No reduction in cerebral metabolism as a result of early moderate hyperventilation following severe traumatic brain injury

Diringer, Michael N.; Yundt, Kent D.; Videen, Tom O.; Adams, R.E.; Zazulia, Allyson R.; Deibert, Ellen; Aiyagari, Venkatesh; Dacey, Ralph G.; Grubb, Robert L.

doi:10.3171/jns.2000.92.1.0007

Cited by 154 publications

(83 citation statements)

References 28 publications

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“…To analyze the fitted parameters we compare them to gold standard readings from PET studies. OEF is known to be approximately constant across the healthy brain, with quoted average values typically in the range 35%-43% (26,27). This is borne out by the results in Fig.…”

Section: Discussionmentioning

confidence: 70%

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Quantitative BOLD: The effect of diffusion

Dickson

Ash

Williams

et al. 2010

Magnetic Resonance Imaging

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Purpose: To make the quantitative blood oxygenation level-dependent (qBOLD) method more suitable for clinical application by accounting for proton diffusion and reducing acquisition times. Materials and Methods:Monte Carlo methods are used to simulate the signal from diffusing protons in the presence of a blood vessel network. A diffusive qBOLD model was then constructed using a lookup table of the results. Acquisition times are reduced by parallel imaging and by employing an integrated fieldmapping method, rather than running an additional sequence.Results: The addition of diffusion to the model is shown to have a significant impact on predicted signal formation. This is found to affect all fitted parameters when the model is applied to real data. Parallel imaging and integrated fieldmapping allowed the GESSE (gradient echo sampling of a spin echo) acquisition to be made in less than 10 minutes while maintaining high signal-to-noise ratio (SNR). Conclusion:By incorporating integrated field mapping and parallel imaging techniques, GESSE data were acquired within clinically acceptable acquisition times. These data fit closely to the diffusive qBOLD model, providing more realistic and robust measurements of T 2 and blood oxygenation than the static model.

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Section: Discussionmentioning

confidence: 70%

“…There is, however, no established average of vCBV with which we may compare our results. CBV values from PET studies of the healthy brain are typically in the range 3%-4.5% (26,27). Deoxygenated blood is thought to account for the majority of this, but the exact percentage is unknown.…”

Section: Discussionmentioning

confidence: 99%

Quantitative BOLD: The effect of diffusion

Dickson

Ash

Williams

et al. 2010

Magnetic Resonance Imaging

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“…et , 2004Diringer et al, 2000Diringer et al, , 2002. It is useful to consider the sources of variability in PET data in the setting where we are trying to address the significance of changes between normal physiology and disease states, or changes that are the consequence of an intervention.…”

Section: Methodological Issuesmentioning

confidence: 99%

Intersubject Variability and Reproducibility of ¹⁵O PET Studies

Coles

Fryer

Bradley

et al. 2005

J Cereb Blood Flow Metab

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Oxygen-15 positron emission tomography ( 15 O PET) can provide important data regarding patients with head injury. We provide reference data on intersubject variability and reproducibility of cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolism (CMRO 2 ) and oxygen extraction fraction (OEF) in patients and healthy controls, and explored alternative ways of assessing reproducibility within the context of a single PET study. In addition, we used independent measurements of CBF and CMRO 2 to investigate the effect of mathematical correlation on the relationship between flow and metabolism. In patients, intersubject coefficients of variation (CoV) for CBF, CMRO 2 and OEF were larger than in controls (32.9%72.2%, 23.2%72.0% and 22.5%73.4% versus 13.5%71.4%, 12.8%71.1% and 7.3%71.2%), while CoV for CBV were lower (15.2%72.1% versus 22.5%72.8%) (Po0.001). The CoV for the test-retest reproducibility of CBF, CBV, CMRO 2 and OEF in patients were 2.1%71.5%, 3.8%73.0%, 3.7%73.0% and 4.6%73.5%, respectively. These were much lower than the intersubject CoV figures, and were similar to alternative measures of reproducibility obtained by fractionating data from a single study. The physiological relationship between flow and metabolism was preserved even when mathematically independent measures were used for analysis. These data provide a context for the design and interpretation of interventional PET studies. While ideally each centre should develop its own bank of such data, the figures provided will allow initial generic approximations of sample size for such studies.

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“…Toutes ces études ont eu recours à des critères de substitution tels que la saturation en oxygène de la veine jugulaire ou l'imagerie métabolique du cerveau. [10][11][12][13] Une certaine cohérence existe entre ces études, soutenant que l'hyperventilation peut modifier de façon nuisible les paramètres mesurés et pourrait augmenter les zones potentiellement ischémiques du cerveau. Il est possible que cela soit dû à une constriction artérielle, provoquant non seulement une réduction de la PIC mais aussi une ischémie dans le même temps.…”

Section: L'hyperventilation Dans Les Soins Intensifs Neurologiquesunclassified

“…All have used surrogate endpoints such as jugular venous oxygen saturation or metabolic imaging of the brain. [10][11][12][13] There is reasonable consistency among these studies that hyperventilation can adversely alter the measured parameters and may increase the areas of potentially ischemic brain. Presumably, this is due to arterial constriction, not only resulting in a reduction of ICP but also producing ischemia at the same time.…”

Section: Hyperventilation For Neurocritical Carementioning

confidence: 99%

L’hyperventilation: un vent néfaste qui souffle parfois favorablement

Gelb

Chan

2008

Can J Anesth/J Can Anesth

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H yperventilation has been an integral part of the management of neurosurgical patients for the past 50 years. It has been so emblematic that a blindfolded individual could easily identify a neurosurgical operating room by the sound of the hard working ventilator. However, the routine use of hyperventilation has been re-evaluated with the emergence of evidence that it could be harmful.The first description of the benefits of hyperventilation in neuroanesthesia was published in 1957. 1 In the report, Furness reviewed the outcomes of 72 patients receiving "adequate ventilation" with a fixed ventilatory frequency of 20 breaths·min -1 during craniotomy. Although there was no formal assessment of the operating conditions and no measurement of arterial carbon dioxide tension (PaCO 2 ), "gradually the neurosurgeons were completely convinced" that hyperventilation produced better conditions compared with their previous experience using spontaneous ventilation. The report neglected to distinguish among the roles of hypocapnia, mechanical ventilation vs spontaneous breathing, and the contribution of muscle relaxation. 2,3 These latter were the subject of much debate and some research over the next decade. Neurophysiology of hyperventilationHyperventilation increases cerebral perivascular pH, resulting in cerebral arterial vasoconstriction and the decrease in cerebral blood flow (CBF) and cerebral blood volume (CBV). The CBV response to hyperventilation is blunted when compared to that of CBF. In general, for every mmHg decrease in PaCO 2 , there is a 1% decrease in CBV and a 2-3% decrease in CBF. 4 It is the reduction in CBV associated with hyperventilation that explains the decrease in intracranial pressure (ICP). 4,5 This response gradually normalizes over 12-24 hr. If hyperventilation is extended beyond this period, a restoration to normal PaCO 2 values may result in hyperemia and elevated ICP. Hyperventilation for neurocritical careGiven its favourable effect on ICP in experimental circumstances, aggressive hyperventilation was seen as a cheap, easy, and reversible treatment for patients with intracranial hypertension. Other perceived benefits included a redistribution of CBF to ischemic regions of the brain and the reversal of acidosis in the brain and cerebrospinal fluid (CSF). 4 Despite these claims, good outcome studies demonstrating a clear benefit of hyperventilation in the operating room or the neurocritical care unit were lacking. Indeed, studies using ICP as a surrogate endpoint often reported variable responses after hyperventilation in critically ill patients. 6,7 We believe this may be attributed to the heterogeneity of the human diseases as opposed to the controlled environment in the laboratory.The enthusiasm for hyperventilation therapy came to a sudden halt when almost 17 years ago Muizelaar et al. 8 reported the deleterious effect of prolonged hyperventilation in brain injured patients. A total of 113 patients with severe head injury were randomized to receive hyperventilation (PaCO 2 , 24-28 mmHg), h...

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No reduction in cerebral metabolism as a result of early moderate hyperventilation following severe traumatic brain injury

Cited by 154 publications

References 28 publications

Quantitative BOLD: The effect of diffusion

Quantitative BOLD: The effect of diffusion

Intersubject Variability and Reproducibility of ¹⁵O PET Studies

L’hyperventilation: un vent néfaste qui souffle parfois favorablement

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No reduction in cerebral metabolism as a result of early moderate hyperventilation following severe traumatic brain injury

Cited by 154 publications

References 28 publications

Quantitative BOLD: The effect of diffusion

Quantitative BOLD: The effect of diffusion

Intersubject Variability and Reproducibility of 15O PET Studies

L’hyperventilation: un vent néfaste qui souffle parfois favorablement

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Intersubject Variability and Reproducibility of ¹⁵O PET Studies