Sepsis-induced brain state instability

Abstract

Sepsis-associated brain dysfunction (SABD) is a frequent severe complication of sepsis and the systemic inflammatory response syndrome. It is associated with high mortality and a majority of survivors suffer long-term neurological consequences. Here, we studied the effects of SABD on oscillatory brain states in an acute rat model of sepsis induced by high dose LPS (10 mg/kg). To focus on intrinsically generated brain state dynamics, we used a urethane model that spares oscillatory activity in REM- and NREM-like sleep states. Soon after the intraperitoneal LPS injection we observed a robust fragmentation of both oscillatory states resulting in a three-fold increase in the number of state transitions that lasted for several hours, although the overall time spent in either state did not change. Analysis of power spectra showed opposing shifts in low frequency oscillations (1-9 Hz) that resulted in increased similarity between both states in 2-D state space. The described spectral characteristics of sepsis-induced EEG state instability might point to a mechanism underlying severe sleep fragmentation as described both in sepsis patients and in SABD animal models.