Hemodilution Combined With Hypercapnia Impairs Cerebral Autoregulation During Normothermic Cardiopulmonary Bypass

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• 作者：Ervin E. &Scaron ; everdija ; EKP^* ; Nousjka P.A. Vranken ; BASc^* ; ^{nousjka.vranken@mumc.nl" class="auth_mail" title="E-mail the corresponding author} ; Antoine P. Simons ; EKP ; PhD^* ; Erik D. Gommer ; MSc ; PhD^&dagger ; ; John H. Heijmans ; MD ; PhD^&Dagger ; ; Jos G. Maessen ; MD ; PhD^* ; Patrick W. Weerwind ; CCP ; PhD^*
• 关键词：cardiopulmonary bypass ; cerebral autoregulation ; cerebral carbon dioxide reactivity ; hemodilution
• 刊名：Journal of Cardiothoracic and Vascular Anesthesia
• 出版年：2015
• 出版时间：October 2015
• 年：2015
• 卷：29
• 期：5
• 页码：1194-1199
• 全文大小：203 K

文摘

To investigate the influence of hemodilution and arterial pCO₂ on cerebral autoregulation and cerebral vascular CO₂ reactivity.

Design

Prospective interventional study.

Setting

University hospital-based single-center study.

Participants

Forty adult patients undergoing elective cardiac surgery using normothermic cardiopulmonary bypass.

Interventions

Blood pressure variations induced by 6/minute metronome-triggered breathing (baseline) and cyclic 6/min changes of indexed pump flow at 3 levels of arterial pCO₂.

Measurements and Main Results

Based on median hematocrit on bypass, patients were assigned to either a group of a hematocrit≥28% or<28%. The autoregulation index was calculated from cerebral blood flow velocity and mean arterial blood pressure using transfer function analysis. Cerebral vascular CO₂ reactivity was calculated using cerebral tissue oximetry data. Cerebral autoregulation as reflected by autoregulation index (baseline 7.5) was significantly affected by arterial pCO₂ (median autoregulation index amounted to 5.7, 4.8, and 2.8 for arterial pCO₂ of 4.0, 5.3, and 6.6 kPa, p≤0.002) respectively. Hemodilution resulted in a decreased autoregulation index; however, during hypocapnia and normocapnia, there were no significant differences between the two hematocrit groups. Moreover, the autoregulation index was lowest during hypercapnia when hematocrit was<28% (autoregulation index 3.3 versus 2.6 for hematocrit≥28% and<28%, respectively, p = 0.014). Cerebral vascular CO₂ reactivity during hypocapnia was significantly lower when perioperative hematocrit was<28% (p = 0.018).

Conclusions

Hemodilution down to a hematocrit of<28% combined with hypercapnia negatively affects dynamic cerebral autoregulation, which underlines the importance of tight control of both hematocrit and p_aCO₂ during CPB.