Biomedical subjects

P Bolognese

Publications and source records attributed to P Bolognese.

7 recordsLinked to original sources

PubMed1998

Continuous intracranial multimodality monitoring comparing local cerebral blood flow, cerebral perfusion pressure, and microvascular resistance.

Maintaining cerebral perfusion pressure (CPP) above 70 mmHg is currently a mainstay of neurosurgical critical care. Shalmon, et al. recently showed poor correlation between CPP and regional cerebral blood flow (CBF) [1]. To study the relationship between CPP and CBF, at a microvascular level, we retrospectively analyzed multimodality digital data from 12 neurosurgical critical care patients in whom a combined intracranial pressure (ICP)--laser Doppler flowmetry (LDF) probe (Camino, San Diego) had been placed. Over the entire interval of continuous monitoring for all patients, 97% of local CBF data was at ischemic levels below a CPP of 70 mmHg. For CPP above 70 mmHg, local CBF data had considerable dispersion ranging from ischemic (71%), to normal (19%), and hyperemic (10%) levels. Elevated jugular bulb oxyhemoglobin saturation levels (SjO2) complemented intervals of hyperemia. Autoregulation was impaired or absent in all monitored patients. We conclude that with disrupted autoregulation, CPP above 70 mmHg does not necessarily insure adequate levels of cerebral perfusion. Restoration and maintenance of adequate cerebral perfusion should be performed under the guidance of direct CBF monitoring.

Adolescent↗

PubMed1997

Intramedullary pressure in syringomyelia: clinical and pathophysiological correlates of syrinx distension.

OBJECTIVE: The pathophysiological effects of syrinx distension are incompletely understood. Although it is generally assumed that the accumulation of fluid within syrinx cavities can contribute to neurological dysfunction, there are no reports describing intramedullary pressure in syringomyelia. The purpose of the current study was to measure syrinx pressures in patients with progressive clinical deterioration and to correlate these data with neurological deficits and intraoperative physiological findings. METHODS: Intramedullary fluid pressure was measured manometrically in 32 patients undergoing syrinx shunting procedures. The data were correlated with syrinx morphology, intraoperative somatosensory evoked potentials, laser Doppler measurements of local spinal cord blood flow (six patients), and neurological findings before and after syrinx decompression. RESULTS: Syrinx pressures recorded under atmospheric conditions ranged from 0.5 to 22.0 cm H2O (mean = 7.7 cm). There was a significant elevation of the cardiac pulse (mean = 0.7 cm H2O) and the respiratory pulse (mean = 1.1 cm H2O) that was consistent with raised cerebrospinal fluid pressure. Syrinx pressures decreased to subatmospheric levels after surgical drainage. In 18 of 24 patients with predrainage somatosensory evoked potential abnormalities, syrinx decompression produced a consistent reduction of N20 latencies (mean change = 0.49 ms +/- 0.094 SE right, P = 0.002; 0.61 ms +/- 0.089 SE left, P = 0.001) and a similar but less consistent increase in N20 amplitudes (mean change = 0.17 mV +/- 0.103 SE right, P = 0.115; 0.31 mV +/- 0.097 SE left, P = 0.027). Measurements of local spinal cord blood flow revealed very low baseline values (mean = 12.2 arbitrary units +/- 13.9 standard deviation), which increased to intermediate levels (mean = 144.7 arbitrary units +/- 42.6 standard deviation) after syrinx decompression. Patients with syrinx pressures greater than 7.7 cm H2O tended to have more rapidly progressive symptoms, exhibited greater improvements after shunting, and had a higher incidence of postoperative dysesthetic pain. CONCLUSION: The current study is the first to measure intramedullary pressure in a human disease. Evidence is presented that distended syringes are associated with varying levels of raised intramedullary pressure that can accentuate or induce neurological dysfunction by the compression of long tracts, neurons, and the microcirculation. Symptoms referrable to raised intramedullary pressure are potentially reversible by syrinx decompression.

Adolescent↗

PubMed1996

Continuous postoperative lCBF monitoring in aneurysmal SAH patients using a combined ICP-laser Doppler fiberoptic probe.

Cerebral vasospasm remains the principal cause of morbidity and mortality following successful clipping of intracranial aneurysms. Current management often requires subjective judgments concerning presumed abnormalities of cerebral blood flow. In this study, a combined intracranial pressure (ICP)-laser Doppler flowmetry (LDF) fiberoptic probe that permits continuous monitoring of local cerebral blood flow (lCBF) was used in the postoperative management of 20 aneurysm patients. Using this probe, lCBF was simultaneously recorded and integrated on a real time basis with other physiological parameters, including ICP, systemic arterial pressure, pulmonary arterial pressure, central venous pressure, and pulse oximetry. The combined probe also provided the ability to obtain precise and detailed information concerning the presence or absence of cerebral autoregulation and CO2 vascular reactivity, and allowed calculation of the cerebral vascular resistance. Continuous monitoring of lCBF in this manner complemented by transcranial Doppler and angiographic data permitted early detection of cerebral ischemia, helped to differentiate cerebral ischemia from edema and hyperemia, was useful in titrating blood pressure and fluid management, provided direct feedback about the effectiveness of instituted therapies, and determined early on when medical management was of no avail and that interventional neuroradiology was indicated. Evidence is presented that the presence of angiographic vasospasm and increased velocities on TCD do not always correlate with ischemia in the microcirculation and that direct measurements of lCBF are often at variance with calculations of cerebral perfusion pressure (CPP).

Adult↗

PubMed1996

Intraoperative improvement of somatosensory evoked potentials and local spinal cord blood flow in patients with syringomyelia.

This report is the first to correlate data concerning intraoperative somatosensory evoked potentials (SSEPs) and local spinal cord blood flow (ISCBF) in patients with syringomyelia. In a consecutive study, bilateral median nerve SSEPs were recorded intraoperatively in 13 patients undergoing a syrinx shunt to the posterior fossa cisterns (syringocisternostomy). ISCBF was measured in five of these patients using laser doppler flowmetry (LDF) calibrated in arbitrary units (AU). SSEP recordings obtained 30 min after syrinx decompression demonstrated a slight but consistent reduction of N20 latencies (mean change: 0.53 ms right, p < 0.003; 0.58 ms left, p < 0.001) concurrent with a similar but less consistent increase of N20 amplitudes (0.16 mV right, p = 0.256; 0.29 mV left, p = 0.03). Prior to shunting, LDF recordings from the spinal cord overlying syrinxes revealed very low ISCBF values in five of five patients (mean LDF, 13.2 AU +/- 15.3 SD). Immediately after shunting, there was a dramatic rise of ISCBF (mean LDF, 241.2 AU +/- 106.3 SD) associated with visualized hyperemia of the spinal cord and pial vessels. The ISCBF fell to intermediate levels after 2 min (157.2 AU +/- 33.0 SD) and remained at these levels during the interval of recording (5 min). Hyperventilation testing in two patients prior to shunting revealed no change in ISCBF consistent with a loss of CO2 vascular reactivity and a paradoxical increase of ISCBF in one patient 5 min after shunting. Each patient in this study experienced neurological improvement in the immediate postoperative period associated with collapse or disappearance of the syrinx on magnetic resonance imaging scans. Because syrinx shunting results in an acute decompression of the distended spinal cord, it is possible that the rapid improvement of SSEPs reflects a relief of mechanical factors such as stretching and compression of nervous tissue. However, the LDF findings in this study suggest that distended spinal cord cavities are also capable of producing regional ischemia. A significant reduction of ISCBF is a possible contributing cause of neurological injury and SSEP abnormalities. Intraoperative improvement of SSEPs and ISCBF were found to correlate well with neurological recovery following syringocisternostomy. Our results indicate that SSEP monitoring can provide useful information during surgical procedures for syringomyelia and that further experience with LDF monitoring may provide insights into the pathophysiology of this condition.

Adolescent↗

PubMed1993

Laser-Doppler flowmetry in neurosurgery.

Laser-Doppler flowmetry (LDF) provides a reliable measurement of local cerebral blood flow (lCBF) as demonstrated by multiple validation studies. This article evaluates the clinical applications of LDF in neurosurgery. With the availability of modified probes, it is possible to carry out LDF monitoring of neurosurgical patients in the intensive care unit. Currently, there are multiple systemic and intracranial parameters that are interactive and separately monitored. A multi-channeled digital data acquisition system allows these data to be compiled in a single computer environment for the interpretation of lCBF changes. Guidelines are suggested for the clinical use of LDF monitoring, and the technical features of monitoring including the interpretation of data are summarized.

Cerebrovascular Circulation↗

PubMed1988

Intraoperative use of laser Doppler in the study of cerebral microvascular circulation.

Laser Doppler (LD) flowmetry has been used for evaluation of microcirculatory flow in a variety of human tissues, including skin, muscle, retina and recently the brain. In the present paper, intraoperative Laser Doppler recordings have been performed in 72 cases, in basal conditions and after stimulation. The morphology of basal recordings obtained from normal cortical areas were analyzed and three different rhythmical variations were identified; these rhythmical variations are described and explained. Several kinds of stimulation have been used: hypotensive drugs, mannitol, nimodipine, eupaverine, hypercapnia, decompressive manoeuvres and temporary occlusion of the ICA in the neck. Laser Doppler recordings obtained during and after these stimulations are reported and explained. The results have been evaluated in order to verify the reliability and the reproducibility of this technique in the study of the cerebral microvascular circulation intraoperatively.

Adult↗

PubMedDate not supplied

[The measurement of cochlear flow by laser Doppler in man: the preliminary results].

Laser-Doppler flowmetry is presently one of the methods of choice in measuring cochlear blood flow. The techniques is non-invasive and is based on the frequency shift of the laser beam induced by the red blood cell movement. Previous studies of cochlear blood flow carried out on animals and humans demonstrated the reliability of laser-Doppler flowmetry and its usefulness in understanding inner ear microcirculation physiology. In this paper we present preliminary data obtained from three patients examined under general anesthesia while undergoing tympanoplasty. Results showed that tracings, whose baseline is proportional with the blood flow, are characterized by waves correlated to pulse beat and automatic ventilation. Moreover, intrinsic contractions of inner ear vessels (waves of vasomotion) as exist in cerebral microcirculation, were observed. Pharmacological hypotension hypocapnia and the application of epinephryne determine a significant reduction of cochlear blood flow. These results suggest that while cochlear blood flow is related to systemic pressure, it has an intrinsic control system. As well since we did not obtain any modification in bone conduction threshold after surgery, we conclude that laser-Doppler flowmetry is a safe technique.

Adolescent↗