Bedside ultrasonography in the differential diagnosis of pulmonary pathologies in the intensive care unit

Ultrasound-based imaging in neurocritical care patients: a review of clinical applications

OBJECTIVE

To analyze the diagnostic, monitoring, and procedural applications of ultrasound (US) imaging in neurocritical care (NCC) patients.

METHOD

US imaging has been extensively validated in various subset of critically ill patients, but not specifically in the NCC population. We reviewed the clinical applications of US imaging for heart, vascular, brain, and lung evaluation and for possible procedural uses in NCC patients. Major neurosurgical books, journals, testimonials, authors' personal experience, and scientific databases were analyzed.

RESULTS

Cardiac US imaging provides accurate information at NCC arrival to stratify risk factors, including presence of atrial septal defect/patent formen ovale, abnormal ventricular function, or pericardial effusion, and to monitor cardiac anatomy and function during the NCC stay for guiding goal-directed therapy. Vascular US in NCC patients has three especially relevant indications: to screen anatomy and flow in extracranial supra-aortic arteries, to diagnose deep vein thrombosis, and to optimize the safety of central venous catheterization. Brain US has important clinical applications in the NCC, including transcranial Doppler and emerging techniques for cerebral blood flow evaluation with contrast-enhanced US imaging. Lung US, as demonstrated in other intensive care unit patients, provides accurate diagnosis of anatomical and functional abnormalities and enables diagnosis of pleural effusion, pneumothorax, lung consolidation, pulmonary abscess and interstitial-alveolar syndrome, and lung recruitment/derecruitment. US imaging can effectively guide percutaneous tracheostomy.

CONCLUSION

In conclusion, US imaging is an important diagnostic tool that provides real-time information at the bedside to stratify risk, monitor for complications, and guide invasive procedures in NCC patients.

The diagnosis and management of pleural effusions in the ICU

Pleural effusions are common in critically ill patients. Most effusions in intensive care unit (ICU) patients are of limited clinical significance; however, some are important and require aggressive management. Transudative effusions in the ICU are commonly caused by volume overload, decreased plasma oncotic pressure, and regions of altered pleural pressure attributable to atelectasis and mechanical ventilation. Exudates are sequelae of pulmonary or pleural infection, pulmonary embolism, postsurgical complications, and malignancy. Increases in pleural fluid volume are accommodated principally by chest wall expansion and, to a lesser degree, by lung collapse. Studies in mechanically ventilated patients suggest that pleural fluid drainage can result in improved oxygenation for up to 48 hours, but data on clinical outcomes are limited. Mechanically ventilated patients with pleural effusions should be semirecumbant and treated with higher levels of positive-end expiratory pressure. Rarely, large effusions can cause cardiac tamponade or tension physiology, requiring urgent drainage. Bedside ultrasound is both sensitive and specific for diagnosing pleural effusions in mechanically ventilated patients. Sonographic findings of septation and homogenous echogenicity may suggest an exudative effusion, but definitive diagnosis requires pleural fluid sampling. Thoracentesis should be carried out under ultrasound guidance. Antibiotic regimens for parapneumonic effusions should be based on current pneumonia guidelines, and anaerobic coverage should be included in the case of empyema. Decompression of the pleural space may be necessary to improve respiratory mechanics, as well as to treat complicated effusions. While small-bore catheters inserted under ultrasound guidance may be used for nonseptated effusions, surgical consultation should be sought in cases where this approach fails, or where the effusion appears complex and septated at the outset. Further research is needed to determine the effects of pleural fluid drainage on clinical outcomes in mechanically ventilated patients, to evaluate weaning strategies that include pleural fluid drainage, and to better identify patients in whom pleural effusions are more likely to be infected.

Ultrasound in the surgical intensive care unit

PURPOSE OF REVIEW

Critically ill patients are subjected to a variety of diagnostic and therapeutic procedures. It is desirable to make these interventions as timely, safe, and effective as possible. Bedside ultrasound and echocardiography are tools that allow for diagnosis of many conditions, without subjecting the patient to radiation, dye, and the risks of transport. In addition, ultrasound guidance of procedures may improve safety and efficacy. This review analyzes the literature on ultrasound and echocardiography use in the ICU.

RECENT FINDINGS

There is evidence supporting the use of bedside echocardiography and ultrasound for the diagnosis of chest, abdominal, and other pathologic conditions in the ICU. There is also evidence to support ultrasound guidance of vascular access and other procedures. There are multiple reports of novel uses of bedside echocardiography and ultrasound in the ICU.

SUMMARY

There is substantial literature supporting ultrasound and bedside limited echocardiography in the critical care setting. In addition, there are frequent reports of new applications for these technologies in the literature. The role of ultrasound and bedside limited echocardiography in the critical care setting is likely to expand in the future and become a part of daily care in every surgical intensive care unit.

Monitoring the mechanically ventilated patient

In the intensive care setting, monitored data relevant to the output, efficiency, and reserve of the respiratory system alert the clinician to sudden untoward events, aid in diagnosis, help guide management decisions, aid in determining prognosis, and enable the assessment of therapeutic response. This review addresses those aspects of monitoring we find of most value in the care of patients receiving ventilatory support. We concentrate on those modalities and variables that are routinely available or easily calculated from data readily collected at the bedside.