By color Doppler ultrasonography, blood flow velocity in the anterior cerebral artery (ACA), basilar artery (BA) and internal cerebral vein (ICV) was measured serially in neonates with intracranial hematoma. In a neonate with a supratentorial subdural hematoma exceeding 16% of cranial volume (patient 1), preoperative Doppler study showed a decreased mean peak flow velocity (ACA: 7 cm/s and BA: 23 cm/s) and an endodiastolic retrograde flow pattern both in ACA and BA, and no blood flow in ICV. Postoperative studies revealed transient hyperemia with a high endodiastolic peak flow velocity in ACA and BA and a continuous flowpattern in ICV. In neonates with intracerebral hematoma with a 7.9% (patient 2) and 8.6% (patient 3) cranial volume, preoperative Doppler studies showed the mean peak flow velocity in ACA and BA respectively to be 35 and 63 cm/s in patient 2 and 28 and 32 cm/s in patient 3, while the resistance index in ACA and BA respectively was 0.80 and 0.80 in patient 2 and 0.72 and 0.80 in patient 3. Postoperative studies 3 days after surgery showed increased mean peak flow velocities and a decreased resistance index both in ACA and BA. Continuous flow pattern in ICV was detected before and after surgery in both patients. Functional outcome was satisfactory in all patients. Perioperative hemodynamic changes in infants with intracranial mass lesions can be reflected in changes in blood flow velocities in basal cerebral vessels. Evaluation of cerebral hemodynamic changes by color Doppler ultrasonography provides valuable information for the selection of treatment modalities and postoperative management.
To examine the effect of changes in temperature on the cerebral circulation during the rewarming period of cardiopulmonary bypass (CPB), we measured blood flow velocity in the middle cerebral artery by transcranial Doppler ultrasound (TCD) and the arteriovenous oxygen content difference (a-vDO2) by intermittent sampling from the jugular venous bulb during cardiac surgery in 11 patients (mean age±SD: 55.4±10.0 years) . The mean blood flow velocity was 43.5±16.9cm/s in the pre-rewarming period and 50.9±19.5cm/s during rewarming, thereby indicating a significant increase during rewarming (P<0.05) . In addition, a-vDO2was 1.74±1.00 vol.% in the pre-rewarming period and 3.09±1.24 vol.% during rewarming, showing a significant increase during rewarming (P<0.01) . This widening of a-vDO2suggests that oxygen demand was excessive relative to oxygen supply despite the increase in cerebral blood flow. We concluded that rewarming alters the cerebral circulation rapidly and may increase the risk of unbalanced cerebral oxygenation. Rapid evaluation of the cerebral circulation may be necessary during specific periods of CPB such as rewarming.
We investigated changes in thin layer thickness between the skull and the brain in association with changes in intracranial pressure (ICP) in human subjects using our ultrasound (UT) system. A thin-disc-type prototype probe (5 MHz) was attached to the supra-auricular areas of seven adult volunteers. ICP was varied by changing posture between the sitting and supine positions, and Valsalva's maneuver, or neck compression in the supine position. Our UT system was triggered at 200 msec after the peak time of R wave on the ECG. The interference echoes from the thin layer were clearly visualized utilizing our revised algorithm of FFT-Cepstrum analysis with the maximum entropy method. The thickness of the thin layer in the supine or sitting position decreased significantly during Valsalva's maneuver or neck compression in the supine position (Wilcoxon U test, p<0.05) . The thickness of the thin layer was quite similar to that of the dura mater. The reproducibility of the data was confirmed using theKolmogorov-Smirnov test. Our ultrasound system for ICP measurement appears to be useful for estimating changes in ICP levels of human subjects.