Cerebral Blood Flow Velocity In Patients Research Articles

Cerebral blood flow velocity and oxygenation in neonatal aortic arch repair at two perfusion temperatures.

(i) To monitor cerebral blood flow velocity (CBFv) throughout aortic arch repair surgery and during the recovery period. (ii) To examine the relationship between transcranial doppler ultrasound (TCD) and near-infrared spectroscopy (NIRS) during cardiac surgery. (iii) To examine CBFv in patients cooled to 20°C and 25°C. During aortic arch repair and after surgery, measurements of TCD, NIRS, blood pH, pO2, pCO2, HCO3, lactate, Hb, haematocrit (%) and temperature (core and rectal) were recorded in 24 neonates. General linear mixed models were used to examine differences over time and between two cooling temperatures. Repeated measures correlations were used to determine the relationship between TCD and NIRS. CBFv changed during arch repair (main effect of time: P = 0.001). During cooling, CBFv increased by 10.0 cm/s (5.97, 17.7) compared to normothermia (P = 0.019). Once recovering in paediatric intensive care unit (PICU), CBFv had increased from the preoperative measurement by 6.2 cm/s (0.21, 13.4; P = 0.045). CBFv changes were similar between patients cooled to 20°C and 25°C (main effect of temperature: P = 0.22). Repeated measures correlations (rmcorr) identified a statistically significant but weak positive correlation between CBFv and NIRS (r = 0.25, P≤0.001). Our data suggested that CBFv changed throughout aortic arch repair and was higher during the cooling period. A weak relationship was found between NIRS and TCD. Overall, these findings could provide clinicians with information on how to optimise long-term cerebrovascular health.

Neurally adjusted ventilatory assist preserves cerebral blood flow velocity in patients recovering from acute brain injury

Neurally adjusted ventilatory assist (NAVA) has never been applied in patients recovering from acute brain injury (ABI) because neural respiratory drive could be affected by intracranial disease with detrimental effects on cerebral blood flow (CBF) velocity. Our primary aim was to assess the impact of NAVA and pressure support ventilation (PSV) on CBF velocity. In fifteen adult patients recovering from ABI and undergoing invasive assisted ventilation, PSV and NAVA were applied over 30-min-lasting trials, in the following sequence: PSV1, NAVA, and PSV2. While PSV was set to deliver a tidal volume ranging between 6 and 8 ml kg−1 of predicted body weight, in NAVA the level of assistance was chosen to achieve the same inspiratory peak airway pressure as PSV. At the end of each trial, a sonographic evaluation of CBF mean velocity was bilaterally obtained on the middle cerebral artery and an arterial blood gas sample was taken for analysis. CBF mean velocity was 51.8 [41.9,75.2] cm s−1 at baseline, 51.9 [43.4,71.0] cm s−1 in PSV1, 53.6 [40.7,67.7] cm s−1 in NAVA, and 49.5 [42.1,70.8] cm s−1 in PSV2 (p = 0.0514) on the left and 50.2 [38.0,77.7] cm s−1 at baseline, 47.8 [41.7,68.2] cm s−1 in PSV1, 53.9 [40.1,78.5] cm s−1 in NAVA, and 55.6 [35.9,74.1] cm s−1 in PSV2 (p = 0.8240) on the right side. No differences were detected for pH (p = 0.0551), arterial carbon dioxide tension (p = 0.8142), and oxygenation (p = 0.0928) over the entire study duration. NAVA and PSV preserved CBF velocity in patients recovering from ABI.Trial registration: The present trial was prospectively registered at www.clinicatrials.gov (NCT03721354) on October 18th, 2018.Electronic supplementary materialThe online version of this article (10.1007/s10877-020-00523-w) contains supplementary material, which is available to authorized users.

Cerebral Blood Flow Velocities Measured by Transcranial Doppler Ultrasonography in Children with Sickle Cell Disease in Africa.

Background: Sickle cell anemia (SCA) is one of the commonest monogenic disorders, with 90% of the world's population living in sub-Saharan Africa. Cerebrovascular accident (CVA) is a major cause of morbidity, but its clinical prediction in resource rich countries has allowed effective primary and secondary prevention. Measurements of time-averaged maximum of the mean (TAMM) cerebral blood flow velocity (CBFv) in the internal carotid/middle cerebral (ICA/MCA) arteries by Transcranial Doppler (TCD) ultrasonography and of mean overnight oxyhemoglobin saturation (SpO2) have been useful in predicting CVA. The criteria used in Western populations may not be appropriate to children living in Africa.Aims: The aims of this study were to evaluate the TAMM CBFv in patients with SCA in Kilifi district hospital, Kenya, to assess risk factors associated with high ICA/MCA TAMM CBFv and to examine any association with neurological complications.Study design: This was a cross sectional descriptive study, where TCD ultrasonography was performed on all SCA patients attending the outpatient clinic at CGMR-C, Kilifi, Kenya in 2002. Previous data from 1990 and follow-up data from 2004 were included.Results: In 140 patients with SCA, aged 3 months to 16 years, the median ICA/MCA TAMM CBFv was 116cm/sec (SD 38, range 0–219 cms/s) compared with 97 (SD 24, range 46–190) cm/sec in 142 controls aged 2 months to 14 years (p=0.0001). 28 SCA patients (20%) had TAMM CBFv greater than and 16 (11%) had TAMM CBFv less than 2 standard deviations from the mean for controls in one or both ICA/MCA's, but only seven (5%) had a velocity above 170 cm/sec (one >200cm/sec), with the highest proportion of patients aged between 5–9 years (p=0.02). In only two of the patients with low velocities, both with previous CVA, was there no ultrasound signal from either side. 45 (32%) SCA patients had a second TCD after 2 years (two after 14 years). Of the 21 restudied who had high TAMM CBFv at baseline, 14 remained high and 2 became low. Of the 15 restudied who had low TAMM CBFv at baseline, 14 remained low and none became high. Patients with abnormal TCD had lower daytime SpO2 oxygen saturation (p=0.01) and hematocrit (p=0.05). Abnormal TCD was also associated with lower haemoglobin level, red blood cell count and higher white cell count, but not significantly. Neurological abnormalities included history of convulsions in 25 (18%) and history of CVA in 5 (4%). Of those with CVA, maximum TAMM CBFv on either side were 157, 156, 108, 0 and 0; the last patient subsequently died. Three patients who had convulsions in the interim attended for follow-up TCD; compared with those without seizures there was a trend for a greater increase in TAMM CBFv in these patients (p=0.06).Conclusion: Compared with the developed world, in Africa a smaller proportion of patients with SCA have conditional or abnormal TCDs or CVA, although convulsions are common. The proportion of those with low velocities, perhaps due to ICA/MCA occlusion with moyamoya, may increase with time. Further population-based studies in a birth cohort will determine whether cerebrovascular disease is rare or lethal and, together with imaging and neuropsychology, will establish whether abnormal TCD predicts neurological events in Africa.

Spontaneous oscillations in cerebral blood flow velocities in middle cerebral arteries in control subjects and patients with epilepsy.

Cardiac arrhythmias mediated by the sympathetic nervous system have been implicated in sudden, unexplained deaths in patients with epilepsy. Cerebral blood flow velocities (CBFV) as measured by transcranial Doppler are characterized by slow spontaneous oscillations in part attributed to changes in sympathetic activity (M waves, 3 to 9 cycles per minute) and to discharges of monoaminergic neurons in the brain stem (B waves, 0.5 to 2 cycles per minute). This study was designed to compare spontaneous fluctuations of CBFV in patients with epilepsy with those in normal control subjects. Simultaneous registrations of scalp electroencephalograms, with electrodes placed according to the 10-20 System, and transcranial Doppler recordings of both middle cerebral arteries were performed in 27 patients (9 with primary generalized epilepsy, 18 with focal epilepsy). Data analysis of CBFV was based on the envelope curves of the Doppler spectrum. A fast Fourier transformation over the 20-minute CBFV curve was performed, and the amplitudes of B and M waves were calculated and compared with those in 20 normal, age-matched control subjects. While the amplitudes of the B waves in both groups were similar, patients with epilepsy showed significantly increased M waves. Patients with focal epilepsy did not present asymmetries between the normal hemisphere and the side of the epileptic focus with respect to both M and B waves. Enhanced M waves in epileptic patients may reflect increased sympathetic activity even in the absence of seizures. This study provides further evidence for an autonomic dysfunction as a possible mechanism for sudden unexplained death in patients with epilepsy.

Sleep Apnea Syndrome and Cerebral Hemodynamics

The dynamics of cerebral blood flow velocity (CBFV) during sleep were investigated in the right middle cerebral artery of 10 patients with sleep apnea syndrome (SAS) (mean age, 37 years) and 10 healthy control subjects (mean age, 32 years) throughout the entire sleep period. A computer-assisted pulsed (2 MHz) transcranial Doppler ultrasonography system was modified for continuous long-term and on-line recording of cerebral hemodynamics. Concurrently, simultaneous polysomnography, continuous BP recordings, and measurement of the end-expiratory carbon dioxide were undertaken. CBFV showed comparable nocturnal profiles in both groups with decreases during non-rapid eye movement (NREM) sleep and increases during rapid eye movement (REM) sleep, indicating that the general pattern of brain perfusion during normal sleep is maintained in SAS. Sleep stage changes were not regularly accompanied by corresponding changes in CBFV. This reflected a quantitative uncoupling between cerebral electrical activity and cerebral perfusion during sleep and indicated a dissociation in the activity of central regulatory mechanisms. Sleep stage-related analysis showed slightly reduced CBFV in patients with SAS compared with healthy control subjects during wakefulness and the first NREM sleep period, suggesting depressed brain activity in the patient group. The higher CBFV values observed in patients with SAS compared with control subjects during REM sleep and sleep stage 2, both preceding and following REM sleep, underline the influence of dynamically changing sleep patterns on cerebral perfusion in these patients. Reproducible rapid decreases in CBFV were related to EEG arousals. Since apneas are terminated by arousals, these results showed that direct neuronal influences on brain perfusion during apnea are evident.