Impacts of a Pressure Challenge on Cerebral Critical Closing Pressure and Effective Cerebral Perfusion Pressure in Patients with Traumatic Brain Injury.

INTRODUCTION: Cerebral critical closing pressure (CrCP) comprises intracranial pressure (ICP) and arteriolar wall tension (WT). It is the arterial blood pressure (ABP) at which small vessels close and circulation stops. We hypothesized that the increase in WT secondary to a systemic hypertensive challenge would lead to an increase in CrCP and that the "effective" cerebral perfusion pressure (CPPeff; calculated as ABP - CrCP) would give more complete information than the "conventional" cerebral perfusion pressure (CPP; calculated as ABP - ICP). OBJECTIVE: This study aimed to compare CrCP, CPP, and CPPeff changes during a hypertensive challenge in patients with a severe traumatic brain injury. PATIENTS AND METHODS: Data on ABP, ICP, and cerebral blood flow velocity, measured by transcranial Doppler ultrasound, were acquired simultaneously for 30 min both basally and during a hypertensive challenge. An impedance-based CrCP model was used. RESULTS: The following values are expressed as median (interquartile range). There were 11 patients, aged 29 (14) years. CPP increased from 73 (17) to 102 (26) mmHg (P ≤ 0.001). ICP did not change. CrCP changed from 23 (11) to 27 (10) mmHg (P ≤ 0.001). WT increased from 7 (5) to 11 (7) mmHg (P ˂ 0.005). CPPeff changed less than CPP. CONCLUSION: The CPP change was greater than the CPPeff change, mainly because CrCP increased simultaneously with the WT increase as a result of the autoregulatory response. CPPeff provides information about the real driving force generating blood movement.

Transcranial Doppler Plateau Wave in a Patient with Pseudo-Chiari Malformation.

CASE REPORT: A 26-year-old woman presented a superior sagittal and transverse sinus thrombosis with venous infarction. Anticoagulation was started. Six months later headache and visual impairment developed, and intracranial hypertension was diagnosed-secondary pseudotumor cerebri. It was managed with a lumbo-peritoneal shunt (LPS) resulting in a positive initial evolution with initial symptoms resolution, but headache and visual impairment eventually reappeared. Magnetic Resonance Imaging revealed a Pseudo-Chiari malformation, leading to lumbo-peritoneal shunt removal (Friedman et al. Neurology 81:1159-1165, 2013; Moncho et al. Rev Neurol 56(12):623-634, 2013). As symptoms reappeared, a short period of continuous transcranial Doppler neuromonitoring, including a change of head of bed elevation, was performed. A sudden decrease in cerebral blood flow velocity with a dramatic increase in pulsatility index developed when head of bed was moved from 45° to horizontal position. Transcranial Doppler changes were compatible with a plateau wave of intracranial hypertension. A ventricle-peritoneal shunt was inserted, which resulted in symptomatology, imaging, and digital campimetry improvement.

Hypocapnia after traumatic brain injury: how does it affect the time constant of the cerebral circulation?

The time constant of the cerebral arterial bed ("tau") estimates how fast the blood entering the brain fills the arterial vascular sector. Analogous to an electrical resistor-capacitor circuit, it is expressed as the product of arterial compliance (Ca) and cerebrovascular resistance (CVR). Hypocapnia increases the time constant in healthy volunteers and decreases arterial compliance in head trauma. How the combination of hyocapnia and trauma affects this parameter has yet to be studied. We hypothesized that in TBI patients the intense vasoconstrictive action of hypocapnia would dominate over the decrease in compliance seen after hyperventilation. The predominant vasoconstrictive response would maintain an incoming blood volume in the arterial circulation, thereby lengthening tau. We retrospectively analyzed recordings of intracranial pressure (ICP), arterial blood pressure (ABP), and blood flow velocity (FV) obtained from a cohort of 27 severe TBI patients [(39/30 years (median/IQR), 5 women; admission GCS 6/5 (median/IQR)] studied during a standard clinical CO2 reactivity test. The reactivity test was performed by means of a 50-min increase in ventilation (20% increase in respiratory minute volume). CVR and Ca were estimated from these recordings, and their product calculated to find the time constant. CVR significantly increased [median CVR pre-hypocapnia/during hypocapnia: 1.05/1.35 mmHg/(cm3/s)]. Ca decreased (median Ca pre-hypocapnia/during hypocapnia: 0.130/0.124 arbitrary units) to statistical significance (p = 0.005). The product of these two parameters resulted in a significant prolongation of the time constant (median tau pre-hypocapnia/during hypocapnia: 0.136 s/0.152 s, p ˂ .001). Overall, the increase in CVR dominated over the decrease in compliance, hence tau was longer. We demonstrate a significant increase in the time constant of the cerebral circulation during hypocapnia after severe TBI, and attribute this to an increase in cerebrovascular resistance which outweighs the decrease in cerebral arterial bed compliance.

Latin American Consensus Statement for the Use of Contrast-Enhanced Transcranial Ultrasound as a Diagnostic Test for Detection of Right-to-Left Shunt.

BACKGROUND: The role of patent foramen ovale is a field of debate and current publications have increasing controversies about the patients' management in young undetermined stroke. Work up with echocardiography and transcranial Doppler (TCD) can aid the decision with better anatomical and functional characterization of right-to-left shunt (RLS). Medical and interventional strategy may benefit from this information. SUMMARY: a group of experts from the Latin American participants of the Neurosonology Research Group (NSRG) of World Federation of Neurology created a task force to review literature and describe the better methodology of contrast TCD (c-TCD). All signatories of the present consensus statement have published at least one study on TCD as an author or co-author in an indexed journal. Two meetings were held while the consensus statement was being drafted, during which controversial issues were discussed and voted on by the statement signatories. The statement paper was reviewed and approved by the Executive Committee of the NSRG of the World Federation of Neurology. The main objective of this consensus statement is to establish a standardization of the c-TCD technique and its interpretation, in order to improve the informative quality of the method, resulting in expanding the application of TCD in the clinical setting. These recommendations optimize the comparison of different diagnostic methods and encourage the use of c-TCD for RLS screening and complementary diagnosis in multicenter studies.

Early Transcranial Doppler Evaluation of Cerebral Autoregulation Independently Predicts Functional Outcome After Aneurysmal Subarachnoid Hemorrhage.

BACKGROUND: Cerebral autoregulation (CA) impairment after aneurysmal subarachnoid hemorrhage (SAH) has been associated with delayed cerebral ischemia and an unfavorable outcome. We investigated whether the early transient hyperemic response test (THRT), a transcranial Doppler (TCD)-based CA evaluation method, can predict functional outcome 6 months after aneurysmal SAH. METHODS: This is a prospective observational study of all aneurysmal SAH patients consecutively admitted to a single center between January 2016 and February 2017. CA was evaluated within 72 h of hemorrhage by THRT, which describes the changes in cerebral blood flow velocity after a brief compression of the ipsilateral common carotid artery. CA was considered to be preserved when an increase ≥ 9% of baseline systolic velocity was present. According to the modified Rankin Scale (mRS: 4-6), the primary outcome was unfavorable 6 months after hemorrhage. Secondary outcomes included cerebral infarction, vasospasm on TCD, and an unfavorable outcome at hospital discharge. RESULTS: Forty patients were included (mean age = 54 ± 12 years, 70% females). CA was impaired in 19 patients (47.5%) and preserved in 21 (52.5%). Impaired CA patients were older (59 ± 13 vs. 50 ± 9, p = 0.012), showed worse neurological conditions (Hunt&Hess 4 or 5-47.4% vs. 9.5%, p = 0.012), and clinical initial condition (APACHE II physiological score-12 [5.57-13] vs. 3.5 [3-5], p = 0.001). Fourteen patients in the impaired CA group and one patient in the preserved CA group progressed to an unfavorable outcome (73.7% vs. 4.7%, p = 0.0001). The impaired CA group more frequently developed cerebral infarction than the preserved CA group (36.8% vs. 0%, p = 0.003, respectively). After multivariate analysis, impaired CA (OR 5.15 95% CI 1.43-51.99, p = 0.033) and the APACHE II physiological score (OR 1.67, 95% CI 1.01-2.76, p = 0.046) were independently associated with an unfavorable outcome. CONCLUSIONS: Early CA impairment detected by TCD and admission APACHE II physiological score independently predicted an unfavorable outcome after SAH.

Effect of Mild Hypocapnia on Critical Closing Pressure and Other Mechanoelastic Parameters of the Cerebrospinal System.

OBJECTIVE: Brain arterial critical closing pressure (CrCP) has been studied in several diseases such as traumatic brain injury (TBI), subarachnoid haemorrhage, hydrocephalus, and in various physiological scenarios: intracranial hypertension, decreased cerebral perfusion pressure, hypercapnia, etc. Little or nothing so far has been demonstrated to characterise change in CrCP during mild hypocapnia. METHOD: We retrospectively analysed recordings of intracranial pressure (ICP), arterial blood pressure (ABP) and blood flow velocity from 27 severe TBI patients (mean 39.5 ± 3.4 years, 6 women) in whom a ventilation increase (20% increase in respiratory minute volume) was performed over 50 min as part of a standard clinical CO2 reactivity test. CrCP was calculated using the Windkessel model of cerebral arterial flow. Arteriolar wall tension (WT) was calculated as a difference between CrCP and ICP. The compartmental compliances arterial (C a ) and cerebrospinal fluid space (C i ) were also evaluated. RESULTS: During hypocapnia, ICP decreased from 17±6.8 to 13.2±6.6 mmHg (p < 0.000001). Wall tension increased from 14.5 ± 9.9 to 21.7±9.1 mmHg (p < 0.0002). CrCP, being a sum of WT + ICP, changed significantly from 31.5 ± 11.9 mmHg to 34.9±11.1 mmHg (p < 0.002), and the closing margin (ABP-CrCP) remained constant at an average value of 60 mmHg. C a decreased significantly during hypocapnia by 30% (p < 0.00001) and C i increased by 26% (p < 0.003). CONCLUSION: During hypocapnia in TBI patients, ICP decreases and WT increases. CrCP increases slightly as the rise in wall tension outweighs the decrease in ICP. The closing margin remained unchanged, suggesting that the risk of hypocapnia-induced ischemia might not be increased.

Transcranial Doppler Monitoring of Intracranial Pressure Plateau Waves.

BACKGROUND: Transcranial Doppler (TCD) has been used to estimate ICP noninvasively (nICP); however, its accuracy varies depending on different types of intracranial hypertension. Given the high specificity of TCD to detect cerebrovascular events, this study aimed to compare four TCD-based nICP methods during plateau waves of ICP. METHODS: A total of 36 plateau waves were identified in 27 patients (traumatic brain injury) with TCD, ICP, and ABP simultaneous recordings. The nICP methods were based on: (1) interaction between flow velocity (FV) and ABP using a "black-box" mathematical model (nICP_BB); (2) diastolic FV (nICP_FV d ); (3) critical closing pressure (nICP_CrCP), and (4) pulsatility index (nICP_PI). Analyses focused on relative changes in time domain between ICP and noninvasive estimators during plateau waves and the magnitude of changes (∆ between baseline and plateau) in real ICP and its estimators. A ROC analysis for an ICP threshold of 35 mmHg was performed. RESULTS: In time domain, nICP_PI, nICP_BB, and nICP_CrCP presented similar correlations: 0.80 ± 0.24, 0.78 ± 0.15, and 0.78 ± 0.30, respectively. nICP_FV d presented a weaker correlation (R = 0.62 ± 0.46). Correlations between ∆ICP and ∆nICP were better represented by nICP_CrCP and BB, R = 0.48, 0.44 (p < 0.05), respectively. nICP_FV d and PI presented nonsignificant ∆ correlations. ROC analysis showed moderate to good areas under the curve for all methods: nICP_BB, 0.82; nICP_FV d , 0.77; nICP_CrCP, 0.79; and nICP_PI, 0.81. CONCLUSIONS: Changes of ICP in time domain during plateau waves were replicated by nICP methods with strong correlations. In addition, the methods presented high performance for detection of intracranial hypertension. However, absolute accuracy for noninvasive ICP assessment using TCD is still low and requires further improvement.

Multimodality monitoring consensus statement: monitoring in emerging economies.

The burden of disease and so the need for care is often greater at hospitals in emerging economies. This is compounded by frequent restrictions in the delivery of good quality clinical care due to resource limitations. However, there is substantial heterogeneity in this economically defined group, such that advanced brain monitoring is routinely practiced at certain centers that have an interest in neurocritical care. It also must be recognized that significant heterogeneity in the delivery of neurocritical care exists even within individual high-income countries (HICs), determined by costs and level of interest. Direct comparisons of data between HICs and the group of low- and middle-income countries (LAMICs) are made difficult by differences in patient demographics, selection for ICU admission, therapies administered, and outcome assessment. Evidence suggests that potential benefits of multimodality monitoring depend on an appropriate environment and clinical expertise. There is no evidence to suggest that patients in LAMICs where such resources exist should be treated any differently to patients from HICs. The potential for outcome benefits in LAMICs is arguably greater in absolute terms because of the large burden of disease; however, the relative cost/benefit ratio of such monitoring in this setting must be viewed in context of the overall priorities in delivering health care at individual institutions.

Bedside study of cerebral critical closing pressure in patients with severe traumatic brain injury: a transcranial Doppler study.

OBJECTIVE: Cerebral critical closing pressure (CrCP) is the arterial pressure (AP) below which small arterial cerebral vessels collapse. Our objective was to estimate cerebral CrCP in 12 severe TBI patients, relating transcranial Doppler flow velocity (FV) and AP data. METHODS: FV, intracranial pressure (ICP) and invasive AP were prospectively acquired at 50 Hz. CrCP was estimated using three methods (M): M(1): amplitude ratio of FV/AP first harmonics; M(2): AP axis intersection of the regression line between systolic and diastolic values of FV and AP; M(3): AP axis intersection of the regression line between decreasing AP and FV simultaneous values. RESULTS: There were 12 patients. Frequent negative CrCP values were found. Average M(1):-12 mmHg; M(2):-33 mmHg; M(3):-43 mmHg. Correlation between the three methods was significant (P < 0.01). M(1) showed the lowest range and more positive values. The better limits of agreement (Bland and Altman test) were between M(2) and M(3). CONCLUSIONS: The frequently found negative values do not allow us for the moment, to use any of these three methods for clinical guidance.

Basic ultrasound head-to-toe skills for intensivists in the general and neuro intensive care unit population: consensus and expert recommendations of the European Society of Intensive Care Medicine.

PURPOSE: To provide consensus, and a list of experts' recommendations regarding the basic skills for head-to-toe ultrasonography in the intensive care setting. METHODS: The Executive Committee of the European Society of Intensive Care (ESICM) commissioned the project and supervised the methodology and structure of the consensus. We selected an international panel of 19 expert clinicians-researchers in intensive care unit (ICU) with expertise in critical care ultrasonography (US), plus a non-voting methodologist. The panel was divided into five subgroups (brain, lung, heart, abdomen and vascular ultrasound) which identified the domains and generated a list of questions to be addressed by the panel. A Delphi process based on an iterative approach was used to obtain the final consensus statements. Statements were classified as a strong recommendation (84% of agreement), weak recommendation (74% of agreement), and no recommendation (less than 74%), in favor or against. RESULTS: This consensus produced a total of 74 statements (7 for brain, 20 for lung, 20 for heart, 20 for abdomen, 7 for vascular Ultrasound). We obtained strong agreement in favor for 49 statements (66.2%), 8 weak in favor (10.8%), 3 weak against (4.1%), and no consensus in 14 cases (19.9%). In most cases when consensus was not obtained, it was felt that the skills were considered as too advanced. A research agenda and discussion on training programs were implemented from the results of the consensus. CONCLUSIONS: This consensus provides guidance for the basic use of critical care US and paves the way for the development of training and research projects.

Assessment of dynamic cerebral autoregulation in humans: Is reproducibility dependent on blood pressure variability?

We tested the influence of blood pressure variability on the reproducibility of dynamic cerebral autoregulation (DCA) estimates. Data were analyzed from the 2nd CARNet bootstrap initiative, where mean arterial blood pressure (MABP), cerebral blood flow velocity (CBFV) and end tidal CO2 were measured twice in 75 healthy subjects. DCA was analyzed by 14 different centers with a variety of different analysis methods. Intraclass Correlation (ICC) values increased significantly when subjects with low power spectral density MABP (PSD-MABP) values were removed from the analysis for all gain, phase and autoregulation index (ARI) parameters. Gain in the low frequency band (LF) had the highest ICC, followed by phase LF and gain in the very low frequency band. No significant differences were found between analysis methods for gain parameters, but for phase and ARI parameters, significant differences between the analysis methods were found. Alternatively, the Spearman-Brown prediction formula indicated that prolongation of the measurement duration up to 35 minutes may be needed to achieve good reproducibility for some DCA parameters. We conclude that poor DCA reproducibility (ICC<0.4) can improve to good (ICC > 0.6) values when cases with low PSD-MABP are removed, and probably also when measurement duration is increased.

Dynamic Cerebral Autoregulation Reproducibility Is Affected by Physiological Variability.

Parameters describing dynamic cerebral autoregulation (DCA) have limited reproducibility. In an international, multi-center study, we evaluated the influence of multiple analytical methods on the reproducibility of DCA. Fourteen participating centers analyzed repeated measurements from 75 healthy subjects, consisting of 5 min of spontaneous fluctuations in blood pressure and cerebral blood flow velocity signals, based on their usual methods of analysis. DCA methods were grouped into three broad categories, depending on output types: (1) transfer function analysis (TFA); (2) autoregulation index (ARI); and (3) correlation coefficient. Only TFA gain in the low frequency (LF) band showed good reproducibility in approximately half of the estimates of gain, defined as an intraclass correlation coefficient (ICC) of >0.6. None of the other DCA metrics had good reproducibility. For TFA-like and ARI-like methods, ICCs were lower than values obtained with surrogate data (p < 0.05). For TFA-like methods, ICCs were lower for the very LF band (gain 0.38 ± 0.057, phase 0.17 ± 0.13) than for LF band (gain 0.59 ± 0.078, phase 0.39 ± 0.11, p ≤ 0.001 for both gain and phase). For ARI-like methods, the mean ICC was 0.30 ± 0.12 and for the correlation methods 0.24 ± 0.23. Based on comparisons with ICC estimates obtained from surrogate data, we conclude that physiological variability or non-stationarity is likely to be the main reason for the poor reproducibility of DCA parameters.

Reproducibility of dynamic cerebral autoregulation parameters: a multi-centre, multi-method study.

OBJECTIVE: Different methods to calculate dynamic cerebral autoregulation (dCA) parameters are available. However, most of these methods demonstrate poor reproducibility that limit their reliability for clinical use. Inter-centre differences in study protocols, modelling approaches and default parameter settings have all led to a lack of standardisation and comparability between studies. We evaluated reproducibility of dCA parameters by assessing systematic errors in surrogate data resulting from different modelling techniques. APPROACH: Fourteen centres analysed 22 datasets consisting of two repeated physiological blood pressure measurements with surrogate cerebral blood flow velocity signals, generated using Tiecks curves (autoregulation index, ARI 0-9) and added noise. For reproducibility, dCA methods were grouped in three broad categories: 1. Transfer function analysis (TFA)-like output; 2. ARI-like output; 3. Correlation coefficient-like output. For all methods, reproducibility was determined by one-way intraclass correlation coefficient analysis (ICC). MAIN RESULTS: For TFA-like methods the mean (SD; [range]) ICC gain was 0.71 (0.10; [0.49-0.86]) and 0.80 (0.17; [0.36-0.94]) for VLF and LF (p = 0.003) respectively. For phase, ICC values were 0.53 (0.21; [0.09-0.80]) for VLF, and 0.92 (0.13; [0.44-1.00]) for LF (p < 0.001). Finally, ICC for ARI-like methods was equal to 0.84 (0.19; [0.41-0.94]), and for correlation-like methods, ICC was 0.21 (0.21; [0.056-0.35]). SIGNIFICANCE: When applied to realistic surrogate data, free from the additional exogenous influences of physiological variability on cerebral blood flow, most methods of dCA modelling showed ICC values considerably higher than what has been reported for physiological data. This finding suggests that the poor reproducibility reported by previous studies may be mainly due to the inherent physiological variability of cerebral blood flow regulatory mechanisms rather than related to (stationary) random noise and the signal analysis methods.

Between-centre variability in transfer function analysis, a widely used method for linear quantification of the dynamic pressure-flow relation: the CARNet study.

Transfer function analysis (TFA) is a frequently used method to assess dynamic cerebral autoregulation (CA) using spontaneous oscillations in blood pressure (BP) and cerebral blood flow velocity (CBFV). However, controversies and variations exist in how research groups utilise TFA, causing high variability in interpretation. The objective of this study was to evaluate between-centre variability in TFA outcome metrics. 15 centres analysed the same 70 BP and CBFV datasets from healthy subjects (n=50 rest; n=20 during hypercapnia); 10 additional datasets were computer-generated. Each centre used their in-house TFA methods; however, certain parameters were specified to reduce a priori between-centre variability. Hypercapnia was used to assess discriminatory performance and synthetic data to evaluate effects of parameter settings. Results were analysed using the Mann-Whitney test and logistic regression. A large non-homogeneous variation was found in TFA outcome metrics between the centres. Logistic regression demonstrated that 11 centres were able to distinguish between normal and impaired CA with an AUC>0.85. Further analysis identified TFA settings that are associated with large variation in outcome measures. These results indicate the need for standardisation of TFA settings in order to reduce between-centre variability and to allow accurate comparison between studies. Suggestions on optimal signal processing methods are proposed.

Non-invasive intracranial pressure estimation using support vector machine.

Intracranial Pressure (ICP) measurements are of great importance for the diagnosis, monitoring and treatment of many vascular brain disturbances. The standard measurement of the ICP is performed invasively by the perforation of the cranial scalp in the presence of traumatic brain injury (TBI). Measuring the ICP in a noninvasive way is relevant for a great number of pathologies where the invasive measurement represents a high risk. The method proposed in this paper uses the Arterial Blood Pressure (ABP) and the Cerebral Blood Flow Velocity (CBFV) - which may be obtained by means of non-invasive methods - to estimate the ICP. A non-linear Support Vector Machine was used and reached a low error between the real ICP signal and the estimated one, allowing an on-line implementation of the ICP estimation, with an adequate temporal resolution.

Ataque cerebrovascular isquémico en Uruguay: comunicación de los primeros 34 casos trombolizados en el Hospital de Clínicas / Ischemic stroke in Uruguay. First 34 cases of thrombolized patients at the Clinicas Hospital

Introducción: el ataque cerebrovascular (ACV) constituye un problema de salud en Uruguay y en el mundo. Se ha comprobado que la trombolisis intravenosa disminuye la morbimortalidad y las secuelas en los pacientes con ACV isquémicos agudos (nivel de evidencia IA). Objetivos: analizar los casos de ACV isquémico trombolizados en el Hospital de Clínicas y valorar la utilidad de un score de predicción de sangrado intracraneano sintomático en esta población. Material y método: estudio descriptivo, observacional y prospectivo. Población: pacientes trombolizados en el Hospital de Clínicas en el período 2010-2013. Se aplicó score predictivo de hemorragia sintomática a toda la población de trombolizados. Tests estadísticos: test de chi cuadrado, test de student, test de Wilcoxon, se consideraron diferencias estadísticamente significativas aquellas con una p < 0,05. Resultados: treinta y cuatro pacientes trombolizados, promedio de edad 67 años, mayoría mujeres, alto porcentaje de ACV graves, National Institute of Health Stroke Scale (NIHSS) promedio al ingreso: 11, con mejoría estadísticamente significativa al alta. Etiología principal: cardioembolia. Tiempo síntoma aguja promedio: 170 minutos. Hemorragia intracraneana: ocho pacientes (23,5%), fallecieron cuatro de ellos. El puntaje del score de sangrado no predijo el sangrado intracraneano. Conclusiones: en el Hospital de Clínicas, desde la inauguración de la Unidad de ACV, el porcentaje de infartos cerebrales trombolizados ha ido en aumento, siendo actualmente comparable a cifras internacionales. El tiempo síntoma-aguja es menor que en otros estudios. La trombolisis generó un beneficio estadísticamente significativo en la escala de NIHSS. El porcentaje de sangrados fue similar al descrito en la literatura...

One-minute dynamic cerebral autoregulation in severe head injury patients and its comparison with static autoregulation. A transcranial Doppler study.

OBJECTIVE: To compare dynamic and static responses of cerebral blood flow to sudden or slow changes in arterial pressure in severe traumatic brain injury (TBI) patients. DESIGN: Prospective study. PATIENTS AND METHODS: We studied 12 severe TBI patients, age 16-63 years, and median GCS 6. We determined the dynamic cerebral autoregulation: response of cerebral blood flow velocity to a step blood pressure drop, and the static cerebral autoregulation: change in cerebral blood flow velocity after a slow hypertensive challenge. RESULTS: During the dynamic response, the median drop in arterial pressure was 21 mm Hg. Dynamic response was graded between 9 (best) and 0 (worst). The median value was 5; four patients showed high values, (8-9), five patients showed intermediate values (4-6). In three patients (value = 0), the CBFV drop was greater than the cerebral perfusion pressure drop, and maintained through 60 s. The static cerebral autoregulation was preserved in 6/11 patients. The comparison between the two showed four different combinations. The five patients with impaired static cerebral autoregulation showed unfavorable outcome. CONCLUSIONS: A sharp dynamic vasodilator response could not be sustained, and a slow or absent reaction to a sudden hypotensive challenge could show an acceptable cerebral autoregulation in the steady state. We found that patients with impaired static cerebral autoregulation had a poor outcome, whereas those with preserved static cerebral autoregulation experience favorable outcomes.

Direct measurement of intra-abdominal pressure with a solid microtranducer.

OBJECTIVE: To describe a direct intra-abdominal pressure (IAP) measurement technique using a solid microsensor comparing its values with the ones simultaneously obtained by means of Kron's technique. Comparative study between two different methods to measure intra-abdominal pressure in a multidisciplinary intensive care unit of a university hospital. METHODS: In 11 critical patients considered irreversibly ill, IAP was simultaneously measured via Kron's technique (IAPK) and by direct measure (IAPC) through an abdominal tap with a Codman microsensor, inserted through it. Several measurements were obtained at different PEEP levels (0, 10 and 20 cm of H20) and bed inclination (0 degrees , 40 degrees and 60 degrees ). RESULTS: 92 simultaneous measurements of IAPK and IAPC were made. The difference between both measurements (mean +/- SD) were: 0.286 +/- 0.938 mmHg. The correlation coefficient was r = 0.98. Bland-Altman plot showed a narrow distribution: 95% of the differences were between 1.87 mmHg of each averaged value. No complications with IAPC measurements were found. CONCLUSIONS: Direct IAP measurement with a Codman microsensor allows continuous monitoring without urinary tract manipulation, is simple to use and to calibrate, minimally invasive and appropriate for patients at risk to develop abdominal compartmental syndrome. Due to its cost it should be reserved for selected critical patients where standard techniques are contraindicated or can be inaccurate.

Encefalitis a citomegalovirus en un paciente inmunocompetente: análisis clinico, neuropatologico y ultraestructural / Cytomegalovirus encephalitis in an immunocompetent patient: clinical, neuropathological and ultrastructural analysis

Las encefalitis por citomegalovirus en pacientes inmunocompetentes son excepcionales, siendo un patógeno reconocido en pacientes inmunodeprimidos (SIDA, transplantados). Se reporta el caso clínico de una encefalitis por Citomegalovirus en un adulto joven, sin evidencia de enfermedad inmunosupresora, cuyo diagnóstico fue posible mediante la detección de ADN viral en la biopsia cerebral. Se describen además las singularidades clínicas de este caso y los hallazgos de la anatomía patológica y de la microscopía electrónica comparándolos con los reportados en pacientes inmunodeprimidos