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Cerebral Vascular Changes During Acute Intracranial Pressure Drop.

ABSTRACT: OBJECTIVE:This study applied a new external ventricular catheter, which allows intracranial pressure (ICP) monitoring and cerebral spinal fluid (CSF) drainage simultaneously, to study cerebral vascular responses during acute CSF drainage. METHODS:Six patients with 34 external ventricular drain (EVD) opening sessions were retrospectively analyzed. A published algorithm was used to extract morphological features of ICP recordings, and a template-matching algorithm was applied to calculate the likelihood of cerebral vasodilation index (VDI) and cerebral vasoconstriction index (VCI) based on the changes of ICP waveforms during CSF drainage. Power change (?P) of ICP B-waves after EVD opening was also calculated. Cerebral autoregulation (CA) was assessed through phase difference between arterial blood pressure (ABP) and ICP using a previously published wavelet-based algorithm. RESULTS:The result showed that acute CSF drainage reduced mean ICP (P?=?0.016) increased VCI (P?=?0.02) and reduced ICP B-wave power (P?=?0.016) significantly. VCI reacted to ICP changes negatively when ICP was between 10 and 25 mmHg, and VCI remained unchanged when ICP was outside the 10-25 mmHg range. VCI negatively (r?=?-?0.44) and VDI positively (r?=?0.82) correlated with ?P of ICP B-waves, indicating that stronger vasoconstriction resulted in bigger power drop in ICP B-waves. Better CA prior to EVD opening triggered bigger drop in the power of ICP B-waves (r?=?-?0.612). CONCLUSIONS:This study demonstrates that acute CSF drainage reduces mean ICP, and results in vasoconstriction which can be detected through an index, VCI. Cerebral vessels actively respond to ICP changes or cerebral perfusion pressure (CPP) changes in a certain range; beyond which, the vessels are insensitive to the changes in ICP and CPP.

SUBMITTER: Liu X

PROVIDER: S-EPMC7229699 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Cerebral Vascular Changes During Acute Intracranial Pressure Drop.

Liu Xiuyun X Zimmermann Lara L LL Ho Nhi N Vespa Paul P Liao Xiaoling X Hu Xiao X

Neurocritical care 20190601 3

<h4>Objective</h4>This study applied a new external ventricular catheter, which allows intracranial pressure (ICP) monitoring and cerebral spinal fluid (CSF) drainage simultaneously, to study cerebral vascular responses during acute CSF drainage.<h4>Methods</h4>Six patients with 34 external ventricular drain (EVD) opening sessions were retrospectively analyzed. A published algorithm was used to extract morphological features of ICP recordings, and a template-matching algorithm was applied to cal ...[more]

PMID: 30523541

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Project description:OBJECTIVES:The lower limit of cerebral blood flow autoregulation is the critical cerebral perfusion pressure at which cerebral blood flow begins to fall. It is important that cerebral perfusion pressure be maintained above this level to ensure adequate cerebral blood flow, especially in patients with high intracranial pressure. However, the critical cerebral perfusion pressure of 50 mm Hg, obtained by decreasing mean arterial pressure, differs from the value of 30 mm Hg, obtained by increasing intracranial pressure, which we previously showed was due to microvascular shunt flow maintenance of a falsely high cerebral blood flow. The present study shows that the critical cerebral perfusion pressure, measured by increasing intracranial pressure to decrease cerebral perfusion pressure, is inaccurate but accurately determined by dopamine-induced dynamic intracranial pressure reactivity and cerebrovascular reactivity. DESIGN:Cerebral perfusion pressure was decreased either by increasing intracranial pressure or decreasing mean arterial pressure and the critical cerebral perfusion pressure by both methods compared. Cortical Doppler flux, intracranial pressure, and mean arterial pressure were monitored throughout the study. At each cerebral perfusion pressure, we measured microvascular RBC flow velocity, blood-brain barrier integrity (transcapillary dye extravasation), and tissue oxygenation (reduced nicotinamide adenine dinucleotide) in the cerebral cortex of rats using in vivo two-photon laser scanning microscopy. SETTING:University laboratory. SUBJECTS:Male Sprague-Dawley rats. INTERVENTIONS:At each cerebral perfusion pressure, dopamine-induced arterial pressure transients (~10 mm Hg, ~45 s duration) were used to measure induced intracranial pressure reactivity (? intracranial pressure/? mean arterial pressure) and induced cerebrovascular reactivity (? cerebral blood flow/? mean arterial pressure). MEASUREMENTS AND MAIN RESULTS:At a normal cerebral perfusion pressure of 70 mm Hg, 10 mm Hg mean arterial pressure pulses had no effect on intracranial pressure or cerebral blood flow (induced intracranial pressure reactivity = -0.03 ± 0.07 and induced cerebrovascular reactivity = -0.02 ± 0.09), reflecting intact autoregulation. Decreasing cerebral perfusion pressure to 50 mm Hg by increasing intracranial pressure increased induced intracranial pressure reactivity and induced cerebrovascular reactivity to 0.24 ± 0.09 and 0.31 ± 0.13, respectively, reflecting impaired autoregulation (p < 0.05). By static cerebral blood flow, the first significant decrease in cerebral blood flow occurred at a cerebral perfusion pressure of 30 mm Hg (0.71 ± 0.08, p < 0.05). CONCLUSIONS:Critical cerebral perfusion pressure of 50 mm Hg was accurately determined by induced intracranial pressure reactivity and induced cerebrovascular reactivity, whereas the static method failed.

Project description:Introduction: We investigated the effect of hematoma volume reduction with minimally invasive surgery (MIS) on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in patients with large spontaneous intracerebral hemorrhage (ICH). Methods: Post-hoc analysis of the Minimally Invasive Surgery Plus Alteplase for Intracerebral Hemorrhage Evacuation (MISTIE III) study, a clinical trial with blinded outcome assessments. The primary outcome was the proportion of ICP readings ≥20 and 30 mmHg, and CPP readings <70 and 60 mm Hg. Secondary outcomes included major disability (modified Rankin scale >3) and mortality at 30 and 365 days. We assessed the relationship between proportion of high ICP and low CPP events and MIS using binomial generalized linear models, and outcomes using multiple logistic regression. Results: Of 499 patients enrolled in MISTIE III, 72 patients had guideline based ICP monitors placed, 34 in the MIS group and 38 in control (no surgery) group. Threshold ICP and CPP events ≥20/ <70 mmHg occurred in 31 (43.1%) and 52 (72.2%) patients respectively. On adjusted analyses, proportion of ICP readings ≥20 and 30 mmHg were significantly lower in the MIS group vs. control group [Odds Ratio (OR) 0.27, 95% Confidence Interval [CI] 0.11-0.63 (p = 0.002); OR = 0.18, 0.04-0.75, p = 0.02], respectively. Proportion of CPP readings <70 and 60 mm Hg were also significantly lower in MIS patients [OR 0.31, 95% CI 0.15-0.63 (p = 0.001); OR 0.30, 95% CI 0.11-0.83 (p = 0.02)], respectively. Higher proportions of CPP readings <70 and 60 mm were significantly associated with short term mortality (p = 0.04), and (p = 0.006), respectively. Long term mortality was significantly associated with higher proportion of time with ICP ≥ 20 (p = 0.04), ICP ≥ 30 (p = 0.04), and CPP <70 mmHg (p = 0.01). Conclusion: Our results are consistent with the hypothesis that surgical reduction of ICH volume decreases proportion of high ICP and low CPP events and that these variables are associated with short- and long-term mortality.

Project description:The purpose of this study is to investigate whether increases in the blood flow from the heart (the cardiac output), induced by the administration of intravenous fluids, lead to an increase in the blood flow to the vital organs, in patients undergoing bowel surgery. This study will involve 2 phases. Firstly, potential volunteers will be invited to meet the research fellow (medical doctor) undertaking this study, who will check their suitability to participate in the study and who will obtain informed consent. The second phase is the study itself which will take place whilst volunteers are having their bowel operation. They will attend theatre in the normal way, but once they have been anaesthetised (put to sleep), a special monitor called an oesophageal doppler probe will be placed into their oesophagus (food pipe) via the nose. This monitor is frequently used in bowel surgery to help assess how much intravenous fluid to administer to a patient by measuring the cardiac output (the amount of blood pumped out of the heart each minute). Using the cannula (drip) already inserted in the arm to allow administration of the anaesthetic, a special fluid, called an ultrasound contrast agent, will be injected into the drip, to allow a contrast enhanced ultrasound scan of the abdominal organs to be performed, to measure the blood flow to these organs. A small sample of blood will be taken from the earlobe to allow us to measure a chemical in the blood called lactate. After this, intravenous fluid will be administered in order to increase the amount of blood pumped out of the heart. Once the oesophageal doppler monitor suggests that an adequate amount of fluid has been given, a second ultrasound scan will be performed to measure whether blood flow to the abdominal organs has also increased. A further blood sample will be taken from your earlobe to measure any change in lactate level. At the completion of the operation, a third ultrasound scan will be performed and another sample of blood taken from the earlobe, to help assess blood flow to the organs.

Project description:Purpose:To evaluate the alteration of pressure characteristics in the cerebral venous sinuses before and after venous sinus stenting (VSS) using mean sinus pressures (MSPs), sinus pressure gradient (SPG), and sinus pressure pulsatility (SPP) parameters among the idiopathic intracranial hypertension (IIH) patients. Materials and Methods:Prospective evaluation of 45 consecutive IIH patients who underwent VSS at our institution. A written informed consent approved by the Weill Cornell Institutional Review Board was signed by the study participants. All patients (n = 45) were evaluated for MSPs and SPG. In a subgroup of 12 (n = 12) consecutive patients, SPP was measured. MSP was measured using microcatheter at superior sagittal sinus (SSS), transverse sinus (TS), and sigmoid sinus (SS). SPG was measured as trans-stenotic gradient and trans-torcular gradient. SPP was recorded in the dominant TS with a six French intermediate catheter. Statistical analysis was performed using paired student t-test and two sample t-tests tested for both equal and unequal variances. P values below 0.05 were considered significant. Results:The mean age of the study population was 30.6 ± 10 years (7-59 years) and 43 out of 45 are female patients. The mean weight and BMI of the study population were 96 ± 24.7 kg (30.8-144 kg) and 35.6 ± 8.3 kg/M2 (16.4-51.4 kg/M2), respectively. VSS in IIH patients resulted in immediate reduction of MSP in the SSS {? Mean: -8.1 mm Hg [95% confidence interval (CI): -5.0-11.7 mm Hg], p < 0.001} and TS [? Mean: -11.8 mm Hg (95% CI: -7.5 to 13.4 mm Hg), p < 0.001] and increase of MSP in SS [? Mean: 7.5 mm Hg (95% CI: 6-10.1 mm Hg), p < 0.001]. Significant reduction of trans-stenotic SPG reduction [? Mean: -15.7 mm Hg (95% CI: -13.6-17.8 mm Hg), p < 0.001] and SPP [? Mean: -8 mm Hg (95% CI: -2.5-13.4 mm Hg), p < 0.05] was observed following VSS. Conclusion:VSS resulted in immediate alteration of the cerebral venous sinus pressure measurements in patients with IIH.

Dataset Information

Cerebral Vascular Changes During Acute Intracranial Pressure Drop.

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Cerebral Vascular Changes During Acute Intracranial Pressure Drop.

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