Analgesic efficacy of low-dose intrathecal neostigmine in combination with fentanyl and bupivacaine for total knee replacement surgery

Adjuvants in pain medicine. Selection of the drug depending on the desired effect – so which drug to choose?

To date, much research has focused on finding the ideal adjuvant for local anesthetics. Each of them can have different effects. In anesthesiology and pain medicine, depending on the purpose, one or another effect may be desirable. For example, in some situations it is desirable to accelerate the onset of action or prolong the duration of the block, in others the desired effect may be a “response to intravascular administration”, it should also be borne in mind that not all adjuvants are allowed for intrathecal administration.

Adjuvants in clinical regional anesthesia practice: A comprehensive review

Adjuvants are medications that work synergistically with local anesthetics to help enhance the duration and quality of analgesia in regional techniques. Regional anesthesia has become more prevalent as evidence continues to show efficacy, enhancement of patient care, increased patient satisfaction, and improved patient safety. Practitioners in the perioperative setting need to not only be familiar with regional techniques but also the medications used for them. Some examples of adjuvant medications for regional techniques include dexamethasone, alpha 2 agonists such as clonidine and dexmedetomidine, midazolam, buprenorphine, NMDA antagonists, including ketamine and magnesium, neostigmine, sodium bicarbonate, epinephrine, and non-steroidal anti-inflammatory drugs. The aim of the present investigation, therefore, is to provide a comprehensive review of the most commonly used non-opioid adjuvants in clinical practice today. Regional adjuvants can improve patient safety, increase patient satisfaction, and enhance clinical efficacy. Future studies and best practice techniques can facilitate standardization of regional anesthesia adjuvant dosing when providing nerve blocks in clinical practice.

Intrathecal Bupivacaine with Neostigmine and Bupivacaine with Normal Saline for Postoperative Analgesia: A Cost-effective Additive

Context:

In day-to-day practice, subarachnoid block remains the most common type of anesthesia. Bupivacaine is commonly used local anesthetic of neuraxial blockade, though earlier 5% xylocaine and now ropivacaine and levobupivacaine are also used. Additives such as opioids and α₂ agonists are also used. We are using neostigmine as an additive with bupivacaine to see the duration of postoperative analgesia.

Aims:

To compare the efficacy of intrathecal hyperbaric bupivacaine with neostigmine when compared to hyperbaric bupivacaine with normal saline with regard to time of onset and duration of sensory and motor blockade, time to two-segment regression.

Settings and Design:

Randomized, double-blinded study.

Subjects and Methods:

One hundred patients admitted for lower abdominal and lower limb surgeries done under spinal anesthesia (SA) during the period of February 2015–August 2016.

Statistical Analysis Used:

Data were entered into Microsoft excel data sheet and analyzed using SPSS 22 version. Categorical data were represented in the form of frequencies and proportions. Chi-square was used as a test of significance. Continuous data were represented as a mean and standard deviation. Independent t-test was used as a test of significance to identify the mean difference between two groups.

Results:

Mean onset of sensory blockade with neostigmine group was 174.1 ± 107.1 s and in normal saline group 171 ± 35.6 s. Mean onset of motor blockade with neostigmine group was 197.4 ± 111.6 s and in normal saline group was 219.4 ± 73.2 s. Mean two-segment regression with neostigmine group was 110.6 ± 22.7 s and in normal saline group was 71.5 ± 17.1 min. Duration of analgesia with neostigmine group was 336.3 ± 54.5 min and in normal saline group was 188.8 ± 18.4 min.

Conclusions:

Intrathecal neostigmine is associated with significantly prolonged sensory, motor blockade, and effective postoperative analgesia.

The evolution of spinal/epidural neostigmine in clinical application: Thoughts after two decades

Since the first clinical application of analgesia following spinal anticholinesterase by 1940's, several clinical double-blind studies have been conducted to date, where intrathecal doses of neostigmine in humans ranged from 750 to 1 μg, due to side-effects. Conversely, epidural neostigmine has been evaluated in proportionally higher doses and represents an alternative, but still deserves more investigation concerning both acute and chronic pain, as it seems devoid of important side-effects.

Epidural administration of neostigmine-loaded nanofibers provides extended analgesia in rats

Background

In this study, neostigmine-loaded electrospun nanofibers were prepared and then their efficacy and duration of analgesic action were studied after epidural administration in rats by repeated tail flick and formalin tests.

Methods

The neostigmine poly vinyl alcohol (PVA) nanofibers were fabricated by electrospinning methods. The nanofibers (1 mg) were injected into the lumbar epidural space (L5-L6) of rats (n = 6). Cerebrospinal fluid samples of rats were collected 1, 5 and 24 hours after injection and then were sampled once weekly for 4 weeks. Free-neostigmine concentration was measured in the samples spectrophotometrically. Rat nociceptive responses were evaluated by repeated tail-flick and formalin tests for 5 weeks after the nanofibers (1 mg) injection. Locomotor activity of rats was measured in the open-field at the same period.

Results

The cerebrospinal fluid concentration of free neostigmine reached 5 μg/ml five hours after injection and remained constant until the end of the experiments. The tail-flick latency of treated rats was significantly (p < 0.01) increased and remained constant up to 4 weeks. Pain scores of the rats in both phases of formalin test were significantly (p < 0.01) reduced during the same periods, Epidural injection of the nanofibers had no effect on locomotor activity of rats in an open-field.

Conclusions

Our results indicate that the neostigmine nanofibers can provide sustained release of neostigmine for induction of prolonged analgesia after epidural administration. High tissue distribution and penetration of the nanofibers in dorsal horn can increase thermal and chemical analgesia duration without altering locomotor activity in rats for 4 weeks.

Low-dose spinal neostigmine further enhances the analgesic effect of spinal bupivacaine combined with epidural dexamethasone, following orthopedic surgery

BACKGROUND

Opioids are considered mainstream for combined spinal-epidural anesthesia, but frequently limited by adverse effects. The aim of this study was to examine whether low-dose spinal neostigmine, epidural dexamethasone or their combination enhances analgesia from spinal bupivacaine without adverse effects.

MATERIALS AND METHODS

A total of 60 patients undergoing orthopedic surgery were randomized to one of four groups and evaluated for 24-h after surgery for analgesia (time to first rescue analgesic) and rescue analgesic consumption. Patients received 15 mg bupivacaine plus the test drug intrathecally (saline or 1 microgram (μg) neostigmine). The epidural test drug was either saline or 10 mg dexamethasone. The Control group (CG) received spinal and epidural saline. The Neostigmine group (NG), spinal neostigmine and epidural saline; the Dexamethasone group (DG), spinal saline and epidural dexamethasone; and the Neostigmine-dexamethasone group (NDG), spinal neostigmine and epidural dexamethasone.

RESULTS

The CG (282 ± 163 min) and NG (524 ± 142 min) were similar in their times to first rescue analgesic and analgesic consumption. The time to first rescue analgesic was longer for the DG (966 ± 397 min) compared with CG and NG (P < 0.0002), and the DG had less ketoprofen consumption and lower overall visual analogue scale-pain sores compared with CG and NG (P < 0.0005). Addition of 1 mg-neostigmine (NDG) resulted in longer time to rescue analgesic (1205 ± 303 min; P < 0.02) and lower ketoprofen consumption (P < 0.05) compared to DG. Sporadic cases of vesical catheterization and emesis were observed, however adverse effects were similar among groups.

CONCLUSION

Spinal 1 microgram (μg) neostigmine further enhanced analgesia from spinal bupivacaine combined with epidural dexamethasone, without increasing the incidence of adverse effects.