Pulsatility index

Dv, diastolic velocity LMCA, left middle cerebral artery Mv, mean velocity PI, pulsatility index Rl, resistance index Sv, systolic velocity. 

Age-dependent, receptor-mediated drug effects have been observed with dopamine. The effect of dopamine on blood flow (estimated by measuring the pulsatility index by ultrasonography) was assessed in the right renal, superior mesenteric, and middle cerebral arteries in sick premature infants (52). Renal blood flow increased during the dopamine infusion, but mesenteric and cerebral blood flow were not altered. In adults, dopamine does increase blood flow to the intestine, indicating that the lack of response in preterm neonates is related to the immaturity of the mesenteric vascular bed. 

The hemodynamic effects of ritodrine have been assessed in 12 fetuses by cardiac and extracardiac Doppler sonography (1). Ritodrine significantly increased maternal and fetal heart rates, left cardiac stroke volume, and cardiac output. There was also an increase in the pulsatility index of the middle cerebral artery and a fall in the pulsatility index of the umbilical artery during ritodrine infusion. The authors suggested that ritodrine vasodilates fetal vessels in the placenta. 

Penotti, M. E. Fabio A.B. Modena M. Rinaldi U. Omodei P. Vigano. Effect of soy-derived iso-flavones on hot flushes, endometrial thickness, and the pulsatility index of the uterine and cerebral arteries. Pertil. Steril. 2003, 79, 1112-1117. 

Czosnyka, M., Pickard, J., Whitehouse, H. E., and Richards, H. K. (1996) Relationship between transcranial Doppler-determined pulsatility index and cerebrovascular resistance an experimental study. J. Neurosurg. 84, 79-84. 

Flow rate. The flow rate from the pump should be accurate, regardless of the system in which the pump is used. This means that the flow rate actually produced by the pump is the same as that dialled up on the front panel, and that this should not be affected by the rest of the HPLC system (for constant flow pumps, at least). The flow rate should be reproducible and practically free of pulsations. Pulsatile flow can limit the sensitivity of HPLC assays, resulting in a rhythmic variation in the apparent refractive index of the mobile phase flowing through the detector, which ultimately manifests itself in the chromatogram as baseline noise. Various means are employed to attempt to eliminate flow pulsation (see section 5.3). 

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