Pediatric Anesthesiology - Neonatal Emergencies
Nasal Encephalocele, PBLD
19 February, 2004
Greg Gordon, MD
Goals and Objectives - At the conclusion of the case, the resident will have knowledge of and will have discussed:
- Neural tube development, embryology and abnormal outcome.
- Ethical considerations in the neonatal period and the role of the anesthesiologist as a member of the perinatal team.
- Perioperative considerations in the early neonatal period with emphasis on fluid and electrolyte balance.
- Anesthetic and surgical concerns specifically related to the neonate with myelodysplasia.
At 0430 the OB anesthesia team calls you to report that a laboring woman with poor prenatal follow-up care due to illness in the family has been admitted. An ultrasound performed to determine gestational age has indicated a large nasal encephalocele. As a member of the pediatric anesthesia team, you are being called to consult for your expert input. There appear to be many people at her bedside, including her obstetrician, a perinatologist, a neonatologist and the patient's husband. You do your best to look at the chart and take part in the evaluation process. At some point the husband's brother shows up. He happens to be a card-carrying member of the American Civil Liberites Union.
If this patient were to have had appropriate prenatal care, when would this defect have been evident? What is your definition of "large" and what are the implications for delivery? Is there a "best" method of delivery? How are myelodysplasias handled in the delivery room? Are there any other defects or conditions associated with myelopysplasias? How soon should this baby be taken to surgery and why? What will you tell the parents regarding the anesthetic management of the neonate?The parents have expressed concern regarding the child's future and have indicated that they are considering withholding aggressive care both in the neonatal period and long term. The above mentioned brother has threatened legal action if this path were taken and verbal altercations between him and the parents, the rest of the family and the medical team have ensued.
What are the ethical and legal implications of withholding care in a case such as this? What are the anesthesiologist's responsibilities, if any, in this decision making process?
The baby is finally delivered and the parents have consented to surgery, scheduled for first thing in the morning. An evaluaion of the patient in the neonatal ICU four hours after delivery reveals the following: gestational age approximately 35 weeks; birth weight 2156 gm; lab values Na 143, K 5.2, Cl 97, HCO3 18.3, Hct 52. He has one peripheral IV 24-guage infusing D10W at 10 ml/hr.
Comment on these lab values. Are they "normal?" Why is D10W the only IV infusion? Will these lab values change over the next eight hours? How will your intraoperative fluid management differ and will you continue the D10W? Is there any other information or intervention required or desirable prior to the OR?
The baby is brought to the OR and anesthesia is induced. The surgeon of record, Dr. Carmel, arrives as the patient is being positioned. He proceeds with the first of what will be many neruosurgical and reconstructive surgeries, the attempted covering and closure of the encephalocele. In your expert opinion the blood loss has not been substantial, however the patient's blood pressure is 55/17 with a heart rate of 182. Results of an ABG reveal a pH of 7.21, a pO2 of 150 and a pCO2 of 44.
Describe your room set-up in complete detail. What special precautions will you take? How will you accomplish a safe induction? What pharmacologic agents will you use and in what doses? How are these doses different from the older infant? child? Adult? What questions do you anticipate that Dr. Carmel will ask you? What do you think of these vital signs? ABG? Will you "treat the numbers?" How do you measure and track intraoperative blood loss in pediatrics? What will be your criteria for transfusing this patient and to what end point?
The surgery is concluded and the junior neurosurgical resident would like you to extubate in the OR for "postoperative neurological evaluation."
What are your postop plans for this baby? What will you tell this resident?
References
- Gregory GA. Pediatric Anesthesia, Third Ed. Churchill Livingston Inc., 1994
- Porri F, Pradal M, Lemiere C et al. Association Between Latex Sensitization and Repeated Latex Exposure in Children. Anesthesiology 86(3):599-602, 1997 (to abstract)
- William J. Curran. Health Care Law and Ethics, 5th edition Aspen Law and Business, 1998
- Birmingham PK, Dsida RM, Grayhack JJ, Han J, Wheeler M, Pongracic JA, Cote CJ, Hall SC. Do latex precautions in children with myelodysplasia reduce intraoperative allergic reactions? J Pediatr
Orthop. 16(6):799-802, 1996
- Khan AN, Turnbill I, et al. Encephalocele. eMedicine. http://www.emedicine.com/radio/topic246.htm
The most critical period in the embryology of the face is during the first twelve weeks of fetal development. Between the third and fourth weeks of fetal growth the neural fold develops and forms the neural tube on the dorsal aspect of the embryo. Closure of the neural groove begins in the middle of the embryo and extends in a cranial and caudal direction. A key element in understanding development of the face, including the nose, is the importance of the neural crest cells. As the neural tube is forming by closure of the neural groove, neural crest cells migrate laterally and anteriorly around the eye to the frontonasal process. In most of the body the neural crest cells are involved in forming ectodermal components. However, the neural crest cells in the face primarily form mesenchymal cells which provide the bone, cartilage, and muscles of the face.
The nose is formed from the frontonasal process and two nasal placodes which develop dorsal to the stomadeum (primitive mouth). The nasal placodes become more prominent and consist of a medial and lateral process. The medial processes approach one another and eventually fuse in the midline. The lateral processes become less prominent as the maxillary process fuses with them. A deep groove in this region, called the nasal-maxillary groove becomes the nasolacrimal duct. As the external nose is developing, other neural crest cells migrate through the frontonasal process to form the posterior septum, ethmoid bone, and sphenoid. The nasal septum develops around week five from the frontonasal process, growing in an anterior-posterior direction.
During formation of the skull base and nose the mesenchymal structures are formed from several centers which will eventually fuse and begin to ossify. Before their fusion there are recognized spaces between these elements which are important in the development of congenital midline nasal masses. These include the fonticulus frontalis, the prenasal space, and the foramen cecum. The fonticulus nasofrontalis is the space between the frontal and nasal bones. The prenasal space is between the nasal bones and the nasal capsule (the precursor of the septum and nasal cartilages). During fetal development these spaces are normally closed by fusion and ossification. Abnormal development of these structures is thought to be involved in the formation of dermoids, gliomas, and encephaloceles of the nose.
Encephaloceles
Encephaloceles are extracranial herniations of the meninges and/or brain which maintain a subarachnoid connection. If it contains only meninges it is termed a meningocele, when it also contains brain tissue it is called a meningoencephalocele. Ingraham and Matson (11) divided encephaloceles into three categories: occipital, sincipital, and basal. Occipital are the most common at 75%. Sincipital are frontonasal lesions which present as a mass over the nose, glabella, or forehead. The intracranial connection is usually anterior to the cribriform plate. Suwanwela and Suwanwela (21) divided nasal encephaloceles into nasofrontal, nasoethomoidal, and naso-orbital lesions based on the projection of the mass between the nasal and frontal bones, along the side of the nose, or into the medial orbit. He reported that nasofrontal encephaloceles occur directly anterior with short necks and could possibly be excised via an external approach while nasoethmoidal and nasoorbital have long necks and necessitate intracranial closure. Basal lesions make up about 10% of lesions and present as an intranasal or nasopharyngeal mass. Basal lesions herniate either through the cribriform plate or posterior to it which explains their presentation in the nose instead of externally. They rare at 1:35,000 live births in Western Europe, America, Australia, Japan, China, and India but more common at 1:6000 live births in Southeast Asia and Russia. Encephaloceles are often bluish, soft, compressible masses which can be transilluminated. They enlarge with crying or the Valsalva maneuver. A characteristic sign is the Furstenberg test, which is enlargement with compression of the internal jugular veins. They also can cause a widening of the nose or hypertelorism. Intranasal encephaloceles originate medially in the nasal cavity as opposed to gliomas which most often originate laterally.
The embryologic development of encephaloceles is the same as that for gliomas. Failure of the fonticulus frontalis to close properly can lead to a herniation of intracranial contents which maintains its connection to the subarchnoid space. This connection with the central nervous system and the possibility of containing brain tissue make encephalocele and important entity to rule out when a midline nasal mass is found.
ANESTHESIOLOGY 1997;86:599-602
Background: Children with spina bifida are at greater risk for latex and ethylene oxide sensitization. The authors' aim in this study was to evaluate the role of previous surgical procedures in the development of sensitization to latex and ethylene oxide.
Methods: The authors investigated 80 children 1-16 yr old, separated into 3 groups. Two groups had a history of 3 or more general anesthetics: 29 children had spina bifida (spina bifida group) and 31 had undergone multiple surgeries for another disease (multiple surgeries group). A control group of 20 children had undergone less than 1 anesthetic. Clinical manifestations with latex, perioperative anaphylactic reactions, and number of previous anesthetics were recorded. Skin prick tests with a commercial extract of latex, four common inhalant allergens, and radioallergosorbent test to latex and ethylene oxide were performed.
Results: The three groups did not differ significantly with respect to age, sex, and atopic status. Mean number of anesthetics was comparable in the spina bifida and the multiple surgeries group. Latex sensitization was common in the spina bifida group (59%) and in the multiple surgeries group (55%) but not in the control group (0%, P < 0.05). Ethylene oxide sensitization was significantly more frequent in the spina bifida group than in the multiple surgeries group (44% vs. 19%; P = 0.052) and strongly associated with latex sensitization. Mean number of previous anesthetics was greater in children sensitized to latex (8.4 vs. 3.9; P < 0.05).
Conclusion: Results suggest that it is the number of surgical procedures rather than spina bifida per se that is related to sensitization to latex.