Intravenous regional anaesthesia with ketamine

The Role of Intravenous Anesthetics for Neuro: Protection or Toxicity?

The primary intravenous anesthetics employed in clinical practice encompass dexmedetomidine (Dex), propofol, ketamine, etomidate, midazolam, and remimazolam. Apart from their established sedative, analgesic, and anxiolytic properties, an increasing body of research has uncovered neuroprotective effects of intravenous anesthetics in various animal and cellular models, as well as in clinical studies. However, there also exists conflicting evidence pointing to the potential neurotoxic effects of these intravenous anesthetics. The role of intravenous anesthetics for neuro on both sides of protection or toxicity has been rarely summarized. Considering the mentioned above, this work aims to offer a comprehensive understanding of the underlying mechanisms involved both in the central nerve system (CNS) and the peripheral nerve system (PNS) and provide valuable insights into the potential safety and risk associated with the clinical use of intravenous anesthetics.

Intravenous Regional Anesthesia: A Historical Overview and Clinical Review

Intravenous regional anesthesia (IVRA) is an established, safe and simple technique, being applicable for various surgeries on the upper and lower limbs. In 1908, IVRA was first described by the Berlin surgeon August Bier, hence the name "Bier's Block". Although his technique was effective, it was cumbersome and fell into disuse when neuroaxial and percutaneous plexus blockades gained widespread popularity in the early 20^th century. In the 1960s, it became widespread, when the New Zealand anesthesiologist Charles McKinnon Holmes praised its use by means of new available local anesthetics. Today, IVRA is still popular in many countries being used in the emergency room, for outpatients and for high-risk patients with contraindications for general anesthesia. IVRA offers a favorable risk-benefit ratio, cost-effectiveness, sufficient muscle relaxation and a fast on- and offset. New upcoming methods for monitoring, specialized personnel and improved emergency equipment made IVRA even safer. Moreover, IVRA may be applied to treat complex regional pain syndromes. Prilocaine and lidocaine are considered as first-choice local anesthetics for IVRA. Also, various adjuvant drugs have been tested to augment the effect of IVRA, and to reduce post-deflation tourniquet pain. Since major adverse events are rare in IVRA, it is regarded as a very safe technique. Nevertheless, systemic neuro- and cardiotoxic side effects may be linked to an uncontrolled systemic flush-in of local anesthetics and must be avoided. This review gives a historical overview of more than 100 years of experience with IVRA and provides a current view of IVRA with relevant key facts for the daily clinical routine.

Regional intravenous anesthesia in knee arthroscopy

OBJECTIVE

The goal of the study was to investigate the regional intravenous anesthesia procedure in knee arthroscopy and to evaluate the effects of adding ketamine over the anesthesia block charactery and tourniquet pain.

MATERIAL/METHOD

Forty American Society of Anesthesiologists (ASA) II patients who received knee arthroscopy were enrolled. After monitoring, a peripheral IV line was inserted.The venous blood in the lower extremity was evacuated with a bandage, and the proximal cuff of the double-cuff tourniquet was inflated. The patients were randomly split into two groups. While Group P received 80 ml 0.5% prilocaine, Group PK received 0.15 mg/kg ketamine (80 ml in total) via the dorsum of the foot. We recorded onset time of the sensory block, end time of the sensory block, presence of the motor block, the time when the patient verbally reported tourniquet pain and surgical pain, duration of tourniquet tolerance, fentanyl consumption during the operation, time to first analgesic requirement, methemoglobin values at 60 minutes, operative conditions, 24-hour analgesic consumption, discharge time, and hemodynamic parameters.

RESULTS

The body mass index (BMI) of the patients who required general anesthesia was significantly higher than the BMI of other patients. The onset time of the sensory block was shorter for those in Group PK, but the time to first analgesic requirement was longer.

CONCLUSION

Regional intravenous anesthesia using the doses and volumes commonly used in knee arthroscopy may be an inadequate block among patients with high BMI values. Moreover, the addition of ketamine to the local anesthetic solution may produce a partial solution by shortening the onset of sensory block and prolonging the time until the first analgesic is required.

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).

Spinal conduction block by intrathecal ketamine in dogs

In addition to its use for intravenous (I.V.) anesthesia, ketamine can provide pain relief in humans when administered spinally. To elucidate the mechanisms of intrathecal (I.T.) ketamine analgesia, we observed differences in the effects of I.V. and I.T. ketamine on intraspinal evoked potentials (ISEPs) in 28 dogs anesthetized with pentobarbital. Bipolar extradural electrodes were inserted at the cervical and lumbar regions of the spinal cord for recording descending ISEPs represented by the two negative deflections, Waves I and II. I.V. ketamine 2 and 10 mg/ kg did not affect the amplitude and latency of Wave I, whereas the large dose (10 mg/kg) significantly decreased the amplitude but not the latency of Wave II. I.T. ketamine 1 and 5 mg/kg caused significant dose-dependent decreases in both Wave I and II amplitudes and prolongations of both Wave I and II latencies. These I.T. effects on ISEPs are consistent with previous in vitro observations that ketamine blocks axonal conduction. We conclude that axonal conduction block may contribute to the analgesic mechanism of I.T. ketamine.

Comparison of morphine and morphine with ketamine for postoperative analgesia

PURPOSE

The purpose of this study was to compare morphine with ketamine to morphine alone in a double-blind investigation of postsurgical pain control.

METHODS

Forty-two ASA 1 and 2 patients undergoing elective microdiscectomy were administered either 1 mg.ml-1 of morphine (n = 20) or 1 mg.ml-1 of both morphine and ketamine (n = 22) via iv patient controlled analgesia (IVPCA). Pain relief and side effects were assessed at 24 hr after surgery.

RESULTS

The mean (SD) visual analogue scale (VAS) pain rating of 2.3 (1.67) for patients receiving morphine with ketamine was lower (P < 0.001) than the VAS scores of patients receiving only morphine 4.5 (1.54). Patients receiving morphine and ketamine also had less difficulty with side effects, reporting less nausea (P < 0.05), pruritus (P < 0.001), and urinary retention (P < 0.05). Although dysphoria is reported to be a common side effect of ketamine, complaints of dysphoria were rare in both groups, with only one subject (5%) in the morphine with ketamine group and three (15%) subjects receiving morphine alone reporting this side effect.

CONCLUSION

IVPCA ketamine in combination with morphine provides superior postsurgical pain relief at lower dosage and with fewer side effects than morphine alone.

Spinal antinociception: clinical aspects

Recent research has demonstrated the increasing importance of the spinal cord in processing and modulating nociceptive input. Different groups of drugs, each acting by a unique mechanism, have been shown to block nociceptive afferent transmission. None of the currently available spinally administered local anesthetics, opioids or non-opioids produce analgesia without side effects. Non-opioids such as alpha-2-adrenergic agonists may be more suited as adjuvants rather than sole analgesic agents and their main role lies in reducing the dose requirements of other analgesics. Spinal somatostatin and ketamine may have neurotoxic potential. The role of these drugs and of midazolam in pain management appears to be limited. Preliminary results suggest that the neuropeptide octreotide has potent analgesic effects. 'Balanced spinal analgesia' using a combination of low doses of drugs, with separate but synergistic mechanisms of analgesia, may produce the best results. The optimal drug combinations and dosages remain to be determined. It is essential that animal neurotoxicity studies followed by controlled clinical trials are performed before widespread spinal administration of new drugs.

Use of ketamine in acute severe asthma

Two patients with acute severe asthma, who failed to respond to conventional therapy, were given intravenous ketamine in sub-anaesthetic doses with good results. A bolus dose of 0.75 mg/kg was followed by the same dose over 10 min with relief of bronchospasm in both cases. An infusion of ketamine at a rate of 0.15 mg/kg/h was used in each case to prevent recurrence of bronchospasm. Intravenous ketamine can be used to relieve acute intractable bronchospasm provided expert anaesthetic help is at hand. A review of the literature concerning its use in such situations is also presented.

Ketamine as analgesic for total intravenous anaesthesia with propofol

A prospective study of 18 patients who underwent noncardiac surgery was performed to study the use of ketamine as an analgesic during total intravenous anaesthesia with propofol. A comparison was made with the combination propofol/fentanyl. The propofol/ketamine combination resulted in haemodynamically stable anaesthesia without the need for additional analgesics. Postoperative behaviour was normal in all patients and none of the patients reported dreaming during or after the operation. Propofol seems to be effective in eliminating side effects of a subanaesthetic dose of ketamine in humans. We recommend the propofol/ketamine combination for total intravenous anaesthesia for surgery when stable haemodynamics are required.

A double-blind comparison of epidural ketamine and diamorphine for postoperative analgesia

Twenty patients who had abdominal hysterectomy under general anaesthesia were randomly assigned to receive either epidural ketamine (30 mg), or epidural diamorphine (5 mg) peri-operatively and on first request for analgesia. Failure to obtain satisfactory analgesia with one of the agents was treated by epidural administration of the other. Pain was assessed by an independent observer, and by the patient using a visual analogue scale. The mean (SD) pain score on recovery from general anaesthesia, on a scale of 0-4, was 2.9 (1.2) for the ketamine group and 1.0 (1.0) for the diamorphine group (p less than 0.01). The mean (SD) time to first request for analgesia was 272 (206) and 72 (41) minutes in the diamorphine and ketamine groups respectively (p less than 0.01). All patients in the diamorphine group obtained adequate analgesia, but all patients in the ketamine group were changed to epidural diamorphine. Epidural ketamine does not appear to be a sufficiently effective alternative to epidural diamorphine for routine use in postoperative pain.

Ketamine: an update on the first twenty-five years of clinical experience

In nearly 25 years of clinical experience, the benefits and limitations of ketamine analgesia and anaesthesia have generally been well-defined. The extensive review of White et al. and the cardiovascular review of Reves et al. are broad in their scope and have advanced the understanding of dissociative anaesthesia. Nevertheless, recent research continues to illuminate different aspects of ketamine pharmacology, and suggests new clinical uses for this drug. The identification of the N-methylaspartate receptor gives further support to the concept that ketamine's analgesic and anaesthetic effects are mediated by separate mechanisms. The stereospecific binding of (+)ketamine to opiate receptors in vitro, more rapid emergence from anaesthesia, and the lower incidence of emergence sequelae, make (+)ketamine a promising drug for future research. Clinical applications of ketamine that have emerged recently, and are likely to increase in the future, are the use of oral, rectal, and intranasal preparations for the purposes of analgesia, sedation, and anaesthetic induction. Ketamine is now considered a reasonable option for anaesthetic induction in the hypotensive preterm neonate. The initial experience with epidural and intrathecal ketamine administration has not been very promising but the data are only preliminary in this area. The use of ketamine in military and catastrophic settings is likely to become more common. The clinical availability of midazolam will complement ketamine anaesthesia in several ways. This rapidly metabolized benzodiazepine reduces ketamine's cardiovascular stimulation and emergence phenomena, and does not have active metabolites. It is dispensed in an aqueous medium, which is usually non-irritating on intravenous injection, unlike diazepam. The combination of ketamine and midazolam is expected to achieve high patient acceptance, which never occurred with ketamine as a sole agent. Finally, it is necessary to point out the potential for abuse of ketamine. While ketamine is not a controlled substance (in the United States), the prudent physician should take appropriate precautions against the unauthorized use of this drug.