The study will examine the quality of two sedation techniques (dexmedetomidine and pentobarbital) used for children aged 3 to 24 months who are undergoing a transthoracic echocardiography (TTE).

Currently there are two sedation methods used for children less than 24 months of age undergoing transthoracic echocardiography (TTE).

• One method provides sedation by mouth with the drug pentobarbital,
• The other provides sedation through the nose with the drug dexmedetomidine.

The choice of which method is used is based on evaluation of the patient's medical history and the preference of the anesthesiologist. To our knowledge, no study has compared these two sedation techniques for quality of care. The proposed study will help us determine which method yields the best quality and will allow us to improve the healthcare experience of our patients.

Inclusion Criteria:

• Outpatients, scheduled to receive sedation for elective transthoracic echocardiography
• The subject must be a candidate for both anesthetic techniques. A staff member of the Division of Cardiac Anesthesiology will make this decision.
• The subjects must be 3 months to 24 months (inclusive of the 24th month).
• The subject's legally authorized representative has given written informed consent to participate in the study.

Exclusion Criteria:

• The subject has a history of cardiac conduction system disease (e.g. 1st or 2nd degree Atrioventricular block) or channelopathy (e.g. long QT syndrome).
• The subject is taking digoxin, alpha-adrenergic or beta-adrenergic agonist or antagonist (e.g., clonidine, propranolol, albuterol), anti-arrhythmic medications, or vasodilators (e.g. ACE inhibitors) on the day of the study procedures. It is routine for children taking these medications to hold them on the day of their procedure, as requested by the clinical team.
• The subject has received a dose of any other sedative within 48 hours.
• The subject has life-threatening, medical conditions (American Society of Anesthesiologists Physical Status 4, 5). The American Society of Anesthesiologists (ASA) classification scale is a measure of physical status or how healthy the patient is. For our study, we will focus on children which are defined as ASA I, II or III which means a healthy child (ASA I), a child with a systemic disease that is mild and well controlled (ASA II) or a child with systemic disease that is severe and controlled (ASA III).
• The subject is allergic to or has a contraindication to any of the drugs or masking flavored syrup used in the study.
• The subject has previously been treated under this protocol.
• The subject has Trisomy 21 (exaggerated risk of bradycardia)
• The subject has severe coarctation of the aorta (risk of exaggerated vasoconstriction)
• The subject has Moyamoya disease (risk of recurrent stroke)