关节软骨源性多孔支架复合自体软骨细胞修复兔关节软骨缺损的长期疗效观察

[目的]对关节软骨源性多孔支架复合自体软骨细胞复合体修复兔膝关节软骨缺损的长期效果进行观察和评价。[方法]实验动物新西兰大白兔共10只,分两组:(1)关节软骨源性支架对照组:缺损内置入关节软骨源性支架;(2)关节软骨源性支架复合细胞组:缺损内置入关节软骨源性支架-自体软骨细胞复合体。手术后15个月取材做大体摄像,甲醛固定、10%EDTA脱钙,石蜡切片,采用四种组织化学染色法(HE、奥新兰(AB)、甲苯胺兰(TO)、藩红花"O"染色)和Ⅱ型胶原免疫组化染色,观察修复后的兔关节软骨组织细胞形态特征。[结果]关节软骨源性支架对照组,大体观察关节表面有凹陷。石蜡切片HE染色见未修复缺损处为梭形细胞,纤维软骨,缺损处AB、甲苯胺兰、藩红花"O"染色为阴性,Ⅱ型胶原染色为阳性;关节软骨源性支架复合细胞组,大体见关节软骨表面修复平整、光滑。常规HE染色镜下见软骨全层修复良好,为透明软骨细胞,可见软骨陷窝潮线排列结构。细胞外基质特染:AB、甲苯胺兰、藩红花"O",Ⅱ型胶原特种染色均为阳性。[结论]组织学观察结果发现,关节软骨源性支架组为纤维软骨组织结构,未能完全修复膝关节软骨缺损;而关节软骨源性支架复合细胞组关节软骨缺损修复良好,未见退变,具有软骨组织的特征。     

骨关节炎软骨下骨研究进展

骨关节炎是最常见的关节疾病,其病理以关节软骨退变、软骨下骨硬化与骨赘形成为特点。目前骨关节炎的始发病理尚不明确,既往许多研究聚焦于关节软骨并认为软骨下骨的改变继发于关节软骨的退变;然而近年研究报道关节软骨下骨低骨密度,尤其是膝骨关节炎的软骨下骨,软骨下骨呈高转换,以及骨吸收抑制剂治疗骨关节炎有效,都提示软骨下骨在骨关节炎的病理机制中具有重要地位。本文就骨关节炎软骨下骨的研究进展做一综述。     

关节软骨损伤和缺损修复策略

关节软骨的损伤是临床中常见的疾病。由于关节软骨自身修复能力有限,采用关节镜下清创术、软骨移植、软骨细胞移植、组织工程技术及凝胶类关节软骨修复材料是目前对关节软骨损伤进行修复的主要手段。本文对目前用于关节软骨损伤和缺损修复的主要策略及各类修复技术的优缺点进行了综合评述。关节镜下清创术对早期骨性关节炎疗效显著;软骨及软骨细胞移植对小面积软骨缺损修复效果较为理想;组织工程技术是目前对关节软骨损伤和缺损修复的一个热点方向,但存在支架材料与软骨缺损区整合不紧密等问题;凝胶类关节软骨修复材料具有与自然关节软骨相似的力学和生物摩擦学特性,但其生物活性及与自然关节软骨间的结合强度有待进一步提高,如何实现材料生物活性、生物力学性能和生物摩擦学性能功能一体化是凝胶类关节软骨修复材料亟待解决的焦点问题。     

创伤性关节炎发生机制相关性研究

创伤性关节炎发生机制研究显示,关节软骨凋亡或坏死引起关节软骨数量减少,导致关节软骨退变;关节生物力学及其关节周围环境应力改变引起关节软骨细胞及基质之间的动态平衡破坏,进一步引发关节软骨退变;关节损伤后关节液中细胞炎症介质对关节软骨的作用及介质之间相互作用在关节软骨退变中起着重要作用;关节损伤疾病发展过程及关节软骨代谢均与患者个体基因学关系密切。研究明确关节损伤后各种因素在创伤性关节炎中的作用及各种因素之间的联系,有助于更深入地了解创伤性关节炎的发生机制,更好地制定相关治疗方案,以治愈或延缓创伤性关节炎的发生发展。     

不同应力环境对兔骨髓间充质干细胞修复关节软骨缺损的影响

目的探讨不同应力环境对骨髓间充质干细胞(MSCs)修复关节软骨缺损的影响. 方法将日本大耳白兔15只制成髌骨外侧脱位动物模型,平均分成3组,每组5只:即单纯载体脱位组(对照组)、移植物正常应力组及移植物脱位组.对兔MSCs进行分离、培养,以兔MSCs为种子细胞构建自体组织工程移植物修复关节软骨缺损.6周后处死动物,观察修复组织的成分和结构. 结果术后6周,移植物正常应力组修复组织浅层为软骨组织,甲苯胺蓝染色接近正常关节软骨;深层为软骨下骨,与正常关节软骨结构相似.移植物脱位组为骨组织所修复,缺损周围的正常关节软骨变薄,软骨下血管侵入正常关节软骨内,遗留在股骨髁滑车槽内的移植物在滑车槽正常关节软骨表面形成新生类透明软骨组织.单纯载体脱位组为纤维组织修复. 结论 MSCs修复关节软骨缺损,只有在正常应力状态下修复效果最佳;提示维持负重关节正常的应力刺激,对组织工程软骨修复组织的形成和维持必不可少.     

低磁场MRI在膝关节软骨损伤中的价值

目的分析关节软骨损伤的低磁场MRI、CT和常规X线平片（CR）表现,评价低磁场MRI在关节软骨损伤检查、诊断中的临床应用价值。方法分析5例有膝关节损伤病史,且经膝关节镜手术证实为关节软骨损伤患者的膝关节MRI、CT和CR所见,着重观察关节软骨和软骨游离体,并与关节镜手术结果对照分析。结果 5例关节软骨骨折在MRI上均有表现异常,其中软骨信号异常3例,软骨凹陷2例,软骨连续性中断2例,软骨缺损1例,软骨缺损伴关节内游离软骨体1例。5例均有关节腔、囊积液,2例见轻微骨挫伤。CT仅1例见局部骨皮质毛糙,但均可见不同程度关节囊肿胀;CR除见局部关节周围软组织稍肿胀外,均无异常改变。结论低磁场MRI在关节软骨损伤检查诊断中同样具有很大优势,对急性关节软骨损伤显示准确,可准确评价急性膝关节损伤的范围、程度,决定治疗方案。     

以软骨下骨硬化为靶点的骨关节炎治疗研究进展

骨关节炎(OA)是以关节软骨退变、软骨下骨硬化为主要特征的关节退行性疾病.病理特点为关节软骨变性破坏、软骨下骨硬化或囊性变、关节边缘骨质增生、滑膜病变、关节囊挛缩、韧带松弛或挛缩、肌肉萎缩无力等.近年来研究发现软骨下骨硬化是OA的一个病因,软骨下骨硬化优于并加速软骨退变,进而加速OA的发生发展.抑制或延缓软骨下骨硬化对...     

前交叉韧带重建术后通过二次关节镜可发现明显的关节软骨损伤：系统综述

目的 评估前交叉韧带（anterior cruciate ligament, ACL）重建术后,关节软骨在二次关节镜下的软骨损伤情况。方法 基于PubMed和Embase两大数据库,两名研究人员独立检索2018年3月之前公开发表的关于ACL重建术后二次关节镜下软骨情况的临床研究,并对检索结果的参考文献进行了回顾性检索。两位研究者从研究设计、样本大小、手术技术等方面对所纳入文献进行质量评价,并独立地提取出各个研究的作者、发表时间、病人数量、移植物类型、手术方法、二次关节镜的发现（尤其是软骨的情况和相关影响因素）以及病人的术后表现等数据。结果 纳入10篇研究文献,共计788名在ACL重建术后进行了二次关节镜手术的病人,病人从重建手术到二次关节镜手术的平均时间为19.6个月。在所有研究中,通过二次关节镜均发现了明显的关节软骨退行性改变,以关节软骨的软化和纤维化最为常见;在不同区域的关节软骨中,以髌股关节的软骨损伤最为常见。可能影响ACL重建术后关节软骨改变的因素无确定结论,但多个研究证明半月板的完整性与软骨损伤有关。结论 ACL重建术后,通过二次关节镜,可以发现明显的以软骨的软化和纤维化为主要表现的退行性关节软骨改变,其中髌股关节软骨最易受影响;半月板的不完整可能是关节软骨损害的危险因素之一。     

关节软骨下骨缺损植入不同填充物对关节软骨早期组织形态的影响

目的研究关节软骨下骨缺损行骨移植或骨水泥修复后,关节软骨的早期组织形态学改变。方法 32只新西兰大白兔,随机分为A、B、C、D四组,在胫骨内侧髁距胫骨平台关节面5 mm处,模拟临床膝关节周围良性骨肿瘤局部病灶刮除术,建立关节软骨下骨缺损动物模型,分别填充不同材料修复骨缺损(A组自体髂骨、B组骨水泥、C组骨水泥联合自体髂骨、D组空白对照)。术后4周取造模侧胫骨平台关节软骨行大体观察、HE染色组织学观察,观察关节软骨的早期形态学改变。同时将各组组织学观察结果行软骨退变的病理学Mankin评分,并行统计学分析。结果大体观察:A组与正常关节软骨接近,关节软骨表面光滑平整,浅蓝白色,无裂纹、糜烂及溃疡形成;B组表面粗糙,苍白或灰黄色,滑膜增生,部分有骨赘及软骨塌陷形成;C组表面光滑,发黄,滑膜增生;D组关节软骨表面光滑,颜色较A组稍深,基本与A组相似。组织学HE染色观察:A组6例正常,2例表现为早期退变,Mankin评分为(0.875±1.642)分;B组7例表现为中期退变,1例表现为早期退变,Mankin评分(6.875±0.991)分;C组6例表现为早期退变,2例正常,Mankin评分为(3.250±2.053)分;D组5例表现正常,3例表现为早期退变,Mankin评分为(1.500±2.138)分。A组与D组间及A组与C组间差异无统计学意义(P0.05),B组与A组间及B组与C组间差异有统计学意义(P0.01)。结论在关节软骨下骨缺损程度相同的情况下,自体骨对早期关节软骨的影响最小,骨水泥加重关节软骨的损伤,骨水泥与关节软骨间填充部分自体骨可减轻或延缓骨水泥对关节软骨的损伤。     

关节内骨折软骨修复的实验研究

在27只成年狗的股骨内髁造成关节内骨折,分组给予加压或不加压、加外固定或不加外固定治疗。术后定期取材,用光镜、透射及扫描电镜等观察关节内骨折软骨断端的修复过程、修复组织性质及近骨折线处软骨对损伤的反应。结果表明:软骨缺乏自身修复能力;加压固定只能使软骨断端产生被动粘合;关节内骨折后既软骨有细胞的退变与坏死又有细胞的代谢增加及细胞的增殖;来自髓腔的修复组织既使在光镜下类似透明软骨,在电镜下也为纤维软骨;关节制动,短期细胞出现代谢抑制,久之出现退变。     

Vasopressor hormone response following mesenteric traction during major abdominal surgery

Background : We investigated the vasopressor hormone response following mesenteric traction (MT) with hypotension due to prostacyclin (PGI₂) release in patients undergoing abdominal surgery with a combined general and epidural anesthesia. Methods : In a prospective, randomized, placebo-controlled study we administered 400 mg ibuprofen (i.v.) in 42 patients scheduled for abdominal surgery. General anesthesia was combined with epidural anesthesia (T4-L1). Before as well as 5, 15, 30, 45, and 90 min after MT we recorded plasma osmolality, hemodynamics and measured 6-keto-PGFlα (stabile metabolite of PGI₂), TXB₂ (stabile metabolite of thromboxane A₂) active renin, and arginine vasopressin (AVP) plasma concentrations by radioimmunoassay. Catecholamine levels were assessed by high-pressure liquid chromatography (HPLC) with electrochemical detection. Results : Following MT, arterial hypotension occurred along with a substantial PGI₂ release. This was completely abolished by ibuprofen administration. Although plasma levels of 6-keto-PGF_1α (1133 (708) vs. 60 (3) ng/L, median (median absolute deviation), P=0.0001, placebo vs. ibuprofen) remained significantly elevated, blood pressure was restored within 30 min after MT in the placebo group. At the same point in time plasma concentrations of TXB² (164 (87) vs. 58 (1) ng/L, P=0.0001), epinephrine (46 (33) vs. 14 (6) ng/L, P=0.001), AVP (41 ± (18) vs. 12 (7) ng/L, P=0.0004), and active renin (27 (12) vs. 12 (4) ng/L, P = 0.001) were significantly higher in placebo-treated patients. Conclusion : Under combined general and epidural anesthesia arterial hypotension following MT due to endogenous PGI₂ release is associated with enhanced release of AVP, active renin, epinephrine and thromboxane A₂, presumably contributing to hemodynamic stability within 30 min after MT.     

A Teaspoon Pump for Pumping Blood with High Hydraulic Efficiency and Low Hemolysis Potential

Abstract: Virtually all blood pumps contain some kind of rubbing, sliding, closely moving machinery surfaces that are exposed to the blood being pumped. These valves, internal bearings, magnetic bearing position sensors, and shaft seals cause most of the problems with blood pumps. The original teaspoon pump design prevented the rubbing, sliding machinery surfaces from contacting the blood. However, the hydraulic efficiency was low because the blood was able to "slip around" the rotating impeller so that the blood itself never rotated fast enough to develop adequate pressure. An improved teaspoon blood pump has been designed and tested and has shown acceptable hydraulic performance and low hemolysis potential. The new pump uses a nonrotating "swinging" hose as the pump impeller. The fluid enters the pump through the center of the swinging hose; therefore, there can be no fluid slip between the revolving blood and the revolving impeller. The new pump uses an impeller that is comparable to a flexible garden hose. If the free end of the hose were swung around in a circle like half of a jump rope, the fluid inside the hose would rotate and develop pressure even though the hose impeller itself did not "rotate"; therefore, no rotating shaft seal or internal bearings are required.     

Microspheres Based Detoxification System: A New Method in Convective Blood Purification

Abstract: A variety of protein-bound or hydrophobic substances, accumulating as a result of pathologic conditions such as exogenous or endogenous intoxications, are removed poorly by conventional detoxification methods because of low accessibility (hemodialysis), insufficient adsorption capabilities (hemosorption), low efficiency (peritoneal dialysis), or economic limitations (high-volume plasmapheresis). Combining advantages of existing methods with microspheric technology, a module-based system was designed. Major operating parameters of the latter can be modified to allow for adjustment to individual clinical situations. An extracorporeal blood circuit including a plasmafilter is combined with a secondary high-velocity plasma circuit driven by a centrifugal pump. Different microspheric adsorbers can be combined in one circuit or applied in sequence. Thus, a prolonged treatment can be tailored using specially designed selective adsorber materials. Comparing this system with existing methods (high-flux hemodialysis, molecular adsorbent recycling system), results from our in vitro studies and animal experiments demonstrate the superior efficiency of substance removal.     

Tissue perfusion in relation to cardiac output during continuous positive-pressure ventilation and administration of propranolol or verapamil

Background : Our objective was to determine whether administration of propranolol or verapamil modifies the hemodynamic adaptation to continuous positive-pressure ventilation (CPPV), in particular the regional distribution of cardiac output (CO).
Methods : General hemodynamics and regional blood flows assessed by microsphere technique (15 (μm) were recorded in 16 anesthetized pigs during spontaneous breathing (SB) and CPPV with 8 cm H₂O end-expiratory pressure (CPPV8) before and after intravenous administration of propranolol (0.3 mg · kg⁻¹ followed by 0.15 mg · kg⁻¹ · h⁻¹, n=8) or verapamil (0.1 mg · kg⁻¹ followed by 0.3 mg · kg⁻¹ · h⁻¹, n=8).
Results : CPPV8 depressed CO by 25% without shifts in its relative distribution with the exception of a noteworthy increase in adrenal perfusion. Propranolol increased arterial blood pressure, and due to a fall in heart rate, CO dropped by 25%. The kidneys and, to a lesser extent, the splanchic region and central nervous system received increased fractions of the remaining CO at the expense of skeletal muscle flow. Similar patterns were seen during SB and CPPV8 such that the combination of propranolol and CPPV8 depressed CO by 50%. The circulatory effects of verapamil were less evident but myocardial perfusion tended to increase.
Conclusions : The combination of propranolol or verapamil with CPPV does not result in any specific hemodynamic interaction in anesthetized pigs, except that the combined effect of propranolol and CPPV may severely reduce CO.     

Bariatric Surgery in Some "Central and East-European (former Eastern bloc)"Countries - Current Status and Prediction for the Next Millennium

Background: Obesity is increasing globallly, including in the formerly "Eastern Bloc" countries. Methods: A survey was made of obesity and bariatric surgery. Results: In the 8 East and Central European countries studied, with total population 300 million, roughly 43% of the population was overweight (BMI 25-30), 23% obese (BMI > 30), with about 15 million people morbidly obese (BMI > 40). From 0-10 morbidly obese individuals/100,000/year undergo bariatric surgery. Conclusion: Most countries were found to provide inadequate treatment for obesity.The majority of the morbidly obese are not treated effectively. However, health-care awareness of obesity and bariatric surgeons are slowly increasing.     

Volatile anaesthetics reduce adhesion of blood platelets under low-flow conditions in the coronary system of isolated guinea pig hearts

Background : Inhibitory effects of volatile anaesthetics on platelet aggregation have been demonstrated in several studies. However, the influence of volatile anaesthetics on intracoronary platelet adhesion has not been elucidated so far.
Methods : Isolated hearts of guinea pigs were perfused with buffer in the absence or presence of volatile anaesthetics (0.5 and 1 MAC) at constant coronary flow rates of 5 ml/min for 25 min, then 1 ml/min for 30 min and again 5 ml/min for 10 min. Before, during and after low-flow perfusion, a bolus of human platelets was applied into the coronary system. To simulate thrombogenic conditions, 0.3 U/ml human thrombin was infused during low-flow perfusion and reperfusion. The number of platelets sequestered to the endothelium was calculated from the difference between coronary in- and output of platelets. The myocardial production of lactate and consumption of pyruvate and coronary perfusion pressure were also determined.
Results : At a flow rate of 5 ml/min only about 3% of the applied platelets did not emerge from the coronary system, in any group. In contrast, 13.1±1.2% (mean±SEM) of infused platelets became adherent in low-flow perfusion in the control group without anaesthetic. The adherence was reduced with each 1 MAC isoflurane (to 6.2±1.2%), sevoflurane (to 4.4±0.9%) or halothane (to 3.2±1.5%) (each P <0.05 vs. control). Volatile anaesthetic, 0.5 MAC, did not inhibit platelet adhesion to a statistically significant extent in any case. Perfusion pressure and metabolic parameters were not statistically different between the control and the hearts exposed to anaesthetics.
Conclusion : Volatile anaesthetics in a concentration of 1 MAC can reduce the adhesion of platelets in the coronary system under reduced flow conditions. This action does not arise from vasodilation or inhibition of ischaemic stress.     

Synergistic interaction between the effects of propofol and midazolam with fentanyl on phrenic nerve activity in rabbits

Background: It has been shown that the depressive effects of both propofol and midazolam on consciousness are synergistic with opioids, but the nature of their interactions on other physiological systems, e. g. respiration, has not been fully investigated. The present study examined the effect of propofol and midazolam alone and in combination with fentanyl on phrenic nerve activity (PNA) and whether such interactions are additive or synergistic. Methods: PNA was recorded in 27 anaesthetised and artificially ventilated rabbits. In three groups, propofol, fentanyl and midazolam were administered intravenously in incremental doses to construct dose-response curves for the depressant effects of each one on PNA. In another two groups, the effect of pretreatment with either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. on the effects of propofol and fentanyl respectively on PNA were studied. Results: Propofol and fentanyl caused a dose-dependent depression of PNA with complete abolition at the highest total doses of 16 mg · kg^?1 i. v. and 32 μg · kg^?1 i. v., respectively. In contrast, midazolam in incremental doses to a total of 0.8 mg · kg^?1 reduced mean PNA by 63%, but approximately 12% of PNA remained at a total dose as high as 6.4 mg · kg^?1. The mean ED₅₀s, calculated from dose-response curves, were 5.4 mg · kg^?1, 3.9 μg · kg^?1 and 0.4 mg · kg^?1 for propofol, fentanyl and midazolam, respectively. Initial doses of either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. acted synergistically with subsequent doses of either propofol or fentanyl to abolish PNA at total doses of 8 mg · kg^?1 and 8 μg · kg^?1, respectively. Conclusion: Fentanyl has a synergistic interaction with both propofol and midazolam on PNA and hence potentially on respiration.     

Influence of dopexamine hydrochloride on haemodynamics and regulators of circulation in patients undergoing major abdominal surgery

Background: Catecholaminergic support is often used to improve haemodynamics in patients undergoing major abdominal surgery. Dopexamine is a synthetic vasoactive catecholamine with beneficial microcirculatory properties. Methods: The influence of perioperative administration of dopexamine on cardiorespiratory data and important regulators of macro- and microcirculation were studied in 30 patients undergoing Whipple pancreaticduodenectomy. The patients received randomized and blinded either 2 μg · kg^?1 · min^?1 of dopexamine (n=15) or placebo (n=15, control group). The infusion was started after induction of anaesthesia and continued until the morning of the first postoperative day. Endothelin-1 (ET-1), vasopressin, atrial natriuretic peptide (ANP), and catecholamine plasma levels were measured from arterial blood samples. Measurements were carried out after induction of anaesthesia, 2 h after onset of surgery, at the end of surgery, 2 h after surgery, and on the morning of the first postoperative day. Results: Cardiac index (CI) increased significantly in the dopexamine group (from 2.61±0.41 to 4.57±0.78 1 · min^?1 · m^?2) and remained elevated until the morning of the first postoperative day. Oxygen delivery index (DO₂I) and oxygen consumption index (VO₂I) were also significantly increased in the dopexamine group (DO₂I: from 416±91 to 717±110 ml/m² · m²; VO₂I: from 98±25 to 157±22 ml/m² · m²), being significantly higher than in the control group. pHi remained stable only in the dopexamine patients, indicating adequate splanchnic perfusion. Vasopressive regulators of circulation increased significantly only in the untreated control patients (vasopressin: from 4.37±1.1 to 35.9±12.1 pg/ml; ET-1: from 2.88±0.91 to 6.91±1.20 pg/ml). Conclusion: Patients undergoing major abdominal surgery may profit from prophylactic perioperative administration of dopexamine hydrochloride in the form of improved haemodynamics and oxygenation as well as beneficial influence on important regulators of organ blood flow.     

A comparison of the inhibitory effects of four volatile anaesthetics on the metabolism of chlorzoxazone, a substrate for CYP2E1, in rabbits

Background: Halothane inhibits in vitro and in vivo activity of cytochrome P-450 (CYP) 2E1. There are several fluorinated volatile anaesthetics besides halothane, and most of them are defluorinated by CYP2E1. It is unclear whether other fluorinated anaesthetics inhibit the in vivo activity of CYP2E1.
Methods: We compared the inhibitory effects of therapeutic concentrations of four inhalational anaesthetics, halothane, enflurane, isoflurane, and sevoflurane, on chlorzoxazone metabolism in rabbits receiving artificial ventilation.
Results: All four inhalational anaesthetics decreased arterial blood pressure and increased plasma chlorzoxazone concentration. However, no significant differences in the plasma chlorzoxazone concentration were found between the four anaesthetics. The estimated chlorzoxazone clearance increased after beginning inhalation with all four agents, but no significant difference in clearance was noted between agents.
Conclusions: At therapeutic concentrations, the in vivo inhibitory effect on chlorzoxazone metabolism was similar for all four inhalational anaesthetics examined, even though their chemical characteristics and extent of hepatic metabolism differ considerably.     

Systemic analgesia adapted to the children's condition

A concept of balanced analgesia using nonsteroidal anti-inflammatory drugs (NSAIDs), paracetamol (acetaminophen), opioids, and corticosteroids can also be used in patients with pre-existing illnesses. NSAIDs are the most effective treatment for acute pain of moderate intensity in children; however, these drugs should be avoided in patients at increased risk for serious side effects, e.g. patients with renal impairment, bleeding tendency, or extreme prematurity. NSAIDs can be given with minimal risks to the younger child with mild to moderate asthma, and, in these patients, the use of steroids can be encouraged; in addition to their antiemetic and analgesic action, a beneficial effect on asthma symptoms can be expected. In the non-intubated child with cerebral trauma, exaggerated sedation caused by opioids and increased bleeding tendency caused by NSAIDs must be avoided. In neonates and small infants, the oral administration of sucrose or glucose is helpful to minimize pain reaction during short uncomfortable interventions.