[Indications for the use of magnesium in anesthesia and intensive care]

Efficacy and Safety of Intravenous Magnesium Sulfate in Spinal Surgery: A Systematic Review and Meta-Analysis

Optimizing pain management in spinal surgery is crucial for preventing adverse events due to delayed mobilization. Magnesium sulfate has potential benefits in spinal surgery because of its analgesic properties and modulation of neurotransmitters and autonomic nervous system. Existing evidence regarding the use of magnesium sulfate is partial and controversial, necessitating a comprehensive meta-analysis to evaluate its efficacy and safety. The aim of this study was to conduct a comprehensive meta-analysis to evaluate the efficacy and safety of magnesium sulfate in spinal surgery compared to other available options. This meta-analysis adhered to the PRISMA guidelines. Patients undergoing spinal surgery were included, with the intervention group receiving intravenous magnesium sulfate (MS) at various doses or combinations, whereas the comparison group received other alternatives or a placebo. The efficacy and safety outcomes were assessed. Data were collected from multiple databases and analyzed using Review Manager version 5.4. Heterogeneity was assessed and fixed- or random-effects models were applied. The meta-analysis included eight studies (n = 541). Magnesium sulfate demonstrated significant reductions in pain at 24 h (MD -0.20, 95% CI: -0.39 to -0.02) and opioid consumption (SMD -0.66, 95% CI: -0.95 to -0.38) compared to placebo. Additionally, a decrease in the use of muscle relaxants (SMD -0.91, 95% CI: -1.65 to -0.17) and remifentanil (SMD -1.52, 95% CI: -1.98 to -1.05) was observed. In contrast, an increase in extubation time (MD 2.42, 95% CI: 1.14 to 3.71) and verbal response (MD 1.85, 95% CI: 1.13 to 2.58) was observed compared to dexmedetomidine. In conclusion, magnesium sulfate administration in spinal surgery reduced pain and opioid consumption, and prolonged orientation and verbal response. No significant differences in blood pressure or heart rate were observed between the groups.

Intra-articular injection of magnesium chloride attenuates osteoarthritis progression in rats

OBJECTIVE

To explore the effects of Mg²⁺ on the expression of osteoarthritic markers in human cartilage and synovium tissue explants. To investigate the therapeutic effect of intra-articular injection of Mg²⁺ in an established rat OA (Osteoarthritis) model of anterior cruciate ligament transection with partial medial meniscectomy (ACLT + PMM).

DESIGN

Human cartilage and synovium explants were collected from total knee replacement surgeries and incubated with MgCl₂ (20 mmol/L) in vitro. A rat OA model was established by ACLT + PMM surgery in 450-500 g male Sprague Dawley (SD) rats. To select the optimal dose, intra-articular injections of MgCl₂ (0.05, 0.5, 5 mol/L) were performed at 4 weeks after the surgery every 3 days for 2 weeks. The effect of optimized MgCl₂ was further determined by histology, immunohistochemistry, and quantitative real-time polymerase chain reaction.

RESULTS

The expressions of osteoarthritic markers in human cartilage and synovium explants were inhibited by Mg²⁺in vitro. Immunohistochemical analysis further suggested the inhibitory effects of Mg²⁺ on the expression of MMP-13 and IL-6 in the human tissue explants. Cartilage degeneration and synovitis in ACLT + PMM rats were significantly improved by intra-articular injections of Mg²⁺ (0.5 mol/L). Immunohistochemical analysis also showed the regulatory effects of Mg²⁺ on osteoarthritic markers in both cartilage and synovium in rats, consistent with in vitro results.

CONCLUSION

Intra-articular injections of Mg²⁺ at 0.5 mol/L attenuate the progression of OA in the ACLT + PMM rat model. Such effect was at least in part explained by the promotion of cartilage matrix synthesis and the suppression of synovial inflammation.

Effect of continuous magnesium sulfate infusion on spinal block characteristics: A prospective study

Background:

Spinal anesthesia is an established mode of anesthesia for lower limb orthopedic surgeries. The limitations of the technique are short duration of action and limited post-operative analgesia. Concomitant use of intravenous infusion of magnesium sulfate may have an effect on the block characteristics and duration of action of intrathecal bupivacaine.

Methods:

A total of 80 American Society of Anesthesiologists I and II patients, either sex, 20-60 years of age scheduled for elective orthopedic fixation of fracture of long bones of lower limbs under spinal anesthesia were included. Spinal anesthesia administered with 2.5 ml heavy bupivacaine mixed with 10 mcg fentanyl. The groups were then divided to receive an infusion of injection magnesium sulfate 50 mg/kg/h over 15 min followed by 15 mg/kg/h until the end of the surgery (Group M) and 15 ml of Normal Saline over 15 min followed by 100 ml/h until the end of surgery (Group S). Onset, duration of sensory and motor block and amount of post-operative analgesic were noted.

Results:

A total of 6 patients (Group M) and seven patients (Group S) had inadequate block and excluded from the study. Mean block height was T6. Time required to achieve block height was 8.82 min versus 7.42 min in Groups M and S respectively (P = 0.04). Mean duration of motor block was longer in group M (160.63 ± 17.76 min) compared with Group S (130.12 ± 20.70 min) (P = 0.000). Time for regression of sensory block to T12/L1was 206.88 ± 20.96 min (Group M) and 163.88 ± 15.46 min (Group S) (P = 0.000). Hemodynamic parameters were similar and statistically not significant. Need for first analgesic requirement was after 262.88 ± 21.11 min in group M and 193.25 ± 17.74 min in the group S (P = 0.000). Mean dosage of tramadol needed in first 24 h was less in group M (190 ± 30.38 mg vs. 265 ± 48.30 mg, P = 0.000).

Conclusion:

Use of intravenous magnesium with spinal anesthesia reduces post-operative pain and analgesic consumption.

Intra-articular magnesium sulfate (MgSO4) reduces experimental osteoarthritis and nociception: association with attenuation of N-methyl-D-aspartate (NMDA) receptor subunit 1 phosphorylation and apoptosis in rat chondrocytes

OBJECTIVE

To study the effects of intra-articular injection of magnesium sulfate (MgSO(4)) on the development of osteoarthritis (OA) and to examine concomitant changes in the nociceptive behavior of rats.

METHODS

OA was induced in Wistar rats with intra-articular injection of collagenase (500 U) in the right knee; the left knee was left untreated. In the OA+MgSO(4) group (n=7), the treated knee was injected with 500-microg (0.1-ml) MgSO(4) twice a week for 5 consecutive weeks starting at 1 week after collagenase injection; in the OA group (n=7), the same knee was injected with the same amount of physiological normal saline. In the MgSO(4) group (n=6), naïve rats received only MgSO(4) injections; in the control group (n=6), naïve rats received only physiological normal saline injections. Nociceptive behavior (mechanical allodynia and thermal hyperalgesia) on OA development was measured before and at 1, 2, 4, 6, and 8 weeks after collagenase injection, following which the animals were sacrificed. Gross morphology and histopathology were examined in the femoral condyles, tibial plateau, and synovia. Immunohistochemical analysis was performed to examine the effect of MgSO(4) on N-methyl-D-aspartate (NMDA) receptor subunit 1 phosphorylation (p-NR1) and apoptosis in the articular cartilage chondrocytes.

RESULTS

OA rats receiving intra-articular MgSO(4) injections showed a significantly lower degree of cartilage degeneration than the rats receiving saline injections. MgSO(4) treatment also suppressed synovitis. Mechanical allodynia and thermal hyperalgesia showed significant improvement in the OA+MgSO(4) group as compared to the OA group. Moreover, MgSO(4) attenuated p-NR1 and chondrocyte apoptosis in OA-affected cartilage.

CONCLUSIONS

Our results indicate that local intra-articular administration of MgSO(4) following collagenase injection in an experimental rat OA model (1) modulates chondrocyte metabolism through inhibition of cell NMDA receptor phosphorylation and apoptosis, (2) attenuates the development of OA, and (3) concomitantly reduces nociception.

Role of magnesium sulfate in postoperative pain management for patients undergoing thoracotomy

OBJECTIVE

The purpose of this study was to investigate the effect of magnesium sulfate on pain management for post-thoracotomy patients.

DESIGN

A prospective, randomized, controlled clinical study.

SETTING

University hospital.

PARTICIPANTS

Twenty-four patients undergoing thoracotomy.

INTERVENTIONS

After thoracotomy operations, patients were assigned to 2 groups. The control group received intravenous morphine (0.5 mg/h infusion, 0.3 mg patient-controlled anesthesia dose, 15-minute lockout time) via patient-controlled analgesia, and the magnesium group received magnesium sulfate (30-mg/kg bolus, 10 mg/kg/h infusion for 48 hours) plus the same patient-controlled analgesia protocol.

MEASUREMENTS AND MAIN RESULTS

Visual analog scale for pain score, sedation score, mean arterial pressure, heart rate, and valid and invalid analgesic demand were recorded. Serum magnesium levels were determined at postanesthesia care unit admission, at 24 hours, and at 48 hours. Side effects were also recorded. There were no significant differences between groups with respect to demographics, sedation score, and pain score. Cumulative mean morphine consumption was found to be higher in the control group compared with the magnesium group at 4, 8, and 48 hours (5.6 +/- 1 mg v 3.2 +/- 0.6 mg [p < 0.0001], 10.2 +/- 1.8 mg v 7.2 +/- 1.6 mg [p = 0.0003), and 40.2 +/- 4.5 mg v 34.8 +/- 6.3 mg [p = 0.02], respectively).

CONCLUSION

Postoperative use of magnesium sulfate reduced opioid consumption for pain after thoracotomy operations.

The therapeutic use of magnesium in anesthesiology, intensive care and emergency medicine: a review

PURPOSE

To review current knowledge concerning the use of magnesium in anesthesiology, intensive care and emergency medicine.

METHODS

References were obtained from Medline(R) (1995 to 2002). All categories of articles (clinical trials, reviews, or meta-analyses) on this topic were selected. The key words used were magnesium, anesthesia, analgesia, emergency medicine, intensive care, surgery, physiology, pharmacology, eclampsia, pheochromocytoma, asthma, and acute myocardial infarction.

PRINCIPLE FINDINGS

Hypomagnesemia is frequent postoperatively and in the intensive care and needs to be detected and corrected to prevent increased morbidity and mortality. Magnesium reduces catecholamine release and thus allows better control of adrenergic response during intubation or pheochromocytoma surgery. It also decreases the frequency of postoperative rhythm disorders in cardiac surgery as well as convulsive seizures in preeclampsia and their recurrence in eclampsia. The use of adjuvant magnesium during perioperative analgesia may be beneficial for its antagonist effects on N-methyl-D-aspartate receptors. The precise role of magnesium in the treatment of asthmatic attacks and myocardial infarction in emergency conditions needs to be determined.

CONCLUSIONS

Magnesium has many known indications in anesthesiology and intensive care, and others have been suggested by recent publications. Because of its interactions with drugs used in anesthesia, anesthesiologists and intensive care specialists need to have a clear understanding of the role of this important cation.

Effect of intra-operative magnesium sulphate on pain relief and patient comfort after major lumbar orthopaedic surgery

The effects of intra-operative magnesium sulphate on pain relief after major lumbar surgery were investigated in 24 patients. Patients were randomly allocated to receive either an infusion of 50 mg x kg(-1) magnesium sulphate or an equivalent volume of saline at induction of anaesthesia. Anaesthesia was induced with propofol and remifentanil. Tracheal intubation was facilitated using rocuronium. Maintenance was achieved with remifentanil and sevoflurane in nitrous oxide/ oxygen. Intra-operative monitoring included standard equipment and neuromuscular transmission. During surgery, neuromuscular block recovery was longer in the magnesium group. Postoperative opioid consumption and pain scores were lower in the magnesium group. The first night's sleep and the global satisfaction scores were better in the magnesium group. The results of the study support magnesium sulphate as a useful adjuvant for postoperative analgesia after major lumbar surgery.

Magnesium potentiates neuromuscular blockade with cisatracurium during cardiac surgery

PURPOSE

Magnesium potentiates the effect of nondepolarizing neuromuscular blocking agents. It is used in cardiac anesthesia to prevent hypertension and arrhythmias. This study was performed to measure the interaction between magnesium and cisatracurium in cardiac surgery.

METHODS

Twenty patients scheduled for elective cardiac surgery were randomly assigned to receive magnesium sulfate (70 mg x kg(-1) at induction followed by 30 mg x kg(-1) x hr(-1)) or placebo. The ulnar nerve was stimulated and the electromyographic response of the adductor pollicis was measured. Cisatracurium 0.1 mg x kg(-1) was given at induction, followed by 0.05 mg x kg(-1) when the first twitch in the train-of-four reached 25%.

RESULTS

Ionized magnesium was 1.32 +/- 0.24 mmol x L(-1) in the treatment group vs 0.47 +/- 0.4 mmol x L(-1) in the control group. Duration of action of the intubating dose was longer in the magnesium group (74 +/- 20 min) than in the placebo group (42 +/- 6 min, P = 0.0001). Duration of the first maintenance dose was 69 +/- 16 min in the magnesium group vs 35 +/- 7 min in the placebo group (P = 0.0001). Total dose of cisatracurium administered throughout surgery was 0.19 +/- 0.07 mg x kg(-1) in the magnesium group compared with 0.29 +/- 0.01 mg x kg(-1) in the placebo group (P = 0.017). Hemodynamic variables and temperature were similar in both groups.

CONCLUSION

In patients undergoing cardiac surgery, administration of magnesium sulfate, resulting in ionized levels of 1.3 mmol x L(-1), results in a 30-35 min prolongation of the neuromuscular blockade induced with intubating and maintenance doses of cisatracurium and does not alter hemodynamic stability.

Successful resuscitation of serious bupivacaine intoxication in a patient with pre-existing heart failure

PURPOSE

In dogs intoxicated with bupivacaine, clonidine is effective to treat conduction disturbances and dobutamine corrects myocardial depression. We report the case of a patient who experienced severe bupivacaine cardiotoxicity and who was treated successfully using these medications.

CLINICAL FEATURES

In a patient with pre-existing heart failure a surgical procedure to fix a humeral fracture was necessary. Preoperatively, heart failure was controlled with transcutaneous nitroglycerin and iv deslanoside. A bupivacaine bolus was administered iv accidentally (a mixture of bupivacaine 75 mg, 15 micro g clonidine). The patient developed nodal rhythm with extreme bradycardia, severe shock and convulsions. Seizures were controlled with thiopentone/succinylcholine. Epinephrine iv boluses (0.1 mg x 3) restored blood pressure (BP) to 50/30 mmHg and heart rate (HR) to 60 (nodal rhythm). Following 75 micro g clonidine iv, BP rose to 90/70 and HR to 90 min. Cardiac rhythm reverted to sinus rhythm with first degree atrio-ventricular block. Echocardiography showed hyperkinesia and relative hypovolemia that was controlled with iv administration of terlipressin and glucagon. Subsequent dobutamine infusion stabilized hemodynamic conditions. It was decided to proceed with surgery using a midazolam/sufentanil based general anesthetic. In the intensive care unit, recovery, extubation and weaning from the dobutamine infusion were realized within 16 hr of the event.

CONCLUSIONS

In this patient with preoperative heart failure, clonidine was effective to treat bupivacaine induced conduction disturbances. Epinephrine and dobutamine were effective to treat myocardial depression and terlipressin effectively controlled vasodilatation.

Magnesium oxide augmentation of verapamil maintenance therapy in mania

The authors compared the antimanic effects of a verapamil-magnesium oxide (V-M) combination with a verapamil-placebo combination (V-P) in patients pretreated with verapamil. BPRS scores and serum magnesium levels were compared. The V-M combination was found to be significantly more effective than V-P in reducing manic symptoms (P=0.015). Serum magnesium levels were significantly higher in the V-M group (P<0.04). These data suggest that magnesium may increase antimanic efficacy of verapamil by mechanisms which may operate at the intracellular level. The magnesium-verapamil combination may have clinical application as an adjunct to verapamil in the maintenance therapy of mania.