Cerebral blood flow autoregulation and transcranial doppler sonography in patients with cirrhosis

Abstract

Impairment of cerebral blood flow (CBF) autoregulation may have serious implications for patients with cirrhosis if arterial hypotension occurs during coma, anesthesia, bleeding, or sepsis. In this study, CBF autoregulation was investigated in patients with cirrhosis with no or mild encephalopathy. Ten patients (median age, 45 years; range, 30 to 61 years) and six healthy volunteers (median age, 30 years; range, 21 to 61 years) were included. Catheters were placed in a radial artery and in the internal jugular vein. Baseline CBF was measured using single-photon emission computed tomography (SPECT) with concomitant measurements of cerebral arteriovenous oxygen content differences (AVDO 2). CBF autoregulation was evaluated using the AVDO 2 method and changes in mean flow velocity in the middle cerebral artery (V mean) as determined by transcranial Doppler (TCD). Mean arterial pressure (MAP) was increased by 30 mm Hg by intravenous norepinephrine, and subsequently decreased by a combination of lower body negative pressure and ganglion blockade, whereas AVDO 2 and V mean were measured at each 5 mm Hg change in MAP. CBF was 61 (range, 45 to 78) mL 100 g −1 min −1 in patients with cirrhosis and 65 (range, 53 to 88) mL 100 g −1 min −1 in volunteers (not significant [NS]). There were no regional differences in CBF between the two groups. Arterial carbon dioxide tension was 31 (23 to 35) mm Hg in patients with cirrhosis and lower, compared with 36 (range, 34 to 37) mm Hg in the volunteers ( P < .01). For evaluation of autoregulation, MAP was raised to 116 (range 100 to 145) and then decreased to 39 (range, 34 to 50) mm Hg. In 8 of 10 patients with cirrhosis, a lower limit of autoregulation of 74 (range 64 to 103) mm Hg was identified, similar to the value of 74 (range, 53 to 79) mm Hg in the controls. In the two remaining patients with cirrhosis, no lower limit could be established. A statistically significant correlation between V mean and CBF below the lower limit of autoregulation was found in patients with cirrhosis (CBF = 22 + 0.75 · V mean; r 2 = .60; P < .005). CBF autoregulatory capacity seems generally preserved in patients with cirrhosis but the lower limit may be impaired in some patients and can be reliably evaluated using TCD sonography.