Laboratory tests of renal function

The kidneys are vital organs in the management of fluid balance, waste product removal, electrolyte homeostasis, acid–base balance and endocrine function. Waste products removed by the kidney are urea, uric acid and creatinine; other foreign products with similar physiochemical properties are also excreted. Urea and uric acid are by products of protein metabolism and creatinine is generated by the metabolism of creatine compounds from muscle. The kidney regulates fluid and electrolyte balance through controlling the composition and volume of urine. In the proximal convoluted tubule and the loop of Henle, 90% of sodium, potassium, calcium and magnesium are reabsorbed. Acid–base balance is achieved by regulating the excretion of hydrogen ions and bicarbonate buffering. The kidney also has a number of endocrine functions including the production of renin and erythropoietin as well as hydroxylation of vitamin D. The kidneys receive 25% of cardiac output, generating 170–200 litres of ultrafiltrate per day. Urine output is approximately 1.5 litres per day, which is concentrated ultrafiltrate through selective reabsorption of solutes and water. In this article we will discuss tests frequently used to assess renal function.     

电阻抗断层成像技术用于呼气末正压滴定的研究进展

适当的呼气末正压（PEEP）是保护性肺通气策略的重要组成部分,PEEP可以保持肺泡开放,减少肺萎陷伤。尽管个体化PEEP已被越来越多的临床医师认可,但最佳的PEEP滴定方法尚存争议。电阻抗断层成像（EIT）是一种无创、无辐射的成像技术,可在床边实时动态评估肺功能,将肺通气过程中的阻抗变化以动态图像呈现,能够反映PEEP调整前后肺内通气及气体分布变化,因此,EIT可用于滴定个体化PEEP。本文简要概括EIT的基本原理及监测指标,阐述临床应用EIT指导下的PEEP（PEEPEIT）滴定方法,旨在加强对EIT的优点和局限性的理解,为优化个体化PEEP的设置提供参考。     

Impaired renal function due to raised intraabdominal pressure

A 19-year-old male developed renal failure after a laparotomy for liver trauma (urinary output of 30 ml/h, plasma creatinine 220 mol/l). Surgical decompression of the abdomen was performed without any attempt at correcting the underlying pathology. This reduced the intraabdominal pressure (IAP) from 40 to 24 cm H₂O and resulted in a massive diuresis (530 ml/h). Twenty-four hours later the plasma creatinine peaked at 280 mol/l and then returned to within the normal range. This case report confirms that there is a direct relationship between IAP and renal function.     

Evaluation of conventional weaning criteria in patients with acute respiratory failure

We evaluated the reliability of conventional weaning criteria from a ventilator during 33 weaning trials on 25 patients with acute respiratory failure (ARF). Of 13 criteria, a ratio of maximal voluntary ventilation to minute ventilation (MV) 2, a vital capacity 12ml·kg^–1, a spontaneous respiratory rate 25 breaths·min^–1, and a MV 10l·min^–1 appeared to be useful for predicting successful weaning outcome. However, even using those criteria, there were many falsely-negative cases. The alveolar-arterial P_{O 2} gradient 350mmHg at an Fi _{O 2} 1.0 was not useful as a predictor of weaning outcome. The present study demonstrates that conventional criteria are frequently inaccurate for predicting weaning outcomes and suggests that the use of some of these criteria may unnecessarily prolong the length of ventilator support. Since ventilation of most patients with poor oxygenation can be successfully discontinued by placing them on a continuous positive airway pressure system, these results suggest that the improvement of oxygenation is not an indispensable prerequisite for weaning from mechanical ventilators.(Okamoto K, Iwamasa H, Dogomori H, et al.: Evaluation of conventional weaning criteria in patients with acute respiratory failure. J Anesth 4: 213–218, 1990)     

实验性急性胰腺炎大鼠胰岛微血管的电镜观察

目的 :了解实验性急性胰腺炎大鼠早期胰岛微血管的超微结构变化 ,并探讨其与急性胰腺炎的关系。方法 :采用皮下注射超大剂量雨蛙素诱发大鼠急性水肿性胰腺炎 ,用扫描电镜和透射电镜观察急性胰腺炎早期胰岛微血管的形态和变化。结果 :①在透射电镜下 ,胰岛毛细血管内皮细胞肿胀 ,管腔狭窄、不规则 ,内皮细胞“窗孔”数量增加。②在扫描电镜下 ,胰岛毛细血管外形不规则 ,与外分泌部毛细血管之间的吻合明显减少 ;毛细血管表面可见铸型剂形成的泡状物。结论 :急性胰腺炎早期即有胰岛微血管损伤的表现 ,推测其与胰腺炎的进展密切相关。     

Detection of allelic loss within the β1-interferon gene in childhood acute lymphoblastic leukemia using differential PCR

Summary Deletion of the short arm of chromosome 9p involving the 1-interferon (IFN) gene has been implicated in the process of malignant transformation in lymphomas and acute lymphoblastic leukemias. Since cytogenetic analysis is frequently unsuccessful in clinical samples, we used a recently described differential PCR technique to detect losses within the 1-IFN gene in 86 acute leukemias. Using differential PCR, no 1-IFN deletion was detected in 44 acute myeloid leukemia (AML) and eight control samples. However, five of 42 acute lymphoblastic leukemia (ALL) probes (12%) exhibited loss of the 1-IFN gene (three common ALL, two T-ALL). Cytogenetic analysis was performed independently in three of these five cases and revealed abnormalities of chromosome 9p in two samples. Two of five T-ALL cases exhibited a loss within the 1-IFN gene, compared with 3/29 c-ALLs, suggesting a predominance of IFN gene loss in T-ALLs. These data indicate that PCR can be used for rapid detection of gene dosage phenomena in clinical leukemia samples.     

Release of chemoattractants and neutrophil activation in acute myocardial infarction immediately after successful recanalization of the infarct-related vessel by angioplasty

The study investigated inflamatory responses in evolving myocardialinfarction. Fifteen patients with acute myocardial infarction,who had undergone balloon recanalization of the infarct-relatedcoronary artery within 4 h after onset of symptoms, were examined.Blood samples were obtained through the guiding catheter andfrom the pulmonary artery before and immediately after successfulrecanalization. After recanalization, plas from the pulmonaryartery was 47% (quartiles: l9%, 78; P =0·001) more chemotacticto neutrophils from normal donors than before recanalization.Furthermore, significant changes in neutrophil function werefound in the pulmonary artery. Compared to the values beforerecanalization, the nitroblue tetrazolium score rose by 31%(quartiles: 4%, 37% P=0·003), FMLP-stimulated superoxideanion production by 10% (quartiles: 0%, 39% P=0·020),and chemotaxis by 46% (quartiles: 0%, 81%, P=0·011),while neutrophil filterability decreased by 28% (quartiles:15%, 47%; P=0·010). No significant changes in neutrophilparameters were found in the arterial blood The study indicatesthat chemoattractants are released in the early reperfusionperiod of evolving myocardial infarction. These chemoattractantsmay act as inflammatory mediators causing neutrophil activation.