Cerebral Autoregulation and CO₂ Reactivity Before and After Elective Supratentorial Tumor Resection

Abstract

Background 

The effect of surgical decompression of tumor on autoregulation and CO₂ reactivity is not known. We examined the effect of elective tumor resection on cerebral autoregulation and CO₂ reactivity.

Methods 

Patients with supratentorial tumors undergoing elective craniotomy for tumor resection under standard anesthesia underwent cerebral autoregulation and CO₂ reactivity testing immediately before and between 6 and 24 hours after surgery. Transient hyperemic response of the middle cerebral artery after the release of 10 second compression of the ipsilateral common carotid artery was used to calculate the transient hyperemic response ratio (THRR). THRR>1.1 defined the normal autoregulation. Voluntary hyperventilation was titrated to reduce the ETCO₂ by 10 mm Hg below baseline and CO₂ reactivity was calculated.

Results 

Thirty-five patients (26 male and 9 female) were studied. Overall, cerebral autoregulation was intact before and after tumor resection for the cohort (THRR 1.27±0.10 and 1.30±0.12, P=0.11). However, cerebral autoregulation was impaired preoperatively in 7 (20%) patients and remained impaired in all 7 patients after tumor resection. Larger tumor size (P=0.002), and midline shift more than 5 mm (P<0.001) were associated with impaired cerebral autoregulation. Twenty-eight (80%) patients who had intact preoperative cerebral autoregulation maintained autoregulation postoperatively. CO₂ reactivity was within normal limits before and after surgery in all patients and did not change between the 2 periods (3.41±0.46/mm Hg and 3.60±0.63%/mm Hg, P=0.07).

Conclusion 

Preoperative cerebral autoregulation was impaired in a significant number of patients with large supratentorial tumor size and midline shift more than 5 mm and was associated with postoperative impaired cerebral autoregulation during the first 24 hours after the surgery.