Barbiturates preanesthetic

Preanesthetic drugs may be omitted in those 60 years or older because many of the medical disorders for which these drugsare contraindicated are seen in older individuals For example, atropine and glycopyrrolate, drugs that can be used to decrease secretions of the upper respiratory tract, are contraindicated in certain medical disorders such as prostatic hypertrophy, glaucoma, and myocardial ischemia. Other preanesthetic drugs that depress the central nervous astern (CN, such as narcotics barbiturates and antianxiety drugs with or without antiemetic properties may be contraindicated in the older individual. 

The preanesthetic drug is usually selected by the anesthesiologist and may consist of one or more drug (Table 35-2). A narcotic (see Chap. 19), antianxiety drug (see Chap. 30), or barbiturate (see Chap. 26) may be given to... 

Hypnotic Short-term treatment of insomnia, because barbiturates appear to lose their effectiveness in sleep induction and maintenance after 2 weeks. If insomnia persists, seek alternative therapy (including nondrug) for chronic insomnia. Preanesthetic Used as preanesthetic sedatives. 

Recovery is sufficiently rapid with most intravenous drugs to permit their use for short ambulatory (outpatient) surgical procedures. In the case of propofol, recovery times are similar to those seen with sevoflurane and desflurane. Although most intravenous anesthetics lack antinociceptive (analgesic) properties, their potency is adequate for short superficial surgical procedures when combined with nitrous oxide or local anesthetics, or both. Adjunctive use of potent opioids (eg, fentanyl, sufentanil or remifentanil see Chapter 31) contributes to improved cardiovascular stability, enhanced sedation, and perioperative analgesia. However, opioid compounds also enhance the ventilatory depressant effects of the intravenous agents and increase postoperative emesis. Benzodiazepines (eg, midazolam, diazepam) have a slower onset and slower recovery than the barbiturates or propofol and are rarely used for induction of anesthesia. However, preanesthetic administration of benzodiazepines (eg, midazolam) can be used to provide anxiolysis, sedation, and amnesia when used as part of an inhalational, intravenous, or balanced anesthetic technique. 

Barbiturates, such as mephobarbital (Mebaral) and sodium pentobarbital (Nembutal), are used as preanesthetics, promoting sleep. 

In contrast to the barbiturates, benzodiazepines do not produce an anesthetized state. They may be used as a preanesthetic in order to lessen anxiety, to be followed by a barbiturate and then the general anesthesia gas such as halothane. 

Amobarbital, a barbiturate, is used as a sedative to treat insomnia and as a preanesthetic medication. The barbiturates were used extensively in the past as hypnotic-sedatives but have been replaced by the much safer benzodiazepine derivatives (see Table 9). They do continue to be used as anesthetics (e.g., thiopental) and anticonvulsants (e.g., phenobarbital). The primary mechanism of action of barbiturates is to increase inhibition through the gamma-aminobutyric acid (GABA) system (see Figure 50). Anesthetic barbiturates also decrease excitation via a decrease in calcium conductance. The most commonly used barbiturates are thiopental (Pentothal), methohexital (Brevital), secobarbital (Seconal), pentobarbital (Nembutal), amobarbital (Amytal), and phenobarbital (Luminal). 

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