Optic nerve sheath diameter measured sonographically as non-invasive estimator of intracranial pressure: a systematic review and meta-analysis

Brain ultrasonography: methodology, basic and advanced principles and clinical applications. A narrative review

Brain ultrasonography can be used to evaluate cerebral anatomy and pathology, as well as cerebral circulation through analysis of blood flow velocities. Transcranial colour-coded duplex sonography is a generally safe, repeatable, non-invasive, bedside technique that has a strong potential in neurocritical care patients in many clinical scenarios, including traumatic brain injury, aneurysmal subarachnoid haemorrhage, hydrocephalus, and the diagnosis of cerebral circulatory arrest. Furthermore, the clinical applications of this technique may extend to different settings, including the general intensive care unit and the emergency department. Its increasing use reflects a growing interest in non-invasive cerebral and systemic assessment. The aim of this manuscript is to provide an overview of the basic and advanced principles underlying brain ultrasonography, and to review the different techniques and different clinical applications of this approach in the monitoring and treatment of critically ill patients.

Optic nerve sheath diameter ultrasonography at admission as a predictor of intracranial hypertension in traumatic brain injured patients: a prospective observational study

OBJECTIVE

Intracranial hypertension and impaired cerebral autoregulation are common causes of secondary injuries in patients with traumatic brain injury (TBI). The primary outcome of this study was to assess whether a noninvasive method to estimate intracranial pressure (ICP) based on the ultrasonography of the optic nerve sheath diameter (ONSD) measured at the time of neurocritical care unit (NCCU) admission is correlated with the mean ICP during NCCU stay. Secondary outcomes were to assess whether ONSD is correlated with the dose of ICP > 20 mm Hg and impaired autoregulation during NCCU stay and with instantaneous ICP and whether ONSD is associated with NCCU mortality.

METHODS

This prospective observational monocentric study included adults with severe TBI. ONSD was measured at NCCU admission, immediately after invasive ICP insertion. ONSD-predicted noninvasive ICP (nICPONSD) was calculated according the formula: nICPONSD = 5 × ONSD - 14 (nICPONSD in mm Hg, ONSD in mm). Autoregulation was measured using the pressure reactivity index (PRx).

RESULTS

In total, 100 patients were included in this study. ONSD was significantly correlated with mean ICP (r = 0.46, p < 0.0001), with mean PRx (r = 0.21, p = 0.04), and with the dose of ICP > 20 mm Hg during NCCU stay (r = 0.49, p < 0.0001). Admission nICPONSD was shown to be significantly correlated with instantaneous ICP (r = 0.85, p < 0.001). ONSD at admission was significantly correlated with NCCU mortality (p = 0.02).

CONCLUSIONS

ONSD measured at NCCU admission can give important information about patients at risk of developing intracranial hypertension and impaired autoregulation. ONSD examination could be useful to screen patients at admission to determine who would benefit from further invasive ICP monitoring.

A comparison of non-invasive versus invasive measures of intracranial pressure in hypoxic ischaemic brain injury after cardiac arrest

AIM

Increased intracranial pressure (ICP) in hypoxic ischaemic brain injury (HIBI) can cause secondary ischaemic brain injury and culminate in brain death. Invasive ICP monitoring is limited by associated risks in HIBI patients. We sought to evaluate the agreement between invasive ICP measurements and non-invasive estimators of ICP (nICP) in HIBI patients.

METHODS

Eligible consecutive adult (age>18) cardiac arrest patients with HIBI were included as part of a single centre prospective interventional study. Invasive ICP monitoring and nICP measurements were undertaken using: a) transcranial Doppler ultrasonography (TCD), b) optic nerve sheet diameter ultrasound (ONSD) and c) jugular venous bulb pressure (JVP). Multiple measurements applied in linear mixed-effects models were considered to obtain the correlation coefficient between ICP and nICP as well as their predictive abilities to detect intracranial hypertension (ICP≥20mm Hg).

RESULTS

Eleven patients were included (median age of 47 [range 20-71], 8 males and 3 females). There was a linear relationship between ICP and nICP with ONSD (R=0.53 [p<0.0001]), JVP (R=0.38 [p<0.001]) and TCD (R=0.30 [p<0.01]). The ability to predict intracranial hypertension was highest for ONSD and TCD (area under the receiver operating curve (AUC)=0.96 [95% CI: 0.90-1.00] and AUC=0.91 [95% CI: 0.83-1.00], respectively). JVP presented the weakest prediction ability (AUC=0.75 [95% CI: 0.56-0.94]).

CONCLUSIONS

ONSD and TCD methods demonstrated agreement with invasively-monitored ICP, suggesting their potential roles in the detection of intracranial hypertension in HIBI after cardiac arrest.

Clinical complications during veno-arterial extracorporeal membrane oxigenation in post-cardiotomy and non post-cardiotomy shock: still the achille's heel

Extracorporeal membrane oxygenation (ECMO) is life-saving for potentially reversible heart failure and respiratory injuries not responsive to conventional therapies. Technological innovations have produced over the years significant improvements in ECMO devices (pump, cannula design and oxygenator) and have allowed a better risk/benefit profile. Alongside with recognized advantages in the treatment of very sick patients, ECMO remains an invasive procedure for mechanical circulatory support (MCS) and it is associated with complications that strongly influence the prognosis. Current review was designed to provide a comprehensive outline on ECMO complications, analyzing risk factors and strategies of management, focusing on adult population undergoing veno-arterial ECMO (VA-ECMO) therapy.