Double-blind comparison of extradural block with three bupivacaine-ketamine mixtures in knee arthroplasty

Effects of Ketamine and Tramadol As Adjuvants to Bupivacaine in Spinal Anesthesia for Unilateral Open Ovarian Cystectomy: A Randomized Controlled Trial

BACKGROUND

Spinal anesthesia offers numerous advantages and desirable features. However, it is associated with various side effects related to local anesthetic agents used. Reducing the dose of local anesthetic in spinal anesthesia can help minimize side effects but may lead to a diminished analgesic effect or failure of anesthesia. Therefore, adding an adjuvant may enhance the benefits while mitigating side effects.

OBJECTIVE

This study aimed to evaluate the effects of ketamine and tramadol as adjuvants to bupivacaine on the duration of spinal analgesia. The objectives were to compare the three groups and prove their analgesic effects, safety, and superiority. The primary outcomes were the duration of spinal analgesia, as well as the onset and duration of both sensory and motor blocks. Secondary outcomes included the heart rate, mean arterial pressure, and the incidence of undesired effects such as nausea, vomiting, sedation, shivering, and postoperative headache.

METHODS

In this double-blind randomized controlled trial, 120 female patients undergoing elective open unilateral ovarian cystectomy under spinal anesthesia were studied. The inclusion criteria included patients aged 16-45 years with a physical status classified as American Society of Anesthesiologists (ASA) class I and II. Patients were randomly allocated into three groups: group B (n=40) received only bupivacaine, group BK (n=40) received bupivacaine mixed with preservative-free ketamine, and group BT (n=40) received bupivacaine mixed with preservative-free tramadol.

RESULTS

The mean duration of spinal analgesia, measured in minutes, showed significant differences (P < 0.001) between group BK (165 ± 4) and group B (170 ± 5). There was also a significant difference between group BT (313 ± 8) and group B (170 ± 5) (P < 0.001). Additionally, significant differences were observed between group BK (165 ± 4) and group BT (313 ± 8) (P < 0.001).

CONCLUSION

The administration of 25 mg of ketamine and 25 mg of tramadol as adjuvants to bupivacaine in spinal anesthesia significantly affected the postoperative duration of analgesia. Tramadol prolonged the duration of spinal anesthesia, while ketamine shortened it. The use of both adjuvants did not result in undesired effects.

Inhibition of Voltage-Gated Na+ Channels by Bupivacaine Is Enhanced by the Adjuvants Buprenorphine, Ketamine, and Clonidine

BACKGROUND AND OBJECTIVES

Regional anesthesia includes application of local anesthetics (LAs) into the vicinity of peripheral nerves. Prolongation or improvement of nerve blocks with LAs can be accomplished by coapplication with adjuvants, including buprenorphine, ketamine, and clonidine. While the mechanisms mediating prolonged or improved LA-induced effects by adjuvants are poorly understood, we hypothesized that they are likely to increase LA-induced block of voltage-gated Na channels. In this study, we investigated the inhibitory effects of the LA bupivacaine alone and in combination with the adjuvants on neuronal Na channels.

METHODS

Effects of bupivacaine, buprenorphine, ketamine, and clonidine on endogenous Na channels in ND7/23 neuroblastoma cells were investigated with whole-cell patch clamp.

RESULTS

Bupivacaine, buprenorphine, ketamine, and clonidine are concentration- and state-dependent inhibitors of Na currents in ND7/23 cells. Tonic block of resting channels revealed an order of potency of bupivacaine (half-maximal inhibitory concentration [IC50] 178 ± 8 μM) > buprenorphine (IC50 172 ± 25) > clonidine (IC50 824 ± 55 μM) > ketamine (IC50 1377 ± 92 μM). Bupivacaine and buprenorphine, but not clonidine and ketamine, induced a strong use-dependent block at 10 Hz. Except for clonidine, all substances enhanced fast and slow inactivation. The combination of bupivacaine with one of the adjuvants resulted in a concentration-dependent potentiation bupivacaine-induced block.

CONCLUSIONS

We demonstrate that buprenorphine, ketamine, and clonidine directly inhibit Na channels and that they potentiate the blocking efficacy of bupivacaine on Na channels. These data indicate that block of Na channels may account for the additive effects of adjuvants used for regional anesthesia.

Adjuvants to local anesthetics: Current understanding and future trends

Although beneficial in acute and chronic pain management, the use of local anaesthetics is limited by its duration of action and the dose dependent adverse effects on the cardiac and central nervous system. Adjuvants or additives are often used with local anaesthetics for its synergistic effect by prolonging the duration of sensory-motor block and limiting the cumulative dose requirement of local anaesthetics. The armamentarium of local anesthetic adjuvants have evolved over time from classical opioids to a wide array of drugs spanning several groups and varying mechanisms of action. A large array of opioids ranging from morphine, fentanyl and sufentanyl to hydromorphone, buprenorphine and tramadol has been used with varying success. However, their use has been limited by their adverse effect like respiratory depression, nausea, vomiting and pruritus, especially with its neuraxial use. Epinephrine potentiates the local anesthetics by its antinociceptive properties mediated by alpha-2 adrenoreceptor activation along with its vasoconstrictive properties limiting the systemic absorption of local anesthetics. Alpha 2 adrenoreceptor antagonists like clonidine and dexmedetomidine are one of the most widely used class of local anesthetic adjuvants. Other drugs like steroids (dexamethasone), anti-inflammatory agents (parecoxib and lornoxicam), midazolam, ketamine, magnesium sulfate and neostigmine have also been used with mixed success. The concern regarding the safety profile of these adjuvants is due to its potential neurotoxicity and neurological complications which necessitate further research in this direction. Current research is directed towards a search for agents and techniques which would prolong local anaesthetic action without its deleterious effects. This includes novel approaches like use of charged molecules to produce local anaesthetic action (tonicaine and n butyl tetracaine), new age delivery mechanisms for prolonged bioavailability (liposomal, microspheres and cyclodextrin systems) and further studies with other drugs (adenosine, neuromuscular blockers, dextrans).

A procedure-specific systematic review and consensus recommendations for postoperative analgesia following total knee arthroplasty

The PROSPECT Working Group, a collaboration of anaesthetists and surgeons, conducts systematic reviews of postoperative pain management for different surgical procedures (http://www.postoppain.org). Evidence-based consensus recommendations for the effective management of postoperative pain are then developed from these systematic reviews, incorporating clinical practice observations, and transferable evidence from other relevant procedures. We present the results of a systematic review of pain and other outcomes following analgesic, anaesthetic and surgical interventions for total knee arthroplasty (TKA). The evidence from this review supports the use of general anaesthesia combined with a femoral nerve block for surgery and postoperative analgesia, or alternatively spinal anaesthesia with local anaesthetic plus spinal morphine. The primary technique, together with cooling and compression techniques, should be supplemented with paracetamol and conventional non-steroidal anti-inflammatory drugs or COX-2-selective inhibitors, plus intravenous strong opioids (high-intensity pain) or weak opioids (moderate- to low-intensity pain).

New drugs for neuraxial blockade

Recent years have seen a dramatic increase in the number of agents used for neuraxial blockade. Together with the developments in local anaesthetics and opioids, completely new categories of agents have been investigated for intrathecal and epidural use. A review of the recent literature reveals the potential for improvement in achieving balanced anaesthesia and analgesia, in particular combining agents to reduce adverse effects.

A double-blind comparison of intrathecal S(+) ketamine and fentanyl combined with bupivacaine 0.5% for Caesarean delivery

BACKGROUND

In this prospective, randomized, double-blind, controlled study, we investigated the sensory, motor and analgesic block characteristics of S(+) ketamine, fentanyl and saline given intrathecally (IT) in addition to 0.5% plain bupivacaine (10 mg) for spinal analgesia.

METHODS

Ninety ASA I or II adult patients undergoing Caesarean section were randomly allocated to receive 1.0 mL of 0.9% saline in Group S (n = 30), 0.05 mg kg-1 of S(+) ketamine (1.0 mL) in Group K (n =30) or 25 microg (1.0 mL) of fentanyl in Group F (n =30) following 10 mg of plain bupivacaine 0.5% IT. We recorded onset and duration of sensory and motor block, time to reach the maximal dermatomal level of sensory block and duration of spinal analgesia.

RESULTS

The onset time of sensory and motor block was significantly shorter in Groups K and F than in Group S (P < 0.014). Their duration was significantly longer in Group F than in Groups K and S (P < 0.009). The time to reach the maximal dermatomal level of sensory block was significantly shorter in Groups K and F than in Group S (P < 0.001). The duration of spinal analgesia was significantly longer in Group F than in Groups K and S (P < 0.001).

CONCLUSION

In patients undergoing Caesarean section with spinal analgesia, the addition of S(+) ketamine (0.05 mg kg-1) IT to 10 mg of spinal plain bupivacaine (0.5%) led to rapid onset of both sensory and motor blockade and enhanced the segmental spread of spinal block without prolonging the duration of spinal analgesia, whereas fentanyl provided prolonged analgesia.

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.

Comparison of caudal ketamine with lidocaine or tramadol administration for postoperative analgesia of hypospadias surgery in children

BACKGROUND

This study was designed to investigate whether the addition of tramadol or lidocaine to ketamine would enhance the quality of intra- and postoperative analgesia for hypospadias surgery in children.

METHODS

Sixty-two ASA PS I or II children, between 1 and 10 years of age, scheduled for hypospadias surgery were recruited. Anesthesia was induced with 6-8% sevoflurane and maintained with 0.5-2.5% sevoflurane-50% N2O in oxygen. Children were allocated randomly to receive one of two study drugs. Children in group KL received caudal ketamine (0.25 mg.kg(-1)) plus lidocaine (2%, 2 mg.kg(-1)) and in group KT ketamine (0.25 mg.kg(-1)) plus tramadol (1 mg.kg(-1)). Systemic blood pressure, heart rate, peripheral O2 saturation, sedation, and pain scores (CHEOPS) were recorded at 1, 5, 10, 15, 30, 45 min and 1, 2, 3 h following recovery from anesthesia.

RESULTS

Duration of analgesia was similar in the two groups (P > 0.05). CHEOPS in group KL was lower than in group KT during the study period, except at first 15 min. Sedation scores were higher in group KL than group KT in the first 10 min (P < 0.05). Incidence of postoperative nausea and vomiting was similar in the two groups (P > 0.05) Sevoflurane concentration required was significantly lower in group KL than group KT peroperatively (P < 0.001).

CONCLUSIONS

Caudal ketamine (0.25 mg.kg(-1)), plus lidocaine (2% 2 mg.kg(-1)) significantly reduced sevoflurane concentration compared with ketamine (0.25 mg.kg(-1)) + tramadol (1 mg.kg(-1)). We suggested that both ketamine + lidocaine and ketamine + tramadol provided very effective and long duration of analgesia, similarly. However, analgesia quality is superior in the ketamine-lidocaine group postoperatively.

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.

Comparison of caudal ropivacaine, ropivacaine plus ketamine and ropivacaine plus tramadol administration for postoperative analgesia in children

BACKGROUND

The aim of this study was to compare the effect of single-dose caudal ropivacaine, ropivacaine plus ketamine and ropivacaine plus tramadol in children for postoperative pain management.

METHODS

Following ethics committee approval and informed parental consent, 99 ASA PS I or II children, between 1 and 10 years of age, scheduled for elective inguinal hernia repair with general anaesthesia, were recruited. After induction of anaesthesia and placement of a laryngeal mask airway (LMATM), the patients were randomly divided into three groups to receive either caudal ropivacaine alone (0.4%, 2 mg x kg(-1)) in group R (n = 32) or ropivacaine (0.2%, 1 mg x kg(-1)) plus ketamine (0.25 mg x kg(-1)) in group RK (n = 33) or ropivacaine (0.2%, 1 mg x kg(-1)) plus tramadol (1 mg x kg(-1)) in group RT (n = 34) with a total volume of 0.5 ml x kg(-1). Systemic blood pressure (SBP and DBP), heart rate (HR), peripheral O2 saturation (SpO2), respiratory rate (RR), sedation and pain scores were recorded at 5, 10, 15 and 30 min, 1, 3, 4 and 6 h following recovery from anaesthesia. Pain was evaluated by Children's Hospital of Eastern Ontario Pain Scale, and sedation with a five-point sedation test.

RESULTS

No difference was found regarding age, weight and duration of operation between the groups (P > 0.05). No patient experienced hypotension, bradycardia or respiratory depression. Duration of analgesia was longer in group RT (1377 +/- 204 min) than group R (1006 +/- 506 min) (P = 0.001). In the tramadol group, fewer patients required supplementary analgesics in the first 24 h (P = 0.005). Sedation scores were below 2 in all groups. Incidence of postoperative nausea and vomiting was higher in group RT (eight patients) and group RK (seven patients) than group R (one patient, P = 0.032).

CONCLUSIONS

Ropivacaine (0.4%), ropivacaine (0.2%) plus ketamine (0.25 mg x kg(-1)) and ropivacaine (0.2%) plus tramadol (0.5 mg x kg(-1)) provided sufficient analgesia in children, but the duration of analgesia was longer in the RT group.

Effects of S(+) ketamine added to bupivacaine for spinal anaesthesia for prostate surgery in elderly patients

BACKGROUND AND OBJECTIVE

Intrathecal ketamine as the sole anaesthetic agent has demonstrated a lack of cardiovascular depression that should be of advantage in an elderly population. S(+) ketamine has three-times the analgesic potency of R(-) ketamine and its antinociceptive effects after intrathecal administration in rats are known. We decided to evaluate the effects of intrathecal S(+) ketamine added to a small dose of spinal bupivacaine in elderly patients undergoing transurethral prostate surgery.

METHODS

Forty males over 60 yr old, scheduled for transurethral prostate resection under spinal anaesthesia, were studied in a prospective, double-blinded, randomized way. Patients were allocated to receive either bupivacaine 10 mg or bupivacaine 7.5 mg combined with S(+) ketamine 0.1 mg kg(-1). Spinal block onset time, maximum sensory level, duration of blockade, haemodynamic variables, postoperative analgesic requirements and adverse events were recorded.

RESULTS

Onset times of motor and sensory block were shorter in the bupivacaine plus S(+) ketamine group. Incomplete motor block of the lower extremities was seen in 80% of the patients in bupivacaine plus S(+) ketamine group. Duration of complete motor block and spinal analgesia was shorter in the bupivacaine plus S(+) ketamine group. There was no significant difference in arterial pressure. Heart rate decreased after spinal anaesthesia in the bupivacaine plus S(+) ketamine group and was significantly lower until the end of anaesthesia. The incidence of adverse effects was not different between groups.

CONCLUSIONS

Intrathecal S(+) ketamine administered with a low dose of bupivacaine provides shorter motor and sensory block onset time, shorter duration of action and less motor blockade in elderly males.

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 analgesia for pain relief following hip or knee replacement

BACKGROUND

Hip and knee replacement are common operative procedures to improve mobility and quality of life. Adequate pain relief is essential in the postoperative period to enable ambulation and initiation of physiotherapy. Lumbar epidural analgesia is a common modality for pain relief following these procedures. However, there is no systematic review of the evidence comparing the efficacy of epidural analgesia with other postoperative analgesic modalities. As the use of epidural analgesia may delay the initiation of anticoagulant thromboprophylaxis due to the potential risk of epidural hematoma, a synthesis of the evidence is necessary to determine whether or not alternative analgesic modalities are worse, equivalent, or better than epidural analgesia.

OBJECTIVES

Our objective is to answer the question: "Is lumbar epidural analgesia more efficacious than systemic analgesia or long-acting spinal analgesia for postoperative pain relief in patients after elective hip or knee replacement?"

SEARCH STRATEGY

MEDLINE, EMBASE, CINAHL, LILACS, and the Cochrane Controlled Trials Register were searched from their inception to June 2001. Reference lists of review articles and included studies were also reviewed for additional citations.

SELECTION CRITERIA

A study was included if it was a randomized or pseudo randomized controlled clinical trial of patients undergoing hip or knee replacement, in which postoperative lumbar epidural analgesia was compared to other methods for pain relief. Study selection was performed unblinded in duplicate.

DATA COLLECTION AND ANALYSIS

Data were collected unblinded in duplicate. Information on the patients, methods, interventions, outcomes (pain relief, postoperative function, length of stay) and adverse events were recorded. Methodological quality was assessed using a validated 5-point scale. Meta-analysis was conducted when sufficient data existed from two or more studies. Heterogeneity testing was performed using the Breslow-Day method. The fixed effects model was used unless heterogeneity was present, in which case, a random effects model was used. Continuous data were summarized as weighted mean differences (WMD) or standardized mean differences (SMD) with 95% confidence intervals (CI). Dichotomous data were summarized as odds ratios (OR) and numbers-needed-to-treat (NNT) or numbers-needed-to-harm (NNH) with their respective 95% CI. Graphical representation of continuous data used the MetaView program.

MAIN RESULTS

In the first four to six hours after surgery, patients receiving epidural analgesia had less pain at rest, based on visual analog scores (VAS), than patients receiving systemic analgesia (SMD -0.77; 95% CI -1.24 to -0.31). This effect was not statistically significant by 18 to 24 hours (SMD -0.29; 95% CI -0.73 to 0.16). These observations were based only on studies evaluating populations consisting of total knee replacements alone or mixed populations of total hip or total knee replacements. For pain relief with movement after surgery, patients receiving epidural analgesia reported lower pain scores than patients receiving systemic analgesia in all four studies examining these outcomes. The choice of epidural agents may also influence the extent to which epidural analgesia differs from systemic analgesia. The differences between epidural analgesia and systemic analgesia in the frequency of nausea and vomiting (OR 0.95; 95% CI 0.60 to 1.49) or depression of breathing (OR 1.07; 95% CI 0.45 to 2.54) were not statistically significant. Sedation occurred less frequently with epidural analgesia (OR 0.30; 95% CI 0.09 to 0.97) with a number-needed-to-harm of 7.7 (95% CI 3.5 to 42.0) patients for the systemic analgesia group. Retention of urine (OR 3.50, 95% CI 1.63 to 7.51; NNH 4.5, 95% CI 2.3 to 12.2), itching (OR 4.74, 95% CI 1.76 to 12.78; NNH 6.8, 95% CI 4.4 to 15.8), and low blood pressure (OR 2.78, 95% CI 1.15 to 6.72; NNH 6.7, 95% CI 3.5 to 103) were more frequent with epidural analgesia compared to systemic analgesia. There were insufficient numbers to draw conclusions on the edural analgesia compared to systemic analgesia. There were insufficient numbers to draw conclusions on the effect of epidural analgesia on serious postoperative complications, functional outcomes, or length of hospital stay.

REVIEWER'S CONCLUSIONS

Epidural analgesia may be useful for postoperative pain relief following major lower limb joint replacements. However, the benefits may be limited to the early (four to six hours) postoperative period. An epidural infusion of local anesthetic or local anesthetic-narcotic mixture may be better than epidural narcotic alone. The magnitude of pain relief must be weighed against the frequency of adverse events. The current evidence is insufficient to draw conclusions on the frequency of rare complications from epidural analgesia, postoperative morbidity or mortality, functional outcomes, or length of hospital stay.

The comparison of caudal ketamine, alfentanil and ketamine plus alfentanil administration for postoperative analgesia in children

BACKGROUND

Our aim was to compare the effect of single dose caudal ketamine, alfentanil or a mixture of both drugs in the treatment of pain after hypospadias repair surgery in children.

METHODS

The group comprised 109 boys, ASA I-II, aged 1-9 years, who were undergoing hypospadias repair surgery as day cases. The children were randomly divided into three groups for postoperative analgesia: group 1, only alfentanil (20 microg x kg(-10) was given caudally; group 2, ketamine (0.5 mg x kg(-1)) alone; and group 3, alfentanil (20 microg x kg(-1))-ketamine (0.5 mg x kg(-1)) was given caudally. The analgesic effect of caudal block was evaluated using the Children's Hospital of Eastern Ontario Pain Scale (CHEOPS) and sedation was assessed using a five-point sedation score. The first analgesic requirement time and the number of supplementary analgesics required by each child in a 24-h period were also recorded.

RESULTS

No statistical differences were found in demographic characteristics, haemodynamic and respiratory parameters, objective pain scores, postoperative sedation scores and duration of surgery among the groups. The median time to first analgesia was significantly shorter in group 1 than in groups 2 and 3 (P=0.009, P=0.001). Significantly more patients in group 1 required additional postoperative analgesia (paracetamol 15 mg x kg(-1)) compared with groups 2 and 3 (P < 0.001).

CONCLUSIONS

Caudal administration of ketamine 0.5 mg.kg-1 with or without alfentanil in children produced satisfactory postoperative analgesia without respiratory depression or other side-effects.

Evaluation of the safety and efficacy of epidural ketamine combined with morphine for postoperative analgesia after major upper abdominal surgery

STUDY OBJECTIVE

To evaluate the efficacy of the combination of epidural ketamine and morphine compared with epidural morphine alone for postoperative pain relief following major upper abdominal surgery.

STUDY DESIGN

Prospective, randomized, double-blinded study.

SETTING

Tertiary care referral and teaching hospital.

PATIENTS

46 ASA physical status I and II patients who underwent major upper abdominal procedures.

INTERVENTIONS

Patients were randomly allocated to one of the two treatment groups: patients in Group 1 received epidural morphine 50 microg/kg whereas patients in Group 2 received epidural ketamine 1 mg/kg combined with 50 microg/kg of morphine postoperatively.

MEASUREMENTS

A blinded observer using a visual analog scale (VAS) for pain assessment followed up patients for 48 hours postoperatively. Top-up dose of epidural morphine was provided when VAS was higher than 4. Analgesic requirements and side effects were compared between the two groups.

RESULTS

Only 40 patients completed the study. There were no differences between the two groups with respect to age, gender, weight, duration, or type of surgical procedure or intraoperative opioid requirements. Onset of analgesia was faster (p < 0.001) in Group 2 (11 min) than in Group 1 patients (25 min). The time for first requirement of analgesia was significantly (p < 0.01) longer (19.8 +/- 9.8 hours) in Group 2 patients than Group 1 (12.8 +/- 6.2 hours). Total number of supplemental doses of epidural morphine required in the first 48 hours postoperatively was also significantly less (p < 0.005) in Group 2 compared to Group 1. Patients in Group 2 had higher sedation scores than Group I patients for the first 2 hours postoperatively. None of the patients in either group developed hallucinations or respiratory depression. Other side effects such as pruritus, nausea, and vomiting were also similar in both groups.

CONCLUSIONS

The addition of epidural ketamine 1 mg/kg to morphine 50 microg/kg improved analgesia after major upper abdominal surgery without increasing side effects.

Small-dose S(+)-ketamine reduces postoperative pain when applied with ropivacaine in epidural anesthesia for total knee arthroplasty

Reduction of nociceptive input through blockade of N-methyl-D-aspartate (NMDA) receptors has been reported. We compared the effects of epidural S(+)-ketamine versus placebo on postoperative pain in a randomized, double-blinded study in 37 patients undergoing unilateral knee arthroplasty. After lumbar epidural anesthesia with ropivacaine (10 mg/mL, 10-20 mL), 19 patients received 0.9% epidural saline, and 18 patients received 0.25 mg/kg epidural S(+)-ketamine 10 min before surgical incision. After surgery, patient-controlled epidural analgesia with ropivacaine was provided. During the first 8 h after surgery, visual analog scale pain rating was similar between groups. Twenty-four and 48 h after surgery, patients anesthetized with ropivacaine had higher visual analog scale ratings at rest and during movement (P < 0.05) than patients anesthetized with S(+)-ketamine and ropivacaine. Forty-eight hours after surgery, patients anesthetized with ropivacaine also consumed more ropivacaine (558 +/- 210 mg) (P < 0.01) than those anesthetized with S(+)-ketamine and ropivacaine (319 +/- 204 mg). Adverse events were similar between groups. Patients who received S(+)-ketamine and ropivacaine rated the quality of their pain therapy better than those who received ropivacaine alone (P < 0.05). We conclude that the combination of S(+)-ketamine and ropivacaine in epidural anesthesia increases postoperative pain relief when compared with ropivacaine.

IMPLICATIONS

Epidural S(+)-ketamine applied with ropivacaine before surgery is a rational approach to decrease injury-induced pain sensitization. Epidural blockade with an N-methyl-D-aspartate receptor antagonist and a local anesthetic may provide better analgesia in the postoperative period than a local anesthetic alone.

The Epidural and Intrathecal Administration of Ketamine

An overview of the spinal administration of ketamine is presented. Ketamine acts as a noncompetitive antagonist of the NMDA receptor Ca(++ channel pore. This effect provides interesting possibilities in pain therapy. However, there are still contrasting results that seem to be due to a lack of comparative controlled studies. The presence of systemic and neurotoxic effects presently limits clinical use).

Effects of intrathecal ketamine added to bupivacaine for spinal anaesthesia

We prospectively studied 30 healthy female patients undergoing intracavitory brachytherapy applicator insertion for carcinoma of the cervix under spinal anaesthesia. Patients were randomly allocated to receive either intrathecal bupivacaine 10 mg alone or bupivacaine 7.5 mg combined with preservative-free ketamine 25 mg. Spinal block onset, maximum sensory level, duration of blockade, haemodynamic variables, postoperative analgesic requirements and adverse events were recorded. Onset of sensory and motor block and duration of spinal analgesia were comparable between groups. Duration of motor blockade was shorter (p = 0.0416) and requirement for intravenous fluids in the peri-operative period was less (p = 0.0159) in the ketamine group. Significantly more patients in the ketamine group had adverse events, such as sedation, dizziness, nystagmus, 'strange feelings' and postoperative nausea and vomiting. Although the addition of ketamine to spinal bupivacaine had local anaesthetic sparing effects, it did not provide extended postoperative analgesia or decrease the postoperative analgesic requirements. Moreover, the central adverse effects of ketamine limit its spinal application.

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

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