Review articleEffect of prehospital ultrasound on clinical outcomes of non-trauma patients—A systematic review☆
Introduction
The use of point of care ultrasound (US) in the emergency settings has developed over the past decades. Ultrasound has been studied extensively in a variety of clinical settings and is now considered an essential diagnostic adjunct in both the emergency department and in the intensive care unit for managing patients with cardiopulmonary instability.1, 2, 3, 4, 5 Ultrasound is considered a class I recommendation in a variety of emergency clinical situations.1, 3, 4 Studies have demonstrated that integration of a focused US examination in the patient assessment results in a more accurate initial diagnosis with an improved patient management.6, 7
Advances in technology have made prehospital US possible and physicians, paramedics, and aeromedical crews worldwide are currently using US as an adjunct to clinical assessment in trauma patients, cardiac arrest, hemodynamic instability, respiratory failure, suspected abdominal aortic aneurysm, intracranial pathology, fetal monitoring and vascular access.8, 9, 10, 11, 12, 13, 14 The medical indications for performing emergency US do not differ between the in- and the prehospital care setting. However, less diagnostic possibilities are present prehospitally, hence the indication for performing an US can be different from the in-hospital assessment (e.g. X-ray detection of pneumothorax). Furthermore, the prehospital US performance is even more focused than the in-hospital US, and should only be performed if there is a potential change in triage or immediate treatment, as opposed to the in-hospital US where the triage between hospitals has already been done, and there is a need for a precise diagnosis. Moreover a number of factors distinguish prehospital care from in-hospital settings. Environmental factors such as noise, limited workspace in ambulance and helicopters, weather, light and limited resources. The need for rapid transport to advanced diagnostics and definitive care mandates the prehospital care providers to decrease on-scene time and any new prehospital diagnostic adjunct should also be evaluated in this context. The 2010 European Resuscitation Council guidelines on cardiopulmonary resuscitation recognize ultrasound as a potential valuable diagnostic tool and in a consensus report a European expert group has identified prehospital US as one of the top five research priorities in physician-provided pre-hospital critical care.15, 16
Whether US in the prehospital setting can lead to improvement in diagnosis, triage or treatment is uncertain. A systematic review of the literature is warranted to guide evidence based triage decisions, prehospital interventions, and public policies regarding prehospital US.
Section snippets
Objectives
The aim of this systematic review was to determine, whether prehospital US examinations affect outcomes in non-trauma patients. The specific clinical research question addressed was: “Does prehospital US improve survival for non-trauma patients (primary outcome). Does prehospital US change the diagnosis, treatment, transfer decision, or hospital response (secondary outcomes)”.
Protocol and registration
We developed a protocol using the PRISMA guidelines17 and it was registered in the PROSPERO database (www.crd.york.ac.uk/PROSPERO), registration number: CRD42012002632, before the search was conducted.
Eligibility criteria
The selected studies included non-trauma patients of all ages who had an US examination performed in the pre-hospital setting. Eligible studies accepted for further evaluation were interventional studies (randomized and non-randomized), observational controlled and uncontrolled cohort studies and
Study selection
The MEDLINE search yielded 1031 hits; the EMBASE search yielded 574 hits; output from the CENTRAL search yielded 102 hits (Fig. 1). A total of 1707 unique papers were identified and screened by title and abstract of which 1654 was excluded. Fifty three papers were retrieved in full text and assess for eligibility. Of these 43 were excluded (Table 1).8, 9, 10, 14, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53
Summary of evidence
The main finding of this systematic review regarding the use of US in non-traumatic patients in the prehospital setting was a very large heterogeneity between the identified studies and all included studies had high risk of bias. This precludes a conclusive answer as to whether prehospital US examinations affect outcomes in non-trauma patients. Studies with a design using control groups, preferably randomized trials, are warranted in order to determine the clinical impact of prehospital US.
Limitations
As we did not analyze current and previous literature on critical care ultrasound outside the context of pre-hospital care our analysis and results are not to be generalized or extrapolated to all emergency or critical care ultrasound usage. We were only able to include 10 studies in this review, all of great heterogeneity and high risk of bias. The SIGN 50 checklist18 was used to assess the risk of bias in the included studies. Although it is possible to assess observational studies by this
Conclusions
Based on the current literature on prehospital care US it is not possible to assess whether prehospital US improves outcomes of non-trauma patients, due to a large heterogeneity and high risk of bias. In spite of this current publications consistently suggest US as a helpful tool in prehospital decision-making. Further studies are warranted in order to determine the clinical impact of prehospital US.
Conflict of interest statement
Søren Steemann Rudolph has received a single teaching fee from SECMA, the Danish distributor of Sonosite © ultrasound equipment. Rasmus Hesselfeldt has received a single teaching fee from SECMA, the Danish distributor of Sonosite © ultrasound equipment. Christian Svane, Martin Kryspin Sørensen and Jacob Steinmetz declare no conflict of interest.
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A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2013.09.012.