Smith F G, Abu-Amarah I
Department of Physiology and Biophysics, University of Calgary, Alberta, Canada.
Am J Physiol. 1997 Jul;273(1 Pt 2):H339-46. doi: 10.1152/ajpheart.1997.273.1.H339.
The purpose of the present study was to investigate the systemic and renal hemodynamic effects of hemorrhage in the newborn to determine whether the newborn is capable of restoring blood pressure in the face of blood loss at hemorrhage of up to 20% of vascular volume. Experiments were carried out in conscious, chronically instrumented lambs and consisted of measurements before, during, and after hemorrhage at 0 (n = 9), 10 (n = 8), 15 (n = 8), and 20% (n = 8) of blood volume. Right atrial pressure decreased but only after 20% hemorrhage. There was a transient decrease in blood pressure at 10-15% hemorrhage and a sustained decrease in blood pressure after 20% hemorrhage (from 82 +/- 7 to 66 +/- 9 mmHg). Heart rate increased transiently after 15% hemorrhage (from 173 +/- 32 to 204 +/- 66 beats/min); heart rate remained increased for 60 min after 20% hemorrhage from 171 +/- 17 to 214 +/- 31 beats/min. There were no changes in renal vascular resistance in response to hemorrhage of up to 20% of vascular volume. These observations provide evidence that the newborn is capable of buffering blood pressure in response to blood loss of up to 20% of vascular volume and that the renal bed does not appear to contribute to the restoration of blood pressure after blood loss early in life.
本研究的目的是调查新生儿出血时的全身和肾脏血流动力学效应，以确定新生儿在失血达血容量20%时是否有能力恢复血压。实验在清醒、长期植入仪器的羔羊身上进行，包括在失血0（n = 9）、10%（n = 8）、15%（n = 8）和20%（n = 8）血容量时，分别于出血前、出血期间和出血后进行测量。右心房压力仅在失血20%后下降。失血10%-15%时血压短暂下降，失血20%后血压持续下降（从82±7降至66±9 mmHg）。失血15%后心率短暂增加（从173±32次/分钟增至204±66次/分钟）；失血20%后心率在60分钟内持续增加，从171±17次/分钟增至214±31次/分钟。失血达血容量20%时，肾血管阻力无变化。这些观察结果表明，新生儿在失血达血容量20%时能够缓冲血压，且在生命早期失血后，肾床似乎对血压恢复没有作用。
