Among full-term, head-down babies, cord prolapse is quite rare, occurring in 0.4 percent. Among frank breech babies the incidence is 0.5 percent, among complete breeches 5 percent, and among footling breeches 15 percent.Head entrapment is caused by the failure of the fetal head to negotiate the maternal midpelvis. At full term, the fetal bitrochanteric diameter (the distance between the outer points of the hips) is about the same as the biparietal diameter (the transverse diameter of the skull)—simply put the size of the hips are the same as the size of the head. The relatively larger buttocks dilate the cervix as effectively as the head does in the typical head-down presentation. In contrast, the relative head size of a preterm baby is greater than the fetal buttocks. If the baby is preterm, it may be possible for the babys body to emerge while the cervix has not dilated enough for the head to emerge. Because the umbilical cord—the babys oxygen supply—is significantly compressed while the head is in the pelvis during a breech birth, it is important that the delivery of the aftercoming fetal head not be delayed. If the arm is extended alongside the head, delivery will not occur. If this occurs, the Løvset manoeuvre may be employed, or the arm may be manually brought to a position in front of the chest. The Løvset manoeuvre involves rotating the fetal body by holding the fetal pelvis.
Its use must be monitored by direct measurement of serum theophylline levels to avoid toxicity. It can also cause nausea, diarrhea, increase in heart rate, abnormal heart rhythms, and CNS excitation (headaches, insomnia, irritability, dizziness and lightheadedness). Seizures can also occur in severe cases of toxicity, and are considered to be a neurological emergency. Its toxicity is increased by erythromycin, cimetidine, and fluoroquinolones, such as ciprofloxacin. Some lipid-based formulations of theophylline can result in toxic theophylline levels when taken with fatty meals, an effect called dose dumping, but this does not occur with most formulations of theophylline. Theophylline toxicity can be treated with beta blockers. In addition to seizures, tachyarrhythmias are a major concern. Theophylline should not be used in combination with the SSRI fluvoxamine. Spectroscopy
UV-visible spectroscopy
Theophylline is soluble in 0.1N NaOH and absorbs maximally at 277 nm with an extinction coefficient of 10,200 (cm−1 M−1). Proton nuclear magnetic resonance spectroscopy (1H-NMR)
The characteristic signals, distinguishing theophylline from related methylxanthines, are approximately 3.23δ and 3.41δ, corresponding to the unique methylation possessed by theophylline. The remaining proton signal, at 8.01δ, corresponds to the proton on the imidazole ring, not transferred between the nitrogen. The transferred proton between the nitrogen is a variable proton and only exhibits a signal under certain conditions. Carbon nuclear magnetic resonance spectroscopy (13C-NMR)
The unique methylation of theophylline corresponds to the following signals: 27.7δ and 29.9δ. The remaining signals correspond to carbons characteristic of the xanthine backbone. Natural occurrences
Theophylline is naturally found in cocoa beans.