Efficacy of Different Dose of Dexmedetomidine Combined With Remifentanil in Colonoscopy

A Randomized Controlled Trial

Li Jia; Meng Xie; Jing Zhang; Jingyu Guo; Tong Tong; Yuying Xing


BMC Anesthesiol. 2020;20(225) 

In This Article


Dexmedetomidine has advantages during colonoscopy as it allows the patient to cooperate during the procedure.[12,13] Few studies examined the dexmedetomidine-remifentanil combination. Therefore, this study aimed to evaluate the effects of different doses of the dexmedetomidine-remifentanil combination in colonoscopy. The results strongly suggest that dexmedetomidine 0.3 μg·kg− 1 combined with remifentanil was effective for colonoscopy and had few adverse reactions.

Dexmedetomidine is a new type of highly selective α2 receptor agonist and has eight times the affinity to α2 receptors as clonidine.[10,11,16] Compared with clonidine, dexmedetomidine has stronger sedative, analgesic, and anxiolytic effects.[10,11,16] Its sedative and hypnotic characteristics are that the patients can be awakened and cooperate, and the sleep state is similar to that of natural sleep.[10,11,16] It is also the only sedative that allows patients to be easily awakened to cooperate without breathing depression.[10,11,16] Bekker et al.[17] reported for the first time the use of dexmedetomidine for craniotomy and left temporal tumor resection, during which it could be used to locate the language area and awaken intraoperatively during surgery. Ramsay et al.[18] used dexmedetomidine as the only intravenous anesthetic in the laser ablation for severe subglottic stenosis and artificial upper trachea replacement. The patients' blood oxygen saturation was above 90% without oxygen inhalation, and hemodynamics were relatively stable. The results of this study showed that the hemodynamic parameters and respiratory parameters of the three groups of participants were within the clinically normal range, and SpO2 was above 98% in all participants, which was consistent with the results of the above studies.

Cortinez et al.[19] showed that dexmedetomidine had mild-to-moderate analgesic effects on cold compression tests, but had limited effects on acute pain such as electricity and thermal pain. Its analgesic mechanism is different from opioids, which can have a synergistic effect and reduce the amount of opioids.[20] Therefore, the combination of dexmedetomidine and opioids can achieve the purpose of analgesia and sedation. Remifentanil is a new type of short-acting μ opioid receptor agonist. Wilhelm et al.[21] reported that after remifentanil anesthesia, the patients could be waked up faster, and the orientation was recovered faster. Neurocognitive tests showed that it was better than fentanyl, which was more suitable for short outpatient surgery. Therefore, in this study, dexmedetomidine and remifentanil were used for painless colonoscopy. This combination has been reported before for colonoscopy,[13] but the exact dose of dexmedetomidine has not been examined within the same trial.

The recommended dose of dexmedetomidine for general anesthesia is a loading dose not exceeding 1 μg·kg− 1. Due to the synergistic effect with remifentanil, the present study examined three doses (0.2, 0.3, and 0.4 μg·kg− 1) combined with remifentanil 1–2 μg·kg− 1 and 0.1 μg·kg− 1·min− 1 maintenance dose.[22] Remifentanil at a rate of 0.1 ± 0.05 μg·kg− 1·min− 1 did not affect ventilation and wakefulness.[23] Therefore, in this study, the loading dose of remifentanil was 1 μg·kg− 1, and the maintenance dose was 0.1 μg·kg− 1·min− 1. After remifentanil was given at a loading dose, the time to peak efficacy was 1.6 min.[24] Therefore, colonoscopy started 2 min after the administration of remifentanil, and dexmedetomidine also began to have effect at this time since, after dexmedetomidine infusion, the rapid distribution-related half-life is about 6 min.[25]

The results of the present study showed that only two patients in group I had body movements that interfered with the examination, but the examination could be completed after the addition of propofol. Both groups II and III achieved satisfactory analgesic effects, and the patients were quiet, with no or only mild body movements, which showed that dexmedetomidine combined with remifentanil was effective for analgesia during colonoscopy. The SBP, HR, and RR of the participants during the examination in the three groups were lower than before surgery. During the examinations, the minimum BIS value in the three groups was about 73, and all patients could wake up at any time. Except for one patient in group III who needed assistance for turning over, they could turn over on their own and cooperate to change the position. At the end of the examination, the rate of excellent and good anesthesia for groups II and III reached 100%. This showed that dexmedetomidine combined with remifentanil was suitable for colonoscopy.

During the examination and after the operation, no hypotension occurred in the three groups, and the occurrence of nausea and vomiting was low, but the occurrence rate of bradycardia in group III was higher than that in groups I and II. Dexmedetomidine is a highly selective α2 receptor agonist, which activates post-synaptic α2 receptors in the central nervous system and simultaneously inhibits sympathetic nerve activity, causing lower blood pressure and heart rate.

During the examination, the minimum BIS value in groups I and II were decreased to about 86, and the minimum BIS value in group III was about 73. When all patients were waked up or talked to, the BIS value could return to more than 90. Except for one participant in group III who needed assistance, all the other patients were able to cooperate with the examiner to turn over the body on their own, and most patients did not experience any discomfort. It indicated that dexmedetomidine 0.2–0.4 μg·kg− 1 could produce good sedation, which was consistent with the results of Souter et al..[26] Nevertheless, the minimum BIS value in group III was lower than those in the other two groups, suggesting that 0.4 μg·kg− 1 dexmedetomidine combined with remifentanil had a risk of deeper sedation when used for colonoscopy.

This trial has limitations. It was performed at a single center. There was no control group. Only three doses of dexmedetomidine were tested, without changes in the dose of remifentanil. Finally, besides BIS, no objective score was used.