Preoperative epidural ketamine in combination with morphine does not have a clinically relevant intra- and postoperative opioid-sparing effect

Dexmedetomidine or Fentanyl, Which One Is Better as an Adjunct Drug in Epidural Anesthesia and Causes More Postoperative Pain Reduction? A Comparative Study, a Randomized Clinical Trial

Objectives

This study compared dexmedetomidine to fentanyl as an adjunct to ropivacaine for epidural anesthesia in patients undergoing femoral neck fracture surgery.

Methods

A total of 56 patients in two different groups with dexmedetomidine and fentanyl underwent the epidural anesthesia method by ropivacaine. This study compared the onset and duration of sensory block, duration of motor block, visual analog scale (VAS) analgesia, and sedation score. The VAS and hemodynamics (e.g., heart rate and mean arterial pressure) were measured every 5 to 15 minutes, then every 15 minutes to the end of the surgery, and then in the 1st, 2nd, 4th, 6th, 12th, and 24th hours after surgery.

Results

In the fentanyl group, the onset time of the sensory block was longer (P < 0.001), and the duration of the block was shorter than in the dexmedetomidine group (P = 0.045). In the fentanyl group, the onset time of motor block was longer than in the dexmedetomidine group (P < 0.001). The mean highest VAS score for each patient in the dexmedetomidine group was 4.9 ± 0.6, compared to the fentanyl group (5.8 ± 0.9), with a significant difference between the two groups (P < 0.001). The sedation score was higher from the 30th minute (P = 0.01) to the 120th minute (P = 0.04) in the patients of the dexmedetomidine group than in the fentanyl group. Side effects, such as dry mouth, hypotension, and bradycardia, were more common in the dexmedetomidine group, and nausea and vomiting were more common in the fentanyl group; however, there were no differences between the groups. There was no respiratory depression in both groups.

Conclusions

This study presented that dexmedetomidine as an adjuvant in epidural anesthesia for orthopedic femoral fracture surgery shortens the onset time of sensory and motor block, increases analgesia length, and prolongs anesthesia. Sedation with dexmedetomidine is better than fentanyl, with fewer side effects, and more effective as preemptive analgesia.

Epidural dexmedetomidine infusion for perioperative analgesia in patients undergoing abdominal cancer surgery: randomized trial

Objective

To assess the postoperative analgesic efficacy of epidural dexmedetomidine added to bupivacaine infusion for patients undergoing major abdominal cancer surgery.

Methods

Patients scheduled for major upper abdominal cancer surgery were allocated to group bupivacaine (n =32), in which patients received epidural bupivacaine infusion (6 mL/h bupivacaine 0.1%) for 48 hours postoperatively, or group bupivacaine + dexmedetomidine (n=32), in which patients received epidural dexmedetomidine added to bupivacaine infusion (6 mL/h of bupivacaine 0.1% + dexmedetomidine, 0.5 µg/mL) for 48 hours postoperatively. The cumulative morphine consumption, the time to first analgesic request, and the VAS pain score were evaluated.

Results

The cumulative morphine consumption was significantly reduced in group bupivacaine + dexmedetomidine compared with group bupivacaine: mean ± SD of 10.40±5.16 mg vs 23.23±8.37 mg with an estimated difference (95% CI) of −12.83 (−16.43, −9.24), (P<0.001). The time to the first analgesic demand was significantly delayed in group bupivacaine + dexmedetomidine compared with group bupivacaine: median (IQR) of 6 (1.75, 8.25) h vs 1 (0, 4)h, (P<0.001). The mean collapsed over time of overall VAS pain scores at rest and movement was significantly reduced in group bupivacaine + dexmedetomidine compared with group bupivacaine : mean ± SE of 1.6±0.08 vs 2.38±0.08 with an estimated difference (95% CI) of −0.8 (−1, −0.86), (P<0.001), and mean ± SE of 2.17±0.07 vs 3.25±0.07 with an estimated difference (95% CI) of −1.1 (−1.27, – 0.89), (P<0.001), respectively.

Conclusion

Epidural infusion of dexmedetomidine added to bupivacaine for patients undergoing major abdominal cancer surgery significantly reduced morphine consumption, delayed time to first analgesic supplementation, and decreased pain intensity during the first 48 hours postoperatively without harmful derangement on hemodynamics.

An Update on Drugs Used for Lumbosacral Epidural Anesthesia and Analgesia in Dogs

This review aims to report an update on drugs administered into the epidural space for anesthesia and analgesia in dogs, describing their potential advantages and disadvantages in the clinical setting. Databases searched include Pubmed, Google scholar, and CAB abstracts. Benefits of administering local anesthetics, opioids, and alpha₂ agonists into the epidural space include the use of lower doses of general anesthetics (anesthetic “sparing” effect), perioperative analgesia, and reduced side effects associated with systemic administration of drugs. However, the potential for cardiorespiratory compromise, neurotoxicity, and other adverse effects should be considered when using the epidural route of administration. When these variables are considered, the epidural technique is useful as a complementary method of anesthesia for preventive and postoperative analgesia and/or as part of a balanced anesthesia technique.

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.

Effect of intravenous patient controlled ketamine analgesiaon postoperative pain in opium abusers

Background:

Acutepostoperative pain is among the worst experience that patient scan undergo, and many analgesics have been used to suppress it; especially in chronic opium abusers. Ketamine is an N-methyl-D-aspartate antagonist analgesic, having both anesthetic and analgesic properties, which are not affected to the same extent in chronic opium abusers.

Objectives:

In this study, we assessed the analgesic effects of ketamine added to morphine as a patient-controlled analgesia method for acute pain management, compared with a placebo, inchronic maleopium abusers.

Patients and Methods:

After institutional review board approval for ethical considerations, a randomized double-blinded placebo controlled clinical trial was conducted. A total of 140 male patients aged 18-65 years, undergoing orthopedic surgery, were entered into the study after matching inclusion and exclusion criteria. All patients received the same anesthesia method; while the first group received ketamine (1mg/mL) and morphine (0.5 mg/mL) as a patient-controlled analgesia (70 patients), the second group received morphine (0.5 mg/mL) plus normal saline (70 patients). P value less than 0.05 was considered statistically significant.

Results:

The ketamine and morphine group of patients experienced less postoperative pain and required less postoperative rescue analgesia. However, the unwanted postoperative side effects were nearly the same; although increased levels of postoperative nausea and vomiting were observed in the ketamine and morphine group

Conclusions:

This study demonstrated improved analgesic effects after using intravenous patient controlled analgesia with ketamine on postoperative pain in opium abusers.

Analgesic Effects of Intravenous Ketamine during Spinal Anesthesia in Pregnant Women Undergone Caesarean Section; A Randomized Clinical Trial

Background

Suitable analgesia after cesarean section helps mothers to be more comfortable and increases their mobility and ability to take better care of their infants.

Objectives

Pain relief properties of ketamine prescription were assessed in women with elective cesarean section who underwent spinal anesthesia with low dose intravenous ketamine and midazolam and intravenous midazolam alone.

Patients and Methods

Sixty pregnant women scheduled for spinal anesthesia for cesarean section were randomized into two study groups. Ketamine (30 mg) + midazolam (1 mg = 2CC) or 1mg midazolam (2CC) alone, was given immediately after spinal anesthesia. Pain scores at first, second and third hours after CS operation, analgesic requirement and drug adverse effects were recorded in all patients.

Results

Ketamine group had significant pain relief properties in compare with control group in first hours after cesarean section (0.78 ± 1.09 vs. 1.72 ± 1.22, VAS score, P = 0.00). Total dose of meperidine consumption in women of ketamine group was significantly lower than women of control group (54.17 ± 12.86 vs. 74.44 ± 33.82 mg, P = 0.02). There were no significant drug side effects in participated patients.

Conclusions

Intravenous low-dose ketamine combined with midazolam for sedation during spinal anesthesia for elective Caesarean section provides more effective and long lasting pain relief than control group.

Ketamine and remifentanil interactions on the sevoflurane minimum alveolar concentration and acute opioid tolerance in the rat

BACKGROUND

Ketamine is used at low doses for its analgesic and antihyperalgesic properties when combined with opioids but also when opioid-induced hyperalgesia and tolerance appear. In this study we determined the interaction of ketamine and remifentanil on the minimum alveolar concentration (MAC) of sevoflurane in rats and to determine whether ketamine may block acute opioid tolerance (AOT).

METHODS

Male Wistar rats were anesthetized with sevoflurane, and the MAC was determined before and after ketamine administration (10, 20, 40, and 80 mg kg(-1) or saline) alone or combined with remifentanil (120 and 240 μg kg(-1) h(-1), low and high doses, respectively). One additional group received the lowest ketamine dose after starting a remifentanil infusion. Finally, naloxone was administered to determine the potential action of ketamine on opioid receptors. MAC was determined from intratracheal gas samples, and tail clamping was used as a supramaximal stimulus. End-tidal anesthetic concentrations were assayed using a side stream gas analyzer. Statistical analysis was performed with an analysis of variance.

RESULTS

Ketamine and remifentanil dose-dependently reduced the MAC. Adding the low dose of remifentanil to ketamine did not improve the MAC reduction, whereas the high dose of remifentanil enhanced ketamine reduction in a subadditive fashion. Nevertheless, ketamine was unable to block the development of AOT to remifentanil at either dose. Finally, naloxone blocked the MAC reduction produced by ketamine.

CONCLUSIONS

A subadditive effect between ketamine and remifentanil was found on the sevoflurane MAC reduction rats. In addition, ketamine was unable to block AOT. The clinical relevance of these findings should be elucidated in future studies to reduce anesthetic requirements.

The Efficacy of Epidural Ketamine on Shivering during Transurethral Resection of the Prostate under Epidural Anesthesia

PURPOSE

Ketamine may decrease core-to-peripheral redistribution of heat through direct central sympathetic stimulation and inhibition of norepinephrine uptake into postganglionic sympathetic nerve endings. The purpose of this study was to evaluate the efficacy of epidural ketamine in preventing shivering during transurethral resection of the prostate (TURP) under epidural anesthesia.

MATERIALS AND METHODS

Ninety-three male patients scheduled for TURP under epidural anesthesia were enrolled in this study. Patients were randomized into one of three groups. Group 1 consisted of 31 patients who received epidural 0.75% ropivacaine, group 2 consisted of 32 patients who received epidural ketamine (0.2 mg/kg) in addition to 0.75% ropivacaine, and group 3 consisted of 30 patients who received epidural ketamine (0.4 mg/kg) in addition to 0.75% ropivacaine. Shivering and side effects such as hypotension, bradycardia, nausea, and hallucination were recorded during the anesthesia and for 2 hours while in the postanesthetic recovery room.

RESULTS

Shivering was statistically more frequent in group 1 than in the other groups. The incidence of sedation was significantly higher in group 3 than in the other groups. The incidences of side effects such as hypotension, bradycardia, and nausea were significantly higher in group 1 than in the other groups.

CONCLUSIONS

In this study, epidural ketamine 0.2 mg/kg and 0.4 mg/kg was shown to have a lower incidence of shivering and other side effects except sedation. In patients who undergo TURP under epidural anesthesia, the prophylactic use of low-dose epidural ketamine would be helpful in preventing any adverse effects, including shivering.

Uso de morfina, xilazina e meloxicam para o controle da dor pós-operatória em cadelas submetidas à ovariossalpingo-histerectomia

Foram realizados estudos empregando-se analgésicos por via epidural e subcutânea em cadelas de diferentes raças e idades, submetidas à castração mediante celiotomia. Vinte animais foram tranquilizados e anestesiados com tiletamina-zolazepam, e aleatoriamente distribuídos em quatro grupos (n=5), de acordo com o fármaco e a via de administração. Os do grupo morfina (GM) foram submetidos à anestesia epidural no espaço lombossacro, com morfina (0,1mg/kg) associada ao cloreto de sódio a 0,9%. Aos do grupo xilazina (GX), foram administrados xilazina (0,2mg/kg) e cloreto de sódio a 0,9%. Os do grupo meloxicam (GME) receberam 0,2mg/kg do anti-inflamatório meloxicam associado ao cloreto de sódio a 0,9%, injetado pela via subcutânea. Os do grupo-controle (CG) receberam apenas cloreto de sódio a 0,9%. O volume final para as injeções epidurais foi padronizado para 0,3mL/kg. A mensuração inicial da concentração de cortisol plasmático, do ritmo cardíaco, da frequência respiratória e os parâmetros comportamentais foram registrados imediatamente antes do procedimento cirúrgico (M1). Registros adicionais foram apresentados às 2, 6, 12 e 24 horas após o procedimento cirúrgico (M2, M3, M4 e M5, respectivamente). As variáveis comportamentais foram avaliadas por meio de sinais clínicos e seus respectivos escores. Em GX foram observadas depressão respiratória, bradicardia e concentração de cortisol mais alta do que o registrado no GM. A analgesia obtida pelo meloxicam foi considerada ineficiente. É possível concluir que a morfina, via epidural, promoveu menor incidência de efeitos colaterais e melhor analgesia e bem-estar animal.

Useful adjuvants for postoperative pain management

Adjuvants are compounds which by themselves have undesirable side-effects or low potency but in combination with opioids allow a reduction of narcotic dosing for postoperative pain control. Adjuvants are needed for postoperative pain management due to side-effects of opioid analgesics, which hinder recovery, especially in the increasingly utilized ambulatory surgical procedures. NMDA antagonists have psychomimetic side-effects at high doses, but at moderate doses do not cause stereotypic behavior but allow reduction in opioid dose to obtain better pain control. Alpha-2 adrenergic agonists cause sedation, hypotension and bradycardia at moderate doses, but at low doses can be opioid sparing especially in spinal administration. Gabapentin-like compounds have low potency against acute pain, but in combination with opioids allow a reduction in opioid dose with improved analgesia. Corticosteroids may have only a limited role as adjuvants while acetylcholine esterase inhibitors may have too many side-effects. Newer adjuvants will be needed to reduce opioid dose and concomitant side-effects, even more as same day surgeries become more routine.

Effects of preoperative epidural administration of racemic ketamine for analgesia in sheep undergoing surgery

OBJECTIVE

To investigate the effects of preoperative epidural administration of racemic ketamine to provide analgesia in sheep undergoing experimental hind limb orthopedic surgery.

ANIMALS

12 adult sheep (weight range, 51.4 to 67.2 kg).

PROCEDURE

Sheep were anesthetized with guaifenesin, thiopental, and isoflurane; after induction of anesthesia, sheep received a lumbosacral epidural injection of ketamine (1 mg/kg; n = 6) or saline (0.9% NaCl) solution (1 mL/7 kg; 6 [control group]). Respiratory and cardiovascular variables were recorded before and at intervals during and for 6 hours after anesthesia. During that 6-hour postoperative period, analgesia was evaluated subjectively with a numeric ranking scale that included assessments of comfort, posture, movement, and response to wound palpation; buprenorphine was administered when a score > 3 (maximum score, 10) was achieved. Rectal temperature, heart and respiratory rates, and lameness were evaluated daily for 2 weeks after surgery.

RESULTS

At all evaluations, cardiovascular and respiratory variables were comparable between the 2 groups. Compared with control sheep, time to first administration of rescue analgesic was significantly longer and total dose of buprenorphine administered during the 6- hour postoperative period was significantly decreased for ketamine-treated sheep. During the second week following surgery, ketamine-treated sheep had significantly less lameness than control sheep.

CONCLUSIONS AND CLINICAL RELEVANCE

In sheep undergoing hind limb surgery, preoperative epidural administration of ketamine appears to provide analgesia in the immediate postoperative period and has residual analgesic effects, which may contribute to more rapid return of normal function in surgically treated limbs.

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.

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.

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.

Analgesic effects of epidurally administered levogyral ketamine alone or in combination with morphine on intraoperative and postoperative pain in dogs undergoing ovariohysterectomy

OBJECTIVE

To evaluate the analgesic and adverse effects of epidurally administered levogyral (S[+]) ketamine alone or in combination with morphine on intraoperative and postoperative pain in dogs undergoing ovariohysterectomy.

ANIMALS

30 dogs scheduled for ovariohysterectomy.

PROCEDURE

Dogs were randomly allocated to 1 of 3 groups. Dogs in group 1 received S(+) ketamine (1 mg/kg), dogs in group 2 received S(+) ketamine (0.5 mg/kg) and morphine (0.05 mg/kg), and dogs in group 3 received S(+) ketamine (1 mg/kg) and morphine (0.025 mg/kg). The skin was incised 15 minutes after epidural administration of analgesics. Heart rate (HR), respiratory rate (RR), systolic blood pressure (SBP), oxygen saturation as measured by pulse oximetry, and arterial blood gases were obtained before anesthesia, 15 minutes after epidural administration of analgesics, 15 and 30 minutes after initiation of surgery, and at the end of surgery. During the intraoperative period, an increase of > or =20% in baseline values for HR, RR, and SBP was considered a sign of intraoperative pain. Signs of pain and adverse effects were assessed at 2, 4, and 8 hours postoperatively.

RESULTS

There were no significant differences in intraoperative or postoperative measurements among the 3 groups. No dogs had intraoperative signs of pain. Mean postoperative pain assessment scores were <3.5 in all 3 groups. Salivation was the most frequent adverse effect in dogs in groups 1 and 3, and sedation occurred more frequently in dogs in groups 2 and 3.

CONCLUSIONS AND CLINICAL RELEVANCE

All 3 analgesic regimens provided good respiratory and cardiovascular stability intraoperatively and adequate postoperative analgesia with minimal adverse effects.

Ketamine and postoperative pain – a quantitative systematic review of randomised trials

Ketamine, an N-methyl-D-aspartate receptor antagonist, is known to be analgesic and to induce psychomimetic effects. Benefits and risks of ketamine for the control of postoperative pain are not well understood. We systematically searched for randomised comparisons of ketamine with inactive controls in surgical patients, reporting on pain outcomes, opioid sparing, and adverse effects. Data were combined using a fixed effect model. Fifty-three trials (2839 patients) from 25 countries reported on a large variety of different ketamine regimens and surgical settings. Sixteen studies tested prophylactic intravenous ketamine (median dose 0.4 mg/kg, range (0.1-1.6)) in 850 adults. Weighted mean difference (WMD) for postoperative pain intensity (0-10 cm visual analogue scale) was -0.89 cm at 6 h, -0.42 at 12 h, -0.35 at 24 h and -0.27 at 48 h. Cumulative morphine consumption at 24 h was significantly decreased with ketamine (WMD -15.7 mg). There was no difference in morphine-related adverse effects. The other 37 trials tested in adults or children, prophylactic or therapeutic ketamine orally, intramuscularly, subcutaneously, intra-articulary, caudally, epidurally, transdermally, peripherally or added to a PCA device; meta-analyses were deemed inappropriate. The highest risk of hallucinations was in awake or sedated patients receiving ketamine without benzodiazepine; compared with controls, the odds ratio (OR) was 2.32 (95%CI, 1.09-4.92), number-needed-to-harm (NNH) 21. In patients undergoing general anaesthesia, the incidence of hallucinations was low and independent of benzodiazepine premedication; OR 1.49 (95%CI 0.18-12.6), NNH 286. Despite many published randomised trials, the role of ketamine, as a component of perioperative analgesia, remains unclear.

Effect of pre-emptive ketamine on sensory changes and postoperative pain after thoracotomy: comparison of epidural and intramuscular routes

BACKGROUND

In this study we have evaluated the efficacy of ketamine via i.m. and epidural routes for the control of post-thoracotomy pain.

METHODS

The study was randomized, double blinded and placebo controlled. With the approval of the Faculty Ethics Committee, 60 patients undergoing elective thoracotomy were randomized into three equal groups. Group IM had i.m. ketamine 1 mg kg(-1) in 2 ml plus epidural normal saline; Group EPI had epidural ketamine 1 mg kg(-1) in 10 ml plus i.m. normal saline; Group C had epidural normal saline 10 ml plus i.m. normal saline 10 ml. Anaesthesia was standardized. Postoperative analgesia was maintained with epidural patient-controlled analgesia using bupivacaine and morphine. Visual analogue scale values and analgesic consumption were evaluated at 2, 4, 6, 8, 10, 12, 24 and 48 h after surgery. The areas of allodynia, pin-prick hyperalgesia and pressure hyperalgesia were measured at 48 h, and days 15 and 30 in all groups.

RESULTS

Intraoperative fentanyl requirement was significantly lower in Group EPI than Group C. The morphine and bupivacaine requirements were significantly lower in Group EPI than the other two groups in the postoperative period. There was reduced pin-prick hyperalgesia and touch allodynia in the EPI group. There were no side-effects attributable to ketamine.

CONCLUSION

The results of the present study demonstrate that pre-emptive epidural ketamine is effective in reducing intra- and postoperative analgesic requirements, hyperalgesia and touch allodynia.

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.

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.

Epidural administration of tiletamine/zolazepam in horses

OBJECTIVES

To evaluate the analgesic, physiologic, and behavioral effects of the epidural administration of tiletamine/zolazepam in horses.

STUDY DESIGN

Prospective, double-blind, randomized experimental study.

ANIMALS

Five adult, healthy horses aged 10-16 years and weighing (mean +/- SD) 400 +/- 98 kg.

METHODS

The horses were sedated with 1.0 mg kg(-1) intravenous (IV) xylazine, and an epidural catheter was placed into the first intercoccygeal intervertebral space. After a 48-hour resting period, epidural tiletamine/zolazepam, 0.5 mg kg(-1) (treatment I) or 1.0 mg kg(-1) (treatment II), diluted up to 5 mL in sterile water, was administered with a 1-week interval between the treatments. Heart rate, respiratory rate, arterial blood pressure, and sedation were evaluated. In order to evaluate the respiratory effects, blood from the carotid artery was withdrawn at time 0 (baseline), and then after 60 and 240 minutes. Analgesia was evaluated by applying a noxious stimulus with blunt-tipped forceps on the perineal region, and graded as complete, moderate, or absent. Data were collected before tiletamine/zolazepam administration and at 15-minute intervals for 120 minutes, and 4 hours after tiletamine/zolazepam administration. Data were analyzed with anova and Bonferroni's test with p < 0.05.

RESULTS

The results showed no significant difference between treatments in cardiovascular and respiratory measurements. Sedation was observed with both doses, and it was significantly different from baseline at 60, 75, and 90 minutes in treatment II. Moderate analgesia and locomotor ataxia were observed with both the treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

The results suggest that caudal epidural 0.5 and 1.0 mg kg(-1) tiletamine/zolazepam increases the threshold to pressure stimulation in the perineal region in horses. The use of epidural tiletamine/zolazepam could be indicated for short-term moderate epidural analgesia. There are no studies examining spinal toxicity of Telazol, and further studies are necessary before recommending clinical use of this technique.

Interaction Between Epidurally Administered Ketamine and Pethidine in Dogs

The present study was designed to test the hypothesis that a synergistic interaction could be recorded after epidural administration of ketamine-an N-methyl-D-aspartate (NMDA) antagonist and pethidine--an opioid agonist. Twelve adult mongrel dogs of either sex were randomly divided in three groups A, B and C of four animals each. Ketamine (5%) at 2.5 mg/kg and pethidine (3%) 2 mg/kg were injected at lumbosacral epidural space in animals of groups A and B, respectively. In animals of group C ketamine (2.5 mg/kg) and pethidine (2 mg/kg) were injected. Heart rate increased significantly up to 15 min in group A, whereas in groups B and C, the increase was non-significant for a period of 10 and 45 min, respectively. Respiration increased gradually up to 45-60 min in group A and for 15-20 min in group B. However, in animals of group C respiration fell below the baseline during the first 10-15 min and then returned near the baseline. Rectal temperature decreased only marginally in all the groups. Ketamine alone produced complete analgesia at tail and perineal region for a period of 5-10 min and then moderate analgesia for the next 20-30 min. Analgesia at the flank was moderate to complete between 5 and 15 min. In group B complete analgesia was only moderate at the tail and perineal region up to 30 min. In animals of group C, complete analgesia was observed only at perineal region for a very short period (5 min). Analgesia was not associated with sedation in any of the groups but animals of groups A and C showed signs of motor incoordination. Results of the study suggest rather antagonistic than synergistic interaction between epidurally administered ketamine and pethidine. Further studies are needed to confirm the antagonistic interaction between the two drugs.

Current status of pre-emptive analgesia

PURPOSE OF REVIEW

The controversy over preemptive analgesia continues unabated, with studies both supporting and refuting its efficacy. The timing of an analgesic intervention and presence of a placebo control may have significant impact on the interpretation of results and may have led to the premature conclusion that preemptive analgesia is of limited clinical utility. A review of the recent literature using strict definitions of preemptive and preventive analgesia is required in order to clarify the broader issue of the benefits of perioperative analgesia.

RECENT FINDINGS

A total of 27 studies, published from April 2001 to April 2002, were found to evaluate preemptive (n = 12) or preventive analgesia (n = 15). Evidence for a benefit of preventive analgesia was strong, with 60% of studies finding reduced pain or analgesic consumption beyond the clinical duration of action of the analgesic intervention. Evidence for a benefit of preemptive analgesia was equivocal, with 41.7% of studies demonstrating that preincisional treatment reduces pain or analgesic consumption to a greater extent than does postincisional treatment.

SUMMARY

Studies that used a preventive design had a greater likelihood of finding a beneficial effect. The application of preventive perioperative analgesia (not necessarily preincisional) is associated with a significant reduction in pain beyond the clinical duration of action of the analgesic agent, in particular for the N-methyl-D-aspartate antagonists. The classical definition of preemptive analgesia should be abandoned in favor of preventive analgesia. This will broaden the scope of inquiry from a narrow focus on preincisional versus postincisional interventions to one that aims to minimize postoperative pain and analgesic requirements by reducing peripheral and central sensitization arising from noxious preoperative, intraoperative and postoperative inputs.