Evaluation of a method for noninvasive intracranial pressure assessment during infusion studies in patients with hydrocephalus

2000 ◽  
Vol 92 (5) ◽  
pp. 793-800 ◽  
Author(s):  
Bernhard Schmidt ◽  
Marek Czosnyka ◽  
Jens Jürgen Schwarze ◽  
Dirk Sander ◽  
Werner Gerstner ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Intracranial Pressure ◽  
Time Course ◽  
Cerebral Blood Flow Velocity ◽  
Absolute Error ◽  
Content Type ◽  
Arterial Blood ◽  
Potential Clinical Benefit ◽  
The Mean ◽  
Fine Print

Object. A mathematical model previously introduced by the authors allowed noninvasive intracranial pressure (nICP) assessment. In the present study the authors investigated this model as an aid in predicting the time course of raised ICP during infusion tests in patients with hydrocephalus and its suitability for estimating the resistance to outflow of cerebrospinal fluid (Rcsf).Methods. Twenty-one patients with hydrocephalus were studied. The nICP was calculated from the arterial blood pressure (ABP) waveform by using a linear signal transformation, which was dynamically modified by the relationship between ABP and cerebral blood flow velocity. This model was verified by comparison of nICP with “real” ICP measured during lumbar infusion tests. In all simulations, parallel increases in real ICP and nICP were evident. The simulated Rcsf was computed using nICP and then compared with Rcsf computed from real ICP. The mean absolute error between real and simulated Rcsf was 4.1 ± 2.2 mm Hg minute/ml. By the construction of simulations specific to different subtypes of hydrocephalus arising from various causes, the mean error decreased to 2.7 ± 1.7 mm Hg minute/ml, whereas the correlation between real and simulated Rcsf increased from R = 0.73 to R = 0.89 (p < 0.001).Conclusions. The validity of the mathematical model was confirmed in this study. The creation of type-specific simulations resulted in substantial improvements in the accuracy of ICP assessment. Improvement strategies could be important because of a potential clinical benefit from this method.

Relationship of perfusion pressure and size to risk of hemorrhage from arteriovenous malformations

1992 ◽  
Vol 76 (6) ◽  
pp. 918-923 ◽  
Author(s):  
Robert F. Spetzler ◽  
Ronald W. Hargraves ◽  
Patrick W. McCormick ◽  
Joseph M. Zabramski ◽  
Richard A. Flom ◽  
...  
Keyword(s):  
Perfusion Pressure ◽  
Feeding Artery ◽  
Content Type ◽  
Arterial Blood ◽  
The Mean ◽  
Feeding Pressure ◽  
Risk Of Hemorrhage ◽  
Relationship Of ◽  
The Relationship ◽  
Fine Print

✓ The relationship between the size of an arteriovenous malformation (AVM) and its propensity to hemorrhage is unclear. Although nidus volume increases geometrically with respect to AVM diameter, hemorrhages are at least as common, in small AVM's compared to large AVM's. The authors prospectively evaluated 92 AVM's for nidus size, hematoma size, and arterial feeding pressure to determine if these variables influence the tendency to hemorrhage. Small AVM's (diameter ≤ 3 cm) presented with hemorrhage significantly more often (p < 0.001) than large AVM's (diameter > 6 cm), the incidence being 82% versus 21%. Intraoperative arterial pressures were recorded from the main feeding vessel(s) in 24 of the 92 patients in this series: 10 presented with hemorrhage and 14 presented with other neurological symptoms. In the AVM's that had hemorrhaged, the mean difference between mean arterial blood pressure and the feeding artery pressure was 6.5 mm Hg (range 2 to 15 mm Hg). In the AVM's that did not rupture, this difference was 40 mm Hg (range 17 to 63 mm Hg). Smaller AVM's had significantly higher feeding artery pressures (p < 0.05) than did larger AVM's, and they were associated with large hemorrhages. It is suggested that differences in arterial feeding pressure may be responsible for the observed relationship between the size of AVM's and the frequency and severity of hemorrhage.

Effects of intravenous nitroglycerin on the intracranial pressure and volume pressure response

1983 ◽  
Vol 58 (4) ◽  
pp. 562-565 ◽  
Author(s):  
Ghaleb A. Ghani ◽  
Yung Fong Sung ◽  
Michael S. Weinstein ◽  
George T. Tindall ◽  
Alan S. Fleischer
Keyword(s):  
Blood Pressure ◽  
Intracranial Pressure ◽  
Fluid Pressure ◽  
Pressure Response ◽  
Mean Blood Pressure ◽  
Intravenous Nitroglycerin ◽  
Content Type ◽  
Ventricular Fluid Pressure ◽  
The Mean ◽  
Fine Print

✓ Ventricular fluid pressure (VFP) and volume-pressure response were measured during nitroglycerin (NTG) infusion in nine patients anesthetized with N2O and fentanyl. The patients' ventilation was controlled, and PaCO2 was kept at 32 ± 4 mm Hg. When an infusion of 0.01% NTG was given intravenously to decrease the mean blood pressure to 95.1%, 84.7%, and 78.2% of control, the VFP increased from control levels of 9.94 ± 2.14 mm Hg to 12.89 ± 2.25, 15.6 ± 2.85, and 14.43 ± 3.45 mm Hg, respectively. The volume-pressure response showed a significant increase when blood pressure decreased to 84.7% and 78.2% of control. These results suggest that intravenous NTG caused an increase in the intracranial pressure and a decrease in the intracranial compliance.

In vivo assessment of the window of barrier opening after osmotic blood—brain barrier disruption in humans

2000 ◽  
Vol 92 (4) ◽  
pp. 599-605 ◽  
Author(s):  
Tali Siegal ◽  
Rina Rubinstein ◽  
Felix Bokstein ◽  
Allan Schwartz ◽  
Alexander Lossos ◽  
...  
Keyword(s):  
Blood Brain Barrier ◽  
Time Course ◽  
Photon Emission ◽  
Brain Barrier ◽  
Therapeutic Window ◽  
Content Type ◽  
Blood Brain ◽  
The Mean ◽  
Fine Print

Object. Osmotic blood—brain barrier (BBB) disruption induced by intraarterial infusion of mannitol is used in conjunction with chemotherapy to treat human brain tumors. The time course to barrier closure, or the so-called therapeutic window, has been examined in animals but little information is available in humans. The authors, therefore assessed the time course to barrier closure after osmotic BBB disruption in humans.Methods. Disruption of the BBB was demonstrated using 99mTc-glucoheptonate (TcGH) single-photon emission computerized tomography (SPECT) scanning in 12 patients who were treated monthly with combination chemotherapy in conjunction with BBB disruption. The primary diagnosis was primary central nervous system lymphoma in seven patients and primitive neuroectodermal tumors in five. The TcGH (20 mCi) was injected at 1- to 480-minute intervals after osmotic BBB disruption, and patients underwent SPECT scanning after 4 hours. A total of 38 studies was performed. Good-to-excellent BBB disruption was obtained in 29 procedures and poor-to-moderate disruption was seen in the other nine studies.The TcGH indices correlated with the degree of BBB disruption as measured postprocedure on contrast-enhanced CT scans (r = 0.852). Mean baseline TcGH indices were 1.02 ± 0.07. For the group of patients with good-to-excellent disruptions the mean indices at 1 minute postdisruption measured 2.19 ± 0.18. After 40 minutes no significant change was noted (mean index 2.13 ± 0.2). Then the indices declined more steeply and at 120 minutes after the disruption the index was 1.36 ± 0.02. A very slow decline was noted between 120 and 240 minutes after mannitol infusion. At 240 minutes the barrier was still open for all good-to-excellent disruptions (index 1.33 ± 0.08) but at 480 minutes the mean indices had returned to the baseline level.Conclusions. Results of these in vivo human studies indicate that the time course to closure of the disrupted BBB for low-molecular-weight complexes is longer than previously estimated. The barrier is widely open during the first 40 minutes after osmotic BBB disruption and returns to baseline levels only after 6 to 8 hours following the induction of good or excellent disruption. These findings have important clinical implications for the design of therapeutic protocols.

Effect of systemic arterial hypotension on the rate of cerebrospinal fluid formation in dogs

1974 ◽  
Vol 41 (3) ◽  
pp. 350-355 ◽  
Author(s):  
Michael E. Carey ◽  
A. Richard Vela
Keyword(s):  
Blood Pressure ◽  
Cerebrospinal Fluid ◽  
Mean Arterial Blood Pressure ◽  
Content Type ◽  
Arterial Blood ◽  
Ventriculocisternal Perfusion ◽  
Fluid Formation ◽  
The Mean ◽  
Csf Production ◽  
Fine Print

✓The rate of cerebrospinal fluid (CSF) production in dogs was measured by ventriculocisternal perfusion with artificial CSF containing inulin. In normotensive animals, the average CSF production was 36 ± 6 µl/min. When the mean arterial blood pressure was reduced to 62 ± 1 mm Hg, the CSF production fell to 22 ± 5 µl/min, a 39% reduction in fluid formation. The authors briefly discuss various hypotheses to explain this reduction.

Cerebral autoregulation following head injury

2001 ◽  
Vol 95 (5) ◽  
pp. 756-763 ◽  
Author(s):  
Marek Czosnyka ◽  
Piotr Smielewski ◽  
Stefan Piechnik ◽  
Luzius A. Steiner ◽  
John D. Pickard
Keyword(s):  
Head Injury ◽  
Cerebral Autoregulation ◽  
Perfusion Pressure ◽  
Content Type ◽  
Arterial Blood ◽  
Head Injured ◽  
The Mean ◽  
Injured Patients ◽  
The Relationship ◽  
Fine Print

Object. The goal of this study was to examine the relationship between cerebral autoregulation, intracranial pressure (ICP), arterial blood pressure (ABP), and cerebral perfusion pressure (CPP) after head injury by using transcranial Doppler (TCD) ultrasonography. Methods. Using ICP monitoring and TCD ultrasonography, the authors previously investigated whether the response of flow velocity (FV) in the middle cerebral artery to spontaneous variations in ABP or CPP provides reliable information about cerebral autoregulatory reserve. In the present study, this method was validated in 187 head-injured patients who were sedated and receiving mechanical ventilation. Waveforms of ICP, ABP, and FV were recorded over intervals lasting 20 to 120 minutes. Time-averaged mean FV and CPP were determined. The correlation coefficient index between FV and CPP (the mean index of autoregulation [Mx]) was calculated over 4-minute epochs and averaged for each investigation. The distribution of averaged mean FV values converged with the shape of the autoregulatory curve, indicating lower (CPP < 55 mm Hg) and upper (CPP > 105 mm Hg) thresholds of autoregulation. The relationship between the Mx and either the CPP or ABP was depicted as a U-shaped curve. Autoregulation was disturbed in the presence of intracranial hypertension (ICP ≥ 25 mm Hg) and when mean ABP was too low (ABP < 75 mm Hg) or too high (ABP > 125 mm Hg). Disturbed autoregulation (p < 0.005) and higher ICP (p < 0.005) occurred more often in patients with unfavorable outcomes than in those with favorable outcomes. Conclusions. Autoregulation not only is impaired when associated with a high ICP or low ABP, but it can also be disturbed by too high a CPP. The Mx can be used to guide intensive care therapy when CPP-oriented protocols are used.

Reduction of blood flow in the adenohypophysis of rats by bromocriptine

1985 ◽  
Vol 63 (1) ◽  
pp. 120-124 ◽  
Author(s):  
Andras A. Kemeny ◽  
Jan A. Jakubowski ◽  
Emil Pasztor ◽  
Anthony A. Jefferson ◽  
Richard Wojcikiewicz
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Wistar Rats ◽  
Content Type ◽  
Selective Effect ◽  
Arterial Blood ◽  
Male Wistar Rats ◽  
The Mean ◽  
Hydrogen Clearance ◽  
Fine Print

✓ The possibility that bromocriptine has a selective effect on blood flow in the adenohypophysis was examined in rats. Twenty-four anesthetized male Wistar rats underwent measurement of blood flow using the hydrogen clearance method. Intravenous injection of 50 µg/kg bromocriptine reduced the blood flow in both the medial and lateral parts of the adenohypophysis to about 70% of the baseline value. Simultaneously measured cerebral cortical and white matter flows were unchanged. Similar results were obtained following administration of a higher dose (500 µg/kg) of bromocriptine. This phenomenon cannot be attributed to the decrease in blood pressure. The course of change in blood flow in the medial and lateral adenohypophysis did not follow that of the mean arterial blood pressure, and the alteration of blood pressure remained within the limits of autoregulation in the adenohypophysis. The results indicate that bromocriptine is capable of reducing blood flow selectively in the pituitary region. This mechanism may contribute to the clinical usefulness of this drug.

Cerebral perfusion pressure, intracranial pressure, and head elevation

1986 ◽  
Vol 65 (5) ◽  
pp. 636-641 ◽  
Author(s):  
Michael J. Rosner ◽  
Irene B. Coley
Keyword(s):  
Intracranial Pressure ◽  
Cerebral Perfusion Pressure ◽  
Cerebral Perfusion ◽  
Perfusion Pressure ◽  
Pressure Waves ◽  
Content Type ◽  
Arterial Blood ◽  
Head Elevation ◽  
Adequate Hydration ◽  
Fine Print

✓ Previous investigations have suggested that intracranial pressure waves may be induced by reduction of cerebral perfusion pressure (CPP). Since pressure waves were noted to be more common in patients with their head elevated at a standard 20° to 30°, CPP was studied as a function of head position and its effect upon intracranial pressure (ICP). In 18 patients with varying degrees of intracranial hypertension, systemic arterial blood pressure (SABP) was monitored at the level of both the head and the heart. Intracranial pressure and central venous pressure were assessed at every 10° of head elevation from 0° to 50°. For every 10° of head elevation, the average ICP decreased by 1 mm Hg associated with a reduction of 2 to 3 mm Hg CPP. The CPP was not beneficially affected by any degree of head elevation. Maximal CPP (73 ± 3.4 mm Hg (mean ± standard error of the mean)) always occurred with the head in a horizontal position. Cerebrospinal fluid pressure waves occurred in four of the 18 patients studied as a function of reduced CPP caused by head elevation alone. Thus, elevation of the head of the bed was associated with the development of CPP decrements in all cases, and it precipitated pressure waves in some. In 15 of the 18 patients, CPP was maintained by spontaneous 10- to 20-mm Hg increases in SABP, and pressure waves did not occur if CPP was maintained at 70 to 75 mm Hg or above. It is concluded that 0° head elevation maximizes CPP and reduces the severity and frequency of pressure-wave occurrence. If the head of the bed is to be elevated, then adequate hydration and avoidance of pharmacological agents that reduce SABP or prevent its rise are required to maximize CPP.

Bilirubin as a cerebrospinal fluid marker of sentinel subarachnoid hemorrhage: a preliminary report in pigs

2004 ◽  
Vol 101 (6) ◽  
pp. 1026-1029 ◽  
Author(s):  
Chad J. Morgan ◽  
Gail J. Pyne-Geithman ◽  
Edward C. Jauch ◽  
Rakesh Shukla ◽  
Kenneth R. Wagner ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Subarachnoid Hemorrhage ◽  
Time Course ◽  
Isotonic Saline ◽  
Bilirubin Concentration ◽  
Content Type ◽  
Arterial Blood ◽  
Potential Marker ◽  
Yorkshire Pigs ◽  
Fine Print

Object. A model of subarachnoid hemorrhage (SAH) in pigs was developed to investigate bilirubin concentration in cerebrospinal fluid (CSF) as a potential marker of sentinel SAH. Methods. Seven male Yorkshire pigs received a 250-µl injection of either whole autologous arterial blood (four animals) or isotonic saline (three animals) into the cisternae magna in an effort to produce volumetrically a model of sentinel SAH and a control injection model, respectively. Cerebrospinal fluid volumes of 100 µl were then collected from both the lumbar cistern and cisternae magna at 1 to 2-hour intervals for a total of 24 hours postinjection. The CSF was then tested for bilirubin. Mean concentrations of bilirubin (± standard deviation [SD]) obtained from the lumbar cistern 24 hours following the injection of blood or saline were 4.38 ± 1.04 µM in the SAH animals and 1.02 ± 0.05 µM in the controls. At 24 hours postinjection, mean concentrations (± SD) of cisternae magna bilirubin were 7.29 ± 1.33 ÉM and 1.33 ± 0.14 µM in the SAH animals and controls, respectively. In the SAH group, both the lumbar cistern and cisternae magna bilirubin concentrations differed significantly from baseline values 12 hours following SAH. Conclusions. Elevated concentrations of CSF bilirubin can be detected following a low-volume SAH, and the production of bilirubin occurred over a predictable time course. Twelve hours after hemorrhage, an elevated CSF bilirubin concentration was an indicator of hemolysis occurring in the subarachnoid spaces. The presence of bilirubin in CSF is a potential marker for differentiating SAHs from traumatic lumbar punctures in humans.

Effects of head elevation on intracranial hemodynamics in patients with ventriculoperitoneal shunts

1994 ◽  
Vol 81 (6) ◽  
pp. 829-836 ◽  
Author(s):  
Sotaro Higashi ◽  
Kazuya Futami ◽  
Hiroshi Matsuda ◽  
Junkoh Yamashita ◽  
Masaaki Hashimoto ◽  
...  
Keyword(s):  
Photon Emission ◽  
Fluid Pressure ◽  
Upright Position ◽  
Differential Pressure ◽  
Control Group ◽  
Content Type ◽  
Arterial Blood ◽  
Head Elevation ◽  
The Mean ◽  
Fine Print

✓ The present study was performed to investigate the effects of head elevation on intracranial hemodynamics in patients with ventriculoperitoneal (VP) shunts. The series included 35 hydrocephalic patients and five individuals without hydrocephalus who were used as controls. The hydrocephalic patients were divided into three groups: 15 patients who received VP shunts with a differential-pressure valve (DP group); 11 who received VP shunts with a variable-resistance valve (VR group), and 13 hydrocephalic patients (Hyd group) who had not received shunts (four underwent VP shunts later). The cerebral blood flow (CBF) of patients in the supine and upright positions was measured by technetium-99m hexamethylpropylenamine oxide (HMPAO) single-photon emission computerized tomography in each patient, using the subtraction technique. Cerebral perfusion pressure (CPP) was taken as the difference between the mean arterial blood pressure and ventricular fluid pressure, both referenced to the level of the foramen of Monro. The patients' heads were elevated stepwise from supine to upright. Percent changes of the mean CBF in the upright position (%ΔmCBFupr) were 24.9% ± 4.3% (mean ± standard error of the mean) in the DP group, 6.2% ± 2.7% in the VR group, 3.5% ± 2.6% in the Hyd group, and 4.5% ± 2.2% in the control group. Patients in the DP group showed a pathological increase in CPP with head elevation, whereas those in the Hyd and VR groups showed a physiological decrease in CPP. Three patients with differential-pressure valves, whose %ΔmCBFupr was markedly high, developed low-intracranial pressure syndrome. In conclusion, shunted patients with a DP valve showed pathological intracranial hemodynamics in the upright position. This pathological hemodynamic stress in patients with long-standing differential-pressure valve implantation may induce pathological changes in the brain such as subependymal gliosis.

Effects of nifedipine on intracranial pressure in neurosurgical patients with arterial hypertension

1988 ◽  
Vol 69 (2) ◽  
pp. 213-215 ◽  
Author(s):  
Akio Tateishi ◽  
Takanobu Sano ◽  
Hiroshi Takeshita ◽  
Toshihisa Suzuki ◽  
Hisao Tokuno
Keyword(s):  
Intracranial Pressure ◽  
Arterial Hypertension ◽  
Cerebral Perfusion ◽  
Perfusion Pressure ◽  
Content Type ◽  
Neurological Signs ◽  
Arterial Blood ◽  
Neurosurgical Patients ◽  
The Mean ◽  
Made In

✓ The effects of nifedipine, 20 mg administered via a nasogastric tube, on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) were examined. Nifedipine was administered to treat arterial hypertension (> 180 mm Hg, systolic). Ten measurements were made in eight patients with cerebrovascular disease or head trauma. The mean arterial blood pressure (MABP) and ICP were measured before and for 30 minutes after the administration of nifedipine. The MABP gradually decreased and reached its lowest value at approximately 10 minutes after initiation of nifedipine administration, and thereafter remained unchanged. The MABP decreased significantly from 128 ± 8 (mean ± standard deviation) to 109 ± 7 mm Hg, and the CPP decreased from 105 ± 11 to 84 ± 10 mm Hg. The ICP increased by 1 to 10 mm Hg in eight of 10 measurements, and the mean change of ICP from 19 ± 7 to 22 ± 6 mm Hg was statistically significant. These changes were not accompanied by alterations in neurological signs. The results suggest that enteral nifedipine produces a small but statistically significant increase in ICP. Accordingly, neurological signs must be closely observed to detect deterioration, which can be caused by an increase in ICP and/or a decrease in CPP.

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