Preoperative Medication: Sedative Hypnotics and Other Agents and Issues

⁴Special issues -- preoperative medication differences between adult and pediatric patients 

• ⁴Overview:

  •  Review of the general rationale for the use of sedative-hypnotic drugs:

    1. Reduce anxiety

    2. Produce sedation/amnesia

    3. Promote soon as anesthesia induction by inhalational methods

  • Use of preoperative agents in pediatric patients may not be completely successful in as high as 20% of cases. 

    • Preoperative agent use has not been shown to decrease adverse psychological postsurgical consequences. 

  • After about six months-one-year of age, administration of a sedative-hypnotic agent may be beneficial to the patient.

    •  Probably, intramuscular injection should be avoided, with the older child preferentially receiving drugs orally and children in the preschool age group receiving drugs rectally.

• ⁴Sedative-hypnotics

  • Midazolam (Versed) [may be given intramuscularly, 0.2 mg/kg, if necessary] is given by the preferred oral route  following mixing of 0.5-0.75 mg/kg of the drug with a flavored agent such as syrup, cola, or fruit juice to mask the bitter-tasting drug.

    • Time to onset: sedation (not sleep) should be observed  in about 15 minutes with a duration of action of about 30-60 minutes.

  • Oral ketamine (Ketalar): 20-30 minutes before induction, oral ketamine (Ketalar) at a dosage of 5-10 mg may be given. 

    •  Problems associated with ketamine (Ketalar) would include preoperative/postoperative delirium as well as oral secretion.

  • Methohexital (Brevital): This agent may be given just prior to surgery at a dosage of 20-30 mg/kg using the rectal route of administration; however, intramuscular administration may also be employed.

  • Other Routes of Administration:

    • Nasal route of administration (nasal atomizer)-associated with bitter aftertaste 

      • Midazolam (Versed) 0.2 mg/kg by this route of administration;

      • Ketamine (Ketalar) 3-8 mg/kg by this route of administration

    • Rectal route of administration:

      • Ketamine (Ketalar): 5 mg/kg by this route of administration

      • Midazolam (Versed): 0.3-1 mg/ kg by this route of administration

• ⁴Anticholinergic drugs:

  • Overview:

    • The use of anticholinergic agents is especially important because children  have easily-induced vagal reflexes that may induce bradycardia.  

      •   Bradycardia may be particularly harmful and children because the child's cardiac output is more dependent on heart rate compared to adult patients.

    • Bradycardia may be induced through the vagal reflex by the surgical activity itself, airway manipulation, or by anesthetic drugs such as halothane (Fluothane) or succinylcholine (Anectine)

  • Most pediatric patients may be given an anticholinergic agent just after anesthesia induction and placement of the intravenous catheter. 

    • This procedure is dependent on an absence of contraindications to atropine.

    • Intramuscular injection as an option is possible and if implemented, the injection would occur just after the child loses consciousness during induction

    • An alternative to atropine would be glycopyrrolate (Robinul); however, scopolamine might be used because of its ability to produce sedation, amnesia, and to reduce airway secretion.

  • Special concerns:

    • Anticholinergic drugs decrease effective temperature regulation by preventing sympathetic cholinergic mediation of sweating.

      • Sweat glands are innervated by sympathetic cholinergic fibers that depend on available muscarinic receptors for activity.

        • Anticholinergic drugs are competitive antagonists at these receptor sites and therefore interfere with sweat gland activity.

      • Accordingly, a child with a fever might be exhibited a worsening of the fever subsequent to anticholinergic medication.

    • Because anticholinergic drugs are likely to cause  a thickening of secretion, one might select not to use anticholinergic drugs if inspissation of secretion is undesirable, for example in a cystic fibrosis patient.

    • A patient with trisomy 21 (Down syndrome) may be more sensitive to cardiovascular effects of atropine and more likely to exhibit mydriasis. 

References

• ¹Preoperative Medication in Basis of Anesthesia, 4th Edition, Stoelting, R.K. and Miller, R., p 119- 130, 2000) 

• Hobbs, W.R, Rall, T.W., and Verdoorn, T.A., Hypnotics and Sedatives; Ethanol In, Goodman and Gillman's The Pharmacologial Basis of Therapeutics, pp. 364-367 (Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc., 1996.

• ³Sno E. White The Preoperative Visit and Premedication in Clinical Anesthesia Practice pp.  576-583 (Robert Kirby & Nikolaus Gravenstein, eds) W.B.  Saunders Co., Philadelphia, 1994

• ⁴John R. Moyers and Carla M. Vincent Preoperative Medication in Clinical Anethesia, 4th edition, 551-565, (Paul G. Barash, Bruce. F. Cullen, Robert K. Stoelting, eds) Lippincott Williams & Wilkins, Philadelphia, PA, 2001

• ⁵Gertler, R., Brown, H. C, Mitchell, D.H and Silvius, E.N Dexmedetomidine (Precedex): a novel sedative-analgesic agent, BUMC Proceedings 2001; 14:13-21.