Anesthetic management of a newborn with occipital meningocele for magnetic resonance imaging.

Cranial Meningocoele is a term which represents herniation of meninges and cerebrospinal fluid through the congenital defect in the cranium. Anaesthetic challenges in the management of neonates with occipital meningocoele include airway management and proper positioning of the neonate without pressure on the meningocoele sac so as to preventthe rupture of the membranes. Associated congenital anomalies also can cause anaesthesia and procedure related complications. Other difficulties include performing a difficult airway case in an unfamiliar environment outside operation theatre. We report a case of 6 day old neonate with occipital meningocoele posted for MRI brain and the successful anaesthetic management.

INTRODUCTION

Myelomeningocele is a complex congenital spinal anomaly, occurring due to the neural tube defect during the 1st month of gestation. A failure of spinal neural tube to close by 28 days postconception causes this defect in the vertebral column. Meningocele is the less serious condition. In this form the meninges or membranes protrudes through the characteristic defect in the vertebrae. In myelomeningocele, the spinal cord also bulges through the defect within the sac.

Neurologic deficits are present at birth and are dictated by the level of the lesion. Paralysis and sensory deficits can occur below the level of the lesion. It can be associated with other congenital anomalies such as intestinal malrotation, renal anomalies, cardiac malformations and tracheoesophageal fistula.

Magnetic resonance imaging (MRI) is an imaging technique used in medical settings to get good quality images. It has a powerful magnetic field that makes it difficult to perform anesthetic procedures in the MRI suite. Anesthesia machine and monitors should be MRI compatible. MRI of infants and pediatric patients <5 years requires adequate depth as they are usually uncooperative. Claustrophobia and loud noise makes it even worse. Most of the time general anesthesia is recommended as depth of anesthesia could not be judged with deep sedation.[1]

CASE REPORT

A 6-day-old male neonate presented to our hospital with a 8 cm × 8 cm swelling in the back of the head (diagnosed to be occipital meningocole from neurosonogram) and was posted for MRI brain to confirm the diagnosis and to know the contents and extent of the swelling.

Baby was delivered at term gestation by normal vaginal delivery, cried immediately after birth, weighing 3.2 kg at birth and had history of swelling in the back of head since birth.

On examination of the baby in neonatal intensive care unit (NICU), baby was active, positioned supine with the head turned to a side, baby had 8 cm × 8 cm cystic swelling arising from the occipital region [Figure 1] with no congenital anomalies, had an umbilical catheter in situ, heart rate was 122/min, respiratory rate of 46/min, room air oxygen saturation was 100%, baby had limited neck extension, had no neurological deficit, cardiac and respiratory systems examination was within normal limits. The plan was to take the baby for MRI brain the next day under general anesthesia, nil per oral for a period of 4 h from breast milk was advised and the baby was put on intravenous dextrose normal saline (DNS) at maintenance rate (12 ml/h).

Figure 1

Neonate with occipital meningocoele (original)

Concerns were, positioning of the baby and the airway management due to limited neck extension.

On the day of MRI, baby was shifted to the operating room, a warmer was placed at the foot end of the OR table, baby was placed on the OR table in supine position with the head turned to a side, monitors (oxygen saturation, electrocardiogram, noninvasive blood pressure) were connected, baseline vitals were noted and stable. Intravenous fluid (DNS with Ringer lactate) was administered to the baby at a maintenance rate of 12 ml/h infusion. Premedicated with atropine 0.1 mg and fentanyl 5 mcg intravenously. Baby was induced with titrated doses of sevoflurane 2–8%. After checking for mask ventilation, injection atracurium 2 mg was given and ventilated for 3 min.

Baby was then brought to the edge of the OR table with the head lying out of the table but supported by two residents from both sides. Under direct laryngoscopic vision, trachea was intubated with 3.0 mm uncuffed endotracheal tube and tube was fixed after confirming adequate bilateral equal air entry.

Baby was then shifted to the MRI room by manual ventilation with the manual resuscitator bag with oxygen at 3 L/min and with the monitors. During the transport, vitals were stable.

In the MRI room, baby was positioned supine on the MRI table over a pile of blankets so as to elevate the whole body and the head was positioned straight supported underneath by gauze bandages. Monitors were re-connected; endotracheal tube was connected to circuit, maintained on oxygen: Nitrous oxide 1:1 and sevoflurane 2% and manual ventilation. Neuromuscular blocking (NMB) repeated with injection atracurium 0.5 mg bolus doses as required.

During the procedure, vitals were stable. At the end of procedure residual NMB was reversed with injection neostigmine 0.25 mg and injection atropine 0.1 mg. Baby was extubated once fully awake with spontaneous limb movements and reaching onto ET tube.

Baby was shifted to the recovery room and monitored for 2 h and then shifted back to NICU. MRI report came to be meningocele [Figure 2] and baby was taken up for surgery at a later date.

Figure 2

Magnetic resonance imaging picture (original)

DISCUSSION

Cranial meningocele refers to the herniation of meninges through a bony defect in the skull and meningomyelocele contain neural elements along with the meninges in the herniated sac.[2] An encephalocele contains elements of brain tissue also within the sac. The defect is more often in the occipital bone.[3] Neonates with encephalocele can have associated sensory and motor deficits, hydrocephalus, and other associated congenital anomalies.

Airway management of neonates and pediatric population is difficult compared with adult due to anatomic variations. Short neck, large tongue and large head are some of the reasons why pediatric airway is difficult. Difficult airway cart with ventilation masks, tracheal tubes, airways, scope blades etc., should be kept ready. Devices for maintaining normothermia like circulating warm-air devices, airway humidifiers, fluid warming devices should be kept ready.[4]

Neonates with meningocele may have restricted neck extension and difficult airway, making intubation difficult. One more concern is positioning of the neonate for intubation and subsequent positioning during the procedure. Complications most commonly encountered during anesthetic management of meningomyelocele include bradycardia, bronchospasm, endobroncial intubation, hypoxemia and laryngospasm.[5]

The perioperative anesthetic plan includes airway management, meticulous fluid administration, management of hypothermia and proper positioning of the baby. Care should be taken to avoid pressure on the sac. Intubation can be attempted in one of the ways described below:

Lateral position[6]

In the supine position after getting the child's head beyond the edge of the table with an assistant supporting the head[7]

The baby can be placed on a pile of blankets and the sac protected in a dough-nut shaped support or held by an assistant.

Only after checking for adequate mask ventilation, NMB agents should be administered. Endotracheal tube should be carefully secured and taped. These children have a higher incidence of latex allergy manifesting as bronchospasm and cardiac collapse intraoperatively.[8]

In one case report where MRI of a child with sickle cell anemia had to be done, the challenges that the anesthesia team had to face was avoiding hypothermia to prevent sickling, while maintaining a cold environment for the proper functioning of MRI machine. They overcome the difficulties by doing MRI in a BrainSuite, which was an advanced operating neurosurgical room that contain MRI machine with limited magnetic field and had warming devices.[9]

In one study comparing the efficacy of oral chloral hydrate intravenous pentobarbital and intravenous propofol, for deep sedation in MRI suite, it was found that the adverse effects were more with propofol but recovery was faster with propofol. Smaller infants had adequate depth of anesthesia with chloral hydrate while bigger children required deeper level of anesthesia.[10] This report shows that even though Propofol is an effective drug for sedation, there is always a risk for respiratory depression and accessing airway is difficult once MRI starts.

Extubation in a difficult airway scenario, as in our case, should be carried out once the criteria are met with intact cough and gag reflex and the child is fully awake and breathing well. Causes for delayed recovery include hypothermia, inadequate reversal, prolonged effect of muscle relaxants and malnutrition.