Definitions
Sedation is a medically controlled state of depressed consciousness or unconsciousness. Sedation can be divided into conscious sedation, deep sedation, and general anesthesia. In conscious sedation, the patient maintains the ability to respond to external stimulation. In deep sedation, patients are not easily aroused. In general anesthesia, patients are not arousable by stimulation.
The important clinical distinction between these states revolves around the ability of the patient to maintain his or her protective reflexes. The consciously sedated patient maintains protective reflexes, such as gagging and swallowing, and therefore can keep his or her airway patent without assistance. The deeply sedated patient may lose these reflexes and may not be able to maintain his or her airway. The patient under general anesthesia has lost protective reflexes and is unable to maintain his or her airway.
There are no sharp boundaries between conscious sedation, deep sedation, and general anesthesia. Furthermore, patients may rapidly move from conscious sedation through deep sedation to general anesthesia. Therefore, clinics that sedate children must be prepared to manage all levels of sedation and general anesthesia, even if only conscious sedation is intended.
Published Rules Concerning Pediatric Sedation
The Joint Commission on Accreditation of Health Care Organizations mandates an institution-wide policy for pediatric sedation. It is advisable to follow each institution's established sedation policy, if such a policy exists. Guidelines for the monitoring and sedation of children are published by the American Academy of Pediatrics (AAP). These guidelines are quite extensive and include documentation, informed consent, patient preparation, pre-sedation evaluation, monitoring, post-sedation care, discharge criteria, and instructions, as well as follow-up (see addendum #1 in the original guideline document).
Appropriate Personnel and Equipment
Safe sedation requires an appropriately trained individual (ATI) with experience and training in pediatric sedation, pediatric airway maintenance, and pediatric advanced life support (PALS). The ATI not only explains the sedation procedure to the family, but screens the child for negative outcome factors, such as significant upper airway obstruction, apnea, reactive airway disease, risk for vomiting and aspiration, and uncontrolled seizures. A consultation with a pediatric anesthesiologist or intensivist about a child with risk factors may be necessary before the sedation procedure.
An emergency cart with equipment and drugs suitable for children of all ages and sizes should be readily available. Functioning suction apparatus with appropriate suction catheters, as well as positive-pressure oxygen delivery system capable of administering greater than 90% oxygen, are also mandatory. The ATI continually monitors the patient with a pulse oximeter throughout the procedure. The patient is monitored until awakening and the institution's discharge criteria are met.
Avoidance of Sedation
For many pediatric nuclear procedures, sedation and its attendant risks are avoidable by having an attentive and caring approach to children. The pain of most nuclear medicine procedures is limited to a single venipuncture or catheterization of the bladder. For patients in whom the pain of venipuncture is a limiting factor, topical lidocaine preparations are available. These are best used one to two hours before injection. They may be prescribed before the procedure and applied by a parent at home before arriving in the nuclear medicine clinic. Xylocaine jelly can be used for difficult urethral catheterizations (particularly in males). Giving full information about the examination to the parents and child at the time the appointment is made reduces anxiety levels in both parents and child.
Many nonpharmacologic strategies are available to help the child cooperate and hold still during a nuclear medicine exam. Cooperation can be maximized in many instances by allowing the parents to be with their child during the examination and letting the child have the comfort of a pacifier, bottle, blanket, or stuffed animal. Depending on the age of the child, a reassuring description of the procedure can be provided before and during the procedure by a technologist who has a good rapport with children. The room can be decorated to make it more interesting and comfortable for the child. The distraction of a child's attention by reading of a story or viewing television or a VCR allows reduction of patient motion. Parents can be instructed to schedule the procedure during the younger child's nap time to maximize the chances that he or she will sleep during the procedure. In addition, a "papoose," sandbags, or adhesive tape can be used to restrain infants and younger children. Use of these strategies can avoid sedation while allowing acquisition of quality images.
Choosing A Sedation Regimen
Sedation regimens vary greatly from one institution to another and even among physicians in the same department. There is no consensus on the best protocol for the sedation of children. The choice of drugs and route of administration depends on the patient's age, history of underlying illness (e.g., mental deficiency, cardiac or respiratory illness), experience and familiarity with certain drugs, institutional protocols, length of procedure, and availability of support (reversal drugs).
In infants and young children, rectally or (more commonly) orally administered drugs are adequate for sedation. Rectal absorption tends to be erratic and the oral method is usually the preferred route of administration. Chloral hydrate is commonly used in infants and young children (usually up to 15 kg) and is recommended by the American Academy of Pediatrics (AAP) as an "effective sedative with a low incidence of acute toxicity when administered orally in the recommended dosage for short-term sedation." Chloral hydrate in a dose of 50 to 70 mg/kg (maximum total accumulated dose of 100 mg/kg) is usually adequate to achieve sedation. The maximum total dose varies according to the guidelines of the individual institution.
In older patients and children with mental deficiency, parenteral sedation, usually intravenous, may be the preferred method. Intravenous sedation allows for rapid induction and recovery, with better scheduling of sedation cases during high volume periods. However, intravenous sedation must be titrated for each patient, using the recommended dosage range.
Pentobarbital sodium (Nembutal) is popular because it is a short acting barbiturate with low incidence of respiratory depression. It is commonly used in dosages of 2 to 6 mg/kg. The maximum dosage varies according to the guidelines of the individual institution. Nembutal is contraindicated in patients with porphyria and may require higher doses in patients being treated for a seizure disorder. Versed is often coupled with Nembutal in doses of 0.1 mg/kg intravenously, for a maximum total dose of 2.5 mg. Other intravenous sedation regimens (opiates and benzodiazepines) are used less frequently in the pediatric population. Reversal drugs are required to treat overdoses, such as naloxone (Narcan) for opiates and flumazenil (Romazicon) for benzodiazepines.
Classes of drugs used for parenteral sedation: Dosages vary and can be generated by the pediatric anesthesiology or critical care section of the individual institution.
- Barbiturates including pentobarbital sodium (Nembutal)
- Opiates including meperidine (Demerol) and fentanyl (Sublimaze)
- Benzodiazepines including diazepam (Valium) and midazolam (Versed)
- Phenothiazines including chlorpromazine (Thorazine) and Promethazine (Phenergan)
- Neuroleptic agents including ketamine (Ketalar)
Sedation protocols use drugs singly or in combination. The use of analgesic opiates, such as fentanyl and meperidine (as part of DPT--Demerol, Phenergan, and Thorazine), is rarely necessary for most nuclear medicine procedures. Also, opiates may cause respiratory depression, especially if administered rapidly. Ketamine can cause hallucinations in older children.
Midazolam can be used alone or as an adjunct with other sedation drugs, such as opiates and barbiturates, and may be used orally, intravenously, rectally, or intranasally. Recently, there is a growing enthusiasm for the use of intranasal midazolam with its predominantly amnestic effect in children undergoing pre-anesthetic sedation, echocardiography, and short surgical procedures. Nasally administered midazolam in a dose of 0.2 mg/kg has been shown to have very minimal respiratory depression and a relatively short duration of sedation, approximately 35 to 45 minutes. Orally administered midazolam in a dose of 0.5 to 0.75mg/kg is available in flavored syrup. Although the rate of absorption is slower than intranasally administered midazolam, the unpleasantness of the nasal drops is avoided and, in general, the oral form is better accepted by patients. It obviates the need for intravenous access and may be suited for some nuclear medicine procedures. It also has a predominantly amnestic effect in children undergoing pre-anesthetic sedation, echocardiography, urethral catheterization, and short surgical procedures. The exact dosages and preferred routes of administration should be ascertained from the guidelines of the individual institution.
The nuclear medicine physician should consult with the anesthesiology department in each institution for specific recommendations on dosages and combinations of sedative drugs. Consultation with an anesthesiologist is particularly important in patients with a history of significant snoring, abnormal airway (i.e., micrognathia), congenital heart disease, reactive airways disease, and increased intracranial pressure.
Developing A Sedation Policy
A written pediatric sedation policy is strongly recommended. The policy should follow institution-wide policy for pediatric sedation and also follow the guidelines of the American Academy of Pediatrics. Many institutions have sedation committees with representation from anesthesiology, nursing, intensive care, pediatrics, and pediatric imaging. This committee can serve as a source of information for the development of the sedation policy in nuclear medicine.
Written medication protocols for sedation are also strongly recommended. Many sedation protocols are available for pediatric sedation, not all of which are appropriate for nuclear imaging procedures. The exact protocol or set of protocols should be tailored to the age of the patient, the pain or discomfort level of the procedure, the length of the imaging procedure, and most important, the experience of physicians in each clinic. The best source of specific sedation protocols is likely to be the institution's anesthesiologist or intensivist, or preferably, pediatric anesthesiologist or pediatric intensivist. These individuals should have the greatest experience in sedation and should know the latest information on various sedation methods.
The American Academy of Pediatrics recommends that written informed consent be obtained from parents according to each institution's protocol. Consultation with the institution's legal counsel may be helpful to determine guidelines for obtaining such consent.
