Lack of pre-emptive analgesic effect of (R)-ketamine in laparoscopic cholecystectomy

Ketamine, benzoate, and sarcosine for treating depression

Studies have demonstrated the beneficial therapeutic effects of sarcosine, benzoate, and ketamine (including esketamine and arketamine) on depression. These drugs mainly act by modulating N-methyl-d-aspartate glutamate receptors (NMDARs) and reducing inflammation in the brain. Although ketamine, benzoate, and sarcosine act differently as the antagonists or coagonists of NMDARs, they all have demonstrated efficacy in animal models or human trials. In vitro and in vivo studies have indicated that sarcosine, benzoate, and ketamine exert their anti-inflammatory effects by inhibiting microglial activity. This review summarizes and compares the efficacy of the possible therapeutic mechanisms of sarcosine, benzoate, ketamine, esketamine, and arketamine. These compounds act as both NMDAR modulators and anti-inflammatory drugs and thus can be effective in the treatment of depression.

Perioperative intravenous ketamine for acute postoperative pain in adults

BACKGROUND

Inadequate pain management after surgery increases the risk of postoperative complications and may predispose for chronic postsurgical pain. Perioperative ketamine may enhance conventional analgesics in the acute postoperative setting.

OBJECTIVES

To evaluate the efficacy and safety of perioperative intravenous ketamine in adult patients when used for the treatment or prevention of acute pain following general anaesthesia.

SEARCH METHODS

We searched CENTRAL, MEDLINE and Embase to July 2018 and three trials registers (metaRegister of controlled trials, ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP)) together with reference checking, citation searching and contact with study authors to identify additional studies.

SELECTION CRITERIA

We sought randomised, double-blind, controlled trials of adults undergoing surgery under general anaesthesia and being treated with perioperative intravenous ketamine. Studies compared ketamine with placebo, or compared ketamine plus a basic analgesic, such as morphine or non-steroidal anti-inflammatory drug (NSAID), with a basic analgesic alone.

DATA COLLECTION AND ANALYSIS

Two review authors searched for studies, extracted efficacy and adverse event data, examined issues of study quality and potential bias, and performed analyses. Primary outcomes were opioid consumption and pain intensity at rest and during movement at 24 and 48 hours postoperatively. Secondary outcomes were time to first analgesic request, assessment of postoperative hyperalgesia, central nervous system (CNS) adverse effects, and postoperative nausea and vomiting. We assessed the evidence using GRADE and created a 'Summary of findings' table.

MAIN RESULTS

We included 130 studies with 8341 participants. Ketamine was given to 4588 participants and 3753 participants served as controls. Types of surgery included ear, nose or throat surgery, wisdom tooth extraction, thoracotomy, lumbar fusion surgery, microdiscectomy, hip joint replacement surgery, knee joint replacement surgery, anterior cruciate ligament repair, knee arthroscopy, mastectomy, haemorrhoidectomy, abdominal surgery, radical prostatectomy, thyroid surgery, elective caesarean section, and laparoscopic surgery. Racemic ketamine bolus doses were predominantly 0.25 mg to 1 mg, and infusions 2 to 5 µg/kg/minute; 10 studies used only S-ketamine and one only R-ketamine. Risk of bias was generally low or uncertain, except for study size; most had fewer than 50 participants per treatment arm, resulting in high heterogeneity, as expected, for most analyses. We did not stratify the main analysis by type of surgery or any other factor, such as dose or timing of ketamine administration, and used a non-stratified analysis.Perioperative intravenous ketamine reduced postoperative opioid consumption over 24 hours by 8 mg morphine equivalents (95% CI 6 to 9; 19% from 42 mg consumed by participants given placebo, moderate-quality evidence; 65 studies, 4004 participants). Over 48 hours, opioid consumption was 13 mg lower (95% CI 10 to 15; 19% from 67 mg with placebo, moderate-quality evidence; 37 studies, 2449 participants).Perioperative intravenous ketamine reduced pain at rest at 24 hours by 5/100 mm on a visual analogue scale (95% CI 4 to 7; 19% lower from 26/100 mm with placebo, high-quality evidence; 82 studies, 5004 participants), and at 48 hours by 5/100 mm (95% CI 3 to 7; 22% lower from 23/100 mm, high-quality evidence; 49 studies, 2962 participants). Pain during movement was reduced at 24 hours (6/100 mm, 14% lower from 42/100 mm, moderate-quality evidence; 29 studies, 1806 participants), and 48 hours (6/100 mm, 16% lower from 37 mm, low-quality evidence; 23 studies, 1353 participants).Results for primary outcomes were consistent when analysed by pain at rest or on movement, operation type, and timing of administration, or sensitivity to study size and pain intensity. No analysis by dose was possible. There was no difference when nitrous oxide was used. We downgraded the quality of the evidence once if numbers of participants were large but small-study effects were present, or twice if numbers were small and small-study effects likely but testing not possible.Ketamine increased the time for the first postoperative analgesic request by 54 minutes (95% CI 37 to 71 minutes), from a mean of 39 minutes with placebo (moderate-quality evidence; 31 studies, 1678 participants). Ketamine reduced the area of postoperative hyperalgesia by 7 cm² (95% CI -11.9 to -2.2), compared with placebo (very low-quality evidence; 7 studies 333 participants). We downgraded the quality of evidence because of small-study effects or because the number of participants was below 400.CNS adverse events occurred in 52 studies, while 53 studies reported of absence of CNS adverse events. Overall, 187/3614 (5%) participants receiving ketamine and 122/2924 (4%) receiving control treatment experienced an adverse event (RR 1.2, 95% CI 0.95 to 1.4; high-quality evidence; 105 studies, 6538 participants). Ketamine reduced postoperative nausea and vomiting from 27% with placebo to 23% with ketamine (RR 0.88, 95% CI 0.81 to 0.96; the number needed to treat to prevent one episode of postoperative nausea and vomiting with perioperative intravenous ketamine administration was 24 (95% CI 16 to 54; high-quality evidence; 95 studies, 5965 participants).

AUTHORS' CONCLUSIONS

Perioperative intravenous ketamine probably reduces postoperative analgesic consumption and pain intensity. Results were consistent in different operation types or timing of ketamine administration, with larger and smaller studies, and by higher and lower pain intensity. CNS adverse events were little different with ketamine or control. Perioperative intravenous ketamine probably reduces postoperative nausea and vomiting by a small extent, of arguable clinical relevance.

Efficacy of Low-dose Ketamine as Sole Analgesic Agent in Maintaining Analgesia and Intraoperative Hemodynamics During Laparoscopic Gynecological Surgeries

BACKGROUND

Ketamine, in low doses, is known to possess intense analgesic properties. The available literature shows wide variation regarding the time and dose of administration of ketamine during surgery.

AIM

The aim of this study was to evaluate the effect of intraoperative administration of ketamine when used as sole analgesic in low doses, on hemodynamics and postoperative analgesia in patients undergoing laparoscopic gynecological surgery and compared on the basis of duration of surgery.

SETTINGS AND DESIGN

This prospective, observational study was conducted from July to December 2015, over a period of 6 months in a tertiary care medical college and hospital.

MATERIALS AND METHODS

Seventy patients between 23 and 55 years planned for laparoscopic gynecological surgery were recruited. Ketamine was given in a dose of 0.5 mg/kg preoperatively and then repeated every ½ hourly in a dose of 0.25 mg/kg throughout the surgery. Hemodynamic parameters, time to the first rescue analgesia and complications were recorded for the first 8 h. Statistical evaluation was done and result expressed as percentage. Paired t-test was employed for the comparison of numerical variables within the group.

RESULTS

Seventy percent of the patients did not require any postoperative rescue analgesia during the first 8 h after surgery. None of the patients complained of pain immediately after extubation, and 16% of the patients had minor postoperative complications. The intraoperative hemodynamic profile was significantly altered. Duration of surgery and dose of ketamine required did not affect the duration of analgesia.

CONCLUSION

Ketamine in low dose proved to be an efficacious analgesic even in the long duration laparoscopic gynecological surgeries. It stabilizes intraoperative hemodynamics thereby reducing the requirement of other anesthetic and antihypertensive agents.

Laparoscopic surgery: a narrative review of pharmacotherapy in pain management

Laparoscopic surgery is widespread, and an increasing number of surgeries are performed laparoscopically. Early pain after laparoscopy can be similar or even more severe than that after open surgery. Thus, proactive pain management should be provided. Pain after laparoscopic surgery is derived from multiple origins; therefore, a single agent is seldom sufficient. Pain is most effectively controlled by a multimodal, preventive analgesia approach, such as combining opioids with non-opioid analgesics and local anaesthetics. Wound and port site local anaesthetic injections decrease abdominal wall pain by 1-1.5 units on a 0-10 pain scale. Inflammatory pain and shoulder pain can be controlled by NSAIDs or corticosteroids. In some patient groups, adjuvant drugs, ketamine and α2-adrenergic agonists can be helpful, but evidence on gabapentinoids is conflicting. In the present review, the types of pain that need to be taken into account while planning pain management protocols and the wide range of analgesic options that have been assessed in laparoscopic surgery are critically assessed. Recommendations to the clinician will be made regarding how to manage acute pain and how to prevent persistent postoperative pain. It is important to identify patients at the highest risk for severe and prolonged post-operative pain, and to have a proactive strategy in place for these individuals.

Intravenous sub-anesthetic ketamine for perioperative analgesia

Ketamine, an N-methyl-d-aspartate antagonist, blunts central pain sensitization at sub-anesthetic doses (0.3 mg/kg or less) and has been studied extensively as an adjunct for perioperative analgesia. At sub-anesthetic doses, ketamine has a minimal physiologic impact though it is associated with a low incidence of mild psychomimetic symptoms as well as nystagmus and double vision. Contraindications to its use do exist and due to ketamine's metabolism, caution should be exercised in patients with renal or hepatic dysfunction. Sub-anesthetic ketamine improves pain scores and reduces perioperative opioid consumption in a broad range of surgical procedures. In addition, there is evidence that ketamine may be useful in patients with opioid tolerance and for preventing chronic postsurgical pain.

Effect of preinduction low-dose ketamine bolus on intra operative and immediate postoperative analgesia requirement in day care surgery: A randomized controlled trial

BACKGROUND

Availability of narcotics is an issue in developing countries, and low-dose ketamine offers an alternative to these drugs.

OBJECTIVE

The objective of this study is to evaluate the effect of a preemptive dose of low-dose ketamine on intra operative and the immediate postoperative analgesic requirements.

DESIGN

Randomized double-blind control trial.

SETTINGS

This study has been performed in the operating rooms and postanesthesia care unit at Aga Khan University Hospital, Karachi, Pakistan.

MATERIALS AND METHODS

Totally, 60 adult American Society of Anesthesiologists I and II patients undergoing day care surgery were randomly allocated into two groups, Group A (ketamine group) and Group B (saline group).

INTERVENTION

All patients underwent general anesthesia. Propofol 2 mg/kg was used as an induction agent; laryngeal mask airway (size 3 for females and 4 for males) was inserted. Following induction patients in Group A received ketamine 0.3 mg/kg and Group B saline bolus in a blinded manner. All patients were administered injection fentanyl 1 μg/kg as an analgesic and anesthesia was maintained with oxygen 40%, nitrous oxide 60% and isoflorane 1-2 minimum alveolar concentration. Patients breathed spontaneously on Lack circuit. Postoperatively rescue analgesia was provided with intravenous morphine 0.1 mg/kg when patient complained of pain.

MAIN OUTCOME MEASURES

We observed analgesic effects of low-dose ketamine intra operatively and narcotic requirements in immediate postoperative period for day care surgeries.

RESULTS

There was no significant difference in demographic data in between groups. Saline group required more rescue analgesia (morphine) postoperatively (P < 0.001). No significant psychotomimetic symptoms were noted in either group.

CONCLUSION

Low-dose ketamine 0.3 mg/kg provided adequate co-analgesia with fentanyl 1 μg/kg and was effective in a reduction of morphine requirement in the postoperative phase with minimal adverse effects.

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.

Preoperative low-dose ketamine has no preemptive analgesic effect in opioid-naïve patients undergoing colon surgery when nitrous oxide is used - a randomized study

BACKGROUND

The analgesic properties of ketamine are associated with its non-competitive antagonism of the N-methyl-D-aspartate receptor; these receptors exhibit an excitatory function on pain transmission and this binding seems to inhibit or reverse the central sensitization of pain. In the literature, the value of this anesthetic for preemptive analgesia in the control of postoperative pain is uncertain. The objective of this study was to ascertain whether preoperative low-dose ketamine reduces postoperative pain and morphine consumption in adults undergoing colon surgery.

METHODS

In a double-blind, randomized trial, 48 patients were studied. Patients in the ketamine group received 0.5 mg/kg intravenous ketamine before surgical incision, while the control group received normal saline. The postoperative analgesia was achieved with a continuous infusion of morphine at 0.015 mg∙kg-¹∙h-¹ with the possibility of 0.02 mg/kg bolus every 10 min. Pain was assessed using the Visual Analog Scale (VAS), morphine consumption, and hemodynamic parameters at 0, 1, 2, 4, 8, 12, 16, and 24 hours postoperatively. We quantified times to rescue analgesic (Paracetamol), adverse effects and patient satisfaction.

RESULTS

No significant differences were observed in VAS scores between groups (P>0.05), except at 4 hours postoperatively (P=0.040). There were no differences in cumulative consumption of morphine at any time point (P>0.05). We found no significant differences in incremental postoperative doses of morphine consumption in bolus, except at 12 h (P =0.013) and 24 h (P =0.002). The time to first required rescue analgesia was 70 ± 15.491 min in the ketamine group and 44 ± 19.494 min in the control (P>0.05). There were no differences in hemodynamic parameters or patient satisfaction (P>0.05).

CONCLUSIONS

Preoperative low-dose-ketamine did not show a preemptive analgesic effect or efficacy as an adjuvant for decreasing opioid requirements for postoperative pain in patients receiving intravenous analgesia with morphine after colon surgery.

Does intravenous ketamine enhance analgesia after arthroscopic shoulder surgery with ultrasound guided single-injection interscalene block?: a randomized, prospective, double-blind trial

Ketamine has anti-inflammatory, analgesic and antihyperalgesic effect and prevents pain associated with wind-up. We investigated whether low doses of ketamine infusion during general anesthesia combined with single-shot interscalene nerve block (SSISB) would potentiate analgesic effect of SSISB. Forty adult patients scheduled for elective arthroscopic shoulder surgery were enrolled and randomized to either the control group or the ketamine group. All patients underwent SSISB and followed by general anesthesia. During an operation, intravenous ketamine was infused to the patients of ketamine group continuously. In control group, patients received normal saline in volumes equivalent to ketamine infusions. Pain score by numeric rating scale was similar between groups at 1, 6, 12, 24, 36, and 48 hr following surgery, which was maintained lower than 3 in both groups. The time to first analgesic request after admission on post-anesthesia care unit was also not significantly different between groups. Intraoperative low dose ketamine did not decrease acute postoperative pain after arthroscopic shoulder surgery with a preincisional ultrasound guided SSISB. The preventive analgesic effect of ketamine could be mitigated by SSISB, which remains one of the most effective methods of pain relief after arthroscopic shoulder surgery.

Anaesthetic regimens for day-procedure laparoscopic cholecystectomy

BACKGROUND

Day surgery involves admission of selected patients to hospital for a planned surgical procedure with the patients returning home on the same day. An anaesthetic regimen usually involves a combination of an anxiolytic, an induction agent, a maintenance agent, a method of maintaining the airway (laryngeal mask versus endotracheal intubation), and a muscle relaxant. The effect of anaesthesia may continue after the completion of surgery and can delay discharge. Various regimens of anaesthesia have been suggested for day-procedure laparoscopic cholecystectomy.

OBJECTIVES

To compare the benefits and harms of different anaesthetic regimens (risks of mortality and morbidity, measures of recovery after surgery) in patients undergoing day-procedure laparoscopic cholecystectomy.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (Issue 10, 2013), MEDLINE (PubMed) (1987 to November 2013), EMBASE (OvidSP) (1987 to November 2013), Science Citation Index Expanded (ISI Web of Knowledge) (1987 to November 2013), LILACS (Virtual Health Library) (1987 to November 2013), metaRegister of Controlled Trials (http://www.controlled-trials.com/mrct/) (November 2013), World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) portal (November 2013), and ClinicalTrials.gov (November 2013).

SELECTION CRITERIA

We included randomized clinical trials comparing different anaesthetic regimens during elective day-procedure laparoscopic cholecystectomy (irrespective of language or publication status).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trials for inclusion and independently extracted the data. We calculated the risk ratio, rate ratio or mean difference with 95% confidence intervals based on intention-to-treat or available data analysis.

MAIN RESULTS

We included 11 trials involving 1069 participants at low anaesthetic risk. The sample size varied from 40 to 300 participants. We included 23 comparisons. All trials were at a high risk of bias. We were unable to perform a meta-analysis because there were no two trials involving the same comparison. Primary outcomes included perioperative mortality, serious morbidity and proportion of patients who were discharged on the same day. There were no perioperative deaths or serious adverse events in either group in the only trial that reported this information (0/60). There was no clear evidence of a difference in the proportion of patients who were discharged on the same day between any of the comparisons. Overall, 472/554 patients (85%) included in this review were discharged as day-procedure laparoscopic cholecystectomy patients. Secondary outcomes included hospital readmissions, health-related quality of life, pain, return to activity and return to work. There was no clear evidence of a difference in hospital readmissions within 30 days in the only comparison in which this outcome was reported. One readmission was reported in the 60 patients (2%) in whom this outcome was assessed. Quality of life was not reported in any of the trials. There was no clear evidence of a difference in the pain intensity, measured by a visual analogue scale, between comparators in the only trial which reported the pain intensity at between four and eight hours after surgery. Times to return to activity and return to work were not reported in any of the trials.

AUTHORS' CONCLUSIONS

There is currently insufficient evidence to conclude that one anaesthetic regimen for day-procedure laparoscopic cholecystectomy is to be preferred over another. However, the data are sparse (that is, there were few trials under each comparison and the trials had few participants) and further well designed randomized trials at low risk of bias and which are powered to measure differences in clinically important outcomes are necessary to determine the optimal anaesthetic regimen for day-procedure laparoscopic cholecystectomy, one of the commonest procedures performed in the western world.

Preemptive use of diclofenac in combination with ketamine in patients undergoing laparoscopic cholecystectomy: a randomized, double-blind, placebo-controlled study

BACKGROUND

To examine the combined preemptive effects of low-dose ketamine, diclofenac, and their combination on postoperative pain in patients undergoing laparoscopic cholecystectomy.

METHODS

A total of 80 consecutive patients, American Society of Anesthesiologists physical status I or II, were recruited to the study. Patients were randomized to one of the following groups: group 1 received 100-mL isotonic saline intravenously (i.v.) 20 minutes before the induction of anesthesia and 5-mL isotonic saline i.v. before skin incision as a placebo; group 2 received 100-mL isotonic saline i.v. 20 minutes before the induction of anesthesia and 0.15-mg/kg ketamine diluted in 5-mL isotonic saline i.v. before skin incision; group 3 received diclofenac 1 mg/kg diluted in 100-mL isotonic saline i.v. 20 minutes before the induction of anesthesia and 5-mL isotonic saline i.v. before skin incision; and group 4 received a combination of the same diclofenac sodium and ketamine doses at the same time. Abdominal and shoulder pain intensity was assessed using the visual analog scale and verbal rating scale during 24 hours postoperatively.

RESULTS

Patients receiving diclofenac had a significantly lower pain score between 2 and 6 hours after surgery compared with patients receiving placebo. One hour after surgery, patients receiving a combination of diclofenac and ketamine had a significantly lower pain score compared with patients receiving placebo and ketamine alone. Patients from all the 4 study groups required postoperative analgesic; however, the time to diclofenac sodium request was longer in patients receiving a combination of diclofenac and ketamine compared with patients receiving placebo (p<0.001), ketamine (p<0.001), or diclofenac (p=0.03) alone.

CONCLUSIONS

The preemptive administration of a combination of low-dose ketamine plus diclofenac sodium improved postoperative analgesia after laparoscopic cholecystectomy, whereas ketamine at a dose of 0.15 mg/kg did not elicit a preemptive analgesic effect.

Peri-operative ketamine with the ambulatory elastometric infusion pump as an adjuvant to manage acute postoperative pain after spinal fusion in adults: a prospective randomized trial

Background

In this study, we assessed the effectiveness of ketamine as an alternative to non-steroidal anti-inflammatory drugs (NSAID), to manage acute postoperative pain after spinal fusion when given intravenously via a patient-controlled analgesia (PCA) pump in which the dose was proportional to that of fentanyl.

Methods

Forty patients undergoing 1-2 level spinal fusion were enrolled in this study. Patients were intraoperatively randomized into two groups to receive intravenous PCA consisting either of fentanyl 0.4 µg/ml/kg (control group) or fentanyl 0.4 µg/ml/kg with ketamine 30 µg/ml/kg (ketamine group) after intravenous injection of a loading dose. The loading dose in the control group was fentanyl 1 µg/kg with normal saline equal to ketamine volume and in the ketamine group it was fentanyl 1 µg/kg with ketamine 0.2 mg/kg. The verbal numerical rating scale (NRS), fentanyl and ketamine infusion rate, and side effects were evaluated at 1, 24, and 48 hours after surgery.

Results

There were no significant differences in patient demographics, duration of surgery and anesthesia or intra-operative opioids administration. We did not find any significant differences in the mean infusion rate of intraoperative remifentanil or postoperative fentanyl or in the side effects between the groups, but we did find a significant difference in the NRS between the groups.

Conclusions

Based on our results, we conclude that a small dose of ketamine (0.5-2.5 µg/kg/min) proportional to fentanyl is not only safe, but also lowers postoperative pain intensity in patients undergoing spinal fusion, although the opioid-sparing effects of ketamine were not demonstrated.

Opioid-free single-incision laparoscopic (SIL) cholecystectomy using bilateral TAP blocks

A 30 year old woman who was 8 weeks postpartum with a history of cholelithiasis and gallstone pancreatitis, and who was status-post endoscopic retrograde cholangiopancreatography (ERCP) with sphincterotomy, was treated with a single-incision laparoscopic (SIL) cholecystectomy. A transversus abdominis plane block (TAP) was performed after induction of anesthesia. The patient required no intraoperative or postoperative opioids.

A systematic review of interventions to facilitate ambulatory laparoscopic cholecystectomy

OBJECTIVES

  We aimed to perform a systematic review of the literature to identify interventions that may facilitate ambulatory laparoscopic cholecystectomy (LC).

METHODS

The PubMed and CENTRAL databases were interrogated for key MeSH headings. To be eligible for systematic review, trials were required to include outcome measures of postoperative pain, nausea or vomiting and time to discharge following LC. Interventions were subsequently assessed for the level of evidence and grade of recommendation given.

RESULTS

A total of 331 trials were identified, 68 of which met the predefined study inclusion criteria. Interventions which met Level I, Grade A recommendation included the administration of 8 mg i.v. dexamethasone, preoperative administration of analgesia including the use of non-steroidal anti-inflammatory or COX II inhibitors, intraoperative use of an anti-emetic, pre-incisional use of bupivacaine, administration of intraperitoneal bupivacaine on establishment of pneumoperitoneum, and avoidance of drains.

CONCLUSIONS

  High-quality evidence describing interventions that minimize barriers to ambulatory LC exists. Further studies will be required to determine the optimal combination of these interventions.

Preemptive analgesic effect of ketamine in patients undergoing elective cesarean section

OBJECTIVES

In this study, the preemptive effect of a small dose of ketamine on postoperative wound pain and morphine consumption in patients undergoing elective cesarean section was evaluated.

METHODS

In a randomized, double-blind clinical trial, 60 women with American Society of Anesthesiologists class I and II identification undergoing elective cesarean section were enrolled. In the case group, the patients received 0.5 mg/kg ketamine, and in the control group, they received isotonic saline, 5 minutes before the induction of anesthesia. Anesthesia was induced with 4 mg/kg thiopental followed by 1.5 mg/kg succinylcholine. A further neuromuscular block was achieved by using 0.2 mg/kg of atracurium. Anesthesia was maintained with nitrous oxide 50% and halothane in oxygen. The lungs were mechanically ventilated. After fetus delivery, fentanyl (2 microg/kg) and morphine (0.15 mg/kg) were given intravenously. In the postanesthesia care unit and in the ward, all patients received morphine. Pain was assessed by the Visual Analog Scales at 2, 6, 12, and 24 hours postoperatively; the amount of morphine used and side effects were recorded.

RESULTS

There was no significant difference between the patients considering their operative details, homodynamic variables, side effects, and Apgar scores of their babies at first and fifth minutes. Significantly, lower amounts of morphine were used in the case group (4.8 mg+/-2.5 mg vs. 8.1 mg+/-4.2 mg) during the first 2 hours after surgery (P=0.01), but the difference was not significant during 2 to 24 hours (3.2+/-2.2 vs. 3.1+/-2.3). There were no statistical differences between the groups in pain 2, 6, 12, and 24 hours postoperatively.

DISCUSSION

Intraoperative low-dose ketamine had no effect on morphine consumption during 2 to 24 hours after surgery. No significant differences were seen in the pain scores of the 2 groups during the study period. The preoperative administration of 0.5 mg/kg ketamine in patients undergoing cesarean section did not elicit a preemptive analgesic effect.

Effects of perioperative S (+) ketamine infusion added to multimodal analgesia in patients undergoing ambulatory haemorrhoidectomy

Background and objective

Perioperative low-dose ketamine has been useful for postoperative analgesia. In this study we wanted to assess the analgesic effect and possible side-effects of perioperative low-dose S (+) ketamine when added to a regime of non-opioid multimodal pain prophylaxis.

Methods

Seventy-seven patients scheduled for haemorrhoidectomy were enrolled in this randomized, double-blind, controlled study. They received oral paracetamol 1–2 g, total intravenous anaesthesia, intravenous 8 mg dexamethasone, 30 mg ketorolac and local infiltration with bupivacaine/epinephrine. Patients randomized to S (+) ketamine received an intravenous bolus dose of 0.35 mg kg−1 S (+) ketamine before start of surgery followed by continuous infusion of 5 μg kg−1 min−1 until 2 min after end of surgery. Patients in the placebo group got isotonic saline (bolus and infusion). BISTM monitoring was used. Pain intensity and side-effects were assessed by blinded nursing staff during PACU stay and by phone 1, 7 and 90 days after surgery.

Results

In patients randomized to S (+) ketamine emergence from anaesthesia was significantly longer (13.1 min vs. 9.3 min; p < 0.001). BIS values were significantly higher during anaesthesia (maximal value during surgery: 62 vs. 57; p = 0.01) and when opening eyes (81 vs. 70, p < 0.001). Pain scores (NRS and VAS) did not differ significantly between groups.

Conclusions

The addition of perioperative S (+) ketamine for postoperative analgesia after haemorrhoidectomy on top of multimodal non-opioid pain prophylaxis does not seem to be warranted, due to delayed emergence and recovery, more side-effects, altered BIS readings and absence of additive analgesic effect.

The preventative analgesic effect of preincisional peritonsillar infiltration of two low doses of ketamine for postoperative pain relief in children following adenotonsillectomy. A randomized, double-blind, placebo-controlled study

BACKGROUND

In literature, the use of ketamine for the preventative analgesia in the management of postoperative pain is controversial. The purpose of the present study was the clinical assessment of the efficacy of preincisional peritonsillar infiltration of two doses of ketamine on postoperative pain relief compared with peritonsillar saline in children undergoing adenotonsillectomy.

METHODS/MATERIALS

Seventy-five ASA physical status I and II patients, aged 3-12 years, scheduled for adenotonsillectomy were enrolled in this randomized, double-blind, placebo-controlled study. Patients were divided into three groups of 25 each and received a local peritonsillar infiltration of 0.9% saline (group S), ketamine 0.5 mg x kg(-1) (group K1), or ketamine 1 mg x kg(-1) (group K2). All medications were 2 ml in volume which was applied 1 ml per tonsil 3 min prior to tonsillectomy. The Children's Hospital of Eastern Ontario Pain Scale (CHEOPS) and Wilson sedation scale were used to evaluate pain levels and sedative conditions, respectively.

RESULTS

Group S had significantly higher CHEOPS scores than group K1 and K2. Both K1 and K2 groups had comparable scores, which were not statistically significant (P > 0.05). During 24 h after surgery, 16 patients in group S and no patients in groups K1 or K2 needed analgesics (P < 0.001).

CONCLUSIONS

A 0.5 or 1 mg.kg(-1) dose of ketamine given at approximately 3 min before surgery by peritonsillar infiltration provides efficient pain relief during 24 h after surgery without side-effects in children undergoing adenotonsillectomy.

Ketamine increases the frequency of electroencephalographic bicoherence peak on the alpha spindle area induced with propofol

BACKGROUND

The reticular and thalamocortical system is known to play a prominent role in spindle wave activity, and the spindle wave is related to the sedative effects of anaesthetics. Recently, bispectral analysis of the EEG has been developed as a better method to indicate nonlinear regulation including the thalamocortical system linking to the cortical area. In the present study, in order to explore the interference of ketamine with the nonlinear regulation of the sub-cortical system, we examined the effect of ketamine on spindle alpha waves through the bispectral analysis.

METHODS

The study included 21 patients. Anaesthesia was induced and maintained using a propofol-TCI system (target-controlled infusion, with target concentration 3.5 microg ml(-1)). An A-2000 BIS monitor was used and the raw EEG signals were collected via an RS232 interface on a personal computer. Bicoherence, the normalized bispectrum, and power spectrum were analysed before and after i.v. administration of 1 mg kg(-1) racemic ketamine.

RESULTS

Propofol caused alpha peaks in both power and bicoherence spectra, with average frequencies of 10.6 (SD 0.9) Hz and 10.7 (1.0) Hz, respectively. The addition of ketamine significantly shifted each peak to frequencies of 14.4 (1.4) Hz and 13.6 (1.5) Hz, respectively [P < 0.05, mean (SD)].

CONCLUSIONS

Ketamine shifted the alpha peaks of bicoherence induced by propofol to higher frequencies. This suggests that ketamine changes the alpha spindle rhythms through the modulation of the nonlinear sub-cortical reverberating network.

Low dose ketamine: a therapeutic and research tool to explore N-methyl-D-aspartate (NMDA) receptor-mediated plasticity in pain pathways

Ketamine is a dissociative anaesthetic that has been used in the clinic for many years. At low, sub-anaesthetic doses, it is a relatively selective and potent antagonist of the N-methyl-D-aspartate (NMDA) receptor. It belongs to the class of uncompetitive antagonists and blocks the receptor by binding to a specific site within the NMDA receptor channel when it is open. Like other compounds of this class, ketamine can cause hallucinations or other untoward central effects which limit its use in the clinic. Nevertheless, because of the evidence on the importance of NMDA receptor-mediated pLasticity in chronic pain, low doses of ketamine have been explored in a wide range of pain conditions. The majority of studies with ketamine have shown efficacy; however, it has not been possible to separate safely the pain relief from the side effects of the drug. Hence, clinical use of ketamine as a pain treatment is very limited. Nevertheless, ketamine has served as a useful tool to provide a compelling rationale for developing other NMDA antagonists. Some of the new compounds of this class, particularly those acting at the NR2B subtype of the NMDA receptor, have shown promise in preclinical and clinical studies.

The antiallodynic effect of NMDA antagonists in neuropathic pain outlasts the duration of the in vivo NMDA antagonism

Clinical reports have described a long-lasting relief in neuropathic pain patients treated with NMDA receptor antagonists; it is unclear, however, what mediates this effect. In this work, we have used two NMDA antagonists of different class to investigate if the antiallodynic effects in a rat neuropathy model can outlast their in vivo NMDA antagonism. Both the uncompetitive NMDA antagonist ketamine and the glycine(B) antagonist MRZ 2/576 inhibited neuronal responses to iontophoretic NMDA in anaesthetised rats with the time course consistent with their known pharmacokinetics (t(1/2) approximately 10-12min, similar in control and nerve-injured rats). Surprisingly, the antiallodynic effects of the same doses of the NMDA antagonists in the neuropathic pain model were long-lasting (>3h with ketamine, >24h with MRZ 2/576). The effect of ketamine was further prolonged (>24h) when combined with a short-acting opioid, fentanyl, which only produced a short effect ( approximately 40min) when given alone. The duration of centrally mediated side effects of ketamine and MRZ 2/576 was short, similar to the in vivo NMDA antagonism. We speculate that NMDA receptor blockade may down-regulate the central sensitisation triggered by nerve injury, resulting in a long-lasting antiallodynic effect. Development of short-acting NMDA antagonists could represent a strategy for improving their tolerability.

Lack of a pre-emptive effect of low-dose ketamine on postoperative pain following oral surgery

PURPOSE

The aim of this study was to assess the effect of pre- vs postincisional low-dose iv ketamine on postoperative pain in outpatients scheduled for oral surgery under general anesthesia.

METHODS

Eighty-four patients were randomly assigned to receive intravenously saline before and after surgery in Group 1, ketamine 300 microg x kg(-1) iv before and saline after surgery in Group 2, saline before and ketamine 300 microg x kg(-1) iv after surgery in Group 3. Postoperative analgesia consisted of iv proparacetamol and ketoprofen. Rescue analgesia consisted of nalbuphine 200 microg x kg(-1) iv. Analgesia at home consisted of oral ketoprofen, and acetaminophen with codeine as rescue analgesia. A telephone interview was conducted on the first and second postoperative days.

RESULTS

There were no significant differences between groups with respect to pain scores, the number of patients requiring nalbuphine in the postanesthesia care unit (PACU), (36.7%, 38.7%, and 39.5% for Groups 1, 2, and 3 respectively), or nalbuphine consumption in the PACU (66.5 microg x kg(-1) +/- 16.8, 75.9 microg x kg(-1) +/- 17.5, 66.7 microg x kg(-1) +/- 21.6 for Groups 1, 2, and 3 respectively). The number of rescue analgesic tablets taken at home, and time to first request for rescue analgesia, sedation scores, or side-effects were similar amongst groups. No patient required nalbuphine in the ambulatory care unit.

CONCLUSIONS

There was no benefit to pre-emptive administration of ketamine 300 microg x kg(-1) iv whether administered pre- or postoperatively.

The influence of timing of systemic ketamine administration on postoperative morphine consumption

STUDY OBJECTIVE

To determine the influence of timing of systemic ketamine administration on postoperative morphine consumption.

DESIGN

Prospective randomized study.

SETTING

Operating rooms, postanesthesia care unit, and gynecology service of a university hospital.

PATIENTS

Forty-five patients undergoing laparotomy for benign gynecologic pathologies were randomized into 3 groups.

INTERVENTIONS

In Group 1, before surgical incision, patients received 0.5 mg/kg ketamine IV, followed by normal saline infusion and normal saline IV at wound closure in group 1 (n = 15). In group 2 (n = 15), patients received 0.5 mg/kg ketamine IV before surgery, followed by ketamine infusion 600 mug . kg(-1) . h(-1), until wound closure and normal saline IV at that time. In the other group (group 3, n = 15), patients received normal saline IV before surgery, followed by saline infusion and then 0.5 mg/kg ketamine IV at wound closure. In the postoperative period, patient-controlled analgesia IV morphine was used for postoperative pain relief. First requested analgesic medication time was recorded. Postoperative pain was assessed by measuring morphine consumption at 0 to 2, 0 to 4, and 0 to 24 hours and visual analog scale (VAS) pain scores in response to cough at 2nd, 4th, and 24th hours and during rest at 0 to 2, 0 to 4, and 0 to 24 hours after surgery.

MEASUREMENT AND MAIN RESULTS

First requested analgesia was shorter in group 1 than the others (P < .01). Mean VAS pain scores in response to cough at 24th hour in groups 2 and 3 were significantly lower than in group 1 (P < .001 and P < .01, respectively). Mean VAS pain scores during rest at 0 to 24 hours in groups 2 and 3 were significantly lower than in group 1 (P < .01 and P < .05, respectively). Morphine consumption was lower in groups 2 and 3 at 0 to 2 hours (P < .001 and P < .01). Moreover, morphine consumption at 0 to 4 hours in group 2 was significantly lower (P < .01).

CONCLUSIONS

Lower pain scores and morphine consumption in groups 2 and 3 may be related to higher plasma ketamine concentrations caused by the higher doses and later administration. Our findings suggest that a single preoperative dose of ketamine provided less analgesia compared with other dosing regimens that included intraoperative infusions or postoperative administration.

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.

The changing role of non-opioid analgesic techniques in the management of postoperative pain

Given the expanding role of ambulatory surgery and the need to facilitate an earlier hospital discharge, improving postoperative pain control has become an increasingly important issue for all anesthesiologists. As a result of the shift from inpatient to outpatient surgery, the use of IV patient-controlled analgesia and continuous epidural infusions has steadily declined. To manage the pain associated with increasingly complex surgical procedures on an ambulatory or short-stay basis, anesthesiologists and surgeons should prescribe multimodal analgesic regimens that use non-opioid analgesics (e.g., local anesthetics, nonsteroidal antiinflammatory drugs, cyclooxygenase inhibitors, acetaminophen, ketamine, alpha 2-agonists) to supplement opioid analgesics. The opioid-sparing effects of these compounds may lead to reduced nausea, vomiting, constipation, urinary retention, respiratory depression and sedation. Therefore, use of non-opioid analgesic techniques can lead to an improved quality of recovery for surgical patients.

Peri-operative ketamine for acute post-operative pain: a quantitative and qualitative systematic review (Cochrane review)

BACKGROUND

Post-operative pain management is usually 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. The objective of this systematic review was to evaluate the effectiveness and tolerability of ketamine administered peri-operatively in the treatment of acute post-operative pain in adults.

METHODS

Studies were identified from MEDLINE (1966-2004), EMBASE (1980-2004), the Cochrane Library (2004) and by hand searching reference lists from review articles and trials. The manufacturer of ketamine (Pfizer AS, Lysaker, Norway) provided search results from their in-house database, PARDLARS. Randomized and controlled trials (RCTs) of adult patients undergoing surgery, being treated with peri-operative ketamine, placebo or an active control were considered for inclusion.

RESULTS

Eighteen trials were excluded. Thirty-seven trials were included. Twenty-seven out of 37 trials found that peri-operative ketamine reduced rescue analgesic requirements or pain intensity, or both. Quantitative analysis showed that treatment with ketamine reduced 24-h patient-controlled analgesia (PCA) morphine consumption and post-operative nausea and vomiting (PONV). Adverse effects were mild or absent.

CONCLUSION

In the first 24 h after surgery, ketamine reduces morphine requirements. Ketamine also reduces PONV. Adverse effects are mild or absent. These data should be interpreted with caution as the retrieved studies were heterogenous and the result of the meta-analysis can not be translated into any specific administration regimen with ketamine.

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.

A procedure-specific systematic review and consensus recommendations for postoperative analgesia following laparoscopic cholecystectomy

BACKGROUND

Laparoscopic cholecystectomy has advantages over the open procedure for postoperative pain. However, a systematic review of postoperative pain management in this procedure has not been conducted.

METHODS

A systematic review was conducted according to the guidelines of the Cochrane Collaboration. Randomized studies examining the effect of medical or surgical interventions on linear pain scores in patients undergoing laparoscopic cholecystectomy were included. Qualitative and quantitative analyses were performed. Recommendations for patient care were derived from review of these data, evidence from other relevant procedures, and clinical practice observations collated by the Delphi method among the authors.

RESULTS

Sixty-nine randomized trials were included and 77 reports were excluded. Recommendations are provided for preoperative analgesia, anesthetic and operative techniques, and intraoperative and postoperative analgesia.

CONCLUSIONS

A step-up approach to the management of postoperative pain following laparoscopic cholecystectomy is recommended. This approach has been designed to provide adequate analgesia while minimizing exposure to adverse events.

The efficacy of preemptive analgesia for acute postoperative pain management: a meta-analysis

Whether preemptive analgesic interventions are more effective than conventional regimens in managing acute postoperative pain remains controversial. We systematically searched for randomized controlled trials that specifically compared preoperative analgesic interventions with similar postoperative analgesic interventions via the same route. The retrieved reports were stratified according to five types of analgesic interventions: epidural analgesia, local anesthetic wound infiltration, systemic N-methyl-d-aspartic acid (NMDA) receptor antagonists, systemic nonsteroidal antiinflammatory drugs (NSAIDs), and systemic opioids. The primary outcome measures analyzed were the pain intensity scores, supplemental analgesic consumption, and time to first analgesic consumption. Sixty-six studies with data from 3261 patients were analyzed. Data were combined by using a fixed-effect model, and the effect size index (ES) used was the standardized mean difference. When the data from all three outcome measures were combined, the ES was most pronounced for preemptive administration of epidural analgesia (ES, 0.38; 95% confidence interval [CI], 0.28-0.47), local anesthetic wound infiltration (ES, 0.29; 95% CI, 0.17-0.40), and NSAID administration (ES, 0.39; 95% CI, 0.27-0.48). Whereas preemptive epidural analgesia resulted in consistent improvements in all three outcome variables, preemptive local anesthetic wound infiltration and NSAID administration improved analgesic consumption and time to first rescue analgesic request, but not postoperative pain scores. The least proof of efficacy was found in the case of systemic NMDA antagonist (ES, 0.09; 95% CI, -0.03 to 0.22) and opioid (ES, -0.10; 95% CI, -0.26 to 0.07) administration, and the results remain equivocal.

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.

Ketamine as Adjuvant Analgesic to Opioids: A Quantitative and Qualitative Systematic Review

Animal studies on ketamine and opioid tolerance have shown promising results. Clinical trials have been contradictory. We performed a systematic review of randomized, double-blind clinical trials of ketamine added to opioid analgesia. Thirty-seven trials with 51 treatment arms and 2385 patients were included. Studies were divided into 5 subgroups: IV ketamine as single dose (n = 11), continuous infusion (n = 11), patient-controlled analgesia (PCA) (n = 6), epidural ketamine with opioids (n = 8), and studies in children (n = 4). Outcome measures included pain scores, time to first request for analgesia, supplemental analgesics, and adverse events. Efficacy was estimated by statistical significance (P < 0.05) of outcome measures as reported in studies and also by calculation of weighted mean difference for pain scores during the first 24 h after surgery. As compared to morphine alone, IV PCA with ketamine and morphine did not improve analgesia. Intravenous infusion of ketamine decreased IV and epidural opioid requirements in 6 of 11 studies. A single bolus dose of ketamine decreased opioid requirements in 7 of 11 studies. Five of 8 trials with epidural ketamine showed beneficial effects. Adverse effects were not increased with small dose ketamine. We conclude that small dose ketamine is a safe and useful adjuvant to standard practice opioid-analgesia.

Ketamine does not decrease postoperative pain after remifentanil-based anaesthesia for tonsillectomy in adults

BACKGROUND

There are conflicting results concerning the pre-emptive effect of ketamine on central sensitization following surgery. The aim of this prospective, randomized, double-blind, placebo-controlled study was to assess the effect of the N-methyl-D-aspartate receptor antagonist ketamine on postoperative morphine consumption and pain score after remifentanil-based anaesthesia in adult patients scheduled for tonsillectomy.

METHODS

We studied 40 adult patients undergoing elective tonsillectomy. Total intravenous anaesthesia was induced and maintained with remifentanil (0.125-1.0 microg kg(-1) min(-1)) and propofol target-controlled infusion. Patients in group K received a bolus dose of ketamine 0.5 mg kg(-1) immediately after anaesthetic induction, followed by a continuous infusion of 2 microg kg(-1) min(-1). Saline was administered in the same sequence in group S. Propofol, remifentanil, and the study drug infusions were discontinued at the end of surgery.

RESULTS

Intraoperative remifentanil consumption (0.57 +/- 0.18 in group K vs. 0.55 +/- 0.14 microg kg(-1) min(-1) in group S), morphine requirement in the PACU (11 +/- 3 in group K vs. 9 +/- 4 mg in group S) and in the ward (22 +/- 11 in group K vs. 25 +/- 14 mg in group S), median time to first analgesia in the ward (338 +/- 126 in group K vs. 328 +/- 144 min in group S), and VAS pain scores were comparable in both groups.

CONCLUSION

Small-dose of ketamine does not seem to be a useful adjunct to remifentanil-based anaesthesia during short, painful surgical procedures.

Improvement of Pain Treatment After Major Abdominal Surgery by Intravenous S(+)-Ketamine

The use of intraoperative racemic ketamine for pain prevention after abdominal surgery is controversial. We compared one preincisional i.v. injection of S(+)-ketamine with its preincisional and repeated intraoperative use in 45 patients undergoing surgery with epidural and general anesthesia. S(+)-ketamine is a new drug formulation that contains the more potent S(+)-stereoisomer of ketamine. Patients were randomized to receive placebo, 0.5 mg/kg preincisional S(+)ketamine, or 0.5 mg/kg preincisional and 0.2 mg/kg intraoperative S(+)-ketamine repeated at 20-min intervals. In the postoperative period, epidural ropivacaine (2 mg/mL; 0.12 mL.kg(-1).h(-1)) was infused for pain therapy. Patients who received repeated S(+)-ketamine reported smaller pain scores than those who received placebo after awakening and 3 and 6 h later (P < or = 0.05). Fewer patients with repeated S(+)-ketamine required additional analgesics than those with placebo (P < or = 0.05). Cumulative consumption of additional diclofenac and dextropropoxyphene at 24 h was less after single (P < 0.05) and repeated (P < 0.05) S(+)-ketamine versus placebo. After awakening, patients who received repeated S(+)-ketamine reported being in a better mood than those in the other groups (P < 0.05). No psychotomimetic side effects were noted. In conclusion, preincisional and repeated intraoperative small-dose S(+)-ketamine added to general and epidural anesthesia causes better postoperative pain relief than general and epidural anesthesia alone.

IMPLICATIONS

After major visceral surgery, preincisional and repeated intraoperative small-dose S(+)-ketamine added to general and epidural anesthesia causes better postoperative pain relief than general and epidural anesthesia alone.

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.

Does ketamine or magnesium affect posttonsillectomy pain in children?

BACKGROUND

Many previous studies have suggested a role for the N-methyl-D-aspartate (NMDA) receptor antagonists ketamine and magnesium in decreasing postoperative pain and analgesic requirements in adults, but none has investigated these medications in children.

METHODS

This randomized, double-blind, placebo-controlled study evaluated the effects of ketamine and magnesium in children undergoing tonsillectomy. Eighty patients, aged 3-12 years, were randomly assigned to four groups. Patients received either ketamine 0.15 mg.kg-1, magnesium sulphate 30 mg.kg-1, ketamine 0.15 mg.kg-1 plus magnesium sulphate 30 mg.kg-1, or placebo intravenously 5 min prior to the start of surgery. Intraoperative analgesia was standardized, and included fentanyl and dexamethasone.

RESULTS

There were no differences among the groups with respect to pain assessment postoperatively. Compared with placebo, the treatment groups did not require less fentanyl in the postanaesthesia recovery room or consume less codeine in the first 24-h postoperatively. There was no evidence of synergism between ketamine and magnesium. There were no differences among the groups in the incidence of nausea, vomiting, sedation, bleeding, or dreaming postoperatively.

CONCLUSION

This study did not demonstrate a decrease in pain or analgesic consumption in children undergoing tonsillectomy when pretreated with a small dose of ketamine and/or magnesium.

Preincisional intravenous low-dose ketamine and local infiltration with ropivacaine reduces postoperative pain after laparoscopic cholecystectomy

BACKGROUND

The preincisional use of ketamine combined with local tissue infiltration with Ropivacaine may reduce noxious input during surgery. The goal of this study was to examine whether this combination improves postoperative pain control after laparoscopic cholecystectomy.

METHODS

A total of 55 patients were randomly assigned to one of three groups. Group 1 received placebos preincisional. Group 2 received preincisional saline IV and local infiltration with 20 ml ropivacaine (10 mg/ml). Group 3 received preincisional ketamine 1 mg/kg IV and local infiltration with 20 ml ropivacaine (10 mg/ml). Postoperative pain was rated at 0, 3, 6, 12, 24, and 48 h postoperatively by visual analogue scale scores (VAS). Cumulative analgesic consumption and time until first analgesic medication request were recorded.

RESULTS

Group 3 experienced significantly (p < 0.05) less pain than group 2 at 6 h and 12 h postoperatively. Groups 2 and 3 did not differ significantly by VAS at 0 h, 3 h, 24 h, and 48 h. Group 1 had significantly higher VAS scores than groups 2 and 3 at 0 h, 3 h, 6 h, 12 h, and 24 h postoperatively. The consumption of analgesics was significantly higher in group 1 than in groups 2 and 3. Although the consumption of analgesics was higher in group 3 than in group 2, this difference did not reach statistical significance. The time to first request for analgesics was significantly longer in groups 2 and 3 than in group 1, with no statistical difference between groups 2 and 3.

CONCLUSION

Preincisional treatment with low-dose IV ketamine and local infiltration with ropivacaine 1% reduces postoperative pain after laparoscopic cholecystectomy.

Adding ketamine to morphine for patient-controlled analgesia after major abdominal surgery: a double-blinded, randomized controlled trial

In this double-blinded, randomized controlled trial we tested if the addition of ketamine to morphine for patient-controlled analgesia (PCA) resulted in improved analgesic efficacy and lower pain scores compared with morphine PCA alone after major abdominal surgery. Seventy-one patients were randomly allocated to receive either morphine 1 mg/mL (Group M) or morphine 1 mg/mL plus ketamine 1 mg/mL (Group MK) delivered via PCA after surgery. No other analgesics or regional blocks were permitted during the 48-h study period. Postoperatively there were no differences between the groups for subjective assessment of analgesic efficacy, pain scores at rest, and on movement, opioid consumption, or adverse events. Group MK patients performed worse in cognitive testing (P = 0.037). There was an increased risk of vivid dreaming in patients who received ketamine (relative risk = 1.8, 95% confidence interval 0.78-4.3). We conclude that small-dose ketamine combined with PCA morphine provides no benefit to patients undergoing major abdominal surgery.

IMPLICATIONS

We performed a randomized, controlled trial comparing the use of ketamine and morphine with morphine alone to relieve pain after major abdominal surgery.Ketamine did not improve pain relief and merely increased side effects.

PCA ketamine and morphine after abdominal hysterectomy

Following a standardized general anaesthetic for total abdominal hysterectomy, patients received either patient controlled analgesia (PCA) with morphine 1 mg/ml (group M, n = 33) or morphine 1 mg/ml plus ketamine 2 mg/ml (group K, n = 37) for 48 hours in a randomized, double-blind fashion. In 43 women the area of allodynia around the scar was mapped as a measure of the degree of central sensitization. A significant reduction in the area of allodynia was found in those receiving ketamine with morphine (42 cm2 [interquartile range (IQR) 57] compared with 57 cm2 [IQR 82] z = -2.0, P = 0.04) in those receiving morphine alone. There were no significant differences between the two groups with respect to age, or weight, or between the subgroups within which the area of allodynia was measured with respect to length of incision. No significant differences were found between the groups with respect to pain scores, total or hourly drug consumption, patient satisfaction, nausea scores or antiemetic use. Patients in group K were more likely to require PCA for a shorter period than those in group M (median 40 hours, IQR 26 versus 48 hours IQR 7). Ten patients in group K were withdrawn because of side-effects (dysphoria n = 4, nausea n = 2, pruritus n = 4) compared with one in group M (nausea n = 1) (P = 0.006). The potential usefulness of ketamine after hysterectomy was offset by a high incidence of adverse effects and a lack of opioid-sparing effects, such that combined intravenous ketamine and morphine PCA as used in this study cannot be recommended for routine care.

Non-opioid postoperative analgesia

Although significant improvement has been made in the treatment of pain in the postoperative period, many patients still experience unnecessary discomfort resulting in distress, higher morbidity and prolonged stay in hospital. The standard pillar of postoperative treatment of severe pain is the use of opioids. However, adverse reactions to opioids make their use unfavourable. A better understanding of the pathophysiology of pain has helped clinicians to a more balanced approach to postoperative pain treatment. The development of the multimodal approach to postoperative analgesia, with the use of different drugs acting via different routes to give good analgesia, with minimal side-effects, represents a major development in the treatment of postoperative pain. Early, aggressive mobilisation and feeding must follow in order to restore normal conditions quickly. Alternatives to opioids should be used as extensively as possible. Local anaesthesia, used as regional blocks or as wound infiltration, is most beneficial. Paracetamol has good basic analgesic properties, and should probably be used in dosages higher than recommended today. The combination with a NSAID results in better and longer-lasting analgesia. The intravenous form propacetamol will increase the possibilities of its use. The new concept of selective COX-2 inhibiting NSAIDs will result in analgesic and anti-inflammatory drugs with fewer side-effects. The well-known inexpensive group of corticosteroids have good analgesic and anti-emetic properties, and are especially interesting to use in patients who do not tolerate NSAIDs. The alpha2-receptor agonists like clonidine, when administered epidurally or intrathecally, are useful adjuncts, but their adverse effects on sedation and hypotension limit their use. NMDA-receptor antagonists are of limited value in the postoperative period. Adenosine and neostigimine are still on a research level but may lead to new, clinically useful analgesic drugs. In the future, cannabinoids, cholecystokinin-receptor antagonists and neurokinin-1 antagonists may become important analgesic drugs.

Effects of ketamine on formalin-induced activity in the spinal dorsal horn of spinal cord-transected cats: differences in response to intravenous ketamine administered before and after formalin

BACKGROUND

Although formalin has been widely used as an algesic substance in rodent studies, the unique biphasic effect seen in rats is not present in humans. Humans, like cats, have a monophasic behavioral response to formalin injection. Electrophysiologically, spinal dorsal horn neurons in cats also have what could be considered a monophasic response after the initial burst of activity following formalin injection. Although several studies of the effects of ketamine on formalin responses have been carried out in rodents, we are unaware of similar studies in cats. We hypothesize that such species differences may explain observed differences in preemptive analgesic effects. Therefore, we examined the effects of ketamine on activity of spinal wide dynamic range (WDR) neurons evoked by formalin injection in cats.

METHODS

We investigated in cats the effect of ketamine on the activity of WDR neurons in the spinal dorsal horn that was evoked by formalin. In addition, we studied the effects of pre- and post-administration of ketamine on the maintained phase of the formalin response. Each dose was a subanesthetic, anesthetic or high anesthetic dose (3.0 mg x kg(-1), 10 mg x kg(-1), and 30 mg x kg(-1)).

RESULTS

Intravenously administered ketamine produced a dose-dependent depression of evoked activity that was significantly greater when the drug was administered before formalin.

CONCLUSION

In spite of the species differences in responses to formalin, there still appears to be a clear preemptive effect of ketamine in the cat. Species differences may not explain apparent differences between human and animal preemptive analgesia.

Ketamine: a new look at an old drug

Ketamine is a major drug for induction of patients with hypovolemia and for general anaesthesia under primitive conditions, but also has excellent properties for more generalized use in children, adults and other fragile patients. Potential beneficial effects on cardiac ischaemia and cerebral injury is presently explored, as well as the effects of ketamine as an potent analgesic drug. Combination with propofol or midazolam for sedation provides analgesia, sleep and spontaneous ventilation. The S-isomer of ketamine has a lower incidence of psychomimetic side effects in equianalgesic doses compared with the racemate or the R-isomer alone.

Ketamine: new uses for an old drug

Over the years, ketamine has found many applications in paediatric anaesthesiology. Recent insights into the mechanism of its central action, and the pharmacology of its isomers have led to a re-evaluation of this drug, expanding the range of indications in adults. The best examples of the uses of ketamine as an analgesic are: in brief diagnostic or therapeutic procedures, during the post-operative period in neonates and infants as well as in paediatric anaesthesia and intensive care.