Is intrathecal magnesium sulfate safe and protective against ischemic spinal cord injury in rabbits?

Comparative effect of transforaminal injection of Magnesium sulphate versus Ozone on oxidative stress biomarkers in lumbar disc related radicular pain

BACKGROUND

We aimed to investigate the effect of transforaminal injection of Magnesium sulphate versus Ozone on pain intensity, functional disability and the oxidative stress biomarkers; superoxide dismutase (SOD) and Glutathione (GSH) in patients with lumbar disc prolapse.

METHODS

This randomized controlled trial was conducted on 135 patients having symptomatic lumbar disc prolapse, received either transforaminal injection of Magnesium sulphate with steroids, Ozone with steroids, or steroids alone. Assessment of pain severity and functional disability were done before intervention, 2 weeks, 1, 3, and 6 months after intervention. Serum SOD and GSH were measured for all included patients before and 2 weeks after intervention.

RESULTS

There was a statistically significant improvement in pain intensity and functional disability 2 weeks after intervention in the three groups, but at 1-month and 3-months after intervention, the significant improvement was in Mg sulphate and Ozone groups only. At 6-months follow up, Mg sulphate group only showed a significant improvement. There was a statistically significant increase in SOD and GSH serum levels, 2-weeks after intervention in both Magnesium sulphate (P-value = 0.002, 0.005 respectively) and ozone groups (P-value < 0.001, < 0.001), but there was no statistically significant change in SOD and GSH serum levels in control group.

CONCLUSION

Transforaminal injection of Mg sulphate in patients with lumbar disc prolapse causes significant long-term improvement (up to 6 months) in pain intensity and functional disability. The serum levels of SOD and GSH were significantly increased at 2 weeks following both transforaminal injection of Mg sulphate and ozone.

The Options for Neuraxial Drug Administration

Neuraxial drug administration, i.e., the injection of drugs into the epidural or intrathecal space to produce anesthesia or analgesia, is a technique developed more than 120 years ago. Today, it still is widely used in daily practice in anesthesiology and in acute and chronic pain therapy. A multitude of different drugs have been introduced for neuraxial injection, only a part of which have obtained official approval for that indication. A broad understanding of the pharmacology of those agents is essential to the clinician to utilize them in a safe and efficient manner. In the present narrative review, we summarize current knowledge on neuraxial anatomy relevant to clinical practice, including pediatric anatomy. Then, we delineate the general pharmacology of neuraxial drug administration, with particular attention to specific aspects of epidural and intrathecal pharmacokinetics and pharmacodynamics. Furthermore, we describe the most common clinical indications for neuraxial drug administration, including the perioperative setting, obstetrics, and chronic pain. Then, we discuss possible neurotoxic effects of neuraxial drugs, and moreover, we detail the specific properties of the most commonly used neuraxial drugs that are relevant to clinicians who employ epidural or intrathecal drug administration, in order to ensure adequate treatment and patient safety in these techniques. Finally, we give a brief overview on new developments in neuraxial drug therapy.

Pharmacological and clinical implications of local anaesthetic mixtures: a narrative review

Various techniques have been explored to prolong the duration and improve the efficacy of local anaesthetic nerve blocks. Some of these involve mixing local anaesthetics or adding adjuncts. We did a literature review of studies published between 01 May 2011 and 01 May 2021 that studied specific combinations of local anaesthetics and adjuncts. The rationale behind mixing long- and short-acting local anaesthetics to hasten onset and extend duration is flawed on pharmacokinetic principles. Most local anaesthetic adjuncts are not licensed for use in this manner and the consequences of untested admixtures and adjuncts range from making the solution ineffective to potential harm. Pharmaceutical compatibility needs to be established before administration. The compatibility of drugs from the same class cannot be inferred and each admixture requires individual review. Precipitation on mixing (steroids, non-steroidal anti-inflammatory drugs) and subsequent embolisation can lead to serious adverse events, although these are rare. The additive itself or its preservative can have neurotoxic (adrenaline, midazolam) and/or chondrotoxic properties (non-steroidal anti-inflammatory drugs). The prolongation of block may occur at the expense of motor block quality (ketamine) or block onset (magnesium). Adverse effects for some adjuncts appear to be dose-dependent and recommendations concerning optimal dosing are lacking. An important confounding factor is whether studies used systemic administration of the adjunct as a control to accurately identify an additional benefit of perineural administration. The challenge of how best to prolong block duration while minimising adverse events remains a topic of interest with further research required.

Review of adjuvants to local anesthetics in peripheral nerve blocks: Current and future trends

In recent anesthetic practice, peripheral nerve blocks (PNBs) are used extensively for surgical anesthesia and nonsurgical analgesia. PNBs offer many benefits over other anesthetic techniques in a certain population of patients, and in some specific clinical setting, that may contribute to faster and safer pain relief, increased patient satisfaction, reduced hospital stay, and decreased overall healthcare cost. The technique involves the injection of the anesthetic in the vicinity of a specific nerve or bundle of nerves to block the sensation of pain transmitting to a specific portion of the body. However, the length of analgesia when a single anesthetic is used for PNB may not last long. Therefore, the practice of adding an additional agent called adjuvant has been evolved to prolong the analgesic effect. There are many such adjuvants available that are clinically being used for this purpose imparting great efficacy and safety to the anesthetic process. The adjuvants molecules are generally classified as opioids, alpha-2 agonist, steroids, etc. Most of them are safe to use and show little or no adverse event related to neurotoxicity and tissue damage. Although there is extensive use of such adjuvants in the clinical field, none of the molecules is approved by the FDA and is used as an off-label drug. The risk to benefit ratio must be assessed while using such an agent. This review will try to delineate the basic need of adjuvant in peripheral nerve block and will discuss the advantages and limitations of using different adjuvants and will discuss the future prospect of such application.

A randomized clinical trial of intrathecal magnesium sulfate versus midazolam with epidural administration of 0.75% ropivacaine for patients with preeclampsia scheduled for elective cesarean section

Background and Aims:

Magnesium sulfate and midazolam have been used as adjuvants to local anesthetics via intrathecal and epidural routes to augment the quality of block and prolong postoperative analgesia. This study compares addition of intrathecal magnesium sulfate versus intrathecal midazolam to epidurally administered isobaric ropivacaine as a part of combined spinal epidural technique in pre-eclamptic parturients undergoing elective cesarean section.

Material and Methods:

After institutional ethics committee approval and written informed consent, 50 pre-eclamptic parturients were randomly allocated to one of the two groups of 25 each to either receive intrathecal magnesium sulfate (50 mg) or intrathecal midazolam (1 mg) in combination with epidural ropivacaine (0.75%; 14–16 ml). The onset and duration of sensory and motor blockade, duration of postoperative analgesia, postoperative visual analogue scores for pain, and perioperative side effects were noted. Data were analyzed statistically using Graphpad.com software.

Results:

Onset times to sensory and motor blockade were faster in midazolam than in magnesium group (P < 0.01). Duration of sensory and motor blockade, and time to first request of analgesia were significantly longer in the magnesium group compared to the midazolam group (P < 0.01). The fetal outcomes according to APGAR scores were comparable in both the groups, the median APGAR score at 1 minute was 8 and at 5 minutes was 10 in both the groups.

Conclusion:

Intrathecal magnesium with epidural ropivacaine significantly prolonged postoperative analgesia compared to intrathecal midazolam without any complications. Perioperative hemodynamics were comparable in both groups.

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).

Ultrasound as a safe and reliable guidance for subarachnoid puncture in rabbits

Purpose:

To evaluate a model for studying the toxicity in nervous tissue and meninges using ultrasound to guide needle insertion into the subarachnoid space of rabbits, with the objective of avoiding injuries triggered by the puncture and by intraneural injection of solutions.

Methods:

Forty-five adult female rabbits were divided into 3 groups (G): G1 underwent subarachnoid puncture, G2 underwent subarachnoid injection of saline solution and G3 underwent subarachnoid injection of 0.5% hyperbaric bupivacaine. A needle was inserted into the S1-S2 subarachnoid space guided by ultrasound. The sensitivity and motility of the animals were evaluated for 3 days, after which the animals were sacrificed for removal of lumbar and sacral portions of the spinal cord for histological examination by light microscopy and immunohistochemistry.

Results:

All animals had motor function and pain sensitivity on the evaluation period. No animal had complication during or after the procedures.

Conclusion:

Ultrasound is a useful and safe method for the correct identification of the subarachnoid space of rabbits.

Cold bupivacaine versus magnesium sulfate added to room temperature bupivacaine in sonar-guided femoral and sciatic nerve block in arthroscopic anterior cruciate ligament reconstruction surgery

BACKGROUND

Cooling of local anesthetic potentiates its action and increases its duration. Magnesium sulfate (MgSo₄) added to local anesthetic prolongs the duration of anesthesia and postoperative analgesia with minimal side effects.

AIM

The aim of this prospective, randomized, double-blind study was to compare the effect of cold to 4°C bupivacaine 0.5% and Mg added to normal temperature (20-25°C) bupivacaine 0.5% during sonar-guided combined femoral and sciatic nerve blocks on the onset of sensory and motor block, intraoperative anesthesia, duration of sensory and motor block, and postoperative analgesia in arthroscopic anterior cruciate ligament (ACL) reconstruction surgery.

PATIENTS AND METHODS

A total of 90 American Society of Anesthesiologists classes I and II patients who were scheduled to undergo elective ACL reconstruction were enrolled in the study. The patients were randomly allocated to 3 equal groups to receive sonar-guided femoral and sciatic nerve blocks. In Group I, 17 ml of room temperature (20-25°C) 0.5% bupivacaine and 3 ml of room temperature saline were injected for each nerve block whereas in Group II, 17 ml of cold (4°C) 0.5% bupivacaine and 3 ml of cold saline were injected for each nerve block. In Group III, 17 ml of room temperature 0.5% bupivacaine and 3 ml of MgSo₄ 5% were injected for each nerve block. The onset of sensory and motor block was evaluated every 3 min for 30 min. Surgery was started after complete sensory and motor block were achieved. Intraoperatively, the patients were evaluated for heart rate and mean arterial pressure, rescue analgesic and sedative requirements plus patient and surgeon satisfaction. Postoperatively, hemodynamics, duration of analgesia, resolution of motor block, time to first analgesic, total analgesic consumption, and the incidence of side effects were recorded.

RESULTS

There was no statistically significant difference in demographic data, mean arterial pressure, heart rate, and duration of surgery. Onset of both sensory and motor block was significantly shorter in both Groups II and III compared to Group I. Intraoperative anesthetic quality was comparable between groups with good patient and surgeon satisfaction. The time to first analgesia was significantly longer in Groups II and III compared to Group I with nonsignificant difference between each other. Moreover, the total opioid consumption was significantly lower in Groups II and III and duration of analgesia and motor block were significantly longer in Groups II and III compared to Group I. There was no difference in the incidence of side effects.

CONCLUSIONS

The use of cold 0.5% bupivacaine or the addition of Mg to normal temperature 0.5% bupivacaine prolongs the sensory and motor block duration without increasing side effects and enhances the quality of intra- and post-operative analgesia with better patient satisfaction in sonar-guided femoral and sciatic nerve block for arthroscopic ACL reconstruction surgery.

Comparison of different doses of magnesium sulphate and fentanyl as adjuvants to bupivacaine for infraumbilical surgeries under subarachnoid block

Background and Aims:

Spinal anaesthesia is used for many years for surgeries below the level of umbilicus. It has certain disadvantages such as limited duration of blockade and post-operative analgesia. This study was undertaken to evaluate the effects of additives fentanyl and magnesium sulphate along with bupivacaine during spinal anaesthesia for prolongation of analgesia and motor blockade.

Methods:

This randomised study was conducted in 120 patients of either sex of American Society of Anesthesiologists physical status I and II, posted for infraumbilical surgeries. Patients were randomly allocated to four groups and were given the following drugs intrathecally as per group distribution; group A - bupivacaine 15 mg (0.5% heavy) with fentanyl 25 μg, group B - bupivacaine 15 mg (0.5% heavy) with magnesium 100 mg, group C - bupivacaine 15 mg (0.5% heavy) with magnesium 50 mg and group D - bupivacaine 15 mg (0.5% heavy) with 0.5 ml normal saline. Parameters monitored were duration of analgesia along with haemodynamic parameters and side effects. Data were analysed using the Student's t-test for the continuous variables and two-tailed Fisher exact test or Chi-square test for categorical variables.

Results:

There was significant increase in duration of analgesia in group A (374.37 min) and B (328.13 min) as compared to group C (274.87 min) and D (246.03 min). In group A, all haemodynamic parameters decreased by more than 20%, compared to baseline parameters, which was clinically and statistically significant as compared to other groups. There was also increase in duration of motor blockade in groups A and B.

Conclusion:

Addition of magnesium sulphate at 100 mg dose or fentanyl 25 μg as adjuvants to intrathecal bupivacaine significantly prolongs the duration of analgesia, though in the given doses, magnesium provides better haemodynamic stability than fentanyl, with fewer side effects.

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.

Magnesium as an adjuvant for caudal analgesia in children

BACKGROUND

There is a need for an adjuvant agent of caudal block that prolongs its duration and improves the analgesic efficacy to fasten functional recovery. Magnesium is an N-methyl-D-aspartate receptor antagonist that functions as an analgesic. This study was aimed to evaluate whether magnesium as an adjuvant for caudal block in children can improve postoperative analgesia and functional recovery.

METHODS

Eighty children, 2-6 years of age, undergoing inguinal herniorrhaphy, were included in this prospective, randomized, double-blinded study. For caudal block, Group R received ropivacaine 1.5 mg·ml(-1), 1 ml·kg(-1) and Group RM received the same dose of ropivacaine mixed with 50 mg of magnesium. The Parents' Postoperative Pain Measure (PPPM) score, analgesic consumption, functional recovery, and adverse effects were evaluated at 6, 24, 48, and 72 h after surgery, as well as daily thereafter until the child showed full functional recovery.

RESULTS

The PPPM score after hospital discharge was significantly lower for Group RM than for Group R at all times (P < 0.05). Children in Group RM required less fentanyl for rescue analgesia in the recovery area (16.2% vs 39.5%, P = 0.034) and less oral analgesics after discharge (20.5% vs 52.6%, P = 0.007). The time to return of normal functional activity was shorter in Group RM (P < 0.05). The incidence of adverse effects did not differ between groups.

CONCLUSIONS

As an adjuvant for caudal analgesia, 50 mg magnesium provided superior quality of analgesia and faster return of normal functional activity than local anesthetic alone in children.

Accidental intrathecal injection of magnesium sulfate for cesarean section

Magnesium sulfate is used frequently in the operation room and risks of wrong injection should be considered. A woman with history of pseudocholinesterase enzyme deficiency in the previous surgery was referred for cesarean operation. Magnesium sulfate of 700 mg (3.5 ml of 20% solution) was accidentally administered in the subarachnoid space. First, the patient had warm sensation and cutaneous anesthesia, but due to deep tissue pain, general anesthesia was induced by thiopental and atracurium. After the surgery, muscle relaxation and lethargy remained. At 8-10 h later, muscle strength improved and train of four (TOF) reached over 0.85, and then the endotracheal tube was removed. The patient was evaluated during the hospital stay and on the anesthesia clinic. No neurological symptoms, headache or backache were reported. Due to availability of magnesium sulfate, we should be careful for inadvertent intravenous, spinal and epidural injection; therefore before injection must be double checked.

Comparative efficacy of two different dosages of intrathecal magnesium sulphate supplementation in subarachnoid block

BACKGROUND

Spinal anaesthesia is the primary anaesthetic technique for many types of surgeries. Adjuncts to the local anaesthetics (LA) used in spinal anaesthesia can exhibit undesirable side-effects like respiratory depression, urinary retention, pruritis, haemodynamic instability and nausea and vomiting, limiting their use. Magnesium when used in therapeutic doses avoids all of these side-effects.

MATERIALS AND METHODS

We conducted a randomized double blind study on 90 patients, 30 in each group, scheduled for orthopaedic lower limb surgery under subarachnoid block. Group I: received bupivacaine (0.5%), 12.5 mg + 0.5 ml of preservative free 0.9% normal saline, Group II received bupivacaine (0.5%), 12.5 mg + 0.2 ml (50 mg) of preservative free 25 % magnesium sulphate + 0.3 ml of preservative free 0.9% normal saline Group III: received bupivacaine (0.5%) 12.5 mg + 0.3 ml (75 mg) of 25 % magnesium sulphate + 0.2 ml of preservative free 0.9% normal saline for subarachnoid block. The onset and duration of sensory block, the highest dermatomal level of sensory block, motor block, time to complete motor block recovery and duration of spinal anaesthesia were recorded.

STATISTICAL ANALYSIS

ANOVA was applied to determine the significance of difference between different groups. If p-value was significant then Turkey's Post Hoc Multicomparison test was applied. Values of p<0.05 were considered to be statistically significant.

RESULTS

The time of maximum sensory block, time of onset of motor block, duration of sensory block, duration of motor block and time of analgesia request were prolonged in patients given magnesium 50mg and 75mg along with local anaesthetic intrathecally.

CONCLUSION

N-methyl-D-aspartate (NMDA) receptor antagonist, magnesium when administered intrathecally along with local anaesthetics prolongs the duration of spinal analgesia without adverse effects.

Mechanisms underlying cell death in ischemia-like damage to the rat spinal cord in vitro

New spinal cord injury (SCI) cases are frequently due to non-traumatic causes, including vascular disorders. To develop mechanism-based neuroprotective strategies for acute SCI requires full understanding of the early pathophysiological changes to prevent disability and paralysis. The aim of our study was to identify the molecular and cellular mechanisms of cell death triggered by a pathological medium (PM) mimicking ischemia in the rat spinal cord in vitro. We previously showed that extracellular Mg²⁺ (1 mM) worsened PM-induced damage and inhibited locomotor function. The present study indicated that 1 h of PM+Mg²⁺ application induced delayed pyknosis chiefly in the spinal white matter via overactivation of poly (ADP-ribose) polymerase 1 (PARP1), suggesting cell death mediated by the process of parthanatos that was largely suppressed by pharmacological block of PARP-1. Gray matter damage was less intense and concentrated in dorsal horn neurons and motoneurons that became immunoreactive for the mitochondrial apoptosis-inducing factor (the intracellular effector of parthanatos) translocated into the nucleus to induce chromatin condensation and DNA fragmentation. Immunoreactivity to TRPM ion channels believed to be involved in ischemic brain damage was also investigated. TRPM2 channel expression was enhanced 24 h later in dorsal horn and motoneurons, whereas TRPM7 channel expression concomitantly decreased. Conversely, TRPM7 expression was found earlier (3 h) in white matter cells, whereas TRPM2 remained undetectable. Simulating acute ischemic-like damage in vitro in the presence of Mg²⁺ showed how, during the first 24 h, this divalent cation unveiled differential vulnerability of white matter cells and motoneurons, with distinct changes in their TRPM expression.

Effect of intrathecal magnesium in the presence or absence of local anaesthetic with and without lipophilic opioids: a systematic review and meta-analysis

Spinal anaesthesia is the primary anaesthetic technique for many types of surgery. Adjuncts to the local anaesthetics (LA) used in spinal anaesthesia can exhibit undesirable side-effects, limiting their use, but magnesium may have advantages in this respect. We sought randomized control trials (RCTs) in patients undergoing all types of surgery and in women in labour to compare the effect of intrathecal magnesium sulphate ± LA ± lipophilic opioid (experimental group) with the use of either intrathecal lipophilic opioids ± LA or LA only (control group). The primary outcome was the duration of spinal anaesthesia. Secondary outcomes were: onset and time to maximal sensory blockade, onset of motor block, and duration of sensory and motor blockade. We found 15 RCTs comprising 980 patients. The duration of spinal anaesthesia was significantly increased in the experimental group [standardized mean difference (SMD) -1.05 (-1.70, -0.41) (P = 0.001)], compared with the control group. This increased duration of spinal anaesthesia was seen in non-obstetric studies, SMD -1.38 (-2.11, -0.66) (P = 0.0002), but not in obstetric studies, SMD -0.55 (-1.87, 0.77) (P = 0.41). There was no delay in the onset of sensory or motor blockade. The incidence of hypotension and pruritus was similar in both groups. Heterogeneity was high in all outcome measures. The duration of spinal anaesthesia may be increased by the addition of magnesium to lipophilic opioids ± LA.

The analgesic efficacy and safety of neuraxial magnesium sulphate: a quantitative review

Eighteen published trials have examined the use of neuraxial magnesium as a peri-operative adjunctive analgesic since 2002, with encouraging results. However, concurrent animal studies have reported clinical and histological evidence of neurological complications with similar weight-adjusted doses. The objectives of this quantitative systematic review were to assess both the analgesic efficacy and the safety of neuraxial magnesium. Eighteen trials comparing magnesium with placebo were identified. The time to first analgesic request increased by 11.1% after intrathecal magnesium administration (mean difference: 39.6 min; 95% CI 16.3-63.0 min; p = 0.0009), and by 72.2% after epidural administration (mean difference: 109.5 min; 95% CI 19.6-199.3 min; p = 0.02) with doses of between 50 and 100 mg. Four trials monitored for neurological complications: of the 140 patients included, only a 4-day persistent headache was recorded. Despite promising peri-operative analgesic effect, the risk of neurological complications resulting from neuraxial magnesium has not yet been adequately defined.

Comparison of postoperative analgesic effect of intrathecal magnesium and fentanyl added to bupivacaine in patients undergoing lower limb orthopedic surgery

OBJECTIVE

To compare the analgesic efficacy and side effects of magnesium and fentanyl as an additive to intrathecal bupivacaine.

METHODS

Ninety adult patients scheduled for femur surgery under spinal anesthesia were randomly allocated to one of the following three groups to receive intrathecally: bupivacaine 15 mg combined with 0.5 mL magnesium 10%; bupivacaine 15 mg combined with 0.5 mL fentanyl; or bupivacaine 15 mg combined with 0.5 mL distilled water (control). The time to first analgesic request, sensory and motor blockade onset time, duration of sensory and motor blockade, analgesic requirement in the first 12 hours after surgery, and the incidences of hypotension, bradycardia, hypoxemia and ephedrine were recorded.

RESULTS

Magnesium caused a significant delay in the onset of both sensory and motor blockade compared with the fentanyl (95% CI 3 to 4; p < 0.001) and control (95% CI 3.5-5; p < 0.001) groups. The duration of spinal analgesia in group F (fentanyl) was significantly greater than in group C (control) (95% CI 365-513; p < 0.001) and group M (magnesium) (95% CI 385-523; p < 0.001). The total amount of methadone consumption over 12 hours was significantly lower in the magnesium and fentanyl groups than in the control group (5 mg vs. 5.666 ± 1.728 mg; p = 0.04).

CONCLUSION

Addition of intrathecal magnesium sulfate to spinal anesthesia induced by bupivacaine significantly prolonged the onset of both sensory and motor blockade compared with fentanyl. Although magnesium failed to prolong the time to first analgesic requirement as seen with fentanyl, it reduced the total consumption of opioids in the first 12 hours postoperatively compared with the control group.

Magnesium sulfate does not protect spinal cord against ischemic injury

OBJECTIVE

We tested various doses of MgSO(4) to investigate the effect of Mg on a spinal cord ischemia.

METHODS

Rats were treated with either MgSO(4) (30, 100, or 300 mg/kg; group Mg(low), group Mg(medium), group Mg(high), respectively, n = 10 for each) or saline (control group; n = 10) before ischemia. Spinal cord ischemia was induced using a balloon-tipped catheter placed on proximal descending aorta. During surgery, hemodynamic variables were recorded before ischemia, during aortic occlusion and after reperfusion. Neurologic function was assessed using the motor deficit index (MDI; 0 = normal, 6 = complete paralysis) until seven days after reperfusion, and histologic examination of spinal cord was performed.

RESULTS

After reperfusion, the mean arterial pressure in the group Mg(high) was significantly lower than other groups. Compared to the control group, the groups Mg(low) and Mg(medium) did not show any difference in MDI and the group Mg(high) showed significantly higher MDI. The number of normal motor neurons was similar among other groups except the group Mg(high) had a significantly fewer normal motor neurons.

CONCLUSIONS

Intravenous MgSO(4) with low or medium dose (30, or 100 mg/kg) did not improve neurological injury following spinal cord ischemia. Furthermore, higher dose of MgSO(4) (300 mg/kg) resulted in hemodynamic instability and aggravated neurologic outcome.

Effects of adjunct intrathecal magnesium sulfate to bupivacaine for spinal anesthesia: a randomized, double-blind trial in patients undergoing lower extremity surgery

PURPOSE

The aim of this study was to evaluate the effect of additional magnesium sulfate (MgSO(4)) 100 mg to intrathecal (IT) isobaric 0.5% bupivacaine 3 ml on spinal anesthesia in patients undergoing lower extremity orthopedic surgery.

METHODS

In a double-blind randomized clinical trial, 79 American Association of Anesthesiologists (ASA) I or II adult patients undergoing lower extremity orthopedic surgery were recruited. The patients were randomly allocated to receive 100 mg MgSO(4) 5% (0.2 ml) plus 15 mg of bupivacaine 0.5% (MgSO(4) group) or 15 mg bupivacaine 0.5% combined with 0.2 ml normal saline (control group) intrathecally. Response to treatment was assessed as onset and duration of sensory block, the highest level of sensory block, time to complete motor block recovery, duration of spinal anesthesia, and postoperative analgesic requirement.

RESULTS

The onset of the sensory block was slower in the MgSO(4) group than in the control group (13.3 vs. 11.6 min, P = 0.04), and the duration of the sensory blockade was significantly longer in the MgSO(4) group than the control group (106.5 vs. 85.5 min, P = 0.001). Total analgesic requirements for 24 h following surgery were lower in the MgSO(4) group than in the control group (96.8 vs. 138.5 mg, P = 0.001). Mean duration of spinal anesthesia was not significantly different between two groups (178.0 vs. 167.4 min, P = 0.23).

CONCLUSION

In patients undergoing lower extremity surgery with spinal anesthesia, the addition of 100 mg IT MgSO(4) to 15 mg bupivacaine without opioid supplement, prolonged the duration of the sensory block, decreased postoperative analgesic consumption, and significantly prolonged the onset of spinal anesthesia.

NT-3-secreting human umbilical cord mesenchymal stromal cell transplantation for the treatment of acute spinal cord injury in rats

An animal model for clip spinal cord injury (SCI) was used to determine whether Neurotrophin-3 (NT-3) genetically modified human umbilical mesenchymal stem cells (NT-3-HUMSCs) could promote the morphologic and functional recovery of injured spinal cords. Using the Basso, Beattie, and Bresnahan scores and a grid test, the rats in the HUMSC-treated and NT-3-HUMSCs groups had significantly improved locomotor functional recovery more than the control group. In comparison, the NT-3-HUMSCs group achieved better functional recovery than the HUMSCs group at the end of 12 weeks after SCI. The functional recovery was accompanied by increased intensity of 5-HT fibers, increased volume of spared myelination, and decreased area of the cystic cavity in the NT-3-HUMSCs group compared with the HUMSCs group. Moreover, transplanted NT-3-HUMSCs survived and produced larger amounts of NT-3 than the HUMSCs in the host spinal cord. These results show that NT-3 enhanced the therapeutic effects of HUMSCs after clip injury of the spinal cord.

Relief of postherpetic neuralgia with transforaminal epidural injection of magnesium -a case report-

Although postherpetic neuralgia (PHN) is a common chronic pain syndrome, the pathophysiology of this disorder is not well known and management is often very difficult. N-Methyl-D-Aspartate (NMDA) receptor antagonists are known to be effective in PHN, and magnesium, a physiological blocker of NMDA receptors, is widely used to treat various chronic pain disorders. Here, we present a case of the PHN refractory to conventional treatment, which was treated successfully with transforaminal epidural injection of magnesium sulphate at the affected dermatome.

Is magnesium sulfate by the intrathecal route efficient and safe?

The polypharmacological approach to the treatment of postoperative pain has become routine in an attempt to minimize the adverse side effects of opioids. Magnesium sulphate is a noncompetitive antagonist of the N-methyl-d-aspartate (NMDA) receptor and thus can modify nociceptive modulation. Intravenous administration of magnesium sulphate can improve postoperative analgesia and decrease the requirement for postoperative opiates, but the effects are inconsistent and have not been reliably accompanied by a reduction in the incidence of morphine-related adverse events. Several studies have shown that the administration of magnesium by the intrathecal route is safe and, in combination with opiates, extends the effect of spinal anaesthesia in both animal and human studies. The analysis of these studies justifies further investigation of the use of magnesium sulphate by the intrathecal route.

Evaluation of the effect of magnesium sulphate vs. clonidine as adjunct to epidural bupivacaine

For treatment of intra and postoperative pain, no drug has yet been identified that specifically inhibits nociception without associated side effects. Magnesium has antinociceptive effects in animal and human models of pain. The current prospective randomised double-blind study was undertaken to establish the effect of addition of magnesium or clonidine, as adjuvant, to epidural bupivacaine in lower abdominal and lower limb surgeries. A total of 90 American Society of Anesthesiology (ASA) grade I and II patients undergoing lower abdominal and lower limb surgeries were enrolled to receive either magnesium sulphate (Group B) or clonidine (Group C) along with epidural bupivacaine for surgical anaesthesia. All patients received 19 ml of epidural bupivacaine 0.5% along with 50 mg magnesium in group B, 150 mcg clonidine in Group C, whereas in control group (Group A), patients received same volume of normal saline. Onset time, heart rate, blood pressure, duration of analgesia, pain assessment by visual analogue score (VAS) and adverse effects were recorded. Onset of anaesthesia was rapid in magnesium group (Group B). In group C there was prolongation of duration of anaesthesia and sedation with lower VAS score, but the incidence of shivering was higher. The groups were similar with respect to haemodynamic variables, nausea and vomiting. The current study establishes magnesium sulphate as a predictable and safe adjunct to epidural bupivacaine for rapid onset of anaesthesia and clonidine for prolonged duration of anaesthesia with sedation.

Efficacy and vasodilatory benefit of magnesium prophylaxis for protection against spinal cord ischemia

Prevention of paraplegia remains an imperative issue in thoracoabdominal aortic surgery. The aim of this study was to assess the efficacy of a prophylactic magnesium infusion in a rat spinal cord ischemia model and to demonstrate spinal blood flow increase caused by the infusion. The study was conducted in two parts. Firstly, the neuroprotective effect of magnesium was assessed using a rat model with two different ischemic times: 10 min and 14 min. Spinal cord ischemia was induced by occlusion of the descending aorta. Rats in the treatment group were given a 100 mg/kg magnesium sulfate infusion before ischemia. Secondly, relative changes in spinal cord blood flow before and during ischemia were recorded using the laser Doppler flowmetry technique. Changes in blood flow were compared between the magnesium and control groups. Rats pretreated with magnesium showed good overall recovery after both 10 min (incidence of paraplegia 62.5% control vs. 37.5% Mg, n = 8 each) and 14 min (85.7% control vs. 57.1% Mg, n = 7 each) of ischemia, although the differences compared with controls were statistically insignificant. However, the magnesium group showed significantly better neurological performance during the early postischemic period. Comparison of changes in spinal circulation revealed less reduction in blood flow during ischemia in the magnesium-treated group. In conclusion, magnesium may have potential prophylactic benefits during ischemia by exerting a neuroprotective effect through vasodilation of the spinal cord vasculature. To our knowledge, this vasodilatory effect on the spinal cord has not previously been investigated. Optimization of the treatment regimen, however, is required.

Epidural magnesium reduces postoperative analgesic requirement

BACKGROUND

Magnesium has antinociceptive effects in animal and human models of pain. Our hypothesis was that the addition of magnesium to postoperative epidural infusion of fentanyl may decrease the need for fentanyl.

METHODS

Fifty patients undergoing hip surgery were enrolled to receive either fentanyl (Group F) or fentanyl plus magnesium sulphate (Group FM) for 24 h for epidural analgesia. All patients were equipped with a patient-controlled epidural analgesia device and the initial settings of a demand bolus dose of fentanyl 25 microg. In Group FM, patients received 50 mg magnesium sulphate epidurally as an initial bolus dose followed by a continuous infusion of 100 mg day(-1). Ventilatory frequency, heart rate, blood pressure, pain assessment using a visual analogue scale (VAS), sedation scores and fentanyl consumption were recorded in the postoperative period.

RESULTS

There was no significant difference between groups in the time to first analgesic requirement. Compared with Group F, patients in Group FM received smaller doses of epidural fentanyl (P < 0.05). The cumulative fentanyl consumption in 24 h was 437 (SD110) microg in Group F and 328 (121) microg in Group FM (P < 0.05). Patients in Group F showed a higher VAS score in the first hour of the postoperative period (P < 0.05). The groups were similar with respect to haemodynamic and respiratory variables, sedation, pruritus, and nausea.

CONCLUSION

Co-administration of magnesium for postoperative epidural analgesia results in a reduction in fentanyl consumption without any side-effects.