By Lucy Piper
Stimulus-induced rhythmic, periodic or ictal discharges (SIRPIDs) in critically ill patients are not independently associated with in-hospital death, but are often associated with other electrographic abnormalities signalling poor outcomes, electroencephalography (EEG) findings show.
SIRPIDs were identified in 43 (10.3%) of 416 critically ill encephalopathy patients from three different intensive care units and while they were more common in the 104 patients who died, at 17.3% versus 8.0% in survivors, this association was not significant when other prognostic factors were considered.
The patients most likely to die during a median hospital stay of 15 days were older patients (odds ratio [OR]=1.02) and those with anoxic brain injury (OR=3.49) and absent reactivity on EEG testing (OR=8.14), the researchers report in JAMA Neurology.
"Although any significantly abnormal EEG findings may be prognostically unfavourable, the ability to sustain EEG reactivity after stimulation, even when aberrant, indicates less severe cerebral injury and, consequently, an improved chance of survival", the team observes.
SIRPIDs, although not associated with mortality, were commonly linked to electrographic abnormalities associated with poor outcomes. Only seven patients with SIRPIDs had normal background alpha activity, while EEG background reactivity other than SIRPID response was seen in 74.4% of patients.
The abnormalities that were independently associated with SIRPIDs included generalised periodic discharges with triphasic morphological features (OR=3.66) and sporadic sharp waves and periodic discharges (OR=2.59). SIRPIDs were also significantly associated with antiepileptic therapy use (OR=3.24) and electrographic seizures (OR=2.85).
Researcher Alejandro Rabinstein (Mayo Clinic, Rochester, Minnesota, USA) and colleagues were surprised to find that electrographic seizures were not associated with mortality, whereas epileptiform discharges were. They propose that "a greater preservation of neuronal circuitry is necessary for electrographic seizures to occur; hence, seizures may indicate less severe cerebral injury."
Patients with clinical seizures also had better outcomes than those without, possibly because they received more aggressive anti-epileptic treatment, say the authors, or because these patients had encephalopathy due to a postictal state rather than non-seizure-related causes associated with a worse prognosis.
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