a 48-year - old man underwent right partial glossectomy with neck dissection for tongue cancer under general anesthesia .
past medical history showed that he had been diagnosed with diabetes mellitus ( dm ) for five years and that he is a 30 pack - year smoker . during the five hours of operation , his vital signs were kept stable and blood sugar levels were well controlled between 82 - 84 mg / dl .
pulse oxygen saturation ( spo2 ) , pulse rate , and non - invasive blood pressure ( nibp ) were stable during immediate postoperative period in the recovery room .
he began complaining of troubled breathing and showed agitation 30 minutes after arrival in the recovery room .
we informed his otolaryngologist of the situation and relieved the dressing bandage around his neck . as his oxygen saturation gradually decreased to 0% , we started bag - mask ventilation .
although severe hypoxemia occurred , it did not lead to cardiac arrest , which was known from palpable pulse of radial artery throughout the course .
his heart rate remained above 40 beats / min . at the same time , his otolaryngologist arrived and immediately opened the incision site for decompression .
all vital signs were unremarkable ( spo2 98 - 99% , heart rate 80 - 120 beats / min , and temperature 36.0 - 36.2 ) , except blood pressure . it was checked below 90/60 mmhg twice during the 2 hours of operation , and ephedrine 10 mg was injected . on average , the mean arterial pressure was kept between 60 - 80 mmhg . at the end of the operation ,
bispectral index ( bis ) was increased to 90 and his eyes were opened spontaneously ; he was extubated .
however , soon after extubation , he showed generalized tonic - clonic seizure and it was only discontinued by inhalation of sevoflurane and administration of thiopental .
he was reintubated and phenytoin , lorazepam , and midazolam were administered to control the seizures .
he was admitted to the intensive care unit ( icu ) in a sedated state .
six hours later , when a tactile stimulus was applied , he developed widespread myoclonic seizures on all four limbs , even under infusion of large dose of anticonvulsants .
two days later , he was still deeply sedated to control myoclonic seizures , but the frequency and duration of seizures were only mildly reduced .
his brain computed tomogram ( ct ) showed no remarkable evidence of hypoxic brain damage and his electroencephalogram ( eeg ) study showed normal findings . on day 10 of hospitalization , his sedatives were completely withdrawn and he became alert with a frowned face and myoclonus affecting both knees and ankles .
three weeks later , magnetic resonance ( mr ) brain imaging did not show any abnormalities ( fig .
myoclonic status epilepticus ( mse ) within the first 24 hours after cardiopulmonary resuscitation ( cpr ) is generally considered as an accurate predicting factor of deleterious outcome enough to discontinue the treatment .
it is limited to ' 24 hours ' because mse is categorized into acute and chronic types , which have completely different prognosis .
chronic mse is called lance - adams syndrome , mostly shown a few days after cpr . since las shows much favorable prognosis compared to that of acute mse , it is important to remember the different clinical features of las .
moreover , las can develop acutely , which can lead to misdiagnosis even more easily , as in our case .
in addition to the time course , las is distinguished from acute mse by several clinical features , such as awareness , intention myoclonus , and normal brain ct or eeg .
the pathophysiology of las is elusive , but the mechanism of hypoxic brain injury has been assumed to be an important role . it is based on the fact that patients in previous reports of las were the survivors of ' hypoxic ' cardiac arrest rather than ' circulatory ' cardiac arrest [ 3 - 5 ] .
patients with pure hypoxic event seem to have far better outcome than those with circulatory cardiac arrest .
hypoxia produces hypercapnia , which results in increase of cerebral blood flow secondary to cerebrovascular dilation .
this results in the brain to be continuously supplied with nutrients and glucose and toxic metabolites to be removed by the circulation .
toxic metabolites , including lactic acid   and free radicals   damage not only astrocytes , but glial and mesenchymal cells as well .
time course in the present case showed acute mse that have easily led us to misdiagnosis .
it is important to differentiate between the two types of mse because therapeutic strategy must be established accordingly .
patients with las are aware , but it can be masked by deep sedation to control seizure .
eeg and brain ct can be delayed since mse is difficult to control even with high dose of anticonvulsants . moreover , as seen in our case , some patients with las can start myoclonic activity within 24 hours after cpr .
not misdiagnosing las , we should well acquaint ourselves with other predictors of poor outcome after cpr comprehensively ; absent pupillary light response or corneal reflexes at 72 hours , extensor or no motor response to pain at 72 hours , bilateral absent cortical responses on somatosensory evoked potentials at 72 hours , and serum neuron - specific enolase higher than 33 g / l . the present case might be regarded as a case of good outcome in spite of post - anoxic mse .
ironically , we did not expect any neurological complication at the time of the event in the recovery room , as anoxic time was around 3 minutes and cardiac arrest had not occurred .
have shown that the most important determinant of hypoxic injury was the duration of anoxia , which is defined as the interval between collapse and the beginning of cpr .
patients with favorable outcomes were anoxic for 4.1 minutes , compared to 8 minutes for patients with unfavorable outcomes .
only one report described the occurrence of las without cardiac arrest , which was assumed to be caused by fat embolism .
the survivor was a young healthy man involved in a traffic accident and his spo2 was decreased to 89% briefly without hypotension during orthopedic surgery .
it is worthy of notice what caused neurologic complications after brief hypoxemia without cardiac arrest .
we can presume that the following factors may have contributed to the development of las ; patient 's vulnerability , co - morbid conditions , surgical factor , and lack of post - hypoxic management .
the patient was a heavy smoker who had a history of dm and tongue cancer .
hyperglycemia is widely known as the main cause of endothelial dysfunction and neuronal cell death .
although his blood glucose had been well controlled , diabetic patients show more exaggerated cortical vasoreactivity and more regional cortical atrophy than non - diabetic patients .
long - lasting cigarette smoking is related to the increase in the level of inflammatory state and endothelial injury , which lead to impair vascular function and blood brain barrier integrity .
in addition , the hematoma in the neck may have compressed the jugular vein and/or the carotid artery compromising the cerebral blood flow as well , although circulatory arrest was not evident .
these factors could make our patient vulnerable to hypoxemia inhibiting cerebrovascular dilation and a maintenance of cerebral blood flow , which made similar processes to circulatory cardiac arrest .
thus , if patients who are predisposed to hypoxic injury were exposed to brief severe hypoxemia without cardiac arrest , they should be regarded as survivors of cardiac arrest and be provided with appropriate post - resuscitation managements . in this case
, blood pressure was not elevated enough to ensure adequate cerebral blood flow during 2 hours of surgical removal of hematoma after recovery from hypoxemia .
the mean arterial blood pressure is recommended to be maintained between 80 - 100 mmhg , at least for the first 24 hours after cardiac arrest .
blood glucose levels between 70 - 140 mg / dl are known to be associated with good neurologic outcome . since hyperthermia worsens neurologic outcome , fever must be avoided .
it is clear that acute onset mse does not always mean a poor neurologic outcome , but it does need more cautious approaches of diagnosis for several reasons .
short episodes of hypoxemia can occur at any time of anesthesia and bring detrimental neurologic consequences .
therefore , if those people with high risk of hypoxic injury have experienced hypoxemia , even for a short time , we should closely monitor them .
although it is not proven clearly , we may consider providing them an intensive post - resuscitation management to minimize unexpected complications .
 myoclonic status epilepticus ( mse ) within the first 24 hours after cardiopulmonary resuscitation ( cpr ) predicts poor prognosis , enough to discontinue the treatment . 
 in contrast , chronic mse appearing a few days after cpr is called lance - adams syndrome ( las ) , which is characterized by preserved intellect and a favorable prognosis . 
 we herein report a case of las , which developed after a transient hypoxic event without an overt cardiac arrest due to hematoma formation in the neck after partial glossectomy . 
 differential diagnosis was also challenging as las was developed 8 hours after the hypoxic event . 
Case Report
Discussion