Induction agents used

Rapid recovery and its antiemetic properties make propofol anesthesia very popular as an induction agent for outpatient anesthesia. Propofol can also be used to supplement inhalational anesthesia in longer procedures. Both continuous infusion of propofol for conscious sedation and with opioids for the maintenance of anesthesia for cardiac surgery are acceptable techniques. 

A most important advantage of ketamine over other anesthetic agents is its potential for administration by the IM route. This is particularly useful in anesthetizing children, since anesthesia can be induced relatively quickly in a child who resists an inhalation induction or the insertion of an IV line. Ketamine has a limited but useful role as an IM induction agent and in pediatrics. 

There is good evidence that propofol exerts an anti-emetic effect. The mechanism of this is unclear, but animal studies have shown that it may involve depleting the area postrema of serotonin as well as direct GABA-mediated inhibition, or inhibition of dopamine release in the brain. This probably requires a plasma concentration of over 350 ng-mL-1, and therefore will be seen when propofol is used as an induction agent for very short cases, or when it is used as an infusion in longer cases. Nitrous oxide... 

Barbiturates reduce hepatic blood flow and glomerular filtration rate, but these drugs produce no adverse effects on hepatic or renal function. Barbiturates can exacerbate acute intermittent porphyria by inducing the production of hepatic ct -aminolevulinic acid (ALA) synthase (see Chapter 22). On rare occasions, thiopental has precipitated porphyric crisis when used as an induction agent in susceptible patients. 

Jackson WL Jr. Should we use etomidate as an induction agent for endotracheal intubation in patients with septic shock A critical appraisal. Chest 2005 127 1031-8. 

Eger El, 2nd. Characteristics of anesthetic agents used for induction and maintenance of general anesthesia. Am J Health Syst Pharm. 2004 61(suppl 4) S3-S10. 

The rapid-acting barbiturates, such as methohexital (Brevital), are used as intravenous anesthetics/induction agents. Advantages are rapid anesthesia and short duration of action. A disadvantage is respiratory suppression with higher doses. 

Prostaglandin E2 (PGE2) is an agent used to ripen the cervix for the induction of labor (it is also used for second-trimester abortion) and shows various beneficial effects ... 

By one year post liver transplant both CYP expression and activity are similar to those of normal subjects [67]. Some interesting effects are observed in the first six months after transplant, but some may be due to the induction of specific enzymes by therapeutic agents used in this period. The observation of a tenfold increase in hepatic CYP3A4 content at ten days which then returns to normal at six months is probably due to the administration of prednisolone in the early postoperative period [69]. Other observations are more difficult to explain. An eightfold increase in CYP2E1 as measured by the chlorzoxazone metabolic ratio has been detected in the first month post transplant [70]. CYP2E1-mediated NAPQI formation from paracetamol is also increased by around 137% and 81% on days two and ten post transplant, and returns to normal after six months [71]. 

Disadvantages. Ketamine produces no muscular relaxation. It increases intracranial and intraocular pressure. Hallucinations can occur during recovery (the emergence reaction), but they are minimised if ketamine is used solely as an induction agent and followed by a conventional inhalational anaesthetic. Their incidence is reduced by administration of a benzodiazepine both as a premedication and after the procedure. 

Ketamine relaxes smooth muscles in the airways and may therefore be a useful induction agent in children with asthma (6). If endotracheal intubation is required, lidocaine 1-2 mg/kg intravenously before intubation has been recommended, although the use of a laryngeal mask airway may be more appropriate. When used in combination with midazolam by infusion, ketamine provides analgesia and prevents and relieves bronchospasm (7). 

Propofol is a short-acting intravenous induction agent, which is dissolved in a mixture of long-chain triglycerides and soya bean emulsion. It is now in general use in daycare anesthesia and is being increasingly used in infusions in intensive care units. Recovery from anesthetic doses compares favorably with that after enflurane and isoflurane (1). 

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