Selective spinal analgesia

Intrathecal drug delivery for the management of pain and spasticity in adults: British Pain Society's recommendations for best clinical practice

The British Pain Society updated their recommendations on intrathecal drug delivery (ITDD) for the management of pain and spasticity in adults. The recommendations are primarily evidence based but where necessary comprise the consensus opinion of the working group. The recommendations are accompanied by information for patients and their carers, intended to inform and support patients in their decision making. The updated guidance includes recent evidence base of ITDD use in pain and spasticity, address the issues of drug pump compatibility following the latest manufacturer and Medicines and Healthcare products Regulatory Agency (MHRA) recommendations as well as provide an update on the indications and complication management particularly endocrine complications and intrathecal granuloma formation.

An analytical approach to determining pethidine: An investigation of 18 patients' urine

Pethidine (PET) is an opioid pain-relief medicine with high addiction potential, especially among health professionals. Pethidine is commonly prescribed in Turkey as a pain-relieving medication for operative purposes. Due to its accessibility, low cost, user-friendliness, and effectiveness, PET is often misused by both healthcare professionals and patients. For this reason, analytical determination methods for PET abuse are essential in terms of forensic toxicology. In this study, a fast, reliable, and accurate gas chromatography-mass spectrometry method was developed for the first time in Turkey for the simultaneous detection of PET and its main urinary metabolite norpethidine (NPET). The method was validated in terms of selectivity, linearity, the limit of detection (LOD), the limit of quantification (LOQ), trueness, and precision according to the Scientific Working Group for Forensic Toxicology guidelines. The linear range was between 0.125-25.00 μg/mL for PET and 1.00-20.00 μg/mL for NPET. The LOD values for PET and NPET were 0.05 µg/mL and 0.49 µg/mL, while the LOQ values were 0.125 µg/mL and 1.00 µg/mL, respectively. Extraction efficiencies were calculated as 113% for PET and 104% for NPET. The intra-assay and inter-assay precision results were within acceptable limits. In the presented study, the validated method was applied to the urine of 18 patients collected at the 1st and 3rd hours after receiving PET. All samples in the study were collected under patients' consent and in line with ethical guidelines.

Intrathecal drug delivery for cancer pain at the end of life: a case study

Two-thirds of patients with advanced cancer have pain and, of these, approximately 10-20% do not respond to conventional pain management approaches. This case study concerns a hospice patient who received intrathecal drug delivery for intractable cancer pain at the end of life. This involved working in partnership with a hospital-based interventional pain team. Despite side-effects and complications associated with intrathecal drug delivery and the requirement for inpatient nursing care, intrathecal drug delivery was the best option for the patient. The case identifies the importance of a patient-centred approach to decision-making, effective partnerships between hospice and acute hospital teams, and nurse education as key factors contributing to the provision of safe and effective intrathecal drug delivery.

Clinical Studies that Initiated the Use of Spinal Opioids for the Treatment of Pain: A New Approach to Historical Review

Opioids administered into the spinal space by intrathecal or epidural routes can provide potent and prolonged selective analgesia. Compared to the systemic administration of opioids, spinal administration can bring about analgesia with fewer central and systemic adverse effects. For the past 40 years, spinal opioid analgesia has achieved great popularity in various fields of pain treatment. The aim of this work is to identify clinical studies that initiated the use of spinal opioids for the treatment of pain. To determine the historical role of each of the review's studies, we used the combination of two factors: the study priority in terms of the time of its publication and the degree of its acknowledgement in the form of citation impact. The date of publication was regarded as the primary factor, but only if the count of citations indicated a sufficient acknowledgement by the other authors. The citation impact was assessed as the initial citation count - for a period of five years after the year of article publication - and the total count. Analysis of the related data shows that the clinical studies initiating the use of spinal opioids for the treatment of pain belong to two groups of authors - Wang et al. and Behar et al. Both studies were published in 1979 and described delivery of morphine into the spinal space, although the techniques of administration were different: Wang et al. injected morphine intrathecally, Behar et al. administered morphine epidurally. The response to these studies was overwhelming - close to a dozen reports on this topic were published in 1979 and more than a hundred - in 1980-1981. The total citation response to the Wang et al. article reached 699, and that to Behar et al. - 518. Two earlier records (1900-1901) of the use of intrathecal morphine, by Nicolae Racoviceanu-Pitesti and Otojiro Kitagawa, found no following in medical literature for more than three quarters of a century.

The effect of intraoperative intrathecal opioid administration on the length of stay and postoperative pain control for patients undergoing lumbar interbody fusion

PURPOSE

In an effort to control postoperative pain more effectively in spinal fusion patients, intraoperative intrathecal morphine (ITM) administration is gaining popularity and acceptance with clinicians. This study seeks to determine the impact of intraoperative intrathecal opioid (ITO) administration following lumbar fusion surgery on postoperative pain and length of hospitalization as primary outcomes. Secondary outcomes will investigate postoperative opioid intake and side effects.

METHODS

The retrospective analysis of collected data was performed. The study compared patients undergoing one- or two-level transforaminal interbody fusions between 2019 and 2021 who intraoperatively received two different ITO doses (n = 89) vs. the reference group (n = 48) that did not receive ITO. The patients in the ITO group received either 0.2 mg (n = 44) of duramorph or 0.2 mg duramorph + 50 mcg fentanyl (n = 45). The effect of ITO was evaluated for the first four postoperative days (POD) on pain scores (visual analog scale), length of stay (LOS, hours) and opioid requirement (MED, morphine equivalent dose).

RESULTS

In the ITO group, a significant reduction of postoperative pain scores (t(99) = 4.3, p < 0.001) and opioid intake (t(70) = 2.49, p = 0.015) was noted on POD1. Cohen's d effect sizes were 0.76 and 0.50, meaning that postoperative pain and MED intake were reduced by about ¾ to ½ standard deviations (SD) in the ITO group. Further, multivariate regression models revealed that ITO administration predicted lower postoperative pain scores for the two PODs (β =  - 0.83, p < 0.001; β =  - 0.63, p = 0.022) and MED intake for the first two PODs (β =  - 20.8, p = 0.047; β =  - 16.4, p = 0.030). Mean LOS was 15.4 h less in the ITO group (mean ± SD, 63.4 ± 37.1 vs. 78.8 ± 39.6, p = 0.10).

CONCLUSIONS

In conclusion, our study provides results in a large sample of patients undergoing transforaminal lumbar fusions. The results demonstrated that ITO administration is effective in reducing POD1 pain scores and POD1-2 opioid requirement while not increasing the risk of any opioid-related side effects.

Intraspinal Narcotic Tolerance: Preliminary Experience with Continuous Bupivicaine HCL Infusion via Implanted Infusion Device

Spinal opiate receptor tolerance is the major limitation of continuous intraspinal narcotic analgesia delivered by implanted reservoir pump. Six intractable pain patients receiving continuous epidural morphine were given trials of low dose bupivicaine HCL in order to assess the effects on implanted reservoir function, analgesia, and safety. Daily infusion of 2.6–18.8 mg bupivicaine HCL had no consistent effect on flow rates. Subjectively, three patients had at least partial relief of pain while their intraspinal morphine doses were weaned. No sympathectomy was appreciated at these doses. The future of continuous intraspinal analgesia might require further advances in implantable infusion pump technology to allow manipulation of both daily infusion doses and multiple intraspinal analgesics. Further study is needed to assess the safety and effectiveness of higher continuous intraspinal bupivicaine doses for chronic pain relief.

Review article : The spinal administration of opioids in the treatment of acute and chronic pain: bolus doses, continuous infusion, intraventricular administration and implanted drug delivery systems

The spinal administration of opioids has been a significant addition to the previously available alternatives for pain control for patients with pain related to cancer. This article does not debate the more widespread use of these techniques in patients with nonmalignancy related pain. The incidence of destructive neurolytic procedures has fallen in most centres where spinal opioids have been administered. Some types of cancer pain have proved to be more effectively controlled than others, but in most circumstances potentially reversible procedures, such as outlined in this article, should be given a therapeutic trial before embarking on neuro-destructive procedures.1

It should be reemphasized however, that the spinal route of administration should be instituted only after systemically administered opioids have been shown to be ineffective or associated with intolerable side effects.

Randomised, double-blind controlled trial by dose reduction of implanted intrathecal morphine delivery in chronic non-cancer pain

OBJECTIVE

This study aimed to investigate the efficacy of intrathecal morphine in the long term by hypothesising that a reduction of the intrathecal opioid dose following long-term administration would increase the level of pain intensity.

DESIGN

Randomised, double-blind, controlled, parallel group trial.

SETTING

Department of Pain Management, Russells Hall Hospital, Dudley, UK.

PARTICIPANTS

24 patients with non-cancer pain implanted with morphine reservoirs were assessed for eligibility.

INTERVENTIONS

Participants were randomly allocated to one of two parallel groups in which one of the groups had no change in morphine dose and the other group had a small reduction (20%) in dosage every week during a 10-week follow-up.

OUTCOME

Primary outcomes were visual analogue scale (VAS) pain score change and withdrawal from the study due to lack of efficacy.

RESULTS

9 of the patients assessed for eligibility declined to participate in the study. 15 patients were randomised to control (n=5) or intervention (n=10) and included in an intention-to-treat analysis. Owing to worsening of pain, seven patients withdrew from the study prematurely. None knew prior to withdrawal which arm of the study they were in, but all turned out to be in the dose-reduction arm. The calculation of dropout rates between groups indicated a significant statistical difference (p=0.026) and recruitment was ceased. The VAS change between baseline and the last observation was smaller in the control group (median, Mdn=11) than in the intervention group (Mdn=30.5), although not statistically significant, Z=-1.839, p=0.070; r=-0.47. Within groups, VAS was significantly lower at baseline (Mdn=49.5) than at the last observation (Mdn=77.5) for the reduction group, Z=-2.805, p=0.002; r=-0.627 but not for the control group (p=0.188).

CONCLUSIONS

This double-blind randomised controlled trial of chronic intrathecal morphine administration suggests the effectiveness of this therapy for the management of chronic non-cancer pain. However, owing to the small number of patients completing the study (n=8), further studies are warranted.

TRIAL REGISTRATION

International Standard Randomised Controlled Trials Centre (ISRCTN 33733462).

Neuraxial morphine and respiratory depression: finding the right balance

Morphine is a drug commonly administered via the epidural or intrathecal route, and is regarded by many as the 'gold-standard' single-dose neuraxial opioid due to its postoperative analgesic efficacy and prolonged duration of action. However, respiratory depression is a recognized side effect of neuraxial morphine administered in the perioperative setting. We conducted an extensive review of articles published since 1945 that examine respiratory depression or failure associated with perioperative intrathecal or epidural morphine use. Respiratory depression was previously thought to result from the interaction of opioid in the cerebrospinal fluid with ventral medullary opioid receptors. More recently, the preBötzinger complex located in the medulla has been identified as the site responsible for the decrease in respiratory rate following systemic administration of opioids. Neurons in the preBötzinger complex expressing neurokinin-1 receptors are selectively inhibited by opioids, and therefore are the mediators of opioid-induced respiratory depression. Epidural, intrathecal and plasma pharmacokinetics of opioids are complex, vary between neuraxial compartments, and can even differ within the epidural space itself depending upon level of insertion. Caution should be exercised when prescribing systemic opioids (intravenous or oral) in addition to neuraxial morphine as this can compound the potential for early or delayed respiratory depression. There is a wide range of incidences for respiratory depression following neuraxial morphine in a perioperative setting. Disparity of definitions used for the diagnosis of respiratory depression in the literature precludes identification of the exact incidence of this rare event. The optimal neuraxial opioid dose is a balance between the conflicting demands of providing optimal analgesia while minimizing dose-related adverse effects. Dose-response studies show that neuraxial morphine appears to have an analgesic efficacy 'ceiling'. The optimal 'single-shot' intrathecal dose appears to be 0.075-0.15 mg and the ideal 'single-shot' epidural morphine dose is 2.5-3.75 mg. Analgesic efficacy studies have not been adequately powered to show differences in the incidence of clinically significant respiratory depression. Opioid antagonists such as naloxone to prevent or treat opioid-induced respiratory depression have a number of limitations. Researchers have recently focused on non-opioid drugs such as serotonin receptor agonists. Early evidence suggests that ampakine (α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid [AMPA]) receptor modulators may be effective at reducing opioid-induced respiratory depression while maintaining analgesia. Sodium/proton exchanger type 3 (NHE3) inhibitors, which act centrally on respiratory pathways, also warrant further study.

Retrospective analysis of high-dose intrathecal morphine for analgesia after pelvic surgery

BACKGROUND

The effectiveness of intrathecal opioids (ITOs) for postoperative analgesia has been limited by reduced opioid dosing because of opioid-related side effects, most importantly respiratory depression. To overcome these limitations, high-dose intrathecal morphine was combined with a continuous intravenous (IV) postoperative naloxone infusion. The aim of the present chart analysis was to investigate the safety and efficacy of high-dose ITOs combined with IV naloxone compared with IV opioid analgesia alone.

METHODS

A retrospective chart analysis was performed on 121 female patients requiring major pelvic surgery. Ninety-eight patients received a single injection of high-dose ITOs before administration of typical general anesthesia, followed by an IV naloxone infusion at 5 µg⁄kg⁄h started post-ITO and continued for 22 h postoperatively. Twenty-three patients were given IV morphine (IVM) for postoperative analgesia and served as a reference group. Postoperative pain relief, analgesic consumption and ability to ambulate were assessed for 48 h postoperatively. Treatment safety was assessed by monitoring opioid-related side effects and vital signs. Data are presented as mean ± SD.

RESULTS

Mean ITOs given were morphine 1.1±0.2 mg combined with fentanyl 49 ± 6 µg. The mean worst pain visual analogue scale score in the first 12 h postoperatively was 0.2 ± 0.90 in the ITO group versus 4.3 ± 3.0 in the IVM group (P<0.05). On postoperative day 2, the mean worst pain visual analogue scale score was only 1 ± 1.8 in the ITO group versus 4.1 ± 2.6 in the IVM group (P<0.05). Analgesic requirements were reduced in the ITO group. In the first 24 h, the ITO group used 6.8±10.2 morphine equivalents (mg IV) versus 76.1 ± 44.4 in the IVM group (P<0.05). All patients in the ITO group were able to ambulate in the first 12 h postoperatively compared with 17⁄23 in the IVM group. There was a higher incidence of opioid-related sedation in the IVM group. Other opioid-related side effects were infrequent and minor in both groups.

CONCLUSIONS

High-dose ITOs combined with a postoperative IV naloxone infusion provided excellent analgesia for major pelvic surgery. The IV naloxone infusion combined with high-dose ITOs appeared to control opioid side effects without affecting analgesia.

Plasma concentrations of meperidine and normeperidine following continuous intrathecal meperidine in patients with neuropathic cancer pain

BACKGROUND

Intrathecal administration of meperidine, an opioid with local anesthetic activity, can induce analgesia in patients with intractable cancer pain. However, continuous intrathecal administration may result in the accumulation of normeperidine, responsible for central nervous system toxicity.

METHODS

Ten patients with neuropathic cancer pain, not responding to conventional opioid therapy, were treated with continuous intrathecal administration of meperidine. In all patients, plasma concentrations of meperidine and normeperidine were measured the first days after the start of treatment. Visual analog scale scores were recorded to evaluate pain relief. Quality of life was assessed before and 3 weeks following the start of intrathecal treatment.

RESULTS

In three patients the plasma concentrations of meperidine and normeperidine increased rapidly. In one patient the plasma normeperidine concentration was higher than the meperidine concentration. One patient demonstrated transient symptoms suggestive for central nervous system excitation. Three weeks following the start of treatment, seven patients were available for evaluation of their quality of life. Pain relief and overall quality of life improved during the intrathecal treatment.

CONCLUSION

We conclude that continuous intrathecal administration of meperidine alone, or in combination with clonidine, can provide significant pain relief in patients with poor pain control despite pharmacological treatment. However, accumulation of meperidine and normeperidine resulting in central nervous system toxicity may occur during this treatment.

Continuous Intrathecal Meperidine for Severe Refractory Cancer Pain

The control of severe cancer pain may be problematic despite advances in pain management. Patients with severe intractable pain and/or intractable side effects may require aggressive interventional pain management strategies including the administration of medications by the continuous intrathecal route and/or neurosurgical procedures. Various medications, including opioids, local anesthetics, and alpha-2 agonists may be used intrathecally for the control of cancer pain. Failure of the intrathecal route may require the additional use of neurosurgical procedures such as cordotomy for pain control. We describe a case of severe cancer pain refractory to conventional intrathecal medications and cordotomy that was successfully managed by the addition of meperidine to the intrathecal regimen.

Spinalan�sthesie bei der Arthroskopie des Kniegelenks

BACKGROUND AND OBJECTIVE

Intrathecal morphine provides effective postoperative analgesia but is associated with the risk of respiratory depression. A dose of only 0.1 mg has been shown to be optimal for effective and safe pain relief after abdominal surgery. This study was designed to determine whether the addition of 0.1 mg of morphine to the local anesthetic for spinal anesthesia produces adequate analgesia following arthroscopic knee joint surgery.

METHODS

A prospective, randomized, placebo-controlled, double-blind clinical trial was performed. Forty ASA I/II patients undergoing knee arthroscopy under spinal anesthesia were randomized to receive either mepivacaine 4% with 0.1 mg of morphine or mepivacaine 4% with saline (placebo) intrathecally. Postoperative analgesia consisted of intravenous morphine delivered by patient-controlled analgesia (bolus: 2 mg, lockout time: 5 min). During the study period of 24 h, pain intensity at rest and on movement (visual analogue scale, 0: no pain, 100: maximum pain), vigilance, and vital parameters were recorded every hour.

RESULTS

There were no statistically significant differences between the two groups in postoperative pain scores, morphine requirements, vigilance, blood pressure, heart rate, and breathing frequency. The patients of the morphine group required 12.3+/-10.2 mg (mean+/-SD) and those of the placebo group 11.6+/-8.4 mg of intravenous morphine from patient-controlled analgesia. The pain scores at rest and on movement were 10.0+/-8.1 and 16.0+/-12.6 in the morphine group and 8.2+/-7.9 and 11.7+/-11.3 in the placebo group. We did not observe severe side effects in any of the patients.

CONCLUSION

Intrathecal administration of 0.1 mg of morphine does not contribute to postoperative analgesia after arthroscopic knee joint surgery.

A forensic toxicological dilemma: the interpretation of post-mortem concentrations of central acting analgesics

Dora V., a 88-year-old pensioner suffering from a hiatus hernia, died at the home of an orthopaedist and his wife, an anaesthetist, immediately after she had received a dose of 300 mg pethidine via intravenous infusion in a timeframe of about 90 min. One day before her death a befriended notary of the couple visited Dora V. and obtained a blank signature. After her death, a will was forged using this signature, rendering the couple sole heirs of Dora V.'s estate with a value of several million euros. Post-mortem toxicology was performed in three different institutes of legal medicine. The concentrations of pethidine in peripheral venous blood were between 6.1 and 6.5mg/l and 9.5 and 17.2mg/kg in brain. Pharmacokinetic calculation confirms the given dose. There was no doubt that the cause of death was acute pethidine intoxication. The accused couple claimed that this dose of pethidine was indicated to relief pain, and as the pathologists said in their expert opinions that the hiatus hernia could explain her death, the court had to acquit the accused. This very special case demonstrates that preconceived murder of a sick person with suitable analgesics cannot be proven--at least not with the methods available to forensic toxicology and pathology. This has to be taken into consideration if euthanasia will be legalised under special circumstances.

Analgesic Synergy Between Topical Morphine and Butamben in Mice

Studies have revealed that lidocaine is an effective analgesic when applied topically to the tail of a mouse in the radiant heat tail-flick assay. In addition, the topical combination of lidocaine with morphine revealed synergistic interactions between the two drugs. In the current studies, we demonstrate that topical butamben, benzocaine, and bupivacaine are active in the radiant heat tail-flick assay. In this assay, topical lidocaine has a ceiling effect and displays a biphasic curve, with large doses markedly decreasing the responses almost to baseline levels. In contrast, butamben has an S-shape dose-dependent response in the assay and did not display a biphasic curve as seen with lidocaine, suggesting that topical butamben may have advantages over lidocaine. Both benzocaine and bupivacaine also showed dose-dependent analgesic activity in this model. Like lidocaine, butamben/morphine combinations displayed synergistic interactions. Indeed, the synergy appeared more prominent with a butamben/morphine combination. We also observed synergy between topical benzocaine and morphine. Although the bupivacaine/morphine combination was suggestive of synergy on isobolographic analysis, it did not achieve statistical significance. These studies indicate that a series of local anesthetics are all active topically in the radiant heat tail-flick assay in mice and that several interact synergistically with morphine. Of the local anesthetics tested, butamben seemed to have several pharmacological characteristics, alone and in combination with morphine, which suggest that it may be superior to the other local anesthetics. Together, these observations suggest that topical combinations of opioids and local anesthetics may prove clinically valuable.

IMPLICATIONS

Topical administration of the opioid micro -agonist morphine and the sodium channel inhibitors butamben and benzocaine results in a synergistic interaction for antinociception in radiant heat tail-flick assay in mice, suggesting that the combination of these drugs will enhance rather than detract from the analgesia of either alone.

Epidural and intrathecal analgesia for cancer pain

The three-step analgesic ladder approach developed by the World Health Organization works well in treating the vast majority (70-90%) of patients suffering from pain related to cancer. In those patients who do not get pain relief by this three-step approach, intraspinal agents can be a fourth step in managing pain of malignant origin. Although morphine is the only opioid approved by the US Food and Drug Administration for intraspinal use, many different opioid analgesics are used intraspinally, including hydromorphone, fentanyl, sufentanil, meperidine and methadone in the treatment of cancer pain. Many non-opioid agents have also been used intraspinally either alone or in combination with opioids in the treatment of intractable cancer pain. This chapter summarizes the clinical use of these agents with some practical points.

Implantable devices for pain control: spinal cord stimulation and intrathecal therapies

Untreated chronic pain is costly to society and to the individual suffering from it. The treatment of chronic pain, a multidimensional disease, should rely on the expertise of varying health care providers and should focus not only on the neurobiological mechanisms of the process but also on the psychosocial aspects of the disease. Implantable devices are costly and invasive, and such efficacious therapies should be used only when more conservative and less costly therapies have failed to provide relief of pain and suffering. Spinal cord stimulation provides neuromodulation of neuropathic, but not nociceptive, pain signals and when used for appropriate indications in the right individuals provides approximately 60-80% long-term pain relief in 60-80% of patients trialled for efficacy. Intrathecal therapies with opioids such as morphine, fentanyl, sufentanil or meperidine--or non-opioids such as clonidine or bupivacaine--provide analgesia in patients with nociceptive or neuropathic pain syndromes. Baclofen, intrathecally, provides profound relief of muscle spasticity due to multiple sclerosis, spinal cord injuries, brain injuries or cerebral palsy.

Intrathecal versus IV fentanyl in pediatric cardiac anesthesia

Systemic large-dose opioids are widely used in pediatric cardiac anesthesia, but there are no randomized, prospective studies regarding the use of intrathecal (IT) opioids for these procedures. In this randomized, prospective study, we compared cardiovascular and neurohumoral responses during IT or IV fentanyl anesthesia for pediatric cardiac surgery. Thirty children aged 6 mo to 6 yr were anesthetized with an IV fentanyl bolus of 10 micro g/kg. This was followed by a fentanyl infusion of 10 micro g. kg(-1). h(-1) (Group IV; n = 10), 2 micro g/kg of IT fentanyl (Group IT; n = 10), or combined IV and IT protocols (Group IV + IT; n = 10). Heart rate, mean arterial blood pressure, additional fentanyl doses, time to first analgesic requirement, COMFORT and Children's Hospital of Eastern Ontario Pain Scale scores, and extubation time were recorded. Blood cortisol, insulin, glucose, and lactate levels were measured presurgery, poststernotomy, during the rewarming phase of cardiopulmonary bypass (CPB), and 6 and 24 h after surgery. The patients' urinary cortisol excretion rates were also measured during the first postoperative day. The findings in all three groups were statistically similar, except for higher blood glucose levels during CPB in Group IT compared with Group IV (P < 0.004). Group IV + IT was the only group in which the increases in heart rate and mean arterial blood pressure from presurgery to poststernotomy were not significant. The 24-h urinary cortisol excretion rates ( micro g. kg(-1). d(-1)) were 61.51 +/- 39, 92.54 +/- 67.55, and 40.15 +/- 29.69 for Groups IV, IT, and IV + IT, respectively (P > 0.05). A single IT injection of fentanyl 2 micro g/kg offers no advantage over systemic fentanyl (10 micro g/kg bolus and 10 micro g. kg(-1). h(-1)) with regard to hemodynamic stability or suppression of stress response. The combination of these two regimens may provide better hemodynamic stability during the pre-CPB period and may be associated with a decreased 24-h urinary cortisol excretion rate.

IMPLICATIONS

In this prospective, randomized study, we investigated the adequacy of a single intrathecal injection of fentanyl for intraoperative analgesia, compared the effects of IT and IV fentanyl on stress response, and assessed for an additive effect of IT and IV fentanyl administration in pediatric cardiac anesthesia. The results with these three different anesthetic regimens were similar regarding anesthesia depth and level of stress response. However, the combination of IT and IV routes may provide better hemodynamic stability and a less pronounced stress response, as reflected by 24-h urinary cortisol excretion.

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.

Intrathecal sufentanil and morphine for post-thoracotomy pain relief

In this double-blind randomized study we compared a group of 15 patients undergoing thoracotomy who received a spinal injection of sufentanil 20 microg combined with morphine (200 microg) after induction of general anaesthesia with a control group of the same size. Post-operative pain was rated on a visual analogue scale (VAS) and a verbal rating scale at rest and with a VAS on coughing. In the recovery room, patients received titrated i.v. morphine until the VAS score was <30, and were followed by patient-controlled analgesia (PCA) for 72 h. The intrathecal sufentanil and morphine group had a lower intra-operative requirement for i.v. sufentanil and needed less i.v. morphine for titration in the recovery room. I.v. PCA morphine consumption and pain scores were lower in the active group than in the control group during the first 24 h. There were no differences after this time. Spirometric data (peak expiratory flow, forced vital capacity and forced expiratory volume in 1 s) were similar in the two groups. We conclude that the combination of intrathecal sufentanil and morphine produces analgesia of rapid onset and with a duration of 24 h.

Current trends in perioperative pain management

Wider use of optimized multimodal accelerated postoperative recovery programs require that anesthesiologists step out of traditional operating room anesthesia roles and even beyond current pain management consultant roles. Development of optimal postoperative recovery services requires close collaboration between anesthesiologists, surgeons, nurses, physical therapists, administrators, and others involved in the management of patients after surgery. Optimization of perioperative care is an ongoing process enhanced by clinical investigation; however, making significant improvements to clinical practice does not have to wait for additional research data, but should proceed now, with broader application of techniques known to enhance rehabilitation and recovery. Based on existing data, the challenges of developing perioperative recovery services seem likely to be rewarded with improved patient outcomes and reduced cost.

Evidence-based review of the literature on intrathecal delivery of pain medication

Evidence-based medicine depends on the existence of controlled clinical trials that establish the safety and efficacy of specific therapeutic techniques. Many interventions in clinical practice have achieved widespread acceptance despite little evidence to support them in the scientific literature; the critical appraisal of these interventions based on accumulating experience is a goal of medicine. To clarify the current state of knowledge concerning the use of various drugs for intraspinal infusion in pain management, an expert panel conducted a thorough review of the published literature. The exhaustive review included 5 different groups of compounds, with morphine and bupivacaine yielding the most citations in the literature. The need for additional large published controlled studies was highlighted by this review, especially for promising agents that have been shown to be safe and efficacious in recent clinical studies.

Epidural analgesia and anesthesia

This review describes the beneficial effects of the use of epidural drugs for pre-emptive analgesia, intraoperative analgesia with an inhalant-sparing effect, and prolonged postoperative analgesia. Epidural morphine oxymorphone, or hydromorphone is recommended for use in small animals in combination with a local anesthetic of appropriate duration for procedures involving the hind end, although epidural morphine or hydromorphone may be more appropriate for procedures on the thorax and forelimbs. Side effects are few and can usually be easily managed, with the benefits outweighing any detrimental effects that might occur.

Spinal plasticity of acute opioid tolerance

Spinal acute opioid tolerance remains mechanistically undercharacterized. Expanded clinical use of direct spinal administration of opioids and other analgesics indicates that studies to further understand spinal mechanisms of analgesic tolerance are warranted. Rodent models of spinal administration facilitate this objective. Specifically, acute spinal opioid tolerance in mice presents a plasticity-dependent, rapid, and efficient opportunity for evaluation of novel clinical agents. Similarities between the pharmacology of acute and chronic spinal opioid tolerance, neuropathic pain, and learning and memory suggest that this model may serve as a high through-put predictor of bioactivity of novel plasticity-modifying compounds.

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.

Intrathecal pethidine: pharmacology and clinical applications

Pethidine is the only member of the opioid family that has clinically important local anaesthetic activity in the dose range normally used for analgesia. Pethidine is unique as the only opioid in current use that is effective as the sole agent for spinal anaesthesia. In lower doses, intrathecal pethidine is also an effective analgesic for treating pain in labour. This paper reviews the pharmacology of intrathecal pethidine and clinical experience reported to date. Articles reviewed include those identified by a Medline search using keywords "intrathecal" or "spinal anaesthesia/ anesthesia" and "pethidine" or "meperidine". Reference lists from identified papers were scrutinized to identify further relevant articles.

Bupivacaine decreases epidural meperidine requirements after abdominal surgery

PURPOSE

The purpose of this study was to determine the optimal of three concentrations of bupivacaine (0.0%, 0.05%, 0.10%) to add to an epidural infusion of meperidine (1 mg.ml-1) for postoperative pain relief.

METHODS

In this prospective, double blind study, 60 patients undergoing abdominal surgery with general anaesthesia were randomized into three groups to receive for postoperative epidural analgesia: 1) 1 mg.ml-1 meperidine (0% group), 2) bupivacaine 0.05% and 1 mg.ml-1 meperidine (0.05% group), 3) bupivacaine 0.10% and 1 mg.ml-1 meperidine (0.10% group). Postoperatively, the epidural infusion rate was titrated to produce adequate analgesia and pain was assessed at rest and on movement.

RESULTS

There were no differences in demographic data, average pain scores or side effects among the three groups. However, there was improvement of pain relief at rest over time in the three groups (P < 0.05). Postoperative epidural analgesic infusion rates increased over time for the three groups (P < 0.05) and were lower in the 0.10% group (mean of 10.0 ml.hr-1) than in the 0% group (mean of 12.6 ml.hr-1) (P < 0.05). More than half of the 0% group had serum meperidine concentrations > 400 g.L-1 to control moderate postoperative pain.

CONCLUSION

Although analgesia was identical among groups, the lower serum concentrations of meperidine support the addition of bupivacaine 0.10% to meperidine when administered as a continuous infusion following abdominal surgery.

Intraspinal opioid therapy for chronic nonmalignant pain: current practice and clinical guidelines

The multidimensional nature of chronic nonmalignant pain lends itself to numerous treatment options, which vary in cost and invasiveness. Based on the principle that less invasive and less costly interventions for pain treatment should be attempted first, a continuum of interventions for chronic pain states is presented. Although intraspinal opioid therapy is a relatively invasive and costly modality for pain treatment, it has a rational place in the treatment continuum for some chronic nonmalignant pain patients. A thorough review of the literature, supplemented by clinical experience, provides a foundation for the development of management guidelines.

Patient-controlled epidural analgesia following caesarean delivery: a comparison of pethidine and fentanyl

Pethidine and fentanyl have both been used to provide patient-controlled epidural analgesia (PCEA) following caesarean delivery. Both have been compared with epidural morphine but these drugs have not been compared with each other. Patient-controlled epidural analgesia was used in a prospective, randomized, double-blind, cross-over trial to compare fentanyl and pethidine for postoperative epidural analgesia in women having elective caesarean deliveries. Two groups received either PCEA fentanyl or pethidine with a cross-over to the other drug after 24 hours. Results from 45 patients showed no difference in pain level outcomes, but pethidine scored better in all side-effects except for drowsiness at 48 hours. Patients were more satisfied with pethidine (P = 0.015) and overall 65% of patients preferred pethidine. We conclude that pethidine is a suitable drug for patient-controlled epidural analgesia and leads to greater patient satisfaction than does fentanyl.

Opioids: a pharmacologist's delight!

1. Opioids, in one form or another, have been used for their pain-relieving properties from prehistoric times: they are still the first line medication for the treatment of severe nociceptive pain and are likely to remain so for the foreseeable future. 2. The therapeutic index of opioids used for pain management is low: opioid side effects are essentially extensions of therapeutic effects and no available agent has a marked advantage over the others. When used for opioid 'anaesthesia', differences in therapeutic index are more obvious due to differences in non-opioid effects. 3. Opioid receptors in brain and spinal cord periphery are the main 'therapeutic targets' and clinical dosage strategies have been derived using a variety of systemic (indirect or blood-borne) methods as well as intraspinal and intracerebroventricular (direct) methods: no method, however, is without potential side effects. Peripheral opioid effects are now being exploited with intra-articular injection. 4. Opioid pharmacokinetics and pharmacodynamics are characterized by high inter-subject variability: accordingly, patient-controlled dosage strategies are found to be more successful for pain control than deterministic recipes.

A comparison of caudal epidural bupivacaine with adrenaline and bupivacaine with adrenaline and pethidine for operative and postoperative analgesia in infants and children

This study compares the effectiveness of two drug combinations--(a) bupivacaine with adrenaline and (b) bupivacaine with adrenaline and pethidine--on operative and postoperative pain relief when administered by the caudal route in infants and children. A randomised controlled trial was conducted on fifty children below the age of twelve years: 25 children were randomly allocated to each group. Both groups had a significant period of analgesia in the postoperative period. None of the children in either group required parenteral analgesia. Though the group with pethidine had a longer duration of analgesia and sedation, the very high incidence of vomiting and delay in urination observed in this group would preclude the use of pethidine routinely. No respiratory depression was seen in either group.

Enhancement of the epidural morphine-induced analgesia by systemic nifedipine

We evaluated postoperative pain relief and incidence of side effects of the combination of epidural morphine (0.5 mg) and sublingual nifedipine (10 mg). Thirty-six patients were submitted to elective operations and divided into 4 groups receiving placebo (groups A and B) or morphine (groups C and D) by the epidural route, followed by sublingual placebo (groups A and C) or nifedipine (groups B and D) administered in a double-blind fashion. The mean (+/- S.E.M.) periods of analgesia were 16.6 +/- 1.6 (A), 15 (B) 105 +/- 77.0 (C), and 428.8 +/- 72.0 (D) min. No patient had pruritus, excessive sedation or respiratory depression. Episodes of nausea and/or vomiting requiring no specific therapy were observed in groups A, B and D. Nifedipine-treated groups also had a significant fall in blood pressure which was controlled by rehydration. These results indicate that epidural morphine-induced postoperative pain relief may be enhanced by systemic administration of nifedipine, with easily controlled side effects.

Epidural tramadol for postoperative pain relief

The efficacy of epidurally administered tramadol hydrochloride, a weak centrally acting analgesic, was studied for the relief of postoperative pain. Sixty patients undergoing abdominal surgery were randomly allocated to three treatment groups to be given the following agents by the epidural route: group 1 tramadol 50 mg; group 2 tramadol 100 mg; group 3 10 ml of bupivacaine 0.25%. The drugs were administered at the patients' request with each patient being allowed four doses in the first 24 h following surgery. Blood pressure, pulse rate, respiratory rate, arterial blood gas analyses, pain scores, the interval between doses and the occurrence of any side effects were recorded. Pain scores (assessed using a visual analogue scale) were significantly less (p < 0.05) at 3, 12, and 24 h in patients receiving tramadol 100 mg than in those receiving tramadol 50 mg or bupivacaine. The mean interval between doses for groups 1, 2 and 3 was 7.40 h, 9.36 h and 5.98 h respectively. The mean interval in group 2 was significantly longer than in group 3 (p < 0.05). The incidence of nausea and vomiting in group 2 was significantly higher than in group 3 (p < 0.05).

Intrathecal infusional therapies for intractable pain: patient management guidelines

This article focuses on appropriate patient selection for and management of patients selected for continuous spinal infusional opioid therapy. Patients with cancer-related pain who have undergone sequential strong opioid drug trials, who have intractable, unmanageable side effects, and who have undergone a successful spinal opioid efficacy trial are candidates for implantable spinal infusional therapy. Patients with noncancer-related chronic pain, who have failed all conventional syndrome-specific therapies before neuroablative surgical procedures, including sequential strong opioid drug trials, who have intractable, unmanageable side effects, and who have undergone successful spinal opioid efficacy trial are deemed candidates for implantable spinal infusional therapy. Patients with chronic noncancer-related pain and patient with cancer-related pain who have life expectancies greater than 3 mo all have implanted programmable infusion pumps. Patients with cancer-related pain who have life expectancies less than 3 mo have implanted permanent epidural catheters connected to external pump systems. Management guidelines for complications of therapy broadly categorized as surgical, mechanical, and pharmacologic are presented.

Dose changes in long- and medium-term intrathecal morphine therapy of cancer pain

Intrathecal morphine analgesia for the treatment of cancer pain was administered using implanted ports and drug delivery systems (DDS) in 79 patients. Effective control of the pain was achieved in nearly all patients; in only two patients was the use of the DDS discarded because of relative ineffectiveness. Fifty-three manual drug release systems (41 lumbar, 12 ventricular) and 26 lumbar ports were used. Forty patients survived more than 2 months; the maximum survival time was 560 days (mean survival time, 80 days with a port system, 100 days with a manual DDS). Patients still alive at the time of this study, i.e., with unknown survival time, were excluded. The initial mean daily dose was 8.5 mg in lumbar ports, 2.75 mg in lumbar DDS, and 0.2 mg with intraventricular application. Dose change patterns disclosed no alteration of the initial dose in 18 of 26 port patients, an initial increase in 4, a preterminal increase in 3, and a single intermittent increase in 1 patient. Of 40 lumbar DDS patients, 13 showed a constant dose, 9 an initial, 3 a preterminal, and 5 an intermittent increase. Three patients with less than 2 months' survival time had a rather continuous increase. All long-time survivors (i.e., with more than 2 months' survival time) reached a plateau and remained there until a preterminal if any increase occurred. These findings suggest the morphine dosage to be indicative of the progress of the disease rather than of a drug tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical and pharmacokinetic aspects of the combination of meperidine and prilocaine for spinal anaesthesia

The aim of this study was to determine whether the addition of a small dose of prilocaine could augment the spinal block induced by meperidine and affect intrathecal meperidine pharmacokinetic behaviour. Spinal anaesthesia was performed in 60 men scheduled for endoscopic resection of a prostatic adenoma or bladder tumour under spinal anaesthesia. They were allocated randomly to receive either 1 mg.kg-1 meperidine (Group 1, n = 30), or 1 mg.kg-1 meperidine plus 0.5 mg.kg-1 prilocaine (Group 2, n = 30). Blood samples were collected prior to and for 24 hr after spinal injection in 24 patients (12 in each group). Plasma meperidine levels were assayed by gas chromatography. Complete motor block was achieved in all Group 2 patients, but was incomplete in seven of Group 1 (P less than 0.05). The onset of both motor and sensory blocks was shorter (P less than 0.01) in Group 2 and the duration was longer (P less than 0.05). Coadministration of prilocaine modifies meperidine pharmacokinetic behaviour. The area under curve was 48% greater (P less than 0.01) and Cmax was higher in Group 2 than in Group 1, 145.8 +/- 42.2 vs 107 +/- 20.5 ng.ml-1 (P less than 0.001). No evidence of respiratory depression was noted in any of the patients. Despite the increase in plasma meperidine concentrations, no side effects were observed. The plasma concentrations remained at one third to one sixth the levels reported to induce a respiratory depression. It is concluded that the addition of prilocaine to meperidine improves motor and sensory block during surgery and alters meperidine kinetics without producing major side effects.

Early respiratory depression during caesarean section following epidural meperidine

A case of respiratory depression which occurred following administration of epidural meperidine during Caesarean section is described. Epidural meperidine, 75 mg (10 mg.ml-1) was given after delivery of the infant to provide postoperative analgesia. Oxygen desaturation (SaO2 90%) and a decrease in respiratory rate (4.min-1) were noted 30 min after epidural meperidine was administered. Naloxone, 0.1 mg, was given iv which resulted in prompt improvement in both respiratory rate and oxygen saturation. Vascular absorption of meperidine from the epidural venous plexus is the most probable explanation for this case of early respiratory depression. We recommend a maximum bolus dose of 50 mg of epidural meperidine for pain management after Caesarean section. It is also important to monitor oxygen saturation continuously during the intraoperative period, and to monitor the patient closely in the recovery room for at least one hour for evidence of respiratory depression.