The effect of ketamine on nerve conduction in isolated sciatic nerves of the toad

Efficacy and Safety of Adding Ketamine to Lidocaine in Intravenous Regional Anesthesia: A Meta-analysis of Randomized Controlled Trials

PURPOSE

To systematically evaluate the efficacy and safety of adding ketamine (K) to lidocaine (L) for intravenous regional anesthesia (IVRA).

DESIGN

A systematic review and meta-analysis.

METHODS

A comprehensive search of the Cochrane library, Embase, PubMed, Web of Science, and ProQuest databases, and the Google Scholar search engine was conducted from inception to March 2023. All retrieved articles were imported into Endnote X20 software and independently screened by two researchers according to predetermined inclusion and exclusion criteria. The data were analyzed using Revman 5.4 software and the assessed outcomes included the time of sensory and motor block onset, time of sensory and motor block recovery, fentanyl consumption, time of tourniquet pain onset, intraoperative and postoperative visual analog scale scores, and complications.

FINDINGS

A total of 532 patients from 11 randomized controlled trials were included in the meta-analysis. The results showed that the time of sensory (P < .00001) and motor block onset (P < .00001) were shorter in the L + K group than in the L-only group. The time of sensory (P = .01) and motor block recovery (P = .006) and time of tourniquet pain onset (P < .00001) were longer in the L + K group than in the L-only group. There was a significant reduction in fentanyl consumption (P = .0002) in the L + K group compared to the L-only group. Moreover, the visual analog scale scores in the L + K group were significantly lower than the L-only group 10 minutes (P = .04), 20 minutes (P = .0004), 30 minutes (P < .00001), and 40 minutes (P < .0001) after tourniquet inflation, and 5 minutes (P < .00001), 15 minutes (P = .04), 30 minutes (P = .008), 1 hour (P = .002), 2 hours (P < .00001), and 4 hours (P < .00001) after tourniquet deflation. There was no evidence that the use of K as an adjuvant in IVRA increased adverse effects.

CONCLUSIONS

The addition of K to L in IVRA shortened the onset time, prolonged the block time, and reduced intraoperative and postoperative pain without increasing complications.

Narrative Review: Low-Dose Ketamine for Pain Management

Pain is the leading cause of medical consultations and occurs in 50-70% of emergency department visits. To date, several drugs have been used to manage pain. The clinical use of ketamine began in the 1960s and it immediately emerged as a manageable and safe drug for sedation and anesthesia. The analgesic properties of this drug were first reported shortly after its use; however, its psychomimetic effects have limited its use in emergency departments. Owing to the misuse and abuse of opioids in some countries worldwide, ketamine has become a versatile tool for sedation and analgesia. In this narrative review, ketamine's role as an analgesic is discussed, with both known and new applications in various contexts (acute, chronic, and neuropathic pain), along with its strengths and weaknesses, especially in terms of psychomimetic, cardiovascular, and hepatic effects. Moreover, new scientific evidence has been reviewed on the use of additional drugs with ketamine, such as magnesium infusion for improving analgesia and clonidine for treating psychomimetic symptoms. Finally, this narrative review was refined by the experience of the Pain Group of the Italian Society of Emergency Medicine (SIMEU) in treating acute and chronic pain with acute manifestations in Italian Emergency Departments.

Subcutaneous Ketamine in Depression: A Systematic Review

Background: Ketamine has been shown to produce a rapid and robust antidepressant effect. Though numerous routes of administration have been studied, subcutaneous (SC) has proven to be a convenient and cost-effective route making its use particularly relevant in developing countries. Here we provide a systematic review covering the use of SC racemic ketamine and esketamine in depression, including its efficacy, safety and tolerability. Methods: A systematic literature search was carried out, from inception through March, 2021, using PubMed/MEDLINE, EMBASE and Web of Science, with no limits of language. After identifying 159 potentially relevant articles, 12 articles were selected after applying our inclusion/exclusion criteria. These comprised two randomized clinical trials, five case-reports and five retrospective studies. Given the small number of studies found and their heterogeneous nature, a meta-analysis was not considered appropriate. Here we provide a synthesis of these data including participant characteristics, dose range, efficacy, safety/ tolerability. Risk of bias was accessed using the Cochrane risk of bias tool. Results: SC Ketamine was administered to unipolar and bipolar patients a single or multiple doses, weekly or twice-weekly, a dose-titration approach was made in major studies, dose ranged from 0.1 to 0.5 mg/Kg of racemic ketamine and 0.5-1 mg/Kg of esketamine. Across all studies, SC ketamine showed a rapid and robust antidepressant effect, with response/ remission rates from 50 to 100% following both single or multiple doses, with transitory side effects. Conclusion: SC racemic ketamine and esketamine in depression is a promising strategy showing beneficial efficacy and tolerability. Future studies exploring the SC route, its cost-effectiveness, and a direct comparison with IV and intranasal (IN) protocols are warranted. Systematic Review Registration: CRD42019137434.

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).

Adjuvant Agents in Regional Anesthesia in the Ambulatory Setting

PURPOSE OF REVIEW

A majority of surgical practice has involved ambulatory centers with the number of outpatient operations in the USA doubling to 26.8 million per year. Local anesthesia delivery provides numerous benefits, including increased satisfaction, earlier discharge, and reduction in unplanned hospital admission. Further, with the epidemic of opioid mediated overdoses, local anesthesia can be a key tool in providing an opportunity to reduce the need for other analgesics postoperatively.

RECENT FINDINGS

Adjuvants such as epinephrine and clonidine enhance local anesthetic clinical utility. Further, dexmedetomidine prolongs regional blockade duration effects. There has also been a significant interest recently in the use of dexamethasone. Studies have demonstrated a significant prolongation in motor and sensory block with perineural dexamethasone. Findings are conflicting as to whether intravenous dexamethasone has similar beneficial effects. However, considering the possible neurotoxicity effects, which perineural dexamethasone may present, it would be prudent not to consider intravenously administered dexamethasone to prolong regional block duration. Many studies have also demonstrated neurotoxicity from intrathecally administered midazolam. Therefore, midazolam as an adjuvant is not recommended. Magnesium prolongs regional block duration but related to paucity of studies as of yet, cannot be recommended. Tramadol yields inconsistent results and ketamine is associated with psychotomimetic adverse effects. Buprenorphine consistently increases regional block duration and reduce opioid requirements by a significant amount. Future studies are warranted to define best practice strategies for these adjuvant agents. The present review focuses on the many roles of local anesthetics in current ambulatory practice.

Local Anesthetic Peripheral Nerve Block Adjuvants for Prolongation of Analgesia: A Systematic Qualitative Review

Background

The use of peripheral nerve blocks for anesthesia and postoperative analgesia has increased significantly in recent years. Adjuvants are frequently added to local anesthetics to prolong analgesia following peripheral nerve blockade. Numerous randomized controlled trials and meta-analyses have examined the pros and cons of the use of various individual adjuvants.

Objectives

To systematically review adjuvant-related randomized controlled trials and meta-analyses and provide clinical recommendations for the use of adjuvants in peripheral nerve blocks.

Methods

Randomized controlled trials and meta-analyses that were published between 1990 and 2014 were included in the initial bibliographic search, which was conducted using Medline/PubMed, Cochrane Central Register of Controlled Trials, and EMBASE. Only studies that were published in English and listed block analgesic duration as an outcome were included. Trials that had already been published in the identified meta-analyses and included adjuvants not in widespread use and published without an Investigational New Drug application or equivalent status were excluded.

Results

Sixty one novel clinical trials and meta-analyses were identified and included in this review. The clinical trials reported analgesic duration data for the following adjuvants: buprenorphine (6), morphine (6), fentanyl (10), epinephrine (3), clonidine (7), dexmedetomidine (7), dexamethasone (7), tramadol (8), and magnesium (4). Studies of perineural buprenorphine, clonidine, dexamethasone, dexmedetomidine, and magnesium most consistently demonstrated prolongation of peripheral nerve blocks.

Conclusions

Buprenorphine, clonidine, dexamethasone, magnesium, and dexmedetomidine are promising agents for use in prolongation of local anesthetic peripheral nerve blocks, and further studies of safety and efficacy are merited. However, caution is recommended with use of any perineural adjuvant, as none have Food and Drug Administration approval, and concerns for side effects and potential toxicity persist.

Effect of ketamine as an adjuvant in ultrasound-guided supraclavicular brachial plexus block: A double-blind randomized clinical trial study

Background:

Supraclavicular brachial plexus block is one of the most effective anesthetic procedures in operations for the upper extremity. Ketamine has been reported to enhance the analgesic effects of local anesthetics. We have conducted this study to assess whether coadministration of ketamine can prolong the local analgesic effect of lidocaine in the supraclavicular brachial plexus block for patients undergoing elective upper extremity surgery.

Materials and Methods:

Sixty adult patients undergoing elective surgery of the elbow, forearm, wrist or hand were randomly allocated in two groups of 30 patients each. Group 1 (ketamine group) received 5 mg/kg lidocaine 1.5% plus 2 mg/kg ketamine, Group 2 (control group) received 5 mg/kg lidocaine 1.5% and saline. The outcome measures included severity of pain by using visual analog scale (VAS, 0 = no pain 10 cm = the most severe pain), time of first request for analgesia, and total dose of postoperative opioid administration. The data was analyzed using the χ² test, student's t-test, Kaplan-Meier survival analysis, and Multivariate analysis tests.

Results:

Patients in the control group had a higher VAS than patients who received ketamine, at all time points during the first 24 hours after surgery (all P < 0.05). The time of first request for analgesia in the ketamine group was significantly more than in the control group (8.93 ± 1.0 vs. 7.30 ± 1.9, respectively, P < 0.001).

Conclusion:

The addition of ketamine to lidocaine in the ultrasound-guided brachial plexus block could decrease the postoperative pain and need for analgesic. Therefore, it could be considered as an option in the brachial plexus block to enhance the analgesic action of lidocaine.

Ketamine in pain management

For ketamine's fiftieth birthday, a narrative review of this unique drug in pain management is presented. Its history is traced from its conception, and its heritage, as a phencyclidine offspring, delineated. The earliest roots of the conceptions concerning the mechanisms of action are sought, and then followed in preclinical as well as clinical research. The major proposed mechanisms in the literature are commented on and evaluated. The growth of the clinical evidence for perioperative pain, acute pain, and chronic pain is followed from early attempts to systematic reviews. Finally, an attempt is made to foresee what the next 50 years might hold in store for our 50 years old.

Clinically useful adjuvants in regional anaesthesia

PURPOSE OF REVIEW

In this review, emphasis is placed on adjuvant drugs that are already in clinical use. The list of adjuvants studied during the review period includes adrenaline, clonidine, ketamine, neostigmine, nondepolarizing muscle relaxants, and nonsteroidal antiinflammatory drugs. Some future aspects are considered in a couple of experimental studies on slow-release local anaesthetic formulations.

RECENT FINDINGS

Adrenaline not only acts as a vasoconstrictor, it may also produce analgesia through an alpha2-adrenergic mechanism. Adrenaline may facilitate the uptake of the local anaesthetic into nerves. The addition of adrenaline to a mixture of ropivacaine and fentanyl clearly improves thoracic epidural analgesia. Several recent studies have shown a synergism of clonidine with local anaesthetics in various types of blocks, as well as with spinal opioids. Bradycardia and hypotension may be associated with the use of clonidine. Neostigmine may cause antinociception both in the spinal cord and in peripheral nerves. Neostigmine has been found to potentiate the effect of spinal opioids, but gastrointestinal side effects are frequent. Biodegradable microcapsules containing bupivacaine and dexamethasone have been tested in humans and found to produce analgesia for several days (intercostal block). Local inflammatory reactions and paraesthesias, however, were observed in 30% of cases.

SUMMARY

Adrenaline and opioids may be regarded as the best investigated and most important adjuvants in regional anaesthesia. Other drugs, such as clonidine and neostigmine, may prolong analgesia in various regional anaesthetic techniques, but possible side effects may limit their clinical application. Further development is needed concerning extra-long acting analgesic formulations.

Effect of alkalinization on the local analgesic efficacy of ketamine in the abaxial sesamoid nerve block in horses

The objective of this study was to determine the effects of the alkalinization on the local analgesic efficacy of 1% ketamine in the abaxial sesamoid nerve block in horses. Thirty-six mature healthy horses were randomly assigned to four groups for the following treatments; an abaxial sesamoid block with 5 mL of saline solution (control saline); an abaxial sesamoid block with 5 mL of a solution containing 1% ketamine (KETs 1%); an abaxial sesamoid block with 5 mL of a solution containing saline solution and 0.5 mEq of sodium bicarbonate (control bicarbonate); and an abaxial sesamoid block with 5 mL of a solution containing 1% ketamine and 0.5 mEq of sodium bicarbonate (KETb 1%). All blocks were performed in one randomly selected front leg. To determine analgesia, hoof withdrawal from thermal stimulus from radiant heat lamp was assessed. Before each block, the hoof withdrawal reflex latency (HWRL) (time between lamp illumination and withdrawal of the hoof) was determined; after the block, local analgesic effects were determined using the heat lamp at 2 and 5 min after the injection and then every 5 min for 1 h. In KETs 1% group, there were significant increases in HWRL between basal values and values from 2 to 10 min after an abaxial sesamoid block. In KETb 1% group, significant increases in HWRL was collected between the basal value and values from 2 to 25 min following an abaxial sesamoid block. In KETs 1% group, of the nine horses, four had an abaxial sesamoid block that was unsuccessful. However, in KETb 1% group, only one of the nine horses had an abaxial sesamoid nerve block that was unsuccessful. The alkalinization of a 1% ketamine solution produced a more consistent and persistent local analgesia in horses when compared with 1% ketamine solution alone.

Evaluation of the local analgesic effect of ketamine in the palmar digital nerve block at the base of the proximal sesamoid (abaxial sesamoid block) in horses

OBJECTIVE

To evaluate the local analgesic effect of ketamine in a palmar digital nerve block at the base of the proximal sesamoid (abaxial sesamoid block) in horses.

ANIMALS

36 mature healthy Andalusian horses.

PROCEDURE

Horses were randomly assigned to 4 groups of 9 horses each and received an abaxial sesamoid block in a randomly chosen forelimb with 1 of the following: saline (0.9% NaCl) solution, 1% ketamine solution, 2% ketamine solution, or 3% ketamine solution. To determine analgesia, the radiant heat lamp-hoof withdrawal model was used as a noxious thermal stimulus. Before each nerve block, baseline hoof withdrawal reflex latency (HWRL, time between lamp illumination and withdrawal of the hoof) was determined; after the nerve block, local analgesic effects were determined by measuring HWRL at 2 and 5 minutes after injection and then every 5 minutes for a total period of 1 hour.

RESULTS

Significant differences in HWRL were found between baseline values and values at 2 to 15 minutes following a nerve block with ketamine. Significant differences were found between HWRL values at every time point from 2 to 10 minutes following a nerve block with saline solution, compared with 1 or 2% ketamine solution. Similarly, significant differences were found between HWRL values at every time point from 2 to 15 minutes following a nerve block with saline solution, compared with 3% ketamine solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Abaxial sesamoid block with ketamine ensures adequate analgesia in horses with an onset of action of 2 minutes and a maximal duration of action of 15 minutes.

Patient-controlled bupivacaine wound instillation following cesarean section: the lack of efficacy of adjuvant ketamine

STUDY OBJECTIVE

To assess the analgesic efficacy of ketamine when administered as an adjuvant to bupivacaine for patient-controlled wound instillation following cesarean section.

DESIGN

Prospective, randomized, double-blind study.

SETTING

Large referral hospital.

PATIENTS

50 term parturients undergoing cesarean section.

INTERVENTION

In all cases, a standard spinal anesthetic was administered. On completion of the surgery, a multihole 20 G epidural catheter (B. Braun, Melsungen, Germany) was placed above the fascia such that the tip was sited at the point which demarcated 50% of the length of the surgical wound. Thereafter, the catheter was connected to a patient-controlled drug delivery device. The device was filled with either 0.125% bupivacaine (bupivacaine group) or 0.125% bupivacaine and ketamine (1 mg/mL) (bupivacaine-ketamine group). Postoperatively, wound instillation was performed via the patient-controlled analgesia device. During the first 6 postoperative hours, a co-investigator administered "rescue" morphine (2 mg IV). Thereafter, "rescue" dipyrone (1 g) was administered on patient request.

MEASUREMENTS AND MAIN RESULTS

At all time intervals, visual analog scale (VAS) for pain at rest, on coughing, and during leg raise were similar between the groups. All patients (100%) in both treatment groups received "rescue" morphine. Similarly, the number of doses of 2 mg "rescue" morphine administered was unaffected by patient randomization. The total "rescue" morphine administered during the first 6 postoperative hours was 11.2 +/- 4.6 mg versus 11.3 +/- 5.6 mg for the bupivacaine group and bupivacaine-ketamine group, respectively. The number of pump infusions during the 24-hour study period was 9 +/- 2 and 9 +/- 3 for the bupivacaine group and bupivacaine-ketamine group, respectively. The volume infused via the delivery device was similar between the groups (81 +/- 18 mL vs. 85 +/- 24 mL for the bupivacaine group and bupivacaine-ketamine group, respectively). Psychomental and cognitive function as measured by the Digit Symbol Substitution and Mini Mental Tests were unaffected by adjuvant ketamine administration. Patient satisfaction was similar between the groups.

CONCLUSION

Adjuvant local ketamine does not enhance bupivacaine-induced wound instillation following cesarean section.

No enhancement of sensory and motor blockade by ketamine added to ropivacaine interscalene brachial plexus blockade

BACKGROUND

Ketamine can enhance anesthetic and analgesic actions of a local anesthetic via a peripheral mechanism. The authors' goal was to determine whether or not ketamine added to ropivacaine in interscalene brachial plexus blockade prolongs postoperative analgesia. In addition, we wanted to determine the incidence of adverse-effects in patients undergoing hand surgery.

METHODS

Sixty adults scheduled for forearm or hand surgery under the interscalene brachial plexus block were prospectively randomized to receive one of the solutions of the study. Group P received 0.5% ropivacaine 30 ml, group K received 0.5% ropivacaine 30 ml with 30 mg ketamine, and group C received 0.5% ropivacaine with 30 mg ketamine i.v. Loss of shoulder abduction, elbow flexion, wrist flexion and loss of pinprick in the C4-7 sensory dermatomes were assessed at 1-min intervals. Adverse-effects were assessed every 5 min. The duration of the sensory and motor blocks was assessed after operation. Adverse-effects were also recorded.

RESULTS

The onset time of sensory or motor blockade and the duration of sensory or motor blockade were similar in all groups. Adverse-effects occurred in 44% of patients in group K and 94% of group C.

CONCLUSION

This study suggests that 30 mg ketamine added to ropivacaine in the brachial plexus block does not improve the onset or duration of sensory block, but it does cause a relatively high incidence of adverse-effects. These two findings do not encourage the use of ketamine with local anesthetics for brachial plexus blockade.

Transdermal ketamine as an adjuvant for postoperative analgesia after abdominal gynecological surgery using lidocaine epidural blockade

We examined the postoperative analgesia of a controlled delivery ketamine transdermal patch after minor abdominal gynecological surgery using lidocaine epidural blockade. Fifty-two patients were randomized to one of two groups. Epidural anesthesia was performed with 25 mL 2% plain lidocaine. At the end of the surgical procedure, a controlled delivery transdermal patch containing either ketamine (25 mg/24 h) (Ketamine group) or placebo (Placebo group) was applied. Pain and adverse effects were assessed hourly postoperatively for 24 h. IM dipyrone was available at patient request. The two groups were demographically similar. The time to first rescue analgesic was longer in the Ketamine group (230+/-112 min) compared with the Placebo group (94+/-54 min); (P<0.00001). There were more dipyrone dose injections in 24 h in the Placebo group compared with the Ketamine group (P<0.0001). The incidence of adverse effects was similar between groups. We conclude that the transdermal-controlled delivery of ketamine prolonged the duration of analgesia after minor gynecological procedures.

IMPLICATIONS

Transdermal delivery of ketamine was an useful adjuvant to postoperative analgesia after epidural lidocaine blockade in the population studied.

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).

Ketamine effects on bupivacaine local anaesthetic activity and pharmacokinetics of bupivacaine in mice

This study was designed to document possible changes in bupivacaine (B) local anaesthetic activity and pharmacokinetics in mice after a ketamine (K) injection. In the experiments, bupivacaine (8.25 mg.kg(-1)), was injected into the popliteal space of the right posterior limb: the local anaesthetic activity was assessed according to a sciatic nerve blockade method with three different doses (2, 10 and 40 mg/kg) of ketamine and the kinetics were studied after a 10 mg/kg dose. When ketamine was associated, the local anesthetic activity of bupivacaine was significantly enhanced as well as its elimination half-life. Significantly lower levels of the main metabolite, PPX, were observed, when ketamine was associated, suggesting a metabolic inhibition phenomenon. The ketamine-induced increase in the total anaesthetic effect of bupivacaine may thus be explained by kinetic modifications i.e. a possible inhibiting effect of ketamine on the metabolism of bupivacaine.

Ketamine enhances local anesthetic and analgesic effects of bupivacaine by peripheral mechanism: a study in postoperative patients

Patients with unilateral (n = 14) and bilateral (n = 4) herniorrhaphy participated in this study. With bilateral herniorrhaphy, at the end of the surgery, the wound was infiltrated with a solution of bupivacaine 0.5% and ketamine 0.3% on one side and a solution of bupivacaine 0.5% only, on the other. With unilateral herniorrhaphy, the patients were randomly assigned to one of two groups (n = 7). One group at the end of the surgery received the infiltration with a solution of bupivacaine 0.5% and ketamine 0.3%, the other group received the infiltration with a solution of bupivacaine 0.5% only. The duration of the local anesthetic (response to a von Frey filament) and postoperative analgesic (time to mild spontaneous pain) effects of the infiltrations, as well as wound pain threshold 24 h after surgery (pressure algometry), were determined. In patient with unilateral herniorrhaphy, the addition of ketamine for wound infiltration enhanced the duration of infiltration anesthesia (206 +/- 76 versus 343 +/- 108 min, P < 0.02) and analgesia (240 +/- 45 versus 420 +/- 151 min, P < 0.03). Similar enhancement of the local anesthetic effect was observed in patients with bilateral herniorrhaphy. The increase in pain threshold to pressure on the wound with the addition of ketamine was evident in bilateral herniorrhaphy patients and also with a combination of bilateral and unilateral results (1.39 +/- 0.40 versus 2.35 +/- 0.92 kg, P < 0.02). In the group of five volunteers, the subcutaneous infiltration with 0.3% ketamine produced a local anesthetic effect lasting only 10-20 min. The results indicate that ketamine acting via a peripheral mechanism can profoundly enhance anesthetic and analgesic actions of a local anesthetic administered for infiltration anesthesia.

Intravenous regional anaesthesia with ketamine

Ketamine, 40 ml 0.5% solution, was used in the technique of intravenous regional anaesthesia in 14 patients undergoing upper limb surgery. Satisfactory analgesia was obtained in 12 of the patients. The method is limited by the fact that all patients became unconscious within a few minutes of tourniquet release, and that this could not be prevented by naloxone.

Phase changes induced by ketamine in the vertical vestibulo-ocular reflex in the rabbit

The effect of ketamine has been tested on the phase of the vertical vestibulo-ocular reflex of rabbits sinusoidally oscillated at various frequencies. A significant phase lag, predominantly affecting the macular component of the reflex, was observed. This action resembles that induced by Nembutal in the same preparation. A specific action of ketamine on synaptic transmission is suggested. Erroneous phase relationship between natural stimuli responses can be obtained in experiments employing ketamine.