Pharmacokinetics of epidural morphine and meperidine in humans

Thoracic epidural anaesthesia vs intrathecal morphine in dogs undergoing major thoracic and abdominal surgery: clinical study

BACKGROUND

There is scant clinical research on neuraxial analgesia in dogs undergoing major surgery. With this study we compared the perioperative analgesic effects of thoracic epidural anaesthesia (TEA) and intrathecal morphine (ITM) in dogs scheduled for thoracic or cranial abdominal surgery. The dogs received methadone and dexmedetomidine, were anaesthetized with propofol maintained with sevoflurane, and randomly assigned to receive either TEA (ropivacaine 0.5% at 0.2 mg/kg and morphine 0.1 mg/kg administered at T₁₂-T₁₃) or ITM (morphine 30 μg/kg administered at L₆-L₇). Intraoperative rescue analgesia (iRA) was fentanyl 1 μg/kg administered if heart rate or mean arterial pressure increased by 30% above the pre-stimulation level. Glasgow Pain Composite Scale score (GPCS) dictated the use of postoperative rescue analgesia (pRA) with methadone 0.2 mg/kg.

RESULTS

There was a statistically significant difference in iRA, median time to first fentanyl bolus, median fentanyl dose after surgical opening, and median GPCS score at 30 minutes (min), 1 ,2, 4, 6, and 8 hours (h) between the two groups (p<0.001; p<0.001; p<0.001; p<0.01; p<0.01; p<0.001; p<0.01; p=0.01; p=0.01, respectively). Fewer TEA than ITM group dogs required iRA during surgical opening and pRA: 5% (1/18) and 2/18 (11%), respectively, in the TEA and 83% (16/18) and 10/18 (55%), respectively, in the ITM group. Side effects were urinary retention in 3/18 (16%) TEA group dogs and 2/18 (11%) ITM group dogs and prolonged sedation in 2/18 (11%) in ITM group dogs. TEA and ITM were effective in managing perioperative pain in dogs undergoing thoracic or cranial abdominal surgery.

Epidural Oxycodone for Acute Pain

Epidural analgesia is commonly used in labour analgesia and in postoperative pain after major surgery. It is highly effective in severe acute pain, has minimal effects on foetus and newborn, may reduce postoperative complications, and enhance patient satisfaction. In epidural analgesia, low concentrations of local anaesthetics are combined with opioids. Two opioids, morphine and sufentanil, have been approved for epidural use, but there is an interest in evaluating other opioids as well. Oxycodone is one of the most commonly used opioids in acute pain management. However, data on its use in epidural analgesia are sparse. In this narrative review, we describe the preclinical and clinical data on epidural oxycodone. Early data from the 1990s suggested that the epidural administration of oxycodone may not offer any meaningful benefits over intravenous administration, but more recent clinical data show that oxycodone has advantageous pharmacokinetics after epidural administration and that epidural administration is more efficacious than intravenous administration. Further studies are needed on the safety and efficacy of continuous epidural oxycodone administration and its use in epidural admixture.

Investigation of opioid use and long-term oncologic outcomes for non-small cell lung cancer patients treated with surgery

Opioids are commonly used for postoperative pain control in cancer patients. In addition to pain control, an association between opioid use and long-term oncologic outcomes, such as recurrence or overall survival, has been postulated. The aim of this study was to determine whether postoperative opioid use in patients with non-small cell lung cancer is associated with long-term oncologic outcomes, including recurrence and death. Data obtained from 1009 medical records of patients who underwent curative resection at the National Cancer Center, Korea between January 2006 and December 2010 were retrospectively analyzed. Seven-day opioid use was divided into four quartiles to analyze probability of recurrence and death. Multivariate regression analyses of recurrence and death was conducted, including the calculation of odds ratios. A total of 871 patients were analyzed. When opioid dosage was examined by quartiles, the probability of death and recurrence increased gradually with increasing opioid use. However, in the multivariate regression analysis, the amount of opioid usage did not affect the risk of recurrence or death of lung cancer (P = 0.520 for recurrence; P = 0.659 for death). Opioid use was correlated with outcome when stratified by lung cancer stage (P = 0.004 for recurrence; P = 0.049 for death); however, the odds ratios only slightly increased (1.001 for stage IA–IIIA) for both outcomes. In non-small cell lung cancer patients, the amount of opioid usage does not affect the risk of recurrence and death of lung cancer. There was an association with stage (IA–IIIA), but the effect was negligible. A well-designed prospective study is needed.

A comparison of three types of postoperative pain control after posterior lumbar spinal surgery

STUDY DESIGN

Retrospective, nonrandomized, comparative study.

OBJECTIVE

This study compared the early postoperative analgesic effects and the postoperative nausea and vomiting (PONV) associated with three methods of pain control after posterior lumbar spinal surgery.

SUMMARY OF BACKGROUND DATA

The use of opioids for postoperative pain control is common after spinal surgery; however, PONV is the most frequently encountered side effect, and it is yet to be overcome. The effectiveness of the use of an absorbable low-dose morphine-soaked microfibrillar collagen hemostatic sponge placed on the surface of the dural sac (epidural MMCHS) was compared to patient-controlled analgesia (PCA) and intermittent intramuscular bolus injection of meperidine for postoperative pain control after spine surgery.

METHODS

One hundred sixty-five patients who underwent short-segment posterior lumbar spinal decompression and fusion surgery between January 2007 and July 2007 in the orthopedic department of a medical center were enrolled. For postoperative pain control, 40 patients received epidural MMCHS, 48 patients received PCA, and 77 patients received meperidine injection. Patient ratings of pain intensity (visual analog scale score from 0 [no pain] to 10 [most severe pain]), nausea (from 0 [no nausea] to 5 [severe nausea]), and vomiting (from 0 [no vomiting] to 5 [severe vomiting]) were recorded at 4 hours postoperation and on postoperative days 1, 2, and 3.

RESULTS

The analgesic effect was enhanced significantly in both epidural MMCHS group and the PCA group as compared with the meperidine group on postoperative days 1 and 2 (P < 0.05). On postoperative days 1, 2, and 3, PONV was more severe in the PCA group than in the other two groups (P < 0.05). The side effects of epidural MMCHS were nausea (25%), pruritus (12.5%), vomiting (5%), and hypotension (2.5%).

CONCLUSION

A single low-dose epidural MMCHS is effective for postoperative pain control and minimizes the occurrence of PONV after posterior lumbar spinal surgery.

Evaluation of Epidural Analgesic Paste Components in Lumbar Decompressive Surgery

BACKGROUND:

Adjuncts for pain management in lumbar decompressive surgery are needed to reduce narcotic consumption and promote early mobility.

OBJECTIVE:

To evaluate the efficacy and active components of a previously described epidural analgesic paste in controlling postoperative pain and facilitating early discharge from hospital after lumbar decompressive surgery.

METHODS:

A randomized double-blind controlled trial was conducted. Two-hundred and one patients were randomized to 1 of 4 analgesic epidural pastes at the time of lumbar spinal surgery: combination paste (morphine + methylprednisolone), steroid paste (methylprednisolone alone), morphine paste (morphine alone), or placebo. The primary outcome measures used were analgesic consumption and the McGill Pain Questionnaire (MPQ). Secondary outcome measures were: modified American Spinal Cord Injury Association (ASIA) score, Short Form 36 General Health Survey (SF-36), Aberdeen Pain Index (ABPI), time to ambulation and time to discharge from hospital.

RESULTS:

Administration of combination and steroid paste, but not morphine paste, resulted in a statistically significant reduction in mean pain rating index (PRI) and present pain intensity (PPI) components of the MPQ in the first 3 days after surgery. Likewise, postoperative in-patient narcotic analgesic consumption was reduced in the combination paste and steroid paste group, but not in the morphine paste group. No difference in time to ambulation or discharge, SF-36 scores, ABPI scores, or neurologic recovery was observed.

CONCLUSION:

An analgesic paste containing methylprednisolone acetate is effective at reducing postoperative pain after lumbar decompressive surgery. Mixing effective doses of morphine sulfate in the paste abrogates the expected analgesic effects of epidural morphine.

Epidural, Intrathecal Pharmacokinetics, and Intrathecal Bioavailability of Ropivacaine

BACKGROUND

Ropivacaine is used by the epidural route for postoperative pain management with various neuraxial techniques. Given the widespread use of these techniques and the relative paucity of data on spinal disposition of local anesthetics, we evaluated through an experimental animal model, the spinal disposition of ropivacaine, allowing further studies of factors influencing their intrathecal bioavailability.

METHODS

Sheep received an IV bolus dose of ropivacaine (50 mg), and 1 wk after, an intrathecal dose of ropivacaine (20 mg) followed 3 h later by epidural ropivacaine (100 mg). A simultaneous microdialysis technique was used to measure epidural and intrathecal drug concentrations after both epidural and intrathecal administrations.

RESULTS

Absorption-time plots showed a large variability in the systemic absorption after both intrathecal and epidural administration, with an apparent faster systemic absorption after intrathecal administration. In the intrathecal space, the elimination clearance was around three-times higher than the distribution clearance. In the epidural space, the relative contribution of elimination and distribution to ropivacaine disposition was different, indicating a more pronounced influence of the distribution process. The intrathecal bioavailability after epidural administration was 11.1% +/- 7.6%.

CONCLUSIONS

Using an animal model, we showed that drug dispositions in the intrathecal and epidural compartments are different, and that the intrathecal bioavailability of ropivacaine after epidural administration is low, and highly variable.

Single-Dose Extended-Release Epidural Morphine for Pain Following Hip Arthroplasty

This open-label, serial-cohort pilot study evaluated DepoDur, a new, single-dose, extended-release epidural morphine (EREM) for pain control after hip arthroplasty. Single-dose EREM (10-30 mg) or a single dose of standard morphine sulfate (MS) (5 mg) was administered before surgery and spinal anesthesia. Among the 39 patients enrolled, total 48-hour supplemental fentanyl use was lower (P = 0.011 overall treatment) and median time to first postoperative fentanyl use was three- to six-fold longer (P < 0.001 overall treatment), among 10-, 20-, and 30-mg single-dose EREM patients versus MS patients. EREM patients reported higher levels of satisfaction with pain intensity scores comparable to MS patients. Safety results were similar between groups. Single-dose EREM was generally safe and effective for treating postoperative pain and reduced the need for supplemental analgesia.

Evaluation of a single-dose, extended-release epidural morphine formulation for pain after knee arthroplasty

BACKGROUND

DepoDur is a single-dose, extended-release epidural morphine formulation designed to provide forty-eight hours of pain relief. The drug offers potential advantages over continuous epidural infusions, particularly in patients being treated with anticoagulation therapy. The purpose of this study was to evaluate the efficacy and safety of single-dose epidural DepoDur for pain control following knee arthroplasty.

METHODS

In this multicenter, randomized, double-blind, parallel-group study, patients were randomized to receive a single-dose of DepoDur (20 or 30 mg) or a sham epidural injection thirty minutes before administration of general or regional anesthesia for knee arthroplasty. At their first request for postoperative analgesia, patients who had received DepoDur were given an intravenous bolus of hydromorphone followed by placebo patient-controlled analgesia. Patients who had received the sham epidural were given an intravenous bolus of morphine followed by patient-controlled analgesia with morphine. Patient ratings of pain intensity at rest and with activity, their rating of overall pain control, and postoperative opioid use were recorded. The ability to tolerate physical therapy, the range of motion of the knee, and the need for physical support were assessed as well. Adverse events and vital signs were recorded.

RESULTS

Of 168 patients randomized to receive the 20-mg injection of DepoDur, the 30-mg injection of DepoDur, or the sham epidural injection, fifty-one, fifty-eight, and fifty-five patients, respectively, were included in the efficacy analysis. Compared with the patients treated with intravenous patient-controlled analgesia with morphine, the patients treated with DepoDur had significantly reduced mean pain-intensity-recall scores during the four to eight, four to twelve, four to twenty-four, and four to thirty-hour postdose intervals (p < 0.05 for all comparisons). The patients treated with DepoDur used approximately a threefold lower amount of postoperative opioids in total, with a significant percentage requiring no supplemental opioids. Adverse events common to all groups were nausea (78%), pyrexia (46%), vomiting (43%), pruritus (43%), and hypotension (36%). Respiratory depression was the most common serious adverse event, with serious respiratory depression observed in four DepoDur-treated patients, who were more than sixty-five years of age.

CONCLUSIONS

With appropriate patient selection and monitoring, perioperative single-dose epidural DepoDur was a safe and effective analgesic alternative to postoperative intravenous patient-controlled analgesia following knee arthroplasty, with younger patients benefiting from the 20-mg dose. Additional studies of 10 to 15-mg doses for older patients are warranted.

Determining the plasma concentration of ketamine that enhances epidural bupivacaine-and-morphine-induced analgesia

N-methyl-D-aspartate (NMDA) receptor antagonists enhance opioid-induced analgesia. The plasma concentration of ketamine, an NMDA receptor antagonist that enhances epidural morphine-and-bupivacaine-induced analgesia, is not known. We examined 24 patients with lung carcinoma or metastatic lung tumor who underwent video-assisted thoracic surgery in a placebo-controlled, double-blind manner 4 h after emergence from anesthesia. The morphine + ketamine group (n = 8) and morphine + placebo group (n = 8) received 5 mL volume of 2.5 mg morphine and 0.25% bupivacaine and the placebo + ketamine group (n = 8) received 5 mL volume of saline and 0.25% bupivacaine epidurally at the end of skin closure. Four hours after this anesthesia, in the morphine + ketamine and placebo + ketamine groups, ketamine was administered to successively maintain a stable plasma ketamine concentration of 0, 10, 20, 30, 40, and 50 ng/mL by a target-controlled infusion device, and patients assessed the levels of pain at rest, pain on coughing, somnolence (drowsiness), and nausea using a 100-mm visual analog scale (VAS). In the morphine + placebo group, a placebo (saline) was similarly administered instead of ketamine. In the morphine + ketamine group, the VAS scores for pain at rest and pain on coughing significantly decreased on ketamine administration at a plasma concentration of 20 ng/mL or larger compared with the respective baseline VAS scores (P < 0.05 each). In the placebo + ketamine group, the VAS scores for pain at rest and pain on coughing did not significantly change at any plasma concentration of ketamine as compared to the morphine + placebo group. In the morphine + ketamine group, a plasma concentration of ketamine larger than 20 ng/mL did not further reduce VAS scores for pain at rest and pain on coughing. The VAS scores for drowsiness were comparable among the three groups at any plasma concentration of ketamine. Ketamine at a plasma concentration of 20 ng/mL or larger may enhance epidural morphine-and-bupivacaine-induced analgesia. As an adjunct with epidural morphine-and-bupivacaine and considering the safety of small doses, the minimal plasma concentration of ketamine given IV may be approximately 20 ng/mL.

Effects of thoracic epidural meperidine on arterial oxygenation during one-lung ventilation in thoracic surgery

OBJECTIVE

To compare the effects that the use of general intravenous anesthesia (propofol-fentanyl) (GA) or general anesthesia combined with thoracic epidural anesthesia with meperidine (TEA-M) may have on arterial oxygenation during one-lung ventilation (OLV).

DESIGN

Prospective.

SETTING

Tertiary care hospital.

PARTICIPANTS

Seventy-two patients undergoing OLV for thoracic surgery.

INTERVENTIONS

Patients were prospectively randomized into two groups: GA (n = 37) fentanyl, propofol, rocuronium anesthesia was used; and group TEA-M (n = 35) were anesthetized with propofol, rocuronium and thoracic epidural meperidine (2 mg/kg in 10-12 mL) administered before anesthetic induction. A double-lumen endotracheal tube was inserted, and mechanical ventilation with 100% oxygen was used during study. Mean arterial pressure, heart rate and arterial and venous blood gases were recorded with the patients in the lateral decubitus position in three phases: during two-lung ventilation (TLV), 15 and 30 minutes after beginning OLV (OLV + 15 and OLV + 30 respectively). The authors measured arterial and venous central oxygen tension, arterial and venous central oxygen saturation, arterial and venous central oxygen content and venous admixture percentage (Qs/Qt%).

MEASUREMENTS AND MAIN RESULTS

There were no statistical differences between the two groups for PaO(2) during OLV + 15 (GA = 165 mmHg, TEA-M = 153 mmHg) and OLV + 30 (GA = 176 mmHg, TEA-M = 158 mmHg); and with values for Qs/Qt%.

CONCLUSIONS

It is concluded that GA combined with TEA-M (2 mg/kg) do not affect arterial oxygenation during OLV in thoracic surgery.

Sevoflurane requirements during coloproctologic surgery: difference between two different epidural regimens

STUDY OBJECTIVE

To examine the influence of epidural morphine on the end-tidal sevoflurane concentration titrated to maintain bispectral index (BIS) values between 40 and 50.

DESIGN

Prospective, double-blinded clinical trial.

SETTINGS

Anesthesia department of a university hospital.

PATIENTS

40 ASA physical status I, II, and III patients scheduled for elective coloproctological surgery.

INTERVENTIONS

Patients were randomized to receive via a thoracic epidural catheter either a) bupivacaine 0.25% (10 mL) and saline 0.9% (2 mL) as a bolus followed by an infusion of bupivacaine 0.25% (5 mL/hr) or b) bupivacaine 0.25% (10 mL) and morphine 0.1% (2 mL) as a bolus followed by an infusion of bupivacaine 0.25% plus morphine 0.025% (5 mL/hr). Anesthesia was induced with propofol, fentanyl 2 microg kg(-1) and atracurium and maintained with sevoflurane and nitrous oxide in oxygen. Sevoflurane level was titrated to maintain a BIS value between 40 and 50. After extubation, patients were asked about the presence of pain.

MAIN RESULTS

There was no significant difference between groups of end-tidal sevoflurane concentrations at identical BIS values and hemodynamic values at any time in the study. However, the morphine group had a lower pain score level at extubation than did the plain bupivacaine group (no pain on movement, 79% vs. 31.5%, p < 0.01).

CONCLUSIONS

Adding morphine to the bupivacaine epidural solution did not reduce sevoflurane requirements but did provide high-quality postoperative analgesia, mainly just after tracheal extubation.

Patient-controlled pethidine after major upper abdominal surgery: comparison of the epidural and intravenous routes

We compared epidural (n = 17) and intravenous (n = 20) patient-controlled analgesia (PCA) using pethidine (bolus 10 mg, lockout interval 10 min, 4-h maximum dose 3 mg.kg(-1)) after total gastrectomy. We found that mean (SD) pethidine consumption in the first 24 h was 33% less in the epidural group [255 (85) mg] than in the intravenous group [379 (129) mg, p = 0.002], although most of this difference occurred in the first 8 h. Plasma concentrations of pethidine were lower at 8 h (p < 0.01) in the epidural group, but were similar at 24 h. Pain scores, side-effects, patient satisfaction and patient outcome were similar between groups. Epidural and intravenous pethidine PCA provided similar efficacy after major abdominal surgery, although the epidural route can reduce the amount of pethidine used initially.

Analgesic, hemodynamic, and respiratory effects induced by caudal epidural administration of meperidine hydrochloride in mares

OBJECTIVE

To determine the analgesic, hemodynamic, and respiratory effects induced by caudal epidural administration of meperidine hydrochloride in mares.

ANIMALS

7 healthy mares.

PROCEDURE

Each mare received meperidine (5%; 0.8 mg/kg of body weight) or saline (0.9% NaCl) solution via caudal epidural injection on 2 occasions. At least 2 weeks elapsed between treatments. Degree of analgesia in response to noxious electrical, thermal, and skin and muscle prick stimuli was determined before and for 5 hours after treatment. In addition, cardiovascular and respiratory variables were measured and degree of sedation (head position) and ataxia (pelvic limb position) evaluated.

RESULTS

Caudal epidural administration of meperidine induced bilateral analgesia extending from the. coccygeal to S1 dermatomes in standing mares; degree of sedation and ataxia was minimal. Mean (+/- SD) onset of analgesia was 12 +/- 4 minutes after meperidine administration, and duration of analgesia ranged from 240 minutes to the entire 300-minute testing period. Heart and respiratory rates, rectal temperature, arterial blood pressures, Hct, PaO2, PaCO2, pHa, total solids and bicarbonate concentrations, and base excess were not significantly different from baseline values after caudal epidural administration of either meperidine or saline solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Caudal epidural administration of meperidine induced prolonged perineal analgesia in healthy mares. Degree of sedation and ataxia was minimal, and adverse cardiorespiratory effects were not detected. Meperidine may be a useful agent for induction of caudal epidural analgesia in mares undergoing prolonged diagnostic, obstetric, or surgical procedures in the anal and perineal regions.

A randomised, double-blind comparison of subarachnoid and epidural diamorphine for elective caesarean section using a combined spinal-epidural technique

We have compared the quality of analgesia and incidence of side-effects from subarachnoid and epidural diamorphine for caesarean section, as part of a combined spinal-epidural technique. Sixty patients were studied in a randomised, double-blind, double-dummy assessment. The doses of diamorphine reflect current practice in our hospital and are close to optimal. All patients received 13.25 mg subarachnoid bupivacaine and 37.5 mg epidural bupivacaine. In addition, patients in group 1 received 0.3 mg subarachnoid diamorphine and patients in group 2 received 3 mg epidural diamorphine. All patients were premedicated with ranitidine 150 mg and metoclopramide 10 mg and after surgery received diclofenac regularly and co-dydramol as needed. The duration and quality of analgesia, assessed by verbal rating score, was the same in the two groups. The incidence and severity of pruritus were higher (P< 0.005) in group 1. Postoperative nausea and vomiting were uncommon; 83% of patients in group 1 and 77% in group 2 had none. Subarachnoid and epidural diamorphine provided similar quality analgesia with a low incidence of emetic symptoms. However, pruritus was more common and more severe after subarachnoid diamorphine.

A comparison of patient controlled epidural pethidine versus single dose epidural morphine for analgesia after caesarean section

This double-blind, randomized study of analgesia after caesarean section compared patient controlled epidural analgesia with pethidine (15 mg of a 0.25% solution and a 10 minute lockout period) versus a single bolus of epidural morphine 4 mg. Data were collected on 78 patients at 2, 6, 8, and 24 hours postoperatively and analysed using the Wilcoxon rank sum test. Satisfactory analgesia and nausea/vomiting during the first twenty-four hours did not differ between the two groups. The incidence of pruritus (P < 0.001) was lower in the pethidine group at 2, 6, and 8 hours, with no difference by 24 hours. Therefore PCEA pethidine provides a useful alternative to single-dose morphine after caesarean section, particularly in those patients who have suffered severe morphine-induced pruritus previously.

Side-effects of epidural infusions of opioid bupivacaine mixtures

The incidence of side-effects occurring with epidural diamorphine (0.05 mg.ml-1), fentanyl (2.0 micrograms.ml-1), methadone (0.1 mg.ml-1), morphine (0.05 mg.ml-1) and pethidine (1.0 mg.ml-1) used by infusion in combination with bupivacaine has been compared. One hundred and sixty patients were studied, 32 receiving each opioid. The incidence of nausea and vomiting was significantly greater with morphine than fentanyl (p = 0.0097) and pethidine (p = 0.0021). The incidence of pruritus was significantly greater with morphine and diamorphine than with methadone (p = 0.012) and pethidine (p = 0.027). Morphine was also associated with a significantly greater incidence of urinary retention than pethidine (p = 0.012) and methadone (p = 0.025).

Epidural pethidine: pharmacology and clinical experience

Pethidine is an effective epidural opioid for the treatment of acute pain. Its use has been well described in Australian and New Zealand practice, particularly in the field of obstetric anaesthesia. Reported methods of delivery have included bolus injection, continuous infusion and patient-controlled epidural analgesia. Areas of application have included treatment of postoperative pain, labour pain and intraoperative pain. Because of its intermediate lipid solubility, pethidine may have advantages over many other epidural opioids. However, potential for accumulation of norpethidine limits its use to relatively short durations of treatment.

Epidural meperidine after cesarean section: the effect of diluent volume

We investigated the effect of diluent volume on analgesia and systemic absorption from epidural meperidine after cesarean section in a randomized, double-blind study. At the first request for postoperative analgesia, 36 parturients were given epidural meperidine 25 mg diluted with saline to either 2 mL (12.5 mg/mL), 5 mL (5 mg/mL), or 10 mL (2.5 mg/mL). Visual analog pain scores measured in the first 30 min were greater in the 2-mL group compared with both the 5-mL group (P = 0.028) and the 10-mL group (P = 0.031). Onset of analgesia (time for visual analog pain scores to decrease by 50%) was also slower in the 2-mL group (17.5 min) compared with the 5-mL group (9 min; P = 0.015) and the 10-mL group (12 min; P = 0.003); there were no differences between the 5-mL group and the 10-mL group. Duration of analgesia and plasma concentrations of meperidine were similar among groups. No adverse side effects were recorded. Previous work has suggested that injection of epidural opioids in large volumes increases the potential risk of respiratory depression from cephalad spread of the drug. Therefore, we conclude that analgesia is optimum when epidural meperidine is administered diluted to 5 mL.

A comparison of epidural infusions of fentanyl or pethidine with bupivacaine in the management of postoperative pain

A double-blind randomised clinical trial was undertaken in 40 patients undergoing major abdominal surgery. Postoperative pain relief was provided using epidural infusions of 0.06% bupivacaine with fentanyl 4 micrograms.ml-1 (n = 20) (group F) or with pethidine 1.5 mg.ml-1 (n = 20) (group P). Postoperative pain scores using a visual analogue scale (0-100 mm) were not significantly different between the two groups. Median pain scores were 0-19 mm at all times of assessment indicating that good analgesia was provided by both regimens. There was no significant difference between the epidural infusion rates in the two groups. The side effects and effect on pulmonary function were similar in each group. Nine patients were withdrawn from the study (four from group F, five from group P) due to failure of the epidural technique or other complications. Fourteen patients, equally distributed, required a total of 24 epidural 'top-ups' by an anaesthetist because of inadequate analgesia. We demonstrated no advantage with epidural pethidine over fentanyl when used by infusion in combination with bupivacaine in the management of postoperative pain.

Patient-controlled epidural analgesia after thoracotomy: a comparison of meperidine with and without bupivacaine

The purpose of this study was to compare meperidine to meperidine with bupivacaine when used for patient-controlled epidural analgesia (PCEA) after thoracotomy. For 3 days after thoracotomy patients received thoracic PCEA with meperidine 0.1% plain or with added bupivacaine 0.1% or 0.01%. No background infusion was used. All patients received indomethacin postoperatively for the duration of the study. Patients were assessed with respect to meperidine consumption, analgesia, and side effects. Sixty-six patients participated. Patients in all three groups obtained effective analgesia with median meperidine consumption of 5-6 mg/h. There were no significant differences between groups in meperidine consumption or pain scores at rest or with coughing. The addition of bupivacaine 0.1% reduced the incidence of pruritus (P = 0.036), but 5 of 23 patients in this group were with-drawn from the study because of significant hypotension, oliguria, and/or motor or sensory block (P = 0.006). We conclude that the addition of bupivacaine 0.1% or 0.01% to thoracic PCEA meperidine 0.1% does not affect meperidine requirements or analgesia after thoracotomy. The addition of bupivacaine 0.1% may reduce pruritus, but is associated with signs of excessive sensory, motor, or autonomic blockade in a significant number of patients.

Evaluation of a disposable device for patient-controlled epidural analgesia after caesarean section

We evaluated a disposable device (Baxter PCA Infusor) for patient-controlled epidural analgesia (PCEA) using pethidine in twenty women after lower segment caesarean section. Efficacy, as measured by visual analogue pain scores, was comparable with historical controls from PCEA studies using electronic devices. Three patients reported inadequate analgesia, attributable in two cases to problems with epidural catheter. PCEA was stopped in one patient because of side-effects. Pethidine consumption ranged from 125 to 1500 mg (median 575 mg) in 48 hours. Plasma concentrations of pethidine varied widely. Disposable devices for PCEA after caesarean section provide an alternative to bolus administration or PCEA using more expensive and cumbersome electronic devices, although we suggest currently available apparatus requires modifications to improve clinical performance.

Intra-operative epidural morphine, fentanyl, and droperidol for control of pain after spinal surgery. A prospective, randomized, placebo-controlled, and double-blind trial

The present study was conducted to investigate the analgesic effects of intra-operatively administered epidural morphine in patients undergoing surgery for lumbar disc disease. Three treatment groups were constituted: one with 5.0 mg morphine and 2.5 mg dehydrobenzperidol (DHB) in 10 ml physiological saline, one with 5.0 mg morphine and 0.1 mg fentanyl in the same amount of saline, and one placebo group with saline only. The test solution was injected epidurally via catheter after haemostasis and before closure of the wound. Sixty eight patients were randomly assigned to each of the three groups and subjected to a double-blind evaluation. In the morphine/fentanyl and morphine/droperidol groups, significantly better analgesia was found as compared to the placebo group. No significant difference was found between the morphine/fentanyl and morphine/droperidol groups considering side effects of therapy, as well as duration and quality of analgesia. The side effects in the treatment groups were only slight and not significantly different from the placebo group. It was shown that additional epidural fentanyl offers no significant improvement of postoperative analgesia. No significant reduction of adverse effects could be found in the morphine/droperidol group compared to the morphine/fentanyl group. In conclusion, the intra-operative epidural application of morphine is a safe, effective and simple method for achieving sufficient analgesia in the first 24 hours after lumbar spinal surgery for disc disease.

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.

The addition of epinephrine enhances postoperative analgesia by intrathecal morphine

To investigate whether the addition of epinephrine would enhance postoperative pain relief by intrathecal morphine, we studied 36 patients scheduled to have spinal anesthesia for gynecologic surgery. Patients were randomly allocated to one of three groups: the first received epinephrine 0.12 mg, morphine 0.2 mg, and hyperbaric tetracaine 12 mg intrathecally (EMT group, n = 11); the second received morphine 0.2 mg and hyperbaric tetracaine 12 mg intrathecally (MT group, n = 13); and the third received epinephrine 0.12 mg and hyperbaric tetracaine 12 mg intrathecally (ET group, n = 12). The time to the first request for supplemental analgesics was longest (2182 +/- 251 min, mean +/- SEM) and the injection number of supplemental analgesics was least in the EMT group (P < 0.05). The percentage of patients who received supplemental analgesics in the EMT group (45.5%) was less than the other two groups (P < 0.05). Six patients in the EMT group and one in the MT group needed no additional analgesics during 48 h (P < 0.05 versus the MT and ET groups). The visual analog scale (VAS) pain score was larger in the ET group than the EMT group (P < 0.05), but was similar in the EMT and MT groups. There were no differences among groups in the incidence of nausea and pruritus. Our data show that the addition of epinephrine enhances postoperative analgesia by intrathecal morphine without increasing the incidence of adverse effects as compared with intrathecal morphine alone.

Postthoracotomy pulmonary function: a comparison of epidural versus intravenous meperidine infusions

It has remained unclear whether epidural opioid analgesia permits better recovery of postthoracotomy pulmonary function than an optimal method of systemic opioid administration. Lumbar epidural meperidine infusions were compared with intravenous patient-controlled analgesic (PCA) meperidine infusions in a prospective randomized unblinded study for 72 hours postthoracotomy. Before induction of general anesthesia, patients received a bolus of meperidine, 1 mg/kg, and an infusion of meperidine, 0.33 mg/kg/hr, was started via either a lumbar epidural or intravenous catheter. Postoperatively, the meperidine infusion rates were titrated as needed for analgesia. In addition, the intravenous group received meperidine, 10 mg per dose, as required, from a patient-controlled analgesia pump. No other opioid was administered during the study period. Patients were studied for recovery of spirometric tests of pulmonary function, visual analog pain scores, sedation, arterial blood gases, meperidine dose requirements, radiographic pulmonary complications, and neurologic signs and symptoms. A subgroup of 10 patients (5 from each group) had venous blood samples drawn every 24 hours for 96 hours and assayed for serum meperidine and normeperidine concentrations. Epidural meperidine analgesia was associated with improved postthoracotomy pulmonary function, better analgesia scores, and lower meperidine dose requirements than intravenous PCA meperidine. There were no differences between the epidural versus intravenous PCA subgroups with respect to serum meperidine or normeperidine levels. Normeperidine levels greater than 300 ng/mL were associated with an increased incidence of shakiness and/or tremors. Meperidine provides satisfactory postthoracotomy analgesia via a lumbar epidural infusion. This analgesia is associated with improved recovery of postoperative pulmonary function when compared with an intravenous PCA meperidine infusion.

Epidural opioid analgesia after caesarean section: a comparison of patient-controlled analgesia with meperidine and single bolus injection of morphine

The quality of analgesia, patient satisfaction and incidence of side effects following a single bolus of epidural morphine were compared with patient-controlled epidural analgesia (PCEA) with meperidine during the first 24 hr after elective Caesarean section. Seventy-five women were randomly assigned to three equal groups. Group I received 30 mg epidural meperidine after delivery and PCEA with meperidine; Group 2 received 3 mg epidural morphine after delivery and PCEA with saline in a double-blind fashion. Group 3 received 3 mg epidural morphine after delivery without saline PCEA. Visual analogue pain scores (VAS) were higher with PCEA meperidine from 8-16 hr post-operatively (P < 0.05) than in both epidural morphine groups. Two patients in Group 1 and one in Group 3 required supplemental parental analgesia. The incidence of nausea was 16% in Group 1, compared with 52% in Group 2 and 56% in Group 3 (P < 0.01). Pruritus occurred in 24% of Group 1 patients, 84% of patients in Group 2 and 68% of patients in Group 3 (P < 0.001). Forty-six percent of patients in Group 1 were very satisfied with pain management, compared with 77% in Group 2 and 79% in Group 3. Nurse workload was higher in the PCEA study groups than in Group 3 (P < 0.05). A single bolus of epidural morphine provides superior analgesia and satisfaction at low cost, but with a higher incidence of nausea and pruritus than PCEA with meperidine.

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.

A two-dose epidural morphine regimen in cesarean section patients: pharmacokinetic profile

The maternal pharmacokinetics, metabolism of, and possible neonatal transmission of epidural morphine in cesarean section patients were investigated. Maternal plasma, breast milk, and maternal and neonatal urine concentrations of unconjugated and conjugated (UM and CM) morphine were measured in patients given two 5-mg doses of epidural morphine for post-cesarean section analgesia. The first dose was administered after delivery and the second dose 24 h later. Maternal venous blood samples (n = 10) were collected at times 0, 0.25, 0.5, 1, 2, 3, 4, 6, 12, and 24 h after each dose, and maternal urine was collected for three consecutive 24-h periods (n = 30). Maternal breast milk (n = 30), and neonatal urine samples (n = 20) were also collected. Serum, urine, and breast milk UM and CM levels were measured using radioimmunoassay. Pharmacokinetic values were calculated using noncompartmental analysis. The results were expressed as mean +/- 1 s.e. mean and analyzed using repeated measures analysis of variance and the paired t-test. Maternal serum UM remained 40-50% higher, and CM 50-100% higher in the first hour following dose 2 than the respective values after dose 1 (P < 0.05). Values for AUC, AUMC, T1/2, and MRT increased 28%, 83%, 35% and 36%, respectively, with the second dose (P < 0.05), while CI decreased 19% (P < 0.05) with no significant difference in Vss. Total urinary excretion of morphine decreased significantly from 1.98 +/- 0.15 mg on day 1 to 1.6 +/- 0.2 mg and 0.19 +/- 0.002 mg on days 2 and 3, respectively (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of epidural opioids on gastric emptying in labour

The effect of epidural opioids on gastric emptying was studied in 36 women in labour. Women who had received one dose of epidural bupivacaine were randomised to receive 10 ml of bupivacaine 0.25% alone (n = 8) with fentanyl 50 microg (n = 8) or with diamorphine 2.5 mg (n = 8), or 10 ml of bupivacaine 0.125% alone (n = 4) or with fentanyl 100 microg (n = 4) or with diamorphine 5 mg (n = 4) when they first requested a top-up. Mean+/-SD fentanyl concentrations measured at delivery were, in maternal venous plasma (MV) 0.72+/-0.19 ng/ml and in umbilical venous plasma (UV) 0.75+/-0.3 ng/ml. The mean dose-delivery interval was 280 min (range 107-608 min) and there was a negative correlation between UV/MV and dose-delivery interval. Gastric emptying was assessed by measuring paracetamol absorption following an oral dose of 1.5 g given 30 minutes after the study top-up. Time to peak plasma paracetamol concentration was significantly delayed in the groups given fentanyl 50 and 100 microg and diamorphine 5 mg, compared to the groups given bupivacaine alone, and peak concentration was significantly reduced in the group given diamorphine 5 mg. It is concluded that epidural fentanyl 50 and 100 mg and epidural diamorphine 5 mg delay gastric emptying. The addition of 2.5 mg diamorphine has no significant effect.

Postoperative epidural analgesia

Administration of epidural opioids is a technique that is currently being used by many veterinary anesthesiologists and surgeons to provide postoperative analgesia. The duration of analgesia is prolonged and the degree of sedation is much less than that which occurs with parenterally administered opioids and the risks appears to be minimal.

Thoracic versus lumbar epidural fentanyl for postthoracotomy pain

Thirty patients were prospectively randomized to receive either thoracic or lumbar epidural fentanyl infusion for postthoracotomy pain. Epidural catheters were inserted, and placement was confirmed with local anesthetic testing before operation. General anesthesia consisted of nitrous oxide, oxygen, isoflurane, intravenous fentanyl citrate (5 micrograms/kg), and vecuronium bromide. Pain was measured by a visual analogue scale (0 = no pain to 10 = worst pain ever). Postoperatively, patients received epidural fentanyl in titrated doses every 15 minutes until the visual analogue scale score was less than 4 or until a maximum fentanyl dose of 150 micrograms by bolus and an infusion rate of 150 micrograms/h was reached. The visual analogue scale score of patients who received thoracic infusion decreased from 8.8 +/- 0.5 to 5.5 +/- 0.7 (p < or = 0.05) by 15 minutes and to 3.5 +/- 0.4 (p < or = 0.05) by 45 minutes. The corresponding values in the lumbar group were 8.8 +/- 0.6 to 7.8 +/- 0.7 at 15 minutes and 5.3 +/- 0.9 at 45 minutes (p < or = 0.05). The infusion rate needed to maintain a visual analogue scale score of less than 4 was lower in the thoracic group (1.55 +/- 0.13 micrograms.kg-1 x h-1) than in the lumbar group (2.06 +/- 0.19 microgram.kg-1 x h-1) during the first 4 hours after operation (p < or = 0.05). The epidural fentanyl infusion rates could be reduced at 4, 24, and 48 hours after operation without compromising pain relief. Four patients in the lumbar group required naloxone hydrochloride intravenously.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro determination of human dura mater permeability to opioids and local anaesthetics

The permeability of human thoracic and lumbar dura mater to various compounds in clinical use was determined in vitro. Sections of dura mater, 3 to 4 cm in diameter, obtained at post-mortem were placed between the ports (area = 3 cm2) of two glass chambers (A and B) which fitted tightly together to form a two-chamber apparatus for measuring permeability through the dura. Each chamber contained 5 ml of artificial cerebrospinal fluid. A sample of test drug solution was introduced into one chamber (A) and 50 microliters aliquots were withdrawn from the other chamber (B) at predetermined intervals. Permeability was determined by calculating the rate of diffusion (slope) from the plot of mean drug concentration (chamber B) versus time. Dura mater permeability was shown to be a simple diffusion process and to be independent of lipid-solubility and molecular weight. Permeability appeared to increase with age and may have a linear relationship to the initial concentration.

The influence of adrenaline on postoperative analgesia after subarachnoid morphine

A randomised, double-blind study was conducted to investigate the postoperative effects of subarachnoid morphine, with or without adrenaline, after major gynaecological surgery. Seventy-five women having spinal anaesthesia combined with either sedation or general anaesthesia were randomised to receive subarachnoid morphine 0.25 mg with (group MA) or without (group M) adrenaline 200 micrograms; or normal saline (group C). Groups M (n = 22) and MA (n = 25) differed significantly from control (n = 23) with respect to the quality and duration of postoperative analgesia (P < 0.0002) and to a higher incidence of pruritus (P < 0.02). Groups were similar with respect to the incidence of other postoperative side-effects and respiratory data, although the latter showed a trend to less hypoxaemia in the control group. There was no significant difference in any outcome between groups MA and M. It was concluded that, under the study conditions in a post-gynaecological surgery population, the addition of adrenaline to subarachnoid morphine was of no benefit.

Epidural morphine reduces halothane MAC in humans

The effect of epidural morphine sulphate (4 mg in 10 ml saline) on the minimum alveolar concentration of halothane was investigated in a double-blind, randomized fashion in ten adult patients undergoing abdominal surgery, and compared with the minimum alveolar concentration of halothane after epidural administration of 10 ml saline in a similar group of patients. Morphine sulphate, administered through the epidural catheter 98 +/- 33 min before to skin incision reduced the minimum alveolar concentration of halothane by 28% (0.57% vs 0.78%, P < 0.05).