Cerebrovascular CO reactivity during isoflurane-nitrous oxide anesthesia in patients with chronic renal failure.

Purpose: We assessed the cerebrovascular CO reactivity (COR) in chronic renal failure (CRF) patients without diabetes mellitus (DM), uncontrolled hypertension, peripheral vascular disease, or neurological disease under isoflurane-nitrous oxide anesthesia.

Methods: Forty-nine patients undergoing surgery, including 36 CRF patients (30 receiving dialysis and six pre-dialysis patients) and 13 patients without CRF (controls). Middle cerebral artery flow velocity (VMCA) was measured by transcranial Doppler ultrasonography at an end-tidal CO of 35 to 45 mmHg. COR was calculated as an absolute value (change in VMCA per mmHg PaCO) and a relative value (absolute COR/baseline VMCA × 100). Factors associated with COR were evaluated simultaneously.

Results: Despite no significant differences in the absolute and relative values of COR between the CRF (mean 2.5 cm/s/mmHg; median 5.0%/mmHg) and control (2.4 cm/s/mmHg; 5.0%/mmHg) groups, blood urea nitrogen (BUN) concentrations in the CRF group correlated inversely with both absolute and relative COR. BUN concentration was higher (mean 72 versus 53 mg/dl, p = 0.006) and relative COR was lower (mean 2.6 versus 5.7%/mmHg, p = 0.011) in patients with pre-dialysis CRF (n = 6) versus CRF patients receiving dialysis (n = 30).

Conclusions: COR in CRF patients was not significantly different from that in controls. However, in CRF patients with high BUN concentrations, COR might be impaired, leading to reduced cerebrovascular reserve capacity. Because DM is a major cause of CRF and we excluded DM patients, our results might not be applicable to patients with DM-induced CRF.