Impaired subcortical and cortical sensory evoked potential pathways in septic patients^*

Abstract

Objective 

Sensory evoked potential (SEP) peak latencies were recorded in order to evaluate the incidence and severity of septic encephalopathy, testing the hypothesis that the occurrence of septic encephalopathy is more frequent than generally assumed.

Design 

Prospective cohort study.

Setting 

Medical intensive care unit of a university hospital.

Patients 

Sixty-eight critically ill patients were studied within 48 hrs after the development of severe sepsis (n = 41) or septic shock (n = 27).

Interventions 

None.

Measurements and Main Results 

Septic encephalopathy was defined as prolongation of SEP peak latencies beyond the upper limit of the reference range of subcortical (N13–N20 interpeak latency) and cortical SEP pathways (N20–N70 interpeak latency), as well as asymmetry of peak latencies marked by the presence of subclinical cerebral focal signs. Subcortical SEP pathways were impaired in 34% and cortical SEP pathways in 84% of all patients. The prolongation of the cortical SEP pathway correlated with the Acute Physiology and Chronic Health Evaluation III score (r = 0.23;p < .0001). SEP peak latencies did not differ in patients with severe sepsis compared with those with septic shock. Subclinical cerebral focal signs were present in 24% of the subcortical SEP pathways and in 6% of the cortical SEP pathways.

Conclusions 

Septic encephalopathy occurs more frequently than generally assumed, and its severity is associated with the severity of illness. The impairment of subcortical and cortical SEP pathways was not different between patients with severe sepsis and those with septic shock.