Effect of transient moderate hyperventilation on dynamic cerebral autoregulation after severe head injury
Effect of transient moderate hyperventilation on dynamic cerebral autoregulation after severe head injury
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DOI：
10.1097/00006123-199607000-00008
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发表时间：
1996-07-01
期刊：
影响因子：
4.8
通讯作者：
Winn, HR
中科院分区：
文献类型：
--
作者：
Newell, DW;Weber, JP;Winn, HR
目的：目的：探讨急性中度过度通气对重型颅脑损伤患者脑自动调节功能的影响。方法：应用经颅多普勒超声对10例重型颅脑损伤患者过度通气前后的脑自动调节功能进行动态分析。所有患者均接受人工通气，并持续监测动脉血压、颅内压和呼气末二氧化碳。为了测试自动调节，通过快速释放围绕两条大腿充气的大血压袖带来实现全身血压的快速瞬时降低。这导致平均全身血压下降24 +/- 6 mm Hg，平均持续49 +/- 24秒。采用经颅多普勒超声连续监测双侧大脑中动脉血流速度。大脑中动脉血流速度的百分比变化被用作自动调节反应期间脑血流变化的指标。血压下降后即刻估计的脑血管阻力的变化或调节速率用于分析脑自动调节的有效性。这个值是通过测定血压下降后前5秒大脑中动脉流速的增加率来计算的，相对于脑灌注压的增加率。结果：在pCO（2）为37 mm Hg时，正常碳酸血症期间的平均调节率为每秒11.4 +/- 5%。当pCO（2）降至28 mm Hg时，平均调节速率显著提高（P < 0.001），达到每秒17.7 +/- 6%。自动调节改善，尽管在过度通气期间脑灌注压没有显著变化。自动调节的改善程度与CO2反应性显著相关（r = 0.45，P < 0.05），但无相关性（r =-0.23，P = 0.33）。结论：这些结果证实了重型颅脑损伤时动态自动调节功能紊乱，中度一过性过度通气可暂时性提高自身调节反应的效率，可能是血管张力短暂增加的结果。
OBJECTIVE: This study was undertaken to evaluate the effect of acute moderate hyperventilation on cerebral autoregulation in head-injured patients.METHODS: Dynamic cerebral autoregulation was analyzed by use of transcranial doppler ultrasonography before and after hyperventilation in 10 patients with severe head injury. All of the patients were artificially ventilated and underwent continuous monitoring of arterial blood pressure, intracranial pressure, and end-tidal carbon dioxide. To test autoregulation, rapid transient decreases in systemic blood pressure were achieved by quickly releasing large blood pressure cuffs that were inflated around both thighs. This resulted in a drop of 24 +/- 6 mm Hg in mean systemic blood pressure, which lasted an average of 49 +/- 24 seconds. Cerebral blood flow velocity was monitored continuously in both middle cerebral arteries by use of transcranial doppler ultrasonography. The percentage change in middle cerebral artery velocity was used as an index of the change in cerebral blood flow during the autoregulatory response. The change in estimated cerebrovascular resistance, immediately after the blood pressure drop, or the rate of regulation was used to analyze the effectiveness of the cerebral autoregulation. This value was calculated by determining the rate of increase in middle cerebral artery velocity during the 1st 5 seconds after a blood pressure drop, relative to the rate of increase of the cerebral perfusion pressure.RESULTS: The average rate of regulation during normocapnia at pCO(2) of 37 mm Hg was 11.4 +/- 5% per second. After reduction of the pCO(2) to 28 mm Hg, the average rate of regulation improved significantly (P < 0.001) to 17.7 +/- 6% per second. Autoregulation improved, despite no significant change in the cerebral perfusion pressure during hyperventilation. The degree of improvement in autoregulation was significantly correlated with the CO2 reactivity (r = 0.45, P < 0.05) but did not correlate (r = -0.23, P = 0.33) with the change in arterial pH value after hyperventilation.CONCLUSION: These results confirm the finding that dynamic autoregulation is disturbed in severe head injury and that moderate transient hyperventilation can temporarily improve the efficiency of the autoregulatory response, probably as a result of a transient increase in vascular tone.