Barbiturate overdose is poisoning due to excessive doses of barbiturates. Symptoms typically include difficulty thinking, poor coordination, decreased level of consciousness, and a decreased effort to breathe (respiratory depression). Complications of overdose can include noncardiogenic pulmonary edema. If death occurs this is typically due to a lack of breathing.Barbiturate overdose may occur by accident or purposefully in an attempt to cause death. The toxic effects are additive to those of alcohol and benzodiazepines. The lethal dose varies with a persons tolerance and how the drug is taken. The effects of barbiturates occur via the GABA neurotransmitter. Exposure may be verified by testing the urine or blood.Treatment involves supporting a persons breathing and blood pressure. While there is no antidote, activated charcoal may be useful. Multiple doses of charcoal may be required. Hemodialysis may occasionally be considered. Urine alkalinisation has not been found to be useful. While once a common cause of overdose, barbiturates are now a rare cause. Mechanism
Barbiturates increase the time that the chloride pore of the GABAA receptor is opened, thereby increasing the efficacy of GABA. In contrast, benzodiazepines increase the frequency with which the chloride pore is opened, thereby increasing GABAs potency. Treatment
Treatment involves supporting a persons breathing and blood pressure. While there is no antidote, activated charcoal may be useful. Multiple doses of charcoal may be required. Hemodialysis may occasionally be considered.
Perforation of steel strips is used in the manufacture of some zesters and rasps. Historically, perforation patterns other than linear were used to mark stamps. A series of patents had been issued in the late 19th century for perforation machines to be used on rail lines for ticketing. Libraries and private collections used similar perforating stamps to mark ownership of books. End sheets, title pages, and image plates were punched with the namesake of the collection. Today, similarly elaborate perforation patterns continue to be used in orienteering. Bread bags for some bread often have micro-perforations in the plastic, which is supposed to keep the bread fresh by releasing excess moisture. Similarly, bags of concrete use small perforations to allow air to escape while they are being filled. See also
Film perforations
Punched tape


== References ==