Aplicaciones del dúplex transcraneal codificado en color en la monitorización del enfermo neurocrítico

Transcranial sonography in the critical patient

Transcranial ultrasonography is a non-invasive, bedside technique that has become a widely implemented tool in the evaluation and management of neurocritically ill patients. It constitutes a technique in continuous growth whose fundamentals (and limitations) must be known by the intensivist. This review provides a practical approach for the intensivist, including the different sonographic windows and planes of insonation and its role in different conditions of the neurocritical patients and in critical care patients of other etiologies.

Age-Related Changes in Cerebral Hemodynamics in Children Undergoing Congenital Cardiac Surgery: A Prospective Observational Study

OBJECTIVE

To explore age-related cerebral hemodynamic characteristics before and after pediatric cardiac surgery.

DESIGN

Prospective observational study.

SETTING

Single-center study based at a tertiary care center in Shanghai, China.

PATIENTS

Fifty-three children with congenital heart disease (CHD) aged zero-to-six years undergoing cardiac surgery with cardiopulmonary bypass were enrolled, and 44 children finally were analyzed.

INTERVENTION

Cerebral hemodynamics were measured by transcranial color-coded duplex sonography in the right temporal window before and after surgery. The resistance index (RI), pulsatility index (PI), and cerebral blood flow velocity (CBFV), including time average maximum flow velocity (V_tamax), mean blood flow velocity (V_mean), and the peak systolic flow velocity (V_peak), of the right middle cerebral artery (MCA) and regional cerebral oxygen saturation (rScO₂) of the right frontal lobe were measured and analyzed. Heart rate and mean arterial pressure were also recorded during ultrasound.

MEASUREMENTS AND MAIN RESULTS

RI and PI decreased exponentially with age before and after cardiac surgery. While PI remained unchanged after cardiac surgery, RI was significantly reduced. Furthermore, RI reduction after cardiac surgery was more significant in children >18 months compared to those ≤18 months. CBFV of the right MCA also showed exponential increase with age, but rScO₂ linearly increased. Cardiac surgery significantly changed the cerebral hemodynamics, but it did not affect rScO₂ in children regardless of age.

CONCLUSIONS

Age-related cerebral hemodynamic changes exist in children with CHD. Cardiopulmonary bypass surgery led to greater cerebrovascular dilation in children aged ≤18 months than those >18 months.

Applications of Transcranial Color-Coded Sonography in the Emergency Department

Transcranial color-coded Doppler sonography is a noninvasive bedside ultrasound application that combines both imaging of parenchymal structures and Doppler assessment of intracranial vessels. It may aid in rapid diagnoses and treatment decision making of patients with intracranial emergencies in point-of-care settings. This pictorial essay illustrates the technical aspects and emergency department applications of transcranial color-coded Doppler sonography, and provides some rationale for implementation of this technique into the emergency department practice.

Grupo de Consenso en Doppler Transcraneano en el Diagnóstico de Muerte Encefálica*. Latin American consensus on the use of transcranial Doppler in the diagnosis of brain death

Transcranial Doppler evaluates cerebral hemodynamics in patients with brain injury and is a useful technical tool in diagnosing cerebral circulatory arrest, usually present in the brain-dead patient. This Latin American Consensus was formed by a group of 26 physicians experienced in the use of transcranial Doppler in the context of brain death. The purpose of this agreement was to make recommendations regarding the indications, technique, and interpretation of the study of transcranial ultrasonography in patients with a clinical diagnosis of brain death or in the patient whose clinical diagnosis presents difficulties; a working group was formed to enable further knowledge and to strengthen ties between Latin American physicians working on the same topic. A review of the literature, concepts,and experiences were exchanged in two meetings and via the Internet. Questions about pathophysiology, equipment, techniques, findings, common problems, and the interpretation of transcranial Doppler in the context of brain death were answered. The basic consensus statements are the following: cerebral circulatory arrest is the final stage in the evolution of progressive intracranial hypertension, which is visualized with transcranial Doppler as a "pattern of cerebral circulatory arrest". The following are accepted as the standard of cerebral circulatory arrest: reverberant pattern, systolic spikes, and absence of previously demonstrated flow. Ultrasonography should be used - in acceptable hemodynamic conditions - in the anterior circulation bilaterally (middle cerebral artery) and in the posterior (basilar artery) territory. If no ultrasonographic images are found in any or all of these vessels, their proximal arteries are acceptable to be studied to look for a a pattern of cerebral circulatory arrest.

Transcranial Sonography and Cerebral Circulatory Arrest in Adults: A Comprehensive Review

The diagnosis of brain death remains a clinical challenge for intensive care unit physicians. Worldwide regulations in its diagnosis may differ, and the need of ancillary tests after a clinical examination is not uniform. Transcranial sonography is a noninvasive, bedside, and widely available technique that can be used in the diagnosis of the cerebral circulatory arrest that preceeds brain death. In this paper we review the general concepts, the technical requisites, the patterns of Doppler signal confirming cerebral circulatory arrest, the vessels to insonate, and the options in cases with poor acoustic window. Future research perspectives in the field of transcranial sonography are discussed as well.

[Emergency transcranial doppler ultrasound: predictive value for the development of symptomatic vasospasm in spontaneous subarachnoid hemorrhage in patients in good neurological condition]

PURPOSE

To examine the predictive value of an early transcranial Doppler ultrasound (TCD) study performed in the emergency department in patients with spontaneous subarachoniod hemorrhage (SAH) in good neurological condition, in order to know which patients are at high risk of developing delayed cerebral ischemia (DCI).

DESIGN

A descriptive observational study was carried out involving a period of 3 years.

SETTING

Critical Care and Emergency Department.

PATIENTS

The study consecutively included patients with SAH of grade I-III on the Hunt and Hess scale.

VARIABLES OF INTEREST

DCI (decrease of 2 points in GCS or focal deficit), Mean Velocity (MV) of middle cerebral arteries (MCA), Lindegaard Index (IL). Sonographic vasospasm pattern (SVP) was considered if MCA-MV>120cm/sc and IL>3.

RESULTS

The mean age of the 122 patients was 54.1±13.7 years; 57.3% were women. SVP was detected in 24 patients (19.7%), although high velocities patterns (HVP) were present in 38 patients (31.1%). DCI developed in 21 patients (MV183+/-49cm/sc), all with previous SVP. In this group MV increased 22+/-5cm/sc/day during the first 3 days. The group without HVP (84 patients/MV of 67+/-16.6cm/sc), compared with DCI group, showed differences in highest MV (p<0.001), and also ΔMV/day (8.30+/-4,5cm/sc Vs 22+/-5cm/sc) during the first 3 days (p=0.009). In our series, ROC analysis selected the best cut-off value for ΔMV/day as 21cm/sc (p<0.001).

CONCLUSION

During the first 3 days, an increase of 21cm/s/24h in MCA-MV was associated with the development of symptomatic vasospasm. TCD is a useful tool for the early detection of patients at risk of DCI after SAH.

Transcranial color coded duplex sonography in the intensive care unit

Case report

A case of a 43-year-old male with severe pancreatitis complicated with neurological deterioration is presented.

Methods and result

Different neurosonological examinations using transcranial color coded duplex sonography (TCCS) were combined to obtain a certain diagnosis.

Conclusion

This case illustrates some of the applications of TCCS at bedside in ICU patients. These sonographic explorations are useful in the monitoring of ICU patients, and may avoid hazardous transfers to the radiology department for the patient.

[Transcranial Doppler ultrasonography usefulness in cardiac arrest resuscitation]

An effective tissue perfusion has decisive influence on the final prognosis both during cardiopulmonary resuscitation (CPR) and after recovery of spontaneous circulation (ROSC). The transcranial Doppler ultranosography (TCD) examines the velocity and pulsatility of cerebral blood flow, making it possible to perform "beat to beat" hemodynamic analysis. During CPR, TCD peak systolic velocity reflects cerebral perfusion of the chest compressions. Beyond 2 hours after ROSC, persistence in the cerebral arteries of a hemodynamic TCD pattern (low velocities with high pulsatilities) predicts poor neurological prognosis. Early or delayed presence of a hyperemic TCD pattern (high velocities with low pulsatilities) is associated conclusively with evolution to intracranial hypertension and its appearance during the rewarming process should lead to immediate return to therapeutic hypothermia. The coincidence of hypodynamic cerebral arteries and others with normal or hyperemic TCD patterns may indicate the presence of focal hypoperfusion that could predict stroke after ROSC.

Ultrasonographic cerebral perfusion in assessment of brain death: a preliminary study

OBJECTIVE

The purpose of this series was to describe the ultrasonographic perfusion pattern in patients with brain death.

METHODS

Thirteen patients with different neurologic disorders in whom brain death developed were studied. Transcranial perfusion was analyzed after injection of 2.5 mL of a sulfur hexafluoride ultrasonographic contrast agent. Time-intensity curves were analyzed in predetermined regions of interest.

RESULTS

In all patients, analysis of regions of interest showed no bolus-like curve progression. This finding implies a complete absence of cerebral perfusion.

CONCLUSIONS

Patients with brain death studied by ultrasonographic perfusion techniques have a characteristic pattern.