Effect of adding dexmedetomidine or magnesium sulfate on the characteristics of bupivacaine spinal block in lower abdominal operations

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Abstract

Aim

The aim of this study was to compare intrathecal dexmedetomidine (DXM) and intrathecal magnesium sulfate (MgSO4) as adjuvants to bupivacaine in lower abdominal operations.

Patients and methods

This study was carried out at Al-Zahraa University Hospital and included 60 (ASA I or II) patients of both sexes. The patients were divided into three equal groups: group C (control group) received 15 mg of hyperbaric bupivacaine and 0.1 ml of normal saline; group D (DXM group) received 15 mg of hyperbaric bupivacaine and 0.1 ml (10 μg) of DXM; and group M (MgSO4 group) received 15 mg of bupivacaine and 0.1 ml (50 mg) of MgSO4. The following parameters were recorded: hemodynamic changes (heart rate and blood pressure), onset of sensory block and motor block, and regression time. The sedation level of the patients was assessed using the inverted observer assessment of alertness/sedation scale, in which 1=awake and 5=asleep/unarousable. Postoperative pain was assessed using the visual analogue score (VAS), and adverse effects, if any, were also recorded.

Results

As regards hemodynamic stability, no significant difference was seen among the three groups. The onset of sensory block up to the T10 dermatome was rapid in the DXM group in comparison with the MgSO4 group and the control group (2.19±1.02 vs. 6.35±1.2 and 4.13±1.01, respectively; P<0.001). Moreover, the onset of motor block, according to a Bromage scale score of 3, was rapid in the DXM group in comparison with the MgSO4 group and the control group (3.85±0.81 vs. 7.05±1.28 and 4.51±0.04, respectively; P<0.001).

Results

The regression time of the sensory, up to the T10 dermatome, and motor, according to a Bromage score of 0, block was prolonged in the DXM group (328±51 and 306±32) and in the MgSO4 group (240±56 and 223±48) in comparison with the control group (182±52 and 150±37); the difference between the three groups was statistically highly significant (P<0.001).

Results

The VAS score was low in both groups D and M when compared with the group C. The difference in the intensity of postoperative pain among the three groups was statistically highly significant (P<0.001). The postoperative sedation (observer assessment of alertness/sedation) scale was higher in the groups D and M than in the group C.

Results

Nausea and vomiting recordings showed no significant differences among the three groups. Shivering was recorded in eight patients of group C, in three patients of group M, and in two patients of group D.

Conclusion

DXM is safe as an adjuvant to spinal block with a rapid onset of sensory and motor blockade and prolongation of the duration of action. It also has a sedative effect and yields lower VAS scores. In group M, intrathecal magnesium delayed the onset of action when compared with the groups D and C. The prolongation of the duration of action was higher in the group M when compared with the group C but was lower when compared with the group D. Further, the group M had a lower VAS score than the group C.

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