Measurement of intracranial pressure in the unanesthetized rabbit

MALKINSON, T. J., W. L. VEALE AND K. E. COOPER. Measurement of intracranial pressure in the unanesthetizedrabbit. BRAIN RES. BULL. 3(6) 635–638, 1978.—A method is described for the measurement of intracranial pressure in the unanesthetized, minimally restrained rabbit utilizing a modified subarachnoid screw system. The pressures are transmitted from within the cranium via a flexible saline filled catheter to a fixed external pressure transducer. An index of the relative vertical position of the animal's skull as compared to the fixed transducer is given by means of a second open-ended pressure measuring catheter, the open end of which is fixed to the subarachnoid screw assembly on the animal's skull. The system was found to be a reliable method of measurement of intracranial pressures in the minimally restrained rabbit, and could easily be adapted to other animal species. The method is currently being used to assess the effects of fever on intracranial pressures.     

严重脑外伤后血和脑脊液酸碱平衡变化

通过测定14例脑外伤病人血和脑脊液PO_2、PCO_2、pH、HCO_3~-水平,我们观察到严重脑外伤后出现脑脊液代谢性酸中毒,动脉血呼吸性碱中毒和低氧血症。脑脊液pH值与颅内压水平呈密切的负相关关系。脑脊液pH值是较敏感的预后指标。     

Intracranial venous pressures,hydrocephalus and effects of cerebrospinal fluid shunts

Data concerning venous anatomy, interstitial fluid pressure and cerebral blood flow indicate that obstruction of cerebral venous outflow (as a whole or involving the deep venous system alone) is the essential cause of hydrocephalus. Choroidal and ventricular veins both belong to the deep system. Choroidal venous pressure determines cerebrospinal fluid pressure; pressure in the ventricular veins determines interstitial fluid pressure in the paraventricular white matter. A decrease in deep cerebral blood flow causes paraventricular atrophy. CSFP is higher than interstitial fluid pressure, normally and in venous obstruction. Thus, CSFP prevents venocongestive edema (but not inflammatory edema) of the brain. Collateral venous pathways are described. Venous obstruction causes hydrocephalus only when it leads to insufficient blood flow. Cerebrospinal fluid shunting causes increased CBF as essential therapeutic effect in hydrocephalus, but also causes venocongestive brain edema, which explains the decrease in ventricle size and the side effects of shunting.Presented at the XVI Annual Meeting of the International Society for Pediatric Neurosurgery, Rome 1988     

The effect of large doses of dexamethasone on the cerebrospinal fluid pressure in patients with supratentorial tumors

Summary The effect of large doses of dexamethasone (80 mg) on the cerebrospinal fluid pressure (CSFP) was investigated with continuous lumbar CSFP measurement over 24h in 10 patients with supratentorial cerebral tumors and clinical signs of elevated intracranial pressure. There was a further slight rise in CSFP with an unchanged pressure pattern in the course of observation of the untreated control group. A marked lowering of CSFP was observed within 6h after initial intravenous administration of dexamethasone to seven of the treated patients. In four of the treated patients an unequivocal and in five only a moderate CSFP lowering was measured at the end of the registration. One patient had a slight rise in pressure. The plateau waves of all the patients treated decreased in height, frequency and duration within the first hours, while fluctuations in pressure level and CSFP amplitude were reduced.

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Zusammenfassung Mit der kontinuierlichen lumbalen Liquordruckmessung wurde bei 10 Patienten mit supratentoriellen Hirntumoren und klinischen Zeichen intrakranieller Drucksteigerung über 24 Std die Wirkung hoher Dosen Dexamethason (80 mg) auf den Liquordruck (CSFP) untersucht. Während es bei der Kontrollgruppe (unbehandelte Patienten) im Laufe der Registrierung zu einem weiteren leichten CSFP-Anstieg bei unverändertem Druckmuster kam, wurde bei 7 der behandelten Patienten innerhalb 6 Std nach initialer intravenöser Dexamethasongabe eine deutliche CSFP-Senkung beobachtet. Bei 4 der behandelten Patienten wurde zum Ende der Registrierung eine eindeutige, bei 5 eine nur mäßige CSFP-Senkung gemessen. 1 Patient wies einen leichten Druckanstieg auf. Bei allen behandelten Patienten nahmen die Plateauwellen innerhalb der ersten Stunden an Höhe, Häufigkeit und Dauer ab, Druckniveauschwankungen und Liquordruckamplituden verringerten sich.

     

Cerebrospinal fluid and extracellular fluid: their relationship to pressure and duration of canine hydrocephalus

Fifteen greyhound dogs were made hydrocephalic by the transsphenoidal injection of silicone into the basal cisterns at the level of the tentorial incisura. Six of these animals had ventriculocisternal perfusions 4 weeks later and six at 8 weeks, half at 150 and half at 100 mm H₂O. Three 12-week dogs were perfused at 150 mm H₂O. Serial sections of brain from the ependyma of the left frontal horn to the overlying pia were counted for¹⁴C inulin and³H methotrexate uptake. Tissue concentrations of both markers varied indirectly with distance from ependyma and from pia, and varied directly with perfusion pressure. The data indicate that the diffusional pathway between cere-brospinal fluid (CSF) and extracellular fluid (ECF) can be modified by CSF pressure changes, i.e., CSF flows from the ventricles and subarachnoid space into the extracellular space when CSF pressures are raised. Brain uptake of inulin and methotrexate was significantly increased in the dogs made hydrocephalic 4 weeks prior to perfusion, but was less so in the 8-week hydrocephalics. Uptake of the tracers in three 12-week animals was similar to that found previously in normal dogs at elevated pressures. These findings correspond in location and time to the periventricular lucencies that are seen by computed tomography in human subacute hydrocephalus. They are apparently due to pressure-related changes in the volume of the ECF.     

Intracranial pressure waveform analysis: Computation of pressure transmission and waveform shape indicators

Abstract

We studied transmission of arterial blood pressure to intracranial pressure by observing how the two pressure waveforms varied from baseline conditions to after postural change or jugular compression. Such experiments may lead to pressure waveform-based estimates of intracranial compliance. Using a single database of arterial blood pressure, central venous pressure! and intracranial pressure waveforms collected during baseline, jugular compresison! and head-elevated conditions from six Yucatan minipigs, we computed several numerical indicators of waveform shape to find an estimator of intracranial compliance. Of these indicators, two were based on the Fourier-decomposition of all three waveforms, and one was based on a new method for approximating the systolic slope of the intracranial pressure waveform. We computed amplitude transfer functions for the first six harmonics of the Fourier spectrum! treating intracranial pressure as system output and independently treating arterial blood pressure and central venous pressure as system inputs. Using these same inputs and outputs, we computed a single quotient based on the Fourier coefficients of the first six harmonics of the input and output waveforms. Finally, applying a Gaussian high-pass filter, we computed systolic slope approximations for all intracranial pressure wave cycles contained in a single respiratory cycle. Our third indicator was the mean-normalized variation of the slope approximations over a respiratory cycle. We studied how each composite at baseline varied with baseline mean intracranial pressure and how each composite changed from baseline as a result of a physical manipulation. Our analysis suggests that the composite based on respiratory variation of systolic slope approximations was positively correlated with mean intracranial pressure during baseline. The quotient based on Fourier coefficients with arterial blood pressure input seemed to increase from baseline to jugular compression. Composites that treated central venous pressure as input were both less correlated with mean intracranial pressure during baseline and exhibited less predictable changes from baseline to a physical manipulation than their counterparts that used arterial blood pressure as input. However! none of these apparent trends was statistically significant. The lack of statistically significant results may be due to the nature of the composites and/or the small sample size (n = 6). However, we hope this study stimulates further investigation of both central venous pressure-to-intracranial pressure (in addition to arterial blood pressure-to-intracranial pressure) transfer and automated computation of intracranial pressure waveform systolic slope. Such research may lead to noninvasively determined estimators of intracranial compliance. [Neural Res 1998; 20: 533-541]     

Effects of head-down tilt on the intracranial pressure in conscious rabbits

Head-down tilt (HDT) causes a fluid shift towards the upper body, which increases intracranial pressure (ICP). In the present study, the time course of ICP changes during prolonged exposure to HDT was investigated in conscious rabbits through a catheter chronically implanted into the subarachnoid space. The production of cerebrospinal fluid (CSF) after exposure to 7-days HDT was also examined by a ventriculo-cisternal perfusion method. The ICP increased from 4.3+/-0.4 (mean+/-S.E.M.) mmHg to 8.0+/-0.8 mmHg immediately after the onset of 45 degrees HDT, reached a peak value of 15.8+/-1.9 mmHg at 11 h, and then decreased to 10.4+/-1.1 mmHg at 24 h. During 7-days HDT, it also increased from 4.8+/-0.9 mmHg to 9.2+/-1.6 mmHg immediately after the onset of 45 degrees HDT, reached a peak value of 12.8+/-2.5 mmHg at 12 h of HDT, and then decreased gradually towards the pre-HDT baseline value for 7 days. The rate of CSF production was 10.1+/-0.6 microl/min in rabbits exposed to 7-days HDT, and 9.7+/-0.5 microl/min in control rabbits. These results suggest that the rabbits begin to adapt to HDT within a few days and that the production of CSF is preserved after exposure to 7-days HDT. The time course of ICP changes during HDT in conscious rabbits seems to be considerably different from that in anesthetized rabbits.     

Mechanism of delayed intracranial hypertension after cerebroventricular infusions in conscious rats

Prior studies showed that cerebroventricular infusions of artificial cerebrospinal fluid, 8 μl/min for 10 min, followed by a 10 min rest and a 24 h infusion of 0.5 μl/min, raised cerebrospinal fluid pressure (CSFp) of conscious, unrestrained rats after about 2 h. Here, we report that the 10 min infusion alone evoked a delayed, prolonged rise in CSFp. Pressure during the infusion itself rose and recovered quickly, as is usually reported. Pressure/volume tests, used to calculate resistance to outflow (R_o) and compliance (C), revealed that infusions increasedR_o and decreasedC, after a delay (P < 0.05). The rise in CSFp after infusion was blocked by pretreatment with acetazolamide + ouabain (P < 0.05), but the delayed changes in R_o andC were unaffected. We suggest that the 10 min infusion of a sterile, balanced salt solution has a primary effect that increasesR_o; as CSF synthesis continues, C is exhausted and the delayed rise in CSFp ensues. This non-traumatic method of raising CSFp may be a useful method to study intracranial fluid dynamics.     

颅脑损伤后脑脊液C-反应蛋白与颅内压相关性及临床意义

目的探讨颅脑损伤后脑脊液C-反应蛋白(CRP)与颅内压变化的关系。方法颅脑损伤患者65例,按GCS评分分为轻型组15例,中型组20例,重型组30例。腰椎穿刺检测脑脊液压力,同时采集其伤后1 d内至4 w的脑脊液,以免疫比浊法测定脑脊液中CRP的含量,将脑脊液中CRP的含量与颅内压变化进行比较。结果伤后轻、中、重型各组脑脊液CRP与颅内压变化存在组间差异(P0.01);CRP含量的变化与颅内压变化呈正相关。结论脑脊液中CRP的含量是反映颅脑损伤急性期脑组织损伤的敏感指标,能反映颅脑损伤后颅内压变化趋势。     

血流导向装置在颅内动脉瘤治疗中应用的血流动力学研究进展

血流导向装置（flow diverter,FD）是近年来产生的血管内治疗颅内复杂动脉瘤的新材料。FD设计是通过改建血流的方式将动脉瘤排除在循环系统之外从而重建载瘤动脉,因此FD为复杂动脉瘤的治疗提供了新的思路和手段。临床报道该治疗方式的动脉瘤完全栓塞率可达90%以上。目前FD应用逐渐广泛,本文从血流动力学角度出发针对FD的血流导向能力,以及颅内动脉瘤经FD治疗后影响预后的因素进行了总结。     

Ventriculosubcutaneous shunt for temporary treatment of neonatal post-IVH hydrocephalus: a technical note

A technique for temporary ventricular drainage using a subcutaneous pouch is described for use in neonatal hydrocephalus after intraventricular hemorrhage. The advantages include continuous, valve-regulated ventricular decompression, no exposed tubing, avoidance of electrolyte imbalance and of the loss of CSF, obviation of the need for repeated tapping, and the ability to convert to a peritoneal shunt on an elective basis.     

Raised intracranial pressure with upright posture

We describe the phenomenon of paradoxical intracranial hypertension with upright posture with normal recumbent intracranial pressure (ICP). This effect was measured by direct ICP monitoring in a patient who had a lumboperitoneal shunt for idiopathic intracranial hypertension. Bilateral subtemporal surgical decompression to increase intracranial compliance with confirmatory perioperative pressure monitoring was central to the successful management of this patient.     

Intracranial pressure and cerebral arterial flow velocity indices in childhood hydrocephalus: current review

Because of its noninvasive and repeatable nature, Doppler ultrasound has been increasingly used to assess changes in cerebral haemodynamics in infants and children with hydrocephalus. There is general agreement that a direct correlation exists between the intracranial pressure (from experimental, fontanometric and direct measurement evidence) and the resistance index. In addition, this increasing index has been predominantly due to a reduction in the end-diastolic velocity. Stable ventriculomegaly is associated with normal pulsatility. The cerebral blood flow velocity parameters change significantly following CSF drainage by tapping or shunting. The measurement of intracranial pressure and cerebral blood flow velocity are currently the best ways of assessing the need for CSF diversion and monitoring subsequent shunt function.Presented at the Consensus Conference: Hydrocephalus '92, Assisi, Italy, 26–30 April 1992     

Intracerebroventricular arginine vasopressin causes intracranial pressure to rise in conscious goats

The effects of intracerebroventricular (i.c.v.) infusion of arginine vasopressin (AVP) on intracranial pressure (ICP), blood pressure (BP) and plasma AVP were investigated in conscious goats. The animals were implanted with ventricular (V) and cisternal (C) cannulae under halothane anaesthesia and allowed to recover prior to experimentation. After 30 min infusion of 20 microliter/min artificial cerebrospinal fluid (CSF) alone, to allow the animals to settle, ICP (estimated at both C and V cannulae), BP and plasma AVP were measured. Then the animals were infused with either artificial CSF alone or 1 or 10 pmol/min AVP for a further 150 min. One pmol/min AVP i.c.v. resulted in significant ICP increases of +2.2 cm CSF (C) and +3.1 cm CSF (V) when compared with artificial CSF alone. Ten pmol/min AVP also led to significant ICP rises of +3.2 cm CSF (C) and +4.2 cm CSF (V). There were no significant changes of BP or plasma AVP during the infusions. We conclude that central infusion of AVP leads to elevated ICP in conscious goats by a mechanism that does not involve BP alteration or changes in plasma AVP.     

Intracranial pressure B-waves precede corresponding arterial blood pressure oscillations in patients with suspected normal pressure hydrocephalus

Abstract

B-waves are rhythmic oscillations of intracranial pressure (ICP) with a wavelength of 0.5-2 min. These oscillations are accompanied by corresponding fluctuations of arterial blood pressure (BP). There is controversy in the literature whether the ICP oscillations precede or follow the BP oscillations. This relationship, however, is important for the understanding of the origin and the interactions of ICP B-waves with other parameters. ICP and BP were monitored continuously for one night in nine patients with suspected symptomatic normal pressure hydrocephalus (NPH). Forty-five B-waves were identified and the time delays between the peaks and the onsets of B-waves and their BP-equivalents were measured. The mean (± standard deviation) of the time delays between the peaks of ICP B-waves and corresponding BP-oscillations was 4.2 ±2.4 sec and between the onsets of the oscillations 7 0.3 ±6.6 sec. In all but two B-waves, the ICP peak preceded the BP peak, in all the 45 B-waves the onset of the ICP increase preceded the BP increase (p < 0.004). Our study demonstrates that ICP B-waves precede concomitant changes in BP by several seconds. [Neurol Res 1999; 21: 627-630]     

颅内动脉瘤壁面压力分布的数值模拟研究

目的探讨颅内动脉瘤壁面压力的强度和分布,分析壁面压力对动脉瘤发生及生长的影响。方法结合数字减影血管造影（DSA）,采用计算流体力学（CFD）软件,对20例动脉瘤行血流动力学数值模拟分析,包括分叉管顶瘤8例,侧壁瘤12例。分别记录瘤顶、瘤颈和临近载瘤动脉区域的平均压力值,并分析动脉瘤流场情况。结果20例动脉瘤瘤顶处壁面压力平均为（620．64±446．09）Pa,瘤颈处为（618．89±431．09）Pa,载瘤动脉处为（633．81±448．59）Pa,3个区域压力差异无统计学意义。分叉管顶瘤（411．23±126．28）Pa（766．59±515．46）Pa与侧壁瘤相比,平均壁面压力差异有统计学意义（P〈0．05）。结论动脉瘤内壁面压力与载瘤血管内无明显不同,推测局部压力的改变对动脉瘤发生、生长无影响,由于流场模式的差异导致侧壁瘤与分叉管顶瘤的平均壁面压力显著不同。     

脑灌注压对创伤性脑水肿的影响

目的通过观察不同灌注压(CPP)水平对实验性脑创伤早期脑水肿的影响作用来选择适宜的CPP水平,为临床脑创伤治疗提供参考。方法实验用兔30只,随机分为对照组(无颅脑损伤),高CPP组(90～110mmHg),中CPP组(70～80mmHg),低CPP组(60～70mmHg),和极低CPP组(35～45mmHg)5组,每组6只。对照组不予损伤,其余各组均给予(1100±100)N的撞击力致减速性脑损伤(重伤水平)。伤后80min静脉给予升压药或降压药物调控血压使CPP达到设计要求。伤后6h测脑含水量。结果所有颅脑损伤动物均出现了明显的脑损伤生理反应和病理改变,颅内压(ICP)均明显增高(P<0.001)。脑含水量为:对照组,78.18%±0.32%;高CPP组,81.35%±1.02%;中CPP组,80.27%±0.48%;低CPP组80.31%±0.70%;极低CPP组,81.19%±0.74%。与对照组比较损伤组脑含水量均增加(P<0.001)。高CPP和极低CPP两组脑含水量分别较中、低CPP组增高(P<0.05)。结论兔脑创伤后维持CPP在60～80mmHg之间的中低水平,脑水肿轻;CPP降至50mmHg以下和升至90mmHg以上均加重脑水肿。     

The effect of pharmacologically increased blood pressure on brain circulation

Summary The cerebral angiograms of patients with cerebrovascular diseases, head injury and intracranial tumours obtained under normal and pharmacologically increased blood pressure were compared. Changes in cerebral blood flow, circulation time and arterial diameter were examined. CBF was measured by a semiquantitative densitometric method, arterial diameter by a split-image focusing technique.The majority of patients with normal angiograms showed a virtually constant CBF and circulation time, while there was a slight constriction of the arteries. The functional tests during cerebral angiography revealed disturbances of autoregulation in patients with acute cerebrovascular diseases or with intracranial tumours.

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Zusammenfassung An Patienten mit normalen und pathologischen angiographischen Befunden wurden Serienangiogramme bei normalem und medikamentös gesteigertem Blutdruck durchgeführt. Die Auswertung der Angiogramme erfolgte hinsichtlich Strömungsgröße, Gefäßdurchmesser und Zirkulationszeit. Die Durchströmung wurde mit Hilfe einer semiquantitativen densitometrischen Methode bestimmt. Die Messung des Gefäßdurchmessers erfolgte mit einem Schnittbilddickenmesser.Die meisten Patienten zeigten bei Blutdrucksteigerung eine Konstanthaltung der Strömung und der Zirkulationszeiten, während sich die Arterien meßbar kontrahierten. Bei Patienten mit frischen cerebrovasculären Insulten und Hirntumoren ließen sich mit den angiographischen Belastungstesten Störungen der Autoregulation nachweisen.

     

脑水肿与颅内压的监测和临床观察

脑水肿、颅内压(intracranial pressure,ICP)增高的诊断主要依靠临床观察、影像学检查和ICP监测三者结合.传统的CT和核磁共振虽然可以作为颅内血肿、脑水肿和ICP增高的检测方法,但它们不能对颅内血肿和脑水肿进行实时动态的监测,也不能反映脑水肿、颅内血肿的演变过程,给临床及时治疗带来难度.