Placental Drug transfer ...The safety features

Transfer of drugs from mother to fetus takes place at the level of the placenta mainly by diffusion.

Thus, keeping maternal blood levels of drugs as low as possible is a major strategy for decreasing the amount of drug that reaches the fetus.

In addition, since 75% of the blood in the umbilical vein travels to the liver, a large portion of drug can be metabolized before reaching vital fetal organs.

Drug in the unbilical vein that travels via the ductus venosus to access the inferior vena cava will be diluted with blood from the lower extremities (which has no drug) and this further reduces concentration of drugs inthe fetal blood.

Two things work against this "safety feature":

(1) fetal acidosis during times of distress causes increased perfusion of the heart and brain and thus increases delivery of drug to these important organs.

(2) Fetal pH is lower than maternal pH and results in basic drugs (such as local anesthestics) becoming more ionized when they reach fetal circulation. This effectively traps them on the fetal side of the circulation since ionized molecules cannot easily cross the placenta. This also maintains a gradient for diffusion.

This is known as "ion trapping" and can be quite a significant effect especially during times of fetal distress (pH gets even lower).

Comments

Falling from Height...The Prognostic factors

Falls from Height is Knwon to cause major morbidities and mortalities. There are several prognostic factors for survival that have been identified: Height Age Type of surface Body part that touches the ground first Two other factors are important, but do not have a significant effect on mortality: Circumstances of the fall (suicide, accident, escape) Initial impact with an object before impacting the ground Height . Overall, about half of victims die at the scene, and a total of 70% die before they reach the hospital . The median height leading to death is about 49 feet, or about 4 to 5 storeys. 100% of victims die after falling 85 feet, or about 8 storeys. Age . Mortality increases with age due to pre-existing medical conditions and decreased physiologic reserve. Type of surface . The type of surface struck (i.e. grass, water, construction debris) can also have an effect on secondary injuries and survival. Mortality after striking a hard surface is nearly doubl...

power injectable peripherally inserted central catheters

Clinical experience with power injectable peripherally inserted central catheters in intensive care patients Introduction In intensive care units (ICU), peripherally inserted central catheters (PICC) may be an alternative option to standard central venous catheters, particularly in patients with coagulation disorders or at high risk for infection. Some limits of PICCs (such as low flow rates) may be overcome by the use of power-injectable catheters . Method We have retrospectively reviewed all the power injectable PICCs inserted in adult and pediatric patients in the ICU during a 12-month period, focusing on the rate of complications at insertion and during maintenance. Results We have collected 89 power injectable PICCs (in adults and in children), both multiple and single lumen. All insertions were successful. There were no major complications at insertion and no episodes of catheter-related blood stream infection. Non-infective complications ...

The 12 decision making steps for post dural puncture headache treatment

Treatment decision-making algorithm for postdural puncture headache. 1. When diagnosis is made, all patients should receive supportive measures (reassurance, bed rest, analgesics, hydration, quiet environment). 2. Severity of symptoms should be classified using VAS scale (mild 1–3, moderate 4–6, severe 7–10). 3. Virtually all patients will improve in time even without additional therapy. (dashed lines) 4. Symptoms worsen or fail to resolve within 5 days. 5. Patient preference dictates the choice between pharmacologic (less effective) and epidural blood patch (EBP). 6. In patients with severe symptoms, EBP is strongly suggested. 7. The most common pharmacologic measure is caffeine prescription. 8. The failure, worsening, or recurrence of symptoms after pharmacologic measures favors the use of EBP. 9. In addition to EBP, other epidural treatment options can be considered in select patients (eg, dextran , saline). 10. A period of 24 h should lapse before repeating EBP. 11...

sedationstation

Search This Blog