Head to toe ultrasound: a narrative review of experts’ recommendations of methodological approaches

Critical care ultrasonography (US) is widely used by intensivists managing critically ill patients to accurately and rapidly assess different clinical scenarios, which include pneumothorax, pleural effusion, pulmonary edema, hydronephrosis, hemoperitoneum, and deep vein thrombosis. Basic and advanced critical care ultrasonographic skills are routinely used to supplement physical examination of critically ill patients, to determine the etiology of critical illness and to guide subsequent therapy. European guidelines now recommend the use of US for a number of practical procedures commonly performed in critical care. Full training and competence acquisition are essential before significant therapeutic decisions are made based on the US assessment. However, there are no universally accepted learning pathways and methodological standards for the acquisition of these skills. Therefore, in this review, we aim to provide a methodological approach of the head to toe ultrasonographic evaluation of critically ill patients considering different districts and clinical applications

Transcranial Doppler as a screening test to exclude intracranial hypertension in brain-injured patients: the IMPRESSIT-2 prospective multicenter international study

Background: Alternative noninvasive methods capable of excluding intracranial hypertension through use of transcranial Doppler (ICPtcd) in situations where invasive methods cannot be used or are not available would be useful during the management of acutely brain-injured patients. The objective of this study was to determine whether ICPtcd can be considered a reliable screening test compared to the reference standard method, invasive ICP monitoring (ICPi), in excluding the presence of intracranial hypertension. Methods: This was a prospective, international, multicenter, unblinded, diagnostic accuracy study comparing the index test (ICPtcd) with a reference standard (ICPi), defined as the best available method for establishing the presence or absence of the condition of interest (i.e., intracranial hypertension). Acute brain-injured patients pertaining to one of four categories: traumatic brain injury (TBI), subarachnoid hemorrhage (SAH), intracerebral hemorrhage (ICH) or ischemic stroke (IS) requiring ICPi monitoring, were enrolled in 16 international intensive care units. ICPi measurements (reference test) were compared to simultaneous ICPtcd measurements (index test) at three different timepoints: before, immediately after and 2 to 3 h following ICPi catheter insertion. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) were calculated at three different ICPi thresholds (> 20, > 22 and > 25 mmHg) to assess ICPtcd as a bedside real-practice screening method. A receiver operating characteristic (ROC) curve analysis with the area under the curve (AUC) was used to evaluate the discriminative accuracy and predictive capability of ICPtcd. Results: Two hundred and sixty-two patients were recruited for final analysis. Intracranial hypertension (> 22 mmHg) occurred in 87 patients (33.2%). The total number of paired comparisons between ICPtcd and ICPi was 687. The NPV was elevated (ICP > 20 mmHg = 91.3%, > 22 mmHg = 95.6%, > 25 mmHg = 98.6%), indicating high discriminant accuracy of ICPtcd in excluding intracranial hypertension. Concordance correlation between ICPtcd and ICPi was 33.3% (95% CI 25.6-40.5%), and Bland-Altman showed a mean bias of -3.3 mmHg. The optimal ICPtcd threshold for ruling out intracranial hypertension was 20.5 mmHg, corresponding to a sensitivity of 70% (95% CI 40.7-92.6%) and a specificity of 72% (95% CI 51.9-94.0%) with an AUC of 76% (95% CI 65.6-85.5%). Conclusions and relevance: ICPtcd has a high NPV in ruling out intracranial hypertension and may be useful to clinicians in situations where invasive methods cannot be used or not available. Trial registration: NCT02322970

How to use cerebral ultrasound in the ICU

Cerebral ultrasound is a developing point of care tool for intensivists and emergency physicians, with an important role in the diagnosis of acute intracranial pathology, such as the assessment of cerebrovascular diseases and in the noninvasive intracranial pressure measurement both in the acute clinical settings and in intensive care unit (ICU). The traditional application of transcranial doppler (TCD) by assessing blood flow velocities in the main cerebral arteries, allows the evaluation and follow up of cerebral vasospasm, cerebral perfusion pressure, cerebral autoregulation and intracranial hypertension. The use of TCD, traditionally limited to the neurosonology laboratories settings, has expanded over the last years following the introduction of B-mode ultrasound and color Doppler, the transcranial color-coded duplex ultrasonography (TCCS), opening a new window to the assessment of cerebral anatomy not only in the neurocritical patients, but also in general ICU and emergency room patients. Here we report a brief review with the intent to up-to-date and describe the main applications and use of TCD/TCCS in the setting of Neurointensive Care

Doppler Non-invasive Monitoring of ICP in an Animal Model of Acute Intracranial Hypertension.

BACKGROUND: In many neurological diseases, intracranial pressure (ICP) is elevated and needs to be actively managed. ICP is typically measured with an invasive transducer, which carries risks. Non-invasive techniques for monitoring ICP (nICP) have been developed. The aim of this study was to compare three different methods of transcranial Doppler (TCD) assessment of nICP in an animal model of acute intracranial hypertension. METHODS: In 28 rabbits, ICP was increased to 70-80 mmHg by infusion of Hartmann's solution into the lumbar subarachnoid space. Doppler flow velocity in the basilar artery was recorded. nICP was assessed through three different methods: Gosling's pulsatility index PI (gPI), Aaslid's method (AaICP), and a method based on diastolic blood flow velocity (FVdICP). RESULTS: We found a significant correlation between nICP and ICP when all infusion experiments were combined (FVdICP: r = 0.77, AaICP: r = 0.53, gPI: r = 0.54). The ability to distinguish between raised and 'normal' values of ICP was greatest for FVdICP (AUC 0.90 at ICP >40 mmHg). When infusion experiments were considered independently, FVdICP demonstrated again the strongest correlation between changes in ICP and changes in nICP (mean r = 0.85). CONCLUSIONS: TCD-based methods of nICP monitoring are better at detecting changes of ICP occurring in time, rather than absolute prediction of ICP as a number. Of the studied methods of nICP, the method based on FVd is best to discriminate between raised and 'normal' ICP and to monitor relative changes of ICP

The IN-PANCIA Study: Clinical Evaluation of Gastrointestinal Dysfunction and Failure, Multiple Organ Failure, and Levels of Citrulline in Critically Ill Patients

Gastrointestinal dysfunction and failure (GID and GIF) in critically ill patients are a common, relevant, and underestimated complications in ICU patients. The aims of this study were (1) to determine plasmatic levels of citrulline, glutamine, and arginine as markers of GID/GIF in critically ill patients with or without GID/GIF with or without multiple organ failure (MOF) and (2) to assess the role of intra-abdominal hypertension in these patient groups

Evaluation and Application of Ultra-Low-Resolution Pressure Reactivity Index in Moderate or Severe Traumatic Brain Injury

Background: The pressure reactivity index (PRx) has emerged as a surrogate method for the continuous bedside estimation of cerebral autoregulation and a predictor of unfavorable outcome after traumatic brain injury (TBI). However, calculation of PRx require continuous high-resolution monitoring currently limited to specialized intensive care units. The aim of this study was to evaluate a new index, the ultra-low-frequency PRx (UL-PRx) sampled at ∼0.0033 Hz at ∼5 minutes periods, and to investigate its association with outcome. Methods: Demographic data, admission Glasgow coma scale, in-hospital mortality and Glasgow outcome scale extended at 12 months were extracted from electronic records. The filtering and preparation of time series of intracranial pressure (ICP), mean arterial pressure and cerebral perfusion pressure (CPP), and calculation of the indices (UL-PRx, Δ-optimal CPP), were performed in MATLAB using an in-house algorithm. Results: A total of 164 TBI patients were included in the study; in-hospital and 12-month mortality was 29.3% and 38.4%, respectively, and 64% of patients had poor neurological outcome at 12 months. On univariate analysis, ICP, CPP, UL-PRx, and ΔCPPopt were associated with 12-month mortality. After adjusting for age, Glasgow coma scale, ICP and CPP, mean UL-PRx and UL-PRx thresholds of 0 and +0.25 remained associated with 12-month mortality. Similar findings were obtained for in-hospital mortality. For mean UL-PRx, the area under the receiver operating characteristic curves for in-hospital and 12-month mortality were 0.78 (95% confidence interval [CI]: 0.69-0.87; P<0.001) and 0.70 (95% CI: 0.61-0.79; P<0.001), respectively, and 0.65 (95% CI: 0.57-0.74; P=0.001) for 12-month neurological outcome. Conclusions: Our findings indicate that ultra-low-frequency sampling might provide sufficient resolution to derive information about the state of cerebrovascular autoregulation and prediction of 12-month outcome in TBI patients

The accuracy of transcranial Doppler in excluding intracranial hypertension following acute brain injury: a multicenter prospective pilot study

Untimely diagnosis of intracranial hypertension may lead to delays in therapy and worsening of outcome. Transcranial Doppler (TCD) detects variations in cerebral blood flow velocity which may correlate with intracranial pressure (ICP). We investigated if intracranial hypertension can be accurately excluded through use of TCD

Transcranial Doppler as a screening test to exclude intracranial hypertension in brain-injured patients: the IMPRESSIT-2 prospective multicenter international study

Background: Alternative noninvasive methods capable of excluding intracranial hypertension through use of transcranial Doppler (ICPtcd) in situations where invasive methods cannot be used or are not available would be useful during the management of acutely brain-injured patients. The objective of this study was to determine whether ICPtcd can be considered a reliable screening test compared to the reference standard method, invasive ICP monitoring (ICPi), in excluding the presence of intracranial hypertension. Methods: This was a prospective, international, multicenter, unblinded, diagnostic accuracy study comparing the index test (ICPtcd) with a reference standard (ICPi), defined as the best available method for establishing the presence or absence of the condition of interest (i.e., intracranial hypertension). Acute brain-injured patients pertaining to one of four categories: traumatic brain injury (TBI), subarachnoid hemorrhage (SAH), intracerebral hemorrhage (ICH) or ischemic stroke (IS) requiring ICPi monitoring, were enrolled in 16 international intensive care units. ICPi measurements (reference test) were compared to simultaneous ICPtcd measurements (index test) at three different timepoints: before, immediately after and 2 to 3 h following ICPi catheter insertion. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) were calculated at three different ICPi thresholds (> 20, > 22 and > 25 mmHg) to assess ICPtcd as a bedside real-practice screening method. A receiver operating characteristic (ROC) curve analysis with the area under the curve (AUC) was used to evaluate the discriminative accuracy and predictive capability of ICPtcd. Results: Two hundred and sixty-two patients were recruited for final analysis. Intracranial hypertension (> 22 mmHg) occurred in 87 patients (33.2%). The total number of paired comparisons between ICPtcd and ICPi was 687. The NPV was elevated (ICP > 20 mmHg = 91.3%, > 22 mmHg = 95.6%, > 25 mmHg = 98.6%), indicating high discriminant accuracy of ICPtcd in excluding intracranial hypertension. Concordance correlation between ICPtcd and ICPi was 33.3% (95% CI 25.6-40.5%), and Bland-Altman showed a mean bias of -3.3 mmHg. The optimal ICPtcd threshold for ruling out intracranial hypertension was 20.5 mmHg, corresponding to a sensitivity of 70% (95% CI 40.7-92.6%) and a specificity of 72% (95% CI 51.9-94.0%) with an AUC of 76% (95% CI 65.6-85.5%). Conclusions and relevance: ICPtcd has a high NPV in ruling out intracranial hypertension and may be useful to clinicians in situations where invasive methods cannot be used or not available. Trial registration:   NCT02322970