Assessment of tissue hypoperfusion by subcutaneous microdialysis during septic shock: cases with bacteremia versus nonbacteremia

Introduction

Plasma lactate has been used as a better marker of tissue hypoperfusion in patients with sepsis. Plasma lactate elevation can be delayed compared with tissue hypoperfusion. Microdialysis has been used for an assessment of tissue hypoperfusion in the area of neurosurgery; however, limited studies have been published in the area of septic shock. We hypothesized that septic patients with bacteremia (BA) suffered from more severe hypoperfusion than those with nonbacteremia (Non-BA). We therefore investigated subcutaneous lactate and lactate/pyruvate ratio in cases with BA versus Non-BA for an assessment of tissue hypoperfusion in both groups.

Methods

Cases with septic shock were enrolled between April 2006 and November 2007 in a mixed ICU of a tertiary care hospital in Japan. Microdialysis (CMA/Microdialysis, Sweden) was used as in a previous study [1]. Lactate, pyruvate and glucose in subcutaneous tissue of cases with BA and Non-BA were measured three times with 8-hour intervals after ICU admission. Two groups were then compared in terms of above measurements. All data were reported as medians and interquartile ranges (IQR). The Mann–Whitney U test was used for statistical analysis and P < 0.05 was considered statistically significant.

Results

Fourteen cases were evaluated; the male/female ratio of BA was 2/5 (age 62–86 years) and Non-BA was 4/3 (age 57–88 years). No difference of APACHE II score was observed (mean: BA 30 vs Non-BA 29). The lactate level (mmol/l) in BA (median 3.8, IQR 1.9–5.4) was significantly higher than in Non-BA (median 1.9, IQR 1.6–2.6) (P = 0.012). The glucose level (mmol/l) in BA (median 3.9, IQR 2.6–7.1) was significantly less than that in Non-BA (median 6.3, IQR 4.9–10.1) (P = 0.004). The lactate/pyruvate ratio in BA (median 1.8%, IQR 1.4–2.5%) was significantly higher than those in Non-BA (median 1.4%, IQR 1.2–1.6%) (P = 0.023).

Conclusion

Our data suggest that tissue ischemia was more prominent in septic patients with BA than those with Non-BA. Microdialysis can be a promising method to differentiate between septic shock with BA and Non-BA.