Sex differences in cerebral haemodynamics across the physiological range of PaCO<sub>2</sub>

Minhas, Jatinder S.; Panerai, Ronney B.; Robinson, Thompson G.

doi:10.1088/1361-6579/aae469

Cited by 19 publications

(23 citation statements)

References 30 publications

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“…Increased coherence may alternatively indicate increased linearity or increased signal-to-noise ratio between blood pressure and cerebral flow velocity [24]. Assuming our interpretation is accurate that men and women have similar autoregulation, our results are in agreement with those of other groups, which found no differences in autoregulation assessed by autoregulatory index [19,36] or the slope between blood pressure and middle cerebral flow velocity [37]. However, our results are in contrast to results of our lab's prior studies which found improved autoregulation in women assessed by thigh-cuff maneuvers [7], sit-to-stand maneuvers [15], and squat-to-stand maneuvers [16].…”

Section: Sex Differences In Cerebral Autoregulationsupporting

confidence: 91%

“…However, there are contrasting data in the supine posture, where differences are less apparent. To our knowledge, only a few studies have examined sex differences in cerebral autoregulation when supine and the results are mixed [7,17,19]. Interestingly, Wang et al [17] found improved autoregulation in women when upright but reduced when supine, suggesting body posture may affect cerebral autoregulation differently between the sexes.…”

Section: Introductionmentioning

confidence: 99%

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Cerebrovascular reactivity and cerebral autoregulation are improved in the supine posture compared to upright in healthy men and women

et al. 2020

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Cerebrovascular reactivity and cerebral autoregulation are two major mechanisms that regulate cerebral blood flow. Both mechanisms are typically assessed in either supine or seated postures, but the effects of body position and sex differences remain unclear. This study examined the effects of body posture (supine vs. seated vs. standing) on cerebrovascular reactivity during hyper and hypocapnia and on cerebral autoregulation during spontaneous and slow-paced breathing in healthy men and women using transcranial Doppler ultrasonography of the middle cerebral artery. Results indicated significantly improved cerebrovascular reactivity in the supine compared with seated and standing postures (supine = 3.45±0.67, seated = 2.72±0.53, standing = 2.91±0.62%/mmHg, P<0.0167). Similarly, cerebral autoregulatory measures showed significant improvement in the supine posture during slow-paced breathing. Transfer function measures of gain significantly decreased and phase significantly increased in the supine posture compared with seated and standing postures (gain: supine = 1.98±0.56, seated = 2.37±0.53, standing = 2.36±0.71%/mmHg; phase: supine = 59.3±21.7, seated = 39.8±12.5, standing = 36.5±9.7˚; all P<0.0167). In contrast, body posture had no effect on cerebral autoregulatory measures during spontaneous breathing. Men and women had similar cerebrovascular reactivity and similar cerebral autoregulation during both spontaneous and slow-paced breathing. These data highlight the importance of making comparisons within the same body position to ensure there is not a confounding effect of posture.

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Section: Sex Differences In Cerebral Autoregulationsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Cerebrovascular reactivity and cerebral autoregulation are improved in the supine posture compared to upright in healthy men and women

et al. 2020

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“…First, the small sample size limits the generalizability of the findings. More accurate analyses, for instance looking at sex differences in vasoreactivity or association between PI and outcome, were clearly not feasible [21, 22]. Second, we decided to perform only a moderate degree of short-term HV.…”

Section: Discussionmentioning

confidence: 99%

Cerebral metabolism is not affected by moderate hyperventilation in patients with traumatic brain injury

et al. 2019

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Background Hyperventilation-induced hypocapnia (HV) reduces elevated intracranial pressure (ICP), a dangerous and potentially fatal complication of traumatic brain injury (TBI). HV decreases the arteriolar diameter of intracranial vessels, raising the risk of cerebral ischemia. The aim of this study was to characterize the effects of moderate short-term HV in patients with severe TBI by using concomitant monitoring of cerebral metabolism, brain tissue oxygen tension (PbrO 2 ), and cerebral hemodynamics with transcranial color-coded duplex sonography (TCCD). Methods This prospective trial was conducted between May 2014 and May 2017 in the surgical intensive care unit (ICU) at the University Hospital of Zurich. Patients with nonpenetrating TBI older than 18 years of age with a Glasgow Coma Scale (GCS) score < 9 at presentation and with ICP monitoring, PbrO 2 , and/or microdialysis (MD) probes during ICU admission within 36 h after injury were included in our study. Data collection and TCCD measurements were performed at baseline (A), at the beginning of moderate HV (C), after 50 min of moderate HV (D), and after return to baseline (E). Moderate HV was defined as arterial partial pressure of carbon dioxide 4–4.7 kPa. Repeated measures analysis of variance was used to compare variables at the different time points, followed by post hoc analysis with Bonferroni adjustment as appropriate. Results Eleven patients (64% males, mean age 36 ± 14 years) with an initial median GCS score of 7 (IQR 3–8) were enrolled. During HV, ICP and mean flow velocity (CBFV) in the middle cerebral artery decreased significantly. Glucose, lactate, and pyruvate in the brain extracellular fluid did not change significantly, whereas PbrO 2 showed a statistically significant reduction but remained within the normal range. Conclusion Moderate short-term hyperventilation has a potent effect on the cerebral blood flow, as shown by TCCD, with a concomitant ICP reduction. Under the specific conditions of this study, this degree of hyperventilation did not induce pathological alterations of brain metabolites and oxygenation. Trial registration NCT03822026 . Registered on 30 January 2019.

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“…The careful process of translation from healthy volunteers to ICH patients has involved several steps in both logistical and scientific understanding as to how PaCO 2 change influences CBFV and autoregulatory function. 10,12,18,[23][24][25] The inclusion of individuals with variable locations of ICH is a strength (cortical and lobar involvement); however, this does assume that ICH generally occurs through similar pathophysiological mechanisms irrespective of location. Differences in CA across differing ICH subtypes have yet to be assessed within the literature.…”

Section: Literature Contextmentioning

confidence: 99%

Feasibility of improving cerebral autoregulation in acute intracerebral hemorrhage (BREATHE-ICH) study: Results from an experimental interventional study

Minhas

Panerai

Swienton

et al. 2019

International Journal of Stroke

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Background Cerebral autoregulation is impaired in a multitude of neurological conditions. Increasingly, clinical studies are correlating the nature of this impairment with prognostic markers. In acute intracerebral hemorrhage, impairment of cerebral autoregulation has been associated with worsening clinical outcomes including poorer Glasgow Coma Score and larger hematoma volume. Hypocapnia has been shown to improve cerebral autoregulation despite concerns over hypoperfusion and consequent ischemic risks, and it is therefore hypothesized that hypocapnia (via hyperventilation) in acute intracerebral hemorrhage may improve cerebral autoregulation and consequently clinical outcome. Aims To assess the feasibility and acceptability of the first cerebral autoregulation-targeted intervention in acute intracerebral hemorrhage utilizing a simple bed-side hyperventilatory maneuver. Methods Twelve patients with acute intracerebral hemorrhage within 48 h of onset were enrolled. The experimental setup measured cerebral blood flow velocity (transcranial Doppler), blood pressure (Finometer), and end-tidal CO2 (EtCO2, capnography) at baseline, and in response to hypocapnia (−5 mmHg below baseline) achieved via a 90-s hyperventilatory maneuver. Cerebral autoregulation was evaluated with transfer function analysis and autoregulatory index calculations. Results We observed tolerance to the protocol in a cohort of mild (National Institutes of Health Scale 4) supratentorial intracerebral hemorrhage patients with small volume hematomas without intraventricular extension. Importantly, a significant difference was noted between ipsilateral autoregulatory index at baseline 4.8 (1.7) and autoregulatory index during hypocapnic intervention 7.0 (0.8) (p = 0.0004), reflecting improved cerebral autoregulation, though a dose-dependent effect of EtCO2 on autoregulatory index was not observed. Conclusions In this small study, there was no observed effect on 14-day death and disability in recruited participants. This is the first report of improvement in cerebral autoregulation in acute intracerebral hemorrhage using a non-invasive interventional maneuver, through induction of hypocapnia via hyperventilation. ClinicalTrials.gov Identifier: NCT03324321 URL: https://clinicaltrials.gov/ct2/show/NCT03324321

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Sex differences in cerebral haemodynamics across the physiological range of PaCO₂

Cited by 19 publications

References 30 publications

Cerebrovascular reactivity and cerebral autoregulation are improved in the supine posture compared to upright in healthy men and women

Cerebrovascular reactivity and cerebral autoregulation are improved in the supine posture compared to upright in healthy men and women

Cerebral metabolism is not affected by moderate hyperventilation in patients with traumatic brain injury

Feasibility of improving cerebral autoregulation in acute intracerebral hemorrhage (BREATHE-ICH) study: Results from an experimental interventional study

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Sex differences in cerebral haemodynamics across the physiological range of PaCO2

Cited by 19 publications

References 30 publications

Cerebrovascular reactivity and cerebral autoregulation are improved in the supine posture compared to upright in healthy men and women

Cerebrovascular reactivity and cerebral autoregulation are improved in the supine posture compared to upright in healthy men and women

Cerebral metabolism is not affected by moderate hyperventilation in patients with traumatic brain injury

Feasibility of improving cerebral autoregulation in acute intracerebral hemorrhage (BREATHE-ICH) study: Results from an experimental interventional study

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Sex differences in cerebral haemodynamics across the physiological range of PaCO₂