Oxygen metabolism as an indicator in criteria for hemoperfusion using a polymyxin-B immobilized column introduction

Introduction

It has been reported that hemoperfusion with a column of polymyxin B immobilized on fibers (PMX-DHP) ameliorates hyperdynamic circulation in septic shock and improves survival rate. However, a variety of criteria for the introduction of PMX-DHP in sepsis patients are used by a number of facilities, standard criteria have yet to be established. We introduced PMX-DHP using oxygen metabolism as an indicator, and evaluated the effectiveness.

Subjects and methods

Subjects consisted of 24 sepsis patients (19 men and five women; mean age 60 ± 15.4 years) who had undergone PMX-DHP between January 2003 and October 2004. A thermodilution catheter was inserted into all patients. Mixed venous oxygen saturation (SvO₂), oxygen delivery index (DO₂I), oxygen consumption index (VO₂I), and oxygen extraction ratio (O₂ER) were used as indicators of systemic oxygen metabolism, and the PCO₂ gap (gastric submucosal carbon dioxide partial pressure minus the partial pressure of carbon dioxide in arterial blood) measured by gastric air tonometry was used as the indicator of tissue oxygen metabolism. These parameters were measured before and 24, 48, 72, and 120 hours after PMX-DHP introduction. The severity of infection was evaluated by the Acute Physiology and Chronic Health Evaluation (APACHE) score.

Results

Life expectancy: 18 patients survived; six died. APACHE scores of survivors and non-survivors were 22 ± 4.0 and 24 ± 3.5, respectively. There was no significant difference. In the survivors SvO₂, DO₂I, VO₂I, and O₂ER had shifted to the normal range prior to treatment. Pretreatment, the PCO2 gap was 17 ± 3.6 mmHg in these patients, who presented markedly dysfunctional tissue oxygen metabolism. However, this decreased over time, and at 120 hours after treatment the PCO₂ gap had decreased significantly, improving to values in the normal range. On the other hand, the non-survivors also presented high PCO₂ gap levels before treatment, similar to the survivors. Although DO₂I was within the normal range, VO₂I and O₂ER were lower than normal.

Conclusion

Although dysfunctional tissue oxygen metabolism occurred in both the survivors and non-survivors, non-survivors also presented dysfunctional systemic oxygen intake. These results suggest that early-stage introduction of PMX-DHP is desirable, when systemic oxygen metabolism is stable.