20855
document
Magnesium sulphate only slightly reduces the shivering threshold in humans . BACKGROUND Hypothermia may be an effective treatment for stroke or acute myocardial infarction ; 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 randomly 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 clinically unimportant for induction of therapeutic hypothermia .
20856
Intervention_Pharmacological
Magnesium sulphate
20857
Intervention_Physical
Hypothermia
20858
Intervention_Pharmacological
Magnesium
20859
Intervention_Pharmacological
magnesium
20860
Intervention_Control
control
20861
Intervention_Pharmacological
magnesium
20862
Intervention_Pharmacological
Lactated Ringer 's solution
20863
Intervention_Pharmacological
Magnesium
20864
Intervention_Pharmacological
magnesium
20865
Intervention_Pharmacological
Magnesium
20866
Outcome_Physical
shivering threshold
20867
Outcome_Physical
shivering
20868
Outcome_Physical
sedation
20869
Outcome_Physical
tympanic membrane temperature
20870
Outcome_Other
oxygen
20871
Outcome_Physical
gain of shivering
20872
Outcome_Other
verbal rating score ( VRS )
20873
Outcome_Physical
bispectral index ( BIS ) of the EEG
20874
Outcome_Physical
Peripheral muscle strength
20875
Outcome_Physical
shivering threshold
20876
Outcome_Physical
gain of shivering
20877
Outcome_Physical
muscle strength
20878
Outcome_Physical
shivering threshold
20879
Participant_Condition
shivering threshold in humans .