Clinical review: Bedside lung ultrasound in critical care practice

Lung ultrasound can be routinely performed at the bedside by intensive care unit physicians and may provide accurate information on lung status with diagnostic and therapeutic relevance. This article reviews the performance of bedside lung ultrasound for diagnosing pleural effusion, pneumothorax, alveolar-interstitial syndrome, lung consolidation, pulmonary abscess and lung recruitment/derecruitment in critically ill patients with acute lung injury.     

Comparison of gravimetric and a double-indicator dilution technique for assessment of extra-vascular lung water in endotoxaemia

OBJECTIVE: To compare a molecular double-indicator dilution technique with the gravimetrical reference method for measurement of extra-vascular lung water in porcine endotoxin shock. DESIGN: Open comparative experimental study. SETTING: Animal research laboratory. MEASUREMENTS AND RESULTS: In fourteen anaesthetised, mechanically ventilated landrace pigs, central and pulmonary haemodynamics as well as pulmonary gas exchange were measured. Extra-vascular lung water was quantitated gravimetrically as well as with a molecular double indicator dilution technique. Eight of these animals were subjected to endotoxaemia, the rest serving as sham controls. No difference in extra-vascular lung water was observed between the two methods in sham animals. Furthermore, extra-vascular lung water assessed with the molecular double-indicator dilution technique at the initiation of endotoxin infusion did not differ significantly from the corresponding values for sham animals. Endotoxaemia induced a hypodynamic shock with concurrent pulmonary hypertension and a pronounced deterioration in gas exchange. No increase in extra-vascular lung water was detected with the molecular double-indicator dilution technique in response to endotoxin, whereas this parameter was significantly higher when assessed with the gravimetric method. CONCLUSION: The molecular double-indicator dilution technique showed similar results as the gravimetrical method for assessment of extra-vascular lung water in non-endotoxaemic conditions. However, during endotoxin-induced lung injury the molecular double indicator dilution technique failed to detect the significant increase in extra-vascular lung water as measured by the gravimetric method. These data suggest that the molecular double indicator dilution technique may be of limited value during sepsis-induced lung injury.     

肺部超声诊断新生儿肺炎的临床应用

目的探讨肺部超声对新生儿肺炎的临床诊断价值。 方法对2015年4~10月西安市儿童医院新生儿科连续收治的100例患儿进行肺部超声扫查,分别对双侧肺脏的前上、前下、侧上、侧下、后上、后下6个区域,共12个肺区进行纵向及横向扫查,记录检查当日动脉血气分析结果。由经验丰富的同一名超声医师,在不知晓临床诊断结果前对患儿超声图像进行分析,将超声诊断结果与临床诊断结果进行对照,总结肺炎组与无肺炎组患儿超声图像特征;肺炎组患儿进行超声肺评分（LUS）,将LUS与动脉血气分析的氧分压（PO₂）、二氧化碳分压（PCO₂）、pH值、血氧饱和度（SO₂）进行相关性分析。 结果肺炎组患儿肺部超声声像图特征：（1）超声"彗星尾"征（ULCs）："火箭"征33例（53%）,"磨玻璃"征35例（56%）,"瀑布"征31例（50%）,弥漫性白肺8例（13%）;（2）胸膜下肺实变35例（56%）;（3）胸膜线异常26例（41%）;（4）胸腔积液7例（11%）;（5）肺不张3例（4%）;（6）气胸1例（1%）。肺部超声诊断新生儿肺炎的的特异度为86.84%,敏感度为96.77%,准确性为93.00%,阳性预测值为92.30%,阴性预测值为94.28%。LUS与PO₂、PCO₂、pH值、SO₂相关（r=-0.82、0.64、-0.58、-0.74,P值均<0.05）。 结论肺部超声检查的敏感度较高,可作为临床诊断新生儿肺炎的又一影像学方法,结合LUS,对指导临床治疗新生儿肺炎有一定的应用价值。     

The role of quantitative ultrasound in the assessment of bone: a review

Quantitative ultrasound (QUS) bone measurement is a promising, relatively new technique for the diagnosis of osteoporosis. Unlike to the more established method of bone densitometry [measurement of bone mineral density (BMD) e.g. using dual X-ray absorptiometry (DEXA)], QUS does not use ionizing radiation. It is cheaper, takes up less space and is easier to use than densitometry techniques. The two QUS parameters currently measured are broadband ultrasound attenuation (BUA) and speed of sound (SOS). The reported age-related changes for healthy women range from ?0·27% to ?1·62% per year for BUA and from ?0·06% to ?0·19% per year for SOS. Precision ranges from 1·0 to 3·8% (CV) for BUA and from 0·19 to 0·30% (CV) for SOS. The new method of imaging ultrasound has improved the precision of QUS measurements. QUS is significantly correlated with BMD. Studies with the latest equipment have shown r-values between 0·6 and 0·9 in site-specific measurements, and QUS is thus believed to reflect mainly BMD. However, other studies indicate that QUS measures something other than the actual mineral content of bone, namely bone quality, e.g. in vitro studies have shown that QUS reflects trabecular orientation independently of BMD. In both cross-sectional and prospective studies, QUS seems to be as good a predictor of osteoporotic fractures as BMD. In two large prospective studies, QUS also predicted fracture risk independently of BMD. QUS has just begun to be used systematically for monitoring the response to anti-osteoporotic treatments in prospective trials. In the studies performed, QUS has been found to be useful in the follow-up of patients. QUS is thus a promising new technique for bone assessment.     

肺部超声的临床应用及进展

目前肺部超声已应用于多种肺部疾病的临床诊断,尤其在肺间质综合征、气胸、肺实变、胸腔积液、肺栓塞等疾病诊断中均有较高的敏感性及特异性.近年来肺部超声与心血管超声的联合应用,实现了床旁超声对多种常见危重症疾病的快速排除及诊断,为抢救患者赢得了宝贵的时间.本文就肺部超声的临床应用及进展进行综述.     

单指示剂法与重力法测定急性呼吸窘迫综合征犬血管外肺水的比较研究

目的 比较单指示剂法与重力法测定不同急性呼吸窘迫综合征（ARDS）模型犬血管外肺水（EVLW）的差异。方法 33只犬按随机数字表法分成对照组、油酸静脉注射复制ARDS模型组（油酸组）和盐酸吸入复制ARDS模型组（盐酸组）。用单指示剂法测定ARDS成模前、成模时及成模后10hEVLW；成模后10h处死动物，用重力法（金标准）测定EVLW；并监测血流动力学、血气分析和呼吸力学指标变化。结果 单指示剂法和重力法测定的EVLW呈显著正相关（r=0．8820，P〈0．05）；与重力法相比，单指示剂法测定的EVLW显著增高。对照组单指示剂法和重力法测定的EVLW呈显著正相关（r=0．9870，P〈0．05）；油酸组单指示剂法和重力法测定的EVLW呈显著正相关（r=0．9360，P〈0．05）;盐酸组单指示剂法和重力法测定的EVLW呈显著正相关（r=0．7950，P〈0．05），但其相关性较前两组差。ARDS10h时，盐酸组肺内分流和动脉血二氧化碳分压显著高于油酸组（P〈0．05）。而氧合指数却显著低于油酸组（P〈0．05）。结论 单指示剂法与重力法测定ARDS的EVLW有正相关性，但不同原因导致的ARDS其相关性不同。     

B-lines quantify the lung water content: a lung ultrasound versus lung gravimetry study in acute lung injury

B-lines (also termed ultrasound lung comets) obtained with lung ultrasound detect experimental acute lung injury (ALI) very early and before hemogasanalytic changes, with a simple, noninvasive, nonionizing and real-time method. Our aim was to estimate the correlation between B-lines number and the wet/dry ratio of the lung tissue, measured by gravimetry, in an experimental model of ALI. Seventeen Na-pentobarbital anesthetized, cannulated (central vein and carotid artery) minipigs were studied: five sham-operated animals served as controls and, in 12 animals, ALI was induced by injection of oleic acid (0.1 mL/kg) via the central venous catheter. B-lines were measured by echographic scanner in four predetermined chest scanning sites in each animal. At the end of each experiment, both lungs were dissected, weighed and dried to determine wet/dry weight ratio by gravimetry. After the injection of oleic acid, B-lines number increased over time. A significant correlation was found between the wet/dry ratio and B-lines number (r = 0.91, p < 0.001). These data suggest that in an experimental pig model of ALI/ARDS, B-lines assessed by lung ultrasound provide a simple, semiquantitative, noninvasive index of lung water accumulation, strongly correlated to invasive gravimetric assessment.     

The role of ultrasound in front-of-neck access for cricothyroid membrane identification: A systematic review

PurposeConventional palpation techniques for cricothyroid membrane (CTM) identification are inaccurate and unreliable. Ultrasound plays a multi-faceted role in airway management, however there is limited literature around its use for CTM identification prior to cricothyrotomies. This review sought to compare ultrasound to palpation in the general population, identify its indications in subjects with ill-defined neck anatomy, and determine its role in defining neck anatomy.MethodsTwo reviewers independently assessed titles, abstracts and full-text English articles through the Ovid Medline and EMBASE databases. Studies related to ultrasound for CTM assessment and/or cricothyrotomy in subjects older than 12 years were included.ResultsFourteen studies were selected. Compared to palpation, ultrasound has greater accuracy, but longer CTM identification times in those with normal airway anatomy. Interestingly, ultrasound offers comparable times to palpation in patients with difficult airways. Ultrasound also helps define anatomical parameters in the neutral and extended neck positions thereby underscoring the importance of neck positioning during cricothyrotomies and confirming consensus-based incision recommendations set by the Difficult Airway Society.ConclusionUltrasound appears to be superior to palpation for CTM localization especially in those with difficult airway anatomy and objectively defines neck anatomy. Its pre-emptive use should be incorporated during difficult airway management.     

重症肺部超声临床应用管理流程

床旁肺部超声在危重患者中的应用越来越广泛,很多疾病的诊断思路也因此发生改变,形成重症超声独有的思维。目前循证医学已经证实肺部超声在呼吸循环领域可提高疾病诊断的准确率,在此基础上也建立了相应的诊断流程,而如何理解和运用这些流程对于临床至关重要。笔者就常用的临床肺部超声流程和应用进行简要的介绍。     

Clinical review: Independent lung ventilation in critical care

Independent lung ventilation (ILV) can be classified into anatomical and physiological lung separation. It requires either endobronchial blockade or double-lumen endotracheal tube intubation. Endobronchial blockade or selective double-lumen tube ventilation may necessitate temporary one lung ventilation. Anatomical lung separation isolates a diseased lung from contaminating the non-diseased lung. Physiological lung separation ventilates each lung as an independent unit. There are some clear indications for ILV as a primary intervention and as a rescue ventilator strategy in both anatomical and physiological lung separation. Potential pitfalls are related to establishing and maintaining lung isolation. Nevertheless, ILV can be used in the intensive care setting safely with a good understanding of its limitations and potential complications.     

三七总皂苷对急性肺损伤犬血管外肺水及呼吸力学的影响

目的 探讨三七总皂苷(PNS)对急性肺损伤(ALI)犬血管外肺水(EVLW)与呼吸力学参数的影响.方法 18只犬被随机均分为正常对照组、模型组,PNS治疗组.均给予犬气管插管建立人工气道并实施机械通气支持[潮气量(VT)10 ml/kg,呼气末正压(PEEP)0,吸人氧浓度(FiO2)1.00].静脉注射油酸建立ALI犬模型.成模后PNS组静脉给予PNS 10 mg/kg(溶于葡萄糖注射液中,2.5 ml/min),正常对照组和模型组给予等量葡萄糖注射液.连续监测各组犬的呼吸力学参数及动脉血气.成模后4 h处死动物,采用重力法测定EVLW,计算血管外肺水指数(EVLWI).结果 PNS能显著降低ALI犬的EVLWI[(14.10±1.45)ml/kg比(17.97±0.85)ml/kg,P<0.05],但仍显著高于正常对照组[(8.82±0.54)ml/kg,P<0.01].制模成功后,氧合指数(PaO2/FiO2)及静态肺顺应性(Cst total)显著下降;静脉注射PNS 2 h后PaO2/FiO2和Cst total较模型组显著升高(P<0.05或P<0.01);而气道阻力(Raw)、动脉血二氧化碳分压(PaCO2)则无明显变化,3组间比较差异亦无统计学意义(P均>0.05).结论 PNS对ALI犬具有一定的保护作用,使EVLW降低、肺顺应性增高,有助于改善低氧血症.     

大剂量盐酸氨溴索对肺外型急性呼吸窘迫综合征患者血管外肺水及氧合功能的影响

目的 研究大剂量盐酸氨溴索对肺外型急性呼吸窘迫综合征（ARDS）患者血管外肺水（ELWI）及氧合功能的影响.方法 将68例符合ARDS诊断标准的患者分为治疗组（35例）与对照组（33例）.治疗组予以盐酸氨溴索1005 mg/d静脉注入,3h完成,对照组予以等容量的生理盐水静脉滴注3h,连续治疗7d.比较两组患者治疗前、治疗后3、5、7d动脉氧分压和氧饱和度（SaO2）,氧合指数、心脏指数（CI）、血管外肺水指数（ELWI）和血管通透性指数（PVPI）的变化以及机械通气时间、停留ICU时间、住院时间.结果 两组患者治疗后动脉氧分压、SaO2以及氧合指数均有不同程度的升高,ELWI、PVPI均有下降,且治疗组在治疗后5、7d较对照组改善更为明显（P均＜0.05）.此外,治疗组患者机械通气时间、停留ICU时间以及住院时间均比对照组显著降低（P均＜0.05）.结论 大剂量盐酸氨溴索可以降低ARDS患者肺血管通透性及血管外肺水,改善氧合功能,降低机械通气时间和住院时间.     

Clinical measurement of extravascular lung water

The thermal-dye technique for the measurement of ELW is available for clinical and experimental use. This method is safe and can be performed serially in an individual patient. Although it is invasive, it requires only a central venous catheter and an arterial catheter, which are often already in place for routine hemodynamic monitoring and management. The procedure is accurate under a variety of conditions. Two obstacles argue against its routine application. First, the reliability of this approach appears to be seriously compromised when there are areas of edematous lung with poor blood perfusion. This includes aspiration and perhaps other forms of acute lung injury. Second, it remains to be demonstrated how useful routine measurements of ETVL, even if accurate, are in clinical management. However, regardless of the accuracy of the various methods for determination of ELW, the process of their development has significantly enhanced our knowledge of pulmonary edema formation and fluid distribution. We are at a transition point of soon being able to determine ELW easily. Techniques of reducing ELW can now be assessed directly in patients with pulmonary edema. As these therapies are developed and understood, the demand for the measurement of ELW will become a greater part of clinical medicine, and may stimulate further refinement of methods for quantitating lung water.     

Clinical review: The role of biomarkers in the diagnosis and management of community-acquired pneumonia

In patients with community-acquired pneumonia, traditional criteria of infection based on clinical signs and symptoms, clinical scoring systems, and general inflammatory indicators (for example, leukocytosis, fever, C-reactive protein and blood cultures) are often of limited clinical value and remain an unreliable guide to etiology, optimal therapy and prognosis. Procalcitonin is superior to other commonly used markers in its specificity for bacterial infection (allowing alternative diagnoses to be excluded), as an indicator of disease severity and risk of death, and mainly as a guide to the necessity for antibiotic therapy. It can therefore be viewed as a diagnostic, prognostic, and perhaps even theragnostic test. It more closely matches the criteria for usefulness than other candidate biomarkers such as C-reactive protein, which is rather a nonspecific marker of acute phase inflammation, and proinflammatory cytokines such as plasma IL-6 levels that are highly variable, cumbersome to measure, and lack specificity for systemic infection. Elevated levels of pro-adrenomedullin, copeptin (which is produced in equimolar amounts to vasopressin), natriuretic peptides and cortisol are significantly related to mortality in community-acquired pneumonia, as are other prohormones such as pro-atrial natriuretic peptide, coagulation markers, and other combinations of inflammatory cytokine profiles. However, all biomarkers have weaknesses as well as strengths. None should be used on its own; and none is anything more than an aid in the exercise of clinical judgment based upon a synthesis of available clinical, physiologic and laboratory features in each patient.     

The role of ultrasound in renal insufficiency: the essentials

Sonography is the best screening modality to evaluate patients presenting with renal insufficiency. Ultrasound findings can be normal in patients with renal disease, especially in prerenal azotemia and acute parenchymal renal disease. Echogenic kidneys indicate the presence of parenchymal renal disease; the kidneys may be of a normal size or enlarged. Small kidneys suggest advanced stage chronic kidney disease. Uncommonly, cystic disease of the kidney, especially adult type polycystic kidney disease may be the cause of the patient's renal insufficiency with bilaterally enlarged kidneys containing multiple cysts of various sizes. If hydronephrosis is present, the level and cause of the obstruction should be sought. When ultrasound cannot diagnose the level and cause of obstruction, other imaging modalities, including CT and MRI may be useful. When renovascular disease (arterial stenosis or venous thrombosis) is suspected, spectral and color Doppler can be useful in detecting abnormalities.     

The role of donor antibodies in the pathogenesis of transfusion-related acute lung injury: a systematic review

BACKGROUND: The majority of cases of transfusion‐related acute lung injury (TRALI) are thought to be caused by the presence of leukocyte antibodies in the blood of the donor. We performed a systematic search of the literature to quantify the contribution of donor antibodies to the occurrence of TRALI. STUDY DESIGN AND METHODS: We conducted a systematic search of the PubMed and EMBASE databases. Retrieved articles were judged by three authors independently. Reference lists of all articles were subsequently screened for relevant references. All articles in English, German, French, and Dutch, published at any time before December 2007, were eligible for inclusion. RESULTS: Of 77 articles on leukocyte antibodies in donors involved in a case of TRALI, 14 articles contained sufficient data. These 14 articles reported leukocyte antibodies in 24 of 51 donors (47%) associated with 24 of 28 TRALI cases (86%). Of 15 articles that reported the prevalence of leukocyte antibodies in the general donor population, 2 articles reported a prevalence of 17 percent in (452) randomly selected donors. The odds ratio for developing TRALI was 15 (95% confidence interval [CI], 5.1‐45) for patients who received a transfusion from a donor who tested positive for the presence of leukocyte antibodies, compared to donors who tested negative. Leukocyte antibodies contributed to 80 percent (95% CI, 51%‐92%) of all TRALI cases. CONCLUSION: Leukocyte antibodies were more prevalent in donors involved in TRALI cases than among randomly selected donors. These findings suggest that donor antibodies contribute to four‐fifths of all TRALI cases.     

Simplified lung ultrasound protocol shows excellent prediction of extravascular lung water in ventilated intensive care patients

IntroductionUltrasound of the lung and quantification of B lines was recently introduced as a novel tool to detect overhydration. In the present study, we aimed to evaluate a four-region protocol of lung ultrasound to determine the pulmonary fluid status in ventilated patients in the intensive care unit.MethodsFifty patients underwent both lung ultrasound and transpulmonary thermodilution measurement with the PiCCO system. An ultrasound score based on number of single and confluent B lines per intercostal space was used to quantify pulmonary overhydration. To check for reproducibility, two different intensivists who were blinded as to the ultrasound pictures reassessed and classified them using the same scoring system. The results were compared with those obtained using other methods of evaluating hydration status, including extravascular lung water index (EVLWI) and intrathoracic blood volume index calculated with data from transpulmonary thermodilution measurements. Moreover, chest radiographs were assessed regarding signs of pulmonary overhydration and categorized based on a numeric rating scale.ResultsLung water assessment by ultrasound using a simplified protocol showed excellent correlation with EVLWI over a broad range of lung hydration grades and ventilator settings. Correlation of chest radiography and EVLWI was less accurate. No correlation whatsoever was found with central venous pressure measurement.ConclusionLung ultrasound is a useful, non-invasive tool in predicting hydration status in mechanically ventilated patients. The four-region protocol that we used is time-saving, correlates well with transpulmonary thermodilution measurements and performs markedly better than chest radiography.     

Clinical review: The implications of experimental and clinical studies of recruitment maneuvers in acute lung injury

Mechanical ventilation can cause and perpetuate lung injury if alveolar overdistension, cyclic collapse, and reopening of alveolar units occur. The use of low tidal volume and limited airway pressure has improved survival in patients with acute lung injury or acute respiratory distress syndrome. The use of recruitment maneuvers has been proposed as an adjunct to mechanical ventilation to re-expand collapsed lung tissue. Many investigators have studied the benefits of recruitment maneuvers in healthy anesthetized patients and in patients ventilated with low positive end-expiratory pressure. However, it is unclear whether recruitment maneuvers are useful when patients with acute lung injury or acute respiratory distress syndrome are ventilated with high positive end-expiratory pressure, and in the presence of lung fibrosis or a stiff chest wall. Moreover, it is unclear whether the use of high airway pressures during recruitment maneuvers can cause bacterial translocation. This article reviews the intrinsic mechanisms of mechanical stress, the controversy regarding clinical use of recruitment maneuvers, and the interactions between lung infection and application of high intrathoracic pressures.     

Clinical review: Molecular mechanisms underlying the role of antithrombin in sepsis

In disseminated intravascular coagulation (DIC) there is extensive crosstalk between activation of inflammation and coagulation. Endogenous anticoagulatory pathways are downregulated by inflammation, thus decreasing the natural anti-inflammatory mechanisms that these pathways possess. Supportive strategies aimed at inhibiting activation of coagulation and inflammation may theoretically be justified and have been found to be beneficial in experimental and initial clinical studies. This review assembles the available experimental and clinical data on biological mechanisms of antithrombin in inflammatory coagulation activation. Preclinical research has demonstrated partial interference of heparin – administered even at low doses – with the therapeutic effects of antithrombin, and has confirmed – at the level of cellular mechanisms – a regulatory role for antithrombin in DIC. Against this biological background, re-analyses of data from randomized controlled trials of antithrombin in sepsis suggest that antithrombin has the potential to be developed further as a therapeutic agent in the treatment of DIC. Even though there is a lack of studies employing satisfactory methodology, the results of investigations conducted thus far into the mechanisms of action of antithrombin allow one to infer that there is biological plausibility in the value of this agent. Final assessment of the drug's effectiveness, however, must await the availability of positive, prospective, randomized and placebo-controlled studies.