Abstract
Vasomotion is defined as a spontaneous local oscillation in vascular tone whose function is unclear but may have a beneficial effect on tissue oxygenation. Optical reflectance spectroscopy and laser Doppler fluximetry provide unique insights into the possible mechanisms of vasomotion in the cutaneous microcirculation through the simultaneous measurement of changes in concentration of oxyhemoglobin ([HbO(2)]), deoxyhemoglobin ([Hb]), and mean blood saturation (S(mb)O(2)) along with blood volume and flux. The effect of vasomotion at frequencies <0.02 Hz attributed to endothelial activity was studied in the dorsal forearm skin of 24 healthy males. Fourier analysis identified periodic fluctuations in S(mb)O(2) in 19 out of 24 subjects, predominantly where skin temperatures were >29.3°C (X(2) = 6.19, P < 0.02). A consistent minimum threshold in S(mb)O(2) (mean: 39.4%, range: 24.0-50.6%) was seen to precede a sudden transient surge in flux, inducing a fast rise in S(mb)O(2). The integral increase in flux correlated with the integral increase in [HbO(2)] (Pearson's correlation r(2) = 0.50, P < 0.001) and with little change in blood volume suggests vasodilation upstream, responding to a low S(mb)O(2) downstream. This transient surge in flux was followed by a sustained period where blood volume and flux remained relatively constant and a steady decrease in [HbO(2)] and equal and opposite increase in [Hb] was considered to provide a measure of oxygen extraction. A measure of this oxygen extraction has been approximated by the mean half-life of the decay in S(mb)O(2) during this period. A comparison of the mean half-life in the 8 normal subjects [body mass index (BMI) <26.0 kg/m(2)] of 12.2 s and the 11 obese subjects (BMI >29.5 kg/m(2)) of 18.8 s was statistically significant (Mann Whitney, P < 0.004). The S(mb)O(2) fluctuated spontaneously in this saw tooth manner by an average of 9.0% (range 4.0-16.2%) from mean S(mb)O(2) values ranging from 30 to 52%. These observations support the hypothesis that red blood cells may act as sensors of local tissue hypoxia, through the oxygenation status of the hemoglobin, and initiate improved local perfusion to the tissue through hypoxic vasodilation.
Highlights
Геморрагический шок является разновидностью гиповолемического шока и возникает при значитель ном уменьшении объема циркулирующей крови в ре зультате кровопотери
Animals were administered with polyethylene catheters through the tail artery for invasive measurement of blood pressure, blood shedding and blood infusion
It turned out that in the initial state the chloralhydrate leads to a decrease in blood pres sure and index of perfusion (IP) (Table 1)
Summary
Геморрагический шок является разновидностью гиповолемического шока и возникает при значитель ном уменьшении объема циркулирующей крови в ре зультате кровопотери. В основе патогенеза геморраги ческого и других видов шока лежат грубые расстройства кровообращения (системной гемодина мики и микроциркуляции), приводящие к снижению перфузии и оксигенации тканей, их гипоксии и перехо ду аэробного метаболизма в анаэробный. Состояние микроциркуляции непосредственно влияет на адекватность перфузии и оксигенации тка ней, восстановление которых все чаще рассматривается как главная цель интенсивной терапии шока и других критических состояний [7,8,9]. Что выраженность ишемических и реперфу зионных повреждений в значительной степени опреде ляется сроками, объемом и качественным составом проводимой инфузионно трансфузионной терапии, а также исходным состоянием организма
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More From: American journal of physiology. Heart and circulatory physiology
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