engleski

Effect of cocaine administration on fetal hemodynamics, oxygenation and growth.

Cocaine increases uterine contractility and may cause premature labor and delivery, as well as increased risk of abruptio placentae. Cocaine also increases concentration of catecholamines in placenta, which results with placental vasoconstriction and decreased placental perfusion. This can also be one of the reasons for premature labor. On the other hand, decreased placental blood flow causes disturbance in nutrients and oxygen transfer to the fetus, leading to disturbance in fetal growth. It can be expressed in fetal body parts asymetry, decreased body weight or disturbed development of certain organs. Direct consequence of oxygen transfer disturbance is decrease in partial pressure of oxygen (pO_2), called FETAL HYPOXIA. It has been shown that long-term exposure to cocaine in experimental model causes moderate chronic hypoxia. In normal fetus, the cardiovascular response to hypoxia consists in a heart rate (HR) increase and cerebral vasodilatation. That results with redistribution of fetal blood flow, toward brain. This adaptation can be measured by Color Doppler ultrasound. This is a non-invasive method that shows us cerebro-umbilical ratio (C/U=CRI/URI), ratio between cerebral and umbilical vascular resistance index and is the best way of following fetal blood flow redistribution. Problem is that increased brain perfusion, if present for a longer period, causes brain edema which is first step in development of brain ischemic lesions. Cocaine also affects directly the fetal neurones, through the important role of monoamines in neural differentiation. Results are specific changes in structure and functions of neurones. They, together with brain lesions, cause severe disorders in persons neurological and psychological functions, which express in different forms. Several studies have reported that cocaine passes rapidly into the fetal circulation from the maternal bloodstream, causing intracranial vasoconstriction and decreased cerebral blood flow. These events could lead to cerebral ischemic injuries. But, the latest experiments showed opposite results. They showed that there is no cocaine vasoconstrictive effect at the brain level and that fetus can still adapt to moderate hypoxia. If long term exposure to cocaine can induce chronic hypoxia, one may expect an increase of the brain perfusion in the case of acute hypoxia. On the contrary, experiments showed that fetuses under long-term cocaine exposure have reduced capability of the cerebral vessels to vasodilatate and heart rate to increase during acute hypoxia. This leads us to conclusion that cocaine and chronic hypoxia can cause the loss of reactivity in cerebral blood vessels, making them unable to respond and adapt to further hypoxia, which will result in disfunction of the brain and other organs. CONCLUSION Cocaine passes easily through placenta and causes fetal blood flow disorders, hypoxia, and it also reduces the capability of the cerebral vessels to vasodilatate during acute hypoxia. All these cocaine effects are interrelated and can result with several neurological and psyhological disorders. Therefore cocaine is very harmful for the baby.

nije evidentirano

nije evidentirano