Magnesium as part of balanced general anaesthesia with propofol, remifentanil and mivacurium: a double-blind, randomized prospective study in 50 patients

Analgesic Effects of Magnesium Sulphate as an Adjuvant to Fentanyl for Monitored Anaesthesia Care During Hysteroscopy

BACKGROUND

Magnesium sulphate (MgSO4) is conventionally used in the treatment of eclampsia, refractive arrhythmias, asthma, etc. In our study, we aimed to study the analgesic effects of MgSO4 as an adjuvant to fentanyl and reduce the intraoperative opioid requirement to decrease their adverse effects.

METHODS

A total of 122 patients scheduled for hysteroscopy were randomly divided into two groups. Patients in the magnesium group (group A) received intravenous MgSO4 50 mg/kg in 100 ml of isotonic saline over 15 minutes before anaesthesia induction and then 15 mg/kg per hour by continuous intravenous infusion. Patients in the control group (group B) received an equal volume of isotonic saline as a placebo. All the patients were induced with fentanyl and propofol. Perioperative haemodynamic monitoring and postoperative assessment of pain were done.

RESULTS

Only 18% of the patients in group A required rescue analgesics as compared to 39.3% of patients in group B. The patients receiving MgSO4 displayed lower verbal numeric rating scale scores in the postoperative period. In addition, the intraoperative requirement of fentanyl (101 (21.33) vs. 144 (28.4) µg, mean (SD)) and propofol (121 (13.3) vs. 140 (16.5) mg, mean (SD)) was significantly lower in group A as compared to that in group B.

CONCLUSION

MgSO4, when administered as an adjuvant to opioids, provided effective postoperative analgesia thereby reducing the need for rescue analgesics. It also decreases intraoperative fentanyl consumption and its dose-related side effects.

Is intravenous magnesium sulphate a suitable adjuvant in postoperative pain management? - A critical and systematic review of methodology in randomized controlled trials

A growing worldwide focus on opioid-free anaesthesia entails multimodal analgesic strategies involving non-opioids such as magnesium sulphate (MgSO4). Several systematic reviews have concluded there is beneficial analgesic effect of MgSO4 administration but do not take considerable heterogeneity among the studies into consideration. Medical literature published until June 2021 was searched in PubMed/Medline, Embase, Central and Web of Science: The final search yielded a total of 5,672 articles. We included only randomised controlled trials assessing the effect of intravenous MgSO4 on opioid consumption and acute postoperative pain when compared to either placebo or standardized analgesic treatment. The primary aim was to compare the homogeneity of essential variables and confounders. A post-hoc meta-analysis demonstrated a reduction in both postoperative morphine consumption (-6.12 mg) and pain score (-12.32 VAS points) in favour of the MgSO4-groups. Data for meta-analysis was missing from 19 studies (45%) on morphine consumption and 29 studies (69%) for pain score, the majority of which reports no effect for either morphine consumption or pain score. The calculated heterogeneity among the included studies was considerable for both outcomes; I 2=91% for morphine consumption and I 2=96% for pain score. Although we found a per se reduction in opioid consumption and pain score, methodological heterogeneity and clinical shortcomings of pre-, intra-, and post anaesthetic data precludes conclusions on clinical importance of intraoperative intravenous MgSO4. In addition, the reduction is likely less than what can be gained from using standardized analgesic treatment.

Insights into the spectrofluorometric determination of the neuromuscular blocker mivacurium chloride

Fluorescence spectroscopy is gaining interest in the analysis and quantitative determination of different drugs. This study was carried out to investigate the fluorometric properties of the short-acting muscle relaxant mivacurium in its pure form, injection, and human plasma. It is nondepolarizing skeletal muscle relaxant for intravenous (IV) administration. Mivacurium shows a strong native fluorescence in methanol at 317 nm after excitation at 230 nm (Method I). The critical parameters that may influence the fluorescence of this drug were carefully studied. A linear response between concentration and fluorescence was constructed over the concentration range: 20.0 to 400.0 ng/mL with determination coefficient (r²) equal to 0.9998. Additionally, the correlation coefficient of the linear relationship (r) was found to be 0.9999 with a slope = 2.196 and intercept = -16.61. Limits of quantitation and detection were calculated mathematically to be 17.45 and 5.75 ng/mL respectively. Further estimation of mivacurium in spiked human plasma was performed by construction of specific calibration curve and the obtained correlation coefficient was 0.9948. Moreover, the ability to determine mivacurium in the presence of commonly co-administered drugs were investigated including propofol and thiopental. Method II includes the determination of MVC in the presence of propofol utilizing the first derivative synchronous fluorescence spectroscopy. The results of method II indicated acceptable percentage recoveries from 98.88 to 100.75 %. Statistical evaluation of the results revealed satisfactory accuracy and precision.

A randomized controlled trial of intravenous magnesium sulphate as an adjunct to standard therapy in atrial fibrillation

Background

Magnesium sulphate (MgSO4) has been proven as an analgesic, neuromuscular blocker agent, and treatment of acute asthma.

Objective

The study aimed to assess the safety and efficacy of magnesium sulphate infusion for the treatment of patients with atrial fibrillation.

Methods

A prospective, randomized, double-blind, placebo-controlled study was conducted on 55 atrial fibrillation patients at the Emergency Department. The treatment group consisting of 41 patients received 20 mEq (2.5 g, 10 mmol) magnesium sulphate over a 20-minute period, followed by 20 mEq (2.5 g, 10 mmol) over a 2-hour period intravenously in addition to the standard treatment, and the control group consisting of 14 patients received placebo with a standard treatment. ECG was repeated and monitored upto 24 hours after the infusion.

Results

41 patients received magnesium sulphate and 14 patients received a placebo. The heart rate was 127 bpm – 210 bpm at the presentation to the emergency department and it was reached <100bpm in 70%(n=31) patients after 150 minutes of MgSO4 infusion. Two patients attained a heart rate of <100bpm in Placebo infusion. In the treatment group, 65% of subjects attained normal sinus rhythm at the end of 24 hours of infusion. Magnesium sulphate was more likely than placebo to achieve a heart rate of <100bpm and more likely to convert to sinus rhythm. ECG report reverted to normal in 74.5% in the treatment group and 25.5 % in the Placebo group within 24 hours. The patients in the treatment group stay a mean of 2.25 days in ICU, while the patients in the Placebo group stayed 4.25 days in ICU. Seven patients in the treatment group had minor side effects like flushing, headache, and nausea, which came to normal after 48hrs.

Conclusions

Magnesium sulphate has been shown a better efficacy to control the heart rate and conversion to sinus rhythm when used along with the standard management of Atrial fibrillation.

Impact of intraoperative intravenous magnesium on spine surgery: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

The effectiveness and safety of intraoperative intravenous magnesium (IIM) on spine surgery remain uncertain, as recent randomized controlled trials (RCTs) yielded conflicting results. The purpose of this study was to determine the impact of IIM on spine surgery.

METHODS

A literature search was performed on multiple electronic databases, ClinicalTrial.gov and Google Scholar on July 12th 2021, and reference lists were examined. We selected RCTs comparing the effects of IIM with placebo treatment on spine surgery. We calculated pooled standard mean difference (SMD) or risk ratio (RR) with 95% confident interval (CI) under a random-effect model. We assessed risk of bias using Cochrane risk-of-bias tool and Jadad score was applied to assess the quality of each included trial. Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) was used to determine the confidence in effect estimates. Sensitivity analysis was conducted by omitting each included study one by one from the pooled analysis. PROSPERO Registration: CRD42021266170.

FINDINGS

Fourteen trials of 781 participants were included. Low- to moderate-quality evidence suggested that IIM reduces postoperative morphine consumption at 24 h (SMD: -1·61 mg, 95% CI: -2·63 to -0·58) and intraoperative remifentanil requirement (SMD: -2·09 ug/h, 95% CI: -3·38 to -0·81). High-quality evidence suggested that IIM reduces the risk of postoperative nausea and vomiting compared with placebo (RR: 0·43, 95% CI: 0·26 to 0·71). Besides, moderate-quality evidence suggested that recovery orientation time in the IIM group is longer than control group (SMD: 1·13 min, 95% CI: 0·83 to 1·43).

INTERPRETATION

IIM as adjuvant analgesics showed overall benefits on spine surgery in terms of reducing analgesic requirement and postoperative nausea and vomiting; however, potential risks of IIM, such as delayed anesthetic awakening, should not be ignored. Future evidence will inform the optimal strategy of IIM administration for patients undergoing spine surgery.

FUNDING

This study was funded by Beijing Municipal Natural Science Foundation (Grant No :7212117).

Magnesium for Pain Treatment in 2021? State of the Art

Background: Magnesium (Mg) is commonly used in clinical practice for acute and chronic pain and has been reported to reduce pain intensity and analgesics consumption in a number of studies. Results are, however, contested. Objectives: This review aims to investigate randomised clinical trials (RCTs) on the effectiveness of Mg treatment on pain and analgesics consumption in situations including post-operative pain, migraine, renal pain, chronic pain, neuropathic pain and fibromyalgia. Results: The literature search identified 81 RCTs (n = 5447 patients) on Mg treatment in pain (50 RCTs in post-operative pain, 18 RCTs in migraine, 5 RCTs in renal pain, 6 RCTs in chronic/neuropathic pain, 2 RCTs in fibromyalgia). Conclusion: The level of evidence for the efficacy of Mg in reducing pain and analgesics consumption is globally modest and studies are not very numerous in chronic pain. A number of gaps have been identified in the literature that need to be addressed especially in methodology, rheumatic disease, and cancer. Additional clinical trials are needed to achieve a sufficient level of evidence and to better optimize the use of Mg for pain and pain comorbidities in order to improve the quality of life of patients who are in pain.

Reducing the dose of neuromuscular blocking agents with adjuncts: a systematic review and meta-analysis

BACKGROUND

Acute global shortages of neuromuscular blocking agents (NMBA) threaten to impact adversely on perioperative and critical care. The use of pharmacological adjuncts may reduce NMBA dose. However, the magnitude of any putative effects remains unclear.

METHODS

We conducted a systematic review and meta-analysis of RCTs. We searched Medline, Embase, Web of Science, and Cochrane Database (1970-2020) for RCTs comparing use of pharmacological adjuncts for NMBAs. We excluded RCTs not reporting perioperative NMBA dose. The primary outcome was total NMBA dose used to achieve a clinically acceptable depth of neuromuscular block. We assessed the quality of evidence using the GRADE (Grades of Recommendation, Assessment, Development, and Evaluation) criteria. Data are presented as the standardised mean difference (SMD); I² indicates percentage of variance attributable to heterogeneity.

RESULTS

From 3082 records, the full texts of 159 trials were retrieved. Thirty-one perioperative RCTs met the inclusion criteria for meta-analysis (n=1962). No studies were conducted in critically ill patients. Reduction in NMBA dose was associated with use of magnesium (SMD: -1.10 [-1.44 to -0.76], P<0.001; I²=85%; GRADE=moderate), dexmedetomidine (SMD: -0.89 [-1.55 to -0.22]; P=0.009; I²=87%; GRADE=low), and clonidine (SMD: -0.67 [-1.13 to -0.22]; P=0.004; I²=0%; GRADE=low) but not lidocaine (SMD: -0.46 [-1.01 to -0.09]; P=0.10; I²=68%; GRADE=moderate). Meta-analyses for nicardipine, diltiazem, and dexamethasone were not possible owing to the low numbers of studies. We estimated that 30-50 mg kg^-1 magnesium preoperatively (8-15 mg kg h^-1 intraoperatively) reduces rocuronium dose by 25.5% (inter-quartile range, 14.7-31).

CONCLUSIONS

Magnesium, dexmedetomidine, and clonidine may confer a clinically relevant sparing effect on the required dose of neuromuscular block ing drugs in the perioperative setting.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO: CRD42020183969.

Effect of orally administered magnesium on postoperative pain level and trismus after surgical removal of the lower third molars: a randomized, double-blind, placebo-controlled trial

OBJECTIVES

Pain and trismus are the most common postoperative complications following a surgical removal of the lower third molar. This randomized, double-blind, placebo-controlled clinical trial evaluated the effect of orally administrated magnesium on postoperative pain and trismus after surgical removal of the lower third molars.

MATERIALS AND METHODS

The study was conducted on 80 participants who were divided into two groups. Each group took different oral forms of magnesium citrate. Participants in both groups had their two lower molars surgically removed. For one randomly selected third molar, participants received either magnesium citrate tablets or lozenges. For the surgical removal of the lower third molar of the opposite side, the participants received either placebo tablets or lozenges. The data were analyzed using the Wilcoxon signed-ranked test, the Mann-Whitney U test, and the Spearman rank-order correlation with the level of significance set at p < 0.05. This manuscript was written in accordance with the Consort recommendation.

RESULTS

The results show a statistically significant lower pain level at all tested times (24 h, 48 h, and 72 h postoperatively) for participants who used magnesium preparations in lozenges (p = 0.012, p = 0.013, and p ≤ 0.001) as well as in tablet form (p ≤ 0.001) compared to placebo. The results also show a statistically significant greater mouth opening ability at all tested times (24 h, 48 h, and 72 h postoperatively) between magnesium preparations and the placebo (p ≤ 0.001).

CONCLUSION

Orally administered magnesium (either lozenges or tablets) before and after a lower third molar surgical removal significantly reduces pain intensity and the degree of trismus in the postoperative period.

CLINICAL RELEVANCE

Based on the results of the study, oral magnesium could be used in the oral and maxillofacial surgery to reduce postoperative complications after surgical removal of the lower third molars.

TRIAL REGISTRATION

This study is registered on http:clinicaltrials.gov under protocol no. NCT03398382.

WITHDRAWN: Drugs for preventing postoperative nausea and vomiting

BACKGROUND

Drugs can prevent postoperative nausea and vomiting, but their relative efficacies and side effects have not been compared within one systematic review.

OBJECTIVES

The objective of this review was to assess the prevention of postoperative nausea and vomiting by drugs and the development of any side effects.

SEARCH METHODS

We searched The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 2, 2004), MEDLINE (January 1966 to May 2004), EMBASE (January 1985 to May 2004), CINAHL (1982 to May 2004), AMED (1985 to May 2004), SIGLE (to May 2004), ISI WOS (to May 2004), LILAC (to May 2004) and INGENTA bibliographies.

SELECTION CRITERIA

We included randomized controlled trials that compared a drug with placebo or another drug, or compared doses or timing of administration, that reported postoperative nausea or vomiting as an outcome.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted outcome data.

MAIN RESULTS

We included 737 studies involving 103,237 people. Compared to placebo, eight drugs prevented postoperative nausea and vomiting: droperidol, metoclopramide, ondansetron, tropisetron, dolasetron, dexamethasone, cyclizine and granisetron. Publication bias makes evidence for differences among these drugs unreliable. The relative risks (RR) versus placebo varied between 0.60 and 0.80, depending upon the drug and outcome. Evidence for side effects was sparse: droperidol was sedative (RR 1.32) and headache was more common after ondansetron (RR 1.16).

AUTHORS' CONCLUSIONS

Either nausea or vomiting is reported to affect, at most, 80 out of 100 people after surgery. If all 100 of these people are given one of the listed drugs, about 28 would benefit and 72 would not. Nausea and vomiting are usually less common and, therefore, drugs are less useful. For 100 people, of whom 30 would vomit or feel sick after surgery if given placebo, 10 people would benefit from a drug and 90 would not. Between one to five patients out of every 100 people may experience a mild side effect, such as sedation or headache, when given an antiemetic drug. Collaborative research should focus on determining whether antiemetic drugs cause more severe, probably rare, side effects. Further comparison of the antiemetic effect of one drug versus another is not a research priority.

Effect of magnesium sulfate pretreatment on onset and recovery characteristics of cisatracurium

BACKGROUND

To determine how pretreatment with magnesium sulfate (MgSO(4)) potentiates neuromuscular blocking agents. We investigated how the onset and recovery characteristics of cisatracurium are changed by pretreatment with MgSO(4).

METHODS

After Institutional Review Board approval, a total of 48 ASA I and II patients were devided into 2 groups. Patients in each group received either the MgSO(4) 30 mg/kg (group M) in 0.9% normal saline (total volume 100 ml) or 0.9% normal saline (control group C) alone intravenously for 15 min before induction of anesthesia with propofol, remifentanil and cisatracurium 0.15 mg/kg. Anesthesia was maintained with propofol and remifentanil. Electromyographical responses were measured by train-of-four. Lag time, onset time, total recovery time, clinical duration, recovery index, and recovery time were measured. The mean arterial blood pressure, heart rate, and ionized magnesium were also measured.

RESULTS

The lag time and onset time were significantly shorter in the MgSO(4) group than the control group (P < 0.05). Recovery index, recovery time, clinical duration, and total recovery time showed no significant differences in the MgSO(4) group compared to the control group (P > 0.05). Mean arterial pressure was more significantly increased in the MgSO(4) group than in the control group at the time point immediately after the administration of MgSO(4). Heart rate showed no significant changes in both groups. The concentrations of ionized magnesium were significantly more increased at the all time point (P < 0.05).

CONCLUSIONS

MgSO(4) results in about 29% shortening of onset time of cisatracurium (0.15 mg/kg) without prolongation on the recovery of neuromuscular block.

The Effects of Postoperative Brachial Plexus Block Using MgSO(4) on the Postoperative Pain after Upper Extremity Surgery

BACKGROUND

Although a brachial plexus block can be used to provide anesthesia and analgesia for upper extremity surgery, its effects using MgSO(4) on postoperative pain management have not been reported. The aim of this study was to evaluate brachial plexus block using MgSO(4) on postoperative analgesia.

METHODS

Thirty-eight patients who were scheduled to undergo upper extremity surgery were randomly allocated into two groups: patients receiving axillary brachial plexus block with 0.2% ropivacaine 20 ml and normal saline 2 ml (group S) or 0.2% ropivacaine 20 ml and MgSO(4) 200 mg (group M). Before extubation, the blocks were done and patient controlled analgesia was started, and then, the patients were transported to a postanesthetic care unit. The postoperative visual analogue scale (VAS), opioid consumption, and side effects were recorded.

RESULTS

The two groups were similar regarding the demographic variables and the duration of the surgery. No differences in VAS scores were observed between the two groups. There was no statistically significant difference in opioid consumption between the two groups. Nausea was observed in three patients for each group.

CONCLUSIONS

Axillary brachial plexus block using MgSO(4) did not reduce the level of postoperative pain and opioid consumption.

Effect of clonidine and magnesium sulphate on anaesthetic consumption, haemodynamics and postoperative recovery: A comparative study

This randomised, placebo-controlled, double-blind study was designed to assess the effect of intravenous clonidine and magnesium sulphate on intraoperative haemodynamics, anaesthetic consumption and postoperative recovery. Seventy five patients undergoing elective upper limb orthopaedic surgery were randomised into three groups. Group C received clonidine 3 mug/kg as a bolus before induction and 1mug/kg/hour by infusion intraopertively. Group M received magnesium sulphate 30 mg/kg as a bolus before induction and 10 mg/kg/hour by infusion. Group P received same volume of isotonic saline. Anaesthesia was induced and maintained with fentanyl citrate and propofol. Muscular relaxation was achieved by vecuronium bromide. Induction time, recovery time and consumption of propofol as well as fentanyl citrate were recorded. Induction of anaesthesia was rapid with both clonidine and magnesium sulphate. Time of bispectral index (BIS) to reach 60 was significantly lower in Group C and Group M (P < 0.0001). Requirements of propofol and fentanyl were significantly less in Group C and Group M (P < 0.001). Postoperative recovery was slower in Group M compared with other two groups (P < 0.001). Perioperative use of both clonidine and magnesium sulphate significantly reduced the consumption of propofol and fentanyl citrate. Magnesium sulphate caused a delayed recovery.

Magnesium sulphate has beneficial effects as an adjuvant during general anaesthesia for Caesarean section

BACKGROUND

The use of low concentrations of volatile anaesthetics with avoidance of opioids may induce intraoperative awareness and adverse haemodynamic responses during Caesarean section. Magnesium is well known to reduce anaesthetic requirements and to block noxious stimuli. We investigated whether i.v. magnesium sulphate modulates anaesthetic depth and analgesic efficacy during Caesarean section.

METHODS

Seventy-two patients undergoing Caesarean section were randomly assigned to receive i.v. saline (control group) or magnesium sulphate 30 mg kg(-1) bolus+10 mg kg(-1) h(-1) continuous infusion (Mg 30 group) or 45 mg kg(-1) bolus+15 mg kg(-1) h(-1) continuous infusion (Mg 45 group) after induction. Bispectral index (BIS) value, mean arterial pressure (MAP), and midazolam, fentanyl, and atracurium consumptions were recorded.

RESULTS

BIS values [mean (sd)] at 7.5 and 10 min after surgery and before delivery in the control [64 (9), 66 (8), 67 (8), P<0.001] and the Mg 30 groups [62 (8), P<0.01; 64 (7), 63 (9), P<0.001] were higher than in the Mg 45 group [56 (8), 55 (8), 55 (7)]. MAP was greater in the control group (P<0.05) than in the Mg 30 and Mg 45 groups during the pre-delivery period. The magnesium groups required less midazolam (P<0.05), fentanyl (Mg 30, P<0.05; Mg 45, P<0.01), and atracurium (P<0.001) vs the control group.

CONCLUSIONS

Preoperative i.v. magnesium sulphate attenuated BIS and arterial pressure increases during the pre-delivery period. Magnesium sulphate can be recommended as an adjuvant during general anaesthesia for Caesarean section to avoid perioperative awareness and pressor response resulting from inadequate anaesthesia, analgesia, or both.

Effects of magnesium sulphate on intraoperative anaesthetic requirements and postoperative analgesia in gynaecology patients receiving total intravenous anaesthesia

BACKGROUND

This randomized, double-blind, prospective study was undertaken to evaluate the effects of magnesium sulphate on anaesthetic requirements and postoperative analgesia in patients undergoing total i.v. anaesthesia (TIVA).

METHODS

Fifty patients who underwent gynaecological surgery were randomly divided into two groups. Before induction of anaesthesia, the magnesium group (Group M) received magnesium sulphate 50 mg kg(-1) i.v. as a bolus and then 15 mg kg(-1) h(-1) i.v. by continuous infusion. The control group (Group S) received the same amount of isotonic saline. TIVA (propofol+remifentanil) was administered under bispectral index monitoring during anaesthesia induction and maintenance. Rocuronium was administered before orotracheal intubation and during surgery when the train-of-four count was 2 or more. After operation, patient-controlled analgesia with a solution of ketorolac and morphine was used and the consumption of this solution was recorded. Pain scores at rest and upon movement were evaluated 30 min, 4, 24, and 48 h after surgery.

RESULTS

Patients in Group M required less rocuronium than those in Group S [mean (SD) 0.44 (0.09) vs 0.35 (0.07) microg kg(-1) min(-1), P<0.05]. The total amounts of propofol and remifentanil administered were similar in the two groups. Postoperative pain scores, cumulative analgesic consumption, and shivering incidents were significantly lower in Group M (P<0.05). Mean arterial pressure just after intubation and during the immediate postoperative period was also significantly lower in Group M (P<0.05).

CONCLUSIONS

I.v. magnesium sulphate during TIVA reduced rocuronium requirement and improved the quality of postoperative analgesia.

Magnesium sulphate as an adjuvant to total intravenous anesthesia in septorhinoplasty: a randomized controlled study

BACKGROUND

The current study was designed to assess the effect of magnesium sulphate infusion on hemodynamic parameters, neuromuscular blocking, propofol consumption, serum concentration of magnesium ions, and recovery from anesthesia during total intravenous anesthesia.

METHODS

For this study, 60 patients undergoing septorhinoplasty operations were randomly allocated to receive magnesium sulphate (group M) or saline (group C) intravenously. The patients in group M received 15% magnesium sulphate 50 mg/kg in 100 ml of saline, and those in group C received an equal volume of saline before induction of anesthesia followed by 8 mg/kg/h infusion of either magnesium sulphate (group M) or an equal volume of saline (group C) until the end of surgery. Anesthesia was induced and maintained with propofol, remifentanil infusions, and vecuronium in both groups.

RESULTS

Propofol requirements were significantly lower in group M than in group C (p < 0.05). The hemodynamic variables were similar in the two groups. The neuromuscular potency of vecuronium was greater in group M than in group C (p < 0.05). The verbal numeric scale values for pain were found to be significantly lower in group M than in group C (p < 0.05). Whereas the serum magnesium was in the normal range at the induction of anesthesia in the both groups, it was significantly lower in group C than in group M postoperatively (p < 0.05).

CONCLUSION

Magnesium sulphate can be used safely as an adjuvant to total intravenous anesthesia for day case surgeries, with the effect from potentialization of neuromuscular blockade taken into consideration.

The role of magnesium as an adjuvant during general anaesthesia

Magnesium sulphate is used extensively in the treatment of eclampsia, and is also used to treat refractory arrhythmias, asthma, myocardial ischaemia and acute respiratory failure. We studied the interaction between magnesium sulphate and the anaesthetic agents propofol, rocuronium bromide and fentanyl citrate. This randomised, double blind study was conducted in 50 patients. The magnesium group A (n = 25) received 30 mg x kg(-1) magnesium sulphate before induction of anaesthesia and 10 mg x kg(-1) continuously intra-operatively until the end of surgery. Group B (n = 25) received the same volume of isotonic saline. Propofol, rocuronium and fentanyl infusions were started and the patients lungs' were ventilated with 33% oxygen in nitrous oxide. Anaesthetic depth was maintained at a bispectral index value of between 40 and 60. Muscle relaxation was maintained at a train-of-four count of 1 throughout surgery using neuromuscular monitoring. The fentanyl infusion was titrated to haemodynamic variables: heart rate and blood pressure. We concluded that magnesium sulphate has anaesthetic, analgesic and muscle relaxation effects and significantly reduces the drug requirements of propofol, rocuronium and fentanyl during anaesthesia.

Drugs for preventing postoperative nausea and vomiting

BACKGROUND

Drugs can prevent postoperative nausea and vomiting, but their relative efficacies and side effects have not been compared within one systematic review.

OBJECTIVES

The objective of this review was to assess the prevention of postoperative nausea and vomiting by drugs and the development of any side effects.

SEARCH STRATEGY

We searched The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 2, 2004), MEDLINE (January 1966 to May 2004), EMBASE (January 1985 to May 2004), CINAHL (1982 to May 2004), AMED (1985 to May 2004), SIGLE (to May 2004), ISI WOS (to May 2004), LILAC (to May 2004) and INGENTA bibliographies.

SELECTION CRITERIA

We included randomized controlled trials that compared a drug with placebo or another drug, or compared doses or timing of administration, that reported postoperative nausea or vomiting as an outcome.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted outcome data.

MAIN RESULTS

We included 737 studies involving 103,237 people. Compared to placebo, eight drugs prevented postoperative nausea and vomiting: droperidol, metoclopramide, ondansetron, tropisetron, dolasetron, dexamethasone, cyclizine and granisetron. Publication bias makes evidence for differences among these drugs unreliable. The relative risks (RR) versus placebo varied between 0.60 and 0.80, depending upon the drug and outcome. Evidence for side effects was sparse: droperidol was sedative (RR 1.32) and headache was more common after ondansetron (RR 1.16).

AUTHORS' CONCLUSIONS

Either nausea or vomiting is reported to affect, at most, 80 out of 100 people after surgery. If all 100 of these people are given one of the listed drugs, about 28 would benefit and 72 would not. Nausea and vomiting are usually less common and, therefore, drugs are less useful. For 100 people, of whom 30 would vomit or feel sick after surgery if given placebo, 10 people would benefit from a drug and 90 would not. Between one to five patients out of every 100 people may experience a mild side effect, such as sedation or headache, when given an antiemetic drug. Collaborative research should focus on determining whether antiemetic drugs cause more severe, probably rare, side effects. Further comparison of the antiemetic effect of one drug versus another is not a research priority.

Effects of three different dose regimens of magnesium on propofol requirements, haemodynamic variables and postoperative pain relief in gynaecological surgery

BACKGROUND

In this double-blind, randomized, placebo-controlled study we compared the effects of three different dose regimens of magnesium on intraoperative propofol and atracurium requirements, and postoperative morphine consumption in patients undergoing gynaecological surgery.

METHODS

Eighty women were allocated to four equal groups. The control group received normal saline; magnesium groups received 40 mg kg(-1) of magnesium before induction of anaesthesia, followed by i.v. infusion of normal saline, magnesium 10 mg kg(-1) h(-1) or magnesium 20 mg kg(-1) h(-1) for the next 4 h. Propofol infusion was targeted to keep bispectral index values between 45 and 55. Postoperative analgesia was achieved using PCA with morphine.

RESULTS

Magnesium groups required significantly less propofol [mean (sd) 121.5 (13.3), 102.2 (8.0) and 101.3 (9.7) microg kg(-1) min(-1) respectively] than the control group (140.7 (16.5) microg kg(-1) min(-1)). Atracurium use was significantly higher in the control group than magnesium groups [0.4 (0.06) vs 0.34 (0.06), 0.35 (0.04), 0.34 (0.06) mg kg(-1) h(-1) respectively]. Morphine consumption was significantly higher in control group than magnesium groups on the first postoperative day [0.88 (0.14) vs 0.73 (0.17), 0.59 (0.23), 0.53 (0.21) mg kg(-1) respectively]. The heart rate was lower in magnesium groups and 20 mg kg(-1) h(-1) infusion group demonstrated the lowest values.

CONCLUSION

Magnesium 40 mg kg(-1) bolus followed by 10 mg kg(-1) h(-1) infusion leads to significant reductions in intraoperative propofol, atracurium and postoperative morphine consumption. Increasing magnesium dosage did not offer any advantages, but induced haemodynamic consequences.

A Qualitative Systematic Review of the Role of N-Methyl-d-Aspartate Receptor Antagonists in Preventive Analgesia

We evaluated in a qualitative systematic review the effect of N-methyl-D-aspartate (NMDA) receptor antagonists on reducing postoperative pain and analgesic consumption beyond the clinical duration of action of the target drug (preventive analgesia). Randomized trials examining the use of an NMDA antagonist in the perioperative period were sought by using a MEDLINE (1966-2003) and EMBASE (1985-2003) search. Reference sections of relevant articles were reviewed, and additional articles were obtained if they evaluated postoperative analgesia after the administration of NMDA antagonists. The primary outcome was a reduction in pain, analgesic consumption, or both in a time period beyond five half-lives of the drug under examination. Secondary outcomes included time to first analgesic request and adverse effects. Forty articles met the inclusion criteria (24 ketamine, 12 dextromethorphan, and 4 magnesium). The evidence in favor of preventive analgesia was strongest in the case of dextromethorphan and ketamine, with 67% and 58%, respectively, of studies demonstrating a reduction in pain, analgesic consumption, or both beyond the clinical duration of action of the drug concerned. None of the four studies examining magnesium demonstrated preventive analgesia.

IMPLICATIONS

We evaluated, in a qualitative systematic review, the effect of N-methyl D-aspartate antagonists on reducing postoperative pain and analgesic consumption beyond the clinical duration of action of the target drug (preventive analgesia). Dextromethorphan and ketamine were found to have significant immediate and preventive analgesic benefit in 67% and 58% of studies, respectively.

The use of magnesium to prevent laryngospasm after tonsillectomy and adenoidectomy: a preliminary study

BACKGROUND

Laryngospasm is the most common cause of upper airway obstruction after tracheal extubation. Magnesium has a central nervous system depressant property, which contributes to the depth of anaesthesia. It also has calcium antagonist properties, which provide muscle relaxation. In this study, we aimed to determine the effect of magnesium on preventing laryngospasm.

METHODS

After approval of the Ethics Committee and informed parental consent, 40 patients, ASA I-II, aged 3-12 years, who were scheduled for tonsillectomy or/and adenoidectomy, were randomly divided into two groups. Anaesthesia was induced with sevoflurane, lidocaine 1 mg x kg-1, alfentanil 10 micro g x kg-1, vecuronium 0.1 mg x kg-1 and maintained with sevoflurane 2% and 60% nitrous oxide in oxygen. After intubation, patients in group I received 15 mg.kg-1 magnesium in 30 ml 0.9% NaCl over 20 min. Patients in group II received 0.9% NaCl alone in the same volume. After reversal of neuromuscular blockade, all patients were extubated at a very deep plane of anaesthesia. The incidence of laryngospasm was determined until the time of discharge from the postanaesthesia care unit.

RESULTS

Although laryngospasm was not observed in group I, it was observed in five patients in group II (25%). The incidence of laryngospasm in group II was significantly higher than group I. The plasma magnesium concentrations were significantly higher in group I than group II.

CONCLUSIONS

We found a significant decrease in the incidence of laryngospasm in paediatric patients receiving magnesium. It is suggested that the use of intravenous magnesium intraoperatively may prevent laryngospasm.

Evaluation of effects of magnesium sulphate in reducing intraoperative anaesthetic requirements

BACKGROUND

The present randomized, placebo-controlled, double-blind study was designed to assess the effect of peroperatively administered i.v. magnesium sulphate on anaesthetic and analgesic requirements during total i.v. anaesthesia.

METHODS

Eighty-one patients (36 women, 45 men) undergoing elective spinal surgery were included in one of two parallel groups. The magnesium group received magnesium sulphate 30 mg kg(-1) as a bolus before induction of anaesthesia and 10 mg kg(-1) h(-1) by continuous i.v. infusion during the operation period. The same volume of isotonic solution was administered to the control group. Anaesthesia was maintained with propofol (administered according to the bispectral index) and remifentanil (adjusted according to heart rate and arterial blood pressure) infusions.

RESULTS

A significant reduction in hourly propofol consumption was observed with magnesium administration. For example, the mean infusion rate of propofol in the second hour of the operation was 7.09 mg kg(-1) h(-1) in the control group vs 4.35 mg kg(-1) h(-1) in the magnesium group (P<0.001). The magnesium group required significantly less remifentanil (P<0.001) and vecuronium (P<0.001). No side-effects were observed with magnesium administration.

CONCLUSION

The administration of magnesium led to a significant reduction in the requirements for anaesthetic drugs during total i.v. anaesthesia with propofol, remifentanil and vecuronium.