Single pulse pressure wave analysis by fast Fourier transformation

Abstract

Pressure recordings from 16 patients with normal pressure by hydrocephalus were analysed during controlled intracranial hypertension. Single pulse pressure wave (PPW) analyses were performed on a computer system with programs for automatic computation of mean intracranial pressure (MICP), pulse amplitude (PA), rise time coefficients (RT) and fast Fourier transformation (FFT). We found good correlation between the first harmony, MICP and PA, and between the fifth harmony and RT. The PPW is mainly composed of low-frequency components, but with increasing RT more high-frequency components are present. RT changes as compliance of the brain changes. Therefore the high-frequency components of the FFT may predict changes in the cerebral compliance, although there was no correlation between any of the harmonies and the pressure volume index (PVI). In this investigation PVI was found difficult to perform and evaluate.     

Single pulse pressure wave analysis by fast Fourier transformation

Pressure recordings from 16 patients with normal pressure by hydrocephalus were analysed during controlled intracranial hypertension. Single pulse pressure wave (PPW) analyses were performed on a computer system with programs for automatic computation of mean intracranial pressure (MICP), pulse amplitude (PA), rise time coefficients (RT) and fast Fourier transformation (FFT). We found good correlation between the first harmony, MICP and PA, and between the fifth harmony and RT. The PPW is mainly composed of low-frequency components, but with increasing RT more high-frequency components are present. RT changes as compliance of the brain changes. Therefore the high-frequency components of the FFT may predict changes in the cerebral compliance, although there was no correlation between any of the harmonies and the pressure volume index (PVI). In this investigation PVI was found difficult to perform and evaluate.     

Effect of uridine 5'-diphosphate on cryogenic brain edema in rabbits

This study was undertaken to examine the effect of uridine 5'-diphosphate, administered intravenously or intraperitoneally, on cold injury-induced brain edema in rabbits. Bolus injection or continuous intravenous infusion of uridine 5'-diphosphate 26 hours after a lesion was established had adverse effects, such as increased intracranial pressure and lowered systolic arterial blood pressure and cerebral perfusion pressure for approximately 10-29 minutes, but these parameters did not change appreciably from 29 minutes to 3 hours after administration. Intraperitoneally administered uridine 5'-diphosphate did not affect these parameters appreciably during 3 hours. Thus, the intravenous administration of uridine 5'-diphosphate is harmful under neurosurgical conditions. In contrast, 10 mg/kg/day i.p. uridine 5'-diphosphate pretreatment and posttreatment, beginning 24 hours before and continuing until 24 hours after the insult, significantly reduced neurologic abnormalities, Evans blue extravasation, water content in the injured gray matter, and intracranial pressure without affecting water content in the white matter. Intravenous dexamethasone pretreatment and posttreatment in this setting significantly reduced only neurologic abnormalities. However, there were no significant differences between intraperitoneal uridine 5'-diphosphate and intravenous dexamethasone effects on cold-injured brain.     

Cerebral perfusion pressure management of severe diffuse head injury: effect on brain compliance and intracranial pressure

BACKGROUND: Cerebral perfusion pressure management (CPPM) is an accepted modality of treatment of severe diffuse head injury (SDHI). However, CPPM has the potential to cause transcapillary exudation in the presence of a disrupted blood brain barrier and can lead to further increase of intracranial pressure (ICP) and worsening of compliance. AIMS: This study attempts to evaluate the effect of both transient and prolonged changes in cerebral perfusion pressure (CPP) on ICP and cerebral compliance as measured by the Pressure Volume Index (PVI), and to correlate changes in PVI with outcome at 12 months using the Glasgow Outcome Score. SETTINGS AND DESIGN: Prospective study in a neurosurgical ICU. MATERIAL AND METHODS: Twenty-seven SDHI patients managed using standard protocol to maintain CPP above 70 mmHg. Mean arterial pressure (MAP), ICP and CPP were monitored every half-hour. Daily monitoring of the PVI and ICP was done before, and after the induced elevation of MAP using IV Dopamine infusion. The relationship between CPP, MAP, ICP, PVI and outcome was evaluated. STATISTICAL ANALYSIS USED: The paired and independent samples T-test, and the Pearson correlation coefficient. RESULTS: CPPM rarely leads to progressive rise in ICP. Maintaining CPP above 70mmHg does not influence ICP or PVI. Transient elevations in CPP above 70mmHg may produce a small rise in ICP. Trend of change in PVI influenced outcome despite similar ICP and CPP. CONCLUSION: Elevating the CPP above 70mmHg does not either reduce the ICP or worsen the compliance. Monitoring changes in compliance should form an integral part of CPPM.     

Dexamethasone and Brain Tumor Glucose Uptake; A Positron Emission Tomographic Study

Serial positron emission tomography scans with [¹⁸F]fluorodeoxyglucose (FDG) were acquired from 3 patients with malignant gliomas before and after 24 hours of dexamethasone administration (a total of 40 mg administered intravenously over 24 hours). Peak FDG uptake by the tumor decreased 10 to 20% in the posttreatment scans. The data suggest that at least some of the beneficial effects of dexamethasone on the signs and symptoms of tumor-related increased intracranial pressure might relate to a direct acute effect on glucose metabolism.     

Computerized use of ICP data

An incorrect choice of valve may produce a delay in psychomotor development in shunted hydrocephalic children. The intracranial pressure was measured for 24 h in 20 subjects suffering from nontumoral hydrocephalus, obtaining a pressure/volume index with compliance and perfusion pressure data. Their data were entered into a computer and used to determine the correct valve to be chosen.Abbreviations P 1 initial pressure - P 2 final pressure - PVI pressure/volume index - SP 1 initial pressure after shunt - SP 2 final pressure after shunt - SPVI pressure/volume index after shunt - COMP compliance - SCOMP compliance after shunt     

Predictability of intracranial pressure oscillations in patients with suspected normal pressure hydrocephalus by transcranial Doppler ultrasound

Abstract

Intracranial pressure (ICP) was monitored continuously for one night in 36 patients with suspected symptomatic normal pressure hydrocephalus (NPH) to identify patients who might benefit from subsequent shunting. In 33 of these patients middle cerebral artery (MCA) blood flow velocity by means of transcranial Doppler sonography (TCD) and ICP were recorded simultaneously. ICP B-waves always paralleled changes in the TCD signal (TCD B-wave equivalents). The relative frequency of ICP B-waves was predictable by TCD, albeit slightly underestimated due to a generally lower relative amplitude of the TCD B-wave equivalents. However; the same TCD B-wave equivalent amplitude could be accompanied by quite different ICP changes in different patients. Considering the baseline values in the absence of pressure wavesthere was no significant relationship between ICP and TCD resistance index (Pourcelot) in different patients. Raising ICP by injection of 10 ml saline into the ventricle, however was accompanied by an increased TCD resistance index in the individual patient. As the relative frequency of B-wave activity is assumed to be an indicator for shunt responsiveness, continuous TCD monitoring can be used as a screening procedure to detect the presence and the relative frequency of B-wave activity in patients with suspected NPH. However, since neither the absolute ICP nor the amplitude of spontaneous oscillations can be predicted, TCD monitoring is not suitable to replace ICP monitoring. [Neurol Res 1994; 16: 398-402]     

Simultaneous recording of cerebrospinal fluid pressure and middle cerebral artery blood flow velocity in patients with suspected symptomatic normal pressure hydrocephalus.

CSF pressure (intracranial pressure, in one patient lumbar pressure) was monitored continuously for one night in 23 patients with suspected symptomatic normal pressure hydrocephalus (NPH) to identify patients who might benefit from subsequent shunt surgery. In 20 patients middle cerebral artery (MCA) blood flow velocity by means of transcranial Doppler sonography (TCD) and CSF pressure were recorded simultaneously. In three patients transcranial Doppler signals were insufficient. Spontaneous changes in CSF pressure always paralleled changes in the TCD signal. Equivalents of B-waves as well as intermediate waves (in between B- and A-waves), and C-waves could be identified easily and always appeared in phase. The Doppler signal, however, could not be used to evaluate the absolute changes in CSF pressure. Fast Fourier Transform of the Doppler signal was a useful tool to indicate the relative frequency of B-wave equivalents. In five patients the injection of 10ml saline into the ventricle raised intracranial pressure considerably, but hardly affected the MCA blood flow velocity. Continuous TCD monitoring might be useful as a noninvasive screening procedure in patients with suspected symptomatic NPH before continuous invasive CSF pressure measurements are performed.     

PVI in analyzing pressure volume relationship--effect of a bolus mannitol administration

It has been considered that mannitol reduces a raised intracranial pressure effectively by improving pressure volume relationship. The objective of this study is to determine how the pressure volume status is changed by a bolus mannitol administration with using several biomechanical parameters (intracranial pressure, pressure volume index, and intracranial elastance). Our data indicated that mannitol changed the PVI more sensitively than ICP and elastance. "Estimated Intracranial Volume Change (EICVC)" has been newly defined during mannitol infusion on the basis of PVI and ICP change. EICVC for first 30 minutes-period at which the intracranial pressure most vigorously decreased was only about 5 ml in volume. The temporal course of EICVC and ICP were not different, thus, it could account for the change of ICP properly. However, the temporal course of PVI indicating the intracranial venous blood pooling, can not be explained only by EICVC since the PVI has been changed more rapidly than any other parameters. Therefore, we speculated that the ratio of intracranial components could be more largely altered by mannitol than the net of intracranial volume change. The fundamental mechanism of ICP reduction by mannitol is possibly the brain water movement into venous circulation.     

The effect of oral glycerol on intraventricular pressure in man

Oral glycerol was administered to eight patients with meningeal carcinomatosis or acute leukemia in whom ventricular catheters and Ommaya reservoirs had been implanted for the purpose of intrathecal chemotherapy or chemoprophylaxis. Intraventricular pressure was monitored continuously via the Ommaya reservoirs before and after single doses of 0.5, 1.0 or l.5 gm per kilogram of body weight. The interrelationship between initial pressure, change in pressure, serum osmolarity, and duration of action was investigated, and the ratio of CSF-to-plasma osmolarity was determined 4 to 5 hours after glycerol administration. The effects of chronic 6-hourly and 4-hourly 1 gm per kilogram glycerol doses were studied in a patient with meningeal carcinomatosis and increased intracranial pressure. Our data suggest that as a cerebral dehydrating agent oral glycerol is most effective in patients with markedly increased intracranial pressure. A single 1 gm per kilogram dose is adequate to lower raised intraventricular pressure acutely, but its effect is short-lived. Continuous oral administration must be carefully monitored to avoid the establishment or a reverse osmotic gradient, secondarily increased intracranial pressure, and clinical deterioration.     

Analysis of intracranial pressure pulse wave in experimental hydrocephalus]

PURPOSE: Much has been written about the relationship between the pulse pressure (PP) of the intracranial pressure pulse wave (ICPPW) and ventricular dilatation. Some data suggest that high PP is the cause of ventricular dilatation, and other authors have reported that high amplitude of PP results from decreased intracranial compliance. In order to clarify these points, the amplitude of PP and Pressure-Volume Response (PVR: an indicator of intracranial compliance) were measured in bilateral ventricles using Howchwald's hydrocephalic model (right-left difference in ventricle size is clear, due to hemicraniectomy). METHODS: Hydrocephalus was developed by means of intracisternal injection of a Kaolin powder solution using dogs. The mean ICP, amplitude of the PP, PVR and ventricular size (studied by MR image) were evaluated under pathological conditions induced by the following procedures. Group A: control. Kolin induced hydrocephalus without craniectomy. Group B: Kaolin induced hydrocephalus with right side craniectomy. Group C: Kaolin induced hydrocephalus with right side craniectomy and dural resection. Group D: Kaolin induced hydrocephalus with right side craniectomy, dural resection and temporal muscle resection. RESULTS: Using MR imaging, the same degree of symmetrical ventricle dilatation were identified in all groups except Group D. Group D alone demonstrated the difference of ventricular size (craniectomy side > non craniectomy side). There was no appreciable difference in mean ICP between each group. However the amplitude of PP and the PVR decreased stepwise from Group A to Group D. The difference of the amplitude of the PP and PVR between the right and left ventricles in each group was not significant. Even in the larger ventricle side (right) of Group D, the amplitude of PP was same as that of the left ventricle, and much smaller than that of other groups. CONCLUSION: The results of our research suggest that: 1) There was no relation between the ventricular dilatation and the amplitude of PP. This means that the increased amplitude of PP was not the cause of the ventricular dilatation in this model. 2) These evidences suggest that a high degree of correlation exists between the amplitude of PP and the PVR. This means that PP can be a good parameter of the intracranial compliance in this model.     

重型颅脑损伤患者甘露醇、速尿和白蛋白降颅压作用的临床观察

目的观察甘露醇、速尿和白蛋白在不同使用方法和剂量上的降颅压效果,探讨临床合理的药物降颅压方法。方法124例重型颅脑损伤患者随机分为5组,全部进行持续颅内压(ICP)监测,连续观察静脉使用甘露醇、速尿和白蛋白后的ICP、血钾、血钠和血尿素氮(BUN)的变化。结果甘露醇和速尿降ICP作用明显(P<0.05);半量甘露醇加速尿或白蛋白降ICP作用显著(P<0.05)且持续时间长(P<0.05);降ICP的过程中可能出现电解质、肾功能的异常和ICP的反跳现象。结论半量甘露醇+速尿降ICP的方法值得临床提倡;半量甘露醇联合使用中、大剂量白蛋白在有条件的情况下也是适宜的降ICP方法。     

Platelet monoamine oxidase in Parkinson patients: effect of L-deprenyl therapy

Summary Platelet MAO activity was measured in 79 Parkinson patients (56 males and 23 females) before and during L-deprenyl therapy. Baseline platelet MAO activity was higher in females than in males with no age dependent differences. During chronic L-deprenyl therapy, MAO activity was inhibited greater than 98%. Four hours after the oral administration of the first 5 mg dose of L-deprenyl, platelet MAO activity was inhibited by 86%. By 24 hours, greater than 98%, inhibition was achieved and this degree of inhibition was maintained during continuous L-deprenyl administration. Following oral administration of 10 mg L-deprenyl once a day versus 5 mg L-deprenyl twice a day, the time course of platelet MAO inhibition was similar. Five days after the termination of chronic L-deprenyl therapy, platelet MAO activity was still inhibited by 96%. MAO activity returned to normal by 2 weeks after stopping L-deprenyl. Platelet MAO activity is a useful method of monitoring bioavailability, compliance, dose-response relationship and optimal dosage schedules for L-deprenyl in Parkinson patients.     

连续血液滤过联合甘露醇治疗颅内高压合并肾功能衰竭的临床研究

目的 探讨连续血液滤过联合甘露醇在颅内高压合并肾功能衰竭治疗中的应用价值。 方法 对珠江医院重症医学科收治的9例颅内高压合并肾功能衰竭患者行2～3次连续血液滤过联合甘露醇治疗,监测治疗前后患者颅内压数值、血肌酐及胱抑素浓度。 结果 在应用连续血液滤过联合甘露醇治疗后,患者颅内压数值较治疗前明显降低,血肌酐及胱抑素浓度较治疗前明显下降,差异有统计学意义(P＜0.05)。1例脑干出血患者于治疗第2天死于多器官功能衰竭,其余8例患者均未出现脑疝,平稳渡过脑水肿高峰期。 结论 连续血液滤过联合甘露醇是一种快速有效的治疗颅内高压合并肾功能衰竭的方法。     

Association among intracranial compliance, intracranial pulse pressure amplitude and intracranial pressure in patients with intracranial bleeds

OBJECTIVE: To investigate the association among intracranial compliance (ICC), intracranial pulse pressure amplitude and intracranial pressure (ICP) in patients with intracranial bleeds. METHODS: Five patients with intracranial bleeds had their ICC and ICP monitored during days 1-8 after ictus. The recordings were stored as raw data files and analysed retrospectively. The parameters mean ICC, mean ICP wave amplitude and mean ICP were determined and average values were calculated in 1 hour time periods. RESULTS: A total of 262 1 hour recordings were analysed. There was a significant correlation between mean ICC and mean ICP wave amplitude and between mean ICC and mean ICP. The mean ICP wave amplitude was significantly higher during the 1 hour periods with mean ICC<0.5 ml/mmHg and significantly lower during 1 hour periods with mean ICC 1.5-3.0 ml/mmHg. Correspondingly, in the 159 1 hour recordings with mean ICP wave amplitude> or =5.0 mmHg, mean ICC was significantly lower than in the 103 recordings with mean ICP wave amplitude<5.0 mmHg. Mean ICP was normal (i.e. <20 mmHg) in 260 of 262 (99.2%) of the 1 hour recordings; in the 49 1 hour recordings with mean ICP>15 mmHg, mean ICC was significantly lower than in the 213 recordings with mean ICP<15.0 mmHg. CONCLUSION: In this cohort of pressure recordings, there was a strong association between ICC and intracranial pulse pressure amplitude. There also was a strong association between ICC and mean ICP, but mean ICP was normal in 260 of 262 1 hour recordings (99.2%).     

Characterization of clinical CSF dynamics and neural axis compliance using the pressure-volume index: I. The normal pressure-volume index

The pressure-volume index (PVI) technique was used to measure neural axis compliance, cerebrospinal fluid (CSF) formation (I_f), and CSF absorption (R_o) in 23 children and 7 adults, all free from intracranial masses, who were undergoing diagnostic or therapeutic procedures. Using bolus manipulation of CSF, I_f was 0.36 ± 0.08 ml/min and R_o was 2.8 ± 0.8 mm Hg/ml/min in both adults and children. PVI, as a measure of neural axis compliance or volume buffering capacity, was 25.9 ± 3.7 ml for the adults. Measured PVI in the children varied from 8.2 to 30.1 ml but correlated well (r = 0.93) with predicted PVI based on estimates of intracranial and spinal volumes obtained from external measurements. This study provides normal reference data in humans for assessing CSF hydrodynamics and neural axis compliance using the PVI technique in pathological settings.     

脑室内注射万古霉素治疗术后颅内感染的方法学及药代动力学研究

目的了解脑室内和静脉联合使用万古霉素治疗神经外科术后颅内感染时脑脊液内药代动力学及理化性质变化规律,为建立颅内局部给药方法的标准提供依据。方法选择开颅术后留置术腔/脑室引流管的颅内感染患者10例,万古霉素q12 h静脉给予1 g,持续泵入2 h,同时,经引流管术腔/脑室局部给予10 mg。分别于给药前、后相应时间点采集静脉血及脑脊液标本测定药物浓度及理化性质。结果万古霉素给药开始后1 h血药浓度达到(41.08±15.83)mg/L,48 h谷浓度为(8.10±7.11)mg/L;脑脊液浓度给药后0.25 h为(412.71±464.81)mg/L,48 h谷浓度为(33.62±31.95)mg/L。理化性质无明显变化。结论通过静脉加小剂量脑室给药,可以提高脑脊液万古霉素浓度,可能成为治疗开颅术后严重颅内感染的一种选择,但其安全性、有效性尚需更大规模的研究证实。     

腰大池置管引流联合颅内压监测在交通性脑积水术前的应用

目的探讨腰大池置管引流联合持续性颅内压监测在交通性脑积水术前的应用价值。方法回顾性分析47例交通性脑积水病人的临床资料,术前均行腰大池置管引流和持续颅内压监测。根据脑脊液检验及颅内压监测结果,采用低压分流阀门2例,中压分流阀门39例,高压分流阀门3例,可调压分流阀门3例;进而行内镜辅助脑室一腹腔分流术。结果术后脑积水症状不同程度改善。随访1年,共发生并发症6例（12．8％）,其中脑积水症状复发5例,颅内感染1例。头颅CT复查显示：脑室较术前不同程度缩小44例,无明显变化3例,脑室周围间质水肿消失,分流管位置正常。结论对交通性脑积水病人术前应用腰大池置管引流联合颅内压监侧,合理选择分流阀门,并采用内镜辅助手术,可有效降低脑室一腹腔分流术后并发症的发生率。     

L-arginine reactivity in cerebral vessels after severe traumatic brain injury

Abstract

Objectives: Traumatic brain injury (TBI) causes an early reduction of cerebral blood flow (CBF). The purpose was to study cerebrovascular endothelial function by examining the reactivity of cerebral vessels to L-arginine.

Methods: Fifty-one patients with severe TBI were prospectively studied by measuring cerebral hemodynamics before and after the administration of L-arginine, 300 mg/kg at 12 hours and at 48 hours after injury. These hemodynamic measurements, using transcranial Doppler techniques, included internal carotid flow volume as an estimate of hemispheric CBF, flow velocity in intracranial vessels, CO₂ reactivity, and dynamic pressure autoregulation using thigh cuff deflation and carotid compression methods. Changes in the hemodynamics with L-arginine administration were analyzed using a general linear mixed model.

Results: L-arginine produced no change in mean arterial pressure, intracranial pressure, or brain oxygenation. Overall, L-arginine induced an 11.3% increase in internal carotid artery flow volume (P=0.0190). This increase was larger at 48 hours than at 12 hours (P=0.0045), and tended to be larger in the less injured hemisphere at both time periods. The response of flow velocity in the intracranial vessels was similar, but smaller differences with administration of L-arginine were observed. There was a significant improvement in CO₂ reactivity with L-arginine, but no change in dynamic pressure autoregulation.

Discussion: The low response of the cerebral vessels to L-arginine at 12 hours post-injury with improvement at 48 hours suggests that dysfunction of cerebrovascular endothelium plays a role in the reduced CBF observed after TBI.     

Early changes in peritumorous oedema and contralateral white matter after dexamethasone: a study using proton magnetic resonance spectroscopy.

AIMS: To study the mechanism of action of steroids in patients with peritumorous oedema. METHODS: To investigate early cerebral metabolic changes proton magnetic resonance spectroscopy (1H-MRS) was used before and 11 to 14 hours after treatment with dexamethasone (12 mg oral loading and 4 mg four times daily maintenance). Nine patients (two men, seven women, mean age 54) with pronounced oedema associated with various intracranial tumours (two astrocytomas, three meningiomas, two glioblastoma, and two metastases) were examined using MRI and MRS. SE1500/135 volume selected MRS (mean volume 21 ml) were performed on an oedematous region and a contralateral region. All spectra were acquired with and without water suppression. Metabolite peak area ratios were determined. RESULTS: Regions of oedema had significantly (P < 0.01) higher unsuppressed water than the contralateral regions, as expected. There was no change at this early time point after dexamethasone. The ratio of the area of choline containing compounds to that creatine and phosphocreatine compounds was determined after which the serial ratios of these before and after were calculated (a serial ratio of 1.0 would indicate no change in the choline to creatine ratios after steroid administration). The mean serial ratios for the area of oedema were 1.02 (SEM 0.08) and 1.10 (0.08) for the contralateral volume of interest, indicating no significant changes. However, significant changes (P < 0.02) were found in the N-acetyl-aspartate (NAA)/choline serial ratios (0.86 (0.06) in the area of oedema, 1.20 (0.10) in contralateral brain) and the NAA/creatine serial ratios (0.86 (0.08) for the oedema, 1.25 (0.11) in contralateral brain). CONCLUSIONS: Such rapid changes may be explained either by relatively large alterations in the relaxation characteristics of NAA or, more controversially, by actual changes in the amounts of NAA. It is proposed that steroids act primarily by causing early metabolic changes that are later expressed in improvements in intracranial volume relations.