Magnesium infusion lowers shivering risk in patients undergoing surgery

JAPAN: Shivering is an unpleasant experience for surgical patients and may place strain on the cardiovascular system, as it increases oxygen use. This is common among the patients undergoing surgery, especially among younger patients having a lower core temperature and where surgery is performed for a longer duration. This occurs despite the efforts to keep patients warm and reduce hypothermia. Now, a recent study has found a solution to prevent shivering among such patients.

The review, published in the journal Anesthesia & Analgesia, has found that intravenous administration of magnesium during or immediately after surgery seems to lower the risk of shivering. According to the study, magnesium infusion reduced the proportion of patients who experience shivering in the operating theatre or in recovery from 23% to 9.9%.

Clinical trials regarding the anti-shivering effect of perioperative magnesium have produced inconsistent results. Hiromasa Kawakami, Department of Anesthesiology, Yokohama City University Medical Center, Yokohama, Japan, and colleagues conducted this review and meta-analysis of 64 trials with Trial Sequential Analysis to evaluate the effect of perioperative magnesium on prevention of shivering.

For the purpose, the researchers searched for randomized clinical trials that compared the administration of magnesium to placebo or no treatment in patients undergoing surgeries. The primary outcome of this meta-analysis was the incidence of shivering.

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It involved 64 trials consisting of 4303 patients (2300 and 2003 patients in magnesium and control groups, respectively). They found that:

• The overall incidence of shivering was 9.9% in the magnesium group and 23.0% in the control group.


• In sub-group analysis by route of administration, shivering was reduced when magnesium was administered by intravenous infusion (RR 0.39, 95% CI 0.29 to 0.54; 2,124 participants, 35 trials); by epidural (RR 0.24, 95% CI 0.13 to 0.43; 880 participants, 12 trials) and intrathecally – injected directly into the cerebrospinal fluid (RR 0.64, 95% CI 0.43 to 0.96; 1,120 participants, 16 trials).


• The Z-cumulative curve for IV magnesium crossed the Trial Sequential Analysis monitoring boundary for the benefit even though only 34.9% of the target sample size had been reached.


• The Z-cumulative curve for epidural or intrathecal administration did not cross the Trial Sequential Analysis monitoring boundary for benefit.


• There was no increase in adverse events including the time to extubation, length of stay in a post-anaesthesia care unit, sedation, nausea, itching, low heart rate or low blood pressure. No serious adverse events were noted in any of the studies.

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The NICE 2008 guideline (updated in 2016) makes extensive recommendations about the monitoring of temperature for patients undergoing surgery, use of active warming, and other measures to reduce hypothermia. These include maintaining the ambient temperature of the operating theatre above 21 degrees when the patient is exposed, and ensuring the patient is covered as much as possible. The guideline, however, does not address shivering specifically, nor the use of magnesium to prevent or treat it.

In addition to the two most important interventions to reduce the risk of hypothermia -- temperature measurement and warming -- magnesium also seems to lower the risk of shivering. The study, unfortunately, was not able to look at the impact of magnesium alongside good temperature management. But it gave an additional was not able to look at the impact of magnesium alongside good temperature management.