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 are given an anticholinergic agent, typically atropine, 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.