This prospective, double-blinded, randomised study indicated that preoperative intravenous infusion of butorphanol was effective in reducing the incidence of EA after FESS and making haemodynamics relatively more stable without extending the length of PACU stay.
Prior studies reported that the incidence of EA in adult patients after general anaesthesia can reach 20%[8, 19]. Male gender, type of surgery, inhalation anaesthetics, postoperative pain, and the presence of tracheal and/or urinary catheters are known risk factors for EA[1–4, 8]. The incidence of EA after ENT surgery is even higher, almost up to 55.4%. Owing to the obstruction of the habitual respiratory channels caused by gauze filling in the nasal cavity to stop bleeding after FESS, it is preferred to awake extubation after general anaesthesia. However, awake extubation can lead to a higher agitation incidence. Postoperative pain, as well as the suffocation caused by the gauze strips and blood clots may be the possible reasons for the high incidence of EA after FESS.
The harm of EA is tremendous. It can increase the probability of respiratory and circulatory complications and internal bleeding owing to the excitement of sympathetic nerve, although some patients can relieve themselves. In severe cases, the surgical incision may be ruptured and the intravenous access and drainage tube may fall off suddenly, leading to the failure of the operation. At the same time, the occurrence of EA increases the burden of the medical staff and reduces the satisfaction of patients with disease treatment. At present, analgesic and sedative drugs (such as fentanyl, tramadol, propofol, etc.) are commonly used to prevent and treat EA clinically, but there is a risk of respiratory inhibition or delayed recovery[22–24]. Butorphanol is an opioid receptor agonist–antagonist. Its metabolites can act on κ-receptors and have dual effects of activation and antagonism on µ-receptors. It mainly interacts with these receptors in the central nervous system to indirectly exert anaelgesic, sedative and other pharmacological effects. Patients have no discomfort such as agitation and anxiety. Butorphanol usually exerts its effects after intravenous injection within a timeframe of 3–5 min. Its elimination half-life is 2.5–3.5 h, and its analgesic potency is 5–8 times higher than that of morphine[25–27]. However, respiratory inhibition rarely occurs, and the incidence of adverse reactions is significantly lower than that of morphine and fentanyl. Based on these characteristics, it may become an ideal drug for postoperative reduction of EA.
Some studies found that among the many causes of EA, postoperative pain may be the most important reason for inducing and aggravating agitation during emergence. Butorphanol attracted our attention in the prevention and treatment of EA owing to the fact that it induces sedation and analgesia without respiratory depression. In this study, we demonstrated that administration of butorphanol before anaesthesia induction can effectively reduce the incidence of EA after FESS. We believed that the anaelgesic and sedative effects of butorphanol are the main reasons for reducing the incidence of EA. In our research, the operation duration was approximately 2–3 h. Therefore, the anaelgesic and sedative effects of butorphanol were still working on during the emergence duration. This made patients more tolerant to the sense of asphyxia caused by the tracheal catheters and habitual airway blockage. However, in our study, the incidence of EA in the control group was 31.4%, lower than that in previously reported studies[3, 9]. This may be attributed to the fact that we gave patients an adequate amount of analgesics during the perioperative period to manage the perioperative pain more efficiently. This could be reflected by the NRS score. In our study, both the highest and mean NRS scores in the control group were lower than those in previously reported results[3, 9]. Research studies concerning butorphanol in combination with other drugs used to reduce the incidence of EA are also in progress. Lin et al. found that butorphanol combined with ketamine was more effective than butorphanol or ketamine alone on postoperative EA in patients with gastric cancer.
The time to spontaneous breathing, verbal response and extubation was longer in Group B than Group C, while the residual sedation and length of PACU stay yielded no differences. Compared with Group C, the grade of cough at extubation in Group B was lower. These results may be attributed to the sedative effect of butorphanol. This medication induced patients in a more appropriate state of sedation, and their recoveries were better and without PACU duration prolongations.
While HR was similar in both groups during operation and emergence, the MAP at the end of the operation and at 5 min after extubation were significantly higher in Group B. The incidence of hypotension during PACU in Group B was significantly lower compared with that of Group C. These results indicated that the haemodynamics of patients who received a preoperative intravenous injection of butorphanol were more stable during the perioperative period.
There are several limitations associated with this study. First, we only studied the effectiveness of butorphanol on the incidence of EA in patients aged 18–65 who underwent FESS. Additional studies are warranted for other types of surgery and for children or patients over 65 years. Second, in this study, only one experimental drug dose was set, so we do not know whether a lower or higher dose of butorphanol can reduce the incidence of EA as well.