Intravenous Ketamine or Fentanyl Prolongs Postoperative Analgesia After Intrathecal Neostigmine

Use of Intrathecal Neostigmine as an Adjunct to Other Spinal Medications in Perioperative and Peripartum Analgesia: A Meta-analysis

Intrathecal neostigmine has been used as an adjunct to intrathecal local anaesthetic or opioid to prolong regional analgesia and improve haemodynamic stability, with variable results. This meta-analysis aims to evaluate the effectiveness and side-effects of intrathecal neostigmine in the perioperative and peripartum settings. The literature search was based on Cochrane Controlled Trials Register, EMBASE and MEDLINE (from 1966 to 14 November 2003) databases. Volunteer and animal studies were excluded. We identified 26 studies and 19 were considered suitable for detailed data extraction. Intrathecal neostigmine increased the incidence of nausea and vomiting (OR 5.0, 95% CI: 3.4 to 7.3; P<0.00001), bradycardia requiring intravenous atropine (OR 2.7, 95% CI: 1.4 to 5.4; P=0.005), and anxiety, agitation, or restlessness (OR 10.3, 95% CI: 3.7 to 28.9; P=0.00001). It improved the overall 24 hour VAS score (–1.4 VAS pain score, 95% CI: -1.7 to -1.2, P<0.00001), delayed the time of first request for rescue analgesia (168 min, 95% CI: 125 to 211; P<0.00001), and reduced the total number of rescue injections of nonsteroidal anti-inflammatory drug within the first 24 hours (-0.8, 95% CI: -1.1 to -0.4; P=0.00001). It did not affect the duration of motor blockade (3.5 min, 95% CI: -1.5 to 8.6; P=0.17) or the total amount of ephedrine required (-0.4 mg, 95% CI: -1.5 to 0.7; P=0.5). Adding intrathecal neostigmine to other spinal medications improves perioperative and peripartum analgesia marginally when compared with placebo. It is associated with significant side-effects and the disadvantages outweigh the minor improvement in analgesia achieved.

Comparison of fentanyl versus meperidine as supplements to epidural clonidine-bupivacaine in patients with lower limb orthopedic surgery under combined spinal epidural anesthesia

BACKGROUND

The analgesic and sedative effect of clonidine explain its common use as adjuvant in regional anesthesia, however the hemodynamic instability associated with its neuroaxial administration is the major drawback. Our study hypothesis is to compare the hemodynamic and analgesic effect of epidural fentanyl in comparison to meperidine when added to clonidine in patients undergoing lower limbs orthopedic surgery using combined spinal-epidural anesthesia.

METHODS

One hundred thirty five ASA physical status I or II patients were recruited for lower limb orthopedic surgery. All received 2 mL intrathecal 0.5 % hyperbaric bupivacaine, 10 mL epidural 0.25 % plain bupivacaine, and 1 mL epidural clonidine 2 μg/kg (Clonidine group) and then either 1 ml fentanyl 25 μg (Fentanyl Group) or 1 ml meperidine 25 mg (Meperidine Group). The quality of surgical anesthesia, incidence of hypotension and bradycardia, intra-operative pain assessment, and onset of postoperative pain, sedation scores and side effects in the postoperative period were recorded.

RESULTS

The 1(st) analgesic requirement in the postoperative period was significantly prolonged in the meperidine group (p = 0.001). Significant decrease in the mean arterial blood pressure in fentanyl group was at 15, 30, 45, 60 and 90 min (p = 0.035, 0.019, 0.027, 0.032 and 0.039) respectively, significant decrease in meperdine group was at 15 and 30 min (p = 0.038 and 0.043), while in clonidine group a significant decrease was at 15, 30, 45, and 60 min (p = 0.025, 0.028, 0.036 and 0.042) respectively. Among group changes, the mean arterial blood pressure was significantly higher in meperdine group at 30, 45, 60 and 90 min (p = 0.007, 0.015, 0.029 and 0.033) respectively. A significant decrease in the heart rate in fentanyl group at 15, 30 and 45 min (p = 0.035, 0.018 and 0.029), in meperdine group a significant decrease in the heart rate was at 15 min (p = 0.038), while in clonidine group a significant decrease was at 15, and 30 min (p = 0.016 and 0.003) . Among group changes, the heart rate was significantly higher in meperdine group at 30, 45 and 60 min (p = 0.021, 0.017 and 0.011). VAS were significantly lower in meperdine group in comparison to fentanyl and clonidine groups at 2 h, 3 h and 4 h post-operative period (p = 0.024, 0.001 and 0.039).

CONCLUSION

The combined administration of epidural clonidine and meperidine provided better intraoperative hemodynamics and prolonged postoperative analgesia than epidural clonidine fentanyl combination in patients undergoing lower limb orthopedic surgery.

TRIAL REGISTRATION

Clinical Trail Registry (Clinicaltrail.gov) NCT 02128451 .

WITHDRAWN: Perioperative ketamine for acute postoperative pain

This review has been amended to include further information on Menigaux 2000 pre pre and Menigaux 2000 post included studies.

At July 2014, this review is out of date and has been withdrawn. This review is correct as of the date of publication. The latest version is available in the ‘Other versions’ tab on The Cochrane Library, and may still be useful to readers.

The editorial group responsible for this previously published document have withdrawn it from publication.

Pain relief following Arthroscopy - a comparative study of Intra-articular Bupivacaine, Morphine and Neostigmine

Pain after arthroscopy is quite distressing. Intra-articular bupivacaine produces transient analgesia and reports of analgesia using intra-articular opioids have produced conflicting results. Recently, spinal administration of neostigmine was shown to produce dose-dependant analgesia. However, this was limited by adverse effects. The purpose of this study was to compare the effects on intra-articular neostigmine, bupivacaine and morphine. 75 patients were randomized to receive intra-articular saline, bupivacaine, morphine, neostigmine and bupivacaine-neostigmine after arthroscopic surgery under spinal anaesthesia. Visual analog pain scores (VAS), duration of analgesia as defined as time for first demand for parenteral opioids and the total subsequent consumption of morphine was evaluated. Intra-articular bupivacaine resulted in significant VAS reduction at one and four hours as compared to those receiving intra-articular saline and morphine. Analgesia lasted longer after 500ugm intra-articular neostigmine as compared with bupivacaine, morphine or saline. The need for supplementary analgesia was lowest in the neostigmine group as compared to the other groups. No significant difference was found if bupivacaine was added to neostigmine. Among all the groups, no significant side-effects were observed.

Ketamine has no effect on bispectral index during stable propofol-remifentanil anaesthesia

BACKGROUND

Ketamine 0.15-1 mg kg(-1) decreases postoperative morphine consumption, but 0.5 mg kg(-1) is associated with an increase in the bispectral index (BIS) values that can lead to an overdose of hypnotic agents. The purpose of our investigation was to study the effect of ketamine 0.2 mg kg(-1) administered over a 5 min period on the BIS during stable target-controlled infusion (TCI) propofol-remifentanil general anaesthesia.

METHODS

Thirty ASA I or II patients undergoing abdominal laparoscopic surgery were included in this double-blind, randomized study. Anaesthesia was induced and maintained with a TCI of propofol and remifentanil. After 5 min of steady-state anaesthesia (BIS at 40) without surgical stimulation, patients received either an infusion of ketamine 0.2 mg kg(-1) or normal saline. The test drug was infused over 5 min. Standard parameters and BIS values were recorded every minute until 15 min post-infusion.

RESULTS

The baseline mean (sd) value for the BIS was 37 (6.5) for the ketamine group and 39 (8.2) for the placebo group. The highest mean BIS value during the recording period was 41.5 (8.7) for the ketamine group and 40.1 (8.9) for the placebo group. BIS values were not statistically different between the groups (P=0.62); there was no significant change over time (P=0.65) with no group-time interaction (P=0.55).

CONCLUSIONS

Under stable propofol and remifentanil TCI anaesthesia, a slow bolus infusion of ketamine 0.2 mg kg(-1) administered over a 5 min period did not increase the BIS value over the next 15 min.

The Effect of Intravenous Administration of Dexamethasone on Postoperative Pain, Nausea, and Vomiting After Intrathecal Injection of Meperidine

BACKGROUND

Different drugs have been used to enhance postoperative neuraxial opioid analgesia and reduce adverse effects.

METHODS

We randomized 60 patients into 2 groups to receive either 2 mL saline or 0.1 mg/kg dexamethasone IV before the administration of intrathecal anesthesia (15 mg and meperidine 15 mg). After surgery, patients were asked to score their pain at 6, 12, 18, and 24 h. The presence of postoperative nausea and vomiting (PONV), pruritus and respiratory depression were recorded.

RESULTS

The total dose of diclofenac (P < 0.05), visual analog scale pain score at 6-h intervals (P < 0.001), and the incidence of PONV (P < 0.05) were significantly lower in the dexamethasone group.

CONCLUSIONS

Administration of IV dexamethasone prior to intrathecal meperidine injection enhances analgesia and reduces PONV.

Use of neostigmine in the management of acute postoperative pain and labour pain: a review

Neostigmine is a parasympathomimetic agent that has been recently investigated for use as an adjunct analgesic agent in the perioperative and peripartum period. A number of studies have investigated the intrathecal, epidural, caudal and intra-articular routes of administration of this agent, as well as the addition of neostigmine to local anaesthetics used for brachial plexus block and intravenous regional anaesthesia. While the intrathecal administration of neostigmine produced useful analgesic effects in the postoperative period in some studies, the high incidence of adverse events, mainly nausea and vomiting, limit the clinical usefulness of this route of administration. Several studies investigated the postoperative analgesic effects of epidural neostigmine using a number of different regimens. Overall, this route of administration appeared to improve postoperative analgesia in most studies without increasing the incidence of adverse events, and merits further research. Neuraxial administration of neostigmine appears to be safe in the obstetric population, with no reported adverse effects in the mother or fetus. While intrathecal administration is limited by a high incidence of nausea and vomiting in this patient population, the epidural route appears more promising and requires further investigation. The addition of neostigmine to caudal local anaesthetics was associated with improved postoperative analgesia in a number of studies. A dose of 2 microg/kg proved to be effective in several studies but was associated with an increased incidence of vomiting in some studies. Intra-articular administration of neostigmine 500microg produced a useful analgesic effect in the postoperative period in several studies and was not associated with an increase in the incidence of adverse effects. Studies investigating the efficacy of adding neostigmine to the local anaesthetics used for brachial plexus block and intravenous regional anaesthesia reported conflicting results. Further studies are required to determine the place of the administration of neostigmine by these routes.

Perioperative ketamine for acute postoperative pain

BACKGROUND

Postoperative pain management is often limited by adverse effects such as nausea and vomiting. Adjuvant treatment with an inexpensive opioid-sparing drug such as ketamine may be of value in giving better analgesia with fewer adverse effects.

OBJECTIVES

To evaluate the effectiveness and tolerability of ketamine administered perioperatively in the treatment of acute postoperative pain in adults.

SEARCH STRATEGY

Studies were identified from MEDLINE (1966-2004), EMBASE (1980-2004), the Cochrane Library (2004) and by handsearching reference lists from review articles and trials. The manufacturer of ketamine (Pfizer) provided search results from their in-house database, PARDLARS.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of adult patients undergoing surgery, being treated with perioperative ketamine or placebo. Studies where ketamine was administered in addition to a basic analgesic (such as morphine or NSAID) in one study group, and compared with a group receiving the same basic analgesic (but without ketamine) in another group, were also included.

DATA COLLECTION AND ANALYSIS

Two independent reviewers identified fifty five RCTs for potential inclusion. Quality and validity assessment was performed by two independent reviewers. In the case of discrepancy, a third reviewer was consulted. Patient reported pain intensity and pain relief was assessed using visual analogue scales or verbal rating scales and adverse effects data were collated.

MAIN RESULTS

Thirty-seven trials were included (2240 participants). Eighteen trials were excluded.Twenty-seven of the 37 trials found that perioperative subanaesthetic doses of ketamine reduced rescue analgesic requirements or pain intensity, or both. Quantitative analysis showed that treatment with ketamine reduced 24 hour PCA morphine consumption and postoperative nausea or vomiting (PONV). Adverse effects were mild or absent.

AUTHORS' CONCLUSIONS

Ketamine in subanaesthetic dose (that is a dose which is below that required to produce anaesthesia) is effective in reducing morphine requirements in the first 24 hours after surgery. Ketamine also reduces postoperative nausea and vomiting. Adverse effects are mild or absent.

Kétamine à faibles doses : antihyperalgésique, non analgésique

Recent data in animal experiments as in clinical trials have clearly reported that pain modulation is related to an equilibrium between antinociceptive and pronociceptive systems. Therefore, the apparent pain level could not only be a consequence of a nociceptive input increase but could also result from a pain sensitization process. Glutamate, via NMDA receptors, plays a major role in the development of such a neuronal plasticity in the central nervous system, leading to a pain hypersensitivity that could facilitate chronic pain development. By an action on NMDA receptors opioids also induce, in a dose dependent manner, an enhancement of this postoperative hypersensitivity. "Antihyperalgesic" doses of ketamine, an NMDA receptor antagonist, were able to decrease this central sensitization not only in painful animal but also in human volunteers exposed to different pain models, or in the postoperative period. Many studies have reported that ketamine effects are elicited when this drug is administered the following manner: peroperative bolus (0.1 to 0.5 mg/kg), followed by a constant infusion rate (1 to 2 microg/kg per min) during the peroperative period and for 48 to 72 hours after anaesthesia. Those ketamine doses improved postoperative pain management by reducing hyperalgesia due to both surgical trauma and high peroperative opioid doses. This antihyperalgesic action of ketamine also limited the postoperative morphine tolerance leading to a decrease in analgesic consumption and an increase in the analgesia quality.

Role of Analgesic Adjuncts in Postoperative Pain Management

Postoperative pain remains a major problem. A multi-modal analgesic approach is recommended to optimize pain management and reduce opiate-related adverse effects. Several analgesic adjuncts have been investigated, and many have proved to have a useful analgesic effect. This article reviews the literature regarding use of analgesic adjuncts in the perioperative period.

Safety and efficacy of intranasal ketamine for the treatment of breakthrough pain in patients with chronic pain: a randomized, double-blind, placebo-controlled, crossover study

Few placebo-controlled trials have investigated the treatment of breakthrough pain (BTP) in patients with chronic pain. We evaluated the efficacy and safety of intranasal ketamine for BTP in a randomized, double-blind, placebo-controlled, crossover trial. Twenty patients with chronic pain and at least two spontaneous BTP episodes daily self-administered up to five doses of intranasal ketamine or placebo at the onset of a spontaneous BTP episode (pain intensity > or =5 on a 0-10 scale). Two BTP episodes at least 48 h apart were treated with either ketamine or placebo. Patients reported significantly lower BTP intensity following intranasal ketamine than after placebo (P < 0.0001) with pain relief within 10 min of dosing and lasting for up to 60 min. No patient in the ketamine group required his/her usual rescue medication to treat the BTP episode, while seven out of 20 (35%) patients in placebo group did (P = 0.0135). Intranasal ketamine was well tolerated with no serious adverse events. After ketamine administration, four patients reported a transient change in taste, one patient reported rhinorrhea, one patient reported nasal passage irritation, and two patients experienced transient elevation in blood pressure. A side effect questionnaire administered 60 min and 24 h after drug or placebo administration elicited no reports of auditory or visual hallucinations. These data suggest that intranasal administration of ketamine provides rapid, safe and effective relief for BTP.

A Qualitative Systematic Review of the Role of N-Methyl-d-Aspartate Receptor Antagonists in Preventive Analgesia

We evaluated in a qualitative systematic review the effect of N-methyl-D-aspartate (NMDA) receptor antagonists on reducing postoperative pain and analgesic consumption beyond the clinical duration of action of the target drug (preventive analgesia). Randomized trials examining the use of an NMDA antagonist in the perioperative period were sought by using a MEDLINE (1966-2003) and EMBASE (1985-2003) search. Reference sections of relevant articles were reviewed, and additional articles were obtained if they evaluated postoperative analgesia after the administration of NMDA antagonists. The primary outcome was a reduction in pain, analgesic consumption, or both in a time period beyond five half-lives of the drug under examination. Secondary outcomes included time to first analgesic request and adverse effects. Forty articles met the inclusion criteria (24 ketamine, 12 dextromethorphan, and 4 magnesium). The evidence in favor of preventive analgesia was strongest in the case of dextromethorphan and ketamine, with 67% and 58%, respectively, of studies demonstrating a reduction in pain, analgesic consumption, or both beyond the clinical duration of action of the drug concerned. None of the four studies examining magnesium demonstrated preventive analgesia.

IMPLICATIONS

We evaluated, in a qualitative systematic review, the effect of N-methyl D-aspartate antagonists on reducing postoperative pain and analgesic consumption beyond the clinical duration of action of the target drug (preventive analgesia). Dextromethorphan and ketamine were found to have significant immediate and preventive analgesic benefit in 67% and 58% of studies, respectively.

Potentiation by ketamine of fentanyl antinociception. I. An experimental study in rats showing that ketamine administered by non-spinal routes targets spinal cord antinociceptive systems

BACKGROUND

Ketamine has been found to exert antinociceptive effects in animals and to be analgesic at subanaesthetic doses in humans. This study was designed to investigate the involvement of spinal cord mechanisms in the potentiation of opioid analgesia by parenteral non-spinal administration of ketamine.

METHODS

Thresholds for nociception were measured in an acute pain model in rats that allowed identification of antinociceptive effects due to drug action in the spinal cord. Dose-response curves for the antinociceptive effects of ketamine alone and ketamine in conjunction with the mu opioid fentanyl were constructed.

RESULTS

Intraperitoneal ketamine up to 3.75 mg kg(-1) caused no sedative or antinociceptive effects and intrathecal ketamine caused dose-dependent, spinally mediated antinociceptive effects. Injections of ketamine doses that caused no antinociceptive effects when given alone (intrathecal 25 microg and intraperitoneal 3.75 mg/kg) significantly increased spinally mediated antinociception produced by intrathecal fentanyl injections when assessed using noxious heat (tail-flick test) but not when assessed by noxious electrical current (electrical current threshold test).

CONCLUSIONS

We conclude that ketamine can potentiate the effects of fentanyl by an interaction at the level of the spinal cord even when ketamine is given via a non-spinal route of administration.

The stability of a ketamine-morphine solution

Recent advances in acute pain mechanisms and management have implicated the N-methyl D-aspartate receptor-ion channel complex in the development of postoperative hyperalgesia and acute opioid tolerance. N-methyl D-aspartate receptor antagonists such as ketamine have been used increasingly in clinical studies in an effort to minimize acute postoperative pain and reduce opioid requirements. A mixture of ketamine and an opioid administered in the same solution and syringe would be a practical and useful technique for postoperative epidural analgesia, continuous IV infusion, or patient-controlled IV analgesia. We investigated the stability of a morphine sulfate and racemic ketamine solution in saline at pH 5.5-7.5 over a period of 4 days. Our study demonstrates that the ketamine-morphine mixture at a clinically relevant concentration seems to be stable at room temperature, at a wide range of pH values, for at least 4 days.

IMPLICATIONS

Small-dose ketamine is used with increasing frequency in the acute postoperative setting as an adjunct to traditional opioid analgesics. We show that a racemic ketamine and morphine solution at a clinically relevant concentration seems to be stable at room temperature at a wide range of pH values for at least 4 days.

The effect of dexamethasone on postoperative pain and emesis after intrathecal neostigmine

We evaluated the effect of a single dose of dexamethasone on the incidence and severity of postoperative nausea and vomiting (PONV) after intrathecal injection of tetracaine plus neostigmine. Sixty ASA physical status I patients scheduled for inguinal herniorrhaphy were studied with a randomized, double-blinded, placebo-controlled protocol. The dexamethasone group (Group D) received 10 mg of dexamethasone IV before performance of spinal anesthesia, whereas the placebo group (Group P) received saline. Spinal anesthesia was performed with intrathecal injection of 15 mg tetracaine plus neostigmine 100 microg in both groups. Pain, PONV, and other side effects were evaluated 24 h after surgery. The duration and severity of analgesia and the incidence of PONV were not significantly different between the two groups. Our results demonstrate that a single dose of dexamethasone (10 mg) did not potentiate the analgesic effect or reduce the incidence of PONV after intrathecal injection of tetracaine and neostigmine.

IMPLICATIONS

The results of our evaluation of the effect of IV dexamethasone versus saline control on analgesia and nausea and vomiting after intrathecal neostigmine and tetracaine suggest that IV dexamethasone did not enhance the analgesic effect of neostigmine or reduce the incidence of emesis after intrathecal administration.

Comparison of postoperative analgesic effects of preemptively used epidural ketamine and neostigmine

STUDY OBJECTIVE

To compare the analgesic and side effects of preemptively used epidural ketamine +bupivacaine, neostigmine +bupivacaine, and bupivacaine alone on postoperative analgesia after major abdominal surgery.

DESIGN

Randomized, controlled study.

SETTING

Inpatient anesthesia at the department of surgery of a metropolitan hospital.

PATIENTS

30 ASA physical status I, II, and III patients scheduled for abdominal surgery.

INTERVENTIONS

Group K received 1 mL (50 mg) ketamine and 5 mL (25 mg) bupivacaine epidurally, Group N received 1 mL (0.5 mg) neostigmine and 5 mL (25 mg) bupivacaine epidurally, and Group B received 1 mL saline and 5 mL (25 mg) bupivacaine epidurally 30 minutes before operation. All patients underwent anesthesia induction with thiopental and vecuronium; anesthesia was maintained with isoflorane and vecuronium. For postoperative analgesia, all patients received epidural morphine for 48 hours postoperatively.

MEASUREMENTS AND MAIN RESULTS

Standard monitoring included: 48 hours of analgesic requirement, visual analog scale (VAS), mean arterial pressure (MAP), and heart rate (HR) in the 1st, 2nd, 6th, 12th, 24th, and 48th hours. Data were analyzed using Kruskall-Wallis and Mann Whitney U tests, with a p < 0.05 considered statistically significant. No significant differences were observed regarding MAP and HR among the groups during the study period. In Group N, VAS was significantly lower than Group K and Group B. The total opioid consumption in Group N was significantly lower than in Groups K and B in the first 48 hours after the operation.

CONCLUSIONS

Preemptive neostigmine can be a good choice for postoperative analgesia.

Patient anxiety scores after low-dose ketamine or fentanyl for epidural catheter placement

PURPOSE

To compare the effect of low-dose ketamine with that of low-dose fentanyl on patient anxiety during the identification of the epidural space and catheterization.

METHODS

Sixty patients were randomly assigned to one of three groups: saline group (n=20), saline 2 ml; ketamine group (n=20), 5 mg ketamine; or fentanyl group (n=20), 50 microg fentanyl. Each drug was administered intravenously (iv) five to ten minutes before the epidural procedures began. After epidural catheter placement had been accomplished, anxiety and pain were rated using a visual analog scale.

RESULTS

The anxiety scores given for ketamine(20.2 +/- 18.5, mean +/- SD) and fentanyl (24.6 +/- 20.3) were similar, and both were lower than that for saline (44.1 +/- 32.7) (P=0.0034 and 0.0153 vs saline group, respectively). Pain scores were similar for all three groups. A decrease in hemoglobin oxygen saturation during the procedure was only observed in the fentanyl group, and two patients in fentanyl group had SpO2 <90%.

CONCLUSION

Ketamine, 5 mg iv, is as effective as 50 microg fentanyl, iv, in alleviating patient anxiety and in providing adequate sedation during the procedures necessary for epidural catheter placement, without inducing severe complications.

New developments in epidural anesthesia and analgesia

Several recent advances in epidural anesthesia and analgesia have been reviewed. Perhaps the most exciting area of anticipated future developments relates to the continued development of novel analgesic agents and new epidural delivery systems. There appears to be some movement toward an increased use of intrathecal or peripheral neural blockade techniques for some clinical situations where epidural anesthesia and analgesia have been previously used; however, the ability to provide anesthesia and analgesia to relatively large areas of the body with a single injection or continuous catheter technique without the associated risks of dural puncture and intrathecal catheter placement will continue to assure epidural anesthesia and analgesia techniques a prominent role in anesthesia and pain management.

Use and efficacy of low-dose ketamine in the management of acute postoperative pain: a review of current techniques and outcomes

Ketamine hydrochloride is a well known general anesthetic and short acting analgesic in use for almost 3 decades. The role of the NMDA receptor in the processing of nociceptive input has led naturally to renewed clinical interest in N-methyl-D-aspartate (NMDA) receptor antagonists such as ketamine. This paper reviews the use and efficacy of low-dose ketamine in the management of acute postoperative pain. The literature was obtained from a computer search of the MEDLINE database from 1966 through December 1998. Studies were included for review if they were randomized, prospective, controlled, double-blind and reported pain scores. We evaluate the clinical literature and discuss the efficacy of low-dose ketamine in the management of acute postoperative pain when administered alone or in conjunction with other agents via the oral, intramuscular, subcutaneous, intravenous and intraspinal routes. Low-dose ketamine is defined as a bolus dose of less than 2 mg/g when given intramuscularly or less than 1 mg/kg when administered via the intravenous or epidural route. For continuous i.v. administration low-dose ketamine is defined as a rate of < or =20 microg/kg per min. We conclude that ketamine may provide clinicians with a tool to improve postoperative pain management and to reduce opioid related adverse effects. The evidence suggests that low-dose ketamine may play an important role in postoperative pain management when used as an adjunct to local anesthetics, opioids, or other analgesic agents. Further research is required in the following areas: (a) dose-finding studies for ketamine as an adjunct to opioids and local anesthetics (b) efficacy and optimal route of administration (c) the role of S(+)-ketamine; (d) the influence of ketamine on long-term outcome such as chronic pain (e) long-term physical and chemical stability of mixtures containing ketamine (f) spinal toxicity of ketamine and (g) effects of low-dose ketamine on cognitive and memory functioning after surgery.

The efficacy of intrathecal neostigmine, intrathecal morphine, and their combination for post-cesarean section analgesia

We designed this study to evaluate the postoperative analgesic efficacy and safety of intrathecal (i.t.) neostigmine, i.t. morphine, and their combination in patients undergoing cesarean section under spinal anesthesia. Seventy-nine term parturients were randomly divided into four groups to receive isotonic sodium chloride solution 0.2 mL, neostigmine 25 microg, morphine 100 microg, or the combination of i.t. neostigmine 12.5 microg and morphine 50 microg with i.t. 0.5% hyperbaric bupivacaine 12 mg. There were no significant differences among the four groups with regard to spinal anesthesia, maternal blood pressure and heart rate, or fetal status. Postoperative analgesia was provided by i.v. patient-controlled analgesia (PCA) using fentanyl and ketorolac. Compared with the saline group, the time to first PCA use was significantly longer in the neostigmine group (P < 0.001), with lower 24-h analgesic consumption (P < 0.001). Nausea and vomiting were the most common side effects of i.t. neostigmine (73.7%). Analgesic effectiveness was similar between the neostigmine and morphine groups. Compared with the neostigmine group, the combination group had significantly prolonged analgesic effect and reduced 24-h PCA consumption (P < 0.05) with less severity of nausea and vomiting (P = 0.058). Compared with the morphine group, the combination group tended to have prolonged times to first PCA use (P = 0.054) with a lower incidence of pruritus (P < 0.03).

IMPLICATIONS

Intrathecal (i.t.) neostigmine 25 microg produced postoperative analgesia for cesarean section similar to that of i.t. morphine 100 microg, but with a high incidence of nausea and vomiting. The combination of i.t. neostigmine 12.5 microg and i.t. morphine 50 microg may produce better postoperative analgesia with fewer side effects than i.t. neostigmine 25 microg or i.t. morphine 100 microg alone.

Cholinesterase inhibitors induce growth cone collapse and inhibit neurite extension in primary cultured chick neurons

Cholinesterase inhibitors are commonly prescribed medicines in neurological and anesthesiological clinical practices at relatively high doses. Recent studies report that cholinesterases, originally described as neurotransmitter degradation enzymes, are expressed in the developing central nervous systems. They are hypothesized to play an important role during the establishment of neuronal cytoarchitecture. In this study, the effects of several clinically utilized cholinesterase inhibitors on one potential aspect of neuronal development were examined using a primary culture system of chick central and peripheral neurons. Three cholinesterase inhibitors, physostigmine, neostigmine, and edrophonium, suppressed the activity of the leading edges of the extending axons (the nerve growth cones) dose dependently. Filopoda and lamellipodia of nerve growth cones were collapsed by the exposure to the cholinesterase inhibitors. This action was quick, mostly within 5 min, and partly irreversible. The lowest concentration that could induce statistically significant growth cone collapse was 10(-5) M for physostigmine, 10(-4) M for neostigmine, and 10(-2) for edrophonium, respectively. The ED50 values for the growth cone collapsing activity were approximately, 10(-3) M for physostigmine. 10(-2.5) M for neostigmine, and 10(-2) M for edrophonium both in dorsal root ganglion culture and in retinal culture. Even though the result of this in vitro study cannot be applied directly to the in vivo situation, physicians should consider the potential detrimental effects of cholinesterase inhibitors to growing and regenerating nervous tissues.

Phase I human safety assessment of intrathecal neostigmine containing methyl- and propylparabens

Intrathecal (i.t.) neostigmine produces analgesia in humans with acute experimental, postoperative, and chronic pain. The sole manufacturer of the preservative-free neostigmine solution used in the initial clinical studies no longer markets this preparation. Although solutions containing preservatives are generally avoided for i.t. injection, methyl- and propylparabens have not been demonstrated to be toxic. After preclinical toxicity screening in animals and Food and Drug Administration approval, 12 volunteers received i.t. neostigmine 10, 30, or 100 micrograms, containing these preservatives and glucose. This preparation produced dose-dependent analgesia, nausea, weakness, and sedation similar to the preservative-free preparation. I.t. neostigmine increased acetylcholine but not norepinephrine concentrations in cerebrospinal fluid. Although nitric oxide synthesis has been implicated in analgesia from i.t. neostigmine injection in animals, cerebrospinal fluid concentrations of nitrite as a measure of nitric oxide were not increased by i.t. neostigmine in these volunteers. These data support the investigational application of i.t. neostigmine containing methyl- and propylparabens in the concentrations studied.

IMPLICATIONS

Because intrathecal injection of neostigmine may be a useful analgesic, we performed a Phase I tolerability and safety study of the commercially available neostigmine formulation in human volunteers and found no evidence of toxicity. These data are important to the clinical use of this new therapy.