***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: BACKGROUND Hypothermia may be an effective treatment for stroke or acute myocardial infa rct ion ; however , it provokes vigorous shivering , which causes potentially dangerous haemodynamic responses and prevents further hypothermia . Magnesium is an attractive anti-shivering agent because it is used for treatment of postoperative shivering and provides protection against ischaemic injury in animal models . We tested the hypothesis that magnesium reduces the threshold ( triggering core temperature ) and gain of shivering without substantial sedation or muscle weakness . METHODS We studied nine healthy male volunteers ( 18 - 40 yr ) on two r and omly assigned treatment days : ( 1 ) control and ( 2 ) magnesium ( 80 mg kg(-1 ) followed by infusion at 2 g h(-1 ) ) . Lactated Ringer 's solution ( 4 degrees C ) was infused via a central venous catheter over a period of approximately 2 h to decrease tympanic membrane temperature by approximately 1.5 degrees C h(-1 ) . A significant and persistent increase in oxygen consumption identified the threshold . The gain of shivering was determined by the slope of oxygen consumption vs core temperature regression . Sedation was evaluated using a verbal rating score ( VRS ) from 0 to 10 and bispectral index ( BIS ) of the EEG . Peripheral muscle strength was evaluated using dynamometry and spirometry . Data were analysed using repeated measures anova ; P<0.05 was statistically significant . RESULTS Magnesium reduced the shivering threshold ( 36.3 [ SD 0.4 ] degrees C vs 36.6 [ 0.3 ] degrees C , P = 0.040 ) . It did not affect the gain of shivering ( control , 437 [ 289 ] ml min(-1 ) degrees C(-1 ) ; magnesium , 573 [ 370 ] ml min(-1 ) degrees C(-1 ) ; P=0.344 ) . The magnesium bolus did not produce significant sedation or appreciably reduce muscle strength . CONCLUSIONS Magnesium significantly reduced the shivering threshold . However , in view of the modest absolute reduction , this finding is considered to be clinical ly unimportant for induction of therapeutic hypothermia Summary The effects of intra‐operative magnesium sulphate on  pain relief  after major lumbar surgery were investigated in 24 patients . Patients were r and omly allocated to receive either an infusion of 50 mg.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 st and ard 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 Background : The addition of intrathecal ( IT ) magnesium to spinal fentanyl prolongs the duration of spinal analgesia for vaginal delivery . In this prospect i ve , r and omized , double‐blind , controlled study , we investigated the effect of adding IT magnesium sulphate to bupivacaine – fentanyl spinal anaesthesia In a r and omized , double-blind study with two parallel groups , we assessed the analgesic effect of perioperative magnesium sulfate administration in 46 ASA physical status I or II patients undergoing arthroscopic knee surgery with total IV anesthesia . The patients received either magnesium sulfate 50 mg/kg preoperatively and 8 mg [ center dot ] kg-1 [ center dot ] h-1 intraoperatively or the same volume of isotonic sodium chloride solution IV . Anesthesia was performed with propofol ( 2 mg/kg for induction , 6 - 8 mg [ center dot ] kg- 1 [ center dot ] h- 1 for maintenance ) , fentanyl ( 3 [ micro sign]g/kg for induction ) , and vecuronium ( 0.1 mg/kg for intubation ) . Intraoperative pain was defined as an increase of mean arterial blood pressure and heart rate of more than 20 % from baseline values after the induction of anesthesia and was treated with bolus fentanyl ( 1 - 2 [ micro sign]g/kg ) . Postoperative analgesia was achieved with fentanyl ( 0.5 [ micro sign]g/kg ) and evaluated using the pain visual analog scale for 4 h. During the intraoperative and postoperative periods , patients in the magnesium group required significantly less fentanyl than those in the control group ( control group 0.089 + /- 0.02 [ micro sign]g [ center dot ] kg-1 [ center dot ] min-1 versus magnesium group 0.058 + /- 0.01 [ micro sign]g [ center dot ] kg-1 [ center dot ] min- 1 ; P < 0.05 and control group 0.021 + /- 0.013 [ micro sign]g [ center dot ] kg-1 [ center dot ] min-1 and magnesium group 0.0031 + /- 0.0018 [ micro sign]g [ center dot ] kg-1 [ center dot ] min-1 ; P < 0.01 for intraoperative and postoperative periods , respectively ) . We conclude that , in a clinical setting with almost identical levels of surgical stimulation , IV magnesium sulfate administration reduces intraoperative and postoperative analgesic requirements compared with isotonic sodium chloride solution administration . Implication s : The perioperative administration of IV magnesium sulfate reduces intra- and postoperative analgesic requirements in patients with almost identical levels of surgical stimulus . Our results demonstrate that magnesium can be an adjuvant to perioperative analgesic management . ( Anesth Analg 1998;87:206 - 10 Background and objective : This double‐blind r and omized study tested whether the addition of magnesium or ketamine to morphine for intravenous patient‐controlled analgesia result ed in improved analgesic efficacy and lower pain scores compared with morphine patient‐controlled analgesia alone after major abdominal surgery . Methods : Ninety patients ( 3 × 30 ) were r and omly allocated to receive either morphine 0.4 mg mL−1 ( Group M ) by patient‐controlled analgesia , morphine 0.4 mg mL−1 + MgSO4 30 mg mL−1 ( Group MM ) or morphine 0.4 mg mL−1 + ketamine 1 mg mL−1 ( Group MK ) . Postoperative analgesia was started when the verbal rating scale was ≥2 . Patients were first given a st and ardized loading dose ( 0.05 mg kg−1 ) of the study solution . They were then allowed to use bolus doses of this solution ( 0.0125 mg kg−1 every 20 min without time limit ) . Discomfort , sedation , pain scores , cumulative morphine consumption and adverse effects were recorded up to 24 h after the start of the patient‐controlled analgesia . Results : The level of discomfort , level of sedation and verbal rating scores decreased significantly with time in all groups ( P < 0.05 ) . Both verbal rating and discomfort scores were significantly lower in Groups MM and MK at 15 , 30 and 60 min compared with Group M ( P < 0.001 ) . Cumulative morphine consumption after 12 and 24 h was significantly higher in Group M alone ( median 26 and 49 mg , respectively ) compared with Group MM ( 24.2 and 45.7 mg ) and Group MK ( 24.4 and 46.5 mg ) . Conclusions : In the immediate postoperative period , the addition of magnesium or ketamine to morphine for intravenous patient‐controlled analgesia led to a significantly lower consumption of morphine . However , these differences are unlikely to be of any clinical relevance Background : NMDA receptor activation is considered one of the mechanisms involved in postoperative pain and hypersensitivity . Magnesium is the physiological blocker of the NMDA‐receptor‐complex‐associated calcium ionophore . The aim of this study was to determine if a pre‐ , intra‐ and postoperative infusion of magnesium would reduce postoperative pain Background Because magnesium blocks the N-methyl-d-aspartate receptor and its associated ion channels , it can prevent central sensitization caused by peripheral nociceptive stimulation . However , transport of magnesium from blood to cerebrospinal fluid ( CSF ) across the blood – brain barrier is limited in normal humans . The current study was design ed to evaluate whether perioperative intravenous magnesium sulfate infusion affects postoperative pain . Methods Sixty patients undergoing abdominal hysterectomy received 50 mg/kg intravenous magnesium sulfate as a bolus dose followed by a continuous infusion of 15 mg · kg−1 · h−1 for 6 h ( magnesium group ) or the same volume of isotonic saline ( control group ) . At the end of surgery , serum and CSF magnesium concentration were measured in both groups . The cumulative postoperative analgesic consumption was measured to assess the analgesic effect using a patient-controlled epidural analgesia device . Pain intensities at rest and during forced expiration were evaluated at 6 , 24 , 48 , and 72 h postoperatively . Results At the end of surgery , patients in the magnesium group had significantly greater postoperative serum magnesium concentrations compared with both preoperative and control group values ( P < 0.001 ) . Despite significantly higher serum magnesium concentrations in the magnesium group , there was no significant difference in magnesium concentration measured in postoperative CSF . Cumulative postoperative analgesic doses were similar in both groups . However , there was observed an inverse relation between cumulative postoperative analgesic consumption and the CSF magnesium concentration in both groups . Visual analog pain scores at rest and during forced expiration were similar and less than 4 in both groups . Conclusions Perioperative intravenous administration of magnesium sulfate did not increase CSF magnesium concentration and had no effects on postoperative pain . However , an inverse relation between cumulative postoperative analgesic consumption and the CSF magnesium concentration was observed . These results suggest that perioperative intravenous magnesium infusion may not be useful for preventing postoperative pain STUDY OBJECTIVE We test the hypothesis that intravenous magnesium sulfate is an effective adjunctive medication for treatment of acute migraine .  METHODS In this r and omized , double-blind , placebo-controlled trial , adults presenting to 2 urban emergency departments with headache meeting International Headache Society criteria for acute migraine received either 20 mg of intravenous metoclopramide plus 2 g of intravenous magnesium sulfate or 20 mg of intravenous metoclopramide plus a placebo of intravenous saline solution at 15-minute intervals for a maximum of 3 doses or until pain relief occurred . At 0 , 15 , 30 , and 45 minutes , patients recorded pain intensity using a st and ard visual analog scale ( VAS ) . The primary study end point was the between-group difference in pain improvement when initial and final VAS scores were compared . RESULTS Of 44 patients enrolled ( 21 r and omized to metoclopramide plus magnesium and 23 to metoclopramide plus placebo ) , 42 ( 95 % ) were women . Baseline features were comparable in both groups . Each group experienced a more than 50-mm improvement in VAS score during the study . However , this improvement was smaller in the magnesium group for the primary end point ( 16-mm difference favoring placebo [ 95 % confidence interval ( CI ) -2 to 34 mm ] ) , as was the proportion with normal functional status at their final rating ( 36 % absolute difference also favoring placebo [ 95 % CI 7 % to 65 % ] ) . Using a 50 % reduction in pain to dichotomize VAS scores , the number needed to harm with magnesium plus metoclopramide versus metoclopramide alone is 4 patients ( 95 % CI 2 to 36 ) . CONCLUSION Although this result was unexpected , our data suggest that the addition of magnesium to metoclopramide may attenuate the effectiveness of metoclopramide in relieving migraine . Countertherapeutic cerebral vasodilatation caused by magnesium is a plausible , although unproven , explanation for this finding . Because of the preponderance of women in our trial , these data may not be generalizable to men BACKGROUND Magnesium is a calcium and an NMDA-receptor antagonist and can modify important mechanisms of nociception . We evaluated the co-analgesic effect of magnesium in the postoperative setting after on-pump cardiac surgery . METHODS Forty patients r and omly received either magnesium gluconate as an i.v . bolus of 0.21 mmol kg(-1 ) ( 86.5 mg kg(-1 ) ) followed by a continuous infusion of 0.03 mmol(-1 ) kg(-1 ) h(-1 ) ( 13.8 mg kg(-1 ) h(-1 ) ) or placebo for 12 h after tracheal extubation . After surgery , remifentanil was decreased to 0.05 microg kg(-1 ) min(-1 ) and titrated according to a pain intensity score ( PIS , range 1 - 6 ) in 
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CONCLUSIONS : These trials do not provide convincing evidence that perioperative magnesium may have favorable effects on postoperative pain intensity and analgesic requirements .
Perioperative magnesium supplementation prevents postoperative hypomagnesemia and decreases the incidence of postoperative shivering .