Cerebrovascular CO 2 reactivity during isoflurane-nitrous oxide anesthesia in patients with chronic renal failure

Abstract

Purpose

We assessed the cerebrovascular CO₂ reactivity (CO₂R) 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 CO₂ of 35 to 45 mmHg. CO₂R was calculated as an absolute value (change in VMCA per mmHg PaCO₂) and a relative value (absolute CO₂R/baseline VMCA × 100). Factors associated with CO₂R were evaluated simultaneously.

Results

Despite no significant differences in the absolute and relative values of CO₂R 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 CO₂R. BUN concentration was higher (mean 72 versus 53 mg/dl, p = 0.006) and relative CO₂R 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

CO₂R in CRF patients was not significantly different from that in controls. However, in CRF patients with high BUN concentrations, CO₂R 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.

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