Tag Archives: Concise Critical Appraisal

Indications and Effects of Plasma Transfusions in Critically Ill Children

Plasma transfusions are frequently prescribed for critically ill children, although their indications lack a strong evidence base. Many physicians often transfuse critically ill children who have abnormal coagulation tests and who are not bleeding. Karam et al conducted an international multicenter observational point-prevalence study involving 101 pediatric intensive care units in 21 countries. They sought to characterize indications leading to plasma transfusions in critically ill children and assess the effect of plasma transfusions on coagulation tests.

They found that approximately one-third of transfused patients were not bleeding and had no planned procedure. In addition, in most patients, coagulation tests were not sensitive to increases in coagulation factors resulting from plasma transfusion.

Read the full Concise Critical Appraisal by logging into the SCCM eCommunity. Concise Critical Appraisal is a regular feature aimed at highlighting the best and most relevant literature from a variety of academic journals and encouraging discussion around recent studies and research.

Lung Ultrasound: Better Than a Chest Radiograph?

Ultrasound use in the intensive care unit (ICU) has become increasingly prevalent, especially as more intensivists gain valuable training and experience in this cost-effective imaging modality. In this month’s issue of Intensive Care Medicine, Xirouchaki et al compared the diagnostic performance of lung ultrasound and bedside chest radiography (CXR) for the detection of four pathologic entities: consolidation, interstitial edema, pneumothorax, and pleural effusion.

Forty-two mechanically ventilated patients in a mixed medical-surgical ICU were prospectively enrolled in this blinded, non-randomized trial. Enrollment in the trial was triggered by the need for thoracic computed tomography (CT), which was used as the gold standard for all patients. All patients had a CXR, CT, and ultrasound examination. The primary author performed all ultrasound exams and was blinded to the CT findings; the exams were not reviewed by a blinded radiologist.

Ultrasound had superior sensitivity and specificity for the detection of consolidation, pleural effusion, and interstitial edema when compared to CXR. A positive likelihood ratio of 14.29 was reported for detecting consolidation with ultrasound (100% sensitivity, 78% specificity); a likelihood ratio of 13.4 was reported for diagnosing interstitial edema (94% sensitivity, 93% specificity). Alternatively, CXR had a sensitivity of only 38% for consolidation and a sensitivity of 46% for interstitial edema. Ultrasound identified six of eight pneumothoraces with a sensitivity of 75%. None of the pneumothoraces were clinically significant. The authors concluded that lung ultrasound demonstrated superior diagnostic performance compared to CXR, and may be considered as an alternative to computed tomography (CT) in some instances.

Since patient selection was based on a predefined need for a CT, the study was subject to considerable verification bias. Moreover, all exams were performed by one investigator, and none of the exams were confirmed by a blinded radiologist or second ultrasonographer. All patients were positioned laterally for the exam, and this positioning might have changed the localization for some abnormalities, and may not always be feasible or safe for many ICU patients in other settings. The case mix, plagued by the limitation of a small sample size, was heavily skewed towards trauma patients (n=11) and patients with sepsis (n=18), further limiting the generalizability across diverse ICU patient populations.

Notwithstanding the significant limitations, this work stands as yet another example of how ultrasound might be used in the ICU as a safer and cheaper alternative to other diagnostic modalities. Training, equipment acquisition and quality control remain significant concerns that must be addressed before ultrasound can be reliably used in place of an established “gold standard” such as chest CT.

Concise Critical Appraisal is a regular feature authored by SCCM member Samuel M. Galvagno Jr., DO. Each installment highlights journal articles most relevant to the critical care practitioner.

Is Thoracic Ultrasound an Alternative to Conventional Imaging?

Ultrasound has particular usefulness in the critical care setting, with well-established applications for line placement and echocardiography. Questions remain regarding the validity of replacing traditional adjuncts with ultrasound. A previous Concise Critical Appraisal noted that thoracic ultrasound has been shown to be comparable to chest radiographs. In this review by Ashton-Cleary from Royal Cornwall Hospital in the United Kingdom, evidence is reviewed to evaluate the usefulness of thoracic ultrasound in the ICU.

MEDLINE, EMBASE, and Cochrane’s CENTRAL databases were searched as well as the International Standard Randomized Controlled Trial Number Register for relevant articles between 1995 and 2012. Eighty-eight articles of relevance were identified. The review specifically focused on ultrasound and comparative ability to detect or quantitate four common thoracic conditions in critical care: pleural effusion, consolidation, pulmonary edema, and pneumothorax. In each of the included studies, ultrasound was performed by physicians who were described explicitly or implicitly as having training and experience in the skill. Diagnostic measures for the four conditions were tabulated and included sensitivity, specificity, positive predictive value, negative predictive value, diagnostic accuracy, and area under the curve (AUC).

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