ABSTRACT

    
     Sedation is required for echocardiography in the pediatric age group for accurate diagnosis and reliable studies. The drugs used for sedation for echocardiograms include chloral hydrate and midazolam. Though chloral hydrate continues to be used, there may be concerns regarding its safety. Midazolam may have advantages, especially with the oral form of the drug. The status of these drugs and the role of sedation for other procedures in pediatric cardiology are included.
(Heart Views 2000; 1(8): 314-316) © 2000 Hamad Medical Corporation


Keywords:  ®Pediatric ®sedation ®echocardiography


Introduction

   
     
        Sedation for pediatric echocardiograms is essential for children of younger age group, in contrast to cardiac catheterization, where it may be required for all patients. Echocardiography is a relatively short procedure requiring patient co-operation. There is no pain associated with the procedure, but the fear of new environment may make an apprehensive child anxious and agitated enough not to allow the procedure to be done. This is where the use of children friendly atmosphere may help the child feel comfortable. Parents are always instructed to be at the bedside of the patient when the procedure is performed. There maybe mild discomfort associated with the procedure, which maybe due to some pressure involved with the transducer or contact with the cold sonographic gel. The latter has largely been overcome with the use of gel warmers, though the former varies with sonographers experience. The degree of cooperation that is needed for an echocardiogram can usually be achieved in children older than four or five years. In the newborn, feeding the baby may put him to sleep before the procedure, though, in that case caution with the degree of pressure applied for subcostal views may be necessary.

       Since the duration of the procedure usually varies between 15-45 minutes (occasionally 60 minutes) one requires sedative drug for transthoracic echo with a short duration, quick onset of action, minimal cardiac side effects, and minimal respiratory depression. It should be easy to administer and preferably should have no systemic effects.

       There is a great deal of institutional variability in the use of and protocols for sedation used for outpatient pediatric echocardiograms. The variability may be partially related to hospital conscious sedation protocol requirements. In addition, there is a lack of literature comparing various sedation protocols for pediatric echocardiograms. This maybe related to the fact that though there is no “ideal” sedative suitable for this procedure, any orally administered sedation will work for the procedure. Over the last decade, there has been a focus on newer pediatric sedatives allowing easy administration, short duration of action, and rapid onset with amnesic effects. The oral route remains the most commonly used form of administration but alternative routes have been evaluated. Sedatives used most commonly for echocardiograms have been midazolam and chloral hydrate. 


Transthoracic Echocardiography Sedation

          Choral Hydrate

   
     
       Although chloral hydrate is a safe sedative to use, it has inherent problems and for this reason, newer drugs may be preferred. When given orally, there is a delay in its onset of action. This delay is usually in the range of 15-30 minutes. About 5% of patients may vomit, resulting in no sedation. In addition, 5% of patients may have abnormal reaction to the use of chloral hydrate, resulting in a more excited child than a sedated one. Also, chloral hydrate has been noted to have significant cardiac side effects, though rare. This mainly includes cardiac arrhythmias in susceptible patients. In addition, large studies have noted a 5% decrease in saturation in the cyanotic patient. (1)

       In a non-randomized, uncontrolled study, 405 children with a median age of 13 months (3 weeks to 14 years) were given a median dosage of chloral hydrate of 77 mg/kg. Sedation was achieved in 397 (98%). The time to achieve sedation was 30 minutes or less in 82%, more than 30 but less than 60 minutes in 12%, and more than 60 minutes in 4%; 2% failed to achieve sedation. Decrease in oxygen saturation occurred more commonly in children with trisomy 21 (7/13) than in children without genetic syndromes (17/384). Vomiting occurred in 23 (6%) of the 405 study subjects, usually immediately after drug administration (1).

     To determine factors related to undesirable effects of chloral hydrate in young children undergoing echocardiograms, 140 children aged 0 to 36 months undergoing diagnostic echocardiography were sedated with chloral hydrate per routine (mean dose 87 mg/kg) and observed from the time of sedation throughout the examination. Paradoxical excitement before sedation occurred in 25 children (18%). Length of time until the child reached deep sedation averaged 25 minutes. Three children never fell asleep. Proximity of sedation to naptime was positively correlated to the speed of sedation. Deep sedation was achieved in 131 children (94%). Depth of sleep during the examination was related to child’s age, proximity of sedation to nap time, and recent food ingestions (2).

     The authors of both of the above-cited studies concluded that chloral hydrate is a safe and effective agent for sedation in children with known or suspected congenital heart disease who are undergoing echocardiography in the outpatient cardiology clinic.

       However, there have been other reports of problems with the use of chloral hydrate. The most disturbing includes the risk of the carcinogenic and genotoxic effects of chloral hydrate (3). Death has been reported to occur from chloral hydrate (4).


      Midazolam

   
     
      In view of the problems mentioned with chhloral hydrate, there has been an increase in the use of midazolam for sedation for echocardiograms. Midazolam has sedative, anxiolytic, and marked amnesic properties and is effective orally and parenterally. Its water solubility permits transmucosal (intranasal) absorption. In vivo at physiologic pH, it becomes more lipophilic, allowing it to go through the blood brain barrier. Before 1998, there was no oral preparation of the drug available. The intravenous form was given orally to children but was extremely distasteful and has not resulted in successful clinical usage in children. In view of this, intranasal midazolam as drops or spray has been used in several centers. It has a rapid onset of action (6-10 min) and duration of action (20-30 min), which makes it seem ideal use (5).

      In 1998, the Food and Drug Administration approved midazolam syrup, a clear, purplish-red, cherry flavored liquid that contains an artificial bitterness modifier. The reported acceptance rate by children was 90%. The recommended dose for children is a single dose of 0.25 to 0.5 mg/kg to a maximum dose of 20 mg. Younger children (6 months to less than 6 years of age) and less cooperative children may require a higher dose of up to 1 mg/kg. The dose should be individualized for the patient’s age, level of anxiety, and medical need. The time to onset is usually within 10 to 20 minutes. There has been no published literature on the use of oral midazolam syrup for sedation for echocardiograms.
 

      Fentanyl Oralet

   
      The oral transmucosal preparation, Fentanyl Oralet, is a useful mode of delivering sedation to an anxious child. It provides an effective and non-traumatic form of conscious sedation, especially in children without preexisting IV access. It consists of a confection or candy lozenge on a plastic holder that is available in 200-, 300-, and 400-mg strengths. The recommended dose is 5 to 15 mcg/kg of body weight. Children who weigh over 40 kg may need the higher dosage. It is not recommended for children who weigh less than 15 kg. The peak effect occurs in 20 to 30 minutes from the start of administration if the drug is sucked, not chewed and swallowed. If the lozenge is chewed, the drug is less effective because the liver metabolizes part of it before the drug enters the bloodstream. However, swallowing the drug rapidly does not increase the risk of respiratory depression during the first 15 to 30 minutes, the period of greatest risk for decreased respiration. Since it is not approved for children <15 kg it becomes a less likely option for use for pediatric echocardiography.

Transesophageal Echocardiography and Other Semi-Invasive Procedure Sedation

   
     
      Transesophageal echocardiograms in children may be done under general anesthesia. They have also been performed under sedation with intravenous midazolam along with local anesthesia, but this may be difficult in some of the patients and can potentially result in more trauma.

     In a study involving real-time-3-dimensional echocardiography for diagnosis of congenital heart disease in 75 children, sedation was not required for any of the patients since total acquisition was completed in 5 minutes (6) The advances in technology provided by rapid and accurate acquisition of images may not necessitate sedation for the procedure.

      Patients undergoing cardiac MRI may be sedated with chloral hydrate or additional sedation with other agents. In a structured MRI sedation program evaluation, one thousand eight hundred and fifty-seven children underwent magnetic resonance imaging. Oral sedation consisted of chloral hydrate 90 mg/kg (maximum 2.0 g) orally with or without rectal paraldehyde 0.3 ml/kg. Intravenous sedation consisted of either a propofol 0.5 mg/kg bolus followed by an infusion (maximum 3 mg/kg/hr) or midazolam 0.2-0.5 mg/kg boluses. Oral sedation failed in 50 out of 727 patients (6.9%). Eighty-seven per cent of children aged 5 years and below needed sedation compared with 4.5% of those aged over 10 years. Two patients who had only received chloral hydrate developed significant respiratory depression (8).

     Electrophysiology procedures such as transesophageal pacing maybe done under light sedation with midazolam.


CONCLUSION

   
       The field of pediatric sedation for non-invasive procedures continues to evolve. Oral midazolam needs to be investigated and may provide better sedation than the currently used chloral hydrate. Newer modalities under research like real-time-3D echo may be rapid enough not to require sedation at all.

 References:


1. Napoli KL, Ingall CG, Martin GR. Safety and efficacy of chloral hydrate sedation in children undergoing echocardiography. J Pediatr 1996;129(2): 287-291.

2. Lipshitz M, Marino BL, Sanders ST. Chloral hydrate side effects in young children: causes and management. Heart Lung 1993;22(5):408-414.

3. Salmon AG, Kizer KW, Zeise L, Jackson RJ, Smith MT. Potential carcinogenicity of chloral hydrate—a review. J Toxicol Clin Toxicol 1995;33(2):115-121.

4. Jastak JT, Pallasch T. Death after chloral hydrate sedation: report of a case. J Am Dent Assoc 1988;116(3):345-348.

5. Latson LA, Cheatham JP, Gumbiner CH, Kugler JD, Danford DA, Hofschire PJ, Honts J. Midazolam nose drops for outpatient echocardiography sedation in infants. Am Heart J 1991;121(1 Pt 1):209-210.

6. Balestrini L, Fleishman C, Lanzoni L, et al. Real-time 3-dimensional echocardiography evaluation of congenital heart disease. J Am Soc Echocardiogr 2000;13(3):171-176.

7. Keengwe IN, Hegde S, Dearlove O, Wilson B, Yates RW, Sharples A. Structured sedation programme for magnetic resonance imaging examination in children. Anaesthesia 1999;54(11):1069 –1072.

8. Benson DW Jr, Sanford M, Dunnigan A et al. Transesophageal atrial pacing threshold: role of interelectrode spacing, pulse width and catheter insertion depth. Am J Cardiol 1984;53:63-67.

 

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