We demonstrated the direct impact of a routine POCUS-driven protocol in patients during the early phase after admission to medical–surgical ICUs. A systematic application of POCUS resulted in decreased utilization of conventional diagnostic imaging resources and time of MV, and facilitated a judicious intravenous fluid administration in critically ill patients during the first week of ICU hospitalization. Application of routine POCUS appears to be safe if utilized by appropriately trained intensivist as no complications were directly associated with POCUS use in the study group.
Previous investigations [2, 5] applying particular ICU-sound protocol led to more accurate admission diagnosis in 25.6% to 24.9%. They had an observational design, but are comparable to the 22% accuracy rate of new or corrected diagnoses in our study. Moreover, the majority of our patient population suffered from sepsis. Manno et al. [2] proposed that septic patients may be the most favored subgroup of patients receiving a POCUS protocol because of the myriad of information and therapies that can be tailored to each individual patient.
The main effect of routine utilization of our POCUS protocol was the clinical decision-making, more specifically in pharmacologic management adjustments in shock patients (60%) and ordering of ultrasound-guided procedures (23%). In our study, we found that 23% of our population required ultrasound-guided invasive procedures, which is similar to the 21.6% reported by the Manno group [2]. Vignon et al. [13] described a change in therapeutic management of patients in 51% of the cases, and Bernier-Jean et al. [5] in 44%.
Management of intravascular volume status can be a difficult decision at the bedside. Meticulous fluid management in treating shock patients with heart disease is desirable. In our case, the most common clinical decision was related to fluid management. Similar findings have been described in an observational study [13], but we emphasize the randomized-controlled design of our study. Nonetheless, our direct comparison of timely ultrasound-driven versus conventional management allows us to represent the current practice in the majority of medical centers due to lack of routine utilization of ultrasound by intensivists. Furthermore, positive fluid responsiveness test does not indicated necessity of further fluid administration, our clinical-decision making was determined by the echocardiography measurements (LVEF, IVC distensibility index) in addition to systemic perfusion surrogates (central venous saturation, arteriovenous CO2 difference, and plasma lactate measurements). Finally, in cases of heart failure, we guided restriction of fluids by signs of pulmonary and systemic congestion. However, we acknowledge tolerance to fluids must be assessed with diastolic function parameters and may be in addition to lung ultrasonography [14,15,16].
Our POCUS protocol led to a significantly lower utilization of chest radiography, ultrasound performed by non-intensivist specialists, and CT scans (up to 56% reduction in CT requests). We found a reduction of radiology evaluation utilization from 4.1 in the control group to 2.6 in the POCUS group (63% reduction). This finding differs from other groups reporting 22% to 26% reduction in radiography utilization [17, 18]. Possible explanations include intensivist discretion versus specific protocol, considerable critical care ultrasound expertise by attending intensivist at time of the study, and more availability of fully capable ultrasound devices. Of note, the American College of Radiology expert panel recommended daily radiology for each intubated patient [17]. The direct clinical implications of our findings were associated with lower radiation exposure, less intra-hospital transportation of unstable patients, and inherent economic savings with more sophisticated evaluations, including in improved imaging suites workflow and reduced necessity for personnel to transport patients [19,20,21].
We found a significant correlation between cardiac function (left systolic ventricle function measured by LVEF index) and a negative FB in the first 5 days of ICU management. This might indicate that judicious fluid management and decisions in administration of diuretic agents are facilitated with real-time utilization of POCUS since ICU admission. We did not find a significant correlation between time spent on MV and FB or between duration of MV and LVEF. This can possibly be explained by the heterogeneity of our population. However, there was correlation between lower LVEF and negative FB, since patients with low LVEF are likely to receive less fluids and more diuretics.
We acknowledge several limitations in the current investigation. First, our small patient population avoids finding significant differences in meaningful clinical outcomes, such as mortality. Second, we analyzed only the first 5 days of ICU stay. However, as patients stay longer in the ICU, additional confounding factors not necessarily related with admission diagnosis can affect the outcomes (late-onset, ventilator-associated pneumonia). Mortality was similar between both groups, but it should be noted that future studies with larger patient populations having a shorter time of MV as found in the POCUS group could potentially determine a decrease in mortality related to MV complications. Third, we did not find a significant correlation between normal or high ejection fraction and pulmonary B profile in our study that can imply possible tolerance to fluid administration. However, patients with CHF and preserved EF can be only characterized with advanced echocardiography parameters of diastolic function. We recognize that the lack of diastolic function assessment is another limitation of this study. However, we aimed to evaluate a practical approach for assessment of ventricular function and fluid responsiveness, so we propose further investigation of the correlation between normal or high ejection fraction and pulmonary B profile in addition to diastolic function assessment in septic shock patients.
Finally, the absence of a reposition protocol guided by pre-established ultrasound should be endorsed in multicentric studies.