The use of amplitude-integrated electroencephalography combined with continuous conventional electroencephalography during therapeutic hypothermia for an infant with postnatal cardiac arrest
© Ito et al.; licensee Springer. 2014
Received: 17 February 2014
Accepted: 10 July 2014
Published: 21 July 2014
Amplitude-integrated electroencephalography (aEEG) has been employed in therapeutic hypothermia (TH) trials of neonates after perinatal hypoxic-ischemic encephalopathy (HIE). We present a case report involving the use of aEEG during TH with continuous conventional electroencephalography (cEEG) for an infant who experienced postnatal intraoperative cardiac arrest.
A five-month-old infant developed cardiac arrest during operation. Return of spontaneous circulation was achieved after one hour of cardiopulmonary resuscitation. Therapeutic hypothermia was applied with neuromuscular blockades. During the TH, the brain function and seizures were monitored with aEEG, which can also display continuous cEEG. Intermittent and discrete seizures were detected on aEEG and confirmed with raw cEEG during the TH and rewarming periods. Several kinds of antiepileptic drugs (AEDs) were administered to manage seizures according to the findings of aEEG with cEEG. Seizures were controlled by the treatments, and she showed no clinical seizures after TH and AED discontinuation.
Discussion and evaluation, conclusions
This case indicated the possibility that the use of aEEG with continuous cEEG for a postnatal infant after cardiac arrest was feasible to detect and assess seizures and the effects of antiepileptic therapy while undergoing TH.
Patients with cardiac arrest show high rates of mortality and neurologic morbidity. Therapeutic hypothermia (TH) has been demonstrated to improve the neurological outcome in adults after cardiac arrest, and is now considered the standard of care (Bernard et al. 2002). Based on extrapolation from evidence of existing nonpediatric studies, TH is recommended for children who remain comatose following resuscitation from cardiac arrest (Kleinman et al. 2010). Hypoxic ischemic encephalopathy (HIE) after cardiac arrest may cause seizures, which are associated with a poor outcome (Young et al. 1996). The early detection and appropriate treament of seizures are necessary to improve the neurologic outcome. Conventional electroencephalography (cEEG) is the standard method to confirm seizures. Amplitude-integrated electroencephalography (aEEG) has been introduced for seizure detection in neonates with perinatal asphyxia (van Rooij et al. 2005). This case report presents the use of aEEG combined with continuous cEEG during TH for a five-month-old infant with postnatal cardiac arrest.
Discussion and conclusion
Neurological care for patients who are successfully resuscitated with post cardiac arrest syndrome (PCAS) remains challenging. Patients with PCAS can be occurred with seizures in 15 to 44% of frequency (Khot and Tirschwell 2006). They are frequently nonconvulsive, difficult to control, and associated with higher rates of neurological morbidity and mortality (Krumholtz et al. 1998). Nonconvulsive seizures are electrographic seizures with little or no overt clinical manifestations, which may not be recognized without continuous monitoring. Moreover, the diagnosis of seizures is difficult in clinically ill infants who are intubated, sedated, or administered neuromuscular blockades, such as our case. Therefore, continuous cEEG monitoring is required for prompt and reliable nonconvulsive seizure detection.
The interpretation of cEEG requires an encephalographer with specific training in cEEG. However, in most units, technicians and experienced clinical neurophysiologists are not available 24 hours a day. To improve these limitations of cEEG, a simpler methodology for monitoring the cerebral function has been developed. Over the past decade, aEEG has become a bedside cerebral function monitoring method in the neonatal ICU, especially to monitor the neurologic status, seizures, and effects of therapies, and to predict the neurological outcome following HIE (Spitzmiller et al. 2007). The aEEG tracing is viewed with a highly compressed time scale, at a slow rate of 6 cm/hr, compared to 3 cm/sec of cEEG. With its time-compressed output, aEEG is able to provide a simpler means of following cerebral function trends in the ICU without the need for experienced technicians for the application and interpretation of the analog cEEG system.
The aEEG represents the processed and compressed cEEG signal from one or two channels. The advantages of the simplified electrode system are that it is faster to apply and easier to maintain. However, artifacts those influence the voltage and width of the aEEG band could make aEEG problematic as an assessment tool. Artifacts commonly mistaken for seizrues on aEEG include gross movemet of the subject, muscle activity, and electrical interference (Rosen. 2006). Reviewing the corresponding raw EEG tracing is necessary to confirm seizures seen on aEEG. The aEEG that we used was able to display both tracings of aEEG and cEEG in real time simultaneously. Moreover, the equipment allowed the interpreter to intermittently call up and display the raw cEEG corresponding to a suspicious event observed on the compressed aEEG trace. This may improve the accuracy of aEEG-based diagnosis for seizures in our case.
Seizures appeared at seventy hours during hypothermia and at eighty-four hours during rewarming after the induction of TH in our patient. The duration of treatment with hypothermia has varied in experimental studies. Studies with birth asphyxia showed that TH up to 72 hours after resuscitation has an acceptable safety profile (Gluckman et al. 2005; Shankaran et al. 2005). Several complications associated with TH are impaired coagulation, increased bleeding, impaired immune system and increased infection rates (Sessler 2001). We decided to continue rewarming with using antiepileptic drugs (AEDs) to control seizures in 84 hours after induction of hypothermia because these side effects of TH could affect postoperative condition.
A number of studies have suggested that early intervention for seizures is associated with an effective response to anticonvulsant treatment and a better outcome (Eriksson et al. 2005), although an evidence-based therapeutic protocol for seizures has not yet been developed. However, there is also concern about possible adverse effects of AEDs on the developing brain (Glass and Wirrell 2009; Dzhala et al. 2010) in addition to the potential harm caused by seizures to the immature brain (Glass et al. 2009). The change of AEDs for seizures according to the observation of aEEG in our coma case may be valuable to achieve a better balance between the efficacy of AEDs for seizures and their potential neurotoxicity in the immature brain. The application of aEEG with continuous cEEG could help evaluate the effect of AEDs and avoid their excessive and continuously ineffective use. Based on this single-case experience, we conclude that the use of aEEG with continuous cEEG in infants after cardiac arrest may facilitate assessing the brain function and effect of anticonvulsant therapy during TH.
Informed consent was obtained from the patient’s parent for the publication of this report and any accompanying images.
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