| Backgrounds:Total knee arthroplasty is the most effective treatment of severe knee joint diseases. Most of the patients undergoing total knee arthroplasty are elderly people. And they will suffer from severe postoperative pain. Because the lumbar degenerative diseases in the elderly patients and the conventional routine of perioperative anticoagulant, general anesthesia is the important choice for these patients. Severe pain after total knee arthroplasty will produce the serious impact on rehabilitation and active exercises for the patients. Therefore, the excellent postoperative analgesia is very important to the patients undergoing total knee arthroplasty. The research from home and abroad showed that single shot and continuous femoral nerve block can effectively improve the effect of postoperative analgesia, reduce perioperative opioid consumption, speed up functional exercise and recovery, and reduce the incidence of adverse reaction. Because it is safe and simple to perform, femoral nerve block is most widely used in patients undergoing total knee arthroplasty. But the clinical timing of femoral nerve block is different. Sometimes the clinical timing is before the surgery, sometimes is after the surgery. But whether the different timing of femoral nerve block will produce the effect on postoperative analgesia for the patients undergoing total knee arthroplasty is not known. It is not clear whether the preoperative application of femoral nerve block will produce the preemptive analgesia for the elderly patients undergoing total knee arthroplasty.The research from home and abroad pointed out the orthopedic operation, postoperative pain and age older than 60 years are the risk factors of postoperative cognitive dysfunction.Therefore, it is necessary to prevent and reduce postoperative cognitive dysfunction for the elderly patients undergoing total knee arthroplasty with general anesthesia. Some research showed that the inflammatory response may be the crisis of postoperative cognitive dysfunction. In the early years some researches proposed that the peripheral nerve block technique may bring new hope to the treatment of inflammatory response. Animal experiment and clinical study showed that the peripheral nerve block can improve postoperative pain and inhibit the inflammatory response. Femoral nerve block can effectively improve the effect of postoperative analgesia, reduce perioperative opioid consumption, but it is not clear whether it can produce the effect on the inflammatory response and postoperative cognitive function in the elderly patients undergoing total knee arthroplasty. Objective:This study was to investigate the effects of preoperative femoral nerve block on preemptive analgesia and early cognitive dysfunction in the elderly patients undergoing total knee arthroplasty Methods:Experimental 1: Sixty patients older than 65 years and scheduled for selective total knee arthroplasty were randomly divided into three groups(n=20): control group(group Ⅰ), preoperative block group(group Ⅱ) and postoperative block group(group Ⅲ). Before the induction of anesthesia, ultrasound-guided femoral nerve block was performed and 0.375% ropivacaine 20 ml was injected in group Ⅱ. And at the end of surgery, femoral nerve block was performed in group Ⅲ. Pain at rest was evaluated using VAS score at 2 h, 6 h, 12 h, 24 h, 48 h and 72 h after operation. The active exercise VAS score at 12, 24 h, 48 h and 72 h after operation were recorded. The consumption of sufentanil within 24 h after operation, the number of successfully delivered doses(D1) and the number of attempts(D2) within 24 h after operation were recorded. Dl/D2 was calculated. The adverse reactions were also recorded.Experimental 2: One hundred and twenty patients older than 65 years and scheduled for selective total knee arthroplasty were randomly divided into three groups: control group, femoral nerve block group and obturator nerve block group. All nerve block were performed under the ultrasound guidance before the induction of anesthesia. The data of mean arterial pressure, heart rate at different time points during the surgery were recorded. And the using ratio of vasoactive drugs during the surgery was calculated in every group. The MMSE score was assessed on 1th day before the operation and on the 3, 7th day after the operation using a battery of nine cognitive dysfunction tests.The incidence of postoperative cognitive dysfunction in every group was calculated on the 3, 7th day after the operation.Experimental 3: 40 patients older than 65 years and scheduled for selective total knee arthroplasty under general anesthesia, were randomized into control group and femoral nerve block group. Femoral nerve block was performed under the ultrasound guidance before the induction of general anesthesia in femoral nerve block group. Changes of lactate, PH and blood glucose were observed in arterial blood-gas levels before the surgery, at the end of the surgery and 2 hours later after the surgery. Venous blood samples were collected at different time points for determination of plasma tumor necrosis factor-a, Interleukin-6, β-amyloidprotein and Tau protein levels by ELISA. Results:1. Compared with control group, the VAS score at movement at 12 h after the surgery and the VAS score at rest at 2 h, 6 h, 12 h after the surgery were significantly lower in group Ⅱand group Ⅲ. The consumption of sufentanil were significantly lower within 24 hours after the surgery in group Ⅱand group Ⅲ, while the Dl/D2 was higher in group Ⅱand group Ⅲ during 24 h after operation(P<0.05). And the incidence of nausea and vomiting was significantly decreased in group Ⅱand group Ⅲ(P<0.05). But there was no differences in the VAS score at different time points and the consumption of sufentanil within 24 hours after the surgery.2. Compared with control group, there was no differences in the amount of bleeding, the duration of the surgery and the dosage of propofol in group Ⅱ and group Ⅲ(P>0.05).The dosage of remifental in group Ⅱ were less than in control group(P< 0.05). But no significant difference was found in dosage of remifental between control group and group Ⅲ(P>0.05). Compared with control group, there was no differences in the change of mean arterial pressure,heart rate at different time points and the using ratio of vasoactive drugs during the surgery in group Ⅱand group Ⅲ(P>0.05). And the MMSE score in groupⅡ was higher than in group Ⅰand Ⅲ on the 3th post- operative day(P<0.05). Compared with control group, the incidence of postoperative cognitive dysfunction was decreased in group Ⅱon the 3th postoperative day(P<0.0 5).But there was no differences in MMSE score and the incidence of postoperative cognitive dysfunction between group Ⅰand group Ⅲ on the 3、7th postoperativeday. 3. Compared with control group, there was no differences in the changes of lactate and PH at different time points in group Ⅱ(P>0.05). But the level of blood glucose at the end of operation and 2 hours later after the operation in groupⅡwas less than in control group(P<0.05).Level of plasma tumor necrosis factor-a and Interleukin-6 were significantly decreased at the time points of T1, T2, T3 and T4 in femoral nerve block group than in control group(P<0.05). And the level of plasmaβ-amyloidprotein and Tau protein were also significantly decreased at the time points of T4 and T5 in femoral nerve block group than in control group(P<0.05). But no difference was found in the level of plasma β-amyloidprotein and Tau protein at the time point of T6 between the control group and femoral nerve block group(P>0.05). Conclusion:The results suggested that the femoral nerve block enhance the efficacy of early postoperative analgesia but lack effect of preemptive analgesia in elderly patients undergoing total knee arthroplasty. But the femoral nerve block might produce a potential protective effect on early cognitive dysfunction in the elderly patients undergoing total knee arthroplasty. |
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