Analysis of CO2 vasomotor reactivity and vessel diameter changes by simultaneous venous and arterial Doppler recordings.

BACKGROUND AND PURPOSE The use of flow velocity changes in the middle cerebral artery (MCA) measured by Doppler techniques as an index of corresponding cerebral blood flow (CBF) changes is based on the assumption that the insonated arterial diameter remains stable. The postulate of unchanging vessel calibers during CBF changes, however, is still under debate. We performed simultaneous measurements of arterial and venous blood flow velocities by transcranial Doppler ultrasound during various stages of hypercapnia to analyze diameter changes in the insonated vessels by comparing differences in the vasomotor reactivity. METHODS Simultaneous Doppler recordings of 1 MCA and of a contralateral venous vessel thought to represent the sphenoparietal sinus (SPS) were carried out with a pair of 2-MHz range-gated transducers in 16 young healthy subjects during variations of end-tidal PaCO2. RESULTS During hypercapnia the mean blood flow velocity of the MCA rose from 62. 5+/-10.2 to a maximum of 99+/-12.2 cm/s (vasomotor reactivity of 60. 1+/-17.3%). The corresponding values in the SPS were significantly higher (P<0.001), revealing a rise from 17.8+/-5.7 to 34.9+/-14.3 cm/s (vasomotor reactivity of 91.4+/-25.9%). Exponential and linear regression analyses revealed an identical high correlation (r2=0.97 and 0.98 for the MCA and SPS, respectively). Slopes were 0.034+/-0. 01 on the arterial and 0.048+/-0.01 on the venous side. The CO2 reactivity (percentage per mm Hg, EtCO2) was found to be 4.5+/-1%/mm Hg in the MCA and 6.8+/-1.5%/mm Hg in the SPS. This difference indicates a vasodilation of the MCA in comparison to the venous vessel. CONCLUSIONS We have demonstrated a different reaction pattern between intracranial venous and arterial vessels related to end-tidal CO2. Relating the flow velocities to the square of the vessel diameter and assuming a global rise of CBF and not extensible sinus walls, our results indicate that the MCA undergoes a vasodilation of 9.5+/-7% in maximal hypercapnia.

[1]  R. Aaslid,et al.  Noninvasive transcranial Doppler ultrasound recording of flow velocity in basal cerebral arteries. , 1982, Journal of neurosurgery.

[2]  H. Kontos,et al.  Validity of cerebral arterial blood flow calculations from velocity measurements. , 1989, Stroke.

[3]  Local cerebral blood volume response to carbon dioxide in man , 1978 .

[4]  G. du Boulay,et al.  The anaesthetist's effect upon the cerebral arteries. , 1972, Proceedings of the Royal Society of Medicine.

[5]  R Gelfand,et al.  Relationship of 133Xe Cerebral Blood Flow to Middle Cerebral Arterial Flow Velocity in Men at Rest , 1996, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[6]  R. Aaslid,et al.  Dependency of Blood Flow Velocity in the Middle Cerebral Artery on End-Tidal Carbon Dioxide Partial Pressure—A Transcranial Ultrasound Doppler Study , 1984, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[7]  L Symon,et al.  A Study of Regional Autoregulation in the Cerebral Circulation to Increased Perfusion Pressure in Normocapnia and Hypercapnia , 1973, Stroke.

[8]  Dag I.K. Sjøberg,et al.  Variations in middle cerebral artery blood flow investigated with noninvasive transcranial blood velocity measurements. , 1987, Stroke.

[9]  K. Einhäupl,et al.  Venous Doppler Ultrasound Assessment of the Parasellar Region , 1998, Cerebrovascular Diseases.

[10]  C. Giller,et al.  Cerebral arterial diameters during changes in blood pressure and carbon dioxide during craniotomy. , 1993, Neurosurgery.

[11]  A L Rhoton,et al.  Microsurgical anatomy of the superficial veins of the cerebrum. , 1985, Neurosurgery.

[12]  J. Handa,et al.  Effect of contrast material, hypercapnia, hyperventilation, hypertonic glucose and papaverine on the diameter of the cerebral arteries. Angiographic determination in man. , 1967, Investigative radiology.

[13]  B. Widder,et al.  Doppler C02 and Diamox Test: Decreased Reliability by Changes of the Vessel Diameter? , 1995 .

[14]  M. Matsumoto,et al.  Reactivity of Cerebral Blood Flow to Carbon Dioxide in Various Types of Ischemic Cerebrovascular Disease: Evaluation by the Transcranial Doppler Method , 1993, Stroke.

[15]  H. Henkes,et al.  Blood Flow Velocity and Vasomotor Reactivity in Patients With Arteriovenous Malformations: A Transcranial Doppler Study , 1994, Stroke.

[16]  N L Browse,et al.  Transcranial Doppler measurement of middle cerebral artery blood flow velocity: a validation study. , 1986, Stroke.

[17]  M. Poulin,et al.  Indexes of flow and cross-sectional area of the middle cerebral artery using doppler ultrasound during hypoxia and hypercapnia in humans. , 1996, Stroke.

[18]  P A Schneider,et al.  Noninvasive assessment of CO2-induced cerebral vasomotor response in normal individuals and patients with internal carotid artery occlusions. , 1988, Stroke.

[19]  Rune Aaslid,et al.  Comparison of Flow and Velocity During Dynamic Autoregulation Testing in Humans , 1994, Stroke.

[20]  R G Gosling,et al.  Transcranial measurement of blood velocities in the basal cerebral arteries using pulsed Doppler ultrasound: velocity as an index of flow. , 1986, Ultrasound in medicine & biology.

[21]  H. Wollman,et al.  Effects of extremes of respiratory and metabolic alkalosis on cerebral blood flow in man. , 1968, Journal of applied physiology.