Kurz et al. compared the antishivering characteristic of
Meperidine with low dose naloxone blocking l receptor and
high dose naloxone blocking both l and j receptor; they found
that the Meperidine with low dose naloxone was not affected,
but the antishivering activity was decreased when high dose
was used which indicates that the antishivering effect of
Meperidine is partially mediated through j-opioid receptors
[18] and not through the l-receptor that why it is more effective
than other opioid agents as alfentanil as antishivering
agent [19]. However, Sajedi and Nazemroaya [20] found that
there were no differences in efficacy to control post-operative
shivering among Meperidine, alfentanil, sufentanil, fentanyl,
and tramadol in management of shivering grade and V, and
they concluded that this group of drugs may have other antishivering
mechanism rather than their opioid receptors action.
In the present study, it was observed that five patients in the
Meperidine group suffered from local redness. This was consistent
with the study done by Blunk et al. [21]. They observe that
in the spite of using small dose of Meperidine, local itching and
redness around the site of injection and rarely flushing, severe
hypotension, and tachycardia as a result of mast cell activation
and histamine release may attenuate its use as an antishivering
agent. They requested the need to find another agent with less
side effects especially during regional anesthesia [21].
Concerning the antishivering effect, we observe that although
Meperidine is effective in management of perioperative shivering,
Magnesium sulfate was founded to be significantly more
effective.
Magnesium sulfate is a noncompetitive antagonist of
N-methyl-D-aspartate (NMDA) receptors, and also, it is naturally
occurring calcium antagonist [22]. It was found to be
effective in prevention of shivering [11]. The exact mechanism
by which it prevents shivering is not clear. It may be due to
blocking of NMDA receptors leading to a decrease in norepinephrine,
and 5-HT and both have role in thermoregulatory
control. Magnesium sulfate is an attractive choice for shivering
control because hypomagnesemia commonly is observed during
induced hypothermia [23].
Another action of MgSO4 is modulation of NMDA receptors
at the level of dorsal horn of the spinal cord which affects
the ascending nociceptive transmission [24].
Although Kizilirmak et al. used 30 mg/kg IV bolus of
Magnesium sulfate which is considered smaller than that
we used, they found it enough to stop post-operative shivering
after general anesthesia. This may be due to its use in
the post-operative period when there is no more hypothermia
[11]. Gozdemir et al. [25] studied the effect of
Magnesium sulfate on Perioperative shivering during spinal
anesthesia, and they found that Magnesium sulfate is considered
an excellent agent with less side effect than Meperidine.
In our study, we used smaller dose of Magnesium
sulfate than that used in Gozdemir et al. study and it was
found to be effective.
Using of this, dose of Magnesium sulfate was not associated
with any hemodynamic unstability as higher dose would
cause vasodilatation and subsequent hypotension.
5. Conclusion
It was found that Magnesium sulfate is significantly effective
than Meperidine in management of shivering during spinal
anesthesia with lower incidence of side effect.