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Dehydration affects cerebral blood flow but not its metabolic rate for oxygen during maximal exercise in trained humans.

Trangmar SJ, Chiesa ST, Stock CG, Kalsi KK, Secher NH, González-Alonso J - J. Physiol. (Lond.) (2014)

Bottom Line: In all conditions, reductions in ICA and MCA Vmean were associated with declining cerebral vascular conductance, increasing jugular venous noradrenaline, and falling arterial carbon dioxide tension (P aCO 2) (R(2) ≥ 0.41, P ≤ 0.01) whereas CCA flow and conductance were related to elevated blood temperature.In conclusion, dehydration accelerated the decline in CBF by decreasing P aCO 2 and enhancing vasoconstrictor activity.However, the circulatory strain on the human brain during maximal exercise does not compromise CMRO2 because of compensatory increases in O2 extraction.

View Article: PubMed Central - PubMed

Affiliation: Centre for Sports Medicine and Human Performance, Brunel University, London, UK.

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Relationships between cerebral perfusion and blood CO2 and temperatureLeft panel:  (A), arterial CO2 content (, B), and jugular venous temperature responses to incremental exercise (C). Right panel: ICA blood flow and MCA Vmean group mean correlations with  (D and E), and CCA blood flow group mean correlation to jugular venous temperature (F) in control (open circles), dehydration (filled circles) and rehydration (open squares). *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax). Unless presented, significance for control and rehydration were similar (i.e. panels B and C).
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fig06: Relationships between cerebral perfusion and blood CO2 and temperatureLeft panel: (A), arterial CO2 content (, B), and jugular venous temperature responses to incremental exercise (C). Right panel: ICA blood flow and MCA Vmean group mean correlations with (D and E), and CCA blood flow group mean correlation to jugular venous temperature (F) in control (open circles), dehydration (filled circles) and rehydration (open squares). *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax). Unless presented, significance for control and rehydration were similar (i.e. panels B and C).

Mentions: In the dehydration trial (Fig. 1), body mass in DEH was lower compared to control (75.8 ± 2.7 vs. 78.2 ± 2.7 kg, corresponding to a 3.1 ± 0.3% body mass loss, P < 0.01), and was restored in REH (77.7 ± 2.9 kg). DEH was accompanied by an increased arterial and venous haemoglobin concentration ([Hb]) (P < 0.01; Table 1), indicative of a reduction in blood volume, whereas REH restored these responses. Prior to exercise, intestinal and internal jugular venous temperatures were higher in DEH compared to control (38.3 ± 0.1 vs. 36.8 ± 0.1 and 37.7 ± 0.1 vs. 36.5 ± 0.1°C, respectively, both P < 0.001; Fig. 6C), but were restored to control values in REH (36.5–36.8°C). In DEH, both intestinal and blood temperature remained elevated and increased with work rates to a peak of 38.2 ± 0.1°C (P < 0.01; Fig. 6C). In control, intestinal and internal jugular venous temperature increased progressively to 37.4 ± 0.1 and 37.9 ± 0.1°C, with similar responses observed during REH. Mean skin temperature (Tsk) was unchanged across exercise intensities and between incremental conditions (33.8 ± 0.3, 32.6 ± 0.4 and 33.1 ± 0.3°C in control, DEH and REH, respectively). Heart rate followed the same pattern, with peak values being similar in all three conditions (179 ± 4, 184 ± 2 and 179 ± 3 beats min−1 in control, DEH and REH, respectively).


Dehydration affects cerebral blood flow but not its metabolic rate for oxygen during maximal exercise in trained humans.

Trangmar SJ, Chiesa ST, Stock CG, Kalsi KK, Secher NH, González-Alonso J - J. Physiol. (Lond.) (2014)

Relationships between cerebral perfusion and blood CO2 and temperatureLeft panel:  (A), arterial CO2 content (, B), and jugular venous temperature responses to incremental exercise (C). Right panel: ICA blood flow and MCA Vmean group mean correlations with  (D and E), and CCA blood flow group mean correlation to jugular venous temperature (F) in control (open circles), dehydration (filled circles) and rehydration (open squares). *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax). Unless presented, significance for control and rehydration were similar (i.e. panels B and C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4214665&req=5

fig06: Relationships between cerebral perfusion and blood CO2 and temperatureLeft panel: (A), arterial CO2 content (, B), and jugular venous temperature responses to incremental exercise (C). Right panel: ICA blood flow and MCA Vmean group mean correlations with (D and E), and CCA blood flow group mean correlation to jugular venous temperature (F) in control (open circles), dehydration (filled circles) and rehydration (open squares). *P < 0.05 vs. rest, #P < 0.05 vs. sub-maximal exercise (i.e. ∼40% WRmax). Unless presented, significance for control and rehydration were similar (i.e. panels B and C).
Mentions: In the dehydration trial (Fig. 1), body mass in DEH was lower compared to control (75.8 ± 2.7 vs. 78.2 ± 2.7 kg, corresponding to a 3.1 ± 0.3% body mass loss, P < 0.01), and was restored in REH (77.7 ± 2.9 kg). DEH was accompanied by an increased arterial and venous haemoglobin concentration ([Hb]) (P < 0.01; Table 1), indicative of a reduction in blood volume, whereas REH restored these responses. Prior to exercise, intestinal and internal jugular venous temperatures were higher in DEH compared to control (38.3 ± 0.1 vs. 36.8 ± 0.1 and 37.7 ± 0.1 vs. 36.5 ± 0.1°C, respectively, both P < 0.001; Fig. 6C), but were restored to control values in REH (36.5–36.8°C). In DEH, both intestinal and blood temperature remained elevated and increased with work rates to a peak of 38.2 ± 0.1°C (P < 0.01; Fig. 6C). In control, intestinal and internal jugular venous temperature increased progressively to 37.4 ± 0.1 and 37.9 ± 0.1°C, with similar responses observed during REH. Mean skin temperature (Tsk) was unchanged across exercise intensities and between incremental conditions (33.8 ± 0.3, 32.6 ± 0.4 and 33.1 ± 0.3°C in control, DEH and REH, respectively). Heart rate followed the same pattern, with peak values being similar in all three conditions (179 ± 4, 184 ± 2 and 179 ± 3 beats min−1 in control, DEH and REH, respectively).

Bottom Line: In all conditions, reductions in ICA and MCA Vmean were associated with declining cerebral vascular conductance, increasing jugular venous noradrenaline, and falling arterial carbon dioxide tension (P aCO 2) (R(2) ≥ 0.41, P ≤ 0.01) whereas CCA flow and conductance were related to elevated blood temperature.In conclusion, dehydration accelerated the decline in CBF by decreasing P aCO 2 and enhancing vasoconstrictor activity.However, the circulatory strain on the human brain during maximal exercise does not compromise CMRO2 because of compensatory increases in O2 extraction.

View Article: PubMed Central - PubMed

Affiliation: Centre for Sports Medicine and Human Performance, Brunel University, London, UK.

Show MeSH
Related in: MedlinePlus