Our results showed that compared with 9 mg of bupivacaine alone, the combination of 9 mg of intrathecal bupivacaine with 5 µg of DEX for the cesarean section significantly prolonged the duration of sensory block and the time to first analgesic request, shortened the onset time of sensory and motor block, reduced the incidence of maternal shivering, improved recovery quality of paturients, and caused no adverse effects on newborns or no neurological impairment on parturients in the short term.
Spinal anesthesia, which is block-well, easy to operate, not as complicated as epidural anesthesia [16], and avoiding the risk of general anesthesia, has become the preferred anesthesia type for cesarean section. However, in clinical practice, single spinal anesthesia is often not sufficient to inhibit visceral pain and causes maternal discomfort during the surgery and insufficient postoperative analgesia, which affect parturients’ postoperative recovery quality [5]. Increasing the doses of local anesthetics to prolong the analgesic time can cause adverse effects such as central nervous system problems and cardiotoxicity. In our study, compared with intrathecal 9 mg of bupivacaine alone, the onset time of sensory and motor block of parturients in combination of 9 mg of intrathecal bupivacaine with 5 µg of DEX was significantly shortened, and the duration of sensory block was significantly prolonged by 40 minutes, which is consistent with the research results of Suthar’s [17] and Sushruta’s [18]. The mechanism may be as follows: in the spinal cord, DEX can activate α-2 adrenergic receptor in the dorsal horn neurons, activate the spinal cord intermediate neurons by reducing the neurotransmitter released by the primary afferent end and G-protein-mediated potassium channel, and make the spinal cord intermediate neurons hyperpolarized, thus reducing the pain transmission. In addition, DEX can also block the internal flow of Na + and enhance the blocking effect of local anesthetics on the sodium channel of the cell membrane [19, 20]. However, consisted with the results of a meta-analysis [21] that included 9 RCTs, our study found that motor block duration of paturients in combination of 9 mg of intrathecal bupivacaine with 5 µg of DEX was significantly prolonged, which may suggest that combination with DEX may increase the risk of falls and cause the delay of parturients’ early rehabilitation.
Currently, the commonly used postoperative recovery quality scales were QoR-40 [22] and QoR-15 [23]. However, both of them are developed and verified in non-obstetric patients and day surgery population [24], so there are many items unrelated to cesarean section, and lack of critical elements to evaluate postoperative recovery after delivery, such as the ability to care for newborns [15]. The ObsQoR-11 table proposed by Ciechanowicz S. proved to be reliable, clinically acceptable, and feasible, is effective in patients undergoing elective and emergency cesarean section [15, 25]. In this study, all questionnaire feedback had been received and the results showed that scores in group DB was higher than in both group FB and group B (P < 0.017), suggesting that parturients in combination with 5 ug of DEX have a better recovery quality.
The incidence of shivering was statistically lowered in group DB, which is consistent with Miao’s [11] study results. According to the results of meta-analysis by Miao, DEX can significantly reduce the incidence of shivering in parturients (relative risk (RR) = 0.40; 95% CI = 0.26–0.62; P < 0.001) among 360 women underwent cesarean section with spinal anesthesia. The mechanism of anti-shivering effect of DEX can be inferred that DEX can reduce central thermos-sensitivity by weakening the electrical conductivity of neurons through mediating the α-2 adrenergic receptors in the brain and spinal cord [26, 27]. Hypotension is the common side effect of DEX, but the results of our study found that there were only 33 parturients suffered hypotension in the group DB, although more than patients in group B, the difference was not statistically significant. This may be due to the low dose of intrathecal DEX use.
Compared with group FB, both the onset time of sensory and motor block in group DB were shorter, the duration of sensory and motor block was prolonged, and ObsQoR-11 score was higher, suggesting that the intrathecal 5 µg of DEX was more effective than 20 µg of fentanyl, which may have a better clinical application prospect.
As DEX is applied intrathecally during cesarean section, what we are worried about were the neurological complications and whether DEX affects the fetus. In our study, 300 patients were followed up for 30 days postoperatively, and none of them showed neurological complications of lower limbs and buttocks, proving that intrathecal DEX would not lead to nerve injury in the short term. Ozdamar [28] injected 10 rats with DEX 10 µg through the subarachnoid path and extracted spinal medulla for histological and electron microscopy examination after 7 days, and the results showed that compared with saline group, no signs of neuronal or axonal injury, gliosis, or myelin sheath damage was found. PH, PaO2, and PaCO2 values of umbilical artery and umbilical vein of newborns in 3 groups were within the normal range and showed no statistical difference. Neonates’ Apgar scores at 1 min and 5 min were all beyond 8, and comparisons between groups were not statistically different, and concentration of DEX in umbilical artery and umbilical vein in neonates was too low to be detected, which all suggested that intrathecal 5 µg of DEX could not cause damage on neonates. Li et al. [29] showed similar results, which further confirmed our conclusion.
However, our study also has some limitations. Firstly, the inclusion criteria exclude the parturients over 35 years old, so the external authenticity of the conclusion in our research needs to be further proved. Secondly, we did not investigate the dose-response reaction of DEX via the intrathecal path, and the optimal clinical dose was not determined. Furthermore, the postoperative follow-up period in this study was only 30 days, so it is unknown whether patients had delayed adverse neuron reactions.