scholarly journals The CO2 stimulus for cerebrovascular reactivity: Fixing inspired concentrations vs. targeting end-tidal partial pressures

2016 ◽  
Vol 36 (6) ◽  
pp. 1004-1011 ◽  
Author(s):  
Joseph A Fisher
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Stimulus Change ◽  
Cerebrovascular Reactivity ◽  
Main Concern ◽  
Precise Control ◽  
Trade Offs ◽  
Partial Pressures ◽  
Response Change ◽  
End Tidal

Cerebrovascular reactivity (CVR) studies have elucidated the physiology and pathophysiology of cerebral blood flow regulation. A non-invasive, high spatial resolution approach uses carbon dioxide (CO2) as the vasoactive stimulus and magnetic resonance techniques to estimate the cerebral blood flow response. CVR is assessed as the ratio response change to stimulus change. Precise control of the stimulus is sought to minimize CVR variability between tests, and show functional differences. Computerized methods targeting end-tidal CO2 partial pressures are precise, but expensive. Simpler, improvised methods that fix the inspired CO2 concentrations have been recommended as less expensive, and so more widely accessible. However, these methods have drawbacks that have not been previously presented by those that advocate their use, or those that employ them in their studies. As one of the developers of a computerized method, I provide my perspective on the trade-offs between these two methods. The main concern is that declaring the precision of fixed inspired concentration of CO2 is misleading: it does not, as implied, translate to precise control of the actual vasoactive stimulus – the arterial partial pressure of CO2. The inherent test-to-test, and therefore subject-to-subject variability, precludes clinical application of findings. Moreover, improvised methods imply widespread duplication of development, assembly time and costs, yet lack uniformity and quality control. A tabular comparison between approaches is provided.

scholarly journals Cerebral Blood Flow Reactivity to Changes in Carbon Dioxide Calculated Using End-Tidal versus Arterial Tensions

1991 ◽  
Vol 11 (6) ◽  
pp. 1031-1035 ◽  
Author(s):  
William L. Young ◽  
Isak Prohovnik ◽  
Eugene Ornstein ◽  
Noeleen Ostapkovich ◽  
Richard S. Matteo
Keyword(s):  
Carbon Dioxide ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cerebrovascular Reactivity ◽  
Noninvasive Measurement ◽  
Moderate Correlation ◽  
The Difference ◽  
Highly Correlated ◽  
End Tidal

We retrospectively examined arterial and endtidal estimations of CO2 tension used to calculate cerebrovascular reactivity in 68 anesthetized patients. CBF was measured using the intravenous 133Xe technique at mean ± SD Paco2 values of 28.2 ± 5.2 and 38.8 ± 4.8 mm Hg. The correlation between all Paco2 and end-tidal Pco2 (Petco2) values was y = 0.85 x −0.49 ( r = 0.93, p = 0.0001). There was a moderate correlation between age and the difference between Paco2 and Petco2 ( y = 0.11 x + 0.79; r = 0.73, p = 0.0001). Cerebrovascular reactivity to changes in CO2 (ml 100 g−1 min−1 mm Hg−1) was similar (p = 0.358) when calculated by using either Paco2 (1.9 ± 0.8) or Petco2 (1.8 ± 0.8) and highly correlated ( y = 0.86 x + 0.23; r = 0.91, p = 0.0001). The CBF response to changes in CO2 tension can be reliably estimated from noninvasive measurement of Petco2.

scholarly journals Cerebral blood flow regulation in women across menstrual phase: differential contribution of cyclooxygenase to basal, hypoxic, and hypercapnic vascular tone

2016 ◽  
Vol 311 (2) ◽  
pp. R222-R231 ◽  
Author(s):  
Garrett L. Peltonen ◽  
John W. Harrell ◽  
Benjamin P. Aleckson ◽  
Kaylie M. LaPlante ◽  
Meghan K. Crain ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Menstrual Cycle ◽  
Transcranial Doppler Ultrasound ◽  
Follicular Phase ◽  
Cerebrovascular Reactivity ◽  
Menstrual Phase ◽  
Arterial Blood ◽  
End Tidal ◽  
Late Follicular Phase

In healthy young women, basal cerebral blood flow (CBF) and cerebrovascular reactivity may change across the menstrual cycle, but mechanisms remain untested. When compared with the early follicular phase of the menstrual cycle, we hypothesized women in late follicular phase would exhibit: 1) greater basal CBF, 2) greater hypercapnic increases in CBF, 3) greater hypoxic increases in CBF, and 4) increased cyclooxygenase (COX) signaling. We measured middle cerebral artery velocity (MCAv, transcranial Doppler ultrasound) in 11 healthy women (23 ± 1 yr) during rest, hypoxia, and hypercapnia. Subjects completed four visits: two during the early follicular (∼ day 3) and two during the late follicular (∼ day 14) phases of the menstrual cycle, with and without COX inhibition (oral indomethacin). Isocapnic hypoxia elicited an SPO2 = 90% and SPO2 = 80% for 5 min each. Separately, hypercapnia increased end-tidal CO2 10 mmHg above baseline. Cerebral vascular conductance index (CVCi = MCAv/MABP·100, where MABP is mean arterial blood pressure) was calculated and a positive change reflected vasodilation (ΔCVCi). Basal CVCi was greater in the late follicular phase ( P < 0.001). Indomethacin decreased basal CVCi (∼37%) and abolished the phase difference ( P < 0.001). Hypoxic ΔCVCi was similar between phases and unaffected by indomethacin. Hypercapnic ΔCVCi was similar between phases, and indomethacin decreased hypercapnic ΔCVCi (∼68%; P < 0.001) similarly between phases. In summary, while neither hypercapnic nor hypoxic vasodilation is altered by menstrual phase, increased basal CBF in the late follicular phase is fully explained by a greater contribution of COX. These data provide new mechanistic insight into anterior CBF regulation across menstrual phases and contribute to our understanding of CBF regulation in women.

The effects of graded experimental trauma on cerebral blood flow and responsiveness to CO2

1979 ◽  
Vol 51 (1) ◽  
pp. 18-26 ◽  
Author(s):  
Myles L. Saunders ◽  
J. Douglas Miller ◽  
Donald Stablein ◽  
Gilbert Allen
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Severe Trauma ◽  
Cerebrovascular Reactivity ◽  
Cerebral Injury ◽  
Content Type ◽  
Blood Flows ◽  
Cerebrovascular Resistance ◽  
End Tidal ◽  
The Brain

✓ The effects of graded mechanical cerebral trauma on cerebrovascular reactivity to CO2 was studied in 26 cats. A fluid-wave percussion model was employed which delivered an epidural trauma of fixed duration and variable amplitude. The animals were maintained at arterial normoxia, with constant monitoring of intracranial and systemic arterial pressures, electroencephalograms, and end-tidal CO2. Following trauma, cerebral blood flow was measured using the H2 ion clearance technique at PaCO2 levels ranging sequentially from 20 to 60 mm Hg. Cerebrovascular reactivity for control animals (uninjured) was 2.7%. In the group with mild trauma (0.76 to 1.90 atm) reactivity was impaired (1.7%), and it was abolished in the severely injured group (2.90 to 4.60 atm). Mild injuries did not alter resting blood flows, while severe trauma resulted in a significant decrease in cerebrovascular resistance. Intracranial and systemic arterial pressures were altered proportionately to the level of cerebral injury. The authors propose that trauma to the brain-stem vasoregulatory centers accounts for these findings.

scholarly journals Transcranial Doppler Evaluation of the Cerebral Vasculature in Women Patients who Have Migraine with Aura

Pain Medicine ◽  
2020 ◽  
Vol 21 (11) ◽  
pp. 3012-3017
Author(s):  
Igor Petrušić ◽  
Ana Podgorac ◽  
Aleksandra Radojičić ◽  
Jasna Zidverc-Trajković
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Migraine With Aura ◽  
Transcranial Doppler ◽  
Cerebral Blood Flow Velocity ◽  
Cerebral Arteries ◽  
Transcranial Doppler Sonography ◽  
Cerebrovascular Reactivity ◽  
Breath Holding ◽  
Left And Right

Abstract Background Previous studies suggest that increased cerebrovascular reactivity might be a feature of patients who have migraine with aura (MwA). The correlation between the clinical presentation of migraine with aura and transcranial Doppler parameters remains unclear. Objective The main aim of this study was to explore cerebral blood flow, vascular resistance, and cerebrovascular reactivity in women MwA. Also, the relationships between hemodynamic conditions and aura characteristics are examined. Design Cross-sectional study. Setting Headache Center, Neurology Clinic, Clinical Center of Serbia. Subjects Fifty-four women MwA and 49 healthy controls (HCs). Methods Transcranial Doppler sonography examination was used to determine blood flow mean velocity (MV) and pulsatility index (PI), as well as breath-holding index (BHI), in 15 arterial segments comprising the circle of Willis. Results A total of 54 women MwA and 49 HCs were studied. The PIs of all segments of the left and right middle cerebral arteries and the left and right anterior cerebral arteries were significantly higher in MwA with regards to HCs. Also, both the left and right BHIs were significantly higher in MwA than HCs. In addition, MVs of the right vertebral artery and the first segment of the basilar artery were significantly lower in MwA than HCs. Longer duration of migraine aura showed a weak negative correlation with the PI of the left posterior cerebral artery. Conclusions Our findings suggest increased vessel pulsatility, abnormal cerebrovascular reactivity, and decreased cerebral blood flow velocity in several arterial segments of the Willis circle in women MwA.

scholarly journals Cerebral blood flow autoregulation in ischemic heart failure

2017 ◽  
Vol 312 (1) ◽  
pp. R108-R113 ◽  
Author(s):  
J. R. Caldas ◽  
R. B. Panerai ◽  
V. J. Haunton ◽  
J. P. Almeida ◽  
G. S. R. Ferreira ◽  
...  
Keyword(s):  
Heart Failure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Healthy Volunteers ◽  
Neurological Complications ◽  
Ischemic Heart ◽  
Step Response ◽  
Ischemic Heart Failure ◽  
Arterial Blood ◽  
End Tidal

Patients with ischemic heart failure (iHF) have a high risk of neurological complications such as cognitive impairment and stroke. We hypothesized that iHF patients have a higher incidence of impaired dynamic cerebral autoregulation (dCA). Adult patients with iHF and healthy volunteers were included. Cerebral blood flow velocity (CBFV, transcranial Doppler, middle cerebral artery), end-tidal CO2 (capnography), and arterial blood pressure (Finometer) were continuously recorded supine for 5 min at rest. Autoregulation index (ARI) was estimated from the CBFV step response derived by transfer function analysis using standard template curves. Fifty-two iHF patients and 54 age-, gender-, and BP-matched healthy volunteers were studied. Echocardiogram ejection fraction was 40 (20–45) % in iHF group. iHF patients compared with control subjects had reduced end-tidal CO2 (34.1 ± 3.7 vs. 38.3 ± 4.0 mmHg, P < 0.001) and lower ARI values (5.1 ± 1.6 vs. 5.9 ± 1.0, P = 0.012). ARI <4, suggestive of impaired CA, was more common in iHF patients (28.8 vs. 7.4%, P = 0.004). These results confirm that iHF patients are more likely to have impaired dCA compared with age-matched controls. The relationship between impaired dCA and neurological complications in iHF patients deserves further investigation.

Direct Cerebral Vasodilatory Effects of Sevoflurane and Isoflurane 

1999 ◽  
Vol 91 (3) ◽  
pp. 677-677 ◽  
Author(s):  
Basil F. Matta ◽  
Karen J. Heath ◽  
Kate Tipping ◽  
Andrew C. Summors
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Middle Cerebral Artery ◽  
Flow Velocity ◽  
Cerebral Artery ◽  
Blood Flow Velocity ◽  
End Tidal

Background The effect of volatile anesthetics on cerebral blood flow depends on the balance between the indirect vasoconstrictive action secondary to flow-metabolism coupling and the agent's intrinsic vasodilatory action. This study compared the direct cerebral vasodilatory actions of 0.5 and 1.5 minimum alveolar concentration (MAC) sevoflurane and isoflurane during an propofol-induced isoelectric electroencephalogram. Methods Twenty patients aged 20-62 yr with American Society of Anesthesiologists physical status I or II requiring general anesthesia for routine spinal surgery were recruited. In addition to routine monitoring, a transcranial Doppler ultrasound was used to measure blood flow velocity in the middle cerebral artery, and an electroencephalograph to measure brain electrical activity. Anesthesia was induced with propofol 2.5 mg/kg, fentanyl 2 micro/g/kg, and atracurium 0.5 mg/kg, and a propofol infusion was used to achieve electroencephalographic isoelectricity. End-tidal carbon dioxide, blood pressure, and temperature were maintained constant throughout the study period. Cerebral blood flow velocity, mean blood pressure, and heart rate were recorded after 20 min of isoelectric encephalogram. Patients were then assigned to receive either age-adjusted 0.5 MAC (0.8-1%) or 1.5 MAC (2.4-3%) end-tidal sevoflurane; or age-adjusted 0.5 MAC (0.5-0.7%) or 1.5 MAC (1.5-2%) end-tidal isoflurane. After 15 min of unchanged end-tidal concentration, the variables were measured again. The concentration of the inhalational agent was increased or decreased as appropriate, and all measurements were repeated again. All measurements were performed before the start of surgery. An infusion of 0.01% phenylephrine was used as necessary to maintain mean arterial pressure at baseline levels. Results Although both agents increased blood flow velocity in the middle cerebral artery at 0.5 and 1.5 MAC, this increase was significantly less during sevoflurane anesthesia (4+/-3 and 17+/-3% at 0.5 and 1.5 MAC sevoflurane; 19+/-3 and 72+/-9% at 0.5 and 1.5 MAC isoflurane [mean +/- SD]; P&lt;0.05). All patients required phenylephrine (100-300 microg) to maintain mean arterial pressure within 20% of baseline during 1.5 MAC anesthesia. Conclusions In common with other volatile anesthetic agents, sevoflurane has an intrinsic dose-dependent cerebral vasodilatory effect. However, this effect is less than that of isoflurane.

scholarly journals Higher Aortic Stiffness Is Related to Lower Cerebral Blood Flow and Preserved Cerebrovascular Reactivity in Older Adults

Circulation ◽  
2018 ◽  
Vol 138 (18) ◽  
pp. 1951-1962 ◽  
Author(s):  
Angela L. Jefferson ◽  
Francis E. Cambronero ◽  
Dandan Liu ◽  
Elizabeth E. Moore ◽  
Jacquelyn E. Neal ◽  
...  
Keyword(s):  
Older Adults ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Aortic Stiffness ◽  
Cerebrovascular Reactivity

scholarly journals Effects of GV14 Acupuncture on Cerebral Blood Flow Velocity in the Basilar and Middle Cerebral Arteries and CO2 Reactivity during Hypercapnia in Normal Individuals

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Hyun Ku Lee ◽  
Sang-Kwan Moon ◽  
Chul Jin ◽  
Seung-Yeon Cho ◽  
Seong-Uk Park ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Cerebral Arteries ◽  
Transcranial Doppler Sonography ◽  
Cerebrovascular Reactivity ◽  
Acupuncture Points ◽  
Co2 Reactivity ◽  
Middle Cerebral Arteries

The Governing Vessel 14 (GV14) (Dazhui) is one of the acupuncture points referred to as “seven acupoints for stroke.” Nevertheless, there is a scarcity of research on the effects of acupuncture treatment at GV14. This study investigated the effects of acupuncture at GV14 on cerebral blood flow (CBF), especially that in the basilar artery (BA) and the middle cerebral arteries (MCA). Sixteen healthy men aged 20 to 29 years were enrolled in this study. CBF velocity and cerebrovascular reactivity (CVR) were measured using transcranial Doppler sonography (TCD). The following were assessed: closed circuit rebreathing- (CCR-) induced carbon dioxide (CO2) reactivity, modified blood flow velocity at 40 mmHg (CV40) on BA and MCAs, blood pressure (BP), and heart rate (HR). Observed results were obtained after comparison with the baseline evaluation. Statistically significant elevations in CO2 reactivity were recorded in the BA (3.28 to 4.70, p < 0.001 ) and MCAs (right: 3.81 to 5.25, p = 0.001 ; left: 3.84 to 5.12, p = 0.005 ) after acupuncture at GV14. The CV40 increased statistically significantly only in the BA (45.49 to 50.41, p = 0.003 ). No change was observed in BP (106.83 to 107.08 (mmHg), p = 0.335 ) and HR (77 to 75 (bpm), p = 0.431 ). Acupuncture at GV14 improved CBF velocity. These results could be explained by the regulation of endothelium-dependent vessel dilation effected by acupuncture. This trial is registered with Korean Clinical Trial Registry (http://cris.nih.go.kr; registration number: KCT0004787).

scholarly journals Effects of electrical muscle stimulation on cerebral blood flow

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Soichi Ando ◽  
Yoko Takagi ◽  
Hikaru Watanabe ◽  
Kodai Mochizuki ◽  
Mizuki Sudo ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Effect Size ◽  
Minute Ventilation ◽  
Voluntary Exercise ◽  
Muscle Stimulation ◽  
Electrical Muscle Stimulation ◽  
Involuntary Muscle Contraction ◽  
End Tidal ◽  
Electrical Muscle

Abstract Background Electrical muscle stimulation (EMS) induces involuntary muscle contraction. Several studies have suggested that EMS has the potential to be an alternative method of voluntary exercise; however, its effects on cerebral blood flow (CBF) when applied to large lower limb muscles are poorly understood. Thus, the purpose of this study was to examine the effects of EMS on CBF, focusing on whether the effects differ between the internal carotid (ICA) and vertebral (VA) arteries. Methods The participants performed the experiments under EMS and control (rest) conditions in a randomized crossover design. The ICA and VA blood flow were measured before and during EMS or control. Heart rate, blood pressure, minute ventilation, oxygen uptake, and end-tidal partial pressure of carbon dioxide (PETCO2) were monitored and measured as well. Results The ICA blood flow increased during EMS [Pre: 330 ± 69 mL min−1; EMS: 371 ± 81 mL min−1, P = 0.001, effect size (Cohen’s d) = 0.55]. In contrast, the VA blood flow did not change during EMS (Pre: 125 ± 47 mL min−1; EMS: 130 ± 45 mL min−1, P = 0.26, effect size = 0.12). In the EMS condition, there was a significant positive linear correlation between ΔPETCO2 and ΔICA blood flow (R = 0.74, P = 0.02). No relationships were observed between ΔPETCO2 and ΔVA blood flow (linear: R = − 0.17, P = 0.66; quadratic: R = 0.43, P = 0.55). Conclusions The present results indicate that EMS increased ICA blood flow but not VA blood flow, suggesting that the effects of EMS on cerebral perfusion differ between anterior and posterior cerebral circulation, primarily due to the differences in cerebrovascular response to CO2.

Sign in / Sign up

Export Citation Format

Share Document