Thrombotic, infectious, and procedural complications of the jugular bulb catheter in the intensive care unit

Invasive Neuromonitoring Modalities in the Pediatric Population

Invasive neuromonitoring has become an important part of pediatric neurocritical care, as neuromonitoring devices provide objective data that can guide patient management in real time. New modalities continue to emerge, allowing clinicians to integrate data that reflect different aspects of cerebral function to optimize patient management. Currently, available common invasive neuromonitoring devices that have been studied in the pediatric population include the intracranial pressure monitor, brain tissue oxygenation monitor, jugular venous oximetry, cerebral microdialysis, and thermal diffusion flowmetry. In this review, we describe these neuromonitoring technologies, including their mechanisms of function, indications for use, advantages and disadvantages, and efficacy, in pediatric neurocritical care settings with respect to patient outcomes.

Physiological Monitoring in Patients with Acute Brain Injury: A Multimodal Approach

Neurocritical care management of acute brain injury (ABI) is focused on identification, prevention, and management of secondary brain injury (SBI). Physiologic monitoring of the brain and other organ systems has a role to predict patient recovery or deterioration, guide individualized therapeutic interventions, and measure response to treatment, with the goal of improving patient outcomes. In this review, we detail how specific physiologic markers of brain injury and neuromonitoring tools are integrated and used in ABI patients to develop therapeutic approaches to prevent SBI.

Neurocritical care monitoring of encephalopathic children with acute liver failure: A systematic review

Research on non-invasive neuromonitoring specific to PALF is limited. This systematic review identifies and synthesis the existing literature on non-invasive approaches to monitoring for neurological sequelae in patients with PALF. A series of literature searches were performed to identify all publications pertaining to five different non-invasive neuromonitoring modalities, in line with PRISMA guidelines. Each modality was selected on the basis of its potential for direct or indirect measurement of cerebral perfusion; studies on electroencephalographic monitoring were therefore not sought. Data were recorded on study design, patient population, comparator groups, and outcomes. A preponderance of observational studies was observed, most with a small sample size. Few incorporated direct comparisons of different modalities; in particular, comparison to invasive intracranial pressure monitoring was largely lacking. The integration of current evidence is considered in the context of the clinically significant distinctions between pediatric and adult ALF, as well as the implications for planning of future investigations to best support the evidence-based clinical care of these patients.

Multimodality Monitoring in Neurocritical Care: Decision-Making Utilizing Direct And Indirect Surrogate Markers

Substantial progress has been made to create innovative technology that can monitor the different physiological characteristics that precede the onset of secondary brain injury, with the ultimate goal of intervening prior to the onset of irreversible neurological damage. One of the goals of neurocritical care is to recognize and preemptively manage secondary neurological injury by analyzing physiologic markers of ischemia and brain injury prior to the development of irreversible damage. This is helpful in a multitude of neurological conditions, whereby secondary neurological injury could present including but not limited to traumatic intracranial hemorrhage and, specifically, subarachnoid hemorrhage, which has the potential of progressing to delayed cerebral ischemia and monitoring postneurosurgical interventions. In this study, we examine the utilization of direct and indirect surrogate physiologic markers of ongoing neurologic injury, including intracranial pressure, cerebral blood flow, and brain metabolism.

Comparison of tissue oximeters on a liquid phantom with adjustable optical properties: an extension

Cerebral near-infrared spectroscopy (NIRS) oximetry may help clinicians to improve patient treatment. However, the application of NIRS oximeters is increasingly causing confusion to the users due to the inconsistency of tissue oxygen haemoglobin saturation (StO2) readings provided by different oximeters. To establish a comparability of oximeters, in our study we performed simultaneous measurements on the liquid phantom mimicking properties of neonatal heads and compared the tested device to a reference NIRS oximeter (OxiplexTS). We evaluated the NIRS oximeters FORE-SIGHT, NIRO and SenSmart, and reproduced previous results with the INVOS and OxyPrem v1.3 oximeters. In general, linear relationships of the StO2 values with respect to the reference were obtained. Device specific hypoxic and hyperoxic thresholds (as used in the SafeBoosC study, www.safeboosc.eu) and a table allowing for conversion of StO2 values are provided.

A validation method for near-infrared spectroscopy based tissue oximeters for cerebral and somatic tissue oxygen saturation measurements

We describe the validation methodology for the NIRS based FORE-SIGHT ELITE^® (CAS Medical Systems, Inc., Branford, CT, USA) tissue oximeter for cerebral and somatic tissue oxygen saturation (StO₂) measurements for adult subjects submitted to the United States Food and Drug Administration (FDA) to obtain clearance for clinical use. This validation methodology evolved from a history of NIRS validations in the literature and FDA recommended use of Deming regression and bootstrapping statistical validation methods. For cerebral validation, forehead cerebral StO₂ measurements were compared to a weighted 70:30 reference (REF CX_B) of co-oximeter internal jugular venous and arterial blood saturation of healthy adult subjects during a controlled hypoxia sequence, with a sensor placed on the forehead. For somatic validation, somatic StO₂ measurements were compared to a weighted 70:30 reference (REF CX_S) of co-oximetry central venous and arterial saturation values following a similar protocol, with sensors place on the flank, quadriceps muscle, and calf muscle. With informed consent, 25 subjects successfully completed the cerebral validation study. The bias and precision (1 SD) of cerebral StO₂ compared to REF CX_B was −0.14 ± 3.07%. With informed consent, 24 subjects successfully completed the somatic validation study. The bias and precision of somatic StO₂ compared to REF CX_S was 0.04 ± 4.22% from the average of flank, quadriceps, and calf StO₂ measurements to best represent the global whole body REF CX_S. The NIRS validation methods presented potentially provide a reliable means to test NIRS monitors and qualify them for clinical use.

Intracranial Multimodality Monitoring for Delayed Cerebral Ischemia

Management of patients with aneurysmal subarachnoid hemorrhage focuses on prevention of rebleeding by early treatment of the aneurysm, as well as detection and management of neurologic and medical complications. Early detection of delayed cerebral ischemia and management of modifiable contributing causes such as vasospasm take a central role, with the goal of preventing irreversible cerebral injury. In efforts to prevent delayed cerebral ischemia, multimodality monitoring has emerged as a promising tool in detecting subclinical physiologic changes before infarction occurs. However, there has been much variability in the utilization of this technology. Recent consensus guidelines discuss the role of multimodality monitoring in acute brain injury. In this review, we evaluate these guidelines and the utility of each modality of multimodality monitoring in aneurysmal subarachnoid hemorrhage.

Multimodal neurologic monitoring

Neurocritical care has two main objectives. Initially, the emphasis is on treatment of patients with acute damage to the central nervous system whether through infection, trauma, or hemorrhagic or ischemic stroke. Thereafter, attention shifts to the identification of secondary processes that may lead to further brain injury, including fever, seizures, and ischemia, among others. Multimodal monitoring is the concept of using various tools and data integration to understand brain physiology and guide therapeutic interventions to prevent secondary brain injury. This chapter will review the use of electroencephalography, intracranial pressure monitoring, brain tissue oxygenation, cerebral microdialysis and neurochemistry, near-infrared spectroscopy, and transcranial Doppler sonography as they relate to neuromonitoring in the critically ill. The concepts and design of each monitor, in addition to the patient population that may most benefit from each modality, will be discussed, along with the various tools that can be used together to guide individualized patient treatment options. Major clinical trials, observational studies, and their effect on clinical outcomes will be reviewed. The future of multimodal monitoring in the field of bioinformatics, clinical research, and device development will conclude the chapter.

Comparison of tissue oximeters on a liquid phantom with adjustable optical properties

The SafeBoosC trial showed that cerebral oximetry combined with a treatment guideline can reduce the the burden of hypoxia in neonates by 50% [Brit. Med. J.350, g7635 (2015)]. However, guidelines based on oximetry by one oximeter are not directly usable by other oximeters. We made a blood-lipid phantom simulating the neonatal head to determine the relation between oxygenation values obtained by different oximeters. We calculated coefficients for easy conversion from one oximeter to the other. We additionally determined the corresponding SafeBoosC intervention thresholds at which we measured an uncertainty of up to 9.2% when varying hemoglobin content from 25μM to 70μM. In conclusion, this paper makes the comparison of absolute values obtained by different oximeters possible.

MRI-based methods for quantification of the cerebral metabolic rate of oxygen

The brain depends almost entirely on oxidative metabolism to meet its significant energy requirements. As such, the cerebral metabolic rate of oxygen (CMRO2) represents a key measure of brain function. Quantification of CMRO2 has helped elucidate brain functional physiology and holds potential as a clinical tool for evaluating neurological disorders including stroke, brain tumors, Alzheimer's disease, and obstructive sleep apnea. In recent years, a variety of magnetic resonance imaging (MRI)-based CMRO2 quantification methods have emerged. Unlike positron emission tomography - the current "gold standard" for measurement and mapping of CMRO2 - MRI is non-invasive, relatively inexpensive, and ubiquitously available in modern medical centers. All MRI-based CMRO2 methods are based on modeling the effect of paramagnetic deoxyhemoglobin on the magnetic resonance signal. The various methods can be classified in terms of the MRI contrast mechanism used to quantify CMRO2: T2*, T2', T2, or magnetic susceptibility. This review article provides an overview of MRI-based CMRO2 quantification techniques. After a brief historical discussion motivating the need for improved CMRO2 methodology, current state-of-the-art MRI-based methods are critically appraised in terms of their respective tradeoffs between spatial resolution, temporal resolution, and robustness, all of critical importance given the spatially heterogeneous and temporally dynamic nature of brain energy requirements.

Monitoring of brain and systemic oxygenation in neurocritical care patients

Maintenance of adequate oxygenation is a mainstay of intensive care, however, recommendations on the safety, accuracy, and the potential clinical utility of invasive and non-invasive tools to monitor brain and systemic oxygenation in neurocritical care are lacking. A literature search was conducted for English language articles describing bedside brain and systemic oxygen monitoring in neurocritical care patients from 1980 to August 2013. Imaging techniques e.g., PET are not considered. A total of 281 studies were included, the majority described patients with traumatic brain injury (TBI). All tools for oxygen monitoring are safe. Parenchymal brain oxygen (PbtO2) monitoring is accurate to detect brain hypoxia, and it is recommended to titrate individual targets of cerebral perfusion pressure (CPP), ventilator parameters (PaCO2, PaO2), and transfusion, and to manage intracranial hypertension, in combination with ICP monitoring. SjvO2 is less accurate than PbtO2. Given limited data, NIRS is not recommended at present for adult patients who require neurocritical care. Systemic monitoring of oxygen (PaO2, SaO2, SpO2) and CO2 (PaCO2, end-tidal CO2) is recommended in patients who require neurocritical care.

My paper 20 years later: cerebral venous oxygen saturation studied with bilateral samples in the internal jugular veins

INTRODUCTION

Jugular oxygen saturation monitoring was introduced in neurointensive care after severe traumatic brain injury (TBI) to explore the adequacy of brain perfusion and guide therapeutic interventions. The brain was considered homogeneous, and oxygen saturation was taken as representative of the whole organ. We investigated whether venous outflow from the brain was homogeneous by measuring oxygen saturation simultaneously from the two jugular veins.

METHODS

In 32 comatose TBI patients both internal jugular veins (IJs) were simultaneously explored using intermittent samples; hemoglobin saturation was also recorded continuously by fiber-optic catheters in five patients. In five cases long catheters were inserted bilaterally upstream, up to the sigmoid sinuses.

MAIN FINDINGS

On average, measurements from the two sides were in agreement (mean and standard deviation of the differences between the saturation of the two IJs were respectively 5.32 and 5.15). However, 15 patients showed differences of more than 15 % in hemoglobin saturation at some point; three others showed differences larger than 10 %. No relationship was found between the computed tomographic scan data and the hemoglobin saturation pattern.

DISCUSSION/CONCLUSION

Several groups have confirmed differences between oxygen saturation in the two jugular veins. After years of enthusiasm, interest for jugular saturation has decreased and more modern methods, such as tissue oxygenation monitoring, are now available. Jugular saturation monitoring has low sensitivity, with the risk of missing low saturation, but high specificity; moreover it is cheap, when used with intermittent sampling. Monitoring the adequacy of brain perfusion after severe TBI is essential. However the choice of a specific monitor depends on local resources and expertise.

Noninvasive estimation of oxygen consumption in human calf muscle through combined NMR measurements of ASL perfusion and T₂ oxymetry

The objective of this work was to demonstrate the feasibility of measuring muscle O2 consumption (V˙O2) noninvasively with a combination of functional nuclear magnetic resonance (NMR) imaging methods, and to verify that changes in muscle V˙O2 can be detected with a temporal resolution compatible with physiological investigation and patient ease. T2-based oxymetry of arterial and venous blood was combined with the arterial-spin labeling (ASL)-based determination of muscle perfusion. These measurements were performed on 8 healthy volunteers under normoxic and hypoxic conditions in order to assess the sensitivity of measurements over a range of saturation values. Blood samples were drawn simultaneously and used to titrate blood T2 measurements versus hemoglobin O2 saturation (%HbO2) in vitro. The in vitro calibration curve of blood T2 fitted very well with the %HbO2 (r(2): 0.95). The in vivo venous T2 measurements agreed well with the in vitro measurements (intraclass correlation coefficient 0.82, 95% confidence interval 0.61-0.91). Oxygen extraction at rest decreased in the calf muscles subjected to hypoxia (p = 0.031). The combination of unaltered muscle perfusion and pinched arteriovenous O2 difference (p = 0.038) pointed towards a reduced calf muscle V˙O2 during transient hypoxia (p = 0.018). The results of this pilot study confirmed that muscle O2 extraction and V˙O2 can be estimated noninvasively using a combination of functional NMR techniques. Further studies are needed to confirm the usefulness in a larger sample of volunteers and patients.

Consensus summary statement of the International Multidisciplinary Consensus Conference on Multimodality Monitoring in Neurocritical Care: a statement for healthcare professionals from the Neurocritical Care Society and the European Society of Intensive Care Medicine

Neurocritical care depends, in part, on careful patient monitoring but as yet there are little data on what processes are the most important to monitor, how these should be monitored, and whether monitoring these processes is cost-effective and impacts outcome. At the same time, bioinformatics is a rapidly emerging field in critical care but as yet there is little agreement or standardization on what information is important and how it should be displayed and analyzed. The Neurocritical Care Society in collaboration with the European Society of Intensive Care Medicine, the Society for Critical Care Medicine, and the Latin America Brain Injury Consortium organized an international, multidisciplinary consensus conference to begin to address these needs. International experts from neurosurgery, neurocritical care, neurology, critical care, neuroanesthesiology, nursing, pharmacy, and informatics were recruited on the basis of their research, publication record, and expertise. They undertook a systematic literature review to develop recommendations about specific topics on physiologic processes important to the care of patients with disorders that require neurocritical care. This review does not make recommendations about treatment, imaging, and intraoperative monitoring. A multidisciplinary jury, selected for their expertise in clinical investigation and development of practice guidelines, guided this process. The GRADE system was used to develop recommendations based on literature review, discussion, integrating the literature with the participants' collective experience, and critical review by an impartial jury. Emphasis was placed on the principle that recommendations should be based on both data quality and on trade-offs and translation into clinical practice. Strong consideration was given to providing pragmatic guidance and recommendations for bedside neuromonitoring, even in the absence of high quality data.

Infected internal jugular vein thrombus in a case of infected arterio-venous fistula for dialysis access

Infected internal jugular vein (IJV) thrombus is rare and is sometimes seen in association with jugular vein catheterization and rarely with suppurative upper aero-digestive tract infection. We describe a very rare association of left Infected Internal jugular vein thrombus with an infected arterio-venous fistula in the left elbow region created for dialysis access in a renal failure patient. The infected arterio-venous fistula was addressed surgically by excision and a reverse saphenous vein graft was placed between proximal and distal brachial artery just above it's bifurcation. The patient was put on i.v Clindamycin and Metronidazole for six weeks. Patient recovered uneventfully.

Consensus summary statement of the International Multidisciplinary Consensus Conference on Multimodality Monitoring in Neurocritical Care : a statement for healthcare professionals from the Neurocritical Care Society and the European Society of Intensive Care Medicine

Neurocritical care depends, in part, on careful patient monitoring but as yet there are little data on what processes are the most important to monitor, how these should be monitored, and whether monitoring these processes is cost-effective and impacts outcome. At the same time, bioinformatics is a rapidly emerging field in critical care but as yet there is little agreement or standardization on what information is important and how it should be displayed and analyzed. The Neurocritical Care Society in collaboration with the European Society of Intensive Care Medicine, the Society for Critical Care Medicine, and the Latin America Brain Injury Consortium organized an international, multidisciplinary consensus conference to begin to address these needs. International experts from neurosurgery, neurocritical care, neurology, critical care, neuroanesthesiology, nursing, pharmacy, and informatics were recruited on the basis of their research, publication record, and expertise. They undertook a systematic literature review to develop recommendations about specific topics on physiologic processes important to the care of patients with disorders that require neurocritical care. This review does not make recommendations about treatment, imaging, and intraoperative monitoring. A multidisciplinary jury, selected for their expertise in clinical investigation and development of practice guidelines, guided this process. The GRADE system was used to develop recommendations based on literature review, discussion, integrating the literature with the participants' collective experience, and critical review by an impartial jury. Emphasis was placed on the principle that recommendations should be based on both data quality and on trade-offs and translation into clinical practice. Strong consideration was given to providing pragmatic guidance and recommendations for bedside neuromonitoring, even in the absence of high quality data.

Invasive and noninvasive multimodal bedside monitoring in subarachnoid hemorrhage: a review of techniques and available data

Delayed-cerebral ischemia is a major cause of morbidity and mortality in the setting of aneurysmal subarachnoid hemorrhage. Despite extensive research efforts and a breadth of collective clinical experience, accurate diagnosis of vasospasm remains difficult, and effective treatment options are limited. Classically, diagnosis has focused on imaging assessment of the cerebral vasculature. Recently, invasive and noninvasive bedside techniques designed to characterize relevant hemodynamic and metabolic alterations have gained substantial attention. Such modalities include microdialysis, brain tissue oxygenation, jugular bulb oximetry, thermal diffusion cerebral blood flow, and near-infrared spectroscopy. This paper reviews these modalities and examines data pertinent to the diagnosis and management of cerebral vasospasm.

Update on multimodality monitoring

Brain injury is a dynamic process marked by an initial damaging insult followed by a cascade of physical, electrical, and metabolic changes capable of resulting in further patient disability. These subclinical changes should be detected at a time when therapeutic intervention is most efficacious and preemptive. Multimodality monitoring is the practice by which a variety of brain monitors are utilized to deliver care, specific to the needs of the individual patient, in an attempt to minimize secondary injury and long-term disability. Intracranial pressure, continuous electroencephalography, brain tissue oxygen, cerebral microdialysis, cerebral blood flow, and jugular oximetry monitoring have been utilized to direct treatment of the critical ill neurologic and neurosurgical patient. Optimization of monitoring technique and protocol is an ongoing effort of intensivists in the field of neurocritical care.

Accuracy of the cylinder approximation for susceptometric measurement of intravascular oxygen saturation

Susceptometry-based MR oximetry has previously been shown suitable for quantifying hemoglobin oxygen saturation in large vessels for studying vascular reactivity and quantification of global cerebral metabolic rate of oxygen utilization. A key assumption underlying this method is that large vessels can be modeled as long paramagnetic cylinders. However, bifurcations, tapering, noncircular cross-section, and curvature of these vessels produce substantial deviations from cylindrical geometry, which may lead to errors in hemoglobin oxygen saturation quantification. Here, the accuracy of the "long cylinder" approximation is evaluated via numerical computation of the induced magnetic field from 3D segmented renditions of three veins of interest (superior sagittal sinus, femoral and jugular vein). At a typical venous oxygen saturation of 65%, the absolute error in hemoglobin oxygen saturation estimated via a closed-form cylinder approximation was 2.6% hemoglobin oxygen saturation averaged over three locations in the three veins studied and did not exceed 5% for vessel tilt angles <30° at any one location. In conclusion, the simulation results provide a significant level of confidence for the validity of the cylinder approximation underlying MR susceptometry-based oximetry of large vessels.

MRI estimation of global brain oxygen consumption rate

Measuring the global cerebral metabolic rate of oxygen (CMRO(2)) is a valuable tool for assessing brain vitality and function. Measurement of blood oxygen saturation (HbO(2)) and flow in the major cerebral outflow and inflow vessels can provide a global estimate of CMRO(2). We demonstrate a rapid noninvasive method for quantifying CMRO(2) by simultaneously measuring venous oxygen saturation in the superior sagittal sinus with magnetic resonance susceptometry-based oximetry, a technique that exploits the intrinsic susceptibility of deoxygenated hemoglobin, and the average blood inflow rate with phase-contrast magnetic resonance imaging. The average venous HbO(2), cerebral blood flow, and global CMRO(2) values in eight healthy, normal study subjects were 64%+/-4%, 45.2+/-3.2 mL per 100 g per minute, and 127+/-7 micromol per 100 g per minute, respectively. These values are in good agreement with those reported in literature. The technique described is noninvasive, robust, and reproducible for in vivo applications, making it ideal for use in clinical settings for assessing the pathologies associated with dysregulation of cerebral metabolism. In addition, the short acquisition time (approximately 30 seconds) makes the technique suitable for studying the temporal variations in CMRO(2) in response to physiologic challenges.

Simultaneous bedside assessment of global cerebral blood flow and effective cerebral perfusion pressure in patients with intracranial hypertension

BACKGROUND

We examined a bedside technique transcerebral double-indicator dilution (TCID) for global cerebral blood flow (CBF) as well as the concept of effective cerebral perfusion pressure (CPP(eff)) during different treatment options for intracranial hypertension, and compared global CBF and CPP(eff) with simultaneously obtained conventional parameters.

METHODS

Twenty-six patients developing intracranial hypertension in the course of traumatic brain injury or subarachnoid hemorrhage were prospectively analyzed using a combined assessment during elevated ventilation (n = 15) or osmotherapy (hypertonic saline or mannitol). For calculation of global CBF, injections of ice-cold indocyanine green boluses were performed and temperature and dye concentration changes were monitored in the thoracic aorta and the jugular bulb. CBF was then calculated according to the mean transit time principle. Estimation of CCP, the arterial pressure at which cerebral blood flow becomes zero, was performed by synchronized registration of corresponding values of blood flow velocity in the middle cerebral artery and arterial pressure and extrapolation to zero-flow velocity. CPP(eff) was calculated as mean arterial pressure minus critical closing pressure (CPP(eff) = MAP(c) - CCP).

RESULTS

Elevated ventilation causes a decrease in both ICP (P < 0.001) and CBF (P < 0.001). While CPP(conv) increased (P < 0.001), CPP(eff) decreased during this observation (P = 0.002). Administration of osmotherapeutic agents resulted in a decrease of ICP (P < 0.001) and a temporary increase of CBF (P = 0.052). CPP(conv) and CPP(eff) showed no striking difference under osmotherapy.

CONCLUSION

TCID allows repeated measurements of global CBF at the bedside. Elevated ventilation lowered and osmotherapy temporarily raised global CBF. In situations of increased vasotonus, CPP(eff) is a better indicator of blood flow changes than conventional CPP.

Accuracy and precision of MR blood oximetry based on the long paramagnetic cylinder approximation of large vessels

An accurate noninvasive method to measure the hemoglobin oxygen saturation (%HbO(2)) of deep-lying vessels without catheterization would have many clinical applications. Quantitative MRI may be the only imaging modality that can address this difficult and important problem. MR susceptometry-based oximetry for measuring blood oxygen saturation in large vessels models the vessel as a long paramagnetic cylinder immersed in an external field. The intravascular magnetic susceptibility relative to surrounding muscle tissue is a function of oxygenated hemoglobin (HbO(2)) and can be quantified with a field-mapping pulse sequence. In this work, the method's accuracy and precision was investigated theoretically on the basis of an analytical expression for the arbitrarily oriented cylinder, as well as experimentally in phantoms and in vivo in the femoral artery and vein at 3T field strength. Errors resulting from vessel tilt, noncircularity of vessel cross-section, and induced magnetic field gradients were evaluated and methods for correction were designed and implemented. Hemoglobin saturation was measured at successive vessel segments, differing in geometry, such as eccentricity and vessel tilt, but constant blood oxygen saturation levels, as a means to evaluate measurement consistency. The average standard error and coefficient of variation of measurements in phantoms were <2% with tilt correction alone, in agreement with theory, suggesting that high accuracy and reproducibility can be achieved while ignoring noncircularity for tilt angles up to about 30 degrees . In vivo, repeated measurements of %HbO(2) in the femoral vessels yielded a coefficient of variation of less than 5%. In conclusion, the data suggest that %HbO(2) can be measured reproducibly in vivo in large vessels of the peripheral circulation on the basis of the paramagnetic cylinder approximation of the incremental field.

Head and neck cooling after cardiac arrest results in lower jugular bulb than esophageal temperature

PURPOSE

To determine whether during the initial phase of head and neck cooling, jugular bulb temperature (Tjb; which may reflect brain temperature) is lower than esophageal temperature (Tes).

BASIC PROCEDURES

To compare Tes and Tjb, patients received head or head and neck cooling after cardiac arrest.

MAIN FINDINGS

The first series with head cooling (n = 5; mean age 54 with a range of 41-62 years; 1 female and 4 males; mean body weight 80 kg with a range of 70-85 kg) showed a mean difference of 0.22 degrees C (95% CI, -1.14 to 0.70; P = .55; limits of agreement, -3.17 to 2.73) between Tes and Tjb over 12 hours. For the second series, with head and neck cooling (n = 6, mean age 65 with a range of 56-76 years; 3 females and 3 males; mean body weight 75 kg with a range of 65-91 kg), Tjb was lower than Tes with a difference of 0.60 degrees C (95% CI, 0.22 to 0.99; P = .01; limits of agreement, -3.10 to 4.30). During the first 3 hours, Tjb decreased faster than Tes (1.1 degrees C/h [95% CI, 0.4 to 1.8; P < .01]).

PRINCIPAL CONCLUSION

During the initial phase of therapeutic hypothermia, Tjb seems to be lower than Tes.

Critical appraisal of Perez et al: Jugular venous oxygen saturation or arteriovenous difference of lactate content and outcome in children with severe traumatic brain injury

OBJECTIVE

To review the findings and discuss the implications of jugular venous bulb oxygenation monitoring in children with severe traumatic brain injury.

DESIGN

A critical appraisal of Perez et al, Jugular venous oxygen saturation or arteriovenous difference of lactate content and outcome in children with severe traumatic brain injury.

FINDINGS

Two episodes of jugular venous bulb desaturation and abnormal values of arteriovenous difference in lactate content are associated with poor neurologic outcome in children with severe traumatic brain injury-risk ratio 6.6 (95% confidence interval, 1.5-29.7) and risk ratio 17.6 (95% confidence interval, 2.5-122.5), respectively. This confirms the findings of previously reported adult studies.

CONCLUSIONS

This study is the first to demonstrate that jugular venous monitoring may aid in predicting the neurologic outcome of children with severe traumatic brain injury. More studies need to be performed (particularly on safety) before adopting jugular venous bulb oxygenation monitoring as a prediction tool or, ultimately, as a therapeutic intervention to help manage and improve outcome for children with severe traumatic brain injury.

Jugular bulb oximetry for prediction of vasospasm following subarachnoid hemorrhage

BACKGROUND

Cerebral vasospasm adversely impacts the outcome of those suffering aneurysmal subarachnoid hemorrhage (SAH). Prediction of vasospasm could improve outcomes. We hypothesized that preclinical vasospasm would be heralded by an increase in cerebral oxygen extractions (AVDO2) which could be detected by jugular bulb oximetry. A pilot study was conducted to address this hypothesis.

METHODS

Fourteen consenting patients with aneurysmal SAH, undergoing early surgery, were entered into the study. Four patients were withdrawn from the study secondary to failure of catheters or religious belief. At the time of craniotomy, a jugular bulb catheter was placed. Post-operatively, arterial and jugular bulb blood samples were taken every 12 hours to calculate AVDO2. As this was an observational study, no change in management occurred based on measurements.

RESULTS

Four of 10 patients had clinical vasospasm. These patients had a significant rise in AVDO2 approximately one day prior to the onset of neurologic deficits (P<0.001). Symptoms resolved along with a significant improvement in AVDO2 on instituting hypertensive, hemo-dilutional, and hypervolemic therapy in these patients. The six patients who did not exhibit clinical vasospasm did not demonstrate significant rise in AVDO2.

CONCLUSIONS

Jugular bulb oximetry is simple and cost effective. Increases in AVDO2 using this technique were predictive of clinically evident vasospasm in the subsequent hours to days. This investigation supports a larger study to assess the utility of jugular bulb oximetry in predicting vasospasm in aneurysmal SAH.

Circulatory effects of internal jugular vein compression: a computer simulation study

The effects of compression of the internal jugular veins and the inferior vena cava are simulated using an equivalent electronic circuit, which included simulation of cardiocirculatory phenomena and special features of the cerebral circulation. Compression of the inferior vena cava resulted in a profound decrease in cardiac output (from 4.5 to 1.51min(-1)) and arterial pressure (from 140/85 to 50/35 mmHg). Compression of the internal jugular veins resulted in a negligible decrease in cardiac output and arterial pressure, with a cerebral blood flow that was slightly decreased. Cerebral capillary and internal jugular pressures were considerably increased, leading to obstruction of cerebral veins and increased pressure (from 9 to 22 mmHg) and volume (from 120 to 145 ml) of the cerebrospinal fluid (CSF). Increased cerebral capsule compliance resulted in decreased CSF pressure (from 9 to 8.5 mmHg), but CSF volume increased (from 120 to 190 ml). A small increase in brain volume (from 1,000 ml to 1,060 ml, 6% volume increase) was compensated for by an equal decrease in the volume of CSF. When brain volume was above 1,080 ml, the absorption of CSF was reduced, and its pressure increased.

Intracranial pressure and surgical decompression for traumatic brain injury: biological rationale and protocol for a randomized clinical trial

Commonly, severe traumatic brain injury (TBI) patients undergo amputation of contused brain; the rationale being that edema in presumed unsalvageable cerebrum increases intracranial pressure (ICP). Neuro-critical care expends great effort to control ICP and prevent secondary injury. Non-randomized investigations have employed hemicraniectomy with duraplasty after developing refractory ICP. We undertook a randomized pilot of hemicraniectomy with duraplasty as the initial surgery for severe TBI patients. Goals included reduced ICP therapeutic intensity and return to the operating room, and improved neurological outcome. Upon hospital presentation, the study was to randomize 92 patients with midline shift greater than the size of a surgically removable hematoma. One group was to receive standardized hemicraniectomy and duraplasty; the other would undergo 'traditional' craniotomy (with brain amputation at the neurosurgeon's discretion). A standardized medical protocol followed. The six-month Glasgow Outcome Scale was the primary outcome, with secondary measures including quality of life one year after TBI, duration and frequency of elevated ICP, intensive care unit (ICU) therapeutic intensity, operating room return, and ICU and hospital lengths-of-stay. This article presents the biological rationale and the evidence-based standardized protocols of the study and its outcome measures. The study has stopped and a phase III outcome trial is being organized.

Jugular bulb oximetry during cardiac surgery

Imbalance between cerebral oxygen supply and demand is thought to play an important role in the development of cerebral injury during cardiac surgery. This article presents an overview of cerebral oxygenation monitored by jugular bulb oximetry during cardiac surgery with cardiopulmonary bypass. The general principles of jugular bulb oximetry including physiology, intermittent and continuous monitoring, technical considerations, limitations and potential complications are discussed. Different applications of jugular bulb oximetry during bypass surgery and the possible therapeutic approaches to impaired cerebral oxygenation are described.

Intraoperative monitoring in neuroanesthesia: a national comparison between two surveys in Germany in 1991 and 1997. Scientific Neuroanesthesia Research Group of the German Society of Anesthesia and Intensive Care Medicine

Two surveys initiated by the Neuroanesthesia Research Group of the German Society of Anesthesia and Intensive Care Medicine examined the practice of intraoperative monitoring during intracranial procedures in Germany in 1991 and 1997. Questionnaires were mailed to departments that were registered members of the German Society of Anesthesia and Intensive Care Medicine and that provided neuroanesthesia service on a routine basis in 1991. In 1997, the survey was repeated in the 1991 respondents. In 1991, 68 departments and in 1997, 44 departments returned completed questionnaires, indicating a response rate of 87% for 1991 and of 65% for 1997. Compared with 1991, the standards for monitoring, such as surveillance of oxygenation, ventilation, circulation, and body temperature, were universally applied in adult and pediatric patients in 1997. Overall, there was a 20% increase in neuromuscular blockade monitoring and in the use of electroencephalography and evoked potentials in 1997 compared with 1991. Further brain-specific monitoring was rarely provided in 1997. Overall, jugular venous oximetry was used in 20% and transcranial Doppler ultrasonography in 15% of responding hospitals. To detect venous air embolism in sitting patients, 75% of all responding hospitals used precordial Doppler ultrasonography in both years, whereas transesophageal echocardiography was more often used in 1997 (38%) as compared with 1991 (17%).

IMPLICATIONS

Standards of anesthetic monitoring were surveyed in neuroanesthesia in Germany in 1991 and 1997. Central nervous system monitoring was not the standard of practice.

Limits of intermittent jugular bulb oxygen saturation monitoring in the management of severe head trauma patients

OBJECTIVE

To evaluate, in a prospective, observational study, whether bilateral monitoring of jugular bulb oxyhemoglobin saturation (SjO2), in addition to standard monitoring, results in modification of the management of severe head trauma.

METHODS

The patients underwent bilateral jugular bulb cannulation and observation at 8-hour intervals, during which SjO2 was measured and the neurological condition and physiological variables were assessed. The study group was responsible for evaluating whether the physician's decision-making process was influenced by the detection of SjO2 abnormalities. The SjO2 discrepancy in simultaneous bilateral samples was also evaluated to determine whether it interfered with the interpretation of data and with clinical decision-making. The SjO2-related complications were monitored.

RESULTS

Thirty patients underwent 319 observations. In 96% of patients, SjO2 was normal or high and had no influence on the diagnostic or therapeutic strategies. Treatment decisions were dictated by changes in clinical status and in intracranial and cerebral perfusion pressure. When these parameters were abnormal, treatment was administered, even if SjO2 was normal (101 observations). Conversely, when SjO2 was the only detected abnormality (34 observations), no treatment was administered. Abnormally low SjO2 values, caused by hypovolemia and hypocapnia, were detected in 3.4% of observations and actually modified the management. The discrepancies in simultaneous bilateral samples were substantial and gave rise to relevant interpretation problems. Fifteen percent of jugular catheters showed evidence of bacterial colonization.

CONCLUSION

Intermittent SjO2 monitoring did not substantially influence the management of severe head trauma. Therefore, recommendation for its routine use in all patients seems inadvisable, and indications for this invasive method should no longer be defined on the basis of experts' opinions, but rather on randomized, prospective studies.

Cerebral oxygenation and systemic trauma related factors determining neurological outcome after brain injury

We examined the relationship between clinical and radiological findings, cerebral oxygenation patterns during intensive care management, presence of systemic trauma related injuries and severity of illness in 50 patients (age: 32.3 +/- 12 years, GCS: 8 +/- 4) who were rescued from the accident scene within a 30 min period after trauma. Presence of systemic injuries was quantified using the Injury Severity Score (ISS) and severity of illness was scored using the Acute Physiology and Chronic Health Evaluation (APACHE II). Cerebral oxygenation parameters included continuous monitoring of jugular bulb oxygen saturation (SjvO(2)) for 12 840 h, and 2323 periodical blood sampling for measurement of arteriovenous differences in oxygen content (AVDO(2)), arteriovenous difference of lactate (AVDL) and lactate oxygen index (LOI). Fifteen patients (30%) presented with anisocoria or non-reacting pupils. Diffuse lesions on computed tomography (CT) were found in 34% of the patients and in 66% a mass lesion was removed. The mean ISS was 28 +/- 15.3 and 34 patients (68%) had an APACHE II score between 20 and 29 (mean 24 +/- 15). No statistically significant association between age (P = 0.45), gender (P = 0.83), initial Glasgow Coma Score (GCS) (P = 0.43), episodes of cerebral perfusion pressure (CPP) < 70 mm Hg (P = 0.8), ISS (P = 0.28), pupillary abnormalities (P = 0.57), initial CT findings (P = 0.74), APACHE II scores (P = 0. 36) and outcome could be demonstrated. The number of SjvO(2)desaturations (< 60%) was the only statistically significant factor associated with outcome (P = 0.05). The percentage of patients with poor neurological outcomes (GOS 1-3) was 38% in patients with no or one desaturation episode, and 57.6% in those with multiple desaturations. In conclusion, in patients who are resuscitated early and quickly transferred to the hospital, the number of SjvO(2)desaturations during intensive care management might be associated with outcome more strongly than other clinical and radiological features.

Monitoring of the central nervous system

Clinical studies have shown a close relationship between variables such as hypoxia, increased intracranial pressure, arterial hypotension, or seizures and neurological outcome. This indicates the need for monitoring techniques of the central nervous system including measurements of cerebral blood flow, cerebral oxygenation and neuronal function. Semiquantitative changes in cerebral blood flow can be measured continuously using transcranial Doppler sonography. Measurements of jugular venous oxygen saturation or tissue oxygenation reflect the balance between cerebral oxygen delivery and cerebral oxygen demand. Near-infrared spectroscopy appears to be a technology with potential for non-invasive measurements of cerebral oxygen saturation and mitochondrial oxygen availability. The current technology is, however, of limited clinical utility. Brain electrical monitoring techniques such as electroencephalogram and evoked potentials are sensitive and specific to detect changes in neuronal function caused by cerebral ischaemia. Electroencephalogram and evoked potential measurements of depth of anaesthesia and specific electroencephalogram patterns for pharmacodynamic quantification of drug effects may gear the dosage of anaesthetics according to the anaesthetic effect.