Objective: The cardiac chemoreflex sensitivity is a powerful predictor of autonomic dysfunction in chronic heart failure and after myocardial infarction. The objective of the present study was to characterize cardiac chemoreflex sensitivity in patients with multiple organ dysfunction syndrome (MODS). We also aimed to elucidate the effect of the severity of MODS on the assessment of cardiac chemoreflex sensitivity.
Design: Prospective cohort study.
Setting: Twelve-bed medical intensive care unit in a university center.
Patients: Forty consecutively admitted patients with MODS during a 7-month period. Patients with MODS were identified by an APACHE II score of 20 or more. Sepsis was defined as a Sepsis Score, according to Elebute and Stoner, of 12 or more.
Interventions: The cardiac chemoreflex sensitivity was assessed using the regression of heart interval (ms) versus arterial oxygen pressure (mmHg).
Measurements and results: First, we established a new method to assess cardiac chemoreflex sensitivity and applied it to healthy controls and patients. Second, we found that cardiac chemoreflex sensitivity correlated with the severity of MODS as calculated by the APACHE II score ( r(2)=0.34, p=0.001). This relation was best fitted by a model including minimum heart rate and standard bicarbonate in 24 h ( r(2)=0.5, p<0.001) and Glasgow Coma Scale ( r(2)=0.5, p=0.005). Age, however, did not significantly contribute ( r(2)=0.001, p=0.8).
Conclusions: The calculation of cardiac chemoreflex sensitivity enabled us to quantify an important component of the cardiorespiratory interactions in patients with MODS. Severity of illness was a more pronounced determinant of impaired cardiac chemoreflex sensitivity than age. The quantification of the cardiorespiratory interactions by measuring the cardiac chemoreflex sensitivity has potential to identify a subgroup of patients with worse prognosis.