The effect of intravenous morphine on the level of spinal anesthesia with
lidocaine.
Author(s): Masoudifar M, Aghadavoudi O, Rezvani M, Mashayekhi N.
Affiliation(s): Department of Anesthesiology and Critical Care, Isfahan University of Medical
Sciences, Isfahan, Iran.
Publication date & source: 2012, Med Arh. , 66(2):80-3
One of the major concerns in spinal anesthesia with lidocaine is its short
duration of action. Enhancement is necessary in some situations during surgery,
because surgeons encounter with unexpected events and need more time. Therefore
there is a need to increase anesthesia duration in these situations. Many studies
investigated various additives with different administration routes to enhance
spread and duration of spinal block with lidocaine. Because we only have morphine
sulfate in our clinics and the sulfate compounds are neurotoxic, we cannot
prescribe it by intrathecal route; for this reason we investigated effects of
intravenous morphine on the spinal anesthesia with lidocaine.METHODS: This double
blinded randomized clinical trial study was performed on 36 patients who were
allocated to two groups. All patients underwent spinal anesthesia with lidocaine
by the same method. Patients in the case group received morphine plus midazolam
intravenously as the additive medication and in the control group received normal
saline plus midazolam. Duration, spinal block level, recovery time, sedation
score and adverse effects were compared between the two groups.
RESULTS: This study showed that although intravenous morphine can provide better
safe sedation (p-value < 0.01), it has no effect on the level (p-value: 0.42) and
duration of spinal block (p-value: 0.26). Although heart rate and blood pressure
had significant decrease in the case group (p-value < 0.01 and < 0.05
respectively) but the need for administration of ephedrine was completely similar
in both groups.
CONCLUSION: Although some studies had proved the efficacy of systemic use of
other opioids including fentanyl and sufentanil, morphine had no effect on the
level and duration of spinal block. It can be due to differences in the chemical
structures of these substances. However, intravenous morphine as an additive to
spinal anesthesia with lidocaine can provide acceptable sedation with no major
side effects.
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