Brain function in the vegetative state

in Acta Neurologica Belgica (2002), 102(4), 177-185

Positron emission tomography (PET) techniques represent a useful tool to better understand the residual brain function in vegetative state patients. It has been shown that overall cerebral metabolic rates ... [more ▼]

Positron emission tomography (PET) techniques represent a useful tool to better understand the residual brain function in vegetative state patients. It has been shown that overall cerebral metabolic rates for glucose are massively reduced in this condition. However, the recovery of consciousness from vegetative state is not always associated with substantial changes in global metabolism. This finding led us to hypothesize that some vegetative patients are unconscious not just because of a global loss of neuronal function, but rather due to an altered activity in some critical brain regions and to the abolished functional connections between them. We used voxel-based Statistical Parametric Mapping (SPM) approaches to characterize the functional neuroanatomy of the vegetative state. The most dysfunctional brain regions were bilateral frontal and parieto-temporal associative cortices. Despite the metabolic impairment, external stimulation still induced a significant neuronal activation (i.e., change in blood flow) in vegetative patients as shown by both auditory click stimuli and noxious somatosensory stimuli. However this activation was limited to primary cortices and dissociated from higher-order associative cortices, thought to be necessary for conscious perception. Finally, we demonstrated that vegetative patients have impaired functional connections between distant cortical areas and between the thalami and the cortex and, more importantly, that recovery of consciousness is paralleled by a restoration of this cortico-thalamo-cortical interaction. [less ▲]

Morsure de chien chez un patient splénectomisé

in Revue Médicale de Liège (2002), 57(1), 40-4

We present a case of Capnocytophaga canimorsus fulminant infection linked to a dog bite in a splenectomized patient. Capnocytophaga canimorsus is a gram-negative rod that typically causes septicaemia with ... [more ▼]

We present a case of Capnocytophaga canimorsus fulminant infection linked to a dog bite in a splenectomized patient. Capnocytophaga canimorsus is a gram-negative rod that typically causes septicaemia with disseminated intravascular coagulation in both immunocompromised and immunocompetent hosts. It is associated with high mortality. We also reviewed the literature and provide some recommendations on the management of bite wound as well as on both prevention and treatment of infection in asplenic state. [less ▲]

Etudes par tomographie à émission de positons chez des patients en coma, en état végétatif ou de conscience minimale, en «locked-in syndrome» et en mort cérébrale

in L'évaluation neurophysiologique des comas, de la mort encéphalique et des états végétatifs (2001)

Application du Simplified Acute Physiology Score II (SAPS II) dans une unite de soins intensifs medicaux

in Annales Françaises d'Anesthésie et de Réanimation (2000), 19(7), 510-6

OBJECTIVE: Our study was to assess the validity of SAPS II (New Simplified Acute Physiology Score) to predict the probability of in hospital mortality, in a cohort of patient admitted to a medical ... [more ▼]

OBJECTIVE: Our study was to assess the validity of SAPS II (New Simplified Acute Physiology Score) to predict the probability of in hospital mortality, in a cohort of patient admitted to a medical intensive care unit. STUDY DESIGN: Prospective study. PATIENTS AND METHODS: Out of 467 the 525 patients admitted were included. SAPS score and in hospital mortality prediction were calculated for each of them. RESULTS: In this group, SAPS II offered a satisfactory discrimination power with an area under the curve of 0.843. However, calibration showed a lack of fit (chi 2 = 28.5, P < 0.001), with an overall under prediction of mortality (observed versus expected ratio of 1.12). CONCLUSION: This SAPS II lower predicting accuracy in a specific population and for individual outcome prediction may reduce its interest in clinical decision-making. [less ▲]

Increased Aortic Compliance Maintains Left Ventricular Performance at Lower Energetic Cost

in European Journal of Cardio - Thoracic Surgery (2000), 17(3), 272-8

OBJECTIVE: The aim of this study was to investigate left ventricular contractility and energetic cost of cardiac ejection under conditions of acute increase in aortic compliance. METHODS: In six ... [more ▼]

OBJECTIVE: The aim of this study was to investigate left ventricular contractility and energetic cost of cardiac ejection under conditions of acute increase in aortic compliance. METHODS: In six anaesthetized pigs, ascending aortic compliance was increased by adding a volume chamber in parallel to the ascending aorta. Systemic vascular parameters, including characteristic impedance, peripheral resistance, total vascular compliance, and inertance, were estimated with a four-element windkessel model. Arterial elastance was derived from these parameters. Left ventricular systolic function was assessed by end-systolic pressure-volume relationship (end-systolic elastance), and stroke work. Pressure-volume area was used as a measure of myocardial oxygen consumption. Heart rate remained constant during the experimentation. RESULTS: Adding the aortic volume chamber significantly increased vascular compliance from 0. 95+/-0.08 to 1.17+/-0.06 ml/mmHg (P<0.01), while inductance, characteristic impedance, peripheral resistance, and arterial elastance remained statistically at basal values, respectively 0. 0020+/-0.0003 mmHg.s(2)/ml, 0.105+/-0.009 mmHg.s/ml, 1.27+/-0.12 mmHg.s/ml, and 2.43+/-0.21 mmHg/ml. During the same interval, stroke work and pressure-volume area decreased respectively from 2700+/-242 to 2256+/-75 mmHg.ml (P<0.01), and from 3806+/-427 to 3179+/-167 mmHg.ml (P<0.01). Stroke work and pressure-volume area decreased at matched end-diastolic volumes. In contrast, end-systolic elastance, ejection fraction, and stroke volume remained statistically unchanged, respectively at 2.29+/-0.14 mmHg/ml, 48.1+/-2.1 %, and 32. 4+/-1.7 ml. CONCLUSIONS: These data suggest that, when facing an increased aortic compliance, the left ventricle displays unchanged contractility, but the energetic cost of cardiac ejection is significantly decreased. These data may be of clinical importance when choosing an artificial prosthesis for ascending aortic replacement. [less ▲]

Auditory processing in the vegetative state.

in Brain : A Journal of Neurology (2000), 123 ( Pt 8)

H(2)(15)O-PET was used to investigate changes in regional cerebral blood flow in response to auditory stimulation in patients in the vegetative state. Five patients in a vegetative state of hypoxic origin ... [more ▼]

H(2)(15)O-PET was used to investigate changes in regional cerebral blood flow in response to auditory stimulation in patients in the vegetative state. Five patients in a vegetative state of hypoxic origin were compared with 18 age-matched controls. In addition, the cerebral metabolism of these patients and 53 age-matched controls was studied using [(18)F]fluorodeoxyglucose. In control subjects, auditory click stimuli activated bilateral auditory cortices [Brodmann areas (BA) 41 and 42] and the contralateral auditory association cortices (BA 22). In the patients, although resting metabolism was decreased to 61% of normal values, bilateral auditory areas 41 and 42 showed activation as seen in the controls, but the temporoparietal junction cortex (BA 22) failed to be activated. Moreover, the auditory association cortex was functionally disconnected from the posterior parietal association area (BA 40), the anterior cingulate cortex (BA 24) and the hippocampus, as revealed by psychophysiological interaction analysis. Thus, despite altered resting metabolism, the auditory primary cortices were still activated during external stimulation, whereas hierarchically higher-order multi- modal association areas were not. Such a cascade of functional disconnections along the auditory cortical pathways, from the primary auditory areas to multimodal and limbic areas, suggests that the residual cortical processing observed in the vegetative state cannot lead to the integrative processes that are thought to be necessary for the attainment of the normal level of awareness. [less ▲]

Analysis of Endotoxin Effects on the Intact Pulmonary Circulation

in Cardiovascular Research (1999), 41(1), 275-81

OBJECTIVE: The mechanism of sustained alterations in pulmonary hemodynamics during endotoxin shock remains unclear. To gain more detailed knowledge we used the four-element windkessel model as a ... [more ▼]

OBJECTIVE: The mechanism of sustained alterations in pulmonary hemodynamics during endotoxin shock remains unclear. To gain more detailed knowledge we used the four-element windkessel model as a descriptor of the pulmonary circuit. METHODS: Consecutive changes in characteristic resistance (R1), vascular compliance (C), input resistance (R2) and inductance (L) were continuously assessed following injection of endotoxin in 6 anaesthetised pigs, and were compared with the corresponding values measured in a similar group of sham-operated animals. RESULTS: Endotoxin challenge resulted in a biphasic pulmonary artery pressure response. Blood flow decreased progressively from 2.8 +/- 0.2 l/min to 2 +/- 0.2 l/min. Ohmic pulmonary vascular resistance (PVR) increased gradually from 0.2 +/- 0.04 to 0.76 +/- 0.1 mm Hg s ml-1. The early increase in PAP (from 14 +/- 2 to 27 +/- 4 mm Hg) was mediated by changes in both R1 (from 0.04 +/- 0.01 to 0.06 +/- 0.01 mm Hg s ml-1) and R2 (from 0.16 +/- 0.04 to 0.61 +/- 0.2 mm Hg s ml-1). These responses, in turn, altered the proximal vascular compliance. A subsequent increase in PAP (from 27 +/- 2 to 32 +/- 3 mm Hg) paralleled the specific decline in distal pulmonary vasculature compliance from 0.84 +/- 0.1 to 0.65 +/- 0.1 ml/mmHg. Analysis of the time course of PVR did not allow us to distinguish between vasoconstriction and stiffening of the vascular tree as mechanisms accounting for PAP changes. CONCLUSIONS: Endotoxemia leads to pulmonary hypertension, which is a result of constriction of proximal pulmonary arteries during the early phase, whereas the late phase is characterised by a decline in distal pulmonary vasculature compliance. [less ▲]

Effects of Peep on Systemic Venous Capacitance

in Archives of Physiology & Biochemistry (1998), 105(4), 373-8

The aim of the present study was to determine effects of positive end expiratory pressure (PEEP) application on peripheral venous capacitance and relate them to concomitant central hemodynamic ... [more ▼]

The aim of the present study was to determine effects of positive end expiratory pressure (PEEP) application on peripheral venous capacitance and relate them to concomitant central hemodynamic disturbances. The venous volume-pressure (V/P) relationships were studied in 6 intact anesthetized pigs to describe the effects of PEEP on systemic venous compliance (computed as the slope of the V/P relationship) and unstressed volume (referred to as the extrapolated volume intercept). Cardiac volumes as well as partitioning of circulating blood volume between central (ITBV) and peripheral (PBV) compartments were assessed by thermo-dye dilution techniques. During a 15 cm H2O PEEP application, venous compliance was reduced by 48%, while unstressed volume was increased by 25% and peripheral blood pooling increased from 63 to 74%. As a result, left heart and right ventricular end diastolic volumes were decreased by 8% and by 44%, respectively. It is concluded that increased venous unstressed volume and reduced compliance depicted the distension of the venous tree secondary to PEEP which acted as an impediment to venous return. As a consequence, cardiac output was reduced because of decreased preload. [less ▲]

Correction of Pressure Waveforms Recorded by Fluid-Filled Catheter Recording Systems: A New Method Using a Transfer Equation

in Acta Anaesthesiologica Scandinavica (1998), 42(6), 717-20

BACKGROUND: Pressure measuring systems using fluid-filled catheters can result in the recording of distorted pressure waveforms. It results in phase delay, overestimation of systolic and, to a lesser ... [more ▼]

BACKGROUND: Pressure measuring systems using fluid-filled catheters can result in the recording of distorted pressure waveforms. It results in phase delay, overestimation of systolic and, to a lesser extent, of diastolic pressure. We designed and evaluated a method to correct this pressure waveform distortion using an appropriate transfer equation obtained from the dynamic response of the fluid-filled catheter. This transfer equation is based on the principle that a fluid-filled catheter recording system is considered as an underdamped dynamic system fully characterized by its natural frequency (omega n) and damping ratio (zeta). METHODS: Pressure waveforms, simultaneously recorded in vitro or in vivo by a fluid-filled catheter (Pc) and a micromanometer-tipped catheter (Pref), were used to validate the method. Dynamic response of the catheter used was obtained from a fastflush test. The corrected signal (Ppred) was obtained using omega n, zeta and the following transfer equation: d2Pc/dt2 + 2 omega n zeta dPc/dt + omega n 2Pc = C Ppred (t) After correction of Pc, Ppred was compared, using a linear regression, with Pref taken as reference. RESULTS: Our results showed that Ppred was fitted to Pref with excellent coefficient correlation (0.99). The mean error and the standard error of estimate were respectively -1.16 mmHg and 1.4 mmHg. CONCLUSION: This new method can convert the distorted pressure waveforms transmitted by any fluid-filled catheters into high-fidelity signals. It suppresses the phase delay and the over-estimation of systolic pressure induced by fluid-filled catheters. [less ▲]

Near Fatal Respiratory Distress Following Massive Ether Intravenous Injection

in Intensive Care Medicine (1998), 24(6), 624-5

To the best of our knowledge, no case of ether-induced acute respiratory distress syndrome (ARDS) has been published as yet. A 36-year-old female developed pneumonitis which showed all the characteristics ... [more ▼]

To the best of our knowledge, no case of ether-induced acute respiratory distress syndrome (ARDS) has been published as yet. A 36-year-old female developed pneumonitis which showed all the characteristics of a chemical-associated ARDS due to intravenous self-administration of ether: the hemodynamic investigation demonstrated a normal blood flow pattern with low left-heart filling pressure while the anteroposterior roentgenogram evidenced disseminated bilateral lung edema. Advanced symptomatic respiratory support including inhaled nitric oxide and steroidal anti-inflammatory use was the treatment of choice. [less ▲]