Chapter 68

### INTRODUCTION

Premedication refers to the administration of medication before the induction of anesthesia. These medications are neither part of the surgical patient’s usual medical regimen nor are they part of the anesthetic. They are given to reduce anxiety, control pain, decrease the risk of aspiration pneumonitis, and lower the incidence of postoperative nausea and vomiting. Perioperative beta-blockade and glucocorticoid supplementation are also considered premedication. Antimicrobial therapy for prevention of bacterial endocarditis is briefly reviewed. There are certainly other types of medication that can be given preoperatively, such as erythropoietin for anemia, but these are either not common or not considered the standard of practice.

### ANXIOLYTICS

Anxiety levels are typically high for patients presenting for surgery. Anxiety not only interferes with patient comfort, but also increases stress hormone production, gastric secretions, initial anesthetic requirements, and preoperative procedure difficulty (ie, intravenous placement). Children, in particular, may have high anxiety levels that can lead to lack of cooperation. Many centers withhold anxiety premedication out of concerns for reducing throughput, prolonging recovery room stay, and over sedation. None of these concerns have been validated with judicious administration of anxiolytics.

The classes of medications used for anxiolysis premedication include benzodiazepines and, less commonly, alpha-2 adrenergic agonists. Melatonin and ketamine are occasionally chosen for particularly uncooperative pediatric patients.

Less respiratory depression and hemodynamic effects occur with benzodiazepines compared to other sedative-hypnotic agents. Additionally, the amnestic effects are desirable in the preoperative setting. The three commonly used intravenous benzodiazepines are midazolam, Ativan, and diazepam. Midazolam has the fastest onset of action, has an inactive metabolite, and is well tolerated during parenteral administration. It has, therefore, become the predominant preoperative anxiolytic. In adults, a dose of 1-2 mg is typically sufficient for premedication.

Oral benzodiazepines have found a role in pediatric anesthesia, with liquid midazolam at a dose of 0.5 mg/kg typically producing sedation within 10 minutes. Oral diazepam in tablet form has a long history of use in adults. Consideration of an oral benzodiazepine prescription the night before or the morning of surgery is useful for the particularly anxious adult before they enter a surgical facility.

Clonidine and dexmedetomidine may have a role in reducing anxiety preoperatively and also have some anesthesia sparing effects. The hemodynamic side effects and longer duration of action of these drugs limit their clinical utility.

Ketamine as a premedication is reserved for children who need a deeper level of sedation than oral benzodiazepines may provide. Oral ketamine in a dose of 4-6 mg/kg is usually given in conjunction with oral midazolam and an anti-sialagogue. If this approach is considered too slow or if a child does not cooperate with oral medications, then ketamine 2-4 mg/kg may be given intramuscularly, although this may be painful and risks formation of aseptic abscesses.

Melatonin has recently seen more consideration as a preoperative sedative. ...

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