Capillary Recruitment for Preservation of Cerebral Glucose Influx in Hypoglycemic, Preterm Newborns: Evidence for a Glucose Sensor?

PEDIATRICS ◽  
1992 ◽  
Vol 90 (2) ◽  
pp. 193-195
Author(s):  
L. Skov ◽  
O. Pryds
Keyword(s):  
Blood Volume ◽  
Near Infrared ◽  
Cerebral Blood Volume ◽  
Glucose Sensor ◽  
Blood Glucose Concentration ◽  
Blood Gas ◽  
Capillary Recruitment ◽  
Glucose Levels ◽  
Arterial Blood ◽  
Preterm Newborns

Changes in cerebral blood volume (CBV) were investigated by means of near-infrared spectroscopy in 18 preterm newborns during treatment with intravenous bolus glucose. All newborns were breathing spontaneously, and their postnatal age was 2 hours. Blood glucose concentration ranged between 0.3 and 2.2 mmol/L. Cerebral blood volume began to decrease shortly after the glucose infusion was terminated, and steady state was obtained after approximately 3 minutes. The decrease in CBV averaged 0.15 mL/100 g (range 0.02 to 0.40 mL/100 g). Thereafter, CBV remained constant. Individual reductions in CBV were inversely related to the pretreatment concentration of glucose, whereas there was no relation between changes in CBV and alterations in blood gas values or in mean arterial blood pressure. It is suggested that previously unperfused capillaries are recruited to maintain the glucose transport into neurons of hypoglycemic, preterm newborns. The rapidity whereby vessels adjust to alterations in glucose levels indicates the existence of a cerebral glucose sensor.

Inconsistent detection of changes in cerebral blood volume by near infrared spectroscopy in standard clinical tests

2011 ◽  
Vol 110 (6) ◽  
pp. 1646-1655 ◽  
Author(s):  
D. Canova ◽  
S. Roatta ◽  
D. Bosone ◽  
G. Micieli
Keyword(s):  
Infrared Spectroscopy ◽  
Blood Volume ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Cerebral Blood Volume ◽  
Valsalva Maneuver ◽  
Hemoglobin Concentration ◽  
Clinical Tests ◽  
Arterial Blood ◽  
Total Hemoglobin

The attractive possibility of near infrared spectroscopy (NIRS) to noninvasively assess cerebral blood volume and oxygenation is challenged by the possible interference from extracranial tissues. However, to what extent this may affect cerebral NIRS monitoring during standard clinical tests is ignored. To address this issue, 29 healthy subjects underwent a randomized sequence of three maneuvers that differently affect intra- and extracranial circulation: Valsalva maneuver (VM), hyperventilation (HV), and head-up tilt (HUT). Putative intracranial (“i”) and extracranial (“e”) NIRS signals were collected from the forehead and from the cheek, respectively, and acquired together with cutaneous plethysmography at the forehead (PPG), cerebral blood velocity from the middle cerebral artery, and arterial blood pressure. Extracranial contribution to cerebral NIRS monitoring was investigated by comparing Beer-Lambert (BL) and spatially resolved spectroscopy (SRS) blood volume indicators [the total hemoglobin concentration (tHb) and the total hemoglobin index, (THI)] and by correlating their changes with changes in extracranial circulation. While THIe and tHbe generally provided concordant indications, tHbi and THIi exhibited opposite-sign changes in a high percentage of cases (VM: 46%; HV: 31%; HUT: 40%). Moreover, tHbi was correlated with THIi only during HV ( P < 0.05), not during VM and HUT, while it correlated with PPG in all three maneuvers ( P < 0.01). These results evidence that extracranial circulation may markedly affect BL parameters in a high percentage of cases, even during standard clinical tests. Surface plethysmography at the forehead is suggested as complementary monitoring helpful in the interpretation of cerebral NIRS parameters.

Cerebral oxygen availability by NIR spectroscopy during transient hypoxia in humans

1990 ◽  
Vol 69 (3) ◽  
pp. 907-913 ◽  
Author(s):  
N. B. Hampson ◽  
E. M. Camporesi ◽  
B. W. Stolp ◽  
R. E. Moon ◽  
J. E. Shook ◽  
...  
Keyword(s):  
Heart Rate ◽  
Blood Volume ◽  
Near Infrared ◽  
Cerebral Blood Volume ◽  
Minute Ventilation ◽  
Nir Spectroscopy ◽  
Redox Status ◽  
Total Blood ◽  
Arterial Ph

The effects of mild hypoxia on brain oxyhemoglobin, cytochrome a,a3 redox status, and cerebral blood volume were studied using near-infrared spectroscopy in eight healthy volunteers. Incremental hypoxia reaching 70% arterial O2 saturation was produced in normocapnia [end-tidal PCO2 (PETCO2) 36.9 +/- 2.6 to 34.9 +/- 3.4 Torr] or hypocapnia (PETCO2 32.8 +/- 0.6 to 23.7 +/- 0.6 Torr) by an 8-min rebreathing technique and regulation of inspired CO2. Normocapnic hypoxia was characterized by progressive reductions in arterial PO2 (PaO2, 89.1 +/- 3.5 to 34.1 +/- 0.1 Torr) with stable PETCO2, arterial PCO2 (PaCO2), and arterial pH and resulted in increases in heart rate (35%) systolic blood pressure (14%), and minute ventilation (5-fold). Hypocapnic hypoxia resulted in progressively decreasing PaO2 (100.2 +/- 3.6 to 28.9 +/- 0.1 Torr), with progressive reduction in PaCO2 (39.0 +/- 1.6 to 27.3 +/- 1.9 Torr), and an increase in arterial pH (7.41 +/- 0.02 to 7.53 +/- 0.03), heart rate (61%), and ventilation (3-fold). In the brain, hypoxia resulted in a steady decline of cerebral oxyhemoglobin content and a decrease in oxidized cytochrome a,a3. Significantly greater loss of oxidized cytochrome a,a3 occurred for a given decrease in oxyhemoglobin during hypocapnic hypoxia relative to normocapnic hypoxia. Total blood volume response during hypoxia also was significantly attenuated by hypocapnia, because the increase in volume was only half that of normocapnic subjects. We conclude that cytochrome a,a3 oxidation level in vivo decreases at mild levels of hypoxia. PaCO is an important determinant of brain oxygenation, because it modulates ventilatory, cardiovascular, and cerebral O2 delivery responses to hypoxia.

scholarly journals Can Cerebral Blood Volume Be Measured Reproducibly with an Improved near Infrared Spectroscopy System?

2001 ◽  
Vol 21 (2) ◽  
pp. 110-113 ◽  
Author(s):  
Marjo J. T. Van de Ven ◽  
Willy N. J. M. Colier ◽  
Marco C. van der Sluijs ◽  
Diederik Walraven ◽  
Berend Oeseburg ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Infrared Spectroscopy ◽  
Blood Volume ◽  
Near Infrared Spectroscopy ◽  
Healthy Subjects ◽  
Baseline Level ◽  
Near Infrared ◽  
Cerebral Blood Volume ◽  
Spectroscopy System

In some circumstances, cerebral blood volume (CBV) can be used as a measure for cerebral blood flow. A new near infrared spectroscope was used for determining the reproducibility of CBV measurements assessed by the O2-method. Twenty-seven healthy subjects were investigated. An intrasubject coefficient of variation (CV) was calculated, based on four identical episodes of desaturation–resaturation (O2-method) procedures for CBV measurements. Two trials were performed, with (trial 1) and without (trial 2) disconnecting the equipment. A mean CV of 12.6% and 10.0% was found in trial 1 and 2, respectively. Cerebral blood volume values yield 3.60 ± 0.82 mL 100 g−1. Cerebral blood volume could be measured reproducible in adults using near infrared spectroscopy, if the arterial desaturation is limited to approximately 5% from baseline level.

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