Anesthetic Technique Influences Brain Temperature, Independently of Core Temperature, During Craniotomy in Cats

Erickson, Kirstin M.; Lanier, William L.

doi:10.1213/01.ane.0000061221.23197.ce

Cited by 29 publications

(24 citation statements)

References 33 publications

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“…In the interpretation of our data, it is important to point out that the animals were anesthetized with thiopental, and, as with barbiturate anesthetics in general, the brain metabolic rate should be reduced on the basis of studies by other investigators (38). However, several investigators (14,37) have reported that, if hypotension during deep anesthesia was avoided, the decline in metabolism was minimized. We maintained blood pressure by careful support of body temperature, intravascular fluid support, and mechanically assisted ventilation to maintain oxygenation and normocapnia in normal ranges.…”

Section: Discussionmentioning

confidence: 96%

“…We maintained blood pressure by careful support of body temperature, intravascular fluid support, and mechanically assisted ventilation to maintain oxygenation and normocapnia in normal ranges. We chose thiopental over halothane because halothane anesthesia is associated with dilation of cerebral vessels through a NO mechanism linked to nNOS (14). We will demonstrate well-maintained nNOS mechanisms under thiopental anesthesia.…”

Section: Discussionmentioning

confidence: 99%

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Cerebral microvascular dilation during hypotension and decreased oxygen tension: a role for nNOS

Bauser‐Heaton¹,

Bohlen²

2007

American Journal of Physiology-Heart and Circulatory Physiology

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Bauser-Heaton HD, Bohlen HG. Cerebral microvascular dilation during hypotension and decreased oxygen tension: a role for nNOS. Am J Physiol Heart Circ Physiol 293: H2193-H2201, 2007. First published July 13, 2007; doi:10.1152/ajpheart.00190.2007 and neuronal nitric oxide synthase (nNOS) are implicated as important contributors to cerebral vascular regulation through nitric oxide (NO). However, direct in vivo measurements of NO in the brain have not been used to dissect their relative roles, particularly as related to oxygenation of brain tissue. We found that, in vivo, rat cerebral arterioles had increased NO concentration ([NO]) and diameter at reduced periarteriolar oxygen tension (PO 2) when either bath oxygen tension or arterial pressure was decreased. Using these protocols with highly selective blockade of nNOS, we tested the hypothesis that brain tissue nNOS could donate NO to the arterioles at rest and during periods of reduced perivascular oxygen tension, such as during hypotension or reduced local availability of oxygen. The decline in periarteriolar PO 2 by bath manipulation increased [NO] and vessel diameter comparable with responses at similarly decreased PO 2 during hypotension. To determine whether the nNOS provided much of the vascular wall NO, nNOS was locally suppressed with the highly selective inhibitor N-(4S)- (4-amino-5-[aminoethyl]aminopentyl)-NЈ-nitroguanidine. After blockade, resting [NO], PO 2, and diameters decreased, and the increase in [NO] during reduced PO 2 or hypotension was completely absent. However, flow-mediated dilation during occlusion of a collateral arteriole did remain intact after nNOS blockade and the vessel wall [NO] increased to ϳ80% of normal. Therefore, nNOS predominantly increased NO during decreased periarteriolar oxygen tension, such as that during hypotension, but eNOS was the dominant source of NO for flow shear mechanisms. nitric oxide; brain; arterioles; in vivo; microelectrode; neuronal nitric oxide synthase SUPPRESSION OF NITRIC OXIDE (NO) formation by an intravascular arginine analog decreases cerebral blood flow by 10 -40% (17,18,40,42). This indicates that a source of NO actively influences cerebral resistance vessels at rest. Furthermore, Jones et al. (25) and Kajita et al. (26) found that, during hypotension, the lower limit of brain blood flow autoregulation was increased to ϳ90 mmHg in the presence of nitroarginine compared with ϳ65 mmHg in the natural state. The observations of reduced resting blood flow and impaired flow autoregulation indicate that NO regulation has important roles in both maintaining brain resting blood flow and dilatory responses to hypotension. These various observations would predict that, when the various NO synthase (NOS) isoforms are inhibited, even a mild reduction in arterial blood pressure would compromise brain blood flow and tissue oxygenation.Exactly how NO mechanisms are involved in brain blood flow regulation are difficult to predict but may involve feedback processes linked to oxygen. In studies of the small int...

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Cerebral microvascular dilation during hypotension and decreased oxygen tension: a role for nNOS

Bauser‐Heaton¹,

Bohlen²

2007

American Journal of Physiology-Heart and Circulatory Physiology

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“…Long TE MRSI spectra were only partially water-suppressed for post-acquisition temperature measurement requirements; this was done by decreasing the VAPOR pulse amplitude until a partially-suppressed water signal was visible throughout the VOI region. Linear and second order shims were automatically adjusted with FASTMAP (21) in a 5.8 Â 5.8 Â 5.8 voxel (which included the MRSI-VOI region), leading to waterline widths at half height of [13][14][15][16][17][18][19] Hz inside the MRSI-VOI. MRSI spectra were acquired with 2500 ms TR, 4006.41 Hz spectral width (13.34 ppm) and 2 k points in the time domain.…”

Section: In Vivo Mr Studiesmentioning

confidence: 99%

“…Samples were cut into small pieces with a scalpel, inserted into a pre-weighted HR-MAS microrotor (HZ05538 BL4; 12 mL Teflon spacer, Cortecnet, Paris, France) and weighed: average biopsy sample content was 12.2 AE 6.4 mg. Deuterium oxide (D 2 O 99.995%, Carlo Erba Ré actifs-SDS, Val de Reuil, France) was then added and mixed inside each rotor using a 1 mL syringe (Becton-Dickinson S.A., Madrid, Spain) and the rotors were weighed again: average D 2 O content added was 10.7 AE 4.6 mg. Finally, the dissected samples were studied on a 9.4T magnet (DMX 400 MHz, Bruker BioSpin, Wissembourg, France) equipped with a 1 H- 13 C/ 31 P HR-MAS resonance probe. HR-MAS studies were carried out at room temperature and using the standard 3000 Hz spinning rate for the magnetic field strength.…”

Section: Ex Vivo Hr-mas Studiesmentioning

confidence: 99%

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¹H-MRSI pattern perturbation in a mouse glioma: the effects of acute hyperglycemia and moderate hypothermia

et al. 2009

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MR spectroscopic Imaging (MRSI), with PRESS localization, is used here to monitor the effects of acute hyperglycemia in the spectral pattern of 11 mice bearing GL261 gliomas at normothermia (36.5-37.5 degrees C) and at hypothermia (28.5-29.5 degrees C). These in vivo studies were complemented by ex vivo high resolution magic angle spinning (HR-MAS) analysis of GL261 tumor samples from 6 animals sacrificed by focused microwave irradiation, and blood glucose measurements in 12 control mice. Apparent glucose levels, monitored by in vivo MRSI in brain tumors during acute hyperglycemia, rose to an average of 1.6-fold during hypothermia (p < 0.05), while no significant changes were detected at normothermia, or in control experiments performed at euglycemia, or in normal/peritumoral brain regions. Ex vivo analysis of glioma-bearing mouse brains at hypothermia revealed higher glucose increases in distinct regions during the acute hyperglycemic challenge (up to 6.6-fold at the tumor center), in agreement with maximal in vivo blood glucose changes (5-fold). Phantom studies on taurine plus glucose containing solutions explained the differences between in vivo and ex vivo measurements. Our results also indicate brain tumor heterogeneity in the four animal tumors investigated in response to a defined metabolic challenge.

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Limits on activation‐induced temperature and metabolic changes in the human primary visual cortex

Katz‐Brull

Alsop

Marquis

et al. 2006

Magnetic Resonance in Med

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Changes in cerebral blood flow (CBF) and metabolism are now widely used to map and quantify neural activity, although the underlying mechanism for these changes is still incompletely understood. Magnetic resonance spectroscopy (MRS) at 3T, synchronized with a 32-s block design visual stimulation paradigm, was employed to investigate activation-induced changes in temperature and metabolism in the human primary visual cortex. A marginally significant increase in the local temperature of the visual cortex was found (0.1°C, P ‫؍‬ 0.09), excluding the possibility of a temperature decrease (95% confidence interval (CI) ‫؍‬ 0.0 -0.2°C), which was previously suggested. A comparison with models of thermal equilibrium in the presence of blood flow suggests that an increase in heat production during activation, greater than or at least equal to that produced by the complete oxidative metabolism of the elevated glucose (Glc) utilization accompanying activation, would be required to offset the cooling effects of the increased blood flow. In activated regions of the brain, blood flow and glucose (Glc) consumption increase substantially more than oxygen consumption (1). These changes, along with changes in cerebral blood volume (CBV), lead to the blood oxygenation level-dependent contrast (BOLD) in functional magnetic resonance imaging (fMRI) (1). Both cerebral blood flow (CBF) and metabolism are involved in brain thermoregulation, and pharmacological changes of these processes lead to changes in brain temperature (2). Broad investigations have been concerned with the possible mechanisms that underlie the BOLD effect and its relation to neuronal activation (3). Magnetic resonance spectroscopy (MRS) provides a noninvasive tool to investigate these processes in the conscious human brain, because MRS properties, such as signal area, frequency shift, and line width, can serve as probes of metabolite concentration, temperature, and oxygenation level.Previous MRS studies used prolonged stimulation duration (4 -48 min) (4 -9). However, long slow changes are prone to systematic errors. The contribution of drifts to systematic errors can be diminished with the use of a block design paradigm. We chose multiple 32-s blocks as an optimal timing to follow the BOLD response, oxidative Glc metabolism, and anaerobic glycolysis (3,10). The same block design behavioral paradigm was used for both fMRI and MRS studies (at 3T) in order to explore the physiologic and metabolic correlates of brain activation. MATERIALS AND METHODS SubjectsNine subjects (five men and four women, 28 -57 years of age) underwent MRI, fMRI, and 1 H-MRS of the brain. Informed consent was obtained in accordance with the guidelines of the Institutional Review Board of the Beth Israel Deaconess Medical Center. MRI and Visual StimulationThe studies were performed on a 3T scanner (Signa VH/i, GE Healthcare, Waukesha, WI) equipped with a transmit body coil and a receive-only 7.8-cm surface coil. The subjects entered the scanner in a supine position, and the calcarine fissure wa...

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Anesthetic Technique Influences Brain Temperature, Independently of Core Temperature, During Craniotomy in Cats

Cited by 29 publications

References 33 publications

Cerebral microvascular dilation during hypotension and decreased oxygen tension: a role for nNOS

Cerebral microvascular dilation during hypotension and decreased oxygen tension: a role for nNOS

¹H-MRSI pattern perturbation in a mouse glioma: the effects of acute hyperglycemia and moderate hypothermia

Limits on activation‐induced temperature and metabolic changes in the human primary visual cortex

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Anesthetic Technique Influences Brain Temperature, Independently of Core Temperature, During Craniotomy in Cats

Cited by 29 publications

References 33 publications

Cerebral microvascular dilation during hypotension and decreased oxygen tension: a role for nNOS

Cerebral microvascular dilation during hypotension and decreased oxygen tension: a role for nNOS

1H-MRSI pattern perturbation in a mouse glioma: the effects of acute hyperglycemia and moderate hypothermia

Limits on activation‐induced temperature and metabolic changes in the human primary visual cortex

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¹H-MRSI pattern perturbation in a mouse glioma: the effects of acute hyperglycemia and moderate hypothermia