Significant Reduction In Cerebral Blood Flow Research Articles

Cerebral blood flow and cerebral oxygen consumption in patients with COPD on mechanical ventilation.

To investigate the effect of PaCO2 on cerebral blood flow (CBF) in chronic obstructive pulmonary disease (COPD). Before-after trial. General ICU in a regional hospital. 7 patients undergoing mechanical ventilation because of an exacerbation of COPD. CBF and cerebral metabolic rate of oxygen (CMRO2) of COPD were measured before and after hyperventilation and were compared by those of normal patients. CBF was measured by the Kety-Schmidt technique using 15% N2O. Hyperventilation produced a significant reduction in CBF in COPD with no concomitant change in CMRO2. CMRO2 in COPD was significantly lower than those in normal patients. The regression equation was shifted significantly more to the right in COPD. The sensitivity of CBF in CO2 remained but CMRO2 was reduced markedly in COPD patients.

Effect of Dexmedetomidine, a Selective and Potent ??2-Agonist, on Cerebral Blood Flow and Oxygen Consumption During Halothane Anesthesia in Dogs

The effect of the alpha 2-agonist dexmedetomidine on the cerebral blood flow (CBF) and the metabolic rate for oxygen was studied by a sagittal sinus outflow technique in dogs during halothane anesthesia. Dexmedetomidine was given in a dose (10 micrograms/kg) reported to reduce the anesthetic requirement of halothane by 90%. During 0.9% halothane anesthesia dexmedetomidine caused a significant reduction in CBF without influencing the metabolic rate for oxygen. Reducing the halothane concentration to 0.1% caused no further change in CBF, but increased the metabolic rate for oxygen 19%. The cerebral vasoconstrictive effect, combined with the 90% reduction in MAC for halothane, indicates that dexmedetomidine might be a useful adjunct to inhalation anesthetics during neurosurgery in situations where an increase in CBF should be avoided.

The effect of indomethacin on cerebral blood-flow velocity in premature infants.

The prostaglandin synthetase inhibitor indomethacin is known to cause significant reduction in cerebral blood-flow (CBF) in certain newborn animals. The authors studied the effect of indomethacin on the CBF velocity of small premature infants, using duplex Doppler real-time ultrasound, and made a record of blood pressure (BP) and heart rate. Indomethacin was infused intravenously in five infants. Repeated measurements were made from the anterior cerebral artery for one hour after injection. There was a significant reduction in mean blood-flow velocity of 40 per cent two minutes after the injection, and it remained 35 per cent below pre-dose levels for at least one hour. There was a simultaneous rise of 15 per cent in systemic BP by one minute after injection. It is argued that these these changes represent a significant reduction in CBF, and this may increase the likelihood of border-zone ischaemic infarction in ill premature infants with pre-existing critical cerebral perfusion.

Caffeine consumption, withdrawal and cerebral blood flow.

SYNOPSISRegional cerebral blood flow (CBF) measurements were conducted under resting conditions and after twenty‐four hours of caffeine abstinence in groups of high and low caffeine users. CBF was also measured thirty minutes after the oral administration of 250 rag. of caffeine in the high caffeine users and after a placebo in the low caffeine users. Caffeine administration was associated with significant CBF reduction and caffeine abstinence with significant frontal flow increases in the high caffeine group. The low caffeine group showed no differences between the resting, post‐placebo and post‐caffeine abstinence CBF values.

The effects of high dose mannitol on cerebral blood flow in dogs with normal intracranial pressure.

In normal dogs, bolus administration of a very high dose of mannitol (2 gm/kg) resulted in a small, transient increase in cerebral blood flow (CBF) of approximately 8 percent lasting less than 10 minutes followed by a significant reduction in CBF of approximately 20 percent lasting at least three hours. The increase in CBF may in part be related to changes in cardiovascular and hematological parameters. No explanation is available for the reduction below control values but, since urine losses were not replace in these animals, changes in the state of hydration may have been responsible. It appears that the increase in CBF resulting from mannitol administered by bolus infusion are of neither sufficient magnitude nor duration to explain the protective effect observed in other studies where cerebral blood flow was reduced below ischemic levels. This suggests then, that either the effect of mannitol on CBF is quantitatively different when flow is reduced to critical levels or that the protective effect observed when the cerebral circulation is compromised is based upon a different mechanism than augmentation of flow. Further studies on the effect of mannitol on CBF in ischemic situations, where the cerebral circulation is compromised, are required.

Comparison of effects on cerebral blood flow of rapid reduction in systemic arterial pressure by diazoxide and labetalol in hypertensive patients: preliminary findings.

1 Diazoxide 300 mg and labetalol 150 mg were each injected intravenously on separate occasions into five patients with essentail hypertension. The reduction in BP caused by labetalol was slightly greater than that produced by diazoxide. 2 In contrast the reduction in cerebral blood flow (CBF) by labetalol was not statistically significant, whereas diazoxide gave a greater and statistically significant reduction in CBF. 3 These observations suggest that labetalol may have an advantage over diazoxide for the rapid reduction in BP.

Variations in mean cerebral blood flow under anesthesia at rest and during cortical activation.

More than one cerebral blood flow (CBF) measurement was performed on the same occasion in three groups of patients using the intracarotid 133Xenon technique. In the anesthetized group there was a highly significant reduction in CBF (mean = 24.3%) from the first to the second measurement. In those at rest under local anesthesia there was also a significant fall (mean 9.8%). The third group, who were stimulated during the second estimation, showed no change. A second CBF determination some time after beginning a study is recommended, especially in pharmacological studies, to provide a more reliable resting control, rather than the first value which represents flow in an "activated" brain which has not yet adapted fully to its new environment.