = 0) or mild pain (visual analog pain score = 1 to 3) at rest. The incidence of side effects (hypoventilation, pruritus, and nausea) was less than reported with other epidurally administered opioids. Continuous infusion of lumbar epidural hydromorphone produced safe, predictable analgesia after thoracotomy.

Lumbar epidural fentanyl infusions for post-thoracotomy patients: analgesic, respiratory, and pharmacokinetic effects

Ten patients undergoing a thoracotomy were studied for 24 hours postoperatively to determine the effects of a continuous lumbar epidural fentanyl infusion on postoperative pain, arterial blood gases (ABG), respiratory pattern (respiratory inductive plethysmography, RIP), and fentanyl plasma concentration (CONC). Patients served as their own controls because RIP and ABG data were obtained the night prior to surgery during sleep. Epidural fentanyl was administered as a bolus of 1.5 micrograms/kg followed by an infusion of 1.0 micrograms/kg/h started 1 hour after induction. Insufficient analgesia was treated with a bolus of 0.5 micrograms/kg and an infusion increase of 0.25 micrograms/kg/h. Postoperative assessment included RIP, ABG, CONC, and visual analog pain score (PS). The average infusion rate postoperatively was 1.47 +/- 0.08 micrograms/kg/h (114.3 +/- 8.3 micrograms/h). A mean PS of 2.1 +/- 0.3 was achieved; however, there was a delay in attaining this. There was no significant incidence postoperatively of apnea or slow respiratory rate. A significant but clinically insubstantial increase in PaCO2 and decrease in pH occurred. A steady state CONC of approximately 2.0 ng/mL was reached after 9 hours. The PS correlated with CONC in half the patients (0.60 less than r less than 0.86), indicating a systemic component may have contributed to the analgesic effect.

[Use of morphinomimetics in regional anesthesia]

Pain relief is one of medicine's most important challenges and the first aim of anaesthesia. The most common technique of postoperative analgesia remains intramuscular or subcutaneous opiates. There has been a better understanding of the mechanisms of action of opiates over the last decade, and new techniques and methods of administration have been developed especially their regional application. In 1979, two reports acted as catalysts to promote further studies. Wang et al. reported on the efficacy of intrathecal morphine to relieve unbearable malignant pain in 8 patients whereas Behar et al reported on the efficacy of morphine by epidural route. More recently, several studies pointed out the usefulness of the peripheral perineural route for opiates. However, this remains controversial, as some discrepancies persist in the results. The classification of opiate receptors and their relationship to opiate analgesia, as well as the mechanisms of action of regionally administered opiates are analyzed. The dual pre- and postsynaptic actions of spinal opiates are then considered. The parts played by the different neurotransmitters and pathways are set out. The evidence for opiate receptors at peripheral nerve sites and the different hypotheses suggested to explain the effect of opiates given by the perineural route are discussed. The pharmacokinetics and pharmacodynamics of opiates given by the subarachnoid and epidural routes are considered, in particular with respect to the comparative pharmacology of the commonly used opiates. The adverse effects of spinal opiates are reviewed, with their potential risks, and their clinical and therapeutic implications. Opiates and local anaesthetics given by the spinal route are compared. The clinical applications of intrathecal and epidural opiates are discussed, especially in the fields of postoperative analgesia, treatment of chest trauma, and cancer pain. Lastly, the few controlled studies concerning the use of opiates in peripheral nerve blocks, especially brachial plexus blocks, and the prospects of this new technique of giving opiates regionally are discussed.

Respiratory depression and spinal opioids

Administration of epidural and intrathecal opioids may provide excellent postoperative analgesia, but a minority of patients will suffer dangerous respiratory depression. This review discusses the detection and measurement of respiratory depression and summarizes the relevant literature as it pertains to epidural and intrathecal opioid administration. The respiratory depressant effects and pharmacokinetics of spinal opioids are reviewed. The clinical implications and areas of future investigation are discussed.