We thank Drs. Williams, Gelb, and Talke for their interest and comments on our paper.1
Dr. Williams has highlighted a potential contributor to secondary brain injury that we were unable to control for in our retrospective study. Both hypocapnia and hyercapnia have plausible mechanisms for worsening blood flow to the critically ischemic penumbra. Hypocapnia may result in further cerebral vasoconstriction and, as Dr. Williams has pointed out, may be associated with poor outcome after head trauma. We are aware that studies have shown that hypercapnia may have a neuroprotective effect after ischemia in immature animals, but we are not aware of any clinical evidence in humans to support this finding. The proposed mechanism is that of improved collateral flow due to vasodilation; however, a consequence of vasodilation may ultimately be brain edema and increases to intracranial pressure. Normocapnia is probably a safe goal at this time. Unfortunately, we did not have periprocedural blood-gas tensions available to us but we acknowledge the importance of this information.
We agree with Drs. Gelb and Talke that blood pressure management throughout the precanalization period is likely to be a critical issue. Our interventional team is currently trying to develop institutional guidelines for management of blood pressure in this setting, because current national guidelines are not particularly helpful for this group of patients.
We must apologize for the title of table 1; the use of ‘Baseline’ is misleading—it does not apply to the blood pressure measurements. In this article we did not report any ‘baseline’ (preintervention) blood pressure values. The values in table 1 were those obtained during the procedure—the same values that were reported in the ‘Results’ section (page 400). We did not attempt to define a ‘baseline blood pressure value,’ for the reasons that are outlined in the discussion (page 403, top).
This confusion generated by the misleading title does not detract from the justified concern of Drs. Gelb and Talke that blood pressure management may be important in all phases of acute stroke treatment.
