Left Ventricular Mass Estimation by Echocardiography

Echocardiographic determination of left ventricular mass provides prognostic information that is independent of blood pressure. This prognostic information has a graded and continuous relationship with outcome, and is independent of traditional risk factors. This article addresses the prognostic and clinical utility of echocardiography for detection of left ventricular mass. Recommendations will be offered regarding the use of echocardiography for screening in select individuals.     

Intrapulmonary gas mixing and dead space in artificially ventilated dogs

In this study we have investigated the effects of breath holding and of the physical properties of gases on four different respiratory dead spaces (V _D): the Fowler, the physiological, the washout and the inert gas dead space. The experiments were performed with dogs which were ventilated artifically with breathing patterns with different post-inspiratory breath holding times (t _a) of 0, 0.5, 1.0 and 2.0 s. Tracer amounts of acetone, ether and enflurane were infused continuously into a peripheral vein and a bolus of a mixture of krypton, Freon12 and SF₆ was introduced into the peritoneal cavity. After reaching steady state, samples of arterial blood, mixed venous blood and mixed expired air were taken simultaneously. From the partial pressures (P _a, P _¯V and P respectively) we determined the excretion (=P/P_¯V), retention (R=P_a/P_¯V) and the physiological dead space fraction (V _D,phys/V _T=(1 P/P_a) for each gas, where V _T is tidal volume. Further, we recorded the expirograms of the six tracer gases and of CO₂ from which the Fowler dead space fractions (V _D,Fowler/V _T) of the different gases were determined. Also the washout dead space fractions (V _D,washout/V _T) for He and SF₆ were determined as well as the inert gas dead space fraction (V _D,MIGET/V _T) with the use of the multiple inert gas elimination technique (MIGET).With the exception of V _D,phys/V _T for SF₆, all dead space fractions decreased with increasing t _a. V _D,phys/V _T for the poorly soluble gas SF₆ was considerably larger than V _D,phys/V _T for the remaining gases. For the highly soluble acetone V _Fowler/V _T was considerably smaller than V _D,Fowler/V _T for the other gases. V _{D,washout,SF6}/V _T was always larger than V _D,washout,He/V _T and V _D,Fowler,SF6/V _T. Further, V _D,phys/V _T was larger than V _D,Fowler/V _T for SF₆ and acetone. However, for gases with intermediate solubility in blood V _D,phys/V _T tended to be smaller than V _D,Fowler/V _T. We conclude that the respiratory dead spaces are affected by the breathing pattern and by the physical properties of gases, i.e. their diffusivity in alveolar gas and their solubility in blood or lung tissue.     

动态血压正常高限者的左室肥厚

目的：观察动态血压为正常高限者的左室肥厚情况,为该患者群靶器官损害的防治策略提供依据。方法：根据２４小时动态血压监测结果将病人分为３组：Ｎ组（正常血压组）、ＮＨ组（血压正常高限组）和Ｈ组（高血压组）。以超声心动图检测左室舒张末期内径,舒张末期室间隔和左室后壁厚度等,计算左室重量指数（ＬＶＭＩ）。结果：Ｈ组（１２９±４１）和ＮＨ组（１１５±３２）的ＬＶＭＩ明显高于Ｎ组（９７±２３,Ｐ＝０．００００１和０．００５）,Ｈ组和ＮＨ组间无统计学差异。结论：动态血压正常高限者左室肥厚程度明显重于血压完全正常者。对该人群亦应积极采取措施预防和治疗靶器官损害     

Regulatory volume response of erythrocytes exposed to a gradual and slow decrease in medium osmolality

 A sudden decrease in external medium osmolality (90 mosmol/kg) causes an immediate swelling of trout erythrocytes, followed by a regulatory volume decrease (RVD) due to activation of both a KCl cotransporter and a taurine transport pathway. Here, we determined how trout red cells respond when they are exposed to a gradual and slow decrease in medium osmolality (80 mosmol/kg at a rate of 0.7 mosmol/kg per min). Erythrocytes were unable to regulate their volume efficiently when swollen gradually and it increased continuously throughout the experimental period (120 min). As long as volume was increased slowly by 15–25%, regulatory pathways remained essentially inactivated, erythrocytes losing no significant amount of intracellular osmotically active solutes. Above this swelling threshold, a response was triggered but the quantity of solutes lost via the regulatory pathways was still not sufficient to counterbalance the continuous entry of water due to the slow and gradual decrease in medium tonicity. Received: 18 January 1999 / Received after revision: 10 February 1999 / Accepted: 11 February 1999     

高晶体-高胶体渗透压溶液对受机械性损伤的海马神经细胞容积的影响

观察机械性损伤的海马神经细胞在不同浓度高晶体－ 高胶体渗透压溶液中容积的变化。取原代培养大白鼠胚胎的海马神经细胞,用超声波机械损伤细胞后暴露于含０．５ ｇ／Ｌ、１ ｇ／Ｌ和２．５ ｇ／Ｌ氯化钠的细胞培养基中１５ ｍ ｉｎ。结果显示机械性损伤的细胞明显肿胀（Ｐ＜ ０．０５）。当细胞暴露于不同浓度的高晶体－ 高胶体溶液１５ ｍ ｉｎ 后, 细胞容积与同一实验时间的对照值相比明显下降, 并保持至第７ ｄ （Ｐ＜ ０．０５）。表明受到机械性损伤的海马神经细胞在高晶体－ 高胶体渗透压环境中的容积调节功能丧失或减弱。     

小潮气量通气在急性呼吸窘迫综合征中的应用

应用小潮气量通气致容许性高碳酸血症方法对11例急性呼吸窘迫综合征（ARDS）进行临床观察。设定潮气量为6．4±1．1ml／kg,保持动脉血二氧化碳（PaCQ2）为5．97±1．41kPa,血氧分压8．54±3．19kPa。结果7例存活,未发现气压伤。说明小潮气量通气致一定程度高碳酸血症是临床上值得推荐使用的方法。     

Exercise induces a change in plasma fibrinogen concentration: fact or fiction?

This study examined the effect of exercise on plasma fibrinogen concentrations with simultaneous measurements of plasma volume changes. Eight moderately active males aged 26.6±3.6 years (mean±SD) completed maximal (VO₂max) and submaximal (75% VO₂max for 30 minutes) exercise trials separated by 7 days. Venous blood samples were obtained at rest, immediately postexercise, and following 30 minutes of recovery. Whole blood was analysed for haematocrit and haemoglobin, while citrated plasma was assayed for fibrinogen levels. Values of haematocrit and haemoglobin before and after exercise were utilised for the estimation of plasma volume changes. Plasma volume decreased (p<0.05) immediately following both maximal (−17.7±5.1%) and submaximal (−14.3±4.1%) exercise. Exercise resulted in decreased plasma fibrinogen levels (maximal exercise: from 266.3±14.5 to 222.2±23.9 mg·dL⁻¹; submaximal exercise: from 239.5±45.4 to 209.7±42.4 mg·dL⁻¹) only when postexercise raw data were corrected for the contraction of plasma volume. It is concluded therefore that changes in plasma volume in response to exercise should be taken into account when interpreting exercise effects on plasma fibrinogen concentration.     

Pulmonary Failure After Norwood Procedure: Indication for Extracorporeal Membrane Oxygenation? A Case Report

Today some authors consider univentricular repair a contraindication for postoperative cardiac extracorporeal membrane oxygenation (ECMO). The question is whether or not ECMO is indicated as pulmonary support in case of an overwhelming pulmonary infection during the postoperative course after a Norwood procedure. During the prolonged weaning period after a Norwood procedure using a 4 mm aortopulmonary shunt, proven respiratory syncytial virus (RSV) bronchiolitis occurred at the time of expected weaning from artificial ventilation. Venovenous ECMO was able to improve oxygenation, but when pulmonary opacification failed to resolve, ECMO was terminated after 12 days.     

多普勒超声心动图评估左心室舒张末压的研究

目的探讨多普勒超声心动图评估左室舒张末压的有效方法与指标。方法对６８例病人采用左心导管测压及经胸多普勒超声心动图检测。结果对比研究显示,联合肺静脉与二尖瓣血流频谱分析优于二尖瓣血流频谱分析,肺静脉Ａ峰和二尖瓣Ａ峰时限差值（ＰＡｄ－Ａｄ）与左室舒张末压实测值呈最佳相关性（ｒ＝０．７２,Ｐ＜０．０１）。结论认为应用多普勒超声心动图测定ＰＡｄ与Ａｄ,并以其差值估测左室舒张末压,是一项简便、可靠的无创性评估左室舒张末压的方法。ＰＡｄ－Ａｄ≥０可作为临床判断左室舒张末压增高［≥２．０ｋＰａ（１５ｍｍＨｇ）］的一项半定量指标。     

Atrial natriuretic peptide, sodium retention, and proteinuria in nephrotic syndrome

BACKGROUND.: Oedema formation in the nephrotic syndrome is primarily dueto tubular sodium retention. The pathogenetic role of alphaatrial natriuretic peptide (ANP), a hormonal promoter of natriuresisis unknown. METHODS.: In 31 patients (aged 35±11 years) with nephrotic syndromeand histopathological evidence of primary glomerulonephritis,we investigated plasma ANP concentration and its influence onrenal haemodynamics, natriuresis, and proteinuria (total protein,albumin, IgG excretion). Patients with a compensated treatedform of nephrotic syndrome due to primary glomerulonephritiswere included in the study. Serum creatinine levels were 1.4mg/dl. Diuretic medication was discontinued at least 24 h beforethe investigation was started. Patients were randomly assignedto ANP infusion (0.005 µg/kg*min; group II, n=15) or receivedplacebo (group III, n=16). Ten healthy subjects (group I) servedas normal controls. RESULTS.: In normal subjects (group I), ANP caused an increase in natriuresisfrom 14.5±4.2mmol/h to 26.4±11.1 mmol/h (P<0.01).In patients with nephrotic syndrome (group II), baseline sodiumexcretion of 10.5±6.0 mmol/h was increased to 19.6±14.8mmol/h with ANP infusion (P<0.01). No changes were seen inthe placebo group III. The absolute increase in ANP inducednatriuresis was not significantly different between group Iand II. However, plasma ANP levels were significantly higherin patients with nephrotic syndrome (166±87 pg/ml vs.74±21 pg/ml, P<0.05) and also reached higher levelsafter ANP infusion (P<0.01). Therefore, natriuresis was significantlyreduced when circulating ANP levels were taken into account(P<0.05). ANP administration resulted in an increase of totalprotein excretion in patients with the nephrotic syndrome (groupII, from 219±277 mg/h to 264±268 mg/h). Albuminelimination rose from 128±151 mg/h to 167±170mg/h (P<0.05) and IgG excretion from 4.91±6.67mg/hto 9.27±10.78mg/h (P<0.05). Healthy subjects alsoshowed a small but significant increase in albuminuria (48±38%,P<0.05). Low-dose ANP infusion did not, however, induce anysignificant alteration in GFR, ERPF and blood pressure. CONCLUSION.: ANP plasma concentrations in the steady state are elevated inpatients with the nephrotic syndrome. The natriuretic effectof ANP is reduced when referring to circulating ANP plasma levels.Elevated ANP levels enhance urinary protein excretion in thenephrotic syndrome. This is not due to modulation of GFR orFF, but is most probably attributable to increased glomerularpermeability.