The effects of sympathetic activity induced by ice water on blood flow and brachial artery flow-mediated dilatation response in healthy volunteers

Sympathetic-mediated blunting of forearm vasodilation is similar between young men and women

BACKGROUND

The in-vivo regulation of vascular conductance (VC) is a continuous balance between endothelial vasodilation and sympathetic vasoconstriction. Although women may report blunted sympathetic vasoconstriction along with higher endothelial vasodilation than men, it is currently unknown whether the interaction between vasoconstriction and vasodilation leads to different regulation of VC between sexes. This study assessed sex differences in sympathetic-mediated blunting of endothelial vasodilation after a brief period of ischemia and whether any restriction of vasodilation blunts tissue blood flow (BF) and re-oxygenation.

METHODS

13 young women and 12 young men underwent two 5-min forearm circulatory occlusions followed by reperfusion, one in basal conditions and the other during cold pressor test-induced sympathetic activation (SYMP). Brachial artery diameter and BF, mean arterial pressure, total peripheral resistance (TPR), and thenar eminence oxygenation were collected. Percent changes normalized to baseline values of forearm VC, brachial artery BF and flow-mediated dilation (FMD), TPR, and hand oxygenation after circulatory reperfusion were calculated.

RESULTS

TPR increased during SYMP in men (p = 0.019) but not in women (p = 0.967). Women showed a greater brachial artery FMD than men (p = 0.004) at rest, but sex differences disappeared after normalization to shear rate and baseline diameter (p > 0.11). The percent increases from baseline of peak and average forearm VC after circulatory reperfusion did not differ between sexes in basal conditions (p > 0.98) or during SYMP (p > 0.97), and were restrained by SYMP similarly in both sexes (p < 0.003) without impairing the hand re-oxygenation (p > 0.08) or average hyperemic response (p > 0.09).

CONCLUSIONS

Although women may report blunted sympathetic vasoconstriction than men when assessed separately, the similar sympathetic-mediated restriction of vasodilation suggests a similar dynamic regulation of VC between sexes. SYMP-mediated restrictions of the normal forearm vasodilation do not impair the average hyperemic response and hand re-oxygenation in both sexes.

Transient Reduction of FMD-Response and L-Arginine Accompanied by Increased Levels of E-Selectin, VCAM, and ICAM after Prolonged Strenuous Exercise

We assessed endothelial function by flow-mediated dilatation (FMD), levels of the NO-precursor L-arginine, and markers of endothelial inflammation before, at the finish line, and one week after the Norseman Xtreme triathlon. The race is an Ironman distance triathlon with a total elevation of 5200 m. Nine male participants were included. They completed the race in 14.5 (13.4–15.3) h. FMD was significantly reduced to 3.1 (2.1–5.0)% dilatation compared to 8.7 (8.2–9.3)% dilatation before the race (p < 0.05) and was normalized one week after the race. L-arginine showed significantly reduced levels at the finish line (p < 0.05) but was normalized one week after the race. Markers of endothelial inflammation E-Selectin, VCAM-1, and ICAM-1 all showed a pattern with increased values at the finish line compared to before the race (all p < 0.05), with normalization one week after the race. In conclusion, we found acutely reduced FMD with reduced L-arginine levels and increased E-Selectin, VCAM-1, and ICAM-1 immediately after the Norseman Xtreme triathlon. Our findings indicate a transient reduced endothelial function, measured by the FMD-response, after prolonged strenuous exercise that could be explained by reduced NO-precursor L-arginine levels and increased endothelial inflammation.

Perfusion indices can predict early volume depletion in a blood donor model

INTRODUCTION

Blood donation from healthy donors is used experimental model that surrogates for class 1 hemorrhage in humans. We examined changes in the perfusion index (PI) and plethysmographic variability index (PVI) in healthy blood donors after donating a unit of blood, and we evaluated the usability of these indices in detecting blood loss volumes of less than 750 mL (class 1 hemorrhagic shock trauma patients).

MATERIALS AND METHODS

This study is a prospective, cross-sectional study. 180 healthy volunteers aged 18 and over, who donated blood at the local blood bank, were included in the study consecutively. The age, gender, and body mass index of the volunteers were recorded and, before and after the blood donation, the vital signs and perfusion indices were measured.

RESULTS

Of the donors, 61.7% were men (n = 111), and the median age of all donors was 32 (IQR: 21-39). A statistically significant difference was found between the hemodynamic parameters and PIs before and after the blood donation (p < 0.01 for all parameters; median difference of PI [- 1.45, 95% CI: (- 0.9)-( - 2)], median difference of PVI [6, 95% CI: 7.77-4.23].

CONCLUSION

We evaluated the perfusion indices in the early diagnosis of blood volume loss in patients admitted to the emergency department due to trauma. After the participants donated one unit of blood, we found that their PI decreased and PVI increased compared to the measurements before the blood donation. Considering that major bleeding starts in the very early stage as minor bleeding, it is essential for emergency physicians to recognize class 1 hemorrhagic shock patients. Further, non-invasive and straightforward procedures, such as measuring PI and PVI, can be particularly useful in identifying blood loss volumes of less than 750 mL.

Correction: The effects of sympathetic activity induced by ice water on blood flow and brachial artery flow-mediated dilatation response in healthy volunteers

[This corrects the article DOI: 10.1371/journal.pone.0219814.].