Lower extremity fractures are mainly treated by surgical reduction, but this operation is often affected by the patient’s level of agitation and the type of anesthesia used. The main treatment for lower-extremity fractures is operative reduction. However, operations can often be affected by both agitation and the degree of anesthesia. Therefore, it is of great importance to develop an effective anesthesia program to effectively ensure the progress of surgery.

To discuss the effect of ultrasound-guided nerve block combined with dexmedetomidine anesthesia in lower extremity fracture surgery.

A total of 120 hospital patients with lower extremity fractures were selected for this retrospective study and divided into an observation group (n = 60) and a control group (n = 60) according to the anesthesia scheme; the control group received ultrasound-guided nerve block; the observation group was treated with dextromethomidine on the basis of the control group, and the mean arterial pressure, heart rate (HR), and blood oxygen saturation were observed in the two groups.

The mean arterial pressure of T1, T2 and T3 in the observation group were 94.40 ± 7.10, 90.84 ± 7.21 and 91.03 ± 6.84 mmHg, significantly higher than that of the control group (P < 0.05). The observation group’s HR at T1 was 76.60 ± 7.52 times/min, significantly lower than that of the control group (P < 0.05); The observation group’s HR at T2 and T3 was 75.40 ± 8.03 times/min and 76.64 ± 7.11 times/min, significantly higher than that of the control group (P < 0.05). The observation group’s visual analog score at 2 h, 6 h and 12 h after operation was 3.55 ± 0.87, 2.84 ± 0.65 and 2.05 ± 0.40. the recovery time was 15.51 ± 4.21 min, significantly lower than that of the control group (P < 0.05). Six hours post-anesthesia, epinephrine and norepinephrine in the observation group were 81. 10 ± 21.19 pg/mL and 510. 20 ± 98.27 pg/mL, significantly lower than that of the control group (P < 0.05), and the mini-mental state exam score of the observation group was 25. 51 ± 1.15, significantly higher than that in the control group (P < 0.05).

Ultrasound-guided nerve block combined with dexmedetomidine has a good anesthetic effect in the operation of lower limb fractures and has little effect on the hemodynamics of patients.

Due to increased age and loss of bone elements, the middle-aged and elderly have a higher probability of bone fracture. This is especially true for lower extremity fractures, which have become common and have a considerable effect on quality of life of patients[1,2]. The main treatment for lower-extremity fractures is operative reduction. However, operations can often be affected by both agitation and the degree of anesthesia. Therefore, it is of great importance to develop an effective anesthesia program to effectively ensure the progress of surgery[3].

Ultrasound-guided nerve block is the main anesthetic method for surgical bone fracture reduction. Ultrasound guidance can clarify the paths of puncture tip and drug diffusion more clearly, which not only ensures anesthesia effect, but also helps to avoid unnecessary injury[4,5]. However, according to previous studies[6,7], nerve block anesthesia may lead to an incomplete block; therefore, it is often combined with additional anesthetic drugs to improve the anesthetic effect. Dexmedetomidine is a clinically effective sedative and analgesic narcotic that exerts anesthetic effects by inhibiting α2 adrenergic receptors through antisympathetic action. However, there are few clinical studies on the combined application of ultrasound-guided nerve block and dexmedetomidine, and further analysis is needed[8-10]. In our study, ultrasound-guided nerve block was used in combination with dexmedetomidine to explore the possibility of improved anesthetic effects in lower extremity fracture surgery.

Due to loss of calcium and reduced flexibility, gerontal patients have an increasing morbidity of lower extremity fracture resulting from various events such as falls and traffic accidents each year. After operative fracture reductions, these patients require a long-term bed. Because of the decreased inability to care for themselves along with the stress response to the fracture, patients often experience anxiety, depression, and other emotional reactions, with some patients even developing sleep disorders that have a considerable impact on the recovery and prognosis of patients[14].

Ropivacaine[15] is an amide anesthetic drug, with a clinical use of nerve block anesthesia. It inhibits sodium ion conduction from nerve cells, and blocks the conduction of nerve excitation and pain sensation, causing long-term block effects[16,17]. The sciatic and lumbar plexus nerves can be clearly displayed using ultrasound guidance, thus improving the success rate of the needle puncture and nerve block, reducing the stimulation to the body, preventing damage to important blood vessels and organs, and maintaining the stability of hemodynamics. However, according to some studies[18,19], ropivacaine has drawbacks such as incomplete block and slow onset of anesthesia, and thus needs to be combined with other anesthesia drugs when applied after clinical anesthesia. Dexmedetomidine is an α2 receptor agonist and has been widely used in clinical application of regional block assisted sedation with high selectivity. The literature suggests that dexmedetomidine assisted anesthesia is more effective in improving MAP and HR in patients undergoing brachial plexus block than anesthesia without dexmedetomidine.

In our study, MAP at T1, T2, and T3 in the observation group was significantly higher than that in the control group. HR at T1 was significantly lower than that in the control group, and HR at T2 and T3 were significantly higher than those in the control group. Postoperative recovery times in the observation group were significantly lower than those of the control group, indicating that ultrasonic-guided nerve block combined with dexmedetomidine in lower extremity fracture surgery was more helpful in improving hemodynamics and promoting postoperative recovery of patients than procedures without dexmedetomidine, which was consistent with the conclusions of previous studies. Dexmedetomidine can act on α2 adrenergic receptors, inhibit sympathetic nerve excitation by activating prominent posterior membrane receptors, and reduce blood pressure and HR of patients. In addition, dexmedetomidine can significantly reduce the negative emotions and discomfort that can be induced by lower extremity fracture surgery through deep sedation. It can also reduce the brain tissue damage caused by anesthesia, stabilize the hemodynamic level of patients, and promote postoperative recovery of patients.

Further comparison of postoperative VAS scores of the two groups showed that the VAS score of the observation group was significantly lower than that of the control group at 2 h, 6 h and 12 h after surgery. Epinephrine and norepinephrine levels in the observation group were also significantly lower than those in the control group at 6 h after anesthesia. The MMSE score of the observation group was significantly higher than that of the control group 1d after the operation. Our results suggest that, in lower extremity fracture surgery, an ultrasound-guided nerve block combined with dexmedetomidine is helpful in improving the pain level of patients, inhibiting the secretion of epinephrine and norepinephrine, and improving cognitive function. Α2 adrenergic receptors mainly exist in presynaptic and postsynaptic regions. The negative feedback mechanism can also regulate the release of adenosine triphosphate and norepinephrine to inhibit neuronal excitation and stop the transmission of pain signals. Meanwhile, α2 adrenergic receptors in the spinal cord can specifically bind its agonist dexmedetomidine, which can effectively exert analgesic effects, reduce the VAS score of patients, inhibit stress response, and thus improve the postoperative cognitive function of patients.

This safety study found no significant difference in the incidence of complications between the observation and control groups, verifying that in lower extremity fracture surgery, ultrasound-guided nerve block combined with dexmedetomidine did not increase the incidence of complications, and the safety is generally controllable. Meta-analyses suggested that dexmedetomidine can activate α2 adrenergic receptors in the spinal cord, block the discharge of neurons, reduce the pain-induced antisympathetic effect and unpleasant emotion, reduce the stress response during the operation cycle of patients, reduce the incidence of adverse reactions such as rapid heart rate and elevated blood pressure, and that it is safe and controllable under rational clinical administration[20-22].

Related studies[23,24] have shown that a high dose of dexmedetomidine administered during anesthesia maintenance can cause hypotension and bradycardia, which requires special clinical attention. In addition, patients with rapid intravenous infusion of dexmedetomidine are more prone to severe headache, hypertension, and other adverse symptoms. Therefore, intravenous infusion of dexmedetomidine is not recommended clinically. However, there are some limitations in this study, mainly including the small sample size and it being a single-center study. Further research with a larger sample size and across many institutions would be beneficial.

In conclusion, ultrasound-guided nerve block combined with dexmedetomidine has a good anesthetic effect during the operative reduction of lower limb fractures and has little effect on the hemodynamics of patients.