Continuous Measurement Of Intracranial Pressure Research Articles

Characterising the dynamics of cerebral metabolic dysfunction following traumatic brain injury: A microdialysis study in 619 patients.

Traumatic brain injury (TBI) is a major cause of death and disability, particularly amongst young people. Current intensive care management of TBI patients is targeted at maintaining normal brain physiology and preventing secondary injury. Microdialysis is an invasive monitor that permits real-time assessment of derangements in cerebral metabolism and responses to treatment. We examined the prognostic value of microdialysis parameters, and the inter-relationships with other neuromonitoring modalities to identify interventions that improve metabolism. This was an analysis of prospective data in 619 adult TBI patients requiring intensive care treatment and invasive neuromonitoring at a tertiary UK neurosciences unit. Patients had continuous measurement of intracranial pressure (ICP), arterial blood pressure (ABP), brain tissue oxygenation (PbtO2), and cerebral metabolism and were managed according to a standardized therapeutic protocol. Microdialysate was assayed hourly for metabolites including glucose, pyruvate, and lactate. Cerebral perfusion pressure (CPP) and cerebral autoregulation (PRx) were derived from the ICP and ABP. Outcome was assessed with the Glasgow Outcome Score (GOS) at 6 months. Relationships between monitoring variables was examined with generalized additive mixed models (GAMM). Lactate/Pyruvate Ratio (LPR) over the first 3 to 7 days following injury was elevated amongst patients with poor outcome and was an independent predictor of ordinal GOS (p<0.05). Significant non-linear associations were observed between LPR and cerebral glucose, CPP, and PRx (p<0.001 to p<0.05). GAMM models suggested improved cerebral metabolism (i.e. reduced LPR with CPP >70mmHg, PRx <0.1, PbtO2 >18mmHg, and brain glucose >1mM. Deranged cerebral metabolism is an important determinant of patient outcome following TBI. Variations in cerebral perfusion, oxygenation and glucose supply are associated with changes in cerebral LPR and suggest therapeutic interventions to improve cerebral metabolism. Future prospective studies are required to determine the efficacy of these strategies.

Telemetric intracranial pressure monitoring in children.

Repeated intracranial pressure (ICP) measurements are essential in treatment of patients with complex cerebrospinal fluid (CSF) disorders. These patients often have a long surgical history with numerous invasive lumbar or intracranial pressure monitoring sessions and/or ventriculoperitoneal (VP) shunt revisions. Telemetric ICP monitoring might be an advantageous tool in treatment of these patients. In this paper, we evaluate our experience with this technology in paediatric patients. During a 4-year period, we implanted telemetric ICP sensors (Raumedic NEUROVENT-P-tel) in 20 paediatric patients to minimise the number of future invasive procedures. Patients were diagnosed with hydrocephalus, idiopathic intracranial hypertension (IIH) or an arachnoid cyst. Most patients (85%) had a VP shunt at the time of sensor implantation. In total, 32 sensors were inserted in the 20 patients; the cause of re-implantation was technical malfunction of the implant. One sensor was explanted due to wound infection and one due to skin erosion. We experienced no complications directly related to the implantation/explantation procedures. A total of 149 recording sessions were conducted, including 68 home monitoring sessions. The median implantation period was 523days with a median duration of clinical use at 202days. The most likely consequence of a recording session was non-surgical treatment alteration (shunt valve adjustment or acetazolamide dose adjustment). Telemetric ICP monitoring in children is safe and potentially decreases the number of invasive procedures. We find that telemetric ICP monitoring aids the clinical management of patients with complex CSF disorders and improves everyday life for both patient and parents. It allows continuous ICP measurement in the patient's home and thereby potentially reducing hospitalisations, leading to significant cost savings.

Chronic Intracranial Pressure Sensor to Assist With Control of Hydrocephalus

Hydrocephalus is a medical condition, where excessive accumulation of CerebroSpinal Fluid leads to an abnormal increase of intracranial pressure (ICP). Early and timely detection of elevated ICP is very important to mitigate symptoms during the entire life of the patient to avoid headaches, mental disability, and death caused by abnormal increased ICP. We describe our fabricated active capacitance pressure for continuous ICP measurement. The active sensor consists of two metal plates, which transduces the pressure change to capacitance change. We introduced a novel special connection method between the inside-bonded metal plates to external sensor electronics. We tested biocompatibility of the sensor materials in a sheep. We developed prototypes, and in vitro measurement results demonstrate that the active capacitive sensor achieves good performance: 550–900 mmHg measurement range, 0.094% accuracy, 0.022 mmHg (0.001 pF) resolution, and from ±0.136 to ±0.5 mmHg three months long-term drift for 10 different capacitive pressure sensors. Here, 0.5 mmHg corresponds to 0.14% full-scale output with a full range of 550 to 900 mmHg.

The intracranial pressure curve correlates to the pulsatile component of cerebral blood flow

Current methods to measure cerebral blood flow (CBF) in the neuro critical care setting cannot monitor the CBF continuously. In contrast, continuous measurement of intracranial pressure (ICP) is readily accomplished, and there is a component of ICP that correlates with arterial inflow of blood into the cranial cavity. This property may have utility in using continuous ICP curve analysis to continuously estimate CBF. We examined the data from 13 patients, monitored with an intraventricular ICP device determining the pulsatile amplitude ICPamp as well as the area under the ICP curve (AUCICP). Using an elastance measurement, the ICP curve was converted to craniospinal volume (AUCΔV). The patients were examined with Phase Contrast Magnetic Resonance Imaging (MRI), measuring flow in the carotid and vertebral arteries. This made it possible to calculate CBF for one cardiac cycle (ccCBFMRtot) and divide it into the pulsatile (ccCBFMRpuls) and non-pulsatile (ccCBFMRconst) flow. ICP derived data and MRI measurements were compared. Linear regression was used to establish wellness of fit and ANOVA was used to calculate the P value. No correlation was found between ICPamp and the ccICPMRpuls (P = 0.067). In contrast there was a correlation between the AUCICP and ccCBFMRpuls (R2 = 0.440 P = 0.013). The AUCΔV correlated more appropriately with the ccCBFMRpuls. (R2 = 0.688 P < 0.001). Our findings suggests that the pulsatile part of the intracranial pressure curve, especially when transformed into a volume curve, correlates to the pulsatile part of the CBF.

Telemetric Intracranial Pressure Recording via a Shunt System Integrated Sensor: A Safety and Feasibility Study.

Background The dynamics of intracranial pressure (ICP) after shunt surgery in patients with normal pressure hydrocephalus (NPH) are poorly known. Temporarily implanted parenchymal pressure probes are reliable for accurate ICP monitoring; however, a disadvantage of this method is that the ICP probe has to be explanted after a period of time, requiring additional surgery. We present two patients with NPH with an integrated ICP measuring device in the shunt system that allows for long-term postoperative telemetric monitoring of ICP. Methods Two patients (one man, 66 years old, and one woman, 78 years old) with normal pressure hydrocephalus underwent shunt surgery using the Aesculap-Miethke Sensor Reservoir (Potsdam) as an ICP measuring device integrated in the shunt system. On the first postoperative day and during follow-up examination 3 months later, several measurements of ICP were performed using a handheld device to read the Sensor Reservoir data. Postural changes such as lying down, sitting, and standing with different head postures were assessed according to an experimental protocol in a randomized order during which the ICP was measured. Results There were clear ICP responses due to postural changes, in line with physiologically expected values. Because the highest sampling rate of the Aesculap-Miethke Sensor Reservoir is 1 Hz for continuous measurement of ICP, however, the collected data have to be considered an approximation for actual ICP dynamics. Conclusion The Aesculap-Miethke Sensor Reservoir is an easy-to-use tool to measure ICP changes reliably in patients with a shunt system. The sampling rate and handling of data acquisition may eventually be developed further.

Telemetric Intracranial Pressure Measurement: A Graphical Approach to Data Analysis.

In recent years, radiofrequency identification has been used for the continuous measurement of intracranial pressure (ICP) in patients with a cerebrospinal fluid (CSF) shunt for hydrocephalus . Unlike ICP monitoring in an inpatient setting, measurements in mobile patients outside the hospital provide ICP data that take into account the everyday activities of each individual patient. Common methods of ICP monitoring and analysis cannot be used for those patients. In addition, ICP measurements in mobile patients require considerably longer observation times than in-hospital monitoring. For this reason, ICP measurements over a period of 7 to 10 days must be analyzed effectively and efficiently. A possible approach is to analyze ICP data graphically. Pathologic changes can be expected to be associated with specific patterns that can be detected graphically (e.g., Lundberg A waves). Patients without pathologic ICP values and without intracranial pathologies usually show an approximately normal distribution of ICP data. By contrast, patients with pathologic ICP values are likely to show major deviations from a normal distribution such as changes in minimum and maximum values and multimodal distributions. Against this background, we present a new graphical method for detecting pathologic conditions. This novel method is based on the distribution of ICP data that is assessed using GNU R, a free software package for statistical computing and graphics. A left-skewed distribution indicates CSF shunt overdrainage and a right-skewed distribution suggests CSF shunt underdrainage. In addition, an additive analysis of the number of physiologic ICP values can be helpful in detecting possible causes of CSF shunt overdrainage or underdrainage. The approach presented here shows that patients with hydrocephalus objectively benefited from ICP-guided adjustments of the opening pressure of a shunt valve or the insertion of a valve. This objective improvement was confirmed by the patients' subjective perception of well-being. Further investigations should be performed to examine the influence of multimodal ICP distributions and to assess how data analysis is affected by a drift that can occur when a sensor has been in place for an extended period of time.

Pulsatile cerebrospinal model with cardio-vascular coupling

In this paper we describe a model of the human intracranial space which is extended with the vascular system. We focus on a detailed modelling of the coupling between cerebral vessels and intracranial pressure (ICP). On the one hand, the model is based on a linearisation of the Navier-Stokes equation for the blood vessels and a subsequent geometric discretisation, leading to a distributed parameter approach of coupled ordinary differential equations. On the other hand, a concentrated parameter modelling approach is developed for the intracranial space which is subsequently extended by a production and resorption circuit for the craniospinal fluid. The intention of the model is to describe the transmission of pulsatile blood pressure waves from the cerebral vessels to the ICP, as it can be observed from clinical continuous intracranial pressure measurements. A good agreement of pulsatile ICP is shown in an in-silico study, compared to clinical continuous ICP measurements. An analysis of vascular impedance under variable intracranial compliance and for a non-symmetric Circle-of-Willis completes this study.

Intracranial pressure monitoring in traumatic brain injury

A randomized study has indicated that continuous monitoring of intracranial pressure (ICP) in patients with traumatic brain injury does not improve outcome compared with care based on imaging and clinical examination. The results do not, however, justify elimination of continuous ICP measurement from standard care in patients with head injury.

Clinical system engineering of long-term automatic thermal control during brain hypothermia under changing conditions

Automatic control systems of brain temperature for water surface-cooling were first-ever applied to the brain hypothermic treatment of patients. A patient in ICU was regarded as a unity controlled system with an input (temperature of water into blanket) and an output (tympanic membrane temperature). The proposed algorithm of optimal-adaptive and fuzzy control laws inclusive of our developed cooling and warming machine were well confirmed during the hypothermic course to keep brain temperature of patients within its allowable range. It was well controlled without much influence due to room temperature, metabolic and circulatory change caused by various medical treatments including the effect of nonlinear and time-varying characteristics of individual patients. The clinical control of brain temperature was almost continuously performed in around 10 days, under the brain temperature between 35 degrees C and 37 degrees C scheduled by physicians according to the state of patients. Their state had been monitored during the therapeutic course of pharmacological treatment with almost everyday examinations by CT imaging, referring various vital signs inclusive of the temperature of urinary bladder with continuous measurement of intracranial pressure by a catheter placement in cerebral sinus. The patients had good recovery to their rehabilitation after mild hypothermia by the proposed automatic control systems.

Morphological Clustering and Analysis of Continuous Intracranial Pressure

The continuous measurement of intracranial pressure (ICP) is an important and established clinical tool that is used in the management of many neurosurgical disorders such as traumatic brain injury. Only mean ICP information is used currently in the prevailing clinical practice, ignoring the useful information in ICP pulse waveform that can be continuously acquired and is potentially useful for forecasting intracranial and cerebrovascular pathophysiological changes. The present study introduces and validates an algorithm of performing automated analysis of continuous ICP pulse waveform. This algorithm is capable of enhancing ICP signal quality, recognizing nonartifactual ICP pulses, and optimally designating the three well-established subcomponents in an ICP pulse. Validation of the proposed algorithm is done by comparing nonartifactual pulse recognition and peak designation results from a human observer with those from automated analysis based on a large signal database built from 700 h of recordings from 66 neurosurgical patients. An accuracy of 97.84% is achieved in recognizing nonartifactual ICP pulses. An accuracy of 90.17%, 87.56%, and 86.53% was obtained for designating each of the three established ICP subpeaks. These results show that the proposed algorithm can be reliably applied to process continuous ICP recordings from real clinical environment to extract useful morphological features of ICP pulses.

Reducing intracranial pressure may increase survival among patients with bacterial meningitis.

We reported findings concerning continuous intracranial pressure (ICP) and cerebral perfusion pressure (CPP) measurements and mortality in patients with severe bacterial meningitis treated on the basis of an ICP-targeted approach. Eighteen patients with severe bacterial meningitis were admitted for neurointensive care at Umeå University Hospital (Umeå, Sweden). In 15 patients, ICP was measured continuously through an ICP measuring device. During care, all patients but one developed intracranial hypertension with an ICP of >or=15 mm Hg (14 [93%] of 15 patients). Ten (67%) of 15 patients survived and were discharged, and 5 patients (33%) died. Mean ICP was significantly higher and CPP was markedly decreased in nonsurvivors, compared with survivors. Among the survivors, ICP was gradually reduced. Treatment of patients with severe bacterial meningitis should include neurointensive care and continuous ICP measurement. Increased ICP may be reduced by using the ICP-targeted therapy that closely resembles the "Lund concept."

Prediction of Intracranial Pressure From Noninvasive Transocular Venous and Arterial Hemodynamic Measurements: A Pilot Study

Continuous measurement of intracranial pressure (ICP) requires the invasive placement of epidural, parenchymal, or intraventricular devices. For critical single-point assessments, lumbar puncture may not always be practical. An accurate, reliable, portable and noninvasive method to estimate absolute ICP remains an elusive goal. The arteries that perfuse and the vein that drains the orbit are exposed to the ambient ICP while coursing through the cerebrospinal fluid or optic nerve. The venous outflow pressure (VOP) of the central retinal vein was measured using occlusion in six intensive care patients treated for acute hydrocephalus or brain hemorrhage and in whom transducers of intracranial pressure could provide standardized continuous output. A novel adaptation of the Balliart ophthalmodynamometer was developed for use. Simultaneously, the central retinal (CRA) and ophthalmic (OA) arterial flow velocities were recorded using color Doppler imaging technique. Repeat noninvasive measurements were performed at various ICPs, (n=22 independently collected observations). Linear regression and correlation testing were performed to evaluate these variables for ICP predictability. The VOP increased linearly with ICP (r=0.87). The arterial pulsatility indices for both OA and CRA decreased inversely with ICP (r=0.66). An empiric index combining both venous and arterial parameters (VOP/Gosling Pulsatility Index [GPI]) was significantly more correlated with absolute ICP than either parameter alone (r=0.95, p<0.005, ICP=0.29+0.74 [VOP/GPI(OA)]). The feasibility to estimate ICP from transocular sonographic and dynamometric data is suggested by these preliminary data. Retinal arterial properties are important in modeling the effect of ICP on the venous outflow pressure. Our pilot results serve as a basis on which to conduct a larger prospective and blinded study.

Continuous measurement of intracranial pressure in awake rats after experimental closed head injury

The present study validates a method for continuous measurement of intracranial pressure (ICP) in freely moving rats after experimental induction of impact–acceleration injury. Rats subjected to either mild or moderate trauma were individually placed in a Bas-Ratturn ® system, equipped with a sensor that synchronously turns the cage in response to the locomotor activity of the animal. In this way correct probe positioning is permanently assured and damage due to coiling is avoided. The evolution of ICP and mean arterial blood pressure (MABP) in injured rats was compared with that of a non-traumatized sham group. Since the animals regained consciousness after surgery, interference of anaesthesia on these sensitive parameters should be minimised. The results showed that immediately after induction of neurotrauma, ICP was significantly higher in traumatized rats (sham: 7.7±0.5 mmHg; mild trauma: 10.4±0.7 mmHg; moderate trauma: 14.9±2.4 mmHg; P<0.05). Regression analysis showed a stable ICP up to 3 h post-insult for all three conditions. From 4 h onwards till the end of the experiment at 10 h post-insult, a significant increase in ICP was seen for sham-operated and mildly traumatized rats (16.1±3.4 and 30.5±6.9 mmHg, respectively; P<0.05), but not for moderately traumatized rats (47.3±11.9 mmHg). The method allows observation of ICP for a critical period up to 3 h. As such the method can be regarded as clinically relevant to study early pathological aspects of intracranial hypertension and to define a therapeutic window for pharmacological intervention after traumatic brain injury (TBI).

Monitorage du traumatisé crânien grave durant les 24 premières heures

Monitoring of severely head-injured patients during the first 24 hours. Monitoring of severely head-injured patients is essential to optimize cerebral haemodynamics and thus to limit intracranial hypertension and to prevent the occurrence of secondary systemic cerebral injuries. It includes continuous measurement of intracranial pressure, mean arterial pressure and venous jugular oxygen saturation. Assessment of circulatory velocity in the arteries of the polygon of Willis allows identification of intracranial hypertension, and later, a vasospasm in case of subarachnoid haemorrage. Near infrared spectroscopy is an indirect indicator of cerebral oxygenation. This technique has not yet been validated. Direct tissue measurement of cerebral oxygen content is the most recently developed monitoring tool. Its clinical range of application has still to be specified. These basic monitoring techniques are a standard. They are essential for an undelayed and efficient treatment of complications occurring in head trauma patients.

Intracranial pressure monitoring using a newly developed transducer-tipped ventricular drainage catheter.

A transducer-tipped ventricular drainage catheter (TVDC) was developed to allow continuous measurement of intracranial pressure (i.c.p.) without interrupting cerebrospinal fluid (CSF) drainage. The 8.5 Fr catheter with a double lumen has 16 side holes for CSF drainage and a small silicone strain-gauge transducer on the side of the catheter tip to measure the ICP directly. The transducer is composed of a 2 x 1 mm2 silicone plate. Calibration must be performed before insertion. The calibrated catheter is inserted into the ventricles, usually via the anterior horn of the lateral ventricles to the foramen of Monro. Recalibration is not necessary even if the patient's head is tilted. The TVDC was applied to patients in whom ICP was suspected to be high and in whom the ventricles were large enough for tapping. The ICP wave form and values measured by the TVDC and the manometer method were equivalent. The drift phenomenon did not occur throughout the entire measurement period. The TVDC is very useful for both controlling and monitoring ICP.

Anterior fontanelle pressure variations during sleep in healthy infants.

Our aim was to study the intracranial pressure (ICP) variations during sleep normal infants. Using a noninvasive method, ICP was measured continuously during polysomnography in 12 healthy infants aged from 1 to 11 months (median 3.5 months). We analyzed the variations of mean basal ICP, mean basal pulse pressure amplitude and maximal amplitude of both plateau and B-like waves between transient sleep, quiet sleep and rapid eye movement (REM) sleep. Mean ICP, mean pulse pressure amplitude and B-like wave amplitude increased significantly during transient sleep and REM sleep. Plateau waves occurred during transient sleep and especially REM sleep. By contrast, noninvasive ICP recordings were relatively flat during quiet sleep stages 2 and 3. ICP variations and pressure waves seem to be related to cerebrovascular changes associated with sleep. The physiological ICP variations during sleep must be known in order to allow correct interpretation of continuous ICP measurements in infants.

A clinical comparison of subarachnoid catheters to ventriculostomy and subarachnoid bolts: a prospective study

A subarachnoid catheter (SAC) technique of continuous intracranial pressure (ICP) monitoring is presented and compared to intraventricular catheters (IVC's) and subarachnoid bolts (SAB's) in 40 neurosurgical patients. Thirty-one patients were monitored simultaneously with SAC's and IVC's and nine patients with SAC's and SAB's, and the ICP waveforms and measurements were compared. The duration of monitoring ranged from 15 hours to 11 days, and the initial ICP from 2 to 117 torr. A total of 42 SAC's were placed; two that entered brain parenchyma were redirected. One SAC placement was associated with an intracerebral hematoma. There were no infections. For the 31 patients with SAC's and IVC's, there were 2706 pairs of ICP measurements with a mean difference of -0.12 torr and a standard deviation of 5.29 torr. The waveforms from the SAC's and IVC's were indistinguishable. For the nine patients with SAC's and SAB's, there were 773 pairs of ICP measurements with a mean difference of 1.24 torr and a standard deviation of 32.83 torr. The SAB waveforms were of varying quality and all dampened with time. The paired t-test (ts) demonstrated no statistically significant difference between SAC's and IVC's (ts = - 1.19). An analysis of variance demonstrated the scatter of the measurements obtained from SAB's to be 38.5 times that of SAC's, p less than 0.00005. The SAB is shown to be relatively inaccurate with a wide range of variance, while the SAC is demonstrated to be an accurate, reliable, and safe method of continuous ICP measurement and an acceptable alternative to ventriculostomy.

Measurement of fontanelle pressure (Part I). A new instrument for non-invasive measurement of intracranial pressure via the anterior fontanelle.

Intracranial pressure (ICP) is one of the most important parameters for evaluating intracranial conditons. The skulls of newborns and infants, unlike the tightly sutured skull of adults, provide non-invasive access for measurement of ICPs via the anterior fontanelle. A new transducer has been developed which is convenient for non-invasive, continuous measurement of intracranial pressure through the anterior fontanelle. The new transducer is thinner and lighter than the APT-16 type transducer (Hewlett-Packard). The principles of measurement of ICP with this new transducer, the results of basic experiments, and results obtained from clinical applications are deseribed in this report.

Outcome from severe head injury related to the type of intracranial lesion. A computerized tomography study.

The influence of the type of intracranial lesion on the final outcome in a consecutive series of 277 severely head-injured patients was analyzed. Patients were studied with computerized tomography (CT) and underwent continuous measurement of intracranial pressure. They received identical treatment according to a standardized protocol. Outcome of patients with either epidural hematoma (38 cases), subdural hematoma (56 cases), brain contusion (87 cases), or diffuse brain damage (96 cases) was rather heterogeneous, and serial CT scanning allowed the authors to outline eight consistent anatomical patterns in the whole series which have stronger prognostic significance than the four major lesion categories mentioned above. Patients with pure extracerebral hematoma (19 cases), single brain contusion (45 cases), general brain swelling (41 cases), and normal CT scans (28 cases) had a significantly better outcome than patients developing acute hemispheric swelling after operation for a large extracerebral hematoma (27 cases), patients with multiple brain contusion, either unilateral or bilateral (74 cases), and patients with diffuse axonal injury (43 cases). These anatomical patterns are interesting because, in addition to having clinical and physiopathological significance, they provide useful prognostic information and facilitate improved therapeutic decision-making in severely head-injured patients.

A practical technique for monitoring extradural pressure.

✓ The authors discuss the technical problems involved in the continuous measurement of intracranial pressure, and describe a simple, inexpensive extradural strain gauge system that can be manufactured by most research units. The system has the merits of coplanar construction, a ready zero reference, and simplicity in design and use. The theoretical limits of the extradural method are presented and discussed in relation to transducer design.