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Lili Tang, Panpan Fang, Yuxin Fang, Yao Lu, Guanghong Xu, Xuesheng Liu, "Comparison of Effects between Combined Lumbar-Sacral Plexus Block plus General Anesthesia and Unilateral Spinal Anesthesia in Elderly Patients Undergoing Hip Fracture Surgery: A Pilot Randomized Controlled Trial", Evidence-Based Complementary and Alternative Medicine, vol. 2021, Article ID 6685497, 7 pages, 2021. https://doi.org/10.1155/2021/6685497
Comparison of Effects between Combined Lumbar-Sacral Plexus Block plus General Anesthesia and Unilateral Spinal Anesthesia in Elderly Patients Undergoing Hip Fracture Surgery: A Pilot Randomized Controlled Trial
Purpose. Hip fracture is a common injury in geriatric populations, which is associated with poor quality of life. However, the ideal anesthesia technique for this disease is yet to be identified. This study aimed to compare the combined lumbar-sacral plexus block (CLSB) plus general anesthesia (bispectral index (BIS) 60–80) with the unilateral spinal anesthesia (SA) on activity of daily living in elderly patients undergoing hip fracture surgery. Methods. A total of 124 elderly patients undergoing hip fracture surgery were randomly assigned to two groups. Patients in the SA group received light-specific gravity spinal anesthesia, and patients in the CLSB group received lumbar and sacral plexus block with general anesthesia (BIS 60–80). The primary outcomes were 30-day activity of daily living (ADL). The secondary outcomes were postoperative pain scores, postoperative delirium, in-hospital cost, and major complications. Results. The ADL scores of postoperative day 30 (POD30) in the CLSB group are higher than those in the SA group (27.34 ± 7.01 versus 24.70 ± 6.40, ). Compared to preoperative ADL scores, there were higher increased scores in the CLSB group than in POD30 (CLSB group 8.09 ± 3.39 versus SA group 4.87 ± 3.90, ). Mild-to-moderate pain did not have differences between the two groups (rest pain: 3 versus 2, ; motion pain: 5 versus 4, ). There were no significant differences in incidence of postoperative delirium, PONV, and other complications. Conclusion. The unilateral SA can reduce the deterioration of ADL after hip fracture surgery and provide a better postoperative recovery.
Hip fracture is a common injury in geriatric populations, ranking the second among the causes of hospitalization and disability for elderly patients. It has critical consequences of deteriorated function status, for example, increasing mortality and decreasing quality of life [1, 2]. A large percentage of these patients did not attain their prefracture level of independence and ambulatory status [3, 4]. Thus, no matter for orthopedists or anesthesiologists, it is important to implement occupational therapy interventions to improve the function status and the quality of life among this population.
Activity of daily living (ADL), an important tool to assess the functional status and the quality of life, has been widely used to evaluate postoperative recovery and disease progression . Previous studies had investigated the potential influence of different surgical methods , the early operative time , and the nutritional status  on the activities of daily living after hip fracture surgery. However, evidence to clarify the influence of different types of anesthesia on postoperative ADL is still lacking.
Both the combined lumbar and sacral plexus block (CLSB) with general anesthesia (BIS 60–80) and the unilateral spinal anesthesia (SA) on the operative side had been reported to be safe and effective as regional anesthesia techniques for hip surgery [9–11]. To the authors’ knowledge, there were no studies comparing the superiority of these two anesthesia methods in terms of ADL. Hence, the purpose of this study was to compare the CLSB plus general anesthesia (BIS 60–80) and the unilateral spinal anesthesia plus monitored anesthesia care (MAC) on the postoperative ADL of elderly patients undergoing hip fracture surgery. We hypothesized that the unilateral SA plus MAC would attenuate the deterioration of daily activity compared to the CLSB plus general anesthesia.
2. Materials and Methods
This prospective, controlled, and two parallel-group clinical trial was approved by the ethics committee of the First Affiliated Hospital of Anhui Medical University (approval number: PJ2018-11-06) and registered in the Chinese Clinical Trial Registry (ChiCTR1900025113; principal investigator: Panpan Fang; date of registration: August 12, 2019). The study was conducted in accordance with the principles of the Helsinki Declaration at the First Affiliated Hospital of Anhui Medical University.
2.1. Patients and Randomization
Between August 2019 and December 2019, patients who underwent elective unilateral hip fracture surgeries, including osteosynthesis, artificial femoral head replacement, and total hip replacement, at the First Affiliated Hospital of Anhui Medical University were assessed for eligibility.
The inclusion criteria were as follows: >65 years of age and American Society of Anesthesiologists I–IV. The exclusion criteria were as follows: dementia or severe cognitive dysfunction (simple mental state questionnaire ≥8), unstable mental state or mental disease, reception of psychotropic drugs or abuse of narcotic sedation analgesics, being delirious or history of delirium, anesthesia and surgery within 6 months, other surgeries at the same time, cerebrovascular accidents such as cerebral stroke and transient ischemic attack within 3 months, and prosthesis fracture repair surgery.
The participants were randomized to the CLSB or the SA group with a 1 : 1 allocation using computer-generated randomized numbers. Patients in the CLSB group received lumbar and sacral plexus block with general anesthesia (BIS 60–80), while patients in the SA group received light-specific gravity spinal anesthesia plus MAC. Written informed consent forms were offered to all patients or their legal relatives.
2.2. Anesthetic Management
Heart rate, blood pressure, electrocardiograph, pulse oxygen saturation (SpO2), and BIS were routinely monitored for each patient. After the venous access was available, all patients were injected with 6–8 mL/kg/h of Ringer’s lactate solution or hydroxyethyl starch 130/0.4 sodium chloride before anesthesia. Then, the fluids were adjusted according to the hemodynamic monitoring and blood loss in the operating room.
2.3. CLSB with General Anesthesia (BIS 60–80)
All CLSB procedures were conducted by an attending anesthesiologist well versed with peripheral anesthesia. Before the patient was placed in a lateral decubitus position with the operated side uppermost, flexion of uninjured hip and knee, 5 μg sufentanil was administered intravenously for pain relief.
During the CLSB procedure, oxygen was provided via a face mask with a flow of 5–8 L/min. All peripheral nerve blockades were performed under the guidance of a nerve stimulator (Stimuplex HNS 12, B. Braun Medical Inc., Germany) and ultrasound (FUJIFILM Sonosite Inc., WA, USA). A 12 cm 22-gauge nerve stimulation needle (Stimuplex D, B. Braun Medical Inc., Germany) was advanced perpendicularly to the skin between L3 and L4 transverse processes. An appropriate needle position was confirmed as quadriceps contraction after a stimulating current of 0.4 mA and a frequency of 2 Hz. After negative aspiration with blood, 20 mL of 0.25% ropivacaine was slowly injected.
The sacral plexus nerve block was performed using the transgluteal approach with the same position under ultrasound and nerve stimulation guidance. The sacral plexus was identified by the motor response of the gluteus maximus and gastrocnemius, with a stimulating current of 0.4 mA and a frequency of 2 Hz. Similarly, 20 mL of 0.25% ropivacaine was slowly injected to complete the sacral plexus block. It was considered as a failed procedure in the case of the absence of the right motor responses after three nerve block puncture attempts. Then general anesthesia was applied, and the patient was eliminated from the study.
After confirming successful block using the pinprick test, propofol (1–1.5 mg/kg), sufentanil (0.1–0.2 µg/kg), and cisatracurium besilate (0.2 mg/kg) were used for anesthesia induction . A laryngeal mask (LMA Supreme, Laryngeal Mask Company Ltd., Malaysia) was used for airway management. Mechanical ventilation was set as follows: the tidal volume was set as 6–8 mL/kg, the respiratory rate was set as 10–12 breaths/min, the ratio of expiration: inspiration was set as 2 : 1, and the end-tidal carbon dioxide pressure remained at 35–40 mmHg. The effect-site concentration of propofol was adjusted to maintain the depth of sedation (BIS: 60–80) . The depth of sedation was assessed by observer’s assessment of alertness/sedation (OAA/S) as a supplement.
2.4. Unilateral Spinal Anesthesia plus MAC: Light-Specific Gravity Spinal Anesthesia
All the SA procedures were performed by a skilled attending anesthesiologist. After the patient was placed in a vertical position with the operated side uppermost and flexion of uninjured hip and knee, the puncture sites were selected at L3–4 or L2–3 vertebral interspace. The median side of the spine was opened between 0.5 and 1.0 cm for local infiltration. With both hands holding the protruding needle tip (25 G), the needle was advanced perpendicularly into the spine through the middle of the lumbar vertebral space. The recorded depth was between 3.5 and 5.0 cm. Once encountering bone, the needle tip was slightly tilted to the side of the head by about 10° to 15° and then reinserted until the clear cerebrospinal fluid reflux. Further, 4 mL of 0.25% hypobaric ropivacaine was injected into the subarachnoid space . The sensory block on lower limbs was evaluated using the pinprick test, whereas the motor blockade was evaluated by modified Bromage scale (0 = no motor block, 1 = hip blocked, 2 = hip and knee blocked, and 3 = hip, knee, and ankle blocked). Assessments of motor and sensory blocks in the operated and the nonoperated sides were made at the following times: 3, 5, 10, and 15 minutes after the injection. Successful anesthesia was defined as no pain at T12 and a modified Bromage score ≥2 only on the operated limb. Then, light depth of sedation (BIS 60–80) was maintained by adjusting the effect-site concentration of propofol. The depth of sedation was assessed by observer’s assessment of alertness/sedation (OAA/S) as a supplement. The absence of the right motor response after three spinal puncture attempts was considered as failed, and then general anesthesia was applied.
Intraoperative hypotension was defined as a decrement in systolic blood pressure by more than 20% from preoperative values and/or mean arterial pressure less than 65 mmHg. Patients with intraoperative hypotension were immediately treated with phenylephrine. All operations were completed using the posterior approach and by the same arthroplasty surgeons. All patients were transferred to the postanesthesia care unit (PACU) after showing satisfactory spontaneous breathing.
The criteria for extubation were as follows: recovery of consciousness, the train-of-four ratio >0.9, the tidal volume >6 mL/kg, the breathing rate <30 beats/min, and the maintenance of pulse oximetry (SpO2) at >92% under air inspiration. Postoperative analgesia was achieved by a patient-controlled analgesia (PCA) solution, which was prepared by dissolving sufentanil (2.5 μg/kg) and flurbiprofen axetil (100 mg) in 100 ml of saline. For the loading dose, one bolus was set to 2 mL and background infusion rate was set to 2 ml/h, while the lockout time was set to 15 min. The analgesic goal was postoperative VAS ≤3. If the VAS score ≥4, patients would receive rescue analgesic to relief pain.
2.5. Outcomes Measures
2.5.1. Primary Endpoint
The primary endpoint was the 30-day function status assessed by the Chinese version of the daily living scale (CADL), which includes a physical self-maintenance scale (PSMS) and an instrumental activities of daily living (IADL) scale . The function status before fracture was assessed one day before surgery with CADL by interviewing the patients. The PSMS, normally used to assess the fundamental skills to live, consists of six tasks: ambulating, dressing, eating, grooming, toileting, and bathing. The IADL scale is used to assess more complicated activities that allow an individual to live independently. This scale contains eight tasks: preparing food, taking public transportation, housekeeping, doing laundry, taking medications, making phone calls, shopping, and managing finances. CADL has a total of 14 items and ranged from 14 to 56 points. The single item score is determined by a 4-point numeric rating scale (1 = can do it by oneself, 2 = have some difficulty but can still do it by oneself, 3 = need help to do it, and 4 = cannot do it at all). Higher ADL scores indicate a poor functional status, and 22 points were the cutoff score. Over the cutoff score was defined as impairment in ADL.
2.5.2. Secondary Endpoints
Secondary endpoints included the incidence of postoperative delirium, pain scores, the in-hospital cost, postoperative nausea and vomiting (PONV), and major postoperative complications (stroke and heart failure). All the patients had same discharge criteria: no fever, resumed a normal diet, and well incisions heal. The preoperative mental state was assessed using the simple mental state questionnaire, while perioperative delirium was evaluated by the Confusion Assessment Method (CAM) . The postoperative delirium was assessed twice daily for 7 days or until discharged. Rest pain, motion pain, postoperative nausea and vomiting (PONV), and major postoperative complications were evaluated at 8 : 00 a.m. on the first three days after surgery. Evaluation for ADL score was completed via phone calls on the 30th day after surgery (postoperative day 30, POD30).
A trained researcher in our department conducted all these assessments, and he was blinded to the randomized allocation and intervention in this study.
2.6. Statistical Analysis
We used PASS11.0 (NCSS, LLC., Kaysville, UT, USA) for the sample size calculation. According to our pilot data, we estimated that the mean of ADL incremental value was 5 in SA group and the SD was 4; the mean of ADL incremental value was 8 in CLSB group. Assuming a 5% two-tailed type I error rate, a sample size of 92 was required to detect a significant difference with the power of 90%. Allowing for 15% noncompliance, at least 106 patients were required in the present study.
Data were expressed as mean ± standard deviation, median (interquartile range), or number (proportion, %) and analyzed by SPSS version 16.0 (SPSS Inc., IL, USA). For normal-distribution data, two-tailed Student’s t-test was used. Continuous data that were not normally distributed were analyzed by the Mann–Whitney U test. Categorical data were analyzed using the chi-square (χ2) test or Fisher’s exact test where appropriate. Statistical significance was set at .
Of the 159 patients assessed for eligibility, 10 patients did not meet the inclusion criteria, while 3 refused to participate in the study. Further, 22 patients were excluded from the study. Eventually, 124 patients were randomly assigned to SA and CLSB groups. In the CLSB group, four patients were lost to follow-up and three patients were switched to general anesthesia. In the SA group, two patients were lost to follow-up and five were switched to general anesthesia. Therefore, only 110 patients completed the study (Figure 1). No significant differences were observed in the demographics and baseline data between two groups (shown in Table 1).
Statistics are presented as mean (standard deviation), median (interquartile range), or N/total number of patients (%) as appropriate. ADL, activity of daily living; ASA, American Society of Anesthesiologists; BMI, body mass index; CCI, Charlson comorbidity index; CLSB, combined lumbar and sacral plexus block; SA, spinal anesthesia.
3.1. Primary Outcomes
The ADL scores before fracture were comparable between two groups. The patients in the CLSB group had a higher POD30 ADL score (27.34 ± 7.01 versus 24.70 ± 6.4, ) (shown in Table 2). The ADL scores of POD30 in both groups were increased, compared with the ADL scores before fracture. However, patients in the CLSB group had higher incremental ADL values (8.09 ± 3.39 versus 4.87 ± 3.90, ) and a higher decremental function level (43.04% versus 25.83%, ) compared with the patients in the SA group (Figure 2).
Statistics are presented as mean (standard deviation), median (interquartile range), or N/total number of patients (%) as appropriate. , CLSB group compared with SA group. ADL, activity of daily living; CLSB, combined lumbar and sacral plexus block; POD, postoperative day; PONV, postoperative nausea and vomiting; SA, spinal anesthesia. Grade of PONV: 1a, no nausea or vomiting; 2a, mild nausea and vomiting without no vomitus; 3a, severe nausea and vomiting with vomited matter.
3.2. Secondary Outcomes
In addition, patients in the SA group had a lower in-hospital cost (44264 ± 9115.12 versus 49636 ± 9708.11, ) compared with ones in the CLSB group. There was no patient having stroke or heart failure in both groups. No significant difference was found in the incidence of PONV, postoperative delirium, blood transfusion, and the postoperative pain score between the two groups (shown in Table 2).
No significant difference was observed between two groups in terms of intraoperative crystal, colloid infusion, and intraoperative blood loss. Compared with the CLSB group, patients in the SA group had a shorter residence time in PACU (51.27 ± 14.51 versus 39.82 ± 10.38, ). Time of surgery, time of anesthesia, and the incidence of hypotension were comparable between two groups. The type of surgery was comparable between the two groups (Table 3).
Statistics are presented as mean (standard deviation), median (interquartile range), or N/total number of patients (%) as appropriate. , CLSB group compared with the SA group. CLSB, combined lumbar and sacral plexus block; PACU, postanesthesia care unit; SA, spinal anesthesia.
The results of this study showed a fewer loss of the daily activity in the SA group, compared with the patients in the CLSB group, although the patients in both groups did not return to the preoperative functional status 30 days after surgery. Furthermore, the rate of ADL decrement in the CLSB group was higher than that in the SA group. More items' scores were 3 (need help to do it) to 4 (cannot do it at all) in the CLSB group. Moreover, the patients in the SA group exhibited a shorter residence time in PACU and a lower in-hospital cost.
The functional status and the quality of life after hip fracture surgery are common concerns for orthopedics and anesthesiologists. It has been reported that nearly 33.3% of patients failed to return their prefracture ADL at six months after hip surgery . Kristensen  reported that 13% older patients with hip fracture are no longer able to live alone. In line with previous studies, our data demonstrated that POD30 ADL did not return to the preoperative state through aggressive and proper surgical treatments.
In the current study, the items in PSMS are necessary for basic functional living and the ability to implement IADLs can significantly improve the quality of life. A higher CADL score (impaired ADL) may indicate the need for home healthcare or more medical resources . Our study demonstrated that the CADL score in the CLSB group was also higher than that in the SA group at POD30. This indicates that the patients in the CLSB group perceived greater physical functional disability. Segev-Jacubovski et al. reported that the improved functional ability achieved by therapy intervention can promote health-related quality of life among elderly with hip fracture . Hence, patients in the CLSB group with a higher rate of declined ADL ability need more therapy intervention to recovery.
No difference in the postoperative pain score was found between groups. This may be associated with the successful block of the both groups and the effective postoperative controlled analgesia. Small dose of sufentanil with propofol (1–1.5 mg/kg) in CLSB was just to reduce or avoid the effect of LMA insertion. This method is consistent with the previous study . It is also consistent with previous findings [17, 18] that patients treated with spinal anesthesia had a shorter stay time in PACU and a lower in-hospital cost. Spinal anesthesia was not widely applied in patients undergoing hip surgery due to the potential hemodynamic compromise and urinary retention. However, the superiority of the unilateral spinal anesthesia was confirmed in outpatients’ surgery with fewer complications . Unilateral SA reduced the consumption of general anesthetics and avoided the artificial airway with an exact effect of nerve blocking.
Postoperative delirium is a common complication in elderly patients undergoing hip fracture surgery . However, in the current study, the incidence of postoperative delirium was 5.5% in the SA group and 7.3% in the CLSB group. The lower prevalence of delirium may partially be attributed to strict exclusion of participants and decreased opioids after application of regional anesthesia .
The present study had some limitations. Firstly, the number of PCA boluses and the time of the first postoperative requirement of analgesics were not recorded. Secondly, it is limited to assess the chronic pain 30 days after surgery in our study. Thirdly, the follow-up was only to 30 days after surgery. Therefore, the results of long-term ADL need to be investigated in our future study.
In conclusion, the results indicated that the unilateral SA plus MAC can reduce the deterioration of ADL after hip fracture surgery and can provide a better postoperative recovery. In addition, less cost was found in the SA group. Hence, the unilateral SA plus MAC may be more suitable than CLSB for elderly patients undergoing hip fracture surgery.
The data used to support the findings of this study are included within the article.
Conflicts of Interest
The authors declare no conflicts of interest.
Lili Tang and Panpan Fang contributed equally to the study.
The authors thank all the staff of Department of Anesthesiology, the First Affiliated Hospital of Anhui Medical University, for being helpful in conducting and finishing this research. This work was supported by grants from the National Natural Science Foundation of China (81870841 and 81571039).
- O. Sahota, N. Morgan, and C. G. Moran, “The direct cost of acute hip fracture care in care home residents in the UK,” Osteoporosis International, vol. 23, no. 3, pp. 917–920, 2012.
- S. M. Dyer, M. Crotty, N Fairhall et al., “Fragility fracture network (FFN) rehabilitation research special interest group. a critical review of the long-term disability outcomes following hip fracture,” BMC Geriatrics, vol. 16, no. 1, p. 158, 2016.
- M. Ganczak, K. Chrobrowski, and M. Korzeń, “Predictors of a change and correlation in activities of daily living after hip fracture in elderly patients in a community hospital in Poland: a six-month prospective cohort study,” International Journal of Environmental Research and Public Health, vol. 15, no. 1, pp. 95–108, 2018.
- P. Ariza-Vega, J. J. Jiménez-Moleón, and M. T. Kristensen, “Change of residence and functional status within three months and one year following hip fracture surgery,” Disability and Rehabilitation, vol. 36, no. 8, pp. 685–690, 2014.
- M. Liu, Y. Yue, and Y. He, “Association between chronic obstructive pulmonary disease and activity of daily living among oldest-old in China: based on Chinese longitudinal health longevity survey,” International Journal of Chronic Obstructive Pulmonary Disease, vol. 14, pp. 1959–1966, 2019.
- E. Bonicoli, F. Niccolai, G. Pasqualetti, G. Bini, F. Monzani, and M. Lisanti, “The difference in activity of daily living (ADL) and mortality in patients aged over 80 years with femoral neck fracture treated with hemiarthroplasty or osteosynthesis at 2 years of follow-up,” Injury, vol. 47, pp. 1–4, 2016.
- H. Doruk, M. R. Mas, C. Yıldız, A. Sonmez, and V. Kýrdemir, “The effect of the timing of hip fracture surgery on the activity of daily living and mortality in elderly,” Archives of Gerontology and Geriatrics, vol. 39, no. 2, pp. 179–185, 2004.
- S. Nishioka, H. Wakabayashi, and R. Momosaki, “Nutritional status changes and activities of daily living after hip fracture in convalescent rehabilitation units: a retrospective observational cohort study from the Japan rehabilitation nutrition database,” Journal of the Academy of Nutrition and Dietetics, vol. 118, no. 7, pp. 1270–1276, 2018.
- S. Petchara, S. Paphon, A. Vanlapa, P. Boontikar, and K. Disya, “Combined lumbar-sacral plexus block in high surgical risk geriatric patients undergoing early hip fracture surgery,” Malaysian Orthopaedic Journal, vol. 9, no. 3, pp. 28–34, 2015.
- B. Mei, H. Zha, X. Lu et al., “Peripheral nerve block as a supplement to light or deep general anesthesia in elderly patients receiving total hip arthroplasty,” The Clinical Journal of Pain, vol. 33, no. 12, pp. 1053–1059, 2017.
- M. Kahloul, M. S. Nakhli, A. Chouchene, N. Chebbi, S. Mhamdi, and W. Naija, “Comparison of two doses of hypobaric bupivacaine in unilateral spinal anesthesia for hip fracture surgery: 5 mg versus 7.5 mg,” Pan African Medical Journal, vol. 28, p. 108, 2017.
- M. Kaya, O. . Selma, K. Aslan et al., “A low-dose bupivacaine: a comparison of hyperbaric and hypobaric solutions for unilateral spinal anesthesia,” Regional Anesthesia and Pain Medicine, vol. 29, no. 1, pp. 17–22, 2004.
- M. P. Lawton and E. M. Brody, “Assessment of older people: self-maintaining and instrumental activities of daily living,” The Gerontologist, vol. 9, no. 3 Part 1, pp. 179–186, 1969.
- S. K. Inouye, C. H. Van Dyck, C. A. Alessi, S. Balkin, A. P. Siegal, and R. I. Horwitz, “Clarifying confusion: the confusion assessment method,” Annals of Internal Medicine, vol. 113, no. 12, pp. 941–948, 1990.
- P. Chen, E. S. H. Yu, M. Zhang, W. T. Liu, R. Hill, and R. Katzman, “ADL dependence and medical conditions in Chinese older persons: a population-based survey in Shanghai, China,” Journal of the American Geriatrics Society, vol. 43, no. 4, pp. 378–383, 1995.
- O. Segev-Jacubovski, H. Magen, and A. Maeir, “Functional ability, participation, and health-related quality of life after hip fracture,” OTJR: Occupation, Participation and Health, vol. 39, no. 1, pp. 41–47, 2019.
- C.-C. Chu, S.-F. Weng, K.-T. Chen et al., “Propensity score-matched comparison of postoperative adverse outcomes between geriatric patients given a general or a neuraxial anesthetic for hip surgery,” Anesthesiology, vol. 123, no. 1, pp. 136–147, 2015.
- T. Nishi, T. Maeda, T. Imatoh, and A. Babazono, “Comparison of regional with general anesthesia on mortality and perioperative length of stay in older patients after hip fracture surgery,” International Journal for Quality in Health Care, vol. 1, pp. 1–7, 2018.
- B. Borghi, F. Stagni, S. Bugamelli et al., “Unilateral spinal block for outpatient knee arthroscopy: a dose-finding study,” Journal of Clinical Anesthesia, vol. 15, no. 5, pp. 351–356, 2003.
- E. M. Kim, G. Li, and M. Kim, “Development of a risk score to predict postoperative delirium in patients with hip fracture,” Anesthesia & Analgesia, vol. 130, no. 1, pp. 79–86, 2020.
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