血管升压药给药改善了脑低温引起的灌注不良。

Mori K, Maeda M, Miyazaki M, Iwase H

Department of Neurosurgery, Juntendo University, Shizuoka, Japan.

Neurol Res. 1999 Sep;21(6):585-92. doi: 10.1080/01616412.1999.11740981.

Therapeutic cerebral hypothermia is widely used for the treatment of severe head injury and cerebral ischemia. The effects of cerebral hypothermia on the cerebral blood flow (CBF) and metabolism, and cerebral vasculature in the normal brain were investigated. Thirty-four adult cats were divided into four groups. CBF was monitored by hydrogen clearance. Arteriovenous oxygen difference (AVDO2) and cerebral venous oxygen saturation (ScvO2) were measured in blood samples from the superior sagittal sinus. The cerebral metabolic rate of oxygen (CMRO2) and cerebral vascular resistance (CVR) were calculated. The cerebral blood volume (CBV) was measured using technetium-99m-labeled human serum albumin in 12 cats. Deep cerebral temperature was cooled from 37 degrees C to 25 degrees C using a water-circulating blanket. In the hypothermia group (Group A: n = 10), CBF (51.2 +/- 8.3 ml 100 g-1 min-1 at 37 degrees C) decreased with lower brain temperature (6.1 +/- 2.7 at 25 degrees C). CMRO2 (2.24 +/- 0.75 ml 100 g-1 min-1 at 37 degrees C) was also decreased (0.52 +/- 0.20 at 25 degrees C). AVDO2 (4.3 +/- 1.0 ml 100 g-1 min-1 at 37 degrees C) increased significantly at 31 degrees C (6.6 +/- 1.8; p < 0.05) and ScvO2 (67.8 +/- 7.9% at 37 degrees C) decreased significantly at 29 degrees C (53.7 +/- 9.7; p < 0.05). CBV (5.3 +/- 1.2% at 37 degrees C) decreased significantly at 29 degrees C (3.7 +/- 1.0; p < 0.05) and CVR (3.2 +/- 0.7 mmHg ml-1 100 g-1 min-1 at 37 degrees C) increased significantly at 29 degrees C (13.8 +/- 5.2; p < 0.01). The combined effect of hypothermia with vasopressor (noradrenalin) (Group B: n = 6) or barbiturate (thiopental) administration (Group C: n = 6) on the cerebral metabolic parameters were also examined. Hypothermia with noradrenalin administration significantly improved the ischemic parameters (AVDO2 was 4.7 +/- 1.4 ml 100 g-1 min-1 at 31 degrees C and ScvO2 was 72.2 +/- 6.4% at 29 degrees C). However, hypothermia with barbiturate administration did not improve these metabolic parameters. These results suggest that hypothermia may cause vasoconstriction and misery perfusion in the brain. This potential risk of relative ischemia can be avoided by combination with vasopressor administration.

治疗性亚低温广泛应用于重型颅脑损伤和脑缺血的治疗。本研究调查了亚低温对正常脑血流（CBF）、代谢及脑血管的影响。将34只成年猫分为四组。采用氢清除法监测CBF。从上矢状窦采集血样，测量动静脉氧差（AVDO2）和脑静脉血氧饱和度（ScvO2）。计算脑氧代谢率（CMRO2）和脑血管阻力（CVR）。对12只猫使用99m锝标记的人血清白蛋白测量脑血容量（CBV）。使用水循环毯将深部脑温从37℃降至25℃。在亚低温组（A组：n = 10），CBF（37℃时为51.2±8.3 ml 100 g-1 min-1）随脑温降低而下降（25℃时为6.1±2.7）。CMRO2（37℃时为2.24±0.75 ml 100 g-1 min-1）也下降（25℃时为0.52±0.20）。AVDO2（37℃时为4.3±1.0 ml 100 g-1 min-1）在31℃时显著升高（6.6±1.8；p < 0.05），ScvO2（37℃时为67.8±7.9%）在29℃时显著下降（53.7±9.7；p < 0.05）。CBV（37℃时为5.3±1.2%）在29℃时显著下降（3.7±1.0；p < 0.05），CVR（37℃时为3.2±0.7 mmHg ml-1 100 g-1 min-1）在29℃时显著升高（13.8±5.2；p < 0.01）。还研究了亚低温联合血管升压药（去甲肾上腺素）（B组：n = 6）或巴比妥类药物（硫喷妥钠）给药（C组：n = 6）对脑代谢参数的影响。亚低温联合去甲肾上腺素给药显著改善了缺血参数（31℃时AVDO2为4.7±1.4 ml 100 g-1 min-1，29℃时ScvO2为72.2±6.4%）。然而，亚低温联合巴比妥类药物给药并未改善这些代谢参数。这些结果表明，亚低温可能导致脑血管收缩和脑内灌注不良。联合使用血管升压药可避免这种相对缺血的潜在风险。