腹腔镜下妇科肿瘤切除术中二氧化碳气腹对患者脑血流的影响

目的 观察妇科肿瘤患者腹腔镜手术期间二氧化碳(CO2)气腹对患者脑血流的影响.方法 选择妇科肿瘤行腹腔镜手术的患者40例,美国麻醉医师协会(ASA)分级Ⅰ～Ⅱ级,无心、脑系统疾病,于气腹前、气腹后头低臀高位20 min分别采取桡动脉和颈内静脉血,测定动脉血氧分压(PaO2)、动脉血二氧化碳分压(PaCO2)、动脉血氧饱和度(SaO2)、颈内静脉血氧分压(PjvO2)和颈内静脉血氧饱和度(SjvO2)等值.结果 气腹前SjvO2为(66±7)％,气腹后20min的SjvO2为(84±6)％,颈内静脉血氧含量(CjvO2)气腹前为(9.4±1.6)％,气腹后20 min为(11.6±1.8)％,PaCO2气腹前为(4.2±0.4) kPa,气腹后20 min为(5.3±0.4) kPa,均显著增加(P＜0.01),脑动静脉血氧含量差(Ca-jvDO2)气腹前为(5.1±1.2)％,气腹后为(2.4±0.9)％,显著减少(P＜0.01).结论 妇科肿瘤患者腹腔镜手术期间,CO2气腹对脑循环产生显著影响,脑血流(CBF)显著增加,Ca-jvDO2明显减少.这种变化提示可能存在脑细胞缺氧.     

目标导向液体治疗对脑膜瘤切除术患者脑氧代谢的影响

目的比较目标导向液体治疗(GDFT)与常规输液方法对脑膜瘤切除术患者围术期脑氧代谢的影响。方法择期行仰卧位脑膜瘤切除术患者28例,随机分为两组:GDFT组(G组,n=15)和常规输液组(C组,n=13)。G组补偿性扩容量于麻醉诱导前30min内补充,术中以胸腔内血容积指数(ITBI)在800～1000ml/m2范围内为导向目标。采集动脉血与颈内静脉球部血检测血氧饱和度(SaO2、SjvO2)血氧分压(PaO2、PjvO2)、血氧含量(CaO2、CjvO2)、脑氧摄取率(CERO2)及乳酸含量(aLac、jvLac)。结果与诱导前比较,术中两组CaO2与CjvO2明显下降,而aLac与jvLac明显上升(P<0.05),且术中C组aLac和jvLac明显高于G组(P<0.05)。结论脑膜瘤切除术围术期以ITBI实施GDFT,能稳定心指数,维持有效循环血容量,从而保证脑灌注、改善微循环,降低脑乳酸生成率,不影响脑氧供需平衡。     

低水平呼气末正压通气对全身麻醉腹腔镜胃癌根治术患者脑血流动力学的影响

目的 观察呼气末正压通气对全身麻醉腹腔镜胃癌根治术患者脑血流动力学的影响.方法 择期行全身麻醉腹腔镜胃癌根治术的患者80例,美国麻醉医师协会(ASA)分级Ⅰ～Ⅱ级,采用随机数字表法分为A、B组,每组40例.A组通气参数:潮气量(VT)8ml/kg,呼吸频率(RR) 12次/分,呼气末正压(PEEP)5 cmH2O(1 cmH2O=0.098 kPa).B组通气参数:VT 8 ml/kg,RR 12次/分.于气腹前(T0)、气腹后30 min(T1)、气腹后1 h(T2)、气腹后2h(T3)时记录大脑中动脉平均血流速度(Vm)、平均动脉压(MAP)、心率(HR)、经皮测血氧饱和度(SpO2)、呼气末二氧化碳分压(PetCO2)变化,分别抽取各时点桡动脉血、颈内静脉球部血进行血气分析,记录动脉血氧分压(PaO2)、动脉血二氧化碳分压(PaCO2)、动脉血氧饱和度(SaO2)、血红蛋白(Hb)浓度;颈内静脉血氧分压(PjvO2)和颈内静脉血氧饱和度(SjvO2),根据Fick公式分别计算脑动脉和颈内静脉血氧含量(CjvO2)及其差值(Da-jvO2).结果 与气腹前比较,两组气腹后Vm、SjvO2、PaCO2在各时间点明显升高(P＜0.05).但是A组Vm、SjvO2、PaCO2的上升趋势较B组更为缓和,A组PaCO2在T1、T2分别为(35.5±2.7)、(40.7±3.5)mmHg,明显低于B组的(39.9±3.1)、(49.4±4.7)mmHg(P＜0.05),而Vm在T3为(68.9±8.1)cm/s,明显低于B组的(87.9 ±9.6) cm/s(P ＜0.05).与气腹前比较,气腹后2h两组Da-jvO2明显下降(P＜0.05),组间比较,A组下降幅度明显大于B组(P＜0.05).结论 低水平呼气末正压通气对全身麻醉腹腔镜胃癌根治术患者手术期间能有效降低术中的高二氧化碳血症,维持患者脑血流动力学的稳定,从而改善脑的过度灌注状态,改善患者的脑血流量和脑氧供需平衡.     

盐酸戊乙奎醚对多器官功能障碍综合征病人脑氧供需平衡的影响

目的观察盐酸戊乙奎醚对多器官功能障碍综合征(MODS)病人脑氧供需平衡的影响。方法选择50例发病前无肝脑功能障碍由外科疾病并发MODS的病人,按数字随机法分为观察组(T组,n=35):除综合治疗外,另予盐酸戊乙奎醚2 mg,q12 h,肌注,首量加倍;对照组(C组,n=15):除未使用盐酸戊乙奎醚外,其余治疗方案同T组。监测MODS期间病人动脉血氧含量(CaO2)、颈内静脉血氧饱和度(SjvO2)、氧含量(CjvO2)及动脉和颈内静脉血乳酸盐含量(ABL和JVBL),并计算脑氧摄取率(CERO2),桡动脉颈内静脉血乳酸盐差值(DLA-V)。结果与30 min时比较,C组CjvO2、SjvO2、ABL、JVBL、DLA-V进行性增高,CERO2进行性降低(P<0.05,P<0.01)。与C组比较,T组肌注盐酸戊乙奎醚后48、72 h时CjvO2、SjvO2、ABL、JVBL、DLA-V显著降低,CERO2显著增高(P<0.05,P<0.01)。结论MODS状态下,存在以组织缺氧为主的脑氧供需失衡;盐酸戊乙奎醚可明显改善脑组织缺氧,从而纠正脑氧供需失衡。     

不同麻醉对腹腔镜胆囊切除术患者二氧化碳气腹时脑氧合的影响

目的 观察不同麻醉对腹腔镜胆囊切除术患者二氧化碳气腹时脑氧合的影响。方法 腹腔镜胆囊切除术患者60例，ASAⅠ级或Ⅱ级，随机分为3组（n=20）：异氟醚组（Ⅰ组）、硬膜外复合异氟醚组（Ⅱ组）和硬膜外复合异丙酚组（Ⅲ组）。分别于气腹前即刻、气腹10、30min取桡动脉血和颈内静脉球部静脉血行血气分析，记录动脉血氧分压（PaO2）、动脉血二氧化碳分压（PaCO2）、动脉血氧饱和度（SaO2）、血红蛋白（Hb）浓度、颈内静脉血氧分压（PjvO2）和颈内静脉血氧饱和度（SjvO2）。根据Fick公式分别计算脑动脉和颈内静脉血氧含量及脑动静脉血氧含量差（Da-jvO2）。结果 与气腹前即刻比较，Ⅰ组、Ⅱ组气腹10、30min时SjvO2升高、Da-jvO2降低（P〈0．01）;与Ⅲ组比较，气腹10、30min时Ⅰ组、Ⅱ组SjvO2升高、Da-jvO2降低（P〈0.05）;与Ⅱ组比较，气腹10、30 min时Ⅰ组SjvO2升高、Da-jvO2降低（P〈0．05）。结论 硬膜外复合异丙酚静脉麻醉可改善术中脑组织的氧合，是腹腔镜手术患者较适宜的麻醉方法。     

改良抬胸Trendelenburg位对腹腔镜结直肠癌根治术老年患者脑氧代谢和早期术后认知功能的影响

目的 观察改良抬胸位对腹腔镜结直肠癌根治术老年患者的脑氧代谢和早期术后认知功能的影响.方法 择期拟行腹腔镜结直肠癌根治术患者80例,年龄60～82岁,体重44～69 kg,ASA分级Ⅰ、Ⅱ级,性别不限,按随机数字表法分为2组(每组40例):M组加用定制体位垫使患者呈改良抬胸Trendelenburg体位(简称T位),T组采用T位.于常规全身麻醉插管后平卧位5 min(T1),气腹改良抬胸T位/T位即刻(T2)、30 min(T3)、60 min(T4)和90 min(T5),气腹放气平卧位15 min(T6),分别采集桡动脉和颈静脉球血样,记录血气分析、血糖、乳酸值及MAP等,计算脑动静脉氧含量差(arteriovenous O2 content difference,Ca-jv DO2)及脑葡萄糖摄取(arteriovenous O2 glucose difference,Da-jvglu)等;并于麻醉前,麻醉结束后2、6、24、48、72 h时,采用简易智能量表(mini-mental state exam,MMSE)进行认知功能评分.结果 与T1时比较,两组患者动脉血二氧化碳分压(arterial partial pressure carbon dioxide,PaCO2)在T3-6时均显著升高,MAP在T2时显著降低,两组患者在T3～5时颈静脉球血氧分压(jugular venous partial pressure oxygen,PjvO2)显著升高,T4-5时颈静脉球血氧饱合度(jugular venous oxygen saturation,SjvO2)显著升高(P＜0.05);M组MAP在T4-6时显著升高,T组在T3-6时显著升高(P＜0.05);T组在T6时SjvO2[(75±9)％]显著升高,T5时Caa-jvDO2[(5.2±1.5)％]显著下降,而颈静脉球血乳酸(jugular venous lactate,Lacjv)[(2.0±0.5) mmol/L]显著上升(P＜0.05).与T组比较,M组MAP在T4-6时上升较慢,Ca-jvDO2[(5.9±1.6)％]在T5时无明显下降,Da-jvglu气腹前后差异无统计学意义(P＞0.05),SjvO2 [(75±9)％]和Lacjv[(1.5±0.5) mmol/L]无显著上升,而PaCO2[(34±3) mmHg(1 mmHg=0.133 kPa)]在T6时显著降低(P＜0.05).与T组比较,M组麻醉结束后6、24 h时MMSE评分明显较高;与麻醉前比较,麻醉结束后2h两组MMSE评分显著降低(P＜0.05).结论 改良抬胸T位缓解了气腹后期脑氧供需失衡,麻醉结束后24 h内认知功能下降的发生率明显降低,有利于较长时间手术的安全.     

丙泊酚或异氟醚用于妇科腹腔镜手术时脑氧供需平衡的变化

目的 探讨丙泊酚或异氟醚麻醉下头低位气腹期间脑氧供需平衡及能景代谢的改变.方法 24例ASA Ⅰ或Ⅱ级妇科腹腔镜手术患者,随机均分为丙泊酚组和异氟醚组.两组均在局麻下行颈内静脉逆行穿刺置管达颈静脉球,行桡动脉置管.分别以丙泊酚和异氟醚麻醉诱导及维持,术中维持通气条件不变(潮气量7 ml/kg,频率 14次/分).记录麻醉前(T1)、气腹前(T2)、气腹10 min(T3),20 min(T4)及60 min(T5)时桡动脉及颈I静脉球血气、血糖、乳酸以及呼气二氧化碳分压(PETCO2)等,计算脑葡萄摄取(Da-jglu)、动静脉氧含量差(Da-Jo2)及颈静脉球乳酸含量(Jlac)等.结果 T3～T5时两组颈静脉球血氧饱和度(S1O2)、PETCO2较T2时显著升高(P<0.05或P<0.01);Da-Jo2均显著降低(P<0.05或P<0.01);而Da-jglu及Jlac差异无统计学意义.T2～T5时丙泊酚组S1O2显著低于异氟醚组,T2、T4时Da-Jo2高于异氟醚绀(P<0.05).结论 丙泊酚或异氟醚麻醉下头低位气腹期间脑氧供大于氧需,异氟醚麻醉下脑过度灌注更明显,但未出现能量代谢障碍.     

后腹腔镜手术CO2气腹对脑氧供需平衡的影响

目的探讨后腹腔镜CO2气腹对脑氧供需平衡的影响. 方法选择后腹腔镜下肾及肾上腺肿瘤切除术20例,ASAⅠ～Ⅱ级,分别于气腹前,气腹后10、30、60 min和关气腹后30 min,抽取颈静脉球血和桡动脉血进行血气分析,比较不同时点动脉血PH(aPH )、颈静脉球PH(jvPH)、动脉血二氧化碳分压(PaCO2)、动脉血糖(aGS)、动脉血乳酸(aLac)、颈内静脉血氧分压(PjvO2)、颈内静脉血氧饱和度(SjvO2)、颅内动静脉氧含量差(AjvDO2)、颈内静脉血二氧化碳分压(PjvCO2)、血糖(jvGS)和乳酸(jvLac)的变化. 结果与气腹前比较,气腹后各时间点aPH、jvPH显著降低(P＜0.05);PaCO2、PjvCO2气腹后各时间点与气腹前相比显著升高(P＜0.05);AjvDO2气腹后各时点与气腹前相比显著下降(P＜0.05);jvLac气腹后各时间点与气腹前相比有降低趋势,但无统计学差异(P＞0.05);aGS、 jvGS气腹前后无显著变化(P＞0.05). 结论后腹腔镜手术期间,脑血流量显著增加,未发现脑无氧代谢增加的证据.     

盐酸戊乙奎醚对心肺转流心瓣膜置换术患者脑氧代谢功能的影响

目的 观察盐酸戊乙奎醚对心肺转流(CPB)心瓣膜置换术脑氧代谢功能的影响.方法 60例行心瓣膜置换术患者,随机均分为三组:麻醉诱导后Ⅰ组、Ⅱ组分别静脉注射盐酸戊乙奎醚0.04 mg/kg和0.02 mg/kg,Ⅲ组注射等容量生理盐水.采集诱导后即刻(T1)、阻断升主动脉前(T2)、心脏复跳后(T3)、停止CPB(T4)及术毕(T5)桡动脉及颈静脉球部血样行血气分析,记录并计算颈内动脉、静脉乳酸含量及差值(Laca、Lacjv、Laca-jv)、血氧分压及差值(PaO、PjvO2、Pa-jvO2)、二氧化碳分压及差值(PaCO2、PjvCO2、Pa-jvCO2)、血氧饱和度及差值(SaO2、SjvO2、Sa-jvO2)、颈内动脉、静脉血氧含量及差值(CaO2、CjvO2、Ca-jvO2)及脑氧摄取率(CEO2).结果 与T1时比较,T3～T5时三组Lacjv、Laca-jv均增高,T5时三组Pa-jvO2增高(P＜0.05).Ⅰ组的Lacjv、Laca-jv低于Ⅱ组和Ⅲ组,而SjvO2、Sa-jvO2高于Ⅱ组和Ⅲ组(P＜0.05);T3～T5时Ⅱ组Lacjv、Laca-jv低于Ⅲ组(P＜0.05).T4、T5时Ⅲ组Pa-jvO2诋于Ⅰ组和Ⅱ组(P＜0.05).与T1时比较,T3～T5时三组CaO2、CjvO2、CEO2值均明显降低(P＜0.05).T3～T5时Ⅰ组Ca-jvO2、CFO2高于Ⅱ组、Ⅲ组(P＜0.05).结论 盐酸戊乙奎醚可有效提高CEO2,增加脑组织氧含量并促进脑能量代谢,对脑组织氧供需平衡的维护起到积极作用.     

过度通气对糖尿病病人脑氧供需平衡的影响

目的研究过度通气对手术中糖尿病病人脑氧供需平衡的影响。方法择期全麻下行腹部手术病人30例,2型糖尿病组15例(DM组),非糖尿病组15例(对照组,C组),所有病人术中均随机分别进行三种不同模式机械通气：正常通气量通气[模式I,动脉血二氧化碳分压(PaCO2)维持在35～40mmHg]、轻度过度通气(模式Ⅱ,PaCO2维持在30～35mmHg)、中度过度通气(模式Ⅲ,PaCO2维持在25～30mmHg),检测两组病人在三种不同通气模式下动脉血氧饱和度(SaO2)、动脉血氧分压(PaO2)、动脉血乳酸盐浓度(ABL)、颈内静脉血氧饱和度(SjvO2)、颈内静脉血氧分压(PjvO2)和颈内静脉血乳酸盐浓度(JVBL),并计算病人在不同通气模式下动脉血氧含量(CaO2)、颈内静脉血氧含量(CjvO2)、氧摄取率(CERO2)和颈内静脉与桡动脉血乳酸差(DL A-v)。结果两组病人CjvO2和SjvO2在以模式Ⅲ通气时均明显低于以模式Ⅰ通气,CERO2在模式Ⅲ通气时明显高于以模式Ⅰ通气。DM组病人JVBL和DI A—v在模式Ⅲ通气时均明显高于以模式Ⅰ通气。中度过度通气时,DM组病人DL A-v高于C组。结论中度过度通气可影响2型糖尿病病人脑氧供需平衡,导致大脑组织乏氧代谢增加。     

Histochemical and contractile properties of striated muscles of urethra and levator ani of dogs and sheep

AIMS: To understand their possible importance in long- and short-term control of continence, some properties of the striated muscles of the urethra and pelvic floor (levator ani) of dogs and sheep were investigated, especially fiber types and contractile characteristics. MATERIALS AND METHODS: Striated muscles of urethra and levator ani of 29 male and 6 female dogs and 11 male and 6 female sheep were removed and cut into strips. Some strips were frozen and stained for ATPase at pH 9.4 and 4.3 for fiber typing; others were set up in an organ bath to study contractile responses to nerve stimulation. RESULTS: All muscles contained both type I (slow) and type II fibers, ranging from 97% type II in female greyhound urethra to 60% in female sheep levator ani. For each muscle, there were fewer type II muscles in sheep than in dog. The diameters of the urethral fibers were about 60% of the levator ani in dogs and 34% in sheep. Contraction of the urethral muscle was faster than for levator ani and declined to about 80% of the peak, 500 msec after the beginning of stimulation at 20 Hz. The levator ani contraction rose to a steady level as long as stimulation continued. CONCLUSIONS: Both the levator ani and urethral striated muscles contain slow and fast fiber types. The levator ani muscles are capable of sustained contraction with rapid onset which will produce long-term closure of the urethra. The circular urethral muscle contraction was faster but less well maintained.     

Incorporation and release of85Sr and14C-proline-hydroxyproline in mineral and collagen of bone and incisor teeth of growing rats

The extent to which exchange and reutilization processes of mineral tracers affect skeletal mineral accretion and resorption measurements was evaluated by comparing the rates of appearance and disappearance of⁸⁵Sr and¹⁴C-proline-hydroxyproline in bones and teeth in growing rats for 12 days following simultaneous parenteral injection of these tracers. Expressions for the relative rates of collagen synthesis and breakdown, which unlike mineral metabolism are considered not to be complicated by exchange phenomena, were based on¹⁴C-proline conversion to¹⁴C-hydroxyproline; the specific activity of the latter was determined. Both the mineral and the collagen specific activities reflected the rates and patterns of growth of the samples assayed; rapid growth and a short interval of time between formation and resorption of tissue in themetaphyseal bone which contains the cartilagineous growth plate, slow growth and an interval of time between formation and resorption of tissue indiaphyseal bone and incisor teeth which is longer than the 12 days of the experiment. However, in metaphyseal bone the specific activity collagen/mineral ratio dropped by one half during the 4–12 day interval in contrast to diaphyseal bone and incisor teeth in which no change in this ratio was observed during this period of time. The data indicate that collagen in the metaphyseal growth zone is removed by resorption before it has become fully mineralized, and that exchange is a relatively unimportant factor in the long term kinetics of bone mineral.

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Zusammenfassung Das Ausmaß, bis zu welchem Austausch- und Wiederverwendungsprozesse der mineralen Tracer die Messungen des mineralen Skelett-Auf- und Abbaues beeinflussen können, wurde ausgewertet; zu diesem Zweck wurde die Geschwindigkeit des Auftretens und Verschwindens von⁸⁵Sr und von¹⁴C-Prolin-Hydroxyprolin in Knochen und Zähnen von wachsenden Ratten während der 12 auf die simultane parenterale Injektion dieser Tracer folgenden Tage verglichen.Der Ausdruck für die relative Geschwindigkeit des Kollagen-Auf- und Abbaues, bei welchem im Gegensatz zum Mineralmetabolismus kein Mitwirken des Austauschphänomens vermutet wird, basiert auf der Umwandlung von¹⁴C-Prolin zu¹⁴C-Hydroxyprolin; die spezifische Aktivität des letzteren wurde bestimmt.Aus der spezifischen Aktivität des Minerals sowie jener des Kollagens konnten die Geschwindigkeit und die Art des Wachstums der untersuchten Proben ersehen werden, d.h.schnelles Wachstum und ein kurzes Zeitintervall zwischen Bildung und Resorption des Gewebes imKnochen der Metaphyse, die auch die knorpelige Wachstumsplatte enthält, und andererseitslangsames Wachstum und längeres Zeitintervall (länger als die 12 Tage des Experimentes) zwischen Bildung und Resorption des Gewebes imKnochen der Diaphyse und in den Schneidezähnen. Immerhin fiel die spezifische Aktivität des Kollagen/Mineral-Anteils im Knochen der Metaphyse während dem 4–12tägigen Zeitintervall auf die Hälfte, im Gegensatz zum Knochen der Diaphyse und der Schneidezähne, bei welchen während dieser Zeitspanne kein Unterschied in diesem Verhältnis beobachtet wurde.Diese Ergebnisse zeigen, daß Kollagen in der Wachstumszone der Metaphyse durch Resorption verschwindet, bevor es ganz mineralisiert ist, und daß der Austausch ein relativ unwichtiger Faktor in der Kinetik auf lange Sicht des Knochenminerals ist.

     

Instrumented ligamentotaxis and stabilization of compression and burst fractures of dorsolumbar and mid-lumbar spines

Background:

Controversy continues regarding the best treatment for compression and burst fractures. The axial distraction reduction utilizing the technique employing the long straight rod or curved short rod without derotation to reduce fracture are practised together with short segment posterolateral fusion (PLF). Effects of the early postoperative mobilization without posterolateral fusion on reduction maintenance and fracture consolidation were not evaluated so far. The present prospective study is designed to assess the effectiveness of i) reduction and restoration of sagittal alignment, ii) no posterolateral fusion on the reduced, fractured vertebral body and injured disc, iii) fracture consolidation and iv) the fate of the unfused cephalad and caudal injured motion segments of the fractured vertebra.

Materials and Methods:

The study includes 15 Denis burst and two Denis type D compression fractures between T₁₂ and L₃. The lordotic distraction technique was used for ligamentotaxis utilizing the contoured short rods and pedicle screw fixator. Three vertebrae including the fractured one were fixed. The patients after surgery were braced for ten weeks with activity restriction for 2-4 weeks. The patients were evaluated for change in vertebral body height, sagittal curve, reduction of retropulsion, improvement in neural deficit. The unfused motion segments, residual postoperative pain and bone and metal failure were also evaluated.

Results:

The preoperative and postreduction percentile vertebral heights at, zero (immediate postoperative), at three, six and 12 months followup were 62.4, 94.8, 94.6, 94.5 and 94.5%, respectively. The percentages of the intracanal fragment retropulsion at preoperative, and postoperative at zero, 3, 6 and 12 months followup were 59.0, 36.2,, 36.0, 32.3, and 13.6% respectively.The preoperative and postreduction percentile loss of the canal dimension and at zero, three, six and 12 months were 52.1, 45.0, 44.0, 41.0 and 29% respectively suggesting that the under-reduced fragment was being resorbed gradually by a remodeling process. The mean initial kyphosis of 33° became mean 2° immediately after reduction and mean 3° at the final followup. The fractured vertebral bodies consolidated in an average period of ten weeks (range 8-14 weeks). The restored disc heights were relatively well maintained throughout the observation period. All paraparetic patients recovered neurologically. There were no postoperative complications.

Conclusion:

Instrument-aided ligamentotaxis for compression and burst fractures utilizing the short contoured rod derotation technique and the instrumented stabilization of the fractured spine are found to be effective procedures which contribute to the fractured vertebral body consolidation without recollapse and maintain the motion segment function.     

Principles and Practice of Hemofiltration and Hemodiafiltration

There is growing interest in the convective dialysis therapies, hemofiltration (HF) and hemodiafiltration (HDF). Both require dialysis membranes which are highly permeable to solutes as well as fluid, and in both cases large volumes of ultrafiltration are the condition for convective transport. In HDF the convection is combined with diffusion, and as a consequence, maximum clearance over the entire molecular weight spectrum is achieved. Optimal forms of HDF provide urea clearance 10–15% higher than the corresponding diffusive mode. The larger the solute, the greater is the impact of convection, and β₂-microglobulin (β₂m) levels may be up to 70% reduced. Traditional postdilution HF provides high clearance of medium sized and large molecules. Satisfactory clearance of small solutes requires blood flows in excess of 500 ml/min. With access to practically unlimited volumes of substitution solution through on-line ultrafiltration, predilution HF can now be used. This increases the clearance of small solutes to an acceptable range. For HDF as well as HF, large patient populations consistently treated for longer periods of time are needed to make valid outcome comparisons with other therapies.     

骨折不愈合与延迟愈合的成因与治疗

目的探讨骨折不愈合与延迟愈合的成因、报肯治疗的方法与设果。方法对1990年7月～2004年12月间收治的107例骨折不愈台、54例骨折延迟愈合2例先天性胫骨骨不连进行回顾性研究，分析原因，随访治疗结果。18例延迟愈合行保守治疗，本组其他145例行手术治疗，结果除2例先天性胫骨骨不连外，其余161例的成因中均有医源性因素。10例失去随访，153例平均随访17（6-28）个月，骨折均获骨性连接，愈合时间平均10（6-14）个月，肢体功能恢复良好，结论医源性技术缺陷是骨折不愈合与延迟愈合的主要原因，针对各种不同因素进行合理治疗可获得满意效果。     

Recognition and management of phaeochromocytoma and paraganglioma

Phaeochromocytomas and paragangliomas (PPGL) are catecholamine-secreting neuroendocrine tumours arising from the chromaffin cells in the adrenal medulla. These tumours may be identified incidentally, as part of a work-up for multiple endocrine neoplasia or following haemodynamic surges during unrelated procedures. Advances in perioperative management and improved management of intraoperative haemodynamic instability have significantly reduced surgical mortality from around 40% to less than 3%. Surgery is the definitive treatment in most cases and laparoscopic resection where possible is associated with improved outcomes. Anaesthetic management of PPGL cases represents a unique haemodynamic challenge both before and after tumour resection. In this article we describe the physiology of these tumours, their diagnosis, preoperative optimization methods, intraoperative anaesthetic management and management of postoperative complications.     

Physiology and pharmacology of nausea and vomiting

Nausea and vomiting are both very unpleasant experiences. The physiology is poorly understood; however, understanding what we do know is key to tailoring a preventative or therapeutic antiemetic regime. There are two key sites in the central nervous system implicated in the organization of the vomiting reflex: the vomiting centre and the chemoreceptor trigger zone. There are five key neurotransmitters involved in afferent feedback to these areas. These are histamine (H₁ receptors), dopamine (D₂), serotonin (5-HT₃), acetyl choline (muscarinic) and neurokinin (substance P). Postoperative nausea and vomiting will occur in around one-third of elective patients who have no prophylaxis. This can result in many detrimental effects including patient dissatisfaction, unplanned admission and prolonged recovery. It is therefore essential that clinicians understand how they can prevent and treat nausea and vomiting using either a single agent or a combination of antiemetics to target relevant receptors. Commonly used drugs include antihistamines, dopamine antagonists, serotonin antagonists and steroids. More novel agents are being developed such as aprepitant, a neurokinin receptor antagonist, palonosetron, a 5HT₃ receptor antagonist and nabilone, a synthetic cannabinoid.     

Physiology and pharmacology of nausea and vomiting

Nausea and vomiting are both very unpleasant experiences. The physiology is poorly understood; however, understanding what we do know is key to tailoring a preventative or therapeutic antiemetic regime. There are two key sites in the central nervous system implicated in the organization of the vomiting reflex: the vomiting centre and the chemoreceptor trigger zone. There are five key neurotransmitters involved in afferent feedback to these areas. These are histamine (H₁ receptors), dopamine (D₂), serotonin (5-HT₃), acetyl choline (muscarinic) and neurokinin (substance P). Postoperative nausea and vomiting will occur in around one-third of elective patients who have no prophylaxis. This can result in many detrimental effects including patient dissatisfaction, unplanned admission and prolonged recovery. It is therefore essential that clinicians understand how they can prevent and treat nausea and vomiting using either a single agent or a combination of antiemetics to target relevant receptors. Commonly used drugs include antihistamines, dopamine antagonists, serotonin antagonists and steroids. More novel agents are being developed such as aprepitant, a neurokinin receptor antagonist, palonosetron, a 5HT₃ receptor antagonist, and nabilone, a synthetic cannabinoid.