Estimate Of Pulsatile Cerebral Blood Volume Change Derived From The Intracranial Pressure Signal

✓ The relationship of cerebral blood volume (CBV) to cerebral perfusion pressure (CPP), cerebral blood flow (CBF), and the cerebral metabolic rate for oxygen (CMRO2) was examined in rhesus monkeys. In vivo tracer methods employing radioactive oxygen-15 were used to measure CBV, CBF, and CMRO2. Cerebral perfusion pressure was decreased by raising the intracranial pressure (ICP) by infusion of artificial cerebrospinal fluid (CSF) into the cisterna magna. The production of progressive intracranial hypertension to an ICP of 70 torr (CPP of 40 torr) caused a rise in CBV accompanied by a steady CBF. With a further increase in ICP to 94 torr, CBV remained elevated without change while CBF declined significantly. Cerebral metabolic rate for oxygen did not change significantly during intracranial hypertension. For comparison, CPP was lowered by reducing mean arterial blood pressure in a second group of monkeys. Only CBF was measured in this group. In this second group of animals, the lower limit of CBF autoregulation was reached at a higher CPP (CPP ∼ 80 torr) than when an increase in ICP was employed (CPP ∼ 30 torr).

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Change of cerebral blood volume over the respiratory cycle during elevated intracranial pressure

[1993] Proceedings of the Twelfth Southern Biomedical Engineering Conference ◽

10.1109/sbec.1993.247380 ◽

2002 ◽

Author(s):

M.L. Daley ◽

M. Griffith ◽

J.T. Robertson

Keyword(s):

Intracranial Pressure ◽

Blood Volume ◽

Cerebral Blood Volume ◽

Respiratory Cycle ◽

Elevated Intracranial Pressure

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Intracranial pressure dynamics in patients with acute brain damage

Journal of Applied Physiology ◽

10.1152/jappl.1997.82.4.1270 ◽

1997 ◽

Vol 82 (4) ◽

pp. 1270-1282 ◽

Cited By ~ 16

Author(s):

M. Ursino ◽

C. A. Lodi ◽

S. Rossi ◽

N. Stocchetti

Keyword(s):

Intracranial Pressure ◽

Brain Damage ◽

Blood Volume ◽

Time Constant ◽

Cerebral Blood Volume ◽

Volume Index ◽

Parameter Estimates ◽

Time Pattern ◽

Pressure Dynamics ◽

Parameter Values

Ursino, M., C. A. Lodi, S. Rossi, and N. Stocchetti.Intracranial pressure dynamics in patients with acute brain damage. J. Appl. Physiol. 82(4): 1270–1282, 1997.—The time pattern of intracranial pressure (ICP) during pressure-volume index (PVI) tests was analyzed in 20 patients with severe acute brain damage by means of a simple mathematical model. In most cases, a satisfactory fitting between model response and patient data was achieved by adjusting only four parameters: the cerebrospinal fluid (CSF) outflow resistance, the intracranial elastance coefficient, and the gain and time constant of cerebral autoregulation. The correlation between the parameter estimates was also analyzed to elucidate the main mechanisms responsible for ICP changes in each patient. Starting from information on the estimated parameter values and their correlation, the patients were classified into two main classes: those with weak autoregulation (8 of 20 patients) and those with strong autoregulation (12 of 20 patients). In the first group of patients, ICP mainly reflects CSF circulation and passive cerebral blood volume changes. In the second group, ICP exhibits paradoxical responses attributable to active changes in cerebral blood volume. Moreover, in two patients of the second group, the time constant of autoregulation is significantly increased (>40 s). The correlation between the parameter estimates was significantly different in the two groups of patients, suggesting the existence of different mechanisms responsible for ICP changes. Moreover, analysis of the correlation between the parameter estimates might give information on the directions of parameter changes that have a greater impact on ICP.

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Changes in Cerebral Blood Volume Under Conditions of Increased Intracranial Pressure

Intracranial Pressure V ◽

10.1007/978-3-642-69204-8_146 ◽

1983 ◽

pp. 829-833

Author(s):

T. Kondo ◽

M. Brock ◽

S. Shimazaki ◽

Y. Maki

Keyword(s):

Intracranial Pressure ◽

Blood Volume ◽

Cerebral Blood Volume ◽

Increased Intracranial Pressure

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Cerebrovascular carbon dioxide reactivity assessed by intracranial pressure dynamics in severely head injured patients

Journal of Neurosurgery ◽

10.3171/jns.1995.82.3.0386 ◽

1995 ◽

Vol 82 (3) ◽

pp. 386-393 ◽

Cited By ~ 33

Author(s):

Masaaki Yoshihara ◽

Kuniaki Bandoh ◽

Anthony Marmarou

Keyword(s):

Intracranial Pressure ◽

Glasgow Coma Scale ◽

Blood Volume ◽

Volume Change ◽

Volume Index ◽

Content Type ◽

Coma Scale ◽

Head Injured ◽

Injured Patients ◽

Fine Print

✓ Appropriate management of intracranial pressure (ICP) in severely head injured patients depends in part on the cerebral vessel reactivity to PCO2; loss of CO2 reactivity has been associated with poor outcome. This study describes a new method for evaluating vascular reactivity in head-injured patients by determining the sensitivity of ICP change to alterations in PCO2. This method was combined with measurements of the pressure volume index (PVI), which allowed calculation of blood volume change necessary to alter ICP. The objective of this study was to investigate the ICP response and the blood volume change corresponding to alterations in PCO2 and to examine the correlation of responsivity and outcome as measured on the Glasgow Outcome Scale. The PVI and ICP at different end-tidal PCO2 levels produced by mild hypo- and hyperventilation were obtained in 49 patients with Glasgow Coma Scale scores of less than 8 and over a wide range of PCO2 (25 to 40 mm Hg) in eight patients. Given the assumption that the PVI remained constant during alteration of PaCO2, the estimated blood volume change per torr change of PCO2 was calculated by the following equation: BVR = PVI × Δlog(ICP)/ΔPCO2, where BVR = blood volume reactivity. The data in this study showed that PVI remained stable with changes in PCO2, thus validating the assumption used in the blood volume estimates. Moreover, the response of ICP to PCO2 alterations followed an exponential curve that could be described in terms of the responsivity indices to capnic stimuli. It was found that responsivity to hypocapnia was reduced by 50% compared to responsivity to hypercapnia measured within 24 hours of injury (p < 0.01). The sensitivity of ICP to estimated blood volume changes in patients with a PVI of less than 15 ml was extremely high with only 4 ml of blood required to raise ICP by 10 mm Hg. The authors conclude from these data that, following traumatic injury, the resistance vessels are in a state of persistent vasoconstriction, possibly due to vasospasm or compression. Furthermore, BVR correlates with outcome on the Glasgow Coma Scale, indicating that assessment of cerebrovascular response within the first 24 hours of injury may be of prognostic value.

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