Effect of Dexmedetomidine on Early Postoperative Cognitive Function in Patients Undergoing Arthroscopic Shoulder Surgery in Beach Chair Position: A Randomized Double-Blind Study

This study sought to determine whether intraoperative dexmedetomidine infusion might reduce the incidence of postoperative cognitive dysfunction (POCD) and alleviate the neuroinflammatory response in patients who have undergone arthroscopic shoulder surgery. A total of 80 patients over 60 years of age who had undergone arthroscopic shoulder surgery in the beach chair position were randomly allocated to either the dexmedetomidine group (Group D) or the control group (Group C). Dexmedetomidine (0.6 μg/kg/h) or a comparable amount of normal saline was infused into each group during the surgery. The early incidence of POCD was assessed by comparing cognitive tests on the day before and 1 d after surgery. The neuroinflammatory response with the S100 calcium-binding protein B (S100β) assay was compared prior to anesthetic induction and 1 h following surgery. The incidence of POCD was comparable between groups D (n = 9, 22.5%) and C (n = 9, 23.7%) (p = 0.901). However, the results of the cognitive test revealed a significant difference between the groups after surgery (p = 0.004). Although the S100β levels measured at the end of surgery were significantly higher than those at baseline in both groups (p < 0.001), there was no difference between the groups after the surgery (p = 0.236). Our results suggest that intraoperative dexmedetomidine infusion neither reduce the incidence of early POCD nor alleviated the neuroinflammatory response in patients undergoing arthroscopic shoulder surgery.ope

Family caregivers' responses to a visitation restriction policy at a Korean surgical intensive care unit before and during the coronavirus disease 2019 pandemic

Background: Since the COVID-19 pandemic, restricting family visits in the ICU has increased concerns regarding negative psychosocial consequences to patients and families. Objectives: To compare the quality of life, depressive symptoms, and emotions in family caregivers of ICU patients before and during the COVID-19 pandemic, and to explore families' perceptions and suggestions for the visitation. Methods: A cross-sectional descriptive survey was conducted in 99 family caregivers of adult surgical ICU patients from an urban academic medical center in South Korea (February to July 2021). The WHO's Quality of Life-BREF, Center for Epidemiologic Studies Depression, and Visual Analogue Scale were used to assess quality of life, depressive symptoms, and emotions, respectively. The Family Perception Checklist was used to assess families' perceptions and suggestions about the visitation restriction. Results were compared with the data from our previous survey (n = 187) in 2017. Results: Family caregivers were mostly women (n = 59), adult children (n = 43) or spouse (n = 38) of patients with mean age of 47.34 years. Family caregivers surveyed during the pandemic reported worsening sadness (54.66 ± 28.93, 45.58 ± 29.44, P = 0.005) and anxiety (53.86 ± 30.07, 43.22 ± 29.02, P = 0.001) than those who were surveyed in. While majority of families were satisfied with the visitation restrictions (86.9%), only 50.5% were satisfied with the amount of information provided on the patient's condition. Conclusions: Visitation restriction is necessary during the COVID-19 pandemic despite sadness and anxiety reported in caregivers. Hence, alternative visitation strategies are needed to mitigate psychological distress and provide sufficient information to ICU family caregivers.ope

An Analaysis on the Densification of Liquid phase Sintering with Limited Volume of Liquid

The densification behavior has been analyzed for a liquid phase sintering system with closepacked spherical particles(face-centered cubic structure) and limited volume of liquid. The specimen shrinkage has been calculated on the basis of the two-particle model up to the moment of the liquid filling of tetrahedral sites. As the volume of liquid(V¹) decreases, the shrinkage and densification rates increase because of high capillary pressure. The closure of interconnected pore channels and the liquid filling of tetrahedral sites, however, occur in shorter sintering time for the particles array with higher liquid volume. As V¹decreases, the dominant mechanism for densification changes from the pore filling to the contact flattening. When V¹is less than 0.1 vol% the condition for the liquid filling of tetrahedral sites can not be reached until the densification by contact up to 97% relative density. The applicability and limiation of the present calculation are discussed

A study on the densification during solid-state and liquid-phase sintering

학위논문(박사) - 한국과학기술원 : 무기재료공학과, 1995.2, [ iv, 93 p. ]II-4. 고상 소결의 후기 단계에서 몇가지 치밀화 기구와 입자성장 기구에 대하여 소결기간에 대한 입자크기의 영향 즉 scaling law를 도출하였다. 그 결과 크게 치밀화 속도식과 입자성장 속도식의 입자크기에 대한 의존성이 같은 경우(A=B)와 다른 경우($A \neq B$)로 나눌 수 있다. 이 두 경우의 큰 차이는 $G/G_o-\rho$ 궤적식을 통하여 알 수 있는데 전자의 경우에는 $G/G_o-\rho$ 궤적이 입자크기에 의존하지않으며 후자는 $G/G_o-\rho$ 궤적이 입자 크기에 의존한다는 사실이다. $G/G_o-\rho$ 궤적이 $G_o$의 함수가 아니라는 것은 비교하는 두 계가 같은 치밀화에 도달하였을 때 입자크기의 비도 항상 일정하다. 이것은 후기 소결단계에서 반드시 동반되는 치밀화와 입자성장이 상호작용에도 불구하고 치밀화나 입자성장의 scaling law의 지수값이 치밀화속도상수/입자성장속 도상수의 비나 $G_o$ 등의 소결 조건에 관계없이 항상 일정하다. 반면 $G/G_o-\rho$ 궤적이 $G_o$의 함수인 경우에는 비교하는 두 계가 같은 치밀화에 도달하였을 때에 입자크기의 비가 소결출발점의 입자크기의 비와 달라서 scaling law의 지수값이 소결 조건에 따라 달라진다. 치밀화기구가 동일하지만 입자성장기구가 다르면 치밀화의 scaling law의 지수가 다른 값을 나타낼 수 있다는 것으로부터 scaling law를 적용하여 치밀화기구를 확인하려면 입자성장기구도 동시에 확인해야 함을 알 수 있다. 즉 scaling law를 실제 재료에 적용하려면 치밀화와 입자성장을 동시에 고려해야 하며 이와 더불어 소결 조건의 범위도 고려해야 한다. IV-3. 입자-액상 구조가 주어진 입자 크기와 액상량에 대하여 평형하다고 간주될 수 있는 통상의 최종단계 액상소결에서 입자모양의 변형은 기공채움의 필요조건은 아니다. 액상채움에 의한 치밀화는 입자성장에 의한 입자모양의 변형을 야기시키고 이에 따라 시편 수축을 가져온다. 그러나 입자모양의 변형은 더이상의 치밀화를 느리게 억제할 수 있으며 미세구조 균질화는 변형이 되어 있는 입자구조를 안정화시키고 기공채움을 도와 준다. 이런 치밀화와 시편수축의 과정은 입자성장과 더불어 일어나 므로 결국 입자성장이 그 kinetics를 결정하게 된다. 그러나 액상-입자 구조가 시간에 따라 현저히 변하는 초기 중기 단계에서 액상-입자 구조의 변화는 기공채움과 마찬가지로 치밀화의 중요한 과정이다. 액상량이 매우 작으면 기공채움은 실제로 거의 불가능하며 입자 편평화에 의한 입자모양의 변형이 치밀화와 시편수축에 주된 기구가 될 수 있을 것이다.한국과학기술원 : 무기재료공학과