AUTONOMIC AND HEMODYNAMIC ACTIVITY IN SEPSIS

Abstract

Objectives: The aim is to evaluate early hemodynamic patterns of patients with severe sepsis and septic shock and compare/contrast the effects of sepsis as a primary etiologic event versus sepsis as a secondary complication after trauma, surgery etc. with simultaneously monitored sympathetic (SNS) and parasympathetic nervous system (PSNS) activities measured by the variability of the heart rate (HR) and respiratory rate (RR). Setting: Level 1 university-run trauma service in a public hospital. Methods: Non-invasively monitored the early hemodynamic patterns in 208 severely septic patients beginning shortly after admission to the emergency department (ED). Simultaneously, monitored and compared the spectrum of HR and RR variability patterns, as markers of autonomic activity, with temporal hemodynamic patterns in 73 of these septic patients. The HR variability was measured to evaluate the low frequency area (LFa), which reflects SNS. The high frequency area (RFa) is indicative of PSNS activity. The LFa/RFa, reflects the relationship of SNS to PSNS. Concurrent noninvasive hemodynamic monitoring consisting of: a) cardiac output by bioimpedance, HR, and mean arterial pressure (MAP) to reflect cardiac function, b) pulse oximetry (SapO2) to reflect changes in pulmonary function, and c) transcutaneous oxygen (PtcO2) indexed to the FiO2 as a marker of tissue perfusion/oxygenation. Results: Non-survivors had higher LFa and RFa values than the survivors did. The increased RFa preceded the increases in LFa in non-survivors and a higher percentage of sympathetic activity. These changes were more marked when measured before sedation and pain medication. In survivors, these patterns were associated with increased cardiac index (CI), and HR, normal MAP, SapO2, and normal tissue perfusion indicated by PtcO2/FiO2 ratios. Nonsurvivors had relatively normal CI, hypotension, tachycardia, poor tissue perfusion, borderline SapO2, and reduced oxygen delivery. Conclusions: In the period immediately after ED admission of patients with sepsis increased ANS activity was observed more pronounced in non-survivors. This ANS activity was associated with increased HR, MAP, and CI, and a tendency toward reduced tissue perfusion/oxygenation. INTRODUCTION The aims were to evaluate early hemodynamic patterns of surviving and nonsurviving patients with severe sepsis and septic shock. Second, to compare these hemodynamic patterns with simultaneously monitored sympathetic (SNS) and parasympathetic nervous system (PSNS) activities measured by the variability of the heart rate (HR) and respiratory rate (RR); collectively known as autonomic nervous system (ANS) monitoring. Third, to compare and contrast the effects of sepsis as a primary etiologic event versus sepsis as a secondary complication after trauma, surgery, and other acute illnesses with simultaneously monitored SNS and PSNS activities measured by ANS monitoring. The present study: a) describes the patterns of sympathetic and parasympathetic activities in acute sepsis, b) relates these to the evolving temporal hemodynamic patterns, and c) describes these autonomic and hemodynamic interactions in sepsis as a primary disease, and as a complication of trauma and surgery. Rivers et al (11) showed improved outcome in septic patients with goal-directed therapy started in the emergency department (ED) based on minimally invasive monitoring. Multiple continuously monitored noninvasive hemodynamic values used in the present study provided an integrated approach to major circulatory components: cardiac, pulmonary, and tissue perfusion functions (6,8,12-21). Simultaneous measurements of hemodynamics with ANS activity provide a unique opportunity to study the role of ANS activity in the hemodynamic responses to various clinical septic conditions alone and in combination with surgery, trauma, or other acute emergencies.