TY - JOUR

T1 - Cerebral blood flow and oxygen metabolism measured with the Kety-Schmidt method using nitrous oxide

AU - Taudorf, S

AU - Berg, R M G

AU - Bailey, D M

AU - Møller, K

PY - 2009/2

Y1 - 2009/2

N2 - BACKGROUND: The Kety-Schmidt method is the reference method for measuring global cerebral blood flow (CBF), cerebral metabolic rates (CMR) and flux, especially where scanners are unavailable or impractical. Our primary objective was to assess the repeatability of the Kety-Schmidt method in a variety of different approaches using inhaled nitrous oxide (N2O) as the tracer, combined with photoacoustic spectrometry. A secondary objective was to assess the impact of this tracer on the systemic vascular concentration of nitrite (NO2(-)).METHODS: Twenty-nine healthy male volunteers underwent 61 CBF measurements by breathing a normoxic gas mixture containing 5% N2O until tension equilibrium. Paired blood samples were collected from an arterial and a jugular bulb catheter in the saturation or desaturation phase, by continuous or the discontinuous sampling. N2O concentration was measured with photoacoustic spectrometry after equilibration of blood samples with air. CBF was calculated by the Kety-Schmidt equation. CMR of oxygen (CMRO2) was determined by the Fick principle. NO2(-) in plasma and red blood cells (RBC) was measured by ozone-based chemiluminescence.RESULTS: The most robust approach for CBF measurement was achieved by discontinuous sampling in the desaturation phase [CBF, 64 (95% confidence interval, 59-71 ml)] 100 g/min; CMRO2 1.8 (1.7-2.0) micromol/g/min). The tracer did not influence plasma or RBC NO2(-) (P>0.05 vs. baseline).CONCLUSION: These findings confirm the reliability and robustness of the Kety-Schmidt method using inhaled N2O for the measurement of global CBF and CMR. At the low tracer concentration used, altered NO metabolism is unlikely to have affected cerebral haemodynamic function.

AB - BACKGROUND: The Kety-Schmidt method is the reference method for measuring global cerebral blood flow (CBF), cerebral metabolic rates (CMR) and flux, especially where scanners are unavailable or impractical. Our primary objective was to assess the repeatability of the Kety-Schmidt method in a variety of different approaches using inhaled nitrous oxide (N2O) as the tracer, combined with photoacoustic spectrometry. A secondary objective was to assess the impact of this tracer on the systemic vascular concentration of nitrite (NO2(-)).METHODS: Twenty-nine healthy male volunteers underwent 61 CBF measurements by breathing a normoxic gas mixture containing 5% N2O until tension equilibrium. Paired blood samples were collected from an arterial and a jugular bulb catheter in the saturation or desaturation phase, by continuous or the discontinuous sampling. N2O concentration was measured with photoacoustic spectrometry after equilibration of blood samples with air. CBF was calculated by the Kety-Schmidt equation. CMR of oxygen (CMRO2) was determined by the Fick principle. NO2(-) in plasma and red blood cells (RBC) was measured by ozone-based chemiluminescence.RESULTS: The most robust approach for CBF measurement was achieved by discontinuous sampling in the desaturation phase [CBF, 64 (95% confidence interval, 59-71 ml)] 100 g/min; CMRO2 1.8 (1.7-2.0) micromol/g/min). The tracer did not influence plasma or RBC NO2(-) (P>0.05 vs. baseline).CONCLUSION: These findings confirm the reliability and robustness of the Kety-Schmidt method using inhaled N2O for the measurement of global CBF and CMR. At the low tracer concentration used, altered NO metabolism is unlikely to have affected cerebral haemodynamic function.

KW - Adult

KW - Algorithms

KW - Blood-Brain Barrier

KW - Brain/metabolism

KW - Carbon Dioxide/blood

KW - Cerebrovascular Circulation

KW - Erythrocytes/chemistry

KW - Hematocrit

KW - Humans

KW - Hydrogen-Ion Concentration

KW - Hypocapnia/blood

KW - Male

KW - Nitric Oxide/metabolism

KW - Nitrites/blood

KW - Nitrous Oxide/pharmacokinetics

KW - Oxygen/blood

KW - Oxygen Consumption

KW - Partial Pressure

KW - Plasma/chemistry

KW - Reproducibility of Results

KW - Spectrum Analysis/methods

KW - Young Adult

U2 - 10.1111/j.1399-6576.2008.01788.x

DO - 10.1111/j.1399-6576.2008.01788.x

M3 - Journal article

C2 - 19076112

VL - 53

SP - 159

EP - 167

JO - Acta Anaesthesiologica Scandinavica

JF - Acta Anaesthesiologica Scandinavica

SN - 0001-5172

IS - 2

ER -