Keywords
encephalopathy - postoperative - hypotension - caudal anesthesia - diffusion-weighted
imaging - neonate
Neonatal encephalopathy with seizures after general anesthesia unrelated to local
anesthetic toxicity or not occurring in infants undergoing cardiac or major neurosurgery,
is very uncommon and its cause is unknown in most of cases.[1] An ischemic origin due to cerebral hypoperfusion from perioperative hypotension
has been suggested.[1]
[2] Mean blood pressure (MBP) is considered a good marker of cerebral perfusion but
the physiological blood pressure range that allows adequate cerebral perfusion remains
unknown in neonates.
In response to the concern of potential neurotoxicity in children, the use of caudal
anesthesia combined with light general anesthesia is common and is considered not
to be associated with hypotension in neonates.
Diffusion-weighted imaging (DWI) is a useful clinical tool to assess the extent and
pattern of injury in hypoxia–ischemia-related brain injury. Moderate and prolongated
hypotension with impaired autoregulation is considered to be one of the underlying
mechanisms in the pathogenesis of predominant watershed injury in magnetic resonance.[3]
Brain injury after anorectal malformation neonatal surgery is very uncommon[2] and, to our knowledge, it has not been described under caudal anesthesia.
We present the case of a neonate who presented with seizures due hypoxia–ischemia-related
brain injury demonstrated in DWI following caudal anesthesia to perform a colostomy.
Case Study
A male child born at 39 gestational weeks (birth weight, 3.5 kg), after noncomplicated
vaginal delivery. Previous cardiotocographic monitoring was reassuring, and there
was no need for resuscitation after delivery as the Appearance, Pulse, Grimace, Activity,
and Respiration scores were 9 and 10 in minutes 1 and 5, respectively. Umbilical cord
pH 7.31. Anorectal malformation was noted after birth. The infant was hemodynamically
and neurologically stable before surgery with baseline systolic blood pressure (SBP)
and MBP readings of 60 and 40 mm Hg, respectively. Before undergoing surgery, his
blood glucose levels were 92 mg/dL and he was breathing spontaneously with pCO2 41 mm Hg and oxygen saturation of 97%.
At 36 hours of life, he underwent a colostomy with caudal anesthesia (1 mL/kg levobupivacaine
0.125%) combined with light general anesthesia (sevoflurane, 6% inspired concentration
with a 100% fraction of inspired oxygen, and one dose of 10 mg propofol) with no episodes
of adverse events. Intraoperative records using an automated oscillometric method
revealed SBP values of between 40 and 60 mm Hg and MBP values of 28 and 35 mm Hg.
There were no episodes of hypoxemia, hypocapnia, hypoglycemia, or hyperthermia, neither
during surgery nor in the neonatal intensive care unit postoperatively.
Thirty-two hours after the intervention, the patient presented recurrent clonic movements
of the upper and lower right limb with lethargy. Clinical seizures were recorded by
amplitude-integrated electroencephalography (aEEG) (Brainz Instrument Ltd., New Zealand)
and the background pattern was continuous normal voltage. Seizures were controlled
with one dose of phenobarbital, and it did not recur and the blood glucose level was
normal at that time. Four days after seizures, the child underwent cerebral magnetic
resonance imaging (MRI) without sedation which in DWI showed bilateral involvement
with reduced diffusivity in the watershed areas of the middle cerebral artery and
posterior cerebral artery with involvement of the splenium of the corpus callosum
and sparing of the central gray matter ([Fig. 1]). High signal intensity in T2- and T1-weighted images through parietal–occipital
cortical gray matter and subcortical white matter was also reported.
Fig. 1 Diffusion-weighted imaging. Bilateral involvement with reduced diffusivity in the
watershed areas of the middle cerebral artery and posterior cerebral artery.
At 1 year of age, neurological status assessed by the Hammersmith Infant Neurological
Examination and neurodevelopmental assessment using the Bayley Scales of Infant and
Toddler Development, Third Edition, were normal.
Discussion
Infants who have neonatal surgery for noncardiac congenital anomalies are at risk
of neurodevelopmental delay.[2] The etiology of neurodevelopmental impairments is currently unknown, but several
potential risk factors have been proposed. Among the mechanisms of central nervous
system injury in infants having noncardiac surgery may include hypoxic ischemia, although
this has not been well characterized.
Impaired cerebral autoregulation has been observed in full-term infants receiving
anesthesia and the hypoxic ischemia injury may be attributable to cerebral hypoperfusion.
Inadequate perfusion from hypotension can lead to partial asphyxia and we know that
partial ischemia often causes damage in the watershed areas between major cerebral
blood vessels.[3]
It is widely believed that caudal anesthesia has limited hemodynamic effects. However,
studies measuring cerebral blood flow have reported a decrease in blood flow after
caudal block. In the context of combined general and regional anesthesia, hypotension
can be observed, although this is not widely reflected in the literature.
On the other hand, there is a lack of a consensus definition for intraoperatory hypotension
in neonates with great variability in the threshold used for defining and treating
intraoperatory hypotension. A MBP of 17 mm Hg is considered as −2 standard deviation
for neonates undergoing anesthetized procedures.[4] The lowest SBP of patients with severe postoperative encephalopathy in the case
series by McCann et al[1] ranged from 22 to 40 mm Hg. In our case, intraoperative readings of SBP and MBP
ranged between 40 and 60 and 28 and 35 mm Hg, respectively. Therefore, we believe
that with current normally considered blood pressure thresholds may underestimate
the risk of postoperative encephalopathy.
DWI enables the detection of brain lesions in babies within the first hours after
a hypoxic ischemic insult because they can depict a water mobility impairment before
any signal intensity changes on T1- or T2-weighted images occur. DWI is, therefore,
a sensitive magnetic resonance technique for determining the pattern of brain injury
and the time of hypoxic ischemic insult with normalization of this sequence at 7 days
after insult. The watershed pattern of injury seen is typically thought to follow
“prolonged partial asphyxia” and moderate hypotension.[3] Posterior watershed involvement, with sparing of the anterior areas, has been observed
in cases of neonatal encephalopathy following hypoxia ischaemia[5] and symptomatic hypoglycemia. Hypoxic-ischemic injury in a posterior watershed distribution
are not invariably associated with an adverse outcome,[5] but these infants may develop cerebral visual impairment, cognitive delay, epilepsy,
learning difficulties, as well as behavioral, concentration, and memory problems,
and they must be followed until school age.
In other cases of postoperative encephalopathy, it was difficult to establish the
time of insult and etiology. We know that in states of hypoxia ischemia the seizures
appear between 18 and 48 hours after the insult and DWI findings appear between the
first hours and 7 days after a hypoxic-ischemic insult. In our case, hypoglycemia
was excluded and the chronology of seizures, starting 32 hours after the intervention,
and findings at cerebral magnetic resonance performed 4 days later suggest that the
time of insult could be related with surgery.
In other case series, most of the infants had preoperative neurologic issues, were
preterm infants, or required major neonatal surgery.[1] Our case was a term newborn, neurologically stable before surgery.
We consider perioperative monitoring of blood pressure is not enough in neonatal surgery
and we believe that it is necessary to monitor cerebral oxygenation with near-infrared
spectroscopy and aEEG to detect early brain hypoxic-ischemic injury. This management
would favor performing neuroprotective measures (i.e., hypothermia) within therapeutic
window. Furthermore, MRI should be considered in infants with noncardiac congenital
anomalies after neonatal surgery and long-term follow-up is required to evaluate the
consequences later in life.
